Matrix composition, fabrication technique, and fiber diameter were selected to minimize fiber-matrix reaction and preserve composite strength. Composites may be used in place of superalloys where higher strength or greater strength-to-density ratios are advantageous, and will permit higher operating temperatures in particular applications

Petrasek, D. W.

Signorelli, R. A.

English

NASA Technical Reports Server

December 1974
	 B74-10248 
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. 
Advanced Tungsten
Fiber-Reinforced Nickel Superalloy 
.
Fiber-reinforced metals have been investigated exten-
sively in recent years. One of the promising composite 
types being studied is refractory metal fiber-reinforced 
superalloys. NASA is interested in developing these 
particular composites for use in gas turbines where turbine 
blade temperatures may exceed 1366 K (20000 F). A 
tungsten-hafnium-carbon (W-Hf-C) fiber-reinforced 
nickel-base superalloy has now been developed which has 
a 1000-hour rupture strength of 372 MN/m' (54,000 psi) 
at 1366 K (20000 F). This is equivalent to the 100-hour 
rupture strength of the strongest previously developed 
composite, and is nine times as strong as commercially 
available nickel superalloys. The strength-to-density ratio 
of this composite is also greater than for previous alloys, 
and therefore this composite can be considered for 
applications where reduced weight as well as greater 
strength is desired. 
Previous work has shown that the properties of 
fiber-reinforced materials are greatly affected by the 
fiber-matrix reaction. The strength of the composite is 
determined by the retained strength of the fiber; adverse 
fiber-matrix reaction can substantially reduce fiber 
strength. Accordingly, one of the efforts being made to 
improve the strength of composites is to develop stronger 
fibers. The stronger the fiber, the stronger the composite 
for a given degree of fiber-matrix reaction. The tungsten 
alloy fiber, developed for use with the composite de-
scribed above, contained 0.37 weight percent hafnium and 
0.03 weight percent carbon. The fibers are 0.38 mm 
(0.015 in) in diameter and specially drawn for high 
strength. Production of these tungsten alloy fibers was 
previously announced in NASA Tech Brief 73-10003 (see 
Notes 4 and 5). 
Matrix composition, fabrication technique, and fiber 
diameter were selected to minimize fiber-matrix reaction 
and preserve composite strength. The matrix composition 
in weight percent is: nickel 56, tungsten 25, chromium 
15, titanium 2, and aluminum 2. The composite is 
prepared by slipcasting a powdered superalloy-water 
slurry into an array of fibers. The dried slipcasting is 
consolidated by pressing and heating. Fiber content can 
be varied from zero to 80 volume percent to achieve the
desired reinforcement. The 70 volume percent uridirec-
tional-oriented fiber composite has a 100-hour rupture 
strength of 565 MN/m 2
 (82,000 psi) at 1366 K (2000°F), 
and a 1000-hour rupture strength of 372 MN/M 2
 (54,000 
psi) at 1366 K (20000F). 
Notes: 
1. The strongest refractory-alloy-fiber reinforced super-
alloy developed in the past (announced in NASA Tech 
Brief 70-10183) used tungsten fibers containing 2 
weight percent thorium oxide. This composite has a 
100-hour rupture strength of 338 MN/ M2 (49,000 psi) 
at 1366 K (2000°F) and a 1000-hour rupture strength 
of 255 MN/ M2 (37,000 psi) at 1366 K (20000F). 
2. These fiber-reinforced composites may be used in place 
of superalloys where higher strength or greater 
strength-to-density ratios are advantageous, and will 
permit higher operating temperatures in particular 
applications. 
3. Further information is available in the following 
report: 
NASA TN-D-7773 (N74-34939), Stress-Rupture 
Strength and Microstructural Stability of W-Hf-C 
Wire Reinforced Superalloy Composites 
Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812-337-7833 
Reference: B74-10248 
4. Production of the tungsten alloy fibers was previously 
announced in NASA Tech Brief 73-10003, "Produc-
tion of Small Diameter, High-Temperature-Strength 
Refractory Metal Wires." Further information is avail-
able in the following reports: 
NASA TN-D-6881(N72-29561), High-Temperature 
Strength of Refractory-Metal Wires and Considera-
tion for Composite Application 
(continued overleaf) 
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.
https://ntrs.nasa.gov/search.jsp?R=19740000248 2020-03-17T13:59:27+00:00Z
NASA CR-120925 (N72-26399), Development of 
Wire Drawing Processes for Refractory Metal Fibers 
Copies may be obtained at cost from the Aerospace 
Research Applications Center (address above). 
5. The alloy from which the tungsten fiber was produced 
was also developed by NASA and is described in NASA 
Tech Brief 66-10551, " New Tungsten Alloy Has High 
Strength at Elevated Temperatures." 
6. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B74-10248 
Patent Status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
NASA Patent Counsel 
Mail Stop 500-113 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Source: D.W. Petrasek and R.A. Signorelli 
Lewis Research Center 
(LEW-1 2394) 
B74-10248	 Category 04


Advanced tungsten fiber-reinforced nickel superalloy

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