A bearing composite coating and a process for its production

Abstract

The application provides a bearing composite coating and a preparation process thereof, the bearing composite coating is a multilayer gradient structure, and a Cr adhesive layer, a WC-Cr gradient transition layer, a CeO2 modified high-entropy carbonitride hard layer and a composite lubricating surface layer are sequentially arranged from the surface of a substrate to the outside; raw materials for preparing the CeO2 modified high-entropy carbonitride hard layer include nano cerium dioxide particles; and raw materials for preparing the composite lubricating surface layer include cerium-based fluorocarbon silicon nano composite powder. The synergistic effect of the raw materials in the application enables the bearing composite coating to have good bonding force, hardness and lubricating performance, and can meet the service requirements of the bearing under harsh working conditions.

Description

Technical Field

[0001] This invention relates to the field of bearing surface strengthening technology, specifically to a bearing composite coating and its preparation process. Background Technology

[0002] As a key basic component in the equipment manufacturing industry, bearings face increasingly higher comprehensive and high-performance requirements for the bonding strength, hardness, wear resistance, and lubrication performance of their surface coatings under harsh operating conditions such as high speed, heavy load, and high temperature. With the development of surface modification technologies such as vacuum sputtering and multi-target composite deposition, electronic-specific materials such as high-purity cobalt targets and nickel-platinum alloy targets, with their advantages of high purity, uniform microstructure, and dense and stable film formation, have been gradually applied to the preparation of high-precision functional thin films and wear-resistant protective coatings, providing a material and technological foundation for bearing surface strengthening.

[0003] Existing single-structure or simple composite coatings generally suffer from insufficient interfacial bonding and poor matching of interlayer mechanical properties, making them prone to cracking and peeling under alternating loads. At the same time, it is difficult for coatings to simultaneously achieve synergistic optimization of high hardness, high density and low friction coefficient. The performance matching and synergistic effect between the lubricating phase and the hard phase are insufficient, resulting in bearings with fast wear rate and short life under harsh service environments, making it difficult to meet the requirements of long-term and high-reliability use. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a bearing composite coating and its preparation process.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a bearing composite coating, which has a multi-layer gradient structure. From the surface of the substrate outwards, the coating consists of a Cr bonding layer, a WC-Cr gradient transition layer, a CeO2-modified high-entropy carbonitride hard layer, and a composite lubricating surface layer. The raw materials for preparing the CeO2-modified high-entropy carbonitride hard layer include nano-cerium dioxide particles. The raw materials for preparing the composite lubricating surface layer include cerium-based fluorocarbon silicon nanocomposite powder.

[0007] Using the above technical solutions, the Cr bonding layer can enhance the bonding ability between the coating and the bearing substrate; the WC-Cr gradient transition layer can achieve a smooth transition of coating composition and mechanical properties, and alleviate interlayer stress; the nano-cerium dioxide particles added to the CeO2 modified high-entropy carbonitride hard layer can refine the coating grains, purify the interface, and improve the coating's hardness, density, and high-temperature oxidation resistance; the cerium-based fluorocarbon silicon nanocomposite powder added to the composite lubrication surface layer can reduce the coating's friction coefficient and improve its lubrication performance and wear resistance. The synergistic effect of each layer gives the coating good adhesion, hardness, and lubrication performance, which can meet the bearing's service requirements under harsh working conditions.

[0008] Preferably, the thickness of the Cr bonding layer is 0.3~0.5μm, the thickness of the WC-Cr gradient transition layer is 0.6~1.0μm, the thickness of the CeO2 modified high-entropy carbonitride hard layer is 2.0~3.0μm, and the thickness of the composite lubricating surface layer is 1.0~1.5μm.

[0009] Using the above technical solutions, the appropriate thickness of the Cr bonding layer can improve the bonding strength between the coating and the bearing substrate; the appropriate thickness of the WC-Cr gradient transition layer can alleviate interlayer stress and achieve a smooth transition of mechanical properties; the appropriate thickness of the CeO2 modified high-entropy carbonitride hard layer can ensure that the coating has sufficient load-bearing capacity and structural stability; and the appropriate thickness of the composite lubrication surface layer can enable the coating to maintain stable low friction and wear resistance during service.

[0010] Preferably, the raw materials for preparing the cerium-based fluorocarbon silicon nanocomposite powder include: 4-6 parts of graphene oxide, 40-60 parts of tetraethyl orthosilicate, 20-30 parts of phenolic resin, 0.5-1.5 parts of nickel nitrate, 2-4 parts of cerium nitrate hexahydrate, and 0.5-1.5 parts of 3-aminopropyltriethoxysilane.

[0011] Using the above technical solutions, graphene oxide can provide a two-dimensional layered structure basis for composite powders; tetraethyl orthosilicate and phenolic resin can form a stable precursor, which can be used to prepare one-dimensional silicon carbide nanowires through carbothermal reduction; nickel nitrate can play a catalytic role in the reaction process; cerium nitrate hexahydrate can provide a rare earth cerium source for composite powders; 3-aminopropyltriethoxysilane can aminate the surface of the material to enhance the interfacial bonding of each component.

[0012] Preferably, the preparation method of the cerium-based fluorocarbon silicon nanocomposite powder includes the following steps:

[0013] 1) Preparation of fluorinated graphene:

[0014] Weigh out graphene oxide according to the proportion, and carry out gas-phase fluorination reaction at 300~400℃ in a fluorine-containing inert atmosphere for 2~4h, so that the molar ratio of C to F in the product is (5~10):1, and fluorinated graphene is obtained.

[0015] 2) Preparation of aminated silicon carbide nanowires:

[0016] Weigh tetraethyl orthosilicate and phenolic resin in proportion, dissolve them in anhydrous ethanol, stir in a water bath at 35-45℃ at a speed of 200-300 r / min for 30-40 min to prepare a precursor solution with a total solid content of 15-25%, add nickel nitrate, continue stirring for 30-40 min, and let stand at 75-85℃ for 8-12 h to obtain a gel.

[0017] The gel was dried at 110-130℃ for 10-14h. The dried gel was placed in a tube furnace and heated to 1450-1550℃ at a rate of 4-6℃ / min under argon protection at a flow rate of 180-220 sccm. The temperature was held for 1.5-2.5h. The reaction product was decarbonized at 680-720℃ in a nitrogen or argon atmosphere with an oxygen volume fraction of 0.5-5% for 1.5-2.5h to obtain silicon carbide nanowires.

[0018] Silicon carbide nanowires were dispersed in anhydrous ethanol at a solid-liquid mass-to-volume ratio of 1 g:(8~10) mL. 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 70~80℃ for 4~6 h. The reaction product was centrifuged, washed, and dried to obtain aminated silicon carbide nanowires.

[0019] 3) Cerium nitrate hexahydrate and anhydrous ethanol were mixed at a mass-volume ratio of 1g:(12~16)mL to obtain a cerium nitrate hexahydrate solution. The aminated silicon carbide nanowires obtained in step 2) were added and dispersed for 25~35min under ultrasonic power of 250~350W and frequency of 35~45kHz. Then, the fluorinated graphene prepared in step 1) was added and ultrasonic dispersion was continued for 30~40min with magnetic stirring. The reaction solution was transferred to a reaction vessel and hydrothermally treated at 115~125℃ for 5~7h. After centrifugation, washing, vacuum drying and heat treatment, cerium-based fluorocarbon silicon nanocomposite powder was obtained.

[0020] Using the above technical solution, the preparation method can convert graphene oxide into fluorinated graphene through a gas-phase fluorination reaction; silicon carbide nanowires are obtained through gel preparation, drying, high-temperature carbothermal reduction and decarbonization process, and then aminated silicon carbide nanowires are obtained through 3-aminopropyltriethoxysilane modification treatment; cerium-based fluorocarbon silicon nanocomposite powder can be prepared by ultrasonic dispersion to fully mix cerium nitrate hexahydrate, aminated silicon carbide nanowires and fluorinated graphene, followed by hydrothermal treatment, centrifugation, washing, vacuum drying and heat treatment, so that the components are uniformly combined to form a stable composite structure.

[0021] Preferably, the specific process of centrifugation, washing, vacuum drying, and heat treatment is as follows: the reaction product is centrifuged at 8000~9000 r / min for 8~12 min, washed 2~3 times with anhydrous ethanol, vacuum dried at 75~85℃ and vacuum degree of -0.095~-0.09MPa for 7~9 h, and then heat treated under argon protection at 480~520℃ for 1.5~2.5 h.

[0022] Using the above technical solutions, centrifugation can separate the reaction products from the reaction system; washing with anhydrous ethanol can remove impurities and unreacted substances adhering to the surface of the reaction products; vacuum drying can remove moisture and residual solvent from the reaction products, avoiding the influence of moisture on the product structure; heat treatment under argon protection can thermally decompose cerium nitrate hexahydrate into cerium dioxide nanoparticles under a weak oxidizing atmosphere, while preventing the product from oxidizing during high-temperature treatment and ensuring the stability of the product structure.

[0023] This invention also provides a process for preparing a bearing composite coating, comprising the following steps:

[0024] S1. Pretreatment of the substrate: The surface of the bearing steel substrate is ground and polished until the surface roughness Ra≤0.1μm, then ultrasonically cleaned with acetone and anhydrous ethanol, and then vacuum dried.

[0025] S2. Clamping and Vacuuming: Fix the dried substrate onto the rotatable sample holder, set the revolution speed to 2~5 r / min and the rotation speed to 10~20 r / min, and evacuate to a background vacuum level ≤5.0×10⁻⁶. -3 Pa;

[0026] S3. Plasma cleaning: Introduce argon gas at a flow rate of 180~220 sccm, adjust the working vacuum to 0.3~0.5 Pa, apply a pulse bias voltage of -600~-800V, a duty cycle of 45~55%, and perform glow discharge cleaning for 15~25 min.

[0027] S4, Cr binder layer deposition: Magnetron sputtering is performed on the chromium target to deposit and form a Cr binder layer;

[0028] S5, WC-Cr gradient transition layer deposition: Turn on the tungsten carbide-chromium composite target, power 12~18kW, substrate bias -80~-120V, argon flow rate 250~300sccm, adjust the working vacuum to 0.4~0.6Pa, and deposit for 30~50min.

[0029] S6, CeO2 modified high-entropy carbonitride hard layer deposition: Turn on the high-entropy alloy target and chromium target, with power of 8~12kW and 3~5kW respectively. Feed nano-cerium dioxide particles at a rate of 1~3g / h through the powder feeder. Introduce argon gas at 200~250sccm and nitrogen gas at 80~120sccm. Adjust the working vacuum to 0.6~0.8Pa, substrate bias voltage -150~-200V, temperature 200~250℃. Deposit for 60~90min first, then linearly reduce the nitrogen flow rate to 30~50sccm, and simultaneously linearly introduce acetylene to 50~80sccm. Then maintain this gas flow rate and continue deposition for a total time of 150~200min.

[0030] The high-entropy alloy target is a Ti-Al-Nb-V quaternary alloy target.

[0031] S7. Composite lubricating surface deposition: After the temperature is reduced to 150~180℃, turn on the graphite target and molybdenum disulfide target with power of 6~10kW and 3~5kW respectively, introduce argon gas at 150~200sccm and acetylene gas at 40~60sccm, adjust the working vacuum to 0.8~1.2Pa, and the substrate bias voltage at -100~-150V. Feed the cerium-based fluorocarbon silicon nanocomposite powder into the substrate at a rate of 5~10g / h through the powder feeder and deposit for 60~90min.

[0032] S8. Cooling: After deposition, turn off the heating system and continue to introduce argon gas to make the chamber pressure reach 1~5Pa. Maintain gas convection cooling until the workpiece temperature is below 80℃, then remove the coated workpiece.

[0033] Using the above technical solution, the substrate pretreatment can remove impurities and oxide layers from the surface of the bearing steel substrate, ensuring a clean and flat substrate surface, providing a good base for subsequent coating deposition; clamping and vacuuming can ensure that the deposition environment is free from impurities, and the rotation setting can ensure uniform coating deposition; plasma cleaning can further activate the substrate surface and improve the adhesion between the coating and the substrate; the sequential deposition of each layer can form a structurally complete composite gradient coating, in which the Cr bonding layer enhances the adhesion between the coating and the substrate, the WC-Cr gradient transition layer relieves interfacial stress, the CeO2 modified high-entropy carbonitride hard layer provides hardness and temperature resistance, and the composite lubricating surface layer imparts low friction characteristics to the coating; the cooling process can prevent the high-temperature workpiece from being directly exposed to air, which could lead to coating oxidation or cracking, ensuring the stability of the coating structure and performance.

[0034] Preferably, in step S1, the ultrasonic cleaning conditions are: ultrasonic frequency 35~45kHz, power 250~350W, and cleaning time 10~20min; the vacuum drying conditions are: vacuum degree -0.095~-0.09MPa, temperature 95~105℃, and time 0.8~1.2h.

[0035] Using the above technical solution, the ultrasonic cleaning conditions can fully remove oil and impurities from the surface of the bearing steel substrate, improving the cleanliness of the substrate surface; the vacuum drying conditions can remove moisture from the substrate surface while maintaining the stability of the substrate surface state, providing a smooth and clean base for subsequent coating deposition, which is beneficial to improving the bonding strength between the coating and the substrate.

[0036] Preferably, in step S4, the argon flow rate is adjusted to 250~300 sccm, the working vacuum is 0.4~0.6 Pa, the chromium target is turned on, the power is 8~12 kW, the substrate bias voltage is -100~-150 V, the temperature is 150~200 °C, and the magnetron deposition is carried out for 15~25 min.

[0037] By adopting the above technical solution, the appropriate argon flow rate and working vacuum can ensure the transmission efficiency of sputtered particles and reduce impurity interference; the reasonable combination of target power, substrate bias voltage and temperature can improve the density and thickness uniformity of the chromium bonding layer, enhance the bonding strength between the chromium bonding layer and the bearing steel substrate, and provide a good substrate for the subsequent deposition of WC-Cr gradient transition layer.

[0038] Preferably, in step S5, the mass ratio of WC to Cr in the tungsten carbide-chromium composite target is (75~85):(15~25).

[0039] Using the above technical solution, the WC-Cr gradient transition layer formed by composite target deposition at this ratio has mechanical properties that are between those of the Cr binder layer and the CeO2 modified high-entropy carbonitride hard layer, achieving a smooth transition in coating composition and hardness, relieving interlayer stress, and improving the overall bonding stability of the coating.

[0040] Preferably, the atomic ratio of Ti, Al, Nb, and V in the high-entropy alloy target is (1~1.2):(1~1.2):(1~1.2):(1~1.2).

[0041] By adopting the above technical solution, the four elements can participate in the reaction uniformly during the sputtering process to form a high-entropy carbonitride solid solution with uniform composition. The high-entropy alloy target at this ratio can ensure that the formed high-entropy carbonitride solid solution has the characteristics of each element, so that the CeO2 modified high-entropy carbonitride hard layer has good hardness and toughness, providing reliable load-bearing support for the coating, while also helping to improve the density and high-temperature oxidation resistance of the coating.

[0042] The beneficial effects of this invention are as follows:

[0043] The Cr bonding layer enhances the adhesion between the coating and the bearing substrate; the WC-Cr gradient transition layer enables a smooth transition of coating composition and mechanical properties, alleviating interlayer stress; the nano-cerium dioxide particles added to the CeO2-modified high-entropy carbonitride hard layer refine the coating grains, purify the interface, and improve the coating's hardness, density, and high-temperature oxidation resistance; the cerium-based fluorocarbon silicon nanocomposite powder added to the composite lubrication surface layer reduces the coating's coefficient of friction, improves its lubrication performance and wear resistance, and the synergistic effect of each layer gives the coating good adhesion, hardness, and lubrication performance, meeting the bearing's service requirements under harsh operating conditions. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0046] Table 1

[0047]

[0048] Example 1:

[0049] This embodiment provides a bearing composite coating, which has a multi-layer gradient structure. From the substrate surface outwards, it consists of a Cr bonding layer, a WC-Cr gradient transition layer, a CeO2-modified high-entropy carbonitride hard layer, and a composite lubricating surface layer. The raw materials for preparing the CeO2-modified high-entropy carbonitride hard layer include nano-cerium dioxide particles; the raw materials for preparing the composite lubricating surface layer include cerium-based fluorocarbon silicon nanocomposite powder.

[0050] The Cr binder layer was formed by sputtering deposition using a chromium target; the WC-Cr gradient transition layer was formed by sputtering deposition using a tungsten carbide-chromium composite target, with a WC to Cr mass ratio of 85:15 in the tungsten carbide-chromium composite target; the CeO2-modified high-entropy carbonitride hard layer was formed by co-deposition of a high-entropy alloy target, a chromium target, and nano-cerium dioxide particles. The high-entropy alloy target was a Ti-Al-Nb-V quaternary alloy target with an atomic ratio of 1:1:1:1; the nano-cerium dioxide particles had a particle size of 60 nm; and the composite lubricating surface layer was formed by magnetron sputtering deposition of a graphite target, a molybdenum disulfide target, and cerium-based fluorocarbon silicon nanocomposite powder.

[0051] The raw materials for preparing cerium-based fluorocarbon silicon nanocomposite powder include: 4 parts graphene oxide, 40 parts tetraethyl orthosilicate, 20 parts phenolic resin, 0.5 parts nickel nitrate, 2 parts cerium nitrate hexahydrate, and 0.5 parts 3-aminopropyltriethoxysilane.

[0052] The preparation method of cerium-based fluorocarbon silicon nanocomposite powder includes the following steps:

[0053] 1) Preparation of fluorinated graphene:

[0054] Weigh out graphene oxide according to the specified ratio, and carry out gas-phase fluorination reaction at 300℃ in a fluorine-containing inert atmosphere (a mixture of fluorine and argon in a volume ratio of 3:1) for 2 hours to make the molar ratio of C to F in the product 5:1, thus obtaining fluorinated graphene.

[0055] 2) Preparation of aminated silicon carbide nanowires:

[0056] Weigh tetraethyl orthosilicate and phenolic resin in proportion, dissolve them in anhydrous ethanol, stir at 200 r / min for 30 min in a 35℃ water bath to prepare a precursor solution with a total solid content of 15%, add nickel nitrate, continue stirring for 30 min, and let stand at 75℃ for 8 h to obtain gel.

[0057] The gel was dried at 110℃ for 10h. The dried gel was placed in a tube furnace and heated to 1450℃ at a rate of 4℃ / min under argon protection at a flow rate of 180sccm. The temperature was held for 1.5h. The reaction product was decarbonized at 680℃ in a nitrogen atmosphere containing 0.5% oxygen by volume for 1.5h to obtain silicon carbide nanowires.

[0058] Silicon carbide nanowires were dispersed in anhydrous ethanol at a solid-liquid mass-to-volume ratio of 1 g: 8 mL. 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 70 °C for 4 h. The reaction product was centrifuged, washed, and dried to obtain aminated silicon carbide nanowires.

[0059] 3) Cerium nitrate hexahydrate and anhydrous ethanol were mixed at a mass-volume ratio of 1g:12mL to obtain a cerium nitrate hexahydrate solution. The aminated silicon carbide nanowires obtained in step 2) were added and dispersed for 25 min under ultrasonic power of 250W and frequency of 35kHz. Then, the fluorinated graphene prepared in step 1) was added and ultrasonic dispersion was continued for 30 min with magnetic stirring. The reaction solution was transferred to a reaction vessel and hydrothermally treated at 115℃ for 5 h. After centrifugation, washing, vacuum drying and heat treatment, cerium-based fluorocarbon silicon nanocomposite powder was obtained.

[0060] The specific process of centrifugation, washing, vacuum drying and heat treatment is as follows: the reaction product is centrifuged at 8000 r / min for 8 min, washed twice with anhydrous ethanol, vacuum dried at 75℃ and vacuum degree -0.095 MPa for 7 h, and then heat treated at 480℃ under argon protection for 1.5 h.

[0061] This embodiment also provides a process for preparing a bearing composite coating, including the following steps:

[0062] S1. Pretreatment of the substrate: The surface of the bearing steel substrate is ground and polished until the surface roughness Ra≤0.1μm, and then ultrasonically cleaned with acetone and anhydrous ethanol in sequence. The conditions are ultrasonic frequency 35kHz, power 250W, and cleaning time 10min. The cleaned substrate is then vacuum dried at 95℃ and vacuum degree -0.095MPa for 0.8h.

[0063] S2. Clamping and Vacuuming: Fix the dried substrate onto the rotatable sample holder, set the revolution speed to 2 r / min and the rotation speed to 10 r / min, and evacuate to a background vacuum level ≤ 5.0 × 10⁻⁶. -3 Pa;

[0064] S3. Plasma cleaning: Introduce argon gas at a flow rate of 180 sccm, adjust the working vacuum to 0.3 Pa, apply a -600 V pulse bias voltage, a duty cycle of 45%, and perform glow discharge cleaning for 15 min.

[0065] S4, Cr binder layer deposition: Adjust argon flow rate to 250 sccm, working vacuum degree to 0.4 Pa, turn on chromium target for magnetron sputtering, power 8 kW, substrate bias voltage -100 V, temperature 150 ℃, magnetron deposition for 15 min, depositing a Cr binder layer with a thickness of 0.3 μm.

[0066] S5, WC-Cr gradient transition layer deposition: Turn on the tungsten carbide-chromium composite target, the mass ratio of WC to Cr in the tungsten carbide-chromium composite target is 85:15, the power is 12kW, the substrate bias voltage is -80V, the argon flow rate is 250sccm, the working vacuum is adjusted to 0.4Pa, and the deposition is carried out for 30min to form a WC-Cr gradient transition layer with a thickness of 0.6μm on the Cr binder layer.

[0067] S6. CeO2-modified high-entropy carbonitride hard layer deposition: The high-entropy alloy target and chromium target were turned on with power of 8kW and 3kW respectively. Nano-cerium dioxide particles were fed in at a rate of 1g / h through a powder feeder. Argon gas was introduced at 200sccm and nitrogen gas at 80sccm. The working vacuum was adjusted to 0.6Pa, the substrate bias voltage was -150V, and the temperature was 200℃. Deposition was carried out for 60min. Then the nitrogen flow rate was linearly reduced to 30sccm, and acetylene was linearly introduced to 50sccm. The gas flow rate was then maintained and deposition continued for a total time of 150min. A CeO2-modified high-entropy carbonitride hard layer with a thickness of 2.0μm was formed on the WC-Cr gradient transition layer.

[0068] Among them, the high-entropy alloy target is a Ti-Al-Nb-V quaternary alloy target, with the atomic ratio of Ti, Al, Nb and V being 1:1:1:1;

[0069] S7. Deposition of composite lubricating surface layer: After the temperature is reduced to 150℃, the graphite target and molybdenum disulfide target are turned on with power of 6kW and 3kW respectively. Argon gas is introduced at 150sccm and acetylene at 40sccm. The working vacuum is adjusted to 0.8Pa and the substrate bias is -100V. Cerium-based fluorocarbon silicon nanocomposite powder is fed in at a rate of 5g / h through the powder feeder. After deposition for 60min, a composite lubricating surface layer with a thickness of 1.0μm is formed on the WC-Cr gradient transition layer.

[0070] S8. Cooling: After deposition, turn off the heating system and continue to introduce argon gas to make the chamber pressure reach 1Pa. Maintain gas convection cooling until the workpiece temperature is below 80℃, then remove the coated workpiece.

[0071] Example 2:

[0072] This embodiment provides a bearing composite coating, which has a multi-layer gradient structure. From the substrate surface outwards, it consists of a Cr bonding layer, a WC-Cr gradient transition layer, a CeO2-modified high-entropy carbonitride hard layer, and a composite lubricating surface layer. The raw materials for preparing the CeO2-modified high-entropy carbonitride hard layer include nano-cerium dioxide particles; the raw materials for preparing the composite lubricating surface layer include cerium-based fluorocarbon silicon nanocomposite powder.

[0073] The Cr binder layer was formed by sputtering deposition using a chromium target; the WC-Cr gradient transition layer was formed by sputtering deposition using a tungsten carbide-chromium composite target, with a WC to Cr mass ratio of 75:25 in the tungsten carbide-chromium composite target; the CeO2-modified high-entropy carbonitride hard layer was formed by co-deposition of a high-entropy alloy target, a chromium target, and nano-cerium dioxide particles. The high-entropy alloy target was a Ti-Al-Nb-V quaternary alloy target with an atomic ratio of 1:1.2:1:1.2; the nano-cerium dioxide particles had a particle size of 80 nm; and the composite lubricating surface layer was formed by magnetron sputtering deposition of a graphite target, a molybdenum disulfide target, and cerium-based fluorocarbon silicon nanocomposite powder.

[0074] The raw materials for preparing cerium-based fluorocarbon silicon nanocomposite powder include: 6 parts graphene oxide, 60 parts tetraethyl orthosilicate, 30 parts phenolic resin, 1.5 parts nickel nitrate, 4 parts cerium nitrate hexahydrate, and 1.5 parts 3-aminopropyltriethoxysilane.

[0075] The preparation method of cerium-based fluorocarbon silicon nanocomposite powder includes the following steps:

[0076] 1) Preparation of fluorinated graphene:

[0077] Weigh out graphene oxide according to the specified ratio, and carry out gas-phase fluorination reaction at 400℃ in a fluorine-containing inert atmosphere (a mixture of fluorine and argon in a volume ratio of 3:1) for 4 hours to make the molar ratio of C to F in the product 10:1, thus obtaining fluorinated graphene.

[0078] 2) Preparation of aminated silicon carbide nanowires:

[0079] Weigh tetraethyl orthosilicate and phenolic resin in proportion, dissolve them in anhydrous ethanol, stir at 300 r / min for 40 min in a 45℃ water bath to prepare a precursor solution with a total solid content of 25%, add nickel nitrate, continue stirring for 40 min, and let stand at 85℃ for 12 h to obtain a gel.

[0080] The gel was dried at 130℃ for 14 h. The dried gel was placed in a tube furnace and heated to 1550℃ at a rate of 6℃ / min under argon protection at a flow rate of 220 sccm. The temperature was held for 2.5 h. The reaction product was decarbonized at 720℃ in a nitrogen or argon atmosphere containing 5% oxygen by volume for 2.5 h to obtain silicon carbide nanowires.

[0081] Silicon carbide nanowires were dispersed in anhydrous ethanol at a solid-liquid mass-to-volume ratio of 1 g:10 mL. 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 80 °C for 6 h. The reaction product was centrifuged, washed, and dried to obtain aminated silicon carbide nanowires.

[0082] 3) Cerium nitrate hexahydrate and anhydrous ethanol were mixed at a mass-volume ratio of 1g:16mL to obtain a cerium nitrate hexahydrate solution. The aminated silicon carbide nanowires obtained in step 2) were added and dispersed for 35 min under ultrasonic power of 350W and frequency of 45kHz. Then, the fluorinated graphene prepared in step 1) was added and ultrasonic dispersion was continued for 40 min with magnetic stirring. The reaction solution was transferred to a reaction vessel and hydrothermally treated at 125℃ for 7 h. After centrifugation, washing, vacuum drying and heat treatment, cerium-based fluorocarbon silicon nanocomposite powder was obtained.

[0083] The specific process of centrifugation, washing, vacuum drying, and heat treatment is as follows: the reaction product is centrifuged at 9000 r / min for 12 min, washed three times with anhydrous ethanol, vacuum dried at 85℃ and vacuum degree -0.09 MPa for 9 h, and then heat treated at 520℃ under argon protection for 2.5 h.

[0084] This embodiment also provides a process for preparing a bearing composite coating, including the following steps:

[0085] S1. Pretreatment of the substrate: The surface of the bearing steel substrate is ground and polished until the surface roughness Ra≤0.1μm, and then ultrasonically cleaned with acetone and anhydrous ethanol in sequence. The conditions are ultrasonic frequency 45kHz, power 350W, and cleaning time 20min. The cleaned substrate is then vacuum dried at 105℃ and vacuum degree -0.09MPa for 1.2h.

[0086] S2. Clamping and Vacuuming: Fix the dried substrate onto the rotatable sample holder, set the revolution speed to 5 r / min and the rotation speed to 20 r / min, and evacuate to a background vacuum level ≤ 5.0 × 10⁻⁶. -3 Pa;

[0087] S3. Plasma cleaning: Introduce argon gas at a flow rate of 220 sccm, adjust the working vacuum to 0.5 Pa, apply a -800 V pulse bias voltage with a duty cycle of 55%, and perform glow discharge cleaning for 25 min.

[0088] S4, Cr binder layer deposition: Adjust argon flow rate to 300 sccm, working vacuum degree to 0.6 Pa, turn on chromium target for magnetron sputtering, power 12 kW, substrate bias voltage -150 V, temperature 200 ℃, magnetron deposition for 25 min, depositing a Cr binder layer with a thickness of 0.5 μm.

[0089] S5, WC-Cr gradient transition layer deposition: Turn on the tungsten carbide-chromium composite target, the mass ratio of WC to Cr in the tungsten carbide-chromium composite target is 75:25, the power is 18kW, the substrate bias voltage is -120V, the argon flow rate is 300sccm, the working vacuum is adjusted to 0.6Pa, and the deposition is carried out for 50min to form a WC-Cr gradient transition layer with a thickness of 1.0μm on the Cr binder layer.

[0090] S6. CeO2-modified high-entropy carbonitride hard layer deposition: The high-entropy alloy target and chromium target were turned on with power of 12kW and 5kW respectively. Nano-cerium dioxide particles were fed in at a rate of 3g / h through the powder feeder. Argon gas was introduced at 250sccm and nitrogen gas at 120sccm. The working vacuum was adjusted to 0.8Pa, the substrate bias voltage was -200V, and the temperature was 250℃. Deposition was carried out for 90min. Then the nitrogen flow rate was linearly reduced to 50sccm, and acetylene was linearly introduced to 80sccm. The gas flow rate was then maintained and deposition continued for a total time of 200min. A CeO2-modified high-entropy carbonitride hard layer with a thickness of 3.0μm was formed on the WC-Cr gradient transition layer.

[0091] Among them, the high-entropy alloy target is a Ti-Al-Nb-V quaternary alloy target, with the atomic ratio of Ti, Al, Nb, and V being 1:1.2:1:1.2;

[0092] S7. Deposition of composite lubricating surface layer: After the temperature is reduced to 180℃, the graphite target and molybdenum disulfide target are turned on with power of 10kW and 5kW respectively. Argon gas is introduced at 200sccm and acetylene at 60sccm. The working vacuum is adjusted to 1.2Pa and the substrate bias is -150V. Cerium-based fluorocarbon silicon nanocomposite powder is fed in at a rate of 10g / h through the powder feeder. After deposition for 90min, a composite lubricating surface layer with a thickness of 1.5μm is formed on the WC-Cr gradient transition layer.

[0093] S8. Cooling: After deposition is complete, turn off the heating system and continue to introduce argon gas to make the chamber pressure reach 5Pa. Maintain gas convection cooling until the workpiece temperature is below 80℃, then remove the coated workpiece.

[0094] Example 3:

[0095] This embodiment provides a bearing composite coating, which has a multi-layer gradient structure. From the substrate surface outwards, it consists of a Cr bonding layer, a WC-Cr gradient transition layer, a CeO2-modified high-entropy carbonitride hard layer, and a composite lubricating surface layer. The raw materials for preparing the CeO2-modified high-entropy carbonitride hard layer include nano-cerium dioxide particles; the raw materials for preparing the composite lubricating surface layer include cerium-based fluorocarbon silicon nanocomposite powder.

[0096] The Cr binder layer was formed by sputtering deposition using a chromium target; the WC-Cr gradient transition layer was formed by sputtering deposition using a tungsten carbide-chromium composite target, with a WC to Cr mass ratio of 80:20 in the tungsten carbide-chromium composite target; the CeO2-modified high-entropy carbonitride hard layer was formed by co-deposition of a high-entropy alloy target, a chromium target, and nano-cerium dioxide particles. The high-entropy alloy target was a Ti-Al-Nb-V quaternary alloy target with an atomic ratio of 1:1:1:1; the nano-cerium dioxide particles had a particle size of 70 nm; and the composite lubricating surface layer was formed by magnetron sputtering deposition of a graphite target, a molybdenum disulfide target, and cerium-based fluorocarbon silicon nanocomposite powder.

[0097] The raw materials for preparing cerium-based fluorocarbon silicon nanocomposite powder include: 5 parts graphene oxide, 50 parts tetraethyl orthosilicate, 25 parts phenolic resin, 1 part nickel nitrate, 3 parts cerium nitrate hexahydrate, and 1 part 3-aminopropyltriethoxysilane.

[0098] The preparation method of cerium-based fluorocarbon silicon nanocomposite powder includes the following steps:

[0099] 1) Preparation of fluorinated graphene:

[0100] Weigh out graphene oxide according to the specified ratio, and carry out gas-phase fluorination reaction at 350℃ in a fluorine-containing inert atmosphere (a mixture of fluorine and argon in a volume ratio of 3:1) for 3 hours to make the molar ratio of C to F in the product 7:1, thus obtaining fluorinated graphene.

[0101] 2) Preparation of aminated silicon carbide nanowires:

[0102] Weigh tetraethyl orthosilicate and phenolic resin in proportion, dissolve them in anhydrous ethanol, stir at 250 r / min for 35 min in a 40℃ water bath to prepare a precursor solution with a total solid content of 20%, add nickel nitrate, continue stirring for 35 min, and let stand at 80℃ for 10 h to obtain a gel.

[0103] The gel was dried at 120℃ for 12h. The dried gel was placed in a tube furnace and heated to 1500℃ at a rate of 5℃ / min under the protection of argon at a flow rate of 200sccm. The temperature was held for 2h. The reaction product was decarbonized at 700℃ in a nitrogen or argon atmosphere containing 2% oxygen by volume for 2h to obtain silicon carbide nanowires.

[0104] Silicon carbide nanowires were dispersed in anhydrous ethanol at a solid-liquid mass-to-volume ratio of 1 g: 9 mL. 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 75 °C for 5 h. The reaction product was centrifuged, washed, and dried to obtain aminated silicon carbide nanowires.

[0105] 3) Cerium nitrate hexahydrate and anhydrous ethanol were mixed at a mass-volume ratio of 1g:14mL to obtain a cerium nitrate hexahydrate solution. The aminated silicon carbide nanowires obtained in step 2) were added and dispersed for 30 min under ultrasonic power of 300W and frequency of 40kHz. Then, the fluorinated graphene prepared in step 1) was added and ultrasonic dispersion was continued for 35 min with magnetic stirring. The reaction solution was transferred to a reaction vessel and hydrothermally treated at 120℃ for 6 h. After centrifugation, washing, vacuum drying and heat treatment, cerium-based fluorocarbon silicon nanocomposite powder was obtained.

[0106] The specific process of centrifugation, washing, vacuum drying, and heat treatment is as follows: the reaction product is centrifuged at 8500 r / min for 10 min, washed three times with anhydrous ethanol, vacuum dried at 80℃ and vacuum degree -0.092 MPa for 8 h, and then heat treated at 500℃ under argon protection for 2 h.

[0107] This embodiment also provides a process for preparing a bearing composite coating, including the following steps:

[0108] S1. Pretreatment of the substrate: The surface of the bearing steel substrate is ground and polished until the surface roughness Ra≤0.1μm, and then ultrasonically cleaned with acetone and anhydrous ethanol in sequence. The conditions are ultrasonic frequency 40kHz, power 300W, and cleaning time 15min. The cleaned substrate is then vacuum dried at 100℃ and vacuum degree -0.092MPa for 1h.

[0109] S2. Clamping and Vacuuming: Fix the dried substrate onto the rotatable sample holder, set the revolution speed to 3 r / min and the rotation speed to 15 r / min, and evacuate to a background vacuum level ≤ 5.0 × 10⁻⁶. -3 Pa;

[0110] S3. Plasma cleaning: Introduce argon gas at a flow rate of 200 sccm, adjust the working vacuum to 0.4 Pa, apply a -700 V pulse bias voltage, a duty cycle of 50%, and perform glow discharge cleaning for 20 min.

[0111] S4, Cr binder layer deposition: Adjust argon flow rate to 280 sccm, working vacuum degree to 0.5 Pa, turn on chromium target for magnetron sputtering, power 10 kW, substrate bias voltage -120 V, temperature 180 ℃, magnetron deposition for 20 min, depositing a Cr binder layer with a thickness of 0.4 μm.

[0112] S5, WC-Cr gradient transition layer deposition: Turn on the tungsten carbide-chromium composite target, the mass ratio of WC to Cr in the tungsten carbide-chromium composite target is 80:20, the power is 15kW, the substrate bias voltage is -100V, the argon flow rate is 280sccm, the working vacuum is adjusted to 0.5Pa, and the deposition is carried out for 40min to form a WC-Cr gradient transition layer with a thickness of 0.8μm on the Cr binder layer.

[0113] S6. CeO2-modified high-entropy carbonitride hard layer deposition: The high-entropy alloy target and chromium target were turned on with power of 10kW and 4kW respectively. Nano-cerium dioxide particles were fed in at a rate of 2g / h through the powder feeder. Argon gas was introduced at 220sccm and nitrogen gas at 100sccm. The working vacuum was adjusted to 0.7Pa, the substrate bias voltage was -180V, and the temperature was 220℃. Deposition was carried out for 75min. Then the nitrogen flow rate was linearly reduced to 40sccm, and acetylene was linearly introduced to 65sccm. The gas flow rate was then maintained and deposition continued for a total time of 180min. A CeO2-modified high-entropy carbonitride hard layer with a thickness of 2.5μm was formed on the WC-Cr gradient transition layer.

[0114] Among them, the high-entropy alloy target is a Ti-Al-Nb-V quaternary alloy target, with the atomic ratio of Ti, Al, Nb and V being 1:1:1:1;

[0115] S7. Deposition of composite lubricating surface layer: After the temperature is reduced to 165℃, the graphite target and molybdenum disulfide target are turned on with power of 8kW and 4kW respectively. Argon gas is introduced at 180sccm and acetylene at 50sccm. The working vacuum is adjusted to 1.0Pa and the substrate bias is -120V. Cerium-based fluorocarbon silicon nanocomposite powder is fed in at a rate of 7g / h through the powder feeder and deposited for 75min to form a composite lubricating surface layer with a thickness of 1.2μm on the WC-Cr gradient transition layer.

[0116] S8. Cooling: After deposition, turn off the heating system and continue to introduce argon gas to make the chamber pressure reach 3Pa. Maintain gas convection cooling until the workpiece temperature is below 80℃, then remove the coated workpiece.

[0117] Comparative Example 1:

[0118] A bearing composite coating and its preparation process are disclosed, which differ from Example 3 only in that step S4 is omitted, no Cr bonding layer is deposited, and a WC-Cr gradient transition layer is directly deposited on the bearing steel substrate.

[0119] Comparative Example 2:

[0120] A bearing composite coating and its preparation process differ from Example 3 only in that step S5 is omitted, the WC-Cr gradient transition layer is not deposited, and a CeO2-modified high-entropy carbonitride hard layer is directly deposited on the Cr bonding layer.

[0121] Comparative Example 3:

[0122] A bearing composite coating and its preparation process differ from Example 3 only in that: in step S6, the powder feeder for nano-cerium dioxide particles is turned off (CeO2 particles are not added to the CeO2 modified high-entropy carbonitride hard layer).

[0123] Comparative Example 4:

[0124] A bearing composite coating and its preparation process differ from Example 3 only in that: in step S7, the powder feeder for the molybdenum disulfide target and the cerium-based fluorocarbon silicon nanocomposite powder is turned off (cerium-based fluorocarbon silicon nanocomposite powder is not introduced into the composite lubrication surface layer, and only a pure hydrogen-containing amorphous carbon (aC:H) film is formed on the WC-Cr gradient transition layer).

[0125] Comparative Example 5:

[0126] A bearing composite coating and its preparation process differ from Example 3 only in that: in step 2) of the method for preparing cerium-based fluorocarbon silicon nanocomposite powder, 3-aminopropyltriethoxysilane is not added, and unaminated silicon carbide nanowires are directly used to replace aminated silicon carbide nanowires in equal amounts to participate in the reaction of subsequent step 3).

[0127] Comparative Example 6:

[0128] A bearing composite coating and its preparation process differ from Example 3 only in that step 1 of the preparation method of cerium-based fluorocarbon silicon nanocomposite powder is omitted, and ordinary fluorinated graphene is directly used to participate in the reaction of subsequent steps.

[0129] Comparative Example 7:

[0130] A bearing composite coating and its preparation process differ from Example 3 only in that the gradient gas introduction process in step S6 is omitted, and the N2 and C2H2 flow rates are fixed (70 sccm and 50 sccm, respectively) during the deposition of the CeO2 modified high-entropy carbonitride hard layer, forming a homogeneous monolayer.

[0131] The bearing composite coatings obtained in Examples 1-3 and Comparative Examples 1-7 were subjected to the following performance tests:

[0132] Coating hardness: The hardness was tested using a nanoindenter (Agilent G200) according to the national standard GB / T 4340.1-2009, "Metallic Materials - Vickers Hardness Test - Part 1: Test Method". A Berkovich diamond indenter was used, with a maximum indentation depth set to 200 nm. Ten test points were randomly selected for each sample, and the arithmetic mean was taken as the final hardness value.

[0133] Film-substrate adhesion: Following the industry standard JB / T 8554-1997 "Test Method for Adhesion of Vapor Deposition Thin Films - Scratch Test", the adhesion was tested using a CSM Revetest. A diamond indenter with a radius of 200 μm was used to scratch the coating surface at a rate of 5 mm / min, with the load increasing linearly from 0 N to 100 N. The critical load Lc at which the coating began to peel off was determined by acoustic emission signal analysis and microscopic observation.

[0134] Friction coefficient: The test was conducted using a ball-on-disk friction and wear testing machine (CETRUMT-3) according to the American Society for Testing and Materials (ASTM) standard G99-17, "Standard Test Method for Wear Testing with a Pin-on-Disk Apparatus". Φ6mm GCr15 steel balls were used for the wear pair, with a normal load of 10N, a friction radius of 5mm, a rotational speed of 300r / min, and a test time of 30min. The average value within the last 15min was taken as the steady-state average friction coefficient.

[0135] Wear rate: After the above friction and wear test, the wear volume V of the wear track was measured using a white light interferometer (Zygo NewView 7300). The formula for calculating the wear rate K is: K=V / (F×S), where V is the wear volume (mm). 3 F is the normal load (N), and S is the total sliding distance (m).

[0136] Temperature resistance: Referring to the national standard GB / T 1735-2009 "Determination of heat resistance of paints and varnishes", the coated test pieces were placed in a muffle furnace and kept at different temperatures (starting from 300℃, in increments of 50℃) in an atmospheric environment for 2 hours. After cooling, a scratch test was performed, and the highest treatment temperature at which the critical load Lc was still not lower than 85% of the original value was used as the temperature resistance index.

[0137] Surface roughness: Measured using a surface roughness meter (Taylor Hobson) according to the national standard GB / T 1031-2009 Product Geometric Specification (GPS) Surface Structure Profile Method for Surface Roughness Parameters and Their Values. The sampling length was 0.8 mm, the evaluation length was 4 mm, and the average value was taken from 3 different locations.

[0138] The results are shown in Tables 2 and 3.

[0139] Table 2. Test results of mechanical properties and bonding strength

[0140]

[0141] Table 3. Results of Tribological Properties and Temperature Resistance Tests

[0142]

[0143] Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-7 are analyzed as follows:

[0144] Comparative Example 1: The bonding force Lc decreased from 95 N to 45 N (a decrease of 52.6%), the surface roughness Ra increased from 0.035 μm to 0.042 μm (an increase of 20.0%), the average coefficient of friction increased from 0.052 to 0.062 (an increase of 19.2%), and the wear rate increased from 1.4 × 10⁻⁶. - 7 mm 3 / N·m increased to 3.0×10 -7 mm 3 / N·m (increase of 114.3%). This comparative example omits the deposition of the Cr bonding layer, resulting in the WC-Cr gradient transition layer directly contacting the bearing steel substrate. Due to significant differences in crystal structure, coefficient of thermal expansion, and chemical bonding characteristics between the steel substrate and the WC-Cr layer, and the lack of lattice matching and stress buffering from the Cr metal bonding layer, severe stress concentration and shear deformation occur at the interface, leading to a significant decrease in the interfacial bonding strength. During friction, the coating is prone to overall peeling, and the exposed hard particles exacerbate surface wear, thus increasing the wear rate exponentially.

[0145] Comparative Example 2: Hardness decreased from 3350 HV to 3150 HV (a decrease of 6.0%), bonding force Lc decreased from 95 N to 60 N (a decrease of 36.8%), surface roughness Ra increased from 0.035 μm to 0.050 μm (an increase of 42.9%), average coefficient of friction increased from 0.052 to 0.065 (an increase of 25.0%), and wear rate increased from 1.4 × 10⁻⁶. -7 mm 3 / N·m increased to 3.8×10 -7 mm 3 / N·m (an increase of 171.4%), and the temperature resistance decreased from 400℃ to 375℃ (a decrease of 6.3%). This comparative example omits step S5, and the WC-Cr gradient transition layer is not deposited, allowing the CeO2-modified high-entropy carbonitride hard layer to be directly deposited on top of the Cr binder layer. Due to the significant difference in modulus between the metallic toughness of the Cr layer and the upper ceramic hard layer, and the lack of modulus buffering from the intermediate gradient transition layer, significant shear stress is generated at the interface. Simultaneously, the columnar crystal growth of carbonitrides in the hard layer loses the structural induction of the transition layer, leading to an increase in grain boundary defects, resulting in decreased hardness and susceptibility to microcracks during thermal cycling, thus reducing temperature resistance.

[0146] Comparative Example 3: Hardness decreased from 3350 HV to 2850 HV (a decrease of 14.9%), bonding force Lc decreased from 95 N to 86 N (a decrease of 9.5%), surface roughness Ra increased from 0.035 μm to 0.055 μm (an increase of 57.1%), average coefficient of friction increased from 0.052 to 0.080 (an increase of 53.8%), and wear rate increased from 1.4 × 10⁻⁶. -7 mm 3 / N·m increased to 4.5×10 -7 mm 3 / N·m (an increase of 221.4%), and the temperature resistance decreased from 400℃ to 360℃ (a decrease of 10.0%). In this comparative example, CeO2 nanoparticles were not introduced during the hard layer deposition process, resulting in a lack of pinning effect of second-phase particles in the high-entropy carbonitride grains during growth. This led to grain coarsening and a decrease in grain boundary bonding strength, resulting in a significant reduction in hardness. At the same time, oxygen impurities at the grain boundaries could not be effectively purified by CeO2, easily forming brittle oxides at high temperatures, leading to a decrease in temperature resistance. During friction, the rough grain boundary structure exacerbated abrasive wear, adhesive wear, and fatigue wear, thus significantly increasing the wear rate.

[0147] Comparative Example 4: The average coefficient of friction increased from 0.052 to 0.098 (an increase of 88.5%), and the wear rate increased from 1.4 × 10⁻⁶. -7 mm 3 / N·m increased to 6.0×10 -7 mm 3 / N·m (increase of 328.6%). In this comparative example, no cerium-based fluorocarbon silicon nanocomposite powder was introduced during the deposition of the lubricating surface layer; only a pure hydrogen-containing amorphous carbon (aC:H) film was formed on the WC-Cr gradient transition layer. Due to the lack of a fiber-reinforced skeleton of aminated silicon carbide nanowires and a layered lubricating transfer film of fluorinated graphene, the coating could not form a continuous low-shear lubricating film during friction. At the same time, the lack of the frictional catalytic effect of CeO2 could not promote the self-repair and dynamic replenishment of the carbon-based lubricating film, resulting in a sharp increase in the coefficient of friction. Under high loads, the coating was prone to brittle fracture and peeling, and the wear rate increased significantly.

[0148] Comparative Example 5: Hardness decreased from 3350 HV to 3050 HV (a decrease of 9.0%), bonding force Lc decreased from 95 N to 80 N (a decrease of 15.8%), surface roughness Ra increased from 0.035 μm to 0.052 μm (an increase of 48.6%), average coefficient of friction increased from 0.052 to 0.082 (an increase of 57.7%), and wear rate increased from 1.4 × 10⁻⁶. -7 mm 3 / N·m increased to 4.2×10 -7 mm 3 / N·m (increase of 200.0%), temperature resistance decreased from 400℃ to 370℃ (decrease of 7.5%). In step 2) of the preparation method of cerium-based fluorocarbon silicon nanocomposite powder, 3-aminopropyltriethoxysilane was not added, and unmodified silicon carbide nanowires were directly used to replace aminated silicon carbide nanowires in an equal amount to participate in the reaction of subsequent step 3). The interfacial chemical bonding between silicon carbide nanowires and aC:H carbon matrix was weakened, the interfacial compatibility decreased, resulting in reduced coating toughness and increased surface roughness. During the friction process, unmodified silicon carbide nanowires were easily pulled out or detached from the matrix, not only losing the reinforcing effect, but also acting as hard abrasive particles to aggravate wear. At the same time, the heat generated by interfacial debonding accelerated the thermal degradation of the coating, and the temperature resistance decreased accordingly.

[0149] Comparative Example 6: Hardness decreased from 3350 HV to 3120 HV (a decrease of 6.9%), bonding force Lc decreased from 95 N to 89 N (a decrease of 6.3%), surface roughness Ra increased from 0.035 μm to 0.045 μm (an increase of 28.6%), average coefficient of friction increased from 0.052 to 0.075 (an increase of 44.2%), and wear rate increased from 1.4 × 10⁻⁶. -7 mm 3 / N·m increased to 3.5×10 -7 mm 3 / N·m (an increase of 150.0%), temperature resistance decreased from 400℃ to 380℃ (a decrease of 5.0%). This comparative example replaced fluorinated graphene with unfluorinated graphene. Due to the absence of fluorine atoms, graphene has a higher surface energy, increasing the interfacial shear strength with the aC:H matrix, making it difficult to form an effective lubrication transfer film through interlayer slip during friction. Simultaneously, unfluorinated graphene cannot release active fluorine atoms through CF bond breaking to participate in the chemical repair of the lubrication film, leading to a significant increase in the coefficient of friction. Furthermore, high surface energy graphene tends to aggregate in the matrix, forming stress concentration points, exacerbating coating wear and localized peeling.

[0150] Comparative Example 7: Hardness decreased from 3350 HV to 2780 HV (a decrease of 17.0%), bonding force Lc decreased from 95 N to 70 N (a decrease of 26.3%), surface roughness Ra increased from 0.035 μm to 0.060 μm (an increase of 71.4%), average coefficient of friction increased from 0.052 to 0.088 (an increase of 69.2%), and wear rate increased from 1.4 × 10⁻⁶. -7 mm 3 / N·m increased to 5.0×10 -7 mm 3 / N·m (an increase of 257.1%), and the temperature resistance decreased from 400℃ to 340℃ (a decrease of 15.0%). In this comparative example, the carbon-nitrogen gradient introduction process was not implemented during the hard layer deposition; instead, a fixed flow rate of nitrogen and acetylene was used, resulting in the formation of a homogeneous carbonitride layer rather than a nanocrystalline composite structure with a gradually changing carbon-nitrogen ratio. The lack of a carbon-nitrogen ratio gradient caused significant compositional abrupt changes and residual stress concentration within the coating, resulting in unoptimized grain growth, decreased density, and consequently, significantly reduced hardness and adhesion. At the same time, the homogeneous structure is more prone to phase transformation and oxidation at high temperatures, leading to a substantial decrease in temperature resistance. The increased surface roughness also reflects the porosity and increased defects in the coating structure.

[0151] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bearing composite coating, characterized in that, The bearing composite coating has a multi-layer gradient structure, consisting of a Cr bonding layer, a WC-Cr gradient transition layer, a CeO2-modified high-entropy carbonitride hard layer, and a composite lubricating surface layer, arranged sequentially from the substrate surface outwards. The raw materials for preparing the CeO2-modified high-entropy carbonitride hard layer include nano-cerium dioxide particles. The raw materials for preparing the composite lubricating surface layer include cerium-based fluorocarbon silicon nanocomposite powder.

2. The bearing composite coating according to claim 1, characterized in that, The thickness of the Cr bonding layer is 0.3~0.5μm, the thickness of the WC-Cr gradient transition layer is 0.6~1.0μm, the thickness of the CeO2 modified high-entropy carbonitride hard layer is 2.0~3.0μm, and the thickness of the composite lubricating surface layer is 1.0~1.5μm.

3. The bearing composite coating according to claim 1, characterized in that, The raw materials for preparing the cerium-based fluorocarbon silicon nanocomposite powder, by weight, include: 4-6 parts of graphene oxide, 40-60 parts of tetraethyl orthosilicate, 20-30 parts of phenolic resin, 0.5-1.5 parts of nickel nitrate, 2-4 parts of cerium nitrate hexahydrate, and 0.5-1.5 parts of 3-aminopropyltriethoxysilane.

4. The bearing composite coating according to claim 3, characterized in that, The preparation method of the cerium-based fluorocarbon silicon nanocomposite powder includes the following steps: 1) Preparation of fluorinated graphene: Weigh out graphene oxide according to the proportion, and carry out gas-phase fluorination reaction at 300~400℃ in a fluorine-containing inert atmosphere for 2~4h, so that the molar ratio of C to F in the product is (5~10):1, and fluorinated graphene is obtained. 2) Preparation of aminated silicon carbide nanowires: Weigh tetraethyl orthosilicate and phenolic resin in proportion, dissolve them in anhydrous ethanol, stir in a water bath at 35-45℃ at a speed of 200-300 r / min for 30-40 min to prepare a precursor solution with a total solid content of 15-25%, add nickel nitrate, continue stirring for 30-40 min, and let stand at 75-85℃ for 8-12 h to obtain a gel. The gel was dried at 110-130℃ for 10-14h. The dried gel was placed in a tube furnace and heated to 1450-1550℃ at a rate of 4-6℃ / min under argon protection at a flow rate of 180-220 sccm. The temperature was held for 1.5-2.5h. The reaction product was decarbonized at 680-720℃ in a nitrogen or argon atmosphere with an oxygen volume fraction of 0.5-5% for 1.5-2.5h to obtain silicon carbide nanowires. Silicon carbide nanowires were dispersed in anhydrous ethanol at a solid-liquid mass-to-volume ratio of 1 g:(8~10) mL. 3-aminopropyltriethoxysilane was added, and the mixture was refluxed at 70~80℃ for 4~6 h. The reaction product was centrifuged, washed, and dried to obtain aminated silicon carbide nanowires. 3) Cerium nitrate hexahydrate and anhydrous ethanol were mixed at a mass-volume ratio of 1g:(12~16)mL to obtain a cerium nitrate hexahydrate solution. The aminated silicon carbide nanowires obtained in step 2) were added and dispersed for 25~35min under ultrasonic power of 250~350W and frequency of 35~45kHz. Then, the fluorinated graphene prepared in step 1) was added and ultrasonic dispersion was continued for 30~40min with magnetic stirring. The reaction solution was transferred to a reaction vessel and hydrothermally treated at 115~125℃ for 5~7h. After centrifugation, washing, vacuum drying and heat treatment, cerium-based fluorocarbon silicon nanocomposite powder was obtained.

5. The bearing composite coating according to claim 4, characterized in that, The specific process of centrifugation, washing, vacuum drying, and heat treatment is as follows: the reaction product is centrifuged at 8000~9000 r / min for 8~12 min, washed 2~3 times with anhydrous ethanol, vacuum dried at 75~85℃ and vacuum degree of -0.095~-0.09MPa for 7~9 h, and then heat treated under argon protection at 480~520℃ for 1.5~2.5 h.

6. A process for preparing a bearing composite coating according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Pretreatment of the substrate: The surface of the bearing steel substrate is ground and polished until the surface roughness Ra≤0.1μm, then ultrasonically cleaned with acetone and anhydrous ethanol, and then vacuum dried. S2. Clamping and Vacuuming: Fix the dried substrate onto the rotatable sample holder, set the revolution speed to 2~5 r / min and the rotation speed to 10~20 r / min, and evacuate to a background vacuum level ≤5.0×10⁻⁶. -3 Pa; S3. Plasma cleaning: Introduce argon gas at a flow rate of 180~220 sccm, adjust the working vacuum to 0.3~0.5 Pa, apply a pulse bias voltage of -600~-800V, a duty cycle of 45~55%, and perform glow discharge cleaning for 15~25 min. S4, Cr binder layer deposition: Magnetron sputtering is performed on the chromium target to deposit and form a Cr binder layer; S5, WC-Cr gradient transition layer deposition: Turn on the tungsten carbide-chromium composite target, power 12~18kW, substrate bias -80~-120V, argon flow rate 250~300sccm, adjust the working vacuum to 0.4~0.6Pa, and deposit for 30~50min. S6, CeO2 modified high-entropy carbonitride hard layer deposition: Turn on the high-entropy alloy target and chromium target, with power of 8~12kW and 3~5kW respectively. Feed nano-cerium dioxide particles at a rate of 1~3g / h through the powder feeder. Introduce argon gas at 200~250sccm and nitrogen gas at 80~120sccm. Adjust the working vacuum to 0.6~0.8Pa, substrate bias voltage -150~-200V, temperature 200~250℃. Deposit for 60~90min first, then linearly reduce the nitrogen flow rate to 30~50sccm, and simultaneously linearly introduce acetylene to 50~80sccm. Then maintain this gas flow rate and continue deposition for a total time of 150~200min. The high-entropy alloy target is a Ti-Al-Nb-V quaternary alloy target. S7. Composite lubricating surface deposition: After the temperature is reduced to 150~180℃, turn on the graphite target and molybdenum disulfide target with power of 6~10kW and 3~5kW respectively, introduce argon gas at 150~200sccm and acetylene gas at 40~60sccm, adjust the working vacuum to 0.8~1.2Pa, and the substrate bias voltage at -100~-150V. Feed the cerium-based fluorocarbon silicon nanocomposite powder into the substrate at a rate of 5~10g / h through the powder feeder and deposit for 60~90min. S8. Cooling: After deposition, turn off the heating system and continue to introduce argon gas to make the chamber pressure reach 1~5Pa. Maintain gas convection cooling until the workpiece temperature is below 80℃, then remove the coated workpiece.

7. The preparation process of the bearing composite coating according to claim 6, characterized in that, In step S1, the ultrasonic cleaning conditions are: ultrasonic frequency 35~45kHz, power 250~350W, and cleaning time 10~20min; the vacuum drying conditions are: vacuum degree -0.095~-0.09MPa, temperature 95~105℃, and time 0.8~1.2h.

8. The preparation process of the bearing composite coating according to claim 6, characterized in that, In step S4, adjust the argon flow rate to 250~300 sccm, the working vacuum to 0.4~0.6 Pa, turn on the chromium target, set the power to 8~12 kW, the substrate bias voltage to -100~-150 V, the temperature to 150~200 ℃, and perform magnetron deposition for 15~25 min.

9. The preparation process of the bearing composite coating according to claim 6, characterized in that, In step S5, the mass ratio of WC to Cr in the tungsten carbide-chromium composite target is (75~85):(15~25).

10. The preparation process of the bearing composite coating according to claim 6, characterized in that, The atomic ratio of Ti, Al, Nb, and V in the high-entropy alloy target is (1~1.2):(1~1.2):(1~1.2):(1~1.2).

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