A long-life multi-element rare earth environmental barrier coating and its preparation method

Abstract

This invention discloses a long-life multi-element rare earth environmental barrier coating and its preparation method. The coating comprises a composite coating of a five-rare-earth main component double silicate surface layer and an in-situ generated SiC adhesive layer. The preparation method uses Si powder of a specific particle size and five-rare-earth main component double silicate spherical powder as raw materials. Using thermal spraying technology and argon atmosphere heat treatment, a Si layer is sequentially deposited on the surface of a C / SiC composite material or a C / C composite material. After heat treatment, an in-situ SiC adhesive layer is formed, followed by the deposition of a high-entropy double silicate surface layer. The use of the SiC adhesive layer avoids the disadvantages of traditional Si adhesive layers, such as low melting point and easy oxidation. The reasonable combination of rare earth main components results in high fracture toughness of the surface layer, better resistance to water and oxygen corrosion, and a longer service life. This overcomes the shortcomings of existing Si-based environmental barrier coatings and extends service life.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a long-life multi-element rare earth environmental barrier coating and its preparation method. Background Technology

[0002] The temperature at the air intake end of aero engines is getting higher and higher, exceeding the service temperature of traditional Ni-based superalloys. SiC ceramic matrix composites are used in aero engine hot-end components due to their high melting point and high specific strength. However, due to the presence of water vapor and oxygen in the service environment, SiC is oxidized to SiO2 and then to Si(OH)4, which greatly reduces the service life. At present, environmental barrier coatings are used to solve this problem. The existing environmental barrier coatings have an inner layer of Si adhesive layer and an outer layer of rare earth silicate surface layer.

[0003] Pure silicon has a coefficient of thermal expansion close to that of the substrate, but due to its melting point of 1410℃, its service temperature is limited to below 1400℃. Furthermore, during service, it is oxidized to form thermally generated oxide SiO2. SiO2 undergoes a phase transition during thermal cycling, and the resulting stress can cause the coating to peel off. Meanwhile, existing rare-earth silicate coatings suffer from weak protective performance at 1500℃, inconsistent resistance to water and oxygen corrosion with mechanical properties, and high thermal conductivity, thus limiting the service temperature of current environmental barrier coatings.

[0004] Therefore, designing an adhesive layer with a higher melting point and oxidation resistance, and a top layer that is resistant to water-oxygen corrosion at 1500℃ and has excellent mechanical and thermal insulation properties, in order to improve the service life of environmental barrier coatings, is a problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a long-life multi-element rare earth environmental barrier coating and its preparation method, which improves the melting point of the adhesive layer and the water and oxygen corrosion resistance and mechanical properties of the surface layer, thereby extending the service life of the environmental barrier coating.

[0006] A long-life multi-element rare earth environmental barrier coating has a structure comprising a SiC adhesive layer and a multi-rare earth principal component dual silicate surface layer sequentially deposited on a C / SiC composite material or a C / C composite material matrix; the multi-rare earth principal component dual silicate surface layer has the chemical formula (Yb 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5 )2Si2O7, which has a single β-phase structure, and the adhesive layer has a 6H-type SiC structure. Both the multi-rare earth principal component double silicate surface layer and the adhesive layer have a dense structure, with a density of >95%.

[0007] Furthermore, the thickness of the multi-rare earth principal component disilicate surface layer is 150–300 μm.

[0008] Furthermore, the adhesive layer is 30–70 μm thick.

[0009] A method for preparing a long-life multi-element rare earth environmental barrier coating, comprising the following steps:

[0010] Step S1: Pre-treat the surface of the ceramic matrix composite workpiece;

[0011] Step S2: Preheat the pretreated ceramic matrix composite workpiece;

[0012] Step S3: Apply a layer of Si to the surface of the ceramic matrix composite workpiece using thermal spraying technology to obtain the matrix;

[0013] Step S4: Heat-treat the substrate coated with the Si layer in an inert protective atmosphere to allow the Si layer to react in situ and form a SiC bonding layer.

[0014] Step S5: Using rare earth element dual silicate powder as raw material, a rare earth element dual silicate surface layer is deposited on the SiC bonding layer using thermal spraying technology, and then cooled after spraying.

[0015] Furthermore, in step S1, the workpiece surface pretreatment process is as follows: after soaking in organic solvent, it is dried at 150-200℃, and then sandblasted to make the surface roughness Ra8-12μm.

[0016] Furthermore, in step S2, the preheating temperature is between 600 and 1000°C.

[0017] Furthermore, in step S3, spherical Si powder with a particle size of 25–75 μm is used as raw material. The thermal spraying technology is vacuum plasma spraying, with a chamber pressure of 80–120 Pa, a spraying current of 560–600 A, a main gas argon of 38–42 L / min, an auxiliary gas hydrogen of 2.8–3.2 L / min, a spraying distance of 90–130 mm, a gun speed of 600–1200 mm / s, and a powder feeding speed of 6–10 g / min.

[0018] Furthermore, the heat treatment in step S4 is to heat-treat at 1300-1400℃ in an argon atmosphere for 12-16 hours, so that Si reacts in situ with the substrate to obtain the SiC adhesive layer.

[0019] Furthermore, in step S5, the rare earth principal component disilicate powder is spherical with a particle size range of 30–90 μm. The thermal spraying technology is atmospheric plasma spraying with a spraying power of 38–45 kW, a main gas argon of 50–58 L / min, an auxiliary gas hydrogen of 4.8–5.6 L / min, a spraying distance of 90–130 mm, a gun speed of 600–1200 mm / s, and a powder feeding speed of 30–38 g / min.

[0020] Furthermore, in step S5, compressed air is used for cooling, so that the coating cools at a rate of 40–60 °C / s.

[0021] This invention replaces the traditional Si adhesive layer with a SiC adhesive layer, which has a higher melting point. This increases the melting point of the adhesive layer, enhances its oxidation resistance, and eliminates the problem of TGO (transfer-induced oxidation). Furthermore, SiC has stronger oxygen barrier properties than SiO2, improving the service life of the substrate. Among the rare-earth main elements in the surface layer, Yb exhibits the best overall performance, Lu has excellent resistance to high-temperature, high-speed water vapor corrosion, Ho has excellent mechanical properties, and Sc has low thermal conductivity. Y is used to balance the ionic radius of the dopant elements. The rare-earth bissilicates corresponding to the selected main elements have similar structures, all possessing a β-type monoclinic structure. By combining different rare-earth elements and utilizing the high-entropy effect of lattice hysteresis diffusion and the cocktail effect, a surface layer with stronger resistance to water and oxygen corrosion, higher toughness, and lower thermal conductivity than a single rare-earth bissilicate surface layer is obtained.

[0022] The preparation method provided by this invention uses Si powder and five rare earth principal component disilicate spherical powders as raw materials. A Si layer is sequentially deposited on the surface of a SiC-ceramic matrix composite (CMC) using vacuum plasma spraying, atmospheric plasma spraying, and argon atmosphere heat treatment. After heat treatment, a SiC adhesive layer is formed in situ, followed by the deposition of a high-entropy disilicate surface layer. The use of a SiC adhesive layer avoids the disadvantages of traditional Si adhesive layers, such as low melting point and easy oxidation. The reasonable combination of rare earth principal components results in high fracture toughness and greater resistance to water and oxygen corrosion in the surface layer, leading to a longer service life. This overcomes the shortcomings of existing Si-based environmental barrier coatings and extends service life.

[0023] Furthermore, the workpiece surface is pretreated. Degreasing is to remove contaminants from the workpiece surface, and sandblasting is to improve the surface roughness, which can effectively improve the bonding strength between the adhesive layer and the substrate.

[0024] Furthermore, preheating the workpiece surface before spraying is to improve the bonding between particles during the spraying process and reduce the voids in the coating.

[0025] Furthermore, using Si powder with a specific particle size and rare earth element dual silicate spherical powder as raw materials, the powder has a high temperature and kinetic energy in the flame, resulting in high coating bonding strength and microhardness, as well as low porosity and fewer large pores.

[0026] Furthermore, the workpiece after being coated with the Si layer is heat-treated in an argon atmosphere at 1300–1400℃. This prevents the Si layer from melting and from oxidizing into SiO2, thus giving the in-situ generated SiC layer a good ability to bond the surface layer to the substrate.

[0027] Furthermore, rapid cooling of the coating is to convert the entire surface layer into a single β phase, while the cooling rate cannot be too fast to prevent the coating from cracking due to thermal stress. Attached Figure Description

[0028] Figure 1 This is a cross-sectional schematic diagram of the Si-based environmental barrier bonding layer of the SiC bonding layer-high entropy pentaneous rare earth double silicate surface layer prepared by plasma spraying technology.

[0029] Figure 1 In the middle, HE-RE2Si2O7 in the top layer represents high-entropy rare earth disilicate, and CMC in the bottom layer represents ceramic matrix composites, including C / SiC composites or C / C composites. Detailed Implementation

[0030] The following are specific embodiments provided by the inventors. It should be noted that these embodiments are preferred examples of the present invention and are intended for those skilled in the art to understand the present invention, but the present invention is not limited to these embodiments.

[0031] To address the issues of the traditional environmental barrier coating's Si adhesive layer having too low a melting point and generating oxides upon oxidation, as well as the poor resistance to ultra-high temperature water-oxygen corrosion and weak mechanical properties of the traditional single rare-earth main silicate surface layer, the traditional Si adhesive layer is replaced with a SiC adhesive layer. High-entropy treatment is then applied to the surface material, improving the melting point of the adhesive layer and enhancing the surface layer's resistance to water-oxygen corrosion and mechanical properties, thereby extending the service life of the environmental barrier coating.

[0032] A long-life multi-element rare earth environmental barrier coating has a structure consisting of a SiC adhesive layer and a five-element rare earth double silicate surface layer sequentially deposited on a C / SiC composite material or a C / C composite material matrix. The five-element rare earth double silicate surface layer has a single β-phase structure, and the chemical formula of the five-element rare earth double silicate surface layer material is (Yb 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5 )2Si2O7, the SiC transition layer is a 6H type SiC structure, the five rare earth main element double silicate surface layer and the adhesive layer are both dense structures, and the coating density is >95%.

[0033] With Yb as the core component, disilicate components with β configuration were selected, and the ionic radius deviation was <0.024. Ho component with excellent mechanical properties and Sc component with excellent resistance to water and oxygen corrosion were selected. During service, the surface layer always maintains a single β phase structure. Ho, Y, Yb and Lu randomly replace Yb ​​sites in Yb2SiO7.

[0034] The thickness of the rare earth principal component double silicate surface layer is 150–300 μm.

[0035] The adhesive layer thickness is 30–70 μm.

[0036] A method for preparing a long-life multi-element rare earth environmental barrier coating includes the following steps:

[0037] Step S1: Surface pretreatment of ceramic matrix composite workpiece:

[0038] The ceramic matrix composite workpiece is immersed in an organic solvent for 30-50 minutes, then dried in an oven at 150-200℃, and then sandblasted for 18-30 minutes to achieve a surface roughness of Ra8-12μm.

[0039] Step S2: Preheat the pretreated ceramic matrix composite workpiece at a temperature of 600–1000°C.

[0040] Step S3: Using Si powder as raw material, a Si layer is sprayed onto the substrate surface using thermal spraying technology; the thermal spraying technology is vacuum plasma spraying; the chamber pressure of vacuum plasma spraying is 80-120 Pa, the spraying current is 560-600 A, the main gas argon is 50-58 L / min, the auxiliary gas hydrogen is 4.8-5.6 L / min, the spraying distance is 90-130 mm, the gun speed is 600-1200 mm / s, and the powder feeding speed is 6-10 g / min;

[0041] Step S4: Heat-treat the substrate coated with the Si layer in an inert protective atmosphere to allow the Si layer to react in situ and form a SiC adhesive layer. Specifically, the heat treatment is carried out at 1300-1400℃ in an argon atmosphere for 12-16 hours to obtain the in-situ reacted SiC adhesive layer.

[0042] Step S5: Using rare earth element-based double silicate spherical powder as raw material, a rare earth element-based double silicate surface layer is deposited on the SiC adhesive layer using thermal spraying technology. The thermal spraying technology in this step is either atmospheric plasma spraying or supersonic flame spraying; the atmospheric plasma spraying power is 38-45kW, the main argon gas is 50-58L / min, the auxiliary hydrogen gas is 4.8-5.6L / min, the spraying distance is 90-130mm, and the gun travel speed is 600-1200mm / s. The powder feeding speed in this step is 30-38g / min.

[0043] In steps S3 and S5, the Si powder is spherical with a particle size of 25–75 μm, and the five rare earth principal element disilicate spherical powder has a particle size range of 30–90 μm.

[0044] Example 1

[0045] This invention provides a long-life multi-element rare earth environmental barrier coating and its preparation method, the process flow of which is as follows:

[0046] Step 1: Pre-treat the surface of the C / SiC composite substrate to be coated, including degreasing and roughening. For degreasing, soak in an organic solvent for 30 minutes, then dry the surface in an oven at 150°C, and then use sandblasting to treat the surface of the workpiece to remove the adhering substances and increase the adhesion between the coating and the substrate, so that the roughness after treatment is about Ra8.

[0047] Step 2: Preheat the workpiece to approximately 600℃.

[0048] Step 3: Using Si powder as raw material, a Si layer is deposited on the workpiece surface using vacuum plasma spraying technology. The parameters for Si transition layer deposition are as follows: chamber pressure 80 Pa, spraying current 560 A, spraying distance 90 mm, gun speed 600 mm / s, argon and hydrogen as plasma gases, with argon delivery rate of 50 L / min and hydrogen delivery rate of 4.8 L / min. The Si powder particle size is 25 μm, and the powder feed rate is 6 g / min. The resulting coating thickness is 30 μm.

[0049] Step 4: Place the workpiece after spraying the Si coating in an argon atmosphere heat treatment furnace at 1300℃ for 12 hours to form a SiC bonding layer in situ. The thickness of the SiC bonding layer is 30μm.

[0050] Step 5: Using high-entropy powder (Yb) 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5 Using Si₂O₇ powder as raw material, a five-rare-earth principal element double silicate surface layer was deposited on the workpiece surface using atmospheric plasma spraying technology. The deposition parameters for the five-rare-earth principal element double silicate surface layer were as follows: spraying power of 38kW, spraying distance of 90mm, gun travel speed of 600mm / s, and argon and hydrogen as plasma gases, with an argon gas delivery rate of 50L / min and a hydrogen gas delivery rate of 4.8L / min. The high-entropy powder particle size was 30μm, and the powder feed rate was 30g / min. The resulting coating thickness was 150μm.

[0051] The surface fracture toughness, measured using the indentation method, is 4.5 MPa·m. -2 The thermal conductivity of the surface material, measured using the laser scintillation method, is 1 W / m*K. Using a self-made high-temperature water-oxygen corrosion testing apparatus, the coating was tested for 500 hours at 1500℃ under conditions of 90 vol.% O2 - 10 vol.% H2O. No peeling occurred, and the mass loss was 1.03 × 10⁻⁶. -6 g / cm 2Based on the above process, a long-life multi-element rare earth environmental barrier coating was prepared. The coating structure includes a SiC adhesive layer and a multi-rare earth principal component double silicate surface layer sequentially deposited on a C / SiC composite matrix. The SiC adhesive layer has a thickness of 30 μm, and the multi-rare earth principal component double silicate surface layer has a thickness of 150 μm. The multi-rare earth principal component double silicate surface layer has a single β-phase structure with the chemical formula (Ho). 1 / 5Y 1 / 5 Yb 1 / 5 Lu 1 / 5 Sc 1 / 5 The 2Si2O7 adhesive layer has a 6H-type SiC structure, and the density of both the multi-rare earth principal component double silicate surface layer and the adhesive layer is greater than 95%.

[0052] Example 2

[0053] This invention provides a long-life multi-element rare earth environmental barrier coating and its preparation method, the process flow of which is as follows:

[0054] Step 1: Pre-treat the surface of the C / SiC composite substrate to be coated, including degreasing and roughening. For degreasing, soak in an organic solvent for 35 minutes, then dry the surface in an oven at 160°C, and then use sandblasting to treat the workpiece surface to remove adhering substances and increase the adhesion between the coating and the substrate, so that the roughness after treatment is about Ra9.

[0055] Step 2: Preheat the workpiece to approximately 700℃.

[0056] Step 3: Using Si powder as raw material, a Si layer is deposited on the workpiece surface using vacuum plasma spraying technology. The parameters for Si transition layer deposition are as follows: chamber pressure 90 Pa, spraying current 570 A, spraying distance 100 mm, gun speed 700 mm / s, argon and hydrogen as plasma gases, with argon delivery rate of 52 L / min and hydrogen delivery rate of 5 L / min. The Si powder particle size is 40 μm, and the powder feed rate is 7 g / min. The resulting coating thickness is 40 μm.

[0057] Step 4: Place the workpiece after spraying the Si coating in an argon atmosphere heat treatment furnace at 1325℃ for 13 hours to form a SiC bonding layer in situ. The thickness of the SiC bonding layer is 40μm.

[0058] Step 5, using (Yb) 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5Using Si₂O₇ powder as raw material, a five-rare-earth principal element double silicate surface layer was deposited on the workpiece surface using atmospheric plasma spraying technology. The deposition parameters for the five-rare-earth principal element double silicate surface layer were as follows: spraying power of 40kW, spraying distance of 100mm, gun speed of 700mm / s, and argon and hydrogen as plasma gases, with an argon gas delivery rate of 52L / min and a hydrogen gas delivery rate of 5L / min. The high-entropy powder particle size was 45μm, and the powder feed rate was 32g / min. The resulting coating thickness was 180μm.

[0059] The surface fracture toughness, measured using the indentation method, is 4.6 MPa·m. -2 The thermal conductivity of the surface material, measured using the laser scintillation method, is 0.98 W / m*K. Using a self-made high-temperature water-oxygen corrosion testing apparatus, the coating was tested for 500 hours at 1500℃ with 90 vol.% O2 and 10 vol.% H2O. No peeling occurred, and the mass loss was 1.02 × 10⁻⁶. -6 g / cm 2 Based on the above process, a long-life multi-element rare earth environmental barrier coating was prepared. The coating structure includes a SiC adhesive layer and a multi-rare earth principal component double silicate surface layer sequentially deposited on a C / SiC composite matrix. The SiC adhesive layer has a thickness of 40 μm, and the multi-rare earth principal component double silicate surface layer has a thickness of 180 μm. The multi-rare earth principal component double silicate surface layer has a single β-phase structure with the chemical formula (Ho). 1 / 5Y 1 / 5 Yb 1 / 5 Lu 1 / 5 Sc 1 / 5 The 2Si2O7 adhesive layer has a 6H-type SiC structure, and the density of both the multi-rare earth principal component double silicate surface layer and the adhesive layer is greater than 95%.

[0060] Example 3

[0061] This invention provides a long-life multi-element rare earth environmental barrier coating and its preparation method, the process flow of which is as follows:

[0062] Step 1: Pre-treat the surface of the C / SiC composite substrate to be coated, including degreasing and roughening. For degreasing, soak in an organic solvent for 40 minutes, then dry the surface in an oven at 170°C, and then use sandblasting to treat the surface of the workpiece to remove the adhering substances and increase the adhesion between the coating and the substrate, so that the roughness after treatment is about Ra10.

[0063] Step 2: Preheat the workpiece to approximately 800℃.

[0064] Step 3: Using Si powder as raw material, a Si layer is deposited on the workpiece surface using vacuum plasma spraying technology. The parameters for Si transition layer deposition are as follows: chamber pressure 100 Pa, spraying current 580 A, spraying distance 110 mm, gun speed 800 mm / s, argon and hydrogen as plasma gases, with argon delivery rate of 54 L / min and hydrogen delivery rate of 5.2 L / min. The Si powder particle size is 50 μm, and the powder feed rate is 8 g / min. The resulting coating thickness is 50 μm.

[0065] Step 4: Place the workpiece after spraying the Si coating in an argon atmosphere heat treatment furnace at 1350℃ for 14 hours to form a SiC bonding layer in situ. The thickness of the SiC bonding layer is 50μm.

[0066] Step 5, using (Yb) 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5 Using Si₂O₇ powder as raw material, a five-rare-earth principal element double silicate surface layer was deposited on the workpiece surface using atmospheric plasma spraying technology. The deposition parameters for the five-rare-earth principal element double silicate surface layer were as follows: spraying power of 42kW, spraying distance of 110mm, gun travel speed of 800mm / s, and argon and hydrogen as plasma gases, with an argon gas delivery rate of 54L / min and a hydrogen gas delivery rate of 5.2L / min. The high-entropy powder particle size was 60μm, and the powder feed rate was 34g / min. The resulting coating thickness was 220μm.

[0067] The surface fracture toughness, measured using the indentation method, is 4.58 MPa·m. -2 The thermal conductivity of the surface material, measured using the laser scintillation method, is 1.02 W / m*K. Using a self-made high-temperature water-oxygen corrosion testing apparatus, the coating was tested for 500 hours at 1500℃ under conditions of 90 vol.% O2 - 10 vol.% H2O. No peeling occurred, and the mass loss was 1.11 × 10⁻⁶. -6 g / cm 2 Based on the above process, a long-life multi-element rare earth environmental barrier coating was prepared. The coating structure includes a SiC adhesive layer and a multi-rare earth principal component double silicate surface layer sequentially deposited on a C / SiC composite matrix. The SiC adhesive layer has a thickness of 50 μm, and the multi-rare earth principal component double silicate surface layer has a thickness of 220 μm. The multi-rare earth principal component double silicate surface layer has a single β-phase structure with the chemical formula (Ho). 1 / 5Y 1 / 5 Yb 1 / 5 Lu 1 / 5 Sc 1 / 5The 2Si2O7 adhesive layer has a 6H-type SiC structure, and the density of both the multi-rare earth principal component double silicate surface layer and the adhesive layer is greater than 95%.

[0068] Example 4

[0069] This invention provides a long-life multi-element rare earth environmental barrier coating and its preparation method, the process flow of which is as follows:

[0070] Step 1: Pre-treat the surface of the C / C composite substrate to be coated, including degreasing and roughening. For degreasing, soak in an organic solvent for 45 minutes, then dry the surface in a 190°C oven, and then use sandblasting to treat the workpiece surface to remove adhering substances and increase the adhesion between the coating and the substrate, so that the roughness after treatment is about Ra11.

[0071] Step 2: Preheat the workpiece to approximately 900℃.

[0072] Step 3: Using Si powder as raw material, a Si layer is deposited on the workpiece surface using vacuum plasma spraying technology. The parameters for Si transition layer deposition are as follows: chamber pressure 110 Pa, spraying current 590 A, spraying distance 120 mm, gun speed 900 mm / s, argon and hydrogen as plasma gases, with argon delivery rate of 56 L / min and hydrogen delivery rate of 5.4 L / min. The Si powder particle size is 60 μm, and the powder feed rate is 9 g / min. The resulting coating thickness is 60 μm.

[0073] Step 4: Place the workpiece after spraying the Si coating in an argon atmosphere heat treatment furnace at 1375℃ for 15 hours to form a SiC bonding layer in situ. The thickness of the SiC bonding layer is 60μm.

[0074] Step 5, using (Yb) 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5 Using Si₂O₇ powder as raw material, a five-rare-earth principal element double silicate surface layer was deposited on the workpiece surface using atmospheric plasma spraying technology. The deposition parameters for the five-rare-earth principal element double silicate surface layer were as follows: spraying power of 44kW, spraying distance of 120mm, gun travel speed of 900mm / s, and argon and hydrogen as plasma gases, with an argon gas delivery rate of 56L / min and a hydrogen gas delivery rate of 5.4L / min. The high-entropy powder particle size was 75μm, and the powder feed rate was 36g / min. The resulting coating thickness was 270μm.

[0075] The surface fracture toughness, measured using the indentation method, is 4.67 MPa·m. -2The thermal conductivity of the surface material, measured using the laser scintillation method, is 0.99 W / m*K. Using a self-made high-temperature water-oxygen corrosion testing apparatus, the coating was tested for 500 hours at 1500℃ under conditions of 90 vol.% O2-10 vol.% H2O. No peeling occurred, and the mass loss was 1.08 × 10⁻⁶. -6 g / cm 2 Based on the above process, a long-life multi-element rare earth environmental barrier coating was prepared. The coating structure includes a SiC adhesive layer and a multi-rare earth principal component double silicate surface layer sequentially deposited on a C / SiC composite matrix. The SiC adhesive layer has a thickness of 60 μm, and the multi-rare earth principal component double silicate surface layer has a thickness of 270 μm. The multi-rare earth principal component double silicate surface layer has a single β-phase structure with the chemical formula (Ho). 1 / 5Y 1 / 5 Yb 1 / 5 Lu 1 / 5 Sc 1 / 5 The 2Si2O7 adhesive layer has a 6H-type SiC structure, and the density of both the multi-rare earth principal component double silicate surface layer and the adhesive layer is greater than 95%.

[0076] Example 5

[0077] This invention provides a long-life multi-element rare earth environmental barrier coating and its preparation method, the process flow of which is as follows:

[0078] Step 1: Pre-treat the surface of the C / C composite substrate to be coated, including degreasing and roughening. For degreasing, soak in an organic solvent for 50 minutes, then dry the surface in a 200℃ oven, and then use sandblasting to treat the workpiece surface to remove adhering substances and increase the adhesion between the coating and the substrate, so that the roughness after treatment is about Ra12.

[0079] Step 2: Preheat the workpiece to approximately 1000℃.

[0080] Step 3: Using Si powder as raw material, a Si layer is deposited on the workpiece surface using vacuum plasma spraying technology. The parameters for Si transition layer deposition are as follows: chamber pressure 120 Pa, spraying current 600 A, spraying distance 130 mm, gun speed 1200 mm / s, argon and hydrogen as plasma gases, with argon delivery rate of 58 L / min and hydrogen delivery rate of 5.6 L / min. The Si powder particle size is 75 μm, and the powder feed rate is 10 g / min. The resulting coating thickness is 70 μm.

[0081] Step 4: Place the workpiece after spraying the Si coating in an argon atmosphere heat treatment furnace at 1400℃ for 16 hours to form a SiC bonding layer in situ. The thickness of the SiC bonding layer is 70μm.

[0082] Step 5, using (Yb) 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5 Using Si₂O₇ powder as raw material, a five-rare-earth principal element double silicate surface layer was deposited on the workpiece surface using atmospheric plasma spraying technology. The deposition parameters for the five-rare-earth principal element double silicate surface layer were as follows: spraying power of 45kW, spraying distance of 130mm, gun speed of 1200mm / s, and argon and hydrogen as plasma gases, with an argon gas delivery rate of 58L / min and a hydrogen gas delivery rate of 5.6L / min. The high-entropy powder particle size was 90μm, and the powder feed rate was 38g / min. The resulting coating thickness was 300μm.

[0083] The surface fracture toughness measured using the indentation method is 4.66 MPa·m. -2 The thermal conductivity of the surface material, measured using the laser scintillation method, is 1.01 W / m*K. Using a self-made high-temperature water-oxygen corrosion testing apparatus, the coating was tested for 500 hours at 1500℃ under conditions of 90 vol.% O2 - 10 vol.% H2O. No peeling occurred, and the mass loss was 1.15 × 10⁻⁶. -6 g / cm 2 Based on the above process, a long-life multi-element rare earth environmental barrier coating was prepared. The coating structure includes a SiC adhesive layer and a multi-rare earth principal component double silicate surface layer sequentially deposited on a C / SiC composite matrix. The SiC adhesive layer has a thickness of 70 μm, and the multi-rare earth principal component double silicate surface layer has a thickness of 300 μm. The multi-rare earth principal component double silicate surface layer has a single β-phase structure with the chemical formula (Ho). 1 / 5Y 1 / 5 Yb 1 / 5 Lu 1 / 5 Sc 1 / 5 The 2Si2O7 adhesive layer has a 6H-type SiC structure, and the density of both the multi-rare earth principal component double silicate surface layer and the adhesive layer is greater than 95%.

Claims

1. A long-life multi-element rare earth environmental barrier coating, characterized in that, The coating structure consists of a SiC adhesive layer and a multi-rare-earth principal component double silicate surface layer sequentially deposited on a C / SiC composite material or a C / C composite material matrix; the chemical formula of the multi-rare-earth principal component double silicate surface layer is (Yb 1 / 5 Ho 1 / 5 Y 1 / 5 Lu 1 / 5 Sc 1 / 5 )2Si2O7, which has a single β phase structure, and the adhesive layer has a 6H type SiC structure. Both the multi-rare earth principal component double silicate surface layer and the adhesive layer have a dense structure, with a density of >95%.

2. The long-life multi-element rare earth environmental barrier coating according to claim 1, characterized in that, The thickness of the multi-rare earth principal component disilicate surface layer is 150~300 μm.

3. The long-life multi-element rare earth environmental barrier coating according to claim 1, characterized in that, The thickness of the adhesive layer is 30~70μm.

4. The method for preparing a long-life multi-element rare earth environmental barrier coating as described in claim 1, characterized in that, Please follow these steps: Step S1: Pre-treat the surface of the ceramic matrix composite workpiece; Step S2: Preheat the pretreated ceramic matrix composite workpiece; Step S3: Apply a layer of Si to the surface of the ceramic matrix composite workpiece using thermal spraying technology to obtain the matrix; Step S4: Heat-treat the substrate coated with the Si layer in an inert protective atmosphere to allow the Si layer to react in situ and form a SiC bonding layer. Step S5: Using rare earth primary element double silicate powder as raw material, a rare earth primary element double silicate surface layer is deposited on the SiC bonding layer using thermal spraying technology, and then cooled after spraying. In step S3, spherical Si powder with a particle size of 25-75 μm is used as raw material. The thermal spraying technology is vacuum plasma spraying. The chamber pressure is 80-120 Pa, the spraying current is 560-600 A, the main gas argon is 38-42 L / min, the auxiliary gas hydrogen is 2.8-3.2 L / min, the spraying distance is 90-130 mm, the gun speed is 600-1200 mm / s, and the powder feeding speed is 6-10 g / min. In step S5, the rare earth principal component disilicate powder is spherical with a particle size range of 30–90 μm. The thermal spraying technology is atmospheric plasma spraying with a spraying power of 38–45 kW, a main gas argon of 50–58 L / min, an auxiliary gas hydrogen of 4.8–5.6 L / min, a spraying distance of 90–130 mm, a gun speed of 600–1200 mm / s, and a powder feeding speed of 30–38 g / min.

5. The method for preparing a long-life multi-element rare earth environmental barrier coating according to claim 4, characterized in that, In step S1, the workpiece surface pretreatment process is as follows: after soaking in organic solvent, it is dried at 150~200 ℃, and then sandblasted to make the surface roughness Ra8~12 μm.

6. The method for preparing a long-life multi-element rare earth environmental barrier coating according to claim 4, characterized in that, In step S2, the preheating temperature is 600~1000℃.

7. The method for preparing a long-life multi-element rare earth environmental barrier coating according to claim 4, characterized in that, The heat treatment in step S4 is to heat-treat at 1300-1400 °C in an argon atmosphere for 12-16 hours, so that Si reacts in situ with the substrate to obtain the SiC adhesive layer.

8. The method for preparing a long-life multi-element rare earth environmental barrier coating according to claim 4, characterized in that, In step S5, compressed air is used for cooling, so that the coating cools at a rate of 40~60℃ / s.

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