Preparation method of acid and alkali resistant composite coating of miniature proportional valve

Abstract

The invention discloses a preparation method of an acid and alkali resistant composite coating of a miniature proportional valve. The preparation method comprises the following steps: pretreating the surface of the miniature proportional valve; spraying a ceramic material bottom layer on the surface of the pretreated micro proportional valve by adopting plasma spraying, and then spraying a composite coating material on the ceramic bottom layer; and the micro proportional valve is cured, the surface of the coating is subjected to micromachining through laser treatment, and the micro proportional valve acid and alkali resistant composite coating with the high surface area is formed. The prepared composite coating can effectively resist corrosion of organic acid and alkali with the pH value ranging from 2 to 10. Through the synergistic effect of the ceramic material and the nano additive and surface micromachining treatment, the coating has extremely high hardness and wear resistance. According to the invention, the surface pretreatment process and the composite coating method are optimized, so that firm chemical bonding and mechanical occlusion are formed between the coating and the matrix, and the bonding strength of the coating and the matrix is improved by more than 30% compared with that of the traditional coating.

Description

Technical Field

[0001] The invention relates to the technical field of micro proportional valve manufacturing, in particular to a method for preparing an acid- and alkali-resistant composite coating of a micro proportional valve. Background Art

[0002] As a key component of scientific instruments, micro proportional valves are often used in detection environments containing corrosive substances such as organic acids and alkalis, fluorine sulfides, and phosphides. Traditional micro proportional valve coating technology has many defects. For example, ordinary metal coatings are easily corroded in strong acid and alkali environments, causing the coating to fall off and fail to effectively protect the valve body. Some coatings lack sufficient bonding strength with components such as the valve seat, and stratification is prone to occur during long-term use, affecting the performance and service life of the micro proportional valve. In addition, existing coating processes are difficult to simultaneously meet the micro proportional valve's requirements for wear resistance, corrosion resistance, and adaptability to complex media environments, limiting the application of micro proportional valves in high-precision scientific instruments.

[0003] Therefore, providing a method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve with higher acid- and alkali-resistant, wear-resistant and other properties is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve. The present invention significantly improves the acid- and alkali-resistant performance, wear resistance, and bonding strength between the coating and the substrate of the micro proportional valve by developing new composite coating materials and optimizing the coating process, thereby ensuring that the micro proportional valve can operate stably and reliably in harsh chemical environments, extending its service life, and meeting the requirements of scientific instruments for high precision and high stability of micro proportional valves.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve comprises the following steps:

[0007] (1) Surface pretreatment: Select a micro proportional valve and pretreat the surface of the micro proportional valve;

[0008] (2) Coating: plasma spraying is used to spray a layer of ceramic material base on the pre-treated micro proportional valve surface, and then a composite coating material containing polymer and nano additives is sprayed on the ceramic base by thermal spraying;

[0009] (3) Curing and post-processing: After coating, the micro proportional valve is placed in a high-temperature curing furnace for curing, and then the coating surface is micro-processed by laser processing to form a micro proportional valve acid- and alkali-resistant composite coating with a high surface area.

[0010] Through extensive corrosion and wear testing, the present invention screened a variety of materials and identified a composite system based on ceramics and high-performance polymers. The ceramics, with their high hardness and chemical stability, effectively resist acid and alkali corrosion and particle abrasion. The high-performance polymers, with their excellent flexibility and oil resistance, enhance the coating's impact resistance and tolerance to oil contamination. Using a unique composite process, the ceramic particles are evenly dispersed within the polymer matrix, forming an interpenetrating network structure, resulting in a composite coating that combines the advantages of both.

[0011] Furthermore, the pretreatment method in step (1) is: first, the oxide layer and impurities on the surface of the micro proportional valve are removed by mechanical grinding, and then the surface of the component is chemically cleaned in sequence using a strong acid solution and a strong alkali solution.

[0012] The above scheme can effectively improve the activity of the micro proportional valve surface and enhance the adhesion between the coating and the substrate.

[0013] Furthermore, the strong acid is a hydrochloric acid solution with a mass concentration of 15% to 25%, and the strong base is a sodium hydroxide solution with a mass concentration of 5% to 10%.

[0014] Furthermore, in step (2), the spraying power of the plasma spraying is 30-45 kW, the plasma gas flow rate is 30-50 L / min, the spraying distance is 80-120 mm, and the spraying speed is 300-600 mm / s.

[0015] The ceramic material is silicon carbide or aluminum oxide, and the spraying thickness is 20 to 50 μm.

[0016] Furthermore, the thermal spraying temperature in step (2) is 200-300° C., and the spraying distance is 100-150 mm.

[0017] In this invention, plasma spraying enables ceramic particles to be rapidly deposited on the substrate surface at high temperature and high speed, forming a dense underlying structure and improving the bonding strength between the coating and the substrate. During the thermal spraying process, the polymer can be evenly coated on the ceramic substrate surface at a relatively low temperature, preventing the polymer from decomposing at high temperatures and affecting the coating performance.

[0018] Furthermore, the polymer in the composite coating material containing a polymer and a nano-additive is polyetheretherketone, and the nano-additive is nano-titanium dioxide or nano-zinc oxide;

[0019] The mass ratio of the polymer to the nano additive is 8:1 to 4:1, and the thickness of the composite coating is 30 to 80 μm.

[0020] The present application adds appropriate amount of nano-scale additive in the composite coating material, which can fill the small pores inside the coating, improve the density of the coating, and enhance its corrosion resistance. Meanwhile, the nano additive can also be chemically bonded with the ceramic and polymer, further improving the overall performance of the coating.

[0021] Further, the curing temperature in step (3) is 150-200℃, and the curing time is 2-4h.

[0022] The curing temperature and time of the present application are accurately controlled according to the characteristics of the composite coating material. After curing, the present application uses laser to micro-machine the coating, with the processing mode being surface laser pitting or grid scanning, so as to form a uniform micro-concave structure on the surface, increase the surface area of the coating, control the surface roughness Ra within 1-5μm, and improve its wear resistance and adsorption capacity to the medium.

[0023] The present application has the following advantages:

[0024] 1. Excellent acid and alkali resistance: The composite coating prepared by the present application can effectively resist the corrosion of organic acid and alkali with pH value in the range of 2-10. In the simulated strong acid and alkali detection environment, after long time immersion test, there is no obvious corrosion trace on the surface of the coating, and the performance of the micro proportional valve is not affected, which greatly prolongs the service life of the micro proportional valve in the acid and alkali environment.

[0025] 2. High wear resistance: The synergistic effect of ceramic material and nano additive in the present application, as well as the surface micro-processing treatment, makes the coating have extremely high hardness and wear resistance, which can effectively resist the wear of solid particles and oil stains, and reduce the failure of the coating and the performance decline of the micro proportional valve caused by wear.

[0026] 3. Strong bonding strength: The present application optimizes the surface pretreatment process and composite coating method, so that the coating and the substrate form a firm chemical bonding and mechanical engagement, and the bonding strength between the coating and the substrate is increased by more than 30% compared with the traditional coating, which effectively avoids the occurrence of coating peeling and delamination. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Process flow chart for preparing acid and alkali resistant composite coating of micro proportional valve DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Example 1: Preparation method of acid- and alkali-resistant composite coating for micro proportional valve

[0030] (1) Surface pretreatment: Use diamond abrasive to remove impurities, then use 25% hydrochloric acid solution (pH ≈ 0.3) to clean for 2 minutes, then use 5% sodium hydroxide solution (pH ≈ 12.0) to clean for 1 minute, and finally rinse with deionized water and dry naturally.

[0031] (2) Coating: A 25 μm thick aluminum oxide base layer was prepared on the substrate surface by plasma spraying (power 45 kW, distance 110 mm); then, a composite material of polyetheretherketone and nano-titanium dioxide (mass ratio 8:1) was sprayed on the substrate surface by flame spraying with a thickness of 80 μm.

[0032] (3) Curing and post-processing: The sample was placed in an oven at 180 °C for curing for 3.5 h, and then raster laser engraving was performed using a laser system with a wavelength of 1064 nm and a power of 50 W at a scanning speed of 300 mm / s to form a microstructure with a roughness of Ra ≈ 4.5 μm, further enhancing the wear resistance.

[0033] Example 2: Preparation method of acid- and alkali-resistant composite coating for micro proportional valve

[0034] (1) Surface pretreatment: A micro proportional valve was selected and its surface was mechanically polished with sandpaper to remove the oxide layer and impurities. Subsequently, the surface of the component was chemically cleaned using a 20% hydrochloric acid solution with a pH of 0.5 and a 10% sodium hydroxide solution with a pH of 13, respectively. Each treatment lasted 2 minutes. After cleaning, the component was rinsed with deionized water and dried with hot air.

[0035] (2) Coating: A layer of alumina ceramic base layer with a thickness of 30 μm was sprayed on the surface of the valve body using plasma spraying equipment (spraying power 40 kW, gas flow rate 40 L / min, spraying distance 100 mm); then a composite coating material containing polyetheretherketone (PEEK) and nano-titanium dioxide in a mass ratio of 6:1 was evenly sprayed on the surface of the ceramic base layer using flame thermal spraying with a thickness of 60 μm.

[0036] (3) Curing and post-processing: The coated micro proportional valve was placed in a high-temperature furnace and cured at 175°C for 3 hours. After curing, a nanosecond laser with a wavelength of 1064 nm and a power of 30 W was used to perform microstructural processing on the coating surface at a scanning speed of 100 mm / s and in a grid-staggered manner, forming a surface micro-concave structure with a roughness of Ra≈3 μm.

[0037] Example 3: Preparation method of acid- and alkali-resistant composite coating for micro proportional valve

[0038] (1) Surface pretreatment: After mechanical polishing, the micro proportional valve was cleaned with 15% hydrochloric acid solution (pH 1) and 8% sodium hydroxide solution (pH 12.5) for 90 seconds and 60 seconds, respectively, and then rinsed with deionized water and dried with hot air.

[0039] (2) Coating: A silicon carbide ceramic base layer was coated with a thickness of 40 μm by plasma spraying (35 kW, spraying distance 90 mm); then, a composite coating material of polyetheretherketone and nano-zinc oxide (mass ratio 5:1) was sprayed on the ceramic layer with a thickness of 50 μm using a high-pressure cold spraying device at a temperature of 250 °C and a spraying distance of 120 mm.

[0040] (3) Curing and post-treatment: The sample was placed at 170°C for curing treatment for 2.5 hours. A picosecond laser with a wavelength of 355 nm and a power of 20 W was used at a scanning speed of 200 mm / s to perform pulse scanning on the surface to form a microstructure with Ra≈2.5 μm and enhance the surface specific area.

[0041] Comparative Example (Traditional Single Polymer Coating):

[0042] (1) Surface pretreatment: Use the same mechanical polishing and deionized water cleaning, without acid or alkali chemical treatment.

[0043] (2) Coating: Thermal spraying is used to apply a single polyetheretherketone (PEEK) coating with a thickness of 60 μm, without a ceramic base layer and without nano-additives.

[0044] (3) No curing and no laser treatment.

[0045] Table 1 Comparison of properties between the composite coating of Example 1 of the present invention and the traditional coating

[0046]

[0047] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve, characterized in that: The following steps are involved: (1) Surface pretreatment: Select a micro proportional valve and pretreat the surface of the micro proportional valve; (2) Coating: plasma spraying is used to spray a layer of ceramic material base on the pre-treated micro proportional valve surface, and then a composite coating material containing polymer and nano additives is sprayed on the ceramic base by thermal spraying; (3) Curing and post-processing: After coating, the micro proportional valve is placed in a high-temperature curing furnace for curing, and then the coating surface is micro-processed by laser processing to form a micro proportional valve acid- and alkali-resistant composite coating with a high surface area.

2. The method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve according to claim 1, characterized in that: The pretreatment method in step (1) is: first, the oxide layer and impurities on the surface of the micro proportional valve are removed by mechanical grinding, and then the surface of the component is chemically cleaned in sequence using a strong acid solution and a strong alkaline solution respectively.

3. The method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve according to claim 2, characterized in that: The strong acid is a hydrochloric acid solution with a mass concentration of 15% to 25%, and the strong base is a sodium hydroxide solution with a mass concentration of 5% to 10%.

4. The method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve according to claim 1, characterized in that: The spraying power of the plasma spraying in step (2) is 30-45 kW, the plasma gas flow rate is 30-50 L / min, the spraying distance is 80-120 mm, and the spraying speed is 300-600 mm / s. The ceramic material is silicon carbide or aluminum oxide, and the spraying thickness is 20 to 50 μm.

5. The method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve according to claim 1, characterized in that: The thermal spraying temperature in step (2) is 200-300° C., and the spraying distance is 100-150 mm. The polymer in the composite coating material containing a polymer and a nano additive is polyetheretherketone, and the nano additive is nano titanium dioxide or nano zinc oxide; The mass ratio of the polymer to the nano additive is 8:1 to 4:1, and the thickness of the composite coating is 30 to 80 μm.

6. The method for preparing an acid- and alkali-resistant composite coating for a micro proportional valve according to claim 1, characterized in that: In step (3), the curing temperature is 150-200° C. and the curing time is 2-4 hours.

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