Bearing surface coating and preparation method thereof

Abstract

The invention belongs to the field of coating preparation, and particularly relates to a bearing surface coating and a preparation method thereof. The method comprises the following steps: 1) uniformly mixing an amine compound, a nonmetal simple substance and an inorganic salt in proportion to prepare a precursor; 2) uniformly mixing amino silicon oil, an organic mixed solvent and a catalyst in proportion to obtain a siloxane prepolymer, then performing epoxy group grafting and nanometer enhancement on the prepolymer, and performing reduced pressure filtration to prepare epoxy-organic silicon hybrid resin; and 3) mixing the epoxy-organic silicon hybrid resin, the modified graphene, the composite powder and the single crystal fiber in a gradient manner to prepare the bearing surface coating. Through material design, time-space ordered cooperation of a quadruple protection mechanism is achieved, the technical contradiction of electrical insulativity-hydrogen barrier property-thermal stability in the traditional technology is successfully broken through, the limit working condition adaptation window of the bearing is remarkably expanded, and long-term reliable operation under the high-temperature and high-speed environment with the high electric field and the critical hydrogen concentration is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of coating preparation, and particularly relates to a bearing surface coating and a preparation method thereof. BACKGROUND

[0002] The bearing surface engineering technology contains two core process routes: functional coating deposition and precise surface morphology control, both of which optimize tribological performance and structural stability through different mechanisms. Among them, the functional coating realizes the directional control of the interface performance by constructing a specific component film on the surface of the bearing substrate. The polytetrafluoroethylene coating provides an extremely low friction coefficient due to its unique low surface energy molecular structure; and the ceramic coating such as silicon nitride utilizes its high hardness and excellent wear resistance to significantly reduce the material transfer and surface degradation of the friction pair. These coating technologies significantly reduce energy loss and prolong the service life of bearings.

[0003] However, although the surface engineering technology has made great progress, the high-performance bearing field still faces three key technical bottlenecks: first, the problem of electric erosion damage is increasingly prominent. Under high-speed operating conditions, the thickness fluctuation of the fluid film between the bearing raceway and the rolling body causes transient changes in the current path, forming a micro-discharge circuit. Such electric erosion phenomenon is particularly serious in variable frequency drive systems, which can cause local melting and resolidification of the metal surface, forming a characteristic "pitted" morphology. Second, the risk of hydrogen embrittlement failure continues to exist. Hydrogen embrittlement phenomenon is the strength degradation and early failure caused by the invasion of hydrogen atoms into the metal lattice. Hydrogen atoms preferentially accumulate in dislocations, grain boundaries and other regions, forming high-pressure hydrogen bubbles or brittle hydrides with alloy elements, and causing micro-crack initiation. In the bearing service environment, the decomposition of lubricating oil additives, water vapor penetration and tribological chemical reactions can all serve as hydrogen sources. Typical bearing steel is extremely sensitive to hydrogen, and a small amount of hydrogen penetration can significantly reduce the fatigue life and fracture toughness. Third, the high-temperature stability limitation is obvious. The traditional PTFE coating appears significant softening and decomposition at a temperature threshold of more than 200 DEG C, which is much lower than the instantaneous flash temperature of high-speed heavy-load bearings. The fluorinated gas released by PTFE at high temperature forms fluoride with bearing steel, accelerating the corrosion and fatigue peeling of the material. At the same time, the shedding debris caused by the softening of the coating acts as a "third body" to participate in the wear process, which further aggravates the surface damage rate.

[0004] The core limitation of the existing surface engineering technology is that it cannot realize the synergistic optimization of "electrical insulation-hydrogen barrier-thermal stability". Ceramic coatings such as silicon nitride have excellent wear resistance and certain electrical insulation, but their micro-cracks and pores can still serve as a fast channel for hydrogen atom diffusion; while dense metal coatings with hydrogen barrier ability cannot meet the electrical insulation requirement. This mutual restriction of multi-dimensional technical indicators reflects that the traditional single-function-oriented coating design concept has been difficult to meet the comprehensive performance requirements of bearing systems under extreme working conditions, and a composite surface system based on multiple fields needs to be developed. SUMMARY

[0005] The technical scheme of the present application aims at the technical problems of electric erosion damage, hydrogen embrittlement and poor high-temperature stability of surface coating of conventional bearings, and provides a bearing surface coating and a preparation method thereof.

[0006] The main purpose of the present application is: 1. Blocking the discharge channel by dynamically filling the bearing micro-gap with organic composite materials.

[0007] 2. Strengthening the hydrogen resistance of the coating and inhibiting the hydrogen embrittlement of the bearing material.

[0008] 3. Constructing a high-temperature stable organic-inorganic lubrication network to reduce abrasion under abnormal working conditions.

[0009] 4. Strengthening the interfacial adhesion between the coating and the substrate to prevent high-temperature fatigue peeling.

[0010] To achieve the above-mentioned purposes, the present application adopts the following technical scheme.

[0011] A preparation method of a bearing surface coating, the method comprising: 1) uniformly mixing amine compounds, non-metallic elements and inorganic salts in proportion to prepare a precursor.

[0012] 2) uniformly mixing amino silicone oil, organic mixed solvents and catalysts in proportion to obtain a siloxane prepolymer, then performing epoxy group grafting and nano-enhancing on the prepolymer, and performing reduced pressure filtration to prepare an epoxy-silicone hybrid resin.

[0013] 3) gradient mixing the epoxy-silicone hybrid resin, modified graphene, composite powder and single crystal fiber to prepare a bearing surface coating.

[0014] As a preferred, the amine compound in step 1) is aniline monomer; the non-metallic element in step 1) is graphene; the inorganic salt in step 1) is ammonium persulfate; and the amine compound, non-metallic element and inorganic salt in step 1) are uniformly mixed in a mass ratio of (2.8-3.2):1:(9-10).

[0015] As a preferred, the preparation of the precursor in step 1) is low-temperature polymerization under the condition of nitrogen atmosphere and temperature of 0-10 ℃ for 8-16 h.

[0016] As a preferred, the amino silicone oil in step 2) has an ammonia value of 0.8-1.2 mmol / g; the organic mixed solvent in step 2) is a mixture of dimethylbenzene / n-butanol mixed solvents with a dimethylbenzene concentration of 45-55 wt%; the catalyst in step 2) is a titanate; and the amino silicone oil, organic mixed solvent and catalyst in step 2) are uniformly mixed in a volume ratio of (6-8):(2-3):0.01.

[0017] Preferably, the stirring temperature in step 2) is controlled at 60–65 °C, the stirring speed at 200–300 rpm, and the stirring time at 1–2 h.

[0018] Preferably, in step 2), the epoxy grafting involves adding 2 to 2.5 times the mass of amino silicone oil of bisphenol A type epoxy resin to the siloxane prepolymer and reacting it under a nitrogen atmosphere at a temperature of 80 to 90 °C for 2.5 to 3.5 h; in step 2), the nano-reinforcement involves adding 0.3 to 0.5 wt% of the siloxane prepolymer of trimethoxy-[3-(epoxyethylene methoxy)propyl]silane and reacting it at a temperature of 105 to 115 °C for 2 to 3 h.

[0019] Preferably, step 2) involves vacuum distillation for 60–90 min at an ambient temperature of 120–125 °C and a pressure of -0.10–-0.09 MPa, followed by filtration through a 5 μm metal mesh.

[0020] Preferably, the modified graphene in step 3) is prepared by the following method: graphene oxide is ultrasonically exfoliated in a 0.08–0.12 mol / L nitric acid aqueous solution for 30–50 min, and the ultrasonic exfoliation product is filtered out. The ultrasonic exfoliation product is mixed with ethylenediamine at a mass ratio of 1:(0.3–0.5), and reacted in a nitrogen atmosphere at a temperature of 80–85 °C for 4–5 h. After cooling to room temperature, 700–710 wt% of the ultrasonic exfoliation product in a 0.03–0.07 mol / L nickel chloride aqueous solution is added and ultrasonically treated for 30–50 min. Finally, a 0.08–0.12 mol / L sodium borohydride aqueous solution is added dropwise at a rate of 2 mL / min in an environment of 0–5 °C, and the reaction is continued for 1–1.5 h. The composite powder in step 3) is a molybdenum disulfide / nanodiamond composite powder with a molybdenum disulfide content of 70–78 wt%. The single crystal fiber in step 3) is a silicon carbide whisker.

[0021] Preferably, the gradient mixing process in step 3) is as follows: In the first stage, under the environmental conditions of 58-62 ℃ and 200-300 rpm, epoxy-organosilicon hybrid resin and modified graphene are mixed and stirred at a mass ratio of (10-15):1 for 30-60 min to obtain a premix; In the second stage, under the environmental conditions of vacuum degree ≤0.1 MPa, temperature 115-125 ℃ and rotation speed 1500-2000 rpm, 14-16 wt% of molybdenum disulfide / nanodiamond composite powder with a molybdenum disulfide content of 75 wt% and 4-6 wt% of silicon carbide whiskers are added and mixed and stirred for 30-60 min.

[0022] A bearing surface coating.

[0023] The core of the technical solution of this invention lies in the fact that a three-level protection system is formed by the flexible filling of organic resin, the chemical adsorption of hydrogen storage components and the thermal stability of inorganic reinforcing phase, which synergistically solves the chain failure problem of electro-erosion-hydrogen embrittlement-abrasion-stripping.

[0024] This technology utilizes polyaniline-coated graphene to construct a three-dimensional conductive elastic network, enabling dynamic control of electrical properties. The unique feature of this composite material design lies in its dynamic resistivity response: when the bearing micro-gap exceeds a critical threshold, the material resistivity drops sharply, exhibiting typical insulator-conductor transition behavior. This intelligent response stems from the conductive network reconstruction mechanism of graphene under mechanical strain. Through the local electric field homogenization effect, the gap voltage is controlled below 5 V, far below the air breakdown threshold. This design limits the discharge energy to within 0.1 mJ, significantly lower than the minimum energy threshold required for metal melting, fundamentally blocking the formation path of electrolytic erosion pits and effectively suppressing the occurrence of high-frequency pulsed discharges.

[0025] This technical solution is based on energy gradient design, utilizing nickel-modified graphene to construct a hierarchical hydrogen trapping system, achieving efficient capture and stable storage of diffusing hydrogen atoms / molecules, thereby effectively suppressing hydrogen embrittlement. This multi-level hydrogen trapping mechanism comprises two synergistic electron-energy levels. The primary trap mainly relies on surface physicochemical adsorption mechanisms. Oxygen-containing functional groups at the graphene edges and defect sites achieve initial hydrogen capture through weak hydrogen bond interactions. The polarity of the OH bonds in these functional groups generates a local electric field gradient, which interacts electrostatically with the quadrupole moment of hydrogen molecules. This interaction falls within the category of reversible physicoadsorption. This process exhibits rapid kinetics, low adsorption activation energy, and a "rapid response" to hydrogen in the environment. Its main function is to impede hydrogen diffusion and guide it to secondary trap sites. Although the primary trap formed by this weak interaction has a fast adsorption rate, its binding energy is low, making it unable to permanently fix hydrogen atoms. Its main function is to act as a "dynamic trapping network," reducing the effective diffusion coefficient of hydrogen in the material and creating conditions for subsequent deep trapping. Furthermore, this reversible adsorption also provides a buffering effect, avoiding stress concentration caused by sudden changes in hydrogen concentration. Secondary traps primarily rely on a metal-hydrogen co-bonding mechanism. The active sites formed by nickel nanoparticles on the graphene surface constitute higher-energy secondary traps, achieving stable hydrogen capture. The partially filled d orbitals of nickel atoms interact with the σ antibonding orbitals of hydrogen molecules to form a Kubas-type interaction—a unique bonding mode between physisorption and chemisorption. This interaction leads to a decrease in the d electron density of nickel and an increase in the bond length of hydrogen molecules, causing electrons to partially transfer from the metal d orbitals to the HH antibonding orbitals, thus "activating" the hydrogen molecules without complete dissociation. The binding energy of this nickel-hydrogen interaction is significantly higher than that of primary traps but lower than that of traditional chemisorption, forming an energy "deep well, shallow valley" structure. This bonding energy range allows hydrogen atoms to be firmly captured without entering the metal lattice, while also enabling controlled release under specific conditions, avoiding the formation of hydride phases and brittle fracture. A hydrogen-rich region forms within a 1–2 nm range around the nickel atoms, with local hydrogen concentrations reaching 15–20 times that of the matrix. This nanoscale regulation of hydrogen distribution effectively prevents hydrogen accumulation in sensitive regions such as grain boundaries and dislocations, fundamentally suppressing the initiation of hydrogen embrittlement cracks.

[0026] This invention utilizes a two-stage trap system to achieve comprehensive hydrogen management through the coordinated operation of energy ladders and spatial distribution. The widespread distribution of primary traps forms a spatial "capture network," guiding scattered hydrogen molecules to secondary traps. The secondary traps provide sufficiently deep energy potential wells to ensure that captured hydrogen is not released back into the matrix. This hierarchical design constructs a "one-way valve" mechanism for hydrogen diffusion from an energy perspective: the migration path of hydrogen atoms in the material is redirected, preferentially entering traps rather than accumulating in sensitive regions. By controlling the size and distribution density of nickel nanoparticles, the spatial distribution and energy depth of the secondary traps can be precisely controlled, enabling customized designs for different hydrogen concentrations and service environments.

[0027] The lubrication system is designed with a temperature-driven, stepped phase change path to achieve lubrication protection across the entire temperature range. The core of the system is a molybdenum disulfide / nanodiamond composite structure, where nanodiamonds are embedded in the molybdenum disulfide layers via carbon-molybdenum covalent bonds, inhibiting high-temperature oxidation and exfoliation. As the temperature increases, the material undergoes a three-stage transformation: at room temperature, molybdenum disulfide provides basic lubrication; at 300°C, it partially transforms into molybdenum trioxide; and at 450°C, it further reacts with silicon to form a molybdenum-silicon-oxygen glass phase. This glass phase maintains a stable ultra-low coefficient of friction even at 400°C, demonstrating improved temperature stability of the coefficient of friction compared to traditional PTFE coatings.

[0028] In the chemical bonding pathway, the alkoxy groups of the silane coupling agent undergo a condensation reaction with the hydroxyl groups on the metal surface, forming metal-oxygen-silicon covalent bonds, providing molecular-level interfacial adhesion. In the mechanical anchoring pathway, silicon carbide whiskers with an aspect ratio exceeding 20 penetrate the metal matrix, forming a three-dimensional anchoring network that bears over 70% of the shear stress. Matching the coefficient of thermal expansion is crucial for interfacial stability: the coefficient of thermal expansion of the coating material is precisely matched to that of the bearing steel, effectively suppressing thermal cycling delamination.

[0029] The greatest innovation of this invention lies in achieving a chain response and synergistic effect of the protection mechanism, specifically manifested in four levels of dynamic synergy: First, synergistic suppression of electro-erosion and hydrogen embrittlement: the conductive network blocks discharge, reducing surface molten pits. When the diameter of the molten pit is less than 2 μm, the hydrogen permeation rate is simultaneously reduced to one-tenth of its original value. This synergistic effect cuts off the failure chain of "electro-erosion → hydrogen permeation → hydrogen embrittlement" at its source.

[0030] II. Hydrogen embrittlement suppression-interface enhancement linkage: Multi-level traps control the lattice hydrogen concentration to below 2 ppm, which improves the toughness of the coating-substrate interface, makes the elastic modulus gradient in the interface region more gradual, and reduces the stress concentration effect.

[0031] III. High-Temperature Lubrication-Anti-Peel Synergy: The molybdenum-silicon-oxygen glass film formed at high temperatures works synergistically with nanodiamonds to control the wear rate at an ultra-low level. At the same time, the dual effects of whisker anchoring and chemical bonding greatly improve the interfacial bonding strength, and the coating peel area is still less than 5% after tens of millions of thermal stress cycles.

[0032] III. Dynamic Response Chain under Extreme Conditions: In the rapid cooling cycle test, the system exhibited a three-stage synergistic response: In the thermal shock stage, the shrinkage rate of the resin matrix triggered the whisker compressive stress shielding effect, causing a decrease in the stress peak; in the lubrication maintenance stage, molybdenum disulfide decomposed into molybdenum trioxide to absorb heat, effectively buffering the temperature rise rate; in the high-temperature stage, magnesium hydride thermally activated and decomposed to release hydrogen atoms, preventing the accumulation of brittle phases. In contrast, traditional PTFE coatings failed after only 3 cycles.

[0033] Furthermore, in this invention, trimethoxy-[3-(epoxyethylene methoxy)propyl]silane, as an organic-inorganic hybrid nanounit, plays a crucial reinforcing role in the coating system. After gradient heat treatment, trimethoxy-[3-(epoxyethylene methoxy)propyl]silane forms a unique cage-like structure and organic side group R design, achieving structural control from the molecular to the nanoscale. It forms a strong interaction with the epoxy resin matrix, while the inorganic cage-like framework effectively restricts polymer chain movement, significantly increasing the glass transition temperature of the system. Trimethoxy-[3-(epoxyethylene methoxy)propyl]silane effectively terminates the development of resin microcrack tips, promotes stress redistribution by inducing crazes or shear band formation, and improves material toughness. Specifically functionalized trimethoxy-[3-(epoxyethylene methoxy)propyl]silane molecules participate in the resin crosslinking reaction through their active groups (such as epoxy, amino, and hydroxyl groups), anchoring themselves in the molecular network via covalent bonds. This design not only increases the crosslinking density but also introduces heat-resistant Si-O bonds, raising the resin's thermal decomposition temperature. The introduction of trimethoxy-[3-(epoxyethylene methoxy)propyl]silane significantly improves the epoxy resin's resistance to thermal oxidative decomposition and increases its oxygen index. After high-temperature combustion, the SiO2 formed by the decomposition of trimethoxy-[3-(epoxyethylene methoxy)propyl]silane forms a dense protective layer on the material surface, slowing down the combustion rate and reducing the heat release rate, exhibiting excellent flame-retardant synergistic effects.

[0034] For the coating system of this invention, it is obvious that biphase graphene is used. This phase refers to two different types of graphene. The primary purpose of the ordinary graphene (i.e., the graphene used in step 1) is, as mentioned above, to construct a composite synergistic conductive system, which, in conjunction with polyaniline, achieves dynamic regulation. However, for the technical solution of this invention, there is another important purpose: to form a synergistic effect with the subsequently added modified graphene. Firstly, the conductive network of ordinary graphene can promote the rapid transfer of electrons to the hydrogen storage sites of modified graphene, enhancing the Kubas interaction effect. Secondly, ordinary graphene can form coordination bonds with modified graphene, effectively dispersing the modified graphene and preventing stress concentration caused by modified graphene agglomerates. However, the hydrogen storage sites of modified graphene can also disrupt the continuous structure of graphene to some extent; therefore, the timing and relative amount of both need to be strictly controlled.

[0035] The advantages of this invention are as follows: This invention achieves a spatiotemporally ordered synergy of four protective mechanisms through material design: spatially, it forms a gradient protection of a micron-level conductive network → a nanometer-level hydrogen trap → an atomic-level interfacial bond; temporally, it establishes a dynamic response chain of room-temperature anti-electrolytic corrosion → mid-temperature hydrogen embrittlement prevention → high-temperature lubrication preservation → thermal shock anti-peeling. It successfully overcomes the technical contradiction of "electrical insulation-hydrogen barrier-thermal stability" in traditional technologies, significantly expanding the bearing's extreme operating condition adaptability window and achieving long-term reliable operation under strong electric fields, critical hydrogen concentrations, and high-temperature, high-speed environments. Detailed Implementation

[0036] The present invention will be further described clearly and in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0037] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0038] Example 1: A method for preparing a bearing surface coating, the method comprising: 1) mixing aniline monomer, graphene and ammonium persulfate in a mass ratio of 2.8:1:9 and polymerizing at low temperature for 16 h under a nitrogen atmosphere and a temperature of 0 °C to prepare a precursor.

[0039] 2) Amino silicone oil with an ammonia value of 0.8 mmol / g, 50% xylene / n-butanol mixed solvent, and titanate were mixed uniformly at a volume ratio of 6:2:0.01 and stirred for 2 h at 60 ℃ and 200 rpm to obtain a siloxane prepolymer. Then, bisphenol A type epoxy resin with a mass of 2 times that of amino silicone oil was added to the siloxane prepolymer and reacted for 2.5 h at 80 ℃ under a nitrogen atmosphere to perform epoxy grafting. 0.3 wt% of trimethoxy-[3-(epoxyethylene methoxy)propyl]silane was added and reacted for 3 h at 105 ℃ to perform nano-reinforcement. The mixture was then distilled under reduced pressure for 90 min at 120 ℃ and -0.10 MPa and filtered through a 5 μm metal filter to prepare an epoxy-organosilicon hybrid resin.

[0040] 3) After ultrasonically exfoliating graphene oxide in a 0.1 mol / L nitric acid aqueous solution for 30 min, the ultrasonic exfoliation product was filtered out. The ultrasonic exfoliation product was mixed with ethylenediamine at a mass ratio of 1:0.3 and reacted at 80 °C under a nitrogen atmosphere for 5 h. After cooling to room temperature in the third step, 700 wt% of the ultrasonic exfoliation product in a 0.05 mol / L nickel chloride aqueous solution was added and ultrasonically treated for 30 min. Finally, 0.1 mol / L sodium borohydride aqueous solution was added dropwise at a rate of 2 mL / min under 0 °C and the reaction was continued for 1.5 h to prepare modified graphene.

[0041] 4) Gradual addition of epoxy-organosilicon hybrid resin, modified graphene, molybdenum disulfide / nanodiamond composite powder with a molybdenum disulfide content of 75 wt%, and silicon carbide whiskers. In the first stage, under the conditions of 58 ℃ and 200 rpm, epoxy-organosilicon hybrid resin and modified graphene are mixed and stirred at a mass ratio of 20:1 for 60 min to obtain a premix. In the second stage, under the conditions of 0.1 MPa vacuum, 115 ℃ temperature, and 1500 rpm, 14 wt% of molybdenum disulfide / nanodiamond composite powder with a molybdenum disulfide content of 75 wt% and 4 wt% silicon carbide whiskers are added according to the mass of the premix, and the mixture is stirred for 60 min to prepare a bearing surface coating.

[0042] 5) After coating the bearing surface, the coating is cured in stages: the first stage is kept at 80 ℃ for 1 h; the second stage is kept at 150 ℃ for 2 h; the third stage is kept at 220 ℃ for 1 h; and the fourth stage is kept at 300 ℃ for 0.5 h to make the coated bearing.

[0043] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are shown in Table 1 below.

[0044] Electrolytic corrosion resistance test: In step 4), the coating thickness is 20 μm. A micro-gap array with widths of 10 μm / 20 μm / 50 μm is machined. Under the environmental conditions of 50% humidity and 200 μm electrode spacing, a DC voltage of 5kV is preloaded, held for 30 seconds, and then increased at a rate of 100V / s to break down the coating. The breakdown voltage and discharge current are recorded.

[0045] High-temperature tribological test: In step 4), the coating thickness is 20 μm. Under the environmental conditions of initial temperature of 25 ℃, heating rate of 10℃ / min, sliding speed of 0.2 m / s, and load of 10 N, Si3N4 balls with a diameter of 6.35 mm and surface roughness of 0.05 μm are used as the grinding pair. The friction coefficient is recorded at intervals of 300 ℃, referring to the ASTM D 4060 Taber wear resistance test method.

[0046] Peel resistance test: An accelerated fatigue program was set up with the following conditions: radial load cycle of 5–25 kN, frequency of 20 Hz; temperature cycle range of 25 ℃–300 ℃, dwell time of 10 min; and rotational speed gradient of 1000–5000 rpm, each level held for 30 min. The test was stopped when the coating peel area exceeded 5%, and the number of cycles was recorded.

[0047] Table 1: Performance Characterization Results

[0048] In addition, hydrogen embrittlement sensitivity was tested using 4340 high-strength steel substrate. The specific steps and characterization results are shown in Table 2 below. A 4340 high-strength steel substrate with a diameter of 6 mm and a length of 30 mm was charged with hydrogen for 48 h at an ambient temperature of 25 ℃ and a potential of -1.2 V. Subsequently, a slow strain rate test was conducted in an air environment at room temperature, and the cross-sectional reduction rate and catalytic index of the substrate were calculated.

[0049] Table 2: Performance Characterization Results

[0050] Analysis of the characterization results in Tables 1 and 2 shows that the bearing surface coating prepared in this example exhibits excellent comprehensive performance. Electrolytic corrosion resistance testing reveals that the breakdown voltage of the coating in the micro-gap array is significantly improved. Compared to the uncoated sample, the increased breakdown voltage effectively blocks the discharge channel and reduces the formation of surface molten pits. Simultaneously, the discharge current is effectively controlled, preventing material damage caused by localized high temperatures.

[0051] High-temperature tribological testing results show that the coating maintains a stable ultra-low coefficient of friction even at 300℃, indicating that the lubrication system successfully achieves lubrication protection across the entire temperature range. At room temperature, molybdenum disulfide provides effective solid lubrication for the layered structure; when the temperature rises to 300℃, the composite structure formed by nanodiamonds and molybdenum disulfide inhibits the oxidation-induced increase in the coefficient of friction. At 400℃, an amorphous glassy phase film rich in Si, Mo, and O elements is formed in the friction region, forming a molybdenum-silicon-oxygen glassy phase with unique shear interface characteristics, providing a stable low-friction interface and forming an ideal friction interface with "moderate hardness and good elasticity." This combination of characteristics is key to achieving stable low friction at high temperatures. In addition, nanodiamond particles form a micro-lubricating bearing effect during high-temperature friction, further reducing friction and wear rate, realizing a composite lubrication mechanism of "film lubrication-nano-bearing."

[0052] Peel resistance test results show that the coating, after 10... 7 The fact that the peeling area remained less than 5% after two thermal stress cycles demonstrates the remarkable effectiveness of the interface reinforcement strategy. The interface failure mode shifted from the traditional "brittle sudden failure" to "progressive tough failure," indicating the formation of an energy-absorbing interface structure. The composite interface of "chemical bonding-mechanical anchoring" can reduce the stress concentration factor under thermal cycling stress, effectively inhibiting the initiation and propagation of interface cracks. The thermal expansion coefficient of the coating system is precisely matched with that of the bearing steel. This design achieves a thermal stress self-balancing effect, maintaining the residual stress in the interface region below 150 MPa during thermal cycling, far below the interface bonding strength, which fundamentally ensures the long-term stability of the interface. Simultaneously, the presence of silicon carbide whiskers provides stress shielding and crack deflection effects, effectively preventing rapid propagation of microcracks even under microcrack initiation conditions, ensuring the structural integrity of the coating under extreme thermal cycling conditions.

[0053] In hydrogen embrittlement sensitivity testing, slow strain rate tests on 4340 high-strength steel substrates after hydrogen purging showed that the substrate coated with the coating of this invention exhibited a significantly increased reduction in area and a markedly decreased catalytic index, indicating that the coating effectively inhibits hydrogen embrittlement and improves the substrate's toughness and resistance to hydrogen embrittlement. The traps in the coating effectively capture penetrating hydrogen atoms, controlling the lattice hydrogen concentration at an extremely low level, effectively suppressing the initiation and propagation of hydrogen embrittlement cracks.

[0054] Example 2: A method for preparing a bearing surface coating, the method comprising: 1) mixing aniline monomer, graphene and ammonium persulfate in a mass ratio of 3:1:9.5 and polymerizing at low temperature for 12 h under a nitrogen atmosphere and a temperature of 5 °C to prepare a precursor.

[0055] 2) Ammonia-containing silicone oil with an ammonia value of 1 mmol / g, 50% xylene / n-butanol mixed solvent, and titanate were mixed uniformly at a volume ratio of 7:2.5:0.01. The mixture was stirred for 1.5 h at 63 ℃ and 250 rpm to obtain a siloxane prepolymer. Then, 2.25 times the mass of amino silicone oil bisphenol A epoxy resin was added to the siloxane prepolymer. The mixture was reacted for 3 h at 85 ℃ under a nitrogen atmosphere to perform epoxy grafting. 0.4 wt% of the mass of the siloxane prepolymer trimethoxy-[3-(epoxyethylene methoxy)propyl]silane was added. The mixture was reacted for 2.5 h at 110 ℃ to perform nano-reinforcement. The mixture was then distilled under reduced pressure for 75 min at 123 ℃ and -0.095 MPa. Finally, the mixture was filtered through a 5 μm metal filter to prepare an epoxy-organosilicon hybrid resin.

[0056] 3) After ultrasonically exfoliating graphene oxide in a 0.1 mol / L nitric acid aqueous solution for 40 min, the ultrasonic exfoliation product was filtered out. The ultrasonic exfoliation product was mixed with ethylenediamine at a mass ratio of 1:0.4 and reacted at 83 ℃ under a nitrogen atmosphere for 4.5 h. After cooling to room temperature in the third step, 705 wt% of the ultrasonic exfoliation product in a 0.05 mol / L nickel chloride aqueous solution was added and ultrasonically treated for 40 min. Finally, 0.1 mol / L sodium borohydride aqueous solution was added dropwise at a rate of 2 mL / min at 3 ℃ and the reaction was continued for 1.25 h to prepare modified graphene.

[0057] 4) Gradual addition of epoxy-organosilicon hybrid resin, 50% palladium / magnesium modified graphene, 75wt% molybdenum disulfide / nanodiamond composite powder, and silicon carbide whiskers. In the first stage, under the conditions of 60 ℃ and 250 rpm, epoxy-organosilicon hybrid resin and modified graphene are mixed and stirred at a mass ratio of 23:1 for 45 min to obtain a premix. In the second stage, under the conditions of 0.1 MPa vacuum, 120 ℃ temperature, and 1750 rpm, 15 wt% of the 75 wt% molybdenum disulfide / nanodiamond composite powder and 5 wt% silicon carbide whiskers are added according to the mass of the premix, and the mixture is stirred for 45 min to prepare a bearing surface coating.

[0058] 5) After coating the bearing surface, the coating is cured in stages: the first stage is kept at 80 ℃ for 1.5 h; the second stage is kept at 150 ℃ for 2.5 h; the third stage is kept at 220 ℃ for 1.5 h; and the fourth stage is kept at 300 ℃ for 0.5 h to produce the coated bearing.

[0059] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are shown in Table 3 below.

[0060] Electrolytic corrosion resistance test: In step 4), the coating thickness is 20 μm. A micro-gap array with widths of 10 μm / 20 μm / 50 μm is machined. Under the environmental conditions of 50% humidity and 200 μm electrode spacing, a DC voltage of 5kV is preloaded, held for 30 seconds, and then increased at a rate of 100V / s to break down the coating. The breakdown voltage and discharge current are recorded.

[0061] Hydrogen embrittlement resistance test: A dual electrolytic cell was prepared, with the anolyte containing a 0.1 mol / L NaOH solution and a constant current density of 0.2 mA / cm². 2 The cathode cell contained a 0.1 mol / L sulfuric acid solution, and high-purity hydrogen gas was passed through it. The coated sample was used as a diaphragm with an effective area of ​​1 cm². 2 A hydrogen pressure of 0.5 MPa is applied to the cathode side, and the osmosis current is recorded on the anode side. The hydrogen permeability coefficient is calculated based on Faraday's law.

[0062] High-temperature tribological test: In step 4), the coating thickness is 20 μm. Under the environmental conditions of initial temperature of 25 ℃, heating rate of 10℃ / min, sliding speed of 0.2 m / s, and load of 10 N, Si3N4 balls with a diameter of 6.35 mm and surface roughness of 0.05 μm are used as the grinding pair. The friction coefficient is recorded at intervals of 300 ℃, referring to the ASTM D 4060 Taber wear resistance test method.

[0063] Peel resistance test: An accelerated fatigue program was set up with the following conditions: radial load cycle of 5–25 kN, frequency of 20 Hz; temperature cycle range of 25 ℃–300 ℃, dwell time of 10 min; and rotational speed gradient of 1000–5000 rpm, each level held for 30 min. The test was stopped when the coating peel area exceeded 5%, and the number of cycles was recorded.

[0064] Table 3: Performance Characterization Results

[0065] In addition, hydrogen embrittlement sensitivity was tested using 4340 high-strength steel substrate. The specific steps and characterization results are shown in Table 4 below. A 4340 high-strength steel substrate with a diameter of 6 mm and a length of 30 mm was charged with hydrogen for 48 h at an ambient temperature of 25 ℃ and a potential of -1.2 V. Subsequently, a slow strain rate test was conducted in an air environment at room temperature, and the cross-sectional reduction rate and catalytic index of the substrate were calculated.

[0066] Table 4: Performance Characterization Results

[0067] Analysis of the characterization results in Tables 3-4 shows that the bearing surface coating prepared by this invention exhibits excellent performance in terms of anti-electrolytic corrosion, anti-hydrogen embrittlement, high-temperature lubrication, and anti-peeling. It successfully overcomes the technical contradictions in traditional technologies and provides a strong guarantee for the long-term reliable operation of bearings under strong electric fields, critical hydrogen concentrations, and high-temperature and high-speed environments.

[0068] Example 3: A method for preparing a bearing surface coating, the method comprising: 1) mixing aniline monomer, graphene and ammonium persulfate in a mass ratio of 3.2:1:10, and polymerizing at low temperature for 8 h under a nitrogen atmosphere and a temperature of 10 °C to prepare a precursor.

[0069] 2) Amino silicone oil with an ammonia value of 1.2 mmol / g, 50% xylene / n-butanol mixed solvent, and titanate were mixed evenly at a volume ratio of 8:3:0.01 and stirred for 1 h at 65 ℃ and 300 rpm to obtain a siloxane prepolymer. Then, bisphenol A type epoxy resin of 2.5 times the mass of amino silicone oil was added to the siloxane prepolymer and reacted for 2.5 h at 90 ℃ under a nitrogen atmosphere to perform epoxy grafting. 0.5 wt% of trimethoxy-[3-(epoxyethylene methoxy)propyl]silane was added and reacted for 2 h at 115 ℃ to perform nano-reinforcement. The mixture was then distilled under reduced pressure for 60 min at 125 ℃ and -0.09 MPa and filtered through a 5 μm metal filter to prepare an epoxy-organosilicon hybrid resin.

[0070] 3) After ultrasonically exfoliating graphene oxide in a 0.1 mol / L nitric acid aqueous solution for 50 min, the ultrasonic exfoliation product was filtered out. The ultrasonic exfoliation product was mixed with ethylenediamine at a mass ratio of 1:0.5 and reacted at 85 ℃ under a nitrogen atmosphere for 4 h. After cooling to room temperature in the third step, 710 wt% of the ultrasonic exfoliation product in a 0.05 mol / L nickel chloride aqueous solution was added and ultrasonically treated for 50 min. Finally, 0.1 mol / L sodium borohydride aqueous solution was added dropwise at a rate of 2 mL / min at 5 ℃ and the reaction was continued for 1 h to prepare modified graphene.

[0071] 4) Gradual addition of epoxy-organosilicon hybrid resin, 50% palladium / magnesium modified graphene, 75wt% molybdenum disulfide / nanodiamond composite powder, and silicon carbide whiskers. In the first stage, under the conditions of 62℃ and 300rpm, epoxy-organosilicon hybrid resin and modified graphene are mixed and stirred at a mass ratio of 25:1 for 30 min to obtain a premix. In the second stage, under the conditions of 0.1 MPa vacuum, 125℃ temperature, and 2000rpm, 16wt% of the 75wt% molybdenum disulfide / nanodiamond composite powder and 6wt% silicon carbide whiskers are added according to the mass of the premix, and the mixture is stirred for 30 min to prepare a bearing surface coating.

[0072] 5) After coating the bearing surface, the coating is cured in stages: the first stage is kept at 80 ℃ for 0.5 h; the second stage is kept at 150 ℃ for 1.5 h; the third stage is kept at 220 ℃ for 0.5 h; and the fourth stage is kept at 300 ℃ for 0.5 h to produce the coated bearing.

[0073] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are shown in Table 5 below.

[0074] Electrolytic corrosion resistance test: In step 4), the coating thickness is 20 μm. A micro-gap array with widths of 10 μm / 20 μm / 50 μm is machined. Under the environmental conditions of 50% humidity and 200 μm electrode spacing, a DC voltage of 5kV is preloaded, held for 30 seconds, and then increased at a rate of 100V / s to break down the coating. The breakdown voltage and discharge current are recorded.

[0075] Hydrogen embrittlement resistance test: A dual electrolytic cell was prepared, with the anolyte containing a 0.1 mol / L NaOH solution and a constant current density of 0.2 mA / cm². 2 The cathode cell contained a 0.1 mol / L sulfuric acid solution, and high-purity hydrogen gas was passed through it. The coated sample was used as a diaphragm with an effective area of ​​1 cm². 2 A hydrogen pressure of 0.5 MPa is applied to the cathode side, and the osmosis current is recorded on the anode side. The hydrogen permeability coefficient is calculated based on Faraday's law.

[0076] High-temperature tribological test: In step 4), the coating thickness is 20 μm. Under the environmental conditions of initial temperature of 25 ℃, heating rate of 10℃ / min, sliding speed of 0.2 m / s, and load of 10 N, Si3N4 balls with a diameter of 6.35 mm and surface roughness of 0.05 μm are used as the grinding pair. The friction coefficient is recorded at intervals of 300 ℃, referring to the ASTM D 4060 Taber wear resistance test method.

[0077] Peel resistance test: An accelerated fatigue program was set up with the following conditions: radial load cycle of 5–25 kN, frequency of 20 Hz; temperature cycle range of 25 ℃–300 ℃, dwell time of 10 min; and rotational speed gradient of 1000–5000 rpm, each level held for 30 min. The test was stopped when the coating peel area exceeded 5%, and the number of cycles was recorded.

[0078] Table 5: Performance Characterization Results

[0079] In addition, hydrogen embrittlement sensitivity was tested using 4340 high-strength steel substrate. The specific steps and characterization results are shown in Table 6 below. A 4340 high-strength steel substrate with a diameter of 6 mm and a length of 30 mm was charged with hydrogen for 48 h at an ambient temperature of 25 ℃ and a potential of -1.2 V. Subsequently, a slow strain rate test was conducted in an air environment at room temperature, and the cross-sectional reduction rate and catalytic index of the substrate were calculated.

[0080] Table 6: Performance Characterization Results

[0081] Analysis of the characterization results in Tables 5 and 6 shows that the bearing surface coating prepared by this invention exhibits excellent performance in terms of anti-electrolytic corrosion, anti-hydrogen embrittlement, high-temperature lubrication, and anti-peeling. It successfully overcomes the technical contradictions in traditional technologies and provides a strong guarantee for the long-term reliable operation of bearings in strong electric fields, critical hydrogen concentrations, and high-temperature and high-speed environments.

[0082] Comparative Example 1: Based on Example 2, this example only modifies the reinforcing material; the remaining steps are the same as in Example 2. Specific settings are shown in Table 7 below.

[0083] Table 7: Process Adjustment Comparison Table

[0084] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in Table 8 below.

[0085] Table 8: Performance Characterization Results

[0086] In addition, hydrogen embrittlement sensitivity was tested using 4340 high-strength steel substrate, and the specific characterization results are shown in Table 9 below.

[0087] Table 9: Performance Characterization Results

[0088] Analysis of the characterization results in Tables 8-9 shows that the bearing surface coating prepared in this comparative example exhibits certain basic functionalities in terms of anti-electrolytic corrosion and anti-peeling properties, but shows significant deterioration in two key dimensions: anti-hydrogen embrittlement and high-temperature lubrication performance. In particular, the increased sensitivity to hydrogen embrittlement poses a potential risk to the reliability of the material in service.

[0089] The D1-1 (unmodified graphene) group exhibited slightly better electrical insulation performance than Example 2 in the dielectric breakdown test, with a reduced electrolytic current. This phenomenon stems from the simplification of the conductive network structure, resulting in a coating that exhibits homogeneous electrical insulation properties. However, the electric field response of the D1-1 sample lacks adaptive characteristics. Local high electric field regions cannot shunt energy through conductive pathways, leading to a highly uneven electric field distribution. This improvement in static insulation performance actually sacrifices the ability to control the dynamic electric field.

[0090] In contrast, the electrolytic current of the D1-2 group (excessive modified graphene) surged to 3.5 times that of Example 2, due to the formation of a continuous conductive percolation network by the excessive nickel-modified graphene (Ni@GNs). When the Ni@GNs content exceeds the critical percolation threshold, the nanosheet spacing shortens, falling below the effective electron tunneling distance, thus forming large-scale conductive clusters. These clusters become preferential discharge channels under the influence of an electric field, significantly reducing the coating's electric field withstand capability and lowering the breakdown voltage. This result verifies the "threshold effect" of the amount of modified graphene added on electrical properties—appropriate addition provides adaptive electric field regulation, while excessive addition leads to the collapse of the coating's electrical insulation function.

[0091] Group D1-1 exhibited the most significant degradation in hydrogen embrittlement sensitivity testing, with a hydrogen embrittlement sensitivity index far exceeding that of Example 2. This severe degradation is attributed to the complete absence of a hydrogen trapping system. Hydrogen permeation testing showed that the hydrogen diffusion coefficient of sample D1-1 was approximately two orders of magnitude higher than that of Example 2, indicating that hydrogen atoms migrated almost unimpeded within the material. The multi-level hydrogen trapping function formed by the modified graphene in Example 2 was completely lost: the weak hydrogen bond adsorption provided by the oxygen-containing functional groups at the graphene edge was missing; more critically, the Kubas interaction between nickel nanoparticles and hydrogen molecules was lost, making chemical capture and stable storage of diffusing hydrogen impossible. In contrast, although D1-2 contained an excess of modified graphene, the formation of aggregates significantly reduced the effective hydrogen absorption surface area, and the active sites of nickel nanoparticles within the aggregates had difficulty contacting hydrogen molecules, resulting in an effective hydrogen storage capacity of only about 35% of the theoretical value. This "agglomeration effect" led to a highly uneven distribution of hydrogen traps, forming localized high hydrogen concentration regions, which became preferential sites for hydrogen embrittlement initiation.

[0092] In high-temperature tribological performance testing, the coefficient of friction of sample D1-1 increased sharply at 300 °C, and the wear rate increased by about an order of magnitude. This degradation stemmed from the lack of an effective lubricant phase transfer mechanism. In Example 2, the graphene sheets and lubricant worked synergistically to form a stable transfer film; however, group D1-1 lacked the synergistic protective effects of graphene's "nano-bearing" effect and "inhibition of lubricant oxidation," resulting in a significant increase in the direct metal-to-friction interface area.

[0093] Groups D1-2 exhibited significant fluctuations in the coefficient of friction during high-temperature friction tests. This is attributed to the disruption of the continuity and homogeneity of the friction interface by graphene agglomerates. Excess graphene forms large agglomerates during friction, which cannot effectively embed into the contact interface and instead become "third-body abrasive particles," exacerbating wear. Simultaneously, the agglomerates hinder the uniform distribution of lubricant at the contact interface, leading to an unstable friction state characterized by alternating "dry lubrication" and "liquid lubrication."

[0094] The coating exhibits critical insulation characteristics under voltage gradient conditions, with a breakdown voltage reaching a moderate insulation level. Interfacial adhesion testing shows acceptable basic interfacial stability. These performance indicators suggest that the coating provides basic electrical insulation protection and structural stability under normal service conditions, but is close to the application critical lower limit.

[0095] The comparative coating exhibited significant defects in hydrogen embrittlement sensitivity tests. Slow strain rate tensile tests showed a significantly higher embrittlement index than Example 2, indicating a markedly enhanced deterioration effect of hydrogen on the material's plasticity. From a materials science perspective, the microscopic mechanism of increased hydrogen embrittlement sensitivity can be explained as follows: First, hydrogen atoms lower the Peierls-Nabarro energy barrier for dislocation motion within the material, enhancing the local slip capability of dislocations. Particularly in stress concentration regions, hydrogen-dislocation interactions lead to a local surge in dislocation density, forming strain localization bands. These regions become preferential sites for microcrack nucleation. Simultaneously, hydrogen accumulation at grain boundaries and second-phase interfaces lowers the interfacial binding energy, causing grain boundaries that would normally require high energy to separate to crack under lower stress. Hydrogen directly weakens the metallic bond strength by reducing the electron density of Fe-Fe bonds. Locally high-concentration hydrogen regions promote the formation of metastable phases with different lattice constants and mechanical properties, resulting in stress concentration at the interfaces and accelerating crack propagation.

[0096] Further observation and analysis of the fracture surface microstructure revealed that 85% of the fracture surfaces in the hydrogen-filled samples exhibited intergranular fracture characteristics, a stark contrast to the ductile fracture surfaces of the unfilled samples. Key microscopic fracture surface morphology features included: 1) Significantly reduced dimple depth: The dimple depth in the unfilled samples was generally greater than 5 μm, exhibiting a typical "deep cup-cone" morphology; while the dimple depth in the hydrogen-filled samples was generally less than 1 μm, exhibiting a "shallow disc" shape, indicating a severe reduction in plastic deformation capacity. 2) Numerous secondary cracks appeared: A large number of secondary cracks nearly perpendicular to the main crack were observed on the fracture surface of the hydrogen-filled samples. These cracks mainly propagated along grain boundaries, indicating that hydrogen enrichment at grain boundaries led to grain boundary strength degradation. 3) Significantly reduced reduction in area: The reduction in area of ​​the hydrogen-filled samples was only about 40% of that of the unfilled samples, indicating a severe deficiency in the material's plasticity reserve, which is directly related to the localization of plastic deformation caused by hydrogen. 4) Crack origin at inclusions: Fracture analysis showed that multiple cracks originated around micron-sized inclusions. The hydrogen content in these areas was about 3 to 5 times that of the matrix, confirming that the inclusion-matrix interface is a site where hydrogen is preferentially enriched.

[0097] The fundamental reason for the deterioration of the hydrogen embrittlement resistance of the comparative coating lies in its lack of an effective hydrogen trapping system and hydrogen diffusion barrier capability. Highly diffusible hydrogen atoms in the material can freely migrate to regions with high stress triaxiality, such as crack tips, grain boundaries, and around inclusions, causing the local hydrogen concentration to reach a critical value and triggering the aforementioned hydrogen embrittlement mechanism. The multi-level hydrogen trapping system designed in Example 2 can effectively capture and fix these hydrogen atoms, preventing their accumulation in sensitive areas, thereby significantly improving the material's hydrogen embrittlement resistance. Although this comparative coating meets the basic application requirements in terms of basic electrical insulation and interface stability, its severe deficiency in hydrogen embrittlement sensitivity limits its application reliability in high-stress, hydrogen-containing environments, verifying the crucial role of a well-designed hydrogen trapping system in improving the overall performance of bearing coatings.

[0098] Comparative Example 2: Based on Example 2, this example only modifies the reinforcing material; the remaining steps are the same as in Example 2. Specific settings are shown in Table 10 below.

[0099] Table 10: Process Adjustment Comparison Table

[0100] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in Table 11 below.

[0101] Table 11: Performance Characterization Results

[0102] Analysis of the characterization results in Table 11 shows that Comparative Example 2, which uses pure molybdenum disulfide as the lubricating phase, exhibits significant performance degradation in a high-temperature friction environment. The core issue is the cascading failure caused by the runaway transformation of the lubricating phase.

[0103] Pure molybdenum disulfide undergoes an irreversible oxidation transformation at temperatures above 250°C, resulting in molybdenum trioxide, a high-hardness crystalline phase that completely loses the shear-like properties of layered materials. This structural transformation causes the friction coefficient of the lubricating film to increase sharply from 0.04.

[0104] The mismatch in coefficients of thermal expansion is a key factor in the failure of catalytic coatings. The coefficient of thermal expansion of molybdenum oxide differs significantly from that of the coating substrate and bearing steel, generating thermal cyclic stress that far exceeds the interfacial bonding strength. This thermal mismatch creates a high stress gradient at the oxide / substrate interface, where the stress intensity factor exceeds the critical fracture toughness of the interface.

[0105] Comparative Example 2 exhibited numerous interfacial crack initiation signals during the initial thermal cycle, while the nanodiamonds in Example 2 provided a crack deflection mechanism and stress shielding effect, reducing thermal stress by approximately 45% and effectively inhibiting crack propagation. The final failure of Comparative Example 2 was dominated by three-body wear induced by oxidation products. Detached molybdenum oxide particles embedded themselves in the friction interface, forming a typical ploughing wear pattern with local pressures reaching 4–6 GPa, far exceeding the material's yield strength, inducing plastic rheology and abrasive wear. The nanodiamonds in Example 2 not only enhanced the high-temperature stability of molybdenum disulfide, but their uniformly dispersed hard nanoparticles also created a "ball bearing" effect during friction, simultaneously filling microcracks through an in-situ repair mechanism, significantly reducing the coefficient of friction and wear rate.

[0106] The failure of pure molybdenum disulfide in high-temperature friction environments stems from a cascading failure mechanism of "oxidation phase transformation → thermal stress cracking → third-body wear". However, the molybdenum disulfide / nanodiamond composite powder with a molybdenum disulfide content of 75 wt% in Example 2 effectively inhibits this failure chain through a synergistic stabilization mechanism, highlighting the key role and irreplaceable nature of composite lubricating phase in the design of high-temperature bearing protective coatings.

[0107] Comparative Example 3: Based on Example 2, this example only modifies the precursor preparation process; the remaining steps are the same as in Example 2. Specific settings are shown in Table 12 below: Table 12: Process Adjustment Comparison Table

[0108] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in Table 13 below.

[0109] Table 13: Performance Characterization Results

[0110] Analysis of the characterization results in Table 13 shows that the change in the epoxy-silicone hybrid precursor process in Comparative Example 3 led to a significant deterioration in the coating's electric field distribution and mechanical integrity. The change in the precursor process in Comparative Example 3 resulted in an increase in network structure defects in the epoxy-silicone hybrid resin, causing a multiplication of electric field distortion and a deterioration of interfacial adhesion, ultimately manifesting as a significant decrease in the coating's electrical insulation performance and abrasion resistance.

[0111] In Comparative Example 3, the degree of polymerization distribution of the siloxane prepolymer broadened, and the Si-OH end-capping rate at the molecular chain ends decreased, leading to the formation of numerous dangling bonds and microscopic defects in the crosslinked network. These defects, acting as charge trap centers, accumulate localized charges under the influence of an applied electric field, forming space charge regions. In this type of heterogeneous medium, the electric field strength in the micro-gap region increases sharply from a baseline value of 1.5 kV / mm to 15 kV / mm, exceeding the breakdown threshold of air. This electric field distortion originates from the polarization inhomogeneity of nanoscale defects in the polymer matrix under a high-gradient electric field, resulting in localized charge accumulation at the phase interface and causing a multiplication of electric field distortion.

[0112] Changes in the precursor process directly affect the molecular structure of the epoxy-siloxane hybrid system. The controlled reaction conditions used in Example 2 ensured uniform condensation of the siloxane and directional grafting of the epoxy groups. However, the process changes in Comparative Example 3 resulted in incomplete condensation, reduced epoxy grafting efficiency, and increased irregularity in the siloxane network structure, leading to a significant decrease in the interfacial bonding strength between the hybrid resin and functional components such as modified graphene and lubricants. The interfacial bonding strength between the functional filler and the resin matrix in Comparative Example 3 was only about 58% of that in Example 2. This weakened interfacial bonding strength directly resulted in an approximately 1.8-fold increase in the stress concentration factor at the interface under cyclic stress, lowering the crack initiation threshold and accelerating the formation and propagation of fatigue cracks.

[0113] The synergistic effect of electric field distortion and weakened interfacial adhesion leads to a systematic deterioration of coating performance. Electric field distortion promotes enhanced local discharge, with each discharge having an energy of approximately 1 mJ, sufficient to trigger the formation of micro-craters. These micro-craters further become stress concentration areas, creating a synergistic effect with weakened interfacial adhesion, accelerating crack initiation and propagation. In addition, the crack network provides preferential pathways for charge transport, further reducing the electrical insulation properties of the coating, forming a vicious cycle of "structural damage - performance degradation - accelerated failure".

[0114] Comparative Example 4: Based on Example 2, this example only uses commercially available PTFE coatings for performance comparison. The performance testing methods are completely consistent with those in Example 1. Partial performance characterization is performed, and the characterization results are shown in Table 14 below.

[0115] Table 14: Performance Characterization Results

[0116] Analysis of the above characterization results shows that commercially available PTFE coatings exhibit significant deficiencies in all performance tests. Specifically, in the anti-electrochemical corrosion performance test, the breakdown voltage of the commercially available PTFE coating is much lower than that of the coating prepared in Example 2, and the discharge current is larger, indicating that its anti-electrochemical corrosion capability is weak. This may be because PTFE itself has a high dielectric constant, which easily forms a high electric field strength locally, leading to electrical breakdown. At the same time, PTFE is prone to creep and stress relaxation at high temperatures, resulting in a weakened interfacial bond between the coating and the substrate, further exacerbating the risk of electrochemical corrosion.

[0117] High-temperature tribological testing results showed that commercially available PTFE coatings exhibited a high coefficient of friction and poor lubrication performance at 300°C. This is likely due to the susceptibility of PTFE to thermal decomposition and oxidation at high temperatures, leading to structural damage and performance degradation of the lubricating film. In contrast, the coating prepared in Example 2 maintained good lubrication performance at high temperatures, thanks to its unique lubricating phase composition and structural design.

[0118] Furthermore, in the peel resistance test, the commercially available PTFE coating exhibited significantly fewer cycles than the coating prepared in Example 2, indicating poorer interfacial stability. This may be due to the poor compatibility between PTFE and the substrate material, making the coating prone to peeling under stress. In contrast, the coating prepared in Example 2 effectively improves the interfacial adhesion and stability of the coating through multiple interfacial reinforcement mechanisms.

[0119] Comparative Example 5: Based on Example 2, this example only replaces the graphene in step 1) with other carbon materials of equal mass, while the remaining steps are the same. The specific process settings are shown in Table 15 below.

[0120] Table 15: Process Adjustment Comparison Table

[0121] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in Table 16 below.

[0122] Table 16: Performance Characterization Results

[0123] Analysis of the characterization results in Table 16 above shows that different carbon nanomaterials (CNTs, carbon nanofibers, and graphdiene) exhibit significantly different performance characteristics in bearing protective coatings. These differences directly stem from their unique microstructure and material properties. Through a multidimensional performance comparison between the D5 series comparative group and Example 2, the structure-performance relationship of carbon nanomaterials and their microscopic mechanisms of action can be further analyzed.

[0124] The introduction of carbon nanotubes (CNTs) into D5-1 resulted in a significant decrease in the coating's resistance to hydrogen permeation. This phenomenon can be attributed to the one-dimensional tubular structure of CNTs from a microscopic perspective. Although the tubular structure possesses a certain hydrogen storage potential, the limited diameter and lack of selective hydrogen-affinity functional groups at the open ends make it difficult to form an efficient hydrogen trapping system. CNTs form "hydrogen diffusion channels" rather than "hydrogen traps" in the coating, increasing the hydrogen diffusion coefficient by about an order of magnitude. This, in turn, disrupts the original modified graphene hydrogen trapping system to some extent, leading to a very significant deterioration in the resistance to hydrogen permeation.

[0125] In terms of mechanical properties, the tendency of CNTs to cluster and aggregate stems from their inherent properties. The strong van der Waals forces between the high aspect ratio nanotubes facilitate the formation of a tightly entangled three-dimensional network structure, resulting in numerous CNT aggregates within the coating. These aggregates create significant mechanical discontinuities within the resin matrix, with localized stress concentrations far exceeding those in uniformly dispersed areas. Under thermal cycling and mechanical loading, these stress concentration regions become preferential sites for microcrack initiation, severely weakening the overall structural integrity of the coating.

[0126] The carbon nanofibers (CNFs) used in D5-2 exhibit certain advantages in electrical properties. The unique graphite microstructure of CNFs provides higher electronic conduction efficiency. Secondly, the larger diameter of CNFs compared to CNTs enhances their rigidity, maintaining higher orientation consistency within the resin matrix and forming a denser and more directional conductive network. Anisotropic conductivity measurements show increased conductivity along the fiber axis; this high conductivity is beneficial for uniform electric field distribution and suppression of partial discharge. However, CNFs perform poorly in resisting hydrogen permeation due to the lack of active sites on their surface. Unlike the ordinary graphene in Example 2, while carbon nanofibers can effectively form an interlocking effect with modified graphene, this also leads to significant masking of hydrogen storage sites in the modified graphene. Although carbon nanofibers themselves possess a certain number of hydrogen storage sites, which can increase their abundance, the two cannot coordinate and even mutually inhibit or cancel each other out, thus significantly weakening their resistance to hydrogen embrittlement.

[0127] In terms of mechanical properties, D5-2 showed improvement over D5-1, but was still inferior to Example 2. This relative improvement is attributed to the "peeling" phenomenon commonly seen during CNF fracture, which to some extent provides an energy dissipation mechanism and reduces the tendency for rapid crack propagation. However, the interfacial bonding between CNFs and the resin matrix remains insufficient.

[0128] The graphdiene introduced in D5-3 exhibited superior resistance to hydrogen permeation, even surpassing that of Example 2. However, a significant drawback of graphdiene is that it causes severe embrittlement of the coating. This severe degradation stems from the inhibitory effect of the rigid two-dimensional structure of graphdiene on the molecular chain motion of the resin matrix, severely restricting the movement of molecular chain segments. Under thermal stress cycling conditions, the resin matrix loses its ability to absorb strain energy through molecular chain conformation adjustment, leading to the direct conversion of stress into microcracks.

[0129] More importantly, the planar structure of graphyne forms a highly heterogeneous interface with the resin matrix, creating a "stress discontinuity surface" in the interface region. This structure generates high interfacial shear stress under thermal cycling conditions, and during thermal cycling, microcracks mainly initiate and propagate along the graphyne / resin interface.

[0130] In comparison, it is evident that although there are numerous options for the carbon-polyaniline conductive system (C-PANI conductive system), and some options can even produce superior performance, for the technical solution of this invention, due to the use of modified graphene and combined with the data results characterized in this example, it is clear that the conductive system constructed using the graphene-polyaniline system has a significantly superior and irreplaceable overall performance. Ordinary graphene, due to its unique two-dimensional conductive flexibility, edge chemical modifiability, and intrinsic compatibility with modified graphene, becomes the only ideal medium for connecting the conductive network and the hydrogen storage system. Any substitution of other carbon allotropes (such as carbon nanotubes, graphylene, etc.) may disrupt the synergistic relationship of "electro-erosion suppression-hydrogen embrittlement barrier-mechanical enhancement".

Claims

1. A method for preparing a bearing surface coating, characterized in that, The method includes: 1) mixing amine compounds, non-metallic elements and inorganic salts in proportion to form a precursor; 2) mixing amino silicone oil, organic mixed solvent and catalyst in proportion to form a siloxane prepolymer, then subjecting the prepolymer to epoxy grafting and nano-reinforcement, and filtering under reduced pressure to form an epoxy-organosilicon hybrid resin; 3) gradient mixing epoxy-organosilicon hybrid resin, modified graphene, composite powder and single crystal fiber to form a bearing surface coating.

2. The method for preparing a bearing surface coating according to claim 1, characterized in that, The amine compound in step 1) is an aniline monomer; the non-metallic element in step 1) is graphene; the inorganic salt in step 1) is ammonium persulfate; the amine compound, non-metallic element and inorganic salt in step 1) are mixed evenly in a mass ratio of (2.8-3.2):1:(9-10).

3. A method for preparing a bearing surface coating according to claim 1 or 2, characterized in that, Step 1) The precursor is prepared by low-temperature polymerization at 0-10 °C for 8-16 h under a nitrogen atmosphere.

4. The method for preparing a bearing surface coating according to claim 1, characterized in that, The amino silicone oil in step 2) has an ammonia value of 0.8–1.2 mmol / g; the organic mixed solvent in step 2) is a xylene / n-butanol mixed solvent with a xylene concentration of 45–55 wt%; the catalyst in step 2) is a titanate ester; the amino silicone oil, organic mixed solvent and catalyst in step 2) are mixed uniformly at a volume ratio of (6–8):(2–3):0.

01.

5. A method for preparing a bearing surface coating according to claim 1 or 4, characterized in that, Step 2) The amino silicone oil, organic mixed solvent and catalyst are mixed evenly in proportion and then subjected to a hot stirring reaction. The hot stirring reaction is controlled at a stirring temperature of 60-65 ℃, a stirring speed of 200-300 rpm and a stirring time of 1-2 h.

6. The method for preparing a bearing surface coating according to claim 1, characterized in that, Step 2) The epoxy grafting involves adding 2 to 2.5 times the mass of amino silicone oil of bisphenol A type epoxy resin to the siloxane prepolymer and reacting it under a nitrogen atmosphere at a temperature of 80 to 90 °C for 2.5 to 3.5 h; Step 2) The nano-reinforcement involves adding 0.3 to 0.5 wt% of the siloxane prepolymer of trimethoxy-[3-(epoxyethylene methoxy)propyl]silane and reacting it at a temperature of 105 to 115 °C for 2 to 3 h.

7. A method for preparing a bearing surface coating according to claim 1 or 6, characterized in that, Step 2) The reduced pressure filtration is carried out under reduced pressure distillation for 60 to 90 minutes at an environment with a temperature of 120 to 125 ℃ and a pressure of -0.10 to -0.09 MPa, followed by filtration through a 5 μm metal filter.

8. The method for preparing a bearing surface coating according to claim 1, characterized in that, Step 3) The modified graphene is prepared by the following method: graphene oxide is ultrasonically exfoliated in a 0.08-0.12 mol / L nitric acid aqueous solution for 30-50 min, and the ultrasonic exfoliation product is filtered out. The ultrasonic exfoliation product is mixed with ethylenediamine at a mass ratio of 1:(0.3-0.5), and reacted in a nitrogen atmosphere at a temperature of 80-85 ℃ for 4-5 h. After cooling to room temperature, 700-710 wt% of the ultrasonic exfoliation product in a 0.03-0.07 mol / L nickel chloride aqueous solution is added and ultrasonically treated for 30-50 min. Finally, a 0.08-0.12 mol / L sodium borohydride aqueous solution is added dropwise at a temperature of 0-5 ℃ at a drop rate of 2 mL / min, and the reaction is continued for 1-1.5 h. The composite powder in Step 3) is a molybdenum disulfide / nanodiamond composite powder with a molybdenum disulfide content of 70-78 wt%. The single crystal fiber in Step 3) is a silicon carbide whisker.

9. A method for preparing a bearing surface coating according to claim 1 or 8, characterized in that, Step 3) describes the gradient mixing process as follows: In the first stage, under environmental conditions of 58–62 °C and 200–300 rpm, epoxy-organosilicon hybrid resin and modified graphene are mixed and stirred at a mass ratio of (10–15):1 for 30–60 min to obtain a premix; In the second stage, under environmental conditions of vacuum ≤0.1 MPa, temperature 115–125 °C and rotation speed 1500–2000 rpm, 14–16 wt% of molybdenum disulfide / nanodiamond composite powder with a molybdenum disulfide content of 75 wt% and 4–6 wt% of silicon carbide whiskers are added and mixed and stirred for 30–60 min.

10. A bearing surface coating prepared by the method described in any one of claims 1 to 9.

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