Metal surface corrosion-resistant and wear-resistant coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of metal surface treatment, and particularly relates to a metal surface corrosion-resistant and wear-resistant coating as well as a preparation method and application thereof, and the coating comprises the following components in percentage by weight: 60-75% of nickel-based alloy powder, 5-15% of nano oxide particles, 10-25% of coated graphite particles and 5-10% of a metal binding phase; the coated graphite particles take graphite particles as cores, and the outer layers of the coated graphite particles are coated with metal oxide nano layers. The surface hardness and the wear resistance are obviously improved; the coated graphite particles of the core-shell structure effectively protect the stability of the graphite in a flame spraying high-temperature environment, avoid the problem of failure of functional components in the prior art, and gradually release the graphite in the service process to form a self-lubricating surface and reduce the friction coefficient. Through a multi-component synergistic effect mechanism, the coating can still keep surface integrity under the severe working condition of coexistence of high load and strong corrosion, and the service life of key parts is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to a corrosion-resistant and wear-resistant coating for metal surfaces, its preparation method, and its application. Background Technology

[0002] Metal surface engineering is a key technological field for improving the service performance of equipment components, especially in industries such as aerospace, marine engineering, and high-end equipment manufacturing, where extremely high requirements are placed on the corrosion resistance and wear resistance of metal substrates. As industrial equipment develops towards higher temperatures, higher pressures, and higher speeds, traditional single-function coatings are no longer sufficient to meet the long-term stable operation requirements under complex conditions. Therefore, developing composite functional coatings that combine excellent corrosion resistance and wear resistance has become an important research direction in the field of surface engineering, possessing significant economic and social value for extending the service life of critical components and reducing maintenance costs.

[0003] Flame spraying technology is widely used in the preparation of metal surface coatings due to its advantages such as simple equipment, flexible processes, and wide applicability to materials. Currently, nickel-based alloys are commonly used as the coating matrix material, and specific properties are improved by adding reinforcing phases. However, in practical applications, it has been found that existing coating systems often experience performance degradation during long-term service, especially under conditions of high load and coexistence of strong corrosive media, where the integrity of the coating surface is difficult to maintain, leading to premature failure of the matrix material. In-depth research shows that this is mainly due to uncontrollable physicochemical changes in the internal components of the coating during the preparation process, which prevents the designed functional components from fully functioning in the final coating, thus limiting the improvement of the overall coating performance.

[0004] To address these issues, the industry has explored various improvement solutions, including adjusting powder formulation, optimizing spraying parameters, and employing composite spraying processes. However, these methods often only achieve limited improvements in specific performance aspects and struggle to achieve a synergistic enhancement of both corrosion resistance and wear resistance. Traditional technical approaches face even greater challenges, especially when coatings require both low friction coefficients and high corrosion resistance. Summary of the Invention

[0005] The purpose of this application is to provide a corrosion-resistant and wear-resistant coating for metal surfaces and its preparation method, aiming to solve to a certain extent how to effectively protect the stability of functional components under flame spraying process conditions and achieve synergistic improvement of the corrosion resistance and wear resistance self-lubricating properties of metal surface coatings.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0007] In a first aspect, this application provides a corrosion-resistant and wear-resistant coating for a metal surface, the coating comprising the following components by weight percentage:

[0008] The composition consists of 60-75% nickel-based alloy powder, 5-15% nano-oxide particles, 10-25% coated graphite particles, and 5-10% metallic binder phase.

[0009] The coated graphite particles have a graphite core and are coated with a metal oxide nanolayer.

[0010] In some possible implementations, the nano-oxide particles are Al2O3 or TiO2 with an average particle size of 50~200 nm.

[0011] In some possible implementations, the nickel-based alloy powder is selected from one of 80Ni-20Cr powder, Inconel 625 powder, and Ni60A powder, with an average particle size of 10~50 μm.

[0012] In some possible implementations, the metal binder phase is selected from at least one of nickel powder, chromium powder, cobalt powder, and Ni-15Cr alloy powder, with an average particle size of 1 to 5 μm.

[0013] In some possible implementations, the average particle size of the graphite particles is 1 to 5 μm.

[0014] In some possible implementations, the thickness of the metal oxide nanolayer is 200-400 nm.

[0015] In some possible implementations, the metal oxide nanolayer is an Al2O3 nanolayer or a TiO2 nanolayer.

[0016] Secondly, this application provides a method for preparing a corrosion-resistant and wear-resistant coating on a metal surface, comprising the following steps:

[0017] Prepare the coated graphite particles;

[0018] The coated graphite particles, the nano-oxide particles, the metal binder phase, and the nickel-based alloy powder are mixed in a certain proportion and ball-milled to obtain a mixed powder.

[0019] Flame spraying: The mixed powder is deposited on the surface of a pretreated metal substrate using flame spraying technology to form a coating with corrosion and wear resistance.

[0020] In some possible implementations, the preparation of the coated graphite particles includes: dispersing the graphite particles in a solvent to form a suspension; dissolving a metal precursor in the solvent to form a precursor solution; adding the precursor solution to the suspension under stirring conditions and adjusting the pH value to cause the metal precursor to undergo hydrolysis and condensation reactions, forming a sol and adsorbing onto the surface of the graphite particles to obtain a slurry; aging the slurry to transform it into a gel, followed by drying and pulverizing to obtain a coated precursor powder; calcining the coated precursor powder under an inert atmosphere to transform the gel into the metal oxide nanolayer, and cooling to obtain the coated graphite particles.

[0021] In some possible implementations, the conditions for flame spraying include: using an oxy-acetylene flame spraying device, with an oxygen pressure of 0.5~0.8 MPa, an acetylene pressure of 0.3~0.7 MPa, a spraying distance of 100~200 mm, and a mixed powder feed rate of 80~120 g / min.

[0022] In some possible implementations, the metal precursor is an aluminum salt or an organoaluminum compound, the solvent is water or a mixture of ethanol and water, the pH value is adjusted to 5-8 by adding an alkaline regulator, and the calcination temperature is 600℃-1100℃ for 2-6 hours.

[0023] In some possible implementations, the metal precursor is tetrabutyl titanate or tetraisopropyl titanate, the solvent is ethanol or a mixture of ethanol and water, and diethanolamine is added to the precursor solution as a stabilizer.

[0024] In some possible implementations, the aging process includes stirring for 6 to 12 hours at a temperature of 60°C to 80°C.

[0025] Thirdly, this application provides a metal component whose surface is provided with a coating as described above or a coating obtained by the method for preparing a corrosion-resistant and wear-resistant coating as described above. The metal component is an engine component, marine engineering equipment, or mining machinery part.

[0026] The first aspect of this application provides a corrosion-resistant and wear-resistant coating for metal surfaces. Through optimized component ratios and structural design, it achieves excellent comprehensive performance. Nickel-based alloy powder serves as the main component, providing basic corrosion resistance. Nano-oxide particles are uniformly dispersed in the coating, significantly improving surface hardness and wear resistance. The core-shell structure of the coated graphite particles (graphite core + metal oxide nanolayer) effectively protects the stability of graphite under the high-temperature environment of flame spraying, avoiding the failure problem of functional components in existing processes. Furthermore, it gradually releases graphite during service, forming a self-lubricating surface and reducing the coefficient of friction. The metallic binder phase strengthens the bonding strength between the coating and the substrate, as well as between the internal components. This multi-component synergistic mechanism enables the coating to maintain surface integrity under harsh conditions of high load and strong corrosion, significantly extending the service life of critical components and solving the technical bottleneck of traditional single-function coatings that struggle to simultaneously achieve corrosion resistance and wear resistance with self-lubricating properties.

[0027] The second aspect of this application provides a method for preparing a corrosion-resistant and wear-resistant coating for metal surfaces, which enables a mixed powder containing coated graphite particles to form a gradient structure coating of "hard skeleton-lubricating network-bonding transition" on the surface of a metal substrate. This avoids the defects of functional component deactivation and weakened interfacial bonding in the preparation of traditional composite coatings, and improves the bonding strength of the coating while enhancing corrosion resistance, wear resistance, and self-lubricating properties.

[0028] The metal component provided in the third aspect of this application has the above-mentioned coating on its surface. Relying on the three-dimensional interpenetrating system of nickel-based alloy continuous network, nano-oxide hard phase and core-shell structure graphite lubricating phase, a synergistic protection mechanism of "corrosion barrier-wear resistance-self-lubrication renewal" is formed, realizing long-term protection under extreme working conditions. Detailed Implementation

[0029] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0031] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0032] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0033] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0034] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as µg, mg, g, or kg.

[0035] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0036] Before introducing the embodiments of this application, the research and development background involved in this application will be introduced first.

[0037] As modern industry continues to expand into extreme working environments, surface protection technology for metallic materials faces unprecedented challenges. In the aerospace field, aircraft engine components must resist combustion gas corrosion at temperatures of 400-600℃; marine engineering equipment must operate for extended periods in high-salt-spray, high-humidity environments; and critical components of heavy machinery must withstand continuous high-load friction and wear. These complex conditions place "multi-functional integrated" performance requirements on metal surface coatings—the coating must not only possess excellent corrosion resistance but also high hardness, a low coefficient of friction, and good toughness. Currently, it is widely recognized in the industry that single-function coatings are insufficient to meet the needs of modern high-end equipment, and the development of composite coating systems with multiple protective functions has become a research hotspot in the international surface engineering field. However, the compatibility issues between functional components and the contradictions between preparation processes and performance requirements present significant technical obstacles to achieving this goal.

[0038] Flame spraying, as a mainstream technology for metal surface treatment, is widely adopted by industry due to its advantages such as low cost, high efficiency, and wide applicability to various substrates. In recent years, researchers have attempted to improve coating performance by designing composite powder systems, such as introducing a combination of hard phases and solid lubricating phases into nickel-based alloy matrices. However, numerous experiments have shown that when coatings need to resist both chemical corrosion and mechanical wear simultaneously, a performance contradiction often arises: components that enhance hardness usually lead to increased brittleness and reduced coating toughness; while components that improve tribological properties often sacrifice corrosion resistance. More importantly, the intense thermodynamic conditions during flame spraying can trigger complex phase transitions and chemical reactions in powder components, causing the designed functional components to fail to maintain their original properties in the final coating. Industry experts have recognized that simply adjusting the powder composition ratio or optimizing process parameters is insufficient to fundamentally overcome this technical bottleneck; solutions must be sought from the perspective of collaborative innovation in material microstructure design and preparation processes.

[0039] Based on the aforementioned industry pain points, and through systematic exploration, we proposed an innovative concept for in-situ protection of functional components. We conducted in-depth research on the thermal behavior and chemical evolution of powder particles during flame spraying, discovering that the failure of functional components often stems from their unexpected interactions with the environmental medium during the high-temperature melting stage. Therefore, we envision constructing a protective barrier on the surface of functional components through microstructural design, ensuring their stability during spraying and allowing them to release their functional properties as needed during service.

[0040] The first aspect of this application provides a corrosion-resistant and wear-resistant coating for metal surfaces, comprising the following components by weight percentage:

[0041] The composition consists of 60-75% nickel-based alloy powder, 5-15% nano-oxide particles, 10-25% coated graphite particles, and 5-10% metallic binder phase.

[0042] Among them, the graphite-coated particles have graphite particles as the core and are coated with a metal oxide nanolayer on the outside.

[0043] The corrosion-resistant and wear-resistant coating for metal surfaces provided in the first aspect of this application achieves excellent comprehensive performance through optimized component ratios and structural design. Nickel-based alloy powder serves as the main component, providing basic corrosion resistance; nano-oxide particles are uniformly dispersed in the coating, significantly improving surface hardness and wear resistance; the core-shell structure of the coated graphite particles (graphite core + metal oxide nanolayer) effectively protects the stability of graphite under the high-temperature environment of flame spraying, avoiding the failure problem of functional components in existing processes, and gradually releases graphite during service, forming a self-lubricating surface and reducing the coefficient of friction; the metal binder phase strengthens the bonding strength between the coating and the substrate and the internal components. This multi-component synergistic mechanism enables the coating to maintain surface integrity under harsh conditions of high load and strong corrosion, significantly extending the service life of key components and solving the technical bottleneck of traditional single-function coatings that struggle to simultaneously achieve corrosion resistance and wear resistance with self-lubricating properties.

[0044] In some possible implementations, the nano-oxide particles are Al2O3 particles or TiO2 particles with an average particle size of 50~200 nm.

[0045] The aforementioned nano-oxide particles and coated graphite particles form a complementary and synergistic effect: the former provides rigid support to enhance surface hardness, while the latter achieves self-lubrication through controlled release. Together, they construct a microstructure of "hard skeleton-lubricating network," enabling the coating to maintain stable tribological properties and protective functions in harsh environments such as electrolytes and alternating acids and alkalis, thus solving the technical problem of rapid performance degradation of traditional coatings under complex working conditions.

[0046] In some possible implementations, the nickel-based alloy powder is selected from one of 80Ni-20Cr powder, Inconel 625 powder, and Ni60A powder, with an average particle size of 10~50 μm.

[0047] The aforementioned nickel-based alloy powder, together with the aforementioned nano-oxides and coated graphite particles, forms a triple synergistic mechanism: the nickel matrix provides a continuous corrosion-resistant network, the nano-oxides construct a hard, wear-resistant skeleton, and the coated graphite achieves intelligent lubrication response. This microstructure design reduces the corrosion current density of the coating in 3.5% NaCl solution to 10. -8 A / cm 2 With a particle size range of approximately 1.5, and a friction coefficient consistently below 0.15, this design successfully overcomes the technical bottlenecks of traditional coatings, such as interfacial peeling and rapid consumption of functional components under the coupled effects of alternating loads and corrosive media. This particle size range also ensures that the powder achieves an ideal melting state during flame spraying.

[0048] In some possible implementations, the metallic binder phase is selected from at least one of nickel powder, chromium powder, cobalt powder, and Ni-15Cr alloy powder, with an average particle size of 1 to 5 μm.

[0049] The aforementioned metallic binder phase, within this micron-sized particle size range, ensures both sufficient melting and flow during flame spraying and effectively fills the microscopic gaps between functional components, forming a three-dimensional interpenetrating network structure. The binder system acts like "molecular rivets," firmly anchoring the hard framework of the nano-oxide and the lubricating network of coated graphite to the metal substrate, increasing the coating bonding strength to over 70 MPa. This successfully solves the industry problem of functional components easily peeling off under high-load impact in traditional composite coatings.

[0050] In some possible implementations, the average particle size of the graphite particles is 1~5 μm.

[0051] The average particle size of the aforementioned graphite particles can be any typical but non-limiting point value or a range between any two points, such as 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm. In this case, the risk of excessive oxidation failure under the high temperature environment of flame spraying is avoided, and the coating stress concentration and interface peeling defects are overcome. During the spraying process, the metal oxide shell effectively isolates oxygen intrusion and protects the integrity of the internal graphite. During the service stage, the graphite is released in a gradient through friction and wear, forming a dynamically renewed lubricating film.

[0052] In some possible implementations, the thickness of the metal oxide nanolayer is 200–400 nm.

[0053] The thickness of the aforementioned metal oxide nanolayer can be any typical but not limiting value, such as 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm, or a range between any two values. In this case, a dense and continuous physical barrier can be formed, effectively blocking the erosion of the graphite core by oxygen in the high-temperature flame of flame spraying, thus avoiding the loss of lubrication function caused by graphite oxidation failure in traditional coatings. Furthermore, during service, precise gradient peeling can be achieved through frictional shear force, allowing the internal graphite to be exposed to the friction interface at a controllable rate, dynamically maintaining a low coefficient of friction.

[0054] In some possible implementations, the metal oxide nanolayer is an Al2O3 nanolayer or a TiO2 nanolayer.

[0055] The aforementioned metal oxide nanolayer forms a heterogeneous interface energy barrier with the core graphite, which not only blocks the diffusion path of oxygen atoms along the grain boundary during high-temperature spraying, but also enables the intelligent release of graphite through triboelectrochemical effects during service—when the contact stress of the friction pair exceeds the critical value, the coating layer generates controllable microcracks to precisely release the lubricating components.

[0056] The second aspect of this application provides a method for preparing a corrosion-resistant and wear-resistant coating on a metal surface, comprising the following steps:

[0057] Preparation of coated graphite particles;

[0058] The coated graphite particles, nano-oxide particles, metal binder phase and nickel-based alloy powder were mixed in a certain proportion and ball-milled to obtain a mixed powder.

[0059] Flame spraying: Mixed powders are deposited onto the surface of a pretreated metal substrate using flame spraying technology to form a coating with corrosion and wear resistance.

[0060] The second aspect of this application provides a method for preparing a corrosion-resistant and wear-resistant coating on a metal surface, which forms a gradient structure coating of "hard skeleton-lubricating network-bonding transition" on the surface of a metal substrate by mixing powder containing coated graphite particles. This avoids the defects of functional component deactivation and weakened interfacial bonding in the preparation of traditional composite coatings, improves the bonding strength of the coating, and enhances corrosion resistance, wear resistance, and self-lubricating properties.

[0061] It should be noted that the metal substrate includes, but is not limited to, steel, aluminum alloys, titanium alloys, and copper alloys. Steel includes ordinary carbon steel, low-alloy steel, high-alloy steel, and stainless steel. The surface pretreatment of the metal substrate specifically includes the following steps: First, the surface of the metal substrate to be coated is mechanically ground. Then, the ground surface is ultrasonically cleaned using anhydrous ethanol or acetone. After cleaning, the metal substrate is placed in an oven at 80~100℃ for 30~45 minutes to ensure complete drying. For some applications requiring extremely high surface cleanliness, after mechanical grinding and ultrasonic cleaning, sandblasting can be further performed. Brown corundum abrasive with a particle size of 0.5~1.0mm is used, and the metal substrate surface is sandblasted at a spray angle of 45~60° under a compressed air pressure of 0.4~0.6MPa. The sandblasting time is adjusted according to the substrate material and surface condition.

[0062] In some possible implementations, the preparation of coated graphite particles includes: dispersing graphite particles in a solvent to form a suspension; dissolving a metal precursor in the solvent to form a precursor solution; adding the precursor solution to the suspension under stirring conditions and adjusting the pH value to cause the metal precursor to undergo hydrolysis and condensation reactions, forming a sol and adsorbing onto the surface of the graphite particles to obtain a slurry; aging the slurry to transform it into a gel, followed by drying and pulverizing to obtain coated precursor powder; calcining the coated precursor powder under an inert atmosphere to transform the gel into a metal oxide nanolayer, and cooling to obtain coated graphite particles.

[0063] The above-mentioned method for preparing coated graphite particles first generates a uniform sol layer in situ on the surface of the graphite particles. Precise pH control induces directional hydrolysis of the metal precursor, forming a gel coating layer with a three-dimensional network structure. Subsequently, stepwise calcination under an inert atmosphere transforms the gel into a dense Al₂O₃ or TiO₂ nanolayer with a thickness of 200–400 nm. This creates a Si-OC or Ti-OC covalent bond interface between the graphite core and the metal oxide shell, significantly enhancing the bonding strength. In the high-temperature environment of 2000℃–3000℃ during flame spraying, it effectively blocks oxygen molecule penetration, exhibiting tribological intelligent response characteristics: maintaining an intact passivation film in low-stress areas to provide corrosion resistance, while in high-stress friction areas, the coating layer enables controlled micro-cracks to release graphite in a gradient, forming a dynamically renewed lubricating film and reducing the wear rate of the coating.

[0064] In some possible implementations, the conditions for flame spraying include: using an oxy-acetylene flame spraying device with an oxygen pressure of 0.5~0.8 MPa, an acetylene pressure of 0.3~0.7 MPa, a spraying distance of 100~200 mm, and a mixed powder feed rate of 80~120 g / min.

[0065] In the above-mentioned flame spraying conditions, the oxygen pressure can be any typical but non-limiting point value or a range between any two points, such as 0.5 MPa, 0.6 MPa, 0.7 MPa, and 0.8 MPa; the acetylene pressure can be any typical but non-limiting point value or a range between any two points, such as 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, and 0.7 MPa; the spraying distance can be any typical but non-limiting point value or a range between any two points, such as 100 mm, 120 mm, 150 mm, 180 mm, and 200 mm; and the mixed powder feed rate can be any typical but non-limiting point value or a range between any two points, such as 80 g / min, 90 g / min, 100 g / min, 110 g / min, and 120 g / min. In this configuration, the optimized oxygen-to-acetylene pressure ratio creates a flame atmosphere with sufficient enthalpy and moderate reducing properties. This ensures that the nickel-based alloy powder fully melts to form a continuous matrix while effectively inhibiting the oxidative decomposition of the coated graphite particles at high temperatures. The synergistic effect of the spraying distance and powder feed rate allows functional components with different particle sizes and melting points to undergo differentiated thermal processes during flight, ultimately forming a gradient structure on the matrix surface: "semi-molten hard phase anchoring - partially molten binder phase bridging - controllable distribution of the surface coating phase." This gives the coating both long-lasting corrosion protection and intelligent friction reduction properties.

[0066] In some possible implementations, the metal precursor is an aluminum salt or an organoaluminum compound, the solvent is water or a mixture of ethanol and water, the pH value is adjusted to 5-8 by adding an alkaline regulator, the calcination temperature is 600℃-1100℃, and the time is 2-6 hours.

[0067] In the aforementioned implementation, aluminum salts or organoaluminum compounds exhibit ideal hydrolytic activity and film-forming properties in water or a mixture of ethanol and water. Combined with precise pH control, this promotes directional hydrolysis and condensation reactions of the precursor on the graphite surface, forming a uniform and continuous gel coating layer. Subsequent heat treatment under an inert atmosphere gradually transforms the gel structure into a metal oxide nanolayer with excellent density and interfacial bonding strength. Through the synergistic control of chemical environment and thermodynamic conditions, a stable chemical bonding interface is formed between the coating layer and the graphite core. This constructs an effective anti-oxidation barrier in the extreme high-temperature environment of flame spraying and endows the coating with intelligent responsive characteristics during service—when the frictional stress reaches a critical value, the coating layer generates controllable microcracks, precisely releasing the internal graphite to form a dynamic lubricating film. This enables the coating to exhibit long-term stability under corrosion-wear coupling conditions.

[0068] In some possible implementations, the metal precursor is tetrabutyl titanate or tetraisopropyl titanate, the solvent is ethanol or a mixture of ethanol and water, and diethanolamine is added to the precursor solution as a stabilizer.

[0069] In the above implementation, tetrabutyl titanate or tetraisopropyl titanate is used as the titanium source precursor, combined with an ethanol-based solvent system and diethanolamine stabilizer, to achieve precise molecular-level coating of TiO2 nanolayers on the surface of graphite particles. Diethanolamine, by forming a stable five-membered ring coordination structure with the central titanium atom, effectively regulates the hydrolysis kinetics of the precursor, avoiding the non-uniform deposition and particle agglomeration caused by violent hydrolysis in the traditional sol-gel process. Ethanol, as the main solvent, not only reduces the polarity of the system and slows down the hydrolysis rate, but also creates an ideal microenvironment through synergistic effects with water, enabling the TiO2 precursor to undergo directional deposition on the graphite surface rather than bulk gelation. Crucially, the coordination effect of diethanolamine induces the formation of anatase TiO2 phase rich in oxygen vacancies. Its semiconductor properties allow it to form a self-healing passivation film in a corrosive environment, creating a synergistic effect with the self-lubricating function of the internal graphite. This solves the technical bottleneck of easy cracking and weak bonding of titanium-based coatings, enabling the coating to maintain the electrochemical stability of the base metal and maintain an ultra-low coefficient of friction through friction-induced graphite gradient release under extreme working conditions where alternating loads and strong corrosive media coexist.

[0070] In some possible implementations, the aging process includes stirring at a temperature of 60°C to 80°C for 6 to 12 hours.

[0071] In the aforementioned implementation, the temperature range precisely balances the condensation reaction rate of the gel network with the solvent evaporation rate, avoiding both insufficient cross-linking caused by low-temperature aging and structural shrinkage and cracking caused by high-temperature treatment. Under continuous stirring, the gel precursor molecules undergo an Ostwald ripening process on the graphite surface, promoting the dissolution and redeposition of small particles onto the surface of larger particles, forming a uniform, continuous, and dense coating layer. This aging mechanism creates abundant COM (M=Al or Ti) chemical bonding interfaces between the graphite core and the metal oxide precursor, significantly improving the core-shell bonding strength, while simultaneously constructing a microporous structure in the gel network that facilitates stress buffering. The precursor treated in this way exhibits excellent structural retention during subsequent calcination, resulting in a final metal oxide coating layer that combines high density with moderate toughness. Under the extreme thermal shock of flame spraying, it can effectively block oxygen diffusion, and during service, it can achieve precise release of graphite through the microcrack network.

[0072] The third aspect of this application provides a metal component, the surface of which is provided with the coating as described above or the coating obtained by the above method for preparing corrosion-resistant and wear-resistant coatings, the metal component being an engine component, marine engineering equipment, or mining machinery part.

[0073] The metal component provided in the third aspect of this application has a coating on its surface as described above or a coating obtained by the above method for preparing a corrosion-resistant and wear-resistant coating. Relying on a three-dimensional interpenetrating system of nickel-based alloy continuous network, nano-oxide hard phase and core-shell structured graphite lubricating phase, a synergistic protection mechanism of "corrosion barrier-wear resistance-self-lubrication renewal" is formed, achieving long-term protection under extreme working conditions.

[0074] To enable those skilled in the art to clearly understand the above-described implementation details and operations of this application, and to demonstrate the significant improvement in the performance of the corrosion-resistant and wear-resistant coatings for metal surfaces and their preparation methods in the embodiments of this application, the above technical solutions are illustrated below through multiple embodiments.

[0075] Example 1

[0076] Coating components (by weight percentage):

[0077] Nickel-based alloy powder (Inconel 625 powder, average particle size 30 μm) 70%;

[0078] Al2O3 particles (average particle size 100nm) 10%;

[0079] 15% of the graphite particles were coated.

[0080] Metal binder phase (Cr powder, average particle size 20 μm) 5%;

[0081] Preparation of coated graphite particles:

[0082] 10.0 g of graphite particles (average particle size 3 μm) were ultrasonically dispersed in 150 mL of ethanol-water mixture (volume ratio 1:1) for 30 min to obtain a graphite suspension.

[0083] Dissolve 25.0 g of aluminum nitrate nonahydrate [Al(NO3)3·9H2O] in 50 mL of deionized water to prepare a precursor solution;

[0084] Under mechanical stirring, the precursor solution was slowly added dropwise to the graphite suspension, while the pH was adjusted to 7.0 with 1 mol / L ammonia.

[0085] The mixture was stirred continuously for 6 hours to allow for complete hydrolysis and condensation. It was then aged in a water bath at 70°C for 10 hours to form a gel. After drying at 80°C for 8 hours, the gel was ground through a 200-mesh sieve to obtain the coated precursor powder.

[0086] Under nitrogen protection, the graphite was calcined at 800℃ for 4 hours and then cooled to obtain Al2O3-coated graphite particles (Al2O3 nanolayer thickness 300nm).

[0087] Coating preparation:

[0088] The above components were mixed in proportion and ball-milled at 200 rpm for 4 hours to obtain a mixed powder.

[0089] The oxygen-acetylene flame spraying equipment was used, with the following parameters: oxygen pressure 0.6 MPa, acetylene pressure 0.5 MPa, spraying distance 150 mm, and mixed powder feed rate 100 g / min.

[0090] The coating thickness is controlled at 150±10μm.

[0091] Example 2

[0092] Coating composition: Inconel 625 powder was replaced with 80Ni-20Cr powder, Al2O3-coated graphite particles were replaced with TiO2-coated graphite particles, and the rest were the same as in Example 1;

[0093] Preparation of coated graphite particles:

[0094] 8.0 g of graphite particles (average particle size 3 μm) were ultrasonically dispersed in 120 mL of anhydrous ethanol for 40 min to obtain a graphite suspension.

[0095] 15.0 mL of tetrabutyl titanate and 8.0 mL of diethanolamine were dissolved in 40 mL of anhydrous ethanol to obtain a precursor solution.

[0096] Under nitrogen protection, the precursor solution was slowly added dropwise to the graphite suspension by mechanical stirring, and stirring was continued for 6 hours.

[0097] The mixture was stirred continuously for 6 hours to allow for complete hydrolysis and condensation. It was then aged in a water bath at 70°C for 10 hours to form a gel. After drying at 80°C for 8 hours, the gel was ground through a 200-mesh sieve to obtain the coated precursor powder.

[0098] Calcination at 900℃ for 5 hours under argon protection, followed by cooling, yielded TiO2-coated graphite particles.

[0099] Coating preparation: Same as in Example 1.

[0100] Example 3

[0101] The only difference from Example 1 is that 15g of aluminum nitrate nonahydrate [Al(NO3)3·9H2O] was dissolved in 50mL of deionized water to prepare a precursor solution; the resulting Al2O3-coated graphite particles (Al2O3 nanolayer thickness 200nm) were obtained.

[0102] Example 4

[0103] The only difference from Example 1 is that 30g of aluminum nitrate nonahydrate [Al(NO3)3·9H2O] was dissolved in 50mL of deionized water to prepare a precursor solution; the resulting Al2O3-coated graphite particles (Al2O3 nanolayer thickness 400nm) were obtained.

[0104] Example 5

[0105] The only difference from Example 1 is the flame spraying parameters: oxygen 0.7MPa, acetylene 0.6MPa, spraying distance 120mm, and feed rate 110g / min.

[0106] Comparative Example 1

[0107] Coating components (by weight percentage):

[0108] Inconel 625 powder (average particle size 30μm) 70%;

[0109] Al2O3 particles (average particle size 100nm) 10%;

[0110] Graphite particles (average particle size 3μm) 15%;

[0111] Cr powder (average particle size 20μm) 5%;

[0112] Coating preparation: Same as in Example 1.

[0113] Comparative Example 2

[0114] Coating components (by weight percentage):

[0115] Inconel 625 powder (average particle size 30μm) 70%;

[0116] Al2O3 particles (average particle size 100nm) 10%;

[0117] Physical mixture: 10% graphite particles (average particle size 3μm) + 5% micron-sized Al2O3 (average particle size 1μm);

[0118] Cr powder 5%;

[0119] Coating preparation: Same as in Example 1.

[0120] Comparative Example 3

[0121] The only difference from Example 1 is that the coating material is Ni60A nickel-based alloy powder.

[0122] Furthermore, to verify the advancements of the corrosion-resistant and wear-resistant coating on the metal surface and its preparation method in this application, wear resistance and coefficient of friction were tested according to ASTM G99-17, salt spray corrosion resistance was tested according to ASTM B117, coating adhesion strength was tested according to ASTM C633-13, and electrochemical corrosion performance was tested according to ASTM G59. The test results are shown in Table 1 below.

[0123] Table 1

[0124] sample Coating composition characteristics Wear mass loss (mg) coefficient of friction 1000h salt spray corrosion area (%) Bond strength (MPa) <![CDATA[Corrosion current density (μA / cm 2 )]]> Example 1 <![CDATA[Graphite (300 nm) coated with Al2O3, Inconel 625 matrix]]> 0.018 0.12 0.35 68.5 0.30 Example 2 <![CDATA[Graphite coated with TiO2 (300 nm), 80Ni-20Cr matrix]]> 0.015 0.11 0.15 65.8 0.25 Example 3 <![CDATA[Graphite (200nm) coated with Al2O3]]> 0.021 0.15 0.45 63.2 0.35 Example 4 <![CDATA[Graphite (400 nm) coated with Al2O3]]> 0.025 0.19 0.85 58.5 0.45 Example 5 Optimize spraying parameters 0.017 0.11 0.32 69.0 0.28 Comparative Example 1 Ordinary graphite (uncoated) 0.035 0.28 5.20 45.2 1.80 Comparative Example 2 <![CDATA[Physical mixture of Al2O3 + graphite]]> 0.028 0.22 1.85 48.3 0.65 Comparative Example 3 Traditional nickel-based coatings 0.030 0.25 5.20 52.3 2.50

[0125] As shown above, Example 1 (Al2O3-coated graphite) reduced wear mass loss by 48.6% and 35.7% compared to Comparative Example 1 (ordinary graphite) and Comparative Example 2 (physically mixed Al2O3 + graphite), and reduced salt spray corrosion area by 93.3% and 81.1%, respectively. The effective protection of the graphite core by the metal oxide nanolayer significantly improved the functional stability of the coating throughout its preparation and service life. The coating structure not only prevented the oxidation failure of graphite during flame spraying but also realized the friction-induced graphite gradient release mechanism during service.

[0126] The performance of Examples 3 (200 nm) and 4 (400 nm) was inferior to that of Example 1 (300 nm), confirming that there is an optimal window for coating thickness. The 200 nm thickness was insufficient in protection, leading to early oxidation of graphite, while the 400 nm thickness caused microcrack propagation due to increased brittleness. The 300 nm thickness achieved the best balance between protection and flexibility, enabling the coating to maintain functional integrity in a corrosion-wear coupled environment.

[0127] Example 2 (TiO2 coating + 80Ni-20Cr) showed improved corrosion resistance in salt spray with a corrosion area of ​​0.15% and a corrosion current density of 0.25 μA / cm². 2In terms of performance, it is the best, with its semiconductor-like TiO2 layer forming a self-healing passivation film in a chloride ion environment; while Example 1 (Al2O3 coating + Inconel 625) has a greater advantage in overall mechanical properties.

[0128] Example 5, by adjusting the spraying parameters and increasing the strength to 69.0 MPa, further verified the decisive influence of the precise matching of the flame thermodynamic environment and powder kinetic behavior on the coating interface quality.

[0129] All embodiments were significantly superior to Comparative Example 3 (traditional nickel-based coating), with Example 1 showing an 88.0% reduction in corrosion current density and a 30.9% increase in bonding strength, completely overturning the traditional perception that "corrosion resistance and wear resistance" are mutually exclusive. This breakthrough stems from the synergistic mechanism of the four-level protection system (coated graphite core-shell structure, nano-oxide framework, metal bonding phase bridging, and nickel-based continuous network).

[0130] In summary, this invention successfully solves the common industry problem of functional component deactivation, interface degradation, and performance degradation of metal surface coatings under extreme conditions through molecular-level interface design, multi-scale structural control, and process-material synergistic optimization, providing surface protection for metal components that combines environmental adaptability and service durability.

[0131] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0132] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A corrosion-resistant and wear-resistant coating for metal surfaces, characterized in that, Includes the following components by weight percentage: The composition consists of 60-75% nickel-based alloy powder, 5-15% nano-oxide particles, 10-25% coated graphite particles, and 5-10% metallic binder phase. The coated graphite particles have a graphite core and are coated with a metal oxide nanolayer.

2. The corrosion-resistant and wear-resistant coating for metal surfaces according to claim 1, characterized in that, The nano-oxide particles are Al2O3 particles or TiO2 particles with an average particle size of 50~200 nm.

3. The corrosion-resistant and wear-resistant coating for metal surfaces according to claim 1, characterized in that, The nickel-based alloy powder is selected from one of 80Ni-20Cr powder, Inconel 625 powder, and Ni60A powder, with an average particle size of 10~50 μm; And / or, the metal binder phase is selected from at least one of nickel powder, chromium powder, cobalt powder, and Ni-15Cr alloy powder, with an average particle size of 1~5 μm.

4. The corrosion-resistant and wear-resistant coating for metal surfaces according to claim 1, characterized in that, The average particle size of the graphite particles is 1~5 μm; And / or, the thickness of the metal oxide nanolayer is 200~400 nm.

5. The corrosion-resistant and wear-resistant coating for metal surfaces according to claim 4, characterized in that, The metal oxide nanolayer is an Al2O3 nanolayer or a TiO2 nanolayer.

6. A method for preparing a corrosion-resistant and wear-resistant coating on a metal surface as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Prepare the coated graphite particles; The coated graphite particles, the nano-oxide particles, the metal binder phase, and the nickel-based alloy powder are mixed in a certain proportion and ball-milled to obtain a mixed powder. Flame spraying: The mixed powder is deposited on the surface of a pretreated metal substrate using flame spraying technology to form a coating with corrosion and wear resistance.

7. The preparation method according to claim 6, characterized in that, The preparation of the coated graphite particles includes: dispersing the graphite particles in a solvent to form a suspension; dissolving a metal precursor in the solvent to form a precursor solution; adding the precursor solution to the suspension under stirring conditions and adjusting the pH value to cause the metal precursor to undergo hydrolysis and condensation reactions, forming a sol and adsorbing onto the surface of the graphite particles to obtain a slurry; aging the slurry to transform it into a gel, followed by drying and pulverizing to obtain a coated precursor powder; calcining the coated precursor powder under an inert atmosphere to transform the gel into the metal oxide nanolayer, and cooling to obtain the coated graphite particles. And / or, the conditions for flame spraying include: using an oxy-acetylene flame spraying device, with an oxygen pressure of 0.5~0.8MPa, an acetylene pressure of 0.3~0.7MPa, a spraying distance of 100~200 mm, and a mixed powder feed rate of 80~120g / min.

8. The preparation method according to claim 7, characterized in that, The metal precursor is an aluminum salt or an organoaluminum compound, the solvent is water or a mixture of ethanol and water, the pH value is adjusted to 5-8 by adding an alkaline regulator, and the calcination temperature is 600℃-1100℃ for 2-6 hours. Alternatively, the metal precursor is tetrabutyl titanate or tetraisopropyl titanate, the solvent is ethanol or a mixture of ethanol and water, and diethanolamine is added to the precursor solution as a stabilizer.

9. The preparation method according to claim 7, characterized in that, The aging process includes stirring at a temperature of 60℃ to 80℃ for 6 to 12 hours.

10. A metal component, characterized in that, The surface of the metal component is provided with a coating as described in any one of claims 1 to 5 or a coating obtained by the method for preparing a corrosion-resistant and wear-resistant coating as described in any one of claims 6 to 9, wherein the metal component is an engine component, marine engineering equipment, or mining machinery part.