REPAIR METHOD FOR SEALING SEGMENTS

Abstract

Disclosed is a method for repairing a sealing segments, formed at least partially in a monocrystalline fashion, of a flow channel wall of a turbomachine. At first a repair region of the sealing segment is established, independently of defects which may be present, and subsequently a part of a base material of the sealing segment is removed in the repair region. Subsequently a repair coating is deposited epitaxially in the repair region.

Claims

1. A method for repairing a sealing segment, formed at least partially in a monocrystalline fashion, of a flow channel wall of a turbomachine, wherein the method comprises establishing a repair region of the sealing segment, independently of defects which may be present, and subsequently removing a part of a base material of the sealing segment in the repair region, followed by depositing a repair coating epitaxially in the repair region.

2. The method of claim 1, wherein the repair region is defined by a rotor blade running region of the sealing segment, which region a rotor blade of the turbomachine passes over, or at least sweeps past in an imaginary radial extension of the rotor blade, during operation of the turbomachine.

3. The method of claim 2, wherein the repair region extends over the rotor blade running region, the repair region extending beyond the rotor blade running region by at most about 20% of the extent of the rotor blade running region, in a direction which corresponds to a direction over which the repair region is widened beyond the rotor blade region, on each side where the repair region extends beyond the rotor blade region.

4. The method of claim 2, wherein the repair region extends over the rotor blade running region, the repair region extending beyond the rotor blade running region by at most about 10% of the extent of the rotor blade running region, in a direction which corresponds to a direction over which the repair region is widened beyond the rotor blade region, on each side where the repair region extends beyond the rotor blade region.

5. The method of claim 1, wherein a coating on the base material of the sealing segment, provided in the repair region, is removed before a part of the base material is removed in the repair region.

6. The method of claim 1, wherein removal of material is carried out mechanically by grinding and/or milling.

7. The of claim 1, wherein removal of base material of the sealing segment is carried out until no cracks or pores, or only cracks or pores with a diameter or a maximum extent less than or equal to a limit value according to permissible tolerances of a new sealing segment, are contained in the repair region in the base material.

8. The method of claim 1, wherein the repair coating is formed by a repair material different from the base material and/or a repair material identical to the base material.

9. The method of claim 8, wherein the repair coating comprises a repair material different from the base material.

10. The method of claim 8, wherein the repair coating comprises a repair material identical to the base material.

11. The method of claim 1, wherein the repair coating comprises a plurality of sublayers.

12. The method of claim 1, wherein the repair coating is applied by a generative method.

13. The method of claim 12, wherein the repair coating is applied by deposition welding by high-energy beams.

14. The method of claim 13 wherein the high-energy beams comprise laser beams.

15. The method of claim 13 wherein the high-energy beams comprise electron beams.

16. The method of claim 1, wherein the repair coating after application thereof is shaped mechanically.

17. The method of claim 1, wherein the repair coating after application thereof is shaped by material removal.

18. The method of claim 8, wherein the repair coating comprises a plurality of sublayers.

19. The method of claim 9, wherein the repair coating comprises a plurality of sublayers.

20. The method of claim 10, wherein the repair coating comprises a plurality of sublayers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the appended drawings, purely schematically

[0026] FIG. 1 shows a partial section through a turbomachine with a guide vane and rotor blade pair,

[0027] FIG. 2 shows a cross section through a sealing segment,

[0028] FIG. 3 shows a plan view of a sealing segment, and

[0029] FIG. 4 shows in Subfigures a) to f) the various method steps of an exemplary embodiment of the repair method according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0030] 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.

[0031] FIG. 1 shows a partial section through a turbomachine, for example an aircraft engine, having a shaft 1 that is enclosed annularly by a housing 2, although only a part above the symmetry line or rotation axis (represented by dashes) of the shaft 1 is shown in FIG. 1. A multiplicity of rotor blades 4 are arranged circumferentially around the shaft 1 next to one another in a rotor blade row, and in a plurality of rotor blade rows, on the shaft 1, only one rotor blade row having a rotor blade 4 being shown in FIG. 1. Arranged next to the rotor blade 4, there is a guide vane 3 which is fastened on the housing 2, a plurality of rotor blades in turn being arranged circumferentially around the rotation axis next to one another in a plurality of rotor blade rows. The guide vanes 3 are connected in a fixed manner to the housing 2, while the rotor blades 4 rotate with the shaft 1 during rotation of the latter.

[0032] The housing 2, which has a cylindrical base shape in the highly simplified representation of FIG. 1, may be constructed from a multiplicity of components, and in particular from an outer and inner shell. The components of the inner shell, which are exposed to high temperatures by the gas flowing past, may be at least partially formed from monocrystalline material so as to thus provide sufficient strength at high temperatures.

[0033] The housing 2 may comprise a plurality of sealing segments 9, which may be arranged successively as housing components circumferentially around the rotation axis of the turbomachine and next to one another in the axial direction. In FIG. 1, only cross sections of a few segments 9 can be seen for the sake of simplicity.

[0034] In order to avoid flow losses between the housing 2 and the tips of the rotor blades 4 on the one hand, and the free ends of the guide vanes 3 and the shaft 1 on the other hand, so-called seals are arranged in these regions, specifically on the one hand a so-called outer air seal in the region of the tips of the rotor blades 4 and an inner air seal in the region of the free ends of the guide vanes 3. The outer air seal is arranged on a corresponding sealing segment 9.

[0035] The seals respectively consist of sealing pairs matched to one another, for example a tip armoring 5 on the free ends of the rotor blades 4 with a so-called running-in coating 8, which is arranged opposite the free ends of the rotor blades 4 on the sealing segment 9 of the housing 2.

[0036] Since the gap between the free ends of the rotor blades 4 and the housing 2 may vary depending on the operating conditions, the corresponding seal is configured in such a way that tip armoring 5 grinds onto the running-in coating 8, or grinds into it, in order to ensure optimal sealing. Correspondingly, so-called sealing fins (not shown) may be provided on the tip armoring 5, which fins are each formed as protruding webs and grind defined grooves into the running-in coating 8.

[0037] Correspondingly, armoring 6 with a running-in coating 7 may also be provided at the so-called inner air seal, in which case the arrangement of the armoring 6 and the running-in coating 7 may he carried out optionally on the rotor, i.e. the shaft 1, or the stator, i.e. the guide vane 3. This also applies for the outer air seal.

[0038] FIG. 2 shows a sealing segment 9 in cross section. The sealing segment 9 comprises a body made of a base material 10, on which the running-in coating 8 is arranged. FIG. 3 shows the sealing segment 9 in a plan view.

[0039] The sealing segment is shown in cross section in FIG. 4, the various repair steps of the repair method according to the invention being shown in the Subfigures a) to f). Subfigure a) of FIG. 4 shows the starting state of a worn sealing segment 9, in which two grooves 11, which are caused for example by sealing fins of a corresponding rotor blade 4, are ground into the running-in coating 8.

[0040] Because of the thermal load of the sealing segment during operation, and the resulting diffusion processes inside the material, pores 12 have been formed, which may be present both in the running-in coating 8 and in the base material 10. Furthermore, the thermomechanical loading of the sealing segment 9 has given rise to damage by cracks 13, which may likewise be present both in the running-in coating 8 and in the base material 10. In the sealing segment 9 shown in FIG. 3 and FIG. 4, the width B1 of the running-in coating 8 corresponds to the rotor blade running region, which is defined by the rotor blades 4 passing over or grinding in on the sealing segment.

[0041] Subfigure b) of FIG. 4 shows the state after removal of the running-in coating 8. The running-in coating 8 may, for example, be ground or milled off from the sealing segment 9.

[0042] In addition, base material 10 is removed in a repair region, which has the width B2 that is greater than the width B1 of the running-in coating 8, or of the rotor blade running region, in which case suitable mechanical processing methods such as milling or grinding may again be used.

[0043] In the repair region 14, enough base material 10 is removed so that as far as possible all pores 12 and cracks 13 are removed. Only small-dimensioned residues of cracks 13 and/or pores (not shown), which can be healed by the subsequent epitaxial deposition of a repair coating 15 onto the monocrystalline base material 10, may remain in the base material 10, as is shown in FIG. 4c).

[0044] After removal of the running-in coating 8 and of the base material 10 in the repair region 14, a repair coating 15 is applied in this region by a generative method, for example deposition welding, the application being carried out in such a way that the material of the repair coating 15 grows epitaxially on the monocrystalline base material 10, so that, when the same material is used for the repair coating 15 as for the base material 10, a monocrystalline body is formed. When a different material to the base material 10 is used for the repair coating 15, a material will be selected which has a similar lattice structure and similar lattice constants, so that a quasi-monocrystalline structure can be formed by the epitaxial growth.

[0045] As can be seen in Subfigure d) of FIG. 4, the repair coating 15 may be applied with an overdimension, since mechanical shaping of the repair coating 15, during which excess material of the repair coating 15 is removed by material-removal processing, is subsequently carried out. The corresponding result is represented in Subfigure e) of FIG. 4. A running-in coating 8 may in turn be provided on a correspondingly repaired base body of the sealing segment 9, as is represented in Subfigure f) of FIG. 4, so that, after the repair, an entirely new sealing segment 9 is provided, which has a running-in coating 8 and can be used again in the turbomachine.

[0046] Although the present invention has been described in detail with the aid of the exemplary embodiment, it is clear to the person skilled in the art that the invention is not restricted to this exemplary embodiment, and rather that variants are possible in that individual features may be omitted or different combinations of features may be implemented, so long as the protective scope of the appended claims is not departed from. In particular, the present disclosure comprises all combinations of the proposed individual features.

DEFINITIONS

[0047] In the present description, axial and radial directions refer to the rotation axis of the turbomachine, so that an axial direction is intended to mean the direction in which the rotation axis of the turbomachine extends, while a radial direction is intended to mean the direction which extends away from the rotation axis.

LIST OF REFERENCE NUMBERS

[0048] 1 shaft [0049] 2 housing [0050] 3 guide vane [0051] 4 rotor blade [0052] 5 armoring [0053] 6 armoring [0054] 7 running-in coating [0055] 8 running-in coating [0056] 9 sealing segment [0057] 10 base material or base body [0058] 11 running-in groove [0059] 12 pore [0060] 13 crack [0061] 14 repair region [0062] 15 repair coating