A Novel Manufacturing Processing

Route for Forming High-Density

Ceramic Armor Materials:

Phase I - SBIR

by Ramas V. Raman

prepared by

Ceracon, Inc.

1101 North Market Blvd. #9

Sacramento, CA 95834

under contract

DM 15-01-C-0087

Approved for public release; distribution is unlimited.

1999041315 8
.

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 objective of the Phase I small business innovative research (SBIR) project was to

demonstrate the feasibility of applying the Combustion Synthesis (CS)/Ceracon Consolidation

Process for forming lo-cm-diameter, 2.5cm-thick high-density titanium carbide (Tic) and

titanium diboride (T.&J pieces. The Phase I project demonstrated for the first time the feasibility

of CS initiation to form TiC and TiB, by using Ceracon’s hot, granular media and their in-situ

consolidation. The effects of applied pressure and pressure-transmitting media (PTM)

temperature in controlling density, as well as thermal management issues to prevent cracking in

applying the CSKeracon process to formTiC and TiB,, have been identified. In-situ CSKeracon

consolidation to densities exceeding 98% was demonstrated for fabricating lo-cm-diameter,

2.5-cm-thick TiC pieces. The CSKeracon-processed, high-density TiC specimen has a fine grain

size, microhardness values exceeding 2,500 kg/mm2, and compressive strength of 1.3 GPa. Due

to the use of inexpensive conventional forging equipment and a low-cost grain for both initiating

self-propagating high-temperature synthesis (SHS) and consolidation, this novel approach has the

potential to be significantly more cost effective than currently used conventional hot pressing

(HP) or hot isostatic pressing (HIPing) of Tic and TiB, powders. A set of recommendations for

the technical approach to be followed in process upscaling in Phase II to fabricate larger size tiles

of TiC material is provided.

ii
Table of Contents

I -

1.

2.

2.1

2.2

3.

4.

4.1

4.2

4.3

4.4

4.4.1

4.4.1.1

4.4.1.2

4.4.2

4.4.3

4.4.3.1

4.4.3.2

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

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

Objectives of the Phase I Small Business Innovative Research (SBIR)

Program ....................................................................................................................

Literature Search on CWDynamic Compaction TiC and TiB 2 ...........................

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

TiB2 .....................................................................................................................

Background on the Ceracon Process .....................................................................

CWCeracon Processing of TiC and TiBz (Process Development Using

SubscaIe Specimens)................................................................................................

Identification and Procurement of Elemental Powders.......................................

Powder Blending .................................................................................................

Green Preform Fabrication ..................................................................................

CWCeracon Consolidation ..................................................................................

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

PTM Characteristics ...............................................................................

PTM Temperature ...................................................................................

The E#ect of Applied Pressure on Densijkation and Coordination

of Its Timing ................................................................................................

TiB2........................................................~.......................................................

PTM Characteristics ...............................................................................

PTM Temperature ...................................................................................

5. Thermal Management Issues to Prevent Crack Formation and Specimen

Containment ............................................................................................................

5.1 CWCeracon Processing of lO.l-cm-Diameter x 2.5-cm-Thick TiC ...................

5.2 Post CSKeracon Thermal Management .............................................................

V

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. . .

111
6. Characterization of a lO.l-cm-Diameter x 2.5cm-Thick TiC Specimen........... 20

6.1 Specimen Preparation....................................................................................... 21

6.2 Results and Discussion ..................................................................................... 21

7. Accomplishments ................................................................................................. 24

8. Conclusions .......................................................................................................... 27

9. Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

10. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Distribution List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Report Documentation Page. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

iv
List of Figures

Figure

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

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

The Study of CS in a Differential Thermal Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Delta G vs. Temperature for T& and TiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scanning Electron Microscope (SEM) Micrograph of Surface of TiBz at 1,000x....

CIPed Green Preform of TiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ceracon’s 2,500-Ton Press . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Schematic of an All-Graphite Ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

In-Situ CSKeracon-Processed TiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Optical Micrographs of Sectioned Specimens. Macrocracks Can Be Seen

Transversing the Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Microindentation Hardness Measurements Along the Thickness of the

Specimen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Optical Micrographs of Polished and Etched Sections of Specimen: (a) Small

Grain-Sized Region Close to External Surface; (b) Large Grain-Sized Region

Close to Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fractographs of Tic Obtained by SEM Showing primarily Transgranular

Fracture: (a) Magnification of 500x; (b) Magnification of 1000x . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fractographs of TiC Showing Partial Intergranular Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F&g

5

11

15

16

18

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23

25

26

27

V
INTENTIONALLY LEFTBLANK.

vi
List of Tables

Tables

1. Chemical Analysis of Ti Powder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2. Chemical Analysis of B and Graphite Powders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. CS/Ceracon Test Matrix Experiments on Subscale Specimens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.

5.

&

7

8

10

13 CSKeracon Experiments to Fabricate TiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Processing Parameters for CSKeracon of TiC (10.1 cm Diameter x 2.5 cm

Thickness) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~.............................. 17

6. Compressive Strength and Young’s Modulus of TiC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

.

Vii
INTHCIONALLY LEFl- BLANK.

.

. . . VlU
1. Objectives of the Phase I Small Business Innovative

Research (SBIR) Program

The overall objective of this project was to determine the potential for economically mass

producing low-porosity monolithic ceramic materials by Combustion Synthesis (CS)/Ceracon in the

quantities and sizes required for ballistic applications.

In Phase I, a demonstration of the ability to apply the CSKeracon technique by fabricating

lo-cm-diameter x 2.5cm-thick pieces of titanium carbide (Tic) at 95.57% of theoretical density and

titanium diboride (T&) at 98.57% of theoretical density was required. Microhardness values for

these samples must be comparable with materials prepared by conventional hot-pressing (HP)

methods.

2. Literature Search on CWDynamic Compaction TiC and

TiB2

Because of their attractive physical and mechanical properties, the boride and carbide of titanium

have been the focus of attention in numerous investigations. Results have been reported in which the

effects of the synthesis method, impurity contents, and densification processes on the final product

have been examined. A brief summary of the important observations on selected publications follows.

The summaries are classified under TiC and TiB2 and include discussions on related composite

materials.

2.1 Tic. TiC has been synthesized by combustion and consolidated by dynamic compaction

[ 1 , 21. Samples with relative densities of 98% have been prepared. Their hardness was equal to or

better than 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 1.0. However, at this ratio, the process of

densification is not optimum and it was concluded that an ideal C/Ti ratio of 0.90-0.95 would give

1
This observation is in contrast

synthesized and consolidated

they refer to as “gas-pressure

the desired combination of ease of densilication and high hardness.

to that made by Miyamoto and Koizumi [3]. These authors

substoichiometric titanium carbide (Tic,) in one step using what

combustion sintering.” Under a gas (argon [Ar]) pressure of 100 MPa, they were able to obtain fully

dense Tic, for 0.5 I x I 0.8. Higher x value resulted in lower density products. The authors explain

this in terms of having excess C, which 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. Iron (Fe) impurities were found to degrade the properties of the carbide by

segregating at the grain boundaries [l]. Other impurities in the reactants (Ti + C) can also play a role

in the densification and microstructural development of the carbide [4,5]. The major noncondensable

impurities that were detected in the gas phase above the heated reactants include water, hydrogen,

carbon monoxide, carbon dioxide (H20, Hz, CO, COs), 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 combustion synthesized and densified to 95% by the application of uniaxial

pressure [6]. The application of 27.6 MPa pressure resulted in a TiC microstructure with a typical

grain size of approximately 20 l,ur~ In agreement with the observations of Niiler and co-workers

[4,5], the gases that evolved during combustion were found to contain a significant amount of Hz.

It was proposed that the presence of this gas is the result of an oxidation reaction of the metal (Ti)

by Hz0 or the evolution of dissolved Hz 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 Tic-containing

composites. Composites such as Tic + alumina (Al203) are commercially important as cutting tools.

TiC is added to Al203 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 Al203 [7]. This composite has been

investigated with respect to the feasibility of transformation toughening

zirconia (ZrO2) [8]. In another investigation, it was found that a

through the addition of

composite of Al203 +

. 2
30 weight-percent TiC can be sintered to a density > 97% at 1,950” C if the heating rate up to this

temperature is > 200” C/min [9]. Presumably, higher heating rates diminish the extent of the

interaction between Alz03 and Tic. As indicated previously [7], such an interaction leads to the

formation of gaseous products, which decrease the ultimate relative density of the composite.

2.2 TiB2. As in the case of Tic, numerous investigations have been conducted on T&. Using

a gas pressure of 100 MPa, Miyamoto and Koizumi [3] succeeded in synthesizing and densifying TiBz

up to a relative density of 99%. However, to attain density of this magnitude, the authors found it

necessary to add 20 weight-percent excess Ti. It is interesting to note that the excess Ti appeared

in the product as TisB4 and TiB. Thus the amount of TiBz is decreased by the addition of the excess

Ti. TiBz has also been prepared by combining CS with shock consolidation [2, lo]. Relative

densities in the range of 9698% of theoretical have been achieved. In a manner similar to that used

for Tic [6], TiBz has also been prepared and densified by the application of umaxial pressure (82 atm)

after the initiation of a combustion reaction between the elemental reactants [l l]. The effect of Fe

impurities on the sintering TiBz was investigated [12]. The presence of 0.5 weight-percent Fe leads

to abnormal grain growth when the powder is sintered at 2,000° C in AL It was found, however, that

the addition of boron carbide (B&Z) suppresses grain growth and a 95% dense TiBz can be prepared.

The presence of oxygen as an impurity has a deleterious effect on the densilication of TiB2 by

sintering. It has been proposed that oxygen impurities, presumably in the fort-n of surface oxides,

enhance surface diffusion [12], a process which does not contribute to densification but one which

blunts the driving force for sintering [ 131. Other investigations have also pointed out the detrimental

effect of oxygen as an impurity. However, the interpretation of the role of oxygen differs. It has been

suggested that oxygen enhances mass transport by an evaporation-condensation method through the

species boron trioxide (B203) [ 14, 151. Unfortunately, no attempt has been made to establish the

level of oxygen impurity at which these deleterious effects occur.

As stated previously, the presence of Fe as an impurity in TiBz results in undesirable abnormal

grain growth [ 121. However, its presence as well as the presence of nickel (Ni) is seen as desirable

when TiB2 is to be hot pressed [ 151. It was observed that when the content of Fe + Ni

3
< 0.1 weight-percent the material could only be pressed to a relative density of 188% at 1,600” C,

but when Fe + Ni > 0.3 weight-percent, the densification process was markedly enhanced. In this

same study, it was also observed that the addition of C to TiBz diminished exaggerated grain growth.

It is likely that this effect may be related to, the role of C in reducing oxygen impurity and hence

diminishing the nondensifying mass-transport processes of surface diffusion and evaporation

condensation.

The densification of TiB2 prepared from a solid-state reaction between titanium nitride (TiN) and

amorphous boron (B) was also investigated [ 161. Fine-grained (2-3 pm in diameter) T& was

prepared and densified to a relative density of 98% by HP under a pressure of 20 MPa at 1,800” C

for 5-60 min.

The preparation of composite materials containing TiB2 has been investigated. In particular,

reactions between Ti, aluminum (Al), and B to form a T& + Al composite have been examined

[ 17, 181. In an earlier study [ 181, the addition of up to 20 weight-percent Al to the stoichiometric

mixture of Ti + 2B resulted in T& as a product with no evidence of free AL In contrast, the more

recent study [ 171 showed that Al is present in the product. It should be noted that the earlier study

was conducted in vacuum, while the latter work was carried out in an atmosphere of Ar. It is

therefore likely that under vacuum conditions, excessive evaporation of Al lead to its absence in the

product. Related to this study is an investigation by Halverson et al. [19] on the formation of

T&/B& composites. The goal of this study was to synthesize, by combustion, composites with a

varying ratio of BdC/T&, which would subsequently be infiltrated by Al metal.

3. Background on the Ceracon Process

The Ceracon process is a patented [20], low-cost powder metallurgy process for achieving

near-net shape, full-density parts. It is a simple consolidation technique that uses conventional

powder metallurgy equipment and setup. The Ceracon process is a quasi-isostatic, hot consolidation

technique that uses a ceramic particulate material as pressure-transmitting medium (PTM) instead of

4
.

a gas medium as used in hot isostatic pressing (HIPing). Pressures 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 grain heating and transfer

to the Ceracon die, (3) consolidation, and (4) part removal and grain recycling.

Figure 1. The Ceracon Process.

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. The

various systems processed include Al 6061 and 2124, tool steel, 46X.X steel, Al-Fe-V-Si, TiAl, Cu,

Nd-Fe-B supermagnets, superalloys, Al-Sic MMCs, WC-Co to Fe, Nb Alloys, and YBa2Cu307_x

superconductors.

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

subsequently superimposing pressure on the part in situ had not been explored before. This approach,

5
if successful, will have significant advantages over thermite-induced SHS consolidation approaches,

because:

. technology capability for consolidating parts from conventional materials, such as steel, up

to 17.8 cm diameter x 61 cm long, has already been demonstrated;

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

of immediate specimen access after consolidation is completed; and

. the equipment is easy to set up and operate without the elaborate features required fi-om other

processes, such as HIPing, HP, and CWexplosive consolidation.

4. CWCeracon Processing of TiC and TiBz (Process

Development Using Subscale Specimens)

The work on applying the in-situ CWCeracon processing was carried out initially using subscale

2.5cm-diameter, 0.64-1.21-cm-thick specimens. The details on selection and procurement of

elemental powders, powder blending, green preform fabrication, evaluation of critical Ceracon

process parameters for achieving high density, and identification of thermal management issues to

prevent cracking and specimen containment are summarized below along with the conclusions

regarding upscaling to fabricate lo-cm-diameter, 2.5cm-thick specimens.

4.1 Identification and Procurement of Elemental Powders. Significant prior work has been

carried out leading to identification of the desirable characteristics of elemental powders used in CS

by Niiler, Kecskes, and Kottke [2], Meyers et al. [21], and Holt and Munir [6]. This information was

used in selecting the appropriate elemental Ti, C, B, and TiBz (diluent). Ultrafine MicroTi (~20 pm)

Ti was procured from Micron Metals Inc., Salt Lake City, UT. This particle size and this particular

Ti powder fabrication technique has been identified by a U.S. Army Ballistic Research Laboratory

.

6
(BRL) [22] study to be suitable for CS. The analysis of Ti powder provided by the manufacturer is

shown in Table 1.

0

N

C

Fe

Si

Al

Chlorides

Ti, Minimum

Packed Density 1.72 g/ml

Surface Area 1.60 m’/g

Table 1. Chemical Analysis of Ti Powder

Material Description: Titanium Metal Powder, Dry

Snecification: -20~pm ‘Micro Ti’

99.00% Minimum Balance

0.32% Maximum

0.03% Maximum

0.05% Maximum

0.08% Maximum

0.05% Maximum

0.01% Maximum

0.15% Maximum

il

Two sources were investigated for graphite (C) powder: CERAC Inc. and Consolidated

Astronautics, Inc. Based on the superior combustion characteristics of Consolidated Astronautics’

powder, all processing and upscaling studies exclusively used the Consolidated Astronautics’ graphite

powder. Analysis of this powder is provided in Table 2. The B powder and diluent TiB2 was

procured from CERAC and Union Carbide, respectively (see Table 2).

4.2 Powder Blending. Both dry blending [21] and wet blending [21] have been successfully

used for obtaining a homogeneous blend of Ti and C as well as Ti and B. In view of the dust-free

blending feasibility in a wet medium, this approach was selected for all blending work A rotary jar

mill was used for blending processing. Elemental powders, ethanol, and the milling media (WC-Co

nibs) were mixed in the volumetric ratio of 25%:50%:25%. The ball milling operation was carried

out for a 2-hr period to achieve a blend having excellent homogeneity. The ethanol was removed by

drying the blended slurry in an oven. After ensuring complete evaporation of ethanol, the powder

blend was used in subsequent green preform fabrication operation.
Table 2. Chemical Analysis of B and Graphite Powders

Material Description:

Purity

Size (Fisher)

Spectrographic Analysis (%)

X-ray Diffraction (XRD)

Graphite, C

2p

99.9%

0.54 pm

Al 0.002

Ca 0.01

Fe 0.005

Mg 0.001

Si 0.01

Sr 0.002

Ti 0.01

-

Metal, B

Typ. 1 p or less

99.9+ %

0.21 pm

Al <O.OOl

Ca co.001

Cu 0.001

Fe ~0.001

B matches PDF # 3 l-206

tetraeonal

4.3 Green Preform Fabrication. There are principally two processes available for fabricating

preforms: cold pressing (CP) and cold isostatic pressing (CIPing). Ceracon has capabilities for CP

(up to 10 cm diameter) and CIPing (17.8-cm-diameter, 61-cm-long billets have been demonstrated).

Both processes were evaluated for the fabrication of disk-shaped specimens required in this program.

It was found that both processes work suitably well, and no difference in the combustion

characteristics of the compacts fabricated by either process is noted if the preforms had identical

green densities to start with. The CP was used to fabricate all specimens in the process development

study, while CIPing was perfectly suited and used for the larger lo-cm-diameter, 2.5cm-thick

specimens.

4.4 CSKeracon Consolidation.

44.1 Tic. The following issues were considered to be critical to meeting the goals of BRL

specifications for Tic:

l Complete conversion of Ti + C to Tic.

8
.

l Densification to a minimum of 95.57%.

l Achieving crack-free specimens.

The CSKeracon process evaluation involved test matrix experiments to clearly identify the role

Of:

l PTM characteristics.

l PTM temperature required to initiate CS.

l The amount of pressure required to densi@ and the precise time and pulse duration of

pressure application.

l Thermal management issues to address specimen crack prevention.

The details of each of these parameters and processing issues will be addressed in the following:

4.4. I. I PTh4 Characteristics. The core of the Ceracon process is its use of solid particulates of

carbonaceous and ceramic PTM to affect densification of a part. The use of a variety of PTMs is

protected by several U.S. Patents issued to Ceracon. Using hot PTM to initiate CS heretofore has

not been reported and is considered patentable. The key characteristics relevant to CS is the

identification of the presence of any deleterious reaction between the PTM and compact undergoing

CS reaction. In this project, a carbonaceous PT.M known as 9400 and a mixture PTM consisting of

a blended mixture of 9400 + Al203 were evaluated (Table 3).

The 9400 PTM was found to be nonreacting with the CSed TiC material; whereas the 9400 +

Al203 mixture was found to have some melting and surface bonding of Al203 to the Tic. However,

9
Table 3. CSKeracon Test Matrix Experiments on Subscale Specimens

SN

Delta Times in Seconds

Sample t-l-l Insert - SHS Until Dwell at

PTM SHS Fllll Fllll

Temp Observed Pressure Pressure eci b)

900 1,200 30 3 60

951 1,200 44 4 60

952 1,200 50 4 60

953 1,200 50 4 60

Variable Modified

Same as above

Same as above 9400

Pressure applied 3 s Al/9400

after SHS is observed

Pressure applied 1 s iW9400

after SHS is observed

Pressure applied All9400

when SHS is

observed

Same as above; Al/9400

punch inserted

.3 18cm into die prior

to SHS

Same as above; Al/9400

punch inserted

.635-cm into die prior

Dz 1 Specimen

Recorded Composition

95.0 TiC

95.0 Tic

97.0 TiC

98.0 TiC

95.7 Tic

97.3

95.0

96.0

82.4

TiC

Tic

TiC

Ti, B, and

TiBz

84.6 Ti, B, and

TiBz

83.7 Ti, B, and

TiBz

NOTE: Unless otherwise noted, all samples had the following common parameters: Consolidation at 1.24 GPa, sample

weight for both materials: 10 g; Tic preform size = 2.56 cm diameter x 0.64 cm thick; TiBs preform size =

2.578 cm diameter x 0.952 cm thick; die cavity size = 6.35 cm diameter x 3.81 cm deep.

this surface bond could be easily removed. In view of the ease of flow and part removal, 9400 was

selected and used for the majority of the work.

4.4.1.2 PTM Temperature. The PTM temperature required to initiate CS reaction was

investigated. The combustion initiation temperature for Tic was measured fi-om differential thermal

analysis (DTA) experiments as a fbnction of heating rate. In the range of heating rates investigated,

the initiation temperature was constant at 1,550” C (Figure 2). l?TM temperatures of 1,600” C,

10
1,400” C, and 1,200” C were used to monitor combustion initiation. It was possible to initiate

combustion at a temperature of FTM as low as 1,200” C. The initiation of reaction was visible by

“Fireworks” resulting from the expulsion of small quantities of fiery grain from the die.

Sam lc:

1

TM DTfl fib: MM,18

Net obTI+C DTcl IN MN - Run Date: 8!/18/31 ‘16~4

m

Rate ZSC/M.n.

Iso-therm for 5 Min. at ldooc

Teqeraturs (PC)

Sample size 22.1sMg

Figure 2. The Study of CS in a Differential Thermal Analyzer.

The onset of combustion was consistent and reliable from one run to another. The time from

initial contact of the hot FTM to the green preform to combustion initiation was longer, -4.30 min

for larger size specimens and 60 s for smaller specimens.

11
PTM initiated CS of TiC was carried out without applying any pressure on the PTM. Resultant

specimens were characterized for conversion to TiC using XRD density of the specimens. It was

noted that complete conversion to TiC was achieved using Consolidated Astronautics’ graphite

powder, and a density of 75% of theoretical was achieved with expansion in specimen dimension

noticed, as is typical of specimens undergoing combustion reaction.

4.4.2 The Effect of Applied Pressure on Densification and Coordination of Its Timing. The

Ceracon process used a pressure of up to 0.69 GPa in a die cavity size of 20 cm diameter and

1.38 GPa in a die cavity size of 6.35 cm diameter. In applying pressure in situ to a CS reaction to

form Tic, several experiments were carried out involving (Table 4):

(1)

(2)

(3)

(4)

Application of pressure on the specimen prior to combustion initiation by hot grain and

holding it through combustion. This approach tended to cool the grain prematurely and

resulted in noniuitiation of combustion or a partial combustion reaction.

Application of pressure upon observation of combustion and slowly ramp up the magnitude

of pressure. The densities achieved were only 85% of theoretical for TiC because the

pressure pulse did not superimpose on the material when specimen was at the highest

temperature.

Delay application of pressure after initiation of combustion for a few seconds, then apply

pressure. This worked well leading to full conversion to TiC and high densities achieved.

Delay application of pressure after the observation of combustion for a few seconds but apply

rapid pressurization. This worked the best giving a combination of highest densities (>95%)

and full conversion to Tic.

The mode described in (1) or (4) was used in a majority of the thermal management experiments

and in upscaled fabrication of lo-cm-diameter, 2.5-cm-thick specimen fabrication.

12
Table 4. CSKeracon Experiments to Fabricate TIC

SN

Delta Times in Seconds

PTM Sample Insert - SHS Until Full

Tem~~ture SHS Observed Pressure

Unless otherwise noted, all samples had the following commc

2 1,200

size - 6.35 cm diameter >

No SHS -

>

936 1,400 lmin No pressure

applied

Unless otherwise noted, ah samples had the following commc

939 1,200

size - 8.57 cm diameter >

lrtlin -

931

I

1,400

I

1.6 mm

I

-

I I I

Unless otherwise noted, all samples had the following comma

Same as above; material

from newer batch sample

appears to have exploded at

SHS.

Same as above added;

9400 PTM.

9400 96.0

9400 97.0

942

I parameters: Consolidated at 0.48 GPa; die cavity

size - 1011 cm diameter x 12.7 cm deep; media heated to 1,200” C.

1,200 50s 10 s 40.6-cm diameter x 9400 1ooa

1.78-cm sample with ring;

sample at top edge of ring;

appears that top of sample

l-l Density

Variable Modified Type Recorded

1 parameters: Consolidated at 0.48 GPa; die cavity

12.7 cm deep.

Cold sample placed in 9400 -

heated graphite vessel;

same as PTM temperature. I I

Same as above added: TiT3s 1 9400 1 -

I I

I parameters: Consolidated at 0.48 GPa; die cavity

12.7 cm deep.

943

944

1,200

1,200

3.5 mm

50-60 s

10 s

10 s

is moved out of ring at SHS.

Same as above with sample 9400 103.0a

in middle: appears to barely

have sufficient heat for SHS

to occur.

Same as first; same 9400 100.oa

post-Ceracon condition. I

a Analysis showed Fe contamination leading to high density.

The high-density TiC specimens were found to have a network of surface cracks, similar in

appearance to that reported by Meyers et al. [21]. The cracks originate fi-om thermal shock

experienced by the specimens due to rapid cooling of the specimen after densification and due to the

differential cooling rate between the surface and interior. Another problem noted during

13
consolidation was the shifting of the specimen into two layers, which led to specimen distortion and

differential consolidation of the specimens.

4.4.3 TiB2. The following issues were considered to be critical to meeting the specifications set

for CWeracon-processed TiB2:

Density of at least 98.5%.

Conversion to T&.

Achieving crack-free specimens.

Most of the process parameters and issues discussed previously for TiC are common to TiB2;

however, there are some dserences that are highlighted in the following discussion.

4.4.3.1 PTM Churacteristics. The use of carbon-based media for CSKeracon of Ti + B to form

TiB2 was of concern because of the potential for reaction between carbonaceous media and elemental

Ti to form TiC in addition to TiB2. However, free energy calculations of delta G vs. temperature

show that TiB2 has significantly higher free energy of formation; hence, it should not be a problem

using carbon-based PTM (Figure 3).

4.4.3.2 PTM Temperature. The PTM temperature of 1,200” C was adequate to initiate

combustion readily, however, in carrying out the reaction of pure Ti with B, the reaction process was

significantly more energetic than the reaction of Ti and C leading to specimen disintegration This

problem led to the identification of need for use of d&rent TiB2. Later CSKeracon experiments were

carried out with the addition of 22.5 weight-percent of T&, as suggested from the work of

Meyers et al. [21]. However, the addition of diluent led to obtaining lower density values of 85%.

14
-30000

-60000

i

8 TIE2

q TiC

1000 1500

Temperature (K)

2500

Figure 3. Delta G vs. Temperature for TiB2 and Tic.

The microstructure of the TiBz specimen obtained by CWCeracon is shown in Figure 4. The fine

grain size present shows the process’ capability to achieve densification without grain growth.

Due to the more explosive reaction involved in the formation of the TiBz leading to safety

problems, and due to the high cost of B, we decided to dedicate all the remaining effort in Phase 1

to demonstrating the fabrication 4-in-diameter x 1 -in-thick TiC specimens.

5. Thermal Management Issues to Prevent Crack Formation

and Specimen Containment

In their earlier work on high-speed forging coupled to CS of TiC and TiB2, Meyers et al. [21] had

identified the crack problems and crack origins. Niiler, Kecskes, and Kottke [2] have also addressed

similar issues in the CS/dynamic compaction of TiC and T&.. These studies have identified that

containment of the specimen during CS by using a combination of grafoil and steel concentric outer

rings prevented specimen displacement, and immediate slow cooling of the specimen after

15
Figure 4. Scanning Electron Microscope (SEM) Micrograph of Surface of TiB2 at 1,000x.

CS/dynamic compaction in a furnace for an extended period solved thermal cracking problems.

These findings were incorporated in this work initially, but because of the different material

processing environment present in the Ceracon die vs. hot forging or explosive consolidation, a new

type specimen confinement system was developed and found to be more suitable.

Specifically, the steel ring/grafoil or graphite confinement ring works well for consolidation, but

the high temperatures resulting from CS cause the steel to melt and mix with consolidated TiC

(Table 4), leading to a sign&ant amount of Fe contamination in the Tic,

view of this problem, we have removed the steel ring and designed

confinement ring.

which is unacceptable. In

a one-piece, all-graphite

To overcome the thermal shock problem, a number of techniques were evaluated, including in situ

cooling of a CSKeracon-processed part in the die inside the PTM grain, cooling the part outside the

die in a vessel containing an insulating blanket, and cooling in a furnace. While most cracks were

eliminated, a surface crack was still present, which is most likely due to differential temperatures (as

16
identified by grain size difference) between the interior and exterior of the part. This problem can be

solved by instantaneous removal of a specimen encased in hot PTM grain and placing it in a furnace

and cooling slowly over an extended period of time.

5.1 CSKeracon Processing of lO.l-cm-Diameter x 2.5cm-Thick Tic. The powder blending,

green preform fabrication, and CYCeracon processing parameters were upscaled to the fabrication

of larger TiC specimens and no problems were noted. The final processing parameters used in these

experiments are listed in Table 5.

Table 5. Processing Parameters for CSKeracon of TiC (10.1 cm Diameter x 2.5 cm Thickness)

PTM: 9400

PTM Temperature: 1,200° c

Time to Ignite: -4min3os

Thermal Management: Graphite Ring

Pressure: 0.48 GPa

CIPing of 4 kg of blended Ti and C powder was carried out to fabricate a cylindrical green

preform with a 15.2 cm length and 10.1 cm diameter (Figure 5). Three discs were cut from this

preform for use in CSKeracon processing. The larger 2,500-ton Ceracon press was used in these

experiments (Figure 6).

The original containment fixture consisting of a grafoil inner ring followed by steel was abandoned

in favor of an all-graphite ring as shown in Figure 7. This approach was taken because melting of the

ring lead to contamination of TiC by Fe.

The CSKeracon experiments were then carried out using the following procedure. The graphite

ring and PTM were separately heated to a temperature of 1,200” C. Approximately half the amount

of grain was transferred to the die initially at 1,200” C, and a hot graphite ring at the same

temperature was placed in the semifilled die. The green preform was lowered to approximately the

middle of the ring to allow for anticipated expansion during CS. Approximately 5 min from the time

17
I inch . . . ClPped green preform of TiC Iw _’

-

Figure 5. CIPed Green Preform of Tic.

,.’ *

.I -

‘1 1 ‘,

_-

-7-L_

”

_-

,. I

-, I

Figure 6. Ceracon’s 2,500-Ton Press.

18
PROCESS STEPS1

I) ;+;ST LOAD.

2) PLAbE’%:ThMENT

RIN(3, 1200’~.

AFTER SHS.

DIE

\

/

Figure 7. Schematic of an All-Graphite Ring.

the ring was placed in the die, the initiation of CS reaction was visible by “fireworks” resulting fi-om

some expulsion of red hot, flaming PTM from the die. At this point, the pressure initiation cycle was

initiated and a pressure of approximately 0.48 GPa was applied on the specimen that has just

undergone SHS. Several lO.l-cm-diameter x 2.5-cm-thick specimens of TiC were fabricated in this

manner (Figure 8).

5.2 Post CS/Ceracon Thermal Management. After the consolidation cycle was completed,

pressure was removed Tom the top of the specimen by withdrawing the punch, and the specimen was

allowed to cool in the die amidst the hot PTM grain for a few minutes. After this time, the specimen

was removed from the PTM grain and immediately transported to a vessel containing additional hot

PTM grain surrounded by an insulating blanket of kaowool. The specimen that was cooled in this

19
mbustion svnthesized/Ceracon orocessed TiC

Figure 8. In-Situ CS/Ceracon-Processed Tic.

manner remained intact in one piece with only few surface cracks. Alternatively, specimens were also

transported to a furnace where they were allowed to cool slowly prior to removal. The densities of

these specimens were measured to be consistently exceeding 95.57%. The specimen was then

characterized and tested. Using a diamond saw, the specimen was cut into small cubes for

compression testing, microstructural characterization, and measurement of microhardness, toughness,

and Young’s modulus.

These upscaled Tic fabrication experiments clearly demonstrated the feasibility of fabricating an

integral piece of specified density. These experiments also illustrated the importance of slow and

uniform cooling of the interior and exterior of the specimen after CWCeracon to prevent crack

formation.

6. Characterization of a 10.Lcm-Diameter x 2.5cm-Thick

TiC Specimen

The characterization and testing of 10.1 -cm-diameter TiC specimens was carried out by Professor

Marc Meyers’ group at the University of California, San Diego.

20
6.1 Specimen Preparation. The specimen was sectioned using a diamond saw. Specimens for

mechanical testing were made by grinding cubes with dimensions of 6 x 6 x 6 mm. The parallelism

between opposite faces was very critical in order to ensure reliable mechanical properties; the

precision in machining was kept to 2/10,000 (0.0005 mm). Larger variations in thickness could

significantly affect the mechanical strength. The cubical mechanical specimens were tested in

compression, at a nominal strain rate of 10s4/s. Molybdenum disulfide was used as lubrication

between the specimen and the machine platens (tungsten carbide). A screw-driven Instron with a

20,000~lb capacity was used for testing.

Vickers microindentation hardness measurements were made on a polished surface usjng a load

of 300 gf, in a Leco microhardness testing machine. Specimen preparation for optical microscopy

consisted of diamond polishing down to 0.25 pn~ The specimen was etched for metallographic

observation in a solution of two parts nitric acid, one part hydrofluoric acid, and one part acetic acid.

Metallography was carried out in a Nikon metallograph. For SEM, a unit from Cambridge

Instruments was used.

6.2 Results and Discussion. Figure 9 shows the cross section of the TiC disk. The material has

a very well consolidated appearance; the presence of some cracks in some sections is clear. The

cracks are similar to the ones observed after the SHWdynamic compaction process [21,23]. They

are most probably produced by thermal stresses during the cooling of the specimen.

The microindentation hardness was measured along the thicbess of the specimens, and the results

are shown in Figure 10. The values are found to fluctuate above 2,000 kg/mn?.

The compressive strength of compacts was determined, and the results of three experiments are

shown in Table 6. The compressive strength varied between 1.262 and 1.609 GPa. This value is also

consistent with values obtained by Meyers et al. [21], and LaSalvia, Meyer, and Meyers [23].

Young’s modulus in compression was measured indirectly through the deflection of the specimens

as required in the recorder (correcting for machine stifhress). The values of Young’s modulus, shown

in Table 6, are lower than those for fully compacted and flawless material. Young’s modulus of the

21
t

c

Figure 9. Optical Micrographs of Sectioned Specimens. Macrocracks Can Be Seen

Transversing the Thickness.

22
0 l0 10 20

Top Bottom

Figure 10.

DISTANCE (mm)

Microindentation Hardness Measure’ments Along the Thickness of the

Specimen.

Table 6. Compressive Strength and Young’s Modulus of TiC

Specimen

1

2

3

Compressive Strength Young’s Modulus

(GPa) (GPa)

1.260 164.2

1.370 98.0

1.610 120.0

latter material varies between 400 and 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. Hoke et al. [24]

have introduced corrections into the values of Young’s modulus due to these flaws and are able to

explain the differences.

A preliminary fracture toughness measurement was made by measuring cracks remaining from

the indentation produced by a microhardness tester. This technique was developed by Evans and

23
Charles [25] and has been successfully used by many investigators and correlated with fracture

toughness measurements made by other techniques [25, 26,271. The indentation diagonals, a, are

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 mm. The fracture toughness, K, is obtained from the equation below:

K = 0 16 Ha2C-3n c *

= 0.16 x 0.47 PC-3’2

K, = 1.7 MPa m1’2

The value obtained for K is characteristic of a well-bonded ceramic. Higher magnification optical

micrographs reveal the grain structure in more detail, It is equiaxed and is shown in Figure 11.

SEM of the specimens fractured in the compression test is shown in Figure 12. The fracture is

clearly transcrystahine, and one sees the cleavage steps very well. Figure 13 also shows an area in

which fracture has some intercrystalline features. This primarily transcrystalline fracture is a good

evidence for good bonding between the grains and clean, impurity-free grain boundaries.

7.

(1)

(2)

Accomplishments

The general overall objective of this project of demonstrating a process with potential for

economically mass producing low-porosity monolithic ceramic materials by CWCeracon in

the quantities and sizes required for ballistic applications was accomplished.

The specific overall objective of the ability to apply the CWCeracon process to fabricate

10.1 -cm-diameter x 2.5cm-thick pieces of TiC at 95.57% of theoretical density has been

met. The microhardness values of these samples are comparable to those obtained by

conventional HP.

24
-

”

I

Figure 11.

(a)

Optical Micrographs of Polished and Etched Sections of Specimen: (a) Small

Grain-Sized Region Close to External Surface; (b) Large Grain-Sized Region Close

to Center.

25
.

Figure 12. Fractographs of TiC Obtained by SEM Showing Primarily Transgranular

Fracture: (a) Magnification of 500x; (b) Magnification of 1000x.

26
Figure 13. Fractographs of TIC Showing Partial Intergranular Fracture.

(3) The characterization requirements set by the Contracting Officer’s Technical Representative

(COTR) has been met, including measurement of microhardness, compressive strength,

Young’s modulus, fracture toughness, density, XRD pattern, and SEM of surface and

fracture surfaces. The required microhardness value of 25 GPa for Tic was met.

8. Conclusions

The use of the CWCeracon process is ideally suited for the fabrication of low-porosity monolithic

ceramic materials, especially Tic. Complete conversion Tom Ti + C -> Tic is feasible, and reqluired

densities of 95.57% can be readily achieved. The microstructure consists of larger grains toward the

center of the specimen and smaller grains at the edge, most likely due to the need for better control

in uniformly cooling the specimens. This may also be the reason for the presence of surface cracks

in the specimen.

The economics of this process also looks very promising for the Army to fabricate Tic armor tiles

for ballistic protection. This projection is based on the following reasons. When Tic powder is hot

27
pressed at very high temperatures (2,500” C), it requires a significant consumption of energy. The

energy consumption CSKeracon process is much lower due to the use of temperatures of only

1,200” C. The PTM is inexpensive ($0.5O/lb), recyclable, and environmentally acceptable. The

Ceracon processing technology and preform fabrication technology are already developed for

conventional material systems, and thus technical expertise on the processing technology is readily

available to this project.

9. Recommendations

The CWCeracon process, having met most of BRL goals for Tic in the Phase I program, is ready

for Phase II process development and upscaling. In Phase II, it is recommended that work should

focus on fabricating and demonstrating prototype fabrication of 100 pieces of 15-cm x 15-cm x

2.5-cm-thick tiles of TiC by the CSKeracon process. The work should initially address improving

thermal management to produce totally crack-free specimens, including an understanding of heat

transfer characteristics in the Ceracon environment followed by evaluation of cost issues in

manufacturing TiC tiles. Extensive material characterization and testing of relevant microstructural

and mechanical properties relevant to ballistic performance should also be carried out.

28
1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

10. References

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

and DynamicalIy-Consolidated Titanium Boride and Titanium Carbide.” JournaZ of the

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

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

Ceramics.” Combustion of Plasma Synthesis of High Temperature Materials, pp. 309-314,

edited by 2. A. Munir and J. B. Holt, New York, NY: VCH Publishers, 1990.

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, edited by Z. A. Munir and J. B. Holt, New York, NY:

VCH Publishers, 1990.

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, 1989.

Kecskes L. J., T. Kottke, and A. Niiler. “Powder Purity and Morphology Effects in

Combustion-Synthesis Reactions.” Combustion and Plasma Synthesis of High Temperature

Materials, pp. 157-162, edited by Z. A. Munir and J. B. Holt, New York, NY: VCH Publishers,

1990.

Holt, J. B., and 2. A. Munir. “Combustion Synthesis of Titanium Carbide: Theory and

Experiment.” Journal of Materials Science, vol. 21, no. 1, pp. 25 l-259, 1986.

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. 1333-1337,1989.

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

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

1985.

Borom, M. P., and M. Lee. “Effect of Heating Rate on Densification of Alumina-Titanium

Carbide Composites.” Advanced Ceramic Materials, vol. 1, no. 4, pp. 335-341, 1986.

Ward, R., N. Thadhani, and P. A. Persson. “Shock-Induced Reaction Synthesis-Assisted

Processing of Ceramics.” Combustion and Plasma Synthesis of High Temperature Materials,

pp. 294-302, edited by Z. A. Munir and J. B. Holt, New York, NY: VCH Publishers, 1990.

Zavitsanos, P. D., J. J. Gebhardt, and A. Gatti. ‘The Use of Self-Propagating High-Temperature

Synthesis of High-Density Titanium Diboride.” Combustion and Plasma Synthesis of High

29
-

12. Kang, E. S., C. W. Jang, C. H. Lee, and C. H. Kim. “Effect of Iron and Boron Carbide on the

Densification and Mechanical Properties of Titanium Diboride Ceramics.” Journal of the

American Ceramic Society, vol. 72, no. 10, pp. 1868-1872, 1989.

13. German, R. M., and 2. A. Munir. “Morphology Relations During Surface-Transport Controlled

Sintering.” Metallurgical Transactions B, vol. 6b, no. 2, pp. 289-294, 1975.

14. Baik, S., and P. F. Becher. “Effect of Oxygen Contamination on Densification of TiB2.” JounzuZ

of the American Ceramic Society, vol. 70, no. 8, pp. 527-530, 1987.

15. Finch, C. B., and P. F. Becher. “Effect of Impurities on the Densification of Submicrometer TiE&

Powders.” Advanced Ceramic Materials, vol. 1, no. 1, pp. 50-54, 1986.

16.

17.

Itoh, H. S., S. Naka, T. Matsudaira, and H. Hamamoto. “Preparation of TiBz Sintered Compacts

by Hot Pressing.” Journal of Materials Science, vol. 25, no. lB, pp. 533-536, 1990.

Taneoka, Y., and 0. Odawara. “Combustion Synthesis of the Titanium-Aluminum-Boron

System” Journal of the American Ceramic Society, vol. 72, no. 6, pp. 1047-1049, 1989.

18.

19.

Zavitsanos, P. D., and J. R. Morris, Jr. “Synthesis of Titanium Diboride by a Self-Propagating

Reaction.” Ceramic Engineering and Science Proceedings, VOL 4, no. 7-8, pp. 624-633,1983.

Halverson, D. C., B. Y. Lum, and Z. A. Munir. “Combustion Synthesis of Boride Composites.”

Presented at the Symposium on High-Temperature Materials-IV at the 172nd Meeting of the

Electrochemical Society, Honolulu, HI, October 1987.

20. Ceracon, The Ceracon Process is covered by 29 U.S. Patents. The word ‘Ceracon” and the logo

have been trademarked and registered at the United States Patent Office. Registration No.:

1,361,401, Date of Issue: 24 September 1985.

21. Meyers, M. A., J. C. LaSalvia, L. W. Meyer, D. A. Hoke, and A. Niiler. “Reaction

Synthesis/Dynamic Compaction of Titanium Carbide and Titanium Diboride.” JournuZ de

Physique ZV, pp. C3/123-C31130, vol. 1, no. C3, 1991.

22. Raman, R. V., and A. Niiler. Personal communication. November 199 1.

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

Titanium Carbide by High-Velocity Forging.” Journul of the American Ceramic Society,

vol. 75, no. 3, pp. 592-602, 1992.

Temperature Materials, pp. 170-178, edited by Z. A. Munir and J. B. Holt, New York, NY:

VCH Publishers, 1990.

30
24. Hoke, D. A., M. A. Meyers, L. W. Meyer, and G. T. Gray III. “Reaction Synthesis/Dynamic

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

pp. 77-86,1992.

25. Evans, A. G., and E. A. Charles. “Fracture Toughness Determinations by Indentations.”

Journ.ul of the American Ceramic Society, vol. 59, no. 7-8, pp. 371-372, 1976.

26. Anstis, G. R., P. Chankitul, B. R. Lawn, and D. B. Marshall. “A Critical Evaluation of

Indentation Techniques for Measuring Fracture Toughness: I, Direct Crack Measurements.”

Journul of the American Ceramic Society, vol. 64, no. 9, pp. 533-538, 1981.

27. Marshall, D. B. “Controlled Flaws in Ceramics: A Comparison of Knoop and Vickers

Indentation.” Journul of the American Ceramic Society, vol. 66, no. 2, pp. 127-13 1, 1983.

31
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US ARMY ARDEC

D KAPOOR

S CYTRON

DOVER NJ 07801

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PHYSICS DEFT

WJNELLIS

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ARMY RSRCH OFFICE

A CROWSON

E CHEN

R REEBER

PO BOX 12211

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PADAMS

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THE TITAN CORP

CRT DIV ORD TECHLGY

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WRIGHT LABORATORY

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MUNJTIONS DIV

J FOSTER

EGLIN AFB FL 32542-68 IO

FAJLURE ANALYSIS ASSOC

JNEIL

149 COMMONWEALTH DR

PO BOX 3015

MENLO PARK CA 94025

1 OAK RIDGE NATL LAB

A PAST0

MS 6087 BLDG 4508

BOX 2008

OAK RIDGE TN 3783 1

1 SURMET CORF

S SASTRI

33 B STREET

BURLINGTON MA 01803

2 SNL

FUSION TECHLGY DEPT 653 1

M ULHRLKKSON

R WATSON

ALBURQUERQUE NM 87185

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ATAC MS F68 1

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LOS ALAMOS NM 87545

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DEFT ENGNR SCIENCES AND

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‘34
NO. OF

COPIES

2

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3

1

1

ORGANIZATION

GEORGIA INST OF TECH

SCHL OF MTRL ENG

K LOGAN

NTHADHANI

ATLANTA GA 30332-0245

NEW MEXICO INST

OF MINING AND TECH CTR

FOR EXPLSV TECH AND RSRCH

A MILLER

P PERSSON

MTRLSANDMETENG

OINAL

SOCORRO NM 87801

UNIV OF CALIFORNIA

COLLEGE OF ENGNRNG

ZMUNIR

DAVIS CA 95616

BATJ-ELLE

METALS AND CERAMICS DEPT

R TENAGLIA

505 KING AVENUE

COLUMBUS OH 43201-2693

B BUSOVNE

23414 SHADYCRAFT

TORRANCE CA 90505

35

NO. OF

COPIES ORGANIZATION

ABERDEEN PROVING GROUND

30 USARL

AMSRLWMTE

L KECSKES (15 CPS)

ANTILER

AMSRL WM TA

W GOOCH

W GILLICH

M BURKINS

GHAUVER

T HAVEL

E HORWAT’H

AMSRLWMTD

KFRANK

AMSRL WM TC

EKENNEDY

L MAGNESS

AMSRL WM MC

J LASALVIA

THYNES

J MCCAULEY

DVIECI3NICKJ

JWELLS
INTENTIONALLY LEFT BLANK.

36
i Novel Manufacturing Processing Route for Forming High-Density Ceramic

her Materials: Phase I - SBIR

DAA 15-01-C-0087

I101 North Market Blvd. ##9

iacramento, CA 95834

U.S. Army Research Laboratory

/JTINz AMSRL-WM-TR

AGENCY REPORT N

Il. SUPPLEMENTARY NOTES

12a. DlSTRlBUTlON/AVAlLABlLlTY STATEMENT

Approved for public release; distribution is unlimited.

12b. DISTRIBUTION CODE

3. ABSTl?ACT(Maxlmum 200 words)

The objective of the Phase I small business innovative research (SBIR) project was to demonstrate the feasibility of

applying the Combustion Synthesis (CS)/Ceracon Consolidation Process for forming lo-Cm-diameter, 2.5-cm-thick

high-density titanium carbide (Tic) and titanium diboride (TiB& pieces. The Phase I project demonstrated for the first

time the feasibility of CS initiation to form Tic and TiB, by using Ceracon’s hot, granular media and their in-situ

consolidation. The effects of applied pressure and pressure-transmitting media (PTM) temperature in controlling density,

as well as thermal management issues to prevent crackiug in applying the CWeracon process to form Tic and TiB2, have

been identified. In-situ CWeracon consolidation to densities exceeding 98% was demonstrated for fabricating

lo-cm-diameter, 2&m-thick Tic pieces. The CSKeracon-processed, high-density Tic specimen has a fine grain size,

microhardness values exceeding 2,500 kg&m?, and compressive strength of 1.3 GPa. Due to the use of inexpensive

conventional forging equipment and a low-cost grain for both initiating self-propagating, high-temperature synthesis

(SHS) and consolidation, this novel approach has the potential to be significantly more cost effective than currently used

conventional hot pressing (HP) or hot isostatic pressing (HIPing) of Tic and TiB, powders. A set of recommendations

for the technical approach to be followed in process upscaling in Phase II to fabricate larger size tiles of Tic material

is provided.

14. SUBJECT TERMS

Tic and TiB,, armor materials, rapid consolidation, dense materials, porosity,

agglomeration, Ceracon

15. NUMBER OF PAGES

41

16. PRICE CODE

II. SECURITY CLASSIFICATION 18. SECURITY CLASSIACATION 19. SECURITY CLASSlFlCATlON 20. LIMITATION OF ABSTRACT

OF REPORT CF THIS PAGE OF ABSTRACT

UNCLASSIFIED UNCLASSIPED UNCLASSIPED UL

*#CL, -cl” .-l_QQnzmn atan&@ Fnm XV? f&w 3-@4\

37

I . .,...._.,_\. .--. - __,

Prescribed by ANSI Std. 239-18 293-102
.

IN’TENTIONALLY LEFT BLANK.

.

38
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