An environmental barrier coating for an outer ring block of an engine and a method of making the same

Abstract

This invention belongs to the field of environmental barrier coating technology, specifically relating to an environmental barrier coating for an outer ring block of an engine and its preparation method. The environmental barrier coating comprises, from the inside out: a silicon layer, a ytterbium double silicate layer, a ytterbium monosilica layer, a transition layer, and a wearable layer. Both the transition layer and the wearable layer comprise a mixed oxide containing aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The mass ratios of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer and the wearable layer are 50~70:15~25:10~15:8~10 and 40~60:20~30:15~20:5~8, respectively. The environmental barrier coating exhibits significantly improved wearability, corrosion resistance, and service life under high-temperature operating conditions.

Description

Technical Field

[0001] This invention belongs to the field of environmental barrier coating technology, specifically, an environmental barrier coating for an engine outer ring block and its preparation method. Background Technology

[0002] The outer ring block is one of the key components of an aero-engine, mainly located in the stator section of the high-pressure compressor and turbine. In the high-pressure compressor, the outer ring block is assembled in the inner cavity of the compressor casing, located in the outer ring area of ​​the stator blades, surrounding the rotor blades, and forming the outer wall of the airflow channel. The outer ring block forms a tiny gap (usually on the order of millimeters) with the rotor blade tip to prevent high-pressure gas leakage and maintain the pressure difference.

[0003] The outer ring of an aero-engine is exposed to high-temperature exhaust gases containing oxygen, water vapor, and other corrosive substances. The material of the outer ring is usually a ceramic matrix composite, such as silicon carbide composite. Silicon carbide composites have limited resistance to high-temperature corrosion and require environmental barrier coatings for protection.

[0004] Rare earth silicate coatings Yb2Si2O7 or Y2SiO5 and barium strontium aluminum silicate coatings can be used as environmental barrier coatings for the outer ring blocks of aero engines. However, these coatings have limited wear resistance, corrosion resistance, and service life under high-temperature operating conditions.

[0005] It should be noted that this part of the present invention only provides background technology related to the present invention, and does not necessarily constitute prior art or known technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing environmental barrier coatings for outer ring blocks of aero engines in terms of abrasiveness, corrosion resistance, and limited service life under high-temperature conditions. This invention provides an environmental barrier coating for outer ring blocks of engines and its preparation method, which has significantly improved abrasiveness, corrosion resistance, and service life under high-temperature conditions.

[0007] To achieve the above objectives, in a first aspect, the present invention provides an environmental barrier coating for an outer ring block of an engine, comprising, from the inside out: a silicon layer, a ytterbium double silicate layer, a ytterbium monosilica layer, a transition layer, and a wearable layer. Both the transition layer and the wearable layer comprise a mixed oxide containing aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The mass ratios of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer and the wearable layer are 50~70:15~25:10~15:8~10 and 40~60:20~30:15~20:5~8, respectively.

[0008] In some preferred embodiments, the porosity of the wearable layer is 8%-20%.

[0009] Preferably, the wearable layer comprises a surface layer and an inner layer, wherein the thickness of the surface layer accounts for 60% to 90%, the thickness of the inner layer accounts for 10% to 40%, the porosity of the surface layer is 15% to 20%, and the porosity of the inner layer is 8% to 15%.

[0010] In some preferred embodiments, the thickness of the transition layer is 20 μm to 60 μm, and the thickness of the wear-resistant layer is 800 μm to 1200 μm.

[0011] In some preferred embodiments, the silicon layer is a hafnium oxide modified silicon layer and the mass ratio of hafnium oxide to silicon is 1:4 to 19; the mass ratio of ytterbium oxide to silicon oxide in the double ytterbium silicate layer is 4:1 to 7:3; and the mass ratio of ytterbium oxide to silicon oxide in the single ytterbium silicate layer is 9:1 to 4:1.

[0012] The thicknesses of the silicon layer, the double ytterbium silicate layer, and the single ytterbium silicate layer are 20μm~40μm, 80μm~120μm, and 80μm~120μm, respectively.

[0013] In a second aspect, the present invention provides a method for preparing the environmental barrier coating described in the first aspect, wherein a silicon layer, a ytterbium bisilate layer, a ytterbium monosilate layer, a transition layer, and a wearable layer are sequentially prepared on an outer ring block of an engine. The mass ratios of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer raw material composite powder for preparing the transition layer and the wearable layer raw material composite powder for preparing the wearable layer are 50~70:15~25:10~15:8~10 and 40~60:20~30:15~20:5~8, respectively.

[0014] In some preferred embodiments, the wearable layer is prepared by atmospheric plasma spraying, and the spraying conditions include: a spraying distance of 110mm-140mm, a power of 45kw-50kw, and a powder feeding rate of 300g / min-500g / min; the wearable layer raw material composite powder also has a pore-regulating component and contains a mixed oxide of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in a mass ratio of 85-96:4-15 to the pore-regulating component; the pore-regulating component includes at least one of polystyrene, fluorocarbon resin, silicone resin, polyurethane, and chlorinated rubber; the particle size of the wearable layer raw material composite powder is 15μm-45μm.

[0015] Preferably, the inner and outer layers of the wear-resistant layer are prepared sequentially using atmospheric plasma spraying. The spraying conditions for preparing the inner layer include: a spraying distance of 130mm-140mm, a power of 48kw-50kw, and a powder feeding rate of 300g / min-400g / min. The spraying conditions for preparing the outer layer include: a spraying distance of 110mm-130mm, a power of 45kw-47kw, and a powder feeding rate of 400g / min-500g / min.

[0016] In some preferred embodiments, the transition layer is prepared by atmospheric plasma spraying, and the spraying conditions include: a spraying distance of 90mm-130mm, a power of 47kw-50kw, and a powder feeding rate of 180g / min-270g / min.

[0017] In some preferred embodiments, the silicon layer, the ytterbium-bis(2-3) silicate layer, and the ytterbium-mono(2-3) silicate layer are prepared by atmospheric plasma spraying. The spraying conditions for preparing the silicon layer include: a spraying distance of 80mm-120mm, a power of 32 kW-38 kW, and a powder feeding rate of 150 g / min-250 g / min. The spraying conditions for preparing the ytterbium-bis(2-3) silicate layer include: preheating to 300℃-600℃, a spraying distance of 80mm-120mm, a power of 40 kW-45 kW, and a powder feeding rate of 170 g / min-250 g / min. The spraying conditions for preparing the ytterbium-mono(2-3) silicate layer include: a spraying distance of 90mm-130mm, a power of 37 kW-42 kW, and a powder feeding rate of 200 g / min-270 g / min.

[0018] The environmental barrier coating of the engine outer ring block of the present invention uses a silicon layer, a double ytterbium silicate layer, and a single ytterbium silicate layer in sequence as the inner layers. These layers work together to improve the coating’s thermal shock resistance and water-oxygen corrosion resistance. The outermost layer is a lanthanum aluminate wearable layer, which can enhance the wearability of the environmental barrier coating. A lanthanum aluminate transition layer is set inside the lanthanum aluminate wearable layer, which can enhance the bonding strength between the single ytterbium silicate layer and the wearable layer.

[0019] The environmental barrier coating of the engine outer ring block of the present invention has a transition layer containing aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The addition of neodymium oxide, in a first aspect, [details about Nd+]. 3+ Adsorption at grain boundaries inhibits grain coarsening and refines the transition layer grains, reducing stress concentration points at grain boundaries, preventing grain coarsening-induced grain boundary cracking, improving the thermal shock resistance of the transition layer (thermal cycle life ≥800 cycles), reducing the risk of interface cracking caused by thermal expansion mismatch, and increasing the interfacial contact area between the transition layer and the internal ytterbium monolithic layer and the external wearable layer, reducing the porosity of the transition layer, thereby improving the bonding force between the transition layer and the internal ytterbium monolithic layer and the external wearable layer; secondly, Nd 3+ The ionic radius is 0.098 nm, similar to La. 3+ (Ionic radius 0.106 nm), Al 3+ (ionic radius 0.054 nm), Mg 2+The ionic radii (0.072 nm) differ, and neodymium oxide dissolved in the lattice of lanthanum magnesium aluminate introduces lattice distortion, hindering atomic diffusion and suppressing the crystal transformation of lanthanum magnesium aluminate from the β-Al2O3 hexagonal phase (P63 / mmc) to the γ-Al2O3 cubic phase (Fd-3m) under high temperature conditions. This maintains the stability and consistency of the material's crystal structure, improves the high-temperature volume stability of the transition layer, prevents cracking or porosity of the transition layer, and extends the life of the environmental barrier coating under high-temperature service conditions.

[0020] The wearable layer of the environmental barrier coating of the present invention contains aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The addition of neodymium oxide, in a first aspect, [details about Nd]. 3+ Adsorption at grain boundaries inhibits grain coarsening and refines the wearable layer grains. By refining the wearable layer grains, the number of microcrack initiation points within the wearable layer can be reduced, inhibiting crack propagation during thermal shock cycling and preventing peeling failure. It also enhances the interface contact area between the wearable coating and the transition layer, strengthening their bonding force. Secondly, neodymium oxide dissolved in the lattice of lanthanum magnesium aluminate introduces lattice distortion, hindering atomic diffusion and suppressing the β-Al₂O₃ hexagonal phase formation in lanthanum magnesium aluminate under high-temperature conditions. The transformation of P63 / mmc to the cubic phase of γ-Al2O3 (Fd-3m) maintains the stability and consistency of the material's crystal structure, which can improve the high-temperature volume stability of the wearable layer, prevent the wearable layer from cracking or becoming porous, and extend the service life of the environmental barrier coating in high-temperature service environments. Thirdly, calcium magnesium aluminum silicate, which originates from combustion gas, melts and penetrates into the pores or grain boundaries of the coating at high temperatures, which can easily lead to the corrosion and peeling of the coating. Neodymium oxide reacts with CaO, SiO2, etc. in calcium magnesium aluminum silicate to generate a high-viscosity Nd-Ca-Al-Si-O glass phase, which adheres to the surface of the wearable layer to form a dense barrier layer, which can prevent the calcium magnesium aluminum silicate melt from penetrating into the pores or grain boundaries of the wearable layer, thereby improving the corrosion resistance of the environmental barrier coating. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The inventors of this application have discovered that existing environmental barrier coatings for outer ring blocks of aero engines have limited wear resistance, corrosion resistance, and lifespan under high-temperature service conditions.

[0023] In this regard, firstly, the present invention provides an environmental barrier coating for an outer ring block of an engine, comprising, from the inside out: a silicon layer, a ytterbium double silicate layer, a ytterbium monosilate layer, a transition layer, and a wearable layer. The transition layer and the wearable layer both comprise a mixed oxide containing aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The mass ratios of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer and the wearable layer are 50~70:15~25:10~15:8~10 and 40~60:20~30:15~20:5~8, respectively.

[0024] The environmental barrier coating of the engine outer ring block of the present invention uses a silicon layer, a double ytterbium silicate layer, and a single ytterbium silicate layer in sequence as the inner layers. These layers work together to improve the coating’s thermal shock resistance and water-oxygen corrosion resistance. The outermost layer is a lanthanum aluminate wearable layer, which can enhance the wearability of the environmental barrier coating. A lanthanum aluminate transition layer is set inside the lanthanum aluminate wearable layer, which can enhance the bonding strength between the single ytterbium silicate layer and the wearable layer.

[0025] The environmental barrier coating of the engine outer ring block of the present invention has a transition layer containing aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The addition of neodymium oxide, in a first aspect, [details about Nd+]. 3+ Adsorption at grain boundaries inhibits grain coarsening and refines the transition layer grains, reducing stress concentration points at grain boundaries, preventing grain coarsening-induced grain boundary cracking, improving the thermal shock resistance of the transition layer (thermal cycle life ≥800 cycles), reducing the risk of interface cracking caused by thermal expansion mismatch, and increasing the interfacial contact area between the transition layer and the internal ytterbium monolithic layer and the external wearable layer, reducing the porosity of the transition layer, thereby improving the bonding force between the transition layer and the internal ytterbium monolithic layer and the external wearable layer; secondly, Nd 3+ The ionic radius is 0.098 nm, similar to La. 3+ (Ionic radius 0.106 nm), Al 3+ (ionic radius 0.054 nm), Mg 2+ The ionic radii (0.072 nm) differ, and neodymium oxide dissolved in the lattice of lanthanum magnesium aluminate introduces lattice distortion, hindering atomic diffusion and suppressing the crystal transformation of lanthanum magnesium aluminate from the β-Al2O3 hexagonal phase (P63 / mmc) to the γ-Al2O3 cubic phase (Fd-3m) under high temperature conditions. This maintains the stability and consistency of the material's crystal structure, improves the high-temperature volume stability of the transition layer, prevents cracking or porosity of the transition layer, and extends the life of the environmental barrier coating under high-temperature service conditions.

[0026] As a supporting layer that "connects the upper and lower layers," the transition layer needs to withstand significant mechanical loads (such as centrifugal force) and thermal gradient stress. 3+Adsorbed at grain boundaries, Nd+ fixes the grain boundary positions through electrostatic interactions and lattice matching differences, inhibiting grain boundary sliding, resulting in more uniform atomic diffusion and promoting grain refinement. The mass ratio of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer is 50-70:15-25:10-15:8-10. The relatively high neodymium oxide content significantly reduces porosity caused by "large grains engulfing small grains," improving the compactness of the transition layer and reducing stress concentration caused by porosity. This effectively prevents peeling and cracking of the transition layer, improves its resistance to mechanical loads and thermal gradient stress, ensures the overall coating reliability, and enhances the interlayer bonding between the transition layer and the mono-ytterbium silicate layer, as well as the interlayer bonding between the transition layer and the wearable layer. When the neodymium oxide content in the transition layer exceeds the above range, due to Nd+... 3+ The ionic radius is 0.098 nm, which is similar to the main cations in the matrix (such as Al). 3+ 0.054 nm, Mg 2+ The difference is significant (0.072 nm), Nd 3+ Limited solid solubility in aluminate lattices makes it easy to form rare earth aluminate hard phases (such as NdAlO3, NdAl...). 11 O 19 (etc.), leading to abnormal grain growth, large grain size, reduced grain boundary area, and uneven grain size, resulting in significant stress concentration at the grain boundaries when under stress, making them prone to cracking at the grain boundaries.

[0027] The wearable layer of the environmental barrier coating of the present invention contains aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The addition of neodymium oxide, in a first aspect, [details about Nd]. 3+ Adsorption at grain boundaries inhibits grain coarsening and refines the wearable layer grains. By refining the wearable layer grains, the number of microcrack initiation points within the wearable layer can be reduced, inhibiting crack propagation during thermal shock cycling and preventing peeling failure. It also enhances the interface contact area between the wearable coating and the transition layer, strengthening their bonding force. Secondly, neodymium oxide dissolved in the lattice of lanthanum magnesium aluminate introduces lattice distortion, hindering atomic diffusion and suppressing the crystal transformation from the β-Al₂O₃ hexagonal phase (P63 / mmc) to the γ-Al₂O₃ cubic phase (Fd-3m) under high-temperature conditions. Maintaining stable and consistent material crystal structure can improve the high-temperature volume stability of the wearable layer, prevent cracking or loosening of the wearable layer, and extend the service life of the environmental barrier coating in high-temperature service environments. Thirdly, calcium magnesium aluminum silicate, which originates from combustion gas, melts and penetrates into the pores or grain boundaries of the coating at high temperatures, which can easily lead to coating corrosion and peeling. Neodymium oxide reacts with CaO, SiO2, etc. in calcium magnesium aluminum silicate to generate a high-viscosity Nd-Ca-Al-Si-O glass phase, which adheres to the surface of the wearable layer to form a dense barrier layer, which can prevent the calcium magnesium aluminum silicate melt from penetrating into the pores or grain boundaries of the wearable layer, thereby improving the corrosion resistance of the environmental barrier coating.

[0028] The wearable layer needs to ensure that the coating can be moderately ground, meeting the requirements of easy grinding to protect the grinding object without causing excessive wear and preventing high-pressure gas leakage. It should be ground in the form of tiny debris to avoid large-scale peeling and damage to the grinding object during wear. Neodymium oxide promotes grain refinement and uses grain boundaries to hinder dislocation movement. The mass ratio of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide in the wearable layer is 40~60:20~30:15~20:5~8. The neodymium oxide content is controlled within the above range, which is relatively low, moderately refining the grains while retaining a certain grain boundary sliding ability. This allows the coating to be easily ground, in the form of tiny debris, protecting the grinding object from excessive wear and preventing high-pressure gas leakage.

[0029] If only the transition layer or the wearable coating contains neodymium oxide, the difference in thermal expansion coefficients between the transition layer and the wearable layer will increase. This will cause excessive shear stress (>25MPa) at the interface between the transition layer and the wearable layer due to thermal mismatch during high-speed rotation, resulting in delamination of the transition layer and the wearable layer, peeling off of the wearable layer, and affecting the wearability of the environmental barrier coating.

[0030] The environmental barrier coating of this invention has an abrasion resistance (IDR) value ≤ 20 and a Rockwell hardness (HR15Y) of 60-95. IDR refers to the ratio of the change in blade height before and after the scraping test to the total depth of feed.

[0031] In some preferred embodiments, the porosity of the abrasive coating is 8%-20%. Under this preferred embodiment, controlling the overall hardness and density of the coating makes it easier for the coating to be slightly worn when in contact with rotating components (such as blades). Controlled wear allows for the formation of precise gaps, reducing gas leakage and improving engine efficiency. Simultaneously, it avoids damage to expensive blades, prevents excessive blade wear or coating failure due to thermal stress, and ensures the porosity of the abrasive layer is not less than 8%, which further facilitates control of the cohesive stress within the abrasive layer and improves the coating's fatigue resistance.

[0032] Preferably, the wearable layer comprises a surface layer and an inner layer, wherein the thickness of the surface layer accounts for 60% to 90%, the thickness of the inner layer accounts for 10% to 40%, the porosity of the surface layer is 15% to 20%, and the porosity of the inner layer is 8% to 15%. In this preferred embodiment, the surface layer (60% to 90% of the wearable layer) has a porosity of 15% to 20%, and the inner layer (10% to 40% of the thickness) has a porosity of 8% to 15%. This arrangement facilitates slight wear of the coating during long-term service when it comes into contact with rotating components (such as blades), improving its wear resistance, reducing frictional damage to mating parts, dispersing coating stress, reducing crack propagation, thereby improving the coating's toughness and fatigue resistance, extending its service life, and enhancing the adhesion between the transition layer and the wearable layer.

[0033] In some preferred embodiments, the thickness of the transition layer is 20 μm to 60 μm, and the thickness of the wearable layer is 800 μm to 1200 μm. In this preferred embodiment, a transition layer thickness of not less than 20 μm ensures a sufficient mechanical bonding interface, enhancing the adhesion strength between the wearable layer and the ytterbium monolithic layer and preventing interface peeling. A thickness not exceeding 60 μm prevents thermal stress accumulation and decreased interlayer (transition layer and wearable layer, transition layer and ytterbium monolithic layer) bonding due to excessive thickness, thus preventing interlayer cracking. A wearable layer thickness of not less than 800 μm better meets the wear and tear requirements during long-term service. A thickness not exceeding 1200 μm avoids internal stress concentration caused by excessive thickness, better maintains the toughness of the wearable layer, and reduces the risk of fracture during wearable layer fabrication due to excessive thickness.

[0034] In some preferred embodiments, the silicon layer is a hafnium oxide modified silicon layer and the mass ratio of hafnium oxide to silicon is 1:4 to 19; the mass ratio of ytterbium oxide to silicon oxide in the double ytterbium silicate layer is 4:1 to 7:3; and the mass ratio of ytterbium oxide to silicon oxide in the single ytterbium silicate layer is 9:1 to 4:1.

[0035] The thicknesses of the silicon layer, the double ytterbium silicate layer, and the single ytterbium silicate layer are 20μm~40μm, 80μm~120μm, and 80μm~120μm, respectively.

[0036] In this preferred embodiment, the silicon layer is a hafnium oxide-modified silicon layer with a hafnium oxide to silicon mass ratio of 1:4 to 19 and a silicon layer thickness of 20 μm to 40 μm, which is more conducive to increasing the thermal shock resistance of the environmental barrier coating. In the dual ytterbium silicate layer, the mass ratio of ytterbium oxide to silicon oxide is 4:1 to 7:3, and the thickness is 80 μm to 120 μm, which is more conducive to increasing the high-temperature performance stability of the environmental barrier coating, thereby improving its high-temperature thermal shock resistance. In the single ytterbium silicate layer, the mass ratio of ytterbium oxide to silicon oxide is 9:1 to 4:1, and the thickness is 80 μm to 120 μm, which is more conducive to improving the environmental barrier coating's resistance to water and oxygen corrosion. The preferred mass ratio of ytterbium oxide to silicon oxide in the dual ytterbium silicate layer is 3.5:1 to 7:3, and the preferred mass ratio of ytterbium oxide to silicon oxide in the single ytterbium silicate layer is 9:1 to 4.5:1.

[0037] In a second aspect, the present invention provides a method for preparing the environmental barrier coating described in the first aspect, wherein a silicon layer, a ytterbium bisilate layer, a ytterbium monosilate layer, a transition layer, and a wearable layer are sequentially prepared on an outer ring block of an engine. The mass ratios of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer raw material composite powder for preparing the transition layer and the wearable layer raw material composite powder for preparing the wearable layer are 50~70:15~25:10~15:8~10 and 40~60:20~30:15~20:5~8, respectively.

[0038] The environmental barrier coating prepared by the method of the present invention exhibits a stable and consistent crystal structure of lanthanum magnesium aluminate material under high-temperature conditions. The grains of the lanthanum magnesium aluminate material are refined, and neodymium oxide reacts with CaO, SiO2, etc. in calcium magnesium aluminum silicate to generate a high-viscosity Nd-Ca-Al-Si-O glass phase, which adheres to the surface of the wearable layer to form a dense barrier layer. This improves the wearability and corrosion resistance of the environmental barrier coating, extends its service life under high-temperature conditions, and makes the coating easy to grind in the form of tiny debris, protecting the wear-resistant parts without causing excessive wear and preventing high-pressure gas leakage.

[0039] In some preferred embodiments, the wearable layer is prepared by atmospheric plasma spraying, and the spraying conditions include: a spraying distance of 110mm-140mm, a power of 45kw-50kw, and a powder feeding rate of 300g / min-500g / min; the wearable layer raw material composite powder also has a pore-regulating component and contains a mixed oxide of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in a mass ratio of 85-96:4-15 to the pore-regulating component; the pore-regulating component includes at least one of polystyrene, fluorocarbon resin, silicone resin, polyurethane, and chlorinated rubber; the particle size of the wearable layer raw material composite powder is 15μm-45μm. In this preferred embodiment, when plasma spraying is performed using the aforementioned specific pore-regulating component mixed with oxide, the specific pore-regulating component vaporizes, causing local volume collapse and forming pores. The volatilization process of the specific pore-regulating component forms discontinuous channels in the molten oxide, which then form a connected pore network after cooling. The volume change caused by the decomposition of the specific pore-regulating component leads to uneven stress distribution within the coating, promoting the propagation of microcracks and pores. By employing the aforementioned specific spraying conditions, specific pore-regulating components, specific mass ratio of mixed oxides and pore-regulating components, and specific particle size of the wearable layer raw material composite powder, the synergistic effect makes it easier to achieve a porosity of 8%-20% for the wearable coating.

[0040] Preferably, the inner and outer layers of the wear-resistant layer are prepared sequentially using atmospheric plasma spraying. The spraying conditions for preparing the inner layer include: a spraying distance of 130mm-140mm, a power of 48kw-50kw, and a powder feeding rate of 300g / min-400g / min. The spraying conditions for preparing the outer layer include: a spraying distance of 110mm-130mm, a power of 45kw-47kw, and a powder feeding rate of 400g / min-500g / min. In this preferred embodiment, the wearable layer raw material composite powder contains at least one pore-regulating component selected from polystyrene, fluorocarbon resin, silicone resin, polyurethane, and chlorinated rubber, and the mass ratio of a mixed oxide containing alumina, lanthanum oxide, magnesium oxide, and neodymium oxide to the pore-regulating component is 85~96:4~15. Based on the wearable layer raw material composite powder having a particle size of 15μm~45μm, it is more conducive to achieving a porosity of 8%-15% in the inner layer and 15%-20% in the surface layer of the wearable coating.

[0041] In some preferred embodiments, the transition layer is prepared by atmospheric plasma spraying, and the spraying conditions include: a spraying distance of 90mm-130mm, a power of 47kW-50kW, and a powder feed rate of 180g / min-270g / min. Under this preferred scheme, controlling the spraying distance at 90mm-130mm ensures that the sprayed particles reach a suitable melting and flight state before reaching the ytterbium monolithic layer, which is more conducive to the full wetting and bonding of the particles with the ytterbium monolithic layer, enhancing interfacial adhesion; the power of 47kW-50kW ensures that the particles obtain sufficient energy to achieve efficient melting and spreading, which is more conducive to forming a dense and uniform transition layer structure; the powder feed rate of 180g / min-270g / min can maintain a stable material supply, which is more conducive to controlling the uniformity of the coating thickness, avoiding stress concentration and poor bonding problems caused by excessive thickness or thinness, and ultimately ensuring the excellent connection performance and structural stability of the transition layer.

[0042] In some preferred embodiments, the silicon layer, the ytterbium-bis(2-3) silicate layer, and the ytterbium-mono(2-3) silicate layer are prepared by atmospheric plasma spraying. The spraying conditions for preparing the silicon layer include: a spraying distance of 80mm-120mm, a power of 32-38kW, and a powder feeding rate of 150g / min-250g / min. The spraying conditions for preparing the ytterbium-bis(2-3) silicate layer include: preheating to 300℃-600℃, a spraying distance of 80mm-120mm, a power of 40kW-45kW, and a powder feeding rate of 170g / min-250g / min. The spraying conditions for preparing the ytterbium-mono(2-3) silicate layer include: a spraying distance of 90mm-130mm, a power of 37kW-42kW, and a powder feeding rate of 200g / min-270g / min. In this preferred scheme, a spraying distance of 80mm-120mm, a power of 32-38kW, and a powder feeding rate of 150g / min-250g / min are used to prepare the silicon layer. This allows for precise control of the melting and deposition state of silicon particles, which is more conducive to forming a dense and uniform silicon layer structure and enhances the antioxidant protection of the substrate. The ytterbium bisilicate layer reduces the thermal stress of the coating by preheating at 300℃-600℃. Combined with a spraying distance of 80mm-120mm, a power of 40kW-45kW, and a powder feeding rate of 170-250g / min, this approach further enhances the silicon layer's performance. A powder feeding rate of 0 g / min ensures that the material is fully melted and tightly stacked, which is more conducive to improving the thermal shock resistance and chemical stability of the coating. The single ytterbium silicate layer, with a spraying distance of 90 mm-130 mm, a power of 37 kW-42 kW and a powder feeding rate of 200 g / min-270 g / min, can ensure the uniformity of the coating composition, which is more conducive to optimizing the crystal growth orientation, reducing internal defects, achieving synergistic protection with the double ytterbium silicate layer, and significantly extending the service life of the coating in high-temperature corrosive environments.

[0043] The present invention will be further described in detail below with reference to specific embodiments.

[0044] Example 1

[0045] A method for preparing an environmental barrier coating for an engine outer ring block, comprising the following steps:

[0046] Roughening sandblasting was performed on the SiC-SiC composite substrate of the engine outer ring block. A hafnium oxide modified silicon layer was then prepared on the substrate using atmospheric plasma spraying. The spraying distance was 100 mm, the power was 35 kW, the powder feed rate was 200 g / min, and the hafnium oxide modified silicon layer thickness was 30 μm. A ytterbium bisilicate layer was then prepared on the hafnium oxide modified silicon layer using atmospheric plasma spraying. The temperature was preheated to 450 °C, the spraying distance was 110 mm, the power was 43 kW, and the powder feed rate was 2... A single ytterbium silicate layer was prepared on top of the double ytterbium silicate layer using an atmospheric plasma spraying process with a spraying speed of 20 g / min and a powder feed rate of 110 mm. The single ytterbium silicate layer was then coated to a thickness of 100 μm using the same process. A transition layer with a thickness of 40 μm was then prepared on top of the single ytterbium silicate layer using the same atmospheric plasma spraying process. The mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the powder was [missing information]. The spray ratio is 60:20:13:9, the spraying distance is 110mm, the power is 48kW, the powder feeding rate is 220g / min, and an abrasive layer is prepared on the transition layer using atmospheric plasma spraying. The particle size of the spraying raw material powder is 25~35μm, and the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the spraying raw material powder is 50:25:18:5. The raw material powder includes polystyrene and contains a mixture of oxides of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide. The mass ratio of phenyl ester is 90:10. The inner layer and the outer layer of the wearable layer are sprayed sequentially. The spraying conditions for the inner layer include a spraying distance of 135 mm, a power of 49 kW, and a powder feeding rate of 350 g / min. The spraying conditions for the outer layer include a spraying distance of 120 mm, a power of 46 kW, and a powder feeding rate of 450 g / min. The spraying thickness of the inner layer of the wearable layer is 300 μm, the spraying thickness of the outer layer of the wearable layer is 600 μm, and the total spraying thickness of the wearable layer is 900 μm.

[0047] An environmental barrier coating for an outer ring block of an engine, prepared by the aforementioned method, comprises, from the inside out: a hafnium oxide-modified silicon layer, a ytterbium double silicate layer, a ytterbium monosilica layer, a transition layer, and a wearable layer. In the silicon layer, the mass ratio of hafnium oxide to silicon is 1:12, and the thickness of the hafnium oxide-modified silicon layer is 30 μm. In the ytterbium double silicate layer, the mass ratio of ytterbium oxide to silicon oxide is 3:1, and the thickness of the ytterbium double silicate layer is 100 μm. In the ytterbium monosilica layer, the mass ratio of ytterbium oxide to silicon oxide is 6:1, and the thickness of the ytterbium monosilica layer is 100 μm. Both the transition layer and the wearable coating contain aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The mixed oxide has a transition layer with a mass ratio of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide of 60:20:13:9 and a grain size of 1-3 μm. The transition layer has a thickness of 40 μm. The wearable layer has a mass ratio of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide of 50:25:18:5. The wearable layer consists of a surface layer and an inner layer. The inner layer has a thickness of 300 μm, the surface layer has a thickness of 600 μm, and the total thickness of the wearable coating is 900 μm. The inner layer accounts for 33.3% of the thickness, the surface layer accounts for 66.7%, the surface layer has a porosity of 18%, and the inner layer has a porosity of 12%.

[0048] The wear resistance (IDR) value of the environmental barrier coating of Example 1 was tested under the following conditions: ambient temperature 1300℃, linear velocity 450 m / s, and the IDR value was 13. The hardness of the environmental barrier coating of Example 1 was tested according to the HB5486-1991 test method for hardness of thermally sprayed coatings, and the hardness HR15Y was 65 Rockwell hardness. The fatigue resistance of the environmental barrier coating of Example 1 was tested according to HB 6660-1992, and the result was 5000 cycles of peeling. The interlayer bonding strength between the transition layer and the mono-ytterbium silicate layer, and between the transition layer and the wearable layer of the environmental barrier coating of Example 1 were tested (referencing GB / T 228.1-2010). The interlayer bonding strength between the transition layer and the mono-ytterbium silicate layer was 35 MPa, and the interlayer bonding strength between the transition layer and the wearable layer was 11 MPa. The environmental barrier coating of Example 1 was tested at 1350°C for the duration during which no cracking occurred on the coating surface. The service life under high-temperature conditions was expressed as the holding time, which was 6000 h. The water and oxygen corrosion resistance of the environmental barrier coating of Example 1 was tested under the following conditions: 1350°C, 90% H2O - 10% O2, 300 h. The water and oxygen corrosion resistance was expressed as the coating corrosion depth, which was 0.5 mm.

[0049] Example 2

[0050] The preparation method of the environmental barrier coating in Example 1 is the same, except that the spraying thickness of the inner layer of the abrasive coating is 500 μm, and the spraying thickness of the outer layer of the abrasive coating is 500 μm. Referring to the environmental barrier coating of Example 1, the thickness of the inner layer of the abrasive coating is 500 μm, and the thickness of the outer layer of the abrasive coating is 500 μm, with the inner layer accounting for 50% of the total thickness and the outer layer accounting for 50%. The fatigue resistance test result of the environmental barrier coating in Example 2 is 3500 peeling cycles / time.

[0051] Example 3

[0052] The preparation method of the environmental barrier coating in Example 1 is the same, except that the overall spraying conditions for the abrasive coating are a spraying distance of 135 mm, a power of 49 kW, and a powder feeding rate of 350 g / min. Referring to the environmental barrier coating of Example 1, the abrasive coating, as a whole excluding the surface and inner layers, has an overall porosity of 12%. The IDR value of the environmental barrier coating in Example 3 is 14, and the fatigue resistance test result is 3200 cycles of peeling / cycle.

[0053] Example 4

[0054] The preparation method of the environmental barrier coating in Example 1 is the same, except that the overall spraying conditions for the wearable coating are a spraying distance of 120 mm, a power of 46 kW, and a powder feeding rate of 450 g / min. Referring to the environmental barrier coating of Example 1, the wearable coating, as a whole excluding the surface and inner layers, has an overall porosity of 18%. The interlayer bonding strength between the transition layer and the wearable layer of the environmental barrier coating in Example 4 is 9 MPa, and the fatigue resistance test result is 4000 cycles of peeling / time.

[0055] Example 5

[0056] The preparation method of the environmental barrier coating in Example 1 is the same, except that the mass ratio of the mixed oxides of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide to polystyrene in the abrasive layer spraying raw material powder is 80:20. Referring to the environmental barrier coating of Example 1, the porosity of the surface layer is 30%, and the porosity of the inner layer is 22%. The fatigue resistance test result of the environmental barrier coating in Example 5 is 3800 peeling cycles / time.

[0057] Example 6

[0058] The preparation method of the environmental barrier coating in Example 1 is the same, except that the mass ratio of the mixed oxides of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide to polystyrene in the wear-resistant layer spraying raw material powder is 98:2. Referring to the environmental barrier coating of Example 1, the porosity of the surface layer is 7%, and the porosity of the inner layer is 3%. The environmental barrier coating of Example 6 has an IDR value of 18, a Rockwell hardness of HR15Y of 68, and a fatigue resistance test result of 3300 peeling cycles / cycle.

[0059] Comparative Example 1

[0060] The preparation method of the environmental barrier coating in Example 1 is the same, except that the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the spraying raw material powder of the transition layer is 60:20:13:2. In the environmental barrier coating of Example 1, the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer is also 60:20:13:2. The interlayer adhesion between the transition layer and the mono-ytterbium silicate layer in the environmental barrier coating of Comparative Example 1 is 28 MPa, the interlayer adhesion between the transition layer and the wearable layer is 7 MPa, and the fatigue resistance test result is 2800 cycles of peeling / time.

[0061] Comparative Example 2

[0062] The preparation method of the environmental barrier coating in Example 1 is the same, except that the raw material powder for the sprayed transition layer does not contain neodymium oxide. The transition layer of the environmental barrier coating in Example 1 does not contain neodymium oxide, and the grain size is 5-8 μm. The fatigue resistance test results of the environmental barrier coating in Comparative Example 2 are as follows: 2500 cycles of peeling / time; interlayer adhesion between the transition layer and the mono-ytterbium silicate layer is 26 MPa; interlayer adhesion between the transition layer and the wearable layer is 5 MPa; and the coating surface remains crack-free for 5200 hours at 1350°C.

[0063] Comparative Example 3

[0064] The preparation method of the environmental barrier coating in Example 1 is the same, except that the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the spraying raw material powder for the transition layer is 60:20:13:18. The transition layer also has a mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide of 60:20:13:18. The grain size of the transition layer is 6-20 μm. The fatigue resistance test results of the environmental barrier coating in Comparative Example 3 are 2000 cycles of peeling, the interlayer adhesion between the transition layer and the mono-ytterbium silicate layer is 24 MPa, and the interlayer adhesion between the transition layer and the wearable layer is 4 MPa.

[0065] Comparative Example 4

[0066] The preparation method of the environmental barrier coating in Example 1 is the same, except that the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the spraying raw material powder for the abrasive coating is 50:25:18:1.5. The fatigue resistance test result of the environmental barrier coating in Comparative Example 4 is 2400 cycles of peeling / time, and the interlayer adhesion between the transition layer and the abrasive layer is 6 MPa. Using the same testing method as in Example 1, the water and oxygen corrosion resistance of the environmental barrier coating in Comparative Example 4 is tested, and the coating corrosion depth is 0.8 mm.

[0067] Comparative Example 5

[0068] The preparation method of the environmental barrier coating in Example 1 is the same, except that the raw material powder for spraying the wearable coating does not contain neodymium oxide, and the wearable coating in Example 1 does not contain neodymium oxide. The fatigue resistance test results of the environmental barrier coating of Comparative Example 5 are 2300 cycles of peeling / time, the interlayer adhesion between the transition layer and the wearable layer is 4.5 MPa, and the heat preservation time without cracking of the coating surface at 1350℃ is 5000h. The water and oxygen corrosion resistance of the environmental barrier coating of Comparative Example 5 is tested using the same test method as in Example 1, and the coating corrosion depth is 0.9 mm.

[0069] Comparative Example 6

[0070] The preparation method of the environmental barrier coating in Example 1 is the same, except that the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the spraying raw material powder for the abrasive coating is 50:25:18:15. The mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the abrasive coating of Example 1 is also 50:25:18:15. The IDR value of the environmental barrier coating in Comparative Example 6 is 21, and the fatigue resistance test result is 1900 cycles of peeling / time.

[0071] Comparing Examples 1 and 2, the surface layer of the wear-resistant layer accounts for 60%~90% of the thickness, while the inner layer accounts for 10%~40%. This is more conducive to reducing frictional damage to mating parts during long-term service and improving the fatigue resistance of the coating. Comparing Examples 1 and 3, the wear-resistant layer includes a surface layer and an inner layer. The porosity of the surface layer is 15%-20%, and the porosity of the inner layer is 8%-15%. The higher porosity of the surface layer is more conducive to slight wear when the coating contacts rotating parts (such as blades), reducing frictional damage to mating parts and improving the fatigue resistance of the coating. Comparing Examples 1 and 4, the wear-resistant layer... The coating comprises a surface layer and an inner layer. The porosity of the surface layer is 15%-20%, and the porosity of the inner layer is 8%-15%. The lower porosity of the inner layer is more conducive to improving the bonding force between the transition layer and the wearable layer, thereby improving the fatigue resistance of the coating. Compared with Examples 1 and 5, the porosity of the wearable coating is not higher than 20%, which is more conducive to improving the bonding force between the transition layer and the wearable layer, thereby improving the fatigue resistance of the coating. Compared with Examples 1 and 6, the porosity of the wearable coating is not lower than 8%, which is more conducive to the coating being slightly worn when in contact with rotating parts (such as blades), reducing frictional damage to mating parts, and improving the fatigue resistance of the coating.

[0072] Compared with Comparative Example 1, the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer is 50~70:15~25:10~15:8~10. The higher neodymium oxide content improves the bonding strength between the transition layer and the ytterbium monosilicate layer, as well as between the transition layer and the wearable layer, thus enhancing the coating's fatigue resistance. Compared with Comparative Example 1 and Comparative Example 2, the presence of neodymium oxide in the transition layer refines the grains, improves the crystal stability of the lanthanum magnesium aluminate material, enhances the bonding strength between the transition layer and the ytterbium monosilicate layer, as well as between the transition layer and the wearable layer, further improving the coating's fatigue resistance and extending its service life under high-temperature conditions. Compared with Comparative Example 1 and Comparative Example 3, the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer is 50~70:15~25:10~15:8~10. The lower neodymium oxide content improves the bonding strength between the transition layer and the ytterbium monosilicate layer, as well as between the transition layer and the wearable layer. The bonding strength of the transition layer and the wearable layer is improved, thus enhancing the fatigue resistance of the coating. In Comparative Examples 1 and 4, the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the wearable layer is 40-60:20-30:15-20:5-8. The higher neodymium oxide content improves the bonding strength between the transition layer and the wearable layer, enhancing the fatigue resistance and water-oxygen corrosion resistance of the coating. In Comparative Examples 1 and 5, the presence of neodymium oxide in the wearable layer further enhances the bonding strength between the transition layer and the wearable layer, improving the fatigue resistance, water-oxygen corrosion resistance, and extending the lifespan of the coating under high-temperature service environments. In Comparative Examples 1 and 6, the mass ratio of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the wearable layer is 40-60:20-30:15-20:5-8. The lower neodymium oxide content makes the coating easier to grind, allowing it to be ground into small debris, thus improving the fatigue resistance of the coating.

[0073] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An environmental barrier coating for an outer ring block of an engine, characterized in that, From the inside out, it includes: a silicon layer, a double ytterbium silicate layer, a single ytterbium silicate layer, a transition layer, and a wearable layer. The transition layer and the wearable layer both include a mixed oxide containing aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide. The mass ratios of aluminum oxide, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer and the wearable layer are 50~70:15~25:10~15:8~10 and 40~60:20~30:15~20:5~8, respectively. The porosity of the wear-resistant layer is 8%-20%; The wearable layer comprises a surface layer and an inner layer, wherein the thickness of the surface layer accounts for 60% to 90%, the thickness of the inner layer accounts for 10% to 40%, the porosity of the surface layer is 15% to 20%, and the porosity of the inner layer is 8% to 15%. The thickness of the transition layer is 20μm~60μm, and the thickness of the wear-resistant layer is 800μm~1200μm; The silicon layer is a hafnium oxide modified silicon layer with a hafnium oxide to silicon mass ratio of 1:4 to 19; the mass ratio of ytterbium oxide to silicon oxide in the double ytterbium silicate layer is 4:1 to 7:3; and the mass ratio of ytterbium oxide to silicon oxide in the single ytterbium silicate layer is 9:1 to 4:

1. The thicknesses of the silicon layer, the double ytterbium silicate layer, and the single ytterbium silicate layer are 20μm~40μm, 80μm~120μm, and 80μm~120μm, respectively.

2. A method for preparing the environmental barrier coating according to claim 1, characterized in that, A silicon layer, a double ytterbium silicate layer, a single ytterbium silicate layer, a transition layer, and a wearable layer are sequentially prepared on the outer ring block of the engine. The mass ratios of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide in the transition layer raw material composite powder for preparing the transition layer and the wearable layer raw material composite powder for preparing the wearable layer are 50~70:15~25:10~15:8~10 and 40~60:20~30:15~20:5~8, respectively.

3. The preparation method according to claim 2, characterized in that, The wearable layer is prepared by atmospheric plasma spraying, and the spraying conditions include: a spraying distance of 110mm-140mm, a power of 45kw-50kw, and a powder feeding rate of 300g / min-500g / min; the wearable layer raw material composite powder also contains a pore-regulating component and the mass ratio of a mixed oxide of alumina, lanthanum oxide, magnesium oxide, and neodymium oxide to the pore-regulating component is 85~96:4~15; the pore-regulating component includes at least one of polystyrene, fluorocarbon resin, silicone resin, polyurethane, and chlorinated rubber; the particle size of the wearable layer raw material composite powder is 15μm~45μm.

4. The preparation method according to claim 3, characterized in that, The inner and outer layers of the wear-resistant layer were prepared sequentially using atmospheric plasma spraying. The spraying conditions for preparing the inner layer included: a spraying distance of 130mm-140mm, a power of 48kw-50kw, and a powder feeding rate of 300g / min-400g / min. The spraying conditions for preparing the outer layer included: a spraying distance of 110mm-130mm, a power of 45kw-47kw, and a powder feeding rate of 400g / min-500g / min.

5. The preparation method according to claim 2, characterized in that, The transition layer was prepared by atmospheric plasma spraying, and the spraying conditions included: a spraying distance of 90mm-130mm, a power of 47kw-50kw, and a powder feeding rate of 180g / min-270g / min.

6. The preparation method according to claim 2, characterized in that, The silicon layer, the ytterbium-doped double layer, and the ytterbium-doped single layer were prepared by atmospheric plasma spraying. The spraying conditions for preparing the silicon layer included: a spraying distance of 80mm-120mm, a power of 32kW-38kW, and a powder feeding rate of 150g / min-250g / min. The spraying conditions for preparing the ytterbium-doped double layer included: preheating to 300℃-600℃, a spraying distance of 80mm-120mm, a power of 40kW-45kW, and a powder feeding rate of 170g / min-250g / min. The spraying conditions for preparing the ytterbium-doped single layer included: a spraying distance of 90mm-130mm, a power of 37kW-42kW, and a powder feeding rate of 200g / min-270g / min.