Directionally solidified eutectic superalloys for elevated temperature applications Henry, Michael Francis ; et al. [Gigliotti, Michael Francis Xavier JR.]

Directionally solidified eutectic superalloys for elevated temperature applications

Henry, Michael Francis ; et al.

Patent Application Summary

U.S. patent application number 10/743604 was filed with the patent office on 2005-06-23 for directionally solidified eutectic superalloys for elevated temperature applications. Invention is credited to Gigliotti, Michael Francis Xavier JR., Henry, Michael Francis, Jackson, Melvin Robert, Zhao, Ji-Cheng.

Application Number	20050135962 10/743604
Document ID	/
Family ID	34678690
Filed Date	2005-06-23

United States Patent Application	20050135962
Kind Code	A1
Henry, Michael Francis ; et al.	June 23, 2005

Directionally solidified eutectic superalloys for elevated temperature applications

Abstract

A measurement device for measuring and displaying a physical quantity such as a heartbeat, an atmospheric pressure or temperature, or the like, includes a clock for counting time, a physical quantity measuring device for measuring the physical quantity to be displayed, a processor for determining a plurality of values based on the measured physical quantity and the counted time, a first display for simultaneously displaying the plurality of values and a second display for magnifying at least one of the values and displaying the magnified value.

Inventors:	Henry, Michael Francis; (Niskayuna, NY) ; Jackson, Melvin Robert; (Niskayuna, NY) ; Zhao, Ji-Cheng; (Latham, NY) ; Gigliotti, Michael Francis Xavier JR.; (Scotia, NY)
Correspondence Address:	Paul J. DiConza GE Global Research Center 1 Research Circle, K-1 3A60 Niskayuna NY 12309 US
Family ID:	34678690
Appl. No.:	10/743604
Filed:	December 22, 2003

Current U.S. Class:	420/448 ; 148/410; 148/428
Current CPC Class:	C22C 19/057 20130101
Class at Publication:	420/448 ; 148/410; 148/428
International Class:	C22C 019/05

Goverment Interests

[0001] The U.S. Government may have certain rights in the present invention pursuant to U.S. Air Force Prime Contract No. F33615-98-C-2807, Subcontract No. 01-S441-58-05-C1.

Claims

What is claimed is:

1. An alloy, comprising: a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

2. The alloy of claim 1, wherein the Ni-based matrix comprises, on a weight basis, about 0.8-1.8% Ti.

3. The alloy of claim 1, wherein the Ni-based matrix comprises, on a weight basis, about 5-6% Al, up to about 0.01% B, about 0.15-0.3% C, about 11-13% Co, about 3-5% Cr, about 0.8-1.8% Mo, about 4.5-5.6% Re, about 10-12% Ta, about 5-6% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

4. The alloy of claim 1, wherein the Ni-based matrix comprises, on a weight basis, about 5-6.1% Al, up to about 0.01% B, about 0.15-0.3%C, about 6.25-7.25% Co, about 2-3.1% Cr, up to about 1.1% Mo, about 0.1-1% Nb, about 4.75-5.9% Re, about 9-11% Ta, about 0.5-1.5% Ti, about 5.5-6.8% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

5. The alloy of claim 1, further comprising an aligned eutectic reinforcing fibrous phase disposed within the Ni-based matrix, the aligned eutectic reinforcing fibrous phase comprising a carbide.

6. The alloy of claim 5, wherein the carbide comprises substantially TaC.

7. A directionally solidified eutectic superalloy, comprising: a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities; and an aligned eutectic reinforcing fibrous phase disposed within the Ni-based matrix, the aligned eutectic reinforcing fibrous phase comprising a carbide.

8. The directionally solidified eutectic superalloy of claim 7, wherein the Ni-based matrix comprises, on a weight basis, about 0.8-1.8% Ti.

9. The directionally solidified eutectic superalloy of claim 7, wherein the Ni-based matrix comprises, on a weight basis, about 5-6% Al, up to about 0.01% B, about 0.15-0.3% C, about 11-13% Co, about 3-5% Cr, about 0.8-1.8% Mo, about 4.5-5.6% Re, about 10-12% Ta, about 5-6% W, up to about 1% V, up to about 0.2% Hf. and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

10. The directionally solidified eutectic superalloy of claim 7, wherein the Ni-based matrix comprises, on a weight basis, about 5-6.1% Al, up to about 0.01% B, about 0.15-0.3%C, about 6.25-7.25% Co, about 2-3.1% Cr, up to about 1.1%-Mo, about 0.1-1% Nb, about 4.75-5.9% Re, about 9-11% Ta, about 0.5-1.5% Ti, about 5.5-6.8% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

11. The directionally solidified eutectic superalloy of claim 7, wherein the carbide comprises substantially TaC.

12. An article of manufacture comprising an alloy, the alloy comprising: a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf, and up to about 0. 1% Zr, the balance being essentially Ni and incidental impurities.

13. The article of manufacture of claim 12, wherein the Ni-based matrix comprises, on a weight basis, about 0.8-1.8% Ti.

14. The article of manufacture of claim 12, wherein the Ni-based matrix comprises, on a weight basis, about 5-6% Al, up to about 0.01% B, about 0.15-0.3% C, about 11-13% Co, about 3-5% Cr, about 0.8-1.8% Mo, about 4.5-5.6% Re, about 10-12% Ta, about 5-6% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

15. The article of manufacture of claim 12, wherein the Ni-based matrix comprises, on a weight basis, about 5-6.1% Al, up to about 0.01% B, about 0.15-0.3% C, about 6.25-7.25% Co, about 2-3.1% Cr, up to about 1.1% Mo, about 0.1-1% Nb, about 4.75-5.9% Re, about 9-11% Ta, about 0.5-1.5% Ti, about 5.5-6.8% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

16. The article of manufacture of claim 12, wherein the alloy further comprises an aligned eutectic reinforcing fibrous phase disposed within the Ni-based matrix, the aligned eutectic reinforcing fibrous phase comprising a carbide.

17. The article of manufacture of claim 16, wherein the carbide comprises substantially TaC.

18. The article of manufacture of claim 12, wherein the article of manufacture comprises a gas turbine engine component.

19. The article of manufacture of claim 18, wherein the gas turbine engine component comprises a turbine airfoil.

20. An article of manufacture comprising a directionally solidified eutectic superalloy, the directionally solidified eutectic superalloy comprising: a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf. and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities; and an aligned eutectic reinforcing fibrous phase disposed within the Ni-based matrix, the aligned eutectic reinforcing fibrous phase comprising a carbide.

21. The article of manufacture of claim 20, wherein the Ni-based matrix comprises, on a weight basis, about 0.8-1.8% Ti.

22. The article of manufacture of claim 20, wherein the Ni-based matrix comprises, on a weight basis, about 5-6% Al, up to about 0.01% B, about 0.15-0.3% C, about 11-13% Co, about 3-5% Cr, about 0.8-1.8% Mo, about 4.5-5.6% Re, about 10-12% Ta, about 5-6% W, up to about 1% V, up to about 0.2% Hf. and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

23. The article of manufacture of claim 20, wherein the Ni-based matrix comprises, on a weight basis, about 5-6.1% Al, up to about 0.01% B, about 0.15-0.3% C, about 6.25-7.25% Co, about 2-3.1% Cr, up to about 1.1% Mo, about 0.1-1% Nb, about 4.75-5.9% Re, about 9-11% Ta, about 0.5-1.5% Ti, about 5.5-6.8% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

24. The article of manufacture of claim 20, wherein the carbide comprises substantially TaC.

25. The article of manufacture of claim 20, wherein the article of manufacture comprises a gas turbine engine component.

26. The article of manufacture of claim 25, wherein the gas turbine engine component comprises a turbine airfoil.

Description

FIELD OF THE INVENTION

[0002] The present invention relates generally to directionally solidified eutectic superalloys for elevated temperature applications, such as turbine airfoil applications and the like. More specifically, the present invention relates to directionally solidified eutectic nickel (Ni)-based superalloys comprising a matrix containing an aligned carbide reinforcing fibrous phase, such as an aligned tantalum carbide (TaC) reinforcing fibrous phase. The aligned carbide reinforcing fibrous phase provides preferential strengthening in one direction, resulting in enhanced elevated temperature strength, creep resistance, oxidation resistance, and corrosion resistance properties.

BACKGROUND OF THE INVENTION

[0003] Directionally solidified eutectic Ni-based superalloys, such as NiTaC-14B and the like, are well known to those of ordinary skill in the art. For example, NiTaC-14B has been optimized for use in turbine airfoil applications due to its favorable elevated temperature strength, creep resistance, oxidation resistance, and corrosion resistance properties.

[0004] U.S. Pat. No. 3,904,402 (Smashey) broadly discloses Ni-based alloys containing rhenium (Re) and a carbide reinforcing fibrous phase exhibiting favorable elevated temperature strength, creep resistance, oxidation resistance, and corrosion resistance properties. Smashey discloses the preferred use of 4-7 wt. % vanadium (V) for enhancement of the carbide reinforcing fibrous phase, as well as matrix strengthening. Smashey discloses the limited use of molybdenum (Mo), up to about 3 wt. %, however, the use of Mo is preferably omitted. Smashey also discloses the limited use of tungsten (W), between about 2-4 wt. %.

[0005] U.S. Pat. No. 4,284,430 (Henry) discloses a unidirectionally solidified anisotropic metallic composite body exhibiting transverse ductility and elevated temperature strength properties comprising a eutectic Ni-based superalloy containing about 2-9 wt. % Re, less than about 0.8 wt. % titanium (Ti), at least about 2 wt. % Mo, and less than about 1 wt. % V. Embedded in the matrix is an aligned carbide reinforcing fibrous phase, preferably a predominantly TaC reinforcing fibrous phase. Specifically, the Ni-based alloys contain about 2-9 wt. % Re, about 0-0.8 wt. % Ti, about 0-10 wt. % chromium (Cr), about 0-10 wt. % aluminum (Al), about 3-15 wt. % tantalum (Ta), about 0.1-1 wt. % carbon (C), about 0-10 wt. % cobalt (Co), about 0-10 wt. % W, about 0-1 wt. % V, about 2-10 wt. % Mo, and about 0-3 wt. % niobium (Nb) (columbium (Cb)), the balance being essentially Ni and incidental impurities.

[0006] U.S. Pat. No. 4,292,076 (Gigliotti et al.) discloses a unidirectionally solidified anisotropic metallic composite body exhibiting transverse ductility and elevated temperature strength properties comprising a eutectic Ni-based refractory metal-monocarbide-reinforced superalloy containing boron (B). A reinforcing fibrous phase of the eutectic Ni-based superalloy is an aligned carbide reinforcing fibrous phase, preferably one selected from the monocarbides of Ti, V, Nb (Cb), zirconium (Zr), hafnium (Hf), Ta, and alloys or mixtures thereof. Specifically, the Ni-based alloys contain about 0.5-7 wt. % Re, less than about 0.8 wt. % Ti, and at least an amount in excess of an impurity amount of B. Embedded in the matrix is an aligned carbide reinforcing fibrous phase, preferably a predominantly TaC reinforcing fibrous phase. These Ni-based alloys exhibit favorable elevated temperature strength, creep resistance, oxidation resistance, and corrosion resistance properties. More specifically, the Ni-based alloys contain about 0.5-7 wt. % Re, less that about 0.8 wt. % Ti, about 0.001-0.02 wt. % B, about 2-8 wt. % Cr, about 4-7 wt. % Al, about 5-13 wt. % Ta, about 0. 1-0.7 wt. % C, less than about 5 wt. % Co, less than about 6 wt. % W, less than about 0.2 wt. % V, less than about 5 wt. % Mo, less than about 1 wt. % Nb (Cb), less than about 0.15 wt. % Hf, and less than about 0.15 wt. % Zr, the balance being essentially Ni and incidental impurities.

[0007] Conventional Ni-based superalloys lose strength at very high temperatures due to the fact that the gamma prime strengthening phase begins to dissolve. The addition of an aligned carbide reinforcing fibrous phase provides an important strengthening mechanism in this temperature regime. This is especially important for turbine airfoil applications and the like. The directionally solidified eutectic Ni-based superalloys described above, however, still do not demonstrate the elevated temperature strength, creep resistance, oxidation resistance, and corrosion resistance properties desired at these very high temperatures, performing better than their single crystal counterparts in a temperature regime of only about 100 degrees F. greater. More benefit is required given the cost of producing directionally solidified eutectic Ni-based superalloys (due to their relatively slow directional solidification rates) versus their single crystal counterparts. Thus, what is needed is a directionally solidified eutectic Ni-based superalloy that demonstrates enhanced elevated temperature strength, creep resistance, oxidation resistance, and corrosion resistance properties.

BRIEF SUMMARY OF THE INVENTION

[0008] In one embodiment of the present invention, an alloy includes a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf, and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

[0009] In another embodiment of the present invention, a directionally solidified eutectic superalloy includes a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf. and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities; and an aligned eutectic reinforcing fibrous phase disposed within the Ni-based matrix, the aligned eutectic reinforcing fibrous phase comprising a carbide.

[0010] In a further embodiment of the present invention, an article of manufacture comprising an alloy includes a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf. and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities.

[0011] In a still further embodiment of the present invention, an article of manufacture comprising a directionally solidified eutectic superalloy includes a Ni-based matrix comprising, on a weight basis, about 5-7% Al, up to about 0.025% B, about 0.1-0.5% C, about 3-13% Co, about 2-7% Cr, up to about 5% Mo, up to about 1% Nb, about 2-7% Re, about 10-13% Ta, up to about 1.8% Ti, about 4-7% W, up to about 1% V, up to about 0.2% Hf. and up to about 0.1% Zr, the balance being essentially Ni and incidental impurities; and an aligned eutectic reinforcing fibrous phase disposed within the Ni-based matrix, the aligned eutectic reinforcing fibrous phase comprising a carbide.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a plot of the temperature in the liquid in front of the solid/liquid interface for several variations of furnace parameters related to several directional solidification runs;

[0013] FIG. 2 is a photograph of a microstructure produced using the compositions and methods of the present invention, specifically NiTaC-14B with a light gamma prime etch showing the size of the TaC fibers and the matrix gamma and gamma prime phases;

[0014] FIG. 3 is a photograph of a microstructure produced using the compositions and methods of the present invention, specifically NiTaC-14B with a deep gamma prime etch showing the TaC fiber morphology in the grain centers;

[0015] FIG. 4 is a photograph of a microstructure produced using the compositions and methods of the present invention, specifically NiTaC-14B with a medium gamma prime etch showing the TaC fiber morphology in the grain boundaries;

[0016] FIG. 5 is a photograph of a microstructure produced using the compositions and methods of the present invention, specifically NiTaC-14B with a very deep gamma prime etch showing the high aspect ratio of the TaC fibers;

[0017] FIG. 6 is a plot of the cyclic oxidation results associated with the compositions of the present invention using 61-min cycles to 982 degrees C.;

[0018] FIG. 7 is a plot of the creep-rupture results associated with the compositions of the present invention for testing at 871 degrees C. (1600 degrees F.);

[0019] FIG. 8 is a plot of the creep-rupture results associated with the compositions of the present invention for testing at 982 degrees C. (1800 degrees F.);

[0020] FIG. 9 is a plot of the creep curves for the compositions of the present invention for testing at 871 degrees C.;

[0021] FIG. 10 is a plot of the creep curves for the compositions of the present invention for testing at 982 degrees C.; and

[0022] FIG. 11 is a Larson-Miller parameter plot for time-to-failure in the creep-rupture tests described above.

DETAILED DESCRIPTION OF THE INVENTION

[0023] As described above, the elevated temperature viability of directionally solidified eutectic Ni-based superalloys, such as NiTaC-14B and the like, has been established, however, two key issues remain. First, the relatively low value of maximum directional solidification rate makes the cost of producing components, such as turbine airfoils and the like, from such directionally solidified eutectic Ni-based superalloys too high. Second, the properties of NiTaC-14B and the like still fall short of assumed goals. For example, in some applications it is desired that a directionally solidified eutectic Ni-based superalloy demonstrate elevated temperature strength, creep resistance, oxidation resistance, and corrosion resistance properties similar to SC RenN5 in a temperature regime of about 200 degrees F. greater. In general, NiTaC-14B demonstrates a good balance of elevated temperature properties and has been shown to be superior to CoTaC, arts and .gamma./.gamma.'-.delta., and .gamma./.gamma.'-Mo systems.

[0024] Here three alternative directionally solidified eutectic Ni-based superalloys are presented. The compositions of these three directionally solidified eutectic Ni-based superalloys are provided in Table 1.

1TABLE 1 Directionally Solidified Eutectic Ni-Based Superalloy Compositions Weight Percent Element NiTaC-14B AG207 AG208 AG209 Al 5.300 5.917 5.494 5.604 B 0.015 0.004 0.004 0.000 C 0.430 0.270 0.270 0.270 Co 3.800 7.158 11.944 6.764 Cr 3.800 6.681 4.013 2.561 Mo 3.000 1.432 1.338 0.580 Nb 0.000 0.000 0.000 0.534 Ni 61.555 60.537 55.217 61.102 Re 6.400 2.863 5.160 5.314 Ta 11.400 10.366 11.065 10.018 Ti 0.000 0.000 0.000 1.069 W 4.300 4.772 5.494 6.184

[0025] AG207 is designed to yield TaC fibers in a matrix of RenN5, AG208 is designed to yield TaC fibers in a matrix of RenN6, and AG209 is designed to yield TaC fibers in a matrix of CMSX-10Ri. All three compositions are designed to be slightly hypereutectic so as to provide good, aligned fibers when the exact eutectic composition is not known. In general, the compositions may be described as: AG207 (Ni-5.9A1-0.004B-0.27C-7.2Co-6.7Cr-1.4Mo-2.9Re-10.4Ta-4.8W by wt. %), AG208 (Ni-5.5A1-0.004B-0.27C-11.9Co-4Cr-1.3Mo-5.2Re-11.1Ta-5.5W by wt. %), and AG209 (Ni-5.6A1-0.27C-6.8Co-2.6Cr-0.6Mo-0.5Nb-5.3Re-10Ta-1.1Ti-6.- 2W by wt. %).

[0026] A furnace, such as a modified Bridgman apparatus or the like, is used to perform directional solidification. For example, the furnace may use a gradient wound alumina-tube furnace as a heating element with a water-cooled chill on which an ingot sits during withdrawal.

[0027] A total of eighteen directional solidification runs were conducted using the compositions and equipment described above. The conditions and resulting microstructures of the eighteen ingots are provided in Table 2.

2TABLE 2 Conditions and Resulting Microstructures of Directionally Solidified Ingots DS Run Ingot Diameter No. Alloy (mm) DS Rate (cm/hr) Structure 1 NiTaC-14B 9.5 0.64 dendritic 2 NiTaC-14B 9.5 1.27 cellular 3 NiTaC-14B 9.5 0.64 cellular 4 NiTaC-14B 9.5 1.27 cellular 5 NiTaC-14B 22.2 0.64 cellular 6 NiTaC-14B 22.2 0.64 cellular 7 AG208 9.5 0.64 fibrous 8 AG207 9.5 0.64 fibrous 9 AG209 9.5 0.64 cellular 10 NiTaC-14B 22.2 0.64 fibrous 11 AG209 9.5 0.64 fibrous 12 AG207 22.2 0.64 fibrous 13 AG208 22.2 0.64 dendritic 14 AG208 22.2 0.64 dendritic 15 NiTaC-14B 22.2 0.64 fibrous 16 AG208 9.5 0.64 fibrous 17 AG209 9.5 0.64 N/A 18 NiTaC-14B 9.5 1.27 cellular

[0028] The first seven directional solidification runs produced an unacceptable microstructure. Two additional ingots were processed to measure the gradients in the liquid in front of the solid/liquid interface. Thermocouples were immersed in the liquid in front of the solid/liquid interface, lowered to just touch the solid/liquid interface, and then raised up in several increments while measuring temperature and position. These measurements were repeated for several combinations of furnace control parameters. The results are provided in FIG. 1. From these measurements, furnace parameters were selected to maximize the gradient. In general, some of the 22 mm diameter ingots were run with a thermal gradient of about 55 degrees C./cm and some of the 22 mm diameter ingots were run with a thermal gradient of about 100 degrees C./cm. Thermal gradients were not measured for the 9.5 mm diameter ingots.

[0029] A good fibrous microstructure was obtained in at least one ingot of each composition directionally solidified at 0.64 cm/hr. The typical microstructures produced are shown in FIGS. 2-5 for NiTaC-14B. FIG. 2, a cross-section perpendicular to the directional solidification direction, was prepared with a light gamma prime etch and shows the relative sizes of the TaC fibers, the discontinuous gamma prime phase formed upon cooling, and the continuous gamma phase. FIG. 3, a transverse view with a deep matrix etch, shows the morphology of the TaC fibers, each of the TaC fibers having a substantially square cross-sectional shape. FIG. 4, a cross-section perpendicular to the directional solidification direction, was prepared with a medium matrix etch and shows that the morphology of the TaC fibers breaks down to plate-like in the grain boundaries. FIG. 5, a cross-section perpendicular to the directional solidification direction, was prepared with a very deep matrix etch and shows the high aspect ratio of the TaC fibers. Also visible are minor variations in the cross-sectional size that likely result from local variations in the solidification rate.

[0030] Ingots with good, aligned fibers were machined to produce cyclic oxidation pins and creep-rupture bars. It should be noted that a higher gradient may be required to produce an aligned fibrous structure in AG208 and AG209 than is required in NiTaC-14B. The machined cyclic oxidation pins each had a diameter of about 2.5 mm and a length of about 35 mm. The pins were cycled between room temperature and about 982 degrees C. (1800 degrees F.) in a 61-min cycle with 50 min in the 982 degrees C.-furnace and 11 min out of the 982 degrees C.-furnace. The cyclic oxidation data are provided in Table 3.

3TABLE 3 Cyclic Oxidation Results (61-Min Cycles to 982 Degrees C.) NiTaC-14B NiTac-14B (pin 1) (pin 2) AG207 AG208 AG209 Wt. Wt. Wt. Wt. Wt. Hrs Change Hrs Change Hrs Change Hrs Change Hrs Change Cycl. (mg/cm.sup.2) Cycl. (mg/cm.sup.2) Cycl. (mg/cm.sup.2) Cycl. (mg/cm.sup.2) Cycl. (mg/cm.sup.2) 22.4 0.35 22.4 0.32 27.5 0.39 27.5 0.31 25.4 0.45 53.9 0.54 53.9 0.51 51.9 0.39 51.9 0.31 47.8 0.64 82.4 0.54 82.4 0.54 77.3 0.55 77.3 0.38 73.2 0.64 107.8 0.67 107.8 1.02 101.7 0.39 101.7 0.38 148.4 0.55 125.1 0.73 125.1 0.76 170.8 0.47 170.8 0.46 197.2 0.79 197.2 0.86 269.4 0.31 269.4 0.61 296.9 0.98 296.9 1.08 349.7 0.47 349.7 0.54 366.0 0.76 366.0 0.67 448.4 0.55 448.4 0.77 466.7 0.38 466.7 -0.25 519.5 0.47 519.5 0.85 532.7 -0.35 532.7 -0.79 621.2 0.71 621.2 0.85 630.3 -0.79 630.3 -1.08 695.4 0.63 695.4 0.77 701.5 -1.08 701.5 -1.49 796.1 0.71 796.1 0.77 804.2 -1.17 804.2 -1.37 871.3 0.63 871.3 0.77 872.3 -1.78 872.3 -1.81 974.0 0.63 974.0 0.77 976.0 -2.73 976.0 -3.97 1048.2 0.71 1048.2 0.85 1047.2 -3.30 1047.2 -4.29 1145.8 0.79 1145.8 0.61 1139.7 -4.06 1139.7 -5.53 1204.8 0.79 1204.8 0.61 1219.0 -5.08 1219.0 -8.61 1278.0 0.79 1278.0 0.54 1315.6 -6.00 1315.6 -13.51 1353.2 0.71 1353.2 0.46 1384.7 -6.45 1384.7 -15.44 1462.0 -7.43 1462.0 -20.15 1535.2 -7.91 1535.2 -23.67 1632.8 -9.08 1632.8 -26.57 1707.0 -9.65 1707.0 -29.30 1804.6 -10.70 1804.6 -33.46 1879.8 -11.78 1879.8 -37.82 1976.4 -13.11 1976.4 -43.54 2050.6 -15.18 2050.6 -47.73 2151.3 -16.80 2151.3 -52.72 2226.5 -19.43 2226.5 -55.64 2302.8 -22.73 2302.8 -59.77 2380.0 -25.25 2380.0 -62.28 2478.6 -29.15 2478.6 -66.73 2602.7 -33.75 2602.7 -70.32 2701.3 -39.24 2701.3 -74.46 2775.5 -42.64 2775.5 -75.47 2875.1 -49.85 2875.1 -79.48 2970.7 -54.01 2970.7 -81.89 3049.0 -59.37 3049.0 -83.42 3125.2 -64.61 3125.2 -84.27 3223.9 -69.53 3223.9 -85.45 3319.4 -77.37 3319.4 -87.39 3393.6 -81.34 3393.6 -87.80 3470.9 -85.47 3470.9 -89.10 3572.6 -89.50 3572.6 -89.84 3641.7 -90.90 3641.7 -90.69 3740.3 -92.55 3740.3 -92.28 3820.6 -93.25 3820.6 -93.55 3919.3 -93.92 3919.3 -95.40 3990.4 -94.77 3990.4 -96.35 4092.1 -94.90 4092.1 -98.92 4166.3 -95.63 4166.3 -100.00 4267.0 -96.23 4267.0 -101.43

[0031] The data of Table 3 demonstrates that the cyclic oxidation resistance of AG207 and AG208 is superior to that of NiTaC-14B. The cyclic oxidation results are plotted in FIG. 6.

[0032] At least two creep-rupture tests were performed for each of the alloys of the present invention. The duration of the creep rupture tests ranged from about 22 hours to about 546 hours. The results are provided in Table 4.

4TABLE 4 Creep Rupture Results Time Time Time Time Time Strain DS to to to to to at Rate Temp. Stress 0.2% 0.5% 1.0% 2.0% Fail Fail Alloy (cm/hr) (.degree. C.) (MPa) Env. (hr) (hr) (hr) (hr) (hr) (%) AG207 0.64 871 455 air 1.2 9.0 18.9 33.5 109.1 17.1 AG207 0.64 982 283 air 0.9 6.7 15.3 21.3 22.2 3.2 AG208 0.64 871 455 air 2.1 17.5 41.3 92.1 545.6 24.1 AG208 0.64 982 283 air 1.3 17.5 62.2 101.9 177.4 15.4 AG209 0.64 871 455 air 27.3 56.0 99.7 159.2 414.0 17.4 AG209 0.64 982 283 air 4.6 20.7 61.5 142.7 222.5 17.7 NiTaC- 0.64 871 455 air 0.4 7.7 33.7 93.5 195.4 10.4 14B NiTaC- 0.64 982 283 air 0.2 3.8 22.3 94.2 126.1 12.0 14B NiTaC- 0.64 982 255 air 1.3 14.1 82.0 255.8 322.7 13.0 14B AG207 0.64 982 283 argon 1.3 6.0 18.0 31.0 49.9 13.3 AG207 0.64 1093 138 argon 9.6 25.6 42.8 57.6 61.3 12.6

[0033] A comparison of the creep-rupture results is shown in FIG. 7 for testing at 871 degrees C. (1600 degrees F.) and in FIG. 8 for testing at 982 degrees C. (1800 degrees F.). The data of Table 4 demonstrates that the creep-resistance of AG208 and AG209 is superior to that of NiTaC-14B. AG208 is the superior alloy at 871 degrees C./455 MPa (1600 degrees F./66 ksi) and AG209 is the superior alloy at 982 degrees C./283 MPA (1800 degrees F./41 ksi). The creep curves in air are shown in FIGS. 9 and 10 for the testing at 871 degrees C. and 982 degrees C., respectively.

[0034] The data for the alloys of the present invention are compared in FIG. 11 via a Larson-Miller parameter plot for time-to-failure in the creep-rupture tests. In this construction, the Larson-Miller parameter, LMP, is defined as:

LMP=T[20+log.sub.10(t.sub.f)], (1)

[0035] where T=temperature (K) and t.sub.f=time to fail (hr). FIG. 11 also contains the best fit line from data previously gathered for NiTaC-14B and a mathematical construct that represents a 20 degrees C. increase above this data.

[0036] Although the present invention has been illustrated and described with reference to preferred embodiments and examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve similar results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the following claims.

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