Method for preparing anti-erosion homogeneous high-hardness hydrophobic layer on metal surface

Abstract

The invention discloses a surface modification method for preparing an anti-erosion homogeneous high-hardness hydrophobic layer on a metal surface, which is characterized in that a homogeneous high-hardness hydrophobic surface layer is prepared on the metal surface in situ, a surface hardening layer and a matrix are homogeneous layers, and the coupling effect of good mechanical property and surface hydrophobicity is utilized, so that the hydrophobic surface layer is prepared. And the solid-liquid two-phase erosion resistance of the stainless steel is improved. According to the method, the surface heating layer is subjected to phase change, the hardness and strength of the metal surface layer are improved, the surface roughness is adjusted, then high-energy pulse laser is adopted for surface impact, a non-dot-matrix irregular microstructure is formed on the surface of the hardened layer, and the hydrophobic characteristic is achieved. The surface microstructure of the double strengthened layer subjected to martensite transformation hardening and laser shock is different from a microstructure which is etched and processed by other laser technologies and is regularly and periodically arranged in a dot matrix mode, and meanwhile due to the fact that the strengthened layer belongs to an in-situ hardened layer, good mechanical performance and hydrophobic surface coupling have high solid-liquid two-phase fluid erosion resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification of metal materials, and specifically relates to a surface modification method for in-situ preparing a homogeneous high-hardness, hydrophobic layer on a metal surface. The invention utilizes the dual coupling effect of the mechanical properties of high hardness and hydrophobicity of the surface layer to improve the erosion resistance of martensitic stainless steel to solid-liquid two-phase flow. Background Art

[0002] Martensitic stainless steel has good comprehensive properties such as corrosion resistance and strength, and is widely used in cutting tools, medical equipment, precision machinery and industrial equipment. In addition, martensitic stainless steel is an important material for manufacturing turbine blades. During the operation of the turbine, the blades and other flow-through components are subjected to the action of water flow for a long time, and their surfaces may still be subject to various damages such as corrosion or erosion, resulting in performance degradation and shortened service life. Turbine flow components are in constant contact with water and are subject to corrosive effects from the flow. Reducing surface contact with water can effectively reduce corrosion damage to these components. Imparting hydrophobic properties through surface modification can effectively reduce the infiltration of liquids such as water, and has become an important research direction for improving the overall performance of martensitic stainless steel. Currently, hydrophobic treatment technologies for metal materials mainly include organic coatings, chemical vapor deposition (CVD), physical vapor deposition (PVD), chemical etching, and micro-nanostructuring. However, these preparation methods have certain drawbacks. For example, traditional organic coatings using fluorocarbon resin (PTFE) or silicone (PDMS) coatings have weak adhesion to the metal substrate and are prone to flaking during long-term use. Furthermore, thick coatings can affect the dimensional accuracy of the workpiece, making them difficult to meet the requirements of precision devices. Etching involves creating a rough surface through acid / base etching or laser processing, combined with low-surface-energy modification to achieve a super-hydrophobic effect. However, heterogeneous hydrophobic layers on the surface can pose problems with interfacial bonding and flaking during use. Summary of the Invention

[0003] The present invention provides a surface modification method for preparing a homogeneous, high-hardness, hydrophobic and high-erosion-resistant multifunctional coupled surface hardening layer on the surface of a metal. Existing metal surface modification technologies usually prepare a heterogeneous material structure different from the matrix on the metal surface. This heterogeneous surface material with special properties has an interface bonding problem with the matrix, and the surface material may fall off due to insufficient interface bonding strength during later use. Another approach is to perform surface heat treatment or surface chemical treatment on the metal matrix, which usually can only achieve a change in a single property, such as improving hardness. The present invention proposes an idea of ​​combining dual laser treatment and surface roughness with microstructure, and realizes the preparation of a homogeneous, high-hardness, hydrophobic and erosion-resistant multifunctional coupled surface hardening layer on the surface of 0Cr13Ni5Mo stainless steel. Specifically, the surface of 0Cr13Ni5Mo martensitic stainless steel is subjected to laser rapid heating and cooling treatment, and a phase change occurs in the surface heating layer to increase the hardness and strength of the metal surface layer, adjust the surface roughness, and then use a high-energy pulsed laser for surface impact to form a non-lattice irregular microstructure on the surface of the hardened layer to achieve hydrophobic properties. This dual-strengthening layer, created through martensitic transformation and laser shock treatment, produces a hydrophobic surface microstructure that differs from the regular, periodic arrangement of lattices produced by other laser etching techniques. Furthermore, because the strengthening layer is an in-situ hardened layer, its excellent mechanical properties coupled with the hydrophobic surface provide high resistance to erosion by solid-liquid two-phase fluids. This invention discovers a new capability of high-energy pulsed lasers: forming an irregular, non-periodic microstructure on the metal surface. This structure exhibits hydrophobic properties and represents a novel hydrophobic microstructure that, unlike other periodic lattice microstructures, is easy to implement and low-cost.

[0004] The technical solution adopted in the present invention is: A surface modification method for in-situ preparation of a homogeneous, high-hardness, hydrophobic layer that resists erosion on a metal surface. The dual coupling effect of high hardness and hydrophobicity can effectively improve the erosion resistance of stainless steel. The method comprises the following steps: S1, metal surface grinding pretreatment, using grinding equipment to grind the metal surface to a specific roughness; S2, high-energy laser surface quenching hardening, the surface of the martensitic stainless steel pre-treated by surface grinding is subjected to laser surface quenching rapid heating and rapid cooling; S3, polish the surface of the martensitic hardened layer again to control its surface roughness; in this step, the roughness should be adjusted within a certain range; S4, laser surface shock treatment, uses high-energy pulsed laser treatment to treat the surface of hardened martensitic stainless steel. On the one hand, it further increases the hardness of the surface layer, and on the other hand, it constructs the surface microstructure, increases the contact angle, and improves the hydrophobicity. S5, post-treatment of the sample surface, cleaning and drying the surface; The in-situ preparation of a homogeneous, high-hardness, hydrophobic layer that is resistant to erosion is completed on the metal surface.

[0005] Preferably, the metal is martensitic stainless steel or other metal that can undergo martensitic transformation hardening.

[0006] Preferably, the pretreatment method in step S1 is: the pretreatment includes: polishing the surface with 240 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper to reduce the roughness to Ra1.6 or below, then cleaning the surface with acetone or alcohol and drying it. Further preferably, the metal surface is polished to a surface roughness of Ra1.6. Preferably, the power of the laser surface quenching in step S2 is 2.0kw-4.0kw, the scanning speed is 6-25mm / s, and the spot size is 20*2mm 2 , defocus range is 200-400mm. Preferably, in step S2, the surface of the martensitic stainless steel pre-treated by surface grinding is subjected to laser surface quenching and rapid heating until the temperature is 30-80° C. above the austenite transformation point.

[0007] Preferably, the laser surface quenching heating rate and cooling rate in step S2 are between 1000-1100° C. / s.

[0008] Preferably, after the laser surface quenching in step S2, the Vickers hardness value (HV) of the material surface should be between 340-390, and the depth of the martensite hardened layer should be between 300-600 μm.

[0009] A hardened layer is prepared on the metal surface. The hardened layer is induced by martensitic phase transformation, and the core is the original matrix structure. The laser surface quenching heating and cooling speeds are fast enough to make the surface heating layer obtain austenite and transform into martensite during rapid cooling. The martensite has high hardness, which increases the surface hardness.

[0010] Preferably, the polishing operation in step S3 is to polish the surface with sandpaper of 600, 800, 1000, 1200, 3000 or 5000 mesh, with the surface roughness Ra1.6-0.4.

[0011] Preferably, the laser surface shock treatment method in step S4 is as follows: a laser absorption layer is attached to the metal surface, flowing water is used as a constraining layer, and the high-energy pulsed laser processing parameters are: wavelength 900-1200nm, laser energy 7-11J, spot overlap ratio 40-60%, and spot diameter 2-4mm. Laser shock treatment of the hardened martensitic stainless steel surface using a high-energy pulsed laser not only rehardens the surface layer but also structures the surface microstructure, increasing the contact angle and improving hydrophobicity. The material processed in step S4 has a homogeneous, high-hardness, hydrophobic layer.

[0012] The present invention uses laser for rapid heating and rapid cooling to form a martensitic hardened layer on the surface of 0Cr13Ni5Mo stainless steel. The surface is then polished and the roughness is adjusted within a certain range. A high-energy pulse laser is used again to impact treat the surface martensitic hardened layer. On the one hand, the high-energy pulse laser is used to further change the microstructure and lattice distortion of the metal matrix below the surface to achieve re-hardening of the surface martensitic layer. On the other hand, the surface roughness structure of the martensitic hardened layer is adjusted and improved, and the contact angle of the surface hardened layer is increased, so that the surface of the hardened layer has hydrophobic properties. This high-hardness hydrophobic layer has high erosion resistance and is made of the same material as the metal matrix, with no interface stratification with the matrix.

[0013] No additional materials are required as coatings throughout the entire preparation process, ensuring that the surface hardened layer is made of the same material as the substrate, making the preparation process environmentally friendly and pollution-free. The resulting metal surface is both highly hard and hydrophobic, avoiding issues such as interfacial cracking and surface shedding during solid-liquid two-phase fluid impact. Simultaneously, by improving the microscopic roughness and wetting angle of the stainless steel surface, the surface hardness is enhanced, while also providing hydrophobic properties and improving erosion resistance. This multifunctional coupled surface preparation technology combines homogeneity, high hardness, hydrophobicity, and erosion resistance.

[0014] The beneficial effects of the present invention are: a homogeneous, high-hardness, hydrophobic hardened layer with multifunctional coupling is prepared on the surface of martensitic stainless steel using conventional laser surface hardening modification technology, thereby improving the erosion resistance of the alloy and expanding the application of laser surface hardening technology. Its advantages are: (1) The method of the present invention is to perform high-energy laser rapid heating and rapid cooling on martensitic stainless steel, so that the surface undergoes a martensitic phase transformation to form a hardened layer. The hardened layer has the same composition as the matrix and has no interface. There is no problem of the hardened layer falling off due to external forces during later use. (2) The method of the present invention uses a high-energy pulsed laser to further microstructure the surface hardened layer of martensitic stainless steel. This method, on the one hand, changes the internal crystal structure of the surface hardened layer, improving the performance of the hardened layer, and on the other hand, causes the laser to impact the martensite surface to form a special microstructure with hydrophobic properties. The surface microstructure of the present invention is a non-periodic non-lattice structure, which is novel in terms of hydrophobic microstructure. (3) The method described in the present invention, without adding any other materials, uses dual laser technology to modify the surface of martensitic stainless steel. First, the surface is laser hardened, then the surface roughness is adjusted, and then the surface microstructure is constructed using laser shock, achieving surface hardening, hydrophobicity, and erosion resistance. This method is easy to operate and low-cost, and has potential engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the contact angle of the original surface of martensitic stainless steel, providing a comparison for Examples 1-4.

[0016] Figure 2 is the contact angle of a droplet on the hydrophobic surface prepared in Example 1.

[0017] Figure 3 is the contact angle of the liquid drop on the hydrophobic surface prepared in Example 3.

[0018] Figure 4 is the contact angle of the liquid drop on the hydrophobic surface prepared in Example 4.

[0019] Figure 5 The micro-Vickers hardness in the depth direction below the surface of the materials prepared by the present invention (Examples 1-4).

[0020] Figure 6 This is the microscopic morphology of the material surface prepared in Example 1 of the present invention under SEM.

[0021] Figure 7 The erosion mass loss data of the laser surface modified samples and the original samples of the present invention (Examples 1-4). DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto. The specific embodiments described herein are only for the purpose of illustrating and explaining the present disclosure and are not intended to limit the present disclosure. Equivalent substitutions or corresponding improvements made to the contents of the present invention are still within the scope of protection of the present invention.

[0023] 0Cr13Ni5Mo is selected as a research object and the present invention is described in detail in conjunction with specific embodiments.

[0024] Example 1 A surface modification method for in-situ preparing an erosion-resistant, homogeneous, high-hardness hydrophobic layer on a metal surface, the method comprising the following steps: S1, metal surface grinding pretreatment, using grinding equipment to grind the metal surface to a specific roughness; S2, high-energy laser surface quenching hardening, the surface of the martensitic stainless steel pre-treated by surface grinding is rapidly heated by laser surface quenching; S3, polish the surface of the martensitic hardened layer again to control its surface roughness; the roughness in this step should be appropriate; S4, laser surface shock treatment, uses high-energy pulsed laser treatment to treat the surface of hardened martensitic stainless steel. On the one hand, it further increases the hardness of the surface layer, and on the other hand, it constructs the surface microstructure, increases the contact angle, and improves the hydrophobicity. S5, post-treatment of the sample surface, cleaning and drying the surface; The preparation of a homogeneous, high-hardness, hydrophobic layer that is resistant to erosion is completed on the metal surface.

[0025] Preferably, the metal is 0Cr13Ni5Mo martensitic stainless steel.

[0026] Preferably, the pretreatment method in step S1 is: the pretreatment includes: polishing the surface with 240 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper, cleaning the surface with acetone or alcohol, drying, and storing in an electronic moisture-proof box at a relative humidity of 7% and a temperature of 23°C.

[0027] Further preferably, the metal surface is polished to a surface roughness of Ra1.6. Preferably, the power of the laser surface quenching in step S2 is 2.4 kW, the scanning speed is 12 mm / s, and the spot size is 20*2 mm. 2 , defocus distance 300mm. Preferably, in step S2, the surface of the martensitic stainless steel that has been pre-treated by surface grinding is subjected to laser surface quenching, and is rapidly heated to 80° C. above the austenite transformation point.

[0028] Preferably, in step S2, the laser surface quenching heating rate and cooling rate are 1020° C. / s.

[0029] Preferably, after the laser surface quenching in step S2, the Vickers hardness (HV) of the material surface is 355, and the depth of the martensite hardened layer is 450 microns.

[0030] Preferably, the polishing operation in step S3 is to polish the surface with 1000-grit sandpaper to a surface roughness of Ra1.6.

[0031] Preferably, the laser surface impacting step S4 is performed by attaching a laser absorption layer to the metal surface, using water as a confinement layer, using a high-energy pulsed laser with a wavelength of 1000 nm, a laser energy of 9 J, a spot diameter of 3 mm, and a spot overlap ratio of 50%. After the high-energy pulsed laser impacting, the test surface is cleaned with acetone, dried, and stored in an electronic moisture-proof cabinet.

[0032] The surface hardened layer prepared using the above steps exhibited a contact angle of 111°, indicating hydrophobicity. The surface Vickers hardness (HV) was 355, while the substrate's HV was 315. Under the same erosion conditions, the substrate's erosion mass loss was 64.09 mg, while the surface-modified material's erosion mass loss was 5.56 mg, significantly reducing mass loss and improving erosion resistance. This demonstrated the preparation of a homogeneous, high-hardness, hydrophobic layer that is resistant to surface erosion.

[0033] Example 2 A surface modification method for preparing a multifunctional coupled homogeneous high hardness, hydrophobicity and high erosion resistance on a metal surface, the method comprising the following steps: S1, metal surface grinding pretreatment, using grinding equipment to grind the metal surface to a specific roughness; S2, high-energy laser surface quenching hardening, the surface of the martensitic stainless steel pre-treated by surface grinding is rapidly heated by laser surface quenching; S3, polish the surface of the martensitic hardened layer again to control its surface roughness; the roughness in this step should be appropriate; S4, laser surface shock treatment, uses high-energy pulsed laser treatment to treat the surface of hardened martensitic stainless steel. On the one hand, it further increases the hardness of the surface layer, and on the other hand, it constructs the surface microstructure, increases the contact angle, and improves the hydrophobicity. S5, post-treatment of the sample surface, cleaning and drying the surface; Complete the surface modification of the metal surface to prepare multifunctional coupling with homogeneous high hardness, hydrophobicity and high erosion resistance.

[0034] Preferably, the metal is 0Cr13Ni5Mo martensitic stainless steel.

[0035] Preferably, the pretreatment method in step S1 is: the pretreatment includes: polishing the surface with 240 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper, cleaning the surface with acetone or alcohol, and drying in an electronic moisture-proof box at a set temperature of 23°C.

[0036] Further preferably, the metal surface is polished to a surface roughness of Ra1.6. Preferably, the power of the laser surface quenching in step S2 is 3kw, the scanning speed is 12mm / s, and the spot size is 20*2mm. 2 , defocus distance 300mm. Preferably, in step S2, the surface of the martensitic stainless steel that has been pre-treated by surface grinding is subjected to laser surface quenching, and is rapidly heated to 80° C. above the austenite transformation point.

[0037] Preferably, in step S2, the laser surface quenching heating rate and cooling rate are 1020° C. / s.

[0038] Preferably, after the laser surface quenching in step S2, the Vickers hardness (HV) of the material surface is 375, and the depth of the martensite hardened layer is 450 microns.

[0039] Preferably, the polishing operation in step S3 is to polish the surface with 3000-grit sandpaper to a surface roughness of Ra0.8.

[0040] Preferably, the laser surface impacting step S4 is performed by attaching a laser absorption layer to the metal surface, using water as a confinement layer, using a high-energy pulsed laser with a wavelength of 1000 nm, a laser energy of 9 J, a spot overlap ratio of 50%, and a spot diameter of 3 mm. After the high-energy pulsed laser impacting, the test surface is cleaned with acetone, dried, and stored in an electronic moisture-proof cabinet.

[0041] The surface hardened layer prepared using the above steps exhibited a contact angle of 109°, indicating hydrophobicity. The surface Vickers hardness (HV) was 375, while the substrate's HV was 315. Under the same erosion conditions, the substrate's erosion mass loss was 64.09 mg, while the surface-modified material's erosion mass loss was 5.52 mg, significantly reducing mass loss and improving erosion resistance. This demonstrated the preparation of a homogeneous, high-hardness, hydrophobic layer that is erosion-resistant.

[0042] Example 3 A surface modification method for preparing a multifunctional coupled homogeneous high hardness, hydrophobicity and high erosion resistance on a metal surface, the method comprising the following steps: S1, metal surface grinding pretreatment, using grinding equipment to grind the metal surface to a specific roughness; S2, high-energy laser surface quenching hardening, the surface of the martensitic stainless steel pre-treated by surface grinding is rapidly heated by laser surface quenching; S3, polish the surface of the martensitic hardened layer again to control its surface roughness; the roughness in this step should be appropriate; S4, laser surface shock treatment, uses high-energy pulsed laser treatment to treat the surface of hardened martensitic stainless steel. On the one hand, it further increases the hardness of the surface layer, and on the other hand, it constructs the surface microstructure, increases the contact angle, and improves the hydrophobicity. S5, post-treatment of the sample surface, cleaning and drying the surface; Complete the surface modification of the metal surface to prepare multifunctional coupling with homogeneous high hardness, hydrophobicity and high erosion resistance.

[0043] Preferably, the metal is 0Cr13Ni5Mo martensitic stainless steel.

[0044] Preferably, the pretreatment method in step S1 is: the pretreatment includes: polishing the surface with 240 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper, cleaning the surface with acetone or alcohol, and drying in an electronic moisture-proof box at a set temperature of 23°C.

[0045] Further preferably, the metal surface is polished to a surface roughness of Ra1.6. Preferably, the power of the laser surface quenching in step S2 is 2.4 kW, the scanning speed is 8 mm / s, and the spot size is 20*2 mm. 2 , defocus distance 300mm. Preferably, in step S2, the surface of the martensitic stainless steel pre-treated by surface grinding is subjected to laser surface quenching and rapid heating until the temperature is 80° C. above the austenite transformation point.

[0046] Preferably, in step S2, the laser surface quenching heating rate and cooling rate are 1020° C. / s.

[0047] Preferably, after the laser surface quenching in step S2, the Vickers hardness (HV) of the material surface is 350, and the depth of the martensite hardened layer is 400 microns.

[0048] Preferably, the polishing operation in step S3 is to polish the surface with 3000-grit sandpaper to a surface roughness of Ra0.8.

[0049] Preferably, the laser surface impacting step S4 is performed by attaching a laser absorption layer to the metal surface, using water as a confinement layer, using a high-energy pulsed laser with a wavelength of 1000 nm, a laser energy of 7 J, a spot overlap ratio of 50%, and a spot diameter of 3 mm. After the high-energy pulsed laser impacting, the test surface is cleaned with acetone, dried, and stored in an electronic moisture-proof cabinet.

[0050] The surface hardened layer prepared using the above steps exhibited a contact angle of 113°, indicating hydrophobicity. The surface Vickers hardness (HV) was 350, while the substrate's HV was 315. Under the same erosion conditions, the substrate's erosion mass loss was 47.31 mg, while the surface-modified material's erosion mass loss was 7.26 mg, significantly reducing mass loss and improving erosion resistance. This demonstrated the preparation of a homogeneous, high-hardness, hydrophobic layer that is resistant to surface erosion.

[0051] Example 4 A surface modification method for preparing a multifunctional coupled homogeneous high hardness, hydrophobicity and high erosion resistance on a metal surface, the method comprising the following steps: S1, metal surface grinding pretreatment, using grinding equipment to grind the metal surface to a specific roughness of Ra1.6; S2, high-energy laser surface quenching hardening, the surface of the martensitic stainless steel pre-treated by surface grinding is rapidly heated by laser surface quenching; S3, polish the surface of the martensitic hardened layer again to control its surface roughness; the roughness in this step should be appropriate; S4, laser surface shock treatment, uses high-energy pulsed laser treatment to treat the surface of hardened martensitic stainless steel. On the one hand, it further increases the hardness of the surface layer, and on the other hand, it constructs the surface microstructure, increases the contact angle, and improves the hydrophobicity. S5, post-treatment of the sample surface, cleaning and drying the surface; Complete the surface modification of the metal surface to prepare multifunctional coupling with homogeneous high hardness, hydrophobicity and high erosion resistance.

[0052] Preferably, the metal is 0Cr13Ni5Mo martensitic stainless steel.

[0053] Preferably, the pretreatment method in step S1 is: the pretreatment includes: polishing the surface with 240 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper, cleaning the surface with acetone or alcohol, and drying in an electronic moisture-proof box at a set temperature of 23°C.

[0054] Further preferably, the metal surface is polished to a surface roughness of Ra1.6. Preferably, the power of the laser surface quenching in step S2 is 3.5kW, the scanning speed is 16mm / s, and the spot size is 20*2mm. 2 , defocus distance 300mm. Preferably, in step S2, the surface of the martensitic stainless steel that has been pre-treated by surface grinding is subjected to laser surface quenching, and is rapidly heated to 80° C. above the austenite transformation point.

[0055] Preferably, in step S2, the laser surface quenching heating rate and cooling rate are 1020° C. / s.

[0056] Preferably, after the laser surface quenching in step S2, the Vickers hardness (HV) of the material surface is 380, and the depth of the martensite hardened layer is 450 microns.

[0057] Preferably, the polishing operation in step S3 is to polish the surface with 5000-grit sandpaper to a surface roughness of Ra0.4.

[0058] Preferably, the laser surface impacting step S4 is performed by attaching a laser absorption layer to the metal surface, using water as a confinement layer, using a high-energy pulsed laser with a wavelength of 1000 nm, a laser energy of 11 J, a spot overlap ratio of 50%, and a spot diameter of 3 mm. After the high-energy pulsed laser impacting, the test surface is cleaned with acetone, dried, and stored in an electronic moisture-proof cabinet.

[0059] The surface hardened layer prepared using the above steps exhibited a contact angle of 112°, indicating hydrophobicity. The surface Vickers hardness (HV) was 350, while the substrate's HV was 315. Under the same erosion conditions, the substrate's erosion mass loss was 47.31 mg, while the surface-modified material's erosion mass loss was 7.86 mg, significantly reducing mass loss and improving erosion resistance. This demonstrated the preparation of a homogeneous, high-hardness, hydrophobic layer that is erosion-resistant.

[0060] Comparison of Examples 1-4 reveals that the laser surface quenching power in step S2 is between 2.4-3.5 kW, and the laser heating scanning rate is 8-16 mm / s. High laser power, coupled with a high scanning rate, achieves the surface quenching and hardening effect of step S2. The polished surface roughness Ra in step S3 is between 1.6-0.4, and the high-energy pulsed laser energy in step S4 is 7-11 J. These parameters combine to produce a high-hardness, erosion-resistant, hydrophobic layer on the surface of 0Cr13Ni5Mo martensitic stainless steel.

[0061] Example 5 Based on Example 1, the laser conditions of step S2 are changed, and the rest are the same as Example 1.

[0062] Example 1: The power of the laser surface quenching in step S2 is 2.4 kW, the scanning speed is 12 mm / s, and the spot size is 20*2 mm. 2 , defocusing distance 300mm. Change the power and scanning speed of laser surface quenching, Figure 5 Vickers hardness at different depths below the surface of 0Cr3Ni5Mo after surface modification. Figure 5 The matching of laser power and scanning rate can successfully realize the preparation of surface erosion-resistant and high-hardness hydrophobic layer.

[0063] The power of the laser surface quenching in step S2 of Example 5-1 is 2.4 kW, the scanning speed is 8 mm / s, and the spot size is 20*2 mm. 2 , defocus distance 300mm.

[0064] The power of the laser surface quenching in step S2 of Example 5-2 is 4.5 kW, the scanning speed is 12 mm / s, and the spot size is 20*2 mm. 2 , defocus distance 300mm. The power of the laser surface quenching in step S2 of Example 5-3 is 1.5 kW, the scanning speed is 12 mm / s, and the spot size is 20*2 mm. 2 , defocus distance 300mm. Comparing Example 1 with Example 5-1, the laser power of 2.4 kW and the scanning rates of 12 mm / s and 8 mm / s, respectively, achieved surface hardening of the metal. In Example 5-2, the laser power of 4.5 kW was too high, damaging the metal surface and preventing surface hardening. In Example 5-3, the laser power of 1.5 kW was too low to achieve surface hardening. The key laser power requirements for step S2 are a laser power of 2-3.5 kW and a laser scanning rate of 8-16 mm / s. High laser power requires a high scanning rate.

[0065] Example 6 Based on Example 1, the laser conditions of step S4 are changed, and the rest are the same as Example 1.

[0066] Example 1: In step S4, the surface of the martensitic stainless steel surface that has been quenched and hardened is again subjected to high-energy pulse laser shock strengthening. The operation is that a laser absorption layer is adhered to the metal surface, water is used as a constraining layer, the high-energy pulse laser wavelength is 1000nm, the laser energy is 9J, the spot overlap rate is 50%, and the spot diameter is 3mm.

[0067] In step S4 described in Example 6-1, the surface of the quenched and hardened martensitic stainless steel is again subjected to high-energy pulse laser shock strengthening. The operation is as follows: a laser absorption layer is pasted on the metal surface, water is used as a constraining layer, the high-energy pulse laser wavelength is 1000nm, water is used as a constraining layer, the high-energy pulse laser wavelength is 1000nm, the laser energy is 7J, the spot overlap rate is 50%, and the spot diameter is 3mm.

[0068] In step S4 described in Example 6-2, the surface of the quenched and hardened martensitic stainless steel is again subjected to high-energy pulse laser shock strengthening. The operation is as follows: a laser absorption layer is pasted on the metal surface, water is used as a constraining layer, the high-energy pulse laser wavelength is 1000nm, water is used as a constraining layer, the high-energy pulse laser wavelength is 1000nm, the laser energy is 13J, the spot overlap rate is 50%, and the spot diameter is 3mm.

[0069] In step S4 described in Example 6-3, the surface of the quenched and hardened martensitic stainless steel is again subjected to high-energy pulse laser shock strengthening. The operation is as follows: a laser absorption layer is pasted on the metal surface, water is used as a constraining layer, the high-energy pulse laser wavelength is 1000nm, water is used as a constraining layer, the high-energy pulse laser wavelength is 1000nm, the laser energy is 5J, the spot overlap rate is 50%, and the spot diameter is 3mm. See the results Figure 6-7 By comparing Example 1 with Example 6-1 (comparative example), it can be seen that the laser energy in step S4 is 9J and 7J, which can not only significantly reduce the erosion mass loss, but also the surface contact angle is greater than 90°, and has hydrophobic properties; by comparing Example 1 with Example 6-2 (comparative example) and Example 6-3 (comparative example), it can be seen that the laser energy in step S4 is 13J, the surface is damaged to a certain extent, and the contact angle is 85°, while the laser energy is 5J, the laser impact energy is insufficient, the contact angle is 71°, and there is no hydrophobic property.

[0070] Example 7 Based on Example 1, the conditions of step S3 are changed, and the rest are the same as Example 1. Example 1: The polishing operation in step S3 is to polish the surface with 1000-mesh sandpaper, and the surface roughness is Ra1.6.

[0071] The polishing operation in step S3 of Example 7-1 is to polish the surface with 3000-grit sandpaper, and the surface roughness is Ra0.8. The polishing operation in step S3 of Example 7-2 is to polish the surface with diamond polishing paste, and the surface roughness is Ra0.2. The polishing operation in step S3 of Example 7-3 is to polish the surface with 120-grit sandpaper, and the surface roughness is Ra3.2. Comparison of Example 1 with Example 7-1 (Comparative Example) reveals the surprising discovery that the surface roughness of step S3 plays a key role in the hydrophobicity of the stainless steel surface treated by laser surface impact treatment. Under roughness conditions of 0.4-1.6, combined with laser treatment in step S4, the material achieves both high hardness and hydrophobicity, as well as improved scour resistance. However, treatments below or above this roughness range exhibit contact angles less than 90°, resulting in poor surface hydrophobicity. This is likely because, if the surface roughness Ra of step S3 is 0.2, the surface is also microscopically smooth, and the laser impact alone is unable to microstructure the metal surface, resulting in poor surface hydrophobicity. A surface roughness Ra of 3.2, with its high roughness, weakens the intensity of the laser impact, preventing the laser impact from microstructuring the surface. Comparative Example 1 Based on Example 1, step 3 was removed, and the rest was the same as in Example 1. That is, after high-energy laser surface hardening, no polishing was performed, and high-energy pulse laser shock was performed directly in step S4. Because the surface roughness processed in step S2 was not appropriate, the high-energy pulse laser shock in step S4 could not achieve the surface microstructuring effect, the surface contact was 85°, and there was no hydrophobicity.

[0072] Comparative Example 2 Based on Example 1, step S4 was removed, and the rest was the same as in Example 1. Based on Example 1, step S4 was removed, that is, only surface grinding was performed after high-energy laser surface hardening. Step S4 was removed, and high-energy pulse laser shock was not performed. The surface was only in a state after sandpaper polishing, without the construction of the surface structure by the high-energy pulse laser, the surface contact was 87°, and there was no hydrophobic property.

[0073] Comparative Example 3 Based on Example 1, step S2 is removed, that is, the high-energy laser surface hardening treatment is removed, and surface grinding is performed, that is, step S3, and high-energy pulse laser shock is performed, that is, step S4. The surface Vickers hardness is 315, the surface contact angle is 95°, the hardness is low, the anti-erosion effect is low, and it has a slightly hydrophobic property.

[0074] Comparative Example 4 Based on Example 1, step S2 and step S4 are swapped, and step S1 is completed. The surface of the sample is subjected to laser shock peening treatment, and then the surface is polished and then laser surface quenching treatment is performed. It is found that the surface after laser surface quenching is still slightly oxidized, its contact angle is less than 90°, and it is not hydrophobic.

[0075] Table 1 Surface modification parameters and effects of examples and comparative examples

[0076] Note: Surface hardness greater than 340 indicates a hardened surface relative to the substrate hardness (306). A contact angle greater than 90° indicates hydrophobicity. A contact angle less than 90° indicates no hydrophobicity. In Example 5-2, the laser conditions in step S2 were inappropriate, resulting in surface melting damage, and no further post-processing was performed.

[0077] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The embodiments and features in the embodiments of this application may be arbitrarily combined with each other unless they conflict. The scope of protection of the present invention shall be the technical solutions described in the claims, including equivalent alternatives to the technical features of the technical solutions described in the claims. Equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for preparing a homogeneous, high-hardness, erosion-resistant hydrophobic layer on a metal surface, characterized in that: The method comprises the following steps: S1, metal surface grinding pretreatment, using grinding equipment to grind the metal surface to below a certain roughness; S2, high-energy laser surface quenching hardening, the surface of the martensitic stainless steel pre-treated by surface grinding is subjected to laser surface quenching heating and cooling; S3, grinding the surface of the martensite hardened layer again to control its surface roughness; S4, laser surface shock, uses high-energy pulsed laser processing; S5, post-treatment of the sample surface, cleaning and drying the surface; The in-situ preparation of a homogeneous, high-hardness, hydrophobic layer that is resistant to erosion is completed on the metal surface.

2. The method according to claim 1, wherein: The metal is martensitic stainless steel or other metal that can undergo martensitic transformation hardening.

3. The method according to claim 1, wherein: The pretreatment method in step S1 is as follows: the pretreatment includes: using 240 mesh, 600 mesh, 800 mesh, and 1000 mesh sandpaper to polish the surface to reduce the roughness to Ra1.6 or below, then cleaning the surface with acetone or alcohol and drying it.

4. The method according to claim 3, wherein: The metal surface is ground to a surface roughness of Ra1.

6.

5. The method according to claim 1, characterized in that The power of the laser surface quenching in step S2 is 2.0-4.0 kw, the scanning speed is 6-25 mm / s, and the spot size is 20*2 mm 2 , defocus range is 200-400mm.

6. The method according to claim 1, characterized in that In step S2, the surface of the martensitic stainless steel pre-treated by surface grinding is subjected to laser surface quenching heating until the temperature is 30-80° C. above the austenite transformation point.

7. The method according to claim 1, characterized in that In step S2, the laser surface quenching heating rate and cooling rate are between 1000-1100° C. / s.

8. The method according to claim 1, characterized in that After the laser surface quenching in step S2, the surface hardness of the material should be between 340-400 HV, and the depth of the martensite hardened layer should be between 300-800 μm.

9. The method according to claim 1, characterized in that The polishing operation in step S3 is to polish the surface with 600, 800, 1000, and 1200 mesh sandpaper, and the surface roughness is Ra1.6-Ra0.

4.

10. The method according to claim 1, characterized in that The operation method of the laser surface impact in step S4 is as follows: a laser absorption layer is pasted on the metal surface, water is used as a confinement layer, and the high-energy pulse laser processing parameters are: wavelength 900-1200nm, laser energy 7-13J, spot overlap rate 40-60%, and spot diameter 3mm.

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