Nickel-based alloy with optimized matrix properties

Abstract

The invention relates to a nickel-based alloy having a microstructure with a matrix of -phase and precipitates of -phase. The -phase comprises a percentage by volume of from 50 vol % to 80 vol % in the temperature range of from 1000 C. to 1100 C. The nickel-based alloy comprises 8 to 13 at % aluminum, 3 to 14 at % cobalt, 4 to 12 at % chromium, 0.6 to 8 at % molybdenum, 0 to 6 at % rhenium, 0.5 to 4 at % tantalum, 0.5 to 4 at % titanium, 0.3 to 3.5 at % tungsten, 0 to 4 at % germanium, 0 to 0.6 at % hafnium, 0 to 4 at % ruthenium, balance nickel and unavoidable impurities. The concentrations of molybdenum and tungsten are selected such that the percentage X of molybdenum and tungsten in the -phase, X=0.84 C.sub.Mo+C.sub.W, is greater than 5.5 at % at a temperature of from 1000 C. to 1100 C., C.sub.Mo and C.sub.W being the concentrations of molybdenum and tungsten in at %.

Claims

1. A nickel-based alloy having a microstructure with a matrix of -phase and precipitates of -phase, wherein the -phase comprises from 50 vol % to 80 vol % in a temperature range of from 1000 C. to 1100 C. and the nickel-based alloy comprises, based on a total alloy, from 10 to 13 at % aluminum, from 3 to 14 at % cobalt, from 4 to 12 at % chromium, from 0.6 to 8 at % molybdenum, from 0 to 6 at % rhenium, from 0.5 to 4 at % tantalum, from 0.5 to 4 at % titanium, from 0.3 to 3.5 at % tungsten, from 0 to 4 at % germanium, from 0 to 0.6 at % hafnium, from 0 to 4 at % ruthenium, balance nickel and unavoidable impurities, and wherein a percentage X of molybdenum and tungsten in the -phase, X =0.84 C.sub.Mo +C.sub.W, is greater than 5.5 at % at temperatures in a range of from 1000 C. to 1100 C., C.sub.Mo and C.sub.W representing concentrations of molybdenum and tungsten expressed in at %.

2. The nickel-based alloy of claim 1, wherein a distribution ratio of a concentration of tungsten and or molybdenum in the matrix relative to a respective concentration of tungsten and or molybdenum in the -phase is greater than 1.

3. The nickel-based alloy of claim 1, wherein a distribution ratio of a concentration of tungsten and or molybdenum in the matrix relative to a respective concentration of tungsten and or molybdenum in the -phase is at least 1.5.

4. The nickel-based alloy of claim 1, wherein the alloy has a solidus temperature higher than 1300 C.

5. The nickel-based alloy of claim 1, wherein a -/-mismatch is from 0.15% to 0.25% in a temperature range of from 1000 C. to 1100 C., the -/-mismatch being a difference between lattice constants of the and phases, standardized on an averaged value of the lattice constants.

6. The nickel-based alloy of claim 1, wherein the alloy comprises from 10 to 12 at % aluminum.

7. The nickel-based alloy of claim 1, wherein the alloy comprises from 7 to 12 at % chromium.

8. The nickel-based alloy of claim 1, wherein the alloy comprises from 0.6 to 2 at % molybdenum.

9. The nickel-based alloy of claim 1, wherein the alloy comprises from 2.5 to 3.5 at % tungsten.

10. The nickel-based alloy of claim 1, wherein the alloy comprises germanium.

11. The nickel-based alloy of claim 1, wherein the alloy does not comprise rhenium.

12. A nickel-based alloy, wherein the alloy consists of 10 at % aluminum, 14 at % cobalt, 7 at % chromium, 2 at % molybdenum, 2.5 at % tantalum, 3 at % titanium, balance Ni and unavoidable impurities.

13. The nickel-based alloy of claim 1, wherein the -phase comprises from 60 vol % to 80 vol % in a temperature range of from 1000 C. to 1100 C.

14. The nickel-based alloy of claim 1, wherein the -phase comprises from 70 vol % to 80 vol % in a temperature range of from 1000 C. to 1100 C.

15. The nickel-based alloy of claim 1, wherein the alloy comprises hafnium.

16. The nickel-based alloy of claim 1, wherein the alloy comprises ruthenium.

17. The nickel-based alloy of claim 1, wherein the alloy comprises rhenium.

18. The nickel-based alloy of claim 1, wherein the alloy does not comprise ruthenium.

19. The nickel-based alloy of claim 1, wherein the alloy is present in monocrystalline form.

20. The nickel-based alloy of claim 1, wherein the alloy is present in directionally solidified form.

Description

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(1) The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description making apparent to those of skill in the art how the several forms of the present invention may be embodied in practice.

(2) An alloy including about 10 at % Al, 14 at % Co, 7 at % Cr, 2 at % Mo, 2.5 at % Ta, 3 at % Ti and 2.5 at % W, balance nickel, which has been prepared according to the present invention, has optimized properties in terms of percentage by volume of the -phase, liquidus temperature, mixed crystal hardening, coarsening of the -precipitates and the -/-mismatch. For example, the -/-mismatch has a value of 0.25% and the solidus temperature is 1301 C. The percentage of the -phase is 46 mol % and with values of about 3.5 at % in each case the concentrations of W and Mo in the -phase are high enough for them to contribute significantly to mixed crystal hardening. In addition, the percentages of W and Mo in combination with the selected concentrations of the other alloy components are effective in preventing coarsening of the -phase at high operating temperatures. Particularly through the combination of the properties obtained taking into account the alloy components used, the alloy is extremely well suited for applications at high temperatures, such as in continuous flow machines, and particularly in aircraft turbines.

(3) While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.

(4) To sum up, the present invention provides: 1. A nickel-based alloy having a microstructure with a matrix of -phase and precipitates of -phase, wherein the -phase comprises a percentage by volume of from 50 vol % to 80 vol % in the temperature range of from 1000 C. to 1100 C., and wherein the nickel-based alloy has a chemical composition according to which the nickel-based alloy comprises 8 to 13 at % aluminum, 3 to 14 at % cobalt, 4 to 12 at % chromium, 0.6 to 8 at % molybdenum, 0 to 6 at % rhenium, 0.5 to 4 at % tantalum, 0.5 to 4 at % titanium, 0.3 to 3.5 at % tungsten, 0 to 4 at % germanium, 0 to 0.6 at % hafnium, 0 to 4 at % ruthenium, balance nickel and unavoidable impurities, wherein the chemical composition in terms of the elements molybdenum and tungsten is selected such that the percentage X of molybdenum and tungsten in the -phase, weighted according to the relationship X=0.84C.sub.Mo+C.sub.W, is greater than 5.5 at % at temperatures in the range of from 1000 C. to 1100 C., C.sub.Mo and C.sub.W being the concentrations of molybdenum and tungsten expressed in at %. 2. A nickel-based alloy having a microstructure with a matrix of -phase and precipitates of -phase, wherein the -phase comprises a percentage by volume of from 50 vol % to 80 vol % in the temperature range of from 1000 C. to 1100 C., and wherein the nickel-based alloy has a chemical composition according to which the nickel-based alloy comprises 8 to 13 at % aluminum, 3 to 14 at % cobalt, 4 to 12 at % chromium, 0.6 to 8 at % molybdenum, 0 to 6 at % rhenium, 0.5 to 4 at % tantalum, 0.5 to 4 at % titanium, 0.3 to 3.5 at % tungsten, 0 to 4 at % germanium, 0 to 0.6 at % hafnium, 0 to 4 at % ruthenium, balance nickel and unavoidable impurities, wherein the chemical composition in terms of the element tungsten is selected such that the material parameter , is less than or equal to 0.05, wherein is defined by:

(5) $={\frac{1}{D_{\mathrm{Ni}}}\left[\frac{c_W^{}-c_W}{c_W{D}_W}\right]}^{-1}$ wherein c.sub.w is the concentration of tungsten in the matrix in at %, c.sub.w is the concentration of tungsten in the -phase in at % and D.sub.w is the coefficient of diffusion of tungsten and D.sub.Ni is the coefficient of diffusion of nickel taking into account the solubility differential of the elements between the matrix and the -phase. 3. The nickel-based alloy according to item 2, wherein the chemical composition in terms of the elements molybdenum and tungsten is selected such that the percentage X of molybdenum and tungsten in the -phase, weighted according to the relationship X=0.84C.sub.Mo+C.sub.W, is greater than 5.5 at % at temperatures in the range of from 1000 C. to 1100 C., C.sub.Mo and C.sub.W being the concentrations of molybdenum and tungsten expressed in at %. 4. The nickel-based alloy according to any one of the preceding items, wherein the aluminum percentage is minimized depending on the percentages of germanium, titanium and tantalum, the aluminum percentage being selected particularly in the range of the minimum plus 30%, more particularly plus 20%, preferably plus 10%, when a minimum, average or maximum percentage of the -phase is set. 5. The nickel-based alloy according to item 4, wherein the percentage of germanium, tantalum or titanium is maximized, either for each element individually or taken together, the respective percentage being selected particularly in the range of the maximum minus 30%, more particularly minus 20%, preferably minus 10% when a minimum, average or maximum percentage of the -phase is set. 6. The nickel-based alloy according to any one of the preceding items, wherein the aluminum content is from 9 to 12 at %, particularly from 10 to 12 at %. 7. The nickel-based alloy according to any one of the preceding items, wherein the distribution ratio of the concentration of tungsten and/or molybdenum in the matrix relative to the respective concentration of tungsten and/or molybdenum in the -phase is greater than 1, particularly equal to or greater than 1.5. 8. An article of a nickel-based alloy according to any one of the preceding items. 9. The article according to item 8, wherein the nickel-based alloy is monocrystalline or directionally solidified. 10. The article according to one or both of items 8 and 9, wherein the article is a component, particularly a blade of a continuous flow machine, particularly of a gas turbine or an aircraft engine. 11. A method for producing a nickel-based alloy, particularly according to any one of items 1 to 7, in which in order to determine the chemical composition, in a first step a chemical composition is selected according to which the nickel-based alloy comprises 8 to 13 at % aluminum, 3 to 14 at % cobalt, 4 to 12 at % chromium, 0.6 to 8 at % molybdenum, 0 to 6 at % rhenium, 0.5 to 4 at % tantalum, 0.5 to 4 at % titanium, 0.3 to 3.5 at % tungsten, 0 to 4 at % germanium, 0 to 0.6 at % hafnium, 0 to 4 at % ruthenium, balance nickel and unavoidable impurities, wherein in a second step the chemical composition is selected such that a microstructure with a matrix of -phase and precipitates of -phase is formed in the nickel-based alloy, wherein in a third step the chemical composition is selected such that the -phase has a percentage by volume of from 50 vol % to 80 vol % in the temperature range of from 1000 C. to 1100 C., and wherein in a fourth step the chemical composition is selected in terms of the elements molybdenum and tungsten such that the percentage X of molybdenum and tungsten in the -phase, weighted according to the relationship X=0.84C.sub.Mo+C.sub.W, is greater than 5.5 at % at temperatures in the range of from 1000 C. to 1100 C., C.sub.Mo and C.sub.W being the concentrations of molybdenum and tungsten expressed in at %. 12. A method for producing a nickel-based alloy, particularly according to any one of items 1 to 7, in which in order to determine the chemical composition, in a first step a chemical composition is selected according to which the nickel-based alloy comprises 8 to 13 at % aluminum, 3 to 14 at % cobalt, 4 to 12 at % chromium, 0.6 to 8 at % molybdenum, 0 to 6 at % rhenium, 0.5 to 4 at % tantalum, 0.5 to 4 at % titanium, 0.3 to 3.5 at % tungsten, 0 to 4 at % germanium, 0 to 0.6 at % hafnium, 0 to 4 at % ruthenium, balance nickel and unavoidable impurities, wherein in a second step the chemical composition is selected such that a microstructure with a matrix of -phase and precipitates of -phase is formed in the nickel-based alloy, wherein in a third step the chemical composition is selected such that the -phase has a percentage by volume of from 50 vol % to 80 vol % in the temperature range of from 1000 C. to 1100 C., wherein in a fourth step the chemical composition is selected in terms of the element tungsten such that the material parameter is less than or equal to 0.05, wherein is defined by:

(6) $={\frac{1}{D_{\mathrm{Ni}}}\left[\frac{c_W^{}-c_W}{c_W{D}_W}\right]}^{-1}$ wherein c.sub.w is the concentration of tungsten in the matrix in at %, c.sub.w is the concentration of tungsten in the -phase in at %, D.sub.w is the coefficient of diffusion of tungsten and D.sub.Ni is the coefficient of diffusion of nickel taking into account the solubility differential of the elements between the matrix and the -phase. 13. The method according to item 11, wherein in a further step the chemical composition is selected in terms of the element tungsten such that the material parameter is less than or equal to 0.05, wherein is defined by:

(7) $={\frac{1}{D_{\mathrm{Ni}}}\left[\frac{c_W^{}-c_W}{c_W{D}_W}\right]}^{-1}$ wherein c.sub.w is the concentration of tungsten in the matrix in at %, c.sub.w is the concentration of tungsten in the -phase in at %, D.sub.w is the coefficient of diffusion of tungsten and D.sub.Ni is the coefficient of diffusion of nickel taking into account the solubility differential of the elements between the matrix and the -phase. 14. The method according to any one of items 11 to 13, wherein in the third step, the percentage of aluminum is minimized and the percentage of germanium, titanium and/or tantalum is maximized, either individually or taken together. 15. The method according to any one of items 11 to 14, wherein the percentage of germanium, titanium and/or tantalum either individually or taken together is adjusted such that the percentage of tungsten and/or molybdenum in the matrix, either individually or taken together, is greater, in particular 1.5 times greater than the respective percentage of tungsten and/or molybdenum in the -phase.