ARMY RESEARCH LABORATORY

A Novel Manufacturing Processing

Route for Forming High-Density

Ceramic Armor Materials:

Phase II - SBIR

by Ramas V. Raman

ARL-CR-438 April 1999

prepared by

Ceracon, Inc.

1101 North Market Boulevard

Suite 9

Sacramento, CA 95834

under contract

DAA-92-C-0068

1 gggo414015

Approved for public release; distribution is unlimited.
.

.

The findings in this report are not to be construed as an official

Department of the Army position unless so designated by other

authorized documents.

Citation of manufacturer’s or trade names does not constitute an

official endorsement or approval of the use thereof.

Destroy this report when it is no longer needed. Do not return

it to the originator.
Abstract

The feasibility of a combustion synthesis/Ceracon forging (CSKF) fabrication process for

low-cost high-quality ceramic armor is demonstrated. CS of titanium (Ti) and carbon (C)

forming titanium carbide (Tic) was followed by a quasi-isostatic pressurization and densification

to produce tiles with 95% + densities with sizes of up to 15 cm x 15 cm x 2.5 cm. Several tiles

were fabricated and delivered to the U.S. Army Research Laboratory (ARL) for evaluation and

testing. A cost model, which showed that approximately 60% in cost savings can be realized

with the CWCF method, was developed.

.

.

Temperature measurements and one-dimensional (1 -D) computations were used to develop

thermal management practices to make crack-free tiles. X-ray diffraction (XRD) verified full

conversion of reactants to products. A considerable variation in TiC grain size and

microhardness was found between the surface (- 10 pm, high hardness) and the interior (up to

100 pm, low hardness) that depended on conditions during processing. Fractography showed

transgranular fracture in the interior and intergranular fracture at the surface. Quasi-static

compressive strength was found to be 1.79 GPa, while the flexural strength, determined from

four-point bending tests, was 0.17 GPa.

ii
Table of Contents

.

1.

2.

3.

4.

5.

List of Figures ...................................................

List of Tables ...................................................

Executive Summary ..............................................

Project Achievements ............................................

Introduction ....................................................

Phase II Technical Objectives ......................................

Literature Search on CS of TiC ....................................

Background on the CF Process .....................................

Experimental Setup and Results ....................................

5.1

5.1.1

51.2

5.1.3

5.2

5.3

5.3.1

5.3.2

5.3.2.1

5.3.2.2

5.3.2.3

5.4

5.5

5.6

5.7

5.7.1

5.7.1.1

5.7.1.2

5.7.1.3

5.7.1.4

Identification and Procurement of the Precursor Powders ................

Selection of Ti Particle Size ...................................

c .......................................................

Tic ......................................................

Powder Blending Process ........................................

Cold Preform Fabrication ........................................

Cold Compaction Pressure Optimization .........................

Cold Compaction Process Determination .........................

CIPing ................................................

UCIPing ...............................................

ColdPressing ...........................................

Preparation of Tiles Prior to Consolidation ...........................

Preheating Schedule Prior to Forging ...............................

Effect of TiC Additions .........................................

CS/CF ......................................................

The tign After Being Placed in the PTM ...........................

Storage Time of Powders ..................................

Density of the Preform ....................................

Method of Wrapping the Grafoil Around the Preform ............

Part Preheat Temperature .................................

Page

V

Vii

ix

xi

1

2

3

4

6

6

6

8

8

8

10

10

13

13

16

17

17

19

21

21

22

22

23

23

23

. . .

ill
5.7.1.5 PTM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.7.2

5.7.3

6.

7.

7.1

7.2

7.3

7.3.1

7.3.2

7.3.3

7.3.4

7.3.5

8.

8.1

8.2

8.3

9.

10.

11.

12.

The t,,,,,,, From the First Ignition Until Pressure Application ............

EfSect of Pressure .............................................

Thermal Management to Prevent Crack Formation .....................

Characterization ..................................................

Specimen Preparation ............................................

Microstructural Characterization and Phase Analysis ....................

Mechanical Properties ............................................

Microhardness ...............................................

Compression Strength and Modulus of Rupture Strength ..............

Fracture Toughness ...........................................

Elastic Modulus ..............................................

Dynamic Mechanical Properties .................................

Machining of CS/CF Tiles ...........................................

Ceramic Machining and Grinding ...................................

EDM ..........................................................

Water-Jet Cutting ................................................

Cost Model to Manufacture .........................................

Phase II Accomplishments ..........................................

Recommendations for Phase III ......................................

References ........................................................

Process Conditions for 55 TiC Tiles Having Approximate

Dimensions 5 cm x 5 cm x 2 cm and 10 TiC Tiles Having

Approximate Dimensions 10 cm x 10 cm x 2.5 cm . . . . . . . . . . .

Appendix A:

Appendix B:

Appendix C:

Drawings of the Cold Press, Ceracon Die, and UCIP Die . . . . .

Cost Model for the Manufacture of 1,000 Tiles . . . . . . . . . . . . .

Distribution List ...................................................

Report Documentation Page .........................................

Page

23

24

24

24

32

32

32

33

33

35

36

36

38

39

39

39

40

40

41

41

43

47

53

69

85

89

iv
List of Figures

Figure

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

B-l.

B-2.

B-3.

The Ceracon Process ..............................................

Schematic of Setup to Determine the Effect of Pressure on Combustion Wave

Propagation .....................................................

Effect of CIP Pressure on the Green Density ............................

Setup Used to Measure Reaction Temperatures ..........................

Effect of PT.M Type on Cooling Characteristics of CSed Tic ................

Experimentally Determined Temperature Time Plots for Different Compact

Diameters ......................................................

Temperature Distance Plots for Different Times With (a) Al,O,-Based PTM at

Room Temperature and With (b) A&O,-Based PTM at 500” C ..............

Comparison of Measured and Completed Temperature Histories for

(a) A&O,-Based PTM and (b) Graphite-Based PTM .......................

XRD for a lo-cm x lo-cm Tile (Co-K, Radiation) ........................

Grain Size vs. Position Along Cross Section for (a) 6.35-cm-Square and

(b) 10.2~cm-Square Cross-Sectional TiC Tiles ...........................

Hardness Traverses Along a 10.2-cm Sample Cross Section .................

Fracture Surfaces in (a) Flexure and (b) Compression Specimens .............

Fracture Surface Close to the Specimen Surface ..........................

CSKF 15cm x 15-cm x 2.5~cmTiC Tiles ..............................

Titanium Carbide (Tic) Cold Press Assembly ............................

TiC Cold Press Die ...............................................

Tic Cold Press Die Plate ..... ......................................

V

Page

5

11

13

25

26

27

29

30

33

34

35

37

38

40

55

56

57
Figure

B-4.

B-5.

B-6.

B-7.

B-8.

B-9.

B-10.

B-11.

B-12.

B-13.

TiC Cold Press Punch .....................................

TiC Cold Press Punch Nose ................................

........

........

.

.

TiC Cold Press Load Blocks ........................................

Guide Post Modifications ...........................................

20-cm-Square Die Assembly No. 1 ....................................

20-cm-Square Die Assembly No. 2 ....................................

Uniaxial Cold Isostatic Press (UCIP) Assembled Die ......................

UCIP Left Side ..................................................

UCIP Side Cap ..................................................

UCIP Right Side .................................................

C-l. Flow Chart for Manufacturing of TiC Tiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

m

58

59

60

61

62

63

64

65

66

67

76

.

.

vi
Table

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

A-l.

A-2.

C-l.

c-2.

List of Tables

Chemical Analysis and Cost Comparison of Starting Powders ...............

Effect of Particle Size of Ti on Combustion and Densification Behavior of TiC . .

Effect of CIP Pressure on Green Density ...............................

Effect of CIP Pressure on Ignition Characteristics and Density of the

(Ti+C)Preform ..................................................

Effect of Drying the (Ti+C) Powder Prior to Compaction ..................

Effect of Grafoil Thickness on Final Density and Ignition Time ..............

Effect of Preheat Temperatures on TiC Consolidation .....................

Effect of Presynthesized TiC Additions ................................

Thermophysical Data Used in Computations ............................

Compressive Strength of TiC ........................................

Young’s Modulus of TiC ...........................................

Process Conditions for 5-cm x 5-cm x 2-cm TiC Tiles .....................

Process Conditions for lO-cm x lo-cm x 2.5cm TiC Tiles ..................

Equipment Purchase and Setup Costs ..................................

Manufacturing Costs of 1,000 TiC Tiles ................................

&

7

9

12

14

15

18

20

21

28

36

38

49

52

81

83

Vii
.

INTENTIONALLY LEFTBLANK.

.

. . . Vlll
Executive Summary

The U.S. Army is interested in the development of a manufacturing process for fabrication of

low-cost, high-quality armor tiles for defeating enemy kinetic energy (KE) projectiles. The general

objective of the Phase II effort is to demonstrate an upscaled combustion synthesis/Ceracon forging

(CSKF) process for the fabrication of low-cost ceramic armors. The objective of this Phase II Small

Business Innovative Research (SBIR) effort was to demonstrate the successful utilization of a

quasi-isostatic pressurization method to produce dense (>95%) titanium carbide (Tic) compacts.

CS of Tic followed by quasi-isostatic densification using a granular pressure-transmitting medium

(PTM) (the Ceracon Process) yielded compacts with densities exceeding 95% and sizes of up to

15cmx 15cmx2,5cm(6inx6inx 1 in).

Temperature measurements at the compact surface were made and compared to calculated

one-dimensional (1-D) computations. As expected, the cooling rate of compacts decreased as the

compact diameter increased and as the temperature of the PTM increased. These modeling and

experimental measurements yielded insight into thermal management practices to be used to make

crack-free tiles. X-ray diffraction (XRD) showed that full conversion to Tic occurred. The lattice

parameter from XRD analysis was 0.4334nm. The grain size showed a considerable variation, being

larger (up to 100 pm) at the interior of the compacts and smaller near the surface (- 10 pm). The

grain-size variation was dependent on compact size and determined by the cooling rate, which is

higher at the surfaces. The quasi-static compressive strength was determined and found to be equal

to 1.79 GPa. The flexural strength, determined from four-point bending tests, was equal to

0.17 GPa. Microhardness measurements were made along the cross section, and the values varied

considerably with position, being higher at the surface than in the center. Fractography showed that

the fracture surface varied from transgranular in the center to intergranular at the surface. The

microstructure and mechanical properties of the synthesized/densified compacts were addressed, and

the results were favorable. The cohesion of the grains was excellent, and the compressive and tensile

strengths were acceptable. Prototype quantities of 15-cm x 15-cm x 2.5-cm tiles were fabricated and

ix
delivered to the U.S. Army Research Laboratory (ARL)* for evaluation and testing. A cost model

was developed based on the prototype tile fabrication experience. The model showed that

approximately 60% in cost savings could be realized in the fabrication of Tic via the process

developed in this program.

.

* On September 1992, the U.S. Army Ballistic Research Laboratory (BRLJ was deactivated and subsequently became

part of ARL on 1 October 1992.

X
.

Project Achievements

Originality and Innovation of the Research. The combustion synthesis (CS) process involves

initiation of a self-propagating reaction at low temperatures between elemental components to

synthesize a high-temperature compound (i.e., titanium [Ti] and carbon [C] react to form titanium

carbide [Tic]). However, a stand-alone CS process produces a material with 50% porosity. The

Ceracon forging (CF) process involves application of pressure on a hot, porous structure using a

granular carbonaceous pressure-transmitting medium (PTM). The Ceracon innovation is to combine

the CS and CF processes in one step (CS/CF), whereby in-situ synthesis and densification can be

carried out. The hot carbonaceous particulate in the CF process serves as a combustion initiator and

PTM. Such dual use of a particulate medium for synthesis and densification is novel and original.

This technique has been successfully applied under the U.S. Army Research Laboratory’s (ART_,)

support to fabricate large-size (15 cm x 15 cm x 2.5 cm [6 in x 6 in x 1 in]) Tic tiles.

The Relevance of the Research to the Army and Its Mission. The U.S. Army’s mission is

increasing to support technologies that have use in both military and commercial applications. The

CSEF process technology fulfills both criteria of relevance and specific mission. The cost analysis

for the CS/CF process shows that a dramatic decrease in cost is feasible with the process developed

via the Small Business Innovative Research (SBIR) support. At the same time, the same process is

also applicable for the fabrication of heating element materials for high-temperature furnaces, cutting

tools, and Ti- and nickel (Ni)-base alloys for automotive and aerospace applications.

.

.

The Immediate Commercialization Potential of the Research. The potential for

commercialization of any new technology is dependent on four factors: (1) the need for a product

made using this technology, (2) the cost of the product, (3) the cost of acquiring the technology, and

(4) the quality of the product. Ceracon has identified an immediate need in the areas of cutting tools,

automotive parts, and heating elements. Our cost model shows feasibility of lowering the cost by

60% of the current market prices. The capital equipment required is simple, off-the-shelf, and

inexpensive. The quality of the product made using this technology has been found to be equal or

xi
superior to the products made by current processes. Therefore, the immediate commercialization

potential of this research is rated very high.

.

.

xii
1. Introduction

The fabrication of dense compacts utilizing combustion synthesis (CS) in combination with a

consolidation method is a very attractive technology. Developed in Russia by Merzhanov and

coworkers (Merzhanov and Borovinskaya 1972; Merzhanov 1990), CS is being actively researched

in the U.S. (Holt and Munir 1986; Mtmir 1988; Yi and Moore 1990) and Japan (Yamada, Miyamoto,

and Koizumi 1987; Adachi et al. 1989). In the case of titanium carbide (Tic), the combustion

product has a high porosity and densification through the application of external forces is necessary.

Hot pressing during or after reaction (Yamada, Miyamoto, and Koizumi 1987; Adachi et al. 1989;

Rice 1990; Riley and Niiler 1987) has been applied with considerable success. Dynamic

consolidation by explosives was introduced in the U.S. by Niiler and coworkers (Niiler et al. 1988;

Kecskes, Kottke, and Niiler 1990; Niiler, Kecskes, and Kottke. 1992) and followed by Rabin, Korth,

and Williamson (1990) and Grebe et al. (1992); Russian effort in this area occurred simultaneously

(Shikhverchiev et al. 1992; Molokov and Mukasyan 1992). Consolidation using a high-speed

(12-17 m/s impact velocity) forging press yielded fully dense compacts (LaSalvia, Meyer, and

Meyers 1992; Hoke et al. 1992; Vecchio et al. 1992; Meyers et al. 1993).

The objective of this Phase II Small Business Innovative Research (SBIR) effort is to

demonstrate the successful utilization of a quasi-isostatic pressurization method to produce dense

(>95%), large TiC tiles measuring 15 cm x 15 cm x 2.5 cm (6 in x 6 in x 1 in). This technique (the

Ceracon forging [CFJ process) presents unique advantages over the other methods because it uses

a granular medium to transmit the pressure to the part. This granular medium enables a great degree

of freedom in the shapes to be synthesized and can be preheated to ignite the reactive green powder

compact, so that an ignition mechanism is no longer needed. The thermal properties of the pressuretransmitting medium (PTM) are also very favorable, and thermal stresses (leading to cracking) in

reacteddensified compacts can be minimized.

1
2. Phase II Technical Objectives

The general objective of the Phase II effort is to demonstrate an upscaled CWCF process for the

fabrication of low-cost ceramic armors for the U.S. Army Research Laboratory (ARL).

.

The specific goal of the Phase II effort is to demonstrate prototype fabrication of TiC armor tiles

having dimensions of 15 cm x 15 cm x 2.5 cm; having a minimum of 95.57% density; and meeting

all mechanical property requirements, including microhardness, modulus, and compressive-strength

requirements specified by the Army/ARL for TiC material. A subobjective is to demonstrate the low

cost of this process, as supported by a projected cost analysis for a scaled-up manufacturing system

that uses cost data input for Phase II prototype fabrication. The objectives of the Phase II effort are:

l to demonstrate the feasibility of fabricating TiC tiles having dimensions

- 15 cm x - 15 cm x -2.5 cm in prototype quantities using an upscaled CWCF process;

l to demonstrate that the material is f&e of chemical impurities above a level of 0.015%;

l to demonstrate that crack-f&e integral TiC tiles having a minimum density of 95.57% can be

fabricated;

l to demonstrate that the material meets mechanical property requirements such as

microhardness, compressive strength, fracture toughness, elastic modulus, and dynamic

properties;

l to demonstrate that the material has a fine grain size and is chemically and microstructurally

homogeneous;

l to provide ARL with TiC tiles for testing and field evaluation; and

2
.

l to provide the Army with a plan for manufacturing TiC and a cost model for price per kilogram

and projected savings relative to conventional manufacturing of TiC armor.

3. Literature Search on CS of TiC

TiC has been synthesized by combustion and consolidation by dynamic compaction (Kecskes,

Kottke, and Niiler 1990; Niiler, Kecskes, and Kottke 1990). Samples with relative densities of 98%

have been prepared. Their hardness was equal or better to that obtained with conventionally

prepared (commercial) materials. The hardness, however, showed a dependence on the

stoichiometry of the TiC phase. The maximum hardness corresponded to a carbon/titanium (C/Ti)

ratio of 1 .O. However, at this ratio, the process of densification is not optimum and it was concluded

that an ideal C/Ti ratio of 0.90 to 0.95 would give the desired combination of ease of den&cation

and high hardness. This observation is in contrast to that made by Miyamoto and Koizumi (1990).

These authors synthesized and consolidated Tic, in one step, using what they refer to as

“gas-pressure combustion sintering.” Under an argon (Ar) gas pressure of 100 MPa, they were able

to obtain fully dense Tic, for 0.5/x/0.8. A higher x value resulted in lower density products. The

authors explain this in terms of having excess C that inhibits densification in samples with x > 0.8.

Another important parameter that influences the densification and the microstructure of TiC is the

nature and level of impurities. Impurities of iron (Fe) were found to degrade the properties of the

carbide by segregating at the grain boundaries (Kecskes, Kottke, and Niiler 1990). Other impurities

in the reactants (Ti+C) can also play a role in the densification and microstructural development of

the carbide (Kecskes, Kottke, and Niiler 1989). The major noncondensable impurities that were

detected in the gas phase above the heated reactants include water (H,O), hydrogen (H,), carbon *

monoxide (CO), carbon dioxide (CO,), and hydrocarbons. Most of these types of impurities can be

expelled by outgassing the reactant mixture at 500” C for several hours.

TiC has also been CSed and densified to 95% by the applications of uniaxial pressure (Holt and

Munir 1986). The application of 27.6~MPa pressure resulted in a TiC microstructure with a typical

grain size of approximately 20 pm. In agreement with the observations of Niiler and coworkers

3
(Kecskes, Kottke, and Niiler 1989; Niiler, Kecskes, and Kottke 1990), the gases that evolved during

combustion were found to contain a significant amount of H,. It was proposed that the presence of

this gas is the result of an oxidation reaction of the Ti metal by H,O vapor or the evolution of

dissolved H, from Ti. The latter interpretation is especially important in cases where the Ti is

prepared from a hydride phase.

There are also reports of investigations on the synthesis and densification of TiCcontaining

composites. Composites such as Tic + alumina (AJOJ are commercially important as cutting tools.

TiC is added to A&O, to enhance toughness and limit undesirable grain growth. However, in the

sintering of these composites, undesirable gas evolution leads to pore formation. Gas evolution in

this case is the consequence of interaction between TiC and Al,O, (Kim and Lee 1989). This

composite has been investigated with respect to the feasibility of transformation toughening through

the addition of zirconia (ZrOJ (Cutler, Virkar, and Holt 1985). In another investigation, it was

found that a composite of Al,O, + 30-weight-percent Tic could be sintered to a density of >97% at

1,950” C if the heating rate up to this temperature is >200” C/min (Borom and Lee 1986).

Presumably higher heating rates diminish the extent of the interaction between A&O, and Tic. As

indicated previously (Kim and Lee 1989), such an interaction leads to the formation of gaseous

products that decrease the ultimate relative density of the composite. Prior to this work, consistently

fabricated high-density TiC tiles have not been feasible without the addition of Ni or molybdenum

(MO) metal.

4. Background on the CF Process

The Ceracon process is a patented (U.S. Patent No. 4,539,175 [Lichti and Hofstatter 1985]),

low-cost powder metallurgy process for achieving near-net-shaped, full-density parts. It is a simple

consolidation technique that utilizes conventional powder metallurgy equipment and setup. The

Ceracon process is a quasi-isostatic, hot consolidation technique that utilizes a ceramic particulate

material as a PTM instead of a gas media as used in hot isostatic pressing (HIPing). Pressure up to

1.24 GPa can be used, and materials can be processed at unlimited upper temperatures. The process

consists of four steps, as detailed in Figure 1: (1) fabrication of green preform, (2) part heating and

4
,

1. Pressure transmitting media

.

2. Heated oreform is inserted into

the PTi by robot

3.

(PTM) fills the die

Hydraulic press ram pressurizes

the grain & consolidates the part

to full density 4. The die is cleared and the PTM

is recycled

Figure 1. The Ceracon Process.

grain heating and transfer to the Ceracon die, (3) consolidation, and (4) part removal and grain

recycling.

The low temperature coupled with short time consolidation capabilities of the quasi-isostatic,

hot-consolidation, high-pressure process has been applied to a broad range of material systems

(Raman, Rele, and Kapoor 1992; Raman and Rele 1993). The various systems processed include

Al 6061 and 2124, tool steel, 46XX steel, Al-Fe-V-Si, TiAl, Cu, Nd-Fe-B supermagnets, superalloys,

Al-Sic MMCs, WC-Co to Fe, Nb alloys, and YBqCu,O,, superconductors.

5
6

The idea of using a PTA4 to initiate self-propagating high-temperature synthesis (SHS) reaction

and subsequently superimposing pressure on the part in situ had not been previously explored. This

approach, if successful, will have significant advantages over thermite-induced SHS consolidation

approaches because of:

.

l technology capability for consolidating net-shaped parts from conventional materials, such as

steel, up to a 17.5cm diameter x 60-cm length has already been demonstrated;

l thermal management of the specimen during and after processing is readily possible because of

immediate specimen access after consolidation is completed; and

l the equipment is easy to set up and operate without tire elaborate features required from other

processes such as HIPing, hot pressing, and CS/explosive consolidation

5. Experimental Setup and Results

5.1 Identification and Procurement of the Precursor Powders.

5.1.1 Selection of Ti Particle Size. Phase I of this program used Ultrafine MicroTi Ti (20 pm)

from Micron Metals, Salt Lake City, UT. This particle size was found to be suitable for the Phase I

program (Raman, to be published) for smaller size specimens (c2.5cm diameter and ReigRt); this

was validated in a separate study by BRL (Raman and Niiler 1991). However, tiles of TiC with

dimensions of 5 cm x 5 cm x 2 cm (2 in x 2 in x 0.79 in> or more were found to exhibit a markedly

violent reaction with significant speed of the combustion wave, flare, and an audible explosion The

use of ultratine Ti was thought to be the reason behind the deep laminar cracks and breaking up of

the consolidated tile. Also, higher costs, safety issues arising from storage and use, and higher

oxidation rate of ultrafine Ti powder necessitated a search for a coarser starting material.

-20~pm Ti. Fabrication of crack-free S-cm x 5-cm x 1.25-cm (2 in x 2 in x 0.5 in) TiC tiles on a

repeatable basis was made using the - 100+150 mesh Ti powder. Hence this mesh size was

determined to be the most optimum for this program. Ti powder of mesh size - 60 + 100 was also

tried out and found to have no significant improvement over the - lOO+ 150 mesh Ti powder

regarding the cracking tendencies of the speed of the combustion wave. Table 2 compares the

ignition and densities of 5-cm x 5-cm x 2-cm TiC tiles made using - 100+150 mesh Ti powder and

- 60+ 100 mesh Ti powder.

It is seen that there is no significant difference in densities or in the ignition times by varying the

particle size of the Ti. However, the TiC tiles made using the - 100 +500 mesh Ti powder displayed

fewer cracks on an average, as compared to the ones made using the -60+100 mesh Ti powder.

5.1.2 C. In Phase II, the same 2-pm graphitic C as that used in Phase I was selected. The

chemical analysis and cost are shown in Table 1.

5.1.3 Tic. Very fine particle size (l-l.5 pm) TiC additions were added as a diluent to further

slow down the speed of the ignition wavefront in various amounts to the (Ti+C) tile. The chemical

analysis of the TiC is shown in Table 1.

5.2 Powder Blending Process. Phase I of this program required smaller amounts of powder

(batch size ~250 g), and wet milling was used to blend the powders. Phase II required batch sizes

of approximately 9 kg. Drying of such large batches became a long and arduous process, and the

powders would not dry off completely. Discussion with the contracting officer’s technical

representative (COTR) and technical staff at ARL, as well as our consultant Prof. Marc Meyers

(University of California-San Diego [UC-SD]), revealed that dry milling worked equally well, hence,

dry milling for about 4 hr was consistently used for blending all the Ti and C powders for Phase II.

Aluminum (Al) jars 30 cm long x 17.5 cm diameter with an approximate volume of 7.5 liters,

lined with silicone rubber Type M (supplier K. R. Anderson) were specially built for the blending

8
. . a .

Table 2. Effect of Particle Size of Ti on Combustion and Densification Behavior of TIC

Ceracon

No.

>

5397

5399

5401

5415

5413

5414

5402

5403

5404

1 Mill 1 CIP Data Forge Data

Grafoil Ti

0

PTM Part Time at Time to Theor.

Thickness size Height Width Length Temp. Temp. Temp. Ignite Density

(cm) (mesh) (cm) (cm) (cm) (“C) (“C) (hr:min) (minx) (%)

0.038 Fine 1.905 5.080 5.080 1,208 705 0~25 400 96.5

0.038 Fine 1.918 5.088 5.090 1,212 701 0:17 - 96.2

0.038 Fine 1.918 5.088 5.090 1,212 802 Q45 405 95.7

0.038 Fine 1.961 5.174 5.461 1,209 698 046 417 93.2

0.038 Coarse 1.824 5.367 5.436 1,208 707 0:41 3:57 95.2

0.038 Coarse 1.874 5.392 5.481 1,208 703 0:31 449 95.9

0.064 Coarse 1.539 4.834 4.928 1,212 797 237 3:45 95.8

0.064 Coarse 1.529 5.278 5.283 1,213 800 3:38 3:36 95.9

0.064 Coarse 1.910 5.354 5.499 1,208 801 1:08 5:45 94.9

Common Parameters

?ressure...... . . . . . . . . . . . . . . . 241GPa Strain ..*.................................... Wide

ZpPress . . . . . . . . . . . . . . . . . . . 69MPa Bleed . . . . . . . . . . . . . . . . . . ..s................... Inst.

DieTemperature . . . . . . . . . . . . . ,250” C Hold . . . . . . . . . . . . . . . . . . . . . . . ..*n............. OS

?TM Type . . . . . . . . . . . . . . . . . . . A-20b Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ar at 566 liters/hr

ParticleSize . . . . . . . . . . . . O.. . ..Fiue(-100+15Omesh) Theor. Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.92 g/cm3

Particle Size.. . . . . . . . . . . . . . . . . Coarse (-60+100 mesh) Cooling . . ..*..................*.............. Vermiculite

* CIP = cold isostatic press.

b A-20 = Alz03 PTM with 20 volume-percent 9,400 graphite.
process. A two-tier ball mill (U.S. Stoneware Model 784) was purchased for this project. ZrC,

cylinders (1.2 cm x 1.2 cm long) were used as the media and tilled approximately

45-50 volume-percent of the mill jar. Ti and C powders in the 1:0.9 molar ratio (corresponding to

8 1.58-weight-percent Ti) were weighed out in a protective atmosphere and placed in the mill jar with

the ZrO, media. The mill jar was evacuated and back-filled with high-purity Ar and sealed. The mill

jars were rotated at approximately 65 f 5 rpm for 4-6 hr. Each mill jar produced 2 kg of powder.

Separation of the powder from the media was carried out in air. Initial techniques of manual

separation were slow and took as long as 45 min to 1 hr, so, a device was built that reduced the

separation time to less than 10 min. The blended powders were stored in sealed containers under

Ar immediately after separation.

5.3 Cold Preform Fabrication. This task consisted of two subtasks involving optimization of

pressure used in the cold compaction process and the process steps to enable consistent fabrication

of crack-free uniform-density preforms:

(1) cold compaction pressure and

(2) cold compaction process.

5.3. I Cold Compaction Pressure Optimization. Low densities of the green (Ti+C) preform give

poor strength during handling prior to ignition. Low green strengths show a propensity toward

cracking or breaking of the preform before and during the CWCF cycle. Higher green densities, on

the other hand, have been shown (LaSalvia 1990) to result in higher thermal conductivity for the

preform, resulting in incomplete propagation of the combustion wave front.

Cold isostatic pressing (CIPing) was used as the process to determine the effect of cold

compaction pressure on:

. the green density,

l the time for the initiation of combustion,

10
l the time for completion of combustion, and

l the density of CS material.

Disks of (Ti+C) were CIPed at various pressures (55-380 MPa) into disks, approximately 4.5 cm

in diameter and 1 cm thick. These were inserted into a furnace preheated to 1,200” C in air, one at

a time. A video camera was set up to enable recording of the combustion wave. This setup is shown

in Figure 2. Table 3 and Figure 3 show the expected result of increasing green density with

increasing CIP pressure.

Tube Furnace

Preheated to 1280 C

Muffle

withair

atmosp*re

Camcorder

Figure 2. Schematic of Setup to Determine the Effect of Pressure on Combustion Wave

Propagation.

.

After insertion of the preform disk into the 1,200” C furnace environment, a wave was seen to

initiate at the top edge of the disk. This wave would travel through the disk, and the disk would flare

11
12

Table 3. Effect of CIP Pressure on Green Density

Common Parameters

Atmosphere ................. Air

PTMType .................. 9,400

PTM Temperature ............ 1,200’ C

CIPCube ................... 2.41 cmx2.41 cmx2.41 cm

Iheor. Density (Ti+C) ......... 3.81 g/cm”

up into a conflagration. The time prior to wave initiation, the time from the initiation to flare-up, and

the extent of wave travel before the flare are shown in Table 4.

With an increase in CIP pressure, it takes a longer time to ignite the preform. This is in

accordance with the literature (LaSalvia 1990), whereby researchers have noted increased thermal

conductivities with increased green densities, which result in channeling away the heat, resulting in

longer times for ignition. Also with increasing green densities, the time from wave initiation to

flare-up was reduced, which resulted in increased violence in flare-up. This caused a larger degree

of breaking up and cracking of the part after CS. CIP pressure below 55 MPa would produce very

fragile and difficult-to-handle preforms. Based on the integrity of the part after CS, it was

determined that optimum green densities are obtained by cold compaction around 83 MPa.
90

80

09 70

2

; 60

3 50

.-

tf 40

8

$ 30

$ 2o

10

0 I I I I I I 1 I 1 I I 1

0 10 20 30 40 50 60

Pressure (MPa)

Figure 3. Effect of CIP Pressure on the Green Density.

5.3.2 Cold Compaction Process Determination. Three routes were pursued for cold preform

fabrication:

(2) uniaxial cold isostatic pressing (UCIPing), and

(3) cold pressing.

5.3.2.1 CZPing. CIPing of the (Ti+C) powders into integral crack-free parts was found to

depend on several factors. It was required to CIP the preforms within l-2 days of powder

preparation. Conversations with Marc Meyers’ group revealed that, for obtaining uniform crack-free

parts, it was necessary to dry the parts (in a low-vacuum environment) at around 110” C. The effect

of drying the powder is shown in Table 5.

13
Table 4. Effect of CIP Pressure on Ignition Characteristics and Density of the (Ti+C) Preform

of Combustion

Note: Conditions: CIP disk inserted into a furnace preheated to 1,200” C in air.

a The-or. Density (Ti+C) = 3.811 g/cm3.

b CSed, not consolidated.

’ Theor. Density (Tic) = 4.92 gbn3.

The following observations were made regarding the characteristics of the CIP process.

l CIPing of as-rnihed powders into integral crack-free preforms depends on the storage time

of the powders before CIP. The longer the storage time, the greater the tendency for

breaking during CIP.

.

l CIPing of powders dried at 110” C, within a few hours of the drying process, consistently

produces parts that are crack-free. However, once again, longer storage times led to cracking

probably due to oxidation and/or absorption of excessive moisture, which is released during

thermal exposure of the specimen.

.
L .

. l

Table 5. Effect of Drying the (Ti +C) Powder Prior to Compaction

Zeracon PTM Theor.

No. TYpe Strain Decompression Cooling Method Density Density Drying Method

(cm/cm) (g/cm3) (%)

5158 A-75 Wide Instant Inserted in furnace at 1,100” C 4.37 89 Not Dried

5159 A-75 Wide Instant Inserted in furnace at 1,100” C 4.82 98 Dried24hrat 110” C

5160 A-75 Wide Instant Inserted in furnace at 1,100” C 4.80 98 Dried24hrat 110” C

5161 A-75 Wide Instant Inserted in furnace at 1,100” C 4.81 98 Degassed at 500” C and

600 pm of mercury (Hg)

5162 A-75 60 Instant Cooled overnight at 1,200” C 4.45 90 Degassed at 500” C and

600 pm of Hg

5164 A-20 Wide Instant Cooled in furnace at 1,100 ’ C 4.54 92 Degas& at 500” C and

600pmofHg

5167 A-20 Wide Jnstant Cooled in furnace at 1,100” C 4.68 95 Degassed at 500” C and

600 pm of Hg

Notes: A-75 = A&O, PTM with 75 volume-percent 9,400 graphite.

PTM temperature = 1,200” C.

Pressure = 6.2 x 10s TPa.

CIP pressure = 69 MPa.

Die height = 8.26 cm.
. CIPing of parts with one dimension significantly smaller than the others (for example, in a

plate preform) is very difficult. This was simplified by making a block of (Ti+C) that was

then cut up into several tiles.

. CIPing of parts does not give smooth edges. The edges have to be smoothed out by cutting

with a saw blade.

.

Because of the aforementioned problems, the use of CIP as a manufacturing process was found

to be doubtful. Hence, alternate cold-compaction routes were evaluated.

5.3.2.2 UCZPing. A unique idea for cold compaction of green preforms has evolved in this

Phase II program. Cold pressing and CIPing are the established methods of green-preform

fabrication.

Cold pressing offers advantages of smooth faces, sharp edges, and close dimensional tolerances.

However, cold pressing requires upkeep and maintenance of expensive dies and punches, and

operator error can easily scrap an expensive die set. Increasing part sixes leads to significant increase

in cost.

The innovation of the UCIP process combines the advantages of cold pressing and CIPing. A die

is fabricated through four ground tool steel plates and is bolted together. The punch and die are

polyethylene blocks. The powder is filled in the same way as in cold pressing. The punch and die

assembly is placed in a rubber bag, all of which is CIPed. Polyethylene punches significantly improve

lubrication on die walls, and the life of punch and die are improved significantly. Further, replacement

of either punch or die becomes very inexpensive. Since pressure application and release are slow and

uniform, internal stresses on the part are minimized. To achieve the same density for a UCIPed part

as for a cold-pressed part, a UCIP pressure twice that of the regular CIP pressure is required. At a

UCIP pressure of 138 MPa, a green density of 65% is reached. The design drawings for the UCIP

die for fabricating 15-cm x 15cm x 2.5-cm tiles are attached in Appendix A.

16
.

5.3.2.3 Cold Pressing. Although the UCIP was a novel technique, the slower rate of production

required use of a cold-pressing die. Also, the notched portions of the UCIP die required a redesign

to increase the structural integrity.

Due to the need to stay on schedule, a decision was made to go with traditional cold pressing, and

a die and punch system was designed, fabricated, and installed in the 2,500-ton press. This die was

used successfully in pressing all the tiles required for the Phase II program.

5.4 Preparation of Tiles Prior to Consolidation. During the initial stages of Phase II, smaller

samples were forged. These generated a relatively small increase in the surrounding PTM

temperature. Hence the A&O,-based PTM would not show significant bonding or sticking to the part.

However, with increasing dimensions of the part, a larger amount of heat that melts a larger amount

of Alz03 in the immediate vicinity of the part was generated. The fused and adhered PTM was seen

to result in cracks in the CS/CF part. This perhaps could be attributed to the difference in the cooling

rates and modulus between the molten/adhered A&O, and the Tic.

Hence, it became necessary to introduce a barrier layer that would separate the TiC part from the

PTM, withstand the very high temperatures associated with the CS process, would not bond to the

part, and would not show any unfavorable reactions with the TiC tile. Graphite foil (commercially

known as Grafoil) available in thicknesses of 0.038 cm and 0.064 cm from the Union Carbide

Company was selected as the barrier layer. Table 6 shows the effect of the Grafoil thickness on the

time to ignite and the final density.

It was observed that the Grafoil thickness does not affect the final density of the CWCF 5-cm x

5-cm tiles. However, as expected, a thicker Grafoil resulted in a longer time for ignition. In turn, this

caused slightly more cracking of the TiC tiles. A longer ignition time resulted in a greater degree of

cooling for the PTM, which could result in a greater temperature difference between the part and the

PTM and hence a greater thermal shock. For these very reasons, in addition to the lower cost, the

thinner (0.4 mm) Grafoil was selected for this program

17
Table 6. Effect of Grafoil Thickness on Final Density and Ignition Time

CIP Data Forge Data

Ceracon Grafoil Part Time at Time to Final Final Final Theor.

No. Thickness Height Width Length Temp. Temp. Ignite Height Width Length

(cm)

Density

(cm) (cm) (cm) (“C) (hr) (mims) (cm) (cm) (cm) (%)

Samples With Thin Grafoil

5413 0.038 1.824 5.367 5.436 707 0.68 3:57 1.148 5.817 5.921 95.20

5414 0.038 1.874 5.392 5.481 703 0.52 449 1.247 6.015 6.083 95.90

Samples With Thick Grafoil

5402 0.064 1.539 4.834 4.928 797 2.62

5403 0.064 1.529 5.278 5.283 800 3.63

5404 0.064 1.910 5.354 5.499 801 1.13

3:45 - - - 95.80

3~36 - - - 95.90

5:45 1.140 5.857 5.959 94.90

5405 0.064 1.882 5.639 5.809 798 1.07 5:20 1.158 5.855 5.918 1 96.20

Common Parameter

Dimensions ............................. .5 cm x 5 cm

Ii Particle Size ........................... -6O+lOO mesh

................................... A-20”

RM Temperature ......................... 1,200” C

Die Temperature ......................... .250” C

Iheor. Density (Tic) ...................... .4.92 g/cm3

ForgePressure ............................. 2.41 x l@ TPa

Strain ................................... Wide

Bleed .................................... Inst.

Hold .................................... OS

Atmosphere ............................... Ar at 566 litersbr

Cooling .................................. Vermiculite

a A-20 = A&O, FTM with 20 volume-percent 9,400 graphite.

. .
The effectiveness of the Grafoil as a barrier was demonstrated when, in separate experiments, TiC

tiles were wrapped with the Grafoil either only on the surface (i.e., the 5-cm x 5-cm faces) or on the

sides (i.e., the 5-cm x 2-cm faces). It was seen that, when the parts were wrapped only on the

surface, the A&O, stuck on the sides and the tile showed laminar cracking. However, when the tiles

were wrapped only on the side faces, the part showed surface cracking.

5.5 Preheating Schedule Prior to Forging. One of the drawbacks found regarding the use of

Grafoil was that the foil increased the time to ignite from 3 to 4 min without Grafoil to almost 5 to

8 min with Grafoil wrapping. Also, it was seen that the ignition time range had broadened. This is

very well seen in Appendix B. To reduce the ignition time and the ignition time range, higher PTM

temperatures of 1,300” C and 1,400” C were attempted and proved to be as successful. However,

manufacturing these tiles economically will require the temperatures to be 1,200” C or lower.

This led to the idea of preheating the preform prior to CSKF. The objectives of achieving

repeatable ignition times, achieving ignition with a PTM temperature of 1,200” C, and, in addition,

eliminating an entire step of preheating and degassing the powder prior to cold pressing were all

accomplished by the preheating step.

Table 7 shows the effect of preheating the (Ti+C) tiles at 700” C and 800” C using the

- lOO+ 150 mesh powder as well as the - 60 + 100 mesh powder. It was seen that both preheat

temperatures resulted in parts with similar densities and similar ignition times. However, the

5-cm x 5-cm tiles preheated to 700” C showed a slight improvement over those preheated to 800” C,

after the CSKF process.

Higher temperatures of 850” C and 900” C, although attempted, were not considered viable for

manufacturing, since these temperatures are precariously close to the start ofthe combustion reaction.

The time for which the tile was exposed to the preheat temperature was varied--O.5 hr, 1 hr,

1.5 hr, and 2 hr. The tiles preheated at 700” C for 0.5 hr after CSKF looked the best and showed

a perfectly crack-free surface. Longer times at the preheat temperature were thought to increase the

oxidation of the Ti, resulting in slower ignition of the TiC tile.

19
Table 7. Effect of Preheat Temperatures on TiC Consolidation

Mill CIP Data Forge Data

I

Zeracon Grafoil Ti PTM Part Time at Time to Theor.

No. Thickness Size Height Width Iensth Temp. Temp. Temp. Ignite Density

(cm) (mesh) (cm) (cm) (cm) (“C) (“C) (hr:min) (min: s) (%)

5397 0.038 Fine 1.905 5.080 5.080 1,208 705 0:25 400 96.5

5399 0.038 Fine 1.918 5.088 5.090 1,212 701 0:17 - 96.2

5401 0.038 Fine 1.918 5.088 5.090 1,212 802 0:45 405 95.7

5415 0.038 Fine 1.961 5.174 5.461 1,209 698 0:46 417 93.2

5413 0.038 Coarse 1.824 5.367 5.436 1,208 707 0:41 3:57 95.2

5414 0.038 Coarse 1.874 5.392 5.481 1,208 703 0:31 449 95.9

5402 0.064 Coarse 1.539 4.834 4.928 1,212 797 2:37 3:45 95.8

5403 0.064 Coarse 1.529 5.278 5.289 1,213 800 3:38 3:36 95.9

5404 0.064 Coarse 1.910 5.354 5.499 1,208 801 1:08 5:45 94.9

Common Parameters

Pressure . . . . . . . . . . . . . . . . . . . . . . . 2.41x105TPa Strain _. . . . . . . . . . . . . . . ..a...........*. Wide

C‘IP Press . . . . . . . . . . . . . . . . . . . . . . 69 MPa Bleed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inst.

Die Temperature . . . . . . . . . . . . . . . . 250” C Hold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OS

. . . . . . . . . . . . . . . . . . . . . . . . . . A-20 Atmosphere . . . . . . _ _ e . . . s . . . . . . . . . . . . . . Ar at 566 litersbr

Particle Size . . . . . . . . . . . . . . . . . a . . Fine (-loo+150 Theor. Density (Tic) . . . . . . . . . . . . . . . . . . . . 4.92 g/cm3

mesh) Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vermiculite

E%.rticle Size . . . . . . . . . . . . . . . . . . . . Coarse

(-60+100 mesh)
5.6 Effect of TiC Additions. A large grain size variation was noted in the TiC tiles across the

length, as well as the height. This large variation was believed to crack a few of the tiles being made.

Hence, very fine TiC was added to the (Ti+C) preform to understand the effect of this diluent on the

density and cracking tendency. This is shown in Table 8.

Table 8. Effect of Presynthesized TiC Additions

Common Parameters

CIP Pressure ........... 69 MPa Grafoil .................. 0.038 cm

Part Preheat Temp. ...... 700°C Part.. ................ 5cmx5cm

PTM ................. A-20

Although the addition of TiC reduced the cracking in the CSKF tile, it also adversely affected

the density, reducing it to below acceptable levels. Hence, presynthesized TiC were not incorporated

in the final manufacturing of tiles.

5.7 CWCF. A CF die and punch set (having a square cavity to accommodate 1%cm-square tiles)

was fabricated for the purpose of CS and CF of the Z-cm x 15-cm tiles. The drawings of these are

attached in Appendix A.

The forging of these larger tiles required procedures similar to those of just in time (III.) since

the powder could not be stored for any length of time after the blending operation. Each of the tiles

required miIling of more than 3 kg of powder, and enough powder could be milled for only three tiles

a day. A total of 11 kg of powder was milled every day.

21
More than 50 tiles of 15 cm x 15 cm x 5 cm were cold pressed. An informed and educated

optimization cycle was carried out following experience gained with the 5-cm x 5-cm and the

lo-cm x IO-cm TiC tiles. Appendix B lists all of the process parameters of the tiles. However, due

to the upscaling process, several parameters had to be optimized. A summary of these modifications

is provided next.

Two parameters were found to be critical for the CS/CF process:

(1) time for first ignition (t@) after being placed in PTM.

(2) time allowed for the burn (tbum) process from the first ignition until pressure application.

5.7.1 The tign After Being Placed in the PTM. The process parameters that control tign are

several. However, most of them have been optimized before. The parameters that were modified

during this period included:

(1) storage time of powders,

(2) density of the preform,

(3) method of wrapping the Grafoil around the preform,

(4) part preheat temperature, and

(5) I’TM.

5.7.1.1 Storage Time of Powders. It has been recognized in the past that TiC tiles forged under

identical conditions can show different ti, depending on how long the powders have been stored from

the time they were milled until the time they are forged. It, has also been recognized that the storage

time from milling to cold pressing requires more critical control than the time from cold pressing to

22
forging. For storage times of approximately 1 week, tip’s were consistently around 4.5 min.

However, for storage times of three or more months, ti, was between 6.5 and 10 min. In this period,

an effort was made to have a consistent storage time of approximately 1 week.

5.7.1.2 Density of the Preform. This is among the most important parameters affecting t@.

Previously, densities varied between 2.94 f 0.09 g/cm” for the cold-pressed tile. In this period, the

density was tightly controlled between 2.7 + 0.04 g/cm3.

5.7.1.3 Method of Wrapping the Grafoil Around the Preform. It is recognized that the Grafoil

wrap must prevent the FTM from contacting the hot part, both before and after consolidation. At

the same time, Grafoil should allow for outgassing to occur during the reaction. Such a design for

the Grafoil wrap was also accomplished. Modifications to Grafoil wrapping were carried out such

that the Grafoil could support the much increased weight during transfer of the -3-kg TiC tile.

5.7.1.4 Part Preheat Temperature. The part preheat temperature, based on prior experience,

was selected such that it would not ignite the part in the furnace but, at the same time, would be high

enough such that the additional heat provided by the PTM would ignite the part in the shortest

possible time. The ratio of the tile volume to the surrounding PTM volume is much lower for the

15cm x 15-cm green preform tile than either the lo-cm x lo-cm or 5-cm x 5-cm tile. It can be seen

from Appendix B that, at part temperatures of 750” C (for the 15-cm x 15-cm tiles), as much as

8 + 1 min are required for ignition of the part. However, around temperatures of about 825” C,

shorter times around 4 fi 0.5 min are required. Thus, the preheat temperature was fixed near 825 O C.

.

.

5.7.1.5 PTM. The PTM is also a very critical parameter in producing crack-f?ee tiles. It has been

recognized that the A&O,-graphite combination grain plays an extremely important role and is

superior to graphite-based PTM. It was seen from the tiles forged in the current reporting period that

a higher Al,O, content may be better than a lower A&O3 content in the PTM. This is because a higher

AJO content has a higher heat content and ignites the part faster; similarly, it also does not cool

down slower, which reduces crack formation in the part. However, the TiC tiles do not spread as

much in dimension with a higher Alz03 content in the FTM. It was found that with low-A&O, PTMs

23
(A-20), the horizontal spread was about 5%, whereas, with high-Al,O, PTMs (A-8), the horizontal

spread was less than 2%. So, although the high-A&O, PTM can reduce crack formation, it also gives

less room for machining a 15-cm x 15-cm tile. A high-A&O, content (A-8) was selected as the PTM

for the Phase II SBIR.

5.7.2 The tburn From the First Ignition Until Pressure Application. Previously, in Phase I, the

burn time was controlled through visual observation of the flame on top of the PTM column. In

Phase II, the t,,, varied between 0.5 ruin and 5.5 min. Based on plots of tr,,, against density of the

tile, it was found that with lower bum times the part would still be combusting during pressure

application and the tile would be severely cracked. Whereas, with a longer tbum, the tile density would

seem to drop. An optimized t,,,,,,, was decided to be between 2 and 2.5 min.

5.7.3 Effect of Pressure. Experiments were also conducted to determine the effect of forging

pressure on the density of the part. Initial experiments revealed that, by lowering the pressure from

2.75 x 10’ TPa to 1.38 x 10’ TPa, the density dropped by about 0.3% of the theoretical.

The CS/CF of TiC tiles was carried out using the processing conditions, part preparation

procedure, and processing parameters established from the previously discussed experimental work.

6. Thermal Management to Prevent Crack Formation

Cracking of the TiC during cooling has been found to be a severe problem by Niiler and

coworkers (Niiler et al. 1988; Kecskes, Kottke, and Niiler 1990; Niiler, Kecskes, and Kottke 1992)

and LaSalvia, Meyer, and Meyers (1992) and during Phase I and the initial phase of the Phase II

investigation. Therefore, the cooling of the compacts was experimentally determined. The

experimental configuration to measure the temperatures of the compacts during and after reaction

is shown in Figure 4 and is similar to the setup used by Dunmead, Munir, and Holt (1992).

.

24
i l

I ’

Refractory Brick

Thermocouple 2

Figure 4. Setup Used to Measure Reaction Temperatures.

The experimental configuration consists of a reaction chamber that can be evacuated and

back-filled with an inert gas, a data acquisition system to acquire and process thermocouple readings,

and a variable transformer to ignite the powder. Two thermocouples were used in each experiment.

They consisted of tungsten (W)-5% rhenium (Re) vs. W-26% Re wires and had an average bead size

of 630 pm. The upper temperature limit of these thermocouples is 2,3 16” C, with short-term

exposures of up to 2,760” C. Data were collected over 120 s.

Temperature measurements were carried out to establish the effects of the PTM and of specimen

size on the cooling rate. Excessive thermal stresses in the specimens due to high cooling rates were

a concern because they can lead to macrocrack formation. Therefore, the cooling rates were

measured for compacts using both the A&O,-based and graphite-based PTMs. Figure 5 shows the

results of the cooling experiments. For comparison, the cooling profile for no PTM is included. Due

to the high exothermicity of the Ti+C - TiC reaction, the peak temperature reached exceeded the

25
02 I 3 zs E E8sss . . . . I I I I I I I I I I I I I I I I I I I I 0

I I I I . 0
.

melting point of the W-Re (or W-rhodium [Rh]) thermocouples (-2,800” C). The effect of

thermocouple bead melting on the temperature profile can be seen as a drop in the recorded

temperature. However, in most cases, the thermocouple bead reformed and solidified when the

temperature dropped below its melting point. In Figure 5, the cooling rate in the absence of the PTM

is faster than with the PTM. Thus, the PTM serves as effective thermal insulation and provides a

means of reducing thermal gradients within the compact.

The size of the compact also affects the cooling rate. Figure 6 shows compacts with 3.2-, 6.4,

and 8.9-cm (1.25, 2.5, and 3.5 in) diameters. Although the signals show discontinuities (due to

thermocouple melting), the cooling rate is clearly higher for smaller compacts. This shows that

scaling up is an effective means of further decreasing thermal stresses.

3Ow

2500

u^

0

- 2000

2

z 1500

k

E” 1000

g

500

0

_---

- : 1

_ 1 I.-f

I: . . . . . . .

. . . .

_ .I&

.*. . .

. . ...*

. . . . . .

. .

. .c

- :I . . . . - 1.25” Diameter -

- :I

I -- - 2.5” Diameter

3.5” Diameter

0 20 40

Timft”(sec)

80 100 120

Figure 6. Experimentally Determined Temperature Time Plots for Different Compact

Diameters.

A computer simulation accounting for the cooling behavior of the TiC tiles was generated using

a one-dimensional (1-D) (neglecting edge effect [i.e., infinite diameter]) finite-difference heat

27
transfer program. In A&OS-based PTM simulation, the interface between the TiC compact and the

FTM was initially set at the melting temperature for A&O3 (i.e., 2,145” C). ‘It is reasoned that this

is the maximum temperature that the A&O,-based PTM can reach since any increase above this

temperature would require large amounts of additional energy. The thermophysical data were taken

fromToth (1971), and Storms (1967), and Weast (1973) and are listed in Table 9. Figure 7 shows

the measured and compared cooling curves at the Tic-PTM interface. The correlation between the

results is excellent. This correlation served to celebrate the model. The differences in thermal

properties between the two PTMs used were not significant. The cooling occurred at approximately

the same rate. Figure 8 shows the temperature profiles as a function of time for the Al,O,-based

PT.M. The initial temperature gradients in the specimen were very high, and the effect of these

temperature gradients in the specimen was also very high.

The effect of temperature gradients on the integrity of the compacts can be assessed by

establishing the effect of thermal tensile stresses on existing flaws. One has to assume that flaws are

present in the material; it is common to consider existing flaws with a size equal to the grain diameter.

Table 9. Thermophysical Data Used in Computations

a Measured.

The actuation of flaws results in cracks, and the internal stresses, oth, can be estimated from the

approximate expression

.

oth = EaAT, (1)
.

e Y .

l”‘l”’l”‘1”‘l”‘l”‘.

-0sec

-----2Osec

-0-- 40 set

-----6Osec

_I)_ 80 set

-----1OOsec :

--h- 120sec :

t \-

0 20 40 60 80 100

Distance (mm)

120 140 160

3w

2500

-----1OOsec :

--+- 120sec :

0 20 40 60 80 100 120 140 160

Distance (mm)

Figure 7. Temperature Distance Plots for Different Times With (a) Al,O,-Based PTM at

Room Temperature and With (b) Al,O,-Based PTM at 500” C.

29
3000

2500

u^

“w 2000

E

‘, I I, I I I, II 1, J 11 (“I I”’

.

--• - - Experimental Data

- Computer Simulation -

.

40 60 80 100 120

Time (set)

__*- - Experimental Data

_c_ Computer Simulation -

Q,

g1000 1

c

500 -

0 -“““‘s ” ” ” ” ’ ’ I ” ’ ”

0 20 40 60 80 100 120

Time (set)

Figure 8. Comparison of Measured and Completed Temperature Histories for

(a) A&OS-Based PTM and (b) Graphite-Based PTM.

30
where AT is the temperature differential, a is the linear thermal expansion coefficient (equal to

7.4 x lOA K-r [Cutler, Virkar, and Holt 1985]), and E is Young’s modulus (equal to 400 GPa).

From fracture mechanics,

- Krc=afi,

where K, is the fracture toughness, and 2a is the flaw

equation (l),

AT = K1,

EC+*

(2)

size. Substituting equation (2) into

(3)

Equation (3) gives the maximum allowable temperature differential for a certain flaw size in a

material having a fracture toughness Krc. Assuming that the fracture toughness of TiC is

3 MPa l m1’2, and that flaws of 200 pm exist within it (approximate grain size), a temperature

gradient of 57” C would be sufficient to induce thermal cracking. The existence of thermal gradients

at temperatures above the ductile-to-brittle transition temperature (DBTT) does not, pose a great

problem, since the value of Krc is much larger above the critical transition (1,800” C).

Thus, the initial temperature differential (at times cl20 s) is of no great concern. The thermal

ignition of the compact by preheated PTM decreases the thermal stresses, as shown in Figure 8. The

calculations are conducted for PTM, preheated to a temperature of 500” C. The use of a preheated

PTM reduces the temperature considerably, and the thermal gradients are significantly less severe.

These measurements and calculations show that cooling of the compacts has to be very gradual to

avoid large temperature gradients, especially below the DBTT of TiC (i.e., no observations of data

before/after). They also explain the decrease in cracking, obtained by using the preheated PTM.

31
7. Characterization

7.1 Specimen Preparation. Because of the very high hardness of high-density TiC specimens,

significant time and effort were expended in machining specimens for metallographic and

microstructural evaluation. The use of electrodischarge machining (EDMing) and diamond grinding

was extensively applied to cut, grind, and polish specimens for these characterization tasks.

.

Specimens for optical metallography were polished and etched in an acid mixture consisting of

two parts nitric, one part hydrofluoric, and one part acetic acid. XRD was carried out on a Philips

diffractometer, and scanning electron microscopy (SEM) was carried out using a Cambridge unit.

Quasi-static mechanical tests were conducted in compression and flexural loading (four-point

bending) on specimens that had been EDMed. The compression specimen had dimensions of 4 mm x

4 mm x 6 mm and was tested at a strain rate of 4 x 10s4/s between parallel platens. Stainless steel

shims with a thickness of 25 pm were used at the specimen platen interfaces, and the compression

surfaces of the specimen were polished to 50 pm The four-point bending tests were carried out on

bars with rectangular sections of 4 mm x 4 mm and a length of 30 mm. The external supports were

25.4 mm apart, and the internal loading points were 12.7 mm apart.

7.2 Microstructural Characterization and Phase Analysis. XRD of the as-consolidated

material reveals very clearly that the reaction product is Tic. The peaks are identified in Figure 9.

Co-K, radiation was used, and the lattice parameter was calculated to be equal to 0.433 + 0.0078 nm.

The lattice parameter can be correlated to the stoichiometry of the final product. Storms (1967)

provides a plot listing data of numerous investigators. The C/Ti atomic ratio varies from 1 to 0.5

(there is a wide homogeneity region for TiC in the phase diagram), and the lattice parameter varies

correspondingly, from 0.433 to 0.430 run. The results displayed in Figure 9 indicate that the C/Ti

ratio is 0.9. This is, in essence, the initial composition used in the experiments reported herein.

Optical microscopy of sample cross sections (surface perpendicular to major dimensions of disk)

revealed an equiaxed grain structure with significant differences in grain size.

32
Tic

(200)

Figure 9. XRD for a lo-cm x lo-cm Tile (Co-K, Radiation).

The maximum grain size increased with the size of the specimen. Figure 10 shows plots of grain

size vs. position along the cross section of the 6.4 and 10.2-cm compacts; the thickness of the

compacts are 2 and 2.4 cm, respectively. The grain size variation is clearly evident and is larger for

the larger compact due to its slower cooling rates.

7.3 Mechanical Properties.

7.3.1 Microhardness. The microhardness was measured across and along the cross sections of

the specimens. Figure 11 shows the results for the 10.2-cm compact. Four traverses were made at

1.5 mm, 7.0 mm, 14.0 mm, and 19.5 mm from the edge of the 2.5cm-wide compact. The regions

close to the top, bottom, and lateral surfaces display higher hardness values. The hardness within the

2.5-cm-wide compact is correspondingly lower.

33
Figure 10.

80

70

60

50

40

30

20

0 2 4 6 8 10

DISTANCE (mm)

.

0 5 10 15 20 25

DISTANCE (mm)

Grain Size vs. Position Along Cross Section for (a) 6.35-cm-Square

(b) 10.2-cm-Square Cross-Sectional TIC Tiles.

34

and

.

.
.

-o- 1.5 mmfkomedge

7.0 mm from edge

-t- 14.0 mm from edge

I I I I I ,I 1 f i 1 ‘I”“’ 1 ”“I’

0 30 60 90 120

Distance (mm)

Figure 11. Hardness Traverses Along a 10.2~cm Sample Cross Section.

7.3.2 Compression Strength and Modulus of Rupture Strength. The results of compression

tests are shown in Table IO. The average of five tests is 1.79 GPa. Four-point bending tests (flexural

tests) yielded a modulus of rupture of 0.166 GPa of 10% of the compressive strength.

The fractures generated in the flexure and compression tests were observed by SEM and are

shown in Figure 12. The fractures are primarily transgranular, showing that the grain boundaries are

strong and free of impurities. There is no difference between the fracture surfaces of flexure and

compression specimens, and the morphology is established by the position of specimen with respect

to the compact. Some porosity can be seen in the fracture surfaces. Cleavage facets are also seen,

as well as localized regions where some intergranular fracture occurred. The fracture surface close

to the surface, on the other hand, exhibited a different morphology. As seen in Figure 13, the grain

sizes are much smaller and close to the surface and there is greater porosity. These factors altered

the fracture morphology, and Figure 13 shows the resulting surface. A greater tendency for

intergranular fracture can be seen.

35
Table 10. Compressive Strength of TiC

Sample Outside Center

@Pa) @Pa)

2 1.13 1.28

3 1.11 1.28

4 1.18 1.18

Average Value 1.21 f 0.148 1.24 & 0.049

7.3.3 Fracture Toughness. Fracture toughness measurements were made by measuring cracks

emanating from the indentation produced by a microhardness tester. This technique has been

successfully used by many investigators (Evans and Charles 1976) and correlated with fracture

toughness measurements made by other techniques. The indentation diagonals, 2a, were equal to

0.02 mm when a Vickers indenter with a load, P, of 500 gf was used. The average crack size, c, was

27 pm. The fracture toughness is obtained from

KIc = 0.16Ha2c-3’2

= 0.16 x 0.47 PC-~/~

Kc = 2.6MPa*m1”.

The value obtained for Krc is characteristic of a well-bonded ceramic.

7.3.4 Elastic Modulus. The compressive elastic modulus was measured indirectly through

deflection of the specimens as required in the recorder (correcting for machine stiffness). The values

of Young’s modulus shown in Table 11 are quite lower than those for fully compacted and flawless

36
Figure 12. Fracture Surfaces in (a) Flexure and (b) Compression Specimens.

37
Figure 13. Fracture Surface Close to the Specimen Surface.

Table 11. Young’s Modulus of TIC

Specimen

I

Young’s Modulus

(GPa)

material. Young’s modulus of the latter material varies between 40&500 GPa, while the values

measured fluctuate from 98 to 164 GPa. The differences are possibly partially due to the presence

of the lubricant between the platens. Nevertheless, it is known that cracks and pores affect Young’s

modulus.

7.3.5 Dynamic Mechanical Properties. Five specimens of CSKF TiC were machined for

compressive strength measurements using a Hopkinson bar. The Hopkinson bar tests were carried

38
.

out at the Aeronautical Laboratories of the California Institute of Technology. The experiments were

conducted at a nominal strain rate of 1,000/s. The dynamic compressive strength of the material was

measured to be 2 GPa + 200 MPa.

8. Machining of CS/CF Tiles

. Several machining options were explored in order to find the most economical and least damaging

(crack-inducing) method to machine the final 15-cm x 15-cm x 2.5-cm tile from the CS/CF part.

These included:

l ceramic cutting and grinding,

l EDM machining, and

l water-jet cutting.

Tiles measuring 10.2 x 10.2 x 1.9 cm were provided to service houses experienced in each of the

discussed cutting techniques.

.

8.1 Ceramic Machining and Grinding. Ceramic machining and grinding using diamond

wheels and blades proved to be the most economical route with the least amount of grinding damage

and a step that could be incorporated in the production mode. Bomas Machine Specialties in

Somerville, MA, optimized the grinding and machined all the final 15-cm x 15-cm x 2.5-cm tiles.

However, some edge defects were noticed, especially when the grinding/cutting blade exited the tile.

.

A photograph showing machine tiles is provided in Figure 14.

8.2 EDM. EDM was found to be very competitive with ceramic grinding. Of the several EDM

houses looked into, AccuCut, proved to be the place most suitable for the finishing operation.

However, some tiles had a small amount of A&O3 (coming from the PTM) remaining behind, which

39
.

.

Figure 14. CS/CF 15cm x 15cm x 2.5cm TIC Tiles.

would pose problems to the EDM process. Also, EDM for such small runs was more expensive and

more time consuming than conventional grinding.

8.3 Water-Jet Cutting. Water-jet cutting was found to be the most expensive of the three

routes explored, and serious doubts were expressed by the service houses themselves regarding

large-scale manufacturing using this technology.

9. Cost Model to Manufacture

A cost model to manufacture has been provided in Appendix C.

40
10. Phase II Accomplishments

l A new one-step synthesis-densilication process that allows for the fabrication of 95% dense,

mostly crack-free TiC for armor application was successfully developed and demonstrated.

l This process allows for the fabrication of crack-free TiC tiles of size 15 cm x 15 cm x 2.5 cm.

l A cost analysis of this process based on prototype quantities processed using this technology

shows that the cost to manufacture TiC armor tiles using this process is -60% less than current

costs for the U.S. Army to procure this material.

l The results of this work were presented to an international audience working in the area of CS.

l Modeling work to elucidate the thermal management required in the process was carried out

in collaboration with a university.

l Extensive characterization work to identify grain size, compressive strength, modulus, modulus

of rupture, fracture toughness, and microhardness was carried out.

l It was also found that the same process makes commercially useful inter-metallic compounds

such as TiAl, NiAl, and MoSi, from elemental compounds.

11. Recommendations for Phase III

Ceracon has demonstrated the feasibility of a low-cost process to make dense 15cm x 15-cm x

2.5-cm tiles for armor applications. Prototype quantities of these tiles have been fabricated and

delivered to ARL for evaluation. Ceracon recommends the following.

41
l ARL should provide non-SBIR funding in Phase III to further upscale this low-cost process for

a larger volume of ceramic tiles of interest to the Army.

l ARL should provide support in the form of a Letter of Interest and matching funds in this

technology to Ceracon so that additional sources for funding, such as the Advanced

Technology Program and Technology Reinvestment projects, can be approached for dual-use

applications of this technology.

l ARL can also play a role in helping to further leverage research and development (R&D) in this

area by facilitating cooperative R&D with the former Soviet Union under the Department of

Defense and Department of State programs.

l Commercial opportunities in the area of cutting tools, heating elements, automotive parts, and

wear products shall be pursued using this technology.

42
12. References

Ada&i, S., T. Wada, T. Mihara, M. Koizumi, and 0. Yamada. “Fabrication of Titanium Carbide

Ceramics by High-Pressure Self-Combustion Sintering of Titanium Powder and Carbon Fiber.”

Journal of the American Ceramics Society, vol. 72, no. 5, pp. 805-809, May 1989.

Borom, M. P., and M. Lee. “Effect of Heating Rate on Den&cation of Alumina-Titanium Carbide

Composites.” Advanced Ceramic Materials, vol. 1, no. 4, p. 335-341, April 1986.

Borovinskaya, I. P., E. A. Levashov, and A. S. Rogachev. “Physical, Chemical, and Technological

Base of SHS.” Course of Lectures, The National Education USSR State Committee, Institute

of Structural Macrokinetics, USSR Academy of Sciences and Moscow Steel and Alloys Institute,

Moscow, USSR, 1991.

Cutler, R. A., A. V. Virkar, and J. B. Holt. “Synthesis and Densification of Oxide-Carbide

Composites.” Ceramic Engineering & Science Proceedings, VOL 6, no. 7-8, pp. 715-728,

July-August 1985.

Dunmead, S. D., 2. A. Munir, and J. B. Holt. “Temperature Profile Analysis in Combustion

Synthesis: I. Theory and Background.” Journal of the American Ceramics Society, vol. 75,

no. 1, pp. 175-179, January 1992.

Evans, A. G., and E. A. Charles. “Fracture Toughness Determination by Indentation.” Journal of

American Ceramics Society, vol. 59, no. 7-8, pp. 371-372, July-August 1976.

Grebe, H. A., A. Advani, N. H. Thadhani, and T. Kottke. “ Combustion Synthesis and Subsequent

Explosive Densiflcation of Titanium Carbide.” Metallurgical Transactions A, vol. 23A, no. 9,

pt. 2, pp. 2365-2372, September 1992.

Hoke, D. A., M. A. Meyers, L. W. Meyers, and G. T. Gray. “Reaction Synthesis/Dynamic

Compaction of Titanium Diboride.” Metallurgical Transactions A, vol. 23A, no. 1, pt. 1,

pp. 77-86, January 1992.

Holt, J. B., and Z. A. Munir. “Combustion Synthesis of Titanium Carbide: Theory and

Experiment.” JournaZ of Material Sciences, vol. 21, no. 2, pp. 251-259, February 1986.

Kecskes, L. J.; and A. Niiler. “Impurities in the Combustion Synthesis of Titanium Carbide.”

Journal of the American Ceramic Society, vol. 72, no. 4, pp. 655-661, April 1989.

Kecskes, L. J., A. Niiler, and T. Kottke. “MicrostructuralProperties of Combustion-Synthesized and

Dynamically Consolidated Titanium Boride and Titanium Carbide.” JournaZ of the American

Ceramic Society, vol. 73, no. 5, pp. 1274-1282, May 1990.

43
Kim, Y. W., and J. G. Lee. “Pressureless Sintering of Alumina-Titanium Carbide Composites.”

Journal of the American Ceramic Society, vol. 72, no. 8, pp. 1333-1337, August 1989.

LaSalvia, J. C. “Production of Dense Titanium Carbide by Combining Reaction Synthesis With

Dynamic Compaction.” M.S. Thesis, University of California at San Diego, La Jolla, CA, 1990.

LaSalvia, J. C., L. W. Meyer, and M. A. Meyers. “Densification of Reaction-Synthesized Titanium

Carbide by High-Velocity Forging.” Journal of the American Ceramic Society, vol. 75,

no. 3, pp. 592-602, March 1992.

Lichti, W. P., and A. F. Hofstatter. “Method of Object Consolidation Employing Graphite

Particulate.” U.S. Patent No. 4539,175, September 1985.

Merzhanov, A. G. “Self-Propagating High-Temperature Synthesis: Twenty Years of Search and

Findings.” Combustion and Plasma Synthesis of High-Temperature Materials, pp. l-53,

Z. A. Munir and J. B. Holt (editors), VCH Publishers, New York, NY, 1990.

Merzhanov, A. G., and I. P. Borovinskaya. “Self Propagated High Temperature Synthesis of

Refractory Inorganic Compounds.” Doklady Akademii Nauk SSSR (In Russian), vol. 204, no. 2,

pp. 366-369, May 1972; Doklady Chemistry (English translation), vol. 204, no. 2, pp. 429-432,

May 1972.

Meyers, M. A., J. C. LaSalvia, D. Hoke, J. M. Jamet, and D. K. Kim. “Combustion Synthesis

Densification of Ceramics and Ceramic Composites.” Proceedings of the International

Conference on Advanced Synthesis of Engineering Structural Materials, pp. 43-57, American

Society for Materials International, Materials Park, OH, 1993.

Miyamoto, Y., and M. Koizumi. “Simultaneous Synthesis and Densification of Ceramic

Components Under Gas Pressure by SHS.” Combustion and Plasma-Synthesis of

High-Temperature Materials, pp. 163-169, Z. A. Munir and J. B. Holt (editors), VCH

Publishers, New York, NY, 1990.

Molokov, I. V., and A. S. Mukasyan. “Explosive Treatment of SHS Gas-Solid Systems.”

International Journal of Self-Propagating High-Temperature Synthesis, vol. 1, no. 1,

pp. 155-159, January 1992.

Munir, Z. A. “Synthesis of High-Temperature Materials by Self-Propagating Combustion Methods.”

Ceramic Bulletin, vol. 67, no. 2, pp. 342-349, February 1988.

Niiler, A., L. J. Kecskes, and T. Kottke. “Shock Consolidation of Combustion Synthesized

Ceramics.” Combustion and Plasma-Synthesis of High-Temperature Materials, pp. 309-3 14,

Z. A. Munir and J. B. Holt (editors), VCH Publishers, Inc., New York, NY, 1990.

44
Niiler, A., L. J. Kecskes, and T. Kottke. “Explosive Compaction Processing of Combustion

Synthesized Ceramics and Cermets.” Shock-Wave and High-Strain-Rate Phenomena in

Materials, pp. 293-301, M. A. Meyers, L. E. Murr, and K. P. Staudhammer (editors), Marcel

Dekker, Inc., New York, NY, 1992.

Niiler, A., L. J. Kecskes, T. Kottke, P. H. Netherwood, Jr., and R. F. Benck. “Explosive

Consolidation of Combustion Synthesized Ceramics: Tic and TiB,.” BRL-TR-2951,

U.S. Army Ballistic Research Laboratory, Aberdeen Proving Ground, MD, December 1988.

Rabin, B. H., G. E. Korth, and R. L. Williamson. “Fabrication of Titanium Carbide-Alumina

Composites by Combustion Synthesis and Subsequent Dynamic Consolidation.” Journal of the

American Ceramic Society, vol. 73, no. 7, pp. 21562157, July 1990.

Raman, R. V. “A Novel Manufacturing Process Route for Forming High Density Ceramic Armor

Materials.” Phase I Final Report, DAAA 15-01-C-0087, U.S. Army Ballistic Research

Laboratory, Aberdeen Proving Ground, MD, to be published.

Raman, R. V., and A. Niiler. Personal communication U.S. Army Ballistic Research Laboratory,

Aberdeen Proving Ground, MD, November 1991.

Raman, R. V., and S. V. Rele. “A Novel Processing Route for the Fabrication of Monolithic and

Composite Silicon Nitride.” Silicon Nitride Ceramics, vol. 287, pp. 309-313, I. W. Chen,

P. F. Becher, M. Mitomo, G. Petzow, and T. S Yen (editors), Materials Research Society,

Pittsburgh, PA, 1993.

Raman, R. V., S. V. Rele, and D. Kapoor. “Solid State Densification of Tungsten Heavy Alloys at

Low Temperatures and High Pressures.” Advances in Powder Metallurgy and Particulate

Materials, vol. 2, pp. 421-429, J. M. Capus and R. M. German (editors), Metal Powder

Industries Federation, Princeton, NJ, 1992.

Rice, R. W. “Assessment of the Application of SPS and Related Reaction Processing to Produce

Dense Ceramics.” Ceramic Engineering and Science Proceedings, vol. 11, nos. 9-10,

pp. 1203-1225, September-October 1990.

Riley, M. A., and A. Niiler. “Low Pressure Compaction of SHS Prepared Ceramics.”

BRL-MR-3574, U.S. Army Ballistic Research Laboratory, Aberdeen Proving Ground, MD,

March 1987.

Shikhverdiev, R. M., R. R. Kudashev, 0. Yu. Efimov, N. G. Zaripov, and Yu. A. Gordopolov.

“Shock Wave Effects in the Ti-C SHS System.” International Journal of Self-Propagating

High-Temperature Synthesis, vol. 1, no. 1, pp. 64-66, January 1992.

Storms, E. K. The Refractory Carbides. New York, NY: Academic Press, p, 8, 1967.

Toth, L. E. Transition Metal Carbides and Nitrides. New York, NY: Academic Press, p. 6,197l.

45
Vecchio, K. S., J. C. LaSalvia, M. A. Meyers, and G. T. Gray. “Microstructural Characterization of

Self-Propagating High Temperature Synthesis/Dynamically Compacted and Hot-Pressed

Titanium Carbides.” Metallurgical Transactions A, vol. 23A, no. 1, pt. 1, pp. 87-97,

January 1992.

Von Erlich, P. “Ueber die Binaren Systeme des Titans mit den Elementen Stickstoff, Kohlenstoff,

Bor und Beryllium.” Zeitschrif Jicr Anorganische Chemie, vol. 259, nos. l-4, pp. 1-41,

SUSPENSE: July 1949.

Weast, R. C. Handbook of Chemistry and Physics. 54th edition, CRC Press, Cleveland, OH, 1973.

Yamada, O., Y. Miyamoto, and M. Koizumi. “High-Pressure Self-Combustion Sintering of

Titanium Carbide.” Journal of the American Ceramic Society, vol. 70, no. 9, pp. C206-C208,

September 1987.

Yi, H. C., and J. J. Moore. “Self-Propagating High-Temperature (Combustion) Synthesis (SHS)

of Powder-Compacted Materials.” Journal ofMaterial Science, vol. 25, no. 2B, pp. 1159-l 168,

February 1990.

46
l

Appendix A:

Process Conditions for 55 TiC Tiles Having

Approximate Dimensions 5 cm x 5 cm x 2 cm

and 10 TiC Tiles Having Approximate Dimensions

10 cm x 10 cm x 2.5 cm

47
.

bTFiNTIONALLY LEFT BLANK.

.

48
5112

5113

5114

5115

5117 I=5118

5158

5159 II-5160

II 5161

Table A-l. Process Conditions for 5cm x 5-cm x 2-cm Tic Tiles

69 NA 7 0 1.905 5.mO 5.asO A-75 1200 20 136 NA 3:ll 1.79 loos 100 1.100 - - - 915

69 NA ? 0 1.588 5240 5.240 A-20 1400 2 0 136 NA 448 1.79 100% 100 1,100 - - - 88.9

6 9 NA B 0 2.235 3.505 5.232 A-75 1200 20 53 NA &38 1.79 100% 100 l.mo - - - %.O

69 NA B 0 2.235 3.505 4.928 A-75 1200 20 115 NA 339 1.79 100% 100 1,100 - - - 97.6

69 NA B 0 2.057 3.505 5.410 A-75 1200 20 146 NA 405 1.79 100% 100 1,100 - - - 97.0

69 NA B 0 2.388 4.597 5.715 A-75 1200 20 146 NA 7s 1.79 100% 100 1.100 - - - 90.4

69 NA B 0 2.106 , 4.694 4.681 A-75 1212 20 30 NA 5:Ol 1.79 60 100 I.200 - - - 95.3

69 NA B 0 2329 4.201 5.479 A-75 1203 2 0 5 3 NA 537 1.79 60 Km I.100 - - - 95.3

6 9 NA B 0 2055 5.039 5.568 A-20 1203 20 111 NA 5:51 1.79 lmb 100 1.100 - - - -

69 NA B 0 2.421 4.849 4.943 A-8 12M 20 138 NA NA NA NA NA NA NA NA NA ?

69 NA B 0 2.286 4.636 5.834 A-8 1210 20 130 NA NA NA NA NA NA NA NA NA 7

69 NA B 0 1.974 4.295 5.433 A-20 1211 20 130 N A 539 1.79 100% 100 1,200 - - - 95.1

69 ? 7 0 1.321 4.813 5.060 A-20 1400 20 20 RM 7 1.79 100% 100 verm - - - 7

69 NA 7 0 1.323 5.032 5.1% A-20 1400 20 2n 1:Oo ? 1.79 100% Fast vclm - - - ?

6 9 NA 1 0 1.387 5.113 5.123 A-20 1400 2 0 2xl Oc30 ? 1.79 100% Faa km, - - - 7

69 ? ? 0 1.382 5.812 5.580 A-20 1400 2 0 Warm NA NA NA NA NA NA NA NA NA 7

69 NA ? 0 1.280 5.138 5.123 4335 1400 20 20 NA 1 1.79 m% 100 velm. - - - 7

69 NA 7 0 2.060 5202 5.m 94uO 1197 20 WUIII NA NA NA NA NA NA NA NA NA 7

6 9 7 1 0 - - - 9400 1203 20 20 NA 7 1.79 100% 100 verm, - - - 7

69 NA 7 0 1588 5.08 5.08 A-20 1231 20 20 NA 7 1.79 100% FasI vum. - - - 7
.

.

50

Table A-2. Process Conditions for lo-cm x lo-cm x 2.5cm TiC Tiles

Notes: CQ = cold isomtk mess.

B=lhe.

c=marse.
Appendix B:

Drawings of the Cold Press, Ceracon Die, and UCIP Die

53
.

INTDITIONALLY LEFT BLANK.

54
!

55
.

.

.

.

56
. . .

Y

;MNLg ;M!#I” 6-06-3.

ONE 6oFtE’fO 1.000

TO PLATE.

NOTE I

ST% eoTloN of DIE 9

ATE

FlAlANDPARALLL

VIlHtN .BBe

I I I I

Figure B-3. TIC Cold Press Die Plate.
NOTE: SUFACES A AND t3

MUST BE FLAT AND

PARALLEL WITHIN .002

.

.

mATERI&: CoNlwACT ,

:: 37-41

(9/6/-928-1933 1111 UARKH BLVO

RS20 I2 CERA Co/// INC. ;g+R-. CA

1

Figure B-4. TIC Cold Press Punch.

.

. .
. . . .

NOTE, -ACES MUST FLAT

AND PARALLEL WITHIN .002

~MATERIAL1 CarrrucTI

I Es 37-41 R220 I 2

ToLERANaz uN_ESS OTCERVISE NOTE0

ffzzr I0832-50

(g/6)-926-1933 II01 NARKET BLVL

SUITE 9

CERACON mc.~%YEN70~ cA

ENQ

TIC cao PRESS PuNcHtasE BFlIAN 9-23-93

F’igure B-5. TiC Cold Press Punch Nose.
.50

---_-----__-__-_____~~~~~~~~~~~~~-~~~~~~~--

L

5.00

._l

II0.00I

1.501- 2 REQUIRED

MATERIAL: CoNTtuCT, (S/6)-92&l-I933 1101 MARKET ELVCI

NOTEa SURFACES A AND 8

1018 RS2012 su1rbF 9

MUST BE FLAT AND CERACON I,vc. %YENro* cA

PARALLEL WITHIN .002 ENG

Pap REVISION TiC COLD PRESS BRIAN 9-23-S

.’ 10832-60 LOAD BLOCKS

.

Figure B-6. TiC Cold Press Load Blocks.

. .
/-OANLY 5-0848-5

4 REOUIREP

CONTRACT,

RSZ0 I 2

(916)-926-1933 1101 UARKET 6Lvo

SliInr 9 CERACON I,vc. ~;YENT4 cA

PC0 GUIDE POST

MODIFICATIONS . BRIAN 9-23-93

Figure B-7. Guide Post Modifications.
pm-7

Figure B-8. 200cm-Square Die Assembly No, 1.

.
L

.

I

. . .* . . ‘.. -

.

.

.r.r-. . .: . . ’ . ‘#) -w.*. .

.-‘(r*. :#f:r’.MbirW .; .‘.r;*, ;’ , , l .

.

I

.

63
I

HOSE CLAMP SLOTS 1

Figure B-10. Uniaxial Cold Isostatic Press (UCIP) Assembled Die.

, .
, . . .

r.62 _I t-42 _I p.62 Ir

To* MATERIALI CONTRACT,

ii!JWfW flc 50-w

(9l6)-920-1933 IlBl NARKET bL Vi

RSZ012 SUITE 9

TOLERANCE UMJSS CERA CON INC. ;;;$:nENTo~ cA OTCEFwlSE NOTE0

p3llw w3ISIoN UCIP LEFT SIOE EN8 OSLIN

I Ftszel2-210 I #aJlED

PAQC 2 OF s

Figure B-11. UCIP Left Side.
/J 2

.__.______.. __ ______ _____..________________..___________-..__ m-w-.--.

.__, ____ __..___ _ _________~.______________~~..~~~~~~~~~~~~~..__ e_--.--.

/ N

N- H

._..______.._____________-.________________.._ __________.I__ ____d._.

._..______,.__________ - --------________.._ ----_----- __ me--. ._d

;c I I I I 4

MATER IAL I CCNTRACT ,

!3M’#dRb RC s-a,

(9/6)-928-1933 1111 NARKET tXV1

Rs2012

TOLERANCE UWXS

OTHERWISE NOTE0 L

pf?; Ru

31, II528 I z-220

Figure B-12. UCIP Side Cap.

. .
L

.

. .

SECTICN A-A

NOTES UNLESS OTNnwSE SPECCIEUI

A] lgJlJ*%L aJl?noc SUWAQS m Mw!NT PPnmm

ia) BRlNo AN0 PoLIs4 SlmrACEs A.&CT0 16

l-8 15.00

Figure B-13. UCIP Right Side.
INTENTIONALLY LEFT BLANK.

68
.

Appendix C:

Cost Model for the Manufacture of 1,000 Tiles

69
.

-NTIONALLYLEFI’BLANK.

.

70
Table of Contents

.

C-1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

c-2. Assuulptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C-3. Production and Process Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

c-3.1 CS/CF Process Description ........................................ 74

C-3.2 Production Description ........................................... 74

C-4. Setup Costs and Capital Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

c-4.1 Plant Design and Layout ..........................................

C-4.2 Equipment and Materials Order .....................................

c-4.3 Setup .........................................................

c-4.3.1 Powder Storage Area ..........................................

c-4.3.1.1 Storage Compartment ......................................

C-4.3.1.2 Ball Mill .................................................

C-4.3.2 Cold Pressing of Tic Tiles ......................................

c-4.3.3 Preform Furnace .............................................

c-4.3.4 PTM Heating Furnace .........................................

c-4.3.5 Die Set Carousel System .......................................

C-4.3.6 Robotic Pick-and-Place Arms ...................................

c-4.3.7 PTM Discharge Station ........................................

C-5. Manufacture of 1,000 Tiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

c-5.1 Powder Order and Storage ......................................... 79

C-5.2 Ball Milling and Storage of Milled Powders ........................... 79

c-5.3 Cold Pressing of Green Tiles ....................................... 79

c-5.4 Grafoil Wrap Station ............................................. 80

c-5.5 Preheating of Tiles ............................................... 80

C-5.6 CS/CF of Tic Tiles .............................................. 80

c-5.7 SlowCoolingtheTilesandRecyclingofPTM ......................... 80

C-5.8 Part Identification ................................................ 80

c-5.9 Machining ..................................................... 80

c-5.10 Delivery of Tiles ................................................ 80

C-6. Detailed Budgets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

73

;::

;;

77

77

77

77

78

78

78

78

71
.

blTENTIONALLYLEFI’BLANK.

.

72
C-l. Introduction

Ceracon, Incorporated is providing this cost model for the fabrication of 1,000 titanium

carbide (Tic) tiles fabricated by the combustion synthesis/Ceracon forging (CS/CF) technology

developed by Ceracon under Phase I and Phase II Small Business Innovative Research (SBIR) awards

by the U.S. Army Research Laboratory (ARL). Work completed during Phases I and II successfully

demonstrated fabrication of bulk shape, crack-free, high-density Tic tiles up to 15 cm x 15 cm x 2.5 cm

at temperatures as low as 1,200” C. The development of this novel technology has resulted in the

potential for economically manufacturing this high-temperature ceramic on a large-scale basis at a cost

of 3040% of conventionally prepared Tic. The technology developed at Ceracon under Army support

has paved the way for dual-use applications. In defense industries, it could be used for lightweight

armor, and, in commercial applications, it could be used for cutting tools, heating elements, and

sputtering targets.

C-2. Assumptions

This cost model to prepare 1,000 Tic tiles is based upon the research and technology experience

gained as a result of the SBIR program and the following assumptions:*

l initial studies to fabricate a pilot quantity of l&25 Tic tiles has been completed,

l additional prototype quantities of 100 Tic tiles are fabricated and delivered to ARL,

l the capital equipment and setup is completed, as outlined in section C-4,

l the machining of the tiles will be done using an outside machine shop;

l Although the cost model presented here is for 1,000 tiles, the pilot facility can be readily upgraded to a capacity of

50,000 tiles per year.

73
l the scrap rate for the production of 1,000 Tic tiles is assumed to be 6.5%; and

l Ceracon’s fringe, overhead, and general and administrative rates remain substantially unchanged.

C-3. Production and Process Description

C-3.1 CWCF Process Description. The CS process involves initiation of a self-propagating

reaction at low temperatures between elemental components to synthesize a high-temperature

compound (e.g., titanium yzli] and carbon [C] react to form Tic). However a stand alone CS process

produces a material with 50% porosity. The Ceracon forging (CF) process involves application of

pressure on a hot porous structure using a granular carbonaceous pressure-transmitting medium (PTM).

The Ceracon innovation is to combine the combustion synthesis and CF process in one step (CWCF),

whereby in-situ synthesis and densification can be caked out. This technique has been successfully

applied under ARL,‘s support to fabricate large size (15 x 15 x 2.5 cm) Tic tiles.

C-3.2 Production Description. The Ti and C powders are received in 206~liter drums. C will

be stored in an accessible portion of the receiving area, whereas Ti will be stored in a “safe area” with

the ball mill and the milled (Ti+C) mixture. The safe area will be made of heavy gauge steel, filtered

with dehumidifiers and static removal, and will be fire- and explosion-resistant.

The Ti and C barrels will be lifted by barrel lifters and poured into a 1,125-liter ball milL The ball

mill will have an explosion-proof motor and rubber lining and will use alumina (A&O,) as the milling

media. The mill will be rotated at speeds below the critical speeds, under conditions of dry milling, for

a period of 3 hr. A grating will allow the milled powder to be collected in drums while holding the

media in place. All powder flow passages will be filtered with inert atmosphere ducts and dust

collectors.

74
.

The powder mixture will then be put into a hopper that flows through a control valve into the die

of a cold press. A green preform tile will be pressed at a pressure of 55 MPa. The tile will then be

covered on all sides with precut grafoil sheets.

The green tile will be placed onto a belt furnace where it is heated to a temperature between

600-l ,000” C. Flame curtains and an argon (Ar) environment will provide an inert atmosphere. The

part preheat furnace will be lined with refractory insulating bricks and will be electrically fired. A

pick-and-place robot will pick up the tile from the furnace and hold it in the center of the die while

a Procedyne furnace releases the PTM which has been heated to a temperature between

l,lOO-1,400” C. The dies are individually heated. There are five dies with one die functioning as

the part and PTM discharge station. The dies move on a carousel shuttle system with a 2%-min halt

at every station. After 7% min, the die with the preheated part and ITM shuttles under the punch.

Upon combustion, pressure is applied and the part is consolidated to a high density.

The die will then move to a discharge station where the part is placed in an insulating media for

slow cooling and the FTM is collected and fed into a sieve system. Upon sieving out the fines, the

PTM is returned to the Procedyne furnace.

After slow cooling, the part will then be machined by an outside vendor using diamond

machining and finishing wheels to dimensions of 15 cm x 15 cm x 2.5 cm.

C-4. Setup Costs and Capital Equipment

The setup stage of pilot-scale production will require 3,080 man-hr. The setup period will be

completed in approximately 20-26 weeks from the initiation of the manufacturing program. The

flow chart for pilot-scale production of 1,000 tiles is shown in Figure C- 1.

C-4.1 Plant Design and Layout. A detailed plan of the pilot plant will be completed in

approximately 2-3 weeks from the initiation of the program.

75
SET UP

1 Plant Design and Layout

Equipment and Materials Order

+GGIJ

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..------.~--...~-_..........................._...

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._.._._.._.__-_.....__...............................

MANUFACTURING

Ball Milling and Storage of Milled Powders

11

11

rx$G-J

ICS/CF:CTilenJ

(1

(1

Delivery of 1,000 Tiles b

.

.

.

.

Figure C-l. Flow Chart for Manufacturing of Tic Tiles.

76
C-4.2 Equipment and Materials Order. Quotations from several vendors will be requested

and negotiations canied out for the best price and delivery schedules. This task is expected to be

completed approximately 12-15 weeks from the initiation of the program.

C-43 Setup.

C-4.3.1 Pow&r Storage Area.

C-4.3.1.1 Storage Compartment. Ti powder will be ordered in 206~liter drums containing

approximately 204 kg of Ti in each container. This corresponds to 16 206-liter drums for fabrication

of 1,000 tiles. Eight drums will be procured at the start of the program and eight more midway in

the program. The powder storage area will be a thick-walled steel container to resist fire and

explosion. The storage container will be static proof and fitted with dehumidifiers. This storage

chamber will be roughly 6.1 m x 3.5 m x 2.4 m. The storage compartment is adequate to store

enough powder for 1,000 tiles. If the program is upgraded to the full capacity of 50,000 tiles per

year, storage capacity for 14 206~liter Ti drums will be needed and a larger chamber would be

required.

C-4.3.1.2. Ball Mill. A 1,125~liter ball mill will be purchased. AlzOS media will be used. The

ball mill will be fitted with a rubber liner and will be rotated for 3 hr per batch. The ball mill will

have an explosion-proof motor and dustless discharge housing. Barrel lifters for transfer of powder

and drums for the storage of milled powders will be procured.

C-L?.2 Cold Pressing of Tic Tiles. A 600-ton press, capable,of cold-pressing two tiles at a

time, will be purchased. An automated powder loading system will be purchased, which will drop

the same weight of Tic powder into the die each time. All paths where the powder may be exposed

to the environment will be surrounded by a plastic glove bag arrangement with inert gas flowing.

C-4.3.3 Preform Furnace. A 12.8-m belt furnace lined with ceramic refractory bricks will be

purchased. Thermocouple readouts will be placed along the length of the furnace with provisions

77
to stop the belt and sounding of an alarm if the temperature exceeds 950” C. Inert gas will flow

inside the furnace maintaining an inert environment. Flame curtains will be present at the entry point

as well as the exit. The furnace will have a temperature capability of 1,100” C. Each tile will be in

the furnace for a period of 1.5 hr, and, at any given time, there can be 36 tiles in the furnace with

20 cm between each tile. The belt speed will be 14.2 cm/mm. Each tile will be separated from its

neighboring tile by a ceramic wall so that, if a tile ignites in the furnace, its neighboring tiles will not

be ignited from the heat of the combustion. The furnace will be set on railings.

C-43.4 PTM Healing Furnace. A fluid&d bed furnace (Procedyne) capable of delivering

113 kg/hr of heated FYTM will be procured. Approximately 11.3 kg/hr of PTM per part will be

needed. For capacity production of 50,000 tiles&, an additional Rrocedyne would be required. The

operating temperature will be approximately 1,200 O C. Higher temperature materials for the muffle

of the Procedyne will be used instead of the commonly used Inconel600. A high-temperature

discharge valve will release a predetermined amount of FTM into the die.

C-4.3.5 Die-Set Carousel System. Five die sets will be purchased. Currently, it takes

approximately 10 min for the Tic part to ignite in the die. The part will be placed in the first die,

which is right up against the preform furnace and the FTM Procedyne. The die will shuttle in a

counterclockwise fashion on the carousel arriving in a four-step shuttle mode with the final step in

the 7.5-l O-min cycle being spent under the punch awaiting combustion. After combustion synthesis

and dynamic forging, the die with the part will arrive at the discharge station. The dies will be

heated to 300” C and be made of H-13 steel.

C-U.6 Robotic Pick-and-Place Arms. Robotic pick-and-place arms will pick up the part from

the preform furnace and hold it in the die while the Procedyne discharges hot M’M into the die.

Another pick-and-place arm will place the part after CWCF from the discharge station and insert it

into the slow-cooling media.

.

C-4.3.7 PTM Discharge Station. The PTM will be released into drums. After cooling, the

drums will be poured into a sieve that will remove the fines and, through an auger system, return the

78
recycled PTM to the Procedyne furnace. It is estimated that approximately 10% of the PTM will be

lost in each CS/CF cycle. The discharge station will also incorporate a robotic pick-and-place arm

for removing the part

C-5. Manufacture of 1,000 Tiles

The equipment and layout necessary to manufacture 1,000 tiles has the capacity to produce up

to 50,000 tiles/yr with a few additional pieces of equipment. The actual time required to

manufacture 1,000 tiles is approximately 3 weeks using a standard 8-hr shift, 5 days/week. Including

the time for powder procurement and initial set, the program is projected to be complete within

10-14 weeks from the initiation time.

C-5.1 Powder Order and Storage. Currently, a machined tile weighs 2.82 kg. With current

processing, the starting weight of the tile is 3.69 kg. The losses occur in powder processing,

combustion synthesis, forging, and machining. With the improvements in setup, the losses are

expected to drop by a factor of 25-50%. Assuming a scrap rate of 6.5% for a 1,000 tiles, we will

order 3,250 kg of Ti and 750 kg of C. The 3,250 kg of Ti will arrive in 16 206-l&r drums. The

- lOO+ 160 mesh Ti from Micron Metals will arrive in two consignments of eight drums each. All

necessary safety precautions for storage and safe handling will be followed.

C-5.2 Ball Milling and Storage of Milled Powders. Powder transfer to the ball mill will be

done under dust-free and inert conditions. All powder will be milled 2 days prior to CSKF. The

powder will be milled for 3 hr using Alz03 milling media. It is expected that a technician will be

employed with about 75% of his/her time dedicated to ball milling, storage, inventory of powders,

safety aspects, and transfer of as-received, as well as the milled powders.

C-5.3 Cold Pressing of Green Tiles. A pressure of 55 MPa will be applied to obtain a density

of approximately 70% of theoretical. Once again, dust-free and inert conditions will be maintained

during powder transfer and handling. A person dedicated to cold pressing will be employed, who

will cold press the parts and transfer them to the grafoil wrap station.

79
C-5.4 Grafoil Wrap Station. The preformed tiles will be placed into precut sheets of grafoil

prior to storage. _

C-55 Preheating of Tiles. The tiles will be preheated to approximately 750 O C and held at that

temperature for about 45 min for a uniform heat soak. Thermocouples along the length of the belt

furnace will monitor the temperature of the parts. An inert atmosphere will be maintained in the

furnace. The number of tiles preheated/hour will be determined by the CS/CF consolidation rate and

controlled by the spacing between the tiles or by the speed of the belt furnace. Ceramic barriers on

the belt between the tiles will prevent a chain combustion reaction, if one of the tiles initiates

combustion.

C-5.6 CS/CF of TiC Tiles. The hot tiles will be picked up by the pick-and-place arm and

loaded in the die with the FTM simultaneously discharging into the die.

C-5.7 Slow Cooling the Tiles and Recycling of PTM. After forging, the part will be brought

to a discharge station where the PTM will be recycled. We expect to recycle about 90% of the PTM

with the remaining lost as fines or dust. The part will be cooled in insulating material over a period

of 24 hr.

C-5.8 Part Identification. The part will be issued a unique number, which will identify it by

the batch number of the powder it was milled from, the processing parameters, and the date and time

of CSKF forging.

C-5.9 Machining. Ceramic machining will be employed to machine the specimens to a flat

finish on all sides. Machining of these specimens will be done by an outside vendor for annual

production of 1,000 tiles. However, for full capacity production of 50,000 tiles@, equipment would

be purchased and a dedicated machinist employed for machining.

C-5.10 Delivery of Tiles. After inspection to assure dimensions and density and to check for

any surface irregularities, the specimens will be shipped. Shipping costs are not included in this cost

proposal and would be at the responsibility of the purchaser.

80
C-6. Detailed Budgets

Table C-l displays the equipment purchase and setup, and Table C-2 shows the manufacturing

details of 1,000 Tic tiles.

Table C-l. Equipment Purchase and Setup Costs

81
Table C-l. Equipment Purchase and Setup Costs (continued)

Materials/Supplies

Preform Furnace

Price

($9

350,OOO.OO

Total

($1

350,000.00

Forging Dies and Punches I

5

I

20,OOO.OO I

100,000.00

Forging Carousel Setup I 1 I 110,000.00 I 110,000.00

Pick and Place Systems I 1 I 20,000.00 I 20,000.00

Rails, Guides, Stops, and Belts

Miscellaneous

1 15,000.00 15,ooo.oo

1 200,000.00 200,000.00

Total Materials/Supplies

Setup and Equipment

- - 1,445,000.00

- - 1,538,703.70

l

t

82
Table C-2. Manufacturing Costs of 1,000 TiC Tiles

Direct Labor I Tune I Rate I Total

Manufacturing Project Manager I21,6346 8,653.85

Senior Processing Tech 480 I 14.5000 I 6,960.OO

Processing Technician 480 I 11.5000 I 5520.00

Preforming Technician 320 I 15.0000 I 4,800.OO

Engineering Technician I

360 8.0000 2,880.OO

Techuician 560 I 7.0000 I 3,920.oo

Total Direct Labor I 2,600 I - I 32,733.85

Labor Overhead* 1 109.63 (%) 35,886.12

Subcontracts Rate

(W

Total

(S)

Machining Tilesb I 1,050 I 160.00 1 168,OOO.OO

Materials/Supplies Quantity unit Price Total

(S) (S)

Ti Powder (kg) I 3,250 I 41.80 1 135,850.OO

C Powder (kg) 5.50 I 4,125.OO

I 3,625 I 2.43 1’ 8,808.75

Grafoil Wrap (roll)

* Ceratxm’s existing overhead rate.

b Outside vendor.

’ IO-yr declining: if full capacity of 50,000 parts were produced, depreciation would be spread over 50,000 parts,

significantly lowering the per tile cost.

83
L

Table C-2. Manufacture of 1,000 Tic Tiles (continued)

MaterialdSupplies

l

d Gem’s existing G&l me.

’ Allowance for unexpected costs and profit.

84
NO. O F

COPIES

2

ORGANIZATION

NO. O F

COPW ORGANIZATION

DEFENSETECHNICAL I DIRECTOR

INFORMATION CENTER USARMYRESEARCHLAB

DTIC DDA AMSRLD

8725 JOHN J KINGMAN RD RWWHALIN

STE 0944 2800 POWDER MILL RD

FI’BELVOIR VA 22060-6218 ADELPHI MD 20783-l 145

HQDA

DAMOFDQ

D SCHMIDT

400ARMYPENTAGON

WASHINGTON DC 20310-0460

1 DIRECTOR

USARMYRESEARCHIAB

AMSRLDD

J J ROCCHIO

2800 POWDER MILL RD

ADELPHI MD 20783-l 145

OSD

OUSD(A&T)/ODDDR&E(

RJTREW

THEPENTAGON

WASHINGTON DC 20301-7100

1 DIRECTOR

usARMYREsEARCHLAB

AMSRL CS AS (RECORDS MGMT)

2800 POWDER MILL RD

ADELPHI MD 20783-l 145

DPTY CG FOR RDE HQ

usARMYMATERIELCMD 3

AMCRD

MG CALDWELL

5001 EISENHOWER AVE

ALEXANDRIA VA 22333-0001

DIRECTOR

usARMYRESEARCHLAB

AMSRL CI LL

2800 POWDER MILL, RD

ADELPHI MD 20783-l 145

INST FOR ADVNCD TCHNT.,GY

THE UNIV OF TEXAS AT AUSTIN

PO BOX 202797

AUSTIN TX 78720-2797

4

EEN PROVING GROUND

DIR USARL

AMSRL CI LP (305)

DARPA

B KASPAR

3701 N FAIRFAX DR

ARLINGTON VA 22203-1714

NAVAL SURFACE WARFARE CTR

CODE B07 J PENNELLA

17320 DAHLGREN RD

BLDG 1470 RM 1101

DAHLGREN VA 22448-5 100

US MILITARY ACADEMY

MATHSCICTROFEXCELLENCE

DEPT OF MATHE?kiTICAL. SCI

MAJMDPHLLJPS

THAYERHALL

WEST POINT NY 10996-1786

85
NO. O F

ORGANIZATION COPIES

NO. OF

CopIEs ORGANIZATION

US ARMY ARDEC

D KAPOOR

S CYTRON

DOVER NJ 07801

ARMY RSRCH OFFICE

A CROWSON

ECHEN

RREEBER

PO BOX 12211

RSRCHTRIANGLEPARKNC

27709-2211

US ARMY AVIATION SYS CMD

AVIATION APPLIED TECH DIR

SKINNEY

FT EUSTIS VA 23604-5577

DAHLGREEN LABORATORY

NAVAL SURFC WEAPONS CTR

PADAMS

CODE G 32 AMMUNBR

DAHLGREENVA 22448

NAVAL RSRCH LABORATORY

V PROVENZANO

CODE 2627

WASHINGTON DC 20375

THE TlTAN CORP

CRTDlV ORD TECHLGY

R BROWN

5 117 JOHNSON DRV

PLEASANTON CA 94588

WRIGHT LABORATORY

WLMNMWMDILMORE

MUNITIONS DIV

J FOSTER

EGLIN AFB FL 32542-6810

FAILURE ANALYSIS ASSOC

JNEIL

149 COMMONWEALTH DR

PO BOX 3015

MENLO PARK CA 94025

PHYSICS DEPT

WJNELLIS

LIVERMORE CA 94550

OAK RIDGE.NATL LAB

A PAST0

MS 6087 BLDG 4508

BOX 2008

OAK RIDGE TN 3783 1

sURMETcoRP

S SASTRI

33BSTREET

BURLINGTON MA 01803

SNL

FUSION TECHLGY DEPT 653 1

M ULHRKKSON

R WATSON

ALBUQUERQUE NM 87185

B HOGAN

ATAC MS F681

PO BOX 1663

LOS ALAMOS NM 87545

BATTELLE PACIFIC NW

LABORATORIES

WGURWELL

PO BOX 999

RICHLAND WA 99352

PENNSYLVANIA STAT UNIV

DEPT ENGNR SCIENCES AND

MECHANICS

RGERMAN

227 HAMMOND BLDG

UNTVERSlTYPARKPA

16802-1401

UNlV OF CALIFORNIA

SANDIEGO

DEPTAPPLJEDMECHANICS

ANDENGNRSCIENCES

MMEYERS

MAJL CODE 0411

9500 GILMAN DRIVE

LA JOLLA CA 92093-0411

86
NO. OF

COPIES

2

; 1

. .

/

NO. OF

ORGANIZATION COPIES

GEORGIA INST OF TECH

SCHLOFMTRLENG

KLOGAN 20

NTHADANI

ATLANTA GA 30332-0245

A

1

,

1

3

1

BA’ITELLE

METALS AND CERAMICS DEPT

RTENAGLIA

505 KING AVENUE

COLUBUS OH 43201-2693

B BUSOVNE

23414 SHADYCRAFT

TORRANCE CA 90505

NEW MEXICO INST

OFMINING&TECH

CTRFOREXPLSVTECH&RSRCH

AMJLLER

P PERSSON

MTRLSBiMETENG

OINAL

SOCORRO NM 87801

UNIV OFCALIFORNIA

COXEGEOFENGNRNG

ZMUNIR

DAVIS CA 95616

PRGANV’TION

EEN PROVING GROUND

USARMYRESEARCHLAB

AMSRLWMTE

L KECSKES (5 CPS)

ANBLER

AMSRL WM TA

WGOOCH

WGILLJCH’

MBURKINS

GHAUVER

THAVEL

E HORWATH

AMSRLWMTD

KFRANK

AMSRLWM TC

EKENNEDY

LMAGNESS

AMSRLWMM

DVIECHNICKI

AMSRLWM MC

.JLASALVIA

THYNES

J MCCAULEY

JWELLS

87
l

INTENTIONALLY LEFTBLANK.

88
,REPORT DOdJMENTATlON PAGE Fom, Approved

WB Na 07044188

‘u#knportln2burd*l1~b~~ki~h~lo~.lhourpr~lncl dl lha2m.lwrwbwi kMmctkmnm’chk2~ISJ daa

~mvmpmdmdnldnk2m8d*rm#.aldeonvim~mdmMnp~coMlondLn(#nulion.

*2r*lono(kfmmal~

bl#“~182mlq~klr-rhu*2nyMg~~

1#NdNbl2lhbbUNNhlOWdlh2tMHrdqurm(Irv*r,Dhdm*~ bmmmmopamaumd~1212whron

Processing Route for Forming High-Density Ceramic

Contract #DAA 92-C-0068

BRLOOO-1992-0493

Ramas V. Raman

Ceracon, Inc.

1101 North Market Blvd., Suite 9 TR-RS2012-F-1

Sacramento, CA 95834

U.S. Army Research Laboratory

ATIN AMSRL-WM-TE ARL-CR-438

Aberdeen Proving Ground, MD 21005-5066

Il. SUPPLEMENTARY NOTES

Andrus Niiler, COTR

Lado J. Kecskes, ACOTR

Ea. DlSTRlBUTlONlAVAlLABlLtTY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release; distribution is unlimited.

13. ABBTRACT(hfaxlmum 200 wor&?)

The feasibility of a combustion synthesisKeracon forging (CSKF) fabrication process for low-cost highquality

ceramic armor is demonstrated. CS of titanium (II) and carbon (C) forming titanium carbide (Tic) was followed by

a quasi-isostatic pressurization and densification to produce tiles with 95%+ densities with sixes of up to 15 cm x 15 cm

x 2.5 cm. SeveraI tiles were fabricated and delivered to the U.S. Army Research Laboratory (ARL) for evaluation and

testing. A cost model, which showed that approximately 60% in cost savings can be malized with the CS/CF method,

was developed.

Temperature measurements and one-dimensional (1-D) computations were used to develop thermal management

practices to make crack-free tiles. X-ray diffraction (XRD) verified full conversion of reactants to products. A

considerable variation in Tic grain size and microhardness was found between the surface (- 10 pm, high hardness) and

the interior (up to 100 pm, low hardness) that depended on conditions during processing. Fractography showed

transgramtlar fracture in the interior and intergranular fracture at the surface. Quasi-static compressive strength was

found to be 1.79 GPa, while the flexural strength, determined from four-point bending tests, was 0.17 GPa.

14. SUBJECT TERMS 15. NUMBER OF PAGES

94

umor, Tic, combustion synthesis, Ceracon forging, densification 13. PRICE CODE

17. SECURlTY CLASSIRCATION ia SECURITY CLASWICATI~N 10. SECURlTY CLASSIRCATION 20. UMITATION OF ABSTRACT

OF REPORT OF THIS PAGE OF ABSTRACT

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

JSN 754&01-2806500 89 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. 23818 298-102
hTBNTIONALLY LEFI’ BLANK.
USER EVALUATION SHEET/CHANGE OF ADDRESS

This Laboratory undertakes a continuing effort to improve the quality of the reports it publishes. Your comments/answers

to the items/questions below will aid us in our efforts.

1. AFtL Report Number/Author ARLXR-438 (Raman IPOC: Kecskesl) Date of Report April 1999

2. Date Report Received

3. Does this report satisfy a need? (Comment on purpose, related project, or other area of interest for which the report will

I 4

3

4. Specifically, how is the report being used? (Information source, design data, procedure, source of ideas, etc.)

5. Has the information in this report led to any quantitative savings as far as man-hours or dollars saved, operating costs

avoided, or efficiencies achieved, etc? If so, please elaborate.

6. General Comments. What do you think should be changed to improve future reports? (Indicate changes to organization,

technical content, format, etc.)

Organization

CURRENT

ADDRESS

Name

Street or P.O. Box No.

E-mail Name

City, State, Zip Code

7. If indicating a Change of Address or Address Correction, please provide the Current or Correct address above and the Old

or Incorrect address below.

L

Organization

OLD

ADDRESS

Name

Street or P.O. Box No.

City, State, Zip Code

(Remove this sheet, fold as indicated, tape closed, and mail.)

(DO NOT STAPLE)