Preparation method of wear-resistant and corrosion-resistant protective layer

Abstract

The application discloses a preparation method of a wear-resistant and corrosion-resistant protective layer, which comprises the following steps: firstly, carrying out zinc infiltration treatment on the surface of a steel component; and then, carrying out laser melting treatment on the surface of the component after the zinc infiltration treatment. The wear-resistant and corrosion-resistant protective layer prepared by the method has the advantages of effectively improving the hardness of the base material, increasing the wear resistance of the base material, and effectively improving the corrosion resistance of the surface of the base material. In addition, the zinc in the zinc infiltration layer is further diffused into the base material after the zinc infiltration treatment and the laser strengthening treatment, the roughness of the surface of the base material is reduced, the precision of the friction surface of the base material is improved, and the risk of peeling of the zinc infiltration layer in the friction process is reduced.

Description

Technical Field

[0001] This invention relates to the field of surface protection technology, and more specifically to a method for preparing a wear-resistant and corrosion-resistant protective layer. Background Technology

[0002] Wear and corrosion are the main factors that cause the functional failure and reduced service life of steel components, especially when they are used in marine or humid environments for a long time. Therefore, in order to ensure the working performance of components and extend their service life, a protective layer with wear resistance and corrosion resistance is usually prepared on the surface of the components to protect them.

[0003] Powder zinc diffusion technology is a surface protection process that uses thermal diffusion to obtain a zinc-iron alloy layer on the surface of steel. The principle involves placing a diffusion agent and the steel component together in a diffusion furnace and heating it to approximately 400°C. Active zinc atoms penetrate from the surface of the steel component into the interior, while iron atoms diffuse from the interior outwards, forming a uniform zinc and zinc-iron compound layer on the surface of the component. The zinc-diffused layer has excellent corrosion resistance, but its hardness is relatively low, approximately 350 HV, and its wear resistance is poor. It is mainly used for non-moving components, such as rail fasteners, bolts, and steel beams.

[0004] The existing technology CN107557536A uses a laser to treat the steel surface, forming a refined quenched or fused structure on the component surface, resulting in high hardness and wear resistance. This is followed by zinc diffusion treatment, forming a metallic compound layer on the surface, creating a modified layer with excellent corrosion resistance. However, in practice, it has been found that performing zinc diffusion treatment after laser treatment, which requires a temperature of 350–400℃, is equivalent to a secondary heat treatment on the already high-hardness surface. This leads to a decrease in surface hardness, although the component still exhibits good corrosion resistance. The reduced hardness and higher surface roughness significantly impact the accuracy of the friction surface of the substrate, thus retaining the technical problems of insufficient hardness and poor wear resistance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a wear-resistant and corrosion-resistant protective layer. This method overcomes the shortcomings of existing technologies, and the prepared protective layer exhibits high hardness, excellent wear resistance, corrosion resistance, and superior fatigue resistance.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a wear-resistant and corrosion-resistant protective layer, characterized in that: first, a powder zinc diffusion treatment is performed on the surface of a steel component substrate, and then a laser melting treatment is performed on the surface of the zinc-diffused component.

[0008] Furthermore, the base material of the steel component includes 5CrNiMo, Q235, or H13.

[0009] Furthermore, before the zinc diffusion treatment, the steel component substrate needs to be pretreated. Specifically, it is degreasing with ethyl acetate, washing with water, removing rust by sandblasting or pickling, washing with water again, and then drying.

[0010] Furthermore, the zinc infiltration treatment uses zinc powder as the infiltrator metal, ammonium chloride as the catalyst, and alumina powder as the dispersant to prepare an infiltrator, which is then sprayed onto the pretreated substrate surface and kept at 390–410°C for 3–6 hours.

[0011] Furthermore, the mass ratio of zinc powder, ammonium chloride, and alumina in the penetrant is 0.9–1.1: 0.01–0.04: 1.9–2.1.

[0012] Furthermore, the laser melting and coagulation power is 400-800W, the spot diameter is 2mm, the defocusing amount is 2cm, the scanning speed is 5-20mm / s, and the overlap rate is 15-20%.

[0013] Most specifically, a method for preparing a wear-resistant and corrosion-resistant protective layer is characterized by comprising the following steps:

[0014] (1) Preprocessing

[0015] The steel component substrate is subjected to degreasing, water washing, rust removal, water washing and drying in sequence. Ethyl acetate is used for degreasing, and sandblasting or pickling is used for rust removal. The steel component includes 5CrNiMo, Q235 or H13.

[0016] (2) Zinc diffusion treatment

[0017] A penetrant is prepared by using zinc powder as the penetrant metal, ammonium chloride as the catalyst, and alumina powder as the dispersant. It is sprayed onto the surface of a pretreated steel component substrate and kept at 390–410℃ for 3–6 hours. The mass ratio of zinc powder, ammonium chloride, and alumina is 0.9–1.1:0.01–0.04:1.9–2.1.

[0018] (3) Laser melting

[0019] Laser melting is performed on the substrate surface after step (2). The laser melting power is 400-800W, the spot diameter is 2mm, the defocusing amount is 2cm, the scanning speed is 15-20mm / s, and the overlap rate is 15-20%.

[0020] During the zinc diffusion process, it was found that zinc penetration into the substrate was extremely difficult. Only 10-30% of the zinc diffusion layer penetrated into the substrate, while the rest of the zinc diffusion layer mainly grew outwards from the substrate, forming a protrusion on the substrate surface. This resulted in increased surface roughness of the substrate, which had a significant impact on the precision of the substrate's friction surface. Furthermore, the zinc concentration was higher closer to the outer surface of the zinc diffusion layer, resulting in lower hardness and thus reducing the overall wear resistance of the substrate.

[0021] This invention involves zinc diffusion treatment on the substrate surface, followed by laser melting treatment. During laser scanning, zinc near the interface with the substrate diffuses into the substrate under the action of the laser heat source, further pushing the zinc diffusion layer into the substrate. This forms a uniform zinc-iron alloy layer on the inner surface of the substrate, increasing the thickness of the zinc diffusion layer within the substrate. Zinc has a low vaporization temperature (907℃). Zinc near the outer surface of the protruding zinc diffusion layer on the substrate surface vaporizes at high temperatures, exposing the internal laser alloy layer and improving the overall hardness of the substrate surface. This dual action of "inward pushing" and "outward vaporization" reduces the protrusion of the zinc diffusion layer on the substrate surface, completely transferring the zinc diffusion layer to the inner surface of the substrate. This reduces the possibility of the zinc diffusion layer peeling off from the substrate surface during friction and also minimizes the impact of the zinc diffusion layer on the precision of the substrate's friction surface.

[0022] Furthermore, the zinc-infiltrated layer acts as a powder-laying agent for subsequent laser melting and strengthening. Traditional powder-laying is difficult to apply to complex, irregularly shaped parts and suffers from poor uniformity and poor adhesion to the substrate surface. However, zinc infiltration treatment can form a uniform zinc-infiltrated layer on the surface of complex, irregularly shaped components. Compared to traditional powder-laying methods, this is beneficial for subsequent laser strengthening, as it increases the penetration depth of zinc and thus the penetration thickness of the corrosion-resistant alloy layer.

[0023] The present invention has the following technical effects:

[0024] The wear-resistant and corrosion-resistant protective layer prepared by the method of this invention effectively improves the hardness of the substrate, reaching a hardness of over 800 HV, thus increasing the wear resistance of the substrate. In this invention, zinc diffusion treatment is performed first, followed by laser strengthening treatment, which promotes the further diffusion of zinc in the zinc diffusion layer into the substrate, effectively improving the corrosion resistance of the substrate surface. At the same time, the further diffusion of the zinc diffusion layer into the substrate reduces the roughness of the substrate surface, improves the precision of the substrate friction surface, and reduces the risk of the zinc diffusion layer peeling off during friction. Attached Figure Description

[0025] Figure 1 Cross-sectional morphology of the zinc-diffused layer obtained by zinc diffusion treatment of 5CrNiMo substrate.

[0026] Figure 2Cross-sectional morphology of the zinc-infiltrated layer after laser melting and solidification of 5CrNiMo substrate.

[0027] Figure 3 Cross-sectional scanning and energy dispersive spectroscopy of 5CrNiMo substrate after zinc diffusion treatment.

[0028] Figure 4 Cross-sectional morphology and energy spectrum of 5CrNiMo substrate after zinc diffusion treatment and laser melting.

[0029] Figure 5 Surface morphology and elemental distribution of 5CrNiMo substrate after zinc diffusion treatment and laser melting.

[0030] Figure 6 Comparison of corrosion between 5CrNiMo substrate and 5CrNiMo substrate after zinc diffusion treatment and laser melting. Detailed Implementation

[0031] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0032] Example 1

[0033] A method for preparing a wear-resistant and corrosion-resistant protective layer includes the following steps:

[0034] (1) Preprocessing

[0035] The 5CrNiMo steel components were sequentially degreased, washed with water, derusted, washed with water again, and dried. Ethyl acetate was used for degreasing, and sandblasting or pickling was used for derusting.

[0036] (2) Zinc diffusion treatment

[0037] A penetrant was prepared by using zinc powder as the penetrant metal, ammonium chloride as the catalyst, and alumina powder as the dispersant. It was sprayed onto the surface of the pretreated component and kept at 400℃ for 4 hours. The mass ratio of zinc powder, ammonium chloride and alumina was 1:0.02:2.

[0038] (3) Laser melting

[0039] Laser melting was performed on the substrate surface after step (2). The laser melting power was 600W, the spot diameter was 2mm, the defocusing amount was 2cm, the scanning speed was 15mm / s, and the overlap rate was 18%.

[0040] In this embodiment, after preparing the wear-resistant and corrosion-resistant protective layer, the average hardness of the component substrate surface and cross-section is 884.6 HV and 829.7 HV, respectively. In contrast, the average hardness of the substrate surface after a single zinc diffusion treatment is only 367.2 HV.

[0041] Figure 1 The image shows the cross-sectional morphology of the substrate after zinc diffusion treatment in Example 1. It can be seen that there is a zinc diffusion layer with a thickness of about 100 μm on the surface of the 5CrNiMo steel component substrate. Figure 2 The image shows the cross-sectional morphology after laser melting and solidification on the zinc-treated substrate surface. It can be seen that the zinc-treated area no longer has a protruding zinc layer on the substrate surface. The energy dispersive spectroscopy (EDS) spectrum after zinc treatment is also shown. Figure 3 As can be seen from the energy dispersive spectroscopy (EDS) spectrum after laser melting, some iron diffuses into the zinc-infiltrated layer, while zinc is mainly on the surface of the substrate and does not penetrate much into the substrate interior. Figure 4 As can be seen, after laser strengthening, iron and zinc form an effective interdiffusion, and zinc effectively diffuses into the matrix.

[0042] from Figure 5 As can be seen from the table, Zn and Fe are uniformly distributed in the wear-resistant and corrosion-resistant protective layer prepared by this invention, and there is diffusion between Zn and Fe, resulting in a good zinc infiltration effect. The elemental content distribution on the surface of the wear-resistant and corrosion-resistant protective layer is shown in Table 1.

[0043] Table 1: Surface elemental distribution of the wear-resistant and corrosion-resistant protective layer prepared in Example 1

[0044] C 15.76 36.59 O 19.01 33.12 Fe 33.81 16.88 Zn 31.41 13.40 Total 100.00 100.00

[0045] from Figure 5 As shown in Table 1, the zinc-diffused layer is an alloy layer of zinc and iron, in which Zn and Fe are uniformly distributed.

[0046] Salt spray tests were conducted on 5CrNiMo substrates with the prepared wear-resistant and corrosion-resistant protective layer using an alternating "spraying for 24 hours + drying for 24 hours" method.

[0047] The test temperature was 35±2℃, and the sodium chloride solution concentration was 5±0.1%. The test results are as follows: Figure 6 As shown, the 5CrNiMo substrate without any protective layer developed red rust corrosion after 24 hours of salt spray treatment, while the substrate with the wear-resistant and corrosion-resistant protective layer prepared in this invention did not show any corrosion. Figure 6 a) After 1000 hours of salt spray treatment, the areas on the substrate surface that underwent zinc diffusion treatment and laser melting reinforcement remained unchanged and were not corroded. The areas treated with zinc diffusion alone showed a slight color change, while the corrosion of the substrate without a protective layer deepened further. Figure 6 b) It can be seen that the wear-resistant and corrosion-resistant protective layer prepared by the present invention has excellent corrosion resistance.

[0048] Following the method of laser strengthening followed by zinc diffusion treatment in the existing technology CN107557536A, a protective layer was prepared on a 5CrNiMo substrate using the parameters in Example 1. Due to the outward growth of the zinc diffusion layer, the surface roughness of the substrate increased. The average hardness of the substrate surface and cross section was tested to be 485.8 HV and 452.7 HV, respectively. During long-term friction use, the outward-grown zinc diffusion layer showed obvious peeling.

[0049] Comparative Example 1:

[0050] A method for preparing a wear-resistant and corrosion-resistant protective layer includes the following steps:

[0051] (1) Preprocessing

[0052] The 5CrNiMo steel components were sequentially degreased, washed with water, derusted, washed with water again, and dried. Ethyl acetate was used for degreasing, and sandblasting or pickling was used for derusting.

[0053] (2) Zinc diffusion treatment

[0054] A penetrant was prepared by using zinc powder as the penetrant metal, ammonium chloride as the catalyst, and alumina powder as the dispersant. It was sprayed onto the surface of the pretreated component and kept at 400℃ for 4 hours. The mass ratio of zinc powder, ammonium chloride and alumina was 1:0.02:2.

[0055] (3) Laser melting

[0056] Laser melting was performed on the substrate surface after step (2). The laser melting power was 600W, the spot diameter was 2mm, the defocusing amount was 5cm, the scanning speed was 10mm / s, and the overlap rate was 50%.

[0057] Based on Example 1, Comparative Example 1 adopted a larger defocusing amount and overlap rate, and a smaller scanning speed during the laser melting process. After testing, the resulting protective layer showed that the diffusion of zinc into the substrate was not significant, and the inward movement of the zinc-infiltrated layer was not noticeable. While laser strengthening vaporized the surface zinc, exposing a zinc-iron alloy layer with a higher zinc concentration, a small number of protrusions remained, resulting in low precision of the substrate friction surface. Testing showed that the average hardness of the substrate surface and cross-section were 614.3 HV and 572.5 HV, respectively. During long-term friction testing, a small amount of flaking occurred at the protruding zinc-infiltrated layer areas.

[0058] Example 2

[0059] A method for preparing a wear-resistant and corrosion-resistant protective layer includes the following steps:

[0060] (1) Preprocessing

[0061] The H13 steel component substrate was subjected to degreasing, water washing, rust removal, water washing and drying in sequence. Ethyl acetate was used for degreasing, and sandblasting or pickling was used for rust removal.

[0062] (2) Zinc diffusion treatment

[0063] A penetrant was prepared by using zinc powder as the penetrant metal, ammonium chloride as the catalyst, and alumina powder as the dispersant. It was sprayed onto the surface of the pretreated component and kept at 390℃ for 6 hours. The mass ratio of zinc powder, ammonium chloride, and alumina was 0.9:0.01:2.1.

[0064] (3) Laser melting

[0065] Laser melting was performed on the substrate surface after step (2). The laser melting power was 400W, the spot diameter was 2mm, the defocusing amount was 2cm, the scanning speed was 18mm / s, and the overlap rate was 15%.

[0066] In this embodiment, the average hardness of the wear-resistant and corrosion-resistant protective layer prepared on the surface of the H13 steel component substrate is 868.3 HV and 819.8 HV, respectively. After 1000 hours of salt spray treatment, the substrate surface remained unchanged and was not corroded, demonstrating that the wear-resistant and corrosion-resistant protective layer prepared by this invention has excellent corrosion resistance.

[0067] Example 3

[0068] A method for preparing a wear-resistant and corrosion-resistant protective layer includes the following steps:

[0069] (1) Preprocessing

[0070] The 5CrNiMo steel components were sequentially degreased, washed with water, derusted, washed with water again, and dried. Ethyl acetate was used for degreasing, and sandblasting or pickling was used for derusting.

[0071] (2) Zinc diffusion treatment

[0072] A penetrant was prepared using zinc powder as the penetrant metal, ammonium chloride as the catalyst, and alumina powder as the dispersant. It was sprayed onto the surface of the pretreated component and kept at 410℃ for 3 hours. The mass ratio of zinc powder, ammonium chloride, and alumina was 1.1:0.04:1.9.

[0073] (3) Laser melting

[0074] Laser melting was performed on the substrate surface after step (2). The laser melting power was 800W, the spot diameter was 2mm, the defocusing amount was 2cm, the scanning speed was 20mm / s, and the overlap rate was 20%.

[0075] In this embodiment, the average hardness of the wear-resistant and corrosion-resistant protective layer prepared on the surface of a 5CrNiMo steel component substrate is 862.5 HV and 816.4 HV, respectively. After 1000 hours of salt spray treatment, the substrate surface remained unchanged and showed no corrosion, demonstrating that the wear-resistant and corrosion-resistant protective layer prepared by this invention has excellent corrosion resistance.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant protective layer, characterized in that: First, zinc diffusion treatment is performed on the surface of the steel component. Then, laser melting treatment is performed on the surface of the zinc-dipped component. The laser melting power is 400~800W, the spot diameter is 2mm, the defocusing amount is 2cm, the scanning speed is 5-20mm / s, and the overlap rate is 15~20%.

2. The method for preparing a wear-resistant and corrosion-resistant protective layer as described in claim 1, characterized in that: The zinc infiltration treatment uses zinc powder as the infiltrator metal, ammonium chloride as the catalyst, and alumina powder as the dispersant to prepare an infiltrator, which is then sprayed onto the surface of the pretreated component and kept at 390~410℃ for 3~6 hours.

3. The method for preparing a wear-resistant and corrosion-resistant protective layer as described in claim 2, characterized in that: The mass ratio of zinc powder, ammonium chloride and alumina in the penetrant is 0.9~1.1:0.01~0.04:1.9~2.

1.

4. The method for preparing a wear-resistant and corrosion-resistant protective layer as described in claim 3, characterized in that: Before the zinc diffusion treatment, the steel components need to be pretreated. Specifically, the components are degreased with ethyl acetate, washed with water, sandblasted or pickled to remove rust, washed with water again, and then dried.

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