Method for coating a turbomachine part
By using a ceramic adhesive to fix turbomachine parts to a support for coating and heat treatment, the complexity and cost of machining are reduced, and the entire part is protected, addressing the challenges of existing coating methods for CMC materials.
Patent Information
- Application Number
- FR2023014148
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-12-14
- Publication Date
- 2025-11-21
- Estimated Expiration
- 2043-12-14
AI Technical Summary
The existing methods for coating turbomachine parts made of ceramic matrix composite (CMC) materials are complex and costly due to the need for machining excess lengths for holding during coating, which are then removed, and the machined faces are left unprotected.
A method involving fixing the turbomachine part to a support using a ceramic adhesive, preferably made of graphite, allowing the application of a coating and heat treatment under an oxidizing atmosphere, with the support being removable or integral for handling and protection during the process.
This method simplifies the coating process by eliminating the need for machining and provides comprehensive protection without mechanical damage, ensuring the entire part is coated and protected, including areas not exposed to the engine environment.
Smart Images
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Abstract
Description
Title of the invention: Method for coating a turbomachine part. Technical field
[0001] The present invention relates to the technical field of methods for applying a coating to a turbomachine component. More particularly, the present invention relates to the technical field of methods for applying a coating to a turbomachine component subjected to high temperatures and / or an oxidizing environment, such as a turbine. State of the art
[0002] Ceramic matrix composite (CMC) materials are increasingly used for manufacturing turbomachine parts. These materials can withstand high temperatures, potentially exceeding 1200 °C. Turbomachine parts made of CMC material require less cooling. Since this cooling is generally drawn from the compressor, which impacts the turbomachine's efficiency, CMC turbomachine parts improve engine efficiency, thereby reducing fuel consumption. Furthermore, the low density of this material contributes to a reduction in the overall mass of the turbomachines, leading to further fuel savings and thus a significant reduction in pollutant emissions.To improve the corrosion resistance of turbomachinery parts, especially at higher temperatures, their surface can be coated with a protective layer. This protective coating can form an environmental barrier layer and / or a thermal barrier layer. Generally, it is preferable to coat the entire surface of turbomachinery parts with CMC (carbon-moldable composite) to protect the CMC from the engine environment and from contact with other parts made of metallic materials.
[0003] The coating process typically comprises: - the application of a bonding undercoat, for example by thermal spraying (PT) or chemical vapor deposition (CVD); - the application of a protective layer, for example by PT or by liquid means such as electrophoresis; and - sintering of the bonding undercoat and the protective layer in an air furnace at a temperature above 1200 °C.
[0004] During the application of the primer and the protective layer, the CMC part must be held in place. Currently, this holding is achieved by The prior creation of one or more excess lengths on the part. These excess lengths must be removed before the parts are mounted in the turbomachine. This removal step is generally performed by machining. Since CMC material is difficult to machine, the removal step is therefore complex and costly.
[0005] Moreover, the machined face is left without a coating; it is therefore not protected from the engine environment. Summary of the invention
[0006] The present invention improves the situation. It proposes a method for coating a turbomachine part comprising: - fixing the turbomachine part onto a support using a ceramic adhesive to obtain a solid assembly of the turbomachine part and the support, the support and / or the ceramic adhesive being made of graphite; - the application of a coating to a surface of the turbomachine part, the turbomachine part being held by the support; - heat treatment of the assembly under an oxidizing atmosphere.
[0007] The support is intended to hold the turbomachine part by bonding during the coating application. It allows the turbomachine part to be handled during the coating application. The support is preferably bonded to areas of its surface that are minimally exposed to the engine environment during use. In particular, in the case of a distributor blade having a cavity, the support is preferably bonded to an area of the part's surface located within the cavity.
[0008] One of the advantages of the process is that chemical clamping does not present a risk of mechanical damage, such as scratches or indentations, to the turbomachine part, unlike mechanical clamping which requires tightening on it.
[0009] In addition, there is no need to dismantle the turbomachine part between different operations; the support is integral with the turbomachine part and follows it throughout the treatments to which the turbomachine part is subjected.
[0010] In some cases, functionalization is obtained at the end of the coating process thanks to the ceramic adhesive whose ceramic layer plays the role of protection, for example against diffusion of chemical species.
[0011] Other optional features are as follows.
[0012] The ceramic adhesive can be chosen from an alumina-based adhesive, a mullite-based adhesive and a graphite-based adhesive; and the support is graphite.
[0013] The ceramic adhesive can be a graphite-based adhesive; and the support can be a ceramic matrix composite material.
[0014] The fixing may include the formation of an intercalary space between the turbomachine part and the support, and the injection of the ceramic adhesive into the intercalary space.
[0015] The application of the coating may include: - the application of a bonding undercoat on the turbomachine part; and - the application of a protective layer on the bonding undercoat.
[0016] The application of the bonding undercoat can be carried out by thermal spraying or chemical vapor deposition.
[0017] The application of the protective layer can be carried out by thermal spraying, by chemical vapor deposition or by liquid method.
[0018] The heat treatment can be carried out at a temperature above 700 °C, or even at a temperature above 1200 °C.
[0019] The process may further include, prior to the application of the coating, the consolidation of the bonded assembly by baking the ceramic adhesive, preferably at a temperature between 100 °C and 400 °C. Presentation of the drawings
[0020] Other objectives, features and advantages will become apparent from the description given by way of example which follows and is set out with reference to the drawings below, given by way of illustration and not limitation, among which: Fig. 1
[0021] [Fig.l] is a diagram illustrating a first example of the implementation of the coating process according to a first variant of the invention for coating a turbomachine part having a cavity. Fig. 2
[0022] [Fig.2] is a diagram illustrating a second example of the coating process according to the first variant of the invention for coating a cavity-free turbomachine part. Fig. 3
[0023] [Fig.3] is a diagram illustrating a third example of the coating process according to a second variant of the invention for coating a turbomachine part having a cavity. Fig. 4
[0024] [Fig.4] is a diagram illustrating a fourth example of an embodiment of the coating process according to the second variant of the invention for coating a cavity-free turbomachine part. Fig. 5
[0025] [Fig.5] is a flowchart representing the steps of an example of implementation of the coating process according to the invention. Fig. 6
[0026] [Fig.6] is a flowchart representing the steps of another example of implementation of the coating process according to the first variant of the invention. Fig. 7
[0027] [Fig.7] is a flowchart representing the steps of an example of implementation of the fixing step of [Fig.5] and [Fig.6]. Fig. 8
[0028] [Fig.8] is a flowchart representing the steps of an example of implementation of the actual coating step of [Fig.5] and [Fig.6]. Fig. 9
[0029] [Fig.9] is a diagram representing a cross-section through the thickness of a part of turbomachine coated according to the first variant of the coating process according to the invention. Fig. 10
[0030] [Fig. 10] is a diagram representing a cross-section through the thickness of a turbomachine part coated according to the second variant of the coating process according to the invention. Detailed description
[0031] A method for coating a turbomachine part will be described in more detail below with reference to the figures.
[0032] The coating process comprises, as illustrated in [Fig. 5], fixing S100 the turbomachine part 1 to a support 2 using a ceramic adhesive 3 to obtain a bond between the turbomachine part 1 and the support 2, applying S300 a coating 13, and heat-treating S400 the assembly under an oxidizing atmosphere. The support 2 and / or the ceramic adhesive 3 is made of graphite. During the heat treatment S400, the support 2 can thus be removed from the turbomachine part 1 without damaging it, either by disintegration of the ceramic adhesive 3 or by disintegration of the support 2.
[0033] This process is particularly advantageous for turbomachine parts requiring the application of a coating, especially at high temperatures. For example, ceramic matrix composite turbomachine parts intended for use in an engine environment and therefore subjected to hot gas flow must be protected from this environment by the application of a protective coating forming an environmental barrier layer, called an Environmental Barrier Coating (EBC), or a thermal barrier layer. Thermal Barrier Coating (TBC) in English. This application is followed by a heat treatment step to sinter the protective coating.
[0034] The turbomachine component 1 may, in particular, be a distributor or a distributor sector, a blade, a ring or a ring sector, etc. In the example of [Fig. 1], the turbomachine component 1 is a hollow distributor blade. It comprises a body 11 in which a cavity 14 is formed.
[0035] The S100 attachment of the support 2 to the turbomachine part 1 is preferably made on a surface 19 of the part that is relatively unaffected by the flow of hot gases from the combustion chamber. In this case, in the example of [Fig. 1], the support 2 is attached to an area of the surface of the part located in the cavity 14.
[0036] The thickness of the ceramic adhesive 3 is preferably less than 500 µm. Beyond this upper limit, the adhesive risks being excessively porous.
[0037] The fixing S100 can include the formation S110 of an intercalated space 9 between the turbomachine part 1 and the support 2 as well as the injection S120 of the ceramic adhesive 3 into this intercalated space 9 ([Fig.8]).
[0038] The gap 9 between the turbomachine part 1 and the support 2 corresponds to the required adhesive thickness. It therefore preferably has a dimension less than 500 µm.
[0039] Preferably, the S120 injection is carried out at ambient temperature, in particular between 20 and 25°C.
[0040] The support 2 allows the turbomachine part 1 to be held during the application S300 of the coating and the heat treatment S400. The support 2 is typically a part having a bonding surface whose shape is complementary to that of the surface 19 of the turbomachine part 1, to which the support 2 is bonded. In the case of a turbomachine part 1 having a cavity 14 (see [Fig.1] and [Fig.3]) having an outer surface intended to support the machine environment and an inner surface which is not subjected to the flow of hot gases, the support 2 can be a counterform of the cavity 14 of the turbomachine part 1. In other cases, the support can be an elongated part (see [Fig.2] and [Fig.4]) having at one of its ends a relatively small bonding surface, i.e. that its area corresponds to less than 25% of the total surface 18 to be covered of the turbomachine part 1.
[0041] The support 2 may be made of a ceramic material, for example graphite. It may also be made of a ceramic matrix composite material, in particular an oxide / oxide composite, in which the composition of the fibers of the fibrous reinforcement and that of the matrix include a ceramic based on one or more oxides, for example alumina.
[0042] The ceramic adhesive 3 can be chosen from alumina-based adhesives, mullite-based adhesives and graphite-based adhesives.
[0043] Furthermore, the fastening method described herein also allows for the attachment of a representative sample of the turbomachine part to a surface of the part not subjected to the flow of hot gases. Thus, the sample remains attached to the turbomachine part during its processing. Monitoring of the part can therefore be ensured throughout its manufacture. Moreover, the clamping of the sample to the turbomachine part 1 is resistant to the temperatures applied to the turbomachine part 1. This fastening results in an intermediate assembly comprising the turbomachine part 1, the sample, and the ceramic adhesive 3 between a surface 19 of the turbomachine part 1, which is not intended to be subjected to the flow of hot gases, and the sample.
[0044] The S300 application of the coating may include the S310 application of an adhesion undercoat 131 on the turbomachine part 1 and the S320 application of a protective layer 132 on the adhesion undercoat 131 (see [Fig.8], [Fig.9] and [Fig.10]).
[0045] The adhesion sub-layer 131 is, for example, made of silicon. It facilitates the adhesion of the protective layer 132 to the turbomachine part 1.
[0046] The S310 application of the bonding undercoat 131 can be carried out by thermal spraying or chemical vapor deposition. In the case of thermal spraying, the temperature is preferably above 500 °C.
[0047] The protective layer 132 can be made of a material selected from rare earth silicates. In particular, it allows for the formation of an environmental barrier layer and / or a thermal barrier layer.
[0048] The S320 application of the protective layer 132 can be carried out by thermal spraying or by liquid application. In the case of thermal spraying, the temperature is preferably above 500 °C. An example of a liquid application method is electrophoresis.
[0049] The S400 heat treatment is carried out under an oxidizing atmosphere, for example, in air. Advantageously, it is carried out at a temperature above 1200 °C, enabling the oxidation of the graphite. Since the ceramic adhesive 3 and / or the support 2 are made of graphite, the S400 heat treatment leads to the removal of this graphite element, resulting in the separation of the support 2 from the turbomachine part 1.
[0050] The S400 heat treatment can also allow the sintering of the protective layer 132.
[0051] The coating process described here mainly has two implementation variants.
[0052] In a first embodiment of the invention, the support 2 is made of graphite. Thus, the support 2 is removed during the heat treatment step S400 and forms a sacrificial element. In this embodiment, the ceramic adhesive 3 can be selected from alumina-based adhesives, mullite-based adhesives, and graphite-based adhesives.
[0053] If the ceramic adhesive chosen is alumina-based or mullite-based, it is ceramicized during the S400 heat treatment and forms a protective layer 12 (see [Fig. 1], [Fig. 2], and [Fig. 9]), in particular a diffusion-resistant protective layer, which will remain on the finished turbomachine part. Indeed, during their use, turbomachine parts can come into contact with metallic parts. This contact leads to diffusion of elements between the metal and the ceramic. Thus, the process has the advantage not only of simplifying the coating process of the turbomachine part 1, and in particular of its surface intended to be subjected to the engine environment, but also of allowing the application of a protective layer 12 to another surface.
[0054] If the ceramic adhesive 3 is graphite-based, it is also eliminated during the S400 heat treatment (see [Fig. 10]).
[0055] In an embodiment illustrated in [Fig.6], the process may further include, prior to the application S300 of the coating, the consolidation S200 of the bonded assembly by baking the adhesive, preferably between 100 °C and 400 °C, for a period of between 1 hour and 3 hours.
[0056] In a second embodiment of the invention, the support 2 is not sacrificial and is recovered at the end of the process for subsequent use. In this case, the support 2 may be made of a ceramic matrix composite material, for example oxide / oxide.
[0057] Ceramic adhesive 3 is then a graphite-based adhesive.
[0058] In each of the two variants of the invention, the elimination of the support 2 and / or the ceramic adhesive 3 during the S400 heat treatment avoids a machining step to remove the bond between the turbomachine part 1 and the support 2.
Claims
Demands
1. A method for coating a turbomachine part (1), comprising: - fixing (S 100) the turbomachine part on a support (2) using a ceramic adhesive (3) to obtain a bonded assembly of the turbomachine part and the support, the support and / or the ceramic adhesive being made of graphite; - applying (S300) a coating (13) to a surface of the turbomachine part, the turbomachine part being held by the support (2); - heat treating (S400) the assembly under an oxidizing atmosphere.
2. A method according to claim 1, wherein the ceramic adhesive is selected from an alumina-based adhesive, a mullite-based adhesive and a graphite-based adhesive; and the support is made of graphite.
3. Method according to claim 1, wherein the ceramic adhesive is a graphite-based adhesive; and the support is made of a ceramic matrix composite material.
4. A method according to any one of claims 1 to 3, wherein the fixing comprises the formation (SI 10) of an intercalated space (9) between the turbomachine part and the support, and the injection (S 120) of the ceramic adhesive into the intercalated space.
5. A method according to any one of claims 1 to 4, wherein the application of the coating comprises: - the application (S310) of an adhesion undercoat on the turbomachine part; and - the application (S320) of a protective layer on the adhesion undercoat.
6. A method according to claim 5, wherein the application of the bonding undercoat is carried out by thermal spraying or chemical vapor deposition.
7. A method according to claim 5 or claim 6, wherein the application of the protective layer is carried out by thermal spraying, by chemical vapor deposition or by liquid method.
8. A method according to any one of claims 1 to 7, wherein the heat treatment is carried out at a temperature above 700 °C, or even at a temperature above 1200 °C.
9. A method according to any one of claims 1 to 8, further comprising, prior to the application of the coating, the consolidation (S200) of the bonded assembly by baking the ceramic adhesive, preferably at a temperature between 100 °C and 400 °C. Title: Method for coating a turbomachine part