Preparation method of durable super-hydrophobic surface, metal component and application

Abstract

The application provides a preparation method of a durable super-hydrophobic surface, a metal component and an application. It belongs to the technical field of material surface engineering and functional micro-nano manufacturing technology, and comprises the following steps: performing surface mechanical strengthening treatment on a metal base to form a strengthened layer with higher hardness than the base on the surface layer; performing ablation processing on the surface of the strengthened layer by using pulse laser to construct a multi-stage micro-nano structure; and performing hydrophobization treatment on the surface after the ablation processing, so that the surface reaches a super-hydrophobic state. Through the synergistic construction of the strong and tough bottom layer and the functional surface layer, the mechanical durability, wear resistance and corrosion resistance of the super-hydrophobic surface are significantly improved, and the process is green, environmentally friendly and good in controllability.

Description

Technical Field

[0001] This invention relates to the field of material surface and functional micro / nano manufacturing technology, and particularly to a method for preparing a durable superhydrophobic surface, a metal component, and its application. Background Technology

[0002] Superhydrophobic surfaces are defined as surfaces with a water contact angle greater than 150° and a roll-off angle less than 10°. They have broad application prospects in fields such as self-cleaning, waterproofing and anti-icing, corrosion resistance, and oil-water separation. However, these surfaces face two major challenges in practical applications: first, the surface micro-nano structures have low mechanical strength and are easily damaged under external forces such as friction and impact, leading to failure of hydrophobic properties and poor durability; second, traditional preparation processes, such as chemical etching, template methods, and sol-gel methods, are relatively complex, have limited material adaptability, and poor environmental friendliness, making it difficult to achieve efficient and controllable large-area preparation.

[0003] Laser processing technology, especially picosecond lasers, can precisely construct micro- and nano-structures on the surfaces of various materials due to its extremely high peak power density and extremely low thermal effect, achieving controllable transformations in wettability. However, the substrate support of micro- and nano-structures formed by single laser processing is insufficient, and defects such as microcracks can be introduced, resulting in limited improvements in surface hardness and wear resistance. Ultrasonic rolling (USRP) is a surface mechanical strengthening technique that can introduce intense plastic deformation into the metal surface, refine grains, and generate high dislocation density and residual compressive stress fields, thereby significantly improving surface hardness, fatigue resistance, and wear resistance. However, its ability to control the surface microstructure is limited.

[0004] Therefore, how to combine the strengthening effect of ultrasonic rolling with the precision forming advantage of picosecond laser to prepare a durable functional surface on a metal substrate that has both excellent superhydrophobic properties and high hardness and good wear resistance is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the problem of poor mechanical durability caused by insufficient substrate support for superhydrophobic surface micro-nano structures in existing technologies, this application proposes a method for preparing a durable superhydrophobic surface, a metal component, and its application. This method achieves the synergistic construction of a strong and tough substrate and a functional surface layer, significantly improving the overall performance of the superhydrophobic surface.

[0006] In a first aspect, the present invention provides a method for preparing a durable superhydrophobic surface, comprising: S1. Perform surface mechanical strengthening treatment on the metal substrate to form a strengthening layer on the surface of the metal substrate. The hardness of the strengthening layer is higher than that of the metal substrate. S2. A pulsed laser is used to ablate the surface of the reinforcement layer to construct a multi-level micro-nano structure on the surface of the reinforcement layer. S3. Perform hydrophobic treatment on the surface after ablation to make the surface superhydrophobic.

[0007] Preferably, the surface mechanical strengthening treatment includes at least one of ultrasonic rolling, mechanical rolling or shot peening to introduce plastic deformation and residual compressive stress field in the surface layer.

[0008] More preferably, the surface mechanical strengthening treatment is ultrasonic rolling treatment.

[0009] Preferably, the process parameters for ultrasonic rolling treatment meet the following conditions: The processing speed is 500 mm / min to 1000 mm / min; the vibration amplitude is 10 μm to 15 μm; the rolling gap is 0.03 mm to 0.05 mm; the working air pressure is 0.2 MPa to 0.3 MPa; and the rolling head reciprocates along the surface of the metal substrate at least 3 times.

[0010] Preferably, the pulsed laser is an ultrafast laser.

[0011] Preferably, the ablation process employs a cross-scanning strategy, and the overlap rate of the light spots in the first scanning direction that is perpendicular to each other is greater than or equal to 51%, and the overlap rate in the second scanning direction is greater than or equal to 45%.

[0012] Preferably, the ultrafast laser is a picosecond laser or a femtosecond laser; when the ultrafast laser is a picosecond laser, the ablation process parameters meet the following conditions: The center wavelength is 1064 nm, the pulse width is 10 ps, ​​and the single-pulse energy density is 54 J / cm². 2 ~82J / cm 2 The overlap rate of the light spots is 90% in the first scanning direction and 96% in the second scanning direction; the effective pulse number is 12 to 30.

[0013] Preferably, the overlap rate in the first scanning direction is controlled by adjusting the laser scanning speed, which is set to 160–320 mm / s.

[0014] Preferably, the overlap rate in the second scanning direction is controlled by adjusting the scanning spacing, which is set to 1–5 μm.

[0015] Preferably, the effective pulse number is achieved by adjusting the number of scans. The effective pulse number is 6 in a single scan, and 12 in 2 scans.

[0016] Preferably, the hydrophobic treatment is an air-conditioning aging process without chemical modification.

[0017] Preferably, the air-standing aging treatment includes placing the surface after the ablation process in an air environment for static storage, so that the surface spontaneously adsorbs low surface energy organic matter in the air to achieve the transformation to a superhydrophobic state.

[0018] Preferably, the environmental parameters for air stagnant aging treatment meet the following conditions: The ambient temperature is 20℃~25℃; the relative humidity is 40%~60%; and the storage time is 2 weeks~4 weeks.

[0019] Preferably, the metal substrate is subjected to grinding, polishing, cleaning and drying.

[0020] Preferably, the polishing process involves sequentially polishing the metal substrate with 320-grit, 600-grit, 800-grit, 1200-grit, and 2000-grit silicon carbide sandpaper, with each polishing direction perpendicular to the previous one.

[0021] Preferably, polishing includes polishing the ground metal substrate using a metallographic polishing machine, using 3μm, 1μm diamond suspension and 0.05μm silica suspension as polishing liquids in sequence, and polishing until the surface has a mirror-like gloss.

[0022] Preferably, the cleaning and drying process includes ultrasonically cleaning the polished metal substrate in anhydrous ethanol for 10–30 minutes, removing it, drying it with nitrogen, and storing it in a desiccator for later use.

[0023] Preferably, the material of the metal substrate includes marine steel, low-carbon steel, or stainless steel.

[0024] Secondly, the present invention also provides a durable superhydrophobic metal component, including a metal substrate, the surface of which has a reinforcing layer, the hardness of which is higher than that of the metal substrate. The surface of the reinforcement layer has a multi-level micro-nano structure formed by pulsed laser ablation; The surface of the multi-level micro / nano structure is superhydrophobic.

[0025] Thirdly, the present invention also provides the application of durable superhydrophobic metal components in the fields of ship self-cleaning, corrosion protection of marine equipment, or anti-icing and de-icing.

[0026] The beneficial effects of this invention are: This invention constructs an integrated composite structure of a strong and tough bottom layer and a functional surface layer on a metal substrate through a specific temporal combination of surface mechanical strengthening pretreatment, pulsed laser ablation, and hydrophobication treatment. Specifically, the surface mechanical strengthening pretreatment introduces plastic deformation and residual compressive stress into the substrate surface, significantly improving surface hardness and crack propagation resistance, providing a high-strength mechanical anchoring foundation for subsequent micro / nano structures. Pulsed laser ablation constructs multi-level micro / nano structures in situ on the strengthened layer, utilizing the high load-bearing capacity of the strengthened layer to resist external frictional loads, preventing plastic collapse of the micro / nano structures due to an overly soft substrate. The chemical-free air-conditioning aging treatment endows the surface with environmentally friendly and stable low surface energy characteristics. The synergistic effect of these three processes results in a superhydrophobic surface that maintains a high contact angle and low roll-off angle while significantly improving microhardness. Furthermore, it retains excellent hydrophobic and corrosion-resistant properties even after multiple mechanical wear cycles, effectively overcoming the technical bottleneck of poor mechanical durability of superhydrophobic surfaces. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the preparation method in Example 1 of the present invention; Figure 2 This is a schematic diagram of ultrasonic rolling processing in Embodiment 1 of the present invention and the morphology of the processed sample; Figure 3 This is a schematic diagram of (a) the picosecond laser scanning path and (b) the spot overlap rate of the present invention; Figure 4 The images show a comparison of surface hardness of samples under different processing methods. Figure a shows the sample without ultrasonic rolling and only processed with picosecond laser, while Figure b shows the sample processed with both ultrasonic rolling and picosecond laser. Figure 5 Comparison of surface microstructure (SEM) and three-dimensional structure (confocal) images of samples under different processing methods; where a1 is the SEM image of picosecond laser treatment only without ultrasonic rolling, a2 is the three-dimensional confocal image of picosecond laser treatment only without ultrasonic rolling, b1 is the SEM image of both ultrasonic rolling and picosecond laser treatment, and b2 is the three-dimensional confocal image of both ultrasonic rolling and picosecond laser treatment. Figure 6 Superhydrophobic surface prepared for Example 1: (a) electron microscope image of surface microstructure, (b) water contact angle photograph, (c) roll-off angle photograph; Figure 7 A comparison chart of wear resistance of superhydrophobic surfaces (contact angle as a function of wear cycle). Figure 8 The image shows a comparison of electrochemical polarization curves for samples treated with different methods. The black curve corresponds to the substrate, the red curve corresponds to single laser treatment, the green curve corresponds to single rolling treatment, and the blue curve corresponds to a combination of laser and rolling treatment. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] A method for preparing a durable superhydrophobic surface, comprising: S1. Perform surface mechanical strengthening treatment on the metal substrate to form a strengthening layer on the surface of the metal substrate. The hardness of the strengthening layer is higher than that of the metal substrate. S2. A pulsed laser is used to ablate the surface of the reinforcement layer to construct a multi-level micro-nano structure on the surface of the reinforcement layer. S3. Perform hydrophobic treatment on the surface after ablation to make the surface superhydrophobic.

[0030] By employing the above technical solutions, surface mechanical strengthening treatment refers to applying mechanical force to the surface of a metal substrate, causing it to undergo severe plastic deformation. This introduces high-density dislocation entanglement, grain refinement, and residual compressive stress fields within a certain depth range of the surface layer. This process not only significantly improves the microhardness of the surface layer but, more importantly, provides a high-strength mechanical support base for the subsequent construction of micro / nano structures. The formation of the strengthening layer is a prerequisite for the preparation of durable superhydrophobic surfaces, and its role is to solve the technical problem that traditional superhydrophobic surfaces are prone to plastic collapse or peeling of micro / nano structures under friction or impact loads due to the softness of the substrate.

[0031] After surface mechanical strengthening, the high energy density of pulsed lasers is used to precisely ablate the strengthened layer surface. Since the processed object is now a strengthened, hard surface layer, the heat-affected zone generated during laser ablation is smaller, and the resulting micro / nanostructures exhibit higher geometric retention and structural stiffness. Multi-level micro / nanostructures typically include micrometer-scale rough contours superimposed with nanoscale particles or textures. This cross-scale composite morphology is the physical basis for trapping air to form a stable gas film and achieving superhydrophobic effects. This step is strictly limited to the strengthened layer, ensuring an integrated connection between the micro / nanostructure and the substrate, avoiding the weak interfacial bonding problems that may exist with external coatings or particles. Simultaneously, the non-contact processing characteristics of pulsed lasers prevent secondary mechanical damage to the formed strengthened layer, achieving a perfect fusion of a tough substrate and a functional surface layer.

[0032] Hydrophobication is a functional step that modifies the surface energy of laser-processed surfaces to achieve low surface energy. Newly laser-ablated metal surfaces are typically rich in polar groups or dangling bonds, exhibiting a superhydrophilic state. Hydrophobication is necessary to reduce their surface free energy in order to achieve high contact angles and low roll-off angles for water droplets. In this invention, hydrophobication is a functional limitation, and its implementation can be achieved through physical adsorption of low surface energy substances from the environment, chemical grafting of hydrophobic molecules, or other known or unknown methods capable of reducing surface energy. This step, located at the end of the process flow, aims to impart final wetting functionality to the micro / nanostructure without altering the mechanically reinforced structure and microgeometry already constructed in previous steps.

[0033] In some embodiments, surface mechanical strengthening treatment includes at least one of ultrasonic rolling, mechanical rolling, or shot peening to introduce plastic deformation and residual compressive stress field on the surface.

[0034] Furthermore, the surface mechanical strengthening treatment is ultrasonic rolling.

[0035] By employing the above technical solutions, surface mechanical strengthening treatment induces intense plastic flow in the metal surface material through external mechanical load compression. For example, ultrasonic rolling uses a cemented carbide rolling head to forge and smooth the metal surface at high frequency and low amplitude under the coupled action of static pressure and high-frequency ultrasonic vibration. Regardless of the specific method used, the result is the induction of high-density dislocation entanglement and grain refinement within a certain depth range of the metal surface, thereby significantly improving microhardness. More importantly, because the plastic extension of the surface material is constrained by the internal undeformed matrix, a stable residual compressive stress field is formed on the surface.

[0036] In some embodiments, the process parameters for ultrasonic rolling treatment meet the following conditions: The processing speed is 500 mm / min to 1000 mm / min; the vibration amplitude is 10 μm to 15 μm; the rolling gap is 0.03 mm to 0.05 mm; the working air pressure is 0.2 MPa to 0.3 MPa; and the rolling head reciprocates along the surface of the metal substrate at least 3 times.

[0037] By adopting the above technical solutions, a close coupling effect exists between various factors in this parameter system. Processing speed and vibration amplitude jointly determine the impact energy density per unit area. If the processing speed is below 500 mm / min or the vibration amplitude is greater than 15 μm, excessive energy input will cause excessive plastic flow in the metal surface layer, easily inducing defects such as surface peeling, microcracks, and even flaking. This not only disrupts the surface continuity but also interferes with the focusing quality of subsequent laser spots due to excessive surface roughness. Conversely, if the processing speed is above 1000 mm / min or the vibration amplitude is less than 10 μm, the energy input is insufficient to induce sufficient grain refinement and dislocation proliferation, resulting in an excessively thin reinforcement layer or insignificant hardness improvement, failing to effectively provide mechanical support for the micro / nano structure. Simultaneously, the rolling gap and working gas pressure directly affect the coverage of the reinforced area and the uniformity of stress distribution. The rolling gap is controlled within the range of 0.03mm to 0.05mm, and with at least three reciprocating rolling passes, sufficient overlap between adjacent rolling tracks can be ensured, eliminating unreinforced zones and resulting in a macroscopically uniform distribution of the residual compressive stress field. Maintaining the working air pressure at 0.2MPa to 0.3MPa ensures a constant contact pressure between the rolling head and the workpiece surface. This avoids inconsistent strengthening effects caused by pressure fluctuations and prevents excessive pressure from accelerating wear on the rolling head or causing macroscopic scratches on the workpiece surface.

[0038] In some embodiments, the pulsed laser is an ultrafast laser.

[0039] The ablation process employs a cross-scanning strategy, with the overlap rate of the light spots in the first mutually perpendicular scanning direction being greater than or equal to 51%, and the overlap rate in the second scanning direction being greater than or equal to 45%.

[0040] By adopting the above technical solutions, this invention selects ultrafast lasers as the processing light source, which possess a cold processing effect due to their extremely short pulse widths, typically on the order of picoseconds or femtoseconds. Unlike traditional nanosecond or long-pulse lasers, ultrafast lasers have extremely high peak power densities, enabling the material to be ionized and removed in a very short time, while the heat does not have time to diffuse to the surrounding substrate, thus minimizing the formation of heat-affected zones. This characteristic is crucial for this invention because the processing object is a metal substrate that has undergone surface mechanical strengthening treatment. If long-pulse lasers are used, their significant heat accumulation effect can easily lead to annealing and softening of the strengthening layer, grain coarsening, or even the generation of harmful thermal tensile stress, thereby offsetting the mechanical gains brought about by the previous strengthening treatment. Ultrafast lasers, on the other hand, can accurately construct micro- and nano-structures while completely preserving the high hardness and residual compressive stress state of the strengthening layer, achieving compatibility between functional structure and mechanical properties.

[0041] Regarding the scanning strategy, this invention abandons the conventional unidirectional parallel line scanning method and instead adopts a cross-scanning strategy. Unidirectional scanning often introduces significant anisotropy into the processed surface, meaning there is a significant difference in the microstructure along the scanning direction and perpendicular to the scanning direction. This structural asymmetry leads to the direction dependence of wetting properties and preferential wear along a single texture direction under stress. By first scanning along the first scanning direction and then performing a second scanning direction perpendicular to the first direction, the directional texture traces left by the single scan can be effectively eliminated, allowing the laser energy to be uniformly distributed in the two-dimensional plane, thereby constructing a spatially highly symmetrical and isotropic multi-level micro / nano structure. This uniform structure is not only the geometric basis for obtaining a stable low roll-off angle superhydrophobic state, but also ensures the consistency of surface wear resistance in all directions.

[0042] Furthermore, the overlap rate of the light spots is a key parameter determining the forming quality of micro- and nano-structures. This invention limits the overlap rate in the first scanning direction to be greater than or equal to 51%, and the overlap rate in the second scanning direction to be greater than or equal to 45%, which are thresholds derived from extensive process verification.

[0043] In some embodiments, the ultrafast laser is a picosecond laser or a femtosecond laser; when the ultrafast laser is a picosecond laser, the process parameters for ablation processing meet the following conditions: The center wavelength is 1064 nm, the pulse width is 10 ps, ​​and the single-pulse energy density is 54 J / cm². 2 ~82J / cm 2 The overlap rate of the light spots is 90% in the first scanning direction and 96% in the second scanning direction; the effective pulse number is 12 to 30.

[0044] By adopting the above technical solutions, the interaction mechanism between picosecond laser and reinforcement layer material has been further optimized. Under this specific parameter combination, a micron-sized hump and nano-sized particle composite structure with controllable size and regular morphology can be induced. This specific multi-level micro-nano morphology is the key physical basis for capturing air to form a stable gas film and achieving a low roll-off angle superhydrophobic state.

[0045] In some embodiments, the overlap rate in the first scanning direction is controlled by adjusting the laser scanning speed, which is set to 160–320 mm / s.

[0046] The overlap rate in the second scanning direction is controlled by adjusting the scanning spacing, which is set to 1–5 μm.

[0047] The effective pulse count is achieved by adjusting the number of scans. The effective pulse count is 6 for a single scan and 12 for two scans.

[0048] In some embodiments, the hydrophobication treatment is an air-conditioning aging treatment without chemical modification.

[0049] The air-standing aging treatment includes placing the surface after the ablation process in an air environment for static storage, so that the surface spontaneously adsorbs low surface energy organic matter in the air to achieve the transformation to a superhydrophobic state.

[0050] By adopting the above technical solutions, this treatment method abandons the traditional chemical reagent impregnation and modification process commonly used in the preparation of superhydrophobic surfaces, such as fluorinated silanes, stearic acid, or thiols. Instead, it utilizes the special physicochemical state of the metal surface after laser ablation to achieve functional transformation through aging under natural conditions.

[0051] The mechanism of this process lies in the fact that pulsed laser ablation generates a large number of high-energy active sites, unsaturated dangling bonds, and nanoscale rough structures on the metal surface, resulting in an extremely high surface energy and a superhydrophilic state on the newly processed surface. When exposed to normal air, these highly active sites spontaneously capture and adsorb nonpolar low-surface-energy molecules such as hydrocarbons and volatile organic compounds floating in the air, much like magnets. As the amount of adsorption gradually accumulates, the surface free energy continuously decreases, and the wettability gradually transitions from superhydrophilic to hydrophobic, eventually reaching a stable superhydrophobic state. This hydrophobicization mechanism based on physical adsorption has a certain self-healing potential. Even if some adsorbed molecules are lost due to slight friction, the exposed fresh active sites can continue to adsorb organic matter from the environment to replenish the hydrophobicity during subsequent use, thereby further extending the service life of the component.

[0052] In some embodiments, the environmental parameters for air stabilization and aging treatment meet the following conditions: The ambient temperature is 20℃~25℃; the relative humidity is 40%~60%; and the storage time is 2 weeks~4 weeks.

[0053] By adopting the above technical solution, within this temperature and humidity range, the adsorption rate and saturation level of low surface energy organic matter in the air reach equilibrium, ensuring the repeatability and batch consistency of the superhydrophobic property transformation. It should be understood that in actual large-scale production, fine adjustments can be made within the above range according to the specific microenvironmental conditions of the workshop. As long as the adsorption process reaches saturation equilibrium and does not affect the production cycle, it falls within the protection scope of this invention.

[0054] In some embodiments, the metal substrate is subjected to grinding, polishing, cleaning, and drying.

[0055] The polishing process involves sequentially polishing the metal substrate with 320-grit, 600-grit, 800-grit, 1200-grit, and 2000-grit silicon carbide sandpaper, with each polishing direction perpendicular to the previous one.

[0056] Polishing involves polishing the ground metal substrate using a metallographic polishing machine, successively using 3μm, 1μm diamond suspension and 0.05μm silica suspension as polishing liquids, until the surface has a mirror-like luster.

[0057] The cleaning and drying process involves placing the polished metal substrate in anhydrous ethanol for ultrasonic cleaning for 10–30 minutes, removing it, drying it with nitrogen, and storing it in a desiccator for later use.

[0058] In some embodiments, the material of the metal substrate includes marine steel, low-carbon steel, or stainless steel.

[0059] By adopting the above technical solutions, these metallic materials have good plastic deformation ability and laser absorption characteristics, and can fully respond to the synergistic effect of surface mechanical strengthening and pulsed laser ablation. They are particularly suitable for marine engineering and other scenarios that have dual requirements for corrosion resistance and self-cleaning.

[0060] Example Example 1, as Figure 1 As shown, a method for preparing a durable superhydrophobic surface includes: S1. Take AH36 marine steel plate and cut it into square samples of 20mm × 20mm × 6mm. Grind the samples sequentially using 320-grit, 600-grit, 800-grit, 1200-grit, and 2000-grit silicon carbide sandpaper, with each grinding direction perpendicular to the previous one. After grinding, polish the samples using a metallographic polishing machine, successively using 3μm and 1μm diamond suspensions and 0.05μm silica suspensions as polishing solutions, until the surface achieves a mirror-like finish. After polishing, ultrasonically clean the samples in anhydrous ethanol for 10 minutes, remove them, dry them with nitrogen gas, and store them in a desiccator for later use. The original microhardness of the substrate was measured to be 200 HV.

[0061] S2. Fix the sample treated in step S1 onto the worktable of the ultrasonic rolling equipment. The ultrasonic rolling equipment uses a carbide rolling head to roll the sample surface under the combined action of ultrasonic high-frequency vibration and static pressure. The ultrasonic rolling process parameters are as follows: processing speed 1000 mm / min, vibration amplitude 10 μm, rolling gap 0.05 mm, working air pressure 0.2 MPa. The rolling head rolls back and forth along the sample surface 3 times along the set path. After ultrasonic rolling treatment, the microhardness of the sample surface is increased to 220 HV, which is about 10% higher than that of the substrate. X-ray diffraction (sin 2 The residual stress on the surface was tested using the ψ method, and the results showed that a residual compressive stress of approximately -300 MPa was introduced into the surface.

[0062] S3. Place the pretreated sample from step S2 onto the laser processing platform. This embodiment uses an infrared picosecond laser (model: SS-TI-60A02, Wuhan Huari Precision Laser Co., Ltd.). The laser's performance parameters are as follows: center wavelength 1064nm, pulse width 10ps, maximum output power 65W, repetition frequency 60kHz, power stability ≤1%, beam quality M... 2 ≤1.2. After passing through a beam expander with a magnification of 1.25, the laser beam's scanning path is controlled by a two-dimensional optical scanning galvanometer, and an F-θ field lens with an effective focal length of 160mm is used to ensure focusing accuracy. The laser spot diameter is 50μm. A cross-scanning strategy is adopted, that is, the laser beam scans sequentially along mutually perpendicular x and y directions to form a grid-like ablation region, ultimately processing a square functional area with a size of 3mm×3mm. The laser processing parameters are as follows: single pulse energy density 81.2J / cm². 2 The laser spot overlap rate is 90% in the x-direction and 96% in the y-direction, with an effective pulse count of 12. The x-direction overlap rate is controlled by adjusting the laser scanning speed, which is set to 160 mm / s. The y-direction overlap rate is controlled by adjusting the scanning spacing, which is set to 1 μm. The effective pulse count is achieved by adjusting the number of scans; a single scan produces 6 effective pulses, and two scans yield 12 effective pulses.

[0063] S4. Place the laser-processed sample from step S3 in a clean air environment for static storage. The environmental parameters are: temperature 25℃, relative humidity 50%, and storage time 2 weeks. The sample surface immediately after laser processing is superhydrophilic (water contact angle close to 0°). After 2 weeks of static storage, the sample surface spontaneously transforms into a superhydrophobic state. The sample surface microhardness is 266 HV, the sample surface water contact angle is 158.4°, the roll-off angle is 7.9°, and after 8 wear cycles, the sample surface contact angle is still greater than 140°.

[0064] Examples 2 to 10 describe a method for preparing a durable superhydrophobic surface, differing from Example 1 only in the adjustment of laser parameters, as shown in Table 1. Table 1

[0065] The relationship between the spot overlap rate and the laser scanning speed and scanning spacing is shown in Table 2: Table 2

[0066] Example 11, a method for preparing a durable superhydrophobic surface, differs from Example 1 in that the ultrasonic rolling process parameters in step S2 are: processing speed 500 mm / min, vibration amplitude 15 μm, rolling gap 0.03 mm, and working air pressure 0.3 MPa. All other processing parameters are the same. The final sample has a contact angle of 152° and a microhardness of 255 HV.

[0067] Example 12, a method for preparing a durable superhydrophobic surface, differs from Example 1 in that the laser processing parameters in step S3 are: single-pulse energy density 54.13 J / cm². 2 The overlap rate of the light spot in the x-direction was 81% (corresponding to a scanning speed of 320 mm / s), and the overlap rate in the y-direction was 45% (corresponding to a scanning interval of 5 μm). The effective number of pulses was 30 (5 scans). All other processing parameters were the same. The final sample surface contact angle was 142°, and the microhardness was 245 HV.

[0068] Example 13 describes a method for preparing a durable hydrophobic surface, differing from Example 1 only in that the metal substrate in step S1 is 304 stainless steel. The final sample obtained has a surface contact angle of 152° and a microhardness increase of approximately 20%, indicating that this composite process has good material versatility.

[0069] Comparative Example Comparative Examples 1 to 9: A method for preparing a durable superhydrophobic surface, differing from Examples 2 to 10 only in that ultrasonic rolling treatment is not performed. Comparative Example 10 describes a method for preparing a durable hydrophobic surface. The only difference from Example 1 is that the ultrasonic rolling pretreatment in step S2 is omitted; instead, laser processing in step S3 is performed directly on the cleaned and dried AH36 marine steel plate surface. The laser parameters are the same as in Example 1. All other processing parameters are identical. A single laser-processed sample was obtained. Testing showed that the sample had a contact angle of 153°, meeting the superhydrophobic standard, but its surface microhardness was only 210 HV. Abrasion resistance testing showed that after five wear cycles, the contact angle decreased to below 120°, losing its superhydrophobic properties.

[0070] Comparative Example 11 describes a method for preparing a durable hydrophobic surface. The only difference from Example 1 is that the laser processing in step S3 is omitted; all other processing parameters remain the same, resulting in a single ultrasonically rolled sample. Testing revealed that the sample had a surface microhardness of 220 HV, but a water contact angle of only about 90°, indicating no superhydrophobic properties.

[0071] Comparative Example 12 describes a method for preparing a durable hydrophobic surface. The only difference from Example 1 is that laser processing in step S3 is performed first, followed by ultrasonic rolling in step S2. All other processing parameters remain the same. A sample prepared by laser processing followed by rolling was obtained. Testing showed that the contact angle of this sample was 120° and the microhardness was 230 HV. Analysis suggests that ultrasonic rolling during the post-processing stage disrupted the laser-constructed micro / nano structure, leading to a significant decrease in hydrophobic properties.

[0072] Comparative Example 13, a method for preparing a durable hydrophobic surface, differs from Example 1 only in that, in step S4, the static storage is actually for one week. The final sample obtained has a surface contact angle of 148°, which does not yet fully meet the superhydrophobic standard.

[0073] Performance testing: 1. Microhardness test: The test was conducted using a Vickers microhardness tester (load 100g, holding time 15s).

[0074] 2. Wettability test: Tested using a contact angle meter (droplet volume 2μL, deionized water).

[0075] 3. Abrasion Resistance Test: 320-grit sandpaper is fixed horizontally, with the functional surface of the sample in contact with the sandpaper. A 2kg positive pressure is applied from above, and the sample is abraded reciprocally in a fixed direction, with each cycle consisting of a 10cm travel distance, for a total of 5–8 cycles. After the abrasion cycle, the water contact angle of the sample surface is tested.

[0076] 4. Corrosion resistance test: A CHI760E electrochemical workstation was used, with 3.5% NaCl solution as the simulated seawater electrolyte, and a three-electrode system was used to test the polarization curve.

[0077] Figure 2 This refers to the ultrasonic rolling test equipment and the processed sample. Figure 2 (a) shows the ultrasonic rolling test apparatus used in this application, which integrates an ultrasonic vibration system into a CNC machining platform, drives the rolling head to achieve rotary feed through the spindle, and applies high-frequency ultrasonic impact and static pressure at the same time, which can perform plastic strengthening processing on the sample surface; Figure 2 (b) shows the surface of the metal sample after ultrasonic rolling treatment. The processed area is in a compressed state, and the surface quality is significantly improved, providing an experimental sample for subsequent performance testing and mechanism analysis.

[0078] Figure 3 The laser point is at x (δ) x ) and y (δ) y The diagram shows the overlap ratio in the direction of the laser scanning, which is precisely controlled by setting the laser scanning speed and the grid spacing.

[0079] Figure 4(a) For the sample without ultrasonic rolling, under the same spot overlap ratio, its hardness first increases and then decreases with the increase of the effective pulse number. When other process parameters remain unchanged, the sample hardness first increases and then decreases with the decrease of the spot overlap ratio in the x direction, while it continues to decrease with the decrease of the spot overlap ratio in the y direction. Figure 4 (b) For samples pretreated by ultrasonic rolling, under the same spot overlap rate, the hardness also showed a trend of first increasing and then decreasing with the number of effective pulses. Under the same conditions, the overall hardness of the samples decreased with the decrease of the spot overlap rate in the x and y directions. The hardness test results showed that the hardness of the untreated substrate was about 200 HV; after ultrasonic rolling alone, the hardness increased to about 220 HV; after laser processing alone, the hardness reached about 210 HV; and after using a composite process of ultrasonic rolling followed by laser processing, the hardness could be increased to around 250 HV.

[0080] This indicates that the hardness improvement brought about by the composite process is not a simple additive effect, but rather exhibits excellent synergistic strengthening. The reason for this is that the ultrasonic rolling pretreatment forms an "activation layer" with high dislocation density, fine grain structure, and residual compressive stress on the material surface. This layer can absorb and convert laser energy more efficiently and promote the formation of a denser and harder reinforced microstructure. Figure 5 Only the surface micromorphology of samples under different ultrasonic rolling conditions is shown with laser parameters of 12 effective pulses, 90% overlap in the x-direction and 81% overlap in the y-direction.

[0081] Figure 6 With an energy density of 81.20 J / cm³ 2 The microstructure, contact angle, and roll-off angle of the light spot with a y-direction overlap rate of 96%, an x-direction overlap rate of 90%, and an effective pulse number of 12 are as follows: the contact angle reaches 158.4°, the roll-off angle is 7.9°, and the surface hardness reaches 266HV. This indicates that the composite process has successfully achieved the preparation of a surface with both superhydrophobic properties and high mechanical properties.

[0082] Figure 7 This paper illustrates the change in the surface water contact angle of laser-processed superhydrophobic surfaces under different rolling pretreatment conditions with increasing wear cycles. As shown in the figure, the contact angle of all superhydrophobic surfaces gradually decreases with increasing wear cycles, but the decrease behavior differs significantly. The contact angle of the sample pretreated with ultrasonic rolling decreases more slowly during wear, only showing a significant reduction after the 8th wear cycle. In contrast, the contact angle of the untreated sample decreases more rapidly, exhibiting a sharp decay as early as the 5th wear cycle. These results indicate that ultrasonic rolling pretreatment effectively enhances the substrate support and bonding force of laser-constructed micro / nano structures, thereby significantly improving the mechanical durability and service stability of superhydrophobic surfaces.

[0083] Figure 8 Electrochemical tests were conducted on samples of ship plate steel substrate, samples treated with laser, samples treated with ultrasonic rolling, and samples treated with a combination of both, using an electrochemical workstation. Compared with the ship plate steel substrate, samples treated with laser processing, ultrasonic rolling, and samples treated with a combination of both showed higher corrosion potentials, indicating a significant reduction in corrosion tendency. Simultaneously, the corrosion current density of all treated samples was significantly lower than that of the substrate, indicating that the corrosion rate was effectively suppressed. Therefore, the above treatment methods can significantly improve the corrosion resistance of ship plate steel in seawater environments. Compared with a single treatment method, the composite-treated samples exhibited higher corrosion potentials and superior corrosion resistance.

[0084] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for preparing a durable superhydrophobic surface, characterized in that, include: S1. Perform surface mechanical strengthening treatment on the metal substrate to form a strengthening layer on the surface of the metal substrate, wherein the hardness of the strengthening layer is higher than that of the metal substrate; S2. The surface of the reinforcement layer is ablated using a pulsed laser to construct a multi-level micro-nano structure on the surface of the reinforcement layer. S3. Perform hydrophobic treatment on the surface after the ablation process to make the surface superhydrophobic.

2. The preparation method according to claim 1, characterized in that, The surface mechanical strengthening treatment includes at least one of ultrasonic rolling, mechanical rolling, or shot peening to introduce plastic deformation and residual compressive stress field into the surface layer.

3. The preparation method according to claim 2, characterized in that, When the surface mechanical strengthening treatment is ultrasonic rolling, the process parameters of the ultrasonic rolling treatment meet the following conditions: The processing speed is 500 mm / min to 1000 mm / min; the vibration amplitude is 10 μm to 15 μm; the rolling gap is 0.03 mm to 0.05 mm; the working air pressure is 0.2 MPa to 0.3 MPa; and the rolling head reciprocates along the surface of the metal substrate at least 3 times.

4. The preparation method according to claim 1, characterized in that, The pulsed laser is an ultrafast laser; The ablation process employs a cross-scanning strategy, with the overlap rate of the light spots in the first mutually perpendicular scanning direction being greater than or equal to 51%, and the overlap rate in the second scanning direction being greater than or equal to 45%.

5. The preparation method according to claim 4, characterized in that, The ultrafast laser is a picosecond laser or a femtosecond laser; when the ultrafast laser is a picosecond laser, the ablation process parameters meet the following conditions: center wavelength is 1064 nm, pulse width is 10 ps; single pulse energy density is 54 J / cm². 2 ~82J / cm 2 The overlap rate of the light spot in the first scanning direction is 90%, and the overlap rate in the second scanning direction is 96%; the effective pulse number is 12 to 30.

6. The preparation method according to claim 1, characterized in that, The hydrophobication treatment is an air-conditioning aging treatment without chemical modification; The air static aging treatment includes placing the surface after the ablation process in an air environment for static storage, so that the surface spontaneously adsorbs low surface energy organic matter in the air to achieve the transformation to a superhydrophobic state. The environmental parameters for the air stabilization and aging treatment must meet the following conditions: The ambient temperature is 20℃~25℃; the relative humidity is 40%~60%; and the storage time is 2 weeks~4 weeks.

7. The preparation method according to claim 1, characterized in that, The metal substrate is subjected to grinding, polishing, cleaning and drying processes; The polishing process involves sequentially polishing the metal substrate with 320-grit, 600-grit, 800-grit, 1200-grit, and 2000-grit silicon carbide sandpaper, with each polishing direction perpendicular to the previous one. The polishing process involves polishing the ground metal substrate using a metallographic polishing machine, sequentially using 3μm and 1μm diamond suspensions and 0.05μm silica suspensions as polishing liquids, until the surface has a mirror-like luster.

8. The preparation method according to claim 1, characterized in that, The material of the metal substrate includes marine steel, low-carbon steel, or stainless steel.

9. A durable superhydrophobic metal component, characterized in that, It includes a metal substrate, the surface of which has a reinforcing layer, the hardness of which is higher than that of the metal substrate; The surface of the reinforcement layer has a multi-level micro-nano structure formed by pulsed laser ablation; The surface of the multi-level micro / nano structure is superhydrophobic. The durable superhydrophobic metal component is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of a durable superhydrophobic metal component as described in claim 9 in the fields of ship self-cleaning, corrosion protection of marine equipment, or anti-icing and de-icing.

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