Method for the production of a highly stressable component from an α+γ-titanium aluminide alloy for reciprocating-piston engines and gas turbines, especially aircraft engines

Abstract

A method for the production of a highly stressable component from an +-titanium aluminide alloy for reciprocating-piston engines and gas turbines, especially for aircraft engines, characterized in that the alloy used is a TiAl alloy with the following composition (in atom %): 40-48% Al; 2-8% Nb; 0.1-9% of at least one -phase-stabilizing element selected from Mo, V, Ta, Cr, Mn, Ni, Cu, Fe, Si; 0-0.5% B; and a remainder of Ti and smelting-related impurities,
wherein the deformation is carried out in a single stage starting from a preform with a volume distribution varying over the longitudinal axis, wherein the component is deformed isothermally in the -phase region at a logarithmic deformation rate of 0.01-0.5 1/s.

Claims

1. A method for the production of a highly stressable component from an +-titanium aluminide alloy for reciprocating-piston engines and gas turbines, wherein the alloy used is a TiAl alloy with the following composition (in atom %): 40-48% Al; 2-8% Nb; 0.1-9% of at least one -phase-stabilizing element selected from Mo, V, Ta, Cr, Mn, Ni, Cu, Fe, Si; 0-0.5% B; and a remainder of Ti and smelting-related impurities, wherein a deformation is carried out in a single stage starting from a preform with a volume distribution varying over the longitudinal axis, wherein the component is deformed isothermally in the -phase region at a logarithmic deformation rate of 0.01-0.5 1/s.

2. The method according to claim 1, wherein only Mo, V, Ta, or a mixture thereof is present in the alloy as the -phase-stabilizing element.

3. The method according to claim 1, wherein the content of the -phase-stabilizing element is 0.1-2%.

4. The method according to claim 3, wherein the content of the -phase-stabilizing element 0.8-1.2%.

5. The method according to claim 1, wherein a TiAl alloy of the following composition is used: 41-47% Al; 1.5-7% Nb; 0.2-8% of at least one -phase-stabilizing element selected from Mo, V, Ta, Cr, Mn, Ni, Cu, Fe, Si: 0-0.3% B; and a remainder of Ti and smelting-related impurities.

6. The method according to claim 1, wherein a TiAl alloy of the following composition is used: 42-46% Al; 2-6.5% Nb; 0.4-5% of at least one -phase-stabilizing element selected from Mo, V, Ta, Cr, Mn, Ni, Cu, Fe, Si; 0-0.2% B; and a remainder of Ti and smelting-related impurities.

7. The method according to claim 1, wherein an alloy of the following composition is used: 42.8-44.2% Al, 3.7-4.3% Nb 0.8-1.2% Mo; 0.07-0.13% B; and a remainder of Ti and smelting-related impurities.

8. The method according to claim 1, wherein the deformation temperature in the -phase region is 1,070-1,250C.

9. The method according to claim 1, wherein the preform is produced by casting, by metal injection molding (MIM), by additive methods, especially 3D-printing or laser build-up welding, or by a combination thereof.

10. The method according to claim 1, wherein tools of a highly heat-resistant material are used for the deformation.

11. The method according to claim 10, wherein tools of an Mo alloy are used.

12. The method according to claim 10, wherein the tools are protected by an inert atmosphere during the deformation process.

13. The method according to claim 10, wherein the tools used for the deformation are actively heated.

14. The method according to claim 13, wherein the tools are heated by induction.

15. The method according to claim 1, wherein the preform is heated in a furnace, by induction, or by resistance heating prior to the deformation.

16. The method according to claim 1, wherein the deformation is followed by a heat treatment of the formed component.

17. The method according to claim 16, wherein the heat treatment comprises a recrystallization annealing at a temperature of 1,230-1,270 C.

18. The method according to claim 17, wherein the hold time during the recrystallization annealing is 50-100 minutes.

19. The method according to claim 16, wherein, after the recrystallization annealing, the component is cooled to a temperature of 900-950 C. in 120 seconds or less.

20. The method according to claim 19, wherein the heat treatment is followed by a second heat treatment in which the component is cooled to room temperature and then heated to a stabilizing and stress-relieving temperature of 850-950 C., or in that the component is held at a stabilizing and stress-relieving temperature of 850-950 C. without previous cooling.

21. The method according to claim 20, wherein the hold time at the stabilizing and stress-relieving temperature is 300-360 minutes.

22. The method according to claim 20, wherein a cooling of the component to a temperature below 300 C. at a cooling rate of 0.5-2 K/min is then earned out.

23. The method according to claim 22, wherein the cooling rate is 1.5 K/min.

24. A component made of an +-titanium aluminide alloy, for a reciprocating piston engine, an aircraft engine, or a gas turbine, produced according to the method according to claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The preform which is used comprises a volume distribution which varies over the longitudinal axis; that is, a predetermined basic 3-dimensional shape is already present, from which, by means of the single-stage deformation according to the invention, the finished component is forged. This preform is preferably produced by casting, by metal injection molding (MIM), by additive methods (3D-printing, laser build-up welding, etc.) or by a combination of the possibilities just mentioned.

(2) Tools of a highly heat-resistant material are preferably used for the deformation, preferably tools of an Mo alloy. During the deformation process, the tools are advisably protected from oxidation by an inert atmosphere. To keep the tools at the deformation temperature, they are preferably actively heated by induction, for example, or by resistance heating.

(3) The preform is also heated before the deformation process in a furnace, for example, or by induction or by resistance heating.

(4) The deformation is preferably followed by a heat treatment of the formed component to arrive at the required performance characteristics and for this purpose to convert the -phase, which is favorable for the deformation, into a fine-lamellar +-phase by means of a suitable heat treatment. The heat treatment can comprise a recrystallization annealing at a temperature of 1,230-1,270 C. The hold time during the recrystallization annealing is preferably 50-100 minutes. The recrystallization annealing is carried out in the region of the / transformation temperature. If, as also provided by the invention, the component is cooled to a temperature of 900-950 C. in 120 s or even more quickly after the recrystallization annealing, a close interlamellar spacing of the +-phase will be formed.

(5) A second heat treatment is preferably carried out next, in which the component is first cooled to room temperature and then heated to a stabilizing or stress-relieving temperature of 850-950 C. Alternatively, it is also possible to proceed directly from the temperature of 900-950 C. quickly reached after the recrystallization annealing as previously described to the stabilizing and stress-relieving temperature of 850-950 C. The preferred hold time at the stabilizing and stress-relieving temperature, regardless of how this temperature is reached, is preferably 300-360 minutes.

(6) Upon completion of the hold time, the component temperature is preferably lowered to below 300 C. at a defined cooling rate. The cooling rate is preferably 0.5-2 K/min; that is, the cooling proceeds relatively slowly, which serves to stabilize and stress-relieve the microstructure. The cooling rate is preferably 1.5 K/min.

(7) The cooling step in question can be carried out in a liquid such a oil or in air or in an inert gas.

(8) In addition to the method according to the invention, the invention also pertains to a component made of an +-titanium aluminide alloy, especially for a reciprocating-piston engine, an aircraft engine, or a gas turbine, which is produced by a method of the type described here. A component of this type can be, for example, a blade or a disk of a gas turbine or the like.