Ductile compensation layer for brittle components

Abstract

Disclosed is a blade element of a turbomachine, in particular of a gas turbine, which comprises a fastening element (10) with which the blade element is arranged in a receptacle (11) of the turbomachine. in the region of the fastening element, the blade element has a core region (18) and an envelope region (19) which at least partially envelops the core region. The core region is formed from a blade base material which is more brittle than the envelope material of the envelope region, and the envelope region is formed by a coating. The envelope material is a blade base material which has been modified to achieve a higher ductility or is a pseudoelastic or superelastic material.

Claims

1. A blade element of a turbomachine, wherein the blade element comprises a fastening element with which the blade element is arranged in a receptacle of the turbomachine and comprises, in a region of the fastening element, a core region and an envelope region which at least partially envelops the core region, the core region being formed of a blade base material which is more brittle than an envelope material of the envelope region and the envelope region being formed by a coating, and wherein the envelope material is the blade base material which has been modified to achieve a higher ductility or is a pseudoelastic or superelastic material.

2. The blade element of claim 1, wherein the envelope material is formed by a pseudoelastic or superelastic alloy based on CoNiAl, CoNiGa, AlNiCo or NiMnGa.

3. The blade element of claim 2, wherein the envelope material is formed by Ni.sub.2MnGa.

4. The blade element of claim 3, wherein a wear-resistant layer is applied to the envelope region.

5. The blade element of claim 4, wherein the wear-resistant layer comprises Ti60(Mn,Fe,Cr)25Si5O10.

6. The blade element of claim 4, wherein the wear-resistant layer comprises Ti45Zr38Ni17.

7. The blade element of claim 4, wherein the wear-resistant layer comprises Al35Ni20Co20.

8. The blade element of 2, wherein the envelope material is formed by Al35Ni20Co20.

9. The blade element of claim 8, wherein a wear-resistant layer is applied to the envelope region.

10. The blade element of claim 9, wherein the wear-resistant layer comprises Ti60(Mn,Fe,Cr)25Si5O10.

11. The blade element of claim 9, wherein the wear-resistant layer comprises Ti45Zr38Ni17.

12. The blade element of claim 9, wherein the wear-resistant layer comprises Al35Ni20Co20.

13. The blade element of claim 1, wherein a wear-resistant layer is applied to the envelope region.

14. The blade element of claim 13, wherein the wear-resistant layer is formed by a pseudoelastic or superelastic alloy or by a material based on quasi-crystals.

15. The blade element of claim 13, wherein the wear-resistant layer comprises Ti60(Mn,Fe,Cr)25Si5O10.

16. The blade element of claim 13, wherein the wear-resistant layer comprises Ti45Zr38Ni17.

17. The blade element of claim 13, wherein the wear-resistant layer comprises Al35Ni20Co20.

18. The blade element of claim 1, wherein the envelope region has a porous form.

19. The blade element of claim 1, wherein the envelope region has a compact form.

20. The blade element of claim 1, wherein the fastening element is a blade root and the receptacle is a blade root receptacle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings show in a purely schematic manner in

(2) FIG. 1 a cross section through a blade root of a blade of a turbomachine which is arranged in a blade receptacle in a disk of the turbomachine;

(3) FIG. 2 a partial sectional illustration through a surface region of the blade root shown in FIG. 1; and in

(4) FIG. 3 a sectional view through a surface region of a blade root according to a further embodiment.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(5) 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 drawings making apparent to those of skill in the art how the several forms of the present invention may be embodied in practice.

(6) FIG. 1 shows a schematized cross section through a fastening element 10, in the form of a blade root, of a gas turbine rotor blade, wherein the fastening element 10 of the gas turbine rotor blade is positioned in a receptacle portion 11 (blade root receptacle) of a rotor 12. During operation, the gas turbine blade rotates together with the rotor in the direction of the arrow 13 shown in FIG. 1.

(7) The fastening element 10 of the gas turbine rotor blade has an outer contour 14 shaped like a fir tree, with an inner contour 15 of the receptacle portion 11 being adapted to the outer contour 14 of the fastening element 10. The fastening element 10 contoured like a fir tree has protrusions 16, which engage into correspondingly contoured recesses 17 of the receptacle portion 11.

(8) Within the context of the present invention, the fastening element 10 of the gas turbine rotor blade is formed from two functionally separated regions, specifically from a core region 18 and an envelope region 19 enveloping the core region 18 on all sides. The core region 18 is accordingly embedded in the envelope region 19.

(9) According to the invention, the core region 18 of the fastening element 10 is formed from a relatively brittle and also relatively light material having a relatively low ductility. Thus, the core region 18 can be formed from a ceramic material or from an intermetallic material. When the core region 18 is formed from an intermetallic material, it is preferably formed from a TiAl material.

(10) According to the invention, the envelope region 19 in which the core region 18 is embedded is formed from a material having a relatively high ductility. The envelope region 19 can be formed from a metallic material which is matched to the metallic material of the rotor 12, i.e., has a similar but not identical material composition to the rotor. Thus, for example, the envelope region 19 can be formed from pseudoelastic or superelastic materials.

(11) In the exemplary embodiment shown in FIG. 1, the envelope region 19 is formed with one layer or one ply. Alternatively, the envelope region can also be formed with a plurality of layers or a plurality of plies.

(12) In the exemplary embodiment shown in FIG. 1, the envelope region 19 has a relatively thick form and is applied to a non-net-shape outer contour of the core region 18. The envelope region 19 of the fastening element 10 is machined in such a manner that the outer contour 14 thereof, which defines the outer contour of the fastening element 10, is matched to the inner contour 15 of the receptacle region ii of the rotor 12. In this case, the core region 18 of the fastening element 10, which is formed from the relatively brittle and also relatively light material, can have any desired contour. The envelope region 19, which is formed from a metallic material, can be adapted to the desired net shape using common machining processes.

(13) In contrast thereto, it is also possible that the core region 18 already has a net-shape outer contour and, in terms of its dimensions, is reduced merely by the thickness of the envelope region 19. In this case, the envelope region 19 has a relatively thin form, since in this case no net-shape machining thereof is required.

(14) In the exemplary embodiment of FIG. 1, it has been assumed that the fastening element 10 is a blade root of a gas turbine rotor blade. As already mentioned, the invention is not restricted, however, to the use on rotating rotor blades, but instead the invention can also be used on stationary guide vanes. Stationary guide vanes of this type can have a plurality of hook-like, flange-like or journal-like fastening elements, it then being preferable for each fastening element of the stationary guide vanes to be formed as described with reference to FIG. 1 for a rotor blade.

(15) Alternatively, instead of the surface region of the blade root, it is also possible for the surface region of the blade receptacle to be coated with the ductile material. In this case, in the event of corresponding stresses the surface or coating of the blade root receptacle takes on the reduction of stress peaks in that the blade root presses into the ductile surface or coating of the blade root receptacle.

(16) FIGS. 2 and 3 show in a purely schematic manner a corresponding structure of a surface region of the blade root or of the surface of the blade root receptacle. Reference sign 1 denotes the base material to which a compensation layer 2 made of a ductile material is applied. If the base material 1 is formed from a TiAl material, the compensation layer 2 can likewise be formed from a TiAl material, which, however, has a higher ductility than the base material 1. This can he achieved, for example, by an altered chemical composition of the TiAl material or by an appropriate selection of the deposition conditions for the TiAl material and of a suitable set microstructure.

(17) Moreover, the compensation layer can be formed from superelastic or pseudoelastic materials based on the system CoNiAl, CoNiGa, AlNiCo or NiMnGa. In particular, the compensation layer can be formed from the intermetallic phase Ni.sub.2MnGa.

(18) The compensation layer 2 can be deposited in porous form or can be in the form of a compact layer, in which virtually no pores or free spaces are formed. In the case of a porous layer, a lubricant can be applied to the surface, said lubricant reducing the friction between the blade root and the blade root receptacle and therefore counteracting wear.

(19) Given a compact form of the compensation layer 2, a wear-resistant layer 3 can be provided, as shown in FIG. 3. Various possibilities come into consideration for the wear-resistant layer, it being possible in particular to use wear-resistant layers made of quasi-crystalline materials such as, for example, Te60(Mn,Fe,Cr)25Si5O10, Ti45Zr38Ni17 or Al65Ni20Co15. The use of Al65Ni20Co15 for the compensation layer 2 and the wear-resistant layer 3 is advantageous in particular, since a material of this type can have superelastic properties and also affords wear protection in the case that a quasi-crystalline structure has been set. This also applies to further materials based on AlNiCo. A modification of alloys based on AlNiCo therefore makes it possible to achieve an advantageous combination of very similar layers with wear-resistant properties where a quasi-crystalline structure has been set and the provision of a high ductility by superelastic or pseudoelastic effects. This merely requires minor modifications to the chemical composition, such that corresponding layers bond readily to one another on account of their similar chemical composition.

(20) It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. 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.