A wear-resistant coating for aerospace bearings based on polysilazane and its preparation method

Abstract

The invention belongs to the technical field of coating preparation and provides a wear-resistant coating for aerospace bearings based on polysilazane and a preparation method thereof. The coating comprises the following steps: hydroxylating the surface of silicon carbide, modifying it with a silane coupling agent, and compounding it with a zirconium-based metal organic framework; and simultaneously compounding graphite phase carbon nitride with calcium fluoride to prepare a composite material to form a bottom layer slurry. The surface of MoS2 is modified with ascorbic acid to form a composite material, and its g-C3N4@CaF2 is mixed and dispersed in a polysilazane solution to form an intermediate layer slurry. The MoS2 composite material identical to the intermediate layer is prepared with g-C3N4@CaF2 to prepare a surface layer slurry. The invention utilizes a multi-layer design of a bottom layer, an intermediate layer, and a surface layer, fully utilizing the high hardness and thermal stability of SiC, the porous structure of MOF, and the low friction performance of MoS2. Polysilazane is used as a matrix material and synergistically acts with various functional materials to provide excellent wear resistance and lubricity.

Description

Technical Field

[0001] The invention belongs to the technical field of coating preparation and relates to a polysilazane-based aerospace bearing wear-resistant coating and a preparation method thereof. Background Art

[0002] With the rapid development of modern aerospace technology, spacecraft are continuously striving for higher performance, longer lifespan, and greater reliability. As a key component in spacecraft, aerospace bearings are subjected to demanding conditions such as extreme temperature fluctuations, high-speed operation, high vacuum, and strong radiation in complex operating environments. To improve the service life and operational stability of aerospace bearings, the application of wear-resistant coating technology is particularly important. However, traditional wear-resistant coatings often suffer from insufficient wear resistance and limited adhesion in high-temperature, high-vacuum, and high-friction environments, and are no longer able to fully meet the needs of the aerospace industry.

[0003] As an advanced inorganic polymer material, polysilazane has attracted significant attention in the coatings field in recent years due to its excellent high-temperature stability, oxidation resistance, chemical inertness, and mechanical strength. Polysilazane can be converted into a ceramic silicon-nitrogen material at high temperatures, exhibiting extremely high hardness and excellent wear resistance. Furthermore, the active functional groups in its molecular structure can chemically react with the substrate, significantly improving the adhesion between the coating and the substrate. These properties make polysilazane an ideal coating precursor material for surface protection of aerospace bearings in extreme environments. Therefore, the development of a polysilazane-based wear-resistant coating for aerospace bearings is crucial to further enhance the coating's wear resistance and meet the highest demands for material performance. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a wear-resistant coating for aerospace bearings based on polysilazane and a preparation method thereof. By adopting multifunctional materials such as molybdenum disulfide, graphite phase carbon nitride, silicon carbide, metal organic framework and calcium fluoride, combined with ascorbic acid modification, silane coupling agent modification and calcination process, the surface functionalization and interface enhancement of the material are achieved. The coating adopts a multilayer design of bottom layer, middle layer and surface layer, thereby meeting the needs of actual production.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a wear-resistant coating for aerospace bearings based on polysilazane, the preparation method comprising:

[0007] A1, adding molybdenum disulfide powder to an ethanol-water solution, stirring and dispersing, and then ultrasonically shaking in an ice-water bath. After the ultrasonicated dispersion is centrifuged, the supernatant is collected and washed with ethanol, and the washed molybdenum disulfide is dispersed in deionized water to form a molybdenum disulfide dispersion;

[0008] A2: Ascorbic acid is dispersed in a sodium phosphate solution, and after stirring, a molybdenum disulfide dispersion is added to the sodium phosphate solution. The mixture is heated to a first temperature under a nitrogen atmosphere for sufficient reaction. After the reaction is completed, the mixture is washed, filtered, and vacuum-dried to obtain MoS2@P particles. The MoS2@P particles are then dispersed in anhydrous ethanol, a silane coupling agent is added, and the mixture is heated to a second temperature for stirring and reacting. After the reaction is completed, the mixture is washed, filtered, and vacuum-dried to obtain a surface-modified MoS2@P composite.

[0009] A3, mixing a calcium nitrate tetrahydrate solution and an ammonium fluoride solution, then adding g-C3N4 powder, and heating to a first temperature after ultrasonic vibration to react. After the reaction, centrifugation and washing are completed, and vacuum drying is performed. The dried product is placed under a nitrogen atmosphere and heated to a third temperature for calcination to obtain a g-C3N4@CaF2 composite;

[0010] S1, dispersing silicon carbide in a sodium hydroxide solution, heating to a first temperature for reaction, centrifuging and washing after the reaction is completed to obtain hydroxylated SiC, dispersing the hydroxylated SiC in an ethanol aqueous solution, adding a silane coupling agent, heating to a fourth temperature for reaction, and centrifuging and washing after the reaction is completed to obtain surface-modified SiC;

[0011] S2, dispersing zirconium salt and terephthalic acid in N,N-dimethylformamide, stirring evenly, adding surface-modified SiC, and transferring to a polytetrafluoroethylene-lined stainless steel reactor after ultrasonic dispersion, heating to the fifth temperature for reaction, washing and filtering after the reaction to obtain SiC@MOF, heating the SiC@MOF to the third temperature for calcination under a nitrogen atmosphere to obtain a SiC@MOF composite;

[0012] S3, disperse the SiC@MOF complex and the g-C3N4@CaF2 complex in solvent A, add polysilazane, PVP and tetraethoxysilane after ultrasonic vibration, and stir evenly to form a bottom layer slurry, disperse the MoS2@P complex and the g-C3N4@CaF2 complex in solvent B, add polysilazane and phenyltriethoxysilane after ultrasonic vibration, and stir evenly to obtain an intermediate layer slurry, disperse the MoS2@P complex and the g-C3N4@CaF2 complex in solvent C, add polysilazane and hexamethyldisiloxane after ultrasonic vibration, and stir evenly to obtain a surface layer slurry, and spray the bottom layer slurry, the intermediate layer slurry and the surface layer slurry on the surface of the aerospace bearing substrate in sequence at room temperature. Before spraying the intermediate layer slurry and the surface layer slurry, wait for the previous layer slurry to solidify. After the room temperature curing is completed, a wear-resistant coating for aerospace bearings based on polysilazane is obtained.

[0013] Molybdenum disulfide is a typical two-dimensional layered material. Its crystal structure is composed of three layers of sulfur-molybdenum-sulfur atoms stacked together. The different layers are bonded by weak van der Waals forces. During friction, external shear force can cause slip between MoS2 layers. This slip releases the stress caused by friction and reduces the friction coefficient. This slip mechanism makes MoS2 exhibit excellent self-lubricating properties, especially in vacuum, ultra-high temperature or high load environments. The crystal structure of MoS2 is composed of sulfur atoms and molybdenum atoms formed by strong covalent bonds to form a three-layer structure. The weaker van der Waals forces stack up to form a layered material. Under the action of external shear force, the van der Waals forces between MoS2 layers are weak, which can cause slip between layers. This slip releases friction stress and reduces the friction coefficient. In a vacuum environment, the interlayer slip mechanism of MoS2 relies entirely on its inherent physical properties and is unrelated to the ambient atmosphere. While the van der Waals forces between MoS2 layers are weak, the sulfur-molybdenum covalent bonds within the layers are strong and have high bond energies, enabling it to maintain structural stability under high-temperature conditions. At high temperatures, the sulfur atomic layer on the MoS2 surface prevents direct reaction between oxygen and molybdenum atoms, thereby reducing the risk of oxidation or structural collapse. Nanoscale cracks or defects may appear on the material surface under high temperatures, and the interlayer slip characteristics of MoS2 can mitigate the expansion of these defects through a dynamic stress release mechanism. The high mechanical strength and hardness of the MoS2 intralayer structure ensure that it does not easily undergo plastic deformation or fracture under high loads. Under high loads, high compressive stress is generated at the friction interface. This pressure promotes the breakdown of the van der Waals forces between MoS2 layers, making slip more likely. The occurrence of slip not only reduces shear forces but also buffers the direct impact of the load on the coating substrate.

[0014] Ascorbic acid is a reducing agent with multiple hydroxyl and enol structures in its molecular structure, which can provide electrons to reduce substances in oxidized states. In the reaction, ascorbic acid itself is oxidized to dehydroascorbic acid, which reduces the phosphorus in sodium phosphate from a higher oxidation state to its elemental state. Elemental phosphorus has multiple allotropes, including white phosphorus, red phosphorus, and black phosphorus. Black phosphorus is the most thermodynamically stable form of phosphorus allotrope. At room temperature and pressure, black phosphorus has a layered structure similar to graphite, with each phosphorus atom covalently bonded to three other phosphorus atoms to form a two-dimensional structure. In contrast, white phosphorus has a highly strained tetrahedral structure and is therefore thermodynamically unstable. Red phosphorus is an intermediate state, but its formation requires higher temperatures or special polymerization conditions. Therefore, under mild reducing conditions, the reaction tends to produce the most stable black phosphorus. When ascorbic acid is used as a mild reducing agent, the gradual reduction of sodium phosphate is slow and controlled, avoiding the formation of white or red phosphorus under high temperature conditions. Black phosphorus is a two-dimensional layered material, and its layers are also bonded by van der Waals forces. When shear force is applied to the friction interface, the interlayer van der Waals forces of black phosphorus are easily destroyed, resulting in slippage between layers, which can participate in the lubrication of the friction interface. Microcracks or surface defects are usually generated in the friction interface due to mechanical action. These defects will further lead to local stress concentration and accelerate wear. Phosphorus can be embedded in these cracks or defects through physical filling, reducing stress concentration and inhibiting crack propagation, thereby achieving a self-repairing effect. Due to the two-dimensional structure of the thin film, it has good spreading properties and can be The microcrack surface is effectively covered, and during high-temperature friction, the phosphorus flakes may react with oxygen or other chemicals at the friction interface to generate phosphorus oxides (such as phosphates) or phosphides. These products form a stable protective film at the friction interface, which can inhibit further chemical oxidation or wear. The released phosphide or phosphorus oxide species can chemically react with defects or active sites on the friction interface, and achieve interface repair by forming new chemical bonds (such as MP or MOP bonds, where M refers to the metal element in the matrix material), further enhancing the integrity of the friction interface. The interlayer slip of MoS2 provides dynamic low-friction lubrication, while the two-dimensional structure of phosphorus brings self-healing ability to the friction interface. During the friction process, MoS2 provides a basic low-friction environment. When there is local stress concentration or material wear, phosphorus can be embedded in these cracks or defects through physical filling, reducing stress concentration and inhibiting crack propagation, thereby maintaining the integrity of the overall friction interface. At the same time, the presence of phosphide can passivate the active sites of the friction interface and inhibit interface oxidation and wear. MoS2 reduces the generation of frictional heat through lubrication, while phosphorus protects the interface at high temperatures through its own physical properties and the release of phosphide, forming a multiple protection mechanism.

[0015] g-C3N4 is a two-dimensional layered material. Each layer is a conjugated six-membered ring network based on triazine or cyanuric acid units. The layers are held together by covalent C=N and CN bonds within the layers, while weak van der Waals forces maintain the interlayer bonds. This weak interlayer bonding gives it excellent mechanical flexibility and lubricity. The surface of g-C3N4 is rich in active sites such as amino groups, carbonyl groups, and π-electron clouds. These sites enable surface modification or composites with other materials (such as CaF2) through electrostatic interactions, hydrogen bonding, and π-π interactions. Furthermore, g-C3N4 has a high thermal decomposition temperature and exhibits excellent chemical stability and oxidation resistance at high temperatures. The two-dimensional layered structure of g-C3N4 enables it to reduce the friction coefficient through interlayer slip. During friction, the interlayer van der Waals forces are overcome by shear forces, leading to interlayer slip and the simultaneous release of frictional stress. The surface active sites of g-C3N4 provide chemical binding sites for the growth and deposition of CaF2 nanoparticles. Through these sites, CaF2 nanoparticles can be uniformly distributed and form a stable interface with g-C3N4. Calcium fluoride is an ionic compound with a cubic crystal structure. 2+ and F - Ions are bound by strong ionic bonds. At high temperatures, ion migration may occur on the surface of CaF2 (F - and Ca 2+ The redistribution of the surface atoms leads to a certain degree of relaxation and rearrangement of the surface structure. This rearrangement may reduce the binding force of the surface atoms, thereby forming a slip layer with low shear strength on the surface. F- ions have strong chemical inertness and low surface energy, and can form a stable ion film at the friction interface. This film can reduce the friction between the interfaces. 2+ It is a positively charged ion. The electron cloud on the surface of the friction interface metal or oxide may be partially exposed, resulting in relative negative charge. In a high temperature environment, the oxides that may be generated on the surface of the interface material also have strong negative charge and can attract Ca 2+ , Ca 2+ Ions are adsorbed to the surface of the friction interface material through electrostatic force, forming a positively charged ion adsorption layer. The electrostatically adsorbed Ca 2+ Ions form an “electrochemical barrier” at the crack tip, reducing the active oxygen species (such as O2 - , OH·) diffusion, inhibiting the chemical degradation of cracks. g-C3N4 is dispersed in aqueous solution, and the sheet agglomeration is broken by ultrasonic treatment to form a stable two-dimensional sheet dispersion system. In the CaF2 generation reaction, g-C3N4 is added to the solution, and its surface active sites are used to react with Ca 2+Adsorption occurs, and CaF2 particles gradually deposit on the surface of g-C3N4, forming a g-C3N4@CaF2 composite structure. After calcination under nitrogen atmosphere, CaF2 particles form a tighter bond with the interface of g-C3N4 sheets. g-C3N4 relies on its layered structure to provide low shear strength physical lubrication. Under the action of friction, the layers of g-C3N4 slip to release stress and reduce the friction coefficient. CaF2 releases F - and Ca 2+ ions form a lubricating ion film at the interface, and F- ions form a low-friction lubricating layer on the interface to further reduce the shear force. The formation of the lubricating film works synergistically with the slip of g-C3N4 to improve the lubrication performance of the wear-resistant coating.

[0016] Silicon carbide (SiC) is a thermodynamically stable compound with excellent mechanical strength, high-temperature resistance, and chemical inertness. However, its surface is generally inert and difficult to bond with other materials or molecules. Chemical treatment under alkaline conditions can introduce hydroxyl groups on the SiC surface, thereby enhancing its surface chemical activity. OH- ions in the alkaline solution react with silicon atoms on the SiC surface to form Si-OH groups. During the reaction, the silicon atoms on the SiC surface combine with hydroxide groups in the solution, forming a hydroxylated silicon surface. Silane coupling agents are a class of molecules containing siloxane groups and organic functional groups. They can bond to the surface of inorganic materials through Si-O bonds and simultaneously introduce organic functional groups to the material surface. The siloxane groups in the silane coupling agent solution hydrolyze to form silanols, which condense with the Si-OH groups on the hydroxylated SiC surface to form strong Si-O-Si bonds. The surface of the surface-modified SiC particles is bound to the silane coupling agent molecules through Si-O-Si bonds. This modification not only improves the surface chemical activity of SiC, but also introduces more organic functional groups, thereby enhancing the binding ability with MOF precursors. 4+ It reacts with terephthalic acid in the solvent N,N-dimethylformamide to form a Zr-based MOF. The silane-modified SiC surface provides attachment sites, promoting the growth of MOF on the surface of SiC particles to form a composite structure. In the subsequent calcination stage, the organic part in the MOF is decomposed or carbonized, enhancing the stability and mechanical properties of the composite material while forming a porous structure. SiC introduces a large number of Si-OH groups through surface hydroxylation. These groups provide chemical binding sites for further silane modification. The silane coupling agent binds to the SiC surface through the Si-O-Si bond and introduces active groups (such as amino and carboxyl groups) at the other end of the molecule. These groups can chemically interact with the MOF precursor and promote the growth of MOF on the SiC surface. During the growth of MOF, Zr 4+The MOF chemically coordinates with the functional groups modified on the SiC surface to form a strong interface bond. The strong interface bond ensures the uniform distribution of MOF on the SiC surface, avoiding the interface delamination or cracking problems that may occur in traditional composite materials. The chemical bonding at the interface not only significantly improves the bonding strength between SiC and MOF, but also improves the composite material's resistance to crack propagation through the effective transfer of interfacial energy. After calcination in a nitrogen atmosphere, the MOF shell is partially converted into metal oxides or carbides, further enhancing the high temperature resistance and oxidation resistance of the composite material. The porous structure is retained during the calcination process, providing excellent lubrication properties and mechanical structural properties. The porosity and flexibility of MOF can absorb part of the stress under friction and mechanical load, thereby delaying the formation and propagation of cracks. The high strength of SiC provides a physical barrier to cracks, further improving the crack resistance. Secondly, the chemical inertness of SiC enables it to resist high-temperature oxidation, and MOF further forms a dense protective film after calcination to prevent the penetration of oxygen or water molecules.

[0017] In complex operating environments (such as high temperatures, friction, and oxidation), single-function coatings often struggle to meet diverse performance requirements. Therefore, gradient coatings combine different layers of functional materials to gradually optimize the coating's lubricity and wear resistance. Polysilazane, a precursor material that transforms into a ceramic material through temperature curing, offers high hardness, chemical stability, and high-temperature resistance. It serves as the primary support framework for the underlying layer and also provides a favorable dispersion and bonding interface for functional additives. In the base slurry, the porous structure of Zr-MOF absorbs mechanical impact and relieves stress concentration, thereby improving crack resistance. SiC is a superhard material with excellent wear resistance and high-temperature strength. The hydroxylated SiC undergoes a condensation reaction with the polysilazane matrix to form a stable Si-O-Si bond to enhance the interfacial bonding strength. The two-dimensional layered structure of g-C3N4 has high chemical stability and heat resistance, which can prevent oxygen from penetrating into the substrate at high temperatures. The base slurry enhances the adhesion, wear resistance and crack resistance of the coating; in the middle and surface slurries, the layered structure of MoS2 provides lubrication through interlayer slip. Phosphorus can be embedded in these cracks or defects through physical filling, reducing stress concentration and inhibiting crack propagation, thereby maintaining the integrity of the overall friction interface. At the same time, the presence of phosphide can passivate the active sites of the friction interface, inhibiting interfacial oxidation and wear. The two-dimensional structure of g-C3N4 cooperates with MoS2 in the middle layer to provide lubrication.

[0018] As a preferred technical solution of the present invention, in A1, the mass volume ratio of the molybdenum disulfide powder to the ethanol aqueous solution is 1g:120mL.

[0019] In some optional instances, the frequency of the ultrasonic oscillation is 60-80 KHz, for example, it can be 60.0 KHz, 62.0 KHz, 64.0 KHz, 66.0 KHz, 68.0 KHz, 70.0 KHz, 72.0 KHz, 74.0 KHz, 76.0 KHz, 78.0 KHz or 80.0 KHz, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In some optional examples, the ultrasonic oscillation time is 4-5h, for example, it can be 4.0h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In some optional examples, the concentration of the molybdenum disulfide dispersion is 1 mg / mL.

[0022] As a preferred technical solution of the present invention, in A2, the mass volume ratio of ascorbic acid to sodium phosphate solution is 1g:50mL.

[0023] The mass fraction of the sodium phosphate solution is 2-3 wt.%.

[0024] In some optional examples, the volume ratio of the molybdenum disulfide dispersion to the sodium phosphate solution is 2:5.

[0025] In some optional examples, the first temperature is 80-90°C, for example, it can be 80.0°C, 81.0°C, 82.0°C, 83.0°C, 84.0°C, 85.0°C, 86.0°C, 87.0°C, 88.0°C, 89.0°C or 90.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In some optional examples, the time for sufficient reaction at the first temperature is 6-7h, for example, it can be 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h or 7.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In some optional examples, the mass volume ratio of the MoS2@P particles to anhydrous ethanol is 1 mg:1 mL.

[0028] In some optional examples, the silane coupling agent is 3-aminopropyltriethoxysilane, and its mass is 10-20% of the mass of the MoS2@P particles, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0029] In some optional examples, the second temperature is 40-50°C, for example, it can be 40.0°C, 41.0°C, 42.0°C, 43.0°C, 44.0°C, 45.0°C, 46.0°C, 47.0°C, 48.0°C, 49.0°C or 50.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] In some optional examples, the second temperature stirring reaction time is 5-6h, for example, it can be 5.0h, 5.1h, 5.2h, 5.3h, 5.4h, 5.5h, 5.6h, 5.7h, 5.8h, 5.9h or 6.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, in A3, the molar ratio of the calcium nitrate tetrahydrate to the ammonium fluoride is 1:1.

[0032] In some optional examples, the volume ratio of the calcium nitrate tetrahydrate solution to the ammonium fluoride solution is 1:1.

[0033] In some optional examples, the concentration of the calcium nitrate tetrahydrate solution is 0.1M.

[0034] In some optional examples, the mass volume ratio of the g-C3N4 powder to the calcium nitrate tetrahydrate solution is 1 g:100 mL.

[0035] In some optional examples, the time of the first temperature reaction is 6-7h, for example, it can be 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h or 7.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In some optional examples, the third temperature is 300-310°C, for example, it can be 300.0°C, 301.0°C, 302.0°C, 303.0°C, 304.0°C, 305.0°C, 306.0°C, 307.0°C, 308.0°C, 309.0°C or 310.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In some optional examples, the time for calcining at the third temperature is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] As a preferred technical solution of the present invention, in S1, the mass volume ratio of the silicon carbide to the sodium hydroxide solution is 1g:50mL.

[0039] In some optional examples, the concentration of the sodium hydroxide solution is 1M.

[0040] In some optional examples, the time of the first temperature reaction is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In some optional examples, the silane coupling agent is 3-aminopropyltriethoxysilane, and its mass is 40-50% of the mass of hydroxylated SiC, for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0042] In some optional examples, the fourth temperature is 70-80°C, for example, it can be 70.0°C, 71.0°C, 72.0°C, 73.0°C, 74.0°C, 75.0°C, 76.0°C, 77.0°C, 78.0°C, 79.0°C or 80.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In some optional examples, the fourth temperature reaction time is 6-7h, for example, it can be 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h or 7.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] As a preferred technical solution of the present invention, in S2, the zirconium salt is Zr(NO3)4·5H2O, and the molar volume ratio of the zirconium salt to N,N-dimethylformamide is 1 mmol:50 mL.

[0045] In some optional examples, the molar ratio of the zirconium salt to the terephthalic acid is 1:1.

[0046] In some optional examples, the mass volume ratio of the surface-modified SiC to N,N-dimethylformamide is 0.2 g:50 mL.

[0047] In some optional examples, the fifth temperature is 130-140°C, for example, it can be 130.0°C, 131.0°C, 132.0°C, 133.0°C, 134.0°C, 135.0°C, 136.0°C, 137.0°C, 138.0°C, 139.0°C or 140.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] In some optional examples, the time of the fifth temperature reaction is 14-16 hours, for example, it can be 14.0 hours, 14.2 hours, 14.4 hours, 14.6 hours, 14.8 hours, 15.0 hours, 15.2 hours, 15.4 hours, 15.6 hours, 15.8 hours or 16.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] In some optional examples, the time for calcining at the third temperature is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] As a preferred technical solution of the present invention, in S3, in the base slurry, the mass ratio of the SiC@MOF composite, g-C3N4@CaF2 composite, polysilazane, and PVP is 0.5:0.25:2:0.1.

[0051] In some optional examples, the solvent A is a mixed solution of DMF and anhydrous ethanol in a volume ratio of 3:1.

[0052] In some optional examples, the mass volume ratio of the polysilazane to the solvent A is 1 g:10 mL.

[0053] In some optional examples, when the intermediate layer slurry is prepared, the mass ratio of the MoS2@P complex, g-C3N4@CaF2 complex, polysilazane, and phenyltriethoxysilane is 0.5:0.25:2:0.2.

[0054] The solvent B is a mixed solution of DMF and anhydrous ethanol with a volume ratio of 2:1.

[0055] The mass volume ratio of the polysilazane to solvent B is 1 g:10 mL.

[0056] In some optional examples, in the surface slurry, the mass ratio of the MoS2@P complex, g-C3N4@CaF2 complex, polysilazane, and hexamethyldisiloxane is 0.5:0.25:2:0.2.

[0057] The solvent B is a mixed solution of DMF and anhydrous ethanol in a volume ratio of 1:1.

[0058] The mass volume ratio of the polysilazane to solvent B is 1 g:10 mL.

[0059] In a second aspect, the present invention provides a polysilazane-based aerospace bearing wear-resistant coating prepared by the method for preparing a polysilazane-based aerospace bearing wear-resistant coating according to the first aspect.

[0060] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The interlayer slip of MoS2 provides dynamic low-friction lubrication, and the two-dimensional structure of phosphorus brings self-repairing ability to the friction interface. When there is local stress concentration or material wear, phosphorus can be embedded in these cracks or defects through physical filling, reducing stress concentration and inhibiting crack expansion, thereby maintaining the integrity of the overall friction interface. At the same time, the presence of phosphide can passivate the active sites of the friction interface. MoS2 reduces the generation of friction heat through lubrication, and phosphorus protects the interface at high temperature by releasing phosphide, forming a multiple protection mechanism; (2) g-C3N4 relies on its layered structure to provide physical lubrication with low shear strength. Under the action of friction, the interlayer of g-C3N4 slips to release stress and reduce the friction coefficient, while CaF2 forms a low-friction lubricating layer on the interface by releasing ions. The shear force is reduced in one step, and the formation of the lubricating film and the slip of g-C3N4 work synergistically to improve the lubrication performance of the wear-resistant coating; (3) SiC introduces a large number of Si-OH groups through surface hydroxylation, which promotes the growth of MOF on the SiC surface to form a strong interface bond. The porosity and flexibility of MOF after calcination can absorb part of the stress under the action of friction and mechanical load, thereby delaying the formation and expansion of cracks. The high strength of SiC provides a physical barrier for cracks, further improving the crack resistance; secondly, the chemical inertness of SiC enables it to resist high-temperature oxidation, and MOF further forms a dense protective film after calcination to prevent the penetration of oxygen or water molecules; (4) The gradient coating gradually optimizes the lubrication and wear resistance of the coating through the combination of functional materials at different levels. Polysilazane provides good wear resistance and forms a synergistic effect with other materials to enhance the adhesion and wear resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1This is a SEM image of the g-C3N4@CaF2 composite prepared in Example 1 of the present invention;

[0062] Figure 2 This is a SEM image of the SiC@MOF composite prepared in Example 1 of the present invention;

[0063] Figure 3 This is a TEM image of the SiC@MOF composite prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0064] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0065] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products and have not been subjected to any further purification treatment.

[0066] Example 1

[0067] This embodiment provides a wear-resistant coating for aerospace bearings based on polysilazane, the preparation method of which specifically includes the following steps:

[0068] A1: 1 g of molybdenum disulfide powder was added to 120 mL of ethanol-water solution, stirred and dispersed, and ultrasonicated at 60 kHz for 4.3 h in an ice-water bath. The ultrasonicated dispersion was centrifuged, the supernatant was collected, and washed with ethanol. The washed molybdenum disulfide was dispersed in deionized water to form a 1 mg / mL molybdenum disulfide dispersion.

[0069] A2, 1g of ascorbic acid was dispersed in 50mL of 2.4wt.% sodium phosphate solution, stirred evenly, and then 20mL of molybdenum disulfide dispersion was added to the sodium phosphate solution. Under a nitrogen atmosphere, the temperature was raised to 81°C and the reaction was fully reacted for 6.1h. After the reaction was completed, the particles were washed, filtered, and vacuum dried to obtain MoS2@P particles. Then, 100mg of MoS2@P particles were dispersed in 100mL of anhydrous ethanol, 12mg of 3-aminopropyltriethoxysilane was added, and the temperature was raised to 44°C and stirred for 5.2h. After the reaction was completed, the particles were washed, filtered, and vacuum dried to obtain a surface-modified MoS2@P composite.

[0070] A3: Mix 50 mL of 0.1 M calcium nitrate tetrahydrate solution and 50 mL of 0.1 M ammonium fluoride solution, add 0.5 g of g-C3N4 powder, and heat to 81°C for 6.4 h after ultrasonic vibration. After the reaction, centrifuge, wash, and vacuum dry. The dried product is placed in a nitrogen atmosphere and heated to 308°C for 2.4 h to obtain a g-C3N4@CaF2 composite.

[0071] S1, disperse 1g of silicon carbide in 50mL of 1M sodium hydroxide solution, heat to 88℃ for 2.8h, centrifuge and wash after the reaction to obtain hydroxylated SiC, disperse 400mg of hydroxylated SiC in 40mL of ethanol aqueous solution, add 160mg of 3-aminopropyltriethoxysilane and heat to 72℃ for 6.3h, centrifuge and wash after the reaction to obtain surface-modified SiC;

[0072] S2, 1 mmol of ZrNO 34 5H2O and 1 mmol of terephthalic acid were dispersed in 50 mL of N,N-dimethylformamide, stirred evenly, and then 0.2 g of surface-modified SiC was added. After ultrasonic dispersion, the mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor and heated to 133°C for 14.2 h. After the reaction, the SiC@MOF was washed and filtered to obtain SiC@MOF. Under a nitrogen atmosphere, the SiC@MOF was heated to 306°C and calcined for 2.4 h to obtain a SiC@MOF composite.

[0073] S3, 0.5g of SiC@MOF composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent A, and 2g of polysilazane and 0.1g of PVP were added after ultrasonic vibration, and stirred evenly to form a bottom layer slurry. 0.5g of MoS2@P composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent B, and 2g of polysilazane was added after ultrasonic vibration, and stirred evenly to obtain an intermediate layer slurry. 0.5 g of MoS2@P composite and 0.25 g of g-C3N4@CaF2 composite were dispersed in 20 mL of solvent C, 2 g of polysilazane was added after ultrasonic vibration, and the mixture was stirred evenly to obtain a surface slurry. The bottom layer slurry, the middle layer slurry and the surface layer slurry were sprayed on the surface of the aerospace bearing substrate in sequence at room temperature. Before spraying the middle layer slurry and the surface layer slurry, the previous layer of slurry needed to be cured. After curing at room temperature, a wear-resistant coating for aerospace bearings based on polysilazane was obtained.

[0074] Figure 1 This is the SEM image of the g-C3N4@CaF2 composite prepared in this example. It can be clearly seen that CaF2 is evenly deposited on the surface of g-C3N4 without obvious agglomeration. Figure 2 This is the SEM image of the SiC@MOF composite prepared in this example; Figure 3 This is the TEM image of the SiC@MOF composite prepared in this example.

[0075] Example 2

[0076] This embodiment provides a wear-resistant coating for aerospace bearings based on polysilazane, the preparation method of which specifically includes the following steps:

[0077] A1: 1 g of molybdenum disulfide powder was added to 120 mL of ethanol-water solution, stirred and dispersed, and ultrasonicated at 70 kHz for 4.8 h in an ice-water bath. The ultrasonicated dispersion was centrifuged, the supernatant was collected, and washed with ethanol. The washed molybdenum disulfide was dispersed in deionized water to form a 1 mg / mL molybdenum disulfide dispersion.

[0078] A2, 1g of ascorbic acid was dispersed in 50mL of 2.1wt.% sodium phosphate solution, stirred evenly, and then 20mL of molybdenum disulfide dispersion was added to the sodium phosphate solution. Under a nitrogen atmosphere, the temperature was raised to 89°C and the reaction was fully reacted for 6.8h. After the reaction was completed, the particles were washed, filtered, and vacuum-dried to obtain MoS2@P particles. 100mg of MoS2@P particles were dispersed in 100mL of anhydrous ethanol, 19mg of 3-aminopropyltriethoxysilane was added, and the temperature was raised to 41°C and stirred for 5.7h. After the reaction was completed, the particles were washed, filtered, and vacuum-dried to obtain surface-modified MoS2@P composites.

[0079] A3: Mix 50 mL of 0.1 M calcium nitrate tetrahydrate solution and 50 mL of 0.1 M ammonium fluoride solution, add 0.5 g of g-C3N4 powder, and heat to 89°C for 6.9 h after ultrasonic vibration. After the reaction, centrifuge, wash, and vacuum dry. The dried product is placed in a nitrogen atmosphere and heated to 301°C for 2.1 h to obtain a g-C3N4@CaF2 composite.

[0080] S1, disperse 1g of silicon carbide in 50mL of 1M sodium hydroxide solution, heat to 81℃ and react for 2.6h. After the reaction is complete, centrifuge and wash to obtain hydroxylated SiC. Disperse 400mg of hydroxylated SiC in 40mL of ethanol and water, add 180mg of 3-aminopropyltriethoxysilane and heat to 76℃ and react for 6.8h. After the reaction is complete, centrifuge and wash to obtain surface-modified SiC.

[0081] S2, 1 mmol of ZrNO 345H2O and 1 mmol of terephthalic acid were dispersed in 50 mL of N,N-dimethylformamide, stirred evenly, and then 0.2 g of surface-modified SiC was added. After ultrasonic dispersion, the mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor and heated to 130°C for 15.8 hours. After the reaction, the SiC@MOF was washed and filtered to obtain the SiC@MOF. Under a nitrogen atmosphere, the SiC@MOF was heated to 301°C and calcined for 2.9 hours to obtain the SiC@MOF composite.

[0082] S3, 0.5g of SiC@MOF composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent A, and 2g of polysilazane and 0.1g of PVP were added after ultrasonic vibration, and stirred evenly to form a bottom layer slurry. 0.5g of MoS2@P composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent B, and 2g of polysilazane was added after ultrasonic vibration, and stirred evenly to obtain an intermediate layer slurry. 0.5 g of MoS2@P composite and 0.25 g of g-C3N4@CaF2 composite were dispersed in 20 mL of solvent C, 2 g of polysilazane was added after ultrasonic vibration, and the mixture was stirred evenly to obtain a surface slurry. The bottom layer slurry, the middle layer slurry and the surface layer slurry were sprayed on the surface of the aerospace bearing substrate in sequence at room temperature. Before spraying the middle layer slurry and the surface layer slurry, the previous layer of slurry needed to be cured. After curing at room temperature, a wear-resistant coating for aerospace bearings based on polysilazane was obtained.

[0083] Example 3

[0084] This embodiment provides a wear-resistant coating for aerospace bearings based on polysilazane, the preparation method of which specifically includes the following steps:

[0085] A1: 1 g of molybdenum disulfide powder was added to 120 mL of ethanol-water solution, stirred and dispersed, and ultrasonicated at 80 kHz for 4.1 h in an ice-water bath. The ultrasonicated dispersion was centrifuged, the supernatant was collected, and washed with ethanol. The washed molybdenum disulfide was dispersed in deionized water to form a 1 mg / mL molybdenum disulfide dispersion.

[0086] A2, 1g of ascorbic acid was dispersed in 50mL of 2.9wt.% sodium phosphate solution, stirred evenly, and then 20mL of molybdenum disulfide dispersion was added to the sodium phosphate solution. Under a nitrogen atmosphere, the temperature was raised to 86°C and the reaction was fully reacted for 6.4h. After the reaction was completed, the particles were washed, filtered, and vacuum dried to obtain MoS2@P particles. Then, 100mg of MoS2@P particles were dispersed in 100mL of anhydrous ethanol, 16mg of 3-aminopropyltriethoxysilane was added, and the temperature was raised to 49°C and stirred for 5.9h. After the reaction was completed, the particles were washed, filtered, and vacuum dried to obtain a surface-modified MoS2@P composite.

[0087] A3: Mix 50 mL of 0.1 M calcium nitrate tetrahydrate solution and 50 mL of 0.1 M ammonium fluoride solution, add 0.5 g of g-C3N4 powder, and heat to 86°C for 6.1 h after ultrasonic vibration. After the reaction, centrifuge, wash, and vacuum dry. The dried product is placed in a nitrogen atmosphere and heated to 305°C for 2.9 h to obtain a g-C3N4@CaF2 composite.

[0088] S1, disperse 1g of silicon carbide in 50mL of 1M sodium hydroxide solution, heat to 86℃ for 2.1h, centrifuge and wash after the reaction to obtain hydroxylated SiC, disperse 400mg of hydroxylated SiC in 40mL of ethanol aqueous solution, add 200mg of 3-aminopropyltriethoxysilane and heat to 79℃ for 6.1h, centrifuge and wash after the reaction to obtain surface-modified SiC;

[0089] S2, 1 mmol of ZrNO 34 5H2O and 1 mmol of terephthalic acid were dispersed in 50 mL of N,N-dimethylformamide, stirred evenly, and then 0.2 g of surface-modified SiC was added. After ultrasonic dispersion, the mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor and heated to 139°C for 14.6 hours. After the reaction, the SiC@MOF was washed and filtered to obtain the SiC@MOF. Under a nitrogen atmosphere, the SiC@MOF was heated to 307°C and calcined for 2.5 hours to obtain the SiC@MOF composite.

[0090] S3, 0.5g of SiC@MOF composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent A, and 2g of polysilazane and 0.1g of PVP were added after ultrasonic vibration, and stirred evenly to form a bottom layer slurry. 0.5g of MoS2@P composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent B, and 2g of polysilazane was added after ultrasonic vibration, and stirred evenly to obtain an intermediate layer slurry. 0.5 g of MoS2@P composite and 0.25 g of g-C3N4@CaF2 composite were dispersed in 20 mL of solvent C, 2 g of polysilazane was added after ultrasonic vibration, and the mixture was stirred evenly to obtain a surface slurry. The bottom layer slurry, the middle layer slurry and the surface layer slurry were sprayed on the surface of the aerospace bearing substrate in sequence at room temperature. Before spraying the middle layer slurry and the surface layer slurry, the previous layer of slurry needed to be cured. After curing at room temperature, a wear-resistant coating for aerospace bearings based on polysilazane was obtained.

[0091] Example 4

[0092] This embodiment provides a wear-resistant coating for aerospace bearings based on polysilazane, the preparation method of which specifically includes the following steps:

[0093] A1: 1 g of molybdenum disulfide powder was added to 120 mL of ethanol-water solution, and after stirring and dispersing, the mixture was ultrasonically shaken at 60 kHz for 4.9 h in an ice-water bath. The ultrasonicated dispersion was centrifuged, the supernatant was collected, and washed with ethanol. The washed molybdenum disulfide was dispersed in deionized water to form a 1 mg / mL molybdenum disulfide dispersion.

[0094] A2, 1g of ascorbic acid was dispersed in 50mL of 2.7wt.% sodium phosphate solution, stirred evenly, and then 20mL of molybdenum disulfide dispersion was added to the sodium phosphate solution. Under a nitrogen atmosphere, the temperature was raised to 83°C and the reaction was fully reacted for 6.7h. After the reaction was completed, the particles were washed, filtered, and vacuum dried to obtain MoS2@P particles. Then, 100mg of MoS2@P particles were dispersed in 100mL of anhydrous ethanol, 13mg of 3-aminopropyltriethoxysilane was added, and the temperature was raised to 46°C and stirred for 5.4h. After the reaction was completed, the particles were washed, filtered, and vacuum dried to obtain a surface-modified MoS2@P composite.

[0095] A3: Mix 50 mL of 0.1 M calcium nitrate tetrahydrate solution and 50 mL of 0.1 M ammonium fluoride solution, add 0.5 g of g-C3N4 powder, and ultrasonically vibrate the mixture. Heat the mixture to 83°C and react for 6.7 h. After the reaction, centrifuge, wash, and vacuum dry the mixture. The dried product is placed in a nitrogen atmosphere and heated to 303°C for 2.7 h to obtain a g-C3N4@CaF2 composite.

[0096] S1, disperse 1g of silicon carbide in 50mL of 1M sodium hydroxide solution, heat to 84℃ for 2.4h, centrifuge and wash after the reaction to obtain hydroxylated SiC, disperse 400mg of hydroxylated SiC in 40mL of ethanol aqueous solution, add 170mg of 3-aminopropyltriethoxysilane and heat to 74℃ for 6.5h, centrifuge and wash after the reaction to obtain surface-modified SiC;

[0097] S2, 1 mmol of ZrNO 34 5H2O and 1 mmol of terephthalic acid were dispersed in 50 mL of N,N-dimethylformamide, stirred evenly, and then 0.2 g of surface-modified SiC was added. After ultrasonic dispersion, the mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor and heated to 136°C for 15.3 h. After the reaction, the SiC@MOF was washed and filtered to obtain SiC@MOF. Under a nitrogen atmosphere, the SiC@MOF was heated to 310°C and calcined for 2.2 h to obtain a SiC@MOF composite.

[0098] S3, 0.5g of SiC@MOF composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent A, and after ultrasonic vibration, 2g of polysilazane and 0.1g of PVP were added and stirred to form a bottom layer slurry. 0.5g of MoS2@P composite and 0.25g of g-C3N4@CaF2 composite were dispersed in 20mL of solvent B, and after ultrasonic vibration, 2g of polysilazane was added and stirred to obtain an intermediate layer slurry. 0.5 g of MoS2@P complex and 0.25 g of g-C3N4@CaF2 complex were dispersed in 20 mL of solvent C, 2 g of polysilazane was added after ultrasonic vibration, and the mixture was stirred evenly to obtain a surface slurry. The bottom layer slurry, the middle layer slurry and the surface layer slurry were sprayed on the surface of the aerospace bearing substrate in sequence at room temperature. Before spraying the middle layer slurry and the surface layer slurry, it was necessary to wait for the previous layer of slurry to solidify. After the room temperature curing was completed, a wear-resistant coating for aerospace bearings based on polysilazane was obtained.

[0099] Comparative Example 1

[0100] This comparative example provides a wear-resistant coating for aerospace bearings based on polysilazane. The difference between it and Example 1 is that the mass fraction of the sodium phosphate solution in A2 is adjusted to 4.7 wt.%, which is an increase of 2.3 wt.% compared with Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0101] Comparative Example 2

[0102] This comparative example provides a wear-resistant coating for aerospace bearings based on polysilazane. The difference between it and Example 1 is that the mass fraction of the sodium phosphate solution in A2 is adjusted to 0.1 wt.%, which is 2.3 wt.% less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0103] Comparative Example 3

[0104] This comparative example provides a wear-resistant coating for aerospace bearings based on polysilazane. The difference between it and Example 1 is that the mass of 3-aminopropyltriethoxysilane in S1 is adjusted to 300 mg, which is an increase of 140 mg compared with Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0105] Comparative Example 4

[0106] This comparative example provides a wear-resistant coating for aerospace bearings based on polysilazane. The difference between it and Example 1 is that the mass of 3-aminopropyltriethoxysilane in S1 is adjusted to 20 mg, which is 140 mg less than that in Example 1. The other process parameters and operating conditions are exactly the same as those in Example 1.

[0107] The polysilazane-based aerospace bearing wear-resistant coating prepared in the present invention was tested for hardness according to GB / T 6739-2022; for wear resistance mass loss according to GB / T 1768-2006; for adhesion according to GB / T 9286-2021; and for thermal shock according to GB / T 30873-2014 (400°C / 1h, water quenching five times). The test results are shown in Table 1.

[0108] Table 1 Test results of a wear-resistant coating for aerospace bearings based on polysilazane in Examples 1-4 and Comparative Examples 1-4

[0109] hardness Mass loss (%) Adhesion Thermal shock testing Example 1 5H 0.33 Level 0 No visible cracks Example 2 5H 0.38 Level 0 No visible cracks Example 3 5H 0.34 Level 0 No visible cracks Example 4 5H 0.31 Level 0 No visible cracks Comparative Example 1 3H 0.57 Level 2 Visible cracks Comparative Example 2 3H 0.59 Level 1 Visible cracks Comparative Example 3 2H 0.61 Level 2 Visible cracks Comparative Example 4 3H 0.54 Level 2 Visible cracks

[0110] As can be seen from Table 1, compared with Example 1, the hardness, wear resistance and adhesion of Comparative Example 1 are all lower than those of Example 1, and the thermal shock test result shows visible cracking; the hardness, wear resistance and adhesion of Comparative Example 2 are all lower than those of Example 1, and the thermal shock test result shows visible cracking. This is because the main role of sodium phosphate in the reaction system is to provide phosphate ions, which introduce phosphorus elements into the MoS2 surface through chemical reactions to form a MoS2@P complex. Too high or too low a mass fraction of sodium phosphate will affect the uniformity of surface functionalization and the stability of the generated phosphorus-based coating. In Comparative Example 1, the mass fraction of the sodium phosphate solution is too high. Excessive concentration of phosphate ions may cause the formation of a thick or non-uniform phosphorus modification layer on the surface, forming a fragile interface, resulting in a decrease in the hardness of the coating and hindering the effective reaction between the silane coupling agent and the MoS2 surface. The by-products in the phosphorus modification layer (such as phosphate deposits) may reduce the interfacial bonding force, resulting in a decrease in the adhesion of the coating. Excessive concentration of sodium phosphate may cause a thicker phosphate layer to form on the MoS2 surface. This phosphate layer is prone to breakage or peeling off during friction. At the same time, too many by-products may form a weak interface in the coating, reducing the overall wear resistance. Excessive phosphorus modification may cause the formation of too many phosphate phases in the coating, which are unstable and easily decomposed or expanded at high temperatures, causing the coating to crack during thermal shock. The mass fraction of the sodium phosphate solution in Comparative Example 2 is too low, the phosphorus-modified layer on the MoS2 surface is thin and uneven, and there are fewer surface active sites. In the subsequent coating preparation, the chemical bonding effect between the silane coupling agent and MoS2 is weakened, the phosphorus modification of the MoS2 surface is insufficient, and a stable interface structure cannot be formed in the coating. The insufficiently modified MoS2 particles easily fall off during the friction process, resulting in reduced wear resistance of the coating. At the same time, the insufficiently phosphorus-modified MoS2 particles are unevenly distributed in the coating, resulting in a mismatch in the thermal expansion coefficient. The coating is prone to cracking due to stress concentration during high-temperature cycles.

[0111] As shown in Table 1, compared with Example 1, the hardness, wear resistance, and adhesion of Comparative Example 3 are all lower than those of Example 1, and the thermal shock test results show visible cracking; the hardness, wear resistance, and adhesion of Comparative Example 4 are all lower than those of Example 1, and the thermal shock test results show visible cracking. 3-Aminopropyltriethoxysilane, as a silane coupling agent, can form chemical bonds between components through chemical reactions, thereby improving the interfacial bonding and overall performance of the coating. In Comparative Example 3, there is too much 3-aminopropyltriethoxysilane, and the surface modification layer is too thick. Excessive condensation reactions may occur between silane molecules, generating excess siloxane polymerization byproducts. An overly thick silane layer may form a weak bonding area at the interface, thereby reducing adhesion and hardness. The mechanical strength of the silane layer itself is low, and the silane layer is easily sheared or damaged during friction, reducing wear resistance. In Comparative Example 4, there is too little 3-aminopropyltriethoxysilane. When the amount of 3-aminopropyltriethoxysilane is too low, the silane coupling agent is insufficient to fully cover the SiC. The incompletely modified SiC or MoS2@P particles have weak bonding with the matrix (such as polysilazane) in the coating, and it is difficult to form a strong interface bond with the polysilazane matrix in the coating, thereby reducing the wear resistance.

[0112] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a wear-resistant coating for aerospace bearings based on polysilazane, characterized in that: The preparation method comprises: S1, dispersing silicon carbide in a sodium hydroxide solution to react to obtain hydroxylated SiC, dispersing the hydroxylated SiC in an ethanol aqueous solution, adding a silane coupling agent, wherein the silane coupling agent is 3-aminopropyltriethoxysilane, the mass of which is 40-50% of the mass of the hydroxylated SiC, and reacting to obtain surface-modified SiC; S2, dispersing zirconium salt and terephthalic acid in N,N-dimethylformamide, adding surface-modified SiC to react to obtain SiC@MOF, and calcining SiC@MOF under nitrogen atmosphere to obtain SiC@MOF composite; S3, dispersing the SiC@MOF composite and the g-C3N4@CaF2 composite in solvent A, then adding polysilazane, PVP and tetraethoxysilane to form a bottom layer slurry, dispersing the MoS2@P composite and the g-C3N4@CaF2 composite in solvent B, then adding polysilazane and phenyltriethoxysilane to obtain an intermediate layer slurry, dispersing the MoS2@P composite and the g-C3N4@CaF2 composite in solvent C, then adding polysilazane and hexamethyldisiloxane to obtain a surface layer slurry, and after room temperature curing, a polysilazane-based aerospace bearing wear-resistant coating is obtained; The MoS2@P composite preparation method comprises: Molybdenum disulfide powder is added to an ethanol aqueous solution, stirred and dispersed, and then ultrasonically shaken in an ice-water bath. The ultrasonic dispersion is centrifuged, the upper liquid is collected and washed with ethanol, and the washed molybdenum disulfide is dispersed in deionized water to form a molybdenum disulfide dispersion. Ascorbic acid is dispersed in a sodium phosphate solution, stirred evenly, and then the molybdenum disulfide dispersion is added to the sodium phosphate solution. Under a nitrogen atmosphere, the temperature is raised to a first temperature for sufficient reaction. After the reaction is completed, the temperature is washed, filtered, and vacuum-dried to obtain MoS2@P particles. The MoS2@P particles are then dispersed in anhydrous ethanol, a silane coupling agent is added, the temperature is raised to a second temperature for stirring and reaction, and after the reaction is completed, the temperature is washed and filtered to obtain a surface-modified MoS2@P complex. The g-C3N4@CaF2 composite preparation method comprises: mixing a calcium nitrate tetrahydrate solution and an ammonium fluoride solution, adding g-C3N4 powder, performing ultrasonic vibration and heating to a first temperature for reaction, centrifuging and washing after the reaction, and vacuum drying, placing the dried product under a nitrogen atmosphere, heating to a third temperature and calcining to obtain the g-C3N4@CaF2 composite; The mass fraction of the sodium phosphate solution is 2-3 wt.%.

2. The method for preparing a wear-resistant coating for aerospace bearings based on polysilazane according to claim 1, characterized in that: In S1: The concentration of the sodium hydroxide solution is 1M.

3. The method for preparing a wear-resistant coating for aerospace bearings based on polysilazane according to claim 1, characterized in that: In S2: The zirconium salt is Zr(NO3)4·5H2O, and the molar volume ratio of the zirconium salt to N,N-dimethylformamide is 1 mmol:50 mL; The molar ratio of the zirconium salt to terephthalic acid is 1:

1.

4. The method for preparing a wear-resistant coating for aerospace bearings based on polysilazane according to claim 1, characterized in that: In S3: When forming the bottom slurry: The mass ratio of the SiC@MOF composite, g-C3N4@CaF2 composite, polysilazane, PVP, and tetraethoxysilane is 0.5:0.25:2:0.1:0.2; The solvent A is a mixed solution of DMF and anhydrous ethanol with a volume ratio of 3:1; When the middle layer slurry is obtained: The mass ratio of the MoS2@P composite, g-C3N4@CaF2 composite, polysilazane, and phenyltriethoxysilane is 0.5:0.25:2:0.2; The solvent B is a mixed solution of DMF and anhydrous ethanol with a volume ratio of 2:1; When the surface slurry is obtained: The mass ratio of the MoS2@P composite, g-C3N4@CaF2 composite, polysilazane, and hexamethyldisiloxane is 0.5:0.25:2:0.2; The solvent C is a mixed solution of DMF and anhydrous ethanol with a volume ratio of 1:

1.

5. The method for preparing a wear-resistant coating for aerospace bearings based on polysilazane according to claim 1, characterized in that: The concentration of the molybdenum disulfide dispersion is 1 mg / mL.

6. The method for preparing a wear-resistant coating for aerospace bearings based on polysilazane according to claim 1, characterized in that: In the preparation method of the MoS2@P composite, the silane coupling agent is 3-aminopropyltriethoxysilane, and its mass is 10-20% of the mass of the MoS2@P particles.

7. The method for preparing a wear-resistant coating for aerospace bearings based on polysilazane according to claim 1, characterized in that: The molar ratio of the calcium nitrate tetrahydrate to the ammonium fluoride is 1:1; The volume ratio of the calcium nitrate tetrahydrate solution to the ammonium fluoride solution is 1:1; The concentration of the calcium nitrate tetrahydrate solution is 0.1M.

8. A polysilazane-based aerospace bearing wear-resistant coating is obtained by the method for preparing a polysilazane-based aerospace bearing wear-resistant coating according to any one of claims 1 to 7.

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