A wear-resistant and corrosion-resistant composite coating on a metal substrate surface and a preparation method thereof

Abstract

This invention relates to the field of surface spraying technology, and discloses a thermally sprayed wear-resistant and corrosion-resistant composite coating for metal substrates and its preparation method. The method includes: degreasing, sandblasting, purging, and preheating the surface of the metal substrate; dispersing, drying, and pre-curing Cr3C2 particles in a coating slurry containing flake Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, and silica sol to obtain barrier-coated hard reinforcing particles; spraying NiCrBSi alloy powder, barrier-coated hard reinforcing particles, and Al2O3 particles into granules, followed by thermal spraying, and then impregnating and sealing under negative pressure and curing to obtain the composite coating. This invention distributes the barrier phase at the particle interface around the Cr3C2 hard phase, limiting the spread of corrosive media along the particle interface and wear grooves after wear, thereby improving the service stability of the coating under wear-corrosion coupled conditions.

Description

Technical Field

[0001] This invention relates to the field of surface spraying technology, and more specifically, to a thermally sprayed wear-resistant and corrosion-resistant composite coating for metal substrates and its preparation method. Background Technology

[0002] Existing thermally sprayed wear-resistant and corrosion-resistant composite coatings typically improve coating hardness and wear resistance by introducing hard reinforcing phases such as carbides, oxides, nitrides, or borides into the metal or alloy binder phase. Simultaneously, they enhance the coating's barrier properties against corrosive media by selecting nickel-based, cobalt-based, iron-based, stainless steel-based, or other corrosion-resistant alloy phases. For example, CN108642434A discloses a method for preparing a NiCrBSi-Zr wear-resistant and corrosion-resistant coating. This method utilizes the decomposition of ZrH2 during spraying to form active Zr, improving the bonding interface between Zr particles and the NiCrBSi matrix, reducing porosity and cracks, thereby enhancing the coating's wear and corrosion resistance. However, this method primarily focuses on reducing porosity and cracks in the sprayed coating, without addressing the corrosion propagation path formed by the exposure of the hard reinforcing particle periphery after localized wear. Another type of existing technology blocks the penetration path of corrosive media through pore sealing treatment. For example, CN105543765B involves pore sealing treatment of thermal spray wear-resistant coatings to improve the problem of corrosive media penetration caused by coating pores. However, for pore sealing treatment that is mainly surface impregnation, the sealing effect is mainly concentrated on the pores on the coating surface or shallow connecting channels. After local wear, the pore sealing area may be destroyed, and the wear grooves, hard particle pull-out pits, and the peripheral interface between hard particles and the metal bonding phase may become the expansion channel of corrosive media again.

[0003] Therefore, while existing methods for preparing wear-resistant and corrosion-resistant composite coatings by thermal spraying on metal substrates can improve wear resistance through hard reinforcing phases and reduce the risk of corrosive media penetrating along open pores through post-spray sealing treatment, they still do not fully address the corrosion propagation problems caused by the interface around the hard reinforcing particles, particle pull-out pits, and wear grooves after localized wear. When wear occurs on the coating surface, the interface between the hard reinforcing particles and the metal binder phase is easily exposed, and corrosive media extend along these interfaces into the coating interior and to the outer edge of the wear area, thereby inducing localized peeling of the coating and resulting in insufficient service stability of the composite coating under wear-corrosion coupled conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a thermally sprayed wear-resistant and corrosion-resistant composite coating for metal substrates and its preparation method, so as to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides the following solution: On one hand, the present invention provides a method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface, comprising the following steps: S1. The surface of the metal substrate is sequentially subjected to degreasing and cleaning, sandblasting and roughening, compressed air purging and preheating treatment to obtain the metal substrate to be coated; the surface roughness Ra of the metal substrate after sandblasting is 4μm-10μm, and the temperature of the preheating treatment is 80℃-160℃. S2. Preparation of barrier-coated hard reinforcing particles: Cr3C2 particles are added to the coating slurry for dispersion, so that the coating slurry adheres to the surface of the Cr3C2 particles to obtain Cr3C2 particles with coating slurry attached; the Cr3C2 particles with coating slurry attached are dried and pre-cured to obtain barrier-coated hard reinforcing particles. The coating slurry includes flaky Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, silica sol, and deionized water. Based on mass percentage, the barrier-coated hard reinforcing particles comprise 82%-94% Cr3C2 particles and 6%-18% inorganic barrier coating solids attached to the surface of the Cr3C2 particles; the inorganic barrier coating solids comprise flake-shaped Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, and silica sol cured products. S3. Preparation of composite spray powder: NiCrBSi alloy powder, the barrier-coated hard reinforcing particles and Al2O3 particles are added to an aqueous binder solution for spray granulation and sieving to obtain composite spray powder with a particle size of 20μm-60μm. The composite spray powder comprises, by weight percentage, 28%-45% barrier-coated hard reinforcing particles, 2%-8% Al2O3 particles, and the balance being NiCrBSi alloy powder. S4. NiCrBSi alloy powder is sprayed onto the surface of the metal substrate to be sprayed using a thermal spraying method to form a corrosion-resistant transition layer with a thickness of 30μm-80μm. S5. The composite powder is sprayed onto the surface of the corrosion-resistant transition layer using a thermal spraying method to form a sprayed composite coating with a thickness of 200μm-500μm; the sprayed composite coating contains a particle interface barrier phase derived from the inorganic barrier-coated solid, and the particle interface barrier phase is distributed around the Cr3C2 hard phase. S6. Place the sprayed composite coating in a negative pressure environment of -0.06MPa to -0.09MPa for 10min-30min, then cover the surface of the sprayed composite coating with an aqueous phosphate-silica sol sealing liquid and keep it under a pressure of 0.2MPa-0.6MPa for 5min-20min to obtain the impregnated and sealed composite coating. S7. The composite coating after impregnation and sealing is subjected to heat curing treatment to obtain a thermally sprayed wear-resistant and corrosion-resistant composite coating on the surface of the metal substrate; the heat curing treatment includes first holding at 80℃-120℃ for 20min-60min, and then holding at 180℃-350℃ for 30min-120min.

[0006] Preferably, the metal substrate is a carbon steel substrate, an alloy steel substrate, a stainless steel substrate, an aluminum alloy substrate, a titanium alloy substrate, or a nickel-based alloy substrate; The degreasing and cleaning process includes alkaline degreasing cleaning, deionized water cleaning, and hot air drying. The sandblasting roughening is carried out using brown fused alumina sand, white fused alumina sand, or steel sand, with a sandblasting pressure of 0.4MPa-0.8MPa, a sandblasting distance of 80mm-180mm, and a sandblasting angle of 70°-90°.

[0007] Preferably, the NiCrBSi alloy powder comprises, by mass percentage, Cr 12%-18%, B 2%-4%, Si 3%-5%, Fe 1%-5%, C 0.3%-1.0%, with the balance being Ni; The particle size of the NiCrBSi alloy powder is 15μm-45μm; The NiCrBSi alloy powder is dried before spraying or spray granulation at a temperature of 100℃-160℃ for 1-4 hours.

[0008] Preferably, the particle size of the Cr3C2 particles is 5μm-25μm; The thickness of the flaky Cr2O3 particles is 0.2μm-3μm, and the diameter of the flaky particles is 2μm-20μm; The softening temperature of the borosilicate glass particles is 500℃-750℃, and the particle size is 1μm-10μm. The aluminum phosphate particles have a particle size of 0.5 μm-8 μm.

[0009] Preferably, in the inorganic barrier coated solid, the mass percentage of flaky Cr2O3 particles is 30%-55%, the mass percentage of borosilicate glass particles is 20%-40%, the mass percentage of aluminum phosphate particles is 10%-25%, and the mass percentage of silica sol cured product is 5%-20%. The solid content of the coating slurry is 15%-35%; When the coated slurry is mixed and dispersed with Cr3C2 particles, the stirring speed is 300r / min-900r / min and the dispersion time is 20min-90min.

[0010] Preferably, the drying temperature is 80℃-130℃, and the drying time is 30min-120min; The pre-curing temperature is 180℃-320℃, and the pre-curing time is 30min-120min; After drying and pre-curing, the weight gain of the barrier-coated hard reinforcing particles relative to Cr3C2 particles is 6%-18%.

[0011] Preferably, the Al2O3 particles are α-Al2O3 particles, and the particle size of the Al2O3 particles is 0.5μm-6μm; The binder in the aqueous binder solution is polyvinyl alcohol, sodium carboxymethyl cellulose, or polyvinylpyrrolidone. The water-based adhesive solution contains 1%-5% by mass of the adhesive. The spray granulation process includes: dispersing NiCrBSi alloy powder, barrier-coated hard reinforcing particles, and Al2O3 particles in an aqueous binder solution to obtain a spray granulation slurry; spray drying the spray granulation slurry to obtain agglomerated powder; and sieving the agglomerated powder to retain agglomerated powder with a particle size of 20μm-60μm as composite spray powder.

[0012] Preferably, the thermal spraying method is supersonic flame spraying or atmospheric plasma spraying; When using supersonic flame spraying, the spraying distance is 180mm-350mm, the powder feeding rate is 25g / min-70g / min, the spray gun moving speed is 300mm / s-800mm / s, and the surface temperature of the metal substrate during the spraying process is ≤220℃. When using atmospheric plasma spraying, the spraying current is 400A-700A, the spraying distance is 80mm-140mm, the powder feeding rate is 15g / min-55g / min, the spray gun moving speed is 250mm / s-700mm / s, and the surface temperature of the metal substrate during the spraying process is ≤260℃.

[0013] Preferably, the aqueous phosphate-silica sol blocking solution comprises, by mass percentage, 10%-30% aluminum dihydrogen phosphate, 15%-40% silica sol, 1%-5% boric acid, 0.1%-1.0% wetting agent, and the balance being deionized water; The silica sol contains 20%-40% SiO2 by mass. The wetting agent is a polyether-modified siloxane wetting agent, a nonionic fluorocarbon wetting agent, or an alkylphenol polyoxyethylene ether wetting agent.

[0014] On the other hand, the present invention provides a thermally sprayed wear-resistant and corrosion-resistant composite coating for a metal substrate, comprising a corrosion-resistant transition layer and a composite surface layer located on the surface of the corrosion-resistant transition layer; The composite surface layer comprises a NiCrBSi alloy phase, a barrier-coated Cr3C2 hard reinforcing phase, an Al2O3 hard phase, and a cured phosphate-silica sol blocking phase. The barrier-coated Cr3C2 hard reinforcing phase includes Cr3C2 particles and an inorganic barrier coating phase attached to the surface of the Cr3C2 particles. The inorganic barrier coating phase comprises a Cr2O3 sheet-like barrier phase, a borosilicate glass sealing phase, an aluminum phosphate barrier phase, and a silica sol-cured phase. After the wear-resistant and corrosion-resistant composite coating thermally sprayed onto the surface of the metal substrate undergoes a pre-wear treatment with a wear depth of 30μm-80μm, and then a 96-hour neutral salt spray test, the corrosion expansion width at the outer edge of the wear area is ≤1.5mm.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Before thermal spraying, this invention first attaches an inorganic barrier coating solid, consisting of flake-shaped Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, and a cured silica sol, to the surface of Cr3C2 particles to obtain barrier-coated hard reinforcing particles. Through the above treatment, the anti-corrosion sealing effect, which originally mainly acts on the pores of the coating surface, is moved forward to the surface of the hard reinforcing particles, so that the particle interface barrier phase formed after thermal spraying is distributed around the periphery of the Cr3C2 hard phase. Therefore, when the composite coating experiences local wear, the periphery of the Cr3C2 hard phase, particle pull-out pits, and wear grooves no longer simply become channels for the spread of corrosive media, but can limit the spread of corrosive media along the interface between the hard phase and the NiCrBSi alloy phase through the particle interface barrier phase.

[0016] (2) The wear-resistant reinforcement system is composed of Cr3C2 particles and Al2O3 particles. Cr3C2 particles play a major role in wear resistance support, while Al2O3 particles supplement the distribution of hard phase inside the coating and improve the scratch resistance during wear. At the same time, the NiCrBSi alloy phase acts as a metallic binder and corrosion-resistant continuous phase, enabling the hard reinforcement phase to be stably embedded in the composite surface layer. The above material combination method is beneficial to maintain the wear resistance of the coating while reducing the risk of particle pull-out, interface exposure, and local peeling caused by simply increasing the content of hard particles.

[0017] (3) The inorganic barrier coating solid in this invention is composed of sheet-like Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, and silica sol cured product. The sheet-like Cr2O3 particles can form sheet-like barrier paths around the hard particles, increasing the path length of the corrosive medium along the particle interface; the borosilicate glass particles can provide inorganic sealing during thermal spraying and subsequent curing, reducing the micro-gap connectivity around the hard particles; the aluminum phosphate particles can improve the corrosion resistance and barrier ability of the inorganic coating phase; and the silica sol cured product can enhance the adhesion stability of the inorganic barrier components on the surface of Cr3C2 particles. The above components are not simply mixed into the coating, but are pre-positioned on the surface of Cr3C2 particles, so that the barrier effect is concentrated at the hard particle interface position most easily exposed after local wear.

[0018] (4) A corrosion-resistant transition layer is first formed on the surface of the metal substrate using NiCrBSi alloy powder, and then a composite spray powder containing barrier-coated hard reinforcing particles is sprayed onto the surface of the corrosion-resistant transition layer. The corrosion-resistant transition layer can improve the material transition relationship between the metal substrate and the composite surface layer, reduce the interfacial stress concentration caused by the hard reinforcing phase in the composite surface layer directly acting on the substrate surface, and at the same time provide a continuous corrosion-resistant metal support base for the subsequent composite surface layer, which is conducive to improving the bonding stability between the coating and the metal substrate.

[0019] (5) After the thermal spraying forms the sprayed composite coating, a sealing treatment combining negative pressure maintenance, sealing liquid coverage, and pressurized impregnation is further adopted to allow the aqueous phosphate-silica sol sealing liquid to enter the open channels and interlayer interconnected areas in the sprayed composite coating. Negative pressure treatment helps to remove residual gas from the coating channels, while pressurized impregnation helps the sealing liquid enter the interconnected channels. Subsequent staged heating and curing enables the sealing liquid to form a stable inorganic sealing phase. Thus, the composite coating simultaneously possesses the interfacial barrier effect around the hard particles and the impregnation and sealing effect of the coating channels, which can reduce the risk of corrosive media continuing to expand into the coating interior after local wear. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example

[0021] This embodiment provides a method for preparing a thermally sprayed wear-resistant and corrosion-resistant composite coating on a metal substrate, comprising the following steps: S1. Pretreatment of metal substrate.

[0022] 45# steel plate was selected as the metal substrate, with dimensions of 100mm×50mm×5mm. It was cleaned for 10 minutes at 60℃ using an alkaline degreasing solution (NaOH 10g / L, Na2CO3 25g / L, Na3PO4 20g / L, and sodium dodecylbenzenesulfonate 2g / L, with the balance being water), followed by rinsing twice with deionized water and hot air drying at 90℃ for 20 minutes. Subsequently, it was roughened by sandblasting with brown corundum abrasive at a pressure of 0.6MPa, a distance of 120mm, and an angle of 80°. After sandblasting, residual particles were removed by compressed air, and the surface roughness Ra of the metal substrate was measured to be 6.5μm. The roughened metal substrate was preheated to 120℃ to obtain the metal substrate to be coated.

[0023] S2. Preparation of barrier-coated hard reinforcing particles.

[0024] Cr3C2 particles with a particle size of 15 μm were selected. Flaky Cr2O3 particles with a thickness of 1.0 μm and a sheet diameter of 8 μm were selected. Borosilicate glass particles with a softening temperature of 620℃ and a particle size of 5 μm were selected. Aluminum phosphate particles with a particle size of 3 μm were selected. Alkaline silica sol with a SiO2 mass percentage of 30%, a particle size of 10 nm-20 nm, and a pH of 8.5-10.0 was selected.

[0025] Weigh 1000g of Cr3C2 particles. Separately weigh 54g of flake-shaped Cr2O3 particles, 36g of borosilicate glass particles, 18g of aluminum phosphate particles, and 40g of silica sol, of which 12g is converted to silica sol cured product. Mix the flake-shaped Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, silica sol, and deionized water to prepare a coating slurry with a solid content of 25%. In the solid components of the coating slurry, the mass percentage of flake-shaped Cr2O3 particles is 45%, the mass percentage of borosilicate glass particles (SiO2 68%, B2O3 18%, Al2O3 5%, Na2O 6%, CaO 3%) is 30%, the mass percentage of aluminum phosphate particles is 15%, and the mass percentage of silica sol cured product is 10%.

[0026] Cr3C2 particles were added to the coating slurry and stirred and dispersed at 600 rpm for 60 min, allowing the coating slurry to adhere to the surface of the Cr3C2 particles, resulting in Cr3C2 particles with coated slurry. The Cr3C2 particles with coated slurry were dried at 100℃ for 90 min, and then pre-cured at 250℃ for 60 min to obtain barrier-coated hard reinforcing particles. The weight gain of the barrier-coated hard reinforcing particles relative to Cr3C2 particles was 11.8%. By mass percentage, the barrier-coated hard reinforcing particles comprised 89.4% Cr3C2 particles and 10.6% inorganic barrier coating solids adhering to the surface of the Cr3C2 particles.

[0027] S3. Prepare composite spray powder.

[0028] NiCrBSi alloy powder was selected, and by mass percentage, it comprised 15% Cr, 3% B, 4% Si, 3% Fe, 0.6% C, with the balance being Ni; the particle size of the NiCrBSi alloy powder was 15μm-45μm. The NiCrBSi alloy powder was dried at 120℃ for 2 hours.

[0029] α-Al₂O₃ particles with a particle size of 3 μm were selected. By mass percentage, 35% barrier-coated hard reinforcing particles, 4% α-Al₂O₃ particles, and 61% NiCrBSi alloy powder were weighed. These raw materials were added to a 3% (by mass) polyvinyl alcohol aqueous solution and stirred to obtain a spray-granulated slurry with a solid content of 55%. The stirring speed was 500 r / min, and the stirring time was 40 min. The spray drying inlet air temperature was 180℃, the outlet air temperature was 90℃, and the atomization speed was 12000 r / min. The spray-granulated slurry was spray-dried to obtain agglomerated powder. The agglomerated powder was sieved, and powder with a particle size of 20 μm-60 μm was retained as the composite spray powder.

[0030] S4. Form a corrosion-resistant transition layer.

[0031] NiCrBSi alloy powder was sprayed onto the surface of the metal substrate using supersonic flame spraying to form a corrosion-resistant transition layer with a thickness of 50 μm. The spraying distance was 260 mm, the powder feed rate was 45 g / min, the spray gun moving speed was 500 mm / s, and the surface temperature of the metal substrate was controlled not to exceed 180℃ during the spraying process.

[0032] S5, Forming a sprayed composite coating.

[0033] Supersonic flame spraying uses an oxygen-propane system with an oxygen pressure of 0.8 MPa, a propane pressure of 0.55 MPa, and nitrogen as the carrier gas with a flow rate of 10 L / min.

[0034] A composite powder coating with a thickness of 320 μm was formed by spraying a supersonic flame onto the surface of the corrosion-resistant transition layer. The spraying distance was 260 mm, the powder feed rate was 45 g / min, the spray gun moving speed was 500 mm / s, and the surface temperature of the metal substrate was controlled to not exceed 200 °C during the spraying process. The sprayed composite coating contained a particle-interface barrier phase derived from inorganic barrier-coated solids, distributed around the periphery of the Cr3C2 hard phase.

[0035] S6, Negative pressure-pressurized impregnation and sealing.

[0036] Prepare an aqueous phosphate-silica sol blocking solution. By mass percentage, the aqueous phosphate-silica sol blocking solution comprises 20% aluminum dihydrogen phosphate, 30% silica sol, 3% boric acid, 0.5% polyether-modified siloxane wetting agent (BYK-348), and the balance being deionized water; the silica sol contains 30% SiO2 by mass.

[0037] The sprayed composite coating was placed in a negative pressure environment of -0.08MPa for 20 minutes, and then the surface of the sprayed composite coating was covered with an aqueous phosphate-silica sol sealing solution and kept under a pressure of 0.4MPa for 10 minutes to obtain the impregnated and sealed composite coating.

[0038] S7. Heat curing treatment.

[0039] The composite coating after impregnation and sealing is subjected to heat curing treatment. First, it is kept at 100℃ for 40 minutes, and then the temperature is raised to 260℃ and kept for 60 minutes to obtain a thermally sprayed wear-resistant and corrosion-resistant composite coating on the surface of the metal substrate.

[0040] The composite coating obtained in this embodiment includes a corrosion-resistant transition layer and a composite top layer located on the surface of the corrosion-resistant transition layer. The composite top layer comprises a NiCrBSi alloy phase, a barrier-coated Cr3C2 hard reinforcing phase, an Al2O3 hard phase, and a cured phosphate-silica sol blocking phase; the barrier-coated Cr3C2 hard reinforcing phase comprises Cr3C2 particles and an inorganic barrier coating phase attached to the surface of the Cr3C2 particles. Example

[0041] 304 stainless steel plate was selected as the metal substrate. Sandblasting roughening was performed using 60-mesh white corundum abrasive, with a sandblasting pressure of 0.4 MPa, a sandblasting distance of 80 mm, and a sandblasting angle of 70°. The surface roughness Ra of the metal substrate after sandblasting was 4.0 μm, and the preheating temperature was 80℃.

[0042] The particle size of Cr3C2 particles is 5μm; the thickness of the flaky Cr2O3 particles is 0.2μm and the diameter of the flaky particles is 2μm; the softening temperature of the borosilicate glass particles is 500℃ and the particle size is 1μm; the particle size of the aluminum phosphate particles is 0.5μm.

[0043] In the inorganic barrier-coated solid, the mass percentage of flaky Cr2O3 particles was 30%, borosilicate glass particles were 40%, aluminum phosphate particles were 10%, and the cured silica sol was 20%. The solid content of the coating slurry was 15%, the stirring speed was 300 r / min, and the dispersion time was 90 min. The drying temperature was 80℃, and the drying time was 120 min; the pre-curing temperature was 180℃, and the pre-curing time was 120 min. The weight gain of the barrier-coated hard reinforcing particles relative to Cr3C2 particles was 6.2%.

[0044] The composite spraying powder comprises, by mass percentage, 28% barrier-coated hard reinforcing particles, 2% α-Al2O3 particles, and the balance being NiCrBSi alloy powder; the particle size of the composite spraying powder is 20μm-60μm.

[0045] Atmospheric plasma spraying uses Ar as the main gas and H2 as the auxiliary gas. The Ar flow rate is 40 L / min, the H2 flow rate is 8 L / min, and the spraying voltage is 60 V.

[0046] An atmospheric plasma spraying method was used to form a corrosion-resistant transition layer and a sprayed composite coating. The thickness of the corrosion-resistant transition layer was 30 μm, and the thickness of the sprayed composite coating was 200 μm. The atmospheric plasma spraying current was 400 A, the spraying distance was 80 mm, the powder feed rate was 15 g / min, the spray gun moving speed was 700 mm / s, and the surface temperature of the metal substrate was controlled not to exceed 260 °C during the spraying process.

[0047] During negative pressure impregnation sealing, the negative pressure environment is -0.06 MPa, maintained for 30 minutes; after the sealing liquid covers the area, it is maintained at a pressure of 0.2 MPa for 20 minutes. The heat curing treatment includes first holding at 80℃ for 60 minutes, and then holding at 180℃ for 120 minutes.

[0048] Apart from the differences mentioned above, the remaining steps in this embodiment are the same as in Embodiment 1. Example

[0049] TC4 titanium alloy plate was selected as the metal substrate. Sandblasting roughening was performed using 0.3-0.6mm steel grit, with a sandblasting pressure of 0.8MPa, a sandblasting distance of 180mm, and a sandblasting angle of 90°. The surface roughness Ra of the metal substrate after sandblasting was 10.0μm, and the preheating temperature was 160℃.

[0050] The particle size of Cr3C2 particles is 25 μm; the thickness of the flaky Cr2O3 particles is 3 μm and the diameter of the flaky particles is 20 μm; the softening temperature of the borosilicate glass particles is 750℃ and the particle size is 10 μm; the particle size of the aluminum phosphate particles is 8 μm.

[0051] In the inorganic barrier-coated solid, the mass percentage of flaky Cr2O3 particles was 55%, borosilicate glass particles 20%, aluminum phosphate particles 20%, and silica sol cured product 5%. The coating slurry had a solid content of 35%, a stirring speed of 900 r / min, and a dispersion time of 20 min. The drying temperature was 130℃, and the drying time was 30 min; the pre-curing temperature was 320℃, and the pre-curing time was 30 min. The weight gain of the barrier-coated hard reinforcing particles relative to Cr3C2 particles was 17.6%.

[0052] The composite spraying powder comprises, by mass percentage, 45% barrier-coated hard reinforcing particles, 8% α-Al2O3 particles, and the balance being NiCrBSi alloy powder; the particle size of the composite spraying powder is 20μm-60μm.

[0053] A corrosion-resistant transition layer and a sprayed composite coating were formed using supersonic flame spraying. The thickness of the corrosion-resistant transition layer was 80 μm, and the thickness of the sprayed composite coating was 500 μm. The supersonic flame spraying distance was 350 mm, the powder feed rate was 70 g / min, the spray gun moving speed was 300 mm / s, and the surface temperature of the metal substrate was controlled not to exceed 220℃ during the spraying process.

[0054] During negative pressure impregnation sealing, the negative pressure environment is -0.09 MPa, maintained for 10 minutes; after the sealing liquid covers the area, it is maintained at a pressure of 0.6 MPa for 5 minutes. The heat curing treatment includes first holding at 120℃ for 20 minutes, and then holding at 350℃ for 30 minutes.

[0055] Apart from the differences mentioned above, the remaining steps in this embodiment are the same as in Embodiment 1. Example

[0056] The difference between this embodiment and Embodiment 1 is that 6061 aluminum alloy plate is used as the metal substrate. White corundum abrasive is used for sandblasting, with a sandblasting pressure of 0.45 MPa, a sandblasting distance of 100 mm, and a sandblasting angle of 75°. The surface roughness Ra of the metal substrate after sandblasting is 5.2 μm. The preheating temperature is 90°C.

[0057] The composite spraying powder, by mass percentage, comprises 32% barrier-coated hard reinforcing particles, 3% α-Al₂O₃ particles, and the balance NiCrBSi alloy powder. The corrosion-resistant transition layer thickness is 40 μm, and the thickness of the sprayed composite coating is 260 μm. Supersonic flame spraying is employed, with a spraying distance of 240 mm, a powder feed rate of 35 g / min, and a spray gun moving speed of 650 mm / s. During the spraying process, the surface temperature of the metal substrate is controlled to not exceed 180℃.

[0058] During negative pressure impregnation sealing, the negative pressure environment is -0.07 MPa, maintained for 25 minutes; after the sealing liquid covers the area, it is maintained at a pressure of 0.3 MPa for 15 minutes. The heat curing treatment includes first holding at 90℃ for 50 minutes, and then holding at 220℃ for 90 minutes.

[0059] Apart from the differences mentioned above, the remaining steps in this embodiment are the same as in Embodiment 1. Example

[0060] The difference between this embodiment and Embodiment 1 is that Inconel 718 nickel-based alloy plate is used as the metal substrate. Sandblasting roughening uses 46-mesh brown corundum abrasive, with a sandblasting pressure of 0.7 MPa, a sandblasting distance of 150 mm, and a sandblasting angle of 85°. The surface roughness Ra of the metal substrate after sandblasting is 8.0 μm. The preheating temperature is 140°C.

[0061] The Cr3C2 particles have a particle size of 20 μm; the plate-like Cr2O3 particles have a thickness of 2 μm and a plate diameter of 15 μm; the borosilicate glass particles have a softening temperature of 680℃ and a particle size of 7 μm; and the aluminum phosphate particles have a particle size of 5 μm. The weight gain of the barrier-coated hard reinforcing particles relative to the Cr3C2 particles is 14.5%.

[0062] The composite spraying powder, by weight percentage, comprises 40% barrier-coated hard reinforcing particles, 6% α-Al₂O₃ particles, and the balance NiCrBSi alloy powder. The corrosion-resistant transition layer thickness is 60 μm, and the thickness of the sprayed composite coating is 420 μm. Supersonic flame spraying is employed, with a spraying distance of 300 mm, a powder feed rate of 60 g / min, and a spray gun movement speed of 420 mm / s. During the spraying process, the surface temperature of the metal substrate is controlled to not exceed 220℃.

[0063] During negative pressure impregnation sealing, the negative pressure environment is -0.085 MPa, maintained for 15 minutes; after the sealing liquid covers the area, it is maintained at a pressure of 0.5 MPa for 8 minutes. The heat curing treatment includes first holding at 110℃ for 30 minutes, and then holding at 300℃ for 50 minutes.

[0064] Apart from the differences mentioned above, the remaining steps in this embodiment are the same as in Embodiment 1. Example

[0065] The difference between this embodiment and Embodiment 1 is that in the inorganic barrier-coated solid, the mass percentage of flaky Cr2O3 particles is 50%, the mass percentage of borosilicate glass particles is 25%, the mass percentage of aluminum phosphate particles is 20%, and the mass percentage of the silica sol cured product is 5%. The solid content of the coating slurry is 30%, the stirring speed is 750 r / min, and the dispersion time is 45 min. The weight gain of the barrier-coated hard reinforcing particles relative to the Cr3C2 particles is 13.8%.

[0066] The composite spraying powder comprises, by weight percentage, 38% barrier-coated hard reinforcing particles, 5% α-Al2O3 particles, and the balance being NiCrBSi alloy powder. The remaining steps are the same as in Example 1.

[0067] Comparative Example 1 The difference between this comparative example and Example 1 is that step S2 in Example 1 is omitted. Instead, uncoated Cr3C2 particles, NiCrBSi alloy powder, and α-Al2O3 particles are directly spray-granulated to obtain a composite spray powder. By mass percentage, the composite spray powder comprises 35% Cr3C2 particles, 4% α-Al2O3 particles, and the remainder is NiCrBSi alloy powder. All other steps, thermal spraying parameters, negative pressure-pressurized impregnation sealing parameters, and curing parameters are the same as in Example 1.

[0068] Comparative Example 2 The difference between this comparative example and Example 1 is that, instead of preparing barrier-coated hard reinforcing particles, Cr3C2 particles, flake Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, NiCrBSi alloy powder, and α-Al2O3 particles are directly added to a polyvinyl alcohol aqueous solution for spray granulation. The total amount of each inorganic barrier component added is the same as the mass of the inorganic barrier-coated solid in Example 1. The remaining steps, thermal spraying parameters, negative pressure-pressure impregnation sealing parameters, and curing parameters are all the same as in Example 1.

[0069] Comparative Example 3 The difference between this comparative example and Example 1 is that the coating slurry only includes silica sol and deionized water, without the addition of flaky Cr2O3 particles, borosilicate glass particles, and aluminum phosphate particles. By adjusting the amount of silica sol, the weight gain of the Cr3C2 particles after drying and pre-curing was 11.5%. The remaining steps, thermal spraying parameters, negative pressure-pressurized impregnation sealing parameters, and curing parameters are the same as in Example 1.

[0070] Comparative Example 4 The difference between this comparative example and Example 1 is that the coating slurry includes flake-shaped Cr2O3 particles, silica sol, and deionized water, but does not include borosilicate glass particles and aluminum phosphate particles. By adjusting the amount of flake-shaped Cr2O3 particles and silica sol, the weight gain of the Cr3C2 particles after drying and pre-curing was 11.7%. The remaining steps, thermal spraying parameters, negative pressure-pressurized impregnation sealing parameters, and curing parameters are the same as in Example 1.

[0071] Comparative Example 5 The difference between this comparative example and Example 1 is that the coating slurry includes borosilicate glass particles, silica sol, and deionized water, but does not include flaky Cr2O3 particles and aluminum phosphate particles. By adjusting the amount of borosilicate glass particles and silica sol, the weight gain of the Cr3C2 particles after drying and pre-curing was 11.6%. The remaining steps, thermal spraying parameters, negative pressure-pressurized impregnation sealing parameters, and curing parameters are the same as in Example 1.

[0072] Comparative Example 6 The difference between this comparative example and Example 1 is that after the preparation of the sprayed composite coating, the S6 negative pressure-pressurized impregnation and sealing treatment in Example 1 is not performed; instead, heat treatment is carried out directly according to the heating curing conditions in Example 1. The remaining steps are the same as in Example 1.

[0073] Comparative Example 7 The difference between this comparative example and Example 1 is that after the preparation of the sprayed composite coating, negative pressure maintenance and pressure impregnation are not performed. Instead, an aqueous phosphate-silica sol sealing solution is brushed onto the surface of the sprayed composite coating under normal pressure. After standing for 20 minutes, the same heat curing treatment as in Example 1 is performed. The remaining steps are the same as in Example 1.

[0074] Performance testing The coatings obtained in Examples 1-6 and Comparative Examples 1-7 were subjected to the following tests.

[0075] Microhardness testing: The hardness of the coating cross section was tested using a micro Vickers hardness tester with a load of 2.94 N and a holding time of 15 s. Five points were tested for each group of samples, and the average value was taken.

[0076] Bond strength test: The bond strength between the coating and the metal substrate is tested by the pull-out method. Three samples are tested for each group, and the average value is taken.

[0077] Friction and wear testing: A ball-disc friction and wear test was adopted, with the auxiliary ball being a GCr15 steel ball with a diameter of 6mm, a load of 20N, a sliding speed of 0.10m / s, and a sliding distance of 1000m. The wear rate was calculated after the test.

[0078] Salt spray corrosion testing after pre-wearing: The coating surface was first subjected to quantitative pre-wearing treatment to control the wear groove depth to 50 μm. Then, the pre-weared samples were placed in a neutral salt spray environment for 96 hours. The salt spray medium was a 5% (w / w) NaCl solution, the test temperature was 35℃, and the solution pH was 6.5-7.2. After the test, the maximum corrosion width extending outward from the outer edge of the wear area was measured. Three samples were tested in each group, and the average value was taken.

[0079] Post-corrosion bond strength retention rate test: After the sample is pre-weared and subjected to a 96-hour neutral salt spray test, the bond strength is tested by pull-out method, and the retention rate of the bond strength after corrosion relative to the initial bond strength is calculated.

[0080] Corrosion peeling area ratio test: After the sample is pre-weared and tested with neutral salt spray for 96 hours, the proportion of the area where the coating peeled off within 2 mm of the outer edge of the wear area is counted to the area of ​​the test area.

[0081] The test results are shown in Table 1.

[0082] Table 1

[0083] The test results above show that the microhardness of Examples 1-6 remained at a high level, and the wear rate was low, indicating that Cr3C2 particles and Al2O3 particles can provide stable wear resistance enhancement for the composite coating. After pre-wearing, Examples 1-6 underwent a 96-hour neutral salt spray test, and the corrosion expansion width at the outer edge of the wear area was no greater than 1.5 mm. The composite coating prepared by this invention can still limit the continued expansion of corrosive media along the wear damage area after local wear.

[0084] Compared to Example 1, Comparative Example 1 did not involve inorganic barrier coating of Cr3C2 particles. Although the coating hardness and wear rate did not change significantly, the salt spray corrosion propagation width increased to 3.8 mm after 96 hours of pre-wearing, the post-corrosion bond strength retention rate decreased to 63%, and the corrosion peeling area ratio increased to 9.5%. This indicates that simply using Cr3C2 particles to improve wear resistance cannot solve the problem of the hard particle periphery becoming a corrosion propagation channel after localized wear.

[0085] Compared to Example 1, Comparative Example 2, although it included flake-like Cr2O3 particles, borosilicate glass particles, and aluminum phosphate particles, these components were merely dispersed in the spray powder as ordinary mixed components and were not pre-attached to the surface of the Cr3C2 particles. The corrosion spread width of Comparative Example 2 reached 2.6 mm, indicating that the spatial positioning of the inorganic barrier components plays a crucial role in inhibiting the corrosion spread at the hard particle interface, and simple mixing cannot achieve the particle interface barrier effect of this invention.

[0086] Compared to Example 1, Comparative Example 3 only used silica sol to coat Cr3C2 particles, without adding flake Cr2O3 particles, borosilicate glass particles, and aluminum phosphate particles. The corrosion spread width of Comparative Example 3 was 2.2 mm, indicating that a single silica sol cured product cannot simultaneously provide flake barrier, inorganic sealing, and corrosion-resistant barrier effects, and cannot sufficiently limit the spread of corrosive media along the periphery of hard particles.

[0087] Compared to Example 1, Comparative Example 4 used flake-shaped Cr2O3 particles and silica sol to coat Cr3C2 particles, but did not include borosilicate glass particles and aluminum phosphate particles. The corrosion spread width of Comparative Example 4 was 2.0 mm, indicating that although flake-shaped Cr2O3 particles can increase the spread path of the corrosive medium, without the sealing effect provided by borosilicate glass particles and the corrosion-resistant barrier effect provided by aluminum phosphate particles, it is still difficult to fully seal the micro-gap around the hard particles.

[0088] Compared to Example 1, Comparative Example 5 used borosilicate glass particles and silica sol to coat Cr3C2 particles, but did not add flake-like Cr2O3 particles and aluminum phosphate particles. The corrosion spread width of Comparative Example 5 was 2.4 mm, indicating that relying solely on the glass sealing phase is insufficient to effectively increase the spread path of the corrosive medium along the particle periphery interface, and also insufficient to provide sufficient phosphate barrier effect.

[0089] Compared to Example 1, Comparative Example 6, although using barrier-coated hard reinforcing particles, did not undergo negative pressure-pressurized impregnation sealing treatment. The corrosion spread width was 1.9 mm, and the post-corrosion bond strength retention rate was 75%. This indicates that the particle interface barrier phase can improve corrosion resistance after wear, but the open pores and interlayer connectivity areas of the coating still require further sealing through impregnation treatment.

[0090] Compared to Example 1, Comparative Example 7 used atmospheric pressure brushing of the sealing liquid for surface sealing, and the corrosion spread width was 1.6 mm, slightly higher than 1.5 mm. This result indicates that ordinary atmospheric pressure surface sealing has a certain improvement effect on the porosity of the coating surface, but its ability to treat the internal interconnected channels of the sprayed composite coating is weaker than that of negative pressure-pressurized impregnation sealing treatment. This invention, through negative pressure venting and pressurized impregnation, allows the sealing liquid to more fully penetrate open channels and interlayer interconnected areas, and works synergistically with particle interface barriers, thereby improving the service stability of the composite coating under wear-corrosion coupled conditions.

[0091] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface, characterized in that, Includes the following steps: S1. The surface of the metal substrate is sequentially subjected to degreasing and cleaning, sandblasting and roughening, compressed air purging and preheating treatment to obtain the metal substrate to be coated; the surface roughness Ra of the metal substrate after sandblasting is 4μm-10μm, and the temperature of the preheating treatment is 80℃-160℃. S2. Preparation of barrier-coated hard reinforcing particles: Cr3C2 particles are added to the coating slurry for dispersion, so that the coating slurry adheres to the surface of the Cr3C2 particles to obtain Cr3C2 particles with coating slurry attached; the Cr3C2 particles with coating slurry attached are dried and pre-cured to obtain barrier-coated hard reinforcing particles. The coating slurry includes flaky Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, silica sol, and deionized water. Based on mass percentage, the barrier-coated hard reinforcing particles comprise 82%-94% Cr3C2 particles and 6%-18% inorganic barrier coating solids attached to the surface of the Cr3C2 particles; the inorganic barrier coating solids comprise flake-shaped Cr2O3 particles, borosilicate glass particles, aluminum phosphate particles, and silica sol cured products. S3. Preparation of composite spray powder: NiCrBSi alloy powder, the barrier-coated hard reinforcing particles and Al2O3 particles are added to an aqueous binder solution for spray granulation and sieving to obtain composite spray powder with a particle size of 20μm-60μm. The composite spray powder comprises, by weight percentage, 28%-45% barrier-coated hard reinforcing particles, 2%-8% Al2O3 particles, and the balance being NiCrBSi alloy powder. S4. NiCrBSi alloy powder is sprayed onto the surface of the metal substrate to be sprayed using a thermal spraying method to form a corrosion-resistant transition layer with a thickness of 30μm-80μm. S5. The composite powder is sprayed onto the surface of the corrosion-resistant transition layer using a thermal spraying method to form a sprayed composite coating with a thickness of 200μm-500μm; the sprayed composite coating contains a particle interface barrier phase derived from the inorganic barrier-coated solid, and the particle interface barrier phase is distributed around the Cr3C2 hard phase. S6. Place the sprayed composite coating in a negative pressure environment of -0.06MPa to -0.09MPa for 10min-30min, then cover the surface of the sprayed composite coating with an aqueous phosphate-silica sol sealing liquid and keep it under a pressure of 0.2MPa-0.6MPa for 5min-20min to obtain the impregnated and sealed composite coating. S7. The composite coating after impregnation and sealing is subjected to heat curing treatment to obtain a thermally sprayed wear-resistant and corrosion-resistant composite coating on the surface of the metal substrate; the heat curing treatment includes first holding at 80℃-120℃ for 20min-60min, and then holding at 180℃-350℃ for 30min-120min.

2. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, The metal substrate is a carbon steel substrate, an alloy steel substrate, a stainless steel substrate, an aluminum alloy substrate, a titanium alloy substrate, or a nickel-based alloy substrate; The degreasing and cleaning process includes alkaline degreasing cleaning, deionized water cleaning, and hot air drying. The sandblasting roughening is carried out using brown fused alumina sand, white fused alumina sand, or steel sand, with a sandblasting pressure of 0.4MPa-0.8MPa, a sandblasting distance of 80mm-180mm, and a sandblasting angle of 70°-90°.

3. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, The NiCrBSi alloy powder comprises, by mass percentage, Cr 12%-18%, B 2%-4%, Si 3%-5%, Fe 1%-5%, C 0.3%-1.0%, with the balance being Ni; The particle size of the NiCrBSi alloy powder is 15μm-45μm; The NiCrBSi alloy powder is dried before spraying or spray granulation at a temperature of 100℃-160℃ for 1-4 hours.

4. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, The particle size of the Cr3C2 particles is 5μm-25μm; The thickness of the flaky Cr2O3 particles is 0.2μm-3μm, and the diameter of the flaky particles is 2μm-20μm; The softening temperature of the borosilicate glass particles is 500℃-750℃, and the particle size is 1μm-10μm. The aluminum phosphate particles have a particle size of 0.5 μm-8 μm.

5. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, In the inorganic barrier coated solid, the mass percentage of flaky Cr2O3 particles is 30%-55%, the mass percentage of borosilicate glass particles is 20%-40%, the mass percentage of aluminum phosphate particles is 10%-25%, and the mass percentage of silica sol cured product is 5%-20%. The solid content of the coating slurry is 15%-35%; When the coated slurry is mixed and dispersed with Cr3C2 particles, the stirring speed is 300r / min-900r / min and the dispersion time is 20min-90min.

6. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, The drying temperature is 80℃-130℃, and the drying time is 30min-120min; The pre-curing temperature is 180℃-320℃, and the pre-curing time is 30min-120min; After drying and pre-curing, the weight gain of the barrier-coated hard reinforcing particles relative to Cr3C2 particles is 6%-18%.

7. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, The Al2O3 particles are α-Al2O3 particles, and the particle size of the Al2O3 particles is 0.5μm-6μm; The binder in the aqueous binder solution is polyvinyl alcohol, sodium carboxymethyl cellulose, or polyvinylpyrrolidone. The water-based adhesive solution contains 1%-5% by mass of the adhesive. The spray granulation process includes: dispersing NiCrBSi alloy powder, barrier-coated hard reinforcing particles, and Al2O3 particles in an aqueous binder solution to obtain a spray granulation slurry; spray drying the spray granulation slurry to obtain agglomerated powder; and sieving the agglomerated powder to retain agglomerated powder with a particle size of 20μm-60μm as composite spray powder.

8. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, The thermal spraying method is either supersonic flame spraying or atmospheric plasma spraying; When using supersonic flame spraying, the spraying distance is 180mm-350mm, the powder feeding rate is 25g / min-70g / min, the spray gun moving speed is 300mm / s-800mm / s, and the surface temperature of the metal substrate during the spraying process is ≤220℃. When using atmospheric plasma spraying, the spraying current is 400A-700A, the spraying distance is 80mm-140mm, the powder feeding rate is 15g / min-55g / min, the spray gun moving speed is 250mm / s-700mm / s, and the surface temperature of the metal substrate during the spraying process is ≤260℃.

9. The method for preparing a wear-resistant and corrosion-resistant composite coating by thermal spraying on a metal substrate surface according to claim 1, characterized in that, The aqueous phosphate-silica sol blocking solution comprises, by mass percentage, 10%-30% aluminum dihydrogen phosphate, 15%-40% silica sol, 1%-5% boric acid, 0.1%-1.0% wetting agent, and the balance being deionized water; The silica sol contains 20%-40% SiO2 by mass. The wetting agent is a polyether-modified siloxane wetting agent, a nonionic fluorocarbon wetting agent, or an alkylphenol polyoxyethylene ether wetting agent.

10. A thermally sprayed wear-resistant and corrosion-resistant composite coating on the surface of a metal substrate, characterized in that, The wear-resistant and corrosion-resistant composite coating applied by thermal spraying to the surface of the metal substrate is prepared by the preparation method according to any one of claims 1-9; The thermally sprayed wear-resistant and corrosion-resistant composite coating on the surface of the metal substrate includes a corrosion-resistant transition layer and a composite surface layer located on the surface of the corrosion-resistant transition layer. The composite surface layer comprises a NiCrBSi alloy phase, a barrier-coated Cr3C2 hard reinforcing phase, an Al2O3 hard phase, and a cured phosphate-silica sol blocking phase. The barrier-coated Cr3C2 hard reinforcing phase includes Cr3C2 particles and an inorganic barrier coating phase attached to the surface of the Cr3C2 particles. The inorganic barrier coating phase comprises a Cr2O3 sheet-like barrier phase, a borosilicate glass sealing phase, an aluminum phosphate barrier phase, and a silica sol-cured phase. After the wear-resistant and corrosion-resistant composite coating thermally sprayed onto the surface of the metal substrate undergoes a pre-wear treatment with a wear depth of 30μm-80μm, and then a 96-hour neutral salt spray test, the corrosion expansion width at the outer edge of the wear area is ≤1.5mm.

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