Production of high strength refractory compounds and microconstituents into refractory metal matri

Herbell, T. P.

Quatinetz, M.

Weeton, J. W.

English

NASA Technical Reports Server

UTICS AND SPACE 
WASHINGTON, D.C. 20546 
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METHOD OF PRODUCING REFRACTORY COMPOSITES CONTAINING TANTALUM 
CARBIDE, HAFNIUM CARBIDE, AND HAFNIUM BORIDE 
Filed March 25, 1966 
PQSITES CONTAINING TANTALUM CARBIDE, 
HAFNIUM CARBIDE. AND HAFNIUM 5BRHDE 
Powders of refractory compounds are uniformly dis- 
tributed throughout powders of a refractory metal matrix. 
The resulting mixture is densified by heat and pressure. 
Solution treatment follows in which a portion of the re- 
fractory compound is dissolved into a matrix to form 
a solid solution which is subsequently uniformly repre- 
cipitated throughout the microstructure. 
The invention described herein was made by employees 
of the United States Government and may be manu- 
factured and used 'by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
Another disadvantage is the greater impurity contents 
occur in the dendritic interstices and the grain ,boundaries. 
Subsequently, upon mechanical working and processing. 
micro-constituents and alloying elements that segregate 
during casting are sthingered, elongated, sometimes frag- 
mented, but are rarely homogeneouly distributed. 
In an effort to solve these problems, powder metal- 
lurgy techniques have been proposed to obtain greater 
uniformity of microstructures. While the problem of 
ingotism is avoided by these powder metallurgy tech- 
niques and the process of precipitation is most often 
uniform and well carried out, the usual procedure in 
reacting these types of powders does not permit the in- 
corporation of large quantities of products into the 
15 matrix. Inherent in both the pre-alloyed method and in 
the casting concept is the fact that the quantities of 
refractory compounds produced by reaction or by dis- 
solution and precipitation are limited. 
According to the present invention these types of com- 
or desired amount up to the saturation point 
of illustration, powders of an (AB) compound formed 
from (A) and (B) are distributed throughout a powdered 
matrix (X). The mixture is compacted and densified to 
25 form a fine uniform distribution of (AB) in (X). The 
composite may be heated to a high temperature either 
during or subsequent to fabrication so that a part or all 
of the (AB) dissolves into (X) and forms a partial or 
total solid solution in (X). That portion of the corn- 
ace 
~~~~~~ 
20 pounds can be incorporated in the material in 
Background of the invention 30 
This invention is concerned with the production of 
high strength refractory metals that are stable at high 
temperatures. More particularly, the invention relates to 
the incorporation of refractory compounds and micro- 85 
constituents into a refractory metal matrix. 
Refractory compounds and micro-constituents are in- 
corporated into a refractory metal matrix conventionally 
by melting refractory metals and simultaneously adding 
reactive metals and interstitial compounds to the molten 4 0  
matrix material. Upon consolidation of cast billets or 
ingots and subsequent working a rejection of particles 
of refractory compounds that strengthen the matrix 
occurs. The methods employed for making refractory 
materials are quite similar to those used for superalloys 45 
and non-ferrous metals which involve casting, mechanical 
working, and heat treatment. Other methods utilize pre- 
alloyed powders which react to produce precipitatcs, 
intermetallic compounds, or carbides, and in some caws. 
To illustrate the conventional procedure of the prior 
art, a metal solvent (X) is melted with soluble metals 
(A) and (B),  or (X) may be melted alone with (A) 
and ( B )  being added subsequent to melting. The result- 
ing melt is a liquid solution of the solvent (X) with 55 
(A) and (B) in solution. A precipitate of an (AB) com- 
pound may form on cooling this type of material. How- 
ever, very frequently (A) and ( R )  segregate in eithcr 
the grain boundaries or the dendritic interstices. Somc- 
times (A) and/or (B) combine with (X) to form (10 
other components or phases that segregate. This type of 
segregation is termed ingotism. 
Any of the prior art methods which involves the con- 
ventional melting and casting of refractory metals to 
produce precipitates or other configurations of refractory (jr, 
compounds embedded in ii metalic matrix has an in- 
herent disadv;int;;ge notcd in all cast and wrought protl- 
u c h  This is the segregation of alloying constituents anti 
micro-constituents as a rcsult of the cilsting. SeyrcRiilion 
of these conutitucnts, ;IS well its of alloying elements which 7 0  
takes place during the casting, i\ a rcsult of the previous- 
ly described phenomcnon tcrmcd ingotism. 
refractory compounds are produced. !io 
pound (AB) that dissolves into solution may subsequent- 
ly be precipitated more uniformly throughout the micro- 
structure by heat treating and aging processes. Also, the 
material may be worked subsequent to the dissolution of 
(AB), and the working with aging uniformly or ad- 
vantageously distributes a fine precipitate of ( 
throughout the structure. The residual undissolved par- 
ticles of (AB) in themselves also add dispersion strength 
to the composite. 
The invention utilizes a powder metallurgical process 
in which refractory compounds or oxides are mechanical- 
ly mixed with refractory metal powders, with or without 
attrition or grinding. This is followed by a densificatio 
procedure which includes cold compaction and sintering 
or hot pressing. Mechanical working at  elevated tem- 
peratures that either dissolves portions of the refractory 
compounds or oxides added to the mix or that causes 
the oxides or refractory compounds to react with the 
refractory metal matrix powder can be utilized. In gen- 
eral, consolidation and densification of the product per- 
tains to billets that would subsequently ,be processed by 
other mehods, such as extrusion. The mechanical proc- 
essing further densifies and consolidates the product while 
producing nucleation sites within the product thereby per 
mitting subsequent precipitation of some of the dissolved 
constituents to occur in the nucleation sites so produced. 
The residual undissolved refractory compound particles 
also add dispersion or fiber strength to the compounds. 
It is, therefore, an object of the present invention 
provide an improved process for making refractory met 
base alloy composites in which a quality of refractory 
compounds is added to a metallic matrix in excem 
is possible by conventional casting or pre-alloyed 
methods. 
Another object of the invention is to control the degree 
and homogeneity of alloying reactions in which the par- 
ticle size and distribution of matrix and additive powers 
arc controlled hy incorporating small or large particles 
of refractory compounds into B matrix of small or large 
powders thus varying the ratios of the particla sizes of 
the different constituents. 
A further object of the invention is to provide an im- 
proved alloy by utilizing an initial mechanical distribution! 
which prearranges in a controlled fashion particle spac- 
ing where the incorporated or added particle is a com- 
pound. 
Still another object of the invention is to provide an 
alloy having a better homogeneous distribution than that 
obtained with conventional pre-alloyed powder metallurgy 
approaches, 
Still a further object of the invention is to provide an 
improved method of making an atloy which eliminates 
the steps of casting, comminution and reconsolidation 
which are required in conventional pre-alloyed powder 
metallurgy techniques. 
These and othw objects and advantages of the invention 
will be apparent from the drawing and the specification 
which follows. 15 15 cubic feet per hour. 
TABLE II.-TUNGSTEN BILLET COMPOSITION, PROCESSING AND TESTING 
Composltlon 
Extrusion T& Basulta 
Addltlve 
7 _ _ _ _ _ _ _ _ _ _  Tantalum carblde _ _ _ _ _  8.0 173.6 0.0 BesCtioIL.. .-. 
8 _ _ _ _ _  ~ _ _ _ _  Iiafnlum osrblde _ _ _ _ _ _  8.0 197.6 4.0 --.,-do _ _ _ _ _ _ _ _ _  
De-- _ _  _ _  _ _  - Hafnlum borldo- - .___. 8.0 iat. 7 9.8 _____do ___.__-._ 
In the drawings: 
FIGS. 1 and 2 are electro micrographs of a test speci- 
men illustrating the reprecipitation of a refractory metal 
compound which was added in accordance with the pres- 
ent invention to  a high temperature refractory matrix. 
To illustrate the features of the invention, refractory 
composite specimens were prepared by adding powders 
having a wide range of melting temperatures and reactivi- 
ties to  tungsten. Composites comprising tungsten with 8 
or 10 volume percent of oxide or refractory compounds 
were extruded into bar stock. All the billets were ex- 
truded at a temperature of 4200" F. and a reduction ratio 
Oxides in the form of zirconia, yttria, hafnia, and thoria 
were used as additives. These additives were fibered dur- 
ing extrusion into bar stock. 
The refractory compounds added were hafnium boride, 
nitride and carbides as well as tantalum carbide. 
micrographs of the composites showed the hafnium nitride 
was also fibered during the extrusion process. The other 
refractory compounds were deformed to a small extent 
and reacted with the tungsten. 
The powders used in preparing the billets are shown in 
Tabe I. The compositions of the billets and their proc- 
essing are listed in Table 11. 
The hafnium boride in Table I contained 2.9 percent 
zirconium, titanium, and carbon while the hafnium con- 
tained 3 percent zirconium. 'me hafnium carbide con- 
tained 4.6 percent zirconium, titanium, and boron. 
Nominal 
d 8: l .  
TABLE I.-l3ILLET MATERIALS 
purlty, Partlolo Mdtlng 
woigtit sizo, point I)onslty, 
Matorial permiit niicronv r: g./cc. 
35 
40 
45 
60 
60 
50 
Tungsten _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  WJ. U6 1.2 6,170 io. ao 
Zirconla _ _ _ _ _ _ _ _ _ _ _ _  98.80 2.0 4,802 5.4u 
Yttria . . . . . . . . . . . . . . . . . . . . .  ~ _ _ _ _  1.7 r,a7o 4.84 
Hafnia _ _ _ _ _ _ _ _ _ _ _ _ _ _  00.92 1.u s,m 9.88 
Thoria _ _ _ _ _  _ _  _ _  - ~ _ _  _ _ _ _  _____.__ 2.1 6,622 10.03 
IIafnium boride .... 03.3 6.8 6,880 l l .2070 
14.M) 2% 12.70 lIofnium nltrldo .... 96.6 IIafnium csrbido. _ _  Q5.4 
Tanntiilum oarbldn. - Du. 66 6.0 7,020 14.66 
Qxldes: 
Refractory compounds: 
ith regards to particle size nominally I micron tung- 
sten powder was uscd. The oxides wore nominally 2 76 
t7, Bo 
_I_ 
Examination of the ~un~sten-ref~c~ory-compound 
Stress-rupture tests were run at 3000" F. The stress 
for a 100 hour rupture life for each of the composites was 
obtained from these t . These stresses are listed in the 
last column in Table to provide a ready comparison 
of the strengths of omposites. Table HI 
shows the superiority of composites over the 
fibered composites. 
While tungsten was used as the matrix metal in the 
composites tested, refractory compounds can 
other refractory matrices such as Cb, 'Fa and 
as to lower melting matrices, such as superalloys, in the 
same manner. Other methods of incorporating the re- 
fractory compounds in a matrix or metal include chem- 
ical coprecipitation, electroplating, electrophoritics, ultra- 
sonics, and vaporization with condensation. Also, mechan- 
ical processes including rolling, swaging, forging, drawing 
and explosive deformation can be used instead Of extru- 
sion to work the composite. Explosive deformation tech- 
niques can also be utilized to consolidate the composites 
initially. 
3. A method of producing a metal base alloy corn- 
3,136,039 611964 Keith _ _ _ _ _ _ _ _ _ _  75-203 
3,139,682 711964 Grant _ _ _ _ _ _ _ _ _  29-420.5 
3,143,789 811964 Her _ _ _ _ _ _ _ _ _ _ _ _  75-206 
3,159,908 1211964 Aaders _ _ _ _ _ _ _ _ _ _  75-206 
45 3,180,727 411965 Alexander ___-__ 75-206 
3,189,989 611965 Eldon _ _ _ _ _ _ _ _ _ _ _ _ _  29-4 
3,278,281 1011966 Ehringer _ _ _ _ _ _ _ _  75-206 
3,297,415 111967 Allen _ _ _ _ _ _ _ _ _ _ _ _ _  29-1 
3,369,892 211968 Ellis _ _ _ _ _ _ _ _ _ _ _  M-126 
86 
75-201. 202, 203, 226 


Method of producing refractory composites containing tantalum carbide, hafnium carbide, and hafnium boride Patent

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