Laser cladding high-entropy alloy coating and preparation method thereof

Abstract

The invention relates to the technical field of alloy coatings, and discloses a laser cladding high-entropy alloy coating and a preparation method thereof.The laser cladding high-entropy alloy coating is prepared from, by mass, 25%-45% of Fe, 15%-25% of Cr, 10%-20% of Ni, 5%-15% of Mn, 3%-10% of Al, 0%-5% of Ti, 1%-5% of a nanometer reinforcing phase and 0.1%-0.5% of a flow promoter. Lorentz force generated by an alternating electromagnetic field drives melt convection, so that the diffusion coefficient of segregation-prone elements such as Cr and Ni is increased, the ultrasonic cavitation effect is matched to crush dendritic crystals and promote dispersion of nanoparticles, the segregation index of the elements is reduced, a uniform nanocrystalline-amorphous composite structure is formed through the synergistic effect, and uniform distribution of elements in a molten pool is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy coatings, and particularly to a laser cladding high-entropy alloy coating and a preparation method thereof. Background Art

[0002] A laser cladding high-entropy alloy coating is a high-entropy alloy (High-Entropy Alloy, HEA) coating prepared on the surface of a substrate through laser cladding technology (Laser Cladding). This technology combines the excellent properties of high-entropy alloys and the process advantages of laser cladding, and is widely used in the fields of surface engineering, wear and corrosion resistance, aerospace, etc.

[0003] A high-entropy alloy is an alloy formed by mixing 5 or more main element metal elements in a near-equimolar ratio. The laser cladding high-entropy alloy coating is a cutting-edge direction in the field of surface engineering through the combination of "high-entropy alloy + laser technology". With the progress of composition design and process control in the future, its application scope will be further expanded.

[0004] However, when traditional high-entropy alloy coatings are used, due to the large difference in the diffusion rates of different elements during the rapid solidification process of laser cladding, the element distribution in the molten pool is uneven. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a laser cladding high-entropy alloy coating and a preparation method thereof, which solve the problem that the element distribution in the molten pool is uneven due to the large difference in the diffusion rates of different elements during the rapid solidification process of laser cladding.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: A laser cladding high-entropy alloy coating, comprising the following components by mass percentage: Fe: 25% - 45%, Cr: 15% - 25%, Ni: 10% - 20%, Mn: 5% - 15%, Al: 3% - 10%, Ti: 0% - 5%, nano-reinforcing phase: 1% - 5%, flow aid: 0.1% - 0.5%.

[0007] Preferably, the nano-reinforcing phase includes Al2O3, and the flow aid includes graphene.

[0008] Preferably, the microstructure of the coating is a nanocrystalline-amorphous composite phase, the grain size is 20 - 500 nm, and the volume fraction of the amorphous phase is 10% - 40%.

[0009] Preferably, a preparation method of a laser cladding high-entropy alloy coating, the method comprising the following steps:

[0010] Roughen the surface of the substrate using a sandblaster, then clean it with anhydrous ethanol, and finally dry it in an oven;

[0011] The raw materials are pre-treated, then atomized by gas to produce powder, and after powder classification and screening, the screened raw materials are subjected to modification treatment;

[0012] The modified metal powder is placed on the surface of the substrate and laser cladding is carried out;

[0013] An alternating electromagnetic field is applied, and ultrasonic vibration is synchronously applied;

[0014] Post-treatment is carried out on the place where laser cladding has been performed.

[0015] Preferably, white corundum sand with a mesh size of 24 - 60 is selected, the sandblasting pressure is 0.4 - 0.6 MPa, the sandblasting angle is 70 - 90°, the sandblasting distance is 100 - 150 mm, the cleaning time with absolute ethanol is 10 - 15 minutes, the oven temperature is 50 - 60 °C, and the drying time is 30 - 45 minutes.

[0016] Preferably, for the pre-treatment, the metal raw materials are subjected to arc melting in a water-cooled copper crucible vacuum arc melting furnace under a vacuum environment not lower than 10⁻³ Pa, the melting current is 400 - 600 A, each alloy ingot needs to be repeatedly melted 4 - 6 times, with a single melting time of 3 - 5 minutes. For the gas atomization to produce powder, a close-coupled gas atomization device is used, the atomization pressure is 3 - 5 MPa, the superheat degree is 150 - 200 °C, and argon is used for protection during the atomization process. For the powder classification and screening, a pneumatic classifier is used for particle size classification treatment, and powders with a particle size of 15 - 53 μm are collected. The modification treatment includes placing the classified powder in a radio frequency plasma cleaner and treating it at a power of 100 - 200 W, in an Ar gas atmosphere and a pressure of 10 - 30 Pa for 15 - 30 minutes. Then, a hot-wall type ALD system is used, and 50 - 100 times of Al₂O₃ coating is carried out with TMA / H₂O as the precursor. The coated powder is immersed in a 0.5 - 1.0 mg / mL graphene dispersion liquid with a pH of 8 - 9, subjected to 200 W probe ultrasound for 30 - 60 minutes, allowed to stand for self-assembly for 2 - 4 hours, and then vacuum dried at 60 °C for 12 hours.

[0017] Preferably, during the laser cladding, argon protection is used, the laser power is 2 - 5 kW, the scanning speed is 5 - 20 mm / s, and the spot diameter is 1 - 4 mm.

[0018] Preferably, for the application of the alternating electromagnetic field, the frequency is 10 - 50 Hz, the magnetic field strength is 0.5 - 1 T, and for the synchronous application of ultrasonic vibration, the frequency is 20 - 40 kHz, and the amplitude is 5 - 15 μm.

[0019] Preferably, during the post-treatment, the power during laser remelting is 60% - 80% of the original power, the scanning speed is 1.2 - 1.5 times the original speed, and the laser remelting power is not lower than 1.2 kW.

[0020] Preferably, after laser remelting, in the vacuum annealing furnace, the temperature is 600-900 °C, and it is heat-preserved for 1-3 hours for annealing treatment.

[0021] The present invention provides a laser cladding high-entropy alloy coating and a preparation method thereof. It has the following beneficial effects:

[0022] 1. In the present invention, the Lorentz force generated by the alternating electromagnetic field drives the melt convection, which improves the diffusion coefficients of easily segregated elements such as Cr and Ni. Combining with the ultrasonic cavitation effect to break dendrites and promote the dispersion of nanoparticles, the element segregation index is reduced. Through the synergistic effect, a uniform nanocrystalline-amorphous composite structure is formed, realizing the uniform distribution of elements in the molten pool.

[0023] 2. In the present invention, a dense passivation barrier is formed by Al2O3 nanoparticles in the coating. Combining with the characteristic of the amorphous phase without grain boundaries, the pitting potential is improved. The pinning effect of nano-Al2O3 controls the grain size within 20-500 nm. At the same time, the amorphous phase absorbs energy through shear bands, increasing the hardness, achieving the effect of improving the corrosion resistance and strength of the coating.

[0024] 3. In the present invention, the graphene coating used in the flow aid improves the fluidity of non-spherical powders. Combining plasma activation and 50-100 times of ALD coating, a nano-enhanced layer can be constructed on the surface of ordinary gas atomized powders, replacing high-cost spherical powders, achieving the improvement of fluidity while reducing costs. Description of the Drawings

[0025] Figure 1 It is a schematic flow chart of the method of the present invention. Detailed Embodiments

[0026] Next, in combination with the drawings of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] Please refer to the attached Figure 1 , an embodiment of the present invention provides a laser cladding high-entropy alloy coating, which includes the following components by mass percentage: Fe: 25% - 45%, Cr: 15% - 25%, Ni: 10% - 20%, Mn: 5% - 15%, Al: 3% - 10%, Ti: 0% - 5%, nano-enhanced phase: 1% - 5%, flow aid: 0.1% - 0.5%.

[0028] Specifically, a multi-principal element solid solution is formed by Fe, Cr, Ni, Mn, and Al. The Fe-Cr-Ni-Mn-Al multi-element system stabilizes a simple solid solution through high configurational entropy, avoiding brittle intermetallic compounds. At the same time, Cr and Ni enhance corrosion resistance, and Al and Ti enhance high-temperature oxidation resistance. The nano-reinforcing phase refines the grain size and increases the hardness, while suppressing abnormal grain growth during laser cladding. The flow aid improves the powder flowability and promotes uniform heat diffusion in the molten pool, forming a non-crystalline phase to freeze the element distribution and prevent solidification segregation.

[0029] The nano-reinforcing phase includes Al2O3, and the flow aid includes graphene.

[0030] Specifically, Al2O3 nanoparticles improve the wear resistance and high-temperature performance of the coating through high hardness and thermal stability, while graphene has superlubricity and high thermal conductivity, which not only improves the powder flowability but also promotes uniform heat diffusion in the molten pool, ultimately achieving the synergistic optimization of the coating porosity <0.5% and the bonding strength >350 MPa.

[0031] The microstructure of the coating is a nano-crystalline / amorphous composite phase, with the grain size ranging from 20 to 500 nm and the volume fraction of the amorphous phase being 10% - 40%.

[0032] Specifically, the nano-crystalline phase provides high strength, and the amorphous phase absorbs energy through shear bands, improving the fracture toughness and overcoming the "strength-toughness inversion" problem of traditional coatings. The grain-boundary-free characteristic of the amorphous phase blocks the corrosion channels, increasing the pitting potential to >0.8 V. At the same time, the enrichment of Cr elements in the nano-crystalline phase forms a dense passivation film, and a proportion of 10% - 40% can inhibit high-temperature grain coarsening.

[0033] A preparation method of a laser-cladded high-entropy alloy coating, the method comprising the following steps:

[0034] Roughen the surface of the substrate using a sandblaster, then clean it with absolute ethanol, and finally dry it in an oven;

[0035] Pretreat the raw materials, then atomize the powder by gas atomization, and after powder classification and screening, perform modification treatment on the screened raw materials;

[0036] Place the modified metal powder on the surface of the substrate and perform laser cladding;

[0037] Apply an alternating electromagnetic field and simultaneously apply ultrasonic vibration;

[0038] Perform post-treatment on the laser-cladded area.

[0039] Specifically, the surface of the substrate is sandblasted by a sandblasting machine to increase the surface roughness of the substrate and establish a mechanical interlocking structure, thereby enhancing the bonding strength of the coating. Through cleaning with absolute ethanol, oil stains, impurities and other pollutants on the surface of the substrate can be removed to avoid their influence on the bonding between the coating and the substrate. Drying treatment is carried out using an oven to avoid water residue and ensure that there are no pore defects at the cladding interface to prevent pores from being generated during cladding;

[0040] Pretreatment of the raw materials can remove gas impurities in the raw materials and ensure the uniformity of alloy composition. Through gas atomization powder making, metal powders with uniform particle size and good sphericity can be obtained. Through powder classification and screening, it is ensured that the powder particle size meets the requirements of laser cladding. Modification treatment can optimize the surface properties of the powder, enhance the combination of nano-reinforcing phase and flow aid with the metal powder, and create conditions for improving the coating performance;

[0041] The modified metal powder is placed on the surface of the substrate and then laser cladding is carried out to melt the metal powder and form a good metallurgical bond with the surface of the substrate. Utilizing the characteristics of rapid heating and cooling of laser energy, a high-entropy alloy coating with dense structure and excellent performance is obtained;

[0042] Applying an alternating electromagnetic field during laser cladding can generate electromagnetic stirring on the liquid metal in the molten pool, promote the uniform diffusion of solute elements, reduce composition segregation. Synchronously cooperating with ultrasonic vibration, cavitation effect and mechanical vibration effect can be generated, breaking coarse grains, refining the coating structure, and at the same time accelerating the discharge of bubbles and inclusions, thereby effectively improving the density and comprehensive performance of the coating;

[0043] Post-treatment eliminates surface defects generated during laser cladding, makes the coating surface smoother and flatter, optimizes the coating microstructure, improves the crystal structure, enhances the toughness and fatigue resistance of the coating, and further improves the comprehensive service performance and service life of the coating.

[0044] White fused alumina sand with 24 - 60 mesh is selected, the sandblasting pressure is 0.4 - 0.6 MPa, the sandblasting angle is 70 - 90°, the sandblasting distance is 100 - 150 mm, the cleaning time with absolute ethanol is 10 - 15 minutes, the oven temperature is 50 - 60 °C, and the drying time is 30 - 45 minutes.

[0045] Specifically, white fused alumina with a mesh size of 24-60 is used to treat the substrate surface under a sandblasting pressure of 0.4-0.6 MPa, a sandblasting angle of 70-90°, and a sandblasting distance of 100-150 mm, which can effectively remove the oxide film and impurities on the substrate surface, and at the same time form an appropriate roughness, providing a good mechanical interlocking foundation for the coating and the substrate. Then, it is cleaned with anhydrous ethanol for 10-15 minutes to remove the residual oil and fine particles after sandblasting and avoid contamination. After that, it is dried in an oven at 50-60 °C for 30-45 minutes to remove the moisture on the substrate surface and prevent defects such as pores and cracks caused by the vaporization of moisture during the subsequent laser cladding process, thereby significantly enhancing the bonding strength between the coating and the substrate and providing guarantee for the preparation of high-quality laser cladded high-entropy alloy coatings.

[0046] For pretreatment, the metal raw materials are subjected to arc melting using a water-cooled copper crucible vacuum arc melting furnace in a vacuum environment of not less than 10-3 Pa. The melting current is 400-600 A, and each alloy ingot needs to be repeatedly melted 4-6 times, with a single melting time of 3-5 minutes. Gas atomization powder making is carried out using a close-coupled gas atomization device, with an atomization pressure of 3-5 MPa and a superheat degree of 150-200 °C. Argon is used for protection during the atomization process. Powder classification and screening are carried out using an air classifier for particle size classification, and powders with a particle size of 15-53 μm are collected. The modification treatment includes placing the classified powders in a radio frequency plasma cleaner and treating them at a power of 100-200 W, in an Ar gas atmosphere and a pressure of 10-30 Pa for 15-30 minutes. Then, a hot-wall type ALD system is used to perform 50-100 times of Al2O3 coating with TMA / H2O as the precursor. After that, the coated powders are immersed in a 0.5-1.0 mg / mL graphene dispersion solution with a pH of 8-9, sonicated with a 200 W probe for 30-60 minutes, allowed to stand for self-assembly for 2-4 hours, and then vacuum dried at 60 °C for 12 hours.

[0047] Specifically, not less than 10 -3Under a vacuum environment of Pa, using a water-cooled copper crucible vacuum arc melting furnace, the metal raw materials are pretreated by melting at a current of 400 - 600 A, melting repeatedly 4 - 6 times with each time lasting 3 - 5 minutes. This can remove gas impurities in the raw materials, ensure uniform alloy composition, and improve the quality of alloy ingots. The close-coupled gas atomization equipment makes powder under an atomization pressure of 3 - 5 MPa, a superheat degree of 150 - 200 °C and argon protection, and can obtain metal powders with uniform particle size, good sphericity and high purity. The powders of 15 - 53 μm are collected by an air classifier, making the powders have a high sphericity of not less than 90%. Radio frequency plasma cleaning can activate the powder surface and enhance the subsequent coating effect. Using TMA / H2O as the precursor for 50 - 100 times of Al2O3 coating, the nano-reinforcing phase is uniformly attached to the powder surface, refining the grains and increasing the hardness. Immersing the powders in the graphene dispersion liquid, after ultrasonic treatment, static self-assembly and vacuum drying, the role of graphene as a flow aid can be fully exerted, improving the powder fluidity, promoting uniform heat diffusion in the molten pool, and preventing solidification segregation, thus providing high-quality raw material powders for preparing laser cladding high-entropy alloy coatings with excellent performance.

[0048] During laser cladding, argon protection is adopted, laser power: 2 - 5 kW, scanning speed: 5 - 20 mm / s, spot diameter: 1 - 4 mm.

[0049] Specifically, during laser cladding, argon protection is adopted, which can form an inert gas barrier on the surface of the molten pool, effectively isolate the air, prevent the metal powder and the substrate from being oxidized at high temperature, and ensure the stability of the coating chemical composition. A laser power of 1 - 5 kW can provide sufficient energy to quickly melt the metal powder and achieve good metallurgical bonding with the substrate, while avoiding excessive evaporation of the molten pool, burning loss of alloy elements due to too high power, or insufficient cladding due to too low power. The scanning speed of 5 - 20 mm / s and the spot diameter of 1 - 4 mm cooperate with each other, which can control the shape, size and cooling rate of the molten pool, ensure uniform cladding layer thickness, avoid defects such as molten pool collapse and lack of fusion, and at the same time is conducive to forming fine and uniform microstructures, improving the density and comprehensive performance of the coating, and finally obtaining a laser cladding high-entropy alloy coating with excellent quality and reliable performance.

[0050] An alternating electromagnetic field is applied, with a frequency of 10 - 50 Hz and a magnetic field intensity of 0.5 - 1 T. At the same time, ultrasonic vibration is applied, with a frequency of 20 - 40 kHz and an amplitude of 5 - 15 μm.

[0051] Specifically, an alternating electromagnetic field with a frequency of 10 - 50 Hz and an intensity of 0.5 - 1 T is applied to generate a Lorentz force to drive the directional flow of the melt, improving the uniformity of the distribution of alloy elements. The cavitation effect generated by simultaneously applying ultrasonic waves with an amplitude of 5 - 15 μm and a frequency of 20 - 40 kHz can break dendrites and promote the dispersion of nanoparticles, refining the grain size to 20 - 500 nm. At the same time, the acoustic streaming effect generated by the ultrasonic waves can eliminate pores, improving the microstructure uniformity of the cladding layer, enhancing the bonding strength, and reducing the residual stress through synergistic effects.

[0052] During post - treatment, the power during laser remelting is 60% - 80% of the original power, the scanning speed is 1.2 - 1.5 times the original speed, and the laser remelting power is not less than 1.2 kW.

[0053] Specifically, an energy input of 60% - 80% of the original power and not less than 1.2 kW can eliminate surface micropores and lack - of - fusion defects, while avoiding grain coarsening caused by excessive heat input. The rapid scanning at 1.2 - 1.5 times the original speed promotes the formation of a composite structure of nanocrystals and amorphous phases, thereby reducing the surface roughness of the coating, reducing the residual stress by 40 - 50%, and simultaneously improving the hardness uniformity and corrosion resistance, ultimately achieving the synergistic optimization of the surface integrity and service performance of the coating.

[0054] After laser remelting, in a vacuum annealing furnace, the temperature is 600 - 900 °C, and it is kept warm for 1 - 3 hours for annealing treatment.

[0055] Specifically, keeping warm for 1 - 3 hours in the temperature range of 600 - 900 °C can eliminate the internal residual stress of the coating and promote the uniform diffusion of elements. Low - temperature annealing at 600 - 700 °C can maintain the structural stability of nanocrystals, while high - temperature treatment at 800 - 900 °C can induce the strengthening of nano - precipitation phases. The vacuum environment prevents high - temperature oxidation and ensures the surface finish of the coating, thereby improving the hardness uniformity, fracture toughness, and high - temperature stability of the coating, achieving the synergistic optimization of the coating microstructure and mechanical properties.

[0056] Example 1:

[0057] Weigh each raw material according to mass percentage. The weighed raw materials and their mass percentages are as follows: Fe: 25%, Cr: 15%, Ni: 10%, Mn: 5%, Al: 3%, Ti: 0%, nano - reinforcing phase (Al2O3): 1%, flow aid (graphene): 0.1%.

[0058] Using a sandblasting machine, select white fused alumina sand with 24 meshes, set the sandblasting pressure to 0.4 MPa, the sandblasting angle to 70°, and the sandblasting distance to 100 mm. Roughen the surface of the substrate, and then clean the roughened substrate with anhydrous ethanol for 10 minutes. Place the cleaned substrate in an oven, set the oven temperature to 50 °C, and the drying time to 30 minutes;

[0059] Place the weighed metal raw materials in a vacuum environment not lower than 10 -4 Pa, and use a water-cooled copper crucible vacuum arc melting furnace for arc melting. Set the melting current to 400 A. Each alloy ingot needs to be repeatedly melted 4 times, and the single melting time is 3 minutes. Then use a close-coupled gas atomization device for powder making. Set the atomization pressure to 3 MPa and the superheat degree to 150 °C. Protect with argon during the atomization process. Then use an air classifier to perform particle size classification on the prepared powder, collect the powder with a particle size of 15 μm, and make the powder have a high sphericity of not less than 90%. Place the classified powder in a radio frequency plasma cleaner and process it for 15 minutes under the conditions of a power of 100 W, an Ar gas atmosphere, and a pressure of 10 Pa. Use a hot-wall ALD system to coat the powder with Al2O3 50 times using TMA / H2O as the precursor. Immerse the coated powder in a 0.5 mg / mL graphene dispersion with a pH of 8, use a 200 W probe ultrasonic treatment for 30 minutes, and then let it stand for self-assembly for 2 hours. Then dry it in vacuum at 60 °C for 12 hours;

[0060] Place the metal powder that has been modified on the surface of the treated substrate, use argon protection, set the laser power to 1 kW, the scanning speed to 5 mm / s, and the spot diameter to 1 mm for laser cladding, so that the metal powder melts and forms a metallurgical bond with the substrate surface;

[0061] Apply an alternating electromagnetic field during the laser cladding process, set the frequency to 10 Hz and the magnetic field strength to 0.5 T, and simultaneously apply ultrasonic vibration, set the frequency to 20 kHz and the amplitude to 5 μm;

[0062] Set the power during laser remelting to 60% of the original laser cladding power, set the scanning speed to 1.2 times the original speed. After laser remelting, place the workpiece in a vacuum annealing furnace, set the temperature to 600 °C, and hold for 1 hour for annealing treatment.

[0063] Example 2:

[0064] Weigh each raw material according to mass percentage. The weighed raw materials and their mass percentages are: Fe: 35%, Cr: 20%, Ni: 15%, Mn: 10%, Al: 6.5%, Ti: 2.5%, nano-reinforcing phase (Al2O3): 3%, flow aid (graphene): 0.3%.

[0065] Using a sandblasting machine, select 42-mesh white fused alumina sand, set the sandblasting pressure to 0.5 MPa, the sandblasting angle to 80°, and the sandblasting distance to 125 mm. Roughen the surface of the substrate, and then clean the roughened substrate with anhydrous ethanol for 12.5 minutes. Place the cleaned substrate in an oven, set the oven temperature to 55 °C, and the drying time to 37.5 minutes;

[0066] Place the weighed metal raw materials in a vacuum environment not lower than 10 -4 Pa, and use a water-cooled copper crucible vacuum arc melting furnace for arc melting. Set the melting current to 500 A. Each alloy ingot needs to be repeatedly melted 4 times, with a single melting time of 4 minutes. Then use a close-coupled gas atomization device for powder making. Set the atomization pressure to 4 MPa and the superheat to 175 °C. Protect with argon during the atomization process. Then use an air classifier to perform particle size classification on the prepared powder, collect the powder with a particle size of 34 μm, and make the powder have a high sphericity of not less than 90%. Place the classified powder in a radio frequency plasma cleaner and treat it for 22.5 minutes under the conditions of a power of 150 W, an Ar gas atmosphere, and a pressure of 20 Pa. Use a hot-wall ALD system to coat the powder with Al2O3 75 times using TMA / H2O as the precursor. Immerse the coated powder in a 0.75 mg / mL graphene dispersion with a pH of 8.5, use a 200 W probe ultrasonic treatment for 45 minutes, then let it stand for self-assembly for 3 hours, and then vacuum dry at 60 °C for 12 hours;

[0067] Place the metal powder that has been modified on the surface of the treated substrate, use argon protection, set the laser power to 3 kW, the scanning speed to 12.5 mm / s, and the spot diameter to 2.5 mm for laser cladding, so that the metal powder melts and forms a metallurgical bond with the substrate surface;

[0068] Apply an alternating electromagnetic field during the laser cladding process, set the frequency to 30 Hz and the magnetic field strength to 0.75 T, and synchronously apply ultrasonic vibration, set the frequency to 30 kHz and the amplitude to 10 μm;

[0069] The power during laser remelting is set to 70% of the original laser cladding power, the scanning speed is set to 1.35 times the original speed. After laser remelting, place the workpiece in a vacuum annealing furnace, set the temperature to 7500 °C, and hold for 2 hours for annealing treatment.

[0070] Example 3:

[0071] Weigh each raw material according to the mass percentage. The weighed raw materials and their mass percentages are as follows: Fe: 45%, Cr: 25%, Ni: 20%, Mn: 15%, Al: 10%, Ti: 5%, nano-reinforcement phase (Al2O3): 5%, flow aid (graphene): 0.5%.

[0072] Use a sandblasting machine, select 60-mesh white corundum sand, set the sandblasting pressure to 0.6 MPa, the sandblasting angle to 90°, and the sandblasting distance to 150 mm to roughen the surface of the substrate. Then, clean the roughened substrate with anhydrous ethanol for 15 minutes. Place the cleaned substrate in an oven, set the oven temperature to 60 °C, and the drying time to 45 minutes;

[0073] Place the weighed metal raw materials in a vacuum environment of not less than 10 -4 Pa, and use a water-cooled copper crucible vacuum arc melting furnace for arc melting. Set the melting current to 600 A. Each alloy ingot needs to be melted repeatedly 6 times, and the single melting time is 5 minutes. Then, use a close-coupled gas atomization device for powder making. Set the atomization pressure to 5 MPa and the superheat to 200 °C. Protect with argon during the atomization process. Then, use an air classifier to perform particle size classification on the prepared powder. Collect the powder with a particle size of 53 μm to make the powder have a high sphericity of not less than 90%. Place the classified powder in a radio frequency plasma cleaner and process it for 30 minutes under the conditions of a power of 200 W, an Ar gas atmosphere, and a pressure of 30 Pa. Use a hot-wall ALD system to coat the powder with Al2O3 100 times using TMA / H2O as the precursor. Immerse the coated powder in a 1.0 mg / mL graphene dispersion with a pH of 9, use a 200 W probe ultrasonic treatment for 60 minutes, then let it stand for self-assembly for 4 hours, and then vacuum dry at 60 °C for 12 hours;

[0074] Place the already modified metal powder on the surface of the treated substrate, use argon protection, set the laser power to 5 kW, the scanning speed to 20 mm / s, and the spot diameter to 4 mm for laser cladding, so that the metal powder melts and forms a metallurgical bond with the substrate surface;

[0075] Apply an alternating electromagnetic field during the laser cladding process, set the frequency to 50 Hz and the magnetic field strength to 1 T, and simultaneously apply ultrasonic vibration, set the frequency to 40 kHz and the amplitude to 15 μm;

[0076] The power during laser remelting is set to 80% of the original laser cladding power, the scanning speed is set to 1.5 times the original speed. After laser remelting, place the workpiece in a vacuum annealing furnace, set the temperature to 900 °C, and hold for 3 hours for annealing treatment.

[0077] Control example:

[0078] The component composition is: Fe - 45%, Cr - 25%, Ni - 20%;

[0079] During laser cladding, the laser power is 3.5 kW and the scanning speed is 10 mm / s, followed by mechanical polishing.

[0080] Experimental table

[0081]

[0082]

[0083] According to the above experimental table, the preparation method of the laser - cladded high - entropy alloy coating reduces the cost of raw material use, improves the uniformity of molten pool elements, enhances the powder flow performance, and enhances the coating strength and corrosion resistance.

[0084] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser cladding high-entropy alloy coating, characterized in that, Comprising the following components by mass percentage Composition: Fe: 25% - 45%, Cr: 15% - 25%, Ni: 10% - 20%, Mn: 5% - 15%, Al: 3% - 10%, Ti: 0% - 5%, nano-reinforcement phase: 1% - 5%, flow aid: 0.1% - 0.5%.

2. The laser cladding high-entropy alloy coating according to claim 1, wherein The nano-reinforcement phase includes Al2O3, and the flow aid includes graphene.

3. A laser cladding high-entropy alloy coating according to claim 1, characterized in that, The microstructure of the coating is a nano-crystalline / amorphous composite phase, the grain size is 20 - 500 nm, and the volume fraction of the amorphous phase is 10% - 40%.

4. A method for preparing a laser cladding high-entropy alloy coating, characterized in that, For a laser cladding high-entropy alloy coating according to any one of claims 1 - 3, the method comprises the following steps: Roughen the surface of the substrate using a sandblaster, then clean it with anhydrous ethanol, and finally dry it in an oven; Pretreat the raw materials, then produce powder by gas atomization, perform powder classification and screening, and subject the screened raw materials to modification treatment; Place the metal powder that has been subjected to modification treatment on the surface of the substrate and perform laser cladding; Apply an alternating electromagnetic field and simultaneously apply ultrasonic vibration; Perform post-treatment on the area that has been laser clad.

5. The preparation method of a laser cladding high-entropy alloy coating according to claim 4, characterized in that, Select white corundum sand with a mesh size of 24 - 60, the sandblasting pressure is 0.4 - 0.6 MPa, the sandblasting angle is 70 - 90°, the sandblasting distance is 100 - 150 mm, the cleaning time with anhydrous ethanol is 10 - 15 minutes, the oven temperature is 50 - 60 °C, and the drying time is 30 - 45 minutes.

6. The preparation method of a laser cladding high-entropy alloy coating according to claim 4, characterized in that, The pretreatment is to perform arc melting on the metal raw materials in a vacuum environment not lower than 10-3 Pa using a water-cooled copper crucible vacuum arc melting furnace, the melting current is 400 - 600 A, each alloy ingot needs to be repeatedly melted 4 - 6 times, the single melting time is 3 - 5 minutes, the gas atomization for powder production uses a close-coupled gas atomization device, the atomization pressure is 3 - 5 MPa, the superheat degree is 150 - 200 °C, and argon is used for protection during the atomization process. The powder classification and screening is to perform particle size classification using an air classifier, and collect powder with a particle size of 15 - 53 μm. The modification treatment includes placing the classified powder in a radio frequency plasma cleaner and treating it at a power of 100 - 200 W, in an Ar gas atmosphere and a pressure of 10 - 30 Pa for 15 - 30 minutes. Then, using a hot-wall ALD system, perform 50 - 100 times of Al2O3 coating with TMA / H2O as the precursor. Immerse the coated powder in a 0.5 - 1.0 mg / mL graphene dispersion solution with a pH of 8 - 9, perform 30 - 60 minutes of 200 W probe ultrasound, let it stand for self-assembly for 2 - 4 hours, and then dry it in a vacuum at 60 °C for 12 hours.

7. A method for preparing a laser cladding high-entropy alloy coating according to claim 4, characterized in that, During the laser cladding, argon protection is used, the laser power is 2 - 5 kW, the scanning speed is 5 - 20 mm / s, and the spot diameter is 1 - 4 mm.

8. The preparation method of a laser cladding high-entropy alloy coating according to claim 4, characterized in that, When applying the alternating electromagnetic field, the frequency is 10 - 50 Hz, the magnetic field strength is 0.5 - 1 T, when simultaneously applying ultrasonic vibration, the frequency is 20 - 40 kHz, and the amplitude is 5 - 15 μm.

9. The preparation method of a laser cladding high-entropy alloy coating according to claim 4, characterized in that, When performing post-treatment by laser remelting, the power is 60% - 80% of the original power, and the scanning speed is 1.2 - 1.5 times the original speed. The laser remelting power is not less than 1.2 kW.

10. The preparation method of a laser cladding high-entropy alloy coating according to claim 4, characterized in that, After the laser remelting, in a vacuum annealing furnace, the temperature is 600 - 900 °C, and it is held for 1 - 3 hours for annealing treatment.

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