DE102009060570A1 - Method for producing a rotor / stator seal of a gas turbine - Google Patents

Abstract

The invention relates to a method for applying a ceramic layer (21) to the sealing surfaces (4) of sealing segments (3) of a rotor / stator seal of a gas turbine arranged on the inner circumference of a turbine housing part (1). According to the invention, the ceramic layer (21) is applied while the sealing segments (3) are in the turbine housing part (1) in the installed state.

Description

The invention relates to a method for applying a ceramic layer to the sealing surfaces of arranged on the inner circumference of a turbine housing part sealing segments of a rotor / stator seal of a gas turbine.

In turbo machinery, particularly gas turbines such as jet engines of aircraft, leakage currents through gaps between cooperating and relatively moving rotor and stator components reduce efficiency. In order to minimize this gap losses and thus to keep the efficiency of the turbomachine high, it is necessary to keep the gap between the usually high-speed rotor blades and the rotor surrounding, belonging to the stator sealing surface of the housing during operation of the machine low. This is problematic because rotor blades under high load both by thermal stress as well as by centrifugal forces in the radial direction lengths, while the housing usually only a small thermal expansion and thus enlargement of the housing circumference experiences. The gap is thus variable in the operation of the gas turbine

In order to take account of these gap dimension changes, so-called abradable seals are known (US Pat. US 4,299,865 ). The blade tips of the rotor are made of a hard material or provided with a hard coating and formed the inlet seal of the surrounding stator relatively soft. In various operating conditions, it may then come to a run-in of the blade tips in the stator seal and take place a material removal of the inlet seal, without damaging the blades takes place.

The invention has for its object to provide a method of the type mentioned above, which allows a simple and inexpensive application of an inlet layer (abradable seal) and in particular for a renewal or replacement of a rotor / stator seal in the course of maintenance or repair a gas turbine is suitable.

According to the invention it is provided that the application of the ceramic layer takes place while the sealing segments are in the installed state in the turbine housing part.

First, some terms used in the invention are explained.

A gas turbine is a turbomachine in which the thermal energy of a generated by combustion of hydrocarbons or other fuels hot gas stream is converted into mechanical energy. The invention is particularly applicable to jet or turboprop engines of aircraft.

A rotor / stator seal seals in a rotational movement relative to each other running components of the gas turbine from each other, in particular the blade tips of a rotor against the circumference of a surrounding turbine housing.

In the context of claim 1, the term turbine housing part designates that part of the turbine which has or holds the stator seal surrounding the rotor. In the context of the invention, it may in particular be a module of a jet engine in which the stator seal is arranged.

On the inner circumference of this turbine housing part sealing segments are arranged. The term sealing segments refers to removable or individually replaceable parts, each lining a fraction of the inner circumference of the turbine housing. A plurality of sealing segments extend over the entire circumference of the turbine housing part and together form the stator seal.

The sealing segments have sealing surfaces, which are those surfaces which face the rotor. On these sealing surfaces according to the invention a ceramic layer is applied. The term ceramic layer designates in the context of the invention all materials which have a proportion of ceramic materials and are suitable for forming a so-called abradable seals (inlet seal). As a rule, these ceramic layers are based on materials such as ZrO ₂ , Al ₂ O ₃ and / or other metal, transition metal or rare earth oxides or mixed oxides.

According to the application of the ceramic layer, while the sealing segments are in the installed state in the turbine housing part. This means that the application of the ceramic layer takes place, while the sealing segments in the installed state, d. H. connected to the turbine housing part, form a common, extending over the entire circumference of the turbine housing part sealing surface.

This coating in the installed state has a number of advantages. On the one hand, the gas turbine or the jet engine only has to be disassembled down to the module level, which eliminates the time-consuming and cost-intensive disassembly down to the component level. On the other hand, in the case of a coating in the installed state on the module level, a uniform ceramic layer which has been leveled over the circumference is applied from the outset. At the stand The usual technique of coating the items it comes by unavoidable tolerances in the course of the downstream installation of the sealing segments to discontinuities at the transition or joints in the circumferential direction of adjacent sealing segments, so that usually a post-processing (for example, loops) to produce a over the entire Scope equalized sealing surface is required. In the prior art relatively thick inlet layers must be applied to the individual sealing segments, so that enough substance is present for the after assembly unanticipated precision grinding. This is costly and increases the cost. In addition, the thicker ceramic layers required in the prior art have a tendency to flake off material.

Alternatively, it can be provided in the prior art that the imperfections of the sealing surface over the entire circumference of the stator are accepted and that armored rotor tips can be cut into the ceramic layer during the first motor run. Again, but relatively thick ceramic layers are required again, which have the tendency to flake described.

The application of the ceramic layer is carried out according to the invention particularly preferably by atmospheric plasma spray (APS). In plasma spraying, a plasma jet is used whose thermal energy is generated by the recombination of a previously generated gas plasma. In the plasma jet, the material to be applied is fed as powder. In the case of atmospheric plasma spraying, the material is applied in a normal ambient atmosphere. The use of atmospheric plasma spraying as a method for applying the ceramic layer has the particular advantage that the usually quite large turbine housing parts do not have to be transferred into a controlled atmosphere such as a vacuum chamber. The achievable in the atmospheric plasma spraying quality of the ceramic layer is readily sufficient for the purposes of the invention.

According to the invention, the turbine housing part already referred to several times may be, for example, a so-called high pressure turbine shroud support (HPT Shroud Support) of a jet engine. The inventively possible good sealing effect or the achievement of a small sealing gap can make noticeable in particular in the high-pressure turbine in an improved efficiency and thus a fuel economy. The ceramic layer applied according to the invention preferably has a porosity of 10 to 40% by volume, more preferably 20 to 30% by volume. Such a porosity helps to make the ceramic layer sufficiently soft and to give it so-called enema properties. If the blade tip of the rotor comes into contact with such a ceramic layer, the material or friction pair should be designed so that exclusively or predominantly the ceramic layer sealing surface is removed and no or only slight wear occurs on the blade tip.

In order to achieve porosity, it is preferred that the applied ceramic material at the time of application contain a proportion of a thermally removable substance. This may in particular be a polymer such as a polyester. Thermally removable means that the material escapes largely or completely without leaving any residue from the ceramic layer when it is supplied with thermal energy, leaving behind cavities in the form of pores. The removal can be done by evaporation, sublimation or thermal decomposition or combustion with escape of gaseous decomposition products.

The ceramic material of the ceramic layer is based, for example, on ZrO ₂ (zirconium dioxide), it may be doped with rare earth metal oxides such as Y ₂ O ₃ or others. For example, suitable spray-on ceramic powders may be based on YSZ (yttria stabilized zirconia) and may contain 3 to 9 wt%, preferably 4 to 6 wt% polyester to produce the desired porosity. A suitable powder is available, for example, from Sulzer Metco under the name Metco 2460 NS.

The thickness of the applied ceramic layer may according to the invention be between 0.1 and 0.7 mm, more preferably 0.1 and 0.5 mm. Frequently layers are applied in the range 0.2 to 0.4 or 0.2 to 0.3 mm.

It is preferred within the scope of the invention for an adhesion promoter layer to be applied to the substrate of the sealing segments before the ceramic layer is applied. The thickness of the primer layer is preferably 0.1 mm or less. The primer layer is preferably an MCrAlY layer in which M is preferably a metal selected from the group consisting of nickel, cobalt, iron or combinations thereof. Other elements such as hafnium or silicon as so-called reactive element additions can be added to increase the oxidation resistance and lifetime of the bond coat. The primer layer is preferably also applied by plasma spraying. Possibly. For example, low vacuum plasma spray (LVPS) may be used, but the atmospheric plasma spray already described is preferred. A suitable material for the adhesion promoter layer is, for example, also from Sulzer Metco offers CONiCrALY-based fine-grained powder such as Amdry 365-2.

In the sealing surfaces of sealing segments of a high-pressure turbine (so-called HPT Shrouds) are often cooling air holes available to reduce the thermal load on the HPT Shrouds. It may be advantageous in the context of the invention to close these cooling air holes prior to application of the ceramic layer and any adhesion promoter layers or other layers in order to prevent the cooling air holes are closed or reduced in cross-section impermissibly. According to a variant of the invention, such cooling air holes are temporarily closed with a thermally removable material prior to the application of the ceramic layer (and preferably also before the application of a primer layer or any other intermediate layers). "Thermally removable" means that this material can be removed following the application of the ceramic layer and any post-processing such as grinding or the like by a heat treatment or in a first turbine run is removed by the then occurring heat load. The thermal removal can be carried out in particular by evaporation, sublimation or thermal decomposition to preferably gaseous decomposition products. It is preferably carried out completely or largely without residue.

Preferred thermally removable materials are polymers or plastics. It is preferred that the cooling air holes are closed with a not yet cured mixture of monomers, oligomers and / or prepolymers, which are then brought to cure. The curing can be induced according to the invention by heat or preferably by light or UV radiation. Preference is given to using UV or light-curing plastics, more preferably acrylates and / or methacrylates. For example, they may be epoxy acrylates, urethane acrylates, polyester acrylates, polyether acrylates and silicone acrylates. Corresponding light-curing plastics are familiar to the person skilled in the art. The viscosity and nature of the mixture which has not yet hardened to occlude the cooling air bores is preferably of the form that safe application of a viscous gel is possible and that it does not flow away before hardening or only in a still acceptable manner. Suitable plastics or adhesives are available, for example, from Dymax Europe GmbH, Frankfurt.

The closing of cooling air bores according to the invention prior to the application of the ceramic layer avoids a costly boring of cooling air openings, which is often necessary in the prior art, after application of a ceramic layer. This closure of the cooling air holes is a particularly advantageous aspect of the invention, for which the applicant may also claim protection in the context of the coating of a single, expanded sealing segment, which is thus no longer in the installed state in the turbine housing part.

• a) zur Verfügung stellen des demontierten Turbinengehäuseteils, wobei sich die Dichtsegmente im Einbauzustand in denn Turbinengehäuseteil befinden,
• b) Abtragen von Material von den Dichtflächen der Dichtsegmente,
• c) Aufbringen einer Keramikschicht mittels eines Verfahrens nach einem der Ansprüche 1 bis 12.

The invention further provides a method for repairing sealing surfaces of sealing segments of a rotor / stator seal of a gas turbine arranged on the inner circumference of a turbine housing part, comprising the following steps:

• a) make available the disassembled turbine housing part, wherein the sealing segments are in the installed state in the turbine housing part,
• b) removal of material from the sealing surfaces of the sealing segments,
• c) applying a ceramic layer by means of a method according to one of claims 1 to 12.

• a) Demontieren der Gasturbine und zur Verfügung stellen des demontierten Turbinengehäuseteils, wobei sich die Dichtsegmente im Einbauzustand in dem Turbinengehäuseteil befinden,
• b) Abtragen von Material von den Dichtflächen der Dichtsegmente,
• c) Aufbringen einer Keramikschicht mittels eines Verfahrens nach einem der Ansprüche 1 bis 12, so dass ein Dichtspalt entsteht, der kleiner ist als der Dichtspalt im Neuzustand.

Another object of the invention is a method for repairing a gas turbine having at least one rotor and arranged on the inner circumference of a turbine housing part sealing segments of a rotor / stator seal, wherein in the new state of the gas turbine, a sealing gap between the rotor blade tips and the sealing surfaces of the sealing segments is provided with the steps:

• a) dismantling the gas turbine and providing the disassembled turbine housing part, wherein the sealing segments are in the installed state in the turbine housing part,
• b) removal of material from the sealing surfaces of the sealing segments,
• c) applying a ceramic layer by means of a method according to one of claims 1 to 12, so that a sealing gap is formed which is smaller than the sealing gap in the new state.

In accordance with these two aspects of the invention, the focus is on a repair process in which a targeted new production of the sealing surfaces takes place. Common to the repair method of claims 13 and 14, which is the repair at the level of the turbine housing module without further decomposition into the items, ie in particular with the sealing segments in the installed state. Furthermore, according to the invention, material is removed from the sealing surfaces of the sealing segments, so that space is created for repositioning a ceramic layer according to the method of the invention.

According to a further aspect of the invention, the repaired turbine housing parts or gas turbines before carrying out the method according to the invention on a metallic sealing surface, so neither inventively applied nor other types of ceramic sealing surface. According to one Another aspect of the invention (feature c) of claim 14) in a repair carried out according to the invention, a sealing gap is produced, which is smaller than the sealing gap in the new state of the gas turbine. It is thus a method by which the efficiency of a gas turbine can be increased. This is a particularly important aspect of the invention within the framework of the so-called Green Aviation, in which the fuel consumption and CO ₂ emissions of aircraft engines should be reduced. This aspect of the invention will be explained in more detail below.

The repair methods according to the invention can be used in gas turbines which have a ceramic sealing surface when new and in which it is provided that the blade tips of the rotor run into these sealing surfaces in certain operating states and cause material removal. When using ceramic sealing surfaces in the prior art, the blade tips of the turbine blades are often provided with an armor or on the basis of cubic Bohrnitrid (CBN). When using a ceramic layer applied according to the invention, such armoring is not absolutely necessary.

There are also jet engines for aircraft (for example General Electric CFM56 and CF6-80) which have metallic sealing surfaces. With these motors, precise control of geometry and manufacturing and assembly tolerances should prevent the rotor tips from coming into contact with the metallic sealing surfaces during initial startup or later during operation. In order to safely reduce this unwanted shrinkage in all operating conditions, a relatively large sealing gap is often required, which reduces the efficiency of the engine.

According to the invention, a ceramic layer can also be applied to the sealing surface according to the repair method of claim 14 in gas turbines with metallic sealing surfaces. In this method, the metallic sealing surface is removed in whole or in part, so that space is available for the inventive application of a ceramic sealing surface on the inner circumference of the corresponding turbine housing part. This can be designed and applied so that after reassembly of the gas turbine, the sealing gap is lower than when new with metallic sealing surface. The reduction of the sealing gap is possible because in the ceramic sealing surface applied according to the invention, a running in of the blade tips into the sealing surface can be tolerated. If such shrinkage occurs, only this ceramic layer is removed due to the material pairing of the incoming blade tip into the soft ceramic layer. If, in unfavorable operating conditions, an unintentional run-in of the blade tip into the metallic sealing surface occurs in the case of a metallic sealing surface, the material can also be removed on the blade tips of the rotors, so that the sealing gap is further enlarged and not restored by restoring the sealing surface can be brought to the originally intended level.

The use of atmospheric plasma spraying in carrying out the method according to the invention has the further advantage of a relatively low process temperature. Since the plasma jet transmits only relatively little thermal energy to the sealing segments to be coated, a possible distortion of the assembled components is avoided. As will be explained below in the exemplary embodiment, the module with the built-in sealing segments can be rotated during the coating, so that the exposure time of the plasma jet to a single sealing segment is relatively low and the corresponding segment can cool down during the further rotation of the module before it again comes into contact with the plasma jet.

An embodiment of the invention will be described below with reference to the drawings. Show:

1 a section through a gas turbine section;

2 a top view of the turbine housing;

3 : the interaction of turbine blade and sealing surface during operation;

4 schematically the processing steps in carrying out a repair according to the invention;

5 schematically the procedure for a material removal from the sealing surfaces in the course of preparation of the method according to the invention;

6 : schematically the coating process according to the invention;

7 the invention possible reduction of the sealing gap;

8th : the behavior of a inventively constructed rotor / stator seal in operation.

2 shows in the plan view of a turbine housing 1 , on the inner circumference of receiving segments 2 for the sealing segments 3 are arranged. The over the circumference of the turbine housing 1 abutting sealing segments 3 have at their radially inwardly facing peripheral surfaces sealing surfaces 4 on.

In 1 shows the reference number 5 schematically the rotational symmetry axis of the gas turbine. At the rotor disk 6 are distributed over the circumference a plurality of turbine blades 7 (Rotor blade or rotor blades) arranged. The radially outwardly facing tips of the turbine blade 7 seal against the sealing surfaces 4 the sealing segments 3 off and close with these a sealing gap 8th a, which is the difference of the stator radius 9 and the rotor radius 10 calculated. The arrow 11 denotes the direction of the gas flow flowing through the gas turbine.

3a also shows in 1 illustrated initial state. The sealing segment 3 has a metallic sealing surface in this embodiment. The reference number 13 denotes cooling air holes in the sealing segment 3 ,

In operation of the engine, it may due to thermal expansion and / or in 3b at 12 schematically illustrated rotor eccentricity to a shrinkage of the turbine blade 7 in the sealing surface of the sealing segment 3 come. The shrinkage occurs in the sealing segment 3 one in 3c schematically illustrated inlet notch 14 and the blade length 15 is due to material removal at the top of the turbine blade 7 reduced. The result is an enlarged sealing gap 8a ; the efficiency of the engine is reduced.

4 schematically shows the sequence of a repair method according to the invention. 4a shows the initial state of a sealing segment 3 before repair, which usually involves some removal of the sealing surface 4 may have taken place in the 4a Not shown notch (see reference numeral 14 in 3c ) to be available.

The whole in 4 illustrated repair process takes place in the installed state of the sealing segments in the turbine housing 1 as he is in 2 is shown. In 4 For the sake of clarity, only a single sealing segment is shown in each case.

5 schematically shows a removal of material from the sealing surfaces 4 the sealing segments 3 , A grinding tool 15 is for this purpose against the sealing surfaces 4 to rotate. Instead of grinding, other removal methods such as milling or eroding can be used. The result of the material removal is schematically in 4b shown.

This is followed by a cleaning of the sealing surfaces to be coated 4 , The cleaning preferably comprises degreasing, rinsing with demineralized water and drying, for example at 120 ° C., if appropriate under reduced air pressure.

To prepare the plasma coating, so-called activation blasting is performed. For this purpose, Al ₂ O ₃ -strahlgut the grain size mesh 36 is used. The following beam parameters are suitable for the activation beam:
Rotation speed 15 min ^-1 , two vertical strokes, jet pressure 1.6 bar, nozzle distance 200 mm, spray angle 45 °. It should be avoided that blasting in the cooling air holes 13 arrives.

The applied activation layer is in 4c at 16 shown schematically.

If a ceramic layer with a layer thickness of more than 0.2 or 0.3 mm is to be applied, usually a temporary closing of the cooling air channels 13 make sense. For this purpose, a light-curable PU-based plastic either punctiform by means of a pipette or a similar application instrument or with the aid of shaping masking aids such. B. films with corresponding cutouts, which coincide substantially with the cooling air openings, on the opening of each cooling air hole 13 applied. Subsequently, the plastic is cured by means of light, UV radiation and / or heat. You get in 4d schematically shown Kunststoffpfropfen 17 that the cooling air channels 13 close.

In the next step, an in 4e schematically illustrated adhesion promoter layer 18 applied. For this purpose, a CoNiCrALY-based fine powder (Amdry 365-2) is applied by atmospheric plasma spraying. 6 schematically shows how a coating unit 19 with a plasma jet 20 by relative movement relative to the turbine housing 1 the entire circumference of the sealing surfaces 4 the sealing segments 3 can coat. The following coating parameters are used:
1 stroke, 3.6% vertical speed of the robot, rotation speed 27 min ^-1 . The thickness of the adhesion promoter layer applied in this way is preferably 0.03 to 0.05 mm.

Optionally, an erosion-resistant ceramic interlayer using a ceramic powder such as. B. Praxair 1484 be applied.

Subsequently, the inventive soft ceramic layer (inlet layer) with the coating unit 19 applied. The layer is schematically at 21 in 4f shown.

The coating material used is Metco 2460 NS. The following coating parameters are used:
2 mm single injector, 9 strokes, 1.8% vertical robot speed, rotational speed 33 min ^-1 , spray angle 90 °. The ceramic layer 21 is usually applied in a thickness of 0.2 to 0.7 mm.

In the next step, the sealing surfaces 4 the sealing segments 3 ground down to the desired stator radius. Maybe through the plastic plugs 17 caused unevenness of the sealing surface 4 such as material bumps are removed. After sanding, the plastic plugs protrude 17 to the sealing surface 4 before, as shown schematically in 4g shown.

The plastic plugs 17 are thermally decomposed either by a separate heat treatment or upon commissioning of the engine and substantially residue free from the cooling air holes 13 away. The ready-to-use state thus produced is shown schematically in FIG 4h shown.

7 shows the invention possible reduction of a sealing gap and thus the increase in the efficiency of a jet engine within the framework of the so-called Green / aviation. 7a shows the original state in which the turbine blades 7 against a metallic sealing surface 4 the sealing segments 3 to run. It is a relatively large sealing gap 8th required, through which leakage currents and efficiency losses occur.

7b shows the state after application of a porous ceramic layer 21 according to the method of the invention. Due to its porosity of about 30% by volume, this layer is relatively soft. The sealing gap 8b can be reduced here compared to the initial state. For example, the sealing gap 8th in the order of 0.5 to 2 mm, the amount of the reduced sealing gap 8b may be 0.1 to 0.4, preferably 0.1 to 0.3, more preferably 0.1 to 0.2 mm lower. A seal gap reduction of 0.2 mm in the high-pressure turbine of an engine can, for example, reduce fuel consumption and thus CO ₂ emissions by approx. 0.3%.

8th shows schematically a possible during operation of the engine run-in of turbine blades 7 in the sealing area 4 a sealing segment 3 , It is here again a in 8b schematically with 14 designated inlet notch. Because this inlet notch in the soft ceramic layer 21 occurs, there is no or only a very small material removal at the top of the turbine blade 7 so that its radial length 15 remains essentially unchanged.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4299865 [0003]

Claims (15)

Method for applying a ceramic layer ( 21 ) on the sealing surfaces ( 4 ) of the inner circumference of a turbine housing part ( 1 ) arranged sealing segments ( 3 ) of a rotor / stator seal of a gas turbine, characterized in that the application of the ceramic layer ( 21 ), while the sealing segments ( 3 ) in the installed state in the turbine housing part ( 1 ) are located. A method according to claim 1, characterized in that the application of the ceramic layer ( 21 ) by atmospheric plasma spraying (APS). Method according to claim 1 or 2, characterized in that the ceramic layer ( 21 ) has a porosity of 10 to 40% by volume, preferably 20 to 30% by volume. A method according to claim 3, characterized in that the porosity is effected by a proportion of a thermally removable substance in the applied ceramic material. A method according to claim 4, characterized in that the thermally removable material is a polymer, preferably a polyester. Method according to one of claims 1 to 5, characterized in that the ceramic material of the ceramic layer contains ZrO ₂ . Method according to one of claims 1 to 6, characterized in that the thickness of the applied ceramic layer ( 21 ) Is 0.1 to 0.7 mm, preferably 0.1 to 0.5 mm. Method according to one of claims 1 to 7, characterized in that prior to the application of the ceramic layer, a primer layer ( 18 ) is applied. A method according to claim 8, characterized in that the adhesive layer ( 18 ) has a CoNiCrAlY based material. A method according to claim 8 or 9, characterized in that the thickness of the adhesive layer ( 18 ) Is 0.1 mm or less. Method according to one of claims 1 to 10, characterized in that prior to the application of adhesive layer ( 18 ) and / or ceramic layer ( 21 ) in the sealing surfaces ( 4 ) existing cooling air holes ( 13 ) with a thermally removable material ( 17 ) are closed. Method according to claim 11, characterized in that the thermally removable material ( 17 ) a plastic, preferably a UV or photocurable plastic, more preferably an acrylate and / or methacrylate plastic, more preferably a plastic selected from the group consisting of epoxy acrylates, urethane acrylates, polyester acrylates, polyether acrylates and silicone acrylates. Method for repairing sealing surfaces of sealing segments of a rotor / stator seal of a gas turbine arranged on the inner periphery of a turbine housing part, comprising the steps of: a) providing the dismounted turbine housing part ( 1 ), wherein the sealing segments ( 3 ) in the installed state in the turbine housing part ( 1 b) removal of material from the sealing surfaces ( 4 ) of the sealing segments ( 3 ), c) applying a ceramic layer ( 21 ) by means of a method according to one of claims 1 to 12. Method for repairing a gas turbine, comprising at least one rotor ( 6 . 7 ) and on the inner circumference of a turbine housing part ( 1 ) arranged sealing segments ( 3 ) has a rotor / stator seal, wherein in the new state of the gas turbine, a sealing gap ( 8th ) between the rotor blade tips and the sealing surfaces ( 4 ) of the sealing segments ( 3 ), comprising the steps of: a) disassembling the gas turbine and providing the disassembled turbine housing part ( 1 ), wherein the sealing segments ( 3 ) in the installed state in the turbine housing part ( 1 b) removal of material from the sealing surfaces ( 4 ) of the sealing segments ( 3 ), c) applying a ceramic layer ( 21 ) by means of a method according to one of claims 1 to 12, so that a sealing gap ( 8b ) is formed, which is smaller than the sealing gap ( 8th ) in new condition. Method according to claim 13 or 14, characterized in that the sealing segments ( 3 ) of the turbine housing part provided in step a) ( 1 ) metallic sealing surfaces ( 4 ) exhibit.

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