Method for depositing a hard, fine-grained, non-columnar alloy of tungsten and carbon on a substrate

A method for producing the disclosed material comprises introducing into a chemical vapor deposition (CVD) reactor a mixture of process gases comprised essentially of (1) tungsten hexafluoride, (2) a volatile oxygen- and hydrogen-containing organic compound, and (3) hydrogen; controlling the ratio of the tungsten hexafluoride to the oxygen- and hydrogen-containing organic compound within the CVD reactor so that the W/C atomic ratio is within the range of about 0.5 to about 15; controlling the reaction temperature so it is within the range of above about 300.degree. to less than about 650.degree. C.; controlling the total pressure within the range of about 1 Torr. to about 1,000 Torr.; and controlling the ratio of H.sub.2 to WF.sub.6 within the range of about 4 to about 20; to produce W and W.sub.2 C, W and W.sub.3 C, or W and W.sub.2 C and W.sub.3 C.

FIELD OF THE INVENTION 
This invention relates to high hardness fine grained tungsten-carbon alloys 
and to a process for producing the same. 
BACKGROUND OF THE INVENTION 
High hardness materials are widely used as coatings on various types of 
mechanical components and cutting tools. Such coatings impart wear and 
erosion resistance and thus increase the wear and erosion life of objects 
that have been coated. The high hardness materials can also be used to 
produce free standing objects which are wear resistant. 
Chemical vapor deposition processes can be used to produce high hardness 
coatings and high hardness free standing objects. In a typical chemical 
vapor deposition (CVD) process the substrate to be coated is heated in a 
suitable chamber and then a gaseous reactant mixture is introduced into 
the chamber. The gaseous reactant mixture reacts at the surface of the 
substrate to form a coherent layer of the desired coating. By varying the 
gaseous reactant mixture and the CVD process parameters, various types of 
deposited coatings can be produced. 
Deposits produced by chemical vapor deposition, both for coating substrates 
and for producing free standing objects, have suffered certain drawbacks. 
Although the hardness of the deposits has been satisfactory, the strength 
and toughness of the materials has often been lower than desired. This 
lack of strength and toughness is due in large part to the grain size, 
crystallite size, and structure of the compounds that make up the deposit. 
Unfortunately, regardless of the components of the gaseous reactant 
mixture, typical CVD techniques produce coatings having relatively large 
grains which are arranged in columns. Thus, cross-sectional metallographic 
examination of a typical chemical vapor deposition deposit will show 
grains usually in excess of several microns in size which are arranged in 
columns that extend perpendicularly to the substrate surface. Such 
deposits are typically quite brittle since adjacent columns of grains 
result in long interstitial regions of weakness. Such regions are easily 
fractured and attacked by corrosive agents and erosive media. Because of 
the columnar grain structure, such deposits also have poor surface finish 
and poor wear and erosion resistance properties. 
Robert A. Holzl, U.S. Pat. No. 4,162,345, issued July 24, 1979 discloses a 
method for producing deposits of tungsten and carbon or molybdenum and 
carbon which results in deposits characterized by a structure which is 
free of columnar grains and instead consists essentially of fine, 
equiaxial grains. These deposits have unusually high hardness and tensile 
strength. The Holzl patent discloses use of temperatures varying from 
650.degree. C. to 1,100.degree. C., which are high enough to severely 
degrade the mechanical properties of various carbon steels, stainless 
steels, nickel alloys, titanium alloys and cemented carbide. 
In the method of the Holzl '345 patent, a sequence of events is made to 
take place which, although similar to conventional chemical vapor 
deposition, is not truly that. The Holzl method employs a reactor which is 
essentially similar to a chemical vapor deposition reactor. However, 
according to the Holzl method the apparatus is operated in such a manner 
that the typical chemical vapor deposition process does not take place. 
Typical chemical vapor deposition involves a single reaction by the gases 
in the reactor at the surface of the substrate resulting in the formation 
of a solid phase deposit directly on the substrate surface. On the other 
hand, the Holzl '345 patent describes a deposition process involving at 
least two distinct reaction steps. According to the Holzl method, an 
initial reaction is caused to take place displaced from the surface of the 
substrate. This reaction involves a decomposition or partial reduction of 
a fluoride of tungsten (preferably WF.sub.6) by a substitution reaction 
with an oxygen or oxygen-containing group derived from a gaseous organic 
compound containing hydrogen, carbon and oxygen. Subsequent reaction with 
hydrogen gas results in the formation of the final deposits. The material 
of the Holzl '345 patent is a hard metal alloy, consisting primarily of 
tungsten and carbon. X-ray diffraction analysis of the '345 alloy shows 
that the deposit is akin to tungsten but with a very finely dispersed 
carbide, probably in the form WC. 
Robert A. Holzl, et al, U.S. Pat. No. 4,427,445, issued January 24, 1984 
also discloses a hard fine grained material which can be produced by 
thermochemical deposition, but at temperatures lower than those described 
in the examples of the '345 patent. Thus, where there are large 
differences in the thermal coefficients of expansion between the substrate 
material and the coating material, the '445 methodology reduces adhesion 
problems and problems associated with mechanical distortion, metallurgical 
transformation or stress relief of the substrate. The material of the '445 
Holzl, et al. patent is a tungsten carbon alloy consisting primarily of a 
two phase mixture of substantially pure tungsten and an A15 structure. 
U.S. Pat. No. 3,368,914, discloses a process for adherently depositing 
tungsten carbide of substantial thickness on steel and other metal 
substrates. The process involves first diffusing another metal on the 
surface of the substrate to relax the thermal expansion coefficient zone 
of the metal substrate. The carbide coating is then deposited on the 
diffused surface by CVD. The process claims it is preferably to diffuse 
the metal forming the carbide into the substrate. In one embodiment of the 
claimed process, a thin layer of W is deposited on the metal surface using 
600.degree.-1000.degree. C. temperature. After coating W, the temperature 
is increased to approximately 1000.degree.-1200.degree. C. and held there 
for a significant period of time to permit diffusion of W into the metal. 
The diffused surface is then coated with tungsten carbide using WF.sub.6, 
CO and H.sub.2. In the alternative embodiment, a pack diffusion technique 
is used for achieving diffusion of W into metal. Temperature ranging from 
1000.degree.-1200.degree. C. is used in the pack diffusion step. The 
diffused metal surface is then coated with tungsten carbide. 
U.S. Pat. No. 3,389,977, discloses a method of depositing substantially 
pure tungsten carbide in the form of W.sub.2 C, free from any metal phase. 
Pure W.sub.2 C is deposited on a substrate by reacting WF.sub.6 and CO. 
The substrate is heated to a temperature in excess of 400.degree. C. The 
adherence of W.sub.2 C to steel is improved by first cleaning the surface 
and then depositing with a thin film of W followed by W.sub.2 C using a 
temperature ranging from 600.degree.-1000.degree. C. Since initial 
deposition of tungsten is conducted at or above 600.degree. C., the '977 
process is not feasible for providing erosion and wear resistance coating 
on various carbon steels, stainless steels, nickel and titanium alloys 
without severely degrading their mechanical properties. Additionally pure 
W.sub.2 C deposited according to the teachings of the '977 patent consists 
of columnar grains. The '977 patent does not describe a process for 
depositing W.sub.2 C coating in non-columnar fashion. 
U.S. Pat. No. 3,574,672 discloses a process for depositing W.sub.2 C by 
heating a substrate to a temperature between 400.degree.-1300.degree. C. 
The process described in this patent is essentially the same as disclosed 
in U.S. Pat. No. 3,389,977. 
U.S. Pat. No. 3,721,577 discloses a process for depositing refractory metal 
or metal carbides on ferrous and non-ferrous base materials heated to at 
least 1050.degree. C. The metal carbides are deposited using halide vapors 
of the metal along with methane and hydrogen. 
U.S. Pat. No. 3,814,625 discloses a process for the formation of tungsten 
and molybdenum carbide by reacting a mixture of WF.sub.6 or MoF.sub.6, 
benzene, toluene or xylene and hydrogen. The process is carried out under 
atmospheric pressure and temperatures ranging from 
400.degree.-1000.degree. C. An atomic ratio of W/C in the gaseous mixture 
varying from 1 to 2 is required to yield W.sub.2 C. The process also 
suggests that for some substrates such as mild steel, it is advantageous 
in providing better adhesion to deposit a layer of nickel or cobalt prior 
to tungsten carbide deposition. The process also claims the formation of a 
mixture of tungsten and tungsten carbide in the presence of large 
proportions of free hydrogen. The mixture of W and W.sub.2 C coating 
deposited according to the teaching of the '625 patent consists of 
columnar grains. The '625 patent does not disclose a process for 
depositing a mixture of W and W.sub.2 C in non-columnar fashion. 
British Pat. No. 1,326,769 discloses a method for the formation of tungsten 
carbide by reacting a mixture of WF.sub.6, benzene, toluene or xylene and 
hydrogen under atmospheric pressure and temperatures ranging from 
400.degree.-1000.degree. C. The process disclosed in this patent is 
essentially the same as disclosed in U.S. Pat. No. 3,814,625. 
British Pat. No. 1,540,718 discloses a process for the formation of W.sub.3 
C using a mixture of WF.sub.6, benzene, toluene or xylene and hydrogen 
under sub-atmospheric pressure and temperature ranging from 
350.degree.-500.degree. C. An atomic ratio of W/C in the gaseous mixture 
varying from 3-6 is required to yield W.sub.3 C. The coating deposited 
according to the teaching of British Pat. No. 1,540,718 consists of 
columnar grains. The British '718 patent does not teach a process for 
depositing a non-columnar coating. 
Although the methods of the Holzl patents cited above have been useful in 
producing fine-grained tungsten/carbon alloys containing mixtures of W and 
WC, and W and A15 structure, and the methods described in other cited 
patents have been successful in producing columnar W.sub.3 C or W.sub.2 C 
or mixtures of W and W.sub.2 C, no one has yet disclosed a method for 
producing extremely hard, fine-grained and non-columnar tungsten-carbon 
alloys containing mixtures of tungsten and true carbides in the form of 
W.sub.2 C or W.sub.3 C or a mixture of W.sub.2 C and W.sub.3 C. Such 
alloys would be especially useful since the presence of the W.sub.2 C 
and/or W.sub.3 C carbides in non-columnar microstructure would contribute 
to both the hardness and the tensile strength of the deposited materials.

SUMMARY OF THE INVENTION 
The invention discloses hard, fine-grained, non-columnar, substantially 
lamellar tungsten-carbon alloys consisting essentially of a mixture of a 
substantially pure tungsten phase and a carbide phase, wherein the carbide 
phase is W.sub.2 C or W.sub.3 C, or a mixture of W.sub.2 C+W.sub.3 C. The 
invention also discloses a chemical vapor deposition like method for 
producing the disclosed alloys. According to the method, the alloys are 
deposited thermochemically on a substrate under sub-atmospheric pressure 
to slightly atmospheric, i.e. within the range of about 1 Torr. to about 
1000 Torr., at a temperature of about 300.degree. to about 650.degree. C., 
using a mixture of process gases comprising a tungsten halide, hydrogen, 
and an oxygen- and hydrogen-containing organic compound. 
Tungsten carbon alloys containing W+W.sub.2 C, W+W.sub.3 C, or W+W.sub.2 C 
+W.sub.3 C can be formed using a wide range of process conditions. In 
addition the microstructure, composition, properties, and crystallite size 
of the new alloys can be controlled by manipulating the process parameters 
used to make the alloys. More specifically, by conjunctively controlling 
various interdependent operating parameters, especially the reaction 
temperature within the range of about 300.degree. to about 650.degree. C., 
the feed rate of tungsten halide to the oxygen- and hydrogen- containing 
organic compound to control the W/C atomic ratio within the range from 
about 0.5 to about 15.0, and the ratio of hydrogen to tungsten halide to 
more than a stoichiometric amount required from the reduction of tungsten 
halide, preferably within the range of about 4 to about 20, and more 
preferably within the range of about 5 to about 10, it is possible to 
produce a tungsten carbide alloy containing a carbide phase comprised 
either of W+W.sub.2 C or W+W.sub.3 C or a mixture of W+W.sub.2 C+W.sub.3 
C. Regardless of the composition of the carbide phase, according to the 
method of the invention, the reaction mixture contains more than a 
stoichiometric amount of H.sub.2 required for reduction of the tungsten 
halide to produce W+W.sub.2 C, W+W.sub.3 C, or W+W.sub.2 C+W.sub.3 C. 
The new tungsten carbon alloys of the present invention consist of a 
mixture of W+W.sub.2 C, W+W.sub.3 C, or W+W.sub.2 C+W.sub.3 C phases. 
These alloys are unexpectedly found to have non-columnar grains and a 
lamellar microstructure. The new alloys' hardness values can be 
manipulated by altering process conditions. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention discloses new non-columnar tungsten carbon alloys 
consisting essentially of a mixture of a substantially pure tungsten phase 
and a carbide phase wherein the carbide phase can be comprised of W.sub.2 
C, W.sub.3 C, or a mixture of W.sub.2 C+W.sub.3 C. Unlike alloys of the 
prior art that are produced by conventional vapor deposition techniques, 
the tungsten carbon alloys of the present invention are comprised of 
extremely fine equiaxial grains which average about one micron or less in 
size. In cross-section, the alloys of the present invention exhibit a well 
defined lamellar microstructure with layers less than about 2 micrometers 
thick. The alloys of the invention are essentially free of columnar grains 
and thus are more resistant to corrosion, wear and erosion than are prior 
art alloys composed of columnar grains. 
The method of the present invention is based on the surprising discovery 
that deposits consisting of a mixture of a substantially pure tungsten 
phase and a carbide phase, consisting either of W.sub.2 C or W.sub.3 C or 
a mixture of W.sub.2 C+W.sub.3 C, in a fine grain, non-columnar 
microstructure can be produced by not only controlling the temperature of 
the reaction but also by controlling the W/C atomic ratio and the ratio of 
the hydrogen to tungsten halide which takes place in the initial tungsten 
halide substitution reaction. Since the various operating parameters can 
be interdependent, the operating parameters should be conjunctively 
controlled. As used herein the term "conjunctively controlled" means that 
the operating parameters as whole are controlled; in other words, the 
affect of a change in one parameter will be used in determining the 
operating values for the remaining parameters. For example, a change in 
the reaction temperature may necessitate a change in the ratio of tungsten 
halide to the oxygen- and hydrogen-containing organic compound. 
By carefully selecting appropriate combinations of reaction temperature, 
the W/C atomic ratio and the ratio of hydrogen to tungsten halide, the 
composition of the carbide phase and the characteristics of the tungsten 
carbon alloy can be controlled. Additional refinement of the carbide phase 
can be made by producing the alloys in the presence or absence of a 
diluent or inert gas such as argon, nitrogen and helium. For example, FIG. 
10 is a graphic representation of the processing and compositional data 
from Examples 3A-H through 5A-U, as tabulated in Tables 1 and 2. Using 
that data as guidelines, if one wishes to produce a tungsten carbon alloy 
having a carbide phase consisting of W.sub.2 C and lamellar 
microstructure, this alloy can be produced at a reaction temperature 
ranging from 375.degree.-475.degree. C., using dimethyether (DME) as an 
oxygen- and hydrogen-containing organic compound with WF.sub.6 as the 
tungsten halide, a W/C atomic ratio of less than about 4, for example 
within the range of about 1 to about 3.5 and a H.sub.2 /WF.sub.6 ratio of 
about 10. 
If one wishes to produce a tungsten carbon alloy having a carbide 
consisting of W.sub.3 C and a substantially lamellar microstructure, this 
alloy can be produced at a reaction temperature ranging from 
375.degree.-475.degree. C., using DME, WF.sub.6, a W/C atomic ratio of 
about 2.5 to about 15 and a H.sub.2 /WF.sub.6 ratio of about 10. Finally, 
if one wishes to produce such an alloy having a carbide phase consisting 
of a mixture of W.sub.2 C and W.sub.3 C and a substantially lamellar 
microstructure, this alloy can be produced at the same conditions except 
that the W/C atomic ratio is in the range of about 2 to about 10. 
Using the teaching of the present invention, it will be readily apparent to 
those skilled in the art that, in these new tungsten carbon alloys, the 
composition of the carbide phase can be manipulated by changing, in a 
conjunctively controlled manner, the reaction temperature, the W/C atomic 
ratio, and the ratio of hydrogen to tungsten halide. Using the teaching of 
the present invention, such routine alteration of process parameters is 
now well within the skill of one skilled in the art, making it possible to 
utilize the broad teaching of the present invention to create custom 
tungsten carbon alloys having desired compositions and characteristics. 
Turning now to preferred process conditions for making the tungsten carbon 
alloys of the present invention, with regard to pressure within the 
reaction vessel, preferred pressure is usually sub-atmospheric, down to 1 
Torr., or up to slightly above atmospheric pressure, 1000 Torr. 
With regard to the reaction temperature, temperatures of about 300.degree. 
C. to about 650.degree. C. are preferred; temperatures in the range of 
about 400.degree. C. to about 450.degree. C. are especially preferred. 
With regard to the tungsten halide component of the reaction mixture, 
according to the method of the invention, tungsten fluorides are 
preferred. Tungsten hexafluoride (WF.sub.6) is especially preferred. 
With regard to the hydrogen gas component of the reaction mixture, it is 
essential for the deposition of the alloys to use more than a 
stoichiometric amount of hydrogen required for complete conversion of the 
tungsten fluoride (e.g., WF.sub.6) to hydrogen fluoride (HF). 
With regard to the oxygen- and hydrogen-containing organic compound, 
preferred compounds are selected from group consisting of C.sub.1 -C.sub.4 
alcohols and aldehydes, C.sub.2 -C.sub.4 ethers, epoxides and ketenes and 
C.sub.3 -C.sub.4 ketones, For example, methanol, formaldehyde, ethanol, 
dimethyl ether, ketene (carbomethane), acetaldehyde, ethylene oxide, vinyl 
alcohol, acetone, acrolein, allyl alcohol, methyl ethyl ether, isopropyl 
alcohol, n-propyl alcohol, propylene oxide, propene oxide, 
propiolaldehyde, propionaldehyde, 2-propyne-1-ol, 3-methoxy propyne, vinyl 
ether, diethyl ether, furan, tetrahydrofuran, crotonaldehyde, and 
.alpha.-methyl acrolein. Especially preferred is the two carbon and one 
oxygen-containing organic compound, dimethyl ether (DME). 
Due to the interdependency of the various operating parameters it is to be 
expected that the operating range of the tungsten halide to oxygen-and 
hydrogen- containing organic compound ratio or W/C atomic ratio may change 
depending on the number of carbon atoms in the oxygen- and 
hydrogen-containing organic compound. For example, use of a compound such 
as methanol, with one carbon atom, would be expected to reduce the 
operating range of the tungsten halide to methanol ratio. On the other 
hand, use of a compound such as diethyl ether, which has four carbons, 
would be expected to increase the operating range of the tungsten halide 
to diethyl ether ratio. 
The tungsten/carbon alloys of the present invention can be deposited on a 
number of ferrous metals and alloys such as cast iron, carbon steels, 
stainless steels and high speed steels, non-ferrous metals and alloys such 
as copper, nickel, platinum, rhodium, titanium, aluminum, silver, gold, 
niobium, molybdenum, cobalt, tungsten, rhenium, copper alloys, nickel 
alloys such as inconel and monel, titanium alloys such as Ti/Al/V, 
Ti/Al/Sn, Ti/Al/Mo/V, Ti/Al/Sn/Zn/Mo, Ti/Al/V/Cr, Ti/Mo/V/Fe/Al, 
Ti/Al/V/Cr/Mo/Zr and Ti/Al/V/Sn alloys, non-metals such as graphite, 
carbides such as cemented carbide, and ceramics such as silicon carbide, 
silicon nitride, alumina, etc. In depositing tungsten carbon alloys of the 
present invention on reactive substrate materials, such as cast irons, 
carbon steels, stainless steels, high speed steels, titanium and titanium 
alloys, aluminum and aluminum alloys, and nickel alloys, it is preferred 
to coat the substrate first with a more noble material such as nickel, 
cobalt, copper, silver, gold, platinum, palladium or irridium, by 
electrochemical or electroless techniques or by physical vapor deposition 
such as sputtering. However, no deposition of noble material is required 
for coating non-reactive materials such as copper, nickel, cobalt, silver, 
gold, platinum, rhodium, niobium, molybdenum, tungsten, rhenium, graphite, 
carbides and ceramics. Free standing parts of tungsten/carbon alloys of 
the present invention can be made by depositing the alloy on substrates 
such as copper, nickel, cobalt, silver, gold, molybdenum, rhenium, and 
graphite and then removing these substrates by grinding and chemical or 
electrochemical etching. 
The deposits of the present invention are comprised of mixtures of 
W+W.sub.2 C, W+W.sub.3 C, and W+W.sub.2 C+W.sub.3 C. The deposits are 
characterized by a non-columnar crystal or grain structure consisting 
essentially of homogeneous fine and equiaxial grains having an average 
crystallite size of less than about 0.1 microns. This is in contrast to 
the typical columnar crystal habit of conventional chemical vapor 
deposition. Deposits made by the method of the present invention are 
essentially lamellar and have been found to have unusually high wear and 
erosion resistance and unexpected hardness. 
The Examples which follow illustrate the wide range of operating parameters 
which can be used to create "customized" alloys having desired 
compositions and characteristics. As a control, Examples 1 and 2 
illustrate production of prior art tungsten consisting of columnar grains. 
The non-columnar grain containing alloys of the present invention are 
illustrated in Examples 3-5. More specifically, Examples 3A-I illustrate 
production of tungsten carbon alloys having a carbide phase consisting of 
W.sub.3 C, i.e., a tungsten carbon alloy consisting of W+W.sub.3 C. 
Examples 4A-N illustrate production of tungsten carbon alloys having a 
carbide phase consisting of W.sub.2 C+W.sub.3 C, i.e., a tungsten carbon 
alloy consisting of W+W.sub.2 C+W.sub.3 C. Examples 5A-Z illustrate 
production of alloys having a carbide phase consisting of W.sub.2 C, i.e., 
a tungsten carbon alloy consisting of W+W.sub.2 C. The data in Examples 5Q 
to 5X also illustrate that a diluent such as argon can be used during the 
coating reaction to affect coating hardness without concomitantly 
affecting coating composition or crystallite size. The date in Examples 
3I, 4L to 4N, and 5X to 5Z illustrate the effect of using different 
hydrogen to WF.sub.6 ratio on coating composition. Example 6 illustrates 
that tungsten/carbon alloys can be deposited on cemented carbide without a 
protective layer of noble material. Examples 7 and 8 illustrate that 
tungsten/carbon alloys can be deposited on aluminum and titanium alloys 
with protective layer of noble materials. Example 9 illustrates the 
ceramic materials such as alumina can be deposited with tungsten/carbon 
alloys without a protective layer of noble materials. Examples 10 and 11 
show that tungsten/carbon alloys can be deposited on molybdenum. Example 
12 shows that a tungsten followed by tungsten/carbon alloy coatings can be 
deposited on various metals and alloys. Example 13 illustrates the erosion 
performance of some of the alloys of the present invention. Examples 14 
and 15 illustrate the wear performance of tungsten/carbon alloy (W+W.sub.2 
C) of the present invention. Finally, Examples 16 to 20 illustrate that 
several different oxygen-and-hydrogen containing organic compounds can be 
used to produce tungsten/carbon alloys. 
Using the preferred tungsten halide, tungsten hexafluoride (WF.sub.6), and 
the preferred oxygen- and hydrogen-containing organic compound, dimethyl 
ether (DME), the Examples also illustrate the best mode of making and 
using the present invention. The examples are for illustrative purposes 
only and are not meant to limit the scope of the claims in any way. 
EXAMPLES FOR TUNGSTEN COATING 
Example 1 
Two 0.095 inch .times.1 inch .times.2 inch SIC-6 graphite and three AM-350 
stainless steel specimens were placed in an inductively heated graphite 
furnace inside a gas-tight quartz envelope. Stainless steel specimens were 
electroplated with 3-5 .mu.m thick nickel before coating operation to 
protect them from the attack of corrosive HF gas. The specimens were 
heated to 443.degree. C. and a gaseous mixture of 300 cc/min of WF.sub.6 
and 3,000 cc/min of hydrogen was passed into the furnace over the 
specimens. The total pressure within the system was maintained at 40 Torr. 
The deposition was conducted for 40 minutes; thereafter, the flow of the 
reactive gases was stopped and the specimens were cooled. 
The specimens were found to be coated with a dull, adherent, coherent, and 
non-uniform coating of 12 to 50 micrometers thick tungsten on each side 
(see Tables 1 and 2). The coating consisted of columnar grains as shown in 
FIG. 1. The coating had a very rough surface finish as shown in FIG. 2. 
The average surface finish of uncoated AM-350 stainless steel was 16 
micro-inch; whereas, the average surface finish of the coated specimen was 
36 micro-inch. This indicated that the coating degraded the surface finish 
of the specimen. The coating had a hardness of 510 and 465 Vickers on 
graphite and stainless steel specimens, respectively. 
Example 2 
A number of AM-350 and SS-422 stainless steel and IN-718 specimens (0.095 
inch .times.1 inch .times.2 inch) electroplated with 3-4 .mu.m thick layer 
of either nickel or copper using electrolytic technique were placed in the 
furnace similar to that described in Example 1. The specimens were heated 
to 443.degree. C. and a gaseous mixture of 300 cc/min of WF.sub.6, 3,000 
cc/min of hydrogen, and 4,000 cc/min of argon was passed into the furnace 
over the specimens. The total pressure within the system was the same as 
in Example 1. The deposition, however, was conducted only for 15 minutes; 
thereafter, the flow of the reactive gases was stopped and the specimens 
were cooled. 
All the specimens were coated with a dull, adherent, coherent, and uniform 
coating of 10-12 .mu.m thick tungsten on each side. The coating consisted 
of columnar grains and had rough surface finish. The average surface 
finish of the uncoated AM-350 stainless steel was 16 micro-inch; whereas, 
the average surface finish of the coated specimen was 18 micro-inch. This 
indicated that the degradation of surface finish by tungsten coating could 
be controlled by carefully selecting the process conditions. The hardness 
of tungsten coating varied between 455 to 564 Vickers, as shown in Table 
1. 
This Example shows that both nickel and copper interlayers can be used to 
protect the reactive substrate from the attack of hot HF gas. 
EXAMPLES FOR TUNGSTEN CARBON ALLOY (W+W.sub.3 C) COATING 
Example 3A 
In this Example, several specimens of SIC-6 graphite and nickel plated 
AM-350 stainless steel were coated simultaneously in a single run. All the 
specimens were 0.093 inches thick, 1 inch wide, and 2 inches long. The 
specimens were heated to a temperature of about 440.degree. C. and a 
gaseous mixture of 300 cc/min WF.sub.6, 3,000 cc/min of hydrogen and 40 
cc/min of DME was passed into the furnace over the specimens. A WF.sub.6 
/DME ratio of 7.5 or W/C atomic ratio of 3.75 and a H.sub.2 /WF.sub.6 
ratio of 10.0 were maintained throughout the run. The total pressure was 
maintained at 40 Torr. to provide a DME partial pressure of 0.48 Torr., as 
shown in Table 1. The deposition was conducted for 40 minutes. 
The graphite and stainless steel specimens were coated with a bright, 
smooth, adherent, coherent, and uniform coating. The coating thickness on 
stainless steel specimens was .about.22 micrometer. The coating on both 
graphite and stainless steel specimens was free of columnar grains as 
shown in FIG. 3. The dark areas in the etched cross-section of the coating 
showed areas rich in W.sub.3 C, indicating non-uniform distribution of W 
and W.sub.3 C in the coating. The coating had a smooth surface finish as 
shown in FIG. 4. The average surface finish of the uncoated AM-350 
stainless steel was 16 micro-inch, whereas, the average surface finish of 
the coated specimen was 7 micro-inch. This indicated that the coating 
improved the surface finish of the specimen. The composition of the 
coating was determined by X-ray diffraction. It consisted of a mixture of 
W and W.sub.3 C phases (see Table 2). 
Example 3B 
The CVD run described in Example 3A was repeated with the exceptions of 
using 30 minutes reaction time instead of 40 minutes and 442.degree. C. 
reaction temperature instead of 440.degree. C. Once again graphite and 
stainless steel specimens were coated with a bright, smooth, adherent, 
coherent, and uniform coating. The coating thickness on stainless steel 
and graphite specimens was 15 and 13 micrometers, respectively. The 
coating on graphite and stainless steel specimens was free of columnar 
grains as shown in FIG. 5. The etched cross-section of the coating showed 
some dark areas enriched with W.sub.3 C, indicating that the distribution 
of W and W.sub.3 C in this coating was considerably better than obtained 
in Example 3A. The coating was found to contain a mixture of W and W.sub.3 
C phases by X-ray diffraction (Table 2). 
Example 3C 
The CVD run described in Example 3A was repeated once again with the 
exceptions of using 35 minutes reaction time and 447.degree. C. reaction 
temperature. All the specimens were coated with a bright, smooth, 
adherent, coherent and uniform coating. The coating thickness on graphite 
specimens was 16 micrometers. The coating was, once again, free of 
columnar grains. X-ray diffraction analysis revealed the presence of W and 
W.sub.3 C phases in the coating. The crystallite size of W and W.sub.3 C 
phases determined by X-ray diffraction technique was 102 and 92 .ANG., 
respectively, indicating the fine-grain structure of W+W.sub.3 C coating. 
Example 3D to 3F 
Three different CVD runs were carried out using several AM-350 stainless 
steel and IN-718 specimens. All the specimens were plated with 3-5 .mu.m 
thick nickel using electrolytic technique. The specimens were heated to 
443.degree. C. and a gaseous mixture of 300 cc/min WF.sub.6 and 3,000 
cc/min of hydrogen and passed into the furnace over the specimens. 
Additionally, 300 cc/min of inert argon were passed over the specimens. 
The flow rate of DME was varied from 30 to 50 cc/min in these runs to 
change the WF.sub.6 /DME ratio from 10.0 to 6.0. The W/C atomic ratio 
varied from 5 to 3 in these runs. A total pressure of 40 Torr. was 
maintained to vary DME partial pressure from 0.33 to 0.55 Torr. (see Table 
1). A constant deposition time of 30 minutes and a constant H.sub.2 
/WF.sub.6 ratio of 10.0 were used in these runs. 
All the specimens used in these runs were coated with a bright, smooth, 
adherent, coherent, and uniform coating. The coating thickness on 
stainless steel specimens varied between 10 and 12 .mu.m. The coating 
obtained in all the three runs was free of columnar grains. It had a 
smooth surface finish. The hardness of the coating varied between 2361 and 
2470 Vickers. X-ray diffraction analysis indicated that coating consisted 
of a mixture of W and W.sub.3 C phases (see Table 2). The crystallite size 
of W phase was approximately 140 .ANG. and it was unchanged with 
increasing flow rate of DME or decreasing WF.sub.6 /DME ratio or 
decreasing W/C atomic ratio or increasing DME partial pressure. However, 
the crystallite size of W.sub.3 C unexpectedly increased from 92 to 119 
.ANG. by increasing DME partial pressure from 0.33 to 0.55 or decreasing 
WF.sub.6 /DME ratio from 10 to 6 or decreasing W/C atomic ratio from 5 to 
3. 
Comparing Examples 3B and 3E, it can be seen that the addition of inert 
argon reduces DME partial pressure without changing coating composition. 
This observation indicates that the ratio of WF.sub.6 /DME or W/C atomic 
ratio is very critical for controlling coating composition. 
Example 3G 
To determine the effect of coating temperature, another CVD run was 
conducted using reaction conditions and specimens identical to those used 
in Example 3F. A lower temperature (431.degree. C.) was used for coating. 
All the specimens were coated with smooth, bright, adherent, coherent and 
uniform coating. Coating thickness on AM-350 specimens was 8 .mu.m. It had 
non-columnar grains and consisted of a mixture of W and W.sub.3 C phases. 
The crystallite size of W and W.sub.3 C phases was found to be similar to 
that observed in Example 3F (see Table 2). 
This Example shows that W+W.sub.3 C coating can be deposited at lower 
temperature. 
Example 3H 
In this Example, a SIC-6 graphite specimen was coated in a CVD run. The 
specimen was heated to a much lower temperature 371.degree. C. and a 
gaseous mixture of 350 cc/min of WF.sub.6, 3,500 cc/min of hydrogen and 65 
cc/min of DME was passed into the furnace over the specimen. A total 
pressure of 40 Torr. was used to provide a DME partial pressure of 0.66 
Torr. The ratio of WF.sub.6 /DME and H.sub.2 /WF.sub.6 used in this 
Example were 5.38 and 10.0, respectively. Additionally, the W/C atomic 
ratio used in this Example was 2.69. 
The graphite specimen was coated with a bright, smooth, adherent, coherent, 
and uniform coating. Coating thickness was approximately 6 .mu.m. It was 
free of columnar grains and consisted of a mixture of W and W.sub.3 C 
phases. 
This Example clearly shows that a mixture of W and W.sub.3 C coating can be 
deposited at extremely low temperature (.about.370.degree. C.). 
Additionally, it shows that high DME partial pressure or low WF.sub.6 /DME 
ratio or low W/C atomic ratio can be used at low temperature to yield 
W+W.sub.3 C coating. 
Example 3I 
In this Example, several specimens of AM-350 stainless steel and graphite 
were coated in a run. The stainless steel specimens were nickel plated 
prior to coating using electrolytic technique. The specimens were heated 
to a temperature of about 445.degree. C. and a gaseous mixture of 30 
cc/min WF.sub.6, 3,300 cc/min of hydrogen and 60 cc/min of DME was passed 
into the furnace over the specimens. A total pressure of 40 Torr. was 
maintained in the run to give 0.66 Torr. partial pressure of DME. A 
WF.sub.6 /DME ratio of 5.0, a W/C atomic ratio of 2.5 and a H.sub.2 
/WF.sub.6 ratio of 11.0 were used during the run. The deposition was 
conducted for 40 minutes (see Table 1). 
All the specimens were coated with a bright, smooth, adherent, coherent, 
and uniform coating. The coating thickness on AM-350 stainless steel 
specimens were .about.14 .mu.m. The coating was free of columnar grains 
and consisted of a mixture of W and W.sub.3 C phases. 
This Example clearly shows that a mixture of W and W.sub.3 C coating can be 
deposited using high H.sub.2 /WF.sub.6 ratio (.about.11.0). Additionally, 
it shows that high DME partial pressure or low WF.sub.6 /DME ratio or low 
W/C atomic ratio can be used to yield W+W.sub.3 C coating. 
EXAMPLES FOR TUNGSTEN CARBON ALLOY (W+W.sub.2 C+W.sub.3 C) COATING 
Example 4A 
In this Example, several specimens of AM-350 and SS-422 stainless steel and 
IN-718 were coated simultaneously in a run. All the specimens were nickel 
plated prior to coating using electrolytic technique. The specimens were 
heated to a temperature of about 445.degree. C. and a gaseous mixture of 
300 cc/min WF.sub.6, 3,000 cc/min. of hydrogen and 55 cc/min. of DME was 
passed into the furnace over the specimens. A total pressure of 40 Torr. 
was maintained in the run to give 0.66 Torr. partial pressure of DME. A 
WF.sub.6 /DME ratio of 5.45, a W/C atomic ratio of 2.72 and a H.sub.2 
/WF.sub.6 ratio of 10.0 were also maintained during the run. The 
deposition was conducted for 20 minutes (see Table 1). 
All the specimens were coated with a bright, smooth, adherent, coherent, 
and uniform coating. The coating thickness on AM-350 stainless steel 
specimens was .about.8 .mu.m. The coating was free of columnar grains and 
consisted of coarse layered structure (see FIG. 6). The etched 
cross-section of the coating showed uniform distribution of W, W.sub.2 C 
and W.sub.3 C. The distribution of W, W.sub.2 C and W.sub.3 C was 
considerably better than the distribution of W and W.sub.3 C in the 
coatings described in Examples 3A and 3B. Furthermore, the coating had a 
smooth surface finish as shown in FIG. 7. The average surface finish of 
uncoated specimen was 16 micro-inch; whereas, the average surface finish 
of coated specimen was 5 micro-inch. This, therefore, indicated that the 
coating significantly improved the surface finish. The composition of the 
coating determined by X-ray diffraction revealed presence of a mixture of 
three phases, namely W, W.sub.2 C and W.sub.3 C (see Table 2). 
Comparing this Example to Examples 3A to 3H, it can be seen that the use of 
lower WF.sub.6 /DME ratio or lower W/C atomic ratio or higher DME partial 
pressure unexpectedly results in the formation of W+W.sub.2 C+W.sub.3 C 
coating rather than W+W.sub.3 C coating. Besides difference in coating 
composition, the microstructure of W+W.sub.2 C+W.sub.3 C coating shown in 
FIG. 6 is dramatically different from the W+W.sub.3 C coating shown in 
FIG. 3. The hardness of W+W.sub.2 C+W.sub.3 C coating, however, is very 
similar to that of W+W.sub.3 C coating. 
Comparing this Example to Example 3H, it can be seen that reaction 
temperature is very important for controlling coating composition and 
microstructure. Example 3H resulted in the formation of W+W.sub.3 C 
coating despite the use of lower WF.sub.6 /DME ratio or lower W/C atomic 
ratio or higher DME partial pressure. 
Example 4B 
The CVD run described in Example 4A was repeated using a number of AM-350 
specimens. The reaction conditions used were the same with the exceptions 
of using 443.degree. C. reaction temperature, 15 minutes reaction time and 
300 cc/min of argon gas. The addition of argon gas did not alter the 
WF.sub.6 /DME, W/C atomic and H.sub.2 /WF.sub.6 ratios, but reduced the 
DME partial pressure to 0.60 Torr. All the specimens were coated with a 
bright, smooth, adherent, coherent, and uniform coating. The coating 
thickness was 5 .mu.m. The coating was free of columnar grains and had 
coarse layered structure. X-ray diffraction analysis of the coating 
indicated the presence of W, W.sub.3 C and trace amounts of W.sub.2 C 
phases. 
This Example, demonstrates the importance of WF.sub.6 /DME ratio or W/C 
atomic ratio and temperature for controlling coating composition. A small 
drop in temperature in this Example compared to Example 4A causes a 
dramatic reduction in the amount of W.sub.2 C in the coating. A small 
decrease in DME partial pressure while maintaining WF.sub.6 /DME ratio or 
W/C atomic ratio, however, does not cause a change in overall coating 
composition. 
Example 4C 
In this Example several AM-350, SS-422 and IN-718 specimens similar to 
those used in Example 4A were coated using the reaction conditions very 
similar to those used in Example 4B with the exceptions of using slightly 
higher DME flow rate and reaction time. The DME flow rate used was 60 
cc/min causing WF.sub.6 /DME ratio to decrease to 5.0, W/C atomic ratio to 
decrease to 2.50 and DME partial pressure increase to 0.66 Torr. A H.sub.2 
/WF.sub.6 ratio used during coating was 10.0 . All the specimens were 
coated with a bright, smooth, adherent, coherent, and uniform coating. The 
coating was free of columnar grains and had coarse layered structure. The 
coating thickness was 12 .mu.m. It had a hardness of over 2,000 Vickers. 
X-ray diffraction analysis of the coating revealed the presence of W, 
W.sub.3 C and a trace amount of W.sub.2 C. This Example, therefore, 
indicated that a decrease in WF.sub.6 /DME ratio from 5.45 to 5.0 or W/C 
atomic ratio from 2.72 to 2.50 and increase in DME partial pressure from 
0.60 to 0.66 were not effective in changing coating composition. The 
crystallite size of W and W.sub.3 C determined by X-ray diffraction was 80 
and 52 .ANG., respectively, indicating fine-grained microstructure of the 
coating. The crystallite sizes of W+W.sub.2 C+W.sub.3 C coating was 
somewhat smaller than that of W+W.sub.3 C coating (compare Examples 3H and 
Example 4C). 
Comparing this Example to Example 3I, it can be seen that H.sub.2 /WF.sub.6 
ratio is very important for controlling coating composition and 
microstructure. Example 3I resulted in the formation of W+W.sub.3 C 
coating despite the use of similar WF.sub.6 /DME ratio, W/C atomic ratio 
and DME partial pressure. 
Example 4D 
The CVD run described in Example 4C was repeated using similar specimens 
and reaction conditions with the exception of using lower reaction time 
(20 min.) and slightly higher DME flow rate (62 cc/min.). Use of 62 
cc/min. DME flow rate reduced WF.sub.6 /DME ratio to 4.84, reduced W/C 
atomic ratio to 2.41 and increased DME partial pressure to 0.68 Torr. It, 
however, did not result in any change in H.sub.2 /WF.sub.6 ratio. Once 
again, all the specimens were coated with a bright, smooth, adherent, 
coherent and uniform coating. The coating thickness was 5 .mu.m. It was 
free of columnar grains and had coarse layered structure. X-ray 
diffraction analysis revealed presence of W, W.sub.2 C and W.sub.3 C 
phases in the coating. The crystallite size of W and W.sub.2 C phases in 
the coating are summarized in Table 2. 
This Example shows that at certain DME partial pressure or WF.sub.6 /DME 
ratio or W/C atomic ratio, a small increase in DME partial pressure or 
decrease in WF.sub.6 /DME ratio or W/C atomic ratio causes a major change 
in coating composition. A small increase in DME partial pressure causes 
the amount of W.sub.2 C in the coating to increase from trace amount to 
minor component. 
Example 4E 
The CVD run described in Example 4A was repeated using same type of 
specimens and similar reaction conditions with the exception of using 
higher reaction temperature (451.degree. C. as opposed to 445.degree. C.). 
All the specimens were coated with a bright, smooth, adherent, coherent 
and uniform coating. The coating thickness on AM-350 specimens was 13 
.mu.m. It was free of columnar grains and had coarse layered 
microstructure. The coating consisted of W, W.sub.2 C and W.sub.3 C 
phases, indicating no major change in coating composition by increasing 
reaction temperature from 445.degree. to 451.degree. C. 
Example 4F 
Several AM-350 stainless steel and SIC-6 graphite specimens were placed in 
the reactor described earlier. AM-350 stainless steel specimens were 
electroplated with 4-5 .mu.m thick nickel prior to coating operation. The 
reactor was heated to 462.degree. C. and a flow of 300 cc/min of WF.sub.6, 
3,000 cc/min of hydrogen and 60 cc/min of DME was established through the 
reactor for 35 minutes. A total pressure of 40 Torr. was maintained during 
the reaction. These flow ratio and pressure resulted in a WF.sub.6 /DME 
ratio of 5.0, a W/C atomic ratio of 2.50, a H.sub.2 /WF.sub.6 ratio of 
10.0, and DME partial pressure of 0.71 Torr. All the specimens were coated 
with a bright, shiny, smooth, adherent and coherent coating. The coating 
thickness on AM-350 specimens was 15 .mu.m. It was free of columnar grains 
and consisted of fine layered structure. X-ray diffraction analysis 
revealed that the coating consisted of a mixture of W, W.sub.2 C, and 
W.sub.3 C phases, as shown in Table 2. The crystallite size of the coating 
varied from 73 to 164 .ANG., as shown in Table 2. 
This Example, therefore, demonstrates that a mixture of W, W.sub.2 C, and 
W.sub.3 C coating can be formed by using WF.sub.6 /DMF ratio of 5.0 or W/C 
atomic ratio of 2.50, H.sub.2 /WF.sub.6 ratio of 10.0, DME partial 
pressure of 0.71 Torr., and a temperature of 462.degree. C. It also 
demonstrates that coating microstructure changes to fine layered structure 
by increasing the reaction temperature. 
Example 4G 
An experiment similar to that described in Example 4F was carried out 
again. This time only SIC-6 graphite specimens were used. The flow rate of 
DME was increased from 60 to 70 cc/min to provide a WF.sub.6 /DME ratio of 
4.29 or W/C atomic ratio of 2.14 and a DME partial pressure of 0.83 Torr. 
A H.sub.2 /WF.sub.6 ratio of 10.0 was maintained during the run. A 
reaction time of 40 min. was used. Other conditions were kept the same. 
Once again, all the specimens were coated with a bright, smooth, adherent 
and coherent coating of 13 .mu.m thickness. The coating was free of 
columnar grains, and consisted of fine layered structure. X-ray 
diffraction analysis of the coating revealed presence of W, W.sub.2 C and 
trace amount of W.sub.3 C phases (see Table 2). The crystallite size of 
the coating varied from 120 to 150 .ANG., as shown in Table 2. 
This Example clearly shows that a coating consisting of a mixture of W, 
W.sub.2 C and W.sub.3 C can be formed by using 462.degree. C. temperature, 
4.29 WF.sub.6 /DME ratio or W/C atomic ratio of 2.14, 10.0 H.sub.2 /WF6 
ratio and 0.83 Torr. DME partial pressure. It also indicates that 
increasing DME partial pressure or decreasing WF.sub.6 /DME ratio or W/C 
atomic ratio is responsible for reducing the amount of W.sub.3 C in the 
coating. 
Example 4H 
A CVD experiment using SIC-6 graphite specimens was carried out in a 
reactor similar to that described earlier. This time flow rate of 300 
cc/min. of WF.sub.6, 3,000 cc/min. of hydrogen and a very low flow 40 
cc/min. of DME was used. A reaction time of 40 min. and a total pressure 
of 40 Torr. were used for the coating experiment. These flow rates and 
pressure provided WF.sub.6 /DME ratio of 7.5 W/C atomic ratio of 3.75, 
H.sub.2 /WF.sub.6 ratio of 10.0 and DME partial pressure of 0.48 Torr. A 
reaction temperature of 467.degree. C. was used. All the specimens were 
coated with a bright, smooth, adherent and coherent coating of .about.22 
.mu.m thickness. The coating was free of columnar grains and consisted of 
coarse layered structure. X-ray diffraction analysis revealed that the 
coating consisted of a mixture of W, W.sub.3 C and trace amount of W.sub.2 
C phases. 
Comparing Examples 3A, 3B and 3C to Example 4H, it can be seen that 
increasing reaction temperature from .about.447.degree. C. to 467.degree. 
C. results in an unexpected change in coating composition. This Example, 
therefore, shows the importance of reaction temperature in controlling 
coating composition. 
Example 4I 
CVD experiment described in Example 4H was repeated with 35 cc/min. of DME 
rather than 40 cc/min. Other conditions were kept constant. The reduction 
in DME flow rate caused WF.sub.6 /DME ratio to increase to 8.57, W/C 
atomic ratio increase to 4.23 and DME partial pressure to drop to 0.42 
Torr. A H.sub.2 /WF.sub.6 ratio of 10.0, however, was maintained during 
the run. Once again, all the specimens were coated with a bright, smooth, 
adherent and coherent coating of .about.21 .mu.m thickness. The coating 
was free of columnar grains and consisted of coarse layered structure. 
X-ray diffraction analysis revealed that the coating consisted of a 
mixture of W, W.sub.3 C and trace amount of W.sub.2 C phases. This Example 
showed that a mixture of W, W.sub.2 C and W.sub.3 C can be formed at 
467.degree. C., 8.57 WF.sub.6 /DME ratio, W/C atomic ratio of 4.23, 10.0 
H.sub.2 /WF.sub.6 ratio and 0.42 Torr. DME partial pressure. 
Example 4J 
CVD experiment described in Example 4I was repeated with using 50 Torr. 
total pressure and 474.degree. C. reaction temperature. The change in 
total pressure caused DME partial pressure to increase from 0.42 to 0.52, 
but it did not affect the WF.sub.6 /DME, W/C atomic and H.sub.2 /WF.sub.6 
ratios. All the specimens were coated with a bright, smooth, adherent, and 
coherent coating of .about.22 .mu.m thickness. The coating was free of 
columnar grains, and consisted of coarse layered structure. X-ray 
diffraction analysis revealed that the coating consisted of a mixture of 
W, W.sub.2 C and W.sub.3 C phases.a 
This Example shows that increasing both temperature and DME partial 
pressure cause the amount of W.sub.2 C in the coating to increase (compare 
Examples 4I and 4J). This finding is unexpected. 
Example 4K 
CVD experiment described in Example 4J was repeated with using 100 Torr. 
total pressure, 24 cc/min. DME, 400 cc/min. WF.sub.6 and 4,000 cc/min. 
hydrogen flow rates, 477.degree. C. reaction temperature, and 15 min. 
reaction time. These flow rates and pressure caused WF.sub.6 /DME ratio, 
W/C atomic ratio and DME partial pressure to increase to 16.7, 8.35 and 
0.54 Torr., respectively. A constant H.sub.2 /WF.sub.6 ratio of 10.0, 
however, was used during the run. All the specimens were coated with a 
bright, smooth, adherent, and coherent coating of 20 .mu.m thickness. The 
coating was free of columnar grains, and consisted of coarse layered 
structure. X-ray diffraction analysis revealed that the coating consisted 
of a mixture of W, W.sub.3 C and a trace amount of W.sub.2 C phases. 
This Example, therefore, indicates that a mixture of W, W.sub.2 C and 
W.sub.3 C can be formed by using 477.degree. C. temperature, 16.7 WF.sub.6 
/DME ratio, 8.35 W/C atomic ratio, 10.0 H.sub.2 /WF.sub.6 ratio and 0.54 
Torr. DME partial pressure. 
Example 4L 
In this Example, several AM-350 and IN-718 specimens similar to those used 
in Example 4A were coated. The specimens were heated to a temperature of 
about 445.degree. C. and a gaseous mixture of 220 cc/min. WF.sub.6, 2,400 
cc/min. of hydrogen, 3,000 cc/min. of argon and 60 cc/min. of DME was 
passed into the furnace over the specimens. A total pressure of 40 Torr. 
was maintained in the run to give 0.42 Torr. partial pressure of DME. A 
WF.sub.6 /DME ratio of 3.33, W/C atomic ratio of 1.67, and a H.sub.2 
/WF.sub.6 ratio of 12.0 were also maintained during the run. The 
deposition was conducted for 90 minutes (see Table 1). 
All the specimens were coated with a bright, smooth, adherent, coherent, 
and uniform coating. The coating thickness was AM-350 stainless steel 
specimens was .about.13.mu.. The coating was fine of columnar grains and 
consisted of course layered structure. X-ray diffraction analysis of the 
coating indicated the presence of W, W.sub.2 C and W.sub.3 C phases (see 
Table 2). 
This example, therefore, indicates that a mixture of W, W.sub.2 C and 
W.sub.3 C can be formed using 445.degree. C. temperature, 3.33 WF.sub.6 
/DME ratio, 1.67 W/C atomic ratio, 12.0 H.sub.2 /WF.sub.6 ratio, and 0.42 
Torr. DME partial pressure. It also indicates that a low WF.sub.6 /DME 
ratio or W/C atomic ratio can be used to produce W+W.sub.2 C coating 
provided a H.sub.2 /WF.sub.6 ratio of 12.0 is used. This example also 
indicates the importance of H.sub.2 /WF.sub.6 ratio for controlling 
coating composition. 
Examples 4M and 4N 
In these examples, several AM-350 and IN-718 specimens similar to those 
used in Example 4A were coated. The specimens were heated to a temperature 
of about 445.degree. C. and a gaseous mixture of 200 cc/min WF.sub.6, 
2,400 cc/min of hydrogen, 6,000 cc/min argon and 60 cc/min of DME was 
passed into the furnace over the specimens in both runs. A total pressure 
of 40 Torr. was maintained in the run to give 0.28 Torr. partial pressure 
of DME. A WF.sub.6 /DME ratio of 3.33, W/C atomic ratio of 1.67 and a 
H.sub.2 /WF.sub.6 ratio of 12.0 were also maintained during the two runs. 
The deposition was conducted for 90 and 80 minutes, respectively (see 
Table 1) 
All the specimens were coated with a right, smooth, adherent, coherent, and 
uniform coating. The coating thickness on AM-350 stainless steel was 
.about.12.mu.. the coating was free of columnar grains and consisted of 
coarse layered structure. X-ray diffraction analysis of the coating 
indicated the presence of W, W.sub.2 C and W.sub.3 C phases (see Table 2) 
These examples show that a mixture of W, W.sub.2 C and W.sub.3 C can be 
formed using extremely low DME partial pressure provided WF.sub.6 /DME 
ratio or W/C atomic ratio is maintained below certain level. 
Comparing examples L and M it is clearly evident that the addition of 
diluent argon simply lowers the partial pressure of DME. It does not 
effect WF.sub.6 /DME, W/C atomic and H.sub.2 /WF.sub.6 ratios. Therefore, 
it does not cause any changes in coating composition. 
EXAMPLES FOR TUNGSTEN-CARBON ALLOY (W+W.sub.2 C) COATING 
Example 5A 
Five 0.095 inch.times.1 inch.times.2 inch SIC-6 graphite specimens were 
placed in an inductively heated graphite furnace inside a gas-tight quartz 
envelope. The specimens were heated to a temperature of 477.degree. C. and 
a gaseous mixture of 400 cc/min of WF.sub.6, 4000 cc/min of hydrogen, and 
65 cc/min of DME was passed into the furnace over the specimens. The total 
pressure within the system was maintained at 100 Torr. to provide a DME 
partial pressure of 1.46 Torr. The ratios of WF.sub.6 /DME, W/C atomic and 
H.sub.2 /WF.sub.6 used were 6.15, 3.08 and 10.0, respectively. The 
deposition was conducted for 15 minutes; thereafter, the flow of the 
reactive gases was stopped and the specimens were cooled. 
The specimens were found to be coated with a bright, smooth, adherent, 
coherent, and uniform coating of 25 micrometers thick on each side (see 
Table 1). The coating was free of columnar grains. It consisted of 
extremely fine grains. Additionally, it had a well defined layered 
microstructure with layers 1-2 .mu.m thick. The coating had a hardness of 
2512 Vickers. The composition of the coating was determined by X-ray 
diffraction. It was comprised of a mixture of W and W.sub.2 C phases, as 
shown in Table 2. 
Comparing this Example to Example 4K, it can be seen that increasing DME 
partial pressure and decreasing WF.sub.6 /DME ratio or W/C atomic ratio 
simultaneously causes a unexpected change in coating composition. 
Additionally, it results in higher coating hardness. 
Example 5B 
Several AM-350 and SiC-6 graphite specimens were coated in a reactor 
similar to that described in Example 5A. A reaction temperature of 
463.degree. C., total pressure of 40 Torr. and flow rate of 300 cc/min 
WF.sub.6, 3,000 cc/min hydrogen and 85 cc/min of DME were used for the 
reaction. Reaction time used was 50 min. These conditions provided 
WF.sub.6 /DME ratio, W/C atomic ratio and DME partial pressure of 3.53 
1.77 and 1.00 Torr., respectively. These conditions also provided H.sub.2 
/WF.sub.6 ratio of 10.0. All the specimens were coated with a bright, 
smooth, adherent, coherent, and uniform coating of 25 .mu.m thick (AM-350) 
on each side (see Table 1). The coating was free of columnar grains. 
Additionally, it had a well defined fine layered microstructure with 
layers less than 1 .mu.m apart. The coating had a hardness of 2758 
Vickers. The coating was found to contain a mixture of W and W.sub.2 C 
phases. The crystallite size of the coating was less than 50 .ANG.. 
This Example, therefore, shows that a mixture of W and W.sub.2 C can be 
formed by using 463.degree. C. temperature, 3.53 WF.sub.6 /DME ratio, 1.77 
W/C atomic ratio, 10.0 H.sub.2 /WF.sub.6 ratio and 1.00 Torr. DME partial 
pressure. Additionally, it indicates that the crystallite size of the 
coating is considerably smaller than that noted in Examples 3 and 4. 
Furthermore, it indicates that the hardness of the coating is considerably 
higher than that noted in Examples 3 and 4. 
Example 5C 
CVD experiment described in Example 5B was repeated with the exception of 
using 443.degree. C. temperature and 35 minutes reaction time. All the 
specimens were, once again, coated with bright, smooth, adherent, 
coherent, and uniform coating of 20 .mu.m thick on each side (see Table 
1). The coating was free of columnar grains. It consisted of a well 
defined fine layered structure, as shown in FIG. 8. The etched 
cross-section of the coating showed very uniform distribution of W and 
W.sub.2 C. The coating had a smooth surface finish as shown in FIG. 9. The 
average surface finish of uncoated AM-350 stainless steel specimen was 54 
micro-inch; whereas, the coated specimen had an average surface finish of 
33 micro-inch. This, therefore, indicated that W+W.sub.2 C coating 
considerably improved the surface finish of the specimen. X-ray 
diffraction analysis of the coating revealed the presence of W and W.sub.2 
C phases in the coating. The crystallite size was less than 50 .ANG. (see 
Table 2). 
This Example shows that a mixture of W and W.sub.2 C can be formed at lower 
temperature (443.degree. C.) as well. 
Examples 5D to 5L 
A number of CVD experiments were conducted to coat AM-350, AM-355 and 
SS-422 stainless steel, SiC-6 graphite and IN-718 specimens simultaneously 
in a run. Reaction temperature was varied in a very narrow range; it was 
varied from 440.degree. to 445.degree. C. (see Table 1). Total pressure 
was kept constant at 40 Torr. in all these runs. The flow rates of 
WF.sub.6 and hydrogen were also kept the same in these runs. Flow rates of 
DME was varied from 70 to 100 cc/min. Additionally, diluent argon gas was 
used in some experiments and not used in others. The WF.sub.6 /DME ratio 
was varied from 3.00 to 4.29, the W/C atomic ratio varied from 1.5 to 
2.65, and the partial pressure of DME was varied from 0.76 to 1.08 Torr. 
However, the ratio of H.sub.2 /WF.sub.6 was maintained at 10.0 in all the 
experiments. Reaction time was also varied in these experiments, as shown 
in Table 1. 
All these experiments yielded bright, smooth, adherent, coherent, and 
uniform coating of varying thicknesses (see Table 1). The coating obtained 
in all these experiments was free of columnar grains. It consisted of well 
defined fine layered structure. The coating obtained in these experiments 
was extremely hard, as shown in Table 1. Additionally, it consisted of 
mixture of W and W.sub.2 C phases (see Table 2). The crystallite size of 
the coating was less than 50 .ANG. (see Table 2). 
These Examples show wide variations in process conditions that can be used 
to produce W+W.sub.2 C coating. 
Examples 5M and 5N 
Two CVD experiments were conducted to coat AM-350, AM-355 and SS-422 
stainless steel, SiC-6 graphite and IN-718 specimens simultaneously in a 
run. Reaction conditions used in these experiments were the same with the 
exception of using two different flow rate of DME (see Table 1). The 
partial pressure of DME used in these runs was 0.76 and 0.97 Torr., 
WF.sub.6 /DME ratio used was 3.33 and 4.29, and W/C atomic ratio used was 
1.67 and 2.15. The ratio of H.sub.2 /WF.sub.6 used in these experiments 
was 10.0. All the specimens were coated with bright, smooth, adherent, 
coherent, and uniform coating (see Table 1 for coating thickness). The 
coating was free of columnar grains. It consisted of fine layered 
microstructure. Coating was extremely hard, as shown in Table 1. It 
consisted of a mixture of W and W.sub.2 C phases (see Table 2). The 
crystallite size of the coating with higher DME partial pressure or lower 
WF.sub.6 /DME ratio or lower W/C atomic ratio was similar to the one 
obtained with lower DME partial pressure or higher WF.sub.6 /DME ratio or 
higher W/C atomic ratio. 
Example 50 and 5P 
These Examples were repeats of Examples 5M and 5N with the exception of 
using 454.degree. C. reaction temperature. Once again, all the specimens 
were coated with bright, smooth, adherent, coherent, and uniform coating 
(see Table 1). The coating was free of columnar grains. It consisted of 
fine layered microstructure. The coating was extremely hard, as shown in 
Table 1. It comprised of W and W.sub.2 C phases with crystallite size less 
than 50 .ANG.. 
Examples 5Q to 5U 
A number of CVD experiments were conducted to coat AM-350, AM-355 and 
SS-422 stainless steel and IN-718 specimens simultaneously in a run. 
Reaction temperature in these runs was varied from 421.degree. to 
445.degree. C. Total pressure, flow rates of WF.sub.6, hydrogen and DME 
were kept constant in these runs (see Table 1). A diluent argon gas was 
used in all these runs, and its flow rate was varied from 1,500 to 1,800 
cc/min. The flow rate of diluent was considerably higher than used before. 
The partial pressure of DME was varied from 0.69 to 0.74 Torr.; however, 
the WF.sub.6 /DME, W/C atomic and H.sub.2 /WF.sub.6 ratios were kept 
constant in these runs. Reaction time was also varied in these 
experiments. 
All the specimens used in these runs were coated with bright, smooth, 
adherent, coherent, and uniform coating (see Table 1 for coating 
thickness). The coating was free of columnar grains. It consisted of fine 
layered microstructure. The hardness of coating was around 2,400 Vickers, 
which was considerably lower than that observed at very low argon or no 
argon flow rates. The coating consisted of W and W.sub.2 C phases, and the 
crystallite size of the coating was less than 50 .ANG. (see Table 2). 
These Examples clearly show that a diluent can be used during coating 
reaction without affecting coating composition and crystallite size. 
However, the diluent is found to affect coating hardness. The change in 
coating hardness probably is related to change in coating rate. 
Comparing Examples 5T and U to Examples 4L, M and N it can be seen that the 
ratio of H.sub.2 /WF.sub.6 is very important for controlling the coating 
composition. It has already been shown in Examples 5P to 5U that simply 
increasing diluent flow rate does not cause any changes in overall coating 
composition provided WF.sub.6 /DME, W/C atomic and H.sub.2 /WF.sub.6 
ratios are kept constant. Examples 4L and 4N, on the other hand, show that 
increasing H.sub.2 /WF.sub.6 ratio from 10.0 as used in Examples 5P to 5U 
to 12.0 changes the coating composition from W+W.sub.2 C to W+W.sub.2 
C+W.sub.3 C. These examples, therefore, demonstrate the importance of 
H.sub.2 /WF.sub.6 ratio. 
Example 5V 
Several AM-350 and IN-718 specimens were coated in a reactor similar to 
that described in Example 5A. A reaction temperature of 445.degree. C., 
total pressure of 40 Torr. and flow rate of 200 cc/min. WF.sub.6, 2,000 
cc/min. hydrogen, 3,500 cc/min. argon and 60 cc/min. of DME were used for 
the reaction. Reaction time used was 90 min. These conditions provided 
WF.sub.6 /DME ratio of 3.33, W/C atomic ratio of 1.67, H.sub.2 /WF.sub.6 
ratio of 10.0 and DME partial pressure of 0.42 Torr. All the specimens 
were coated with a bright, smooth, adherent, coherent, and uniform coating 
of .about.9 .mu.m thick (AM-350) on each side (see Table 1). The coating 
was fine of columnar grains. Additionally, it had a well defined five 
layered microstructure with layers less than 1 .mu.m apart. The coating 
had a hardness of 2035 Vickers. The coating was found to contain a mixture 
of W and W.sub.2 C phases (see Table 3). The crystallite size of the 
coating was less than 50 .ANG.. 
This example, therefore, shows that low flow ratios of WF.sub.6, hydrogen 
and DME can be used to produce W and W.sub.2 C coatings provided WF.sub.6 
/DME, W/C atomic and H.sub.2 /WF.sub.6 ratios are maintained. 
Examples 5W and 5X 
Several AM-350 and IN-718 specimens were once again coated in a reactor 
using two different runs using 445.degree. C. temperature, 40 Torr. total 
pressure and flow rate of 100 cc/min. WF.sub.6, 1,000 cc/min. hydrogen and 
30 cc/min. DME. Additionally, 5,000 cc/min. of argon was used in Example 
W; whereas, only 4,000 cc/min. of argon was used in Example X. Reaction 
time used in these runs was 150 and 180 minutes, respectively. These 
conditions provided WF.sub.6 /DME, W/C atomic and H.sub.2 /WF.sub.6 ratios 
of 3.33, 1.67 and 10.0, respectively. All the specimens were coated with a 
bright, smooth, adherent, coherent and uniform coating of .about.9 .mu.m 
thick on each side (see Table 1). The coating was free of columnar grains 
and consisted of a mixture of W and W.sub.2 C phases. 
These examples, once again, show that low flow rates of WF.sub.6, hydrogen 
and DME can be used to produce W and W.sub.2 C coatings provided WF.sub.6 
/DME, W/C atomic and H.sub.2 /WF.sub.6 ratios are maintained. 
Example 5Y 
In this example several AM-350 and IN-718 specimens were coated in a run. A 
reaction temperature of 445.degree. C., total pressure of 40 Torr. and 
flow rate of 200 cc/min. WF.sub.6, 1,600 cc/min. of hydrogen, 4,000 
cc/min. of argon and 60 cc/min. of DME were used for the reaction. 
Reaction time used was 100 min. These conditions provided WF.sub.6 /DME 
ratio, W/C atomic ratio and DME partial pressure of 3.33. 1.67 and 0.41 
Torr., respectively. The ratio of H.sub.2 /WF.sub.6 used was 8.0, which 
was greater than the stoichiometric ratio required for complete conversion 
of WF.sub.6 to HF gas. All the specimens were coated with a bright, 
smooth, adherent, coherent, and uniform coating of .about.9 .mu.m thick on 
each side. The coating was free of columner grains and consisted of a 
mixture of W and W.sub.2 C phases. 
This example, therefore, shows that a mixture of W and W.sub.2 C can be 
produced provided a certain ratio of WF.sub.6 /DME or W/C atomic ratio and 
more than stoichiometric amount of hydrogen required for complete 
conversion of WF.sub.6 to HF are used. 
Example 5Z 
In this example, several AM-350 and IN-718 specimens were coated in a run. 
A reaction temperature of 445.degree. C., total pressure of 40 Torr. and 
flow rate of 200 cc/min WF.sub.6, 1,200 cc/min. hydrogen, 4,500 cc/min. 
argon and 60 cc/min. DME were used for the reaction. The reaction time 
used was 130 min. These conditions provided WF.sub.6 /DME ratio, W/C 
atomic ratio and DME partial pressure of 3.33, 1.67 and 0.40 Torr., 
respectively. The ratio of H.sub.2 /WF.sub.6 used was 6.0, which was 
greater than the stoichiometric ratio required for complete conversion of 
WF.sub.6 and HF gas. All the specimens were coated with a bright, smooth, 
adherent, coherent, and uniform coating of .about.10 .mu.m thick on each 
side. The coating was free of columner grains and consisted of a mixture 
of W and W.sub.2 C phases. 
This example, once again, shows that a mixture of W and W.sub.2 C can be 
produced provided a certain ratio of WF.sub.6 /DME or W/C atomic ratio and 
more than stoichiometric amount of hydrogen required for complete 
conversion of WF.sub.6 to HF are used. 
Example 6 
In this Example, two specimens of cemented carbide (94% tungsten carbide 
and 6% cobalt) were coated in a run. The specimens were not nickel plated 
prior to coating experiment. The specimens were heated to a temperature of 
about 445.degree. C. and a gaseous mixture of 300 cc/min. WF.sub.6, 3,000 
cc/min. of hydrogen and 55 cc/min. of DME was passed into the furnace over 
the specimens. A total pressure of 40 Torr. was maintained in the run to 
give 0.66 Torr. partial pressure of DME. A WF.sub.6 /DME ratio of 5.45, 
W/C atomic ratio of 2.73, and H.sub.2 /WF.sub.6 ratio of 10.0 were 
maintained during the run. The deposition was conducted for 20 minutes. 
The specimens were coated with a bright, smooth, adherent, coherent, and 
uniform coating. The coating thickness was .about.8 .mu.m. The coating was 
free of columnar grains and consisted of layered structure. The etched 
cross-section of the coating showed uniform distribution of W, W.sub.2 C 
and W.sub.3 C. The coating had a smooth surface finish. 
This example therefore shows that the tungsten/carbon alloy coatings of the 
present invention can be deposited on cemented carbide. Additionally, it 
shows that there is no need to provide a nickel or copper inter-layer to 
protect the cemented carbide while depositing tungsten/carbon alloys. 
Example 7 
In this example, two specimens of titanium alloy (Ti/6Al/4V) were coated in 
a run. Both the specimens were plated with 4-5 .mu.m thick nickel using 
electroless nickel technique. The specimens were heated to a temperature 
of about 445.degree. C. and a gaseous mixture of 300 cc/min. WF.sub.6, 
3,000 cc/min. of hydrogen and 55 cc/min. of DME was passed into the 
furnace over the specimens. A total pressure of 40 Torr. was maintained in 
the run to give 0.66 Torr. partial pressure of DME. A WF.sub.6 /DME ratio 
of 5.45 or W/C atomic ratio of 2.73 was also maintained during the run. A 
H.sub.2 /WF.sub.6 ratio of 10.0 was also maintained during the run. The 
deposition was conducted for 20 minutes. 
The specimens were coated with a bright, smooth, adherent, coherent, and 
uniform coating. The coating thickness was .about.8 .mu.m. The coating was 
free of columnar grains and consisted of layered structure. X-ray 
diffraction analysis revealed the presence of W, W.sub.2 C and W.sub.3 C 
in the coating. 
This example clearly shows that titanium alloys can be coated with 
tungsten/carbon alloys described in the present invention. However, a 
protective nickel layer is required before coating titanium alloys with 
tungsten/carbon alloys. 
Example 8 
In this example, several specimens of 2219 aluminum were coated in a CVD 
run. All the specimens were plated with 4-5 .mu.m thick nickel using 
electroless technique. The specimens were heated to a temperature of about 
371.degree. C. and a gaseous mixture of 350 cc/min. WF.sub.6, 3,500 
cc/min. of hydrogen and 65 cc/min. of DME was passed into the furnace over 
the specimens for 20 minutes. A total pressure 40 Torr. was used to 
provide a DME partial pressure of 0.66 Torr. The ratio of WF.sub.6 /DME 
used was 5.38. Additionally, the H.sub.2 /WF.sub.6 and W/C atomic ratios 
used were 10.0 and 2.69, respectively. 
All the specimens were coated with a bright, smooth, adherent, coherent and 
uniform coating. Coating thickness was approximately 5 .mu.m. It was free 
of columnar grains and consisted of a mixture of W and W.sub.3 C phases. 
This example clearly shows that tungsten/carbon alloy can be deposited on 
aluminum. However, a protective nickel layer is required before coating 
aluminum with tungsten/carbon alloys. 
Example 9 
In this example, two specimens of alumina (Al.sub.2 O.sub.3) were coated in 
a run. The specimens were not nickel plated prior to coating experiment. 
The specimens were heated to a temperature of about 443.degree. C. and a 
gaseous mixture of 300 cc/min. of WF.sub.6, 3,000 cc/min. of hydrogen, 70 
cc/min. of DME and 300 cc/min. of argon was passed into the furnace over 
the specimens. A total pressure of 40 Torr. was maintained in the run to 
give 0.76 Torr. partial pressure of DME. A WF.sub.6 /DME ratio of 4.29 and 
W/C atomic ratio of 2.15 were also maintained during the run. 
Additionally, a H.sub.2 /WF.sub.6 ratio of 10.0 was maintained during the 
run. The deposition was conducted for 40 minutes. 
The specimens were coated with a bright, smooth, adherent, coherent and 
uniform coating of .about.12 .mu.m thickness. The coating was free of 
columnar grains and consisted of layered structure. X-ray diffraction 
revealed the pressure of W, W.sub.2 C and W.sub.3 C in the coating. The 
coating had a smooth surface finish. 
This example shows that tungsten/carbon alloy coatings of the present 
invention case be deposited of ceramic substrates such as alumina. 
Additionally, it shows that there is no need to provide a nickel or copper 
interlayer to protect the ceramic substrates while depositing 
tungsten/carbon alloys. 
Example 10 
In this example, two six-inch long and 1/4" diameter molybdenum rods were 
coated in a run. The molybdenum rods were not nickel plated prior to 
coating experiment. The rods were heated to a temperature of about 
445.degree. C. and a gaseous mixture of 300 cc/min. WF.sub.6, 3,000 
hydrogen and 40 cc/min. of DME was passed into the furnace over the 
specimens for 90 minutes. A total pressure of 40 Torr. was used to provide 
a DME partial pressure of 0.48 Torr. The ratio of WF.sub.6 /DME used was 
7.5. Additionally, the H.sub.2 /WF.sub.6 and W/C atomic ratio used were 
10.0 and 3.75, respectively. 
Both rods were coated with a bright smooth, adherent, coherent and uniform 
coating of .about.13 .mu.m thickness. It was free of columnar grains and 
consisted of a mixture of W and W.sub.3 C phases. 
This example shows that tungsten/carbon alloys of the present invention run 
be deposited on molybdenum without a protective interlayer. 
Example 11 
The experiment described in Example 10 was repeated with the exception of 
using higher (55 cc/min.) DME flow rate. This high DME flow rate provided 
a DME partial pressure of 0.66 Torr. The WF.sub.6 /DME and W/C atomic 
ratios used were 5.5 and 2.75, respectively. The ratio of H.sub.2 
/WF.sub.6 used was 10.0. 
Both rods were, once again, coated with a bright, smooth, adherent, 
coherent and uniform coating of .about.11 .mu.m thickness. It was free of 
columnar grains and consisted of mixture of W, W.sub.2 C and W.sub.3 C 
phases. 
This example clearly shows that tungsten/carbon alloys of the present 
invention can be deposited on molybdenum without a protective interlayer. 
Example 12 
In this example, a two step coating process was used. Several AM-350, 
Ti/6Al/4V and IN-718 specimens were placed in an inductively heated 
furnace. All the specimens were plated with 3-4 .mu.m thick nickel using 
either electrolytic or electroless technique prior to CVD experiment. The 
specimens were heated to a temperature of about 442.degree. C. and a 
gaseous mixture of 300 cc/min. WF.sub.6 and 3,000 cc/min. of hydrogen was 
passed into the furnace over the specimens for five minutes to coat them 
with tungsten. After coating the specimens with tungsten for five minutes, 
a gaseous mixture of 300 cc/min. WF.sub.6, 3,000 cc/min. of hydrogen and 
40 cc/min. of DME was passed into the furnace for 55 minutes to provide 
tungsten/carbon alloy coating. A total pressure of 40 Torr. was maintained 
during the run to provide a DME partial pressure of 0.48 Torr., a WF.sub.6 
/DME ratio of 7.5, and a W/C atomic ratio of 3.75, respectively. 
Additionally, a H.sub.2 /WF.sub. 6 ratio of 10.0 was used during the 
coating steps. 
All the specimens were coated with 2-3 .mu.m thick tungsten followed by 
27-28 .mu.m thick tungsten/carbon alloy. The coating was bright, smooth, 
adherent, coherent and uniform. The tungsten interlayer had a well defined 
columnar structure; whereas, tungsten/carbon alloy had non-columnar 
structure. It consisted of a mixture of W and W.sub.3 C phases. 
This example clearly shows that the tungsten/carbon alloys can be deposited 
on various substrates with a tungsten interlayer. 
Example 13 
The erosion performance of some of the coated specimens was determined 
using a miniature sandblast unit. Crushed glass with average particle size 
of 50 micrometers was directed at the coated and uncoated specimens at an 
angle of 90.degree. for 10 minutes using the test procedure summarized in 
Table 3. The erosion performance of uncoated and coated specimens was 
determined based upon weight loss as well as calculated volume loss in 10 
minutes. 
AM-350 stainless steel specimens uncoated and coated in Examples 3C, 4F and 
5C with W+W.sub.3 C, W+W.sub.2 C+W.sub.3 C and W+W.sub.2 C coatings, 
respectively, were tested for erosion performance. The test results 
summarized in Table 4 indicated that coated specimens outperformed 
uncoated specimen both on weight loss basis as well as volume loss basis. 
Surprisingly, the erosion performance of W+W.sub.2 C+W.sub.3 C coating was 
far superior to that of W+W.sub.3 C coating (see Table 4). Additionally, 
erosion performance of W+W.sub.2 C coating was considerably better than 
that of W+W.sub.2 C+W.sub.3 C and W+W.sub.3 C coatings. 
This Example, therefore, shows that coatings described in this application 
provide good erosion and wear protection. Additionally, the degree of 
erosion and wear protection required can be manipulated by altering the 
coating composition. 
Example 14 
The wear performance of W+W.sub.2 C coating was determined using a 
block-on-ring test. The test machine was made by Falex Corporation, 
Aurora, Illinois. The wear performance of uncoated 4620 steel rings was 
determined against coated and uncoated 440C steel blocks. The test was 
conducted in a mineral oil having a viscosity of 62.5 centipoise. The oil 
contained 3.0 .mu.m alumina particles in a concentration of 2 gm/litre. 
The block-on-ring test was performed using a load of 250 lb. and 
90.degree. oscillating motion at 60 rpm for 20,000 cycles. Wear scar width 
and weight loss were measured to determine and compare the wear 
performance of coated and uncoated specimens. 
The test results summarized in Table 5 indicated that the coated block 
outperformed the uncoated block both on the basis of wear scar on the ring 
and weight loss by the ring. 
This example, therefore, shows that tungsten/carbon alloy coatings 
described in the present invention provide good wear protection. 
Example 15 
The wear performance of W+W.sub.2 C coating was once again determined using 
a pin-on-disc test. The test machine was made by Falex Corporation. The 
wear performance of uncoated and coated 440C steel pins was determined 
against uncoated SiC disc. The test was conducted in a mineral oil having 
a viscosity of 62.5 centipoise. It contained 3.0 .mu.m alumina in a 
concentration of 2 gm/liter. The pin-on-disc test was conducted using a 
load of 4 lbs and continuous motion at 150 rpm. The wear performance of 
the coated and the uncoated 440C steel pins was compared based upon the 
pin wear rate. 
The test results summarized in Table 6 indicated that the coated 440C steel 
pin outperformed the uncoated pin; the pin wear rate on the coated 
specimen was .about.18.5 times lower than the uncoated specimen despite 
running it more than two times longer distance. 
This example shows that tungsten/carbon alloy coatings discussed in this 
application provide good wear protection. 
Example 16 
Several Am-350, SS-422 and IN-718 specimens are coated in an inductively 
heated graphite reactor similar to that described in earlier examples. A 
reaction temperature of 445.degree. C., a total pressure of 40 Torr and 
flow rate of 300 cc/min. WF.sub.6, 3,000 cc/min. hydrogen and 20 cc/min. 
of diethyl either (DEE) are used for the reaction and at a reaction time 
of 50 minutes. These conditions provide WF.sub.6 /DEE ratio, W/C atomic 
ratio and DEE partial pressure of 15.0, 3.75, and 0.24 Torr, respectively. 
A H.sub.2 /WF.sub.6 ratio of 10.0 is maintained during the run. Based on 
the previous examples set forth above, all of the specimens are expected 
to be coated with a bright, smooth, adherent, coherent, and uniform 
coating of .about.20 .mu.m thick on each side. The coating is expected to 
be free of columnar grains and a mixture of W and W.sub.3 C phases. 
Example 17 
CVD experiment described in Example 16 is repeated with using 40 cc/min. 
DEE instead of 20 cc/min. The increase in DEE flow rate causes a decrease 
in WF.sub.6 /DEE ratio to 7.5, a decrease in W/C atomic ratio to 1.88, and 
an increase in DEE partial pressure to 0.48 Torr. All the other reaction 
conditions are maintained the same as described in Example 16. All the 
specimens are expected to be coated with a bright, smooth, adherent, 
coherent, and uniform coating of .about.15 .mu.m thick on each side. The 
coating is expected to be free of columnar grains and a mixture of W and 
W.sub.2 C phases. 
Example 18 
Several AM-350, SS-422 and In-718 specimens are coated in an inductively 
heated graphite reactor similar to that described in earlier examples. A 
reaction temperature of 445.degree. C., total pressure of 40 Torr. and 
flow rate of 33 cc/min. WF.sub.6, 3,000 cc/min. hydrogen and 40 cc/min. of 
ethanol are used for the reaction. Reaction time used is 50 min. These 
conditions provide WF.sub.6 /ethanol ratio, W/C atomic ratio and ethanol 
partial pressure of 7.5, 3.75 and 0.48 Torr, respectively. A H.sub.2 
/WF.sub.6 ratio of 10.0 is also used during the reaction. All the 
specimens are expected to be coated with a bright, smooth, adherent, 
coherent, and uniform coating of .about.20 .mu.m thick on each side. The 
coating is expected to be free of columnar grains and a mixture of W and 
W.sub.3 C phases. 
Example 19 
CVD experiment described in Example 18 is repeated with using 80 cc/min. 
ethanol instead of 40 cc/min. The increase in ethanol flow rate causes a 
decrease in WF.sub.6 /ethanol ratio to 3.75, a decrease in W/C atomic 
ratio to 1.88, and an increase in ethanol partial pressure to 0.95 Torr. 
All the other reaction conditions are maintained the same as described in 
Example 3. All the specimens are expected to be coated with a bright, 
smooth, adherent, coherent, and uniform coating and .about.15 .mu.m thick 
on each side. The coating is expected to be free of columnar grains and a 
mixture of W and W.sub.2 C phases. 
Example 20 
CVD experiment described in Example 3 is repeated again with using 80 
cc/min. methanol instead of 40 cc/min. of ethanol. This flow rate of 
methanol results in WF.sub.6 /methanol ratio, W/C atomic ratio, and 
methanol partial pressure of 3.75, 3.75, and 0.95 Torr, respectively. All 
the other reaction conditions are maintained the same as described in 
Example 18. All the specimens are expected to be coated with a brigh, 
smooth, adherent, coherent, and uniform coating of .about.20 .mu.m thick 
on each side. The coating is expected to be free of columnar grains and a 
mixture of W and W.sub.3 C phases. 
EXPERIMENTAL 
X-RAY Diffraction (XRD) Instrumental Apparatus and Experimental Procedures 
Diffraction experiments were performed using a manually-controlled Siemens 
D500 and, in a few cases, a Philips APD 3720. For most scans on the 
Siemens and all scans on the Philips, graphite-monochromatized CuK.alpha. 
radiation (.lambda.=1.54178.ANG.) was employed; for some scans on the 
Siemens, vanadium-filtered CrK.alpha. radiation (.lambda.=2.29092.ANG.) 
was used. The Siemens had a 1.degree. fixed divergence slit, 1.degree. 
scatter slits, a soller slit in the diffracted beam, a 0.15.degree. 
detector slit, and, for CuK.alpha. radiation, a 0.15.degree. slit in the 
diffracted beam monochromator. The Philips had a variable divergence slit 
which kept the sample illumination length fixed at 13.2 mm. Both 
instruments had scintillation x-ray detectors. Data output for the Siemens 
was by strip-chart recording; that for the Philips was in the form of 
digitized diffraction traces which were stored in files in a dedicated 
Micro PDP 11-23 computer. 
The volume of sample illuminated by x-rays varied with the type of 
diffractometer and radiation employed. The Siemens illumination area 
decreased as the diffraction angle (2.theta.) increased, while the Philips 
illumination area was constant and independent of 2.theta.. The 
penetration depth is a function of x-ray wavelength, the linear absorption 
coefficient of the sample, and diffraction angle. A rough calculation 
showed that 99% of CuK.alpha. diffracted intensity for a reflection whose 
d-spacing was 2.25.ANG. (2.theta..about.40.degree.) came from the top 
.about.2.5 .mu.m of these tungsten-rich materials. The corresponding 
penetration depth for CrK.alpha. radiation was .about.1.3 .mu.m. The 
region between 1.3 .mu.m and 2.5 .mu.m, which effectively could not be 
probed by CrK.alpha. x-rays, accounted for .about.10% of the total 
CuK.alpha. diffracted intensity. 
Diffraction scans were made for the purpose of phase identification and, in 
some cases, for measuring cyrstallite size. Survey scans over wide angular 
regions (usually, 5.degree.-90.degree. for CuK.alpha. and 
15.degree.-115.degree. for CrK.alpha.) at rapid scan rates (5.degree./min. 
or 2.degree./min.) were initially obtained. If there was some doubt about 
the presence of a weakly-diffracting phase, scans were repeated at a 
slower (1.degree./min.) scan rate. d-spacings were calculated employing 
the Bragg equation: 
EQU .lambda.=2d sin .theta.. (1) 
Relative intensities were taken directly from the strip-chart recordings 
(Siemens) or plotted diffraction traces (Philips). 
Phases were identified manually by comparing observed d-spacings and 
relative intensities with those found in Powder Diffraction File (PDF) 
cards 2-1134 (W.sub.2 C), 2-1138 (W.sub.3 C)*, and 4-806 (W). Due to 
preferred crystallite orientation, more attention was paid to the 
positions of lines than to their intensities. 
FNT * PDF card 2-1138 is actually for W.sub.3 O. W.sub.3 c and W.sub.3 O are 
structurally isomorphous. To determine whether the coating consists of 
W+W.sub.3 C or W+W.sub.3 O, an Auger Emission Spectra (AES) depth profile 
was performed on a CVD produced tungsten/carbon alloy coating. Within the 
detection limits of the technique (&gt;0.1 atomic percent) no oxygen was 
observed within the coating depth of .about.3600.ANG. that was profiled. 
However, approximately 5.3 atomic percent carbon was observed within the 
depth profiled, indicating that the coating consisted of W+W.sub.3 C 
rather than W+W.sub.3 O. 
Certain isolated peaks in the scans were rescanned slowly (1/2.degree./min. 
or 1.degree./min.) for the purpose of estimating crystallite size. The 
crystallite size is given by the Scherrer equation:** 
##EQU1## 
where c is a constant set to 0.9 and 
EQU .beta.=(.beta..sub.1.sup.2 -.beta..sub.o.sup.2).sup.1/2, (3) 
where .beta..sub.1 is the full width at half-maximum (FWHM) of the observed 
diffraction line and .beta..sub.o is the FWHM of a diffraction line of a 
highly-crystalline reference material. The reference material used was 
Linde C alumina. .beta..sub.o was obtained by linear interpolation between 
the FWHM's of reference diffraction lines whose .theta.-values spanned 
that of the observed line. 
FNT ** B. D. Cullity, "Elements of X-ray Diffraction" (Reading, Mass: 
Addison-Wesley, 1978), p. 284 
Interpretation of XRD Results 
Based on phase composition, the materials can be divided into three groups. 
Some were binary mixtures of W and W.sub.3 C; some were ternary mixtures 
of W, W.sub.3 C and W.sub.2 C; and still others were binary mixtures of W 
and W.sub.2 C. The crystallite sizes were uniformly small, almost always 
less than 200.ANG. and often less than 100.ANG.. 
FIG. 11 is a Siemens CuK.alpha. scan of a W/W.sub.3 C/W.sub.2 C mixture. 
This pattern is rather more crystalline than the average, and shows 
clearly that all three phases are present. FIG. 12 is a Siemens CuK.alpha. 
scan of a ternary mixture, but in this case a trace amount of W.sub.2 C is 
present in the sample. FIG. 13 is a Siemens CuK.alpha. scan of a ternary 
mixture and here a trace amount of W.sub.3 C is present in the sample. 
FIG. 14 is a Siemens CrK.alpha. scan of a very low-crystalline, almost 
amorphous W/W.sub.2 C mixture. FIG. 15 is a typical scan of a W/W.sub.3 C 
mixture. No W.sub.2 C was detected in this scan. 
3 TABLE 1 
Example 3 Example 1 Example 2 A B C D E F G H I 
Substrate SiC-6 AM-350 IN-718 AM-350 SS-422 AM-350 AM-350 SiC-6 SiC-6 
AM-350 AM-350 AM-350 AM-350 SiC-6 AM-350 Graphite Stainless Steel 
Graphite Graphite Graphite Temperature, .degree.C. 443 443 440 442 
447 443 443 443 431 371 445 Pressure, Torr. 40 40 40 40 40 40 40 40 40 
40 40 Deposition Time, Min. 40 15 40 30 35 30 30 30 30 20 40 Flow 
Rates, Std. cc/min WF.sub.6 300 300 300 300 300 300 300 300 300 350 300 
H.sub.2 3,000 3,000 3,000 3,000 3,000 3,000 3,000 3,000 3,000 3,500 
3,300 DME -- -- 40 40 40 30 40 50 50 65 60 Argon -- 4,000 -- -- -- 300 
300 300 300 -- -- H.sub.2 /WF.sub.6 Ratio 10 10 10 10 10 10 10 10 10 
10 11 WF.sub.6 /DME Ratio -- -- 7.50 7.50 7.50 10 7.5 6.0 6.0 5.38 5.00 
DME partial pressure, Torr. -- -- 0.48 0.48 0.48 0.33 0.44 0.55 0.55 
0.66 0.66 W/C Atomic Ratio -- -- 3.75 3.75 3.75 5.00 3.75 3.00 3.00 
2.69 2.50 Coating Thickness, .mu.m 12-40 12-50 10-12 22 15 13 16 12 10 
12 8 6 14 Vickers Hardness, Kg/mm.sup.2 510 .+-. 23 465 .+-. 49 564 .+-. 
25 455 .+-. 50 511 .+-. 54 -- -- -- -- 2395 .+-. 15 2470 .+-. 53 2361 
.+-. 
105 -- -- -- 
Example 4 A B C D E F G H I J K L M N 
Substrate AM-350 AM-350 AM-350 AM-350 AM-350 AM-350 SiC-6 SiC-6 SiC-6 
SiC-6 SiC-6 AM-350 AM-350 AM-350 Graphite Graphite Graphite 
Graphite Graphite Temperature, .degree.C. 445 443 443 443 451 462 462 
467 467 474 477 445 445 445 Pressure, Torr. 40 40 40 40 40 40 40 40 40 
50 100 40 40 40 Deposition Time, Min. 20 15 40 20 20 35 40 40 40 40 15 
90 90 80 Flow Rates, Std. cc/min WF.sub.6 300 300 300 300 300 300 300 
300 300 300 400 200 200 200 H.sub.2 3,000 3,000 3,000 3,000 3,000 3,000 
3,000 3,000 3,000 3,000 4,000 2,400 2,400 2,400 DME 55 55 60 62 55 60 70 
40 35 35 24 60 60 60 Argon -- 300 300 300 -- -- -- -- -- -- -- 3,000 
6,000 6,000 H.sub.2 /WF.sub.6 Ratio 10 10 10 10 10 10 10 10 10 10 10 12 
12 12 WF.sub.6 /DME Ratio 5.45 5.45 5.00 4.84 5.45 5.00 4.29 7.50 8.57 
8.57 16.7 3.33 3.33 3.33 DME partial pressure, Torr 0.66 0.60 0.66 0.68 
0.66 0.71 0.83 0.48 0.42 0.52 0.54 0.42 0.28 0.28 W/C Atomic Ratio 2.73 
2.73 2.50 2.42 2.73 2.50 2.15 3.75 4.28 4.28 8.35 1.67 1.67 1.67 Coating 
Thickness, .mu.m 8 5 12 5 13 15 13 22 21 22 20 13 12 12 Vickers Hardness, 
Kg/mm.sup.2 2248 .+-. 70 2179 .+-. 29 2224 .+-. 46 -- 2395 .+-. 30 2414 
.+-. 69 2241 .+-. 71 -- -- -- 1657 .+-. 
122 2,290 2,422 2,341 Example 5 A B C D E F G H I J K L 
M Substrate SiC-6 AM-350 AM-350 AM-350 AM-350 AM-350 AM-350 AM-350 
AM-350 AM-350 AM-350 AM-350 AM-350 Graphite Temperature, .degree.C. 477 
463 443 443 440 445 445 445 445 445 445 443 431 Pressure, Torr. 100 40 
40 40 40 40 40 40 40 40 40 40 40 Deposition Time, Min. 15 50 35 20 20 70 
30 40 40 40 40 40 30 Flow Rates, Std. cc/min WF.sub.6 400 300 300 300 
3,000 300 300 300 300 300 300 300 300 H.sub.2 4,000 3,000 3,000 3,000 
3,000 3,000 3,000 3,000 3,000 3,000 3,000 3,000 3,000 DME 65 85 85 85 90 
85 90 90 100 90 80 70 70 Argon -- -- -- 300 300 -- 300 300 300 300 300 
300 300 H.sub.2 /WF.sub.6 Ratio 10 10 10 10 10 10 10 10 10 10 10 10 10 
WF.sub.6 /DME Ratio 6.15 3.53 3.53 3.53 3.33 3.53 3.33 3.33 3.00 3.33 
3.75 4.29 4.29 DME partial pressure, torr 1.45 1.00 1.00 0.92 0.97 1.00 
0.97 0.97 1.08 0.97 0.87 0.76 0.76 W/C Atomic Ratio 3.08 1.76 1.76 1.76 
1.67 1.76 1.67 1.67 1.50 1.67 1.88 2.15 2.15 Coating Thickness, .mu.m 25 
25 20 8 Not 27 8 12 14 12 12 10 6 Determined Vickers Hardness, 
Kg/mm.sup.2 2512 .+-. 119 2758 .+-. 77 -- 2746 .+-. 51 -- 2758 .+-. 31 
2660 .+-. 30 2851 .+-. 66 3054 .+-. 156 2836 .+-. 188 2758 .+-. 15 2434 
.+-. 102 2857 .+-. 
173 Example 5 N O P 
Q R S T U V W X Y Z 
Substrate AM-350 AM-350 AM-350 AM-350 AM-350 AM-350 AM-350 AM-350 
AM-350 AM-350 AM-350 AM-350 AM-350 Temperature, .degree.C. 431 454 454 
442 434 421 443 445 445 445 445 445 445 Pressure, Torr. 40 40 40 40 40 
40 40 40 40 40 40 40 40 Deposition Time, Min. 30 30 30 40 80 115 85 65 
90 150 180 100 130 Flow Rates, Std. cc/min WF.sub.6 300 300 300 300 300 
300 300 300 200 100 100 200 200 H.sub.2 3,000 3,000 3,000 3,000 3,000 
3,000 3,000 3,000 2,000 1,000 1,000 1,600 1,200 DME 90 70 90 90 90 90 90 
90 60 30 30 60 60 Argon 300 300 300 1,500 1,500 1,800 1,500 1,800 3,500 
5,000 4,000 4,000 4,500 H.sub.2 /WF.sub.6 Ratio 10 10 10 10 10 10 10 10 
10 10 10 8 6 WF.sub.6 /DME Ratio 3.33 4.29 3.33 3.33 3.33 3.33 3.33 3.33 
3.33 3.33 3.33 3.33 3.33 DME partial pressure, Torr 0.97 0.76 0.97 0.74 
0.74 0.69 0.74 0.69 0.42 0.19 0.23 0.41 0.40 W/C Atomic Ratio 1.67 2.15 
1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 Coating Thickness, 
.mu.m 6.4 8 3 6 13 17 19 13 9 9 9 9 10 Vickers Hardness, Kg/mm.sup.2 
2897 .+-. 15 3210 .+-. 15 -- -- 2469 .+-. 53 2470 .+-. 53 2472 .+-. 110 
2398 .+-. 
109 2,035 2,315 2,167 2,100 2,289 
TABLE 2 
__________________________________________________________________________ 
Coating Composition 
__________________________________________________________________________ 
Example 3 
Example 1 
Example 2 
A B C D E F G H I 
__________________________________________________________________________ 
Composition 
W Major Major Minor 
Minor 
Minor 
Minor 
Minor 
Major 
Major 
Major 
Major 
W.sub.2 C None None None None 
None None 
None None 
None None 
None 
W.sub.3 C None None Major 
Major 
Major 
Major 
Major 
Minor 
Major 
Major 
Major 
Crystallite Size, .ANG. 
W -- -- -- -- 102 140 140 181 124 -- 95 
W.sub.2 C -- -- -- -- -- -- -- -- -- -- -- 
W.sub.3 C -- -- -- -- 92 111 119 86 87 -- 61 
__________________________________________________________________________ 
Example 4 
A B C D E F G H I J K L M N 
__________________________________________________________________________ 
Com- 
position 
W Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
W.sub. 2 C 
Major 
Trace 
Trace 
Major 
Trace 
Minor 
Major 
Trace 
Trace 
Major 
Trace 
Minor 
Trace 
Trace 
W.sub.3 C 
Major 
Major 
Major 
Minor 
Major 
Major 
Trace 
Major 
Minor 
Major 
Minor 
Minor 
Minor 
Minor 
Cry- 
stallite 
Size, .ANG. 
W -- -- 80 138 -- 164 150 -- -- -- -- 100 128 134 
W.sub.2 C 
-- -- 52 -- -- 86 -- -- -- -- -- 83 -- -- 
W.sub.3 C 
-- -- -- 107 -- 73 120 -- -- -- -- 48 74 74 
__________________________________________________________________________ 
Example 5 
A B C D E F G H I J K L 
__________________________________________________________________________ 
Composition 
W Major 
Minor 
Minor 
Major 
Major 
Major Major 
Major 
Major 
Major 
Major 
Major 
W.sub.2 C Minor 
Major 
Major 
Major 
Major 
Major Major 
Major 
Major 
Major 
Major 
Major 
W.sub.3 C None 
None 
None None 
None 
None None 
None 
None None 
None 
None 
Crystallite Size, .ANG. 
W -- .ltoreq. 50 
.ltoreq.50 
-- .ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
W.sub.2 C -- .ltoreq.50 
.ltoreq.50 
-- .ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
W.sub.3 C -- -- -- -- -- -- -- -- -- -- -- -- 
__________________________________________________________________________ 
Example 5 
M N O P Q R S T U V W X Y Z 
__________________________________________________________________________ 
Com- 
position 
W Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
Major 
W.sub.2 C 
Minor 
Minor 
Minor 
Minor 
Trace 
Minor 
Trace 
Minor 
Minor 
Minor 
Minor 
Minor 
Minor 
Major 
W.sub.3 C 
None 
None 
None 
None None 
None 
None 
None 
None None 
None 
None 
None 
None 
Cry- 
stallite 
Size, .ANG. 
W 83 .ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
W.sub.2 C 
58 .ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
.ltoreq.50 
W.sub.3 C 
-- -- -- -- -- -- -- -- -- -- -- -- -- -- 
__________________________________________________________________________ 
Composition: 
Concentration of W, W.sub.2 C and W.sub.3 C in the coating is determined 
based upon relative peak intensities of W, W.sub.2 C and W.sub.3 C phases 
Terms: 
In Table 2, the term "Major" denotes a phase concentration exceeding 30 
weight percent; the term "Trace" denotes a phase concentration less than 
weight percent; the term "Minor" denotes a phase concentration varying 
between 5 and 30 weight percent; the term "None" denotes not detected. 
TABLE 3 
______________________________________ 
Erosion Test Procedure 
______________________________________ 
Nozzle Diameter 0.045 inch 
Stand Off Distance 
0.5 inch 
Erosion Media Crushed Glass 
(50 .mu.m Average Particle Size) 
Supply Pressure 45 psig 
Flow Rate of 1.0 g/min 
Erosion Media 
Erosion Test Standard 
Weight Loss in 10 Minutes 
______________________________________ 
TABLE 4 
__________________________________________________________________________ 
Erosion Test Results 
Erosion Performance 
Relative to Uncoated 
Calculated 
AM-350 Stainless 
Coating Weight 
Volume Loss, 
Steel 
Composition 
Loss, g 
cc Weight Basis 
Volume Basis** 
__________________________________________________________________________ 
Uncoated AM-350 
Stainless Steel 
N/A 0.00579 
7.31 .times. 10.sup.-4 
-- -- 
Coated AM-350 
Stainless Steel 
Example 3C 
W + W.sub.3 C 
0.00042 
2.63 .times. 10.sup.-5 
13.8 27.8 
Example 4F 
W + W.sub.2 C + W.sub.3 C 
0.00016 
1.00 .times. 10.sup.-5 
36.2 73.1 
Example 5C 
W + W.sub.2 C 
0.00010 
0.63 .times. 10.sup.-5 
57.9 116 
__________________________________________________________________________ 
##STR1## 
##STR2## 
TABLE 5 
______________________________________ 
Wear Test Results 
440C Steel 4620 Steel 
Wear Weight Loss, mg 
Block Ring Scar, mm Ring Block 
______________________________________ 
Uncoated Uncoated 1.37 3.52 0.01 
Coated Uncoated 0.89 0.06 0.07 
Coated Uncoated 0.79 0.10 0.19 
______________________________________ 
TABLE 6 
______________________________________ 
Wear Test Results 
Total Sliding 
440C Steel Distance, Pin Wear Rate, 
Pin SiC Disc cm .times. 10.sup.5 
cm.sup.3 /gm cm .times. 10.sup.-15 
______________________________________ 
Uncoated 
Uncoated 5.6 1.72 
Coated Uncoated 13.4 0.093 
______________________________________ 
Conclusion 
Thus it can be seen that the present invention discloses extremely hard, 
fine grained, non-columnar tungsten-carbon alloys which consist 
essentially of a mixture of a substantially pure tungsten phase and at 
least one carbide phase wherein the carbide phase consists of W.sub.2 C or 
W.sub.3 C or a mixture of W.sub.2 C and W.sub.3 C. The new alloys are 
harder and more resistant to fracture, corrosion, erosion and wear than 
are tungsten-carbon alloys of the prior art that are produced by 
conventional chemical vapor deposition techniques and thus are composed of 
large columnar grains. 
The present invention also discloses a method for producing the new 
tungsten-carbon alloys wherein the composition of the alloy's carbide 
phase can be controlled by controlling the temperature at which the 
reactions are run, the ratio of tungsten halide to oxygen- and 
hydrogen-containing organic compound and the ratio of hydrogen to tungsten 
halide. Thus the method makes it possible for those skilled in the art to 
produce custom alloys having desired carbide characteristics. 
Various modifications of the invention in addition to those shown and 
described herein will become apparent to those skilled in the art from the 
foregoing description and examples. Such modifications are intended to 
fall within the scope of the appended claims.