A method for producing a wear-resistant coating on the surface of an epoxy resin panel by means of plasma spraying and the resulting coating structure

Abstract

The application belongs to the technical field of surface engineering, and particularly relates to a method for preparing a wear-resistant coating on the surface of an epoxy resin plate by plasma spraying and a coating structure obtained by the method. In view of the technical problems that the surface hardness of the epoxy resin plate is low, the wear resistance is poor, and high-temperature plasma spraying easily causes thermal damage, a multi-layer gradient thermal buffer layer is designed, and an asymmetric plasma spraying process is used, so that the obtained coating structure is sequentially a bonding and heat insulation layer, a thermal expansion transition layer, a dense interface layer and a wear-resistant layer, and the inherent contradiction between the high-temperature plasma spraying technology and the low heat resistance of the epoxy resin is successfully solved. The application realizes the direct preparation of a metal-based or ceramic-based coating with high bonding strength and excellent wear resistance on the surface of an epoxy resin matrix, breaks through the limitation of traditional technology, and provides a new solution for the surface strengthening of a polymer-based composite material. The wear rate of the obtained coating can be reduced to less than 1% of the original matrix, and the application range of the epoxy resin plate in a heavy-load and high-wear environment is significantly expanded.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology, specifically relating to a method for preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board and the resulting coating structure, thereby forming a composite coating structure with high adhesion, high wear resistance and excellent corrosion resistance. Background Technology

[0002] Epoxy resin sheets are widely used in electronics, aerospace, and transportation due to their advantages such as lightweight, high strength, corrosion resistance, and ease of processing. However, the low surface hardness and poor wear resistance of epoxy resin severely limit its application in frictional and abrasive environments. Traditional surface strengthening methods all have certain limitations. For example, physical vapor deposition (PVD) and chemical vapor deposition (CVD) technologies require high-temperature or vacuum environments, which can easily lead to thermal deformation or degradation of the epoxy resin matrix, and are also costly. Conventional thermal spraying technologies have excessively high temperatures (usually exceeding 3000℃), far exceeding the glass transition temperature of epoxy resin (usually 120~180℃). Existing low-temperature spraying technologies, such as cold spraying, can avoid overheating of the substrate, but the coating bonding strength is low, and the improvement in wear resistance is limited.

[0003] The patent with publication number CN119663625A proposes a method to improve the interfacial bonding performance of carbon fiber reinforced epoxy resin matrix composites. It improves the interfacial bonding performance between carbon fiber and epoxy resin matrix by combining air plasma treatment with polyamide-amine dendritic macromolecule grafting. However, this method can only improve the interfacial bonding force between carbon fiber and epoxy resin matrix, and cannot prepare a metal-ceramic composite coating with high bonding strength and high wear resistance on the surface of epoxy resin sheet.

[0004] The patent with publication number CN107384117A proposes an epoxy resin-based composite wear-resistant coating material and its preparation method. It prepares an organic resin-based composite wear-resistant coating by physically blending epoxy resin, polyurethane prepolymer and wear-resistant filler. After coating and curing, the coating is formed. However, it cannot solve the problem of thermal damage to the epoxy resin matrix during high-temperature spraying, nor can it achieve the preparation of ceramic wear-resistant coatings with high density and high bonding strength.

[0005] The patent with publication number CN121699477A proposes an epoxy resin wear-resistant coating and its preparation method. It combines polytetrafluoroethylene with modified inorganic fillers into the epoxy resin system to prepare an organic wear-resistant coating and coat it on the surface of a metal substrate. However, the wear resistance can only be improved to a limited extent by the combination of fillers in the organic system, and it cannot achieve the performance of high hardness and high wear resistance metal ceramic coating.

[0006] The patent with publication number CN101921979A proposes a method for preparing a sealing coating by plasma spraying. On a high-temperature alloy metal substrate, a sealing coating of NiAlW alloy underlayer and Al / BN top layer is prepared by plasma spraying to serve the sealing requirements of aero-engine casing. The substrate is a high-temperature alloy metal substrate. However, it does not consider the thermal damage of high-temperature plasma spraying to low-heat-resistant substrates. It cannot meet the spraying requirements of epoxy resin substrates, and it cannot solve the inherent contradiction between high-temperature plasma spraying and the low heat resistance of epoxy resin.

[0007] The patent with publication number CN106567028A proposes a method for preparing a nano-ceramic coating on the surface of a polymer matrix. The method involves preparing the nano-ceramic coating on the surface of the polymer matrix by spraying a suspension flame. However, this method cannot achieve high-power and high-efficiency coating preparation, nor can it form a metal-ceramic gradient composite coating structure. It can only control the substrate temperature to a limited extent by adjusting the flame parameters and spraying distance. It cannot isolate the thermal influence of the high-temperature jet on the epoxy resin matrix from the structural source, which can easily cause thermal deformation and thermal degradation of the substrate.

[0008] The patent with publication number CN116926532A proposes a method for preparing a metallized coating on a polymer surface based on cold gas dynamic spraying and laser remelting. By combining cold gas dynamic spraying with laser remelting, a metallized conductive coating is prepared on the surface of the polymer matrix. However, it cannot prepare a ceramic wear-resistant coating, but can only prepare a metallized coating, and the improvement in wear resistance is extremely limited.

[0009] There are currently no reports of successfully applying high-temperature plasma spraying technology directly to epoxy resin matrices. The main technical obstacle is the huge contradiction between the high temperature of plasma jets (up to 10,000~20,000K) and the low heat resistance of epoxy resins. Summary of the Invention

[0010] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing a wear-resistant coating on the surface of epoxy resin sheet by plasma spraying and the resulting coating structure. By using a substrate-thermal buffer layer-wear-resistant layer spraying method, a multi-layer gradient thermal buffer layer is prepared and thermal spraying process parameters are optimized, thereby successfully preparing a coating with high hardness and excellent wear resistance on the epoxy resin surface.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] A method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin sheet includes the following steps:

[0013] Step 1: Surface pretreatment of epoxy resin substrate

[0014] First, the epoxy resin substrate is degreased using organic solvents. Anhydrous ethanol and analytical grade acetone are used sequentially as solvents to remove organic oil stains, fingerprints, and mold release agent residues from the epoxy resin surface. Then, the surface is rinsed with deionized water to remove residual solvents. After cleaning, it is placed in a forced-air drying oven at 40~60℃ for 20~40 minutes to dry. After drying, the substrate surface is treated with fine-grained sandblasting using a sandblasting machine. White alumina sand with a particle size of 50~100μm is selected. The sandblasting air pressure is controlled at 0.3~0.6MPa, the sandblasting distance is controlled at 100~150mm, and the sandblasting angle is controlled at 70~90°. After sandblasting, the substrate surface is repeatedly rinsed with anhydrous ethanol to wash away the sand particles on the surface and in the pores. After drying, the surface pretreatment is completed.

[0015] Step 2: Using atmospheric plasma spraying technology, a four-layer gradient structure is prepared sequentially during the spraying process.

[0016] First layer of spraying: Use epoxy resin-aluminum composite powder with a particle size of 15~25μm, spraying distance of 120~150mm, control the substrate surface temperature to be below 80℃, and prepare the bonding and heat insulation layer.

[0017] Second layer spraying: Use aluminum-based composite powder containing 20~30 vol% nano alumina, spraying distance 100~120 mm, control the substrate surface temperature below 100℃, and prepare thermal expansion transition layer;

[0018] The third layer of spraying: using pure nickel powder with a particle size of 5~10μm, spraying distance of 80~100mm, to prepare a dense interface layer with a density greater than 95%, and controlling the substrate surface temperature below 120℃.

[0019] Fourth layer spraying: Use wear-resistant layer powder with a particle size of 20~45μm, spraying distance of 80~200mm to prepare the wear-resistant layer;

[0020] During the spraying process, a coaxial infrared thermometer is used to collect the surface temperature of the substrate in real time. When the temperature is 10~30℃ below the glass transition temperature of the substrate, the spraying is paused and air is used to accelerate cooling to a safe temperature before the spraying continues.

[0021] Step 3: Post-coating treatment

[0022] The coated workpiece is placed in a heat treatment furnace under vacuum or inert atmosphere protection, heated to 80-120°C at a rate of 1-5°C / min, held at that temperature for 1-3 hours, and then cooled to room temperature with the furnace to complete the preparation of the wear-resistant coating.

[0023] In the method for preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board, in the first, second and third layer spraying steps of step two, the plasma gas is argon and hydrogen, the main gas Ar flow rate is 30~40 slpm, the secondary gas H2 flow rate is 5~15 slpm, and the spraying gas pressure is 0.6~0.8MPa; the powder feeding gas Ar flow rate is 1.5~2.5 slpm, the powder feeding gas pressure is 0.4~0.6MPa, and the powder feeding rate is 10~30g / min.

[0024] In the method for preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board, in the first layer of spraying in step two, the epoxy resin-aluminum composite powder used is epoxy resin-coated aluminum powder with an aluminum core particle size of 10~20μm and an outer coating of epoxy resin micro powder with a particle size of 1~5μm and a mass fraction of 4~6%. The spraying power is 25~35kW and the coating thickness is 20~40μm.

[0025] In the method for preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board, in the second layer of spraying in step two, the particle size of epoxy resin-aluminum composite powder is 15~30μm, the spraying power is 30~40kW, and the coating thickness is 30~60μm.

[0026] In the method for preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board, in the third layer of spraying in step two, the spraying power is 30~40kW and the coating thickness is 10~30μm.

[0027] In the method for preparing a wear-resistant coating on the surface of epoxy resin board by plasma spraying, in the fourth layer of spraying in step two, the plasma gas is argon and hydrogen, the flow rate of the main gas Ar is 45~55 slpm, the flow rate of the secondary gas H2 is 5~15 slpm, the spraying gas pressure is 0.6~0.8MPa, the spraying power is 28~35kW, and the spray gun scanning speed is 20~30mms. -1 The powder feeding gas Ar flow rate is 2.0~2.5 slpm, the powder feeding gas pressure is 0.4~0.6MPa, the powder feeding rate is 20~40g / min, the single-pass thickness is 5~8µm, and the wear-resistant layer thickness is 200~400μm.

[0028] In the method for preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board, in the fourth layer of spraying in step two, the wear-resistant layer powder has a core-shell structure, with nickel brazing components forming the shell layer of the core-shell structure, accounting for 10%~20% of the mass of the wear-resistant layer powder, corresponding to a core layer silicon carbide-cobalt powder mass percentage of 80%~90%; the core layer is silicon carbide-cobalt particles of 85~90wt%SiC-10~15wt%Co, and the shell layer is nickel brazing components, whose composition and content are: 8~12wt%Cr, 1~5wt%B, 2~5wt%Si, 8~10wt%Fe and the balance Ni.

[0029] In the method for preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board, in the fourth layer of spraying in step two, the wear-resistant layer powder is an alumina-titanium oxide composite powder with a composition of 87wt%Al2O3-13wt%TiO2.

[0030] A method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin board yields a coating structure comprising a four-layer gradient structure from the epoxy resin matrix to the surface: an adhesive and heat-insulating layer, a thermal expansion transition layer, a dense interface layer, and a wear-resistant layer. The adhesive and heat-insulating layer is a coating formed by spraying epoxy resin-aluminum composite powder; the thermal expansion transition layer is a coating formed by spraying aluminum-based composite powder containing nano-alumina; the dense interface layer is a metal coating with a density greater than 95% formed by spraying ultrafine pure nickel powder; and the wear-resistant layer is a ceramic coating formed by spraying wear-resistant powder.

[0031] The coating structure obtained by the method of preparing a wear-resistant coating by plasma spraying on the surface of epoxy resin board has a porosity of less than 2%, no macroscopic cracks, and good interfacial bonding between layers; the coating microhardness is HV. 1kg / 15s ≥800, coating bonding strength ≥35MPa, no significant damage after immersion in cold water thermal shock cycling at 150℃ for 10~20 cycles; in pin-disc wear test with load of 150N, friction radius of 2.00mm, and SiN as the friction material, volumetric wear rate ≤10%. -5 mm 3 / N·m.

[0032] The design concept of this invention is:

[0033] This invention constructs a four-layer gradient thermal buffer layer structure from the epoxy resin matrix to the ceramic wear-resistant layer. On the one hand, it achieves a gradual transition in the coefficient of thermal expansion from the epoxy resin matrix to the ceramic surface layer, fundamentally solving the problems of interface cracking and poor adhesion caused by the huge difference in the coefficient of thermal expansion between the polymer matrix and the ceramic coating. On the other hand, the multi-layer structure forms a progressively insulating thermal protection barrier, isolating the thermal impact of high-temperature plasma jets on the epoxy resin matrix from the structural source, laying the structural foundation for the application of high-temperature plasma spraying.

[0034] Simultaneously, a phased dynamic precision temperature control strategy matching the gradient structure is implemented. The temperature of the spraying working surface is collected in real time by a coaxial infrared thermometer. When the temperature approaches the glass transition temperature of the substrate, the spraying is immediately suspended and compressed air is used to accelerate cooling. This achieves closed-loop precise control of the substrate temperature during the spraying process, completely eliminating the risk of substrate overheating from a process perspective.

[0035] Based on this, a specific organic solvent degreasing and white corundum blasting roughening substrate pretreatment process ensures the cleanliness and roughness of the substrate surface, providing an excellent bonding foundation for the bottom coating; the core-shell structure wear-resistant layer powder improves the melting sufficiency and coating density of the top layer powder, enhancing wear resistance; and a low-temperature heat treatment process under vacuum / inert atmosphere eliminates internal stress between multiple coating layers, further improving interfacial bonding stability. Finally, a composite coating structure with high bonding strength, high wear resistance, and excellent corrosion resistance is directly prepared on the surface of epoxy resin board, realizing the successful application of high-temperature plasma spraying technology on low-heat-resistant epoxy resin substrates.

[0036] The advantages and beneficial effects of this invention are as follows:

[0037] 1. This invention, through the innovative strategy of "gradient thermal buffer layer + dynamic precision temperature control", successfully applies high-temperature and high-efficiency plasma spraying technology directly to epoxy resin matrix that is not resistant to high temperatures for the first time, solving a long-standing technical contradiction and breaking through the technical prejudice in this field.

[0038] 2. The coating prepared by this invention has a bonding strength and hardness that reach or even exceed the level of traditional spray coatings on metal substrates, improving the wear resistance of epoxy resin by two orders of magnitude and greatly expanding its engineering application range.

[0039] 3. Throughout the entire spraying process, the present invention ensures that the substrate temperature remains within a safe range through process design, thereby avoiding thermal damage to the epoxy resin substrate and maintaining the original excellent mechanical properties of the epoxy resin substrate.

[0040] 4. This invention achieves a step-by-step matching of the coefficient of thermal expansion from the epoxy resin matrix to the ceramic surface layer through a four-layer gradient structure design, solving the problem of interface cracking and peeling caused by thermal expansion mismatch between the polymer matrix and the ceramic coating. At the same time, through the step-by-step heat insulation structure design, the thermal influence of high-temperature plasma jet on the matrix is ​​isolated from the source. Combined with dynamic temperature control process, it realizes the stable application of high-temperature plasma spraying on epoxy resin matrix.

[0041] 5. The coating prepared by this invention has excellent interfacial bonding stability. After a thermal shock test of immersion in cold water at 150°C, the coating showed no significant changes after 20 cycles, with no cracking, blistering, or peeling.

[0042] 6. The coating hardness of this invention is significantly improved, with a microhardness (HV) of [missing value]. 1kg / 15s The hardness can reach 1250±85, which is at or even exceeds the hardness level of traditional plasma spray coatings on metal substrates.

[0043] 7. The wear resistance of this invention achieves a qualitative leap. Under the conditions of a distributor-disc wear test, with a load of 150N, a friction radius of 2.00mm, and SiN as the friction material, the volumetric wear rate of the coating is only 0.5% of that of the untreated epoxy resin matrix, which improves the wear resistance of epoxy resin by two orders of magnitude.

[0044] 8. The coating structure of the present invention is complete and has high density. It forms a complete gradient structure without macroscopic cracks from the substrate to the surface. The interfaces between the layers are well bonded, the wear-resistant layer is fully melted, and the porosity is less than 2%. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the wear-resistant layer powder structure. In the diagram, 1 represents silicon carbide-cobalt particles, and 2 represents nickel-containing brazing components.

[0046] Figure 2 This is a scanning electron microscope (SEM) image of the wear-resistant layer powder.

[0047] Figure 3 The image shows the scanning electron microscope (SEM) morphology of the coating prepared in Example 1.

[0048] Figure 4 The image shows the scanning electron microscope (SEM) morphology of the coating prepared in Example 2. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0050] Example 1

[0051] In this embodiment, an epoxy resin board with external dimensions of 30mm×30mm×5mm is used as the matrix, and its glass transition temperature Tg=155℃.

[0052] (1) Surface pretreatment:

[0053] Cleaning: Sonicate for 10 minutes each in anhydrous ethanol and analytical grade acetone to remove oil, fingerprints and mold release agent residue. Rinse with deionized water and dry in a 50°C oven for 30 minutes.

[0054] Sandblasting: White alumina (white corundum) abrasive with a particle size of 70μm was used for sandblasting at a distance of 120mm and an angle of 85° under an air pressure of 0.45mPa. After sandblasting, the surface of the epoxy resin matrix and the pores were repeatedly rinsed with anhydrous ethanol to remove the abrasive particles. Finally, the surface was dried with a hair dryer.

[0055] (2) Gradient thermal buffer layer spraying:

[0056] An atmospheric plasma spraying system is used, with argon and hydrogen as the plasma gases. The main gas Ar flow rate is 35 slpm, the secondary gas H2 flow rate is 8 slpm, and the spraying gas pressure is 0.6MPa. The powder feeding gas Ar flow rate is 2 slpm, the powder feeding gas pressure is 0.4MPa, and the powder feeding rate is 20g / min.

[0057] First layer (adhesive / insulation layer): Sprayed with epoxy resin-coated aluminum powder (aluminum core particle size 10~20μm, outer coating of 5% by mass epoxy resin micro powder, epoxy resin micro powder particle size 1~5μm). Process parameters: spraying power 30kW, spraying distance 140mm, substrate surface temperature controlled below 75℃ by auxiliary cooling air, coating thickness approximately 30μm.

[0058] Second layer (thermal expansion transition layer): Sprayed aluminum-based nano-alumina composite powder (Al-25vol% nano-Al2O3, composite powder particle size 15~30μm). Process parameters: spraying power is 32kW, spraying distance is 110mm, substrate surface temperature is controlled below 95℃, and coating thickness is about 40μm.

[0059] The third layer (dense interface layer): sprayed with pure nickel powder (particle size 5~10μm). Process parameters: spraying power of 33kW, spraying distance of 90mm, coating density >96% by adjusting the spray gun scanning speed, substrate surface temperature controlled below 110℃, coating thickness of approximately 20μm.

[0060] (3) Wear-resistant layer spraying (fourth layer):

[0061] like Figures 1-2 As shown in this embodiment, the wear-resistant layer powder has a core-shell double-layer structure. The core layer, consisting of silicon carbide-cobalt particles 1, constitutes the core wear-resistant phase, accounting for 85 wt%. The shell layer, containing nickel brazing components 2, forms a metallic coating layer, accounting for 15 wt%, which can uniformly coat the outer surface of the core layer. On one hand, the nickel brazing components in the shell layer significantly improve the melting performance of the ceramic powder during plasma spraying, while also enhancing the coating density and interlayer bonding strength. On the other hand, it can isolate the high-temperature plasma jet, preventing the silicon carbide-cobalt composite phase from decomposing and burning during spraying. The wear-resistant layer powder is generally spherical, with a particle size distribution concentrated in the range of 20~45μm. The excellent sphericity and concentrated particle size distribution ensure good flowability and powder feeding stability during plasma spraying, avoiding process problems such as powder feeding blockage and uneven spraying. At the same time, the spherical powder can achieve uniform heating and full melting in the plasma jet.

[0062] The core layer consists of silicon carbide-cobalt particles (88wt% SiC-12wt% Co), and the shell layer is a nickel-containing brazing component, specifically composed of 10wt% Cr, 3wt% B, 3.5wt% Si, 9wt% Fe, and the balance Ni.

[0063] When spraying the wear-resistant powder coating of the core-shell structure, an atmospheric plasma spraying system was used. The plasma gases were argon and hydrogen, with a primary gas Ar flow rate of 40 slpm and a secondary gas H2 flow rate of 10 slpm. The spraying gas pressure was 0.8 MPa, the spraying power was 34 kW, the spraying distance was 100 mm, and the spray gun scanning speed was 25 mm / s. The powder feeding gas Ar flow rate was 3 slpm, the powder feeding gas pressure was 0.6 MPa, the powder feeding rate was 30 g / min, and the single-pass thickness was 5~8 µm. A coaxial infrared thermometer was used for monitoring. When the substrate surface temperature reached 138℃, the spraying was automatically paused, and compressed air was used to cool it down to below 100℃ before resuming until the wear-resistant layer thickness reached 300 µm.

[0064] (4) Post-processing:

[0065] After the wear-resistant coating is applied, the workpiece is placed in an argon-protected heat treatment furnace, heated to 110°C at a rate of 3°C / min, held at that temperature for 2 hours, and then cooled to room temperature with the furnace. This heat treatment reduces the internal stress between the sprayed coating layers, ensuring coating quality.

[0066] The performance test results are as follows:

[0067] Coating bonding strength: After immersion in cold water and hot vibration at 150℃ for 20 cycles, there was no significant change, and the bonding strength reached 46MPa.

[0068] Coating microhardness (HV) 1kg / 15s ): 1250 ± 85.

[0069] Wear performance (pin-disc wear test, load 150N, friction radius = 2.00mm, friction material = SiN): volumetric wear rate 2.7×10 -6 mm 3 / N·m, only for untreated epoxy resin matrix (5.4×10 -4 mm 3 0.5% of (N·m).

[0070] Coating morphology: such as Figure 3As shown in the SEM, a complete gradient structure without macroscopic cracks is formed from the substrate to the surface. The interfaces between the layers are well bonded. The nickel brazing component in the shell layer effectively improves the meltability of the ceramic powder during the plasma spraying process. With the plasma spraying process parameters, the wear-resistant layer melts fully. The wear-resistant layer powder melted by the high-temperature plasma jet impacts the substrate to form a continuous and dense structure with tight interparticle bonding and a porosity of <2%.

[0071] Example 2

[0072] In this embodiment, the same substrate as in Example 1 is used.

[0073] Surface pretreatment: Same as in Example 1.

[0074] Gradient thermal buffer layer and wear-resistant layer spraying:

[0075] To compare the processes, key parameters were adjusted: the second layer (thermal expansion transition layer) was omitted, and the third layer (dense interface layer) was directly sprayed onto the first layer (adhesive / insulation layer). The upper limit of the process temperature control for each layer was the same as in Example 1.

[0076] The wear-resistant layer material was changed to alumina-titanium oxide composite powder (87wt%Al2O3-13wt%TiO2, AT13 wear-resistant ceramic powder, particle size 25~45μm), and the core-shell structure was no longer used.

[0077] When spraying the wear-resistant layer, the trigger temperature for pausing cooling is set to 145℃ (close to Tg).

[0078] Post-processing: Same as in Example 1.

[0079] The performance test results are as follows:

[0080] Coating bonding strength: After immersion in cold water and hot vibration at 150℃, local blistering of the coating occurred after 10 cycles, and the bonding strength reached 35MPa.

[0081] Coating microhardness (HV) 1kg / 15s ): 950 ± 110.

[0082] Wear performance: Volumetric wear rate is 8.9 × 10⁻⁶ -6 mm 3 / N·m.

[0083] Substrate integrity: The substrate strength retention rate was 95.1%, but slight heat discoloration was observed locally at the coating edge.

[0084] Coating morphology: such as Figure 4As shown in the SEM, a small number of microcracks exist between the first and third layers, and the porosity of the wear-resistant layer is approximately 4%. Example 2 omitted the second thermal expansion transition layer, resulting in a decrease in the matching of the coating system's thermal expansion coefficients. Furthermore, the use of a non-core-shell alumina-titanium oxide composite powder reduced powder meltability, leading to increased coating porosity and insufficient density. This indicates that reducing the transition layer and relaxing temperature control have detectable negative impacts on coating quality and substrate protection, but are still far superior to traditional methods.

[0085] Comparative Example 1

[0086] Surface pretreatment: Same as in Example 1.

[0087] Spraying process (simulating low-temperature cold spraying):

[0088] A cold spray system is used, with nitrogen as the working gas, a pressure of 3.0 mPa, and a temperature of 500℃.

[0089] Pure aluminum powder (particle size 15~45μm) is directly sprayed as a coating.

[0090] The performance test results are as follows:

[0091] Coating bonding strength: After immersion in cold water at 150℃ and hot vibration, the coating peels off over a large area after 10 cycles.

[0092] Coating microhardness: (HV) 1kg / 15s 75 ± 10 (intrinsic hardness of aluminum only).

[0093] Wear performance: Volumetric wear rate is 1.2 × 10⁻⁶ -4 mm 3 The N·m value is superior to that of the original epoxy resin, but is about 44 times higher than that of Example 1 of this invention.

[0094] This comparison quantitatively demonstrates that although cold spraying can protect the substrate, its coating is far inferior to the coating obtained by the present invention through innovative gradient structure and controllable high temperature process in key performance indicators such as bonding strength and wear resistance, highlighting the significant advantages of the present invention in performance improvement.

[0095] The results demonstrate that this invention successfully resolves the inherent contradiction between high-temperature plasma spraying technology and the low heat resistance of epoxy resin by designing a multi-layer gradient thermal buffer layer, employing an asymmetric plasma spraying process, and using a special core-shell structure powder. This invention enables the direct preparation of metal-based or ceramic-based coatings with high bonding strength and excellent wear resistance on the surface of an epoxy resin matrix, breaking through the limitations of traditional technologies and providing a novel solution for surface strengthening of polymer-based composite materials. The wear rate of the resulting coating can be reduced to less than 1% of the original substrate, significantly expanding the application range of epoxy resin sheets in heavy-duty, high-wear-resistance environments.

Claims

1. A method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin sheet, characterized in that, Includes the following steps: Step 1: Surface pretreatment of epoxy resin substrate First, the epoxy resin substrate is degreased using organic solvents. Anhydrous ethanol and analytical grade acetone are used sequentially as solvents to remove organic oil stains, fingerprints, and mold release agent residues from the epoxy resin surface. Then, the surface is rinsed with deionized water to remove residual solvents. After cleaning, it is placed in a forced-air drying oven at 40~60℃ for 20~40 minutes to dry. After drying, the substrate surface is treated with fine-grained sandblasting using a sandblasting machine. White alumina sand with a particle size of 50~100μm is selected. The sandblasting air pressure is controlled at 0.3~0.6MPa, the sandblasting distance is controlled at 100~150mm, and the sandblasting angle is controlled at 70~90°. After sandblasting, the substrate surface is repeatedly rinsed with anhydrous ethanol to wash away the sand particles on the surface and in the pores. After drying, the surface pretreatment is completed. Step 2: Using atmospheric plasma spraying technology, a four-layer gradient structure is prepared sequentially during the spraying process. First layer of spraying: Use epoxy resin-aluminum composite powder with a particle size of 15~25μm, spraying distance of 120~150mm, control the substrate surface temperature to be below 80℃, and prepare the bonding and heat insulation layer. Second layer spraying: Use aluminum-based composite powder containing 20~30 vol% nano alumina, spraying distance 100~120 mm, control the substrate surface temperature below 100℃, and prepare thermal expansion transition layer; The third layer of spraying: using pure nickel powder with a particle size of 5~10μm, spraying distance of 80~100mm, to prepare a dense interface layer with a density greater than 95%, and controlling the substrate surface temperature below 120℃. Fourth layer spraying: Use wear-resistant layer powder with a particle size of 20~45μm, spraying distance of 80~200mm to prepare the wear-resistant layer; During the spraying process, a coaxial infrared thermometer is used to collect the surface temperature of the substrate in real time. When the temperature is 10~30℃ below the glass transition temperature of the substrate, the spraying is paused and air is used to accelerate cooling to a safe temperature before the spraying continues. Step 3: Post-coating treatment The coated workpiece is placed in a heat treatment furnace under vacuum or inert atmosphere protection, heated to 80-120°C at a rate of 1-5°C / min, held for 1-3 hours, and then cooled to room temperature with the furnace to complete the preparation of the wear-resistant coating. In the first layer of spraying in step two, the epoxy resin-aluminum composite powder used is epoxy resin coated aluminum powder with an aluminum core particle size of 10~20μm and an outer coating of 4~6% epoxy resin micro powder with a particle size of 1~5μm. The spraying power is 25~35kW and the coating thickness is 20~40μm. In the fourth layer of spraying in step two, the wear-resistant layer powder has a core-shell structure. The nickel brazing component serves as the shell layer of the core-shell structure, accounting for 10%~20% of the mass of the wear-resistant layer powder, corresponding to a mass percentage of 80%~90% for the core layer silicon carbide-cobalt powder. The core layer consists of silicon carbide-cobalt particles, composed of 85~90wt% SiC and 10~15wt% Co. The shell layer contains nickel brazing components, with the following composition and content: 8~12wt% Cr, 1~5wt% B, 2~5wt% Si, 8~10wt% Fe, and the balance Ni.

2. The method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin sheet according to claim 1, characterized in that, In step two, during the first, second, and third layer spraying, the plasma gases are argon and hydrogen. The flow rate of the main gas Ar is 30-40 slpm, the flow rate of the secondary gas H2 is 5-15 slpm, and the spraying gas pressure is 0.6-0.8 MPa. The flow rate of the powder feeding gas Ar is 1.5-2.5 slpm, the powder feeding gas pressure is 0.4-0.6 MPa, and the powder feeding rate is 10-30 g / min.

3. The method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin sheet according to claim 1, characterized in that, In the second layer of spraying in step two, the spraying power is 30~40kW and the coating thickness is 30~60μm.

4. The method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin sheet according to claim 1, characterized in that, In the third layer of spraying in step two, the spraying power is 30~40kW and the coating thickness is 10~30μm.

5. The method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin sheet according to claim 1, characterized in that, In the fourth layer of spraying in step two, the plasma gases are argon and hydrogen. The flow rate of the main gas Ar is 45~55 slpm, the flow rate of the secondary gas H2 is 5~15 slpm, the spraying gas pressure is 0.6~0.8MPa, the spraying power is 28~35kW, and the spray gun scanning speed is 20~30mms. -1 The powder feeding gas Ar flow rate is 2.0~2.5 slpm, the powder feeding gas pressure is 0.4~0.6MPa, the powder feeding rate is 20~40g / min, the single-pass thickness is 5~8µm, and the wear-resistant layer thickness is 200~400μm.

6. A coating structure obtained by the method for preparing a wear-resistant coating by plasma spraying on the surface of an epoxy resin sheet according to any one of claims 1 to 5, characterized in that, The coating structure consists of four gradient layers from the epoxy resin matrix to the surface: an adhesive and heat insulation layer, a thermal expansion transition layer, a dense interface layer, and a wear-resistant layer. The adhesive and heat insulation layer is a coating formed by spraying epoxy resin-aluminum composite powder. The thermal expansion transition layer is a coating formed by spraying aluminum-based composite powder containing nano-alumina. The dense interface layer is a metal coating with a density greater than 95% formed by spraying ultrafine pure nickel powder. The wear-resistant layer is a ceramic coating formed by spraying wear-resistant powder.

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