Partial recoating of a ceramic layer system, and ceramic layer system

Abstract

The invention relates to a process for locally recoating a ceramic layer system (1), wherein first a recess (16) is produced in a ceramic layer system (1) by means of a layer removal process, a ceramic coating being locally completely removed and a metal coating being locally at least partially removed, a metal adhesion-promoter layer (7) then being applied, and preferably a protection means (19) being used around the recess (16), and, after the metal adhesion-promoter layer (7') has been completely applied or repaired, a slope is produced within the recess (16) in its edge regions by the incremental removal of material of the ceramic layer (10) around the recess (16), and then in the last step new ceramic material (31) is applied in the modified recess (16').

Description

[0001] Partial recoating of a ceramic layer system and ceramic layer system

[0002] The invention relates to the partial re-coating of a ceramic layer system and a ceramic layer system.

[0003] Ceramic layer systems comprising a metallic substrate with at least one ceramic layer as protection against high temperatures and / or corrosion are known and are used in the chemical industry, in furnaces and in turbines, in particular gas turbines.

[0004] An exemplary ceramic layer is disclosed in EP 1 707 653 B1.

[0005] Due to wear and tear during use, sometimes only local wear of a ceramic layer is present.

[0006] The current approach involves removing the entire component and recoating it completely. Particularly with coating systems consisting of a metallic base layer and a ceramic top layer, it is more labor-intensive to completely remove and reapply these metal and ceramic layers.

[0007] Metallic and ceramic layers are applied by spraying.

[0008] US 6,274,193 Bl discloses a repair in which the metallic coating is infused.

[0009] It is therefore an object of the invention to solve the above-mentioned problem. This object is achieved by a method according to claim 1 and a ceramic layer system according to claim 4.

[0010] The subclaims list further advantageous measures which can be combined as desired to achieve further advantages.

[0011] Figures 1 and 6 show a ceramic screening system and a process is shown schematically in Figures 2 to 5.

[0012] A ceramic layer system 1 is shown schematically in Figure 1.

[0013] The ceramic layer system 1 comprises at least: a metallic substrate 4, which in the case of turbine components is a nickel- or cobalt-based superalloy.

[0014] For better bonding due to the different thermal expansion coefficients of metal and ceramic, a metallic adhesion promoter layer 7 is present, which forms an oxide layer (TGO) in use, which serves to bond a ceramic layer 10.

[0015] The metallic adhesion promoter layer 7 is preferably based on a NiCoCrAlY alloy.

[0016] The metallic adhesion promoter layer 7 preferably represents a coating, i.e. not a pure diffusion layer.

[0017] The ceramic layer 10 can be formed in one layer or two layers, i.e., comprise different materials in a two-layer system.

[0018] Examples of this are an underlying ceramic layer of partially stabilized zirconia PSZ such as 7YSZ and an upper ceramic layer of fully stabilized zirconia FSZ such as 20YSZ.

[0019] Due to wear, the layer thickness of the TBC has been locally reduced or is no longer present (not shown). Therefore, the ceramic layer 10 is locally removed by means of a decoating process, in particular by means of a laser 13 (Fig. 2).

[0020] Also preferably, the metallic adhesion promoter layer 7 is removed locally (Fig. 2).

[0021] Waterjet removal with / without abrasive material or other methods such as laser irradiation or laser beams guided in the waterjet can also be used.

[0022] Preferably, no material of the substrate 4 is removed.

[0023] The ceramic layer system 1 ' after the local removal of the ceramic layer 10 according to Figure 1 then has a depression 16.

[0024] In the next step (Fig. 3), a metallic bonding layer is locally restored in the depression 16 by a coating system 22, so that a repaired bonding layer 7' is formed. The same material as in the original layer system 1 can be used, but it is not required.

[0025] Likewise, material removed from the substrate 4 can be compensated for by the metallic adhesion promoter layer in the recess 16, if necessary.

[0026] During the coating with the metal, the remaining surface of the ceramic layer system 1 ' is at least partially provided with a protection 19 ( Fig . 3 ), but at least around the depression 16 .

[0027] However, it cannot be completely prevented that metal is cut off from the metallic coating material around the edge area of ​​the recess 16.

[0028] In any case, there is metallic material on the side surface 17 of the recess 16 of the remaining ceramic layer 10', which must be removed.

[0029] Then, according to Figure 4, the protection 19 is removed and in the next step the existing ceramic of the ceramic layer 10' of the ceramic layer system 1'' is removed around the depression 16 in a wedge-shaped or step-like manner, so that no metallic material is left on the existing ceramic coating 10'' of the ceramic layer system 1''.

[0030] In a final step, ceramic material 31 is applied in the modified depression 16' by another or the same coating system 22, so that the ceramic layer system 11 thus produced is comparable to the original ceramic layer system 1 (Fig. 1).

[0031] The area 34 of the ceramic coating that fills the recess 16' can be made of the same material or a different material is deliberately used to facilitate the use of the ceramic layer system 1 IV to improve .

[0032] Different material here means that at least one component of the ceramic differs by at least 5%, in particular at least 10%, or that a different stabilizer or an additional stabilizer for stabilized zirconium oxide is used.

[0033] Preferably, a segmented coating is present for the ceramic layer 11, for example made of PSZ / FSZ, such as 8YSZ or 8YSZ / 20YSZ (Fig. 5).

[0034] Preferably, a different microstructure, such as in particular highly porous material 34' instead of a segmented microstructure, is then applied for the ceramic layer part 34' in the depression 16' (Fig. 6).

[0035] This material 34' in the trough 16' preferably has a porosity greater than 12%, in particular greater than 18%, and is in any case 5%, absolutely 10%, larger than the surrounding layer regions 10L, 10R (Fig. 6).

[0036] Preferably, the ceramic layer 10 represents a segmented layer of yttria stabilized zirconium oxide and the layer part 34 ' preferably comprises yttria and additionally zirconium oxide stabilized with ytterbium oxide.

[0037] Likewise, the ceramic layer can have different thicknesses for the ceramic layer in an extension direction 12 of the ceramic layer system 11, so that different thicknesses are also used for the region 34', in which, for example, a continuous transition from one layer thickness 10L to the thinner layer thickness 10R is created or, as shown in Figure 6, a gradation preferably takes place centrally between the two different layer thickness regions 10L, 10R.

[0038] Thinner generally means that the layer thickness is at least 5%, in particular at least 10% thicker or thinner.

Claims

Patent claims 1. A method for the local recoating of a ceramic layer system (1), in which a depression (16) is first created in a ceramic layer system (1) by means of a decoating method, wherein at least one ceramic coating is completely removed locally and optionally a metallic coating is at least partially removed locally, wherein then optionally a metallic adhesion promoter layer (7) is applied locally, wherein preferably a protection (19) is used at least on the surface of the ceramic layer (1') around the depression (16), and after the complete application or repair of the metallic adhesion promoter layer (7'), a bevel of the ceramic layer (1'') is created within the depression (16) in its edge regions by material of the ceramic layer (10'') around the depression (16) being gradually removed, and then, in the last step, new ceramic material (31) is applied into the modified depression (16').

2. The method according to claim 1, wherein a microstructure of the layer (11) is produced for the new region (34, 34') which is different from the microstructure of the ceramic layer (10) of the ceramic layer system (1), preferably the ceramic layer (10) is a segmented layer and the new region (34, 34') has a significantly higher porosity and / or is not segmented.

3. Method according to claim 1 or 2, wherein the material of the layer (11) for the rich (34) a material is used which is different from the material of the ceramic layer (10) of the ceramic layer system (1), preferably the ceramic layer (10) represents a segmented layer of yttrium oxide stabilized zirconium oxide and a ceramic layer part (34, 34') in the depression (16') has yttrium oxide and ytterbium oxide stabilized zirconium oxide.

4. Ceramic layer system (11, 111), in particular produced according to a method according to one or more of claims 1, 2 or 3, in which the ceramic layer system (11) has three different regions (10L, 34, 34', 10R), wherein a central region (34, 34') between two regions (10L, 10R) has a significantly higher porosity and / or a significantly different material than the surrounding regions (10L, 10R).

5. Ceramic layer system according to claim 4, wherein the region (34') has a stepped or decreasing coating thickness.

6. Ceramic layer system according to claim 4 or 5, wherein the region (10L, 10R) surrounding the region (34, 34') has a segmented microstructure.

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