Masking means for covering a thermal spray layer on a component of a fluid machine, and method for processing a component of a fluid machine

Abstract

The invention relates to a masking means (14) for covering a surface region (12) of a component (10) of a fluid machine, in particular for covering a thermal spray layer, wherein the masking means (14) comprises at least one crosslinkable elastomer pre-product with a dynamic viscosity ranging between 21000 mPas and 39000 mPas at a temperature of 25±0.2°C. The invention also relates to a method for processing a component (10) of a fluid machine in which at least one surface region (12) of the component (10) is first covered by such a masking means (14) and the component (10) is then processed.

Description

[0001] Masking agent for covering a thermal spray layer on a component of a turbomachine and method for machining a component of a turbomachine

[0002] Description

[0003] The invention relates to a masking agent for covering a thermal spray layer on a component of a turbomachine and to a method for machining a component of a turbomachine.

[0004] Components of turbomachinery, especially components for aircraft engines, typically require multiple processing steps. For example, surface areas of certain components are coated with thermal spray coatings to make the surface of the component more resistant to thermal stress, corrosive influences, and abrasion. However, such components often require additional processing steps, such as mechanical and / or chemical post-processing. During these processes, tools or media may be used to which the surface or coating of the component is not resistant, thereby altering its functional properties.In order to protect the surface of the component at least in critical areas during these subsequent processing steps, the surface of the component is usually protected with a coolant during mechanical processing and with a mask during chemical processing or a cleaning process.

[0005] To date, thermal spray coatings, e.g. dimensional correction coatings, wear protection coatings, running-in coatings, etc. have not been protected from the coolant before turning with this coolant. If the coating is not allowed to come into contact with the coolant during turning, the layers are turned without the use of a coolant, which can lead to damage to the component. If a coolant is used on a component that has already been coated and influences the coating properties, the spray coating must then be removed and reapplied. Conversely, particularly with thermal spray coatings and other porous surfaces, there is a risk that masking agent will penetrate the open porosity and remain there at least partially even after the masking has been removed. This can also have a negative impact on the functional properties of the component. EP 3 374 534 B1 describes the primarily automated masking of surfaces.A method for automated paint coating is known from EP 1 490 443 B1.

[0006] The object of the present invention is to provide a masking agent that, on the one hand, ensures more reliable masking of a thermal spray coating, but, on the other hand, does not cause damage to this surface upon removal. A further object of the invention is to provide a method for machining a component of a turbomachine that avoids the aforementioned problems with sensitive surface areas of the machined component.

[0007] The objects are achieved according to the invention by a masking agent having the features of patent claim 1 and by a method according to patent claim 5. Advantageous embodiments with expedient further developments of the invention are specified in the respective subclaims, wherein advantageous embodiments of the masking agent are to be regarded as advantageous embodiments of the method and vice versa.

[0008] A first aspect of the invention relates to a masking agent for covering a surface area of ​​a component of a turbomachine, in particular for covering a thermal spray coating of the component. According to the invention, more reliable masking of the surface area without the risk of damaging the masked surface area upon removal of the masking agent is achieved in that the masking agent comprises at least one crosslinkable elastomer precursor with a dynamic viscosity at 25±0.2 °C between 21,000 mPas and 39,000 mPas. In other words, the masking agent according to the invention contains at least one elastomer precursor that can be thermally, photochemically, and / or ionically crosslinked to form an elastomer. In the simplest embodiment, the masking agent according to the invention can also consist exclusively of this elastomer precursor.The crosslinkable elastomer precursor already exhibits a high dynamic viscosity at 25±0.2 °C between 21,000 mPas and 39,000 mPas (at 20 rpm), which can be further increased by crosslinking the elastomer precursor to form an elastomer. The masking agent thus enables precise and effective coverage of the component's surface area. The defined dynamic viscosity ensures targeted application and good adhesion to the surface, even on porous surfaces of spray coatings, without penetrating deeply into them. Using this masking agent effectively protects the component's surface during subsequent processing steps. It forms a protective layer that protects against potential surface damage, such as that caused by a thermal spray coating. Furthermore, the masking agent can be easily removed after crosslinking, usually without leaving any residue.This reduces the labor required for preparing and post-processing the component for various processing steps and increases process efficiency. The defined dynamic viscosity of the elastomer precursor also enables precise control of the application behavior and layer thickness of the masking agent. This enables uniform and consistent coverage of the surface area to be protected. Precise protection of the surface area to be masked also reduces or ideally completely eliminates the need for time-consuming preparatory work such as removing coatings, as well as post-processing such as repairing damaged spray coating areas, etc. This leads to corresponding time and cost savings in the manufacturing process. If the viscosity of the elastomer precursor is already sufficient, crosslinking can be omitted in certain cases.Generally, "a" / "an" should be read as an indefinite article in this disclosure, meaning, unless expressly stated otherwise, "at least one." Conversely, "a" / "an" can also be understood as "only one."

[0009] In an advantageous embodiment of the invention, it is provided that the at least one elastomer precursor is photocrosslinkable, and that the masking agent additionally comprises at least one photoinitiator. In contrast to thermal crosslinking, photocrosslinking is significantly less time- and energy-intensive, environmentally friendly and emission-free, and requires considerably less mechanical effort. Furthermore, this method can prevent significant temperature-related changes in the viscosity of the elastomer precursor, since no heating of the elastomer precursor is necessary, as the crosslinking reaction can be carried out at room temperature.In addition, even complex three-dimensional geometries, such as those regularly encountered in components for turbomachines, can be reliably and easily coated with the masking agent with locally varying heating, and the masking agent can then be quickly cured by exposure to UV light.

[0010] Further advantages arise from the masking agent additionally containing a fluorescent additive. With the help of a fluorescent additive, both the application and subsequent removal of the masking agent from the component can be easily controlled and monitored. In particular, it is particularly easy to check whether any residues of the masking agent remain on the component after removal. These residues can then be specifically removed in a corresponding cleaning step until no fluorescent signal is detectable. Cleaning can be performed, for example, using solvents and / or by burning out the thermoplastic masking residues.

[0011] In a further advantageous embodiment of the invention, the at least one elastomer precursor comprises (meth)acrylate monomers, in particular hexanediol di(meth)acrylate and / or isobomyl (meth)acrylate and / or trimethylolpropane tri(meth)acrylate, and / or (meth)acrylate oligomers, in particular urethane (meth)acrylate oligomers. This makes it possible to produce a masking layer that exhibits high tensile strength, extensibility, hardness, chemical resistance, and adhesion to the component. Within the scope of the present disclosure, the term (meth)acrylate is generally understood to mean corresponding acrylates, methacrylates, and any mixtures thereof.

[0012] A second aspect of the invention relates to a method for machining a component of a turbomachine, in which at least one surface region of the component is first covered with a masking agent according to the first aspect of the invention and the component is then machined. The method according to the invention brings about particularly simple and reliable masking of surface regions of the component to be protected during the subsequent machining step(s). Due to the high viscosity of the masking agent, it penetrates only slightly or not at all into layers such as porous thermal spray coatings. The masking agent can be applied either by hand and / or by a robot, thus enabling precise masking of different components.After processing, the masking can be quickly and reliably removed from the component by hand and / or machine due to its elastic properties. Further features and their advantages can be found in the descriptions of the first aspect of the invention.

[0013] In an advantageous embodiment of the invention, it is provided that the surface area of ​​the component is cleaned before applying the masking agent. This ensures reliable application and adhesion of the masking agent to the surface. Alternatively or additionally, the surface area is covered with a covering agent, in particular an adhesive tape, onto which the masking agent is then applied. This can provide additional protection for sensitive and / or porous surface areas of the component. Furthermore, the adhesion of the masking agent to the surface can be improved. Likewise, removal of the masking agent can be facilitated by removing it from the component together with the covering agent. Alternatively or additionally, it is provided that the masking agent is crosslinked, preferably photochemically, after application to the surface area.This further increases the viscosity of the masking agent and ensures a particularly reliable masking effect as well as easy removal.

[0014] In a further advantageous embodiment of the invention, the masking agent is applied to the surface area by bead application, with adjacent beads preferably being arranged offset from one another. Bead application allows for contactless application with a certain "flying height," i.e., with a certain distance between a bead application nozzle tip and the component surface. The bead can optionally also be pressed outward to create a flat masking. By arranging adjacent or contiguous beads offset from one another, particularly reliable masking without gaps can be ensured. Alternatively or additionally, the masking agent is applied to the surface area with a layer thickness of at least 0.5 mm.This also ensures a seamless, continuous and therefore reliable masking of the relevant surface area.

[0015] In a further advantageous embodiment of the invention, it is provided that a Ni-based plasma spray coating and / or a thermally sprayed abradable coating and / or a thermally sprayed wear protection layer of the component is / are covered at least in certain areas by means of the masking agent. This allows the numerous advantages of the masking according to the invention to be realized for various surface areas that were previously difficult to mask.

[0016] Further advantages arise from the fact that, after the surface area has been covered, the component is chemically processed, in particular cleaned, stripped, and / or coated with a testing agent and / or a cooling lubricant and / or a splash guard layer. This allows many different components for turbomachines to be masked and processed in various ways. In a further advantageous embodiment of the invention, it is provided that the masking agent is at least partially removed from the component after processing the component, in particular by peeling it off and / or by applying a solvent and / or by burning it out. This allows simple and complete removal of the masking agent from the component after it has been used.

[0017] Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respective combination specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments are to be regarded as encompassed and disclosed by the invention that are not explicitly shown and explained in the figures, but which emerge and can be produced by separate combinations of features from the explained embodiments. Embodiments and combinations of features are also to be regarded as disclosed that therefore do not have all the features of an originally formulated independent claim.Furthermore, embodiments and combinations of features are to be considered disclosed, in particular by the embodiments presented above, which go beyond or deviate from the combinations of features presented in the claims. This shows:

[0018] Fig. 1 is a perspective detailed view of a blade cluster of an aircraft engine with a Ni-based plasma spray coating;

[0019] Fig. 2 is a perspective view of the blade cluster in which the Ni-based plasma spray layer is covered with a masking agent;

[0020] Fig. 3 is a perspective view of the blade cluster, wherein the masking agent is removed without residue after machining the blade cluster;

[0021] Fig. 4 is a perspective detailed view of a run-in coating of a housing part of an aircraft engine; Fig. 5 is a perspective detailed view of the housing part, wherein the run-in coating is covered with the masking agent;

[0022] Fig. 6 is a perspective detailed view of a fin coating of a rotor of an aircraft engine;

[0023] Fig. 7 is a perspective detailed view of the fin coating covered with the masking agent;

[0024] Fig. 8 is a perspective detailed view of a running-in lining of a rotor of an aircraft engine; and

[0025] Fig. 9 is a perspective detailed view of the inlet coating covered with the masking agent.

[0026] FIG. 1 shows a perspective detailed view of a component 10 of an aircraft engine, designed as a blade cluster, with a surface area 12 having a Ni-based plasma spray coating. In the case of damage to such titanium-based blade clusters 10, shot peening is required after blending. To subsequently remove the contaminants from the titanium material caused by the blasting, cleaning with nitric acid-containing cleaning agents is subsequently provided. However, the nitric acid used attacks the existing Ni-based plasma spray coating 12. A mechanical device for protecting the plasma spray coatings 12 cannot be used due to the complex geometry. Mechanical cleaning, on the other hand, is very complex and cost-intensive.By masking with a masking agent 14 according to the invention, cleaning of the component 10 with nitric acid-containing cleaners was made possible without damaging the existing spray layer 12 or requiring re-treatment after cleaning. The masking agent 14 is based on cross-linkable elastomer precursors with the highest possible dynamic viscosity between 21,000 and 39,000 mPas (cP) at 25±0.2°C and 20 rpm. This allows the masking agent 14 to be applied evenly and with good adhesion to the surface area 12 of the component 10 to be protected, for example, without running down vertical surfaces. If the masking agent 14 is not resistant to subsequently used media, or in the event of adhesion problems, a band or tape can generally also be first applied to the surface area 12 and the highly viscous masking agent 14 applied to it.Other special preparations can also be made, for example when applying to the edges of the surface area 12 to be protected, in order to reliably prevent the masking agent 14 from penetrating into corresponding component areas. Before application, the surface area 12 can be cleaned to reliably remove protective substances or lubricants and to ensure good adhesion of the masking agent 14. In general, application is preferably carried out first at the border areas of the surface to be covered. Application in the coating area is preferably contactless with immediate (UV) curing. In the case of a bead application, the individual beads are preferably applied staggered to guarantee tightness. Curing should generally also take place after each bead and / or layer. The layer thickness is generally at least 0.5 mm.

[0027] The masking agent 14 can preferably be photochemically polymerized, whereby it acquires its final dimensional stability, cohesion, and adhesion in order to optimally protect the surface region 12 for subsequent processing steps. The masking agent 14 preferably contains crosslinkable monomers and / or oligomers (in particular urethane acrylate) and optionally one or more photoinitiators, modifiers, and / or (fluorescent) dye(s). As a result, the masking agent 14 is particularly chemically and mechanically resistant, at least in the polymerized state, without significantly infiltrating surface regions 12 with open porosity or entering into a chemical reaction with the thermal spray coating to be protected.

[0028] Fig. 2 shows a perspective view of the blade cluster 10, in which the surface region 12 of the Ni-based plasma spray layer is covered with the masking agent 14 according to the invention. It can be seen that, despite the complex surface geometry, the masking agent 14 covers the surface region 12 with a uniform layer thickness and protects it from damage during subsequent chemical and / or mechanical processing steps.

[0029] Fig. 3 shows a perspective view of the blade cluster 10, wherein the masking agent 14 is removed residue-free from the surface area 12 with the Ni-based plasma spray layer after processing the blade cluster 10. The removal can generally be performed manually and / or mechanically. Since the masking agent 14 does not penetrate into the open porosity of the plasma spray layer due to its high viscosity, no masking agent residues remain there after removal. Should residues of the masking agent 14 unexpectedly remain, they can be removed by cleaning, if necessary with a solvent, and / or by burning off. If a possibly fluorescent dye is added to the masking agent 14, it can be easily checked visually whether all residues have been completely removed.

[0030] Fig. 4 shows a perspective detailed view of a thermally sprayed run-in coating on a component 10 of an aircraft engine, designed as a housing. The high open porosity of this surface area 12 is evident. Deviations can be detected on such components 10 that require reworking of the dimensional correction layers (not shown). If the dimensional correction layers of these components 10 are reworked, the following process steps, among others, must be performed:

[0031] - Pre-turning of the area to be coated (dimensional correction layer) with cooling lubricant (KSS);

[0032] - Cleaning; and

[0033] - Dye penetrant testing (FPI testing).

[0034] When performing these processing steps, no media such as coolant or FPI penetrant may penetrate the existing abrading coating 12. Until now, this requirement could not be met, which meant that in addition to the dimensional correction layers, the abrading coating 12 also had to be stripped and reapplied. By masking the abrading coating 12 with the aid of the masking agent 14 according to the invention, the dimensional correction layers can be partially repaired, while the complex and costly stripping and reapplying of the abrading coating 12 can be avoided.

[0035] Fig. 5 shows a perspective detailed view of the housing part 10, wherein the run-in coating 12 is covered with the masking agent 14. The composition and use of the masking agent 14 correspond to those of the previous example. The removal of the masking agent 14 after completion of the processing steps can again be accomplished by simple manual and / or mechanical stripping. Fig. 6 shows a perspective detailed view of a thermally sprayed fin coating 12 (wear protection layer) of a component 10 of an aircraft engine designed as a rotor (blisk). For reasons unknown, the surface of this blisk 10 could not be wetted during crack testing. The repeated cleaning of the fin coating 12 already present on the component 10 using a cleaning agent that is unproblematic for the fin coating 12 did not result in the desired wettability.An alternative cleaning method with an alkaline cleaner would damage the unprotected fin coating 12. By masking the fin coating 12 with the masking agent 14 according to the invention, the component 10 could be cleaned with the more effective alkaline cleaning agent without damaging the fin coating 12 or without having to remove and replace the fin coating 12. Fig. 7 shows a perspective detailed view of the fin coating 12, which is covered with the masking agent 14 to enable cleaning with the alkaline cleaning agent. After cleaning, the masking agent 14 could be easily removed again.

[0036] Fig. 8 shows a perspective detailed view of a surface area 12 formed as a run-in coating on a component 10 of an aircraft engine designed as a rotor. The open-pore structure of the run-in coating 12 can once again be seen. This structure has previously made masking or covering difficult or even impossible due to the risk of conventional masking agents penetrating it. As already mentioned, a band or tape (not shown) can also be applied first, to which the masking agent 14 according to the invention is then applied. If the viscosity of the (uncrosslinked) masking agent 14 is sufficiently high, direct application is also possible here. Fig. 9 shows a perspective detailed view of the run-in coating 12, which is directly covered with the masking agent 14.

[0037] The parameter values ​​specified in the documents for defining process and measurement conditions for characterizing specific properties of the subject matter of the invention are to be considered within the scope of the invention, even in the case of deviations—for example, due to measurement errors, system errors, weighing errors, DIN tolerances, and the like. List of reference symbols:

[0038] 10 components

[0039] 12 Surface area 14 Masking agent

Claims

Patent claims 1. Masking agent (14) for covering a surface area (12) of a component (10) of a turbomachine, in particular for covering a thermal spray layer, characterized in that it comprises at least one crosslinkable elastomer precursor with a dynamic viscosity at 25±0.2 °C between 21000 mPas and 39000 mPas.

2. Masking agent (14) according to claim 1, characterized in that the at least one elastomer precursor is photocrosslinkable and that the masking agent (14) additionally comprises at least one photoinitiator.

3. Masking agent (14) according to claim 1 or 2, characterized in that it additionally comprises a fluorescent additive.

4. Masking agent (14) according to one of claims 1 to 3, characterized in that the at least one elastomer precursor comprises (meth)acrylate monomers, in particular hexanediol di(meth)acrylate and / or isobornyl (meth)acrylate and / or trimethylolpropane tri(meth)acrylate, and / or (meth)acrylate oligomers, in particular urethane (meth)acrylate oligomers.

5. A method for machining a component (10) of a turbomachine, in which at least one surface region (12) of the component (10) is first covered with a masking agent (14) according to one of claims 1 to 4 and the component (10) is then machined.

6. The method according to claim 5, characterized in that the surface area (12) of the component (10) is cleaned before application of the masking agent (14) and / or covered with a covering agent, in particular an adhesive tape, to which the masking agent (14) is then applied, and / or that the masking agent (14) is crosslinked, preferably photochemically, after application to the surface area (12).

7. Method according to claim 5 or 6, characterized in that the masking agent (14) is applied to the surface area (12) by means of bead application, wherein adjacent beads are preferably arranged offset from one another, and / or that the masking agent (14) is applied to the surface area (12) with a layer thickness of at least 0.5 mm.

8. Method according to one of claims 5 to 7, characterized in that by means of the masking agent (14) a Ni-based plasma sprayed layer and / or a thermally sprayed running-in coating and / or a thermally sprayed wear protection layer of the component (10) is covered at least in regions.

9. Method according to one of claims 5 to 8, characterized in that the component (10) is chemically processed after the covering of the surface region (12), in particular cleaned, stripped and / or coated with a testing agent and / or a cooling lubricant and / or a splash protection layer.

10. Method according to one of claims 5 to 9, characterized in that the masking agent (14) is at least partially removed from the component (10) after the processing of the component (10), in particular by peeling off and / or by applying a solvent and / or by burning out.

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