Al-rich high-temperature TiAl alloy

Abstract

The present invention relates to a TiAl alloy for use at high temperatures which has aluminum and titanium as main constituents. The TiAl alloy has an aluminum content of greater than or equal to 50 at. % and a matrix of -TiAl and at least one phase of Al and Ti incorporated in the -TiAl matrix which is different from -TiAl, as well as depositions of oxides and/or carbides and/or silicides. In addition, the invention relates to a method for producing the alloy and to the use of the alloy for components of turbo-machines, in particular aircraft engines.

Claims

1. A TiAl alloy for use at high temperatures, wherein the alloy comprises aluminum and titanium as main constituents, has an aluminum content of greater than or equal to 50 at. %, and comprises a matrix of -TiAl and at least one phase of Al and Ti incorporated in the -TiAl matrix which is different from -TiAl and comprises Al and Ti, as well as depositions of oxides and/or carbides and/or silicides.

2. The TiAl alloy of claim 1, wherein the alloy comprises up to 75 at. % of aluminum.

3. The TiAl alloy of claim 1, wherein the alloy comprises up to 65 at. % of aluminum.

4. The TiAl alloy of claim 1, wherein the alloy comprises up to 60 at. % of aluminum.

5. The TiAl alloy of claim 1, wherein the -TiAl matrix occupies at least 50 vol. % of a microstructure of the alloy.

6. The TiAl alloy of claim 1, wherein the -TiAl matrix has a closed or net-like or globular structure.

7. The TiAl alloy of claim 1, wherein the phases of Al and Ti which are different from -TiAl comprise -phase and/or one or more Al-rich intermetallic phases.

8. The TiAl alloy of claim 7, wherein the Al-rich intermetallic phases comprise at least one of Al.sub.3Ti and Al.sub.2Ti.

9. The TiAl alloy of claim 1, wherein the depositions comprise at least ZrO.sub.2 and/or Y.sub.2O.sub.3.

10. The TiAl alloy of claim 1, wherein the alloy comprises one or more of Nb, Mo, W, Co, Cr, V, Zr, Si, C, Er, Gd, Hf, Y, B.

11. The TiAl alloy of claim 1, wherein the alloy comprises the following elements in the indicated percentages: TABLE-US-00002 W from 0 to 3 at. % Si from 0.2 to 0.35 at. % C from 0 to 0.6 at. % Zr from 0 to 6 at. % Y from 0 to 0.5 at. % Hf from 0 to 0.3 at. % Er from 0 to 0.5 at. % Gd from 0 to 0.5 at. % B from 0 to 0.2 at. %.

12. The TiAl alloy of claim 1, wherein the alloy comprises the following elements in the indicated percentages: TABLE-US-00003 Nb from 4 to 25 at. % and/or Mo from 1 to 10 at. % and/or W from 0.5 to 3.0 at. % and/or Co from 0.1 to 10 at. % and/or Cr from 0.5 to 3.0 at. % and/or V from 0.5 to 10.0 at. %.

13. A method for producing the TiAl alloy of claim 1 or a component produced from the alloy, wherein the method comprises (i) producing the alloy by melt metallurgy and drawing it in monocrystalline form or casting it in polycrystalline form, or (ii) producing the alloy at least partially by powder metallurgy.

14. The method of claim 13, wherein according to (ii) at least portions of alloying constituents are alloyed mechanically.

15. The method of claim 13, wherein the alloy is melted by arc melting in vacuo or under a protective gas atmosphere and/or is cast by centrifugal casting.

16. The method of claim 13, wherein the alloy is subjected to hot isostatic pressing and/or isothermal forging after it has been cast or produced by powder metallurgy.

17. The method of claim 13, wherein the method further comprises subjecting the alloy and/or a component produced from the alloy to a single- or multi-step heat treatment.

18. A component of a turbomachine, wherein the component comprises the alloy of claim 1.

19. The component of claim 18, wherein the component is an aircraft engine.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The only FIGURE shows, purely schematically, an exemplary embodiment of a structure of a TiAl alloy according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(2) 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 in combination with the FIGURE making apparent to those of skill in the art how the several forms of the present invention may be embodied in practice.

(3) The FIGURE shows a microstructure of a TiAl alloy according to the invention in a purely schematic representation.

(4) FIG. 1 shows, in a sectional view, globular -TiAl grains 1 which form the -TiAl matrix. Carbides 4 and silicides 5 as well as oxides 6 are deposited at some of the grain boundaries and stabilize the grain boundaries. Within the -TiAl grains, depositions of intermetallic phases, such as Al.sub.3Ti and Al.sub.2Ti, are to be seen, which are in the form of globular depositions 3 or in the form of lamellar depositions 2 in the -TiAl grains or between the -TiAl grains 1.

(5) Oxide particles 7, for example in the form of yttrium oxide or zirconium oxide, which are distributed in finely dispersed form and have a mean or maximum particle size in the range of less than or equal to 1 m, preferably in the nanometer range, are further incorporated in the -TiAl grains.

(6) Such a material offers a balanced property profile with a low specific weight, high mechanical strength, sufficient ductility and good high-temperature behavior, with high creep resistance and good oxidation resistance, in particular for components which are subjected to high mechanical stresses at high temperatures, such as, for example, components of gas turbines or aircraft engines.

(7) 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.

LIST OF REFERENCE NUMERALS

(8) 1 -TiAl grains of the -TiAl matrix

(9) 2 Lamellar TiAl depositions

(10) 3 Globular TiAl depositions

(11) 4 Carbides

(12) 5 Silicides

(13) 6 Oxides

(14) 7 Oxides (distributed in finely dispersed form)