Mechanical properties of vapor deposited tungsten are improved by selective incorporation of various nonmetallic impurities. Addition of trace quantities of carbon, nitrogen, or oxygen can significantly increase both low and high temperature yield strength without greatly affecting ductile-to-brittle transition temperature

Chin, J.

Lindgren, J. R.

Weinberg, A. F.

English

NASA Technical Reports Server

August 1972
	 B72-10454 
[IJ	 NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Nonmetallic Impurities Improve Mechanical Properties

of Vapor-Deposited Tungsten 
Certain mechanical properties of vapor-deposited 
tungsten can be improved by the selective incorpora-
tion of various nonmetallic impurities. The addition 
of trace quantities of carbon, nitrogen, or oxygen 
can significantly increase both the low- and high-
temperature yield strength without greatly affecting 
the ductile-to-brittle transition temperature (D BTT). 
These results represent the basic findings of a 
study aimed at achieving greater control of the 
properties of vapor-deposited tungsten. Specifi-
cally, it was found that the addition of carbon in 
concentrations of from 250 to 300 ppm raised the 
low-temperature yield strength from 345 x 106 N/rn2 
(50 ksi) to nearly 1380 x 106 N/rn 2
 (200 ksi) and the 
yield strength at 18000C from less than 27.6 x 10 6
 N/rn2 
(4 ksi) to about 62.1 x 10 6
 N/rn2
 (9 ksi), while the 
DBTT stayed below 200°C. Nitrogen additions within the 
additive range studied were equivalent to carbon in pro-
ducing strength increases. The effect of oxygen on high-
and low-temperature yield strengths was somewhat less. 
Two principal techniques were used to add the 
desired impurity: One involved gas-metal reactions 
to introduce an impurity into previously deposited 
tungsten; the other involved the codeposition of the 
impurity with the tungsten. In the case of carbon, 
the first technique was performed by immersing 
vapor-deposited tungsten specimens in a rich mix-
ture of methane in hydrogen gas at about 1650°C, 
to form a carbon-rich surface layer. The specimen 
was then annealed at a higher temperature to es-
tablish an equilibrium solid solution in the metal, 
and the remaining carbide layer was machined from
the surface before any property measurements were 
made. The second technique entailed adding meth-
ane to the hydrogen and tungsten hexafluoride gas 
mixture normally used in tungsten vapor deposition. 
These two techniques were selected in order to 
separate the effect of the additive from that caused 
by any alteration introduced by second-phase nuclea-
tion if the additive is incorporated during deposition. 
Notes: 
1. Background information on the process of tung-
sten vapor deposition is presented in NASA 
Tech Brief 67-10232. A practical application of 
this process in forming large mechanical struc-
tures from refractory metals is presented in 
NASA Tech Brief 71-10212. 
2. Requests for further information may be directed 
to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B72-10454 
Patent status: 
No patent action is contemplated by NASA. 
Source: J. Chin, A. F. Weinberg, and

J. R. Lindgren of

Gulf General Atomic

under contract to

Lewis Research Center

(LEW- 10800) 
Category 04 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Nonmetallic impurities improve mechanical properties of vapor-deposited tungsten

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