METHOD FOR COATING THERMAL/ENVIRONMENTAL BARRIER COATING

Abstract

The present disclosure discloses a method for coating an environmental barrier coating, comprising: coating an aluminum film layer on a surface of a rare earth silicate ceramic layer, and heat treating the aluminum film layer to form a rare earth aluminate phase at least in pores of a side of the rare earth silicate ceramic layer facing the aluminum film layer. An environmental barrier coating prepared by the above method is also disclosed.

Claims

1. A method for coating an environmental barrier coating, comprising: coating an aluminum film layer on a surface of a rare earth silicate ceramic layer formed by thermal spraying; and heat treating the aluminum film layer to form a rare earth aluminate phase at least in pores of a side of the rare earth silicate ceramic layer facing the aluminum film layer.

2. The method for coating an environmental barrier coating according to claim 1, wherein the aluminum film layer has a thickness of 2-5 m.

3. The method for coating an environmental barrier coating according to claim 2, wherein the aluminum film layer is coated by a magnetron sputtering method.

4. The method for coating an environmental barrier coating according to claim 1, wherein the rare earth silicate ceramic layer is selected from the group consisting of a Lu.sub.2Si.sub.2O.sub.7 ceramic layer, a Lu.sub.2SiO.sub.5 ceramic layer, a Yb.sub.2SiO.sub.5 ceramic layer and a Yb.sub.2SiO.sub.5 ceramic layer.

5. The method for coating an environmental barrier coating according to claim 4, wherein the heat treating is performed by holding at a temperature of 700-800 C. for 2-4 h, and then raising the temperature to 1300-1350 C. and holding for 20-24 h.

6. The method for coating an environmental barrier coating according to claim 5, wherein the temperature is raised at a rate of 5-30 C./min.

7. The method for coating an environmental barrier coating according to claim 1, wherein before the coating an aluminum film layer on a surface of a rare earth silicate ceramic layer, the method further comprises: coating the rare earth silicate ceramic layer on a surface of a mullite layer.

8. The method for coating an environmental barrier coating according to claim 7, wherein before the coating the rare earth silicate ceramic layer on a surface of a mullite layer, the method further comprises: coating the mullite layer on a surface of a silicon layer.

9. An environmental barrier coating, wherein the environmental barrier coating is obtained by using the method for coating an environmental barrier coating according to claim 1.

10. The method for coating an environmental barrier coating according to claim 1, wherein the aluminum film layer is heat-treated to form the rare earth aluminate phase in the pores on the side of the rare earth silicate ceramic layer facing the aluminum film layer, and to form a rare earth aluminate phase layer on the side of the rare earth silicate ceramic layer facing the aluminum film layer.

11. The method for coating an environmental barrier coating according to claim 3, wherein operating parameters of the magnetron sputtering method comprise: a magnetron target current of 3-6 A, and a bias voltage of 150-250 V.

12. The method for coating an environmental barrier coating according to claim 4, wherein the rare earth silicate ceramic layer is the Yb.sub.2SiO.sub.5 ceramic layer, and a Yb.sub.3Al.sub.5O.sub.12 coating is formed after heat treating the surface on which the aluminum film layer is deposited.

13. The method for coating an environmental barrier coating according to claim 5, wherein the heat treatment is a vacuum heat treatment, in which an oxygen partial pressure is less than 210.sup.3 Pa.

14. The method for coating an environmental barrier coating according to claim 7, wherein the surface of the mullite layer is coated with the rare earth silicate ceramic layer by using an air plasma spraying method or a plasma spraying-physical vapor deposition method.

15. The method for coating an environmental barrier coating according to claim 7, wherein the mullite layer has a thickness of 50-80 m; and the rare earth silicate ceramic layer has a thickness of 80-100 m.

16. The method for coating an environmental barrier coating according to claim 8, wherein the silicon layer has a thickness of 40-60 m.

17. The method for coating an environmental barrier coating according to claim 8, wherein the surface of the silicon layer is coated with the mullite layer by using an air plasma spraying method or a plasma spraying-physical vapor deposition method.

18. The method for coating an environmental barrier coating according to claim 8, wherein before the coating the mullite layer on a surface of a silicon layer, the method further comprises: coating the silicon layer on a surface of a substrate.

19. The method for coating an environmental barrier coating according to claim 18, wherein the surface of the substrate is coated with the silicon layer by using an air plasma spraying method or a plasma spraying-physical vapor deposition method.

20. The method for coating an environmental barrier coating according to claim 18, wherein the substrate is a silicon carbide-based composite substrate.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate technical solutions of embodiments of the present disclosure, drawings required for use in the embodiments will be described briefly below. It should be understood that the following drawings are merely illustrative of some embodiments of the present disclosure, and therefore should not be considered as limitation on the scope. It will be understood by those of ordinary skill in the art that other related drawings can also be obtained from these drawings without any inventive effort.

[0014] FIG. 1 is an SEM image of a cutting plane of a coating obtained after the aluminum film is coated and before the heat treatment is performed in the process of preparing the environmental barrier coating in an embodiment;

[0015] FIG. 2 is an SEM image of a cutting plane of the environmental barrier coating prepared in the embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0016] In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below. If no specific conditions are specified in the embodiments, they are carried out under normal conditions or conditions recommended by manufacturers. If the manufacturers of reagents or instruments used are not specified, the reagents or instruments are conventional products commercially available.

[0017] The present disclosure provides an environmental barrier coating and a coating method thereof, which are intended to further improve the service performance and service life of an environmental barrier coating using a rare earth silicate ceramic layer as an isolation layer.

[0018] This disclosure is implemented as follows.

[0019] In a first aspect, the embodiments of the present disclosure provide a method for coating an environmental barrier coating, comprising:

[0020] coating an aluminum film layer on a surface of a rare earth silicate ceramic layer;

[0021] heat treating the aluminum film layer to form a rare earth aluminate phase at least in pores of a side of the rare earth silicate ceramic layer facing the aluminum film layer.

[0022] In an optional embodiment, the aluminum film layer is heat-treated to form a rare earth aluminate phase in the pores on the side of the rare earth silicate ceramic layer facing the aluminum film layer, and to form a rare earth aluminate phase layer on the side of the rare earth silicate ceramic layer facing the aluminum film layer.

[0023] In an optional embodiment, the thickness of the aluminum film layer is 25 m.

[0024] In an optional embodiment, the method for spraying the aluminum film layer is magnetron sputtering method.

[0025] In an optional embodiment, the operating parameters of the magnetron sputtering method are as follows: a magnetron target current of 36 A and a bias voltage of 150250 V.

[0026] In an optional embodiment, the rare earth silicate ceramic layer includes Lu.sub.2Si.sub.2O.sub.7, Lu.sub.2SiO.sub.5, Yb.sub.2SiO.sub.5 and Yb.sub.2SiO.sub.5 ceramic layers.

[0027] In an optional embodiment, the rare earth silicate ceramic layer is a Yb.sub.2SiO.sub.5 ceramic layer, and a Yb.sub.3Al.sub.5O.sub.12 coating is formed after heat treating the surface on which the aluminum film layer is deposited.

[0028] In an optional embodiment, the heat treatment is performed by holding at a temperature of 700800 C. for 24 h, and then raising the temperature to 13001350 C. and holding for 2024 h.

[0029] In an optional embodiment, the heat treatment is a vacuum heat treatment in which the oxygen partial pressure is less than 210.sup.3 Pa.

[0030] In an optional embodiment, the temperature is raised at a rate of 530 C./min.

[0031] In an optional embodiment, before spraying an aluminum film layer on the surface of the Yb.sub.2SiO.sub.5 ceramic layer, the method further comprises:

[0032] coating a rare earth silicate ceramic layer on a surface of a mullite layer.

[0033] In an optional embodiment, the surface of the mullite layer is coated with the rare earth silicate ceramic layer by using air plasma spraying or plasma spraying-physical vapor deposition method;

[0034] In an optional embodiment, the mullite layer has a thickness of 5080 m; and the rare earth silicate ceramic layer has a thickness of 80100 m.

[0035] In an optional embodiment, before coating the rare earth silicate ceramic layer on the surface of the mullite layer, the method further comprises: coating the mullite layer on the surface of a silicon layer.

[0036] In an optional embodiment, the thickness of the silicon layer is 4060 m;

[0037] In an optional embodiment, the surface of the silicon layer is coated with a mullite layer by using air plasma spraying or plasma spraying-physical vapor deposition method.

[0038] In an optional embodiment, before coating the mullite layer on the surface of the silicon layer, the method further comprises: coating the silicon layer on a surface of a substrate; and in an optional embodiment, the surface of the substrate is coated with a silicon layer by using air plasma spraying or plasma spraying-physical vapor deposition method.

[0039] In an optional embodiment, the substrate is a silicon carbide-based composite substrate.

[0040] In a second aspect, the embodiments of the present disclosure provide an environmental barrier coating, which is obtained by using the method for coating an environmental barrier coating according to any one of the foregoing embodiments.

[0041] In a third aspect, the embodiments of the present disclosure provide an application of the environmental barrier coating as described in the foregoing embodiments in the aerospace field.

[0042] The present disclosure has the following beneficial effects:

[0043] For the method for coating an environmental barrier coating obtained by the present disclosure through the above design, since an aluminum film layer is provided on the surface of the rare earth silicate and then heat treatment is performed, molten aluminum enters the pores on the surface of the rare earth silicate ceramic layer to fill the pores, and the molten aluminum reacts with the rare earth oxide and silicon dioxide to form a more dense and water-resistant rare earth aluminate phase, with the rare earth oxide and silicon dioxide generated by the decomposition of the rare earth silicate ceramic layer under the thermal environment. The present disclosure effectively improves the service performance of the environmental barrier coating and prolongs the service time thereof.

[0044] For the environmental barrier coating obtained by the present disclosure through the above design, since it is prepared by using the method provided by the present disclosure, it has good service performance and long service time. When used in the aerospace field, it can significantly improve the service performance and service life of the aerospace equipment.

[0045] The environmental barrier coating, the coating method and application thereof provided by the embodiments of the present disclosure will be specifically described below.

[0046] The inventors have discovered that the main reasons why the performance of existing rare earth silicate environmental barrier coatings needs to be further improved are as follows:

[0047] in the process of forming the rare earth silicate environmental barrier coating by coating, the rare earth silicate is easily decomposed into the rare earth oxide and SiO.sub.2 during the thermal spraying deposition process, and these two substances generated by the decomposition have relatively low water-oxygen corrosion resistance; when preparing the environmental barrier coatings by thermal spraying, due to the thermal effect, there are micro-cracks on the coating surface to varying degrees, and these micro-cracks make it easy for the water and oxygen channels to form during the service process of coatings, thereby leading to early failure of the coatings; and the cracks will be formed in the process of thermal cycle, thereby making it difficult to further increase the service life of rare earth element coatings.

[0048] Method for coating an environmental barrier coating, comprises:

[0049] S1. sequentially providing a silicon layer, a mullite layer, and a rare earth silicate ceramic layer on the surface of the substrate.

[0050] The silicon layer, the mullite layer, and the rare earth silicate ceramic layer were prepared on the surface of the silicon carbide-based composite by a thermal spraying method. The thermal spraying method may be air plasma spraying or plasma spraying-physical vapor deposition method.

[0051] The silicon layer is used as a bonding layer, which firmly bonds the silicon carbide-based composite, used as a substrate, to the mullite.

[0052] The mullite has a coefficient of thermal expansion similar to that of silicon-based ceramic materials, good chemical compatibility with the silicon-based ceramic materials, and excellent corrosion resistance. Therefore, the mullite was used as the intermediate layer.

[0053] Rare earth silicates have better surface stability. The coating obtained by sequentially providing a silicon layer, a mullite layer, and a rare earth silicate layer is an environmental coating that is widely used and has better performance in the prior art.

[0054] A common air plasma spraying or plasma spraying-physical vapor deposition method is used to sequentially form a silicon layer, a mullite layer, and a rare earth silicate ceramic layer on the surface of the substrate. It should be noted that the method for providing the above coating is not limited to the air plasma spraying or plasma spraying-physical vapor deposition method, and other existing methods for providing barrier coatings are also applicable.

[0055] However, rare earth silicate is generally prepared by a solid-phase reaction sintering method, i.e., is obtained by a sintering reaction of the rare earth oxide and SiO.sub.2 at a high temperature. During the spraying process, the temperature of the local plasma is much higher than its melting point, which leads to the decomposition of part of rare earth silicate. Although the subsequent heat treatment for the coating causes the decomposed products to react again to form rare earth silicate, the decomposed products could not react completely, and there were still some residual oxidation products, which react with water vapor under a high-temperature water-oxygen environment to form compounds to evaporate, causing the coating to have a porous structure and produce cracks in the process of thermal cycle, which destroys the service performance of the coating.

[0056] The rare earth silicate referred to in the present disclosure is preferably a rare earth silicate commonly used in environmental barrier coatings, and is specifically selected from Lu.sub.2Si.sub.2O.sub.7, Lu.sub.2SiO.sub.5 and Yb.sub.2SiO.sub.5.

[0057] In order to overcome the defects caused by the preparation process of the rare earth silicate ceramic layer and further improve the performance of the environmental barrier coating, the following operations were performed on the surface of the rare earth silicate ceramic layer:

[0058] S2. coating an aluminum film layer on a surface of a rare earth silicate ceramic layer.

[0059] After the rare earth silicate ceramic layer is provided, an aluminum film layer is coated on its surface by using a magnetron sputtering method.

[0060] Specifically, in order to make the coating coated uniformly and firmly, the operating parameters of the magnetron sputtering method are as follows: a magnetron target current of 36 A, and a bias voltage of 150250 V.

[0061] S3. heat treating the aluminum film layer to form a rare earth aluminate phase at least in pores of a side of the rare earth silicate ceramic layer facing the aluminum film layer.

[0062] There are certain micro-cracks on the surface of the rare earth silicate ceramic layer. Under the heat treatment, the molten aluminum penetrates into the coating and seals the coating cracks near the surface. In addition, the Al film fusion-covering on the surface of the environmental barrier coating and the Al infiltrated in the cracks will react with the rare earth oxide phase and the SiO.sub.2 phase in the environmental barrier coating. The molten Al first reacts with SiO.sub.2 to form the Al.sub.2O.sub.3 phase, and then Al.sub.2O.sub.3 phase continues to react with the rare earth oxide to form a rare earth aluminate phase. Through the above steps, rare earth aluminate phase is obtained at least in the pores of the surface of the rare earth silicate coating, and such rare earth aluminate phase is denser and has water and oxygen corrosion resistance.

[0063] Preferably, the heat treatment conditions are reasonably adjusted to form a rare earth aluminate phase in the pores on the side of the rare earth silicate ceramic layer facing the aluminum film layer, and to form a rare earth aluminate phase layer on the side of the rare earth silicate ceramic layer facing the aluminum film layer. In addition to forming the rare earth aluminate phase in the pores, rare earth aluminate phase layer, which is dense and has water and oxygen corrosion resistance, is also formed on the surface of the rare earth silicate ceramic layer to further improve the performance of the environmental barrier coating.

[0064] Preferably, in the preferred embodiments of the present disclosure, the rare earth silicate is preferably Yb.sub.2SiO.sub.5, and a Yb.sub.3Al.sub.5O.sub.12 coating is formed after heat treating the surface on which the aluminum film layer is deposited.

[0065] Yb.sub.3Al.sub.5O.sub.12 has a regular dodecahedron garnet-type crystal structure and is generally crystallized in an isometric system. It has a good thermal compatibility with Yb.sub.2SiO.sub.5 (Yb.sub.3Al.sub.5O.sub.12 has a coefficient of thermal expansion of 7.510.sup.6 K.sup.1 and Yb.sub.2SiO.sub.5 has a coefficient of thermal expansion of 7810.sup.6 K.sup.1), and meanwhile, has relatively high strength and fracture toughness and low heat conductivity coefficient (theoretical heat conductivity coefficient being 1.22 w/m.Math.k). Yb.sub.3Al.sub.5O.sub.12 is limited by its material characteristics, and it is easy to generate relatively large stress cracks in the process of thermal spraying, which causes relatively large defects in the coating. However, in the present disclosure, Yb.sub.3Al.sub.5O.sub.12 is synthesized in situ by performing vacuum heat treatment on an aluminum film layer used as a reaction material and the decomposition products of the Yb.sub.2SiO.sub.5 ceramic layer, which not only effectively solves the defects of the original Yb.sub.2SiO.sub.5 ceramic layer generated during the spraying process, but also avoids the relatively large stress cracks caused by directly forming the Yb.sub.3Al.sub.5O.sub.12 protective layer in the process of preparation, and which not only can improve the service performance and service time of the environmental barrier coating on the basis of the existing environmental barrier coating using Yb.sub.2SiO.sub.5 ceramic layer as the surface layer, but also can make Yb.sub.3Al.sub.5O.sub.12 play an advantage in the field of high temperature protection.

[0066] Preferably, in order to ensure that the overall performance of the prepared environmental barrier coating is better, the thickness of the silicon layer is 4060 m, the thickness of the mullite layer is 5080 m, and the thickness of the Yb.sub.2SiO.sub.5 ceramic layer is 80100 m.

[0067] Preferably, in order to ensure that the thickness of the prepared Yb.sub.3Al.sub.5O.sub.12 coating is more suitable for environmental barrier coatings, and to ensure that sufficient molten aluminum can penetrate into the cracks and pores of the Yb.sub.2SiO.sub.5 ceramic layer under a vacuum heat treatment, the thickness of the aluminum film layer is 25 m.

[0068] Preferably, the melting point of pure aluminum is known to be about 667 C., in order to ensure that the Yb.sub.3Al.sub.5O.sub.12 phase can be obtained by heat treatment, the vacuum heat treatment is performed by holding at 700800 C. for 24 h, and then raising the temperature to 13001350 C. and holding for 2024 h. The temperature is maintained at 700-800 C. for 2-4 h to make the Al film remolten and fully penetrate into the coating pores and spread evenly on the coating (if the time is too short, Al cannot fully penetrate into the pores and spread). At the same time, Al will also undergo the preoxidation reaction to form Al.sub.2O.sub.3. It is then heated to the temperature (1300-1350 C.) for the reaction between Al.sub.2O.sub.3 and Yb.sub.2O.sub.3, so that Al.sub.2O.sub.3 and Yb.sub.2O.sub.3 react in situ to generate Yb.sub.3Al.sub.5O.sub.12, making the Yb.sub.3Al.sub.5O.sub.12 protective layer cover the coating uniformly.

[0069] Preferably, in order to avoid air interference reaction, the heat treatment is a vacuum heat treatment, and the oxygen partial pressure is less than 210.sup.3 Pa. Of course, in other embodiments of the present disclosure, the heat treatment may also be performed in an inert gas atmosphere, which can also achieve the effect of preventing air from participating in the reaction.

[0070] More preferably, the temperature is raised at a rate of 530 C./min. The temperature raised rate is guaranteed within a certain range, which not only ensures the heating efficiency, but also avoids relatively large thermal stress generated in the coating caused by the too fast rate, which stress may introduce defects and damage the mechanical properties of the original coating.

[0071] The environmental barrier coating provided by the embodiments of the present disclosure is obtained by coating by using the method for coating an environmental barrier coating provided by the embodiments of the present disclosure. The coating has good resistance to water and oxygen corrosion and long service life. The coating is suitable for the aerospace field. When the coating is used as the coating of an aero-engine, the service life of the aero-engine can be greatly prolonged.

[0072] The features and performances of the present disclosure will be further described in detail below in combination with the embodiments.

Embodiment 1

[0073] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0074] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using air plasma spraying, with the coatings successively having thicknesses of 50 m, 50 m and 80 m;

[0075] preparing an aluminum film layer with a thickness of 3m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 3 A and a bias voltage of 150 V;

[0076] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 800 C. kept for 2 h, 1300 C. kept for 24 h, a temperature raising rate of 5 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 P; and

[0077] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 2

[0078] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0079] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using plasma spraying-physical vapor deposition, with the coatings successively having thicknesses of 50 m, 50 m and 80 m;

[0080] preparing an aluminum film layer with a thickness of 3 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 3 A and a bias voltage of 150 V;

[0081] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 700 C. kept for 2 h, 1300 C. kept for 24 h, a temperature raising rate of 10 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0082] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 3

[0083] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0084] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using plasma spraying-physical vapor deposition, with the coatings successively having thicknesses of 50 m, 50 m and 80 m;

[0085] preparing an aluminum film layer with a thickness of 2 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 3 A and a bias voltage of 150 V;

[0086] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 700 C. kept for 2 h, 1350 C. kept for 20 h, a temperature raising rate of 10 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0087] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 4

[0088] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0089] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using air plasma spraying, with the coatings successively having thicknesses of 50 m, 50 m and 80 m;

[0090] preparing an aluminum film layer with a thickness of 2 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 3 A and a bias voltage of 250 V;

[0091] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 800 C. kept for 2 h, 1350 C. kept for 20 h, a temperature raising rate of 5 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0092] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 5

[0093] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0094] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using plasma spraying-physical vapor deposition, with the coatings successively having thicknesses of 50 m, 50 m and 80 m;

[0095] preparing an aluminum film layer with a thickness of 5 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 4 A and a bias voltage of 230 V;

[0096] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 800 C. kept for 4 h, 1350 C. kept for 24 h, a temperature raising rate of 10 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0097] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 6

[0098] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0099] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using air plasma spraying, with the coatings successively having thicknesses of 50 m, 50 m and 80 m;

[0100] preparing an aluminum film layer with a thickness of 5 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 4 A and a bias voltage of 200 V;

[0101] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 800 C. kept for 4 h, 1350 C. kept for 24 h, a temperature raising rate of 5 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0102] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 7

[0103] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0104] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using air plasma spraying, with the coatings successively having thicknesses of 40 m, 80 m and 100 m;

[0105] preparing an aluminum film layer with a thickness of 4 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 5 A and a bias voltage of 170 V;

[0106] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 750 C. kept for 3 h, 1320 C. kept for 22 h, a temperature raising rate of 30 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0107] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 8

[0108] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0109] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using air plasma spraying, with the coatings successively having thicknesses of 60 m, 70 m and 90 m;

[0110] preparing an aluminum film layer with a thickness of 4 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 4 A and a bias voltage of 170 V;

[0111] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 720 C. kept for 3 h, 1320 C. kept for 23 h, a temperature raising rate of 20 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0112] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

Embodiment 9

[0113] The method for coating an environmental barrier coating provided by this embodiment includes the following operating steps:

[0114] preparing a Si coating, a mullite coating, and a Yb.sub.2SiO.sub.5 coating on the surface of silicon carbide-based composite substrate by using air plasma spraying, with the coatings successively having thicknesses of 60 tm, 60 m and 90 m;

[0115] preparing an aluminum film layer with a thickness of 3 m on the surface of the Yb.sub.2SiO.sub.5 coating by using the magnetron sputtering, wherein the conditions of the magnetron sputtering are as follows: a magnetron target current of 4 A and a bias voltage of 170 V;

[0116] heat treating the Yb.sub.2SiO.sub.5 coating deposited with the aluminum film layer, wherein the conditions of heat treatment are as follows: 720 C. kept for 3 h, 1320 C. kept for 23 h, a temperature raising rate of 25 C./min, and a vacuum oxygen partial pressure less than 210.sup.3 Pa; and

[0117] cooling to a room temperature, to obtain the environmental barrier coating on the surface of the substrate.

EXPERIMENTAL EXAMPLE 1

[0118] The coating, obtained after the aluminum film layer is coated and before the vacuum heat treatment is performed in the preparing process of Embodiment 1 was cut, the section after the cutting was polished, and then subjected to a scanning electron microscope to obtain a microstructure diagram as shown in FIG. 1.

[0119] The final coating prepared in Embodiment 1 was cut, and the section after the cutting was polished and then subjected to a scanning electron microscope to obtain a microstructure diagram as shown in FIG. 2.

[0120] It can be seen from FIG. 1 that there are pores in the Yb.sub.2SiO.sub.5 ceramic layer.

[0121] It can be seen from FIG. 2 that the pores on the surface of the Yb.sub.2SiO.sub.5 ceramic layer are filled with Yb.sub.3Al.sub.5O.sub.12 after the heat treatment.

[0122] To sum up, for the method for coating an environmental barrier coating provided by the present disclosure, since an aluminum film layer is provided on the surface of the rare earth silicate and then heat treatment is performed, molten aluminum enters the pores on the surface of the rare earth silicate ceramic layer to fill the pores, and the molten aluminum reacts with the rare earth oxide and silicon dioxide to form a more dense and water-resistant rare earth aluminate, with the rare earth oxide and silicon dioxide generated by the decomposition of the rare earth silicate ceramic layer under the thermal environment. The present disclosure effectively improves the service performance of the environmental barrier coating and prolongs the service time thereof.

[0123] Further, in addition to enabling the rare earth aluminate phase to be generated in the pores on the surface of the rare earth silicate ceramic layer, the heat treatment also enables the rare earth aluminate phase layer to be formed on the surface of the rare earth silicate ceramic layer, which can further improve the performance of the environmental barrier coating.

[0124] Further, when the rare earth silicate is Yb.sub.2SiO.sub.5, heat treatment is performed at an appropriate temperature to generate Yb.sub.3Al.sub.5O.sub.12, which has good thermal compatibility with Yb.sub.2SiO.sub.5. The Yb.sub.3Al.sub.5O.sub.12 layer has relatively high strength and fracture toughness and low heat conductivity coefficient, which can make the obtained environmental barrier coating have the characteristics of high density and excellent resistance to water and oxygen corrosion. Performing heat treatment on the aluminum film layer to form the Yb.sub.3Al.sub.5O.sub.12 coating effectively avoids the defects of large stress cracks produced during the thermal spraying process, and enables the Yb.sub.3Al.sub.5O.sub.12 coating to be effectively used in the field of high-temperature protective coatings.

[0125] Since the environmental barrier coating provided by the present disclosure is prepared by the method provided by the present disclosure, it has a dense and water-resistant rare earth aluminate phase layer on its surface, and the pores on the outward side of the ceramic layer containing the rare earth silicate are also filled, therefore, the environmental barrier coating has good service performance and long service life.

[0126] The above mentioned are only preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. For those skilled in the art, various modifications and changes can be made to the present disclosure. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

INDUSTRIAL APPLICABILITY

[0127] For the method for coating an environmental barrier coating provided by the present disclosure, since an aluminum film layer is provided on the surface of the rare earth silicate and then heat treatment is performed, molten aluminum enters the pores on the surface of the rare earth silicate ceramic layer to fill the pores, and the molten aluminum reacts with the rare earth oxide and silicon dioxide to form a more dense and water-resistant rare earth aluminate phase, with the rare earth oxide and silicon dioxide generated by the decomposition of the rare earth silicate ceramic layer under the thermal environment. The present disclosure effectively improves the service performance of the environmental barrier coating and prolongs the service time thereof.

[0128] For the environmental barrier coating provided by the present disclosure, since it is prepared by using the method provided by the present disclosure, it has good service performance and long service time. When used in the aerospace field, it can significantly improve the service performance and service life of the aerospace equipment.