Method for preparing al-al2o3-tpu hybrid corrosion-resistant coating by low-pressure cold spraying and application thereof

Abstract

The application provides a method for preparing an Al-Al2O3-TPU mixed corrosion-resistant coating by low-pressure cold spraying, and the method comprises the following steps: performing surface treatment on a substrate, and sequentially performing polishing, polishing, cleaning, drying and sand blasting to obtain a substrate to be sprayed; mechanically mixing Al powder, Al2O3 ceramic particles and thermoplastic polyurethane (TPU) powder to obtain cold spraying pre-made powder; spraying the cold spraying pre-made powder onto the substrate to be sprayed under low pressure, and performing polishing and correction after the coating is cooled and solidified to obtain an Al-Al2O3-TPU mixed corrosion-resistant coating. The coating prepared by the method has good compactness and uniformity, has good mechanical properties and corrosion resistance, can be applied to marine engineering environment, and can resist seawater scouring and corrosion.

Description

Technical Field

[0001] The invention belongs to the technical field of surface engineering, and particularly relates to a method for preparing an Al-Al2O3-TPU mixed corrosion-resistant coating by low-pressure cold spraying and an application thereof. Background Art

[0002] In the field of surface additive remanufacturing, the development and application of corrosion-resistant coatings have received widespread attention. This is because corrosion-resistant coatings can effectively protect the substrate, extend its service life, reduce maintenance costs, and improve economic benefits. Among various metal materials, Al metal is widely used in various industrial fields such as chemical, petroleum, and marine industries due to its excellent corrosion resistance. However, there are many problems with traditional corrosion-resistant coating preparation technology, such as the generation of pores and cracks, and higher spraying problems causing deformation of the metal substrate, phase change, and thermal stress damage. In order to solve this problem, many scholars have studied methods to improve coating quality from different aspects, such as selecting appropriate coating preparation methods and continuously optimizing the process to improve coating quality, and introducing suitable filler materials to seal pores and defects in the coating to improve the quality of the coating and thus improve corrosion resistance.

[0003] Traditional coating preparation methods, such as thermal spraying and electroplating, usually require high energy consumption to generate high temperatures to make the metal material molten or semi-molten, and then spray it onto the surface of the substrate through high-speed airflow to cause thermoplastic deformation and cooling, forming a layered coating. Due to its inherent technical limitations, the prepared coating has many defects, such as pores, cracks, and unmelted particles. These defects can serve as transmission channels for corrosive media in actual working conditions. The corrosive media can penetrate into the interior of the substrate and cause corrosion of the equipment, reducing the service life of the equipment. In addition, traditional coating preparation technology also has complex process flows and is prone to environmental pollution. Therefore, it is necessary to find a low-energy, environmentally friendly coating preparation method. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a method for preparing an Al-Al2O3-TPU hybrid corrosion-resistant coating by low-pressure cold spraying and its application. The coating can be applied to marine engineering environments and can resist seawater erosion and corrosion.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing Al-Al2O3-TPU hybrid corrosion-resistant coating by low-pressure cold spraying, the method comprising:

[0006] S1. Substrate preparation: The substrate is subjected to surface treatment, and is sequentially ground, polished, cleaned, dried, and sandblasted to obtain the substrate to be sprayed;

[0007] S2, mechanically mixing Al powder, Al2O3 ceramic particles, and thermoplastic polyurethane TPU powder to obtain a cold spray preformed powder;

[0008] S3, cold spraying the preformed powder obtained in S2 onto the substrate to be sprayed obtained in S1 at low pressure, and after the coating is cooled and solidified, polishing and correcting are performed to obtain an Al-Al2O3-TPU hybrid corrosion-resistant coating;

[0009] The process parameters of the low-pressure cold spraying are: the working gas is compressed air, the carrier gas pressure is 0.2-0.5 MPa, the carrier gas temperature is 150-200° C., the nozzle is 10-20 mm away from the substrate, and the spraying speed is 30-60 g / min.

[0010] Preferably, the substrate in S1 is 316L stainless steel.

[0011] Preferably, the Al powder in S2 is a nearly spherical powder with a particle size of 10 μm to 40 μm and a purity of ≥99.9%; the Al2O3 ceramic particles are irregular particles with a particle size of 20 μm to 50 μm and a purity of ≥99.9%; the thermoplastic polyurethane TPU powder has a particle size of 20 μm to 50 μm and a purity of ≥99.9%.

[0012] Preferably, the cold spray preformed powder in S2 is composed of the following raw materials in mass fractions: 35% Al powder, 35% Al2O3 ceramic particles, and the remainder being thermoplastic polyurethane TPU powder.

[0013] Preferably, the mechanical mixing time in S2 is 8 hours.

[0014] Preferably, the average thickness of the Al-Al2O3-TPU mixed corrosion-resistant coating in S3 is 500 μm to 2 mm.

[0015] Preferably, the annual average immersion corrosion rate of the Al-Al2O3-TPU hybrid corrosion-resistant coating in S3 is 0.011~0.012mm / a, and the annual average erosion corrosion rate is 0.012~0.013mm / a; the bonding strength between the Al-Al2O3-TPU hybrid corrosion-resistant coating and the substrate is 23.62~26.36MPa, and the porosity of the Al-Al2O3-TPU hybrid corrosion-resistant coating is 2.35%~2.67%.

[0016] The present invention also provides the application of the Al-Al2O3-TPU mixed corrosion-resistant coating prepared by the above method, and the Al-Al2O3-TPU mixed corrosion-resistant coating is used in marine engineering.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention combines Al metal powder, Al2O3 ceramic particles, and polymer TPU to create a composite coating with multiple excellent properties. Each material plays a unique role in the coating, providing comprehensive protective effects. The composite coating is prepared using low-pressure cold spray technology, which enables efficient deposition at lower temperatures, reducing the impact of thermal stress on the substrate and coating, and improving the coating's adhesion and overall performance. The resulting coating not only exhibits excellent mechanical strength and corrosion resistance, but also possesses good thermal stability and toughness, making it suitable for a variety of demanding applications.

[0019] The Al-Al2O3-TPU hybrid coating prepared by low-pressure cold spraying in this invention has good adhesion, low porosity, and excellent corrosion resistance, while avoiding the thermal damage to the substrate that may be caused by traditional high-temperature thermal spraying. Its advantages over existing technologies are mainly as follows:

[0020] (1) Improve coating density and uniformity

[0021] Selecting a TPU powder particle size within the range of 20 to 50 μm ensures the fluidity and deposition efficiency of the powder during the spraying process, thereby forming a uniform and dense coating; spraying is carried out within the optimal temperature range of 150 to 200 ° C, which not only ensures the plastic deformation of the Al metal powder, but also ensures the full melting and filling of the TPU powder, significantly improving the density and surface smoothness of the coating.

[0022] (2) Enhance the mechanical properties and corrosion resistance of the coating

[0023] The use of TPU powder with a purity of ≥99.9% ensures the stability and corrosion resistance of the coating in high temperature and marine environments, extending the service life of the coating; by designing a suitable coating material ratio, it not only has good mechanical strength and toughness, but also has excellent wear resistance and impact resistance, adapting to a wider range of application scenarios.

[0024] (3) Energy conservation and environmental protection

[0025] Compared with traditional thermal spraying methods, the cold spraying process can achieve efficient coating preparation at a lower temperature, reducing energy consumption, thermal pollution to the environment and the risk of metal powder oxidation.

[0026] (4) Adapt to various application environments

[0027] The coating formed by using Al-Al2O3-TPU mixed material has good comprehensive properties such as seawater corrosion resistance, high temperature resistance, wear resistance and high strength, and is suitable for various application fields such as ocean, aviation, and chemical industry.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the SEM image of the Al-Al2O3 mixed prefabricated powder of Example 1.

[0030] Figure 2 This is a physical picture of the TPU powder of Example 1.

[0031] Figure 3 This is a pore test distribution diagram of the Al-Al2O3-TPU mixed corrosion-resistant coating prepared in Example 1.

[0032] Figure 4 This is a graph showing the seawater immersion corrosion and erosion corrosion rates of the Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in Example 1 of the present invention.

[0033] Figure 5 This is a microscopic image of the Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in Example 1 of the present invention, including (a) a surface SEM image and (b) a cross-sectional schematic diagram. DETAILED DESCRIPTION

[0034] Example 1

[0035] The method of preparing Al-Al2O3-TPU mixed corrosion-resistant coating by low-pressure cold spraying in this embodiment is as follows:

[0036] S1. Substrate preparation: The aluminum-based material is surface treated by grinding, polishing, cleaning, drying, and sandblasting in sequence to obtain the substrate to be sprayed; the preliminary treatment of the substrate can ensure that the substrate surface is clean, dry and roughened, and enhance the adhesion of the coating.

[0037] S2, mechanically mixing Al powder, Al2O3 ceramic particles, and thermoplastic polyurethane TPU powder for 8 hours to obtain a cold spray preformed powder;

[0038] After Al powder and Al2O3 ceramic particles are mixed, the SEM image of the Al-Al2O3 mixed prefabricated powder is as follows: Figure 1 , Al powder is a nearly spherical powder with a particle size of 10μm to 40μm (purity ≥99.9%), Al2O3 ceramic particles are irregular particles with a particle size of 20μm to 50μm (purity ≥99.9%, oxygen content O2 ≤300ppm); the particle size of thermoplastic polyurethane TPU powder is 20μm to 50μm, purity ≥99.9% ( Figure 2 ); the cold spray preformed powder is composed of the following mass fractions of raw materials: Al powder 35%, Al2O3 ceramic particles 35%, the balance being thermoplastic polyurethane TPU powder;

[0039] Thermoplastic polyurethane TPU powder was purchased from Huafeng Thermoplastic Polyurethane Co., Ltd.

[0040] In this embodiment, the particle size of each raw material in the cold spray preformed powder is small, which ensures the fluidity and deposition efficiency of the powder during the spraying process, thereby forming a uniform and dense coating. This is not only suitable for cold spraying technology, but can effectively improve the deposition rate and fill the tiny pores in the Al coating. In addition, the smaller particle size can improve the flatness of the coating surface and reduce the roughness of the coating.

[0041] The use of high-purity TPU powder ensures the stability and corrosion resistance of the coating in high temperature and marine environments, extending the service life of the coating; by designing a suitable coating material ratio, it not only has good mechanical strength and toughness, but also has excellent wear resistance and impact resistance, adapting to a wider range of application scenarios.

[0042] S3, cold spraying the cold spray preformed powder obtained in S2 onto the substrate to be sprayed obtained in S1 at low pressure, and after the coating is cooled and solidified, grinding and correcting are performed to obtain an Al-Al2O3-TPU hybrid corrosion-resistant coating with an average thickness of 500 μm;

[0043] The low-pressure cold spraying process parameters are: compressed air as the working gas, a carrier gas pressure of 0.5 MPa, a carrier gas temperature of 150°C, a nozzle distance of 10 mm from the substrate, and a spray rate of 30 g / min. During the cold spraying process, the Al powder undergoes plastic deformation at high temperature and high speed, meshing with the substrate. The Al2O3 ceramic particles act as a reinforcing composite material, enhancing the coating's hardness and strength. The TPU powder, through melting, wetting, and cooling, forms a sealing layer during the spraying process, filling pores and defects in the Al-based coating and enhancing the coating's overall corrosion resistance.

[0044] The spraying of this embodiment is carried out at a low temperature (150°C), which will not damage the substrate and polymer, and ensures both the plastic deformation of the Al metal powder and the sufficient melting and filling of the TPU powder, thereby significantly improving the density and surface smoothness of the coating.

[0045] Compared with traditional thermal spraying methods, the cold spraying process can achieve efficient coating preparation at a lower temperature, reducing energy consumption, thermal pollution to the environment and the risk of metal powder oxidation.

[0046] The main functions of each element in the Al-Al2O3-TPU mixed corrosion-resistant coating are as follows:

[0047] Function of Al element:

[0048] (1) Enhance mechanical properties

[0049] As a metal material, Al has high hardness and strength, which can improve the hardness and strength of the overall coating and improve its impact resistance and wear resistance.

[0050] (2) Improve corrosion resistance

[0051] Al can quickly form a dense Al2O3 film in the air. This film has good chemical stability and excellent corrosion resistance to a variety of acids, alkalis and salt solutions. This enables the coating to work stably for a long time in harsh chemical environments and can effectively prevent further corrosion of the substrate by oxygen and moisture.

[0052] (3) Enhance coating toughness

[0053] The toughness of Al can make the coating less likely to crack when subjected to mechanical stress or thermal stress. When subjected to impact or vibration, the presence of Al can provide a certain buffering effect, protecting the substrate from damage and thus extending the service life of the coating.

[0054] Function of Al2O3 ceramic particles:

[0055] (1) Ceramic particles have extremely high hardness, and incorporating them into the coating can significantly improve the overall hardness and wear resistance of the coating.

[0056] (2) It has excellent chemical stability and can effectively resist the erosion of corrosive media in the marine environment.

[0057] (3) Ceramic particles can fill tiny defects and pores in the coating, increase the density of the coating, and thus improve the overall performance of the coating.

[0058] (3) It has good thermal stability and can maintain its physical and chemical properties in high temperature environment, thus enhancing the stability of the coating under high temperature conditions.

[0059] TPU function:

[0060] (1) Function of binder:

[0061] As a binder, TPU can effectively combine aluminum-based materials and alumina ceramic particles to form a uniform and dense coating structure. Its excellent bonding performance ensures the overall stability and durability of the coating.

[0062] (2) Flexibility:

[0063] TPU has excellent flexibility, which can effectively compensate for the brittleness of aluminum-based coatings. This flexibility allows the coating to absorb energy when impacted or deformed, reducing the occurrence of cracks.

[0064] (3) Compatibility with Al:

[0065] The good compatibility between TPU and Al-based materials enables them to form a stable bonding interface, enhancing the adhesion of the coating. This bonding is crucial to the overall performance of the coating, especially under dynamic loads or in corrosive environments.

[0066] (6) Excellent chemical corrosion resistance and wear resistance:

[0067] TPU's chemical structure gives it excellent chemical resistance, making it resistant to erosion by corrosive media such as seawater and salt spray. In addition, TPU has good wear resistance, which can improve the wear resistance of the coating and extend its service life.

[0068] In order to analyze the seawater corrosion resistance of the coating, the corrosion resistance of the coating samples was tested using two different experimental methods: immersion corrosion and scouring corrosion. Three parallel samples were used in each set of experiments. Before the test, the polished samples were ultrasonically cleaned and then placed in a drying oven for drying. In the immersion corrosion experiment, the sample blocks were immersed in a 3.5wt% NaCl solution for 180 hours. In order to simulate a more severe corrosion environment, the corrosive solution was replaced every 48 hours. The scouring corrosion experiment was carried out in accordance with the GB10124-1988 standard. The corrosive medium contained 3.5wt% NaCl and 7.62kg / m 3 A solution of mud and sand. In order to ensure the fluidity of the corrosive medium, an electric propeller was used to increase the agitation during the experiment, the liquid flow rate reached 5m / s, and the corrosion time was set to 180h. To ensure the accuracy of the detection, the detection surface of the coating sample was in full contact with the corrosive medium, while the other surfaces were coated with epoxy resin to isolate the corrosion. The sample was embedded in the disc of the scouring corrosion device, completely immersed in the corrosive medium, and tested under stirring conditions. The main goal of the experiment was to evaluate the corrosion depth (or amount of corrosion) and the corrosion rate of the coating. After the experiment was completed, an electronic balance with an accuracy of 0.0001g was used to measure the weight change of the sample before and after corrosion to calculate the corrosion rate.

[0069] At the same time, an Al single-element coating was prepared using the same cold spraying technology as a control group to illustrate the advantages of the Al-Al2O3-TPU hybrid coating.

[0070] The Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in this embodiment has an annual average immersion corrosion rate of 0.011 mm / a, and an annual average erosion corrosion rate of 0.012 mm / a.

[0071] like Figure 3As shown, the porosity of the coating surface SEM images was analyzed using Image J analysis software. The distribution of defective pores is shown in the red area in the figure. The porosity is calculated based on the pore ratio, that is, porosity = (pore area / total coating area) × 100%. The calculated porosity of the Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in this example is 2.67%.

[0072] The coating prepared by thermal spraying of alloy coating powder has a porosity of about 10%. For example, the porosity of Al-Al2O3 coatings thermally sprayed by oxyacetylene flame is as high as 10% to 15%. High porosity may lead to a decrease in the corrosion resistance and wear resistance of the coating. In addition, thermal spraying can cause oxidation and decarburization of the substrate, and the presence of oxide impurities in the coating, affecting the quality and service life of the coating. The Al-Al2O3-TPU hybrid coating prepared by the present invention using low-pressure cold spraying has good adhesion, low porosity, and excellent corrosion resistance, while avoiding the problems of thermal oxidation and substrate thermal damage that may be caused by traditional high-temperature thermal spraying.

[0073] The Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in this embodiment has good comprehensive properties such as seawater corrosion resistance, high temperature resistance, wear resistance and high strength, and is suitable for various application fields such as ocean, aviation, and chemical industry.

[0074] like Figure 4 As shown, the Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in this example has an annual average immersion corrosion rate that is 78.43% lower than that of the cold-sprayed Al single-element coating, and a 78.18% lower erosion corrosion rate. This demonstrates that the addition of Al2O3 ceramic particles and polymer TPU to the Al-based coating can significantly improve the coating's resistance to seawater corrosion and wear erosion.

[0075] like Figure 5 As shown, from Figure 5 (a) It can be seen that Al2O3 particles of various sizes and irregular shapes are embedded in the Al-based coating. In addition, surface defects such as cracks and holes are effectively filled due to the presence of TPU, which enhances the overall strength and toughness of the coating. Figure 5 As can be seen from the cross-sectional schematic diagram shown in (b), the Al2O3 ceramic particles dispersed inside the Al-based coating can significantly enhance the overall mechanical properties and toughness. The filling of local cracks and holes inside the coating can improve the bonding strength between the coating and the substrate due to TPU filling. By filling the defects, a "bridging" effect is formed, which can effectively reduce the porosity of the coating, reduce the stress concentration caused by holes, and prevent further expansion of cracks, thereby improving the wear resistance and corrosion resistance of the coating and enhancing the coating's crack resistance.

[0076] The bonding strength of the Al-Al2O3-TPU mixed corrosion-resistant coating prepared in the embodiment to the substrate is 26.36 Mpa. The high bonding strength is due to the synergistic effect of the special low-pressure cold spraying process and the Al near-spherical powder, the irregularly shaped Al2O3 powder and the TPU powder. First, the Al powder particles have good plastic deformation ability, which can fill the micro-unevenness on the surface of the substrate during the spraying process. Second, the addition of irregularly shaped Al2O3 particles can enhance the mechanical interlocking action between the coating and the substrate. Finally, the presence of TPU provides good flexibility and buffering effect, which can absorb stress and reduce the risk of cracking. The advantages include that the coating is not easy to peel off during use, provides more durable wear protection, can better resist mechanical impact and vibration, can effectively prevent the penetration of corrosive media, improves the overall stability and durability of the coating, and prolongs the service life of the substrate.

[0077] In the embodiment, the mass fraction of each raw material in the cold spraying pre-made powder is: Al powder 35%, Al2O3 ceramic particles 35%, and TPU powder 30%. An appropriate amount of TPU and Al2O3 ceramic particles can significantly improve the impact resistance and wear resistance of the coating, while too much TPU will make the coating too soft, affecting the hardness and strength of the Al-based coating, and too low a proportion cannot effectively fill the pores and defects in the Al-based coating and cannot fully play its advantages. In order to illustrate the advantages of the selection and amount of coating raw materials in the present application, coatings with different raw material ratios were prepared using the same preparation technology and process parameters, and their bonding strengths were tested for illustration, as shown in Table 1.

[0078] Table 1 Performance of coatings prepared with different raw material ratios

[0079]

[0080] Example 2

[0081] The method for preparing the Al-Al2O3-TPU mixed corrosion-resistant coating by low-pressure cold spraying in the embodiment is as follows:

[0082] S1, substrate preparation: the surface of the 316L stainless steel material is treated by polishing, polishing, cleaning, drying and sandblasting in sequence to obtain a substrate to be sprayed;

[0083] S2, mechanically mixing Al powder, Al2O3 ceramic particles and thermoplastic polyurethane (TPU) powder for 8 hours to obtain a cold spraying pre-made powder;

[0084] The Al powder has a particle size of 10 μm to 40 μm and a purity of ≥99.9%; the Al2O3 ceramic powder has an irregular polygonal shape, a particle size of 20 μm to 50 μm, a purity of ≥99.9%, and an oxygen content of O2 ≤300 PPM; the thermoplastic polyurethane (TPU) powder has a particle size of 20 μm to 50 μm and a purity of ≥99.9%; the cold spray preformed powder is composed of the following raw materials in mass fractions: 35% Al powder, 35% Al2O3 ceramic particles, and the balance thermoplastic polyurethane (TPU) powder;

[0085] The cold spray preformed powder is composed of the following raw materials by mass fraction: 35% Al powder, 35% Al2O3 ceramic particles, and the balance thermoplastic polyurethane TPU powder;

[0086] S3, cold spraying the preformed powder obtained in S2 onto the substrate to be sprayed obtained in S1 at low pressure, and after the coating is cooled and solidified, polishing and correcting are performed to obtain an Al-Al2O3-TPU hybrid corrosion-resistant coating with an average thickness of 2 mm;

[0087] The process parameters of the low-pressure cold spraying are: the working gas is compressed air, the carrier gas pressure is 0.2 MPa, the carrier gas temperature is 200° C., the nozzle is 20 mm away from the substrate, and the spraying speed is 60 g / min.

[0088] The Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in this embodiment has an annual average immersion corrosion rate of 0.012 mm / a, and an annual average erosion corrosion rate of 0.013 mm / a; the porosity of the coating is 2.35%; and the bonding strength between the Al-Al2O3-TPU hybrid corrosion-resistant coating and the substrate is 23.62 MPa.

[0089] The Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in this embodiment can be used in marine engineering.

[0090] The hybrid corrosion-resistant coating is prepared by uniformly mixing Al metal powder, metal oxide ceramic particles Al2O3, and polymer thermoplastic polyurethane (TPU) powder in a certain proportion to obtain a pre-made powder for cold spraying, and then spraying the pre-made powder onto the surface of the substrate using a low-pressure cold spraying method to obtain a hybrid corrosion-resistant coating. Al metal powder is mainly used as the main matrix of the coating. It has excellent corrosion resistance and can form a dense oxide film in a marine environment to improve the corrosion resistance of the coating. Al2O3 ceramic particles have extremely high hardness. When added to the coating as a reinforcing phase, they can significantly improve the strength, hardness and wear resistance of the coating, and can effectively resist erosion and wear from corrosive media such as mud and sand in a marine environment. TPU mainly acts as a binder and filling material. It melts during low-pressure cold spraying and fills the micropores and defects in the coating to improve the density of the coating, reduce the voids in the coating, and help prevent the infiltration of corrosive media. In addition, its excellent flexibility and wear resistance can compensate for the brittleness of the aluminum-based coating itself, improve the wear resistance of the Al-based coating, and prevent the coating from cracking, peeling or failure under external impact or mechanical stress. The equipment required is simple and the process is convenient.

[0091] The Al-Al2O3-TPU hybrid corrosion-resistant coating prepared in this embodiment has the following advantages:

[0092] (1) Seawater corrosion resistance:

[0093] This composite coating performs well in marine environments and can effectively resist corrosive media in seawater. It is particularly suitable for marine engineering, ships, offshore platforms and other fields.

[0094] (2) Long life protection:

[0095] The various components in the coating work together to provide long-term effective protection, extending the service life of the substrate and reducing the frequency and cost of maintenance and replacement.

[0096] (3) Wide range of applications:

[0097] In addition to marine engineering, this composite coating can also be used in aerospace, chemical equipment, energy industry and other fields that require high wear resistance, high corrosion resistance and high temperature performance, and has broad market prospects.

[0098] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing an Al-Al2O3-TPU hybrid corrosion-resistant coating by low-pressure cold spraying, characterized in that: The method is: S1. Substrate preparation: The substrate is subjected to surface treatment, and is sequentially ground, polished, cleaned, dried, and sandblasted to obtain the substrate to be sprayed; S2. Mechanically mixing Al powder, Al2O3 ceramic particles, and thermoplastic polyurethane (TPU) powder to obtain a cold spray preformed powder; the Al powder is a nearly spherical powder with a particle size of 10 μm to 40 μm and a purity of ≥99.9%; the Al2O3 ceramic particles are irregular particles with a particle size of 20 μm to 50 μm and a purity of ≥99.9%; the thermoplastic polyurethane (TPU) powder has a particle size of 20 μm to 50 μm and a purity of ≥99.9%; the cold spray preformed powder is composed of the following raw materials in mass fractions: 35% to 75% Al powder, 15% to 35% Al2O3 ceramic particles, and the remainder thermoplastic polyurethane (TPU) powder; S3, cold spraying the cold spray preformed powder obtained in S2 onto the substrate to be sprayed obtained in S1 at low pressure, and after the coating is cooled and solidified, polishing and correction are performed to obtain an Al-Al2O3-TPU mixed corrosion-resistant coating; The process parameters of the low-pressure cold spraying are: the working gas is compressed air, the carrier gas pressure is 0.2-0.5 MPa, the carrier gas temperature is 150-200°C, the nozzle distance to the substrate is 10-20 mm, and the spraying speed is 30-60 g / min.

2. The method for preparing an Al-Al2O3-TPU hybrid corrosion-resistant coating by low-pressure cold spraying according to claim 1, characterized in that: The substrate described in S1 is 316L stainless steel.

3. The method for preparing an Al-Al2O3-TPU hybrid corrosion-resistant coating by low-pressure cold spraying according to claim 1, characterized in that: The mechanical mixing time in S2 is 8 h.

4. The method for preparing an Al-Al2O3-TPU hybrid corrosion-resistant coating by low-pressure cold spraying according to claim 1, characterized in that: The average thickness of the Al-Al2O3-TPU hybrid corrosion-resistant coating in S3 is 500 μm~2 mm.

5. An application of an Al-Al2O3-TPU hybrid corrosion-resistant coating prepared by the method according to any one of claims 1 to 4, characterized in that: The Al-Al2O3-TPU mixed corrosion-resistant coating is used in marine engineering.

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