Preparation method of high-wear-resistant ceramic composite bearing

Abstract

The application discloses a kind of preparation methods of high wear-resistant ceramic composite bearing, comprising the following steps: S1, raw material gradient premix preparation;S2, gradient green compact forming and furnace loading;S3, magnetron sputtering (SPS) collaborative sintering;S4, ceramic body interface activation treatment;S5, / hydroxyapatite gradient transition layer preparation;S6, precision post-processing and performance detection.The application solves the problem that traditional ceramic bearing causes inner and outer layer performance homogenization due to raw material homogenization mixing, sintering density is insufficient, interface treatment is simple, coating adhesion is weak and easy to fall off, and post-processing precision is low, which makes it difficult to meet the demand of high wear-resistant, high stability and severe working condition.

Description

Technical Field

[0001] This invention relates to the field of bearing processing technology, specifically to a method for preparing a high wear-resistant ceramic composite bearing. Background Technology

[0002] In industrial production and high-end equipment, bearings, as the core basic components for realizing the rotational transmission of mechanical parts, directly determine the operating efficiency, stability, and service life of equipment. As modern industry develops towards high precision, high load, and long-cycle continuous operation, traditional metal bearings, due to their inherent defects such as low hardness, easy wear, and weak corrosion resistance, are no longer able to meet the demands of harsh working conditions. Ceramic materials, with their excellent hardness, superior wear resistance, good chemical stability, and high-temperature resistance, have become the ideal choice for preparing high-performance bearings. Therefore, ceramic composite bearings have become an important research direction in the bearing field. Currently, the preparation technology of ceramic composite bearings focuses on further improving their comprehensive performance through material formulation optimization, structural design innovation, and process improvement. Among these, gradient structure design allows different parts of the bearing to adapt to different performance requirements, multi-field synergistic sintering can optimize the microstructure of the ceramic body, and interface modification and functional transition layer preparation can enhance surface wear resistance and bonding performance. These technological directions jointly drive the development of ceramic composite bearings towards high wear resistance and high reliability.

[0003] Currently, traditional ceramic bearing manufacturing technologies have many shortcomings in practical applications, making it difficult to meet the stringent requirements of high wear resistance scenarios: 1. In the raw material processing stage, traditional processes mostly adopt a homogenized mixing method, failing to adjust the formula according to the performance differences between the inner and outer layers of the bearing. This results in homogenized overall bearing performance, making it impossible to simultaneously meet the toughness requirements of the inner layer and the high wear resistance requirements of the surface layer. Under complex working conditions, problems such as inner layer fracture or rapid surface wear are prone to occur; 2. In the sintering process, traditional sintering technologies mostly rely on a single heating mechanism, lacking the synergistic effect of multiple energy fields. This easily leads to insufficient density of the ceramic body, resulting in defects such as pores and microcracks, significantly reducing the mechanical strength and fatigue resistance of the bearing; 3. Traditional interface treatment processes are relatively simple and fail to effectively activate the surface of the ceramic body. The subsequent coatings or transition layers have weak adhesion to the body, making it easy for the coating to peel off during use, further aggravating wear; 4. Traditional post-processing has low precision, poor surface roughness control, and insufficient performance testing indicators, making it difficult to ensure the consistency and stability of ceramic bearings. These shortcomings greatly limit the application of traditional ceramic bearings in high-end fields. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing high wear-resistant ceramic composite bearings. This method solves the problems of traditional ceramic bearings, which suffer from homogenized inner and outer layer performance due to uniform mixing of raw materials, insufficient sintering density, weak coating adhesion and easy peeling due to simple interface treatment, and low post-processing precision, making it difficult to meet the requirements of high wear resistance and high stability under harsh working conditions.

[0005] To achieve the above objectives, the present invention provides a method for preparing a high wear-resistant ceramic composite bearing, comprising the following steps:

[0006] S1. Prepare basic ceramic particles, graphene and binder. Take two portions of basic ceramic particles, add different amounts of graphene and different amounts of binder to the two portions of basic ceramic particles respectively and mix them to obtain inner layer premix and surface layer premix.

[0007] S2. The inner layer premix is ​​pre-compressed, and the pre-compressed inner layer premix is ​​covered with the surface premix and pre-compressed again to obtain a gradient green embryo.

[0008] S3. The gradient green body is loaded into the sintering equipment to perform gradient sintering under the action of alternating magnetic field and pulsed current to obtain the ceramic body.

[0009] S4. Heat-treat the ceramic body in a nitrogen-oxygen mixed atmosphere.

[0010] S5. Sequentially deposited on the surface of the ceramic body using electron beam deposition technology. bottom layer and / Hydroxyapatite composite top layer;

[0011] S6. Grind, clean, and test the performance of the ceramic body processed by electron beam deposition technology.

[0012] The present invention further specifies that: in step S1, the basic ceramic particles are composed of 90-95% silicon nitride powder, 3-5% yttrium oxide powder, and 1-3% alumina powder by mass percentage; the amount of graphene added to the surface layer is 5-10 wt% based on the mass of the basic ceramic particles, and the amount of graphene added to the inner layer is 1-3 wt% based on the mass of the basic ceramic particles; the binder is a composite binder composed of chitosan and hydroxyapatite in a mass ratio of 3:1, and the amount of binder added to the inner layer premix is ​​2-4%, and the amount of binder added to the surface layer premix is ​​3-5%.

[0013] The present invention further comprises: the silicon nitride powder of the basic ceramic particles being α phase with an α phase content ≥92%; the silicon nitride powder having a particle size of 0.8-5μm and a 1-3μm particle size accounting for ≥80% of the silicon nitride powder; the yttrium oxide powder of the basic ceramic particles having a median diameter of 0.95-1.05μm; and the alumina powder of the basic ceramic particles having a purity ≥99.9% and a median diameter of 0.75-0.85μm.

[0014] The present invention further comprises: in step S1, the inner layer premix is ​​prepared by ball milling at a ball-to-material ratio of 10:1 at a speed of 250-300 r / min for 8-10 h, and the surface layer premix is ​​prepared by ball milling at a ball-to-material ratio of 12:1 at a speed of 280-320 r / min for 10-12 h; after ball milling, the inner layer premix and the surface layer premix are dried and sieved, the inner layer premix is ​​sieved through a mesh size of 200 mesh, and the surface layer premix is ​​sieved through a mesh size of 300 mesh.

[0015] The present invention further specifies that: the pre-compression process of the inner layer premix in step S2 is as follows: the inner layer premix is ​​pre-compressed at 15-20MPa for 10-15min to form an inner layer preform; the surface premix is ​​covered to a thickness of 1.0-1.5mm and then pre-compressed again at 20-25MPa for 8-10min.

[0016] The present invention further specifies that: the alternating magnetic field parameters in step S3 are 50-200Hz and 0.1-0.5T, the pulse current parameters are 10-20kA and the duty cycle is 10-30%; the gradient sintering process is as follows: the temperature is increased from room temperature to 500℃ at 5℃ / min and held for 2h, then increased to 1200℃ at 20℃ / min and held for 1h, then increased to 1550℃ at 3℃ / min and held for 3-4h, and finally cooled to 800℃ and air-cooled.

[0017] The present invention further specifies that, in step S3, the alternating magnetic field parameters are adjusted according to the bearing size requirements: when the inner ring diameter of the bearing is 20-30mm, the alternating magnetic field parameters are 50-70Hz / 0.15-0.25T; when the inner ring diameter of the bearing is 30-50mm, the alternating magnetic field parameters are 70-100Hz / 0.25-0.3T; when the outer ring diameter of the bearing is 50-70mm, the alternating magnetic field parameters are 100-150Hz / 0.35-0.45T; and when the outer ring diameter of the bearing is 70-100mm, the alternating magnetic field parameters are 150-200Hz / 0.45-0.5T.

[0018] The present invention further specifies that: in step S4, the oxygen content of the nitrogen-oxygen mixed atmosphere is 1-3% and the total pressure is 0.1-0.12 MPa; the heat treatment process is: heating to 700-900℃ at 3-5℃ / min and holding for 0.5-1.5h, followed by furnace cooling.

[0019] The present invention further includes: in step S5 The thickness of the bottom layer deposition is 50-100 nm. The deposition thickness of the hydroxyapatite composite top layer is 100-150 nm, of which The mass ratio of hydroxyapatite to hydroxyapatite is 2:1; bottom layer and The hydroxyapatite composite top layer was deposited and then annealed at 300°C for 1 hour in a nitrogen atmosphere.

[0020] The present invention further specifies that: in step S6, the grinding is performed using a 1200-1500 mesh diamond grinding wheel, and the surface roughness Ra is controlled to be ≤0.08μm; the cleaning is performed using an anhydrous ethanol and nitric acid mixture in a volume ratio of 9:1, which is ultrasonically cleaned for 15-20 minutes; and the performance testing includes density testing and hardness testing.

[0021] The advantages of adopting the above technical solution are as follows: The technology utilizes a gradient premixing design to prepare inner and outer layer premixes separately, achieving a gradient distribution of raw material components in the ceramic bearing. Simultaneously, it combines magnetron sputtering (SPS) synergistic sintering technology, leveraging the synergistic effect of alternating magnetic fields and pulsed currents, and adapting magnetic field parameters to the bearing dimensions to perform gradient sintering of the green body. This process design not only effectively improves the density and structural uniformity of the ceramic body, avoiding the internal and external performance differences that easily occur in traditional sintering, but also, through the gradient addition of graphene, gives the inner layer of the bearing good toughness and the outer layer strong wear resistance. The appropriate selection of composite binders enhances the bonding between raw materials, providing a stable foundation for subsequent molding and sintering processes. This allows the ceramic bearing body to possess excellent mechanical properties and wear resistance potential from the initial preparation stage, laying a solid structural foundation for subsequent performance improvements.

[0022] In the above-mentioned technology, the ceramic body interface is activated through a process called ceramic body interface activation treatment. The interfacial bonding state of the ceramic body is optimized by heat treatment in a nitrogen-oxygen mixed atmosphere, and then electron beam deposition technology is used to prepare the ceramic body. The hydroxyapatite gradient transition layer, through its gradient transition design between the bottom and top composite layers, effectively improves the bonding performance between the ceramic body and the external environment, reducing interface defects. Subsequent nitrogen atmosphere annealing further enhances the structural stability of the transition layer. Simultaneously, the application of precision grinding and specific ratio cleaning processes ensures that the bearing surface reaches high-standard quality, while the performance testing stage specifically controls the core indicators of density and hardness. This entire process endows the ceramic bearing with not only excellent surface wear resistance and interfacial bonding strength but also stable overall performance, effectively solving problems such as interface detachment and excessively rapid surface wear that are common in traditional ceramic bearings. It meets the high requirements for bearing performance stability and durability in high-wear-resistant applications, significantly improving the bearing's service life and application adaptability. Attached Figure Description

[0023] Figure 1 This is a simplified view of the preparation method flow of the present invention. Detailed Implementation

[0024] This invention provides a method for preparing a high wear-resistant ceramic composite bearing, comprising the following steps:

[0025] S1. Prepare basic ceramic particles, graphene and binder. Take two portions of basic ceramic particles, add different amounts of graphene and different amounts of binder to the two portions of basic ceramic particles respectively and mix them to obtain inner layer premix and surface layer premix.

[0026] S2. The inner layer premix is ​​pre-compressed, and the pre-compressed inner layer premix is ​​covered with the surface premix and pre-compressed again to obtain a gradient green embryo.

[0027] S3. The gradient green body is loaded into the sintering equipment to perform gradient sintering under the action of alternating magnetic field and pulsed current to obtain the ceramic body.

[0028] S4. Heat-treat the ceramic body in a nitrogen-oxygen mixed atmosphere.

[0029] S5. Sequentially deposited on the surface of the ceramic body using electron beam deposition technology. bottom layer and / Hydroxyapatite composite top layer;

[0030] S6. Grind, clean, and test the performance of the ceramic body processed by electron beam deposition technology.

[0031] Further: In step S1, the basic ceramic particles are composed of 90-95% silicon nitride powder, 3-5% yttrium oxide powder, and 1-3% alumina powder by mass percentage; the amount of graphene added to the surface layer is 5-10 wt% based on the mass of the basic ceramic particles, and the amount of graphene added to the inner layer is 1-3 wt% based on the mass of the basic ceramic particles; the binder is a composite binder composed of chitosan and hydroxyapatite in a mass ratio of 3:1, and the amount of binder added to the inner layer premix is ​​2-4%, and the amount of binder added to the surface layer premix is ​​3-5%.

[0032] Further: the silicon nitride powder in the basic ceramic particles is α phase and the α phase content is ≥92%, the silicon nitride powder particle size is 0.8-5μm and the proportion of 1-3μm particles in the silicon nitride powder is ≥80%; the median diameter of the yttrium oxide powder in the basic ceramic particles is 0.95-1.05μm; the purity of the alumina powder in the basic ceramic particles is ≥99.9%, and the median diameter of the alumina powder is 0.75-0.85μm.

[0033] Further: In step S1, the inner layer premix is ​​prepared by ball milling at a ball-to-material ratio of 10:1 at a speed of 250-300 r / min for 8-10 h, and the surface layer premix is ​​prepared by ball milling at a ball-to-material ratio of 12:1 at a speed of 280-320 r / min for 10-12 h; after ball milling, the inner layer premix and the surface layer premix are dried and sieved, with the inner layer premix sieved at a mesh size of 200 and the surface layer premix sieved at a mesh size of 300.

[0034] Further: In step S2, the pre-compression process of the inner layer premix is ​​as follows: the inner layer premix is ​​pre-compressed at 15-20MPa for 10-15min to form an inner layer preform; the surface premix is ​​covered to a thickness of 1.0-1.5mm and then pre-compressed again at 20-25MPa for 8-10min.

[0035] Further: in step S3, the alternating magnetic field parameters are 50-200Hz and 0.1-0.5T, and the pulse current parameters are 10-20kA and 10-30% duty cycle; the gradient sintering process is as follows: from room temperature, the temperature is increased to 500℃ at 5℃ / min and held for 2h, then increased to 1200℃ at 20℃ / min and held for 1h, then increased to 1550℃ at 3℃ / min and held for 3-4h, and finally cooled to 800℃ and air-cooled.

[0036] Further: In step S3, the alternating magnetic field parameters are adjusted according to the bearing size requirements: when the inner ring diameter of the bearing is 20-30mm, the alternating magnetic field parameters are 50-70Hz / 0.15-0.25T; when the inner ring diameter of the bearing is 30-50mm, the alternating magnetic field parameters are 70-100Hz / 0.25-0.3T; when the outer ring diameter of the bearing is 50-70mm, the alternating magnetic field parameters are 100-150Hz / 0.35-0.45T; when the outer ring diameter of the bearing is 70-100mm, the alternating magnetic field parameters are 150-200Hz / 0.45-0.5T.

[0037] Further: in step S4, the oxygen content of the nitrogen-oxygen mixed atmosphere is 1-3% and the total pressure is 0.1-0.12 MPa; the heat treatment process is: heating to 700-900℃ at 3-5℃ / min and holding for 0.5-1.5h, followed by furnace cooling.

[0038] Further: in step S5 The thickness of the bottom layer deposition is 50-100 nm. The deposition thickness of the hydroxyapatite composite top layer is 100-150 nm, of which The mass ratio of hydroxyapatite to hydroxyapatite is 2:1; bottom layer and The hydroxyapatite composite top layer was deposited and then annealed at 300°C for 1 hour in a nitrogen atmosphere.

[0039] Further: in step S6, grinding is performed using a 1200-1500 mesh diamond grinding wheel, and the surface roughness Ra is controlled to be ≤0.08μm; the cleaning is performed using an anhydrous ethanol and nitric acid mixture in a volume ratio of 9:1, which is ultrasonically cleaned for 15-20 minutes; the performance testing includes density testing and hardness testing.

[0040] Specific embodiment 1 of the present invention:

[0041] Fabrication of a high wear-resistant ceramic composite bearing with an inner ring diameter of 25mm and an outer ring diameter of 60mm.

[0042] S1. The basic ceramic particles are composed of 93% silicon nitride powder, 4% yttrium oxide powder, and 3% alumina powder by mass percentage. Among them, the silicon nitride powder is α phase with an α phase content of 93%, a particle size range of 0.8-5μm, and 82% of the particles are 1-3μm. Silicon nitride powder with these parameters can lay the foundation for the formation of a dense ceramic body in subsequent sintering and reduce the internal voids of the finished product. The yttrium oxide powder has a median diameter of 1.0μm, which can help regulate the grain growth rate during the ceramic sintering process and avoid the performance degradation caused by excessively large grains. The alumina powder has a purity of 99.95% and a median diameter of 0.8μm, which can fill the tiny gaps between silicon nitride particles and optimize the microstructure of the ceramic. Graphene is then added. The amount of graphene added to the inner layer premix is ​​1.5 wt% based on the mass of the base ceramic particles. This amount ensures a tight bond between the inner and outer layer premixes, preventing interlayer separation. The amount of graphene added to the outer layer premix is ​​7 wt% based on the mass of the base ceramic particles. This higher amount significantly enhances the wear resistance of the bearing surface and extends bearing life. A composite binder composed of chitosan and hydroxyapatite in a 3:1 mass ratio is used. 3% of the inner layer premix is ​​added to prevent it from becoming too hard due to excessive binder, which could affect subsequent molding operations. 4% of the outer layer premix is ​​added to improve its molding stability and reduce the risk of cracking after molding. Next, ball milling is performed. The inner layer premix is ​​ball-milled for 9 hours at a ball-to-material ratio of 10:1 and a speed of 270 r / min, while the surface layer premix is ​​ball-milled for 11 hours at a ball-to-material ratio of 12:1 and a speed of 300 r / min. These ball milling parameters ensure that the raw material particles are fully mixed, eliminate component segregation, and ensure that the components in each area are uniform. After ball milling, the powder is dried. After drying, the inner layer premix is ​​passed through a 200-mesh sieve, and the surface layer premix is ​​passed through a 300-mesh sieve. The particle size of the powder is controlled by screening to avoid large particles affecting the subsequent molding density and to ensure that the density of each layer of the gradient green body is uniform.

[0043] S2. Place the inner layer premix in a special molding mold and pre-press it at 18MPa for 12 minutes. This pressure and time allow the inner layer premix to initially form and possess a certain strength, preventing deformation or collapse when covering it with the surface premix later. Then, evenly cover the surface premix onto the surface of the inner layer preform, controlling the surface premix coverage thickness to 1.2mm. This thickness meets the wear resistance requirements of the bearing surface while avoiding excessive thickness that could lead to material waste or difficulties in interlayer bonding. After covering, perform a second pre-press on the entire structure, setting the pressure to 22MPa and the pre-pressing time to 9 minutes. These second pre-pressing parameters ensure a tight fit between the surface premix and the inner layer preform, reducing interlayer gaps and improving the overall structural integrity of the gradient green body. Finally, carefully load the prepared gradient green body into the designated station of the sintering equipment, ensuring that the green body is placed stably within the equipment to prevent displacement of the green body during sintering, which could lead to product dimensional deviations or structural damage.

[0044] S3. Based on the size characteristics of the bearing inner ring diameter of 25mm and outer ring diameter of 60mm in this embodiment, the alternating magnetic field parameters are set as follows: the magnetic field frequency corresponding to the inner ring is 60Hz and the magnetic field strength is 0.2T, and the magnetic field frequency corresponding to the outer ring is 120Hz and the magnetic field strength is 0.4T. These targeted magnetic field parameters can ensure that the magnetic field acts uniformly on the inner and outer ring areas of the green blank, avoiding uneven sintering due to size differences; the pulse current parameter is set to 10-20kA and the duty cycle is 20%. This current parameter can provide sufficient energy to the raw material particles during the sintering process, promote particle diffusion and reaction, and accelerate the sintering process. The sintering process begins by heating from room temperature to 500°C at a rate of 5°C / min, holding at this temperature for 2 hours. This slow heating gradually removes residual moisture and volatile binder components from the green body, preventing rapid heating that could cause bubbles or cracking. Next, the temperature is increased to 1200°C at a rate of 20°C / min and held for 1 hour. This rapid heating accelerates the initial reaction between the raw materials, preparing for subsequent high-temperature sintering. Then, the temperature is increased to 1550°C at a rate of 3°C / min and held for 3.5 hours. This slow heating combined with prolonged holding promotes complete sintering of ceramic particles, forming a dense ceramic structure and improving the strength and hardness of the ceramic body. After sintering and holding, heating is stopped when the temperature inside the equipment drops to 800°C, allowing the ceramic body to air-cool naturally to room temperature. This slow cooling prevents internal stress caused by excessive temperature differences, thus preventing cracking or deformation and ultimately resulting in a structurally complete ceramic body.

[0045] S4. Place the sintered ceramic body into a heat treatment furnace and introduce a nitrogen-oxygen mixed atmosphere into the furnace. Control the oxygen content of the mixed atmosphere to be 2% and the total pressure to be 0.11 MPa. These atmosphere parameters can form a thin and uniform oxide layer on the surface of the ceramic body, enhancing the bonding force between the subsequent gradient transition layer and the ceramic body, while avoiding excessive oxidation that would lead to a decline in the surface properties of the ceramic. Set the heat treatment program to heat to 800℃ at a heating rate of 4℃ / min, and hold at this temperature for 1 hour. The gentle heating rate and holding time can moderately activate the ceramic surface, optimize the surface microstructure, and avoid damage to the ceramic surface caused by excessively high-temperature and rapid treatment. After the holding time is completed, turn off the heating device of the heat treatment furnace and allow the ceramic body to cool to room temperature with the furnace. Cooling with the furnace can further stabilize the chemical state and microstructure of the ceramic surface, providing good surface conditions for the subsequent deposition of the gradient transition layer.

[0046] S5. Using electron beam deposition technology, first deposit electron beam deposition on the surface of the ceramic substrate after interface activation treatment. The bottom layer is controlled to have a deposition thickness of 70nm. The bottom layer provides a stable adhesion base for the subsequent composite top layer, ensuring a strong bond between the gradient transition layer and the ceramic body, preventing detachment. After the bottom layer deposition is completed, the process continues... Substrate surface deposition / hydroxyapatite composite top layer, in which The mass ratio of the composite top layer to hydroxyapatite is 2:1, and the thickness of the composite top layer is 120nm. This ratio and thickness can take into account both the wear resistance and surface compatibility of the gradient transition layer, thereby improving the overall performance of the bearing. After the deposition process, the ceramic body with the gradient transition layer is transferred to a nitrogen-protected furnace and annealed at 300℃ for 1 hour in a nitrogen atmosphere. The annealing treatment can eliminate the internal stress generated inside the gradient transition layer during the deposition process, improve the structural stability of the transition layer, and avoid delamination or cracking during subsequent use.

[0047] S6. A 1300-mesh diamond grinding wheel is used to grind the ceramic body with a gradient transition layer. This grit size allows for precise control of the surface finish of the ceramic body, ensuring a surface roughness of Ra≤0.08μm, reducing frictional resistance during bearing use and improving smooth operation. After grinding, a cleaning solution of anhydrous ethanol and nitric acid in a 9:1 volume ratio is prepared. The ceramic body is then immersed in the cleaning solution for 18 minutes of ultrasonic cleaning. Ultrasonic cleaning effectively removes residual debris and surface impurities from the grinding process, preventing impurities from adhering and affecting the bearing's wear resistance and service life. After cleaning and natural drying, the ceramic composite bearing undergoes density and hardness testing. Density testing verifies whether the ceramic body meets the designed density requirements, while hardness testing ensures the bearing has sufficient wear resistance, ultimately guaranteeing that the product performance meets the usage standards.

[0048] In summary, this embodiment focuses on the preparation of a high-wear-resistant ceramic composite bearing with an inner ring diameter of 25mm and an outer ring diameter of 60mm, strictly adhering to the parameters outlined in the documentation. In S100, raw materials are mixed in a specific ratio with differentiated additions of graphene and binders, followed by ball milling and sieving to ensure raw material uniformity and interlayer bonding. In S200, appropriate pressure and time are used for molding to ensure the integrity of the green body structure. In S300, magnetic field parameters are set according to the bearing dimensions, and pulsed current and gradient temperature sintering are employed to form a dense ceramic body. In S400, the interface is activated under a specific nitrogen and oxygen atmosphere to create conditions for transition layer deposition. In S500, a specified thickness of [unclear - possibly referring to a specific material or process] is deposited. A hydroxyapatite gradient transition layer is applied and annealed to improve bonding stability; S600 is ground with a 1300-mesh grinding wheel and ultrasonically cleaned with a specific cleaning solution, followed by performance testing, to finally obtain a bearing that meets the requirements.

[0049] Specific embodiment 2 of the present invention:

[0050] Fabrication of high wear-resistant ceramic composite bearings with an inner ring diameter of 40mm and an outer ring diameter of 80mm:

[0051] S1. The basic ceramic particles are composed of 95% silicon nitride powder, 3% yttrium oxide powder, and 2% alumina powder by mass percentage. Among them, the silicon nitride powder is the α phase with an α phase content of 94%, a particle size range of 0.8-5μm, and 85% of the particles are 1-3μm. The higher α phase content and particle proportion can further improve the compactness and mechanical strength of the ceramic body after subsequent sintering, and reduce the performance deficiencies of large-size bearings due to loose structure. The median diameter of the yttrium oxide powder is 0.95μm, which can better integrate into the silicon nitride particle system and help suppress abnormal grain growth during sintering. The alumina powder has a purity of 99.9% and a median diameter of 0.75μm. The high purity and fine particle size can further fill the gaps between silicon nitride particles, optimize the ceramic microstructure, and improve the overall uniformity. When graphene is added, the amount of graphene added to the inner layer premix is ​​2.5 wt% based on the mass of the base ceramic particles. This amount ensures the bonding between the inner and outer layers while appropriately enhancing the strength of the inner layer, adapting to the stress requirements of large-size bearings. The amount of graphene added to the outer layer premix is ​​9 wt% based on the mass of the base ceramic particles. This higher amount significantly enhances the wear resistance of the outer layer of large-size bearings, coping with the greater wear pressure during the use of large-size bearings. The binder is a composite binder composed of chitosan and hydroxyapatite in a mass ratio of 3:1. The amount added to the inner layer premix is ​​2.5%. This amount balances the formability and strength of the inner layer premix, avoiding molding difficulties caused by large-size inner layer preforms being too hard or too soft. The amount added to the outer layer premix is ​​4.5%. This higher amount improves the molding stability of large-size outer layer premixes, reducing the risk of cracking due to excessive size after molding. Ball milling is performed on the inner layer premix at a ball-to-material ratio of 10:1 and a rotation speed of 250 r / min for 8 hours, while the surface layer premix is ​​ball-to-material at a ball-to-material ratio of 12:1 and a rotation speed of 320 r / min for 12 hours. The ball milling parameters are set according to the different needs of the inner and surface layers to ensure uniform mixing of raw materials and avoid component segregation in large-size premixes. After ball milling, the powder is dried, and the inner layer premix is ​​passed through a 200-mesh sieve, while the surface premix is ​​passed through a 300-mesh sieve. The particle size of the powder is controlled by screening to ensure uniform density of each layer of the large-size gradient green body and to avoid structural instability after molding due to uneven particle size.

[0052] S2. Place the inner layer premix into a large-size special molding die and pre-press it at 15MPa for 15 minutes. This pressure and time allow the large-size inner layer premix to fully form, providing sufficient strength to support the subsequent coverage of the surface premix and preventing deformation of the preform due to excessive size. Then, evenly cover the surface premix onto the surface of the inner layer preform, controlling the surface premix coverage thickness to 1.5mm. This thickness meets the higher wear resistance requirements of the large-size bearing surface and ensures a reasonable bonding ratio between the surface and inner layers. After covering, perform a second pre-press on the entire structure, setting the pressure to 25MPa and the pre-pressing time to 8 minutes. The higher second pre-press pressure allows the surface premix to bond tightly with the inner layer preform, reducing interlayer voids in the large-size green blank and improving the overall structural integrity. Slowly load the prepared gradient green blank into a sintering equipment suitable for large-size products, ensuring the green blank is accurately positioned and stably placed within the equipment to prevent displacement of the green blank during sintering, which could lead to excessive dimensional deviations in the large-size product.

[0053] S3. Based on the large size characteristics of the bearing in this embodiment, with an inner ring diameter of 40mm and an outer ring diameter of 80mm, the alternating magnetic field parameters are set as follows: the magnetic field frequency for the inner ring is 85Hz and the magnetic field strength is 0.28T, and the magnetic field frequency for the outer ring is 180Hz and the magnetic field strength is 0.48T. These magnetic field parameters can be adapted to different parts of the large-size bearing to ensure that the magnetic field acts uniformly on the entire green blank and avoid sintering differences caused by uneven magnetic field in large-size green blanks. The pulse current parameter is set to 18kA and the duty cycle is 25%. The higher current and duty cycle can provide more energy for the sintering of large-size green blanks and promote the full diffusion reaction of raw material particles. The sintering process is initiated by gradually increasing the temperature from room temperature to 500°C at a rate of 5°C / min and holding for 2 hours. This slow heating process removes moisture and binder from the large-sized green body, preventing rapid heating from causing bubbles or cracks inside the green body. Next, the temperature is increased to 1200°C at a rate of 20°C / min and held for 1 hour to accelerate the initial reaction between the raw materials, laying the foundation for high-temperature sintering. Then, the temperature is increased to 1550°C at a rate of 3°C / min and held for 4 hours. This longer holding time ensures that the large-sized ceramic green body is fully sintered, forming a dense structure and preventing incomplete sintering due to its large size. After the sintering holding period, heating is stopped when the temperature inside the equipment drops to 800°C, allowing the ceramic body to air-cool to room temperature within the equipment. This slow cooling process prevents internal stress caused by excessive temperature differences in the large-sized ceramic body, preventing cracking or deformation, and ultimately yielding a large-sized ceramic body with a complete structure.

[0054] S4. Place the sintered large-size ceramic body into a heat treatment furnace and introduce a nitrogen-oxygen mixed atmosphere into the furnace. Control the oxygen content of the mixed atmosphere to 3% and the total pressure to 0.12 MPa. A slightly higher oxygen content can form a more uniform oxide layer on the surface of the large-size ceramic body, enhance the bonding force between the subsequent gradient transition layer and the ceramic body, and adapt to the stress requirements of the large-size bearing. Set the heat treatment program and heat to 900℃ at a heating rate of 5℃ / min. After reaching this temperature, hold for 0.5h. The fast heating rate and appropriate holding time can efficiently complete the surface activation of the large-size ceramic body and optimize the surface microstructure. After the holding time is completed, turn off the heating device and allow the ceramic body to cool to room temperature with the furnace. Cooling with the furnace can stabilize the ceramic surface state and provide good conditions for the subsequent deposition of the gradient transition layer.

[0055] S5. Using electron beam deposition technology, first deposit electron beam deposition on the surface of the ceramic substrate after interface activation treatment. The bottom layer is deposited with a thickness controlled at 100 nm. A thicker bottom layer provides a more stable adhesion base for the gradient transition layer of the large-size ceramic body, ensuring a strong bond. After the bottom layer deposition is completed, the process continues... Substrate surface deposition / hydroxyapatite composite top layer, in which The mass ratio of the composite top layer to hydroxyapatite is 2:1, and the composite top layer has a deposition thickness of 150nm. The thicker composite top layer can enhance the wear resistance and surface protection of large-size bearings and cope with the operating pressure of large-size bearings. After the deposition process, the ceramic body with the gradient transition layer is transferred to a nitrogen-protected furnace and annealed at 300℃ for 1 hour in a nitrogen atmosphere. The annealing treatment can eliminate the internal stress inside the large-size gradient transition layer, improve the structural stability of the transition layer, and avoid delamination during subsequent use.

[0056] S6. A 1500-grit diamond grinding wheel is used to grind the large-size ceramic body with a gradient transition layer. The finer grit of the grinding wheel allows for more precise control of the surface accuracy of the large-size ceramic body, ensuring a surface roughness Ra≤0.08μm, reducing frictional resistance during the operation of the large-size bearing, and improving operational stability. After grinding, a cleaning solution with anhydrous ethanol and nitric acid in a volume ratio of 9:1 is prepared. The ceramic body is immersed in the cleaning solution and ultrasonically cleaned for 20 minutes. The longer cleaning time can more thoroughly remove grinding debris and impurities from the surface of the large-size ceramic body, preventing impurities from affecting bearing performance. After cleaning and drying, the density and hardness of the large-size ceramic composite bearing are tested. The tests verify whether the density and hardness of the large-size product meet the standards, ensuring that it has sufficient strength and wear resistance to meet the requirements for the use of large-size bearings.

[0057] In summary, this embodiment is designed for large-size bearings with an inner ring diameter of 40mm and an outer ring diameter of 80mm, and is manufactured according to the parameters specified in the documentation. In S100, the raw material ratio and the amounts of graphene and binder added are adjusted, and ball milling and sieving are performed to meet the requirements of large-size green bodies. In S200, higher secondary pre-pressing pressure is used for molding to ensure interlayer bonding in the large-size green body. In S300, a higher frequency and intensity magnetic field and appropriate current are set according to the size, and the high-temperature holding time is extended to ensure full sintering of the large-size ceramic body. In S400, a nitrogen-oxygen atmosphere with a slightly higher oxygen content is used to activate the interface. In S500, the thickness of the transition layer deposition is increased to improve the wear resistance and protection capabilities of the large-size bearing. In S600, grinding with a 1500-mesh grinding wheel and longer ultrasonic cleaning, combined with testing, ensures that the large-size bearing possesses sufficient strength and wear resistance.

[0058] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A method of making a high wear resistant ceramic composite bearing, characterized by: The method comprises the following steps: S1, preparing base ceramic particles, graphene and a binder, taking two portions of base ceramic particles, adding different contents of graphene and different contents of the binder into the two portions of base ceramic particles respectively and mixing to obtain an inner layer premix and a surface layer premix; S2, pre-pressing the inner layer premix, covering the surface layer premix with the pre-pressed inner layer premix and pre-pressing again to obtain a gradient green body; S3, loading the gradient green body into a sintering device to perform gradient sintering on the gradient green body under the action of an alternating magnetic field and a pulse current to obtain a ceramic body; S4, performing heat treatment on the ceramic body in a nitrogen-oxygen mixed atmosphere; S5, sequentially depositing Ti3C2T x bottom layer and Ti3C2T x hydroxyapatite composite top layer; S6, performing grinding, cleaning and performance detection on the ceramic body processed by the electron beam deposition technology.

2. The method of claim 1, wherein the ceramic composite bearing has a high wear resistance. The base ceramic particles in the step S1 are composed of 90-95% of silicon nitride powder, 3-5% of yttrium oxide powder and 1-3% of aluminum oxide powder by mass percentage; the surface layer addition amount of the graphene is 5-10wt% based on the mass of the base ceramic particles, the inner layer addition amount of the graphene is 1-3wt% based on the mass of the base ceramic particles; the binder is a composite binder composed of chitosan and hydroxyapatite at a mass ratio of 3:1, the addition amount of the binder in the inner layer premix is 2-4%, and the addition amount of the binder in the surface layer premix is 3-5%.

3. The method of claim 2, wherein the ceramic composite bearing has a hardness of at least 9 GPa. The silicon nitride powder of the base ceramic particles is in α phase and the content of the α phase is ≥92%, the particle size of the silicon nitride powder is 0.8-5μm, and the proportion of 1-3μm particles in the silicon nitride powder is ≥80%; the median diameter of the yttrium oxide powder of the base ceramic particles is 0.95-1.05μm; the purity of the aluminum oxide powder in the base ceramic particles is ≥99.9%, and the median diameter of the aluminum oxide powder is 0.75-0.85μm.

4. The method of claim 1, wherein the ceramic composite bearing has a high wear resistance. The inner layer premix in the step S1 is prepared by ball milling at a ball-to-material ratio of 10:1 at a rotating speed of 250-300r / min for 8-10h, and the surface layer premix is prepared by ball milling at a ball-to-material ratio of 12:1 at a rotating speed of 280-320r / min for 10-12h; the inner layer premix and the surface layer premix are dried and sieved after ball milling, the inner layer premix is sieved at a mesh size of 200 meshes, and the surface layer premix is sieved at a mesh size of 300 meshes.

5. The method of claim 1, wherein the ceramic composite bearing has a high wear resistance. The pre-pressing process of the inner layer premix in the step S2 is to pre-press the inner layer premix at 15-20MPa for 10-15min to form an inner layer green body; the surface layer premix is covered to a thickness of 1.0-1.5mm and then pre-pressed at 20-25MPa for 8-10min for the second time.

6. The method of claim 1, wherein the ceramic composite bearing has a high wear resistance. The alternating magnetic field parameters in the step S3 are 50-200Hz and 0.1-0.5T, and the pulse current parameters are 10-20kA and a duty cycle of 10-30%; the gradient sintering process is as follows: increasing the temperature from room temperature to 500℃ at a rate of 5℃ / min and keeping the temperature for 2h, then increasing the temperature to 1200℃ at a rate of 20℃ / min and keeping the temperature for 1h, then increasing the temperature to 1550℃ at a rate of 3℃ / min and keeping the temperature for 3-4h, and finally decreasing the temperature to 800℃ and then air cooling.

7. The method for preparing a high wear-resistant ceramic composite bearing according to claim 6, characterized in that: In step S3, the alternating magnetic field parameters are adjusted according to the bearing size requirements: when the inner ring diameter of the bearing is 20-30mm, the alternating magnetic field parameters are 50-70Hz / 0.15-0.25T; when the inner ring diameter of the bearing is 30-50mm, the alternating magnetic field parameters are 70-100Hz / 0.25-0.3T; when the outer ring diameter of the bearing is 50-70mm, the alternating magnetic field parameters are 100-150Hz / 0.35-0.45T; when the outer ring diameter of the bearing is 70-100mm, the alternating magnetic field parameters are 150-200Hz / 0.45-0.5T.

8. The method of claim 1, wherein the ceramic composite bearing has a high wear resistance. In step S4, the oxygen content of the nitrogen-oxygen mixed atmosphere is 1-3% and the total pressure is 0.1-0.12 MPa; the heat treatment process is as follows: heat up to 700-900℃ at 3-5℃ / min and hold for 0.5-1.5h, then cool with the furnace.

9. The method of claim 1, wherein the ceramic composite bearing has a high wear resistance. In step S5, Ti3C2T x The underlying deposition thickness is 50-100 nm, and the Ti3C2T x The deposition thickness of the hydroxyapatite composite top layer is 100-150 nm, of which Ti3C2T x The mass ratio of Ti3C2T to hydroxyapatite is 2:1; x The underlying layer and Ti3C2T x The hydroxyapatite composite top layer was deposited and then annealed at 300°C for 1 hour in a nitrogen atmosphere.

10. The method of claim 1, wherein the ceramic composite bearing has a high wear resistance. In step S6, grinding is performed using a 1200-1500 mesh diamond grinding wheel, and the surface roughness Ra is controlled to be ≤0.08μm; the cleaning is performed using an anhydrous ethanol and nitric acid mixture in a volume ratio of 9:1, which is ultrasonically cleaned for 15-20 minutes; the performance testing includes density testing and hardness testing.

Images