Method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating through low-pressure cold spraying and application thereof

Abstract

The invention provides a method for preparing a Ti-Al2O3-PVDF (Polyvinylidene Fluoride) mixed seawater corrosion-resistant coating by low-pressure cold spraying, which comprises the following steps: carrying out surface treatment on a base material, and sequentially grinding, polishing, cleaning, drying and sandblasting to obtain a base material to be sprayed; the preparation method comprises the following steps: mechanically mixing Ti powder, Al2O3 ceramic particles and polyvinylidene fluoride (PVDF) powder to obtain cold spraying prefabricated powder; and the cold spraying prefabricated powder is subjected to low-pressure cold spraying to a to-be-sprayed base material, after the coating is cooled and cured, polishing and correction are conducted, and the Ti-Al2O3-PVDF mixed seawater corrosion resistant coating is obtained. The prepared coating not only has excellent mechanical strength and corrosion resistance, but also has good thermal stability and toughness, is suitable for various harsh application environments, especially can be applied to ocean engineering environments, and can resist seawater scouring and corrosion.

Description

Technical Field

[0001] The invention belongs to the technical field of surface engineering, and specifically relates to a method for preparing a Ti-Al2O3-PVDF mixed seawater 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, titanium (Ti) 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 the preparation technology of traditional corrosion-resistant coatings, 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 the quality of coatings from different aspects, such as selecting appropriate coating preparation methods and continuously optimizing the process to improve the quality of coatings, and introducing suitable filling materials to seal the pores and defects in the coating to improve the quality of the coating, thereby improving the corrosion resistance. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating by low-pressure cold spraying and its application in view of the deficiencies of the above-mentioned prior art. The method introduces Al2O3 ceramic particles to reinforce the composite material, and PVDF is used as a filling material to fill the pores and cracks in the coating, and studies the preparation process, performance and application of the mixed coating to improve the coating quality, thereby improving the corrosion resistance. At the same time, the method has many advantages as mentioned above, and can provide new ideas and methods for improving the surface properties of metal materials, promote the development and application of low-pressure cold spraying technology, and meet the needs of modern industrial development.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating by low-pressure cold spraying, the method comprising:

[0005] S1. Substrate preparation: Surface treatment of 45# stainless steel substrate is carried out by grinding, polishing, cleaning, drying and sandblasting in sequence to obtain the substrate to be sprayed;

[0006] S2, mechanically mixing Ti powder, Al2O3 ceramic particles, and polyvinylidene fluoride PVDF powder to obtain cold spray preformed powder;

[0007] S3, spraying the cold spray prefabricated powder obtained in S2 onto the substrate to be sprayed obtained in S1, and after the coating is cooled and solidified, grinding and correction are performed to obtain a Ti-Al2O3-PVDF mixed seawater corrosion resistant coating;

[0008] The process parameters of the low-pressure cold spraying are: the working gas is compressed air, the carrier gas pressure is 0.4-0.6 MPa, the carrier gas temperature is 250-350° C., the nozzle is 15-25 mm away from the substrate, and the spraying speed is 20-40 g / min.

[0009] Preferably, the substrate in S1 is a 45# stainless steel-based material.

[0010] Preferably, the Ti powder in S2 is nearly spherical particles of varying sizes, with a particle size of 10 to 40 μm and a purity of ≥99.9%; the Al2O3 ceramic particles are irregular polygonal particles, with a particle size of 20 to 50 μm and a purity of ≥99.9%; the polyvinylidene fluoride PVDF powder has a particle size of 20 to 50 μm and a purity of ≥99.9%.

[0011] Preferably, the cold spray preformed powder in S2 is composed of the following raw materials in mass fractions: 35% Ti powder, 35% Al2O3 ceramic particles, and the remainder polyvinylidene fluoride PVDF powder.

[0012] Preferably, the mechanical mixing time in S2 is 8 hours.

[0013] Preferably, the average thickness of the Ti-Al2O3-PVDF mixed seawater corrosion resistant coating in S3 is 500 μm to 2 mm.

[0014] Preferably, the annual average immersion corrosion rate of the Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating in S3 is 0.067~0.075mm / a, and the annual average erosion corrosion rate is 0.450~0.530mm / a; the bonding strength between the Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating and the substrate is 21.62~26.46MPa; the porosity of the Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating is 1.22%~1.28%.

[0015] The present invention also provides the application of the Ti-Al2O3-PVDF mixed seawater corrosion resistant coating prepared by the above method, and the Ti-Al2O3-PVDF mixed seawater corrosion resistant coating is used for marine engineering.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The Ti-Al2O3-PVDF hybrid coating prepared by low-pressure cold spraying in the present invention has good adhesion, low porosity, and excellent corrosion resistance, while avoiding the problem of thermal damage to the substrate that may be caused by traditional high-temperature thermal spraying. The advantages compared with the prior art are mainly the following:

[0018] (1) Improve coating density and uniformity

[0019] Selecting a PVDF powder particle size within the range of 20 to 50 μm ensures the fluidity and deposition efficiency of the powder during spraying, thereby forming a uniform and dense coating; spraying is carried out within the optimal temperature range of 250 to 350 ° C, which not only ensures the plastic deformation of the Ti metal powder, but also ensures the full melting and filling of the PVDF powder, significantly improving the density and surface smoothness of the coating.

[0020] (2) Enhance the mechanical properties and corrosion resistance of the coating

[0021] Using PVDF 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, and is suitable for a wider range of application scenarios.

[0022] (3) Energy conservation and environmental protection

[0023] Compared with traditional thermal spraying methods, cold spraying technology can achieve efficient coating preparation at lower temperatures, reduce energy consumption, and reduce thermal pollution to the environment and the risk of metal powder oxidation.

[0024] (4) Adapt to various application environments

[0025] The coating formed by using Ti-Al2O3-PVDF 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.

[0026] The present invention is further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a SEM image of the Ti-Al2O3 mixed prefabricated powder of Example 1 of the present invention.

[0028] Figure 2 This is a physical picture of the PVDF powder of Example 1 of the present invention.

[0029] Figure 3 This is the pore distribution diagram of the Ti-Al2O3-PVDF mixed corrosion-resistant coating prepared in Example 1

[0030] Figure 4 This is a graph of the seawater immersion corrosion and erosion corrosion rates of the Ti-Al2O3-PVDF mixed corrosion-resistant coating prepared in Example 1 of the present invention.

[0031] Figure 5 This is a microscopic image of the Ti-Al2O3-PVDF hybrid corrosion-resistant coating prepared in Example 1 of the present invention, wherein (a) is a surface SEM image and (b) is a schematic cross-sectional view. DETAILED DESCRIPTION

[0032] Example 1

[0033] The method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying in this embodiment is as follows:

[0034] S1. Substrate preparation: The 45# stainless steel substrate 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.

[0035] S2, mechanically mixing Ti powder, Al2O3 ceramic particles, and polyvinylidene fluoride PVDF powder for 8 hours to obtain cold spray preformed powder;

[0036] After mixing Ti powder and Al2O3 ceramic particles, Ti-Al2O3 mixed prefabricated powder is obtained, and the SEM image is as follows Figure 1 The Ti powder is a nearly spherical particle of varying sizes, with a particle size of 10 to 40 μm and a purity of ≥99.9%; the Al2O3 ceramic particles are irregular polygonal particles, with a particle size of 20 to 50 μm and a purity of ≥99.9%; the particle size of the polyvinylidene fluoride PVDF powder is 20 to 50 μm and a purity of ≥99.9% ( Figure 2 ); the cold spray preformed powder is composed of the following raw materials by mass fraction: 35% Ti powder, 35% Al2O3 ceramic particles, and the balance is polyvinylidene fluoride PVDF powder;

[0037] In this embodiment, 35% Ti and 35% Al2O3 ceramic particles in the raw material ratio ensure that the coating maintains good mechanical properties, and 30% PVDF can provide good adhesion and toughness without affecting the conductivity and high temperature resistance of the coating too much. Reasonable ratio can achieve synergistic effects between the components and improve the overall performance of the coating.

[0038] Polyvinylidene fluoride (PVDF) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0039] S3, spraying the cold spray prefabricated powder obtained in S2 onto the substrate to be sprayed obtained in S1, and after the coating is cooled and solidified, grinding and correction are performed to obtain a Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating with an average thickness of 500 μm;

[0040] The process parameters of the low-pressure cold spraying are: the working gas is compressed air, the carrier gas pressure is 0.4 MPa, the carrier gas temperature is 250° C., the nozzle is 15 mm away from the substrate, and the spraying speed is 20 g / min.

[0041] In this embodiment, the Ti powder undergoes plastic deformation and meshes with the substrate at high temperature and high speed during the cold spraying process. The Al2O3 ceramic particles serve as a reinforcing phase composite material to improve the hardness and strength of the coating. The PVDF powder is melted, wetted and cooled to build a sealing layer during the spraying process to fill the pores and defects of the Ti-based coating, thereby enhancing the overall corrosion resistance of the coating. The use of low-pressure cold spraying technology to prepare this composite coating can achieve efficient deposition of the coating at a lower temperature, reduce the impact of thermal stress on the substrate and coating, and improve the adhesion and overall performance of the coating.

[0042] The preparation method of this embodiment can be carried out at low temperature without damaging the substrate and polymer. The main functions of each element in the coating are as follows:

[0043] Role of Ti element:

[0044] (1) Enhanced mechanical properties

[0045] As a metal material, Ti has high hardness and strength, which can improve the hardness and strength of the overall coating and improve its impact resistance and wear resistance.

[0046] (2) Improve corrosion resistance

[0047] Ti can quickly form a dense titanium oxide TiO2 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.

[0048] (3) Enhance coating toughness

[0049] The toughness of Ti 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 titanium can provide a certain buffering effect, protecting the substrate from damage and thus extending the service life of the coating.

[0050] Al2O3 function:

[0051] (1) Ceramic particles have extremely high hardness, and adding them into the coating can significantly improve the overall hardness and wear resistance of the coating.

[0052] (2) It has excellent chemical stability and can effectively resist the erosion of corrosive media in the marine environment.

[0053] (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.

[0054] (3) It has good thermal stability and can maintain its physical and chemical properties in a high temperature environment, thus enhancing the stability of the coating under high temperature conditions.

[0055] PVDF function:

[0056] (1) Acting as a binder and filler in the coating, it can effectively fill the tiny pores and defects in the coating and increase the density of the coating.

[0057] (2) It has excellent chemical corrosion resistance and can effectively resist corrosive media in seawater, especially in seawater environment.

[0058] (3) High toughness and impact resistance can significantly improve the overall toughness of the coating and reduce cracking and peeling of the coating during use.

[0059] (4) It has high thermal stability and can remain stable in high temperature environments without decomposition, ensuring the stable performance of the coating under high temperature conditions.

[0060] In order to evaluate the seawater corrosion resistance of the coating, two experimental methods, immersion corrosion and erosion corrosion, were used, and three parallel specimens were used in each experiment. The specimens were polished, ultrasonically cleaned and dried.

[0061] Immersion corrosion test: The sample was immersed in 3.5wt% NaCl solution for 180 hours, and the solution was replaced every 48 hours. Erosion corrosion test: According to GB10124-1988 standard, the sample was immersed in 3.5wt% NaCl and 7.62kg / m 3 The sample was placed in a solution of corundum with a liquid flow rate of 5 m / s and a corrosion time of 180 hours. The test surface of the sample was in full contact with the corrosive medium, and the other surfaces were isolated with epoxy resin. After the experiment, an electronic balance with an accuracy of 0.0001 g was used to measure the weight change of the sample before and after corrosion, and the corrosion rate and depth were calculated.

[0062] At the same time, a Ti single-element coating was sprayed using the same preparation technology and process parameters as a control experiment, and the comparison illustrates the advantages of the Ti-Al2O3-PVDF mixed corrosion-resistant coating.

[0063] The Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating prepared in this embodiment has an annual average immersion corrosion rate of 0.067 mm / a, and an annual average scour corrosion rate of 0.450 mm / a.

[0064] from Figure 4 It can be seen that the annual average corrosion rate of the Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating is 45.96% lower than that of the Ti-based single-element coating, and the erosion corrosion rate is 45.98% lower. This shows that adding Al2O3 ceramic particles and polymer PVDF to the Ti-based coating can greatly improve the coating's resistance to seawater corrosion and wear erosion.

[0065] The porosity of the Ti-Al2O3-PVDF mixed corrosion-resistant coating prepared in this embodiment is 1.22%, and the pore distribution is as follows: Figure 3 Shown in the red area.

[0066] The bonding strength between the Ti-Al2O3-PVDF hybrid corrosion-resistant coating prepared in this embodiment and the substrate is 26.46 MPa.

[0067] like Figure 5 As shown in Figure (a), the SEM image of the coating surface shows that the coating is compact and dense, with high density, no obvious defects and pores, and a large number of Al2O3 ceramic particles are distributed on the surface and embedded in the Ti-based coating, and the pores are filled with PVDF. From the cross-sectional schematic diagram of Figure (b), it can be seen that a large number of Al2O3 ceramic particles are dispersed inside the coating, which can significantly enhance the overall mechanical properties and toughness. The local cracks and holes inside are filled with PVDF by melting, forming a "bridging" effect, which significantly reduces the porosity of the coating, prevents the further expansion of the cracks, and enhances the toughness of the coating.

[0068] The coating prepared in this embodiment not only has excellent mechanical strength and corrosion resistance, but also has good thermal stability and toughness, and is suitable for various harsh application environments. The various components in the coating work together to provide long-term and effective protection, extend the service life of the substrate, and reduce the frequency and cost of maintenance and replacement. The Ti-Al2O3-PVDF hybrid seawater corrosion-resistant coating prepared in this embodiment performs well in the marine environment and can effectively resist corrosive media in seawater. It is particularly suitable for marine engineering, ships, offshore platforms and other fields. It 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.

[0069] Example 2

[0070] The method of preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying in this embodiment is as follows:

[0071] S1. Substrate preparation: Surface treatment of 45# stainless steel substrate is carried out by grinding, polishing, cleaning, drying and sandblasting in sequence to obtain the substrate to be sprayed;

[0072] S2. Mechanically mix Ti powder, Al2O3 ceramic particles and polyvinylidene fluoride PVDF powder for 8 hours to obtain cold spray preformed powder; the Ti powder is nearly spherical particles of varying sizes, with a particle size of 10 to 40 μm and a purity of ≥99.9%; the Al2O3 ceramic particles are irregular polygonal particles, with a particle size of 20 to 50 μm and a purity of ≥99.9%; the polyvinylidene fluoride PVDF powder has a particle size of 20 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% Ti powder, 35% Al2O3 ceramic particles, and the remainder polyvinylidene fluoride PVDF powder;

[0073] Polyvinylidene fluoride (PVDF) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0074] S3, low-pressure cold spraying the preformed powder obtained in S2 onto the substrate to be sprayed obtained in S1, and after the coating is cooled and solidified, grinding and correction are performed to obtain a Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating with an average thickness of 2 mm;

[0075] The process parameters of the low-pressure cold spraying are: the working gas is compressed air, the carrier gas pressure is 0.6 MPa, the carrier gas temperature is 350° C., the nozzle is 25 mm away from the substrate, and the spraying speed is 40 g / min.

[0076] The annual average immersion corrosion rate of the Ti-Al2O3-PVDF hybrid seawater corrosion-resistant coating prepared in this embodiment is 0.075 mm / a, and the annual average erosion corrosion rate is 0.530 mm / a; the bonding strength between the Ti-Al2O3-PVDF hybrid seawater corrosion-resistant coating and the substrate is 21.62 MPa, and the porosity of the Ti-Al2O3-PVDF hybrid seawater corrosion-resistant coating is 1.28%.

[0077] The Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating prepared in this embodiment can be used in marine engineering.

[0078] The above 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 change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a Ti-Al2O3-PVDF mixed seawater 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 a substrate to be sprayed; S2, mechanically mixing Ti powder, Al2O3 ceramic particles, and polyvinylidene fluoride PVDF powder to obtain cold spray preformed powder; S3, low-pressure cold spraying the prefabricated powder obtained in S2 onto the substrate to be sprayed obtained in S1, and after the coating is cooled and solidified, grinding and correction are performed to obtain a Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating; The process parameters of the low-pressure cold spraying are: the working gas is compressed air, the carrier gas pressure is 0.4-0.6 MPa, the carrier gas temperature is 250-350° C., the nozzle is 15-25 mm away from the substrate, and the spraying speed is 20-40 g / min.

2. The method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying according to claim 1, characterized in that: The substrate described in S1 is 45# stainless steel-based material.

3. The method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying according to claim 1, characterized in that: The Ti powder in S2 is nearly spherical particles of varying sizes, with a particle size of 10 to 40 μm and a purity of ≥99.9%; the Al2O3 ceramic particles are irregular polygonal particles, with a particle size of 20 to 50 μm and a purity of ≥99.9%; the polyvinylidene fluoride PVDF powder has a particle size of 20 to 50 μm and a purity of ≥99.9%.

4. The method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying according to claim 1, characterized in that: The cold spray preformed powder in S2 is composed of the following raw materials in mass fractions: 35% Ti powder, 35% Al2O3 ceramic particles, and the remainder polyvinylidene fluoride PVDF powder.

5. The method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying according to claim 1, characterized in that: The mechanical mixing time in S2 is 8 hours.

6. The method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying according to claim 1, characterized in that: The average thickness of the Ti-Al2O3-PVDF mixed seawater corrosion resistant coating in S3 is 500 μm to 2 mm.

7. The method for preparing Ti-Al2O3-PVDF mixed seawater corrosion resistant coating by low pressure cold spraying according to claim 1, characterized in that: The annual average immersion corrosion rate of the Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating in S3 is 0.067-0.075 mm / a, and the annual average erosion corrosion rate is 0.450-0.530 mm / a; the bonding strength between the Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating and the substrate is 21.62-26.46 MPa; the porosity of the Ti-Al2O3-PVDF mixed seawater corrosion-resistant coating is 1.22%-1.28%.

8. An application of a Ti-Al2O3-PVDF mixed seawater corrosion resistant coating prepared by the method according to any one of claims 1 to 7, characterized in that: The Ti-Al2O3-PVDF mixed seawater corrosion resistant coating is used in marine engineering.

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