Method for preparing coating by coating refractory high-entropy alloy powder with Ni and coating

Abstract

According to the method for preparing the laser cladding coating through the Ni-coated refractory high-entropy alloy powder and the coating, the refractory high-entropy alloy powder is prepared, the Ni-coated refractory high-entropy alloy powder is prepared, the outer surface of the refractory high-entropy alloy powder is evenly coated with nickel in a chemical plating mode, the Ni-coated refractory high-entropy alloy powder is formed, and the Ni-coated refractory high-entropy alloy powder is prepared. The composite powder is of a core-shell structure; the surface of a laser cladding matrix is treated, specifically, the surface of the matrix is polished to be smooth and subjected to ultrasonic cleaning treatment, and oxide and impurities are removed; and laser cladding is conducted, the Ni-coated refractory high-entropy alloy powder serves as a cladding material, the cladding material is cladded on the surface of a base body in a synchronous powder feeding mode under the inert atmosphere through the laser cladding technology, and the refractory high-entropy alloy coating is formed on the surface of the base body.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refractory high-entropy alloys, and particularly relates to a method for preparing a laser cladding coating by coating refractory high-entropy alloy powder with Ni and the coating. BACKGROUND

[0002] A refractory high-entropy alloy is a new type of alloy composed of multiple refractory elements, including Mo, W, Nb, Ta and Hf, Zr, Ti, V and other high-melting-point alloy elements. Compared with traditional FCC-phase high-entropy alloy, the refractory high-entropy alloy composed of BCC phase generally has higher high-temperature strength and microhardness, and excellent high-temperature mechanical properties, high-temperature oxidation resistance, friction and wear properties, corrosion resistance and radiation resistance, and is expected to be applied in the fields of aviation, aerospace, nuclear energy, petroleum and chemical industry and the like.

[0003] Laser cladding (LC) is an advanced technical means for realizing surface strengthening of metal materials based on digital control coating preparation developed rapidly in recent years. Compared with traditional refractory high-entropy alloy coating preparation technology, laser cladding preparation of refractory high-entropy alloy coating has the following advantages: (1) high energy density, fast processing speed, less material waste and environmentally friendly process; (2) high coating preparation accuracy, optional zone laser cladding, and controllable coating thickness of about 0.1-1.5 mm; (3) small substrate distortion, low coating dilution, and metallurgical bonding with the substrate; (4) good compactness of the cladding layer, high bonding strength and excellent performance. However, the refractory high-entropy alloy prepared by laser cladding generally has the problem of serious cracking of the coating due to the generation of many brittle phases and impurity phases in the laser cladding process, thereby causing the performance of the coating to decrease.

[0004] The prior art CN202310326520.0 discloses a method for inhibiting thermal cracks in laser additive manufacturing of refractory high-entropy alloy and application, which adds trace small atomic elements or carbides to the pre-alloy powder or mixed elemental powder of the refractory high-entropy alloy to inhibit oxygen enrichment at the grain boundary of the refractory high-entropy alloy, reduce the brittleness of the grain boundary, and improve the generation of cracks in the refractory high-entropy alloy. However, this method has the problem of uneven mixing of the powder, and the ball milling of the powder reduces the sphericity of the powder, resulting in poor flowability of the powder, low utilization rate of the powder, and limited effect on inhibiting the cracking of the coating in the laser cladding process. The prior art CN202210462970.8 discloses an application of refractory high-entropy alloy powder material in additive manufacturing, however, the particle size of the carbide powder added to eliminate the cracks of the coating is greatly different from that of the high-entropy alloy powder, which easily causes uneven powder output during the preparation process, resulting in the decrease of the performance of the coating, and cannot effectively eliminate the cracks and other defects generated in the laser cladding process.

[0005] The laser cladding preparation of refractory high-entropy alloy coating, on the one hand, due to the inevitable introduction of a certain content of oxygen element, leading to the oxygen content sensitive refractory high-entropy alloy often in the laser cladding process along the grain expansion of thermal cracks, greatly reducing the performance of the coating; on the other hand, the cladding process will generate some brittle phase and impurity phase, so that the coating cracks, also can cause the decline of coating quality. In order to solve the refractory high-entropy alloy in the laser cladding process due to the crack and forming problem caused by brittleness.

[0006] The above information disclosed in the background section is only intended to enhance the understanding of the background of the present application, and therefore can contain information that is not prior art known to those of ordinary skill in the art. SUMMARY

[0007] The present application provides a method for preparing laser cladding coating by coating refractory high-entropy alloy powder with Ni, which uses laser cladding technology to cladding Ni-coated refractory high-entropy alloy powder on the surface of the substrate to form a refractory high-entropy alloy coating. The use of the coated powder described in the present application to prepare the coating not only has various excellent properties of refractory high-entropy alloy materials, but also takes into account the excellent properties of metal matrix materials. The refractory high-entropy alloy powder has low oxygen and carbon content and good flowability after chemical Ni plating, which can be used not only for laser cladding preparation, but also for additive manufacturing 3D printing, thermal spraying and other preparation methods, thus widening the application range of the material engineering field. The laser cladding coating obtained by the present application has a dense structure, few microdefects, high bonding strength and excellent performance. The Ni coating described in the present application has the following effects: (1) enhancing the oxidation resistance, Ni has good high-temperature oxidation resistance, which can reduce the oxidation of the powder during cladding; improving the interface bonding. (2) The Ni coating layer avoids the outward diffusion of refractory high-entropy alloy elements, ensuring that the coating does not deteriorate due to dilution; effectively blocking the combination of coating elements and substrate elements to produce brittle phase and impurity phase, leading to the generation of coating cracks and quality decline; (3) The Ni coating layer and the substrate elements can form a Ni-rich soft phase, greatly improving the toughness of the coating and effectively reducing the coating cracking phenomenon during laser cladding. The service life of high-entropy alloy in extreme environment is greatly prolonged.

[0008] A method for preparing laser cladding coating by coating refractory high-entropy alloy powder with Ni includes, Step 1, preparing refractory high-entropy alloy powder, wherein the expression of refractory high-entropy alloy is W a Mo b Ta c X dWherein, X is any one or two of Nb, Ti, V, Zr, Hf; a, b, c, d are atomic percentages, 15%≤a≤50%, 15%≤b≤50%, 15%≤c≤50%, 0%<d≤50%, and a+b+c+d=100%; the refractory high-entropy alloy ingot is obtained by vacuum induction levitation melting after taking corresponding element elements according to the atomic ratio of the refractory high-entropy alloy; the refractory high-entropy alloy ingot is processed into a rod by using the wire electrical discharge machining technology, and then the rod is processed into a refractory high-entropy alloy powder by using the plasma rotating electrode method. Step 2, preparation of Ni-coated refractory high-entropy alloy powder, wherein the outer surface of the refractory high-entropy alloy powder is uniformly coated with nickel by chemical plating to form the Ni-coated refractory high-entropy alloy powder, which is a core-shell type composite powder. Step 3, processing the surface of the laser cladding substrate, the surface of the substrate is first polished by sandpaper to remove surface oxides and impurities, then ultrasonic cleaned with anhydrous ethanol and dried to ensure that the surface of the substrate is clean and free of impurities.

[0009] Step 4, laser cladding, the Ni-coated refractory high-entropy alloy powder is used as the cladding material, and the cladding material is cladded on the surface of the substrate in a synchronous powder feeding manner under an inert atmosphere by using the laser cladding technology, and a refractory high-entropy alloy coating is formed on the surface of the substrate.

[0010] In the preferred embodiment of the method, in step 1, the high-entropy alloy components are selected based on the high-entropy effect, slow diffusion effect, lattice distortion effect and cocktail effect of the high-entropy alloy, the high mixing enthalpy of thermodynamics, the low component saturation vapor pressure, the high reaction product volatilization enthalpy, the high reaction product melting point, and the high-temperature ablation self-healing characteristics, the low high-temperature oxygen diffusion coefficient, the high high-temperature strength, and the dense oxidation product layer of the high-entropy alloy; based on the high-entropy material formation criterion, the expression of the refractory high-entropy alloy used is finally determined as WaMobTacXd, wherein X is any one or two of Nb, Ti, V, Zr, Hf; a, b, c, d are atomic percentages, 15%≤a≤50%, 15%≤b≤50%, 15%≤c≤50%, 0%<d≤50%, and a+b+c+d=100%.

[0011] Preferably, the refractory high-entropy alloy powder has a particle size of 15-50 μm, an impurity content of ≤0.1%, and an oxygen content of ≤100 ppm, so as to ensure good powder uniformity and high flowability.

[0012] In the method, in step 2, the chemical plating method includes, Coarsening, wherein 1-5 g of KF is mixed with 1 L of deionized water at room temperature, 20-50 ml of HF is added after stirring uniformly, 20-70 g of refractory high-entropy alloy powder is added to the solution after mixing, stirring for 3-5 min, separating the coarsening liquid after standing and settling, and then washing the powder with deionized water for 3-5 times; Sensitization, wherein 10-40 g of SnCl2 is dissolved in 15-50 ml of HCl at room temperature, and then added to 1 L of deionized water, and then the coarsened powder is added to the solution, stirring for 3-5 min, separating the sensitization liquid after standing and settling, and then washing the powder with deionized water for 3-5 times; Activation, wherein 0.1-0.4 g of PdCl2 is dissolved in 10-50 ml of HCl at room temperature, and then poured into 1 L of deionized water, and then the sensitized powder is added to the solution, stirring for 3-5 min, separating the activation liquid after standing and settling, and then washing the powder with deionized water for 3-5 times; Drying, wherein the activated powder is dried using a vacuum drying oven to obtain dry powder for use; Chemical nickel plating, wherein 50-150 g of Na3C6H3O2·7H2O complexing agent is poured into 500 ml of deionized water, fully dissolved to obtain a first solution, and stirred uniformly; 40-100 g of Ni2SO4·6H2O main salt is poured into 500 ml of deionized water, fully dissolved, and then poured into the first solution to obtain a second solution, and stirred uniformly; 30-800 g of H3BO3 is poured into 500 ml of deionized water, fully dissolved, and then poured into the second solution to obtain a third solution, and stirred uniformly; 30-80 g of NaH2PO2 is poured into 500 ml of deionized water, fully dissolved, and then poured into the third solution to obtain a fourth solution, and mixed uniformly, and then the PH value of the fourth solution is adjusted to 7-11, the solution is heated to 35-75℃ using a water bath, the dry powder is added to the fourth solution, and an electric stirring paddle or a magnetic stirring paddle is used for 20-70 min, and then the solution is filtered, the chemical plating powder is washed with deionized water for 3-5 times, and then dried to obtain Ni-coated refractory high-entropy alloy powder.

[0013] In a preferred embodiment of the method, in step 3, the oxide film on the surface of the substrate is removed by sanding, and the surface of the substrate is polished to be free of oil stains, rust stains, and having a metallic luster, which is considered that the oxide film on the surface of the substrate is removed, and the substrate is cleaned with alcohol ultrasonic cleaning to ensure that there is no oxide doping between the coating and the substrate surface, and to achieve high-quality bonding of the coating and the substrate.

[0014] In the method, in step 4, the Ni-coated refractory high-entropy alloy powder is loaded into a powder feeder; The laser cladding process parameters are set as follows: laser power 600-3000 W, scanning speed 5-30 mm / s, spot diameter 1-7 mm, overlap rate 30%-70%, powder feeding speed 5-30 g / min, and protective gas flow 10-25 L / min; The laser cladding is performed in a protective atmosphere with an oxygen concentration of ≤200 ppm; The substrate preheating temperature is 200-400℃, so as to reduce thermal stress and improve coating forming quality.

[0015] In the method, the substrate is a steel substrate, the protective gas is argon, and the laser cladding is performed in a closed atmosphere cabin to isolate O and N elements in the air.

[0016] In the method, the refractory high-entropy alloy powder has a particle size of 15-53 μm.

[0017] In the method, the nickel layer of the core-shell structure composite powder has a thickness of 0.5-5 μm, and the composite powder formed after Ni coating has a particle size of 15.5-58 μm.

[0018] In the method, the Ni layer on the surface of the Ni-coated refractory high-entropy alloy powder is uniform and has no clustering phenomenon, and the flowability is 8-15 s / 50 g.

[0019] A refractory high-entropy alloy coating is made according to the method.

[0020] In the preferred embodiment of the refractory high-entropy alloy coating, the crack quality of the refractory high-entropy alloy coating is evaluated to reach level I (strict) according to the national standard GB_T 42401-2023 Laser Cladding Repair Defect Quality Classification.

[0021] In the refractory high-entropy alloy coating, the thickness of the refractory high-entropy alloy coating is 0.5-1.5 mm, and the hardness is 850 HV 0.2 .

[0022] In the refractory high-entropy alloy coating, the refractory high-entropy alloy coating comprises a Ni-rich soft phase and a BCC structure refractory high-entropy alloy hard phase.

[0023] Compared with the prior art, the present application has the following advantages: when the laser cladding technology is used to prepare the refractory high-entropy alloy coating on the surface of the base body, the high energy density input is needed for the melting and fullness of the refractory high-entropy alloy particles, under the high energy density input, the molten pool is deep, the molten base body material diffuses into the coating through the convection mass transfer, which causes the dilution of the coating, the refractory alloy powder is heavy, the base body iron element is light, the base body element floats up, which causes the base body element to mix more, so that the composition of the coating changes greatly, and the mutual diffusion of the coating elements and the base body elements generates many brittle phases and impurity phases (such as FeTa, FeW, etc.), which seriously reduces the quality and performance of the coating. At the same time, the high energy density also causes a deeper heat affected zone of the base body, which causes the recrystallization annealing of the base body, which changes the original performance of the base body material. In order to avoid such a situation, the present application uses the chemical plating Ni to coat the refractory high-entropy alloy powder and prepare the laser cladding coating. After the coating of Ni, the coating can effectively inhibit the dilution of the base body element to the coating, the composition of the coating does not change, the quality is improved, and the brittle phase and impurity phase generated by the combination of the base body element and the coating element are avoided, which ensures that the performance of the coating will not decrease. At the same time, the soft phase generated by the combination of Ni and the base body element can play a toughening role, effectively alleviate the cracking of the coating in the laser cladding process, avoid the generation of coating cracks, and the prepared coating also has high hardness. The thickness of the refractory high-entropy alloy coating is 0.5-1.5mm, the coating is mainly composed of the Ni-rich soft phase and the BCC structure refractory high-entropy alloy hard phase, the coating has dense structure, high hardness, no brittle phase, impurity phase and crack, etc. The preparation method of the present application has the advantages of simple process, high efficiency, good forming quality, high powder utilization rate and green environmental protection. BRIEF DESCRIPTION OF DRAWINGS

[0024] Various other advantages and benefits of the present application will become apparent to those of ordinary skill in the art, upon reading the following detailed description of the preferred embodiment. The accompanying drawings are included to provide a better understanding of the preferred embodiment and are not to be considered an limitation of the present application. Obviously, other embodiments of the application can be used without departing from the present application, and thus, the following drawings are included to provide a more thorough disclosure of the present application and are not to be considered limiting of the scope of the application. It should be noted that the same reference numerals are used throughout the several views to indicate the same or similar components.

[0025] In the drawings: Figure 1 The scanning electron microscope (SEM) and EDS element surface scanning analysis diagram of the Ni layer coated on the surface of the WMoTaNb particles in Example 1 by chemical plating nickel are shown in the figure, from which it can be seen that the refractory high-entropy alloy powder coated with Ni still maintains a high degree of spherical shape, the powder has good dispersibility, and there is no accumulation and clustering phenomenon, which is beneficial to the preparation of the laser cladding coating. Figure 1The EDS surface scan of the middle (b) image shows that the Ni element is uniformly distributed and the Ni coating layer on the surface is uniformly and densely distributed. Figure 2 The image shows the cross-sectional SEM morphology and elemental distribution of WMoTaNb particles after a Ni layer was coated onto the surface using electroless nickel plating in Example 1. It can be seen that a 3 μm thick black Ni layer is attached to the surface of the WMoTaNb particles. Figure 2 The elemental surface scan of Figure (b) clearly reveals a ring of Ni element distribution on the outer surface of the powder particles; Figure 3 The surface penetrant test image of the laser cladding coating of WMoTaNb powder coated with chemically plated Ni in Example 1 shows that there is no red penetrant visible in the coating, the surface coating is macroscopically free of defects, and the quality is good. Figure 4 and Figure 5 Cross-sectional SEM microstructure and EDS elemental surface scan of the coating prepared in Example 1 show that the coating has a uniform thickness, is metallurgically bonded to the substrate, and has a dense and defect-free structure. in: Figure 5 The cross-sectional EDS elemental surface scan of the coating prepared in Example 1 shows that the structure is dense and Ni is mainly enriched around the WMoTaNb particles. From the side, it can be seen that the Ni coating layer effectively prevents the matrix elements from diluting the coating and improves the mechanical properties of the coating. Figure 6 The image shows the SEM morphology of the refractory high-entropy alloy WMoTaNb powder prepared in Comparative Example 1. This powder has high sphericity and a particle size distribution of 15-53 μm. Figure 7 The penetrant testing image of the refractory high entropy alloy WMoTaNb coating surface prepared for Comparative Example 1 shows that there are many cracks on the surface of the refractory high entropy alloy coating without Ni coating, indicating that its cladding effect is very poor. Figure 8 The SEM morphology of the cross-sectional microstructure of the refractory high-entropy alloy WMoTaNb coating prepared for Comparative Example 1 shows that the coating always has large through cracks, and its surface has poor cladding effect and is prone to cracking. Figure 9 SEM images and elemental distribution diagrams of Ni-coated refractory high-entropy alloy powder prepared for Counterexample 1 are shown in the images. It is clear from the images that the Ni layer coating is uneven and the sphericity is poor, which does not achieve the effect described in this invention. Figure 10 To implement Counterexample 1, a penetrant testing image of the laser cladding coating surface was prepared. The image showed that the surface was covered with crisscrossing cracks, but the number of cracks was slightly reduced compared to the coating in Comparative Example 1.

[0026] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0027] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0028] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0029] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0030] like Figures 1 to 10 As shown, a method for preparing a laser cladding coating using Ni-coated refractory high-entropy alloy powder includes, Step 1: Prepare refractory high-entropy alloy powder, wherein the expression for the refractory high-entropy alloy is W. a Mo b Ta c X d Where X is any one or two of Nb, Ti, V, Zr, and Hf; a, b, c, and d are atomic percentages, 15%≤a≤50%, 15%≤b≤50%, 15%≤c≤50%, 0%<d≤50%, and a+b+c+d=100%. After weighing the corresponding elemental substances according to the atomic ratio of the refractory high entropy alloy, the refractory high entropy alloy ingot is obtained by vacuum induction suspension melting method. The refractory high entropy alloy ingot is processed into rods by electrical discharge wire cutting technology, and then the rods are made into refractory high entropy alloy powder by plasma rotating electrode method. Step 2: Prepare Ni-coated refractory high-entropy alloy powder, wherein nickel is uniformly coated on the outer surface of the refractory high-entropy alloy powder by chemical plating to form Ni-coated refractory high-entropy alloy powder, which is a core-shell type composite powder. Step 3: Process the surface of the laser cladding substrate, including grinding, polishing and ultrasonic cleaning of the substrate surface to remove oxides and impurities; Step 4, laser cladding: The Ni-coated refractory high-entropy alloy powder is used as the cladding material. Laser cladding technology is used to clad the cladding material onto the surface of the substrate in an inert atmosphere by synchronous powder feeding, and a refractory high-entropy alloy coating is formed on the surface of the substrate.

[0031] In a preferred embodiment of the method, step 2, the chemical plating method includes, For roughening, 1-5 g of KF is mixed with 1 L of deionized water at room temperature. After stirring evenly, 20-50 ml of HF is added. After mixing, 20-70 g of refractory high entropy alloy powder is added to the solution and stirred for 3-5 min. After standing and settling, the roughening liquid is separated, and the powder is washed with deionized water 3-5 times for later use. Sensitization involves dissolving 10-40 g of SnCl2 in 15-50 ml of HCl at room temperature, adding the dissolved SnCl2 to 1 L of deionized water, then adding the coarsened powder to the solution, stirring for 3-5 min, allowing it to settle, separating the sensitization solution, washing the powder with deionized water 3-5 times, and setting it aside for later use. Activation involves dissolving 0.1-0.4 g of PdCl2 in 10-50 ml of HCl at room temperature, then pouring the solution into 1 L of deionized water. The sensitized powder is then added to the solution, stirred for 3-5 min, allowed to settle, and the activation solution is separated. The powder is then washed 3-5 times with deionized water and set aside for later use. Drying, in which the activated powder is dried in a vacuum drying oven to obtain dried powder for later use; In the electroless nickel plating process, 50-150 g of complexing agent Na3C6H3O2•7H2O is poured into 500 ml of deionized water, fully dissolved to obtain the first solution, and stirred evenly. Pour 40-100 g of the main salt Ni2SO4•6H2O into 500 ml of deionized water, dissolve it completely, then pour it into the first solution to obtain the second solution, and stir well. Dissolve 30-800g of H3BO3 in 500ml of deionized water, then pour the solution into the second solution to obtain the third solution, and stir well. Dissolve 30-80g of NaH2PO2 in 500ml of deionized water until fully dissolved, then pour the solution into the third solution to obtain the fourth solution. After mixing evenly, adjust the pH of the fourth solution to 7-11. Heat the solution to 35-75℃ using a water bath. Add the dried powder to the fourth solution and stir with an electric stirrer or magnetic stirrer for 20-70 minutes. After the stirring is complete, filter the solution and wash the chemically plated powder with deionized water 3-5 times. Dry the powder to obtain Ni-coated refractory high-entropy alloy powder.

[0032] In a preferred embodiment of the method, in step 4, the Ni-coated refractory high-entropy alloy powder is loaded into a powder feeder. Set the laser cladding process parameters as follows: laser power 600~3000W, scanning speed 5~30 mm / s, spot diameter 1~7 mm, overlap rate 30%~70%, powder feeding speed 5~30 g / min, protective gas flow rate 10~25 L / min; Laser cladding is performed in a protective atmosphere with an oxygen concentration of ≤200ppm; The substrate preheating temperature is 200~400℃ to reduce thermal stress and improve coating forming quality.

[0033] In a preferred embodiment of the method, the substrate is a steel substrate, the protective gas is argon, and the laser cladding is performed in a closed atmosphere chamber to isolate O and N elements in the air.

[0034] In a preferred embodiment of the method, the particle size of the refractory high-entropy alloy powder is 15~53μm.

[0035] In a preferred embodiment of the method, the nickel layer thickness of the core-shell composite powder is 0.5~5μm, and the particle size of the composite powder formed after Ni coating is 15.5~58μm.

[0036] In a preferred embodiment of the method, the Ni layer on the surface of the Ni-coated refractory high-entropy alloy powder is uniform and free of agglomeration, and has a flowability of 8~15 s / 50 g.

[0037] A refractory high-entropy alloy coating, which is prepared according to the method described above.

[0038] In a preferred embodiment of the refractory high-entropy alloy coating, the coating thickness is 0.5~1.5mm and the hardness is 850HV. 0.2 .

[0039] In a preferred embodiment of the refractory high-entropy alloy coating, the refractory high-entropy alloy coating comprises a Ni-rich soft phase and a BCC-structured refractory high-entropy alloy hard phase.

[0040] In one embodiment, the method includes, Step 1, Preparation of Refractory High-Entropy Alloy Powder: It should be noted that this invention utilizes the high-entropy effect, slow diffusion effect, lattice distortion effect, and cocktail effect of high-entropy alloys. The selection of high-entropy alloy components is based on thermodynamic factors such as high mixing enthalpy, low saturated vapor pressure of the components, high volatilization enthalpy of the reaction products, and high melting point of the reaction products. Kinetic factors include high-temperature ablation self-healing properties, low high-temperature oxygen diffusion coefficient, high high-temperature strength, and dense oxide product layer. Based on the high-entropy material formation criteria, the final expression for the refractory high-entropy alloy used is determined to be W. a Mo b Ta c X d Where X is any one or two of Nb, Ti, V, Zr, and Hf; a, b, c, and d are atomic percentages, 15%≤a≤50%, 15%≤b≤50%, 15%≤c≤50%, 0%<d≤50%, and a+b+c+d=100%.

[0041] This invention employs a plasma rotating electrode method to prepare refractory high-entropy alloy powder. First, the corresponding elemental substances are weighed according to the atomic ratio of the refractory high-entropy alloy. Then, a refractory high-entropy alloy ingot is obtained through vacuum induction suspension melting. The obtained ingot is then processed into rods of the required size using electrical discharge wire cutting technology. Finally, the rods are processed into refractory high-entropy alloy powder using the plasma rotating electrode method. To ensure the powder meets the requirements for laser cladding, this invention preferably uses spherical high-entropy alloy powder with a particle size of 15-53 μm, an impurity content ≤ 0.1%, and an oxygen content ≤ 200 ppm to ensure good powder uniformity and high flowability.

[0042] Step 2, Preparation of Ni-coated refractory high-entropy alloy powder: The Ni-coated refractory high-entropy alloy powder provided by this invention is obtained through a chemical nickel plating process.

[0043] The following details the electroless nickel plating process.

[0044] (1) Roughening: Mix 1~5 g KF with 1L deionized water at room temperature, stir evenly, add 20~50 ml HF, after mixing, add 20~70 g refractory high entropy alloy powder to the solution, stir for 3~5 min, let stand to settle, separate the roughening liquid, and wash the powder with deionized water 3~5 times for later use. (2) Sensitization: Dissolve 10-40 g of SnCl2 in 15-50 ml of HCl at room temperature. After dissolving, pour it into 1 L of deionized water, add the coarsened powder to the solution, stir for 3-5 min, let it stand to settle, separate the sensitization solution, wash the powder with deionized water 3-5 times, and set aside for use. (3) Activation: Dissolve 0.1~0.4 g of PdCl2 in 10~50 ml of HCl at room temperature. After mixing, pour into 1 L of deionized water, add the activated powder to the solution, stir for 3~5 min, let stand and settle, separate the activation solution, wash the powder with deionized water 3~5 times, and set aside for use. (4) Drying: The activated powder is dried in a vacuum drying oven and set aside for later use; (5) Electroless nickel plating: The specific steps are as follows: 1) Pour 50~150 g of Na3C6H3O2•7H2O (complexing agent) into 500ml of deionized water and dissolve it completely; 2) Pour 40~100 g of Ni2SO4•6H2O (main salt) into 500 ml of deionized water, dissolve it completely, and then pour it into the solution prepared in 1) above; 3) Dissolve 30-80g of H3BO3 in 500ml of deionized water, then pour it into the solution prepared in step 2); 4) Finally, dissolve 30-80g of NaH2PO2 in 500ml of deionized water, then pour the solution into the solution prepared in step 3). 5) After the above solutions are mixed evenly, adjust the pH of the solution to 7~11, heat the solution to 35~75℃, add the dried powder from step (4) to the solution, stir with a paddle / magnetic force for 20~70 min, filter the solution after the end, and wash the chemically plated powder with deionized water 3~5 times, and dry it for later use.

[0045] The present invention yields a powder coating with uniformity, a thickness of 0.5~5μm, good dispersibility, no agglomeration, and a flowability of 8~15s / 50g.

[0046] This invention yields a powder material with low oxygen and carbon content, good fluidity, and high stability after electroless Ni plating of a high-entropy alloy. The Ni layer will not peel off after long-term storage. It can be used for laser cladding, additive manufacturing 3D printing, and thermal spraying, thus broadening the engineering application fields of this material.

[0047] Step 3, laser cladding: The second objective of this invention is to provide a method for preparing a high-quality laser cladding coating using Ni-coated refractory high-entropy alloy powder, as detailed below: The substrate material used in this invention is a steel substrate. In order to meet the requirements of laser cladding, the substrate surface is treated. The main process includes first grinding with silicon carbide or diamond sandpaper to remove surface oxides and impurities, then fine polishing on a polishing cloth with metallographic polishing agent, and finally ultrasonic cleaning and drying to ensure that the substrate surface is clean and free of impurities, so as to avoid the introduction of impurities and the generation of other substances during the actual cladding process, thereby reducing the quality and performance of the coating.

[0048] The process parameters for preparing laser cladding coatings are as follows: laser power 600-3000W, scanning speed 5-30 mm / s, spot diameter 1-7 mm, overlap rate 30%-70%, powder feeding speed 5-30 g / min, and protective gas flow rate 10-25 L / min.

[0049] Furthermore, considering the impact of O and N elements in the ambient air on coating quality, a high-concentration Ar2 protective atmosphere chamber was constructed to ensure that the oxygen concentration in the laser cladding environment is ≤200ppm, thus isolating O and N elements from adverse effects on coating quality. Additionally, to mitigate the significant thermal stress during laser cladding, the heating stage preheats the substrate to 200-400℃, reducing the adverse effects of excessive temperature gradients. A layer of metallic Ni is coated onto the surface of the refractory high-entropy alloy powder. This inhibits the outward diffusion of refractory high-entropy alloy elements during laser cladding, preventing coating dilution and avoiding reactions between coating and substrate elements that could lead to the formation of various brittle and impurity phases. Moreover, the Ni layer on the surface of the refractory high-entropy alloy powder can form a Ni-rich soft phase with the substrate elements, effectively preventing crack formation during coating preparation and improving coating quality and performance. The coating quality meets the Class I flaw detection standard according to the national standard GB-T42401-2023 "Classification of Defect Quality for Laser Cladding Repair". This invention features simple process, controllable composition, and green environmental protection, and has great application prospects in aerospace, nuclear power and other fields.

[0050] Example 1 This embodiment provides a method for preparing a laser cladding coating using Ni-coated refractory high-entropy alloy powder. The preparation method is as follows: Step 1, Preparation of Refractory High-Entropy Alloy Powder: 1) In this embodiment, high-purity metal particles with a purity ≥ 99.99% are weighed according to the following atomic percentage composition for later use: W 25 at.%, Mo 25 at.%, Ta 25 at.%, Nb 25 at.%.

[0051] 2) Place the weighed elemental particles into a vacuum induction levitation furnace in order of increasing melting point, and heat at 5×10⁻⁶ ℃. -3Under a vacuum of Pa, the alloy was repeatedly melted 6 times, each time until a homogeneous melt was formed. The melt was then cooled in the furnace to obtain a refractory high-entropy alloy ingot with a single-phase BCC structure, an impurity content of ≤0.1%, and an oxygen content of ≤100ppm.

[0052] 3) Using wire electrical discharge machining (EDM) technology, the refractory high-entropy alloy ingot obtained above is cut into round bars with a diameter of 30mm and a length of 150mm. Then, the surface oxide layer is removed by sanding with 1000# SiC sandpaper, and the surface oil and impurities are removed by ultrasonic cleaning with alcohol and acetone.

[0053] 4) The obtained rod is clamped in a plasma rotating electrode apparatus, melted by vacuum plasma and rotated at a high speed of 50,000 r / min and a vacuum degree of 5 × 10⁻⁶. -3 Pa was used to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder was then sieved using a vibrating screen to obtain WMoTaNb refractory high entropy alloy powder with a particle size of 15~53 micrometers.

[0054] Step 2, prepare Ni-coated refractory high-entropy alloy powder: In this embodiment, a chemical Ni plating method is used to coat refractory high-entropy alloy powder. The refractory high-entropy alloy powder used is 50g of WMoTaNb; the specific chemical Ni plating process is as follows: (1) Roughening: Mix 2g KF with 1L deionized water at room temperature, stir evenly, add 30 ml HF, after mixing, add 50g high entropy alloy powder to the solution, stir for 4 min, let stand and settle, separate the roughening liquid, wash the powder with deionized water 3 times, and set aside for use. (2) Sensitization: Dissolve 20 g of SnCl2 in 40 ml of HCl at room temperature. After dissolution, add 1 L of deionized water, then add the coarsened powder to the solution, stir for 4 min, let it stand and settle, then separate the sensitization solution, and wash the powder 3 times with deionized water for later use. (3) Activation: Dissolve 0.1 g of PdCl2 in 20 ml of HCl at room temperature, mix and add 1 L of deionized water. Add the activated powder to the solution, stir for 4 min, let it stand to settle and separate the activation solution. Wash the powder with deionized water 3 times and set aside for use. (4) Drying: The activated powder is dried in a vacuum drying oven and set aside for later use; (5) Electroless nickel plating: The specific steps are as follows: 1) Pour 100 g of Na3C6H3O2•7H2O (complexing agent) into 500 ml of deionized water and dissolve it completely to obtain the first solution; 2) Pour 60 g of Ni2SO4•6H2O (main salt) into 500 ml of deionized water, dissolve it completely, then pour it into the first solution to obtain the second solution, and stir well. 3) Dissolve 54g of H3BO3 in 500ml of deionized water, then pour the solution into the second solution to obtain the third solution, and stir well. 4) Finally, pour 50g of NaH2PO2 into 500ml of deionized water and dissolve it completely. Then pour the solution into the third solution to obtain the fourth solution and stir well. 5) After the above solution is mixed evenly, adjust the pH value of the solution to 9, heat the solution to 50°C using a water bath, add the dried powder from step (4) to the solution, stir with an electric stirrer for 45 minutes, filter the solution after the end, wash the chemically plated powder three times with deionized water, and dry it in a vacuum drying oven for later use.

[0055] Step 3, process the surface of the laser cladding substrate: This embodiment uses gun steel plate as the substrate; the specific processing method is as follows: 1) Use 600#~2000 SiC sandpaper to polish the substrate surface until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0056] 2) Clean the polished substrate with anhydrous ethanol as a cleaning agent. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0057] Step 4, laser cladding The Ni-coated refractory high-entropy alloy powder prepared in step 2 above was loaded into a powder feeder. The laser cladding parameters were set as follows: synchronous continuous powder feeding, laser power of 1200W, scanning speed of 10mm / s, cladding overlap rate of 50%, argon gas flow rate of 20L / min, and powder feeding speed of 12g / min. Furthermore, considering the influence of O and N elements in the ambient air on the coating quality, the experiment was conducted in an atmosphere chamber with a high concentration of Ar2, ensuring an oxygen concentration ≤200ppm to isolate the adverse effects of O and N elements on the coating. To mitigate the significant thermal stress during laser cladding, a small heating stage was used to preheat the substrate to 400℃. After these conditions were met, laser cladding began, ultimately yielding a refractory high-entropy alloy coating with good forming quality, low surface roughness, high hardness, and no cracks.

[0058] The powder obtained in this embodiment has a Ni layer thickness of 3 μm, good dispersibility, no agglomeration, and a flowability of only 9 s / 50g, making it the optimal embodiment. Figure 1The image shows the surface SEM morphology and elemental distribution morphology of the Ni-coated refractory high-entropy alloy WMoTaNb prepared in this embodiment. It can be seen that the Ni layer is uniformly coated and well dispersed, and the coating effect is also good as can be seen by elemental surface scanning.

[0059] Example 2 This embodiment provides a method for preparing a laser cladding coating using Ni-coated refractory high-entropy alloy powder. The preparation method is as follows: Step 1, Preparation of Refractory High-Entropy Alloy Powder: 1) In this embodiment, high-purity metal particles with a purity ≥ 99.99% are weighed according to the following atomic percentage composition for later use: W 20 at.%, Mo 20 at.%, Ta 20 at.%, Nb 20 at.%, Ti 20 at.%.

[0060] 2) Place the weighed elemental particles into a vacuum induction levitation furnace in order of increasing melting point, and heat at 5×10⁻⁶ ℃. -3 Under a vacuum of Pa, the alloy was repeatedly melted 6 times, each time until a homogeneous melt was formed. The melt was then cooled in the furnace to obtain a refractory high-entropy alloy ingot with a single-phase BCC structure, an impurity content of ≤0.1%, and an oxygen content of ≤100ppm.

[0061] 3) Using wire electrical discharge machining (EDM) technology, the refractory high-entropy alloy ingot obtained above is cut into round bars with a diameter of 30mm and a length of 150mm. Then, the surface oxide layer is removed by sanding with 1000# SiC sandpaper, and the surface oil and impurities are removed by ultrasonic cleaning with alcohol and acetone.

[0062] 4) The obtained rod is clamped in a plasma rotating electrode apparatus, melted by vacuum plasma and rotated at a high speed of 50,000 r / min and a vacuum degree of 5 × 10⁻⁶. -3 Pa was used to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder was then sieved using a vibrating sieve to obtain WMoTaNbTi refractory high entropy alloy powder with a particle size of 15~53 micrometers.

[0063] Step 2, prepare Ni-coated refractory high-entropy alloy powder: The difference between this embodiment 2 and embodiment 1 in step 2 is as follows: In this embodiment, the refractory high-entropy alloy WMoTaNbTi powder used in step 2 for chemical Ni plating is 25g, the Ni plating temperature is 35℃, the pH value of the plating solution is 7.5, the Ni plating time is 25 minutes, and the rest is the same as in embodiment 1; Step 3, process the surface of the laser cladding substrate: In this embodiment, step 3 is the same as step 3 in embodiment 1.

[0064] Step 4, laser cladding In this embodiment, the laser power in step 4 is 600W, the scanning speed is 6mm / s, the powder feeding speed is 6g / min, the substrate is preheated to 200℃, and the rest of the implementation is the same as in embodiment 1.

[0065] The coating prepared in this embodiment has no macroscopic defects and a dense microstructure. Its hardness is lower than that of the coating prepared in Example 1.

[0066] Example 3 This embodiment provides a method for preparing a laser cladding coating using Ni-coated refractory high-entropy alloy powder. The preparation method is as follows: Step 1, Preparation of Refractory High-Entropy Alloy Powder: 1) In this embodiment, high-purity metal particles with a purity ≥ 99.99% are weighed according to the following atomic percentage composition for later use: W 20 at.%, Mo 20 at.%, Ta 20 at.%, Nb 20 at.%, V 20 at.%.

[0067] 2) Place the weighed elemental particles into a vacuum induction levitation furnace in order of increasing melting point, and heat at 5×10⁻⁶ ℃. -3 Under a vacuum of Pa, the alloy was repeatedly melted 6 times, each time until a homogeneous melt was formed. The melt was then cooled in the furnace to obtain a refractory high-entropy alloy ingot with a single-phase BCC structure, an impurity content of ≤0.1%, and an oxygen content of ≤100ppm.

[0068] 3) Using wire electrical discharge machining (EDM) technology, the refractory high-entropy alloy ingot obtained above is cut into round bars with a diameter of 30mm and a length of 150mm. Then, the surface oxide layer is removed by sanding with 1000# SiC sandpaper, and the surface oil and impurities are removed by ultrasonic cleaning with alcohol and acetone.

[0069] 4) The obtained rod is clamped in a plasma rotating electrode apparatus, melted by vacuum plasma and rotated at a high speed of 50,000 r / min and a vacuum degree of 5 × 10⁻⁶. -3 Pa was used to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder was then sieved using a vibrating sieve to obtain WMoTaNbV refractory high entropy alloy powder with a particle size of 15~53 micrometers.

[0070] Step 2, prepare Ni-coated refractory high-entropy alloy powder: The difference between this embodiment 2 and embodiment 1 in step 2 is as follows: In this embodiment, 70g of refractory high-entropy alloy WMoTaNbV powder was used for chemical Ni plating in step 2, the Ni plating temperature was 70℃, the pH value of the plating solution was 11, the Ni plating time was 70 minutes, and the rest were the same as in embodiment 1. Step 3, process the surface of the laser cladding substrate: In this embodiment, step 3 is the same as step 3 in embodiment 1.

[0071] Step 4, laser cladding In this embodiment, the laser power in step 4 is 3000W, the scanning speed is 25mm / s, the powder feeding speed is 20g / min, the substrate is preheated to 300℃, and the rest of the implementation methods are the same as in embodiment 1.

[0072] The coating prepared in this embodiment has no macroscopic defects and a dense microstructure. It also has a lower hardness than the coating prepared in Example 1.

[0073] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: This comparative example did not undergo the chemical Ni plating treatment in step 2 of Example 1, and the rest of the implementation methods are the same as in Example 1.

[0074] Counterexample 1 Step 1, Preparation of Refractory High-Entropy Alloy Powder: 1) In this embodiment, according to the following atomic percentage composition, weigh out the corresponding high-purity metal element particles with a purity ≥99.99% for later use: W 25 at.%, Mo 25 at.%, Ta 25 at.%, Nb 25 at.%.

[0075] 2) Place the weighed elemental particles into a vacuum induction levitation furnace in order of increasing melting point, and heat at 5×10⁻⁶ ℃. -3 Under a vacuum of Pa, the alloy was repeatedly melted 6 times, each time until a homogeneous melt was formed. The melt was then cooled in the furnace to obtain a refractory high-entropy alloy ingot with a single-phase BCC structure, an impurity content of ≤0.1%, and an oxygen content of ≤100ppm.

[0076] 3) Using wire electrical discharge machining (EDM) technology, the refractory high-entropy alloy ingot obtained above is cut into round bars with a diameter of 30mm and a length of 150mm. Then, the surface oxide layer is removed by sanding with 1000# SiC sandpaper, and the surface oil and impurities are removed by ultrasonic cleaning with alcohol and acetone.

[0077] 4) The obtained rod is clamped in a plasma rotating electrode apparatus, melted by vacuum plasma and rotated at a high speed of 50,000 r / min and a vacuum degree of 5 × 10⁻⁶. -3 Pa was used to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder was then sieved using a vibrating screen to obtain WMoTaNb refractory high entropy alloy powder with a particle size of 15~53 micrometers.

[0078] Step 2, prepare Ni-coated refractory high-entropy alloy powder: In this embodiment, refractory high-entropy alloy powder is coated with Ni by chemical plating. The refractory high-entropy alloy powder used is 80g of WMoTaNb. The specific chemical Ni plating process is as follows: (1) Roughening: Mix 2g KF with 1L deionized water at room temperature, stir evenly, add 30 ml HF, after mixing, add 80g high entropy alloy powder to the solution, stir for 4 min, let stand and settle, separate the roughening liquid, wash the powder with deionized water 3 times, and set aside for use. (2) Sensitization: Dissolve 20 g of SnCl2 in 40 ml of HCl at room temperature. After dissolution, add 1 L of deionized water, then add the coarsened powder to the solution, stir for 4 min, let it stand and settle, then separate the sensitization solution, and wash the powder 3 times with deionized water for later use. (3) Activation: Dissolve 0.1 g of PdCl2 in 20 ml of HCl at room temperature, mix and add 1 L of deionized water. Add the activated powder to the solution, stir for 4 min, let it stand to settle and separate the activation solution. Wash the powder with deionized water 3 times and set aside for use. (4) Drying: The activated powder is dried in a vacuum drying oven and set aside for later use; (5) Electroless nickel plating: The specific steps are as follows: 1) Pour 100 g of Na3C6H3O2•7H2O (complexing agent) into 500 ml of deionized water and dissolve it completely to obtain the first solution; 2) Pour 60 g of Ni2SO4•6H2O (main salt) into 500 ml of deionized water, dissolve it completely, then pour it into the first solution to obtain the second solution, and stir thoroughly. 3) Dissolve 54g of H3BO3 in 500ml of deionized water, then pour the solution into the second solution to obtain the third solution, and stir thoroughly. 4) Finally, pour 50g of NaH2PO2 into 500ml of deionized water and dissolve it completely. Then pour the solution into the third solution to obtain the fourth solution and stir thoroughly. 5) After the above fourth solution is mixed evenly, adjust the pH value of the solution to 12, heat the solution in a water bath to 80°C, add the dried powder from step (4) to the solution, stir with an electric stirrer for 80 min, filter the solution after the end, and wash the chemically plated powder three times with deionized water and dry it for later use.

[0079] In this embodiment, the Ni-plated powder was uneven, some particles were not successfully plated with Ni, the sphericity of the remaining Ni-plated powder was ≤60%, the powder particles were in large clusters, and the powder flowability was 30 s / 50g.

[0080] Step 3, process the surface of the laser cladding substrate: This embodiment uses gun steel plate as the substrate; the specific processing method is as follows: 1) Use 1000#~2000 SiC sandpaper to polish the substrate surface until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0081] 2) Clean the polished substrate with anhydrous ethanol as a cleaning agent. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0082] Step 4, laser cladding The Ni-coated refractory high-entropy alloy powder prepared in step 2 above was loaded into a powder feeder. The laser cladding parameters were set as follows: synchronous continuous powder feeding, laser power of 3500W, scanning speed of 20mm / s, cladding overlap rate of 40%, argon gas flow rate of 15L / min, and powder feeding speed of 15g / min. No preheating of the substrate was performed during the experiment, and laser cladding was conducted in an atmospheric environment. The final laser-clad coating had a rough surface, lacked metallic luster, and showed macroscopically visible cracking. Figure 10 As shown.

[0083] This invention employs electroless nickel plating to coat a uniform and dense Ni coating layer onto the surface of refractory high-entropy alloy powder (such as WMoTaNb). The thickness of the Ni coating layer is controlled between 0.5 and 5 μm. After electroless nickel plating, the refractory high-entropy alloy powder maintains a high sphericity (>90%), low O and C content, and good flowability (8~15 s / 50g). This coated powder is not only suitable for laser cladding but can also be used in advanced manufacturing technologies such as additive manufacturing (3D printing) and thermal spraying, thus broadening the application scope of this material in the engineering field.

[0084] The laser cladding coating obtained by this invention exhibits macroscopic defects-free structure, dense microstructure, high bonding strength, and excellent performance. The effects of Ni coating with the refractory high-entropy alloy described in this invention on laser cladding coatings are as follows: 1) It prevents the outward diffusion of refractory high-entropy alloy elements, ensuring that the coating's performance does not decline due to dilution; it effectively prevents the formation of brittle phases and impurity phases by the combination of coating elements and matrix elements, thus avoiding the generation of coating cracks and quality degradation; 2) It enhances oxidation resistance; Ni has excellent high-temperature oxidation resistance, which can reduce powder oxidation during cladding; it also improves interfacial bonding; 3) The Ni coating layer can react with matrix elements to generate a Ni-rich soft phase, acting as a "buffer layer" to alleviate thermal stress concentration; the Ni soft phase improves the fracture toughness of the coating and reduces the tendency to crack. In this invention, a refractory high-entropy alloy with the expression of WaMobTacXd is selected, where X is selected from one or two of Nb, Ti, V, Zr, and Hf; the atomic percentages satisfy 15% ≤ a, b, c ≤ 50%, 0% < d ≤ 50%, and a + b + c + d = 100%; the preparation method is vacuum induction melting + plasma rotating electrode process (PREP) to obtain powders with high sphericity and low oxygen content.

[0085] In the electroless nickel plating of this invention, in order to improve the surface activity of the refractory high-entropy alloy powder to make the coated Ni layer dense, uniform and not fall off, an HF+KF mixed solution, a SnCl2 / HCl solution and a PdCl2 / HCl solution are used successively, and three-step pretreatment of roughening, sensitization and activation provides good catalytic sites for subsequent electroless plating; finally, Ni deposition is completed in a plating solution containing NiSO4, NaH2PO2, H3BO3 and a complexing agent; among them, by controlling the pH value to be 7-11, the temperature to be 35-75 °C, and the stirring time to be 20-70 min, the coating thickness of the Ni layer is precisely controlled. After coating, the powders maintain good dispersibility and do not agglomerate or cluster; the Ni layer adheres firmly to the powder surface and is not easy to fall off after long-term storage; Before laser cladding, the surface of the gun steel substrate is polished with SiC sandpaper, polished and ultrasonically cleaned to remove the oxide film and oil stains, improve the interfacial bonding force, and clean the surface to promote the metallurgical bonding between the molten powder and the substrate; reduce the pollution source, remove the surface oxides and impurities, and prevent them from entering the molten pool and causing defects. Select an appropriate process, set the laser power to 600-3000 W; the scanning speed to 5-30 mm / s; the spot diameter to 1-7 mm; the overlapping rate to 30%-70%; the powder feeding speed to 5-30 g / min; the protective gas flow rate to 10-25 L / min; preheat the substrate to 200-400 °C during cladding, which helps to ease the temperature gradient and reduce thermal strain; improve the forming quality temperature; in order to reduce the influence of impurities, strictly control the O and N contents to avoid the generation of cracks caused by oxide inclusions, and the oxygen concentration in the cladding environment ≤ 200 ppm. Finally, a refractory high-entropy alloy coating is cladded on the gun steel surface in a synchronous powder feeding manner under the protection of an inert atmosphere.

[0086] The coating is composed of a Ni-rich soft phase and a BCC-structured hard phase; the coating thickness is controlled to be 0.5-1.5 mm; the structure is dense, without cracks, brittle phases and impurity phases, achieving the synergistic optimization effect of quality and performance; among them, the soft phase improves toughness, and the hard phase maintains high strength and hardness; extends the service life and is suitable for long-term service in extreme environments.

[0087] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for preparing a laser cladding coating using Ni-coated refractory high-entropy alloy powder, characterized in that, It includes, Step 1: Prepare refractory high-entropy alloy powder, wherein the expression for the refractory high-entropy alloy is W. a Mo b Ta c X d Where X is any one or two of Nb, Ti, V, Zr, and Hf; a, b, c, and d are atomic percentages, 15%≤a≤50%, 15%≤b≤50%, 15%≤c≤50%, 0%<d≤50%, and a+b+c+d=100%. After weighing the corresponding elemental substances according to the atomic ratio of the refractory high entropy alloy, the refractory high entropy alloy ingot is obtained by vacuum induction suspension melting method. The refractory high entropy alloy ingot is processed into rods by electrical discharge wire cutting technology, and then the rods are made into refractory high entropy alloy powder by plasma rotating electrode method. Step 2: Prepare Ni-coated refractory high-entropy alloy powder, wherein nickel is uniformly coated on the outer surface of the refractory high-entropy alloy powder by chemical plating to form Ni-coated refractory high-entropy alloy powder, which is a core-shell type composite powder. Step 3: Process the surface of the laser cladding substrate, including grinding, polishing and ultrasonic cleaning of the substrate surface to remove oxides and impurities; Step 4, laser cladding: The Ni-coated refractory high-entropy alloy powder is used as the cladding material. Laser cladding technology is used to clad the cladding material onto the surface of the substrate in an inert atmosphere by synchronous powder feeding, and a refractory high-entropy alloy coating is formed on the surface of the substrate.

2. The method according to claim 1, characterized in that, Preferably, in step 2, the electroless plating method includes, For roughening, 1-5 g of KF is mixed with 1 L of deionized water at room temperature and stirred evenly. Then, 20-50 ml of HF is added and mixed. 20-70 g of refractory high-entropy alloy powder is added to the solution and stirred for 3-5 min. After standing and settling, the roughened liquid is separated and the powder is washed with deionized water 3-5 times for later use.

3. The method according to claim 1, characterized in that, In step 4, the Ni-coated refractory high-entropy alloy powder is loaded into the powder feeder; Set the laser cladding process parameters as follows: laser power 600~3000W, scanning speed 5~30 mm / s, spot diameter 1~7mm, overlap rate 30%~70%, powder feeding speed 5~30 g / min, protective gas flow rate 10~25 L / min.

4. The method according to claim 3, characterized in that, The substrate is a steel substrate, the protective gas is argon, and the laser cladding is carried out in a closed atmosphere chamber to isolate O and N elements in the air.

5. The method according to claim 1, characterized in that, The particle size of the refractory high-entropy alloy powder is 15~53μm.

6. The method according to claim 1, characterized in that, The nickel layer thickness of the core-shell composite powder is 0.5~5μm.

7. The method according to claim 1, characterized in that, The Ni-coated refractory high-entropy alloy powder has a uniform Ni layer on its surface without clustering, and a flowability of 8~15 s / 50 g.

8. A refractory high-entropy alloy coating, characterized in that, It is made by the method according to any one of claims 1-7.

9. The refractory high-entropy alloy coating according to claim 8, characterized in that, The thickness of the refractory high-entropy alloy coating is 0.5~1.5mm.

10. The refractory high-entropy alloy coating according to claim 8, characterized in that, The hardness of the refractory high-entropy alloy coating is 850 HV. 0.2 .

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