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Energy Efficiency and Renewable Energy 

Office of FreedomCAR and Vehicle Technologies 

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March 2004 

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A.	 Smart Materials for Diesel Fuel Injector ....................................................................... 7


B.	 Cost-Effective Smart Materials for Diesel Engine Applications ................................... 15


C.	 Low-Cost Manufacturing Processes for Ceramic and Cermet Diesel 


 Engine Components ................................................................................................... 21


D. Intermetallic-Bonded Cermets...................................................................................... 29


E.	 Low-Cost, High-Toughness Ceramics .......................................................................... 33


 ."5&3*"-4'03&9)"645"'5&353&"5.&/5 

A.	 Materials for Exhaust Aftertreatment ........................................................................... 37


B.	 Development of Materials Analysis Tools for Studying NOx 


Absorber Catalysts........................................................................................................ 43


C.	 Development of NOx Sensors for Heavy Vehicle Applications.................................... 49


D. Ultra-High-Resolution Electron Microscopy for Characterization of


 Catalyst Microstructures and Deactivation Mechanisms .......................................... 55


E. 	 Microstructural Changes in NOx Trap Materials under Lean and 


 Rich Conditions at High Temperature ....................................................................... 61


F.	 Aftertreatment Catalyst Materials Research ................................................................. 67


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A. 	High-Temperature Advanced Materials for Lightweight Valve


 Train Components...................................................................................................... 73


B.	 Thick Thermal Barrier Coatings for Low-Emission, High-Efficiency 


 Diesel Engine Components ........................................................................................ 77


C. Cermet Composites for Wear Applications.................................................................. 85


D.	 Processing and Characterization of Structural and Functional Materials


 for Heavy Vehicle Applications .................................................................................. 89


E.	 NDE Development for Ceramic Valves for Diesel Engines.......................................... 97


F. 	 Durability of Diesel Engine Component Materials...................................................... 103 


G. Life Prediction of Diesel Engine Components ............................................................. 109 


H. Low-Cost Manufacturing of Precision Diesel Engine Components ............................ 117 


I.	 Infrared-Based Temperature Measurement in Diesel Exhaust


 Aftertreatment Filters.................................................................................................. 123


J. 	 Advanced Cast Austenitic Stainless Steels for 


 High-Temperature Components ................................................................................ 129 


K.	 Microstructure and Creep Properties of TiAl/Ti3Al In-Situ Composites ...................... 133 


L. 	 Synthesis of Powders for Titanium Carbide/Nickel Aluminide Cermets .................... 139 


M. Diesel Exhaust Gas Recirculation Corrosion Effects .................................................... 145 


N. Laser Surface Texturing of Lubricated Ceramic Parts .................................................. 147 


O. Ti-6Al-4V Billet Feedstock Manufacture and Evaluation ............................................. 153 


iii 
P.	 High-Density Infrared Surface Treatment of Materials for 


 Heavy-Duty Vehicles ................................................................................................... 157 


Q. High-Temperature Aluminum Alloys ........................................................................... 161 


R.	 Development of Titanium Component Applications in


 Heavy-Duty Diesel Engines ......................................................................................... 167 


 5&45"/%."5&3*"-445"/%"3%4   

A. Modification of Engineering Materials for Heavy-Vehicle Applications ..................... 169 


B.	 Implementing Agreement for a Programme of Research and Development


 on Advanced Materials for Transportation Applications ........................................... 175 


C. Mechanical Property Test Development....................................................................... 181 


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iv 
Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

)&"7:7&)*$-&13016-4*0/."5&3*"-4

Advanced materials are an enabling technology for fuel-efficient heavy-vehicle truck 

engines. The Heavy Vehicle Propulsion Materials Project is organized around the following 

technology issues: fuel systems; exhaust aftertreatment; air handling, hot section and 

structural components; and standards. 

.BUFSJBMTGPS'VFM4ZTUFNT

The fuel systems for diesel engines are complex, expensive systems that are critically 

important to meeting the efficiency and emissions targets of the Office of FreedomCAR and 

Vehicle Technologies (OFCVT). Virtually every path to improving the control of the 

combustion process in order to improve efficiency and reduce emissions depends on 

improvements in the fuel injection system. 

Fuel injectors are highly precise systems. The individual components must fit together −6

with clearances that are sometimes smaller than 1×10 meters. Control of the combustion 

process requires precise control of the size, shape, and surface finish of the injector 

components. The current systems for reliably controlling multiple injections are limited by 

the ability of mechanical and electronic systems to respond precisely and quickly enough to 

provide the additional control of injection. Smart materials, such as piezoelectric materials, 

offer the potential for better control of fuel injection and have recently been introduced for 

automobiles. However, a number of improvements in materials and manufacturing methods 

for the materials are yet required for heavy vehicles. 

Presently, the fuel system represents a significant portion of the cost of a heavy-duty diesel 

engine. Enabling materials and cost-effective precision manufacturing processes are 

instrumental in developing improved fuel injection systems. In addition to new and improved 

materials, improved manufacturing and inspection methods for the injector components are 

being developed. 

Two important research and development (R&D) efforts were completed in FY 2003. A 

coordinated project was completed for developing the materials and manufacturing 

technology for a new generation of wear- and scuff-resistant fuel system components. The 

participants included Cummins Engine Company, CoorsTEC, Oak Ridge National Laboratory 

(ORNL), Southern Illinois University at Carbondale, and the University of Colorado. The 

material developed is a cermet made of a nickel aluminide matrix and a titanium carbide (TiC) 

ceramic phase. The material is very wear- and scuff-resistant and can be engineered to match 

the coefficient of thermal expansion of steel. Cummins, the user of the material, provided all 

the design and materials requirements and performed the prototype testing. CoorsTEC, a 

ceramic manufacturer that presently supplies zirconia ceramic components to Cummins, is 

developing the cermet manufacturing technology. ORNL invented the nickel aluminide–TiC 

cermet and performed much of the cermet processing and microstructure development. The 

University of Colorado developed processes for synthesis of cost-effective powders for 

manufacture of the material. Southern Illinois University at Carbondale developed two lowcost manufacturing processes for the cermet material: low-pressure injection molding and 

continuous sintering in a belt furnace. 

The feasibility of piezoelectric actuators for heavy-duty diesel engine fuel injectors was 

demonstrated in a recently-completed project. Detroit Diesel Corporation (DDC), completed a 

project that had the objective of developing technical requirements for a valve actuator 

system, including advanced piezoelectric materials that would enable faster and more precise 

1 

FY 2003 Progress Report	 Heavy Vehicle Propulsion Materials 

control of the injection rate characteristics of a heavy-duty diesel injector. ORNL and Wayne 

State University provided materials development and testing for the project. DDC’s research 

resulted in the following conclusions: 

1.	 A piezoelectric (piezo) stack is a viable actuation device for future diesel fuel injection 

equipment involving multiple actuators. 

2.	 Piezo actuation provides substantially faster mechanical and hydraulic response times than 

prevailing commercial solenoid actuator technology. 

3.	 Hydraulic amplification of piezo stack displacement can generate required diesel injector 

control valve motion. 

4.	 Hysteresis of a piezoelectric stack is not expected to play a significant role in a pulsed 

application such as a fuel injection system. 

5.	 Open-loop control of input voltage may be of adequate complexity for a mature piezo 

actuator application in a diesel fuel injection system. 

6.	 Commercially available piezo stacks have adequate material properties and technical 

characteristics for fuel injection. 

.BUFSJBMTGPS&YIBVTU"GUFSUSFBUNFOU

The reduction of nitrogen oxide (NOx) and particulate emissions is critically important to 

OFCVT’s program and is highly materials-dependent. The U.S. Department of Energy’s goals 

for improved efficiency of heavy vehicles are greatly complicated by engine design and 

exhaust aftertreatment technologies designed to meet the mandatory U.S. Environmental 

Protection Agency (EPA) emission regulations for 2007 and 2010. Materials and systems 

research is being conducted to minimize the potentially negative effects of emission-reduction 

technologies on fuel economy and to result in both cleaner and more efficient engines. 

The durability of exhaust aftertreatment systems in heavy vehicles is a concern. Lifetimes 

of at least 500,000 miles are expected, and a million-mile lifetime is desired (compared with 

100,000 miles for automobiles). Exposure of the aftertreatment systems to high temperatures, 

vibration, erosion, and chemical attack by species in the oil and fuel results in degradation of 

performance. In an effort to develop more durable systems, the effects of exposure during 

service on the microstructure and microchemistry of the aftertreatment systems are being 

characterized. The development of advanced NOx sensors is being conducted to facilitate 

optimal engine and aftertreatment control strategies. 

Accomplishments in FY 2003 include significant progress in a collaborative Ford Motor 

Company–ORNL program that seeks to facilitate deployment of a NOx trap for lean diesel or 

gasoline exhaust. The effort includes (1) investigating materials issues related to deterioration 

of NO trap performance after aging as a result of thermal and sulfation-desulfation cycles and x

(2) investigating materials that are robust under the lean NOx trap operating conditions. The 

second objective includes the synthesis of new materials. 

Research conducted at the High Temperature Materials Laboratory at ORNL is focused on 

the development and use of new capabilities and techniques for ultra-high-resolution 

transmission electron microscopy to characterize the microstructures of catalytic materials of 

interest for reduction of NO emissions in diesel and automotive exhaust systems. This x 

research aims to demonstrate the effects of reaction conditions on changes in morphology of 

heavy metal species on “real” catalyst support materials, typically oxides. 

Exhaust aftertreatment materials projects are ongoing at both Caterpillar, Inc., and 

Cummins. These projects are significant in that they represent a departure from an earlier 

culture in which the diesel engine companies relied heavily on catalyst manufacturers to 

2 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

provide the needed technologies and did not actively participate in the development of 

catalyst materials. These diesel engine manufacturers are actively collaborating with catalyst 

suppliers in the development of improved catalyst materials and are contributing to the 

development of a fundamental understanding of catalyst performance that is important to 

both suppliers and users of catalyst systems. 

Ford and ORNL are collaborating on the development of a NOx sensor that can be used in 

systems for on-board remediation of diesel engine exhaust. The sensor should have an 

operating temperature of 600–700o

C and be able to measure NOx concentrations from 0 to 

1500 ppm at oxygen levels from 5 to 20 vol %. Prototype sensing elements are fabricated by 

patterning electronically conductive and catalytic layers onto oxygen-ion-conducting 

substrates. The sensing elements are characterized for NOx

 response, oxygen sensitivity, and 

response time. These results, along with microstructural characterization, should point to the 

correct combination of materials chemistry, materials processing, and sensor design required 

for the desired sensor performance. 

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Engine design strategies for meeting EPA emission requirements have resulted in the need 

for significantly higher turbocharger boost. The higher boost requirements result in higher 

heat of compression and greater thermal and fatigue loads on turbocharger components. 

Caterpillar began a new project in 2003 to design and fabricate a cost-competitive diesel 

engine turbocharger, using lightweight titanium materials, that provides a reduction in both 

fuel consumption and transient emissions. Caterpillar has designed a series turbocharger for 

use on the C15 engine platform. It consists of one turbo wheel and two compressor wheels 

that are attached to a single rotating drive shaft. This compact design will replace a twoturbocharger system presently installed in the C15 engine. Titanium aluminide will be used 

for the turbo wheel, and one of the compressor wheels will be made from a titanium alloy. 

In a related project, Dynamet Technologies, Inc. is conducting an R&D project to develop 

low-cost Ti-6Al-4V billet feedstock using a blend of titanium and alloy powders and 

inexpensive Ti-6Al-4V machine turnings. Dynamet will evaluate this low-cost titanium alloy 

feedstock as starting billet material for casting, forging, and extrusion operations. 

Caterpillar and ORNL won a 2003 R&D 100 Award for the development of CF8C-Plus cast 

stainless steel. The new high-temperature stainless steel may have near-term applications in 

diesel engine exhaust manifolds and turbocharger housings. The future direction for this 

project includes completing the evaluation of thermal fatigue properties and aging resistance 

after 10,000 hours, characterizing microstructural changes after selected high-temperature 

testing or aging, and evaluating the effects of different commercial-scale casting processes on 

properties of CF8C-Plus steel. 

Caterpillar, in a collaboration with Argonne National Laboratory and ORNL, has a project 

to design and fabricate prototype engine valves from silicon nitride and titanium aluminide 

materials that are 30% lighter than steel valves, provide a 200% increase in service lifetime, 

and may increase fuel efficiency by 10% in a camless engine design. Caterpillar is also 

developing innovative approaches to thermal barrier coatings and wear-resistant coatings for 

engines. The durability of thermal sprayed coatings, particularly thermal barrier coatings, 

3 

FY 2003 Progress Report	 Heavy Vehicle Propulsion Materials 

remains the major technical challenge to their implementation in new engine designs. New 

approaches to coating design and fabrication are being developed to aid in overcoming this 

technical hurdle. Specific objectives are 

• Laser technologies of surface dimpling, cleaning, and laser-assisted spraying to enhance 

adherence and increase coating strength. 

• Development of phosphate-bonded composites for thermal management coatings. 

• Evaluation of quasicrystalline materials as potential thermal barrier and wear coatings. 

.BUFSJBMTBOE5FTUJOH4UBOEBSET

OFCVT has an International Energy Agency (IEA) “Implementing Agreement for a 

Programme of Research and Development on Advanced Materials for Transportation 

Applications” (IA-AMT). The objectives of the IA-AMT are (1) to identify and evaluate 

promising new processing and surface engineering technologies capable of improving 

materials performance in transportation systems and (2) to promote and implement precompetitive development and verification of advanced characterization methods appropriate 

for advanced materials for transportation applications. Annex III, which was approved in July 

2002, consists of two subtasks on contact reliability of advanced engine materials, including 

structural ceramics, composites, and nanostructured friction/wear coatings. Subtask 1 is an 

information exchange; Subtask 2 focuses on the development of standard test methods and 

procedures for determining the rolling contact fatigue resistance of advanced materials. The 

European Community plans to invite the United Kingdom to join the IA-AMT because of its 

interest in participating in Annex III. Preliminary discussions have been held with 

government officials from Canada concerning the initiation of a new Annex on 

lightweighting of materials. 

A new activity to be conducted under the IEA program is being developed by the National 

Institute of Standards and Technology (NIST). The objectives of this new effort are as follows: 

• Organize an international cooperative research program on an integrated surface 

modification technology under the auspices of the IEA. 

• Design and identify surface features and patterns that can achieve friction reduction and 

enhanced durability for heavy-duty diesel engine components. 

• Develop the understanding and appropriate models to explain texturing effects on 

frictional characteristics. 

• Develop appropriate thin films and coatings to achieve synergistic and complementary 

relationships with texturing to enhance performance. 

• Discover and develop the surface chemistry for protecting the films and coatings that work 

in synergy with the textures. 

NIST also leads a project to develop standard testing methods for advanced materials, 

primarily ceramics. Step by step, we are building a national and international standards 

infrastructure to facilitate the commercial utilization of new advanced materials in engine 

applications. The generic test method standards developed to date have proved to be so 

practical, reliable, and versatile that they are now being used to support a wide range of 

applications, including surgical implants in humans and even ceramic military body armor. 

Test methods relevant to ceramic materials and heavy-vehicle propulsion applications are 

investigated, refined, and standardized. Round-robins are conducted as necessary. Standard 

Reference Materials (SRMs) are created to support the test methods and materials 

4 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

specifications. Procedures are standardized by the American Society for Testing and Materials 

(ASTM) and/or the International Organization for Standards (ISO). In FY 2003, SRM 2831 for 

Vickers Hardness of Ceramics and Hard Metals was finished. This SRM complements ASTM 

and ISO test methods standards for Vickers hardness of hard materials, and new material 

specification standards such as ASTM F 2094 for silicon nitride for ball bearings. 

Rogelio Sullivan Sidney Diamond Team Leader, Materials Technologies Technology Development Area Specialist Office of FreedomCAR and Vehicle

 Technologies 

Energy Efficiency and Renewable Energy 

Office of FreedomCAR and Vehicle

 Technologies 

Energy Efficiency and Renewable Energy 

5 
Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

."5&3*"-4'03'6&-4:45&.4

"4NBSU.BUFSJBMTGPS%JFTFM'VFM*OKFDUPS

Urvish Joshi, Yury Kalish, Craig Savonen, Vijay Venugopal,* and Naeim Henein* 

Detroit Diesel Corporation 

13400 Outer Drive, West 

Detroit, MI 48239-4001 

(313) 592-5315; fax: (313) 592-7888; e-mail: craig.savonen@detroitdiesel.com 

*Wayne State University 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: Detroit Diesel Corporation, Detroit, Michigan 

0CKFDUJWFT

• Develop technical requirements for a valve actuator system, including advanced piezoelectric 

materials that would enable faster and more precise control of the injection rate characteristics 

of a heavy-duty diesel injector. 

• Enable the heavy-duty diesel engine to meet future emission standards without suffering gross 

fuel economy penalties, while mitigating the costs and complexities of prerequisite exhaust 

aftertreatment systems. Hardware fabrications in this project include a pre-prototype piezobased actuator system suitable for bench test characterization and mechanical design 

integration with a production injector body. 

"QQSPBDI

• Characterize and validate, by static and dynamic testing, those candidate piezo stacks that 

promise to meet the gross requirements of the high-pressure diesel fuel injection application. 

Down-select the most promising candidate(s) for further evaluation and integration. 

• Design and develop an amplification system to achieve the total required control valve stroke 

anticipated for the future diesel fuel injector. 

• Complete a characterization study of advanced reference two-actuator fuel injector systems by 

experimental fixture 

engine testing 

simulation 

• Synergize a combination of computational and experimental results to establish detailed 

material and system requirements for a superior piezoelectric material application in the heavyduty diesel fuel injector. 

7 

•

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

"DDPNQMJTINFOUT

• Completed first-generation refinement of pre-load and electrical drive current in candidate 

piezo stacks to avoid high tensile forces, achieve minimum response time, and minimize 

displacement over-shoot under dynamic operation. 

• Measured piezo stack power consumption to support the expectation for lower overall power 

consumption from a mature, well-applied piezo stack, as compared with a solenoid actuator 

performing a similar function. 

• Designed and fabricated a hydraulic amplification module including the mechanical elements 

required to attach to a production injector body for bench demonstration purposes. Definitive 

finite element analysis confirmed the need for a design revision to the original hydraulic 

amplification module concept. Iterations on the design led to considerable simplification and 

implications of improved robustness, crucial to ultimately pursuing a production-feasible 

assembly. 

Integrated the revised amplification system module with a production injector body yielding a 

pre-prototype piezo injector, which was subsequently tested on an experimental fixture. 

*OUSPEVDUJPO

The importance of research in fuel 

injection equipment to reduce 

environmental pollutants from the 

automotive industry, including light-duty 

and heavy-duty vehicles, has been greatly 

emphasized. One technical focus is the 

advancement of basic fuel injector 

technology to provide more precise delivery 

and atomization of fuel to the combustion 

chamber across a broader range of 

operational control. 

The general objective of this project is to 

accelerate the assessment of the maturity of 

emerging piezoelectric materials to fulfill the 

requirements of future diesel engine fuel 

injectors. Specific requirements of this 

material application and challenges of the 

operating environment are being quantified. 

An extensive candidate search was carried 

out for so-called smart materials, such as 

piezo stacks, that could actuate the control 

valve in a heavy-duty diesel injector. 

This program is a joint research effort 

carried out by Wayne State University and 

Detroit Diesel Corporation and funded by 

DOE. 

The more specific technical objective of 

this project is to use computational and 

experimental methods to substantiate a 

design and application strategy to maximize 

the advantage of piezoelectric materials, 

compared with conventional solenoid 

materials, in a diesel fuel injector operating 

environment. The premise of the base 

piezoelectric material advantage is that it can 

provide 

• An order-of-magnitude reduction in 

response time 

• Much higher force 

• More precise control of the start, rate 

shape, and duration of the injection 

event 

• More precise timing and delivery 

quantity of a multiple injection event 

• Less energy consumption 

The research was initiated with a 

screening study of available piezoelectric 

devices. Various piezoelectric devices were 

selected for this purpose. Broadly, these can 

be classified as either high-voltage or lowvoltage/multilayer co-fired stacks. Key 

performance parameters of piezo stacks 

related to fuel injection applications were 

evaluated as the following table indicates: 

8 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

driving source, and the amplification 

Applied Input Input Operating Duty 

preload voltage current frequency cycle 

Displacement Rise Delay Fall time System 

time time compliance 

From the completed experiments, it was 

evident that the displacement produced by 

these candidate stacks was insufficient 

compared with the total displacement 

requirements of most historical control valve 

applications in the heavy-duty diesel fuel 

injection environment. Therefore, three 

options were possible: 

1.	 Select much larger stacks that can 

produce higher displacements. 

2.	 Design an amplification system to 

increase the stroke using existing stacks. 

3.	 Search for the best fit of prevailing piezo 

stack capability with emerging fuel 

injector technology. 

The first option was deemed impractical 

because of the physical limitations of the 

stack sizes, as well as the cost concerns for 

expensive piezo materials. The intermediate 

solution was deemed to be a reasonable 

approach in spite of considerations for 

implied energy losses and system 

complexities. Hence, conceptual design was 

initiated of a pre-prototype amplification 

system that could couple piezo stacks with a 

diesel fuel injector. Again, in the study of 

potential amplification design concepts, 

various approaches were considered, 

including mechanical, hydraulic, and hybrid 

amplification systems. 

From these three general approaches, the 

hydraulic amplification system was selected 

because of its simplicity and inherently 

improved control of design issues. A 

prototype control valve actuator system was 

built and tested. This actuator system testing 

revealed that the system performance (e.g., 

valve stroke versus response time) would 

have to be improved substantially. Finally, a 

revised control valve actuator system 

concept consisting of the actuator itself, the 

system was shown to achieve higher 

displacements. 

3FTVMUT

This report focuses on the activities 

completed for FY 2003: 

1.	 Failure analysis of the piezo stack 

2.	 Design and fabrication of the hydraulic 

amplification system 

3.	 Integration of the hydraulic amplification 

system with the injector 

4.	 Reference characterization of emerging 

two-actuator fuel injection systems 

'BJMVSF"OBMZTJTPGUIF1JF[P4UBDL

As is well known, piezo stacks incorporate 

relatively brittle ceramic materials. Hence 

proper care must be taken to assemble the 

stack into the actuator mechanism. Various 

design issues must be resolved to ensure that 

the piezo stack operates efficiently and 

without failure, especially with the reliability 

and durability emphasis of the heavy-duty 

transportation industry. 

Scanning electron microscopy (SEM) 

pictures from this project (Figures 1 and 2) 

show samples tested earlier this year. Stack 

layers are fractured, and electrodes are shortcircuited and burned. Post-mortem analysis 

indicated that the stack would fracture only 

when the tensile forces in the stack were 

present or if there were intermittent impact 

loads on the stack. 

Piezo stacks require some minimum 

preload force to preclude tensile forces from 

arising within the stack during normal 

cyclical operation. As the electrical current 

increases and in turn increases the force 

generated in the stack, higher-input electrical 

current calls for a higher preload. Otherwise, 

when the threshold is passed whereby 

inertial force becomes greater than the 

preload applied on the stack, even the 

modest tensile forces created can precipitate 

a physical failure of the stack. 

9 

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

'JHVSF Failure analysis: Separation of layers of 

multilayer piezo stack. 

'JHVSF. Failure analysis: Fractured piezo stack 

layers and burnt electrodes leaving 

voids. 

Conversely, if the preloads are very high, 

then it is especially crucial to apply the 

preload uniformly over the entire stack crosssection to prevent the cracking of the 

ceramic layers. Otherwise, the stack is 

subjected to uneven forces and stress/strain 

gradients, with some portion of the stack 

under compression and some portion of the 

stack under tension, which will also lead the 

stack to fracture. If the stack is to operate in 

dynamic conditions, as expected for a diesel 

injector application, it becomes increasingly 

important to apply an appropriate level of 

uniform preload over the entire stack plane. 

Therefore, the design of the marriage 

between the piezoelectric stack and its 

encapsulating structure must ensure that the 

loads and adequate preloads subjected to the 

stack are substantially co-axial with the stack 

axis. Similarly, the mating surfaces between 

the stack and the encapsulating structure 

must be within a predetermined tolerance of 

parallelism, influenced by local 

perpendicularity and planarity. 

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The working principle of the 

amplification is illustrated by Figures 3 and 

4. When the stack is actuated, the stack 

pushes the piston downward, which in turn 

pressurizes the working fluid in the fluid 

chamber. The fluid pushes the plunger 

upward along with the attached control 

valve. Thus the required control valve 

motion is achieved. 

The development of the motion 

amplification system progressed through 

'JHVSF Working of hydraulic amplification 

system for piezo injector. 

'JHVSF. Hydraulic amplification system details 

with three O-rings. 

10 

Heavy Vehicle Propulsion Materials 

several design iterations. Design was largely 

guided by finite element analysis, spring and 

O-ring calculations, and numerous 

interactions with vendors. The final design of 

the amplification module is represented by 

Figure 5, while the exploded view of the 

production “mule” injector body outfitted 

with the piezo electric actuation system is 

shown in Figure 6. The amplification system 

was assembled (Figure 7) and tested on an 

experimental fixture (Figure 8). 

'JHVSF Final design: Piezo-electric 

control valve actuator of 

electronic unit injector. 

'JHVSF Piezo injector assembly: Exploded 

view.

FY 2003 Progress Report 

'JHVSF. Piezo injector with integrated 

amplification system module.

'JHVSF Test fixture for piezo injector.

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Two-actuator injectors exhibit promising 

potential compared with the single-actuator 

injector. Fixture test results quantified that a 

11 

FY 2003 Progress Report 

range of pressure traces and instantaneous 

rate shape control, as depicted in Figure 9, 

could be achieved by a two-actuator injector 

system, even though operational instability 

is apparent for some operating conditions. 

Nonetheless, NOx reduction with marginal 

fuel economy penalty using the two-actuator 

injector (Figure 10) was readily demonstrated 

with engine testing. 

'JHVSF Two actuator fuel 

system fixture test results: 

Injection rate 

characteristics. 

'JHVSF. Two actuator fuel 


system
 engine test results: 

NOx benefits. 

Simulation of the two-actuator injector 

was performed while incorporating 

representative performance characteristics of 

available piezo stacks. Such characterization 

confirmed that the linear displacement 

versus voltage characteristics of the piezo 

stack could be exploited under dynamic 

operation. Relative to a solenoid candidate, 

Heavy Vehicle Propulsion Materials 

response times were halved while overshoot 

travel was contained to within 30% of total 

displacement. Force measurement also 

confirmed the need to adjust to a higher 

preload during dynamic operation of the 

stack in order to avoid failure (Figure 11). 

Research shows that displacement losses are 

high in the amplification system of the piezo 

injector module. Hence a more feasible 

solution is application of the piezo stack to 

the needle control valve of the two-actuator 

injector. The potential of this application 

was gauged by simulating the needle control 

valve of a two-actuator injector with shorter 

response, as promised by piezo stack 

characterizations. Ensuing simulation results 

(Figure 12) suggest that more precise 

minimum pilot injection quantities and pilot 

gaps are possible when a faster needle 

control response is implemented. 

'JHVSF Hydraulic simulation results for 

piezo stack characterization: 

Displacement and force 

characteristics. 

12 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

'JHVSF Hydraulic simulation results 

for two actuator fuel 

injector: Multiple injection. 

,FZ5FDIOJDBM0CTFSWBUJPOT

• In combination with the pre-prototype 

amplification system module, the 

demonstrated piezo injector control valve 

motion was limited. The main causes can 

be enumerated as 

High displacement losses in the 

amplification system module during 

return motion due to local O-ring 

expansion 

Higher-than-estimated friction forces 

in various moving parts 

Aeration in the hydraulic chamber 

Insufficient spring return force 

• Reference characterization of the twoactuator injector highlighted that the 

most feasible and promising application 

of the piezo stack is to apply it 

synergistically to emerging two-actuator 

fuel injection technology. Similarly, the 

application of piezo stacks is most 

suitable for those actuators requiring 

smaller displacements, such as the needle 

control valve application (Figure 13). In 

this way, the need for motion 

amplification may be reduced or 

eliminated while the benefits of short 

piezo actuator response times are 

maximized with the flexibility of dual 

actuation. 

'JHVSF Schematic of single-actuator EUI and 

advanced two-actuator EUI. 

$PODMVTJPOT

• The piezo stack is a viable actuation 

device for future diesel fuel injection 

equipment involving multiple actuators. 

• Piezo actuation provides substantially 

faster mechanical and hydraulic response 

times compared with prevailing 

commercial solenoid actuator 

technology. 

• Hydraulic amplification of piezo stack 

displacement can generate required diesel 

injector control valve motion. 

• Hysteresis of a piezoelectric stack is not 

expected to play a significant role in a 

pulsed application such as a fuel injection 

system. 

• Open-loop control of input voltage may 

be of adequate complexity for application 

of a mature piezo actuator to a diesel fuel 

injection system. 

• Commercially available piezo stacks have 

adequate material properties and 

technical characteristics for fuel injection 

application. 

• Both stack failures encountered in this 

program are attributed to mechanical 

system design and not to piezo material 

or stack manufacturing issues. 

13 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

• Piezo stacks cannot operate in tension. 

Adequate compressive preload must 

exceed tensile forces of stack acceleration 

in dynamic operation. 

• Better fuel injection characteristics and 

emission benefits are achievable with a 

two-actuator injection system. 

• Application of smart materials to the 

• Uneven loading of the stack can readily 

destroy piezo stack layers and must be 

avoided. 

needle control valve of the two-actuator 

injector would improve the multiple 

injection capabilities of the two-actuator 

• The actuator design has to overcome fuel injection system. 

various challenges, namely local aeration, 

O-ring forces, displacement losses, and 

force balance. Increased control of the 

return motion of the control valve could 

be achieved with such improvements. 

14 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

#$PTU&GGFDUJWF4NBSU.BUFSJBMTGPS%JFTFM&OHJOF"QQMJDBUJPOT

J. O. Kiggans, Jr., F. C. Montgomery, T. N. Tiegs, and L. C. Maxey*


Metals and Ceramics Division


Oak Ridge National Laboratory 


P.O. Box 2008, MS-6087 

Oak Ridge, TN 37831-6087 

(865) 574-8863; fax: (865) 574-4357; e-mail: kiggansjojr@ornl.gov 

*

Engineering Science and Technology Division 

DOE Technology Development Area Specialist: Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

0CKFDUJWFT

• Develop a lower-cost lead zirconate titanate (PZT) powder for PZT stack actuators used for fuel 

injectors. 

• Improve the mechanical properties, in particular the strength, of the low-cost PZT materials. 

• Manufacture multilayer PZT stacks with low-cost PZT powder. 

• Develop a test apparatus for measuring the reliability of PZT stack actuators. 

"QQSPBDI

• Reformulate commercial PZT-4 powder by including a low-temperature sintering aid and 

incorporating high-energy attrition milling. 

• Investigate chemical additives that can strengthen the low-cost PZT materials. 

• Manufacture multilayer stacks from low-cost PZT powders using tape casting and lamination 

techniques. Use screen printing to apply silver or Ag-Pd (90 wt%/10 wt%) for the interlayer 

electrodes. 

• Fabricate a computer-controlled test apparatus for testing the reliability of commercial and inhouse PZT stacks. 

"DDPNQMJTINFOUT

• Developed ceramic additives that allow a commercial PZT powder to sinter at a temperature 

below the melting point of silver. These additives also enhance the piezoelectric properties of 

the low-temperature sintered material. 

• Increased the fracture strength of the low-temperature sintered material by about 50% by 

including a non-soluble oxide into the matrix. 

• Fabricated multilayer stacks with silver and Ag-Pd (90 wt%/10 wt%) interlayer electrodes. 

15 

x

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

• Fabricated a computer-controlled test apparatus for measuring the reliability of multiplayer PZT 

stacks. 

• Stroked a commercial PZT actuator stack for >50 million cycles with continuous data collection 

using the Oak Ridge National Laboratory (ORNL) reliability apparatus. The data indicate that 

the displacement of a commercial stack steadily degrades with increasing cycles. 

'VUVSF%JSFDUJPO

• The initiative on low-cost PZT materials for PZT stack actuators has been completed and will not 

continue for FY 2004. However, development plans for continuation of this effort are in place 

should additional effort be required by heavy vehicle stakeholders. In this regard, discussions 

are under way with a diesel engine manufacturer regarding reliability testing of PZT stacks for 

fuel injector applications. 

*OUSPEVDUJPO

Major drivers in diesel engine research are 

the desire to increase fuel efficiency and to 

reduce the pollution of the environment. 

Recent studies have shown that multiple fuel 

injections per combustion cycle (rather than 

the conditional one injection per cycle) can 

increase the fuel efficiency and lower the 

NO and particulate emissions from diesel 

engines. Varying the rate and shape of the 

injection cycle and using multiple injections 

can improve power, emissions, and fuel 

economy. Because of the present speed 

limitations of magnetic solenoid valves, 

multiple injections of fuel are possible only 

at engine idle speeds. The need for multiple 

injection capability per combustion cycle has 

stimulated research into the development of 

high-speed actuators. The leading candidate 

devices for these actuators are piezoelectric, 

based on PZT, and magnetostrictive, based 

on Terfenol-D. Because of its lower material 

costs and performance capability, PZT is the 

favored candidate. 

PZT materials are widely used for 

actuators in applications requiring precision 

control and high force with small sizes. 

Multilayered PZT materials have been studied 

and are favored for their low power 

consumption and high precision control.1,2,3 

In comparison with conventional actuators, 

PZT transducers demonstrate higher energy 

densities, larger actuation forces, greater 

positioning accuracy, and shorter response 

times. However, widening the application of 

PZT transducers requires improvement in the 

properties of the PZT materials (greater 

strains and temperature stability desired) and 

reduction of the materials costs, where the 

Pt-Ag or Pd-Ag electrode materials represent 

the largest material factors. 

"QQSPBDI

The following approach was taken to 

study the effect of low-temperature sintering 

agents and strengthening agents on PZT-4 

powder. Numerous PZT powder batches were 

prepared using attrition milling with 

sintering aids and several types of 

strengthening agents. For the initial powder 

batch, the particle size was measured after 

defined milling periods to determine 

optimum milling time. After milling, the 

slurries were dried, the powder cakes were 

crushed, and the powders were sieved. PZT 

disks were pressed in a steel die and sintered 

at temperatures suitable for silver electrode 

applications. Samples were poled, after 

which the electrical and mechanical 

properties were measured. Optical 

microscope and scanning electron 

microscope (SEM) examination were 

performed to analyze the microstructures of 

the materials. 

The following approach was taken for the 

fabrication of multilayer stack actuators from 

the low-temperature sintering PZT-4 

materials. Thin sheets (0.02 cm) of the 

16

Heavy Vehicle Propulsion Materials 

powder were tape-cast, and then silver or AgPd (90/10 wt/wt) electrodes were screenprinted onto the dried tapes. Then 25 to 

35 discs were punched from a tape, aligned 

on top of one another in a steel die, and 

laminated to make a stack. Laminate samples 

were sintered and densities measured. Silver 

ink electrodes were painted on the outer flat 

surfaces of each stack, and the ink was used 

to create layer-to-layer interconnections 

down the side of the stacks. The stacks were 

fired at low temperature to bond these silver 

electrodes. Several samples were poled and 

electrical properties measured. Select samples 

were sliced into sections with a diamond saw 

for optical and SEM analysis. 

The third major work this year involved 

the fabrication of a computer-controlled test 

apparatus for testing the reliability of 

multiplayer PZT stacks. ORNL personnel 

fabricated a custom apparatus. 

3FTVMUT

Work was performed with an attritionmilled PZT-4 powder containing the ORNL 

sintering aids. This material was densified to 

full density after 3 hours of heating at 

temperatures greater than 850o

C. This low 

sintering temperature can allow the use of 

cheaper silver inter-electrodes in laminated 

stacks. Furthermore, Figure 1 shows that 

these materials, when sintered at 

temperatures from 800 to 950oC, have 

piezoelectric properties equivalent to those 

reported for PZT-4 that was sintered at 

temperatures exceeding 1200oC. 

However, the strength of the lowtemperature sintered material is lower than 

that of material that is sintered at the higher 

temperatures. Consequently, part two of the 

study involved the use of ceramic additives 

to increase the strength of the lowtemperature sintered material. Figure 2 shows 

that the addition of type 3 ceramic additive 

enhances the strength of the lowtemperature PZT by approximately 50%. 

Figure 3 shows the fracture and polished 

FY 2003 Progress Report 

'JHVSF Piezoelectric properties for PZT 

materials sintered at from 800 to 

950°C. 

'JHVSF Strength values for low-


temperature PZT materials


containing strength additives. 


surfaces of a part containing the type 3 

additive. Each grain of the PZT has several of 

the additive particles both at the grain 

boundaries and within the grains. It is 

believed the ceramic inclusions prevent 

excessive grain growth and may help bond 

PZT particles together more strongly. 

17 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

'JHVSF SEM photos of the fracture surface 

(top) and the polished surface 

(bottom) of ORNL PZT with type 3 

strength additive. 

Several multilayer laminate PZT stacks 

were fabricated as part of the milestones for 

this year. The stacks are made from lowtemperature PZT materials made at ORNL. 

The inner electrodes consist of a lower-cost 

silver and silver/palladium electrode 

material. Figure 4 shows a 33 layer-multilayer 

laminate. 

Fabrication and initial testing of a PZT 

actuator reliability test system were 

completed to reach a program milestone. 

Figure 5 shows a schematic of the test 

apparatus. Figure 6 shows photos of all of the 

major components. The test system includes 

a fixture to hold a PZT stack in compression 

and to measure the displacement, a power 

supply and other electronic equipment 

needed to cycle a piezoelectric stack actuator, 

and a computer with Labview software that 

provides signals to the power supply needed 

'JHVSF Photos of an ORNL PZT stack (top) 

and a schematic that shows the 

architecture of the PZT layers inside 

the part (bottom). 

'JHVSF Schematic of the ORNL custom-built 

reliability apparatus for testing PZT 

stacks. 

for continuous cycling of a PZT actuator. The 

Labview system also collects the voltage, 

current, and displacement during testing. 

Two commercial actuators, 26 mm in length 

and 8.25 mm in diameter, have been tested 

18

Heavy Vehicle Propulsion Materials 

'JHVSF Photos of the ORNL reliability 

apparatus. 

using this apparatus.One of the actuators 

was tested for >50 million cycles. 

Displacement data in Figure 7 show that 

this actuator slowly degraded in performance 

during the test. An additional power supply, 

computer, and associated electronics have 

been purchased to build a second test system 

that can stroke at 10 times the rate of the 

present system and allow faster reliability 

testing. 

$PODMVTJPOT

ORNL has developed a piezoelectric 

powder that has the potential to lower the 

cost of diesel fuel injection actuator stacks by 

allowing the use of internal electrodes made 

from metals that are less expensive than 

platinum or palladium. 

ORNL has found a ceramic additive that 

can strengthen the low-temperature sintered 

piezoelectric powder without degrading the 

piezoelectric properties. 

The ORNL automated test stand for 

measuring the effect that voltage cycling has 

on the displacement of a piezoelectric stack 

will be an important tool to aid in the 

FY 2003 Progress Report 

'JHVSF Displacement curves for a commercial 

stack actuator tested on the ORNL 

reliability apparatus. 

reliability testing of fuel injection system 

actuators. 

3FGFSFODFT

1. L. J. Bowen, T. R. Shrout, W. A. 

Schulze, and J. V. Biggers, “Piezoelectric 

Properties of Internally Electroded PZT 

Multilayers,” Ferroelectrics, 
 59–62 (1980). 

2. W. A. Schulze, T. R. Shrout, S. J. Jang, 

S. Sharp, and L. E. Cross, “Monolithic 

Multilayer Electromechanical Transducers for 

Optical Applications,” Journal of the 

American Ceramic Society, 
 596–597 

(1980). 

3. W. Wersing, H. Wahl, and M. 

Schnoller, “PZT-Based Multilayer 

Piezoelectric Ceramics with AgPd-Internal 

Electrodes,” Ferroelectrics, 
 271–294 

(1988). 

19 


Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

C. Low-Cost Manufacturing Processes for Ceramic and Cermet Diesel Engine 

Components 

Dale E. Wittmer 

Southern Illinois University 

Carbondale, IL 62901 

(618) 453-7006; fax: (618) 453-5847; e-mail:wittmer@engr.siu.edu 

DOE Technology Development Area Specialist: Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: Southern Illinois University, Carbondale, Illinois 

Objectives 

• Investigate low-pressure injection molding and continuous sintering as low-cost manufacturing 

processes for ceramic and cermet diesel engine components. 

Approach 

• Process cermet compositions containing titanium carbide (TiC) and an intermetallic matrix 

phase into simple cylindrical shapes by low-pressure injection molding. 

• Following debinding, sinter the cermets by continuous sintering and by a vacuum-pressure 

sintering cycle developed by Oak Ridge National Laboratory (ORNL). 

• Measure physical properties and compare them with those of conventional methods and 

materials. 

• Investigate the economics of the process by a model developed at Southern Illinois University– 

Carbondale (SIUC) to determine if the process is competitive with current manufacturing 

methods. 

Accomplishments 

• Processed simple cermet shapes by low-pressure injection molding and continuous sintering. 

This method potentially offers a competitive, economical process for the manufacture of small 

parts for diesel engine components. 

• Developed an economic model to determine the cost-effectiveness of processes. 

• Designed a precision mold for a fuel injector plunger that will allow the use of low-pressure 

injection molding to produce very-near-net-shape parts for further testing. 

• Continued interaction with ORNL, CoorsTEC, and Cummins to promote commercialization of 

cermet diesel engine components. 

21 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

Future Direction 

• Conduct injection molding trials of the precision mold for the fuel injector plunger that is 

being machined. 

• Modify the continuous sintering furnace to allow for extremely high transport rates through the 

furnace. If successful, this will allow for improvement of the economics of the process and 

further reduce the cost of the manufacturing process. 

Introduction 

All manufactured parts potentially can 

benefit from improved manufacturing 

processes and the incorporation of advanced 

materials. Injection molding is a highly costeffective method for producing precision 

parts with a minimum of labor cost, and 

continuous sintering has been proven 

industrially to provide an economic 

advantage for sintering many advanced 

ceramics. More recently, continuous 

sintering has been used as a means of rapidly 

sintering cermets composed of TiC in an 

intermetallic matrix. 

To reduce costs, it is essential to minimize 

material waste while maximizing the yield of 

in-specification finished parts. Continuous 

sintering is a potential means of maximizing 

the furnace yield of parts that are within 

specifications while minimizing material 

losses due to furnace-related problems, 

thereby reducing part cost. The continuous 

furnace at SIUC has been used to sinter a 

wide range of pre-alloyed intermetallic-TiC 

formulations and similar formulations where 

the intermetallic is formed by reaction 

sintering of the individual elements. Based 

on this work, the most promising 

intermetallics contained 30–50 vol% of 

nickel aluminide (NiAl), nickel-chromium 

(NiCr), or nickel-chrome-iron (NiCrFe) added 

to a fine-grained commercial TiC. These 

formulations were found to have high 

strength, hardness, toughness, and corrosion 

resistance. In addition, their thermal 

expansion can be engineered to be very close 

to that of cast iron and steel, which will 

reduce thermal expansion mismatch in 

several key diesel engine applications. 

The present work has focused on 

developing an economic model to compare 

the costs associated with processing and 

sintering of these cermets by conventional 

and continuous sintering. To further refine 

this economic model and determine 

conditions that may make cermets more 

economically attractive to the diesel engine 

industry, more experimental data are 

required. 

In addition, a precision mold for the lowpressure injection molder needed to be 

designed and machined to allow for the 

processing of very-near-net-shape parts for 

this study. Interaction was continued with 

ORNL, CoorsTEC, and Cummins to promote 

commercialization of these cermets for diesel 

engine components. 

Approach 

Economic Model 

One of the primary tasks involved the 

development of an economic model for 

comparing both materials and processing 

methods for cermets targeted for use as diesel 

engine components. The cermet is a 

combination of an intermetallic and TiC; the 

intermetallic can be NiAl, CrAl, NiCr, or 

another alloy. Modification of these 

intermetallics may be necessary to obtain the 

properties desired. 

The costs associated with the various 

processes involved in producing these 

intermetallic bonded cermets were compiled 

and input into an economic model that was 

originally developed at SIUC for silicon 

nitride. The model was refined to include 

raw powder cost, binder costs, and process 

costs related to injection molding, 

22 

Heavy Vehicle Propulsion Materials 

debinding, isopressing and sintering. Both 

the continuous sintering process and a 

commercial process based on a 

vacuum/pressure cycle were explored. In 

previous work, continuous sintering was 

found to afford a reduction of up to 50% in 

the cost of sintering over conventional 

methods. Figure 1 shows the continuous 

sintering furnace at SIUC. In the sintering of 

cermets, higher sintering rates and more 

rapid throughput are possible with 

continuous sintering. However, the 

properties required or acceptable for cermets 

for diesel engine applications have not been 

identified. 

Figure 1. Continuous sintering furnace at SIUC. 

Low-Pressure Injection Molding 

In the current work, simple right 

cylinders have been produced by lowpressure injection molding. This requires 

additional manufacturing cost to machine 

this shape into a precision fuel injector 

plunger. In order to make prototypes of 

plungers for fuel injectors that are very near 

net shape, it was necessary to design and 

machine a die set for the low-pressure 

injection molder. Figure 2 shows the lowpressure injection molder at SIUC. 

FY 2003 Progress Report 

Figure 2. Low-pressure injection molder at


SIUC. 


Industrial Collaboration 

Collaboration among SIUC, ORNL, 

CoorsTek, and Cummins has continued since 

the start of this project. Cermets processed 

by low-pressure injection molding and 

continuous sintering have been submitted to 

ORNL for wear testing, and materials have 

been submitted to CoorsTek for evaluation. 

Recently CoorTek has submitted materials to 

SIUC for sintering and evaluation. 

Results 

Economic Model 

One of the major tasks involved the 

development of an economic model for 

comparing both materials and processing 

methods for cermets targeted for use as diesel 

engine components. 

In this model, the most cost reduction 

can be obtained by developing a system that 

can take advantage of continuous sintering. 

For this model, the following parameters 

were used: 

• Production was assumed to be 95% 

efficient for continuous sintering and 

23 

FY 2003 Progress Report 

85% efficient for the production batch 

furnaces. 

• Production was held constant at 

~750,000 parts per year. 

• Each part was assumed to weigh 20 g in 

the green state. 

• Powder costs included binders, and the 

composition was 40 vol% Ni3Al and 60 

vol% TiC with processing by reaction 

sintering. 

• Gas, electric, labor, equipment 

depreciation, and replacement parts were 

set according to the furnace type. 

For this model to be reliable, the 

production of two commercial batch 

furnaces was used, which fixed the 

production at ~750,000 parts per year. This 

production level uses only 26% of the 

capacity of the continuous furnace. At 100% 

capacity, the continuous furnace would be 

capable of sintering about 3 million parts, 

which is the production capacity of nine 

commercial batch furnaces. This means that 

for higher production levels, the 

proportional cost would be lower for 

continuous sintering than predicted by the 

model. 

Figure 3 shows a comparison of the total 

cost of a 20-g cermet part processed by lowpressure injection molding and then sintered 

either by continuous or batch sintering. The 

continuous furnace uses flowing argon gas, 

while the batch furnace requires a 

purge/vacuum cycle followed by low-pressure 

argon sintering. The costs are based on real 

production cost, with 250% overhead 

attached to the manufacturing cost and 

assuming an added cost of 25% for 

machining costs. The continuous optimized 

cost is based on optimizing the production 

volume for the continuous furnace. 

It is believed that with higher sintering 

rates, cermets can be manufactured to be 

competitive with or lower in cost than 

ceramics, such as zirconia, for these 

C

o

st p

er P

art ($) 

Heavy Vehicle Propulsion Materials 

10.00 

8.00 

6.00 

4.00 

2.00 

0.00 

Continuous Batch	 Continuous 

Optimized 

Figure 3. Relative cost comparison for continuous 

sintering vs. batch sintering for diesel 

engine components. 

applications. The advantages of the cermets 

over the ceramics are 

• Lower sintering temperature 

• Potentially faster sintering cycle and 

lower processing costs 

• Machinability by electro-discharge 

machining (EDM) 

The intermetallic phase of the cermet is 

available as an alloy or as independent 

metals or metallic compounds that can be 

reaction-sintered to form similar alloys. The 

advantage of the reaction sintering is a 

reduced cost for the raw materials and the 

capability to produce a finer grain structure 

in the finished cermet. The intermetallic 

used in the cost model was Ni3Al, formed by 

reaction sintering of NiAl and Ni, and the 

source of TiC was Kennametal. 

Other combinations are possible where 

the intermetallic can be NiAl, CrAl, or NiCr 

with or without iron and boron additions. 

Further modification of these intermetallics 

may be necessary to obtain the properties 

desired. Currently the powders used for 

reaction sintering are comparable in cost 

with high-purity ceramics. In article 2E of 

24 

Heavy Vehicle Propulsion Materials 

this volume, ORNL reports that a catalytic 

grade containing aluminum and nickel could 

possibly reduce the material cost even 

further.1

 The ceramics can be processed in 

air, while the cermets require a nonoxidizing atmosphere for sintering. The 

ceramic cannot be easily machined into the 

geometry required for specific diesel 

applications, especially where porting is 

required. Since the cermets investigated can 

be machined by EDM, these complex 

geometries can be readily produced. This 

advantage in manufacturability could make 

the cermets more economically feasible than 

ceramics. 

Low-Pressure Injection Molding 

Previous work in low-pressure injection 

molding focused on developing and 

optimizing a binder system to produce a 

simple cylinder shape approximately 9 mm 

in diameter by 7.5 cm in length. Figure 4 

shows these cermets in the various stages of 

Figure 4. Cermets produced at SIUC (a) as 

injection molded, (b) following binder 

removal, (c) following continuous 

sintering, and (d) following machining. 

FY 2003 Progress Report 

processing, and Figure 5 shows the typical 

microstructure present in the cermets 

investigated. Figure 6 shows the hardness 

results obtained for the cermets, compared 

with values for cast iron. 

Figure 5. Typical microstructure for NiAl-TiC 

cermet. 

Figure 6. Hardness comparison of 

cermets investigated 

with cast iron. 

To better demonstrate the capabilities of 

this process, a commercial fuel injector was 

obtained and dismantled. Figure 7 is a 

schematic of the commercial fuel injector 

showing the exposed fuel injector plunger. 

25 

FY 2003 Progress Report 

Figure 7. Fuel injector layout. 

Based on this fuel injector, a near-net-shape 

mold for making the injector plunger was 

designed and machined at SIUC for use on 

the Peltzman low-pressure injection molding 

machine shown in Figure 2. 

Industrial Collaboration 

SIUC, ORNL, CoorsTek, and Cummins 

have been involved in a confidential 

collaboration; and all data related to this 

project have been the responsibility of the 

individual contributors. What can be 

reported are relative results and results 

obtained independently. CoorsTek and SIUC 

have independently sintered cermets that 

were processed at SIUC and sintered by both 

CoorsTek and SIUC. The results for relative 

density and hardness for one cermet 

formulation are given in Figure 8. As can be 

seen from these results, marginally higher 

Density Hardness 

100 100 

Heavy Vehicle Propulsion Materials 

density and hardness were obtained for the 

cermets sintered at SIUC by continuous 

sintering. More recently, a cermet received 

from CoorTek has been received for 

continuous sintering and evaluation. 

The results of wear testing have been very 

favorable for many of the cermets 

investigated. The hardness, toughness, and 

strength of the cermets investigated are 

responsible for the very high wear resistance. 

The effects of the intermetallic and of 

particle size of the TiC in the cermet on the 

wear resistance are not very well understood. 

Several of the simple cylindrical shapes 

produced at SIUC have been submitted to 

Peter Blau at ORNL for sliding wear 

evaluation. Preliminary results are 

encouraging, and the final results will be 

reported when they are received. 

Conclusions 

An economic model was developed that 

indicates that cermet components for diesel 

engine applications can be competitive with 

the advanced ceramics currently employed. 

Simple cermet shapes were produced by lowpressure injection molding and continuous 

sintering. These methods potentially offer 

very competitive, economical processes for 

the manufacture of small parts for diesel 

engine components. A precision mold was 

designed for a fuel injector plunger that will 

allow the use of low-pressure injection 

molding to produce very-near-net-shape 

parts for further testing. Industrial 

98 98 

Relative Hardness

collaboration and wear testing of cermets 

will be continued. 

References 

R

1. “Low-Cost, High-Toughness Ceramics,” elative Density 

96 96 

94 94 

92 92 

T. N. Tiegs, F. C. Montgomery, and P. A. 

90 90 Menchhofer, in Heavy Vehicle Propulsion CT SIUC CT SIUC Materials: FY 2003 Progress Report, U.S. 

Figure 8. Density and hardness Department of Energy, 2004. 

results for a cermet 

sintered at CoorsTek (CT) 

and SIUC. 

26 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

Publications and Presentations 

J. Hazelwood, D. E. Wittmer, J. Steffen, 

and T. N. Tiegs, “Low-Pressure Injection 

Molding of Intermetallic-TiC Cermets,” 

Proceedings of PM2TEC 2003, Las Vegas, NV, 

June 8–12, 2003. (Received Poster of Merit 

Award.) 

27 


Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

%*OUFSNFUBMMJD#POEFE$FSNFUT

P. F. Becher 

Oak Ridge National Laboratory 

P.O. Box 2008, MS-6068 

Oak Ridge, TN 37831-6068 

(865) 574-5157; fax: (865) 574-6098; e-mail: becherpf@ornl.gov 

DOE Technology Development Area Specialist: Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No.: DE-AC05-00OR22725 

0CKFDUJWFT

•	 Develop materials for diesel engine applications, specifically for fuel delivery systems and wear 

components (e.g., valve seats and turbocharger components). Requirements are excellent 

corrosion resistance in a diesel engine environment, high flexure strength and fracture 

toughness, and compatibility with steels. In addition, they should not cause excessive wear of 

the steel counter face 

"QQSPBDI

•	 Develop processing to combine carbide phases with tri-nickel aluminide (Ni3Al) with a range of 

nickel aluminide contents by liquid-phase sintering. 

•	 Analyze nickel aluminide to (1) optimize the cermet thermal expansion coefficient to that of 

selected steel compositions, (2) maximize fracture strength and toughness of the cermet, and 

(3) minimize wear of both the cermet and steel components. 

•	 Support efforts at Cummins Engines and CoorsTek to develop advanced fuel injector systems 

through materials and failure analysis of prototype components. 

"DDPNQMJTINFOUT

•	 Revealed that Ni3Al-bonded titanium carbide (TiC) cermets with flexure strengths in excess of 1 

GPa, fracture toughness values in excess of 18 MPa¥m, and thermal expansion coefficients 

approaching those of steels could be fabricated by liquid phase sintering. 

•	 Transferred technology to industry and provided support in developing prototype components 

for high-pressure fuel injector systems. 

'VUVSF%JSFDUJPO

•	 This task met its objectives and was completed at the end of FY 2003. 

29 
FY 2003 Progress Report 

*OUSPEVDUJPO

The goal of this task is to develop 

materials for diesel engine applications, 

specifically for fuel delivery systems and wear 

components (e.g., valve seats and 

turbocharger components). These 

applications will require materials that have 

a minimum hardness of 11 GPa and a 

thermal expansion coefficient of between 10 

and 15 × 10 ̄6

/°C. The material should also 

have excellent corrosion resistance in a diesel 

engine environment, flexure strength in 

excess of 700 MPa, and fracture toughness 

greater than 10 MPa¥m to ensure long-term 

reliability. The material should also be 

compatible with steels and should not cause 

excessive wear of the steel counter face. The 

upper temperature limit is 200oC for fuel 

delivery system applications and 815oC for 

other applications. For reciprocating 

components, a low density or specific weight 

is most desirable. Finally, the total material 

processing costs for these advanced materials 

should be competitive with those of 

competing technologies such as TiN or other 

ceramic coatings on high-speed tool steels. 

"QQSPBDI

The objectives listed in the introduction 

provided the guidelines for materials 

selection and the choice of the use of the 

cermet concept to impart toughness to a 

ceramic-based system. The constituent 

materials that were most attractive were 

based on advanced Ni3Al, which can exhibit 

exceptional ductility over a broad range of 

temperature and have excellent corrosion 

resistance. To improve the wear resistance 

and hardness, TiC was selected for the matrix 

material. The combination of these two 

materials offers the opportunity to tailor the 

composition so as to match the thermal 

expansion of steels and develop cermets with 

low specific weight together with high 

fracture toughness and strength. In addition, 

the TiC-Ni3Al combination was readily 

amenable to fabricating components using 

the standard powder metallurgical processing 

Heavy Vehicle Propulsion Materials 

used extensively in industry. These factors 

combined to offer a promising approach to 

developing cermet components for advanced 

fuel injectors, which was the first 

application. The task undertook a study of 

optimizing the cermet properties for this 

application. It also provided technical 

support to CoorsTek, which was responsible 

for scaleup of the process, and to Cummins 

Engines Company, which was responsible for 

testing of the fuel injector components. 

3FTVMUT

The composition of the TiC-Ni3Al cermets 

influences the wear characteristics as 

observed in pin-on-disk rotating wear 

studies. Evidence of this is seen in cermets 

containing 40 vol % in which molybdenum 

or Cr3C2 powder was added to the TiC 

powder prior to attrition milling to reduce 

the TiC particle size. Molybdenum is 

employed as has been indicated to improve 

the wetting of TiC by nickel during liquidphase sintering and improves the strength of 

the interface between the TiC and the Ni.1 

Chromium additions are seen to increase the 

yield stress and hardness of the Ni3Al phase 

to a greater extent than does molybdenum,2,3 

but carbon is seen to be much more 

effective.2,4 The thought was that increasing 

the hardness of the Ni3Al might improve the 

wear resistance. However, evaluation of 

cermets fabricated in this project using these 

additives reveals that the addition resulted in 

better wear performance with regard to the 

wear of both the cermet pin and the steel 

disk materials (Figures 1 and 2). Based on the 

wear surface observations, it appears that 

pull-out and fracture of the TiC grains is 

diminished with the molybdenum addition, 

compared with the response with the Cr3C2 

addition. 

Fracture analysis was conducted on a 

number of metering plungers that had been 

machined by Cummins Engines from rod 

stock provided by CoorsTek using the TiC-50 

vol % Ni3Al composition. These plungers had 

been machined to specifications for insertion 

30 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

'JHVSF Contact surface (left) of (TiC+2 wt % 

Mo) + 40 vol % Ni3Al cermet pin after 

pin-on-disk (tool steel) wear test. Low 

wear coefficients were obtained for both 

pin and disk materials. This is reflected 

by the fact that within the contact zone 

(right) the angular TiC grains (darker 

gray grains) did not cleave and form 

abrasive debris. 

'JHVSF Wear coefficients of both pin and disk 

increase when a Cr3C2 addition to TiC is 

substituted for molybdenum, as 

reflected by the wide wear track on the 

pin (left) and the pullout of TiC grains 

from the surface, evidenced by the dark 

pits within the contact zone (right). 

into a high-pressure (>315 MPa) fuel 

injection test. During preparation, the 

starting rods are machined to profile; a steel 

end cap is added by press fitting; and, finally, 

the end cap is machined to specifications. 

Four of these plungers were received for 

failure analysis and are shown in Figure 3. 

C10-3 and C10-7 both failed during 

machining of press-fit steel end cap, C10 

failed in a 20-hour overpressure test, and C8­

5 successfully completed the 20-hour 

overpressure test. 

Fractographic analysis revealed that the 

two plungers that fractured during 

machining of the steel “top hat” cap 

exhibited large pores and defects on the 

fracture surfaces located in the reduced 

section just below the steel-capped end of 

the plunger. The greatly reduced diameter in 

this area would experience high stresses if 

'JHVSF TiC-Ni3Al cermet fuel injector plungers 

fabricated through collaborative efforts 

at ORNL, CoorsTek, and Cummins 

Engine Company. C8-5 successfully 

completed a 20-hour overpressure 

injector test at Cummins. C10 failed at 

some time during that test. Both C10-3 

and C10-7 failed during the machining 

of the steel “top hat” at Cummins. 

flexure occurred during machining. The 

presence of large pores and defects implies a 

need for improvement in the fabrication 

procedures. Subsequent fractographic 

analysis of flexure bars made from rod stock 

fabricated from one of the powder batches 

that was used (Batch 10) confirms that 

processing defects were an issue. The one 

plunger that failed during the overpressure 

injector tests at Cummins Engines also 

exhibited defects on a secondary fracture 

surface. 

$PODMVTJPOT

Cermets composed of TiC grains bonded 

by a continuous Ni3Al phase, and fabricated 

by industrial-based powder metallurgical 

processing routes, were developed with 

strengths in excess of 1000 MPa, toughness 

values of ~0 MPa•m1/2, and thermal 

expansion coefficients of up to 11 ppm/oC. 

Characterization of cermet pins tested 

against a rotating steel disk in a wear facility 

at Cummins Engine revealed that minor 

additions of molybdenum improve the wear 

resistance compared with chromium-bearing 

31 

FY 2003 Progress Report 

additions. Molybdenum has also been found 

to enhance the liquid-phase sintering and 

mechanical properties of the cermets. 

Evaluation of cermet plungers, both those 

prepared for injector rig tests and those 

exposed in the overpressure injector tests, 

reveals that processing defects were a factor 

in limiting the performance of the cermet 

plungers. Further improvements in the 

cermet processing should improve the 

reliability of the cermet plungers. At the 

same time, it is strongly recommended that 

the actual conditions under which plungers 

fail (e.g., during machining) be carefully 

documented to aid in determining steps to 

take to improve the reliability. 

3FGFSFODFT

1. P. Ettmayer, “Hardmetals and 

Cermets,” Annual Review of Materials 

Science, , 145–64, Annual Reviews Inc., 

Palo Alto, CA, 1989. 

Heavy Vehicle Propulsion Materials 

2. S. C. Huang, C. L. Briant, K.-M. Chang, 

A. I. Taub, and E. L. Hall, “Carbon Effects in 

Rapidly Solidified Ni3Al,” J. Mater. Res., (1) 

60–67 (1986). 

3. R. D. Rawlings and A. E. Staton-Bevan, 

“The Alloying Behavior and Mechanical 

Properties of Polycrystalline Ni3Al (γ’ Phase) 

with Ternary Additions,” J. Mater. Sci., , 

505 (1975). 

4. S. C. Huang, A. I. Taub, and K. M. 

Chang, “Boron Extended Solubility and 

Strengthening Potency in Rapidly Solidified 

Ni3Al,” Acta Metall., (10) 1703–07 (1984). 

1VCMJDBUJPOT

E. Rocha-Rangel, P. F. Becher, and E. LaraCurzio, “Influence of Carbon on the 

Interfacial Contact Angle Between Alumina 

and Liquid Aluminum,” Surface and 

Interface Analysis, 
 151–155 (2003). 

32 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

&-PX$PTU
)JHI5PVHIOFTT$FSBNJDT

T. N. Tiegs, F. C. Montgomery, and P. A. Menchhofer 

Oak Ridge National Laboratory 

P.O. Box 2008, MS-6087 

Oak Ridge, TN 37831-6087 

(865) 574-5173; fax: (865) 574-4357; e-mail: tiegstn@ornl.gov 

DOE Technology Development Area Specialist: Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

0CKFDUJWFT

• Increase the critical fracture toughness (KIc) of structural ceramics for advanced diesel engine 

applications without strength degradation. 

• Develop high-toughness materials that are also low in cost. 

"QQSPBDI

• Develop TiC-based composites with 40–60 vol. % nickel aluminide (Ni3Al) because they have 

expansion characteristics very close to those for steel. 

• Conduct the development effort in collaboration with CoorsTek, Inc., and Cummins Engine on 

processing scale-up and engine testing tasks. 

"DDPNQMJTINFOUT

• Supplied large numbers of sintered blanks for engine testing. 

• Examined several different raw material powder combinations. 

• Found that when elemental aluminum was used, the samples exhibited macroscopic cracking 

due to differential heating and shrinkage resulting from the exothermic reaction between the 

nickel and aluminum. 

• Found that only composites made from the NiAl + nickel combination had mechanical 

properties that were acceptable for engine applications. 

'VUVSF%JSFDUJPO

• Refine the processing parameters with the alternate precursors to improve the mechanical 

performance. 

• Use alternate NiAl sources including an Al-Ni catalyst material, TiC-Ni3Al mixtures developed by 

the University of Colorado, and Ni-Al-TiC blends for reaction synthesis. 

33 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

• Continue to work with CoorsTek Inc. (a parts supplier) for scale-up of the processing and supply 

it with pilot-plant-scale quantities of powder mixtures for injection molding trials. 

• Supply sintered parts produced in conjunction with CoorsTek to Cummins Engine Co. for rig 

testing of machined components. 

*OUSPEVDUJPO

TiC-Ni3Al composites are under 

development for application in diesel 

engines because of desirable physical and 

mechanical properties. For these 

applications, the Ni3Al volume contents are 

on the order of 30 to 50 vol % in order to 

match the thermal expansion of steel. 

Typically, flexural strengths greater than 

1000 MPa at temperatures up to 800oC and 

fracture toughnesses higher than 15 MPa¥m 

are obtained for the composites. The 

composites are densified by liquid-phase 

sintering. Most of the early work used gasatomized Ni3Al particles with fine TiC 

powders. Later work was done using nickel 

and NiAl powders (along with the TiC) to 

form Ni3Al by an in-situ reaction during 

sintering. Over the past few years, the in-situ 

reaction process was developed significantly 

because it produced high mechanical 

properties and developed a fine TiC grain 

size. The finer grain sizes were favored 

because of better wear resistance. 

The fabrication techniques and 

equipment employed in production are very 

similar to those used for the fabrication of 

WC-Co hard metals; thus the processing 

costs are well established. However, when 

the economics of producing the TiC-Ni3Al 

composites were examined, a significant cost 

was associated with the use of the NiAl 

precursor powder (about 55% of the total raw 

material cost). Because the costs of the 

starting raw materials can be a significant 

fraction of the total cost of a component, 

alternative materials for fabricating the 

cermets are of interest. Part of the reason for 

the high cost of the NiAl is that it is 

produced only as a specialty powder at 

present. Elemental nickel and aluminum 

powders are produced in sufficient quantities 

to be relatively cost-effective, so tests were 

done to maximize their usage in the 

composites. Currently, Al-30% Ni powder is 

produced in commercial-level quantities for 

use as a catalyst; consequently, it is a costeffective alternative for an Ni-Al alloy for 

fabricating TiC-Ni3Al composites. 

3FTVMUT

-BSHFCBUDIQSPDFTTJOHPG5J$/J"M

DPNQPTJUFT As reported previously, a series 

of large batches (2 kg) was processed and 

sent to CoorsTek for green forming into rods. 

These were subsequently returned and 

sintered at Oak Ridge National Laboratory 

(ORNL) (Figure 1). The rod blanks were then 

sent to Cummins for final machining into 

test parts. 

'JHVSF Portion of the as-sintered rods prior 

to machining into rig test parts. 

Recently, several large batches of 

composite powder have been produced and 

sent to CoorsTek for injection molding 

testing. To date, five 3-kg mill runs (15 kg 

total) were processed of a composition of 

34 

Heavy Vehicle Propulsion Materials 

50 % TiC-Ni3Al (with 2 % molybdenum). The 

different runs were blended prior to 

shipping. Injection moldings tests are in 

progress. 

"MUFSOBUFQSFDVSTPSTGPS/J"M

GPSNBUJPO All previous work used a 

combination of nickel and NiAl for an in-situ 

reaction to form the Ni3Al. Nickel and 

aluminum powders are produced in 

sufficient quantities to be relatively costeffective, so tests were done to maximize 

their usage in the composites. 

Cermet compositions containing NiAl+Ni 

or the Al-30 Ni product produced by the 

catalyst manufacturer show good 

densification behavior, and the densities 

achieved were >99.5 % T. D. However, the 

samples using elemental aluminum (i.e., 

Ni+Al or Ni+Al+NiAl) show severe 

macroscopic cracking caused by differential 

shrinkage during densification (Figure 2). 

Typically, this behavior is a result of nonuniform heating of the compact. The most 

likely cause of the temperature difference was 

the exothermic reaction that occurs as a 

result of the reaction of the nickel and 

aluminum to form the Ni3Al intermetallic. 

Using the heat of formation for the reactions 

of nickel and aluminum, the adiabatic 

FY 2003 Progress Report 

temperature rise for the 3Ni+AlÆNi Al 3

reaction in the TiC-based composite is 

>1200°C (considering no heat loss to the 

surroundings) and as such is a maximum 

condition. Since the reaction commences at 

~650°C, the temperature increase is higher 

than the melting point of the Ni3Al. In 

contrast, the adiabatic temperature rise in 

the composite for the NiAl+2NiÆNi Al 3

reaction is <300°C. Such an increase would 

not be sufficient to lead to significant 

melting of the Ni3Al that is formed. 

The two compositions that did not crack 

were examined in greater detail for 

mechanical properties and microstructures. 

The toughness and hardness were very 

similar for the different cermets; however, 

the fracture strength for the sample made by 

the reaction of Al-30 Ni (catalyst precursor) 

and nickel had very poor strength compared 

with the other composite (Figure 3). 

Examination of the microstructures revealed 

a significant amount of a second phase 

within the composite made with the Al-30 Ni 

(catalyst precursor), as shown in Figures 4 

and 5. X-ray diffraction could not identify 

any other phases besides the TiC and Ni3Al 

typically observed in these materials. 

1500 

1000 

500 

0 

NiAl+Ni Ni-30Al+Ni 

'JHVSF Visual appearance of samples after 

sintering at a heating rate of 

10oC/minute. Sample compositions: 

NiAl+Ni (left), Ni+Al (center), and 

NiAl+Ni+Al (right). 

Sample Type 

Figure 3. Results from tests of fracture 

strength of composites made with 

either NiAl+Ni or Al-30 Ni+Ni. 

Flexural Strength (MPa) 

35 

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

'JHVSF Microstructure of sample made with 

NiAl+Ni showing uniform distribution 

of TiC grains in Ni3Al matrix and no 

secondary phases. 

'JHVSF Microstructure of sample made with Al30 Ni+Ni showing a second phase 

(black spots) distributed within the TiC 

and Ni3Al. 

$PODMVTJPOT

It has been determined that the Ni-Al 

precursor type can have a significant effect 

on the densification behavior and final 

mechanical properties of TiC-Ni3Al 

composites. When elemental aluminum was 

used, the samples exhibited macroscopic 

cracking as a result of differential heating, 

and shrinkage resulting from the exothermic 

reaction between the nickel and aluminum. 

Reducing the aluminum content and slowing 

the heating rate during the exothermic 

reaction did not eliminate the cracking 

problem. Samples fabricated using the Al-30 

Ni precursor exhibited a second phase in the 

microstructure that is believed to be the 

cause of the low observed strength. Only the 

composites made from the NiAl + Ni 

combination had mechanical properties that 

were acceptable for engine applications. 

1VCMJDBUJPOT1SFTFOUBUJPOT

T. N. Tiegs, F. C. Montgomery, and P. A. 

Menchhofer, “Effect of Ni-Al Precursor Type 

on Sintering and Properties of TiC-Ni3Al 

Composites,” to be published in Proceedings 

of International Conference on Powder 

Metallurgy and Particulate Materials, Las 

Vegas, NV, June 2003. 

36 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

SO2

NO

CO/H2

NO

C3H6

22

By Pass line 

Vent 

H2O 

Pump 

H2O 

Mixing & Preheating Tube 

Reactor 

By Pass line

Vent

H2O

Pump

H2O

Mixing & Preheating Tube

Reactor

Figure 8. Schematics of the ex-situ reactor. 

Figure 9. Ex-situ reactor for controlled 

atmosphere treatment of TEM samples. 

respectively. The gas controller system and 

the water pump have been installed and 

calibrated for a total gas flow of 100cc/min. 

Other Activities 

The synthesis laboratory is now equipped 

to enable preparation of NOx trap materials. 

Several items are on order for setting up a 

benchtop flow reactor in a laboratory at 

NTRC. A graduate student from the 

University of New Mexico is working with 

ORNL to support this project. 

References 

1.	 N. Miyoshi, S. Matsumoto, K. Katoh, T. 

Tanaka, J. Harada, N. Takahashi, K. 

Yokota, M. Sigiura, and K. Kasahra, 

“Development of New Concept ThreeWay Catalyst for Automotive Lena-Burn 

Engines,” SAE paper 95-0809, Society of 

Automotive Engineers. 

2.	 N. Takahashi, H. Shinjoh, T. Iijima, T. 

Suzuki, K. Yamazaki, K. Yokota, H. Suzuki, 

N. Miyoshi, S. Matsumoto, T. Tanizawa, S. 

Tateishi, and K. Kasahara, “The New 

Concept 3-Way Catalyst for Automotive 

Lean-Burn Engine, NOx Storage and 

Reduction Catalyst,” Catalysis Today, 27, 

63–69 (1996). 

66 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

F. Aftertreatment Catalyst Materials Research 

Matthew Henrichsen, Randy Stafford, and Paul McGinn*

Cummins, Inc.


1900 McKinley Ave.


Columbus, IN 47203 


(812) 377-4170; fax: (812) 377-7226; e-mail: 377matthew.henrichsen@cummins.com


*Notre Dame University, South Bend, Indiana 


DOE Technology Development Area Specialist: Dr. Sidney Diamond 


(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 


ORNL Technical Advisor: D. Ray Johnson 


(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov


Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: Cummins, Inc., Columbus, Indiana 

Objectives 

• Develop knowledge and tools necessary to satisfy the U.S. Environmental Protection Agency 

(EPA) 2007 and 2010 diesel emissions regulations while minimizing the total cost of ownership. 

Approach 

• Develop reactors and test methods for understanding the fundamental behavior of catalysts. 

• Evaluate novel base metal oxide catalysts for oxidation of diesel soot with conventional and 

microwave heating. 

• Improve understanding of sulfation and desulfation of commercial NOx reduction catalysts 

through reactor studies. 

Accomplishments 

• Circumvented the limited ability of mass spectrometry to measure concentrations of gases with 

near-identical molecular weights, allowing measurement of, for example, CO in N2. 

• Developed a liquid hydrocarbon injector useable on a wide range of reactors. 

• Designed a dedicated catalyst aging reactor. 

• Designed and constructed a microwave-heated microreactor system. 

• Developed a method for rapid automated screening of base metal oxide catalysts and used it to 

evaluate catalysts produced through combinatorial chemistry. 

Future Direction 

• Conduct sulfation and desulfation studies on commercial catalysts. 

• Compare catalyzed soot oxidation rates with conventional and microwave heating. 

67 
FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

Introduction allows resolution of species of similar 

The 2007 and 2010 EPA regulations on 

particulate and NOx emissions from diesel 

engines are significantly lower than the 

current regulatory standards. These 

regulations are seen as aftertreatment-forcing 

by the diesel industry. 

Though aftertreatment systems have been 

demonstrated that meet the 2007 emissions 

standards, more fundamental knowledge of 

the catalysts and the systems in which they 

operate is needed to optimize system 

performance and improve emissions 

performance with the lowest possible 

economic impact. Catalyst suppliers are 

commonly unwilling to allow third parties 

(such as national laboratories or academic 

institutions) to freely evaluate their 

proprietary catalyst formulations. We are 

developing the reactor systems and methods 

necessary to develop the fundamental 

knowledge of catalyst performance that we 

need for system optimization. 

Catalysts commonly used for soot 

oxidation in catalyzed soot filters are based 

on platinum group metals and cerium 

oxides. The use of platinum group metals 

significantly increases the cost of catalyst 

systems. Base metal oxide catalysts, while 

typically less active than platinum group 

metal catalysts, are much less expensive. 

Oxidation activity has been reported at low 

temperatures with base metal oxides with 

both conventional and microwave heating.1,2 

Because of the large potential impact on 

system cost, we are investigating the 

performance of base metal oxide catalysts. 

Approach 

To develop the tools necessary to develop 

a fundamental understanding of catalyst 

operation, we have pursued several paths. Of 

the many approaches, the three most 

significant are (1) a modification of 

Cummins’ spatially resolved capillary-inlet 

mass spectrometer (SpaciMS) system3

 that 

molecular weights, (2) design of a reactor for 

aging of catalyst cores, and (3) design and 

construction of a microwave-heated reactor. 

Novel base metal oxide catalysts were 

evaluated, in collaboration with Notre Dame 

University, using automated thermal 

gravimetric analysis (TGA) as a rapid 

screening tool to evaluate catalyst powders 

produced by combinatorial chemistry. This 

allows a large range of mixed oxides to be 

evaluated with a minimum of operator 

involvement. To extend this work to 

microwave-heated systems, a microwaveheated TGA was constructed. 

Results 

SpaciMS 

Only a very sensitive and expensive mass 

spectrometer is capable of differentiating 

between molecules with masses that differ by 

a fraction of one atomic mass unit. In the 

reaction systems of interest to the diesel 

industry, molecule pairs that cannot be easily 

differentiated include N2 and CO, NH3 and 

H2O, H2S and 17O2, and various hydrocarbons. 

However, the molecules of these confounded 

pairs have different chemical behaviors. By 

using a catalyst, the difference in chemical 

behavior can be used to separate the signals 

of the confounded species. For example, an 

oxidation catalyst can be used to convert CO 

to CO2, which would allow easy separation of 

N2 and CO. 

In the SpaciMS system, the gas sample is 

drawn into the mass spectrometer through a 

small glass capillary. This capillary is a 

convenient substrate upon which the 

catalyst can be deposited. A micrograph of a 

catalyzed capillary is shown in Figure 1. The 

white material visible on the inner surface of 

the capillary is the catalyst layer. The same 

oxidation catalyst is also capable of 

differentiating between methane and other 

hydrocarbons (see Figure 2). By heating the 

capillary to a higher temperature, it would 

68 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

is an expensive proposition, and collection of 

statistically significant samples would be 

prohibitively expensive. Using performance 

reactors for this task is also time-consuming 

and greatly increases the number of 

performance reactors required to evaluate a 

catalyst formulation or deactivation 

mechanism. 

To reduce the cost of validating catalyst 

formulations, a reactor capable of aging 

several specimens in parallel was designed 

(see Figure 3). The reactor is capable of 

exposing catalyst samples to high 

Figure 1. Capillary with an oxidation temperatures with controlled concentrations 

catalyst on the inner surface. of water, catalyst poisons, and combustion 

products. 

Figure 2.	 Combined CO and C3H6 oxidation 

compared with and without methane. 

The hatchmarked bars indicate the 

concentration of CO2 expected if all 

CO and hydrocarbon were oxidized. 

also be possible to completely oxidize the 

methane so that it would be converted to 

CO2 and measured with the other 

hydrocarbons. 

Dedicated Aging Reactor 

Aging and deactivation of catalysts in use 

has a significant impact on catalyst 

performance. In order to accurately predict 

emissions performance over the lifetime of 

an aftertreatment system, aging must be 

understood. Aging catalysts behind engines 

Figure 3.	 Schematic drawing of the catalyst 

aging reactor. 

Microwave Reactor System 

To quantify the impact of microwave 

heating on catalytic activity, a microwave 

reactor was developed. The microwave 

heating system, except for the portion 

immediately surrounding the reactor, has 

been described previously.4

 A quartz reactor 

vessel is passed through a modified WR340 

waveguide to provide heating. A drawing of 

the modified waveguide is shown in Figure 4. 

A moveable short and a 3-stub tuner are used 

to convert the traveling wave generated by 

the magnetron into a standing wave capable 

of being focused on the reactor. A 

multiprobe optical fiber temperature 

69 

FY 2003 Progress Report 

Figure 4.	 Detailed schematic of the microwave 

reactor cavity. 

measurement system is used to allow precise 

temperature measurement inside the reactor 

bed without distorting the microwave field. 

Specimens heated in the microwave 

reactor consist of catalyst, soot, and quartz 

chips. The quartz chips help to reduce the 

tendency toward thermal runaway in both 

microwave heating and soot oxidation by 

increasing the effective specimen thermal 

mass. When microwave power is applied 

with gas flowing through the reactor, a 

temperature gradient develops in the bed. 

Although this temperature gradient is 

unavoidable, it is predictable; and kinetic 

evaluations can be corrected for its effect on 

reaction rates. A mass spectrometer is used to 

measure the combustion products coming 

out of the catalyst bed. 

Catalyzed soot oxidation has been 

measured in the microwave reactor but has 

not yet been compared with similar data 

from a conventionally heated reactor. 

Heavy Vehicle Propulsion Materials 

Screening of Base Metal Oxide Catalysts 

Mixed base metal oxide catalysts have 

been prepared using a broad range of base 

metals. The basic method has been reported 

in detail elsewhere.5

 The oxidation 

performance of several mixtures was 

examined using TGA. The results of several 

mixtures are shown in Figure 5. 

Oxidation rates are strongly affected by 

the contact between the soot and the catalyst 

material. When they are more intimately 

mixed (tight contact), as with a mortar and 

pestle, the oxidation rate is higher for many 

catalysts. Typically, loose-contact oxidation 

rates match tight-contact oxidation rates 

when a liquid forms (e.g., when the catalyst 

melts) or when there is a vapor phase 

intermediate in the reaction (e.g., NO2 in 

platinum-catalyzed low-temperature soot 

oxidation, or volatilization of chloride salts). 

Contact between soot and catalyst in diesel 

particulate filters is similar to “loose” 

contact. 

In the results shown in Figure 5, the 

oxidation rate is controlled primarily by the 

second component (A, B, C, D, or E) rather 

than the first metal oxide component (X 

or Y). Additionally, the impact of the second 

component is largely independent of the 

relative proportion of the two components. 

The observed low oxidation temperatures 

near 350oC are low enough to be interesting, 

but the similarity of the temperatures for 

Figure 5. Relative peak oxidation rates with 

several catalyst compositions. 

70 

Heavy Vehicle Propulsion Materials 

loose and tight contact indicate that solidsolid catalysis is not the primary mechanism. 

Microwave TGA 

To expand the base metal catalyst 

screening work to microwave heating, a 

microwave TGA system was constructed. The 

system was designed around a commercial 

microwave oven. Figure 6 shows a sketch of 

the equipment. 

Figure 6.	 Schematic of the microwave TGA. 

(1) Sharp 2100W/R-25JT microwave, 

(2) cooling water reservoir, (3) CaF2 

single crystal window, (4) quartz 

sample holder, (5) quartz sleeve and 

hanging rod, (6) modified microwave 

door, (7) GR-120 AD balance, (8) 

Prism DS IR camera, (9) computer, 

(10) pump, (11) steel stand, (12) 

input and output cables connecting 

computer/camera and 

computer/balance, (13) plastic tubing 

for input and output water. 

Temperature measurement is performed 

using an infrared camera (Flir Prism DS) 

through a hole in the door suitably fitted 

with a microwave shield. An infrared camera 

is used to avoid the use of a thermocouple, 

which would distort the microwave fields. 

The camera is used to take a picture of the 

sample periodically (e.g., every 2 seconds), 

which is saved for later analysis to determine 

temperature as a function of time. 

To reduce vibration of the balance, it 

rests on a steel frame that does not contact 

the microwave. The quartz specimen basket 

FY 2003 Progress Report 

is suspended from the balance by a quartz 

rod. The quartz rod is shielded by a quartz 

sleeve to minimize swaying due to air 

circulation in the microwave oven. To assist 

in heating the specimen, a small microwaveabsorbing SiC susceptor is placed under the 

specimen in the bottom of the quartz 

specimen basket. A plastic bottle of water is 

placed inside the microwave cavity to serve 

as a load and to help control the specimen 

heating rate. 

An example of the data obtained for 

heating of just Degussa carbon soot (after 

necessary temperature and weight 

corrections) is shown in Figure 7, along with 

superimposed data from the conventional 

TGA. This curve was obtained with 

~4 minutes of heating in the microwave 

field. As shown in the curve, noticeable soot 

oxidation begins at about 600o

C, as is seen in 

our conventional TGA measurements 

(obtained at a heating rate of 20o

C/min in 

100 ml/min air flow). The weight of the 

material used in these experiments is much 

greater than in conventional TGA because of 

the reduced sensitivity of the balance. The 

comparison shows that the microwave TGA 

data can be reliable. 

Figure 7.	 Microwave and conventional thermal 

gravimetric analysis curves for 

combustion of carbon soot in the air. 

71 

FY 2003 Progress Report 

Summary and Conclusions 

It is possible, with a low-resolution mass 

spectrometer, to differentiate between 

molecules with similar molecular weights by 

differences in their chemical behavior. This 

approach will be useful in evaluating gasphase composition in catalysts operating 

both in reactors and on engines. 

A dedicated aging reactor and a 

microwave reactor were designed, and the 

microwave reactor was constructed. 

Although the reactor bed had a measurable 

temperature gradient during operation, it 

was predictable. Soot was catalytically 

oxidized in the microwave reactor. A detailed 

comparison of microwave and 

conventionally heated reaction rates will be 

completed in the near future. 

A wide variety of mixed-oxide catalyst 

materials were produced, and their catalytic 

activity was evaluated using TGA. A 

microwave TGA was constructed that will 

allow reliable evaluation of microwave 

catalytic activity. Catalyst compositions were 

found that lowered the peak soot oxidation 

temperature to ~350oC with conventional 

heating. Although the low oxidation 

temperature is significant, that catalyst 

formulation may not be sufficiently stable in 

a diesel environment. However, a reduction 

in regeneration temperature of that 

magnitude would reduce the regeneration 

fuel penalty and increase system life. 

Heavy Vehicle Propulsion Materials 

References 

1. J. P. A. Neeft, M. Makkee, and J. A. 

Moulijn, “Catalysts for the Oxidation of Soot 

from Diesel Exhaust Gases. 1. An Exploratory 

Study,” Applied Catalysis B-Environmental, 8, 

57–78 (1996). 

2. M. Fang, J. Ma, P. Li, N. T. Lau, B. Zhu, 

and X. Lu, “Microwave-Assisted Catalytic 

Combustion of Diesel Soot,” Applied Catalysis 

A: General, 159, 211–228 (1997). 

3. N. W. Currier, M. J. Cunningham, 

W. P. Partridge, J. M. Storey, S. A. Lewis, 

R. W. Smithwick, and G. L. DeVault, 

“Exhaust Aftertreatment, Gas Phase 

Measurements in situ,” presented at DEER 

2000: 6th Diesel Engine Emissions Reduction 

Workshop, August 20–24, 2000, to be 

published in the proceedings. 

4. M. Henrichsen and S. Popuri, 

“Development of a Microwave-Assisted 

Particulate Filter,” presented at DEER 2001: 

Seventh Diesel Engine Emissions Reduction 

Workshop, August 5–9, 2001, to be published 

in the proceedings. 

5. H. M. Reichenbach, H. An, and P. J. 

McGinn, “Combinatorial Synthesis and 

Characterization of Mixed Metal Oxides for 

Soot Combustion,” Applied Catalysis B: 

Environmental, 44, 347–354 (2003). 

72 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

4. MATERIALS FOR AIR HANDLING, HOT SECTION, AND 

STRUCTURAL COMPONENTS 

A. High-Temperature Advanced Materials for Lightweight Valve Train Components 

Mark J. Andrews and Jesus Chapa-Cabrera 

Caterpillar Inc. 

Tech Center 854-80 TC-E 

14009 Old Galena Rd. 

Mossville, IL, 61552 

(309) 578-3896; fax: (309) 578-2953; e-mail: andrews_mark_j@cat.com 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: Caterpillar Inc., Tech Center, Mossville, Illinois 

Objectives 

•	 Design and fabricate prototype engine valves from silicon nitride and titanium aluminide 

materials that are 30% lighter than steel valves and provide a 200% increase in service lifetime 

and a 10% increase in fuel efficiency. 

Approach 

•	 Select titanium aluminide (γ-TiAl) and silicon nitride materials for this project because of their 

high corrosion resistance and their ability to maintain superior strength at elevated 

temperatures. 

•	 Base engine valve designs on using an optimization routine in conjunction with a probabilistic 

design approach instead of the traditional deterministic method. 

•	 Develop welding techniques to join TiAl to a titanium alloy in the fabrication of TiAl valves. 

Accomplishments 

•	 By optimizing the probabilistic valve designs, showed ways to modify the valve geometry in 

order to reduce the high operating stresses that are likely to contribute to valve failure. 

•	 Conducted welding trials that showed success in joining TiAl to a titanium alloy, Ti-6V-4Al. 

•	 Developed bench tests to examine the impact and wear resistance of TiAl and silicon nitride 

materials compared with currently used valve seat insert materials. 

73 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

Future Direction 

•	 Machine 50 silicon nitride valve blanks to final print specifications and bench- test them for 

impact resistance, strength, and durability. 

•	 Join TiAl valve heads to titanium alloy valve stems and then machine and bench-test them for 

strength and durability. 

•	 Schedule silicon nitride and TiAl engine valves for natural gas and diesel engine laboratory tests 

after completing bench tests. 

•	 Schedule silicon nitride valves and TiAl for field engine tests after completing laboratory engine 

tests. 

Introduction 

Valves that are presently made from steel 

alloys and used in heavy-duty natural gas 

and diesel engines are reaching material 

performance limits because of increases in 

temperature and pressure loads. Advanced 

materials such as silicon nitride and TiAl, 

known for exceptional corrosion resistance 

and for maintaining high strength at 

elevated temperatures, are the focus of this 

project. The successful demonstration of 

engine valves fabricated from silicon nitride 

and TiAl materials is anticipated to extend 

the component service lifetimes by as much 

as 200% over current valve materials. In 

addition, these lightweight materials will 

enable the future design of a camless engine 

that will permit greater control over the 

combustion process, improving engine 

performance while reducing emissions. 

Approach 

Premature engine valve failures are 

caused by several synergistic factors, one of 

which is the corrosive environment in which 

valves must function. A variety of 

conventional engine component alloys and 

candidate advanced materials were evaluated 

for corrosion resistance using an oil-ash test. 

Test specimens were submerged in engine oil 

that is heated and burned, simulating the 

breakdown of engine oils. The residue or oilash left behind on the test specimens 

contained concentrations of corrosive 

elements such as calcium, sulfur, and 

phosphorus in the form of oxides. After a 

series of oil-ash coatings, the test specimens 

were placed in a furnace at engine 

combustion temperatures for an extended 

time period. Measuring the penetration 

depth after the furnace exposure using 

optical and scanning electron microscopy 

(SEM) is one way to assess the corrosion 

resistance. Figure 1 illustrates the penetration 

depth measured for silicon nitride and TiAl 

compared with Nimonic 80 A and Nimonic 

90 alloys currently used for engine valves. 

The silicon nitride and TiAl materials show 

smaller penetrations from corrosion 

compared with the current valve alloy 

materials. The results from these tests 

indicate that silicon nitride and TiAl 

Figure 1. Corrosion test results illustrated as the 

depth of penetration into material. The 

silicon nitride and TiAl show excellent 

resistance to corrosion when compared 

to the Nimonic 80A and 90, current 

valve materials. 

74 

Heavy Vehicle Propulsion Materials 

materials exhibit excellent corrosion 

resistance when subjected to an engine 

environment, one of the main reasons for 

investigating these materials for this engine 

component. 

The design of engine valves made from 

steel alloys typically follows a deterministic 

approach in that the strength of test 

specimens can easily be scaled to different 

sizes with reliable accuracy. Silicon nitride 

and TiAl are inelastic materials compared 

with most alloys and are known to fail in a 

brittle manner. The brittle nature of these 

advanced materials necessitates using a 

probabilistic approach instead of the 

deterministic approach for component 

design. The key elements in a probabilistic 

design approach are illustrated in Figure 2. 

ASTM standards for test specimens and 

procedures are followed, using a variety of 

test conditions such as temperature and 

loading rate that emulate the operating 

conditions of the design component. The 

strength of test specimens is represented 

using a Weibull distribution function. Finite 

element models of the design component are 

created and used to estimate the critical 

stresses from specified temperature and 

mechanical load boundary conditions. The 

combination of the finite element modeling 

with the test specimen strength data is used 

as input into a specialized computer program 

that estimates the service lifetime of the 

design component. 

Two materials are actually used in the 

fabrication of TiAl engine valves, since 

reliable casting of TiAl for the entire engine 

valve has not been successfully demonstrated 

by casting vendors. The valve head portion is 

cast using TiAl, while the valve stem is made 

from the cylindrical stock of a titanium alloy 

(Ti-6V-4Al), as illustrated in Figure 3. Valve 

fabrication consists of friction welding TiAl 

to the titanium alloy, followed by final 

dimensional machining. 

FY 2003 Progress Report 

Figure 2. Flowchart of probabilistic design 

approach used to estimate service 

lifetimes for engine valves made from 

silicon nitride and TiAl. 

(a) (b) 

Figure 3. Maximum tensile stress comparison 

between the baseline metallic valve 

design (a) and proposed silicon nitride 

valve design using the probabilistic 

approach (b). There is an approximately 

60% reduction in tensile stress from the 

probabilistic valve design as a result of 

dimensional changes. 

Results 

The maximum principal tensile stresses 

in the finite element valve model were 

reduced by combining an optimization 

routine with the probabilistic design 

approach. Changes in the valve geometry 

resulted in stress reductions of approximately 

75 
FY 2003 Progress Report 

60%, as illustrated in Figure 4. The 

importance of this stress reduction will be 

realized in significantly improving the 

probability of survival of an engine valve 

made from these materials, resulting in 

increased service lifetimes. 

Figure 4. Schematic of joining TiAl valve head to 

TiAl valve stem by friction welding. 

Initial friction weld trials have shown 

that the strength of the weld increases as the 

forging force increases and the friction force 

decreases. Figure 5 illustrates the typical 

stages in performing a friction weld of TiAl to 

the titanium alloy, Ti-6V-4Al. 

Figure 5. The relationship of friction weld 

parameters examined in this study. 

Heavy Vehicle Propulsion Materials 

A cost-effective friction welding process 

has been developed that demonstrates the 

successful joining of TiAl to titanium alloy 

materials. Tensile tests conducted on welded 

test specimens have shown that the TiAltitanium alloy weld strength is equivalent to 

the parent TiAl strength. Additional welding 

trials are planned to optimize the process for 

implementing into prototype production. 

Conclusions 

The optimized probabilistic design 

approach has shown ways to reduce stress in 

the valve from geometry changes under 

service load conditions. Incorporating these 

geometry changes in the valve design suggest 

that the service lifetimes of silicon nitride 

and TiAl engine valves will likely be 

significantly longer as a result of the 

noteworthy reduction of tensile stresses in 

the valve model. Future bench tests and 

engine tests using the silicon nitride and TiAl 

valves will help validate the design approach 

used, and verify the anticipated longer 

service lifetimes. 

The development of a successful friction 

welding process that joins a TiAl valve head 

to a titanium alloy (Ti-6V-4Al) valve stem 

identifies a well-known and cost-effective 

fabrication process for manufacturing engine 

valves for these materials. In addition, it 

orchestrates the high-strength TiAl valve 

head in the high-temperature region and the 

more wear-resistant TiAl material in the 

sliding region of the valve guide. 

76 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

B. Thick Thermal Barrier Coatings for Low-Emission, High-Efficiency Diesel Engine 

Components 

M. Brad Beardsley and Jesús Chapa-Cabrera 


Caterpillar Inc. 


Technical Center Bldg. E/854 


P.O. Box 1875 

Peoria, IL 61656-1875 

(309) 578-8514; fax: (309) 578-2953; e-mail: beardsley_m_brad@cat.com 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: Caterpillar Inc., Tech Center, Mossville, Illinois 

Subcontractor: Fraunhofer USA, East Lansing, Michigan 

Objectives 

• Develop new approaches to coating design and fabrication to aid in overcoming hurdles to the 

durability of thermal sprayed coatings. Specific objectives are these: 

― Develop the laser technology of surface dimpling, cleaning, and laser-assisted spraying to 

enhance adherence and increase coating strength. 

― Develop phosphate-bonded composites for thermal management coatings. 

― Evaluate quasicrystalline materials as potential thermal barrier and wear coatings. 

Approach 

• Conduct an initial cost assessment for the laser processing to assess the potential for 

commercialization; the most cost-effective processes will be evaluated for potential impact on 

coating adherence. 

• Measure the mechanical and physical properties of phosphate-bonded composites to determine 

their potential for use as thermal barrier coatings (TBCs). 

• Evaluate the thermal stability of quasicrystalline materials at engine operating temperatures by 

means of diffusion couple experiments. 

Accomplishments 

• Completed cost analysis of laser pre- and post-treatments and selected post laser “tacking” as 

the method for treating coatings to increase adherence. 

• Developed phosphate-bonded composite coatings that survived initial thermal cycling to 650oC 

with good residual adherence to the substrate. 

• Sprayed quasicrystalline coatings using the high-velocity, oxygen-fueled (HVOF) technique and 

began evaluating their thermal conductivities. 

77 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

Future Direction 

• Laser-tack tensile adhesion specimens to evaluate the potential strength increase produced. 

Review laser-assisted thermal spraying results with Fraunhofer USA, which holds patents in this 1

area. Couple a laser with plasma spraying if the review with Fraunhofer shows promise. 

• Further evaluate phosphate-bonded composite coatings under thermal cycling with higher 

thermal gradients and a greater number of cycles. 

• Evaluate diffusion couples of quasicrystalline coatings for coating stability at temperatures 

ranging from 600 to 900oC. Evaluate bond coating chemistry effects on the diffusion of the 

quasicrystalline alloy elements. 

Introduction 

Engine testing of thermal sprayed 

coatings has demonstrated their potential 

benefit as TBCs and wear coatings to reduce 

fuel consumption, wear, and component 

temperatures.2–4 The durability of thermal 

sprayed coatings, particularly TBCs, remains 

the major technical challenge to their 

implementation in new engine designs. New 

approaches to coating design and fabrication 

will be developed to aid in overcoming this 

technical hurdle. 

Laser Technologies 

Three basic areas of laser-augmented 

spray coating work are evaluated: 

1.	 Laser roughening: A substrate is 

roughened via laser machining prior to 

spray coating to create mechanical 

interlocking for better adhesion 

capability. 

2.	 Laser-assisted spray coating: A laser assists 

the spray coating by optically striking 

airborn spray particles or freshly 

embedded particles with relatively low 

peak power density.5 

3.	 Laser tacking: Laser pulses penetrate 

through the coating and into the 

substrate during processing to create 

occasional metallurgical bonds. 

Phosphate-Bonded Composites 

Phosphate-bonded composites consist of 

filler material bonded together by a 

phosphate. The compositions of both the 

filler and the phosphate binder can be widely 

varied and, for this reason, so can the 

properties of the composite. Phosphatebonded composites are well known and have 

been in occasional use for many years as 

refractory mortars and cements; hightemperature, corrosion-resistant coatings; 

temporary bone replacements; fast-cure 

paving cement; and dental cement. 

The false-melt phenomenon of some 

phosphates was discovered at Caterpillar in 

1994.6

 As the binder rises from room 

temperature to 150oC, unbonded water 

escapes, allowing the structure to collapse 

and become more rigid, like a sponge as it 

dries. Efforts on metal-phosphate composites 

at Caterpillar have been aimed at developing 

seal coatings, corrosion-resistant coatings, 

high-temperature adhesives, and, in the 

current study, thermal insulating coatings. 

Quasicrystalline Coatings 

Quasicrystalline materials may provide 

advantages over ceramic TBCs because of 

their unique properties. The low thermal 

conductivity of some quasicrystalline 

materials approaches that of zirconia, and 

their thermal expansion is similar to that of 

steel, aluminum, and cast iron materials used 

in diesel engines. One of the major 

advantages in the use of the quasicrystalline 

78 

Heavy Vehicle Propulsion Materials 

materials based on aluminum is the ability to 

apply the coating via HVOF processing, 

thereby creating a coating with higher 

strength, higher adherence, and higher 

density. Coating structures produced using 

HVOF processes can have near 99% densities, 

compared with the 80–95% densities found 

in plasma-sprayed ceramic TBCs. Coating 

adherences of 65 MPa or greater are common 

for HVOF coatings, while the adherence of 

plasma coatings is generally less than 

50 MPa. 

Approach 

Laser Technologies 

Laser roughening, laser tacking, and laserassisted spray coating of the substrates and 

coatings are being assessed for costeffectiveness in the initial evaluation. The 

adherence of laser-treated coating will be 

measured using ASTM tensile adhesion 

testing techniques if the process is 

determined to be economically feasible. 

Phosphate-bonded Composites 

Caterpillar’s patented phosphate-bonded 

seal coating technology will be used with 

ceramic microspheres to develop new lowthermal-conductivity ceramic composites for 

use as TBCs. Coating the internal diameters 

of cylinder head ports and manifolds to 

reduce heat rejection is the main application 

of interest for these coatings. Mechanical and 

thermal properties of the composites will be 

evaluated and their stability assessed by 

thermal exposure and thermal shock testing. 

Quasicrystalline Coatings 

One quasicrystal, with the stoichiometry 

Al71Co Fe8Cr8, has previously been 13

investigated for use as a TBC in aero 

applications and will be the starting point for 

this investigation.7, 8 This alloy was reported 

to have a bulk thermal conductivity similar 

to that of zirconia and was shown to have 

good high-temperature oxidation. The main 

emphasis of the evaluation will be to spray 

FY 2003 Progress Report 

the material using HVOF processing and 

determine its thermal stability at diesel 

component operating temperatures, using 

diffusion couple techniques. 

Results 

Laser Roughening 

Laser roughening occurs when sufficient 

optical energy impinges a substrate to cause 

either ablation or homogenous boiling. In 

either case, the focused laser removes a small 

volume of material for each laser pulse. The 

micro-machining process takes place where 

the laser is focused on a very small spot 

(usually 25 microns in diameter) and requires 

that the beam be rastered to affect large 

surfaces, which can lead to long processing 

times and high cost. 

Two basic types of pulsed lasers are 

potential candidates for laser roughening: 

femto-second lasers and UV nano-second 

lasers. Each of these lasers processes 

principally in the ablation regime. The femto 

laser creates ablation through a multi-photon 

interaction enabled by extremely high peak 

pulse power (1mJ/130E-15 sec = 7.5 GW). 

Conversely, the UV nanosecond lasers rely 

on the photon energy to initiate the ablation 

process. UV lasers are commercially available 

in 355 and 266 nm (frequency tripled and 

quadrupled Nd:YAG, respectively). 

Table 1 compares the operational 

differences between the two systems and 

characterizes the small volume removal rates 

to be expected for this process. The economic 

merit of this process would have to be 

compared with the value it would provide 

relative to current process limitations and 

relative to alternative pathways to the same 

result through a lower-cost solution such as 

grit blasting, traditionally used to prepare 

surfaces for thermal spray coating. The most 

likely candidates would be small components 

with <1 cm2

 area to be roughened (i.e., fuel 

systems). 

79 

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

Table 1. Comparison of femto lasers and nano- either a CO2 or YAG laser would be used for 

second lasers this process; the CO2 laser is more 

Characteristic Femto lasers UV lasers 

System size 1,000 × 800 × 400 × 200 × 

300 mm 200 mm 

Wavelength 800 nm 355 and 

266 nm 

Beam quality (m2) 1.2 1.1 

Laser average 1 to 3 W 1 to 10 W 

power 

Laser cost $250–300K $125–150K 

Material removal Ablation in 266—ablation 

process vacuum; some 355—some 

plasma melting ablation 

in ambient 

Typical pulse 130 15 

duration femtoseconds nanoseconds 

(1E-15) (1E-9) 

Peak power ~1E-10 W ~1E-5 W 

Typical focus spot 25 microns 10 microns for 

size 266 

Peak power 2E-15 w/cm 2 2E-11 w/cm 2 

density 

Depth 0.5 micron 1–2 microns 

removal/pulse 

Volume 150–200 100–150 

removal/pulse microns 3 microns 3 

Pulse frequency 5,000 Hz 10,000 Hz 

Volume 0.0010 mm3 0.0015 mm 3 

removal/second 

Laser-assisted Spray Coating 

A laser assists spray coating by optically 

striking airborn spray particles or freshly 

embedded particles with relatively low peak 

power density. The purpose of the laserassisted process is to provide shallow melting 

to create a completely dense coating with a 

metallurgical bond onto the substrate. 

Because the process requires relatively low 

power density (<1E-6 W/cm2

), there are 

several candidate lasers from which to 

choose. These are outlined in Table 2. Note 

that the final cost values are expressed in 

$/layer/cm2

. Costs in the range of $0.04 to 

$0.09 may be acceptable if the durability of 

the TBC can be increased. 

Laser Tacking 

Unlike laser-assisted spraying, laser 

tacking would purposely exploit the laser 

key-holing phenomenon. Traditionally, 

economically viable. Two relatively new 

lasers are available—the direct diode laser 

and the fiber laser. The direct diode laser is 

cost-viable. However, the beam comes out as 

an approximately 3×12 mm rectangle; this is 

cost-competitive compared with the CO2 

laser, but it may tack down more than is 

necessary. In addition, the direct diode laser 

does not keyhole but is primarily used in the 

conduction weld (shallow melt) mode. The 

second new laser, the fiber laser, entered the 

kilowatt power range within the past year, 

with a few test lasers just becoming available. 

Currently, the cost for the fiber laser is 

prohibitive, but the costs will come down as 

the technology advances; the expected future 

costs are listed in Table 3. 

Phosphate-bonded Composites 

Composites were produced using packed 

mullite hollow microspheres with a mean 

particle size of 150 μm as the main filler 

(Figure 1). The rest of the open volume was 

then filled with alumina, and the remaining 

space was filled with the Al-Cr-P2O binder. 5

The thermal conductivity of the resulting 

composite was measured and is in the same 

range as plasma-sprayed TBC materials, as 

shown in Figure 2. 

Figure 1. Hollow ceramic microspheres. 

80 
Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

Table 2. Candidate lasers for laser-assisted thermal spray process 

Laser type CO2 Nd:YAG: CW Nd:YAG 

QS_pulsed Fiber laser Direct diode Copper vapor 

Average 

power 

1,000–20,000 

W 

1,000–6,000 

W 

5–100 W 100–2,000 W 100–4,000 W 10–100 W 

Peak/average 1 1–2 1000–4000 1 1 1000 

Near field Round mixed Round top Round Round gauss, Rectangular Round top 

energy profile mode hat gaussian or round top top hat (soft) hat 

(raw beam) hat 

$/watt $50–150 $120–200 $1,000–4,000 $200–1,000 $70–120 $2,000 

Typical peak 3,000 W 2,000 W 200,000 W 700 W 4,000 W 100,000 W 

Power density 3,000 W/mm2 3,000 W/mm2 10,000 

W/mm2 

3,000 W/mm2 1,000 W/mm2 240,000 

W/mm2 

Pulse 

duration 

CW CW 15 nanosec CW CW 60 nanosec 

Pulse 

frequency 

CW CW 10,000 Hz CW CW 10,000 Hz 

Spot 

dimensions 

1.2 mm diam 1.0 mm diam 1.5 mm diam 0.5 mm diam 0.5 × 8 mm 0.75 mm 

diam 

Spot area 1 mm 2 0.7 mm 2 1.7 mm 2 0.2 mm 2 4 mm 2 0.4 mm 2 

Overlap 50% 50% 99.5% 50% 20% 99% 

Scan speed 160 mm/sec 160 mm/sec 100mm/sec 90 mm/sec 20 mm/sec 

Coverage rate 100 mm2/sec 66 mm 2/sec 70 mm 2/sec 22.5 mm 2/sec 128 mm 2/sec 40 mm 2/sec 

Energy 30 J/mm2 30 J/mm2 0.4 J/mm2 31 J/mm2 31 J/mm2 1.5 J/mm2 

deposition (3000 W ave) (2000 W ave) (30 W ave) (700 W ave) (4000 W ave) (60 W ave) 

Dwell rime 16 msec 12 msec 0.003 msec 11 msec 25 msec 0.006 msec 

Asset cost $200K $300K $175K $175K $300K $150K 

O&O cost $150/h $225/h 130 $/h $130/h $225/h $115/h 

Coverage rate 60 cm 2/min 40 cm 2/min 42 cm 2/min 13.5 cm 2/ min 77 cm2/min 24 cm 2/min 

Cost/layer $0.04 $/cm2 $0.09 $/cm2 $0.05 $/cm2 $0.16 $/cm2 $0.05 $/cm2 $0.08 $/cm2 

Figure 2. Thermal conductivity of a phosphatebonded composite coating, consisting 

of hollow ceramic microspheres bound 

with aluminum phosphate binder, 

compared with the conductivity of 

zirconia and mullite thermal barrier 

coatings produced by plasma spraying. 

Different techniques for applying the 

coatings have been explored. The 

consistency of the solution is adjusted using 

acidic water as thinner. Thick pastes and 

tapes of the material were deposited on 

substrates to form coatings. These coatings 

delaminated after thermal cycling to 650oC. 

In order to enhance the contact area and 

apply more uniform coatings, thin slurries 

were applied with paint sprayers. Sprayed 

coatings with different filler-to-binder ratios 

were deposited on grit-blasted cast iron 

surfaces. A thin coating was first applied as a 

fine mist and allowed to dry for at least 

5 minutes. This operation was repeated 

multiple times until the part was completely 

covered. Then a thickness of 2 mm was built 

up by depositing larger amounts in each 

step. Spraying produced the most aesthetic 

and thermal-shock-resistant coatings. A 

section of a coated cast iron diesel engine 

exhaust component is shown in Figure 3. 

After cycling three times to 650oC, the 

coating did not crack or delaminate. Further 

coating deposition and characterization is in 

progress. 

81 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

Table 3. Candidate lasers for tacking 

Laser type CO2 Nd:YAG: CW Nd:YAG: pulse 

pumped Fiber laser Direct diode 

Average power 1,000–20,000 W 1,000–6,000 W 100–1,000W 100–2,000 W 100–4,000 W 

Peak/average 1 1-2 2-10 1.5 1 

Near-field energy Round mixed Round top hat Gaussian Round gauss, or Rectangular top 

profile (raw mode (fiber) (mirrors) round top hat hat (soft) 

beam) 

$/watt $50–150 $120–200 $200–300 $200–1000 $70–120 

Typical peak 3,000 W 2,000 W 10,000W 1,000 W 4,000 W 

Power density 30,000 W/mm2 30,000 

W/mm2 

100,000 W/mm2 30,000 W/mm2

 2500 W/mm2 

Pulse duration 0.2 msec` 0.5 msec 0.1 msec 0.02 msec 2 msec 

Pulse frequency 1,000 Hz 400 Hz 2,000 Hz 10,000 Hz 1,000 Hz 

Duty cycle 20% 20% 20% 20% 20% 

Spot dimensions 0.35 mm diam 0.30 mm diam 0.35 mm diam 0.2 mm diam 1.5 mm diam 

Spot area 0.10 mm2 0.07 mm 2 0.10 mm 2 0.03 mm 2 1.6 mm 2 

% Coverage 5% 5% 5% 5% 20% 

Tack coverage 100 mm2/sec 28 mm 2/sec 200 mm 2/sec 300 mm 2/sec 1,600 mm 2/sec 

Coverage rate 2000 mm2/sec 560 mm 2/sec 4,000 mm 2/sec 6,000 mm 2/sec 8,000 mm 2/sec 

Energy 600 mJ/tack 1,000 mJ/tack 500 mJ/tack 70 mJ/tack 8,000 mJ/tack 

deposition (3,000 W ave) (2,000 W ave) (1,000 W ave) (700 W ave) (4,000 W ave)o 

Asset cost $200k $300k $400k $175k $300k 

O&O cost $150/h $225/h $300/h $130/h $225/h 

Coverage rate 1200 cm2/min 350 cm 2/min 1200 cm 2/min 1800 cm 2/min 2400 cm 2/min 

Cost/cm 2 $0.002 $/cm2 $0.015 $/cm2 $0.004 $/cm2 $0.001 $/cm2 $0.001 $/cm2 

Figure 3. Cast iron manifold section with sprayed 

phosphate-bonded composite coating 

on outer diameter. 

Quasicrystalline Coatings 

Quasicrystalline coatings have been 

produced using HVOF processing. The 

thermal conductivity of the coatings is under 

evaluation. 

Conclusions 

1.	 Laser processing by “keyholing” critical 

coating areas has been selected for further 

evaluation based on the economics of 

this process. Laser-assisted thermal 

spraying will also be evaluated further in 

order to improve coating durability. 

2.	 Phosphate-bonded composite coatings 

have shown promise in thermal cycling 

and will be further evaluated. 

3.	 Quasicrystalline materials show a 

potential to have the coating strength 

properties of HVOF coatings, which will 

enhance their durability in TBC 

applications. 

References 

1. Eckhard Beyer and Steffen Nowotny, 

“Method for applying a Coating by Means of 

Plasma Spraying while Simultaneously 

Applying a Continuous Laser Beam,” U.S. 

Patent No. 6,197,386, March 6, 2001. 

2. R. A. Miller, "Assessment of Fundamental 

Materials Needs for Thick Thermal Barrier 

Coatings (TTBCs) for Truck Diesel Engines," 

DOE/NASA/21749-1, NASA TM-103130, 

82 
Heavy Vehicle Propulsion Materials 

National Aeronautics and Space 

Administration, 1990. 

3. M. B. Beardsley and H. J. Larson, “Thick 

Thermal Barrier Coatings for Diesel 

Components,” DOE/NASA/0332-1, NASA CR190759, National Aeronautics and Space 

Administration, 1992. 

4. M. B. Beardsley, P. G. Happoldt, K. C. 

Kelley, E. F. Rejda, and D. F. Socie, "Thermal 

Barrier Coatings for Low Emission, High 

Efficiency Diesel Engine Applications," Society 

of Automotive Engineers Technical Paper 

Series, 1999-01-2255, Government/Industry 

Meeting, Washington, D.C., 1999. 

5. O. K. C. Sang, A. Ohmori, and K. 

Nakade, “New Approach for Advanced 

Zirconia Thermal Barrier Coatings by PlasmaLaser Hybrid Spraying Technique,” Trans. 

JWRI, 31(2), 207–212 (2002). 

6. Jill E. Crumpacker, Chuong Q. Dam, 

Virgil R. Hester, Kurtis C. Kelley, “Process for 

Forming High Temperature Resistant 

Elements,” U.S. Patent No. 5,620,645, April 

15, 1997. 

FY 2003 Progress Report 

7. P. Archambault, P. Plaindoux, E. BelinFerre, and J. M. Dubois, “Thermal and 

Electronic Properties of an AlCoFeCr 

Approximant of the Decangonal Phase,” Mat. 

Res. Soc. Symp. Proc., 553, 409–414 (1999). 

8. Sanchez, F. J. Garcia, J. M. Algaba, J. 

Alvarez, P. Valles, M. C. Garcia-Poggio, and 

A. Aguero, “Application of Quasicrystalline 

Materials as Thermal Barriers in Aeronautics 

and Future Perspectives of Use for These 

Materials,” Mat. Res. Soc. Symp. Proc. 553, 

447–458 (1999). 

Presentations 

M. B. Beardsley, “Mechanical Property 

Behavior of Thermal Barrier Coatings,” 

presented at the International Thermal Spray 

Conference, May 5–8, 2003, to be published 

in the proceedings. 

83 


Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

$$FSNFU$PNQPTJUFTGPS8FBS"QQMJDBUJPOT

T .M. Yonushonis, R. J. Stafford, M. Henrichsen, D .J. Gust, B. Seegmiller,* and J.


Stephan* 


Cummins, Inc.


Columbus, IN 47202-3005 

(812) 377-7413; fax: (812) 377-7023; e-mail: darryl.j.gust@cummins.com 

*CoorsTek 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No.: DE-AC05-00OR22725 

0CKFDUJWFT

• Optimize material processing of a cermet material comprised of hard titanium carbide (TiC) 

particles in a tough nickel aluminide (Ni3Al) metallic matrix for fabrication of near-net-shape 

components with low wear and scuffing properties. 

• Optimize material processing parameters for a tungsten carbide (WC) powder/cast iron 

composite material with low wear and scuffing properties. 

• Develop potential applications in heavy-duty diesel engine systems for these two previously 

identified unique wear-resistant materials. 

"QQSPBDI

• A single composition of TiC/Ni3Al material is to be processed under optimized powder blending, 

molding and sintering parameters to produce test pieces and prototype near net shape injection 

molded components for evaluation of properties. 

• Sample pre-forms with varying densities and porosity distributions of WC powder are to be 

infiltrated by cast iron, followed by sample characterization. 

"DDPNQMJTINFOUT

• Completed initial TiC/Ni3Al injection molding equipment modifications, material binder 

formulation, mixing/preparation, injection molding trials, debinder and binder decomposition 

tests, sintering development, and test bar property evaluation. 

• Evaluation and comparison of WC compacts showed a change in porosity distribution from the 

original work that produced fully dense test pieces. 

'VUVSF%JSFDUJPO

• Further optimization of binder decomposition and sintering cycles for the TiC/Ni3Al are 

planned to achieve the 99+% density needed. This will also establish the design shrinkage factor 

and allow the prototype tooling to be built. 

85 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

• A small 2 × 2 full factorial test matrix is planned to investigate the distribution of porosity in 

the WC pre-forms to validate the porosity distribution theory and demonstrate success in wear 

prediction of the WC/cast iron composite surface. 

*OUSPEVDUJPO

The continuing reduction of allowable 

engine combustion emissions in current and 

future standards requires operation at higher 

injection pressure and reduced component 

clearances in fuel system components. New 

materials that exhibit very hard wearresistant surfaces are needed by industry to 

use as injector plungers and contact wear 

surfaces for diesel engines. 

Work done under the previous DOE 

Cooperative Agreement DE-FC05-97OR22538 

found two cermet materials that Cummin’s 

was interested in pursuing for possible 

production implementation in diesel 

engines. 

The first material (TiC/Ni3Al) is a TiC 

powder in an Ni3Al metal matrix developed 

in collaboration with Oak Ridge National 

Laboratory (ORNL) and CoorsTek. Extensive 

testing and analysis was done by all three 

partners to help optimize the processing and 

properties. The composition with the suite of 

properties most closely matching Cummins’ 

needs for fuel injector materials was chosen 

for further optimization of the powder and 

processing. 

The second material (WC/cast iron) is a 

WC compact to be added to casting molds 

prior to pouring that would allow cast iron 

infiltration into and through the compact to 

produce a localized hard wear-resistant 

surface. Initial infiltration of the compacts 

showed good wetting and complete 

infiltration. The wear properties of these 

surfaces were between the wear properties of 

zirconia and D4 tool steel (conventional fuel 

injector materials). Repeat infiltrations with 

compacts from additional pressings resulted 

in no iron infiltration of the compact. The 

lack of repeatability led to the current work 

of characterizing and documenting the 

compact manufacture and then optimization 

of the iron infiltration. 

"QQSPBDI

This program covers investigation and 

material processing optimization for two 

unique wear-resistant materials for potential 

application to diesel engine system 

components. The first material is a cermet 

comprised of TiC particles in an Ni3Al 

matrix. A single composition of this material 

was chosen for the material processing 

development to obtain both the optimized 

raw material processing and the optimized 

consolidation and sintering parameters to 

produce a final component with the required 

low wear and scuff properties for a diesel 

engine system application. The material 

processing optimization is in process at 

CoorsTek with guidance from ORNL. 

Property evaluations will be conducted at 

CoorsTek, ORNL, and Cummins to 

characterize the density, strength, fracture 

toughness and wear of the material. 

The second material is a cermet 

comprising WC particles in a cast iron 

matrix. The optimization of WC compact 

components and processing will be studied, 

along with the effects of cast iron 

composition and heat treatment. Evaluation 

of the wear and scuffing properties for the 

different cermet iterations will be used to 

guide the optimization effort. Compact 

manufacture is in process at Applied Powder 

Products, and the iron casting is scheduled at 

Case Western Reserve University (CWRU). 

3FTVMUT

The process optimization of TiC/Ni3Al 

composition has been finalized for the 

equipment (double planetary mixer with 

vacuum/Ar atmosphere operation), binder, 

mixing parameters, and initial molding 

86 

Heavy Vehicle Propulsion Materials 

parameters. The binder formulation was 

chosen to provide wetting of the powder 

during mixing, a strong feedstock matrix for 

injection molding, and a broad working 

viscosity at high solids loading. The molding 

trials conducted over several batches were 

used to optimize part weight, with the last 

batch demonstrating a narrow distribution in 

weight (5.447 ± 0.0104 g). Debinding and 

sintering trials have produced test bars for 

evaluation. The debinding and sintering 

development is continuing. 

The initial trial batch of material sintered 

to 98% density and had a flexural strength of 

787 MPa (below the target value of 

1032 MPa). The strength values and 

statistical distribution of the values are given 

in Figure 1. The wide spread in values and 

lower-than-anticipated strength are thought 

to be due to the lower density with a larger 

than expected flaw population. Additional 

flexural strength tests (three-point bending) 

were conducted on the broken bars from the 

original strength testing; the results are 

shown in Figure 2. The three-point bending 

showed strength 70% greater than the fourpoint bending. This increase in strength was 

greater than would be expected from just 

differences in test span and volume of 

material. The distribution of critical flaws 

FY 2003 Progress Report 

'JHVSF Flexural strength of TiC/Ni3Al cermet in 

three point bending (CoorsTek). 

and work hardening of the intermetallic 

Ni3Al phase are additional factors that could 

influence the failure mechanism in this 

composite microstructure. 

WC compacts were pressed and sintered 

by Applied Powder Products using 1-μm 

powder. These compacts were placed in sand 

molds at CWRU and infiltrated with molten 

iron. Upon cooling, the compacts were 

found to have no iron infiltration (Figure 3). 

This result showed that additional work was 

needed to optimize the compact 

manufacturing and bring the process back 

'JHVSF Flexural strength of TiC/Ni3Al cermet in 

four point bending (CoorsTek). 

'JHVSF Tungsten carbide compact showing no 

iron infiltration after casting. 

87 

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

to the successful infiltration in previous $PODMVTJPOT castings. Evaluation of these WC compacts 

and comparison of the porosity distribution 

with that of WC compacts from 2001 

showed a significant difference in density 

distribution at larger pore sizes (Figure 4). 

This difference in pore distribution is 

thought to impact the penetration of the cast 

iron into the compact during casting. 

'JHVSF Particle size distribution comparison for 

WC compacts from mercury 

porosimitry measurements. 

Process optimization work for the 

TiC/Ni3Al powder is on schedule, and the 

delivery of test pieces for wear evaluation 

and correlation to the previous material 

studies is anticipated by the end of 2003. The 

density is slightly below the necessary level 

of 99+%, affecting the strength measurement 

and giving a wide spread in flexure strength. 

The porosity distribution for the WC 

powder compacts in this work was found to 

be different from that in previous work. The 

current samples did not allow penetration of 

cast iron into the WC powder compact. 

88 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

% 1SPDFTTJOHBOE$IBSBDUFSJ[BUJPOPG4USVDUVSBMBOE'VODUJPOBM.BUFSJBMTGPS)FBWZ

7FIJDMF"QQMJDBUJPOT

J. Sankar, Z. Xu, and S. Yarmolenko 

North Carolina A & T State University 

1601 East Market Street 

Greensboro, NC 27411 

(336) 256-1151, extension 2282; fax: (336) 256-1153; e-mail: sankar@ncat.edu 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No:DE-AC05-00OR22725 

Subcontractor: North Carolina A&T State University, Greensboro, North Carolina 

0CKFDUJWFT

• Produce yttria-stabilized zirconia (YSZ) thin films using a combustion chemical vapor 

deposition (CCVD) technique for solid oxide fuel cells (SOFCs). 

• Investigate the nucleation of YSZ and its controlling parameters. 

• Study the thin film microstructure evolution. 

• Enhance the film deposition rate. 

"QQSPBDI

• Deposit YSZ thin films using a CCVD technique. 

• Characterize the films using scanning electron microscopy (SEM) and X-ray diffraction (XRD). 

• Study the effects of substrate temperature and metal concentration on the nucleation density. 

• Examine the thin film microstructure evolution by experiment and stochastic simulation. 

• Optimize the operation parameters of the CCVD system. 

"DDPNQMJTINFOUT

• Enhanced the nucleation density. 

• Developed a stochastic model to simulate the thin film microstructure evolution. 

• Established a set of conditions for high film growth rates. 

'VUVSF%JSFDUJPO

• Study YSZ film deposition on porous electrodes. 

89 

*OUSPEVDUJPO

YSZ, a material that conducts oxygen 

ions, has conventionally been used as an 

electrolyte in SOFCs and in oxygen sensors 

for pollution and safety monitoring, control 

and automation of industrial processes, and 

energy conservation.1

 Because of the 

relatively low electrical conductivity of the 

YSZ material (about 0.1 S·cm!1 at 1000°C), 

most of the ohmic loss is due to the 

resistance of the electrolyte. To reduce the 

ohmic loss and increase the powergenerating efficiency of a fuel cell, it is 

desirable to use a thin film electrolyte. On 

the other hand, temperatures as high as 

1000°C are usually employed with YSZ to 

obtain a satisfactory level of ionic 

conductivity. The need for high temperatures 

makes material selection difficult and 

increases the product cost greatly. Reducing 

the thickness of the electrolyte would 

increase the ionic conductivity at lower 

temperatures. 

YSZ thin films have usually been 

synthesized by chemical vapor deposition 

(CVD) or electrochemical vapor deposition 

(EVD).2–5 However, the vacuum systems used 

in these techniques require the use of a 

vacuum chamber, which limits the sizes of 

the parts that can be coated and increase 

production costs. A technique called liquid 

fuel CCVD is a promising alternative for 

producing YSZ thin films for industrial 

applications. CCVD works in the open 

atmosphere and offers the potential for 

conformal deposition of films on non-flat 

surfaces. Because no vacuum chamber is 

needed for the process, the film can be 

deposited on parts of any size. The precursor 

concentration in liquid fuel is relatively high 

compared with that usually used in lowpressure CVD processes; therefore, CCVD is 

expected to have a higher deposition rate. 

CCVD is a promising technique for 

producing YSZ thin films for industrial SOFC 

applications at a lower cost than other 

CVD/EVD techniques. 

An SOFC requires that the electrolyte be 

highly dense to avoid any cross-flow of 

oxygen or fuel. The main purpose of this 

research is to produce dense YSZ thin films 

through the study of nucleation and 

microstructure evolution. Methods of 

enhancing the growth rate of YSZ are being 

studied because of the potential for reducing 

the cost of fuel cell manufacturing through 

the use of thin film technology. 

"QQSPBDI

Thin films of YSZ as an electrolyte for 

SOFCs have been deposited using CCVD. The 

deposition system was developed at North 

Carolina A&T State University. Metal-organic 

reagents were dissolved in organic solvent 

(toluene). The solution was mixed with 

oxygen and atomized into small aerosols 

with a nebulizer and then was ignited by a 

pilot flame. Thin films were deposited on 

substrates placed downstream of the aerosol 

flame. 

A nucleation study of YSZ was performed 

by varying the substrate temperature and 

metal concentration in the solvent. At a 

designed condition, depositions were 

conducted for varying time periods. The 

microstructures of these depositions were 

observed and analyzed. The grain growth was 

studied with stochastic modeling. The efforts 

to enhance the film growth rate were carried 

out through studies of the effect of the 

thermophoresis and metal concentration. All 

the present depositions were performed on 

mirror-polished single-crystal silicon 

substrates. The phases of the deposited films 

were examined with XRD, and their 

morphology was characterized through SEM. 

3FTVMUT

/VDMFBUJPO

&GGFDUPGTVCTUSBUFUFNQFSBUVSF The 

temperature of the substrate is an important 

factor that controls nucleation density, 

defined as the number of aggregates created 

per unit of area. To be able to use the image 

90 

Heavy Vehicle Propulsion Materials 

analysis software Image Pro to compute the 

nucleation density, the nucleation time of 

the YSZ particles was set for 130 seconds. The 

depositions were conducted at substrate 

temperatures of 800, 900, 1000, 1100, and 

1200oC and a metal concentration of 1.25E03 M. The as-grown samples were 

characterized with SEM as shown in Figure 1. 

'JHVSF Micrographs of YSZ nuclei nucleated at 

substrate temperatures (a) 800oC, 

(b) 900oC, (c) 1000oC, (d) 1100oC and 

(e) 1200oC at a nucleation time of 

130 seconds and a total metal 

concentration of 1.25×10!3

 M. 

Using the analysis software to count the 

particle number in the specific area, it was 

found that the nucleation rates ranged over −2

an order of magnitude, from 1010 to 1011 cm

in the tested temperature range. The 

nucleation rate variation versus the substrate 

temperature is illustrated in Figure 2. It is 

obvious that the tendency of the nucleation 

rate versus the substrate temperature can be 

divided into two sections. With the substrate 

temperature between 1000 and 1200oC, the 

nucleation rate decreases with the substrate 

temperature; in the substrate temperature 

range of 800 to 1000oC, the nucleation rate 

increases with substrate temperature. The 

former nucleation rate tendency was well 

accepted. As far as we know, the latter 

tendency has not been reported. It is 

proposed that at low substrate temperatures, 

the material species in the gas phase 

condense into the solid phase and coagulate 

into particles. They rebound from the surface 

instead of becoming adsorbed when they 

FY 2003 Progress Report 

'JHVSF YSZ nucleation rate as a function of the 

substrate temperature, according to the 

information in Figure 1. 

hit the substrate surface. This process also 

leads to depletion of species in the gas 

phase that is needed for CVD and then 

partially results in a decrease in the 

nucleation rate. The images in Figure 1 also 

reveal that, on the samples nucleated at the 

low temperatures, there are many large 

nodular particles that support our 

conclusions. 

&GGFDUPGNFUBMDPODFOUSBUJPO Another 

method of enhancing the nucleation rate 

was to increase to deposition flux, i.e., the 

metal concentration, for our experimental 

system. At the low concentrations of 5 × 10−4 

and 1.25 × 10−3, only isolated particles 

presented on the substrate surface after 

depositions of 130 seconds, whereas almost 

continuous films were obtained when the 

concentration was increased to 3 × 10−3

 M 

and up. At the high total metal 

concentrations, the particle size reached up 

to 30–50 nm. From this set of experiments, it 

can be concluded that the lowest metal 

concentration, 5.5×10−4 M, is not suitable if a 

high nucleation rate is demanded. 

4USVDUVSBM&WPMVUJPO

&YQFSJNFOUBMTUVEZ To grasp the 

physics of the evolution process of the YSZ 

thin film, the grain sizes at various stages of 

91 

the processing time were measured for 

statistical post-processing. Figure 3 shows the 

micrographs of YSZ particles/crystallites at 

different processing times. In Figure 3(a), the 

nuclei can hardly be seen after only 

70-second processing, except some large 

particles that are assumed to be 

contamination. From Figures 3(b) to (d), with 

the increase in processing time, the size of 

the particles is increased; however, the 

number of particles is reduced. This 

phenomenon can be interpreted by the 

mechanisms of coarsening and coalescence 

of the growing particles. With increased time 

of processing, the sizes of the particles 

increase. Some secondary nucleation and 

growth on the large particles can be noticed. 

It is also reasonable to assume that the 

secondary nucleation should take place on 

the substrate before all the surface of the 

substrate is covered with particles. The film 

consists of both (111) and (100) oriented 

crystals. The difference in orientation 

originated at the stage when the sizes of 

particles were very small. 

'JHVSF Microstructure of the YSZ particles/ 

crystallites at different processing times: 

(a) 70, (b) 130, (c) 190, (d) 250, (e) 310, 

(f) 370, (g) 430, (h) 490, and (i) 550 

seconds on Si(100) substrates, at a 

substrate temperature of about 1200oC 

and a metal concentration of 

1.25×10!3 M. 

According to the obtained mean particle 

radii, particle growth rate can be estimated 

by plotting the mean diameter versus the 

growing time, as shown in Figure 4. The 

particle growth rate is approximately linear 

during the time period studied (130 to 

430 seconds). The intercept of the line on 

the time axis is about 33.3 seconds, which 

shows the incubation time for nucleation. 

With a prolonged deposition time, a 

continuous thin film can be obtained. 

'JHVSF Particle growth rate vs. processing time, 

based on the data obtained from the 

micrographs, as shown in Figure 3. 

4UPDIBTUJDTJNVMBUJPO The number and 

sizes of the particles were obtained by using 

the image processing software. After 

statistical post-processing, a comparison of 

cumulative distribution functions (CDFs) of 

grain radius normalized by the mean radii is 

given in Figure 5. As can be seen from Figure 

5, there is a distinct dispersion among these 

CDFs plotted in the normalized space. Thus 

the use of a normal grain growth model 

cannot accurately capture the evolution 

process of grains in YSZ thin films. The 

deviation from the normal grain growth 

model is attributed mainly to the 

orientation-dependent grain boundary 

energies and mobility. 

The lognormal distribution has been used 

extensively as the initial distribution of grain 

size.6,7 To validate the use of the lognormal 

92 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

'JHVSF Comparison of CDFs of grain radius in 

normalized space. 

model, a comparison of the initial CDF of 

grain radius at t=130 s with its equivalent 

lognormal distribution is shown in Figure 6. 

As shown in Figure 6, the equivalent 

lognormal distribution can accurately 

capture the true initial grain size distribution. 

A stochastic model was developed by taking 

the radii of the neighboring grains and the 

orientation-dependent constants into 

consideration. The computational efforts 

were greatly reduced by dividing the entire 

population of grains into several sub-groups 

based on the level of their percentiles. It was 

assumed that all grains within each subgroup have an identical behavior of grain 

growth. The orientation-dependent grain 

growth constants were determined from 

curve fitting of the experimental data. An 

example of comparing model prediction with 

the experimental observations is shown in 

Figure 7. 

(SPXUI3BUF

Thermophoresis is a thermal-gradient– 

directed flow of material from hightemperature regions to low-temperature 

regions. Thermophoresis had been found to 

be a strong factor in some CVD 

environments.8

 A temperature gradient 

across a diffusion boundary layer causes a 

thermophoresis effect. In our case, if the 

flame were hotter than the substrate, on 

'JHVSF Illustration of the accuracy of using an 

equivalent lognormal distribution for 

statistical characterization of initial 

grain size distribution. 

'JHVSF Comparison of model prediction with 

measured CDF data of grain radius at t = 

430 s. 

average, the gas molecules from the substrate 

would have a smaller velocity than the gas 

molecules traveling toward the substrate. 

This situation creates a driving force for YSZ 

clusters formed in the direction toward the 

substrate. A larger temperature gradient 

adjacent to the substrate increases the 

thermophoresis effect. The study of the effect 

of thermophoresis was carried out by film 

depositions at different substrate-to-nuzzle 

distances from 51 mm (far into the flame) to 

83 mm (out of the visible end of the flame). 

The film thickness measured on SEM images 

is plotted versus the substrate-to-nozzle 

93 

distance in Figure 8 (solid line). The data can 

be fit by an exponential equation. With the 

increase of the substrate-to-nozzle distance, 

the precursor concentration in the flame 

will be attenuated because of the 

expansion of the flame. Normalization was 

done to eliminate the effect of concentration 

dilution on the film growth rate. The 

normalized thickness data were again plotted 

in the same graph of the originally measured 

data, as shown in curve 2 of Figure 8, the 

dashed line. It is apparently noticeable that 

after normalization, the growth rate of the 

film still follows the exponentially decaying 

mode with the substrate-to-nozzle distance. 

In other words, the parameter substrate-tonozzle distance does play a role in film 

growth. 

'JHVSF Film thickness as a function of the 

substrate-to-nozzle distance, line (1) for 

the original measured data, line (2) for 

the normalized data. 

The effect of the metal concentration on 

the film growth rate is shown in Figure 9. 

Within the range of the concentration 

employed in our experiments, a linear 

relationship was obtained between the film 

growth rate and the concentration. Based on 

observing the morphologies of the samples, 

the films had well-crystallized and faceted 

particles as long as the metal concentrations 

were less than 4.25 × 10−3

 M. Beyond this 

'JHVSF Film growth rate versus metal 

concentration in the liquid solution. 

limitation, the film was in a cauliflower-like 

structure. 

$PODMVTJPOT

According to the investigations we have 

conducted, the CCVD technique has been 

demonstrated to be a promising method for 

film processing of YSZ electrolyte. Nucleation 

density can be improved by controlling the 

substrate temperature and the metal 

concentration appropriately. The analysis of 

the grain growth demonstrated that after the 

initial stage, the grain growth does not 

follow the lognormal mode. A stochastic 

model has been developed to predict the 

grain size in the film at any deposition time. 

The experiments confirmed the 

enhancement of the film growth rates by 

employing the effect of the thermophoresis 

and increasing the metal concentration. 

3FGFSFODFT

1. S. P. S. Badwal, “Ceramic Superionic 

Conductors,” Chapter 11 in Materials 

Sciences and Technology, A Comprehensive 

Treatment, Ed. R. W. Cahn, P. Haasen, E. J. 

Kramer, Vol. 11, p. 570, 1994. 

2. G. Garcia, J. Casado, J. Llibre, and A. 

Figueras, J. Crystal Growth, , 426 (1995). 

3. S-C. Hwang and H-S. Shin, J. Am. 

Ceram. Soc., (10), 2913 (1999). 

94 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

4. U. B. Pal, and S C. Singhal, 

J. Electrochem. Soc., , 937 (1990). 

5. L. G. J. De Haart, Y. S. Lin, K. J. de 

Vries, A. J. Burggraaf, J. Eur. Ceram. Soc., 

(1), 59 (1991). 

6. V. Y. Novikov, Acta Mater. (18), 

4507 (1999) 

7. C. V. Thompson, Annu. Rev. Mater. 

Sci. 
 245 (1990). 

8. W. Bai, K. L. Choy, N. H. J. Stelzer, and 

J. Schoonman, Solid State Ionics, , 225. 

1VCMJDBUJPOT

Z. Xu, J. Sankar, S. Yarmorlenko, “Yttriastabilized Zirconia Coatings Produced Using 

Combustion Chemical Deposition,” Surface 

and Coating Tech., in press, 2003. 

Z. Xu, C. Hilton, B. Watkins, S. 

Yarmolenko, and J. Sankar, “Thin YSZ 

Electrolyte Film Depositions on Dense and 

Porous Substrates,” paper IMECE2003-43330 

in 2003 ASME International Mechanical 

Engineering Congress and RD&D Expo. 

Z. Xu, J. Sankar, S. Yarmolenko, Q. Wei, 

“Nucleation And Growth of Yttria-Stabilized 

Zirconia Thin Films Using Combustion 

Chemical Vapor Deposition,” Materials 

Research Society Symposium Proceedings, 

Vol. 756, pp. 509–514 (2003). 

Z. Xu, S. Yarmolenko, J. Sankar, 

“Enhancement Of YSZ Thin Film Deposition 

Rate In CCVD,” pp. 862–862 in Proceedings 

of 10th International Conference on 

Composites Engineering, New Orleans, 

Louisiana, July 20–26, 2003. 

95 

96 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

&/%&%FWFMPQNFOUGPS$FSBNJD7BMWFTGPS%JFTFM&OHJOFT

Jiangang Sun and W. A. Ellingson 

Argonne National Laboratory 

9700 South Cass Avenue 

Argonne, IL 60439 

(630) 252-5169; fax: (630) 252-4798; e-mail: sun@anl.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No :DE-AC05-00OR22725 

Subcontractor: Argonne National Laboratory, Argonne, Illinois 

0CKFDUJWFT

• Develop a laser-scattering nondestructive evaluation (NDE) method for detecting and 

characterizing subsurface defects/damage in silicon nitride ceramic valves; the NDE data can be 

used to determine the cost-effectiveness and reliability of ceramic valves for diesel engines. 

• Identify strength-limiting flaws and failure mechanisms in silicon nitride ceramics due to 

machining and impact-induced damage. 

"QQSPBDI

• Develop an automated laser-scattering NDE system for fast scanning of entire valves and use the 

system to identify damage and failure mechanisms for ceramic valves from rig/engine tests. 

• Correlate NDE data with detailed surface microstructure data to determine detection sensitivity 

for type, depth, and severity of defects/damage in different silicon nitride ceramics. 

• Establish the correlation of NDE data with mechanical properties so the laser-scattering method 

may predict mechanical properties of ceramics. 

"DDPNQMJTINFOUT

• Completed hardware and software development of an automated laser-scattering NDE system 

for scanning entire valves. This system was used to establish detection sensitivity for 

contact/impact damage and pre-spalls in several NT551 silicon nitride valves that were benchtested for 100 hours. 

• Established laser-scattering detection sensitivity for machining damage in cylindrical SN235P 

silicon nitride specimens. Machining-induced subsurface cracks were clearly identified in roughground rods, but they are not apparent in fine-ground rods. 

97

FY 2003 Progress Report	 Heavy Vehicle Propulsion Materials 

• Characterized cyclic-impact damage in NT551 and SN235P silicon nitrides. The size, depth, and 

severity of detected impact damage (cracks) may be correlated with the impact load. 

'VUVSF%JSFDUJPO

• Further increase data acquisition speed for the automated NDE system so an entire valve can be 

scanned within an hour. A fast detector such as a photomultiply tube will be implemented to 

replace the slower semiconductor detector used in the current system. 

• Determine the detection sensitivity for failure-initiation damage in silicon nitride valves from 

rig/engine tests with more harsh conditions and longer operating durations. 

• Develop theoretical models and image-processing methods for optimized and quantitative 

characterization of strength-limiting subsurface defects and damage in silicon nitride ceramics. 

• Enhance the detection sensitivity on defect depth and establish a correlation of NDE data with 

data from destructive measurement of subsurface microstructure. 

*OUSPEVDUJPO

Advanced ceramics are leading candidates 

for high-temperature engine applications 

that offer improved fuel efficiency and 

engine performance. Among them, silicon 

nitrides are being evaluated as valve train 

materials for diesel engines. For these 

ceramics, however, material defects and 

process-induced or operation-induced 

damage in the subsurface may significantly 

degrade reliability and performance. To 

detect and characterize these defects, 

Argonne National Laboratory (ANL) 

developed a laser-scattering NDE method for 

measurement of detailed subsurface 

microstructure in ceramics. The objective of 

this research is to demonstrate that this 

method can be used to assess/evaluate the 

cost-effectiveness and reliability of ceramic 

valves for diesel engines. The primary effort 

in FY 2003 was to develop an automated 

laser-scattering system for scanning entire 

valves and to investigate the detection 

sensitivity on material defects, machining 

damage, and contact/impact damage for 

candidate silicon nitrides (NT551 and 

SN235P) selected for fabricating into 

prototype valves. This research is being 

conducted in collaboration with Caterpillar, 

Inc. 

"QQSPBDI

The critical region of ceramic 

components for structural applications is the 

near surface (usually to a depth of <200 μm). 

The common types of defects in this region 

are mechanical, such as cracks, spalls, 

inclusions, and voids. Because ceramics are 

partially translucent to light (optical 

penetration depth for silicon nitrides is 

typically >0.1 mm in visible spectrum), a 

laser-scattering method based on crosspolarization detection of optical scattering 

originated from the subsurface can be used 

for noncontact, nondestructive measurement 

of subsurface microstructure in such 

materials. Scanning of the entire surface (flat 

or curved) of a ceramic component and 

construction of a two-dimensional (2D) 

scatter image can be used to readily identify 

subsurface defects, as they exhibit excessive 

scattering over the background, and analyze 

their type and severity. The resolution 

obtained using this method is typically one 

to two orders of magnitude better than that 

of conventional NDE methods such as 

ultrasound and X-ray. Previous studies at 

ANL showed that laser scattering can detect 

and identify strength-limiting flaws and flaw 

98 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

size distribution for several silicon nitride 

ceramics, and that NDE data can be 

correlated with machining conditions and 

mechanical properties. These investigations 

demonstrated the capability of the laserscattering method for predicting material 

microstructural and mechanical properties 

for ceramic valves. 

3FTVMUT

The laser-scattering method was applied 

for detection and characterization of 

subsurface defects/damage in silicon nitride 

valves. An automated NDE system was 

developed to scan entire valves. Figure 1 is a 

photograph of the experimental setup. This 

system uses two rotation and two translation 

stages to align and focus the laser beam on 

the valve surface during the scan, and the 

resulting 2D scattering image data are used to 

identify the location, size, and relative 

severity of subsurface defects/damage. This 

system can therefore be used for inspection 

of the quality of manufactured valves and for 

evaluation of damage and failure 

mechanisms for ceramic valves from 

rig/engine tests. 

'JHVSF Automated laser-scattering system for 

scanning full ceramic valves. 

Figure 2 is a photograph of a typical 

NT551 silicon nitride valve. While impact 

damage in the contact area (against the 

metal seat) is of interest, finite-element 

'JHVSF An NT551 valve showing contact 

surface and laser-scattering scanned 

region. 

modeling predicted that the maximum stress 

may occur at the fillet radius region, so 

subsurface microstructure within the entire 

valve-head surface should be examined. 

Laser-scattering scans were therefore 

performed for the entire valve-head surface, 

from the top of the contact area to the endof 

the fillet radius, as indicated in Figure 2. NDE 

data were obtained for several NT551 siliconnitride valves that were bench-tested for 100 

hours. Figure 3 shows a typical laserscattering image of a valve-head surface. The 

scanned axial length is 19 mm (the top 4-

mm region is the contact area) and is aligned 

in the vertical direction in the image. The 

image data in Figure 3 indicate no significant 

damage from the bench test except the wear 

scars (two darker horizontal stripes) within 

the contact surface. Most of the flaws 

(appearing as high optical-scattering spots) 

are within 50 μm in size, and they are likely 

natural porosity distributions in the ceramic 

material. A few larger flaws are observed near 

the top edge of the valve contact surface. 

'JHVSF Laser-scattering images of valve-head 

section of an NT551 ceramic valve 

after 100-hour bench test. 

Figure 4 shows a comparison of the detailed 

laser-scattering image and a photomicrograph of a typical flaw. The detected flaw is 

clearly seen from the photomicrograph as a 

pre-spall chip partially bonded at the edge. 

99

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

(a) 

(b) 

'JHVSF Detailed laser-scattering image (a) and 

photomicrograph for a flaw at the 

edge of contact surface (b). 

This type of flaw was probably generated 

during valve processing. 

In addition to the material defects such as 

voids and pores that are distributed within 

the ceramic, machining and impact-induced 

damages are two major concerns for the costeffectiveness and reliability of ceramic valves. 

Machining damage is represented by the 

formation of radial, lateral, and median 

cracks under the machined surface. The 

median cracks, which are parallel to the 

machining direction and perpendicular to 

the surface, are thought to cause the greatest 

strength reduction. Machining damage for 

cylindrical silicon nitride specimens was 

evaluated by the laser-scattering method. 

Figure 5 is a photograph of eight SN235P 

rods, four of them machined by fine 

grinding and four by rough grinding. 

Figures 6a and 6b show typical laserscattering images for the fine-ground and 

rough-ground rod, respectively. Material 

defects, likely subsurface pores appearing as 

'JHVSF Photograph of four fine-ground and 

four rough-ground SN235P silicon 

nitride rods. Each is 75 mm long and 

6 mm in diameter. 

individual high-scattering spots, are seen 

distributed throughout the surfaces in both 

rods. Machining damage, the brighter 

horizontal marks along the grinding 

direction, is visible in the image of the 

rough-ground rod (Figure 6b). These 

machining marks are likely median cracks 

that may cause significant strength 

reduction. Machining marks are not 

apparent (indicating less damage) in the fineground rod (Figure 6a).

 (a) (b) 

'JHVSF. Detailed laser-scattering images of (a) 

fine-ground and (b) rough-ground 

SN235P rods; note the grinding 

damage as bright horizontal lines in 

(b). 

Impact damage was evaluated on NT551 

and SN235P rectangular specimens that had 

been subjected to cyclic impact tests. Four 

loads were applied at four different locations 

on each test specimen: 2000, 2500, 3000, 

100 

Heavy Vehicle Propulsion Materials 

and 4000 Newton. The flat polished surfaces 

of the test specimens were loaded with a 

specialized polished silicon nitride sphere 

that had a radius of 3.18 mm. A constant 

load was applied for 106

 cycles in order to 

assess the initiation of cracks and subsequent 

contact damage. The purpose of this 

investigation was to determine laserscattering detection sensitivity on cyclic 

impact damage. 

Figure 7 shows laser-scattering images for 

the surfaces of the impact-tested NT551 and 

SN235P specimens. For the NT551 specimen, 

Figure 7a, dendrite-like scattering structure is 

evident; this structure has been identified as 

the secondary or glassy phase. All impact 

regions for both specimens appear as rings, 

indicating the impact damage to be Hertzian 

in nature. The size of the impact region 

'JHVSF Laser-scattering images of (a) NT551 

and (b) SN235P specimen surfaces; 

each was tested with cyclic impact at 

four indicated loads. 

increases with increasing load, as evidenced 

from the plastic deformation. When the 

scattering images are compared with 

photomicrographs, (Figure 8), impactinduced cracks with higher scattering 

intensities are identifiable in the scattering 

images, suggesting that these cracks have 

different depths and severities. In contrast, 

the extent of subsurface damage cannot be 

predicted from the suface photomicrographs. 

$PODMVTJPOT

An automated laser-scattering NDE system 

was developed to scan entire valves. This 

system uses two rotation and two translation 

stages to align and focus the laser beam on 

the valve surface during the scan; and the 

FY 2003 Progress Report 

(a) 

Laser scattering image Photomicrograph 

(b) 

Laser scattering image Photomicrograph 

'JHVSF Comparison of laser-scattering 

images and photomicrographs for 

3000N-load impact spots in (a) 

NT551 and (b) SN235P specimen. 

resulting 2D scattering image data are used to 

identify the location, size, and relative 

severity of subsurface defects/damage. Laserscattering images were obtained for several 

NT551 silicon nitride valves that were benchtested for 100 hours. These NDE results 

established the detection sensitivity for two 

types of defect/damage: contact/impact 

damage and pre-spalls due to valve 

processing. 

Machining and impact-induced damages, 

two of the major concerns for the costeffectiveness and reliability of ceramic valves, 

were evaluated by laser scattering for 

cylindrical and rectangular NT551 and 

SN235P silicon nitride specimens. The 

machining damage in rough-ground SN235P 

rods can be clearly detected; it likely consists 

of median cracks that may cause significant 

strength reduction. Detection and 

characterization of machining damage may 

help to improve and optimize machining 

conditions for valve manufacturing. The 

impact damage was characterized on NT551 

and SN235P rectangular specimens that had 

101

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

been subjected to cyclic impact tests. By 

comparing the laser scattering images with 

photomicrographs, it was shown that the 

laser-scattering method can identify 

impact-induced cracks having different 

depths and severities. Therefore, the NDE 

data may potentially be used to determine 

the failure probability and reliability of 

ceramic valves that are operated under 

periodic impact stress in diesel engines. 

102 

Heavy Vehicle Propulsion Materials 	 FY 2003 Progress Report 

'%VSBCJMJUZPG%JFTFM&OHJOF$PNQPOFOU.BUFSJBMT

Peter J. Blau with Jun Qu and John J. Truhan Jr* 

Oak Ridge National Laboratory, 

P. O. Box 2008, Mail Stop 6063 

Oak Ridge, TN 37831-6063 

(865) 574-5377; fax: (865) 574-6918; e-mail: blaupj@ornl.gov 

*University of Tennessee, Knoxville 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract Number DE-AC05-00OR22725 

Subcontractor: University of Tennessee, Knoxville, TN 

0CKFDUJWF

• Enable the use of durable, lower-friction moving parts in diesel engines by developing test 

methods to simulate the environment in which engine parts operate, and by conducting 

structural characterization of promising new materials, surface treatments, composites, and 

coatings. 

"QQSPBDI

• Identify diesel engine components that will require advanced materials or surface treatments in 

order to ensure durability while providing low-friction behavior. This work has focused on 

(a) wastegate bushings for exhaust gas recirculation (EGR) components and (b) fuel injector 

plungers. 

• Identify materials, coatings, and/or surface treatments that have the potential to increase the 

durability of the selected engine components. 

• Develop test methods to evaluate the performance of candidate materials under simulated use 

conditions. 

• Develop graphical representations (scuffing control maps) of operating parameters and the wear 

response of the materials to those parameters. 

• Analytically model the effects of applied parameters on the responses of leading candidate 

materials as a guide to materials development and application. 

103

Heavy Vehicle Propulsion Materials 	 FY 2003 Progress Report 

"DDPNQMJTINFOUT

• Designed, built, and used a high-temperature oscillatory scuffing test system that operates at 

wastegate bushing temperatures (~ 600–700oC). 

• Conducted tests on a range of metallic alloys, ceramics, and coatings to determine which of 

these had the best durability under high-temperature conditions. Published a technical report 

on the findings. 

• Developed a novel, pin-on-twin (PoT) scuffing test to evaluate fuel injector materials in diesel 

fuel and low-sulfur fuel. Prepared a mathematical model to more accurately calculate wear loss 

from parts with compound curvatures. 

• Developed criteria for the onset of scuffing damage and evaluated traditional steel fuel injector 

materials as well as ceramics, advanced cermets, and hard coatings in diesel fuel and low-sulfur 

fuel. 

'VUVSF%JSFDUJPO

• Improve the design of the PoT test to enable more realistic simulation of the type of damage 

seen in fuel injector plungers. 

• Develop a graphical representation of the surface damage conditions of fuel injector component 

materials (a scuffing map) to aid designers in selecting more durable materials. 

• Use scuffing maps to model the evolution of localized surface damage and the degradation of 

component durability. 

*OUSPEVDUJPO

The diesel engine industry faces the 

challenges of improving fuel efficiency while 

meeting federal emissions regulations. These 

challenges can be addressed by modifying 

the engine designs and electronic control 

systems for engines and by developing 

exhaust aftertreatments. Such modifications 

affect the mechanical, thermal, and 

chemical environments to which the engine 

materials are subjected, and the current 

structural materials may not perform as well 

as they did in previous designs. 

The objective of this effort is to enable 

the selection and development of durable, 

lower-friction moving parts in diesel engines 

for heavy vehicle propulsion systems 

through the systematic evaluation of 

promising new materials, surface treatments, 

composites, and coating technologies. The 

current approach involves developing test 

methods, conducting microstructural 

analysis of candidate materials, mapping the 

effects of applied parameters on surface 

damage, and modeling. 

In FY 2001, a test method was developed 

to study the high-temperature friction and 

wear characteristics of candidate EGR system 

materials. Selected metallic alloys, ceramics, 

and experimental materials were evaluated 

for their high-temperature scuffing behavior. 

In FY 2002, this effort was extended to 

include an investigation of the scuffing of 

fuel injector component materials. 

Laboratory tests were developed and refined 

to produce and measure the type of finescale surface damage that is observed in 

diesel engine fuel system parts. In FY 2003, 

research continued in two areas: (1) 

evaluating the effects of diesel fuel sulfur 

104 

Heavy Vehicle Propulsion Materials 

reductions on scuffing and (2) materials and 

coatings for high-temperature scuffing 

resistance in EGR components. Analysis of 

surface damage evolution in the 

microstructure was extended by taking 

advantage of a newly upgraded scanning 

acoustic microscope. 

"QQSPBDI

The current approach to improving the 

surface durability of diesel engine 

components has involved extensive 

experimental evaluation, with particular 

focus on characterizing the behavior of 

current and candidate materials under 

conditions that simulate their use. The 

development of analytical models for surface 

degradation, especially for fuel injector 

components, is planned for FYs 2004 and 

2005. 

The focus on EGR components and fuel 

injector plungers was based on past and 

continuing discussions with diesel engine 

manufacturers. Before developing tests to 

evaluate materials for improved durability, it 

was first necessary to understand the 

conditions under which the surfaces of these 

component materials must perform in an 

operating diesel engine. The types of damage 

seen on engine components were reviewed 

in order to ensure that laboratory test 

methods would faithfully reproduce that 

kind of damage. 

FYs 2000–2002 were devoted to selecting 

test geometries, constructing or modifying 

the test apparatus, and obtaining data on 

currently available commercial materials. 

Candidate new materials and surface 

treatments were then evaluated under the 

standardized test conditions to assess their 

potential. This remainder of this report 

summarizes FY 2003 research aimed at 

identifying the best materials choices for two 

engine components, wastegate bushings and 

fuel injector plungers. 

FY 2003 Progress Report 

3FTVMUT#VTIJOH.BUFSJBMT

A wastegate bushing consists of a pin that 

rotates inside a hollow bushing. It is used to 

open and close the valve that controls the 

recirculation of exhaust gases for emission 

control.1

 Smooth, uninterrupted motion is 

essential; but that is difficult to achieve 

considering that the surfaces of the parts are 

exposed to oscillatory motions at 

temperatures as high as 600oC, at which 

traditional lubricants do not work. 

Previously, such components were made of 

austenitic stainless steels, but the demands 

created by new engine designs will require 

more cycles of operation and greater valve 

motion control. Therefore, alternative 

materials or coatings are needed. 

A test apparatus was constructed to 

oscillate a cylindrical pin against a flat plate, 

producing a bow-tie-shaped wear area. The 

geometry was chosen for a variety of reasons: 

providing a linear contact, enabling the 

measurement of frictional torque, keeping 

the fixtures as simple as possible for hightemperature operation, and producing wear 

scars that resembled those on pins taken 

from actual components. Figure 1 shows a 

wear scar produced after 60 minutes of 

testing at 600oC. 

'JHVSF Scar on a test specimen showing 

the typical “bow-tie” shape. 

105

Heavy Vehicle Propulsion Materials 

In order to obtain a comprehensive 

characterization of the test material 

responses, several criteria were combined to 

rank their performance. These included 

average initial stage torque, standard 

deviation in initial torque, average final 

torque, standard deviation in final torque, 

pin specimen wear volume, and surface 

roughness of the lower specimen. A 

summary of the composite scores is given in 

Table 1. Stainless steels of types 303 and 304 

were used as references but were not 

expected to be viable candidates. Test 

couples that involved an Ni3Al intermetallic 

alloy (IC-221) developed at Oak Ridge 

National Laboratory (ORNL) performed very 

well, as did the self-mated combination of 

commercial GallToughTM alloy. The ceramicon-ceramic couple, which ranked fifth, did 

5BCMF Rankings of the material combinations 

for 600oC scuffing resistance (1 = 

highest, 10 = lowest) 

Relative ranking Pin material Tile material 

1 TTZ zirconia Ni3Al alloy, IC 

221 

2 GallToughTM GallToughTM 

3 Stellite 6BTM Ni3Al alloy, IC 

221 

4 Stellite 6BTM Custom 465TM 

5 TTZ zirconia Silicon nitride 

GS-44 

6 Tribonic 20TM Ni3Al alloy, IC 

221 

7 SS 303 SS 304 

8 Stellite 6BTM SS 304 

9 TTZ zirconia SS 304 

10 Stellite 6BTM Pyromet 80TM 

SS = stainless steel 

TTZ = transformation toughened zirconia ceramic 

GallToughTM = a commercial, galling-resistant SS 

from Carpenter Steel 

Stellite 6BTM = a cobalt-based, high-performance 

alloy 

Custom 465TM = a commercial, high-performance 

SS from Carpenter Steel 

Tribonic 20TM = a galling-resistant SS originally 

developed by AK Steel 

Pyromet 80TM = a high-performance SS 

commonly used in engine exhaust valves 

FY 2003 Progress Report 

not perform as well because it did not form a 

lubricative surface oxide or a cushioning 

wear particle layer as did most other material 

pairs. Additional details of this work are 

provided in ORNL report ORNL/TM2003/142, published in March 2003 (see the 

publications list). 

3FTVMUT'VFM*OKFDUPS1MVOHFS.BUFSJBMT

A novel PoT test was developed to 

evaluate the scuffing tendencies of diesel fuel 

injector plunger materials in normal diesel 

fuel and low-sulfur fuel. In this test, a 

cylindrical pin oscillates crosswise on a pair 

of lower cylindrical pins, the axes of which 

parallel the direction of sliding contact (see 

Figure 2). The typical load is 50 N with a 

stroke length of 10 mm and a frequency of 

'JHVSF Specimen arrangement used for 

the pin-on-twin test. 

5 cycles/s. This test produces two notch-like 

wear scars on the upper pin and two wear 

tracks on the lower pins. After a study of 

changes in surface roughness, weight loss, 

and other quantities, the change in friction 

force was selected as a workable criterion for 

the onset of scuffing. Detailed friction force 

changes were captured with a high-speed 

digital data acquisition system (500 data/s). 

106 

Heavy Vehicle Propulsion Materials 

The wave form for the friction-vs-time trace 

of the first stroke is subtracted from that for 

individual strokes obtained at longer and 

longer sliding distances. When a significant 

difference is detected in the pattern, scuffing 

is said to have initiated. Digital records also 

revealed that scuffing in most material 

combinations initiates at the ends of the 

stroke and spreads inward. This is consistent 

with the lubrication concepts developed by 

German investigator R. Stribeck, who 

showed that friction of lubricated contacts is 

related to viscosity, velocity, and contact 2

pressure. In reciprocating sliding (for the 

PoT) the friction force is lowest in the center 

of the stroke where the sliding speed is 

highest; thus damage initiates at the stroke 

ends. 

A variety of materials was evaluated using 

the PoT test in several lubricants: mineral oil, 

diesel fuel 2, and Jet A aviation fuel, a 

surrogate for low-sulfur fuel. Initial tests were 

performed on typical plunger materials such 

as hardened bearing steel (Type 52100). 

More recent experiments focused on 

ceramics, cermets (Ni3Al matrix with TiC 

particles, obtained from ORNL and Southern 

Illinois University), and hard-coated (TiN) 

tool steel materials obtained from a 

commercial source. Table 2 lists recently 

evaluated candidate material combinations 

and their relative resistance to scuffing 

initiation, as determined by friction changes 

in the PoT test procedure. The upper 

oscillating pin was hardened 52100 steel in 

each case. Test results using candidate 

plunger materials for the upper pin instead 

of the lower twins has produced different 

results, and the latter type of test is 

undergoing further analysis to establish the 

standard protocol for further experiments. 

$PODMVTJPOT

• An intermetallic Ni3Al alloy coupled with 

zirconia represents an attractive 

FY 2003 Progress Report 

5BCMF Material combinations and relative 

scuffing initiation time 

5XJOQJOT  

NBUFSJBM %JFTFMGVFM -PX4GVFM

52100 M M 

Zirconia (TTZ) L M 

Cermet (C-10) M M 

Cermet (SIU M L 

1-20) 

Cermet (SIU S M 

3-27) 

TiN-coated S S 

steel 

S = short time (within the first 20 m sliding distance)

M = intermediate time (within 20–36 m sliding 

distance)

L = relatively long time ( > 50 m sliding distance)

TTZ = transformation toughened zirconia ceramic 

C-10 = experimental cermet containing a Ni3Al 

matrix and TiC particles 

SIU = compositions prepared at Southern Illinois 

University 

combination for high-temperature 

scuffing resistance in EGR applications 

• Using a new PoT test and a differential 

friction trace-based scuffing criterion, 

ceramics, cermets, and hard coatings 

were evaluated for use in fuel injection 

systems. Cermets appear promising for 

this application and will be further 

investigated during the next fiscal year. 

• Future plans include the development of 

scuffing maps and models to help select 

materials for reciprocating contacts. 

3FGFSFODFT

1. B. Bhushan, ed., Modern Tribology 

Handbook, Vol. 2, CRC Press, pp.1231–1269, 

2001. 

2. R. Stribeck, “Die Wesentlichen 

Eigenschaften der Gleit- und Rollenlager,” Z. 

Verein. Deut. Ing., (38), 1341–1348, 1902. 

107

Heavy Vehicle Propulsion Materials 	 FY 2003 Progress Report 

1VCMJDBUJPOTBOE1SFTFOUBUJPOT Transportation, Copper Mountain, CO, 

August 3–8, 2003 (to be included in the P. J. Blau, Transient Scuffing of Candidate proceedings). Diesel Engine Materials at Temperatures up J. Qu, P. J. Blau, R. Ott, and J. Truhan, to 600oC, ORNL/TM-2003/142, Oak Ridge “The Development of a Pin-on-Twin Scuffing National Laboratory, 2003. Test to Evaluate Materials for Heavy Duty Jun Qu, Peter J. Blau, and John Truhan, Diesel Fuel Injectors,” poster presented at the “Detecting of the Onset of Localized Scuffing 2003 International Conference on Wear of with the Pin-on-Twin Fuel-Lubricated Test Materials, Washington, D.C., March 31–April for Heavy Duty Diesel Fuel Injectors,w 3, 2003. presented at Boundary Lubrication for 

108 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

G. Life Prediction of Diesel Engine Components 

H. T. Lin, T. P. Kirkland, A. A. Wereszczak, M. K. Ferber, and M. J. Andrews* 

Oak Ridge National Laboratory 

P. O. Box 2008, MS-6068 

Oak Ridge, TN 37831-6068 

(865) 576-8857; fax: (865) 475-6098; e-mail: linh@ornl.gov 

*Caterpillar, Inc. 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Objectives 

•	 Generate database and characterize damage mechanisms of candidate advanced ceramics and 

intermetallic alloys. 

•	 Apply and verify probabilistic life prediction and component design and verification for 

advanced diesel engine components. 

Approach 

•	 Evaluate the dynamic fatigue and rotary bending fatigue performance of candidate silicon 

nitride ceramics and titanium aluminide (TiAl) alloys at elevated temperatures in air before and 

after long-term exposure to simulated engine environments and before and after engine field 

tests. 

•	 Characterize the evolution and role of damage mechanisms and changes in microstructure that 

are linked to the long-term mechanical performance and reliability of ceramics and 

intermetallic alloys. 

•	 Use life prediction codes to predict the probability of failure and reliability of complex-shaped 

components subjected to application conditions. 

Accomplishments 

•	 Completed dynamic fatigue tests at temperatures of up to 1000°C in air for a commercial-grade 

silicon nitride, SN147-31N, purchased from Ceradyne, Inc. 

•	 Completed flexural strength evaluation for an Ni3Al intermetallic alloy after 1000 h of exposure 

to exhaust gas environments. 

•	 Completed a dynamic fatigue database for Kyocera SN235P silicon nitride fabricated with the 

same powder batch for Caterpillar exhaust valve blanks. 

•	 Completed modification of a rotary bending fatigue test rig required for testing TiAl specimens 

at temperatures of up to 800°C in air. 

109 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

Future Direction 

•	 Develop a dynamic fatigue database for a commercial-grade silicon nitride, SN147-31E, 

purchased from Ceradyne, Inc. 

•	 Develop a dynamic fatigue database for flexure test bend bars machined from Kyocera SN235 

exhaust valve blanks to verify mechanical performance. 

•	 Develop a rotary bending fatigue database for TiAl alloys after oil immersion testing at 

temperatures of up to 800°C in air. 

•	 Evaluate the mechanical properties of prototype SN235P silicon nitride exhaust valves after 

bench rig and preliminary engine tests and verify the probabilistic component life prediction. 

Introduction 

Advanced ceramics and intermetallic 

alloys have potential for extensive use in 

applications in advanced diesel engine 

systems because of their superior 

thermomechanical properties at elevated 

temperatures. Implementation of 

components fabricated from these advanced 

materials would lead to significant 

improvements in engine efficiency and longterm durability and to reduction of NOx and 

CO exhaust emissions, as required in the 21st 

Century Truck Program. Interest in these 

materials has focused primarily on research 

in characterization and design methodology 

development (life prediction) for advanced 

silicon nitride ceramics and TiAl alloys to 

enable the manufacture of consistent, 

reliable complex-shaped components for 

diesel engine applications. The valid 

prediction of mechanical reliability and 

service life is a prerequisite for successful 

implementation of these advanced materials 

as internal combustion engine components. 

Three primary goals of this research 

project contribute toward successful 

implementation: 

•	 generation of a mechanical engineering 

database of results of performance tests of 

candidate materials from ambient to high 

temperatures, conducted before and after 

exposure to simulated engine 

environments; 

•	 microstructural characterization of failure 

phenomena in these advanced materials 

and in components fabricated from 

them; 

•	 application and verification of 

probabilistic life prediction methods 

using diesel engine components as test 

cases. 

For all three stages, results will be 

provided to both the material suppliers and 

component end-users to help them refine 

and optimize processing parameters. Doing 

so will help them achieve consistent 

mechanical reliability and validate the 

probabilistic design and life prediction of 

engine components made from these 

advanced materials. 

Approach 

All silicon nitride test bend bars were 

longitudinally or transversely machined, 

according to ASTM standard C1161,1

 from 

production billets purchased from material 

suppliers. Flexure testing was conducted in 

ambient air in four-point bending using 

20−40-mm, α-SiC, semi-articulating fixtures 

at temperatures ranging from 20 to 1000°C 

and at a stressing rate of 30 MPa/s and 0.003 

MPa/s. The 30 MPa/s test condition was 

chosen to evaluate the inert characteristic 

strength as a function of temperature, while 

the 0.003 MPa/s test condition was chosen to 

measure the change in slow crack growth 

(SCG) susceptibility at elevated temperatures. 

Pneumatic actuators were programmed to 

110 

Heavy Vehicle Propulsion Materials 

produce the desired loading rate (and 

corresponding stressing rate) via a personal 

computer. Load was continuously measured 

as a function of time, and flexure strength 

was calculated using ASTM C1161. The 

accumulated strength data were then further 

analyzed. The strengths for each test set were 

fit to a two-parameter Weibull distribution 

using the program CERAMIC,2

 which uses 

maximum likelihood estimation advocated 

in ASTM C1239.3

 Reported results are 

uncensored because fractography analysis 

was not conducted in detail to identify 

strength-limiting flaws for all of the bend 

bars tested. Following dynamic fatigue tests, 

both optical and scanning electron 

microscopy (SEM) analysis were carried out 

on fracture surfaces and polished crosssections of selected bend bars to characterize 

the fracture and degradation mechanisms. Xray analysis was also carried out to evaluate 

the possible phase changes resulting from 

oxidation during dynamic fatigue testing or 

after long-term exposure to simulated engine 

environments, which could possibly cause 

degradation in mechanical performance and 

reliability. 

Results 

Dynamic Fatigue Response of Advanced 

Silicon Nitride Ceramics 

At present there are a limited number of 

material suppliers that could provide 

consistent and reliable material resources and 

supporting efforts to the end users. The lack 

of committed materials suppliers could 

hamper the smooth implementation of 

silicon nitride ceramic components for 

advanced diesel engine applications. Thus it 

is important to extend the database 

generation efforts to other potential 

candidate silicon nitride ceramics, especially 

those manufactured by domestic material 

suppliers. Studies of dynamic fatigue 

behavior in four-point bending for a 

commercial-grade silicon nitride (i.e., SN147­

31N, Ceradyne Advanced Ceramic 

FY 2003 Progress Report 

Operation, Inc., CA) were carried out in 

FY 2003. The database generated will be 

compared with those previously generated 

for SN235 and SN235P silicon nitride 

(Kyocera Industrial Ceramics Corp., WA). 

Note that both SN235 and SN235P were 

down-selected for prototype exhaust valve 

evaluation because of their excellent 

resistance to SCG and diesel engine 

environments. The database will also be 

provided to Caterpillar for probabilistic life 

prediction for exhaust valve components. 

Dynamic fatigue test results at 20 and 

850°C showed that the longitudinally 

machined SN147-31N exhibited inert 

characteristic strength values between those 

obtained for SN235 and for SN235P (as 

shown in Table 1). In addition, the SN147­

31N exhibited Weibull moduli comparable to 

the values obtained for SN235 and SN235P 

under the same test conditions. In addition, 

the strength versus stressing rate curves 

showed that the SN147-31N exhibited a 

fatigue exponent of 47 and 131 at 20 and 

850°C, respectively (Figure 1). The increase in 

fatigue exponent with increased test 

temperature could indicate the onset of SCG 

and/or creep deformation processes, evident 

by the permanent curvature observed for 

those SN147-31N bend bars fractured after 

testing at 850°C and 0.003 MPa/s. 

The effect of machining orientation on 

the mechanical response of SN147-31N 

silicon nitride was also evaluated in FY 2003. 

Mechanical tests for transversely machined 

bend bars would be more representative of 

strength obtained for the ceramic valves, 

which would be transversely machined in 

the actual component production lines. 

Results of dynamic fatigue tests at 20 and 

850°C showed that the transversely 

machined SN147-31N exhibited inert 

characteristic strengths about 14–19% lower 

than those obtained for the longitudinally 

machined specimens (Table 1). A similar 

reduction in strength of transversely 

machined samples was also previously 

reported for the cases of SN235 and SN235P 

silicon nitride. Also, SN147-31N revealed 

111 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

Table 1. Summary of uncensored Weibull and strength distributions for Ceradyne SN147-31N silicon 

nitride and Kyocera SN235P specimens. Data of previously tested transversely machined 

Kyocera SN235/SN235P are used for reference. 

Material 

No. 

tested 

Stressing 

rate 

(MPa/s) oC 

Uncensored 

Weibull 

modulus 

± 95% 

Uncensored 

Weibull 

modulus 

Uncensored 

characteristic 

strength 

(MPa) 

± 95% 

Uncensored 

characteristic 

strength 

(MPa) 

SN235 15 30 20 23.8 15.4, 

33.9 

901 879, 

923 

SN235P 15 30 20 38.1 24.0 

55.8 

666 656, 

676 

SN147­

31N* 

15 30 20 21.73 14.07. 

31.09 

836 814, 

858 

SN147­

31N* 

15 0.003 20 20.70 13.38, 

29.67 

694 675, 

713 

SN147­

31N** 

15 30 20 13.76 8.96, 

19.59 

677 649, 

705 

SN235PCP*** 30 30 20 11.94 8.58, 

15.94 

820 794, 

847 

SN235PCP*** 30 0.003 20 14.56 10.93, 

18.64 

741 721, 

761 

SN235 15 30 850 26.7 18.0, 

36.7 

777 760, 

793 

SN235P 15 30 850 19.3 12.5, 

27.6 

631 612, 

649 

SN147­

31N* 

15 30 850 20.35 13.58, 

28.20 

777 755, 

799 

SN147­

31N** 

15 30 850 18.26 11.67, 

26.47 

639 619, 

659 

SN235 14 0.003 850 18.5 11.8, 

26.8 

744 720, 

767 

SN235P 15 0.003 850 18.2 11.5, 

26.8 

594 575, 

612 

SN147­

31N* 

15 0.003 850 16.19 10.57, 

23.02 

732 706, 

757 

SN147­

31N** 

15 0.003 850 19.95 12.83, 

28.63 

620 602, 

638 

SN235PCP*** 30 30 850 20.56 15.16, 

26.87 

684 671, 

697 

SN235PCP*** 30 0.003 850 19.44 14.49, 

25.01 

621 608, 

633 

*Denotes SN147-31N specimens were longitudinally machined, **denotes SN147-31N specimens were machined 

transversely, and ***denotes SN235P-CP specimens were longitudinally machined from co-processed billets of 

exhaust valve blanks. 

strength values comparable to those of 

SN235P under the same machining and test 

conditions. In addition, there were minor 

differences in Weibull moduli between 

longitudinally and transversely machined 

SN147-31N specimens, suggestive of similar 

strength-limiting flaws governing the 

fracture of specimens. The obtained Weibull 

moduli were also comparable to those 

reported for SN235 and SN235P under the 

same test conditions. 

On the other hand, the strength versus 

stressing rate curves showed that the SN147­

31N exhibited high fatigue exponents (N ~ 

132 and 343) at 850°C, independent of the 

machining orientation (Figure 2). However, a 

permanent curvature was observed for those 

SN147-31N bend bars after testing at 850°C 

and 0.003 MPa/s, indicating onset of SCG 

and/or creep processes, presumably as a 

result of the softening of the secondary 

glassy phase. The contribution of the 

softening of secondary phase(s) to SCG/creep 

processes has also been reported for 

Honeywell GS44 silicon nitride.4

 SEM 

examination on the fracture surface of 

112 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

Figure 1. Strength vs. stressing rate curves of 


SN147-31N silicon nitride,


longitudinally machined. 


Figure 2. Strength vs. stressing rate curves of 

SN147-31N silicon nitride, transversely 

machined. Data from specimens 

longitudinally machined are used for 

reference. 

selected SN147-31N samples tested at 850°C 

and 0.003 MPa/s showed the presence of 

glassy ligaments on silicon nitride grains, 

indicating the softening of the secondary 

phase at test temperature (as shown in 

Figure 3). The addition of oxygen in the 

secondary phase along the crack paths will 

further decrease the softening temperature 

and viscosity, facilitating the time-dependent 

degradation processes. Therefore, dynamic 

fatigue results suggest that the application 

limit of SN147-31N silicon nitride will be 

< 800°C in air. 

Studies of dynamic fatigue for Kyocera 

SN235P silicon nitride, manufactured with 

the same powder batch employed for the 

exhaust valve blanks, were also carried out in 

FY 2003. The objective of this study was to 

verify the mechanical performance of coprocessed SN235P (designated as SN235P-CP) 

Figure 3. SEM fracture surface of SN147-31N 

specimen tested at 850°C and 0.003 

MPa/s. Note that glassy ligaments 

observed on elongated grains indicated 

the softening of secondary phase at 

temperature. 

for Caterpillar exhaust valve application. 

Note that the SN235P-CP MOR bend bars 

were machined using the revised ASTM C116 

standard with a 600-grit surface finish. 

Results of dynamic fatigue tests at 20°C 

showed that the SN235P-CP silicon nitride 

exhibited inert characteristic strengths that 

were about 9% lower and 23% higher than 

those previously obtained for SN235 and 

SN235P silicon nitride, respectively 

(Table 1).5

 The higher inert characteristic 

strength of the SN235P-CP could be 

attributed to the finer surface finish (600 

grit) with respect to the 320-grit surface 

finish employed for the SN235P MOR bars 

tested previously. In addition, the SN235PCP exhibited a lower Weibull modulus (m = 

11.9) than the values obtained for SN235 (m 

= 23.8) and SN235P (m = 38.1), as shown in 

Table 1. The lower Weibull modulus 

obtained by SN235P-CP might result from 

the different strength-limiting flaw 

population present in the SN235P-CP with 

respect to that present in SN235P. Similar 

higher-strength response of SN235P-CP 

compared with SN235P was also observed at 

850°C under the same stressing rate. On the 

other hand, the failure stress versus stressing 

rate curves at 20 and 850°C showed that the 

SN235P-CP exhibited high fatigue exponents 

(N ~ 111 and 93, respectively), indicating 

high resistance to the SCG process (Figure 4). 

113 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

The high fatigue exponents obtained for 

SN235P-CP were consistent with the high N 

values previously obtained for SN235P as 

well as SN235. Therefore, dynamic fatigue 

results suggest that the SN235P-CP would 

meet the application criteria for exhaust 

valve components for advanced diesel 

engines. 

Mechanical Properties of Intermetallic 

Alloys 

We also completed evaluating the 

mechanical properties of an Ni3Al 

intermetallic alloy, fabricated by the 

extrusion process by the University of 

Missouri, after 1000 h of exposure to a diesel 

engine exhaust gas environment at 850°C. 

The Ni3Al alloy has been considered as one of 

the candidate advanced intermetallic alloys 

for exhaust valve applications. The roomtemperature results showed that the Ni3Al 

Figure 4. Failure stress vs. stressing rate curve of 

SN235P silicon nitride longitudinally 

machined and tested at 20 and 850°C in 

air. Note that the SN235P was 

machined from co-processed billets of 

exhaust valve blanks. 

alloy exhibited no strength degradation after 

1000 h of exposure, indicating excellent 

mechanical reliability in an exhaust gas 

environment (Figure 5). SEM examination of 

fracture surfaces of exposed bend bars 

showed the presence of Al2O oxide scale 3

(~10 μm thick) on the surface resulting from 

the oxidation of Ni3Al (Figure 6); and the 

surface exhibited fractures that were 

intergranular in nature. Note that the asmachined Ni3Al bend bars mostly failed as a 

result of the machining mark (flaw). In 

addition, energy-dispersive X-ray analysis 

showed no elements from exhaust gas were 

detected in the bulk region immediately 

underneath the oxide scale, suggesting good 

long-term chemical stability. A study of the 

effects of long-term oil immersion testing at 

850°C in air will be planned to further 

confirm the mechanical reliability and 

chemical stability of Ni3Al alloy in diesel 

engine environments. 

Figure 5. Flexural strength of Ni3Al alloy, asmachined and after 1000 h exposure in 

diesel exhaust gas environment. 

References 

1. “Standard Test Method for Flexural 

Strength of Advanced Ceramics at Ambient 

Temperatures,” ASTM C1161, Annual Book of 

ASTM Standards, Vol. 15.01, American 

Society for Testing and Materials, West 

Conshohocken, PA, 1999. 

2. Life Prediction Methodology for Ceramic 

Components of Advanced Heat Engines, Phase 1, 

ORNL/Sub/89-SC674/1-2, prepared by 

AlliedSignal Engines, Phoenix, AZ, 

DOE Office of Transportation Technologies, 

1995. 

3. “Practice for Reporting Uniaxial 

Strength Data and Estimating Weibull 

Distribution Parameters for Advanced 

Ceramics,” ASTM C1239, Annual Book of 

ASTM Standards, Vol. 15.01, American 

Society for Testing and Materials, West 

Conshohocken, PA, 1999. 

4. A. A. Wereszczak, H. -T. Lin, T. P. 

Kirkland, M. J. Andrews, and S. K. Lee, 

“Strength and Dynamic Fatigue of Silicon 

114 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

Figure 6. SEM fracture surface of Ni3Al bend bar 

after 1000 h exposure to an exhaust gas 

environment and tested at room 

temperature. 

Nitride at Intermediate Temperatures,” J. 

Mater. Sci. 37 (2002) 2669–684. 

5. H. T. Lin, T. P. Kirkland, M. K. Ferber, 

and M. J. Andrews, “Life Prediction of Diesel 

Engine Components,” Heavy Vehicle 

Propulsion System Materials Program 

Bimonthly Technical Progress Report to DOE 

Office of Transportation Technologies, 

January–March 2001. 

Publications 

1. A. A. Wereszczak, H. -T. Lin, T. P. 

Kirkland, M. J. Andrews, and S. K. Lee, 

“Strength and Dynamic Fatigue of Silicon 

Nitride at Intermediate Temperatures,” J. 

Mater. Sci. 37 (2002) 2669–2684. 

115 


Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

H. Low-Cost Manufacturing of Precision Diesel Engine Components 

S. B. McSpadden 

Oak Ridge National Laboratory 

P.O. Box 2008, MS-6069 

Oak Ridge, Tennessee 37831-6069 

(865) 574-5444; fax: (865) 574-6098; e-mail: mcspaddensb@ornl.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Objectives 

• To develop and demonstrate optimized, cost-effective fabrication processes for producing 

precision components for use in diesel engines. 

• To develop and demonstrate optimized, cost-effective, non-destructive testing methods for 

detecting and preventing machining-induced damage in engine components. 

Approach 

• Collaborate with universities (e.g., North Carolina State University and University of Michigan) 

on applied machining research. 

• Collaborate with manufacturers of machine tools (e.g., K.O. Lee Company) and manufacturers 

of consumable materials (such as coolants and grinding wheels) to develop “enabling 

technology” that can be applied to the process of machining exotic materials. 

• Collaborate with manufacturers of diesel engines (e.g., Cummins and Caterpillar), that use our 

facilities to study the fundamentals of machining processes. 

• Continuously improve our instrumentation, data collection and analysis software, and 

machining, grinding and dimensional inspection equipment consistent with our available 

budget. 

Accomplishments 

• Improved the performance of consumable supplies such as the superabrasive grinding wheels 

that are needed to produce precision engine components. 

• Developed nondestructive inspection methods to evaluate machined components for residual 

stresses and subsurface damage caused by the machining process. 

• Investigated machinability issues that have hindered the acceptance of lighter-weight, higherperformance materials in high-volume production applications. 

117 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

Future Direction 

• Continue to develop improved instrumentation and test methodologies for optimizing 

grinding, turning, milling, drilling, and other machining processes. 

• Investigate the aggressive grinding of zirconia with both superabrasive and conventional 

grinding wheels. 

• Address manufacturing issues related to the use of titanium alloys in engine components such 

as crankshafts, camshafts, valves, and other components where high strength and light weight 

are issues. 

• Investigate the use of machining debris (chips and grinding swarf) as an inexpensive source of 

structural materials with extremely fine grain size (tens of nanometers). 

Introduction 

For many materials, such as 

ceramics and hardened tool steels, 

grinding is the only practical 

machining process available to 

producers of heavy-duty diesel engines. 

The cost of consumable grinding wheels 

is a major component in the overall 

cost of the grinding process. Engine 

component manufacturers must choose 

between “conventional” grinding 

wheels that have a relatively low initial 

cost but high operating cost, and 

superabrasive wheels that have a high 

initial cost but much lower operating 

cost. 

Wheel manufacturers are concerned 

with producing wheels that are durable, 

consistent in composition, inexpensive 

to produce, and capable of producing 

large numbers of high-quality parts 

with little variation in dimensions and 

surface texture. The most important 

measure of a wheel’s performance 

relative to these goals is the grinding 

ratio, often called the G-ratio. G-ratio is 

simply the volume of workpiece 

material removed divided by the 

volume of wheel material consumed, 

v 

and it is expressed as G = 

part . A very 

vwheel 

high G-ratio is desirable, which means 

that the denominator, representing the 

volume of worn wheel material, will be 

small relative to the numerator. Because 

superabrasive wheels tend to wear very slowly, 

it is often necessary to grind large volumes of 

workpiece material in order to generate 

measurable wear. Unfortunately, this is 

incongruous with a laboratory test 

environment, where it is desirable to minimize 

the amount of workpiece material removed so 

that test times and waste-disposal costs can be 

minimized. In many cases, a 2-hour laboratory 

grinding experiment will generate a wheel 

wear groove that is only a few microns deep. 

Thus, it is important to develop very accurate 

measurements of wheel wear to minimize error 

and ensure repeatability of test results. 

Conventional grinding wheels, made from 

aluminum oxide or silicon carbide in a 

vitreous bond, can cost anywhere from a few 

dollars to a few hundred dollars, depending on 

their size and composition. These wheels 

typically can be used to produce only a small 

number of production parts before they need 

to be reconditioned—a process called truing. 

The truing process is costly not only because 

the grinder must stop producing parts while 

the truing is done but also because truing 

consumes the grinding wheel at least as fast as 

the process of producing parts. 

Superabrasive grinding wheels are made 

from industrial-quality diamond abrasive 

(natural or synthetic) or from cubic boron 

nitride abrasive in a vitreous, resin, or metallic 

bond system. 

Typically, G for a conventional grinding 

wheel can vary from less than one to a few 

hundred, depending on the workpiece material 

and grinding conditions used. For a 

118 

Heavy Vehicle Propulsion Materials 

superabrasive wheel, G can range from a 

few hundred to several thousand, 

depending on the same conditions. 

However, G does not take into account 

the cost of lost production time; wheel 

material lost in the truing process; or 

the additional time spent in changing 

wheels, additional inventory costs, etc. 

Therefore, the decision as to which type 

of wheel is most cost-effective is not 

straightforward. There is great interest 

among wheel manufacturers and end 

users alike in testing wheel performance 

on specific combinations of grinding 

wheels and workpiece materials. 

During the past year, three different 

grinding wheel manufacturers 

collaborated with ORNL to test new 

abrasive grain and bond systems and to 

evaluate the performance of their 

superabrasive and conventional 

grinding wheels. In addition, Cummins 

Engine conducted wheel performance 

tests at ORNL to evaluate the feasibility 

of using a single grinding wheel for 

grinding parts that may be made from 

either tool steel or zirconia. Their goal is 

to use a single grinding machine to 

grind either type of part material 

without stopping the machine for a 

time-consuming wheel change. 

Approach 

ORNL has developed a systematic 

method for grinding wheel 

performance evaluation. The method 

focuses on a few major process elements 

that can easily be monitored, varied, 

and controlled; and it attempts to hold 

the remaining elements constant 

throughout the evaluation process. 

Figure 1 shows the major elements for a 

surface grinding process. The word 

“element” is used to denote any 

component of the grinding process; it 

can comprise process requirements or 

characteristics, workpiece requirements 

or attributes, parameters that are 

FY 2003 Progress Report 

Figure 1. The major process elements for surface 


grinding can be arbitrarily categorized 


into groups that are constrained and 


selectable but fixed, variable, or 


monitored.


deliberately varied and used to control the 

process, or parameters that are held constant. 

Before selecting a fabrication process, the 

engineer usually knows the workpiece 

requirements—the desired size, shape, 

dimensions, tolerances, surface finish, and 

other elements related to the form and 

function of the workpiece. The required 

production rate is also usually known. These 

elements are usually fixed by design, and they 

constrain the selection of an appropriate 

grinding machine, tooling, etc. 

The engineer has more latitude with 

respect to the selection of an appropriate 

grinding wheel, truing and dressing method, 

and coolant. These choices are based largely on 

prior experience, machinability handbook data 

(when they exist), and recommendations from 

the manufacturers of grinding wheels and 

coolants. Once these process elements are 

chosen, they are usually held constant for 

convenience. A test matrix can then be 

constructed to systematically vary the 

remaining process elements, which usually 

include the material removal rate or the wheel 

speed. During the grinding tests, 

instrumentation and process-monitoring 

software are used to measure and record 

119 

Heavy Vehicle Propulsion Materials 

grinding forces, spindle power, and 

vibration. These data are stored to disk 

in a format that can be easily retrieved 

for later analysis. In addition to these 

important monitored characteristics, 

grinding wheel performance evaluation 

comprises the grinding ratio (G), the 

surface finish of the ground workpiece, 

the specific grinding energy (u), and the 

grinding efficiency (E), all of which can 

be either measured directly or 

calculated from the stored data. 

In addition to collecting and 

analyzing on-machine data, it is also 

necessary to obtain an accurate and 

repeatable measurement of wear on the 

surface of the grinding wheel. During 

the past year, ORNL measured wheel 

wear with three independent, 

nondestructive methods and compared 

the results to determine the most 

effective method of measurement. 

These methods incorporated the Taylor 

Hobson Talysurf surface profiler, the 

Rodenstock non-contact laser profiler, 

and the EMD Legend coordinate 

measuring machine. Each of these 

instruments evaluates the wear profile 

using a slightly different method. Our 

initial results show reasonably good 

agreement among all three methods, 

but the Rodenstock is the fastest and 

simplest instrument to use. 

Results 

Cummins Engine conducted a 

performance evaluation test at ORNL to 

determine if a single grade of 

superabrasive grinding wheel could be 

used to grind both hardened 52100 tool 

steel and zirconia. The grinding wheel 

was mounted on the grinding spindle, 

trued, balanced with an automatic 

balancer, and dressed. (Truing is the 

process of selectively removing material 

from the periphery of the grinding 

wheel to ensure that it has minimal 

run-out; i.e., the wheel “runs true” to 

FY 2003 Progress Report 

the centerline of the grinding spindle. A wheel 

that is not properly trued and balanced will 

generate parts that have a poor surface finish. 

Dressing is the process of removing a thin 

layer of abrasive material and bond material to 

ensure that the abrasive grains are sharp and 

exposed to the workpiece.) 

The primary purpose of the grinding wheel 

performance evaluation test was to generate 

measurable wear on the grinding wheel under 

controlled grinding conditions. The K.O. Lee 

Vigor creep feed surface grinder was used for 

the tests, and the machine setup is shown in 

Figure 2. (The figures shows a conventional 

wheel—not the actual superabrasive wheel 

Figure 2. A typical setup for measuring grinding 

wheel performance on the K.O. Lee 

creep-feed surface grinder. 

used in this experiment.) The wheel rotated in 

a clockwise direction at a fixed speed. It was 

automatically balanced using a 

microprocessor-controlled balancer. The 

workpiece was mounted in a vice atop a 

dynamometer, which was attached to the 

grinder worktable by an electromagnetic 

chuck. The worktable reciprocated to the left 

and right. Coolant was delivered through the 

nozzle at the right of the wheel, and coolant 

velocity was adjusted so that it closely 

matched the wheel velocity. The wheel was 

moved downward a small amount just before 

the worktable moved from left to right and 

was then raised up slightly while the table 

returned to its starting position on the left. 

120 

Heavy Vehicle Propulsion Materials 

This ensured that grinding was done in 

one direction only; this mode of 

grinding is referred to as “up” grinding. 

Tangential and normal forces and 

grinding spindle power consumption 

were measured during each grinding 

cycle. A fixed volume of workpiece 

material was removed during a 

predetermined number of grinding 

cycles. 

The wheel was then moved under 

computer control until it was 

positioned above the wear coupon. 

Since the wheel was wider than the 

workpiece, the center portion of the 

wheel exhibited wear, while the edges 

did not. The wheel was then plunged 

into the wear coupon, and a mirror 

image of the profile was imparted to the 

coupon. 

Using the Rodenstock RM-600 noncontact laser surface-profiling 

instrument to scan the wear coupon, a 

wear profile such as the one shown in 

Figure 3 was generated. The grinding 

wheel diameter was known, and the 

Figure 3. This wheel wear profile was obtained 

from the Rodenstock laser surface 

profiler. The step height, which 

represents radial wear of the grinding 

wheel, is approximately 16 μm. 

area under the wear profile curve was 

assumed to be uniform over the entire 

circumference of the wheel. Therefore, 

the volume of wheel wear could be 

easily calculated. Finally, the grinding 

ratio was computed as the ratio of the 

FY 2003 Progress Report 

volume of workpiece removed to the volume 

of grinding wheel consumed during the test. 

This sequence was repeated for combinations 

of three different table speeds, three different 

downfeeds, and two material types. The wheels 

were then ranked according to their wear 

characteristics. 

The surface roughness of the workpiece is 

also an important consideration in evaluating 

wheel performance. Roughness is strongly 

influenced by the type of wheel used and the 

grinding conditions chosen. Surface finishes 

were measured using the Form Talysurf Model 

120 surface profiling and roughness 

instrument. In addition to being measured for 

surface roughness, each workpiece is evaluated 

qualitatively for burrs, evidence of surface 

regions that have overheated (burning), and 

repetitive surface imperfections (chatter). 

The normal and tangential forces measured 

during the grinding tests were evaluated to 

ensure that the wheel performance was 

consistent throughout the tests and that wheel 

wear occurred in a more or less linear fashion. 

The spindle power consumption was measured 

and recorded during each grinding test. 

Spindle power can be used to compute the 

amount of energy required to remove a specific 

volume of workpiece material. This quantity, 

frequently referred to as specific grinding 

energy (u), is another important measure of 

the overall performance of a grinding wheel. 

Analysis of the test results is not complete at 

this time. However, a number of interesting 

trends were observed. As expected, for 52100 

tool steel (hardened to 58-63 Rc), the grinding 

ratio (G) decreased as the specific material 

removal rate (Q’) increased, as shown in 

Figure 4. It is not clear whether table speed or 

downfeed had the greater influence on G. In 

general, increasing either the table speed or 

downfeed (while holding the other variable 

constant) caused a decrease in G. 

The results for zirconia were surprising. As 

can be seen in Figure 5, over much of the 

range investigated, the G-ratio actually 

increases as the specific material removal 

121 

Heavy Vehicle Propulsion Materials 

Figure 4. For hardened tool steel, grinding ratio 

(G) is inversely proportional to the 

specific material removal rate (Q’) 

within the range of table speeds and 

downfeeds investigated. 

rate increases. The trend line shown is a 

fourth-order polynomial and appears to 

fit the data reasonably well. 

Furthermore, the zirconia appeared to 

grind more easily as table speeds were 

increased. During the most aggressive 

grinding test, the zirconia was being 

ground at removal rates four times as 

high as the highest achievable rate for 

tool steel. 

Figure 5. For zirconia, the relationship between 

grinding ratio (G) and specific material 

removal rate (Q’) within the range of 

table speeds and downfeeds 

investigated is complex. 

Conclusions 

Additional investigation of the 

grinding characteristics of zirconia is 

FY 2003 Progress Report 

warranted to determine an optimum set of 

grinding conditions. Furthermore, the effect of 

“aggressive” grinding conditions on 

mechanical properties and the potential for 

subsurface damage due to machining needs to 

be investigated. 

Publications/Presentations 

S. B. McSpadden, G. R. Hughes, “A 

Systematic Method for Grinding Wheel 

Performance Evaluation,” International Grinding 

2003, Itasca, IL, Society of Manufacturing 

Engineers, 2003. 

A. J. Shih, A. C. Curry, R. O. Scattergood, T. 

M. Yonushonis, D. J. Gust, M. B. Grant, S. B. 

McSpadden, T. Watkins, “Grinding of Zirconia 

using the Dense Vitreous Bond Silicon Carbide 

Wheel,” Journal of Manufacturing Science and 

Engineering, 125, 297–303, (2003). 

A. C. Curry, A. J. Shih, R. O. Scattergood, J. 

Kong, and S. B. McSpadden, “Grinding 

Temperature Measurements in MgO PSZ Using 

Infrared Spectrometry,” J. Am. Ceram. Soc., 86, 

333–341, 2003. 

W. I. Clark, A. J. Shih, C. W. Hardin, R. L. 

Lemaster, S. B. McSpadden, “Fixed Abrasive 

Diamond Wire Machining—Part I: Process 

Monitoring and Wire Geometry and Tension,” 

International Journal of Machine Tools and 

Manufacture, 43, 523–532, 2003. 

W. I. Clark, A. J. Shih, R. L. Lemaster, S. B. 

McSpadden, “Fixed Abrasive Diamond Wire 

Machining—Part II: Experiment Design and 

Results,” International Journal of Machine 

Tools and Manufacture, 43, 533–542, 2003. 

J. Kong, A. J. Shih, R. O. Scattergood, T. M. 

Yonushonis, D. J. Gust, M. B. Grant, and S. B. 

McSpadden, “Cost-Effective Form Grinding of 

Zirconia using Silicon Carbide Wheels and 

Ceramic Grinding Temperature Measurement,” 

presented at the National Science Foundation 

Design, Service and Manufacturing Grantees 

and Research Conference, January 6–9, 2003, 

Birmingham, Alabama. 

Sam McSpadden, “Developing a Grinding 

Process for Today’s Advanced Materials,” 

Grinding and Abrasive Magazine, December– 

March, pp. 20–24, 2003. 

122 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

**OGSBSFE#BTFE5FNQFSBUVSF.FBTVSFNFOUJO%JFTFM&YIBVTU"GUFSUSFBUNFOU'JMUFST

Albert Shih 

University of Michigan 

2250 GG Brown, 2350 Hayward St. 

Ann Arbor, Michigan 48109-9379 

(734) 647-1766; fax: (734) 936-0363; e-mail: shiha@umich.edu 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: University of Michigan, Ann Arbor, Michigan 

0CKFDUJWFT

• Develop a fiber optic system for non-contact, in-situ temperature measurement in diesel 

exhaust aftertreatment filters. 

• Establish calibration methods for the fiber optic temperature measurement system. 

• Measure the temperature distribution in diesel exhaust aftertreatment filters during microwave 

heating. 

"QQSPBDI

• Use infrared thermometry to select suitable optical fiber and infrared sensors as well as the 

system configuration for the application. 

• Perform component tests and blackbody calibration to determine characteristics of the fiber 

optic temperature measurement system. 

• Validate the fiber optic system configurations in microwave-heated diesel particulate filters 

(DPFs). 

• Conduct the temperature measurement testing and analyze the results. 

"DDPNQMJTINFOUT

• Developed a fiber optic radiation thermometry system to measure the inner wall surface 

temperature in a diesel exhaust aftertreatment filter. 

• Demonstrated the system’s capability to measure temperatures ranging from 100 to 400°C in 

the filter channel with large aspect ratio. 

• Applied a sapphire fiber with a 45° angled tip to measure the thermal radiation from a small 

and specific region on the inner filter wall surface perpendicular to the fiber axis. 

123 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

• Using both one-color and two-color thermometry methods, found a small temperature 

discrepancy for channels with large aspect ratio or near blackbody characteristics. 

• Used a multi-channel infrared fiber optic system to study the temperature distribution during 

microwave regenerative heating of DPFs. 

• Tested temperature distribution of DPFs with different levels of soot and catalyst. 

'VUVSF%JSFDUJPO

• Implement this technology in an operating diesel exhaust aftertreatment filter with exhaust 

flow, soot deposition, and catalysts. Provide the data for study of nitrogen oxide (NOx) and 

particulate filter reliability and durability, thermal cycle fatigue, and modeling of the 

regenerative temperature distribution. 

*OUSPEVDUJPO

The accurate, in-situ measurement of 

filter surface temperature is important for the 

development of diesel exhaust aftertreatment 

techniques. The temperature on inner filter 

wall surfaces controls the chemical kinetics 

of the storage and regeneration of NOx and 

particulate matter. New catalytic 

technologies have been applied to lower the 

regeneration temperature, which is beneficial 

for engine fuel efficiency. To study the 

effectiveness of new catalysts and their 

effects on the storage and regeneration 

process, accurate filter wall temperature data 

are required. A uniform temperature 

distribution in the filter is important to 

control the homogeneous chemical reactions 

as well as avoid overheating and thermal 

stress fatigue. 

Diesel exhaust aftertreatment filters are 

typically made of porous ceramic material 

with deep channels to increase the specific 

surface area. Attaching thermocouples to the 

filter wall surface at locations deep within 

the filter channel has proved difficult 

because of the space constraints. As an 

alternative to using a thermocouple, an 

optical fiber can be employed to transmit the 

emitted surface thermal radiation to an 

infrared detector for temperature 

measurement. Using an optical fiber with a 

45o angled tip, the field of view of the fiber 

tip can be narrowed to a small and specific 

region on the filter wall surface. Precise 

thermal mapping of the filter is achieved by 

measuring the surface temperature at various 

locations inside filter channels. 

"QQSPBDI

Two radiation thermometry systems were 

developed that use optical fibers to transmit 

the emitted surface thermal radiation in the 

channels of the diesel exhaust aftertreatment 

filter to outside infrared detectors. 

The first system consists of a sapphire 

fiber with a 45° angled tip, the lead 

sulfide/lead selenide (PbS/PbSe) two-color 

sensor, and a data conditioning and 

acquisition device, as shown in Figure 1. 

Based on two wide-band infrared PbS and 

PbSe detectors, the system is able to measure 

temperatures ranging from 100 to 400°C, the 

regeneration temperature for catalyzed 

filters. As shown in Figure 2, the PbS and 

PbSe detectors are sensitive to infrared 

radiation from 1.0 to 2.8 μm and from 2.8 to 

4.5 μm wavelength, with peaks at 2.5 and 

3.7 μm, respectively. Both PbS and PbSe 

detectors have a broad-spectrum range of 

detection of about 1.8 μm. Since PbS and 

PbSe are photoconductors sensitive only to 

an ac signal, a mechanical chopper (Figure 1) 

was used in front of the sensor’s connection 

to the optical fiber to generate an ac light 

signal input. The PbS/PbSe two-color sensor 

has a sandwiched construction. Only one 

infrared input is required for this sensor. It 

has eliminated the need to split the light to 

124 

Heavy Vehicle Propulsion Materials 

'JHVSF The application of PbS/PbSe two-color 

sensor and sapphire optical fiber for 

measurement of diesel exhaust 

aftertreatment filter temperature; (a) 

experiment setup and (b) close-up view 

of the two-color sensor, chopper, and 

sapphire fiber. 

'JHVSF The relative response of the detectors 

vs wavelength. 

two infrared detectors. As illustrated in 

Figure 1(a), the PbS detector is placed in 

front of the PbSe detector to receive the 

thermal radiation from the optical fiber. By 

employing a sapphire fiber with a 45° angled 

tip, the thermal radiation from a small and 

specific region opposite the polished tip face 

FY 2003 Progress Report 

and perpendicular to the fiber axis is 

measured. The goniometric characteristics of 

this fiber tip geometry were studied using the 

angular scan method when the 45° angled 

tip fiber was used inside a channel in the 

DPF. The fiber tip collects most of the 

thermal radiation from the filter wall surface 

at point A in Figure 1a. A small portion of 

thermal radiation at point B in front of the 

fiber tip is also transmitted to the infrared 

sensor. 

The second radiation thermometry 

system was developed in collaboration with 

Cummins Technical Center. A multi-channel 

fiber optic infrared system (Figure 3) was 

developed to measure the temperature 

'JHVSF Setup for microwave heating 

temperature measurement (a) 

thermometers and transmission fibers 

and (b) close-up view of the silica lightpipes insertion. 

distribution of diesel exhaust aftertreatment 

filters. The system uses multiple silica lightpipes to collect the infrared radiation from 

different locations inside a filter to study the 

temperature distribution during microwave 

regenerative heating of the DPF. 

The sensing material used in this system 

is InGaS, which provides good sensitivity to 

near-infrared radiation in a spectral band of 

1.0 to 1.6 μm. The system is able to measure 

temperature from 150 to 1000°C, which 

125 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

makes it suitable for the observation of a 

wide temperature variation due to 

exothermic reaction in the DPF regeneration 

process. DPFs with different levels of soot 

and catalyst were tested. Temperature 

measurements were performed at 36 

locations on each DPF, and the temporal and 

spatial temperature distribution on each DPF 

during a 10-min microwave heating period 

was obtained. 

3FTVMUT

Both one-color and two-color 

thermometry methods were implemented in 

the first system setup. Figure 4 shows the 

system calibration curves of the one-color 

and two-color methods against a blackbody 

heat source. The wall surface temperature of 

a microwave-heated ceramic filter was 

measured at four locations. The discrepancy 

between the two temperature measurement 

methods was small for the channel with 

large aspect ratio or near blackbody 

characteristics, marked by locations IC and IS 

in Figure 5. 

Three advanced wall-flow DPFs were 

tested by the integration of the multichannel fiber optic temperature 

measurement system with a bench-scale 

microwave heating system. These DPFs are 

the uncatalyzed filter with soot loading, 

catalyzed filter without soot loading, and 

catalyzed filter with soot loading. 

Experimental results show non-uniform 

heating across the filter. The measured 

temperature distributions are used to verify 

numerical modeling results. The interaction 

between catalyst, soot, and microwave power 

changes the heating pattern as well as the 

temperature distribution. During a 10-min 

heating period, a 1-kW microwave power 

setting was able to raise the temperatures 

above 200°C in most areas of a catalyzed 

filter with soot loading. 

'JHVSF Blackbody calibration results: (a) onecolor calibration data points and curves 

and (b) two-color calibration data 

points and curves. 

126 

Heavy Vehicle Propulsion Materials 

'JHVSF Temperature history reported by both 

the one-color and two-color methods in 

the filter channel with large aspect 

ratios. 

$PODMVTJPOT

Fiber optic radiation thermometry 

systems were developed to measure the 

channel wall surface temperature in diesel 

exhaust aftertreatment filters. Experimental 

results show that the system is suitable for 

noncontact, in-situ temperature 

measurement at a specific region within the 

channel of diesel exhaust aftertreatment 

filters. Results of the temporal and spatial 

temperature distribution on DPFs with 

different levels of soot and catalyst lead to a 

better understanding of the diesel exhaust 

aftertreatment regeneration mechanism and 

process and provide important data for the 

study of NOx and particulate filter reliability 

and durability, thermal cycle fatigue, and 

modeling of the regenerative temperature 

distribution. 

"DLOPXMFEHFNFOU

A portion of this research was conducted 

in collaboration with the Cummins 

FY 2003 Progress Report 

Technical Center. We gratefully acknowledge 

the technical support from Dr. Matthew 

Henrichsen, Randy J. Stafford, and Thomas 

M. Yonushonis. 

1VCMJDBUJPOT

B. J. Boothe, A. J. Shih, J. Kong, and W L. 

Roberts, “Goniometric Characteristics of 

Optical Fibres for Temperature Measurement 

in Diesel Engine Exhaust Filters,” 

Measurement Science and Technology, (5), 

563−572, (2003). 

A. C. Curry, A. J. Shih, R. O. Scattergood, 

J. Kong, and S. B. McSpadden, “Grinding 

Temperature Measurements in MgO PSZ 

Using Infrared Spectrometry,” J. Am. Ceram. 

Soc., , 333−341, (2003). 

J. Kong and A. J. Shih, “Infrared 

Thermometry for Diesel Exhaust 

Aftertreatment Filter Temperature 

Measurement,” SAE Transactions 

(submitted). 

J. Kong, M. Bakkal, S. F. Miller, and A. J. 

Shih, “Temperature Measurement in Ceramic 

Grinding, Machining of Bulk Metallic Glass, 

and Electrical Discharge Machining,” pp. 

415−424 in Proceedings of the National 

Science Foundation Workshop on Research 

Needs in Thermal Aspects of Material 

Removal Processes, Stillwater, OK, June 2003. 

J. Kong, A. J. Shih, R. O. Scattergood, T. 

M. Yonushonis, D. J. Gust, M. B. Grant, and 

S. B. McSpadden, “Cost-Effective Form 

Grinding of Zirconia using Silicon Carbide 

Wheels and Ceramic Grinding Temperature 

Measurement,” presented at the National 

Science Foundation Design, Service and 

Manufacturing Grantees and Research 

Conference, January 6–9, 2003, Birmingham, 

Alabama. 

127 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

+"EWBODFE$BTU"VTUFOJUJD4UBJOMFTT4UFFMTGPS)JHI5FNQFSBUVSF$PNQPOFOUT

P. J. Maziasz, R. W. Swindeman, J. P. Shingledecker, N. D. Evans, and M. J. Pollard* 

Oak Ridge National Laboratory 

P.O. Box 2008, MS-6115 

Oak Ridge, TN 37831-6115 

(865) 574-5082; fax: (865) 754-7659; e-mail: maziaszpj@ornl.gov 

*Caterpillar Technical Center 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

CRADA with Caterpillar, CRADA No. ORNL99-0533 

0CKFDUJWFT

•	 Scale up and produce commercial heats of new CN-12-Plus and CF8C-Plus cast austenitic 

stainless steels. 

•	 Establish a more complete database for tensile and creep properties. 

•	 Determine resistance to aging, fatigue, and thermal fatigue relevant to exhaust component 

applications. 

"QQSPBDI

•	 Produce 500-lb air-melted heats of new stainless steels at several foundries. 

•	 Obtain a more complete tensile and fatigue properties database at Caterpillar. 

•	 Determine relative resistance to thermal fatigue at Caterpillar and resistance to creep at Oak 

Ridge National Laboratory (ORNL). 

•	 Determine the best alloy for further scale-up and component applications. 

"DDPNQMJTINFOUT

•	 Produced commercial heats of CF8C-Plus and CN-12-Plus cast stainless steels at two commercial 

foundries. 

•	 Showed that CF8C-Plus had superior strength compared with CN-12 while retaining the high 

ductility of standard CF8C. Established superior aging, fatigue, and thermal resistance 

characteristics of CF8C-Plus up to 850oC. 

•	 Selected CF8C-Plus for further commercial scale-up and broader casting and component 

investigation. 

•	 Won a 2003 R&D 100 Award for CF8C-Plus cast stainless steel. 

129 
Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

'VUVSF%JSFDUJPO

•	 Complete evaluation of thermal fatigue properties and aging resistance after 10,000 h. 

•	 Characterize microstructural changes after selected high-temperature testing or aging. 

•	 Evaluate the effects of different commercial-scale casting processes on properties of CF8C-Plus 

steel. 

*OUSPEVDUJPO

Advanced large diesel engines must have 

higher fuel efficiency as well as reduced 

exhaust emissions without sacrificing 

durability and reliability. They require 

exhaust manifolds and turbocharger 

housings made from materials that can 

withstand temperatures ranging from 70 to 

750°C or higher in a normal duty cycle. Such 

materials must withstand both prolonged, 

steady high-temperature exposure and more 

rapid and severe thermal cycling. New 

technologies to reduce emissions and heavier 

duty cycles will push temperatures in these 

critical components even higher. 

Current diesel exhaust components are 

made from SiMo ductile cast iron, and higher 

engine temperatures push such materials 

well beyond their current strength and 

corrosion limits. The previous cooperative 

research and development agreement 

(CRADA) produced systematic data 

comparing cast CN12 stainless steel and 

SiMo cast iron for such diesel exhaust 

component applications. Those data 

demonstrated a clear tensile strength 

advantage of standard CN12 steel above 550– 

600oC and even larger advantages in creep 

strength and fatigue life above 700oC. The 

previous CRADA project also developed new 

modified CN12 and modified CF8C steels 

with better creep strength and significantly 

better aging resistance and thermal fatigue 

resistance than standard CN12. The purpose 

of this new CRADA project is commercial 

scale-up of these new modified stainless steel 

heats, and development of the systematic 

and thorough database required by designers 

to optimize component design and qualify 

them for trial component production. 

"QQSPBDI

Prior work on lab-scale heats (15-lb 

induction melts with argon cover gas) of 

modified CN12 and modified CF8C and 

screening tests (aging, tensile, creep) at 800– 

850oC at ORNL provided a composition of 

each alloy for commercial scale-up. Hightemperature fatigue testing at Caterpillar 

Technical Center has identified a significant 

advantage of the modified CN12 steel. Two 

commercial stainless steel foundries have 

produced 500-lb heats of the modified CN12 

and modified CF8C steels for testing and 

evaluation. One of those commercial 

foundries has been chosen to produce an 

additional static cast and a new centrifugally 

cast heat of the new modified CF8C steel. 

ORNL is also producing another set of 

laboratory heats to establish the effect of 

other minor additions on the hightemperature strength of the new modified 

CF8C steel. 

5FDIOJDBM1SPHSFTT

Tensile and fatigue testing were 

completed previously, and thermal fatigue 

testing was completed during the third 

quarter of 2003 at Caterpillar. Tensile data on 

the new commercial scale-up heats of the 

standard and modified cast stainless steels 

show CF8C-Plus is about as strong as the 

standard and modified CN12 steels but still 

has the same high ductility as standard CF8C 

steel (Figure 1). An “engineered 

microstructure” alloy design approach gives 

the new CF8C-Plus steel a very stable 

austenite parent matrix phase that is free of 

the ∆-ferrite typically found in standard 

CF8C steel in the as-cast condition (Figure 2). 

The creep strength of CF8C-Plus at high 

130 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

'JHVSFTensile properties measured by 

Caterpillar for the commercial scale-up 

heats of the new modified CN12 and 

CF8C stainless steels at room 

temperature to 850o

C in air.

'JHVSFOptical metallography of as-cast 

microstructures of standard CF8C and 

the new CF8C-Plus steels.

temperatures comes from nano-scale 

dispersions of NbC precipitates that form 

and remain stable and are much finer than 

those found in standard CF8C steel. Because 

CF8C-Plus has no ∆-ferrite, it is also free of 

∆-phase relative to standard CF8C. 

Creep tests of standard CN12 and the 

modified CF8C (CF8C-Plus) at 850oC and 

35 MPa were completed in 2003. The 

modified CF8C ruptured after 24,100 h with 

about 7.8% creep strain, and the test of the 

standard CN12 was stopped at 15,500 h 

without failure and less than 1% creep strain. 

The CF8C-Plus clearly had much better creep 

resistance than standard, commercial CF8C 

at 850oC, and was comparable to CN12 

(Figure 3). 

CF8C-Plus was deliberately designed to 

have a combination of good strength and 

ductility at both higher and lower 

temperatures in order to achieve its best 

'JHVSFCreep-rupture testing (at ORNL) of 

standard, commercial CF8C and and 

CN-12 cast stainless steels and a labscale heat of the new CF8C-Plus steel.

thermal fatigue resistance. Aging of 

tensile/fatigue specimens for 10,000 h at 

700–850oC continued at ORNL this year. 

Aging to 1000 h was completed early in 

2003, and specimen tensile testing began at 

Caterpillar later in 2003. Aging to 10,000 h 

will continue in FY 2004. Microstructural 

analysis of previous aged or creep-tested 

specimens of lab-scale heats of CF8C-Plus 

and CN12-Plus steels was completed in 2003, 

and tested specimens of the new commercial 

heats have been identified for 

microcharacterization early in 2004. 

Isothermal fatigue testing and data 

analysis of the new commercial scale-up 

heats of CF8C-Plus and CN12 Plus were 

completed late in FY 2003 at Caterpillar, and 

thermal fatigue testing is nearly complete. 

Additional lab-heats of CF8C-Plus were cast 

at ORNL to define the effects of other minor 

alloying additions and establish their limits 

for commercial heats. One of the commercial 

foundries was chosen by Caterpillar to 

produce another static sand cast heat and a 

centrifugally cast heat of CF8C-Plus, and 

specimens will be made next year. 

$PODMVTJPOT

ORNL and Caterpillar developed CN-12-

Plus and CF8C-Plus cast stainless steels that 

131 

Heavy Vehicle Propulsion Materials 

have higher creep strength and better aging 

resistance than the standard steels. Both cast 

steels were readily produced and cast as 

larger size commercial ingots. The 

commercial CF8C-Plus steel had much more 

strength than standard CF8C steel at up to 

850oC and is comparable in strength to 

standard CN-12 steel. CF8C-Plus steel has 

much better fatigue and thermal fatigue 

resistance than CN-12 or CN-12-Plus and was 

therefore chosen as the main focus for 

exhaust component applications and further 

commercial scale-up. 

1VCMJDBUJPOT1SFTFOUBUJPOT

P. J. Maziasz and R. W. Swindeman, 

ORNL, P. F. Browning, Solar Turbines, Inc., 

and M. E. Frary, M. J. Pollard, C. W. 

Siebenaler, and T. E. McGreevy, Caterpillar, 

Inc., Development of Low-Cost Austenitic 

Stainless Gas-Turbine and Diesel Engine 

Components With Enhanced HighTemperature Reliability, final ORNL report 

for CRADA ORNL99-0533. 

P. J. Maziasz and R. W. Swindeman, 

“Overview of Selection, Performance, and 

Development of Austenitic Stainless Steels 

for High-Temperature Applications,” 

presented as a keynote talk during the 

plenary session of the ASM Stainless Steel 

and Specialty Materials Conference, October 

7–9, 2002, in Columbus, OH. 

FY 2003 Progress Report 

M. E. Frary, M. J. Pollard, P. J. Maziasz, 

and R. W. Swindeman, “Modified Stainless 

Steel Alloys for High Temperature Engine 

Components,” presented at the ASM 

Stainless Steel and Specialty Materials 

Conference, October 7–9, 2002, Columbus, 

OH. 

4QFDJBM3FDPHOJUJPOTBOE"XBSET

An R&D 100 Award nomination package 

was submitted to R&D Magazine entitled 

“CF8C-Plus, Cast Stainless Steel for HighTemperature Performance,” by ORNL and 

Caterpillar last quarter and won a 2003 R&D 

100 Award. Several articles on this project 

have appeared in newspapers, Energy Insider, 

and several technical publications. 

1BUFOUT*TTVFE

Caterpillar completed an invention 

disclosure and patent application for cast 

austenitic stainless alloys with improved 

performance and filed it with the U.S. Patent 

Office in December 2000. The title is Heat 

and Corrosion Resistant Cast Stainless Steels 

With Improved High Temperature Strength 

and Ductility. Earlier, two separate new 

patent applications were developed and 

submitted to the U.S. Patent Office, one on 

CF8C-Plus steel and the other on the CN12­

Plus steel. 

132 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

K. Microstructure and Creep Properties of TiAl/Ti3Al In-Situ Composites 

Luke Hsiung and Andrea Hodge 

Lawrence Livermore National Laboratory 

P.O. Box 808, L-352 

Livermore, CA 94551-9900 

(925) 424-3125; fax: 925-424-3815; e-mail: hsiung1@llnl.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: Lawrence Livermore National Laboratory 

Objectives 

•	 Exploit thermomechanical processing techniques to fabricate TiAl/Ti3Al in-situ laminate 

composites with lamella widths down to submicron or nanometer length-scales. 

•	 Characterize microstructure and elevated-temperature creep resistance of the in-situ composites. 

•	 Investigate the fundamental interrelationships among microstructures, alloying additions, and 

mechanical properties of the in-situ composites to achieve the desired properties of the in-situ 

composites for high-temperature structural applications. 

Approach 

•	 Chose in-situ composites with nominal compositions of Ti-47Al-2Cr-2Nb and Ti-47Al-2Cr-1Nb0.8Ta-0.2W-0.15B (at. %) for the study. Fabricated the laminate composites at Oak Ridge 

National Laboratory (ORNL) using a thermomechanical process, which involves a hot-extrusion 

(16:1 ratio) of gas-atomized titanium aluminide powder (particle size―200 mesh) canned in 

molybdenum billets, and subsequently hot-extruded the composites at 1400oC. 

•	 Conducted creep tests in a dead-load creep machine with a lever arm ratio of 16:1. Performed 

tests in air in a split furnace with three zones at 760 and 815oC. 

•	 Examined the microstructures of creep-deformed samples using a JEOL-200CX transmission 

electron microscope (TEM). 

•	 Conducted in-situ TEM observation of the motion of interfacial dislocations by electron-beam 

heating of a creep-deformed sample. 

Accomplishments 

•	 Collaborated with ORNL to fabricate in-situ TiAl/Ti3Al laminate composites using hot-extrusion 

processing techniques. 

•	 Conducted in-situ TEM experiment to record a direct observation of interface sliding within the 

in-situ composites. 

133 

FY 2003 Progress Report	 Heavy Vehicle Propulsion Materials 

•	 Characterized and measured the effect of alloying modification on creep resistance of the 

TiAl/Ti3Al in-situ composites. 

Future Direction 

•	 Continue to collaborate with ORNL to fabricate the oxidation- and heat-resistant class of 

TiAl/Ti3Al in-situ laminate composites with higher niobium (Nb) and tungsten (W) additions 

using hot-extrusion techniques. 

•	 Continue to investigate the alloying effect on the microstructural stability and creep properties 

of the in-situ composites at elevated temperatures up to 850oC. 

Introduction 

Two-phase [TiAl (γ-L10) and Ti3Al (α -2 

DO19)] fully lamellar alloys (or in-situ 

laminate composites) have recently attracted 

great attention because of their low density 

(ρ = 3.9 g/cc), high specific strength, 

adequate oxidation resistance, and good 

combination of ambient-temperature and 

elevated-temperature mechanical properties, 

which are of interest for aerospace and 

transportation applications such as hightemperature components in turbine and 

combustion engines. Through alloy design 

and microstructural optimization, significant 

progress has been made to improve both 

room-temperature ductility/toughness and 

high-temperature creep resistance of the insitu composites.1–6 A recent report on the 

formation of nanoscale lamellae (with 

lamellar spacing on the order of 5 to 10 nm) 

within a water-quenched TiAl alloy7

 revealed 

the feasibility of materializing the idea of 

fabricating TiAl nanophase composites. 

However, in parallel, to make an effort to 

develop TiAl nanophase composites, there is 

a need to understand if further refinement of 

the lamellar microstructures would lead to 

adverse effects on high-temperature creep 

properties. 

A previous investigation8

 of the creep 

behavior of a Ti-47Al-2Cr-2Nb (at. %) alloy 

with a refined lamellar microstructure 

revealed that there existed two distinct creep 

regimes. A nearly linear creep behavior was 

observed in a low-stress (LS) regime (i.e. σ < 

300 MPa at 760°C), and power-law 

breakdown was observed in a high-stress (HS) 

regime (i.e. σ > 300 MPa at 760°C). TEM 

investigation of deformation substructures 

within creep-deformed specimens has 

revealed the occurrence of interface sliding 

in the LS regime and deformation twinning 

in the HS regime. This has led us to propose 

that interface sliding associated with viscous 

glide of pre-existing interfacial dislocations is 

the predominant creep mechanism in the LS 

regime, and interface-activated deformation 

twinning in γ lamellae is the predominant 

creep mechanism in the HS regime.8, 9 

Furthermore, we suggested that the solute 

atoms segregated at lamellar interfaces could 

act as short-range barriers to drag the motion 

of interfacial dislocation arrays during 

interface sliding. Accordingly, the main 

purpose of the current investigation was to 

study the effect of alloying modification on 

the creep resistance of the in-situ laminate 

composites. Emphasis was placed upon the 

solute effect on the creep resistance in the LS 

regime to facilitate the effort of developing 

TiAl/Ti3Al nanolaminate composites for hightemperature structural applications. 

Results 

Microstructures of As-extruded Materials 

Typical lamellar microstructures of Ti47Al-2Cr-2Nb and TiAl-47Al-2Cr-1Nb-0.8Ta0.2W-0.15B in-situ composites are shown in 

Figures 1a and 1b, respectively. Similar 

colony grain sizes (< 100 μm) and lamella 

widths were observed within the in-situ 

composites. The width of γ lamellae varies 

134 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

 (a) (b) (c) 

Figure 1. Bright-field TEM image of a typical lamellar microstructure from Ti-47Al-2Cr-1Nb-0.8Ta0.2W-0.15B extruded at 1400oC (a). Bright-field TEM image of an interwoven colony 

boundary in Ti-47Al-2Cr-1Nb-0.8Ta-0.2W-0.15B in-situ composite (b). Tilt view of lamellar 

microstructure showing a dislocation substructure within the in-situ composite (c) (LD 

denotes lattice dislocation, and ID denotes interfacial dislocation). 

between 100 and 350 nm, and the width of 

α2 lamellae varies between 10 and 50 nm. 

These values are considerably finer than 

those in lamellar TiAl alloys fabricated by 

conventional processing techniques. In 

addition, as shown in Figure 1c, interwoventype colony boundaries were developed 

within these two lamellar alloys, which 

could effectively interlock the colony 

boundaries from rotation and sliding when 

deformed at elevated temperatures. 

Creep Data and Deformation Substructures 

Creep data generated from Ti-47Al-2Cr2Nb and T-47Al-2Cr-1Nb-0.2W-0.15B in-situ 

composites tested at 760 and 815oC are 

shown in Figure 2. As can be seen clearly, 

both primary and steady-state creep rates 

significantly decrease as a result of the solute 

additions, and W solute is anticipated to be 

more effective than tantalum (Ta) solute for 

reducing the creep rates. A nearly linear 

creep behavior (n ∼ 1.5) was observed in both 

Ti-47Al-2Cr-2Nb and Ti-47Al-2Cr-1Nb-0.8W0.2W-0.15B composites creep-deformed at 

elevated temperatures with stresses below 

300 MPa (i.e. LS regime). Figure 3a shows a 

typical observation of a viscous glide (zigzag 

motion) of interfacial dislocations observed 

from the specimen deformed at 138 MPa, 

760oC. The zigzag motion of interfacial 

dislocations presumably results from the 

locking-unlocking of dislocation lines from 

solute atoms, which indicates that since the 

activities of glide and climb of lattice 

dislocations become very limited as a result 

of a refined lamellar microstructure, creep 

resistance of refined lamellar TiAl in the LS 

regime is controlled mainly by the mobility 

of interfacial dislocations. The creep 

resistance of refined lamellar TiAl in the LS 

regime may be promoted by reducing the 

mobility of interfacial dislocations by the 

segregation of low-diffusivity solutes such as 

Ta and W to impede the motion of 

interfacial dislocations. Although more 

rigorous investigation is needed of the effects 

of solute segregation at lamellar interfaces on 

the creep resistance of lamellar TiAl in the LS 

regime, Figure 3b shows a preliminary result 

obtained from a Ti-47Al-2Cr-1Nb-0.8Ta0.2W-0.15B sample creep-deformed at 

70 MPa, which demonstrates the promotion 

of creep resistance by the addition of Ta and 

W. Here precipitates, presumably TiB2-type 

boride particles, were observed at α /γ 2

interfaces. Note that the formation of TiB2­

type particles in similar TiAl alloys doped 

135 

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

(a) 

(b) 

Figure 2. Creep data show the effects of W, Ta, 

and boron additions to the creep 

resistance of the in-situ composites at 

815oC. It reveals that W solute is more 

effective than Ta solute for reducing 

both primary and steady creep rates. 

with boron has previously been reported 

elsewhere.10–12 

In-situ TEM observation 

The results of in-situ TEM observations 

made from a creep-deformed sample (138 

MPa, 760oC) are presented in Figure 4 to 

demonstrate the motion of interfacial 

dislocations under an electron-beam heating 

condition. Note that a local heating of a TEM 

sample can be achieved by spotting the 

focused electron-beam (several micron 

meters in size) onto the region of interest in 

(a) 

(b) 

Figure 3. A TEM image showing the zigzag 

motion of interfacial dislocation array 

observed within a sample creepdeformed at the LS regime (760oC, 

136 MPa) (a). Bright-field TEM images 

showing the formation of TiB2-type 

boride particles at α /γ interfaces 2

within a Ti-47Al-2Cr-1Nb-0.8Ta0.2W-0.15B sample creep-deformed at 

760oC, 70 MPa (b). 

the sample. Here, two consecutive in-situ 

images demonstrate the cooperative motion 

of a dislocation array (a total eight interfacial 

dislocations in the array) in a γ/γ interface 

during beam heating, and the array moved 

about 250 nm after beam heating for 20 

seconds. The dislocation array stopped 

moving after the beam was re-spread onto a 

wide region of the TEM sample. This 

observation further supports the idea that 

the creep resistance of TiAl/Ti3A in-situ 

laminate composite in an LS regime can be 

promoted by reducing the mobility of 

interfacial dislocations by the segregation of 

low-diffusivity solutes such as Ta and W to 

136 

Heavy Vehicle Propulsion Materials 

Figure 4. Consecutive in-situ TEM images 

showing the motion of an interfacial 

dislocation array in a γ/γ interface 

(the time period for beam heating: 

20 s). 

impede the motion of interfacial 

dislocations. 

Conclusion 

•

A nearly linear creep behavior [i.e. ε = n

kσ , n ∼ 1.5] has been observed in both Ti47Al-2Cr-2Nb and Ti-47Al-2Cr-1Nb-0.8W0.2W-0.15B in-situ composites with an 

ultrafine lamellar microstructure (γ lamellae: 

100 –300 nm thick, α lamellae: 10–50 nm 2 

thick) creep-deformed at elevated 

temperatures with stresses below 300 MPa. 

The resulting deformation substructure 

and in-situ TEM observation reveal that 

interface sliding through the motion of preexisting interfacial dislocations is the 

predominant deformation mechanism in an 

LS creep regime. Since the operation and 

multiplication of lattice dislocations within 

both γ and α2

 lamellae are very limited at an 

LS level as a result of the refined lamellar 

spacing, creep mechanisms based upon glide 

FY 2003 Progress Report 

and/or climb of lattice dislocations become 

insignificant. Instead, the mobility of 

interfacial dislocation arrays on γ/α and γ/γ 2

interfaces becomes predominant. It has been 

demonstrated that solute segregation at 

lamellar interfaces and interfacial 

precipitation caused by the segregation have 

a beneficial effect on the creep resistance of 

ultrafine lamellar TiAl in an LS creep regime. 

References 

1. Y-W. Kim and D. M. Dimiduk, JOM, 

43(8), 40 (1991). 

2.Y-W. Kim, Acta Metall. Mater. 40, 1121 

(1992). 

3. J. N. Wang, A. J. Schwartz, T. G. Nieh, 

C. T. Liu, V. K. Sikka and D. R. Clemens, in 

Gamma Titanium Aluminides, Ed. Y-W. Kim 

et al., The Materials Society, Warrendale, PA, 

949, 1995. 

4. C. T. Liu, J. H. Schneibel, P. J. Maziasz, 

J. L. Wright, D. S. Easton, Intermetallics 4, 

429 (1996). 

5. C. T. Liu, P. J. Maziasz, J. L. Wright, 

Mat. Res. Soc. Symp. Proc., 460, 83 (1997). 

6. L. M. Hsiung, T. G. Nieh and D .R. 

Clemens, Scripta Mater., 36, 233 (1997). 

7. K. Hono, E. Abe, T. Kumagai, H. 

Harada, Scripta Mater., 35, 495 (1996). 

8. L. M. Hsiung and T. G. Nieh, 

Intermetallics 7, 821 (1999). 

9. L. M. Hsiung, T. G. Nieh, B. W. Choi, 

and J. Wadsworth, Mater. Sci. Eng., A329­

331, 637 (2002). 

10. M. De Graef, D. A. Hardwick, P. L. 

Martin, in Structural Intermetallics, Ed. M. V. 

Nathal et al., The Materials Society, 

Warrendale, PA, 177 1993. 

11. D. J. Larson, C. T. Liu, M. K. Miller, 

Intermetallics 5, 411 (1997). 

12. C. T. Liu, J. L. Wright, S. C. Deevi, 

Mater. Sci. and Engrg., A329–331, 416 

(2002). 

Publications/Presentations 

1. L. M. Hsiung, “Interface Control of 

Creep Deformation in Ultrafine Lamellar 

137 

FY 2003 Progress Report 

TiAl,” Mater. Res. Soc. Symp. Proc. 

(Materials Research Society), 740, 287 

(2003). 

2. L. M. Hsiung and T. G. Nieh, 

“Microstructures and Properties of Powder 

Metallurgy TiAl Alloys,” accepted for 

publication in Materials Science and 

Engineering A, in press. 

3. L. M. Hsiung, A. J. Schwartz, and T.G. 

Nieh, “In-Situ TEM Observations of 

Heavy Vehicle Propulsion Materials 

Interface Sliding and Migration in a 

Refined Lamellar TiAl Alloy,” presented at 

the International Symposium on 

Intermetallic and Advanced Metallic 

Materials―A Symposium Dedicated to Dr. 

C. T. Liu, The Materials Society Annual 

Meeting San Diego, CA, March 3, 2003; 

accepted for publication in Intermetallics, 

in press. 

138 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

-4ZOUIFTJTPG1PXEFSTGPS5JUBOJVN$BSCJEF/JDLFM"MVNJOJEF$FSNFUT

Christopher J. Gump, Michelle G. Zeles, Alan W. Weimer 

University of Colorado 

Department of Chemical and Biological Engineering 

Boulder, CO 80309-0424 

(303) 492-3759; fax: (303) 492-4341; e-mail: alan.weimer@colorado.edu 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No:DE-AC05-00OR22725 

Subcontractor: University of Colorado, Boulder, Colorado 

0CKFDUJWFT

• Develop an understanding of the synthesis of submicron-sized titanium carbide, Ni3Al, and the 

composite intermetallic cermet (TiC/Ni3Al) powder. 

• Synthesize titanium carbide, NiAl, Ni3Al, and TiC/Ni3Al powders via batch and continuous 

processing. 

"QQSPBDI

• Investigate the synthesis of these materials on a small scale (1–5 g) using a well characterized 

thermogravimetric analyzer (TGA). 

• Investigate the effects of using diluent materials during the synthesis of nickel aluminides to 

promote the formation of submicron product powders in a batch process at both a small and 

large scale (50–150 g). (Diluents are presynthesized powdered forms of nickel aluminides and/or 

titanium carbide that act to absorb excess heat released during the chemical reaction and to 

provide extra surface area for melted aluminum to coat.) 

• Synthesize both materials using a continuous-flow, aerosol transport tube reactor. 

"DDPNQMJTINFOUT

• Studied the formation of submicron titanium carbide powders as a function of temperature and 

feed composition in the small-scale batch reactor (TGA). 

• Found that diluent materials allow for the synthesis of submicron nickel aluminide powders in 

the small-scale batch reactor (TGA). 

• Synthesized submicron titanium carbide/nickel aluminide composite materials in the smallscale batch reactor (TGA) using a variety of diluent compositions and amounts. 

The diluent particles participate in the reactions and have their size reduced. 

• Synthesized nickel aluminides in the continuous-flow, aerosol transport tube reactor. No 

diluent materials were used. These experiments served as a base case to help develop an 

understanding of what effects the diluents will have. 

139 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

• Studied the synthesis of titanium carbide in the transport tube as a function of temperature and 

the residence time for the reactants in the reactor. 

'VUVSF%JSFDUJPO

• Optimize the synthesis of titanium carbide to provide for stoichiometric titanium carbide of low 

oxygen content. 

• Explore finishing the titanium carbide product (after synthesis in the aerosol transport tube) in 

a second reactor. 

• Study the effect of diluent materials on the synthesis of nickel aluminides in the aerosol 


transport tube. Both nickel aluminide and titanium carbide diluents will be used. 


• Synthesize larger quantities of the pure and composite materials so that parts can be made from 

them and their physical properties tested. 

*OUSPEVDUJPO

Intermetallics and ceramics are attractive 

materials for applications in many extreme 

environments. Both have physical and 

chemical properties that allow them to 

operate under conditions that many current 

materials cannot withstand. Intermetallics, 

unlike alloys (simple solid mixtures of 

metals), comprise definite atomic ratios of 

atoms that are chemically bonded together 

in a crystalline lattice, such as Ni3Al or TiAl3. 

They have greater strength, higher melting 

points, and better corrosion resistance than 

common alloys. Similarly, ceramics, 

especially non-oxide ceramics like carbides, 

exhibit high toughness and hardness, as well 

as excellent chemical resistance. Composites 

of these two materials, called cermets, 

combine the best properties of both to yield 

exceptional materials. 

However, the very properties that make 

these materials desirable make it difficult to 

fabricate parts from them. Parts are typically 

made from aluminides by synthesizing the 

material in a molten form and then casting 

the liquid. It is desirable to directly 

synthesize the intermetallic and cermet 

(TiC/Ni3Al) as submicron-sized powders. 

The focus of this research is to develop a 

process for directly synthesizing nickel 

aluminide and titanium carbide as powders 

suitable for densification. These materials 

will preferably be of submicron size and have 

tight particle size distributions. 

"QQSPBDI

Titanium carbide will be synthesized via 

the carbothermal reduction of titanium 

dioxide. The reaction is given in Eq. (1). 

Nickel aluminide will be synthesized from 

nickel and aluminum metals. The aluminide 

reaction is given in Eq. (2). It occurs in two 

different compositions. In the first, one atom 

of nickel is reacted with one atom of 

aluminum to form mononickel aluminide 

(NiAl). In the second, three atoms of nickel 

are reacted with one atom of aluminum to 

form trinickel aluminide (Ni3Al) 

 TiO2 + 3 C Æ TiC + 2 CO (1) 

(3) Ni + Al Æ Ni Al (2) 3

The synthesis reactions for both titanium 

carbide and nickel aluminide were at first 

studied using a large-capacity (1–5 g) TGA 

(Figure 1). The TGA is capable of accurately 

measuring small weight changes in reaction 

masses (Figure 2). In cases where the 

reactions generate or consume gases, the 

weight change is a method to monitor the 

progress of the reaction. The synthesis of 

titanium carbide from titanium oxide 

generates carbon monoxide. However, the 

synthesis of nickel aluminide from nickel 

and aluminum results in no weight change. 

140 

Heavy Vehicle Propulsion Materials 

'JHVSF Theta Gravitronic VII TGA. 

'JHVSF Schematic of TGA. 

So for nickel aluminide, the heat evolved by 

the reaction was monitored using a 

differential thermal analyzer (DTA). 

The first step in the aluminide reaction is 

to heat the raw materials to the melting 

point of aluminum (~650o

C). The molten 

aluminum then reacts with the nickel to 

form the desired aluminide. This reaction 

releases a substantial quantity of heat, often 

enough to melt the aluminide that is formed 

(melting point is ~1450o

C). Therein lies the 

problem with directly making the material as 

a powder: the molten liquids, both 

aluminum and aluminide, coalesce to form 

large droplets, not submicron powders. The 

strategy for preventing this was the use of 

diluent materials. Pre-synthesized nickel 

aluminide and/or titanium carbide was 

included in the batch reaction formulation. 

FY 2003 Progress Report 

The diluents provided a surface area for the 

molten aluminum to coat and a heat sink to 

absorb the excess energy of the reaction. 

Surprisingly, previous work in this project 

found that aluminide diluent materials 

actually participated in the reaction and were 

reduced from 10–50 micron particles into 

submicron particles themselves. 

The reactions were also studied using an 

aerosol transport tube reactor (Figure 3). This 

reactor design is already used industrially to 

synthesize tungsten carbide powders for use 

in drill bits in the electronics industry. There 

is also interest in using this reactor to 

synthesize boron carbide for use as ceramic 

armor. The carbothermal reduction of 

titanium dioxide [Eq. (1)] is analogous to 

both of these reactions. So it should be 

possible to synthesize titanium carbide in an 

aerosol transport tube as well. This reactor 

design allows for the continuous synthesis of 

product powders. By controlling the 

residence time of the materials in the reactor 

and the temperature of the reactor, the 

particle size of the products can be 

controlled: longer residence times and higher 

temperatures lead to larger particles. 

'JHVSF Photograph of aerosol transport 

tube reactor. 

A schematic of the aerosol transport tube 

reactor is given in Figure 4. A powder 

consisting of an intimate mixture of the two 

reactants is entrained in a gas flow and 

carried to the reactor. It enters the hot zone 

of the furnace via a water-cooled lance that 

141 

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

reactor. 

'JHVSFSchematic of aerosol transport tube 

extends down into the furnace. This lance 

maintains the raw materials at roughly room 

temperature until they enter the hot zone. At 

that point, thermal radiation from the walls 

of the furnace heats the powders to the 

reaction temperature in a fraction of a 

second. The raw materials react as they fall 

through the furnace, and then they enter the 

expanded cooling zone, where they cool 

rapidly. From there, the powders settle into 

the collection vessel. 

During this year of the research project, 

work was performed on the batch processing 

of aluminides and titanium carbide both to 

elucidate the reaction pathway further and to 

investigate the possibilities of scaling the 

batch process up. Preliminary studies of both 

reactions were also run in the aerosol 

transport tube. 

3FTVMUT

#BUDI1SPDFTTJOH

In an effort to further confirm and 

characterize the breakdown of the diluent 

materials, experiments were run in the TGA 

using titanium aluminide as a diluent 

material. The first experiment, involving 

titanium aluminide and aluminum, showed 

that aluminides could, under the proper 

conditions, absorb aluminum to change the 

stoichiometric ratios of the substituent 

atoms. Trititanium aluminide was 

transformed at least partially into 

monotitanium aluminide. The second 

experiment involved using the trititanium 

aluminide as a diluent for the reaction 

between nickel and aluminum. The product 

material was found to consist of titanium 

dinickel aluminide; the diluent material had 

in fact participated in the chemical reaction. 

The remaining batch experiments were 

run in the large-scale batch reactor. A 

significant effort went first into designing 

and building this reactor, shown in Figures 5 

and 6. It is capable of holding 50–150 g of 

reactants and heating them to 1700o

C. The 

r

'JHVSFSchematic of horizontal tube batch 

eactor. 

'JHVSFSchematic of horizontal tube 

furnace with inserted batch 

reactor. 

first experiment involved synthesizing a 

batch of titanium carbide. Unfortunately, the 

same issues inherent in the industrial-scale 

synthesis became apparent: heat transfer into 

the reaction mass limited the conversion of 

the raw materials. Hence the product ended 

up being only 75% titanium carbide; the 

142 

Heavy Vehicle Propulsion Materials 

remainder was unreacted titanium dioxide 

and carbon. The remaining experiments 

therefore focused on the direct synthesis of 

the cermet material. The reactor was loaded 

with varying mixtures of titanium carbide 

and nickel and aluminum powders and 

heated to 700o

C. Each batch showed two 

types of product morphology. The outer 

sections were fine powders, while the inner 

sections were powders that had agglomerated 

together to form solid masses. The solid mass 

was smallest in the reaction involving the 

largest amount of diluent material. These 

results emphasized the importance of the 

diluent materials: more diluent resulted in 

the greatest amount of powdered product. 

The particle size distributions for the 

powdered products from the three runs are 

shown in Figure 7, along with the 

experimental conditions. 

p

'JHVSFParticle size distribution of 

intermetallic cermet roducts. 

$POUJOVPVT1SPDFTTJOH

The initial nickel aluminide synthesis 

experiments were run in the aerosol 

transport tube reactor without the use of 

diluent materials. These experiments were to 

serve as a base case for comparison with the 

experiments to be run later using diluents. 

This also simplified the analysis of the 

products, since in this reactor it is less clear 

that the raw materials would be in close 

enough proximity to react. Any product 

detected would have to have been made by 

FY 2003 Progress Report 

the reaction. The synthesis of both NiAl and 

Ni3Al was studied in a 3 × 3 matrix of 

temperature (1000, 1200, and 1400o

C) and 

residence time (1.0, 2.0, and 3.0 seconds). 

These 18 experimental runs were analyzed 

via X-ray diffraction to determine if the 

products were formed. To varying degrees in 

all cases, spectrum peaks associated with 

nickel aluminides were evident; however the 

peaks did show that there was some variation 

in the ratio of nickel to aluminum. Also, 

there were varying degrees of unreacted 

nickel and aluminum in the samples. 

However, as previously stated, this is 

expected to be a base case (and worst case). 

The use of diluents should help in making a 

more homogeneous product, as well as 

helping more of the raw materials to react. 

The specific surface areas (a measure of the 

average particle size) for the product powders 

ranged from 0.04 to 0.83 m2

/g, indicating 

average particle sizes ranging from 0.5 to 10 

microns for the experiments. This compares 

favorably with the surface areas of the 

starting materials (0.29 m2

/g for the 1:1 

mixture of nickel and aluminum, and 0.39 2

m /g for the 3:1 mixture of nickel to 

aluminum), since the aluminides are more 

dense than the weighted averages of the 

starting materials. Again, this is also the base 

case for the aluminide synthesis. The use of 

diluents should allow for higher-surface-area 

products to be made. 

The initial work on the synthesis of 

titanium carbide in the aerosol transport 

tube proved to be only marginally successful. 

The reaction was studied at 1900, 2000, 

2100, and 2200o

C using a residence time of 

1.5 seconds. The products ranged from 14 to 

80% pure titanium carbide. These 

experiments used a feed mixture that 

contained 5% carbonized starch to act as a 

binding agent during the feed preparation 

process. Carbonized starch has previously 

been found to assist in driving the reaction 

to completion. Therefore, the next round of 

experiments used a feed in which all of the 

carbon was supplied by carbonized starch. In 

addition, the feed was prepared using a slight 

143 

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

(5%) excess of titanium dioxide. Again, 

previous work had shown that a higher 

quality of product was obtained when the 

feed had excess titanium dioxide. This is 

apparently because the final carbide 

morphology then depends on the 

morphology of the starting titanium dioxide. 

The Degussa P-25 titanium dioxide is a very 

fine submicron powder, so it should yield a 

high-quality titanium carbide product. The 

excess titanium dioxide can be removed by 

reacting the titanium carbide with extra 

carbon at lower temperatures in a batch 

furnace. This will also allow for the 

adjustment of the titanium-to-carbon ratio 

in the finished carbide, a critical parameter 

for physical properties such as hardness and 

toughness. As with the aluminide synthesis, 

a 3 × 3 matrix of experiments was run at 

2100, 2200, and 2300o

C and at residence 

times of 0.5, 1.5, and 2.5 seconds. These 

experiments yielded much better results. In 

most of the runs, all the free carbon was 

converted into the carbide, and in the three 

runs that did contain free carbon, it was 

always lower than 3.1%. That is comparable 

to industrially available carbide. The specific 

surface areas ranged from 0.57 to 5.0 m2

/g for 

the products. This size distribution should 

provide for effective densification into 

finished parts. 

$PODMVTJPOT

More evidence was found for the 

chemical participation of diluent materials in 

the synthesis of intermetallics. This 

participation allows for the batch synthesis 

of submicron powders of nickel aluminide. 

Using this method, it is possible to make 

smaller quantities of intermetallics for 

materials testing or other laboratory tests. 

Composites of intermetallics and ceramics 

were synthesized in the large-scale batch 

reactor. Some reactions did not have 

sufficient diluent materials and formed larger 

agglomerates in addition to the fine powders; 

but in the cases where fine powders were 

formed, the product powders were 

submicron with a relatively tight particle size 

distribution. Both titanium carbide and 

nickel aluminide were successfully 

synthesized in the continuous aerosol 

transport tube. The resulting product 

powders were submicron and, under many 

conditions, completely consumed the 

limiting reagent. They appear to have the 

appropriate physical properties for use in the 

manufacture of parts for use in extreme 

environments. 

144 

Heavy Vehicle Propulsion Materials 	 FY 2003 Progress Report 

M. Diesel Exhaust Gas Recirculation Corrosion Effects 

D. F. Wilson and M. D. Kass 

Oak Ridge National Laboratory 

P.O. Box 2008, 4500-S, MS-6156 

Oak Ridge, Tennessee, 37831-6156 

Phone: (865)-576-4810; fax: (865)-241-0215; e-mail: wilsondf@ornl.gov 

DOE Technology Development Area Specialist: Sid Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Objective 

• Assess the effect of diesel engine operating parameters, especially exhaust gas recirculation 

(EGR) fraction, on corrosion rates of materials of construction. 

Approach 

• Establish working relationships with diesel engine manufacturers. 

• Deploy corrosion probes in manufacturer’s test stands. 

• Evaluate the performance of probes under various test conditions. 

• Determine correspondence between probe performance and that of the materials of 

construction. 

Accomplishments 

• Gained access to a manufacturer test stand and deployed the probe. 

• In conjunction with a manufacturer, obtained corrosion information as a function of various 

operating parameters. 

• Demonstrated probes to be affected following changes in engine operating regimes. 

• Determined that corrosion was not significant until the onset of water condensation. 

Future Direction 

• Continue collaboration with engine manufacturers. 

• Install probes with different “sensing” materials. 

• Determine the correspondence between probe performance and that of the materials of 

construction. 

• Ascertain the cause(s) for corrosion behavior. 

145 
FY 2003 Progress Report 

Introduction 

To reduce NO emissions, EGR systems x

have been deployed in diesel engines. This 

approach reduces peak combustion 

temperatures and hence NOx emissions. 

The use of an EGR system leads to 

accelerated corrosion that is considered to 

be associated with the formation of sulfuric 

acid. While it has been observed that 

corrosion tends to follow dewpoints, there 

are indications of maxima in corrosion 

rates with dewpoint temperature. Two 

regimes have been identified. The first is in 

the temperature range between the 

dewpoint of the acid that forms and the 

dewpoint of water where strong acid is 

formed; the second is below the water 

dewpoint where very weak acid is formed. 

Both of these acids, strong (50–70%) and 

very weak (500 ppm), are very aggressive 

corrodents of the proposed materials of 

containment, aluminum and cast iron. 

Approach 

A CEION corrosion probe was installed 

in a test engine at the manufacturer. The 

Heavy Vehicle Propulsion Materials 

probe was connected to the associated 

interfaces; to data acquisition, corrosion 

rate analysis software; and to display 

systems. The manufacturer exercised the 

engine under various operating conditions, 

including EGR fractions, temperature, and 

gas composition. The data were analyzed to 

determine correlations between corrosion 

rates and engine operating conditions. 

Samples of condensate were collected and 

later analyzed at Oak Ridge National 

Laboratory. 

Conclusions 

Corrosion rates increased significantly 

with onset of water condensation. The 

condensate, having appreciable levels of 

acid, showed a pH of approximately 2.5. As 

anticipated, the concentration of sulfuric 

acid varied with the sulfur content of the 

fuel. 

146 

Heavy Vehicle Propulsion Materials 	 FY 2003 Progress Report 

/-BTFS4VSGBDF5FYUVSJOHPG-VCSJDBUFE$FSBNJD1BSUT

Peter J. Blau with Jun Qu and Laura Riester 

Oak Ridge National Laboratory, 

P. O. Box 2008, Mail Stop 606 

Oak Ridge, TN 37831-6063 

(865) 574-5377; fax: (865) 574-6918; e-mail: blaupj@ornl.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract Number DE-AC05-00OR22725 

0CKFDUJWFT

• Determine the effectiveness of using regular patterns of microscale dimples produced by a laser 

to reduce the friction coefficient of liquid-lubricated surfaces of ceramics. 

• Determine the extent to which the laser surface texturing (LST) process affects the structure of 

the ceramic materials to which the process is applied. 

"QQSPBDI

• Select the proper tests and analyses needed to reveal potential friction reduction benefits of 

dimpled ceramic surfaces for use in lubricated sliding contacts. 

• Obtain transformation-toughened zirconia (TTZ) and silicon carbide ceramic materials, design 

and fabricate test specimens, and provide them to Surface Technologies Ltd. for laser dimpling. 

• Characterize the ceramic materials after LST using a variety of techniques, including electron 

microscopy, nanoindentation, and scanning acoustic microscopy (SAcM). 

• Conduct friction tests in lubricants with different viscosities to determine the extent to which 

the laser surface treatment can reduce friction. Compare results for reciprocating motion, like 

that in engine components, with results for unidirectional sliding, like that found in rotary 

bearings or seals. 

"DDPNQMJTINFOUT

• Conducted reciprocating friction tests of LST ceramics in various lubricants−including diesel oil, 

mineral oil, and water−to determine which frictional conditions benefit more from LST. 

• Investigated the use of SAcM to identify near-surface microfractures due to the laser-induced 

thermal pulses used to form the dimples. 

• Obtained nanohardness data on the thermally affected zones in the material below dimples. 

• Determined the importance of precise alignment and sliding velocity to enable the detection of 

frictional effects of dimpled surfaces. Found that friction reduction in reciprocating contacts is 

difficult to achieve using LST. 

147

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

'VUVSF%JSFDUJPO

• Test LST ceramics in constant-velocity, unidirectional sliding (rather than reciprocating sliding 

as before) to more clearly reveal LST effects on the lubricated friction of ceramics couples. 

• Conduct additional characterization of LST effects on ceramics, especially as compared with 

other methods of surface engineering of these materials. 

*OUSPEVDUJPO

Improving the fuel efficiency of diesel 

engines while enabling them to meet 

emissions requirements presents both design 

and material challenges. Parasitic frictional 

losses in engines can be reduced by a 

combination of strategies such as 

(a) redesigning the engine components, 

(b) reformulating the lubricants, 

(c) improving methods of lubricant filtration 

and delivery, (d) reducing churning losses in 

fluids, (e) changing the operating conditions 

of the engine, (f) substituting more-durable, 

low-friction materials, and (g) altering the 

finish or microscale geometry of the bearing 

surfaces. This project specifically addresses 

the last approach by investigating the 

potential of a technique called LST that was 

developed by Surface Technologies Ltd. in 

Israel. 

In FY 2002 and FY 2003, tests were 

conducted to examine the efficacy of laserproduced dimples on the frictional 

characteristics of TTZ and silicon carbide 

(Hexaloy SA) sliding against flat surfaces of 

ground silicon nitride. In addition, detailed 

microstructural examination and 

characterization of the LST regions was 

performed by a variety of techniques to 

evaluate the possible effects of the process on 

ceramics. Early introduction of LST involved 

its successful application to water pump seals 

in which the mating surfaces were wide and 

flat. Recent work by Japanese investigators 

on water-lubricated silicon carbide dimpled 

by different methods showed the importance 

of dimple spacing and running-in to the 

extent to which dimpling reduced the 

friction coefficient.1

 In 2003, microstructural 

characterization of laser–surface-processed 

ceramics continued, as did additional 

friction experiments using lubricants that 

vary in viscosity. Results of that work 

suggested several future directions for 

FY 2004. 

"QQSPBDI

This project is being conducted in 

parallel with a complementary effort at 

Argonne National Laboratory (ANL) on LST 

metals and LST used in conjunction with 

coatings. Oak Ridge National Laboratory 

(ORNL) efforts have focused on ceramic 

materials. The approach taken is twopronged: (a) conduct controlled friction 

experiments of LST ceramics to evaluate the 

effects of both velocity and lubricant type 

(viscosity) on friction and (b) characterize 

the effects of LST on both the microstructure 

and the near-surface micro-mechanical 

properties of ceramics. To accomplish the 

latter, various techniques are being applied, 

for example, nano-indentation hardness and 

elastic modulus determination, SAcM, and 

scanning and transmission electron 

microscopy. 

3FTVMUT

During FY 2002, reciprocating friction 

tests were conducted on LST-treated flat 

areas on cylinders of zirconia (TTZ), sliding 

against ground silicon nitride tiles in various 

lubricants. Results presented in earlier 

project reports indicated that the most 

noticeable effects of LST occurred with low 

applied loads and high oscillating speeds. 

That finding was consistent with a 

lubrication theory developed by Petroff, 

Stribeck, and others in the early 1900s,2 

namely, that the magnitude of the friction 

148 

Heavy Vehicle Propulsion Materials 

coefficient in lubricated systems is 

proportional to both the velocity of sliding 

and the viscosity of the lubricant, and 

inversely proportional to the force holding 

the surfaces in contact. That work helped 

define the concepts of boundary lubrication, 

mixed film lubrication, and hydrodynamic 

lubrication for plain bearings. Key engine 

components such as piston rings oscillate 

back and forth; that complicates the 

application of Stribeck’s analysis to the 

current project because it was intended for 

components, such as shafts, that always 

rotate in the same direction. 

Further studies on the friction of silicon 

carbide LST cylinders were conducted during 

FY 2003 with less definitive results than the 

earlier work on TTZ. It was concluded that 

the benefits of LST for reciprocating, narrow 

contacts could be detected only for very 

precisely aligned surfaces, if at all. That was 

confirmed by a recent report by Kato3

 in 

which more than a day of water-lubricated 

sliding was required to wear-in the surfaces 

of the ceramics enough to reveal the benefits 

of LST. 

The primary focus of the FY 2003 

research was on characterizing the effects of 

the LST process on the surfaces and micromechanical properties of TTZ and silicon 

carbide. Figure 1 shows the surface of an LST 

zirconia specimen containing rows of round 

(~ 120 μm diameter), shallow (~ 15 μm deep) 

dimples. Figure 2 shows an inclined, 

polished prepared section prepared from the 

same specimen. The low angle of polish 

helps to artificially magnify the near-surface 

features. Slightly darker coloration marks the 

thermally affected zones encircling the 

dimple. Higher magnification reveals a fine 

network of microcracks, presumably due to 

rapid heating and cooling of the ceramic in 

the vicinity of the laser pulse. 

SAcM, the image contrast of which is 

affected by the presence of subsurface flaws, 

revealed additional cracking features not 

visible in either the optical or scanning 

FY 2003 Progress Report 

'JHVSF Pattern of dimples on a TTZ surface. 

'JHVSF Tapered cross-section of a dimple in 

TTZ showing the “splash zone” near 

the dimple rim and the thin heataffected area along the bottom of 

the crater. The splash zone must be 

removed by gentle grinding or by 

wearing-in of the contact surfaces 

for dimple effects to work properly. 

electron microscope (see Figure 3). The 

higher the acoustic frequency, the shallower 

the penetration into the surface, but the 

smaller the flaws that can be detected. The 

SAcM image in Figure 3 shows fringes 

associated with the change in height of the 

crater, but it also reveals subtle cracks around 

the edges of the dimple. 

Nanoindentation studies were conducted 

to determine whether LST had affected the 

micro-mechanical properties of the material. 

149

FY 2003 Progress Report 

'JHVSF Scanning acoustic microscopy 

image of a crater, revealing both 

topography and fine-scale microcracking below the surface of the 

rim regions. Frequency 1.7 GHz. 

Table 1 summarizes results for a series of 

nanoindentation tests in the LST-affected 

regions and in the material well below them 

(bulk). Despite the slightly lower average 

hardness values near the dimples on both 

ceramics, there was no statistical basis to 

conclude that the elastic modulus or the 

average nanoindentation hardness numbers 

were significantly different in the LSTaffected areas. 

$PODMVTJPOT

• LST of zirconia ceramics results in the 

formation of a nanocrystalline zone that 

contains a network of microfractures. The 

mechanical properties of the regions between 

the microfractures are not different from 

those for the bulk material, and the main 

difference seems to be in the size of the grains 

and the presence of the microfractures. If 

wear occurs or if lubrication breaks down, it is 

possible that these fractures could serve to 

nucleate wear particles. Additional 

microscopy is planned. 

Heavy Vehicle Propulsion Materials 

5BCMF Nanoindentation hardness and elastic 

modulus data for polished cross-sections 

of TTZ and silicon carbide (SiC) 

2VBOUJUZ -PDBUJPO 55; 4J$

Average Bulk 16.1 37.0 

nanoindentation 

hardness (GPa) 

Average Near dimples 15.2 32.4 

nanoindentation 

hardness (GPa) 

Average elastic Bulk 262. 493. 

modulus (GPa) 

Average elastic Near dimples 257. 502. 

modulus (GPa) 

• The effects of dimples on friction reduction 

can be obscured if the contact surfaces are not 

precisely aligned during sliding, if they are 

not well run-in, or if the fluid entrainment 

velocity and viscosity of the lubricant are 

insufficient to enable creation of a lubricant 

film. 

• Additional work is needed to examine 

whether unidirectional, lubricated sliding of 

LST ceramic surfaces will reveal a more direct 

benefit from LST. 

• The effects of LST should be compared with 

other emerging surface engineering methods 

to determine which of them provides the 

most robust means of friction reduction in 

ceramics under oscillating or unidirectional 

sliding. 

3FGFSFODFT

1. X. Wang, K. Kato, K. Adachi, and K. 

Aizawa, “The Effect of Laser Texturing of SiC 

on the Critical Load for the Transition of 

Water Lubrication Mode from 

Hydrodynamic to Mixed,” Tribology 

International, , 703–711 (2001). 

2. R. Stribeck, “Die Wesentlichen 

Eigenschaften der Gleit- und Rollenlager,” Z. 

Verein. Deut. Ing.,  (38), 1341–1348 

(1902). 

3. K. Kato, “Water Lubrication of 

Textured Silicon Carbide,” presented at the 

Conference on Boundary Lubrication for 

150 

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

Transportation, Copper Mountain, CO, 

August 3–8, 2003. To be published in the 

proceedings. 

151

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

O. Ti-6Al-4V Billet Feedstock Manufacture and Evaluation 

P. Schwartz, S. M. Abkowitz, and S. Abkowitz 

Dynamet Technology, Inc. 

Eight A Street, Burlington, MA 01803 

(781) 272-5967; fax: (781) 229-4879; e-mail: sabkowitz@dynamettechnology.com 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: Dynamet Technology, Inc., Burlington, Massachusetts 

Objectives 

• Develop a low-cost Ti-6Al-4V billet feedstock using a blend of titanium (Ti) and alloy powders 

and inexpensive Ti-6Al-4V machine turnings. 

• Evaluate this low-cost Ti alloy feedstock as a starting billet material for casting, forging, and 

extrusion operations. 

Approach 

• Develop a procedure for producing low-cost Ti billet using a combination of inexpensive Ti 

alloy machine turnings and Ti and alloy powders. Evaluate the billet for density and 

microstructure. 

• Produce a total of nine billets for use as a starting material in casting, forging, and extrusion 

operations. The three operations will yield Ti-6Al-4V test bars. 

• Evaluate the quality of the test bars produced through chemistry and mechanical testing. 

Accomplishments 

• Selected a supplier of high-quality Ti-6Al-4V turnings. 

• Produced a billet using a core of a turnings/powder blend, surrounded by a solid powder “can,” 

with very low void content. 

• Produced a billet using 100% turnings, achieving full density, using a cold + hot isostatic 

pressing technology with conventional canning in mild steel for the hot isostatic pressing (HIP) 

operation. 

• Produced a high-density billet containing 60% turnings/40% Ti alloy powder that was produced 

using a core of 100% turnings, surrounded by a can made from Ti alloy powder. This billet will 

be used to cast test bars. 

Future Direction 

• Produce eight additional Ti-6Al-4V billets using the procedures being developed by Dynamet. 

These billets will incorporate three selected processing variations. 

153 

FY 2003 Progress Report	 Heavy Vehicle Propulsion Materials 

• Produce test bars from the feedstock using three different technologies that would benefit from 

low-cost feedstock: casting, forging, and extrusion. 

• Evaluate the resulting test bars for chemistry and tensile properties. 

Introduction 

Dynamet proposed to develop Ti-6Al-4V 

alloy billet feedstock manufactured using a 

combination of Ti alloy powder blended with 

inexpensive Ti alloy fine turnings. The 

blended alloy powders plus turnings will be 

consolidated to high density billet by 

isostatic pressing, vacuum sintering, and HIP 

(Figure 1). The process will be optimized to 

produce billets with the highest-possible 

percentage of turnings, thereby minimizing 

billet cost, while maintaining acceptable 

chemistry and process capability. Nine alloy 

billets will be subsequently (a) cast, 

(b) forged and (c) extruded to test bars (three 

billets for each operation). The resulting test 

bars will be evaluated for chemistry and 

mechanical properties. 

Results 

The results to date include the selection 

of a source of fine Ti-6Al-4V turnings, initial 

trials involving the pressing of turnings/ 

powder blends, and further process 

improvements that resulted in a Ti-6Al-4V 

billet with its center composed of 100% 

turnings surrounded by an integral Ti alloy 

can. 

Four suppliers of Ti-6Al-4V turnings have 

been identified and contacted. These 

suppliers have all sent samples, which were 

evaluated for chemistry and compactibility. 

Based upon these evaluations, and the 

supplier’s ability to provide large quantities 

of fine turnings, the turnings from one 

supplier have been selected for this program. 

Initial trials involved mixing the turnings 

with powder, packing the turning/powder 

mixture into Ti-6Al-4V P/M cans, and cold 

isostatic pressing the filled cans to form 

billets. Using this method, Dynamet 

Figure 1. Dynamet’s proposed approach to 

forming low-cost Ti alloy billet involves 

the blending of Ti powder with 

inexpensive Ti-6Al-4V machine 

turnings. 

successfully produced a billet containing a 

low percentage of voids (Figure 2). The 

turnings/powder blend core was surrounded 

by a ring of Ti alloy powder. The outer 

powder layer forms a solid layer of Ti alloy 

during sintering, with no surface-connected 

porosity. This solid skin of Ti allows HIP of 

the billet without canning. While this 

method was successful in producing a billet, 

further trials will concentrate on increasing 

154 

Heavy Vehicle Propulsion Materials 

Figure 2. Cross-section of a billet produced by 

Dynamet from a core of turnings/ 

powder blend and “can” of Ti alloy 

powder. 

the percentage of turnings to maximize the 

economic advantage. 

Further trials used discs die-pressed from 

100% turnings (Figure 3). These discs were 

pressed to 80% density. The discs were 

Figure 3. Discs die-pressed to 80% density from 

high-quality machine turnings. 

stacked and sintered to form a solid cylinder 

of 100% turnings, achieving approximately 

85% density (Figure 4). Dynamet has 

demonstrated that these cylinders can be 

consolidated to full (100%) density using 

HIP. However, because of the cylinder’s 

FY 2003 Progress Report 

Figure 4. The stacked discs are sintered to form 

cylinders of 100% turnings. 

residual interconnected porosity, the 

cylinder had to be canned in a custom-made 

mild steel container, welded and evacuated 

prior to HIP (Figure 5). 

Figure 5. The custom-made evacuated steel “can” 

used to hot isostatically press the 

cylinder made from 100% turnings. 

The next trial was aimed at eliminating 

the need for steel canning. A cylinder made 

from sintered discs of turnings was inserted 

in a thin-wall as-pressed Ti-6Al-4V can made 

with Dynamet’s powder metallurgy/cold 

isostatic pressing technology (Figure 6). This 

can becomes an integral part of the billet 

during the sintering and HIP. The can and 

discs were successfully processed by HIP to 

form an integral billet (Figure 7) without the 

155 

FY 2003 Progress Report 

Figure 6. By enclosing the cylinder of turnings in 

a “can” made from the Ti alloy powder, 

Dynamet eliminated the need for steel 

canning. The can becomes an integral 

part of the billet. 

Figure 7. The solid billet produced using a core of 

100% turnings, and a “can” of Ti 

powder blend. 

Heavy Vehicle Propulsion Materials 

expensive and material- and laborconsuming steps of canning (and decanning) 

in steel. This billet contained approximately 

60% turnings and 40% powder. Future efforts 

will be aimed at processing refinements to 

decrease the thickness of the outer Ti wall, 

thereby increasing the percentage of low-cost 

turnings used in each billet. 

The initial billet produced using the Ti 

alloy can will be supplied to Howmet for 

casting trials and evaluation. 

Conclusions 

Dynamet is developing a viable method 

for commercially producing low-cost Ti-6Al4V billet feedstock by combining 

inexpensive machine turnings with Ti and 

alloy powders. In the ongoing program, the 

applicability of these low cost Ti-6Al-4V alloy 

billets as feedstock for casting, forging, and 

extrusion operations will be assessed. 

Additionally, the resulting properties of the 

finished Ti-6Al-4V alloy material will be 

determined. 

156 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

P. High-Density Infrared Surface Treatment of Materials for Heavy-Duty Vehicles 

T. N. Tiegs, F. C. Montgomery, D. C. Harper, and C. A. Blue 

Oak Ridge National Laboratory 

P.O. Box 2008, MS-6087 

Oak Ridge, TN 37831-6087 

(865) 574-5173; fax: (865) 574-4357; e-mail: tiegstn@ornl.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No:DE-AC05-00OR22725 

Objectives 

• Use high-density infrared (HDI) technology to produce corrosion-resistant and/or wear-resistant 

coatings on metal substrates. 

• Use lighter or more cost-effective bulk materials with coatings applied to surfaces where 

improved properties are required. 

Approach 

• Examine approaches to surface modification that would be of interest for materials for heavyduty vehicles. 

• First, examine the application and formation of adherent, wear-/corrosion-resistant coatings. 

• Base the initial tests on hardmetal compositions applied onto iron-based parts that are currently 

used in diesel engines. 

• Based on these exploratory studies, ascertain further research on the use of HDI technology. 

Accomplishments 

• Demonstrated the ability to produce adherent hardmetal-based coatings on three different 

metal substrates. 

• Showed improved surface hardness for HDI-produced coatings. 

Future Direction 

• Optimize the HDI processing parameters for coating adherence, dimensional control, and 

desired microstructure/phase development. Parameters to be examined include power level, 

scan speed, preheating effects, pulsed power effects (as compared with scanning at constant 

power), blanket atmosphere type, and multiple scan effects (as compared with a single scan at 

high power). 

• Determine the effects of the different processing parameters on the coatings, as well as the 

substrate properties. 

157 

FY 2003 Progress Report 

Introduction 

HDI technology is relatively new to the 

materials processing area and is gradually 

being exploited in materials processing. The 

HDI processing facility at Oak Ridge National 

Laboratory uses a unique technology to 

produce extremely high power densities of 

3.5 kW/cm2

 with a single lamp, which is 

currently the most powerful one in the 

world. Instead of using an electrically heated 

resistive element to produce radiant energy, a 

controlled and contained plasma is used. The 

advantages of the technology include these: 

1.	 Compared with laser technology, it can cover 

large areas. 

2.	 It consists of short-wavelength radiation (0.2– 

1.2 μm). 

3.	 Heating and cooling is rapid. 

4.	 It is capable of attaining very high 

temperatures. 

5.	 It offers the potential for continuous 

processing. 

Because the technology is relatively new, 

its utility to the surface treatment of 

materials for applications in heavy-duty 

vehicles will be explored. In most cases, the 

need for wear resistance, corrosion resistance, 

or high strength is necessary only in selected 

areas of the part that are exposed to the 

working environment or under high stress. 

Therefore, it would be desirable to use 

materials that are lighter or less expensive for 

the bulk of the part, and provide the 

appropriate surface properties only where 

required. In addition, the HDI approach 

would be more cost-effective than other 

competitive processes such as physical vapor 

deposition. 

Results 

The project was initiated, and three 

different iron-based alloys were chosen (gray 

cast iron, 4140 alloy steel, and D2 tool steel). 

Slurry coatings of WC-Ni, WC-Co, WC-Ni3Al, 

and TiC-Ni3Al were fabricated and applied by 

a simple cost-effective spraying technique to 

the surfaces of the different metals. The 

Heavy Vehicle Propulsion Materials 

surfaces were then exposed to the infrared 

lamp under an argon cover gas. The 

appearance of a typical coated metal before 

and after HDI exposure is shown in Figures 1 

and 2, respectively. 

Figure 1. Visual appearance of a cast iron sample 

with an unprocessed WC-Ni coating on 

the surface. 

Figure 2. Visual appearance of a D2 tool steel 

sample with an HDI-processed WC-Ni 

coating on the surface. 

Cross-sections of the coatings and base 

alloys revealed that the coatings are well 

bonded to the substrates, and some chemical 

interaction is evident (Figures 3 and 4). Some 

158 

Heavy Vehicle Propulsion Materials 

Figure 3. Cross-section of a WC-Ni coating on 

4140 alloy steel after HDI processing. 

Figure 4. Cross-section of a WC-Ni3Al coating 

on D2 tool steel after HDI processing. 

large porosity within the coatings and at the 

interfaces with the underlying alloys is also 

observed. The coatings appear to be highly 

dense, although no quantitative 

determinations have been made to date. 

Initial testing showed a significant 

improvement of the hardness in the asfabricated coatings (Figure 5). Interestingly, 

for the same coating composition, 

differences in hardness were observed for the 

three different metal substrates. Evidently, 

there are some mixing effects between the 

substrate and the coating during the hightemperature HDI exposure. 

FY 2003 Progress Report 

Conclusions 

It was determined that adherent 

hardmetal-based coatings could be produced 

using cost-effective slurry deposition 

followed by bonding with the HDI lamp. 

Coatings were fabricated on three different 

metal substrates. Improved surface hardness 

for HDI-produced coatings was observed. It 

was found that the coating hardness is also a 

function of the substrate composition. 

Figure 5. Hardness improvements with HDItreated WC-Co surface coatings on 

4140 alloy steel, D2 tool steel, and 

cast iron. 

159 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

5. TEST AND MATERIALS STANDARDS 

A. Modification of Engineering Materials for Heavy-Vehicle Applications 

Stephen Hsu, Xaiolei Wang, Yhun Chae, and Lewis K. Ives 

National Institute of Standards and Technology 

100 Bureau Drive 

Gaithersburg, MD 20899-8520 

(301) 975-6120; fax: (301) 975-5334 ; e-mail: stephen.hsu@nist.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: National Institute of Standards and Technology, Gaithersburg, Maryland 

Objectives 

• Organize an international cooperative research program on an integrated surface modification 

technology under the auspices of the International Energy Agency (IEA). 

• Design and identify surface features and patterns that can achieve friction reduction and 

enhanced durability for heavy-duty diesel engine components. 

• Develop the understanding and appropriate models to explain texturing effects on frictional 

characteristics. Develop appropriate thin films and coatings to achieve a synergistic and 

complementary relationship with texturing to enhance performance. 

• Discover and develop the surface chemistry for protecting the films and coatings that work in 

synergy with the textures. 

Approach 

• Review the literature database to compile the current practices on surface texturing, thin films, 

and coatings. Understand the cause and effects of the beneficial attributes of texturing used in 

different applications. 

• Based on the current understanding, design various potential surface textures that might 

enhance performance while minimizing deleterious effects. 

• Develop and explore various ways to fabricate these surface textures on appropriate surfaces. 

Compare cost and effectiveness ratios for these fabrication techniques. 

• Develop a test methodology to measure the effects of these textures on friction and wear 

reduction and develop mapping techniques to define the limits of applicability in terms of 

operating parameters such as load and speed for a given materials pair. 

169 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

• Conduct research to develop an integrated system approach to combine the best practices in 

thin films, coatings, and surface chemistry for performances unrealizable by an individual 

approach alone. 

• Concurrently, organize an international cooperative research program under the auspices of the 

IEA to pool resources and share this energy conservation technology worldwide. 

• Under IEA annex IV, seek approval from the IEA executive committee and organize a U.S. 

national working group centered at NIST to provide industrial input and exchange information 

with other national groups. 

Accomplishments 

• Organized a special symposium on an integrated surface modification technology during the 

ASME Joint Tribology Conference on October 27–29, 2003. Speakers from Finland, Sweden, the 

United Kingdom, and Israel described activities in their countries; and DOE, NIST, Argonne 

National Laboratory, Oak Ridge National Laboratory, and the National Science Foundation 

described various research activities in the United States. Caterpillar and others provided an 

industrial perspective and information on industrial needs. More than 100 people attended the 

1-day session (40–50% of the total conference attendees). 

• Developed a proposal on forming an annex IV on integrated surface modification technology. 

Attended the IEA executive committee meeting held in Oakland, California, on October 22, 

2003, and presented the detailed plan to the executive committee. 

• Using a pin-on-disk test, compared the friction reduction characteristics of various geometries 

under the same surface coverage. These features were prepared using photolithography and 

mechanical scribing. 

• Investigated a test design that uses a disk with four different textures separated by untextured 

areas as an efficient means to evaluate and compare several textures in a single test. 

• Found that a surface pattern of elliptical features reduces the coefficient of friction under 

mixed-film lubrication conditions compared with a surface without texture, but only when 

sliding was perpendicular to the long-ellipse axis. 

Future Plans 

• Organize a U.S. national working group under the IEA banner to conduct joint research and 

provide information for international exchange. 

• Examine next the issue of surface texture density and depth of features on elliptical features. 

• Evaluate the test data to determine which feature and pattern characteristics, either singly or in 

combination, are most critical with respect to their effect on the coefficient of friction. Based on 

the outcome, develop parametric equations relating feature and pattern characteristics to the 

coefficient of friction. 

Introduction 

Frictional losses are inherent in all 

mechanical mechanisms that have 

contacting elements in relative motion. 

Reduction of such frictional losses arising in 

the mechanical systems of trucks and 

automobiles alone could result in substantial 

energy savings. Recent studies have shown 

that one means of reducing friction in 

sliding contacts is by introducing an 

appropriately designed surface texture on the 

bearing surfaces. This finding offers a 

significant opportunity for reducing friction 

losses in sliding contacts. The initial studies 

have shown that the effect depends strongly 

170 
Heavy Vehicle Propulsion Materials 

on pattern design, contacting materials, and 

lubricant properties. A full understanding of 

these dependencies has yet to be developed. 

The objective of this project is to identify 

critical pattern features that control friction 

under a broad range of contact conditions 

and develop models to explain these 

relationships. In the few months that this 

project has been under way, test procedures 

have been developed and a number of 

surface texture patterns have been evaluated 

using a laboratory pin-on-disk test. 

Approach 

The effects of different surface texture 

patterns were evaluated with a conventional 

pin-on-disk tribometer, illustrated 

schematically in Figure 1. Load and sliding 

Figure 1.	 Schematic of pin-on-disk test 

configuration. 

speed were varied to control the contact 

conditions. Tests were conducted using 

mineral oil without additives, having a 2

viscosity of 2.73 × 10−5

 m /s @ 40oC. Pin-anddisk specimens were fabricated from coldrolled 1017/1018 steel and 304 stainless steel. 

Friction force was monitored and recorded 

during the test. Two methods were used to 

produce surface textures on specimens. One 

was a photolithography method employing a 

FY 2003 Progress Report 

mask fabricated with features of the size, 

shape, and spacing for the desired texture 

pattern. A photoresist was applied to the 

polished (Ra ≈ 0.01 μm) test surface and 

exposed to light through the mask. After 

development, the specimen was 

electrolytically etched sufficiently to produce 

texture features of the desired depth. The 

other method was by mechanical scribing. A 

scribe (Rockwell “C” indenter) was held 

without rotation in the spindle of a small 

milling machine and pressed against the 

specimen mounted on the milling machine 

table. By controlling the table motion and 

application of the scribe, either indentations 

or grooves could be produced. After scribing, 

the specimen was polished flat to remove the 

raised lips around the scribed features. 

Results 

Table 1 gives the characteristics of two 

different patterns, circular dimples and 

ellipses, that were generated on pin 

specimens by the photolithography method; 

note that the feature area-density and feature 

depth were the same for both patterns. To 

assess the effect of orientation, two sliding 

directions, indicated by arrows in Table 1, 

were investigated for the ellipses. Test results 

for the patterns are shown in Figure 2 and 

compared with a polished pin without 

texture. The pin-and-disk materials in this 

example were cold-rolled 1017/1018 steel. To 

control lubricant film thickness, sliding 

speed and applied load were varied in the 

range of 0.023 m/s-0.23 m/s and 1 N-35 N, 

respectively. In Figure 2, the coefficient of 

friction is plotted as a function of the 

Sommerfeld number (viscosity × speed/load). 

There is little difference in friction behavior 

among the tests except for the elliptical 

pattern with sliding perpendicular to the 

direction of the long-ellipse axis. In this case, 

the coefficient of friction remains low for 

small-Sommerfeld-number values, while the 

other tests exhibit a substantial increase in 

coefficients of friction. Apparently, the 

presence of the elliptical texture pattern for 

171 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

Table 1. Characteristics of two surface textures prepared by photolithography method 

Figure 2.	 Pin-on-disk test results for different 

surface textures produced on a pin 

surface by the photolithography 

method compared with results for a 

pin surface without texture. 

this sliding direction results in a substantial 

extension of the mixed-lubrication regime. 

Complete understanding of the effect, 

however, will require additional 

investigation. 

As a second example, a series of tests was 

conduced on a 304 stainless steel disk 

(Figure 3) scribed with four different 

patterns: (1) grooves (wt) at a spacing of 

111 μm, lying approximately in the radial 

direction; (2) grooves (p) with the same size 

and spacing as (wt) oriented approximately 

parallel to the direction of sliding; 

(3) grooves (ct) similar to (wt) but spaced at 

54 μm; and (4) a pattern of dimples (i) spaced 

Figure 3.	 Disk specimen with four different 

scribed texture patterns. 

at 111 μm. Each pattern covered 

approximately the same area and was 

separated by approximately the same 

circumferential length of untextured surface. 

The path of the cylindrical pin and its 

relative contact size are indicated in Figure 3. 

The variation in coefficient of friction for 

three revolutions of the disk is shown in 

Figure 4 for a test conducted at an applied 

load of 15 N and sliding speed of 10 mm/s. 

The section of the plot corresponding to the 

location where the pin passed over each 

pattern is identified in the figure. In each 

case, the presence of the texture resulted in 

an increase in coefficient of friction 

compared with the intervening untextured 

surface. Among the textures, the pattern of 

172 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

obtained for other loads in the range of 2 N 

to 20 N. 

Conclusions 

Consistent with the findings of other 

investigators, this research found that surface 

texturing can reduce the coefficient of 

friction, offering a promising means for 

reducing energy consumption. However, 

depending on the contact conditions, a 

given texture pattern also can produce an Figure 4.	 Coefficient of friction behavior for increase in coefficient of friction or have no three revolutions of the disk in Figure net effect on coefficient of friction. It is clear 3. 

indentations (i) gave a smaller increase in 

coefficient of friction. Similar results were 

that additional investigation will be required 

to identify the critical texture characteristics 

that affect friction under a given set of 

conditions. 

173 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

# *NQMFNFOUJOH"HSFFNFOUGPSB1SPHSBNNFPG3FTFBSDIBOE%FWFMPQNFOUPO

"EWBODFE.BUFSJBMTGPS5SBOTQPSUBUJPO"QQMJDBUJPOT

M. K. Ferber 

Oak Ridge National Laboratory 

P.O. Box 2008, Building 4515, MS 6068 

Oak Ridge, TN 37831-6068 

(865) 576-0818; fax: (865) 574-6098; e-mail: ferbermk@ornl.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No:DE-AC05-00OR22725 

0CKFDUJWFT

• Facilitate the integration of new technologies into the diesel engine community by 

implementing research that validates the applicability of this technology to improve material 

properties while maintaining acceptable life-cycle costs. 

• Promote commercialization of new materials technologies by developing standard testing and 

characterization methods in conjunction with national and international standards 

communities. 

"QQSPBDI

• Define and implement research under the International Energy Agency (IEA) Implementing 

Agreement entitled “Implementing Agreement For A Programme Of Research And Development 

On Advanced Materials For Transportation Applications” (IA–AMT). 

• Conduct major research themes as annexes under the current Implementing Agreement. 

• Annex II Cooperative Program on Ceramics for Advanced Engines and Other Conservation 

Applications 

• Annex III Cooperative Program on Contact Reliability of Advanced Engine Materials

"DDPNQMJTINFOUT

• Initiated new efforts (subtasks 11 and 13) under Annex II. 

• Defined the scope of work for Annex III 

• Annex II Cooperative Program on Ceramics for Advanced Engines and Other Conservation 

Applications. 

• Issued an invitation to the United Kingdom from the Executive Committee of the 

Implementing Agreement to join the IA-AMT because of its interest in participating in 

Annex III.

175 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

• Held preliminary discussions with government officials from Canada concerning the initiation 

of a new annex on lightweighting of materials. 

'VUVSF%JSFDUJPO

• Develop a plan for the lightweighting materials annex and present it to the Executive


Committee for approval. 


• Initiate a test plan for Annex III. Current participants are United States, Germany, Japan, and 

United Kingdom.

*OUSPEVDUJPO

The IEA was formed via an international 

treaty of oil-consuming countries in response 

to the energy crisis of the 1970s. A major 

objective of the IEA is to promote secure 

energy supplies on reasonable and equitable 

terms. The governing board of the IEA, 

which is composed of energy officials from 

each member country, regularly reviews the 

world energy situation. To facilitate this 

activity, each member country provides 

energy experts who serve temporary staff 

assignments at IEA headquarters. These staff, 

or the secretariat, support the governing 

board by collecting and analyzing energy 

data, making projections in energy usage, 

and undertaking studies on specialized 

energy topics. The governing board is also 

assisted by several standing groups, one of 

which, the Committee on Energy Research 

and Technology (CERT), encourages 

international cooperation on energy 

technology. Implementing agreements (IAs) 

are the legal instruments used to define the 

general scope of the collaborative projects. 

There are currently 40 active IAs covering 

research topics such as advanced fuel cells, 

coal combustion science, district heating and 

cooling, enhanced oil recovery, fluidized bed 

conversion, fusion materials, solar heating 

and cooling, pulp and paper, hydropower, 

heat pumping technologies, hybrid and 

electric vehicles, high-temperature 

superconductivity, wind turbines, and hightemperature materials. A complete listing can 

be found at the IEA website, www.iea.org. 

This progress report summarizes recent 

activities in the IA-AMT. The objectives of 

the IA-AMT are (1) to identify and evaluate 

promising new processing and surface 

engineering technologies capable of 

improving materials performance in 

transportation systems and (2) to promote 

and implement pre-competitive 

development and verification of advanced 

characterization methods appropriate for 

advanced materials for transportation 

applications. 

"QQSPBDI

The collaborative research thrust areas 

(annexes) are defined by the Executive 

Committee of the IA-AMT. Their approach is 

to continually solicit ideas for new projects 

from (1) the technical leaders of the various 

activities, (2) recognized materials experts, 

and (3) special consultants. The IA-AMT 

currently consists of two active annexes: 

Annex II: Cooperative Program on Ceramics 

for Advanced Engines and Other 

Conservation Applications, and Annex III: 

Cooperative Program on Contact Reliability 

of Advanced Engine Materials. 

Annex II currently consists of four active 

projects or subtasks (1, 11, and 13). The 

objective of Subtask 1 is to achieve a 

balanced exchange of technical information 

among the participants on high-performance 

ceramics for advanced engines and other 

conservation applications. 

In Subtask 11, techniques for the 

measurement of thermal and mechanical 

fatigue are being examined. National efforts 

in Japan and the United States focus on the 

development of procedures for evaluating 

the mechanical fatigue behavior of silicon 

176 

Heavy Vehicle Propulsion Materials 

nitride ceramics using either uniaxial flexure 

or rotary bend test specimens. The national 

effort in Germany consists of the 

development of thermal fatigue procedures 

using the laser thermal shock equipment 

evaluated in Subtask 9.1

 The national effort 

in Sweden focuses on the evaluation of the 

fracture surfaces of specimens tested in 

Japan, the United States, and Germany. 

Subtask 11 also includes an international 

effort in which the thermal fatigue behavior 

of a single silicon nitride is compared with 

the mechanical fatigue data generated at a 

temperature that is the same as that at the 

fracture point in the thermal fatigue test. 

Germany is responsible for the thermal 

fatigue testing, and both Japan and the 

United States are conducting mechanical 

fatigue testing. 

Subtask 13 includes a round-robin in 

which a selected silicon nitride material will 

be evaluated in burner rig and oxidation 

facilities located in Japan, Germany, and the 

United States. This effort is motivated by the 

results of recent ceramic gas turbine field 

studies conducted at both Rolls-Royce and 

Solar Turbines, which have demonstrated the 

deleterious effects of the gas turbine 

environment upon silicon nitride 

component lifetime. Specifically, recession of 

non-oxide ceramics such as silicon carbide 

and silicon nitride ultimately leads to 

excessive material loss, which increases the 

stress levels arising from both thermal and 

mechanical loading. Consequently, 

considerable emphasis has been placed on 

the development of environmental barrier 

coatings to act as a diffusion barrier to water 

vapor. 

The effectiveness of environmental 

barrier coating systems is defined by (1) their 

ability to isolate the non-oxide ceramic from 

the water vapor and (2) their phase stability 

in the gas turbine environment. Both aspects 

can be evaluated from burner rig studies. 

Unfortunately, the results obtained from a 

given burner rig system depend upon a 

number of factors, including specimen 

geometry, gas flow/specimen configuration, 

FY 2003 Progress Report 

temperature uniformity, and burner stability. 

The goal of this subtask is to address these 

issues by implementing a round-robin in 

which a selected silicon nitride material is 

evaluated in burner rig facilities located in 

Japan, Germany, and the United States. 

Annex III, which was approved in July 

2002, consists of two subtasks on contact 

reliability of advanced engine materials, 

including structural ceramics, composites, 

and nanostructured friction/wear coatings. 

Subtask 1 is an information exchange; 

Subtask 2 focuses on the development of 

standard test methods and procedures for 

determining the rolling contact fatigue 

resistance of advanced materials. The 

Executive Committee plans to invite the 

United Kingdom to join the IA-AMT because 

of its interest in participating in Annex III. 

3FTVMUT

"OOFY**

The final draft of the U.S. report for 

Subtask 11 was completed. The primary 

objective of this effort was to develop and 

verify techniques for the measurement of 

thermal and mechanical fatigue of structural 

ceramics. A major finding from this work 

concerned the excellent correlation between 

static and dynamic fatigue. The static fatigue 

data measured at 850oC using the GS44 

silicon nitride flexure specimens are shown 

in Figure 1 (circles). As discussed in ref. 2, the 

susceptibility of GS44 to time-dependent loss 

in strength was much greater at this 

temperature than the susceptibility observed 

at temperatures <700oC. The associated 

strength degradation mechanism was 

attributed to softening of the intergranular 

phases, which ultimately led to viscous flow 

and separation of grain facets. Given 

sufficient time, this viscous flow was 

ultimately responsible for the formation of 

cavities within the intergranular phase. For 

example, Figure 10 compares the fracture 

177 

FY 2003 Progress Report 

'JHVSF Comparison of static and dynamic 

fatigue data. 

surfaces of two dynamic fatigue specimens; 

one tested at 30 MPa/s and other at 

0.003 MPa/s. At 0.003 MPa/s, there was 

sufficient time for the cavitation to occur, as 

evidenced by the skeletal pattern of the 

intergranular phase outlining the interfaces 

between adjacent grains. It should be noted 

that similar behavior was observed for a hotisostatically-pressed silicon nitride tested 

under tensile loading at temperatures above 

1200oC.3

 In that study, however, the 

temperatures were sufficiently high to 

activate addition deformation mechanisms, 

including cavitation of the silicon nitride by 

a solution-precipitation process. 

The experimental static fatigue data were 

subsequently fit to the generalized slowcrack-growth expression 

[1−(Sf

/ Si)

N−2

] = (N−2)/2 V(K )IC

 (Y Si

/KIC)

2 (σ/Si

)

N t	 (1) 

where Y is a constant, KIC is the fracture 

toughness, V(K ) and N are the slow-crack- IC

growth constants, V is the crack velocity, t is 

time, σ is the applied stress, S is the inert i

strength, and Sf is the strength after time, t. 

Failure occurs when Sf

 = σ. 

The curve fitting process involved 

choosing values of Si

, N, and V(K ) that IC

minimized the sum of the square of errors 

between predicted and measured lifetimes. 

Heavy Vehicle Propulsion Materials 

The fracture toughness at 850oC was assumed 

to be comparable to the room-temperature 

value reported by the vendor (8 MPa m1/2). 

The resulting values of the crack growth 

parameters estimated using this iterative 

procedure are provided in Table 1. The solid 

line in Figure 1 illustrates the model 

prediction. Note that the value of V(K ) is IC

relatively low. One might expect that it 

should be comparable to the speed of sound, 

given that it is associated with catastrophic 

fracture. However, this parameter actually 

represents the velocity occurring at the 

intersection of the Region I slow-crackgrowth curve with the Region III curve, as 

shown schematically in Figure 2. Because the 

Region III crack growth makes very little 

contribution to the time-dependent failure, it 

is treated as a vertical line in the 

development of the equations describing 

static, dynamic, and cyclic fatigue.1 

The triangles in Figure 1 illustrate the 

results of the dynamic fatigue testing 

conducted at 850°C. For these data, the time 

was calculated by dividing the stress by the 

stressing rate. Note that the experimental 

dynamic fatigue data points are shifted to 

longer times because, in a dynamic fatigue 

test, the stress is not constant but increases 

linearly from zero to final fracture strength. 

The same relationship is reflected by the 

predicted static and dynamic fatigue curves. 

In the latter case, the curve was predicted 

from the static fatigue results by applying the 

slow-crack-growth parameters in Table 1 to 

the expression 

−2

[1−(Sf

/ Si)

N

] = [(N−2)/(2(N+1))] 

V(K )(Y Si/KIC)

2 (σ Si

)

N

 t (2) IC

where the stress, σ, now increases linearly 

with time. Again, at the point of failure, 

Sf = σ. 

1

The contribution of Region II slow crack 

growth to time-dependent failure is also ignored. 

178 

Heavy Vehicle Propulsion Materials 

'JHVSF schematic representation of V-KI 

behavior showing two regions of crack 

growth. Because the slope of Region III 

is very high, its contribution to timedependent failure can be neglected. In 

this case, V (KIC) represented the 

intersection of the Regions I and III 

curves. 

5BCMF Crack growth parameters 

Parameter Value Comments 

Y 1.5 Based on surface cracks 

K

Based on vendors 

IC(MPa m1/2) 8 information 

V(K ) (m/s) 5 × 10−6 

IC

Si (MPa) 800 

N 25 

$PODMVTJPOT

Subtask 11 (Annex II) activities have 

shown that existing slow-crack-growth 

models can be used to reconcile stress 

rupture, strength-stressing rate, and cyclic 

fatigue data. 

FY 2003 Progress Report 

3FGFSFODFT

1. M. K. Ferber, G. Kirchoff, T. Hollstein, 

R. Westerheide, U. Bast, U. Rettit, and M. 

Mizuno, Thermal Shock Testing of Advanced 

Ceramics: Subtask 9 (Final Report), MOO107208, Oak Ridge National Laboratory, Oak 

Ridge, Tennessee, March 2000. 

2. A. A. Wereszczak, H.-T. Lin, T. P. 

Kirkland, “Strength and Dynamic Fatigue of 

Silicon Nitride at Intermediate 

Temperatures,” J. Mater. Sci. 
2669–2684 

(2002). 

3. M. K. Ferber and M. G. Jenkins, 

“Evaluation of the Strength and CreepFatigue Behavior of a HIPed Silicon Nitride,” 

J. Amer. Ceram. Soc. , 	9), 2453–62 1992. 

':1VCMJDBUJPOT1SFTFOUBUJPOT

Mechanical and Thermal Fatigue of 

Silicon Nitride Within IEA Subtask 11, 

Japanese Final Report, January 2003. 

International Energy Agency 

Implementing Agreement For A Programme 

Of Research And Development On Advanced 

Materials For Transportation Applications, 

Annual Report for Fiscal Year 2002, February 

2003. 

Implementing Agreement For A 

Programme Of Research And Development 

On Advanced Materials For Transportation 

Applications, End-Of-Term Report, February 

2003. 

Thermal and Mechanical Fatigue Testing 

of Advanced Ceramics Subtask 11, United 

States Report, June 2003. 

“United States Activities in Subtasks 11 

and 13,” presented at a working group 

meeting held in conjunction with the 27th 

annual Cocoa Beach Conference and 

Exposition on Advanced Ceramics and 

Composites, Cocoa Beach Florida, 

January 29, 2003. 

179 


Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

C. Mechanical Property Test Development 

George D. Quinn 

Ceramics Division Stop 852 

National Institute for Standards and Technology 

Gaithersburg, MD 20899 

(301) 975-5765; fax: (301) 975-5334; e-mail: geoq@nist.gov 

DOE Technology Development Area Specialist: Dr. Sidney Diamond 

(202) 586-8032; fax: (202) 586-2476; e-mail: sid.diamond@ee.doe.gov 

ORNL Technical Advisor: D. Ray Johnson 

(865) 576-6832; fax: (865) 574-6098; e-mail: johnsondr@ornl.gov 

Contractor: Oak Ridge National Laboratory, Oak Ridge, Tennessee 

Prime Contract No: DE-AC05-00OR22725 

Subcontractor: National Institute for Standards and Technology, Gaithersburg, Maryland 

Objectives 

• Develop mechanical test method standards in support of the Propulsion Systems Materials 

Program. Ensure that test method development meets the needs of the DOE engine community 

and considers the general U.S. structural ceramics community, as well as foreign laboratories 

and companies. 

Approach 

• Investigate, refine, and standardize test methods relevant to ceramic materials and heavy 

vehicle propulsion applications. 

• Conduct round-robins as necessary. 

• Create standard reference materials (SRMs) to support the test methods and materials 

specifications. 

• Have procedures standardized by the American Society for Testing and Materials (ASTM) and/or 

the International Organization for Standardization (ISO). 

Accomplishments 

• In FY 2003, finished SRM 2831 for Vickers Hardness of Ceramics and Hard Metals. This SRM 

complements ASTM and ISO test methods standards for Vickers hardness of hard materials and 

new material specifications standards, such as ASTM F 2094 for silicon nitride for ball bearings. 

• Completed a major new study on the detection and characterization of grinding cracks in 

ceramics and published a comprehensive report. We now have a much better understanding of 

how grinding can affect the strength and reliability of ground ceramic test pieces and 

components. We also have a much better understanding of how to control the grinding 

damage. 

• Updated and refined several ASTM standards, including ASTM C 1211 for high-temperature 

flexural strength and C 1322 for fractographic analysis. 

181 

FY 2003 Progress Report 	 Heavy Vehicle Propulsion Materials 

Future Direction 

• Evaluate and refine new test methods, including flexural strength testing of rod-shaped 

specimens and diametral compression strength of pill-shaped specimens. Both of these test 

configurations are highly relevant to many small engine parts, such as valve train or fuel 

injector components. 

• Help to organize a new Applications Subcommittee for the ASTM Committee C-28, Advanced 

Ceramics. In the past, that committee focused on generic property standards, but the committee 

will now venture into more component- or application-specific standards. 

Introduction 

Sixteen formal standard test methods 

have been created as a result of work in this 

project. These include methods for ceramics 

such as flexural strength, elastic modulus, 

Weibull statistical analysis, fractographic 

analysis, and fracture toughness. As a direct 

result of this work, there has been a dramatic 

improvement in test data quality and 

reliability in the structural ceramics field. 

Databases are now more reliable and 

interchangeable. These developments have 

enhanced the credibility of the new materials 

and aided their commercial implementation 

in advanced engines. Engineers and 

designers are more apt to use the new 

materials if the materials are supported by 

good data generated by standard test 

methods. For example, formal standards 

have aided the recent commercial utilization 

of ceramic materials as ball bearings, cam 

rollers, and even human surgical implants. 

Approach 

New methods are devised, or more 

commonly, existent laboratory scale test 

methods are investigated, refined, and 

standardized. Often some preliminary work 

has shown that a particular test method has 

promise, but critical details need to be 

refined, or interlaboratory tests need to be 

conducted to verify within-laboratory 

repeatability or between-lab reproducibility. 

Comprehensive literature reviews and error 

analysis are key steps in the development of 

any formal standard. 

SRMs have an important role in 

supporting overall standardization. An SRM 

is a well-characterized material produced in 

quantity to improve measurement science. It 

is certified for specific engineering, chemical, 

or physical properties and is issued by NIST 

with a certificate that reports the results of 

the characterization and indicates the 

intended use of the material. 

Results 

Hardness and SRM 2831 Finished 

In FY 2003, we completed SRM 2831, 

Vickers Hardness of Ceramics and Hard 

Metals. This SRM is a tungsten carbide disk 

with certified hardness and with 

indentations made by NIST that may be 

measured by users. Users may also make their 

own new indentations to verify correct 

operation and make measurements with 

their own equipment and personnel. 

Hardness is an important attribute of ceramic 

material, and as Table 1 shows, there are two 

SRMs to support the two most common test 

methods to measure hardness. 

Grinding Crack Evaluation Completed 

Nearly all ceramic components, such as 

those shown in Figure 1, need expensive 

finish grinding to final dimensions. Remnant 

grinding cracks may affect the reliability of 

ceramic components in engines. Hence, it is 

important to characterize these potential 

strength-limiting flaws and manage their size 

and severity. Optimization of grinding 

procedures and reduction of machining costs 

182 

Heavy Vehicle Propulsion Materials	 FY 2003 Progress Report 

Table 1.	 Standard reference materials that are 

now available from NIST to support 

ASTM and International 

Organization of Standardization test 

method standards and materials 

specifications. All are available off 

the shelf. 

SRM	 Images 

# 2100 


Fracture 


Toughness of


Ceramics, KIc


# 2830 


Knoop 


Hardness of 


Ceramics


# 2831 

Vickers (a) Hardness of 


Ceramics and


Hardmetals


Figure 1. Ceramic engine components that


require finish grinding.


are crucial in determining whether a ceramic 

component will be cost-effective. 

A NIST Ceramic Machining Consortium 

program was completed in December 2001. 

Follow-on analysis and intensive 

fractographic examination of hundreds of (b) 

Ceradyne sintered reaction-bonded silicon Figure 2. The depth of machining cracks nitride (SRBSN) specimens continued until created by surface grinding SRBSN June 2003, when a major NIST special silicon nitride primarily depends publication on the findings was published. A upon the wheel grit size of the 

short condensed article was written for the grinding wheel. Figure (a) shows the 

Ceramic Engineering and Science Proceedings data from individual crack size 

and will be presented at the Engineering readings and (b) shows the overall 

Science Division meeting of the American trend and interactions with the 

Ceramic Society in Cocoa Beach, Florida, in material’s inherent internal flaws. 

January 2003. Two major journal articles 

183 

FY 2003 Progress Report 

were prepared and submitted to Machining 

Science and Technology in December and 

January 2003. Preprints have been sent to 

key parties in the United States. 

We also learned that sometimes a single 

severe grit in a diamond wheel may control 

performance. A simple grinding crack 

damage map for SRBSN is shown in Figure 3. 

This drawing has been distributed widely to 

machinists and engineers to help them better 

appreciate the depth of grinding damage that 

is likely to be left in ground parts. Several 

different silicon nitrides were studied, and 

the results were compared with all known 

published data for silicon nitride. A stunning 

finding was that silicon nitrides with 

enhanced fracture toughness actually 

develop deeper machining cracks than do 

less tough nitrides. This seemingly 

paradoxical result is explained in the new 

manuscripts. We are also conducting detailed 

R-curve characterization of the SRBSN in 

collaboration with Prof. J. Rödel at the 

Technical University at Darmstadt, Germany. 

Fractographic techniques to recognize 

machining crack damage on fracture surfaces 

have been made much easier. This new 

know-how has been transferred to the 

general community via a series of 

publications and revisions to the ASTM 

fractography standard C 1322. The nature of 

the machining damage is now much better 

understood. New damage maps for 

machining damage in silicon nitride have 

been constructed. Simplified versions will be 

sent to key machine shops to help them 

understand the nature of machining cracks 

from grinding. 

New ASTM Applications Created 

We helped ASTM Committee C 28, 

Advanced Ceramics, create a new 

subcommittee on applications. The 

committee had done a good job in preparing 

generic standard test methods since its 

inception in 1986, but interest in generic 

properties work was waning. Many of the key 

properties have already been standardized. 

Industry wants test methods and standards 

Heavy Vehicle Propulsion Materials 

Figure 3. The depth of cracks (dark regions) 

created by surface grinding SRBSN 

silicon nitride primarily depends upon 

the wheel grit size of the grinding 

wheel. 

for specific components and applications. 

The new applications subcommittee will 

craft such standards and materials 

specification standards. The latter have 

already been prepared in ASTM by 

committees F-34 on Bearings and F-04 on 

Surgical and Medical Devices, based in part 

on Committee C-28’s generic standards. 

ASTM Standards Revised and New ISO 

Standards Advanced 

During FY 2003, we took many of the 

lessons learned from preparation of the 

SRMs, the ceramic grinding study, and other 

sources and made major revisions to the 

ASTM standards for fractographic analysis 

(C 1322), flexural strength at room 

184 

Heavy Vehicle Propulsion Materials 

temperature (C 1161), and flexural strength 

at elevated temperatures (C 1211). Revisions 

to the hardness standards are under way as 

well. Substantial progress was made on 

moving test methods for elevated 

temperature flexural strength (ISO 17565) 

and fracture toughness (ISO 18756) through 

the IOS system. 

Conclusions 

Step by step, we are building a national 

and international standards infrastructure to 

facilitate the commercial utilization of new 

advanced materials in engine applications. 

The generic test method standards developed 

to date have proved to be so practical, 

reliable, and versatile that they are now 

being used to support a wide range of 

applications, including surgical implants in 

humans and ceramic military body armor. 

FY 2003 Publications/Presentations 

1. G D. Quinn, K. Xu, J. A, Salem, and J. J. 

Swab, “SRM 2100: the World’s First Fracture 

Toughness Reference Material,” submitted to 

the Eighth International Conference on the 

Fracture Mechanics of Glasses and Ceramics, 

Houston, February 2003. 

2. J. A. Salem, G. D. Quinn, and M. G. 

Jenkins, “Measuring the Real Fracture 

Toughness of Ceramics –ASTM C 1421,” 

submitted to the Eighth International 

Conference on the Fracture Mechanics of 

Glasses and Ceramics, Houston, February 

2003. 

FY 2003 Progress Report 

3. G. D. Quinn, “Weibull Strength Scaling 

for Standardized Rectangular Flexure 

Specimens,” J. Am. Ceram. Soc., 86(3), 508– 

510 (2003). 

4. G. D. Quinn, “Weibull Effective 

Volumes and Surfaces for Cylindrical Rods 

Loaded in Flexure,” J. Am. Ceram. Soc., 86(3), 

pp. 475–478 (2003). 

5. G. D. Quinn, L. K, Ives, and S. 

Jahanmir, On the Fractographic Analysis of 

Machining Cracks in Ground Ceramics: A Case 

Study on Silicon Nitride, NIST SP 966, National 

Institute of Science and Technology, May 

2003. 

6. G. D. Quinn, L. K, Ives, and S. 

Jahanmir, “Machining Damage Cracks: How 

to Find and Characterize Them by 

Fractography,“ to be published in Ceram. 

Eng. Sci Proc., 24(3) or (4), (2003). 

7. G. D. Quinn, L. K, Ives, and S. 

Jahanmir, “On the Nature of Machining 

Cracks in Ground Ceramics: Part I: SRBSN 

Strengths and Fractographic Analysis,” 

submitted to Machining Science and 

Technology. 

8. G. D. Quinn, L. K, Ives, and S. 

Jahanmir, “On the Nature of Machining 

Cracks in Ground Ceramics: Part II: 

Comparison to Other Silicon Nitrides and 

Damage Maps,” submitted to Machining 

Science and Technology. 

9. G. D. Quinn, L. K. Ives, and S. 

Jahanmir, “Fractography Reveals Machining 

Cracks,” Bul. Amer. Ceram. Soc., 82(7), 11 

(2003). 

10. G. D. Quinn, J. J. Swab, and M. J. 

Motyka, “Fracture Toughness of a Toughened 

Silicon Nitride by ASTM C 1421,” J. Am. 

Ceram. Soc., 86(6), 1043–1045 (2003). 

185 


Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

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ACEM aberration-corrected electron microscope 

ADF annular dark-field 

AMCL Advanced Materials Characterization Laboratory 

ANL Argonne National Laboratory 

ASM American Society for Metals 

ASME American Society of Mechanical Engineers 

ASTM American Society for Testing and Materials 

Ba barium 

BET Brunauer-Emmett-Teller theory 

BMO base metal oxides 

CC current collector 

CCVD combustion chemical vapor deposition 

CDF cumulative distribution function 

CERT Committee on Energy Research and Technology 

CVD chemical vapor deposition 

CF8C an Fe-19Cr-12NiCNb austenitic stainless steel 

CN-12 an Fe-25Cr-13NiCNNb austenitic stainless steel 

CRADA cooperative research and development agreement 

CRT continuously regenerating technology 

CWRU Case Western Reserve University 

DDC Detroit Diesel Corporation 

DOE U.S. Department of Energy 

DPF diesel particulate filter 

DRIFT diffuse reflectance infrared Fourier transform spectroscopy 

DSC dispersion-strengthened composite 

DTA differential thermal analyzer 

EDM electro-discharge machining 

EDS energy dispersive spectroscopy 

EERE Office of Energy Efficiency and Renewable Energy 

EGR engine gas recirculation 

EPA U.S. Environmental Protection Agency 

EPMA electron probe microanalysis 

EVD electrochemical vapor deposition 

FCVT FreedomCAR and Vehicle Technologies 

FTIR Fourier transform infrared spectroscopy 

HC hydrocarbons 

HDI high-density infrared 

HIP hot isostatic pressing 

HShigh stress 

HSWR High-Strength Weight-Reduction Materials Program 

187

FY 2003 Progress Report Heavy Vehicle Propulsion Materials 

HTML High Temperature Materials Laboratory 

HVOF high velocity oxygen-fueled 

IA implementing agreement 

IA-AMT Implementing Agreement for a Programme of Research and 

 Development on Advanced Materials for Transportation

 Applications. 

IEA International Energy Agency 

INEEL Idaho National Engineering and Environmental Laboratory 

ISO International Organization for Standards 

LANL Los Alamos National Laboratory 

LBNL Lawrence Berkeley National Laboratory 

LS low stress 

LSCF La0.6Sr0.4Co0.8Fe0.2O3 

LST laser surface texturing 

NASA National Aeronautics and Space Administration 

NDE nondestructive evaluation 

NiAl nickel aluminide 

NiCr nickel chromium 

NiCrFe nickel chromium iron 

NIST National Institute of Standards and Technology 

NOx oxides of nitrogen 

NO x oxides of nitrogen; nitrites/nitrates species 

NSF National Science Foundation 

NTRC National Transportation Research Center 

OFCVT Office of FreedomCAR and Vehicle Technologies 

ORNL Oak Ridge National Laboratory 

PM particulate matter 

PM parts per million 

PNNL Pacific Northwest National Laboratory 

PoT pin-on-twin oscillating wear test 

Pt platinum 

PZT lead zirconate titanate 

RE reference electrode 

SAcM scanning acoustic microscopy 

SAXS small angel x-ray scattering 

SCG slow crack growth 

SCR selective catalytic reduction 

SE sensing electrode 

SEM scanning electron microscopy 

SiC silicon carbide 

SIUC Southern Illinois University–Carbondale 

SOFC solid oxide fuel cell 

188

Heavy Vehicle Propulsion Materials FY 2003 Progress Report 

SO x

SpaciMS 

SRBSN 

SRM 

SS 

STEM 

TBCs 

TEM 

TFS 

TGA 

Ti 

TiAl

TiC

TTBCs 

TTZ

TWC 

WC

XPS 

XRD

YSZ

 oxy-sulfur species 

spacially resolved mass Spectrometer 

sintered reaction-bonded silicon nitride 

Standard Reference Material 

stainless steel 

scanning transmission electron microscopy 

thermal barrier coatings 

transmission electron microscopy 

thru focal series 

thermal gravimetric analysis (or analyzer) 

titanium 

 titanium aluminide 

 titanium carbide 

thick thermal barrier coatings 

 transformation-toughened zirconia 

three-way catalyst 

 tungsten carbide 

X-ray photoelectron spectroscopy 

 X-ray diffraction 

 yttria-stabilized zirconia 

189