Molybdenum is substituted for tungsten on an atomic basis in a cobalt-based alloy, S-1, thus enabling the alloy to be formed into various mill products, such as tubing and steels. The alloy is weldable, has good high temperature strength and is not subject to embrittlement produced by high temperature aging

Frank, R. G.

Semmel, J. W., Jr.

English

NASA Technical Reports Server

July 1968	 Brief 68-10253 
NASA TECH BRIEF iw 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
High Temperature Alloy 
The problem: 
Electrical power' generators, aerospace propulsion 
devices, and similar applications, because of repeated 
operation at high temperatures over long periods of 
time, often require, as structural materials, alloys 
which are 'initially strong, weldable, and formable into 
a variety of mill products, such as tubing, sheets, etc. 
These alloys also must be oxidation-resistant at high 
temperature and must be structurally stable, i.e., able 
to retain their mechanical properties after high tem-
perature exposure. Generally, cobalt-based alloys 
have been used in applications of these types. In the 
past, these alloys have had one major deficiency. This 
has been their susceptibility to embrittlement or loss 
of ductility upon prolonged exposure to high tempera-
tures. As structural failure must be avoided, this prob-
lem establishes an environmental limitation on the use 
of prior art alloys. Thus there has been a need for an 
alloy of the type described which could withstand 
prolonged exposure to high temperatures without loss 
of ductility. 
The solution: 
An alloy (S-i) which is capable of being formed 
into various mill products, such as tubing and sheet, 
is capable of being welded, has good high temperature 
strength, and is not subject to embrittlement produced 
by high temperature aging. 
How it's done: 
This was accomplished by utilizing a basic alloy 
and substituting molybdenum for tungsten on an 
atomic basis. It has been found that the high tempera-
ture aging of high strength cobalt-based alloys is 
associated with the precipitation of certain metallic 
carbides and intermetallic compounds of cobalt and 
tungsten. These metallic carbides are generally repre-
sented as M0C and M23C6 while the intermetallic corn-
pounds which appear to 'be most detrimental are 
CoW types. 
By replacing part or all of the tungsten with molyb-
denum, and by limiting the tungsten and carbon con-
tents to less than 7 and less than 0.07 percent, re-
spectively, the characteristics of this alloy (S-i) closely 
match ,
 the characteristics of prior art high-strength 
cobalt-based alloys, but are notable for the absence 
of any tendency to embrittle on heat aging above 
1000°F. 
Forming of an 0.5-inch thick, S-i alloy plate into 
a cylinder was performed at room temperature. Weld-
ing and machining operations were performed with 
ease equal to that normally encountered with standard 
alloys. 
Note: 
The superior ductility retention of this alloy (S-i) 
became more clearly evident after aging for 1000 
hours at 1600°F, when it was found that elongation 
had still remained at about 30 percent. By compari-
son, prior art high-temperature cobalt-based alloys 
have an elongation of about 12 to 19 percent after 
aging for 100 hours and 6 to 11 percent after aging 
for 1000 hours. 
Patent status: 
Title to this invention has been waived under the 
provisions of the National Aeronautics and Space Act 
[42 U.S.C. 2457 (f)], to the General Electric Com-
pany, Missiles & Space Division, Cincinnati, Ohio. 
Source: J. W. Semmel, Jr.,

and R. G. Frank
of General Electric Company 
under contract to
Lewis Research Center

(LEW-10377)
Category 03 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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High temperature alloy

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