A high-temperature-resistant and high-stable gradient structure environmental barrier coating adhesive layer and a preparation method thereof

Abstract

The application provides a high-temperature-resistant and high-stable gradient structure environmental barrier coating adhesive layer and a preparation method thereof, which comprises a Si bottom layer, an HfSiO4-Si intermediate layer and an HfSiO4 top layer arranged in sequence. The adhesive layer is prepared by using atmospheric plasma spraying technology. The gradient structure adhesive layer has the advantages of high-temperature resistance, strong combination and high-temperature phase stability, and is expected to break through the bottleneck of low temperature resistance and high-temperature chemical instability of the existing environmental barrier coating adhesive layer system.

Description

Technical Field

[0001] This invention belongs to the technical field of high-temperature protective coating materials, and particularly relates to a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer and its preparation method. Background Technology

[0002] Ceramic matrix composites (CMCs) possess a range of advantages, including high temperature resistance, low density, and excellent high-temperature mechanical properties, making them a promising candidate to replace traditional high-temperature alloys and become the primary material for hot-section components of next-generation high-performance aero-engines. However, in the engine exhaust environment, the service performance of CMC components deteriorates rapidly due to water vapor-oxygen coupled corrosion. Therefore, it is essential to prepare ultra-high temperature, long-life environmental barrier coatings (EBCs) on their surfaces to improve the service reliability and stability of the composite materials.

[0003] Currently, the most widely used third-generation EBCs system consists of a Si binder layer, a mullite interlayer, and a rare-earth silicate environmental barrier layer. The Si binder layer, with its high bonding strength with CMCs and similar coefficients of thermal expansion, plays a crucial role in the entire CMCs-EBCs system. However, the melting point of the Si binder layer is only 1410℃, and this can be significantly lower in the presence of impurities. Furthermore, the SiO2 formed by Si oxidation undergoes an α-β phase transition during alternating heating and cooling, and the resulting tensile stress is the main cause of cracking at the Si / SiO2 interface. Even more seriously, at high temperatures, SiO2 reacts with oxides in the environmental barrier layer to form a glassy phase, causing coating damage and failure. These factors limit the long-term operating temperature of EBCs systems with Si as the binder layer to below 1350℃. With the development of aero-engines towards higher thrust-to-weight ratios, material and structural modification of the Si binder layer has become urgent.

[0004] HfSiO4, as a silicate material, not only has a high melting point (~2758℃), but also a coefficient of thermal expansion similar to that of CMCs matrix (3.11-5.97×10⁻⁶). -6 K -1 HfSiO4 is a novel high-temperature resistant adhesive layer material with great application potential. However, the bonding strength between HfSiO4 and the matrix is ​​relatively low, and during the preparation process, the evaporation of SiO2 can easily lead to adverse phenomena such as component segregation and loose structure, which limits its further application. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer and its preparation method. The adhesive layer has high bonding strength with the substrate, can withstand temperatures up to 1450°C, and maintains chemical stability at the heterogeneous interfaces within the EBCs system at this temperature, which can effectively improve the service temperature and performance of CMCs hot-end components.

[0006] This invention provides a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer, characterized in that it comprises a Si bottom layer with a lattice structure, an HfSiO4-Si intermediate layer, and an HfSiO4 top layer arranged sequentially.

[0007] Preferably, in the HfSiO4-Si interlayer, Si is uniformly distributed in HfSiO4 in the form of dots;

[0008] The mass content of HfSiO4 is between 70% and 90%.

[0009] Preferably, the HfSiO4 mass content in the HfSiO4 top layer is greater than 90%.

[0010] Preferably, the thickness of the Si sublayer of the lattice structure is 10–40 μm;

[0011] The thickness of the HfSiO4-Si interlayer is 10–50 μm;

[0012] The thickness of the HfSiO4 top layer is 20–50 μm.

[0013] This invention provides a method for preparing the high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer described in the above technical solution, comprising the following steps:

[0014] A) Pretreatment of the ceramic matrix composite material matrix;

[0015] B) Atmospheric plasma spraying technology was used to sequentially prepare a Si bottom layer, an HfSiO4-Si intermediate layer and an HfSiO4 top layer with a lattice structure on the surface of the pretreated ceramic matrix composite matrix.

[0016] C) The coating is heat-treated to obtain a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer.

[0017] Preferably, the matrix material is a ceramic matrix composite material;

[0018] The pretreatment includes sequentially cleaning, sandblasting, and plasma jet heating of the substrate material.

[0019] Preferably, in the process of forming a Si substrate with a lattice structure by atmospheric plasma spraying, the substrate material is shielded by a porous mesh tooling, argon and hydrogen are used as plasma, the flow rate of argon is 40-60 L / min, the flow rate of hydrogen is 5-15 L / min, the spraying distance is 80-150 mm, the spraying current is 300-600 A, the powder feed rate is 10-30%, and the particle size of Si powder is 15-60 μm.

[0020] Preferably, during the atmospheric plasma spraying process to form the HfSiO4-Si intermediate layer, argon and hydrogen are used as plasma, with an argon flow rate of 40-80 L / min, a hydrogen flow rate of 5-15 L / min, a spraying distance of 100-200 mm, a spraying current of 500-800 A, a powder feed rate of 10-30%, a Si powder particle size of 15-60 μm, and an HfSiO4 powder particle size of 15-45 μm.

[0021] Preferably, in the process of forming the HfSiO4 top layer by atmospheric plasma spraying, HfO2 and SiO2 with a molar ratio of 1:(1.2-1.8) are used as raw materials, argon and hydrogen are used as plasma, the flow rate of argon is 40-80 L / min, the flow rate of hydrogen is 5-15 L / min, the spraying distance is 100-200 mm, the spraying current is 400-600 A, the powder feeding rate is 10-30%, the particle size of HfO2 powder is 15-45 μm, and the particle size of SiO2 powder is 15-60 μm.

[0022] Preferably, the heat treatment temperature in step C) is 1400–1600°C, and the heat treatment time is 10–30 h.

[0023] This invention provides a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer, comprising a Si bottom layer with a lattice structure, an HfSiO4-Si intermediate layer, and an HfSiO4 top layer arranged sequentially. The adhesive layer is prepared using atmospheric plasma spraying technology. The gradient structure adhesive layer of this invention has advantages such as high temperature resistance, strong bonding, and high-temperature phase stability, and is expected to overcome the bottlenecks of low temperature resistance and high-temperature chemical instability in existing environmental barrier coating adhesive layer systems. Attached Figure Description

[0024] Figure 1 This is a cross-sectional structural schematic diagram of a high-temperature resistant and highly stable gradient structure environmental barrier coating adhesive layer prepared on the surface of a ceramic matrix composite material in one embodiment of the present invention. In this diagram, 1 is the ceramic matrix composite material matrix, 2 is the Si bottom layer with a "lattice structure", 3 is the HfSiO4-Si intermediate layer, and 4 is the HfSiO4 top layer.

[0025] Figure 2 This is a flowchart of a method for preparing a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer on the surface of a ceramic matrix composite material according to one embodiment of the present invention;

[0026] Figure 3 This is a surface morphology diagram of the gradient structure environmental barrier coating adhesive layer in Embodiment 1 of the present invention. Detailed Implementation

[0027] This invention provides a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer, characterized in that it comprises a Si bottom layer with a lattice structure, an HfSiO4-Si intermediate layer, and an HfSiO4 top layer arranged sequentially.

[0028] The adhesive layer provided by the present invention adheres to the substrate with high bonding strength; the substrate material is a ceramic composite matrix, i.e., a CMC matrix. The present invention does not impose any special restrictions on the specific composition of the substrate material, and any ceramic composite matrix conventionally used in the art is acceptable.

[0029] The adhesive layer provided by this invention includes a Si substrate with a lattice structure, which is in contact with the substrate material. The thickness of the Si substrate is preferably 10–40 μm, more preferably 20–30 μm. According to the research of this invention, the Si adhesive layer with the above-mentioned structure and thickness can retain the maximum bonding force with the substrate.

[0030] The adhesive layer provided by this invention includes an HfSiO4-Si intermediate layer in contact with the Si substrate. The preferred content of the HfSiO4 phase in the HfSiO4-Si intermediate layer is between 70% and 90%, more preferably between 80% and 90%, such as 80%, 85%, or 90%, and is preferably within the range of any of the above values ​​as the upper or lower limit. The thickness of the HfSiO4-Si intermediate layer is preferably 10 to 50 μm, more preferably 30 to 50 μm. According to the research of this invention, the HfSiO4-Si intermediate layer with the above-mentioned composition and thickness range can fully consume the HfO2 phase formed due to SiO2 volatilization, while simultaneously exhibiting high-temperature self-healing function.

[0031] The adhesive layer provided by this invention includes an HfSiO4 top layer in contact with the HfSiO4-Si intermediate layer; the preferred content of the HfSiO4 phase in the HfSiO4 top layer is greater than 90%, more preferably greater than 95%, such as 96%, 97%, 98%, 99%, 100%, preferably within the range of any of the above values ​​as the upper or lower limit; the thickness of the HfSiO4 top layer is preferably 20-50 μm, more preferably 20-40 μm. This study found that the HfSiO4 top layer with the above composition and thickness range has excellent oxygen barrier effect and maintains high-temperature chemical stability with surface BSAS, mullite, or rare earth silicate environmental barrier materials.

[0032] The "lattice structure" Si bottom layer used in this invention not only ensures the bonding strength between the adhesive layer and the CMCs matrix, but also suppresses coating peeling caused by Si softening and melting at high temperatures. In the HfSiO4-Si intermediate layer, no chemical reaction occurs between HfSiO4 and Si. The main phase HfSiO4 has extremely low oxygen permeability, effectively avoiding the disadvantage of rapid Si oxidation. The second phase Si is distributed in a dotted form in the HfSiO4 matrix, which can react rapidly with the HfO2 phase precipitated in HfSiO4, and simultaneously soften and melt at high temperatures to fill internal cracks in the coating. In the HfSiO4 top layer, HfSiO4 has excellent chemical stability and will not chemically react with environmental barrier materials such as BSAS, mullite, or rare earth silicates on its surface.

[0033] This invention provides a method for preparing the high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer described in the above technical solution, comprising the following steps:

[0034] A) Pretreatment of the ceramic matrix composite material matrix;

[0035] B) Atmospheric plasma spraying technology was used to sequentially prepare a Si bottom layer, an HfSiO4-Si intermediate layer and an HfSiO4 top layer with a lattice structure on the surface of the pretreated ceramic matrix composite matrix.

[0036] C) The coating is heat-treated to obtain a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer.

[0037] See Figure 2 , Figure 2 This is a flowchart illustrating a method for preparing a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer on the surface of a ceramic matrix composite material, according to one embodiment of the present invention.

[0038] This invention provides a pretreatment method for ceramic matrix composite matrices. The pretreatment method preferably includes the following steps:

[0039] 1) Clean and dry the base material;

[0040] 2) Sandblasting treatment after drying;

[0041] 3) After sandblasting, plasma jet heating is performed.

[0042] In this invention, the matrix material is ultrasonically cleaned with acetone for 10-30 minutes, preferably 15-20 minutes; the drying is carried out in an oven at a temperature of 100-120°C, preferably 110-115°C, for a time of 15-30 minutes, preferably 20-25 minutes.

[0043] In this invention, to increase the surface roughness of the ceramic matrix composite material and thus improve the bonding force between the adhesive layer and the substrate, the cleaned substrate is sandblasted. Preferably, 100-300 mesh quartz sand is used for sandblasting the cleaned substrate, more preferably 150-200 mesh; the sandblasting pressure is 0.1-0.3 MPa, more preferably 0.2-0.3 MPa; and the sandblasting time is preferably 10-30 s, more preferably 15-25 s.

[0044] The present invention heats a sandblasted ceramic matrix composite material matrix with plasma jet heating to bring its surface temperature to 400-600℃, preferably 500-600℃.

[0045] After obtaining the pretreated matrix material, the present invention uses atmospheric plasma spraying technology to sequentially prepare a Si bottom layer with a "lattice structure", an HfSiO4-Si intermediate layer and an HfSiO4 top layer on its surface to obtain a gradient structure adhesive layer.

[0046] In the process of preparing a "lattice structure" Si substrate by atmospheric plasma spraying, a customized porous mesh tooling is used to shield the substrate material. The diameter of the circular holes is preferably 0.2-1 mm, more preferably 0.3-0.4 mm, such as 0.3, 0.35, 0.4 mm, and preferably within the range of any of the above values ​​as the upper or lower limit. The hole spacing is preferably 0.3-0.8 mm, more preferably 0.4-0.5 mm, such as 0.4 mm, 0.45 mm, 0.5 mm, and preferably within the range of any of the above values ​​as the upper or lower limit. Argon and hydrogen are used as plasma, with argon... The flow rate of the gas is preferably 40–60 L / min, more preferably 40–50 L / min, such as 40 L / min, 45 L / min, 50 L / min, 55 L / min, 60 L / min, and preferably a range of values ​​with any of the above as the upper or lower limit; the flow rate of the hydrogen gas is preferably 5–15 L / min, more preferably 6–8 L / min, such as 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 11 L / min, 12 L / min, 13 L / min, 1 4L / min, 15L / min, preferably values ​​within the range of the above values ​​as the upper or lower limit; the spraying distance is preferably 80-150mm, more preferably 100-120mm, such as 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, preferably values ​​within the range of the above values ​​as the upper or lower limit; the spraying current is preferably 300-600A, more preferably 400-550A, such as 300A, 350A, 400A, 450A, 500A, 550A, 6 00A is preferably a range of values ​​with any of the above values ​​as the upper or lower limit; the powder feeding rate is preferably 10-30%, more preferably 20-25%, such as 10%, 15%, 20%, 25%, 30%, preferably a range of values ​​with any of the above values ​​as the upper or lower limit; the particle size of Si powder is preferably 15-60μm, more preferably 15-45μm, specifically such as 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0047] In the process of preparing the HfSiO4-Si interlayer by atmospheric plasma spraying, Si powder and HfSiO4 powder are mechanically mixed in a certain proportion. The preferred mass ratio of Si to HfSiO4 is 1:(2-10), more preferably 1:(6-8), such as 1:6, 1:7, 1:8, and preferably within the range of the above values ​​as the upper or lower limit. Argon and hydrogen are used as plasma, and the preferred flow rate of argon is 40-80 L / min, more preferably 50-65 L / min, such as 40 L / min, 45 L / min, 50 L / min, 55 L / min, 60 L / min, 65 L / min. The flow rate is preferably 70 L / min, 75 L / min, 80 L / min, or any of the above values ​​as the upper or lower limit; the hydrogen flow rate is preferably 5–15 L / min, more preferably 8–12 L / min, such as 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 11 L / min, 12 L / min, 13 L / min, 14 L / min, 15 L / min, or any of the above values ​​as the upper or lower limit; the spraying distance is preferably 100–200 mm, more preferably 120–180 mm. For example, the thickness of the coating can be 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, or 200mm, preferably within the range where any of the above values ​​are the upper or lower limits; the spraying current is preferably 500-800A, more preferably 550-650A, such as 500A, 550A, 600A, 650A, 700A, or 800A, selected within the range where any of the above values ​​are the upper or lower limits; the powder feeding rate is preferably 10-30%, more preferably 20-30%, such as 10%, 15%, 20%, 25%, or 30%. Preferably, the particle size of HfSiO4 powder is 15–45 μm, more preferably 20–40 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and preferably within the range of values ​​mentioned above, with any of the above values ​​as the upper or lower limit. The particle size of Si powder is preferably 15–60 μm, more preferably 15–45 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, and preferably within the range of values ​​mentioned above, with any of the above values ​​as the upper or lower limit.

[0048] In the process of preparing the HfSiO4 top layer by atmospheric plasma spraying, HfO2 powder and SiO2 powder are mechanically mixed in a certain proportion. The preferred molar ratio of HfO2 to SiO2 is 1:(1.2-1.8), more preferably 1:(1.3-1.5), such as 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8. Argon and hydrogen are used as plasma, and the preferred flow rate of argon is 40-80 L / min, more preferably 45-55 L / min, such as 40 L / min, 45 L / min, 50 L / min, 55 L / min. The flow rates are 60 L / min, 65 L / min, 70 L / min, 75 L / min, and 80 L / min, preferably within the range of any of the above values ​​as the upper or lower limit; the hydrogen flow rate is preferably 5–15 L / min, more preferably 8–12 L / min, such as 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 11 L / min, 12 L / min, 13 L / min, 14 L / min, and 15 L / min, preferably within the range of any of the above values ​​as the upper or lower limit; the spraying distance is preferably 100–200 mm. The thickness is preferably 120-150mm, such as 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, and preferably within the range of any of the above values ​​as the upper or lower limit; the spraying current is preferably 400-600A, more preferably 450-550A, such as 400A, 450A, 500A, 550A, 600A, and preferably within the range of any of the above values ​​as the upper or lower limit; the powder feeding rate is preferably 10-30%, more preferably 20-30%, such as 10%, 15%, 20%, 25%. The particle size of HfO2 powder is 15-45 μm, more preferably 20-40 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, preferably within the range of values ​​mentioned above; the particle size of SiO2 powder is preferably 15-60 μm, more preferably 15-45 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, preferably within the range of values ​​mentioned above.

[0049] After obtaining the above gradient structure through atmospheric plasma spraying, the coating is subjected to high-temperature heat treatment to obtain a high-temperature resistant and highly stable gradient structure environmental barrier coating adhesive layer.

[0050] In this invention, the temperature of the vacuum heat treatment is preferably 1400-1600℃, more preferably 1450-1550℃, such as 1400℃, 1450℃, 1500℃, 1550℃, 1600℃, preferably within the range of any of the above values ​​as the upper or lower limit; the time of the high-temperature heat treatment is preferably 10-30 hours, more preferably 15-24 hours, preferably within the range of any of the above values ​​as the upper or lower limit.

[0051] This invention modifies the composition and structure of the Si binder layer in a third-generation environmental barrier coating system to obtain a high-temperature resistant, highly stable gradient structure binder layer, which has the following advantages:

[0052] (1) The “lattice structure” Si substrate described in this invention can maintain the bonding force between the coating and the substrate to the maximum extent, while avoiding interface delamination caused by Si softening and melting or high temperature strength reduction.

[0053] (2) In the HfSiO4-Si intermediate layer described in this invention, the addition of Si can react with the HfO2 precipitated during the spraying process to regenerate HfSiO4, ensuring that the HfSiO4 phase content meets the design requirements. In addition, at high temperatures, the dotted Si softens and melts, which is beneficial for filling the microcracks inside the coating, thereby increasing the service life of the coating.

[0054] (3) The HfSiO4 top layer described in this invention not only has an extremely low oxygen diffusion rate, but also maintains chemical stability with environmental barrier materials such as BSAS, mullite or rare earth silicates on its surface at high temperatures, thus exhibiting excellent chemical stability.

[0055] (4) The preparation method described in this invention utilizes a customized porous mesh tooling to shield the substrate material, enabling the rapid acquisition of a "lattice structure" with controllable size and spacing. The HfSiO4-Si intermediate layer uses HfSiO4 powder and Si powder as raw materials, while the HfSiO4 top layer uses HfO2 and SiO2 as raw materials, resulting in an HfSiO4-HfO2-Si layer and an HfO2-SiO2 layer. During subsequent high-temperature heat treatment, HfO2 and Si in the HfSiO4-HfO2-Si layer react in situ to form the HfSiO4-Si intermediate layer, and HfO2 and SiO2 in the HfO2-SiO2 layer react in situ to form the HfSiO4 top layer. By adjusting the ratio of HfSiO4 and Si, HfO2 and SiO2 sprayed powders, atmospheric plasma spraying process parameters, and high-temperature heat treatment regime, the precipitation of HfO2 phase with high thermal expansion coefficient and high oxygen permeability in the coating is avoided.

[0056] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer and its preparation method, is provided by the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0057] The HfSiO4, Si, HfO2, and SiO2 powders used in the following examples and comparative examples are all commercially available. For instance, the HfO2, SiO2, and Si powders used in this example were purchased from Beijing Gava New Materials Technology Co., Ltd., and the HfSiO4 powder was prepared by Changsha University using a ball milling, high-temperature solid-state sintering, and spray granulation process. These powder preparation processes are well known to those skilled in the art.

[0058] Oxidation performance test:

[0059] The oxidation performance was tested by statically oxidizing the coated samples at 1400℃ in an atmospheric environment for 10h, 50h and 100h respectively, and observing the macroscopic morphology and cross-sectional micromorphology of the coating.

[0060] Thermal cycling performance test:

[0061] The thermal cycling performance is tested using a flame thermal cycling test chamber at a temperature of 1400℃. Each cycle consists of 5 minutes of heating and 2 minutes of cooling. The surface condition of the coating is observed after every 50 cycles. When the area of ​​coating peeling off reaches 10% of the total area, it is considered to have failed.

[0062] Example 1

[0063] (1) Preparation of SiC f / SiC ceramic composite matrix specimen, dimensions are The sample was ultrasonically cleaned with acetone for 15 minutes, and then dried in an oven at 110°C for 20 minutes.

[0064] (2) For SiC f The SiC substrate was sandblasted before coating. The sandblasting abrasive was 220 mesh quartz sand, the sandblasting pressure was 0.3 MPa, and the sandblasting time was 15 seconds.

[0065] (3) SiC f The SiC substrate is mounted on the automatic operating table of the atmospheric plasma spraying equipment and heated by plasma flame to a surface temperature of 600℃.

[0066] (4) Select powder particles with a diameter of 15-60 μm for Si after spray granulation, 15-45 μm for HfSiO4, 15-45 μm for HfO2, and 15-60 μm for SiO2. The granulated powder is a porous spherical powder.

[0067] (5) Mix Si and HfSiO4 powders at a mass ratio of 1:6, mix HfO2 and SiO2 at a molar ratio of 1:1.3, and add Si, HfSiO4-Si and HfO2-SiO2 powders sequentially into the powder feeder of the atmospheric plasma equipment.

[0068] (6) Using atmospheric plasma spraying method on SiC f A lattice-structured Si underlayer was fabricated on a SiC substrate surface. A custom-designed porous mesh tooling was used to shield the substrate material, with 0.3 mm diameter holes and a 0.4 mm spacing. The process parameters were adjusted as follows: argon flow rate 45 L / min, hydrogen flow rate 6 L / min, spraying distance 100 mm, spraying current 400 A, and powder feed rate 20%, resulting in a 25 μm thick lattice-structured Si underlayer.

[0069] (7) An HfSiO4-Si intermediate layer was prepared on the surface of the “lattice structure” Si bonding layer by atmospheric plasma spraying. The process parameters were adjusted as follows: argon flow rate of 55 L / min, hydrogen flow rate of 10 L / min, spraying distance of 120 mm, spraying current of 600 A, and powder feeding rate of 25%, resulting in an HfSiO4-Si intermediate layer with a thickness of 40 μm.

[0070] (8) An HfSiO4 top layer was prepared on the surface of the HfSiO4-Si intermediate layer using atmospheric plasma spraying. The process parameters were adjusted as follows: argon flow rate of 50 L / min, hydrogen flow rate of 10 L / min, spraying distance of 130 mm, spraying current of 500 A, and powder feed rate of 25%. A HfSiO4 top layer with a thickness of 30 μm was obtained, and its surface morphology is as follows. Figure 3 As shown.

[0071] (9) Heat treatment is performed on the deposited coating. The process parameters are adjusted as follows: temperature is 1500℃ and time is 24h.

[0072] The phase composition of the coating obtained in Example 1 was analyzed by XRD. The results showed that the HfSiO4 phase content in the HfSiO4-Si intermediate layer was about 82%, and the HfSiO4 phase content in the top HfSiO4 layer was about 95%. The HfO2 phase was not detected in either layer.

[0073] The microstructure of the coating obtained in Example 1 was examined using a scanning electron microscope. The results showed that the interfaces between the coating layers were tightly bonded, and no obvious cracks or pores were observed at the interfaces. The porosity of the coating was less than 5%.

[0074] Example 2

[0075] The gradient structure adhesive layer was prepared according to the method in Example 1, with the following difference:

[0076] In (4), the thickness of the Si substrate of the "lattice structure" is 30 μm;

[0077] In (5), the thickness of the HfSiO4-Si interlayer is 50 μm;

[0078] In (6), the thickness of the HfSiO4 top layer is 40 μm.

[0079] The antioxidant properties of the gradient structure adhesive layer in Example 2 were tested. The results showed that after oxidation at 1400℃ for 100h, the appearance of the coating did not change significantly compared with that before oxidation, and no molten Si was observed to seep out, indicating that it has excellent antioxidant properties.

[0080] Thermal cycling performance tests were conducted on the gradient structure adhesive layer in Example 2. The results showed that the thermal cycling life of the gradient structure adhesive layer in this example exceeded 1000 cycles.

[0081] Example 3

[0082] A gradient structure adhesive layer was prepared according to the method in Example 2, and a Yb2Si2O7 coating with a thickness of 150 μm was prepared on the surface of the adhesive layer using atmospheric plasma spraying technology.

[0083] The antioxidant properties of the gradient structure adhesive layer in Example 3 were tested. The results showed that after oxidation at 1400℃ for 100h, the appearance of the coating did not change significantly compared with that before oxidation. No c phase HfO2 was observed at the HfSiO4 / Yb2Si2O7 interface, indicating that the coating has good high-temperature chemical compatibility.

[0084] Thermal cycling performance tests were conducted on the gradient structure adhesive layer in Example 3. The results showed that the thermal cycling life of the gradient structure adhesive layer in this example exceeded 1000 cycles.

[0085] The bonding strength of the coating prepared in Example 3 and the Si / Yb2Si2O7 coating of the same thickness were tested according to GB / T 8642 2002 (testing 3 sets of parallel samples), and the results are shown in Table 1. It can be seen that the average bonding strength of the coating prepared in Example 3 is 22.3 MPa, and the bonding strength of the Si / Yb2Si2O7 coating is 24.9 MPa. Both bonding strengths are greater than 20 MPa and differ by only 2.6 MPa, indicating that the gradient structure adhesive layer in this invention has strong bonding force with the substrate.

[0086] Table 1. Bond strength of coating in Example 4, Si / Yb2Si2O7 coating, and coating in Comparative Example 4.

[0087]

[0088]

[0089] Comparative Example 1

[0090] Comparative Example 1 follows the same procedure as Example 1, except that:

[0091] In (6), an atmospheric plasma spraying method was used to prepare a continuous Si underlayer with a thickness of 25 μm on the surface of the CMCs substrate.

[0092] The present invention tested the antioxidant properties of the adhesive layer in Comparative Example 1. The results showed that after oxidation at 1400℃ for 10 hours, obvious blistering was observed on the coating surface. The Si layer softened and melted at high temperature and seeped out of the surface, resulting in the adhesive layer not having antioxidant properties at 1400℃.

[0093] The present invention tested the thermal cycling performance of the adhesive layer in Comparative Example 1. The results showed that the thermal cycling life of the gradient structure adhesive layer in this embodiment was less than 200 cycles.

[0094] Comparative Example 2

[0095] Comparative Example 2 follows the same procedure as Example 1, except that:

[0096] In (5), Si and HfSiO4 powders are mixed at a mass ratio of 1:15, HfO2 and SiO2 are mixed at a molar ratio of 1:1, and Si, HfSiO4-Si and HfO2-SiO2 powders are added sequentially to the powder feeder of the atmospheric plasma equipment.

[0097] The phase composition of the coating obtained in Comparative Example 2 was analyzed by XRD. The results showed that the HfSiO4 phase content in the HfSiO4-Si intermediate layer was about 64%, and the HfO2 phase content was 36%. The HfSiO4 top layer had a HfSiO4 phase content of about 73% and an HfO2 phase content of 27%.

[0098] The microstructure of the coating obtained in Example 1 was examined using a scanning electron microscope. The results showed that there were a large number of pores inside the coating due to the volatilization of SiO2, and the porosity inside the coating was greater than 10%.

[0099] The present invention tested the antioxidant properties of the adhesive layer in Comparative Example 2. The results showed that after oxidation at 1400℃ for 50 hours, obvious cracks appeared on the surface and inside of the coating, resulting in insufficient antioxidant properties of the adhesive layer.

[0100] The present invention tested the thermal cycling performance of the adhesive layer in Comparative Example 2. The results showed that the thermal cycling life of the gradient structure adhesive layer in this embodiment was less than 600 cycles.

[0101] Comparative Example 3

[0102] Comparative Example 3, based on Comparative Example 2, uses atmospheric plasma spraying technology to prepare a Yb2Si2O7 coating with a thickness of 150 μm on the surface of the adhesive layer.

[0103] The present invention tested the antioxidant properties of the adhesive layer in Comparative Example 3. The results showed that after oxidation at 1400℃ for 50h, c-phase HfO2 was observed at the HfSiO4 / Yb2Si2O7 interface inside the coating. A certain number of cracks accompanied the c-phase HfO2, indicating that the antioxidant properties of the adhesive layer were poor.

[0104] The present invention conducted thermal cycling performance tests on the adhesive layer in Comparative Example 3. The results showed that the thermal cycling life of the gradient structure adhesive layer in this embodiment was less than 500 cycles. The reason for the reduced thermal cycling life is that the fracture toughness of the c phase HfO2 is low and its thermal expansion coefficient is significantly higher than that of HfSiO4 and Yb2Si2O7. Due to the accumulation of thermal stress, cracks were initiated and propagated, causing the coating to fail prematurely.

[0105] Comparative Example 4

[0106] Comparative Example 4 has the same procedure as Example 3, except that:

[0107] Step (6) is omitted, and HfSiO4-Si intermediate layer, HfSiO4 top layer and Yb2Si2O7 environmental barrier layer are directly prepared on the surface of CMCs substrate.

[0108] The bonding strength of the coating prepared in Comparative Example 4 was tested according to GB / T 8642 2002, and the results are shown in Table 1. It can be seen that the average bonding strength of the coating in Comparative Example 4 is 14.7 MPa, which is 34% lower than the bonding strength of the coating in Example 4.

[0109] As can be seen from the above embodiments, the present invention provides a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer, comprising a Si bottom layer with a lattice structure, an HfSiO4-Si intermediate layer, and an HfSiO4 top layer arranged sequentially. The adhesive layer is prepared using atmospheric plasma spraying technology. The gradient structure adhesive layer of the present invention has the advantages of high temperature resistance, strong bonding, and high-temperature phase stability, and is expected to overcome the bottlenecks of low temperature resistance and high-temperature chemical instability in existing environmental barrier coating adhesive layer systems. Experimental results show that the adhesive layer and SiC... f The bonding strength of the SiC ceramic composite matrix is ​​>20MPa; after oxidation at 1400℃ for 100h, the appearance of the coating is not significantly different from that before oxidation, and no molten Si infiltration is observed, which shows excellent oxidation resistance; the thermal cycle life of the adhesive layer exceeds 1000 cycles.

[0110] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer, characterized in that, It includes a Si bottom layer with a lattice structure, an HfSiO4-Si intermediate layer, and an HfSiO4 top layer arranged sequentially; In the HfSiO4-Si interlayer, Si is uniformly distributed in HfSiO4 in the form of dots, and the mass content of HfSiO4 is between 70% and 90%. The HfSiO4 content in the top layer is greater than 90% by mass. The thickness of the Si substrate of the lattice structure is 10~40μm; The thickness of the HfSiO4-Si intermediate layer is 10~50μm; The thickness of the HfSiO4 top layer is 20~50μm.

2. A method for preparing the high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer as described in claim 1, comprising the following steps: A) Pretreatment of the ceramic matrix composite material matrix; B) Atmospheric plasma spraying technology was used to sequentially prepare a Si bottom layer, an HfSiO4-Si intermediate layer and an HfSiO4 top layer with a lattice structure on the surface of the pretreated ceramic matrix composite matrix. C) The coating is heat-treated to obtain a high-temperature resistant, highly stable gradient structure environmental barrier coating adhesive layer.

3. The preparation method according to claim 2, characterized in that, The pretreatment includes sequentially cleaning, sandblasting, and plasma jet heating of the substrate.

4. The preparation method according to claim 2, characterized in that, In the process of forming a Si substrate with a lattice structure by atmospheric plasma spraying, the substrate material is shielded by a porous mesh tooling, and argon and hydrogen are used as plasma. The flow rate of argon is 40~60L / min, the flow rate of hydrogen is 5~15L / min, the spraying distance is 80~150mm, the spraying current is 300~600A, the powder feed rate is 10~30%, and the particle size of Si powder is 15~60μm.

5. The preparation method according to claim 2, characterized in that, In the process of forming the HfSiO4-Si intermediate layer by atmospheric plasma spraying, argon and hydrogen are used as plasmas. The flow rate of argon is 40~80L / min, the flow rate of hydrogen is 5~15L / min, the spraying distance is 100~200mm, the spraying current is 500~800A, the powder feed rate is 10~30%, the particle size of Si powder is 15~60μm, and the particle size of HfSiO4 powder is 15~45μm.

6. The preparation method according to claim 2, characterized in that, In the process of forming the HfSiO4 top layer by atmospheric plasma spraying, HfO2 and SiO2 with a molar ratio of 1:(1.2~1.8) are used as raw materials, and argon and hydrogen are used as plasma. The flow rate of argon is 40~80L / min, the flow rate of hydrogen is 5~15L / min, the spraying distance is 100~200mm, the spraying current is 400~600A, the powder feeding rate is 10~30%, the particle size of HfO2 powder is 15~45μm, and the particle size of SiO2 powder is 15~60μm.

7. The preparation method according to claim 2, characterized in that, In step C), the heat treatment temperature is 1400~1600℃ and the heat treatment time is 10~30h.

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