A nickel-cobalt metal-based wear-resistant and corrosion-resistant coating and its preparation method

Abstract

This invention discloses a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating and its preparation method, relating to the field of surface coating technology. The key technical points include the following steps: S1. Degreasing and sandblasting roughening treatment of the metal substrate surface, followed by cleaning and drying with anhydrous ethanol; S2. Preparing a nickel-cobalt metal-based alloy powder, composed of the following components by weight: nickel 55-65 parts, cobalt 20-30 parts, chromium 15-18 parts, molybdenum 4-6 parts, tungsten 3-5 parts, iron 1-3 parts, silicon 0.8-1.5 parts, carbon 0.5-1.2 parts, and boron 0.5-1.0 parts. The technical effect is that through interlayer laser microtexturing treatment, a regular, non-smooth micro-pit array is created on the surface of the sprayed coating. The molten particles of the next layer of sprayed material embed into these micro-pits, forming a strong "mechanical interlocking" effect, greatly improving the interlayer bonding strength and shear resistance, effectively preventing interlayer misalignment and peeling.

Description

Technical Field

[0001] This invention relates to the field of surface coating technology, specifically to a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating and its preparation method. Background Technology

[0002] Nickel-cobalt alloy coatings are widely used in extreme environments such as aero-engine blades, oil drilling tools, and key components of offshore platforms due to their excellent wear resistance and corrosion resistance. Traditional preparation methods, such as plasma spraying and high-velocity oxygen fuel spraying, suffer from defects such as high coating porosity, weak interlayer bonding, and high residual stress. These defects become channels for corrosive media to penetrate, leading to premature coating failure.

[0003] To address these issues, existing technologies often employ modification by adding rare earth elements or ultrafine ceramic particles (such as WC and Cr3C2), or by laser remelting to reduce porosity. However, these technologies neglect the surface physicochemical state of the coating itself, failing to impart hydrophobic properties. Hydrophobicity effectively repels corrosive droplets and is a crucial pathway to improving corrosion resistance. Current methods for imparting hydrophobicity to materials primarily involve adding low surface energy substances (such as fluorinated polymers) or constructing micro / nano structures; however, these foreign substances typically exhibit poor wear resistance and rapidly fail under frictional conditions.

[0004] Therefore, developing a method to simultaneously obtain high strength, high toughness, excellent corrosion resistance and intrinsic hydrophobicity of nickel-cobalt based coatings without adding hydrophobic materials and through innovative preparation processes has significant industrial application value. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating and its preparation method. This method innovatively combines substrate pretreatment, multi-layer gradient spraying, and crucial interlayer laser microtexturing treatment, simultaneously achieving significant improvements in the coating's wear resistance, corrosion resistance, and hydrophobicity without requiring any external hydrophobic additives.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating, comprising the following steps:

[0007] S1. The surface of the metal substrate is degreased and roughened by sandblasting, then cleaned with anhydrous ethanol and dried.

[0008] S2. Prepare nickel-cobalt metal-based alloy powder, which consists of the following components by weight: nickel 55-65 parts, cobalt 20-30 parts, chromium 15-18 parts, molybdenum 4-6 parts, tungsten 3-5 parts, iron 1-3 parts, silicon 0.8-1.5 parts, carbon 0.5-1.2 parts, and boron 0.5-1.0 parts.

[0009] S3. Using a supersonic flame spraying device, a layer of the above alloy powder with a thickness of 50-100μm is sprayed onto the pretreated substrate surface as a base layer. The spraying parameters are: kerosene flow rate 22-26L / h, oxygen flow rate 850-950Nm³ / h, spraying distance 300-350mm, and powder feeding rate 35-45g / min.

[0010] S4. The surface of the bottom coating obtained in step S3 is scanned using a pulsed fiber laser with a laser power of 200-400W, a scanning speed of 500-1500mm / s, a pulse frequency of 20-50kHz, and a spot overlap rate of 50%-70%, forming a regular array of micropits with a diameter of 50-100μm, a depth of 20-50μm, and a spacing of 100-200μm on the coating surface.

[0011] S5. On the bottom surface after S4 treatment, the above alloy powder is sprayed using a supersonic flame spraying device to form an intermediate layer with a thickness of 100-200μm. The spraying parameters are the same as or similar to those in S3.

[0012] S6. Repeat steps S4 and S5: Based on the total coating thickness, repeat n-1 times, where n is the total number of layers, n≥3;

[0013] S7. After completing all cycles, spray the final surface layer, and then use the pulsed fiber laser in low power mode to quickly scan the outermost surface. The laser power is 100-200W and the scanning speed is 2000-3000mm / s to complete the preparation of the coating on the metal substrate surface.

[0014] Preferably, the nickel-cobalt metal-based alloy powder in step S2 has a particle size distribution of 15-53 μm and a sphericity greater than 90%.

[0015] Preferably, the laser microtexturing process in step S4 is carried out under an inert gas protective atmosphere, wherein the inert gas is argon or nitrogen with a purity of 99.99% or higher, and the gas flow rate is 15-25 L / min.

[0016] Preferably, the laser scanning path in step S4 is a cross scan with a mutual 60° angle, so that the resulting micro-pit array is an equilateral triangle.

[0017] Preferably, the longitudinal section of the micropit in step S4 is U-shaped, and the angle between its sidewall and the normal of the coating surface is 10°-30°.

[0018] Preferably, the total number of layers n in step S6 is 3-5 layers, and the total coating thickness is controlled between 300-600 μm.

[0019] Preferably, after the laser light sweep in step S7, the coating is subjected to stress-relief annealing under argon protection at a temperature of 550-650°C for 1-2 hours, and then cooled in the furnace to below 150°C before being removed from the furnace.

[0020] Preferably, in steps S3 and S5, the powder feeding gas of the supersonic flame spraying equipment is nitrogen, and the pressure is 0.7-0.9 MPa.

[0021] Preferably, in step S4, the wavelength of the pulsed fiber laser is 1064 nm.

[0022] Compared with existing technologies, this invention provides a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating and its preparation method, which has the following beneficial effects: Through interlayer laser microtexturing treatment, a regular, non-smooth micro-pit array is created on the surface of the sprayed coating. The molten particles of the next layer of sprayed material are embedded in these micro-pits, forming a strong "mechanical interlocking" effect, greatly improving the interlayer bonding strength and shear resistance, and effectively preventing interlayer misalignment and peeling.

[0023] The micropit structure creates a tortuous, longitudinally extending path within the coating, significantly lengthening the path for corrosive media to penetrate from the surface to the substrate, thereby substantially slowing down the corrosion process. Simultaneously, the remelted, dense layer formed at the bottom of the micropits by rapid laser scanning seals the original pores, blocking lateral corrosion channels.

[0024] The micron-scale protrusions generated by laser microtexturing, combined with the nanoscale roughness naturally formed by subsequent sprayed particle deposition, constitute a stable micro-nano composite structure. This structure can effectively trap air, forming an air film, thereby achieving superhydrophobic properties exceeding 150°. This hydrophobicity originates entirely from the physical structure, rather than from chemical modification, thus exhibiting extremely high mechanical stability and durability. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope (SEM) image of the surface micro-pit array formed after interlayer laser microtexturing treatment in Embodiment 1 of the present invention;

[0026] Figure 2 This is a static water contact angle test diagram of the coating surface in Embodiment 1 of the present invention;

[0027] Figure 3 The bar charts are for the bonding strength test results of the embodiments and comparative examples of the present invention. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Figure 1 The images were obtained by SEM observation at an accelerating voltage of 15 kV and in secondary electron imaging mode. The scale bar in the image is 50 μm.

[0030] Figure 2 The contact angle measurement was performed using an optical imaging method. Under the conditions of room temperature (25±2℃) and relative humidity of 50%–60%, deionized water was used as the test liquid and slowly dripped onto the coating surface at a volume of 2μL. The outline of the water droplet was captured by a high-definition CCD camera, and the contact angle value was calculated by fitting using the accompanying software.

[0031] The coating bonding strength test shall refer to the national standard: GB / T8642-2002 "Determination of Bond Strength of Thermal Spray Coatings";

[0032] The testing steps are as follows:

[0033] Sample Preparation: The coated specimens are processed into standard tensile specimens (10mm diameter round bars or 50mm × 25mm rectangular blocks), retaining the original coating thickness (300-600μm). The coated surface of the specimen is bonded to a steel butt block of the same size using a high-strength structural adhesive (such as epoxy resin), ensuring the bonding surface completely covers the coating and is free of air bubbles. The specimens are cured at room temperature (25±5℃) for 24 hours. After curing, the ends of the bonded specimens are polished with a grinding wheel to ensure uniform stress during tensile testing.

[0034] Equipment parameters: Universal testing machine (such as WE-30 type) is used, with a range of 0-100kN and a tensile rate controlled at 1mm / min.

[0035] Test Procedure: Clamp the specimen in the upper and lower fixtures of the testing machine, ensuring that the specimen axis is aligned with the direction of the tensile force to avoid additional bending moment. Start the testing machine and apply uniform load until the coating separates from the substrate or fractures within the coating, recording the maximum breaking load (F). Each test should be repeated with at least 5 parallel specimens, and outliers (data with deviations exceeding 15% of the average value) should be discarded.

[0036] Calculation results: Bond strength (σ) = maximum breaking load (F) / bonding area between coating and butt joint (A), in MPa.

[0037] The coating porosity test shall be conducted in accordance with the national standard GB / T17407-2010 "Test Method for Porosity of Thermal Spray Coatings";

[0038] Test steps:

[0039] Sample preparation: Cut the sample perpendicular to the coating surface, and polish the cross-section sequentially with 400#, 800#, 1200#, and 2000# sandpaper, then polish to a mirror finish with diamond polishing paste (1-2μm grit). Etch the cross-section with a 4% (v / v) nitric acid alcohol solution for 5-10 seconds to clearly reveal the coating microstructure.

[0040] Equipment parameters: It adopts an optical microscope (such as the BX53M model), with a magnification of 500x, and is equipped with an image acquisition system and analysis software (such as Image-ProPlus).

[0041] Testing Procedure: Images were acquired in different regions of the coating cross-section (at least 5 non-overlapping fields of view), with each field of view having an area of ​​not less than 0.01 mm². The images were converted into black-and-white binary images (pores are black, coating is white) using analysis software, and the total area of ​​pores in each field of view was automatically calculated.

[0042] Calculation results: Porosity (P) = (Total area of ​​pores in all fields of view / Total area of ​​all fields of view) × 100%, and the average value is taken as the final result.

[0043] The microhardness test of the coating is conducted in accordance with the national standard GB / T4340.1-2009 "Metallic materials - Vickers hardness test - Part 1: Test method";

[0044] Test steps:

[0045] Sample preparation: The same sample preparation method as for porosity testing is used, and the coating cross section is polished to a mirror finish (no scratches, no deformation).

[0046] Equipment parameters: Microhardness tester (such as HV-1000 type), test force 200g (1.961N), holding time 15s, diamond indenter is a regular square pyramid (vertex angle 136°).

[0047] Test procedure: Five test points are evenly selected along the coating thickness direction (avoiding the coating-substrate interface by more than 10 μm), with the distance between each point not less than three times the length of the indentation diagonal. The set force value is applied and held for 15 seconds. After unloading, the lengths of the two diagonals of the indentation (d1, d2) are measured, accurate to 0.1 μm.

[0048] Calculation result: Microhardness (HV) = 0.1891 × F / (d1 × d2), where F is the test force (N), d1 and d2 are the diagonal lengths (mm), and the average value of 5 points is taken as the result.

[0049] The self-corrosion potential test references the national standard GB / T10123-2021 "Electrochemical Test Methods for Corrosion of Metals and Alloys";

[0050] Test steps:

[0051] Sample preparation: The coated sample was cut into 10mm × 10mm cubes. The non-test surfaces were sealed with epoxy resin, exposing only 1cm² of the coated surface as the working electrode. Before testing, the exposed surface was cleaned with anhydrous ethanol to remove oil and dirt, and then allowed to air dry.

[0052] Equipment and solutions: An electrochemical workstation (such as the CHI660E model) was used, with a three-electrode system: the working electrode was the coated sample, the reference electrode was a saturated calomel electrode (SCE), and the auxiliary electrode was a platinum sheet (1cm × 1cm). The corrosive medium was a 3.5wt% NaCl solution (prepared with analytical grade NaCl and deionized water), and the solution temperature was controlled at 25±1℃.

[0053] Test procedure: Immerse the three electrodes in NaCl solution and let stand for 30 minutes until the electrode potentials stabilize (potential change ≤ 1 mV / min). Use open circuit potential test mode and record the stabilized potential value, which is the self-corrosion potential (Ecorr), in V (vs. SCE).

[0054] Each test was repeated at least 3 times, and the average value was taken.

[0055] The static water contact angle and roll-off angle test shall refer to the national standard: GB / T30693-2014 "Determination of contact angle of plastic films and sheets";

[0056] Test steps:

[0057] Sample preparation: Ensure the coating surface is flat and free of oil and dust. Blow the surface with compressed air before testing.

[0058] Equipment parameters: Contact angle measuring instrument (such as OCA20), micro-syringe (5μL), lens magnification 20x.

[0059] Static water contact angle test: 5 μL of deionized water is dropped onto the coating surface using a syringe, and the droplet is allowed to stand for 10 seconds. The droplet profile is captured through the instrument lens, and the contact angle (the angle between the droplet and the coating surface) is calculated using an ellipse fitting algorithm. Tests are performed in different areas of the sample (at least 5 points), and the average value is taken as the result.

[0060] Roll-off angle test: Fix the sample on a tiltable platform, add 10 μL of deionized water, and slowly tilt the platform (tilt rate 1° / s). Record the tilt angle of the platform when the droplet begins to roll; this is the roll-off angle. Repeat the test 5 times and take the average value as the result.

[0061] Example 1: A method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating, specifically including the following steps:

[0062] S1. 45# steel is selected as the base material. First, it is ultrasonically degreased at 60℃ for 30 minutes with an alkaline degreasing agent. Then, it is sandblasted with 80-mesh white corundum sand at a pressure of 0.6MPa and a distance of 150mm. After that, it is ultrasonically cleaned with anhydrous ethanol for 10 minutes and dried in an oven at 80℃ for 2 hours.

[0063] S2. Prepare nickel-cobalt metal-based alloy powder, composed of the following components by weight: nickel 55 parts, cobalt 20 parts, chromium 15 parts, molybdenum 4 parts, tungsten 3 parts, iron 1 part, silicon 0.8 parts, carbon 0.5 parts, and boron 0.5 parts; the powder particle size distribution is 15-30 μm, and the sphericity is 92%;

[0064] S3. A supersonic flame spraying device is used to spray a base layer on the pretreated substrate surface, with a thickness controlled at 50μm. The spraying parameters are: kerosene flow rate 22L / h, oxygen flow rate 850Nm³ / h, spraying distance 300mm, powder feeding rate 35g / min, powder feeding gas is nitrogen, and pressure is 0.7MPa.

[0065] S4. The underlying surface is scanned using a pulsed fiber laser with a wavelength of 1064nm under the protection of 99.99% pure argon gas at a flow rate of 15L / min. Laser parameters: power 200W, scanning speed 500mm / s, pulse frequency 20kHz, spot overlap rate 50%. The scanning path is a cross-scan with mutual angles of 60°, forming an equilateral triangular micro-pit array with a diameter of 50μm, a depth of 20μm, and a spacing of 100μm. The longitudinal section of the micro-pit is U-shaped, and the angle between the sidewall and the normal of the coating surface is 10°.

[0066] S5. Continue to spray alloy powder onto the bottom layer surface after S4 treatment to form an intermediate layer with a thickness of 100μm. The spraying parameters are the same as those in S3.

[0067] S6. Repeat steps S4 and S5 once each, with a total of n=3 layers and a total coating thickness of approximately 350μm;

[0068] S7. Spray the final surface layer, then use a pulsed fiber laser in low power mode to quickly and lightly scan the outermost surface. The laser power is 100W and the scanning speed is 2000mm / s. After that, stress-relief annealing is carried out under argon protection. The annealing temperature is 550℃ and the holding time is 1 hour. The furnace is then cooled to below 150℃ before being taken out of the furnace.

[0069] Example 2, S1. 45# steel was selected as the base material. First, the alkaline degreasing agent was used to ultrasonically degrease the steel at 60°C for 30 minutes. Then, the steel was sandblasted with 80-mesh white corundum sand at a pressure of 0.6MPa and a distance of 150mm. After that, the steel was ultrasonically cleaned with anhydrous ethanol for 10 minutes and dried in an oven at 80°C for 2 hours.

[0070] S2. Prepare nickel-cobalt metal-based alloy powder, composed of the following components by weight: 60 parts nickel, 25 parts cobalt, 16.5 parts chromium, 5 parts molybdenum, 4 parts tungsten, 2 parts iron, 1.2 parts silicon, 0.8 parts carbon, and 0.7 parts boron; the powder particle size distribution is 30-40 μm, and the sphericity is 95%.

[0071] S3. The base layer is sprayed using a supersonic flame spraying device with a thickness controlled at 75μm. The spraying parameters are: kerosene flow rate 24L / h, oxygen flow rate 900Nm³ / h, spraying distance 325mm, powder feeding rate 40g / min, powder feeding gas is nitrogen, and pressure is 0.8MPa.

[0072] S4. Laser processing parameters: power 300W, scanning speed 1000mm / s, pulse frequency 35kHz, spot overlap rate 60%; argon flow rate 20L / min; forming an equilateral triangular micro-pit array with a diameter of 75μm, a depth of 35μm, and a spacing of 150μm. The longitudinal section of the micro-pit is U-shaped, and the angle between the sidewall and the normal of the coating surface is 20°.

[0073] S5. Spray the intermediate layer with a thickness of 150μm. The spraying parameters are the same as those for S3.

[0074] S6. Repeat steps S4 and S5 twice each, for a total of n=4 layers and a total coating thickness of approximately 500μm;

[0075] S7. Surface laser light scanning parameters: power 150W, scanning speed 2500mm / s; stress relief annealing temperature 600℃, holding time 1.5 hours; other conditions are the same as in Example 1.

[0076] Example 3, S1. 45# steel was selected as the base material. First, the alkaline degreasing agent was used to ultrasonically degrease the steel at 60°C for 30 minutes. Then, the steel was sandblasted with 80-mesh white corundum sand at a pressure of 0.6 MPa and a distance of 150 mm. After that, the steel was ultrasonically cleaned with anhydrous ethanol for 10 minutes and dried in an oven at 80°C for 2 hours.

[0077] S2. Prepare nickel-cobalt metal-based alloy powder, composed of the following components by weight: nickel 65 parts, cobalt 30 parts, chromium 18 parts, molybdenum 6 parts, tungsten 5 parts, iron 3 parts, silicon 1.5 parts, carbon 1.2 parts, and boron 1.0 part; the powder particle size distribution is 40-53 μm, and the sphericity is 93%.

[0078] S3. The base layer is sprayed using a supersonic flame spraying device with a thickness controlled at 100μm. The spraying parameters are: kerosene flow rate 26L / h, oxygen flow rate 950Nm³ / h, spraying distance 350mm, powder feeding rate 45g / min, powder feeding gas is nitrogen, and pressure is 0.9MPa.

[0079] S4. Laser processing parameters: power 400W, scanning speed 1500mm / s, pulse frequency 50kHz, spot overlap rate 70%; nitrogen flow rate 25L / min; forming an equilateral triangular micro-pit array with a diameter of 100μm, a depth of 50μm, and a spacing of 200μm, the longitudinal section of the micro-pit is U-shaped, and the angle between the sidewall and the normal of the coating surface is 30°;

[0080] S5. Spray the intermediate layer with a thickness of 200μm. The spraying parameters are the same as those for S3.

[0081] S6. Repeat steps S4 and S5 3 times each, for a total of 5 layers and a total coating thickness of approximately 600 μm;

[0082] S7. Surface laser light scanning parameters: power 200W, scanning speed 3000mm / s; stress relief annealing temperature 650℃, holding time 2 hours; other conditions are the same as in Example 1.

[0083] Example 4, S1. 45# steel was selected as the base material. First, the alkaline degreasing agent was used to ultrasonically degrease the steel at 60°C for 30 minutes. Then, the steel was sandblasted with 80-mesh white corundum sand at a pressure of 0.6MPa and a distance of 150mm. After that, the steel was ultrasonically cleaned with anhydrous ethanol for 10 minutes and dried in an oven at 80°C for 2 hours.

[0084] S2. Prepare nickel-cobalt metal-based alloy powder with the following chemical composition by weight: nickel 62 parts, cobalt 28 parts, chromium 17 parts, molybdenum 5.5 parts, tungsten 4.5 parts, iron 2.5 parts, silicon 1.3 parts, carbon 1.0 part, and boron 0.8 parts; the powder particle size distribution is 25-45 μm, and the sphericity is 96%.

[0085] S3. The base layer is sprayed using a supersonic flame spraying device with a thickness controlled at 80μm. The spraying parameters are: kerosene flow rate 25L / h, oxygen flow rate 920Nm³ / h, spraying distance 330mm, powder feeding rate 42g / min, powder feeding gas is nitrogen, and pressure is 0.85MPa.

[0086] S4. Laser processing parameters: power 350W, scanning speed 1200mm / s, pulse frequency 40kHz, spot overlap rate 65%; argon flow rate 22L / min; forming an equilateral triangular micro-pit array with a diameter of 80μm, a depth of 40μm, and a spacing of 160μm. The longitudinal section of the micro-pit is U-shaped, and the angle between the sidewall and the normal of the coating surface is 25°.

[0087] S5. Spray the intermediate layer with a thickness of 180μm. The spraying parameters are the same as those for S3.

[0088] S6. Repeat steps S4 and S5 twice each, with a total of n=4 layers and a total coating thickness of approximately 550μm;

[0089] S7. Surface laser light scanning parameters: power 180W, scanning speed 2800mm / s; stress relief annealing temperature 620℃, holding time 1.8 hours; other conditions are the same as in Example 1.

[0090] Comparative Example 1, compared with Example 2, omits all laser microtexturing treatment in step S4, while the remaining steps and parameters are the same.

[0091] Comparative Example 2, compared with Example 2, only laser treatment was performed after the last layer of spraying, and the intermediate layers were not subjected to laser microtexturing treatment. All other steps and parameters were the same.

[0092] Comparative Example 3, compared with Example 2, the laser power in step S4 was changed to 500W, while the other steps and parameters were the same.

[0093] Comparative Example 4, compared with Example 2, shows that the alloy powder in step S2 does not contain tungsten, the nickel content is increased to 64 parts, and the remaining steps and parameters are the same.

[0094] Comparative Example 5, compared with Example 2, only a single layer of spraying was performed, with a thickness of about 500 μm. Multi-layer spraying and laser treatment cycles were not performed. All other steps and parameters were the same.

[0095] Comparative Example 6, compared with Example 2, the spraying distance in steps S3 and S5 was changed to 250mm, while the other steps and parameters were the same.

[0096] The coatings obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were grouped as follows: JSJ-TC-01, JSJ-TC-02, JSJ-TC-03, JSJ-TC-04, JSJ-TC-05, JSJ-TC-06, JSJ-TC-07, JSJ-TC-08, JSJ-TC-09, and JSJ-TC-010. Performance tests were conducted on the products of the examples and comparative examples, specifically including bonding strength (MPa), porosity (%), microhardness (HV), self-corrosion potential (Vvs.SCE), static water contact angle (°), and roll-off angle (°). The specific test results are detailed in Tables 1 and 2.

[0097] Table 1

[0098]

[0099] Table 2

[0100]

[0101] A laser creates a regular array of micropits on the surface of the coated layer, and the molten particles of the next layer embed into the micropits to form a "mechanical interlocking" effect. Example 2 shows a bonding strength of 78 MPa, which is 50% higher than Comparative Example 2 with only the last laser-treated layer and 73% higher than Comparative Example 1 without laser treatment. This demonstrates that the interlayer microtexture is key to enhanced bonding. The tortuous channels formed by the micropits extend the penetration path of the corrosive medium, and combined with the laser-remelted layer sealing the lateral pores, Example 2 shows a significantly positive shift in self-corrosion potential compared to Comparative Example 1, resulting in a significant improvement in corrosion resistance. This solves the problems of rapid longitudinal penetration and easy lateral corrosion diffusion in traditional coatings.

[0102] The micron-sized protrusions of the laser-etched microstructure combined with the nano-roughness naturally formed by the sprayed particles constitute a stable micro-nano composite structure. This structure can effectively trap air and form an air film. Example 2 shows a static water contact angle of 156° and a roll-off angle of 4.2°, while the contact angle of Comparative Example 1 without laser treatment is only 105°. It can be seen that this structure can achieve superhydrophobicity without chemical modification, and its wear resistance is far superior to that of chemically modified layers.

[0103] In step 4 of this invention, a laser power of 200-400W is used. In contrast, in Comparative Example 3, excessive melting led to increased coating brittleness, reducing the bonding strength to 60MPa. This demonstrates that the bonding strength is better when the laser power is controlled within the 200-400W range. The spraying distance in this embodiment is 300-350mm. In Comparative Example 6 (distance 250mm), the porosity increased to 2.1% due to overheating and oxidation of the particles. This shows that the porosity of this invention is lower. This invention employs a multi-layer structure; Comparative Example 5 uses a single-layer spraying, resulting in a bonding strength of only 38MPa due to stress concentration. This demonstrates that a bonding strength is higher when n is 3-5 layers.

[0104] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating, characterized in that: Includes the following steps: S1. The surface of the metal substrate is degreased and roughened by sandblasting, then cleaned with anhydrous ethanol and dried. S2. Prepare nickel-cobalt metal-based alloy powder, which consists of the following components by weight: nickel 55-65 parts, cobalt 20-30 parts, chromium 15-18 parts, molybdenum 4-6 parts, tungsten 3-5 parts, iron 1-3 parts, silicon 0.8-1.5 parts, carbon 0.5-1.2 parts, and boron 0.5-1.0 parts. S3. Using a supersonic flame spraying device, a layer of the above alloy powder with a thickness of 50-100μm is sprayed onto the pretreated substrate surface as a base layer. The spraying parameters are: kerosene flow rate 22-26L / h, oxygen flow rate 850-950Nm³ / h, spraying distance 300-350mm, and powder feeding rate 35-45g / min. S4. The surface of the bottom coating obtained in step S3 is scanned using a pulsed fiber laser with a laser power of 200-400W, a scanning speed of 500-1500mm / s, a pulse frequency of 20-50kHz, and a spot overlap rate of 50%-70%, forming a regular array of micropits with a diameter of 50-100μm, a depth of 20-50μm, and a spacing of 100-200μm on the coating surface. S5. On the bottom surface after S4 treatment, the above alloy powder is sprayed using a supersonic flame spraying device to form an intermediate layer with a thickness of 100-200μm. The spraying parameters are the same as or similar to those in S3. S6. Repeat steps S4 and S5: Based on the total coating thickness, repeat n-1 times, where n is the total number of layers, n≥3; S7. After completing all cycles, the outermost surface is then rapidly scanned using the pulsed fiber laser in low-power mode, with a laser power of 100-200W and a scanning speed of 2000-3000mm / s, to complete the preparation of the coating on the metal substrate surface.

2. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: The nickel-cobalt metal-based alloy powder in step S2 has a particle size distribution of 15-53 μm and a sphericity greater than 90%.

3. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: The scanning process described in step S4 is carried out under an inert gas protective atmosphere, wherein the inert gas is argon or nitrogen with a purity of 99.99% or higher, and the gas flow rate is 15-25 L / min.

4. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: In step S4, the laser scanning path is a cross scan with a 60° angle between each other, so that the resulting micro-pit array is an equilateral triangle.

5. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: The longitudinal section of the micro-pit in step S4 is U-shaped, and the angle between its sidewall and the normal of the coating surface is 10°-30°.

6. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: The total number of layers n mentioned in step S6 is 3-5 layers, and the total coating thickness is controlled between 300-600μm.

7. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: After laser scanning in step S7, the coating is subjected to stress-relief annealing under argon protection at a temperature of 550-650℃ for 1-2 hours, and then cooled in the furnace to below 150℃ before being removed from the furnace.

8. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: In steps S3 and S5, the powder feeding gas of the supersonic flame spraying equipment is nitrogen, and the pressure is 0.7-0.9 MPa.

9. The method for preparing a nickel-cobalt metal-based wear-resistant and corrosion-resistant coating according to claim 1, characterized in that: In step S4, the wavelength of the pulsed fiber laser is 1064 nm.

10. A nickel-cobalt metal-based wear-resistant and corrosion-resistant coating prepared by the method according to any one of claims 1-9, characterized in that, The coating has a bonding strength with the substrate of ≥70MPa, a porosity of <1%, a microhardness of ≥HV650, a self-corrosion potential of ≥-0.25V in 3.5wt% NaCl solution, a static water contact angle of ≥150°, and a roll-off angle of ≤5°.

Images