Method for improving quality of laser cladding refractory high-entropy alloy coating

Abstract

The invention discloses a method for improving the quality of a laser cladding refractory high-entropy alloy coating, and belongs to the technical field of alloy coatings. The refractory high-entropy alloy coating is composed of WMoTaNb and hydride of Ti or V, the refractory high-entropy alloy coating is a single BCC phase, and the refractory high-entropy alloy coating is prepared through coaxial powder feeding laser cladding. The laser cladding refractory high-entropy alloy coating prepared through an introduction method (solid solution strengthening and in-situ deoxidation) has excellent wear resistance and high-temperature oxidation resistance, the quality and performance of the refractory high-entropy alloy coating are improved through additional powder, and the microhardness of the section of the refractory high-entropy alloy coating reaches up to 674.52 HV0. 2. The coating can be applied to the fields of aerospace, nuclear reactors and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy coatings, and in particular to a method for improving the quality of laser cladding refractory high-entropy alloy coatings. Background Art

[0002] High-entropy alloys (HEAs) are alloys with a primary element ratio of 5 or more and a mixing entropy greater than 1.5R. Due to their unique structure and multi-element composition, HEAs exhibit higher strength, wear resistance, and ductility than traditional alloys. A recently developed class of new metallic materials with exceptional physical, magnetic, chemical, and mechanical properties, HEAs hold great potential for application in aerospace, electronics, chemical engineering, and nuclear reactors.

[0003] In recent years, with the rapid advancement of aerospace technology, higher demands have been placed on material performance. Refractory high-entropy alloys (HEAs) with a single-phase BCC structure have garnered increasing attention. Their excellent mechanical properties, high-temperature resistance, and corrosion resistance make them suitable for engine components, structural materials, high-temperature alloys, and functional components. These properties have made HEAs a key area of research in aerospace materials, providing new insights into the design of materials for next-generation aircraft and spacecraft. With the continued advancement of HEA research, their application in surface engineering has become a research hotspot in recent years. HEAs are expected to be an ideal means of enhancing the specific surface area of critical components in equipment designed for extreme environments, such as wear, corrosion, and heat resistance. Currently, research on HEA coating preparation methods focuses primarily on vapor deposition, thermal spraying, electrochemical deposition, and laser cladding. Laser cladding offers advantages in modern manufacturing, including high precision, high utilization rate, versatility, and environmental friendliness. Furthermore, unlike traditional welding or coating techniques, laser cladding has minimal thermal impact on the substrate, reducing the risk of thermal deformation and damage. Laser cladding technology involves applying laser radiation to a powder substrate, rapidly solidifying it and creating a metallurgical bond, thereby improving various surface properties of the substrate material. Combining the advantages of laser cladding with refractory high-entropy alloys, high-performance coatings can be produced for use in a variety of demanding service environments.

[0004] Prior art CN202410189659.X discloses a preparation process for a wear-resistant, high-temperature softening-resistant high-entropy alloy coating. The coating is prepared on a high-speed steel substrate by utilizing the small difference in thermal expansion coefficient between the coating and the substrate and the high bonding strength. However, the process has certain limitations and requires the thermal expansion coefficients of the substrate and the coating to be adapted, and is only applicable to specific powders and substrates. Prior art CN202111347661.8 discloses a high-performance refractory high-entropy alloy coating prepared on the surface of a titanium alloy, which adopts laser cladding with pre-powdering, but the coating prepared by this process has poor surface morphology and takes a long time, resulting in a large waste of powder. Prior art CN202210373670.2 discloses a preparation method for a refractory high-entropy alloy composite coating. There are a matrix phase and a ceramic phase in this coating. The coating exhibits good mechanical properties and high-temperature wear resistance through the strengthening effect of the ceramic phase, but this coating generates a mixed phase and cannot guarantee the singleness of the phase. The coating produced by this patent has a phase structure of single-phase BCC. The coating with a single-phase BCC structure has the advantages of high strength, good corrosion resistance, good formability and phase stability. The phase change under certain special conditions is more stable than other non-single-phase structural materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for improving the quality of laser cladding refractory high-entropy alloy coatings to solve the above-mentioned problems. Through the synergistic effect of solid solution strengthening and in-situ deoxidation, the coating quality of refractory high-entropy alloys is improved, the prepared coating structure is uniform, the metallurgical bonding between the coating and the substrate is good, there are no obvious defects such as holes and cracks, and it has excellent mechanical properties.

[0006] To achieve the above object, the present invention discloses a method for improving the quality of laser cladding refractory high entropy alloy coating, comprising the following steps: (1) Pre-treating the substrate to remove the oxide film and impurities on the surface of the substrate to obtain a pre-treated substrate; (2) Preparing refractory high entropy alloy powder and hydride powder; the composition expression of the refractory high entropy alloy powder is W a Mo b Ta c Nb d ; wherein a, b, c, and d are the atomic percentages of W, Mo, Ta, and Nb, respectively; 0%≤a≤50%, 0%≤b≤50%, 0%≤c≤50%, 0≤d≤50%; and a+b+c+d=100%; the hydride powder is titanium hydride or vanadium hydride; (3) Mixing refractory high entropy alloy powder and hydride powder, using the mixed powder as a cladding coating material, and using laser cladding technology to clad the mixed powder on the surface of the pretreated substrate in an inert atmosphere in a synchronous powder feeding manner to obtain a refractory high entropy alloy coating.

[0007] Preferably, in step (1), the substrate is any one of a steel substrate, a titanium alloy substrate or a nickel alloy substrate.

[0008] Preferably, in step (2), the composition expression of the refractory high entropy alloy powder is W a Mo b Ta c Nb d In the equation (a), a:b:c:d=1:1:1:1.

[0009] Preferably, in step (3), the particle size of the mixed powder is 10-150 μm, and the molar ratio between the refractory high entropy alloy powder and the hydride powder in the mixed powder is 1:1.

[0010] Preferably, in step (3), the power of laser cladding is: 700W-3600W, the spot diameter is 1-10mm, the scanning speed is 5-30mm / s, the cladding overlap rate is 40%-70%, the powder feeding speed is 0.5-2.5r / min, and the gas flow rate is 5-15L / min.

[0011] Preferably, in step (3), the refractory high entropy alloy powder and the rare earth hydride powder are mixed using a V-type vacuum powder mixer, the mixing time is 4-8 hours, the mixer speed is 20-100 rpm, and the mixer rotates forward for 15 minutes and reverse for 15 minutes during mixing, and pauses for 5 minutes every 30 minutes of mixing.

[0012] Preferably, in step (2), the preparation of the refractory high entropy alloy powder comprises the following steps: weighing the corresponding elemental substances according to the atomic ratio, preparing a refractory high entropy alloy ingot by a vacuum suspension melting method, then cutting the obtained refractory high entropy alloy ingot into rods of actual required size by using electric spark wire cutting technology, and preparing the rods into refractory high entropy alloy powder by using a plasma rotating electrode method; The parameters of the plasma rotating electrode method are: electrode rotation speed of 45000-55000r / min, plasma electrode power of 110-130kW, and refractory high entropy alloy powder with a particle size of 10-90μm can be obtained.

[0013] Preferably, in step (2), the preparation of the hydride powder comprises the following steps: acid-washing, alkali-washing, and drying the raw metal chips, placing them in a hydrogenation furnace, introducing hydrogen, and hydrogenating them at a pressure of 1.0-2.0 MPa for 30-60 minutes at a hydrogenation temperature of 450-700°C, cooling, and ball milling. Because the titanium chips selected as the raw material have a limited single hydrogenation depth, they need to be subjected to secondary hydrogenation after ball milling. The secondary hydrogenation temperature is 450-700°C, the hydrogenation pressure is 0.5-5 MPa, the hydrogenation time is 1-10 hours, and wet milling is performed for 1-6 hours to obtain a hydride powder with a particle size of 25-150 μm.

[0014] Preferably, the refractory high entropy alloy coating prepared in step (3) has a single BCC solid solution structure.

[0015] Therefore, the present invention has the following beneficial effects: The present invention adds hydride powder to the refractory high entropy alloy powder without changing the structure of the original powder cladding into the coating, and does not generate other solid solutions, and remains a single-phase BCC. For example, when TiH2 powder is added, the TiH2 powder will decompose into Ti and H2 in the molten state, wherein the Ti atoms are solid-solution bonded with WMoTaNb to form WMoTaNbTi, which has the same structure as WMoTaNb and remains a single-phase BCC. The effect of Ti improves the strength and corrosion resistance of the coating, and in the laser cladding process of the refractory high entropy alloy, due to its fast cooling and heating characteristics, the refractory high entropy alloy is very easy to adsorb O, resulting in a significant decrease in performance. At this time, H2 will inhibit the adsorption of O by the refractory high entropy alloy during the cladding process, preventing the coating from generating other oxides, thereby improving the coating's strength and plasticity and making it less prone to cracking. Ti and H2 both synergistically improve the quality and performance of the coating. In the laser cladding process, the coating is prepared on the substrate by using synchronous powder feeding laser cladding, and the wear resistance and high-temperature oxidation resistance of the coating are greatly improved. The coating prepared by mixing the two powders has a uniform structure, forms a good metallurgical bond with the substrate, and has no obvious defects such as holes and cracks. The obtained refractory high entropy alloy coating has excellent mechanical properties, making the microhardness of the cross section of the refractory high entropy alloy coating as high as 674.52HV 0.2 .

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the XRD spectrum of the mixed powder of the refractory high entropy alloy powder and XH2 powder prepared in Example 1.

[0018] Figure 2 This is the SEM image of the mixed powder of the refractory high entropy alloy powder and XH2 powder prepared in Example 1.

[0019] Figure 3 This is an SEM image of the cross section of the refractory high entropy alloy coating prepared in Example 1.

[0020] Figure 4 These are the flaw detection images of the refractory high entropy alloy coating prepared in Example 1, where a is the flaw detection image before penetrant testing, and b is the flaw detection image after penetrant testing.

[0021] Figure 5 This is the XRD spectrum of the surface layer of the refractory high entropy alloy coating prepared in Example 1.

[0022] Figure 6 This is an SEM image of the cross section of the refractory high entropy alloy coating prepared in Comparative Example 3. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further illustrated by the following examples.

[0024] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0025] Furthermore, it should be understood that although this specification describes the embodiments, not every embodiment includes only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in the various embodiments may also be appropriately combined to form other embodiments that are understandable to those skilled in the art. These other embodiments are also encompassed within the scope of protection of the present invention.

[0026] Example 1 This embodiment provides a method for improving the quality of laser-clad refractory high-entropy alloy coatings. The quality of the refractory high-entropy alloy coatings is improved through the synergistic effect of solid solution strengthening and in-situ deoxidation. The preparation method is as follows: Step 1, steel substrate surface pretreatment: a. Use 80#, 120#, and 240# sandpaper to polish the surface of the steel substrate in sequence. When the surface of the steel substrate reveals a metallic luster, the surface oxide film is considered to have been removed.

[0027] b. Spray anhydrous ethanol onto the surface of the polished steel substrate and wipe it with a dust-free cloth. Then, place the steel substrate in anhydrous ethanol and ultrasonically clean it for 20 minutes. Finally, place it in a 40°C oven and dry it for 10 minutes to obtain a pretreated steel substrate.

[0028] Step 2: preparing a mixed powder of refractory high entropy alloy powder and hydride powder: WMoTaNb powder is weighed with corresponding elemental single substances according to atomic ratio, and a refractory high-entropy alloy ingot is prepared by vacuum suspension melting. The obtained refractory high-entropy alloy ingot is then cut into rods of actual required size using electric spark wire cutting technology. The rods are then prepared into refractory high-entropy alloy powder using a plasma rotating electrode method; the parameters of the plasma rotating electrode method are: electrode rotation speed of 45,000 r / min, plasma electrode power of 110-130 kW, and refractory high-entropy alloy powder with a particle size of 10-90 μm can be obtained.

[0029] The preparation of TiH2 powder includes the following steps: pickling, alkali washing, and drying metal titanium chips, placing them in a hydrogenation furnace, introducing hydrogen, hydrogenating them at 600°C and controlling the pressure at 1.0 MPa for 30-60 minutes, cooling, ball milling, and secondary hydrogenation at a temperature of 600°C, a hydrogenation pressure of 0.5-5 MPa, a hydrogenation time of 1-10 hours, and wet grinding for 1-6 hours to obtain hydride powder with a particle size of 25-150 μm.

[0030] WMoTaNb powder and TiH2 powder are weighed according to the atomic ratio of W:Mo:Ta:Nb:Ti=1:1:1:1:1, and the powder purity is ≥99.99%. WMoTaNb powder is spherical powder, and TiH2 powder is irregular powder. The mixing time of a V-type vacuum powder mixer is 4 hours, the speed of the powder mixer is 20 rpm, and the mixing is forward for 15 minutes and reverse for 15 minutes, and a pause of 5 minutes is made every 30 minutes of mixing to obtain the cladding powder.

[0031] Step 3, laser cladding: The refractory high-entropy alloy powder prepared in the above step 2 was dried and loaded into a powder barrel. The laser cladding parameters were set as follows: synchronous powder feeding, laser power 700 W, scanning speed 5 mm / s, cladding overlap rate 40%, nitrogen gas flow rate 5 L / min, and powder feeding speed 0.5 r / min. Under argon atmosphere, the refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a cladding layer.

[0032] Step 4: Coating hardness test First, the refractory high-entropy alloy coating prepared in step 3 above was prepared into a 6×6×5 mm sample using wire cutting. Then, the sample cross section was processed and polished in sequence using 240#, 400#, 600#, 800#, 1000#, 1200#, 1500#, and 2000# sandpaper, respectively. Diamond grinding liquid was used to polish it on a polishing machine until a mirror effect appeared. Finally, the hardness was tested using a Vickers hardness tester with a load of 200 g and a load time of 15 s.

[0033] like Figure 4 The laser cladding refractory high entropy alloy coating prepared in this embodiment is shown. Figure 4 A and Figure 4 From the image b, we can see that the coating surface morphology is good and the coating is uniform and neat. From the non-destructive testing image, we can see that the coating has no obvious defects such as cracks and holes.

[0034] Example 2 This embodiment provides a method for improving the quality of laser-clad refractory high-entropy alloy coatings. The quality of the refractory high-entropy alloy coatings is improved through the synergistic effect of solid solution strengthening and in-situ deoxidation. The preparation method is as follows: This embodiment provides a method for synergistically improving the quality of laser cladding refractory high-entropy alloy coatings by solid solution strengthening and in-situ deoxidation as follows: Step 1, titanium alloy substrate surface pretreatment: a. Use 80#, 120#, and 240# sandpaper to polish the surface of the titanium alloy substrate in sequence. When the surface of the titanium alloy substrate reveals a metallic luster, the surface oxide film can be considered removed.

[0035] b. Spray anhydrous ethanol onto the surface of the polished titanium alloy substrate and wipe it with a dust-free cloth. Then, place the titanium alloy substrate in anhydrous ethanol and ultrasonically clean it for 20 minutes. Finally, place it in a 40°C oven and dry it for 10 minutes to obtain the pretreated titanium alloy substrate.

[0036] Step 2: preparing a mixed powder of refractory high entropy alloy powder and hydride powder: WMoTaNb powder is weighed with corresponding elemental single substances according to atomic ratio, and a refractory high-entropy alloy ingot is prepared by vacuum suspension melting. The obtained refractory high-entropy alloy ingot is then cut into rods of actual required size by wire electric discharge cutting technology. The rods are made into refractory high-entropy alloy powder by a plasma rotating electrode method. The parameters of the plasma rotating electrode method are: electrode rotation speed of 45000r / min, plasma electrode power of 110-130kW, and refractory high-entropy alloy powder with a particle size of 10-90μm can be obtained.

[0037] The preparation of VH2 powder includes the following steps: pickling, alkali washing, and drying the metal vanadium chips, placing them in a hydrogenation furnace, introducing hydrogen, and hydrogenating them at a temperature of 500°C and a pressure of 1.0 MPa for 30-60 minutes, cooling, ball milling, and secondary hydrogenation at a temperature of 600°C, a hydrogenation pressure of 2 MPa, and a hydrogenation time of 5 hours. Wet milling for 1-6 hours obtains hydride powder with a particle size of 25-150 μm.

[0038] WMoTaNb powder and VH2 powder are weighed according to the atomic ratio of W:Mo:Ta:Nb:V=1:1:1:1:1, the powder purity is ≥99.99%, the WMoTaNb powder is spherical powder, and the VH3 powder is irregular powder. The mixing time of the powder is 8 hours using a V-type vacuum powder mixer, the speed of the powder mixer is 80 rpm, and the powder mixing is forward for 15 minutes and reverse for 15 minutes, and the powder mixing is paused for 5 minutes every 30 minutes to obtain the cladding powder.

[0039] Step 3, laser cladding: The mixed powder prepared in step 2 above was dried and loaded into a powder barrel. The laser cladding parameters were set as follows: synchronous powder feeding, laser power of 3600 W, scanning speed of 30 mm / s, cladding overlap rate of 70%, nitrogen gas flow rate of 15 L / min, and powder feeding speed of 2.5 r / min. Under an argon atmosphere, the refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a cladding layer.

[0040] Example 3 This embodiment provides a method for improving the quality of laser-clad refractory high-entropy alloy coatings. The quality of the refractory high-entropy alloy coatings is improved through the synergistic effect of solid solution strengthening and in-situ deoxidation. The preparation method is as follows: This embodiment provides a method for synergistically improving the quality of laser cladding refractory high-entropy alloy coatings by solid solution strengthening and in-situ deoxidation as follows: Step 1, nickel-based alloy substrate surface pretreatment: a. Use 80#, 120#, and 240# sandpaper to polish the surface of the nickel-based alloy substrate in sequence. When the surface of the nickel-based alloy substrate reveals a metallic luster, the surface oxide film can be considered removed.

[0041] b. Spray anhydrous ethanol onto the polished surface of the nickel-based alloy substrate and wipe it with a dust-free cloth. Then, place the nickel-based alloy substrate in anhydrous ethanol and ultrasonically clean it for 20 minutes. Finally, place it in a 40°C oven and dry it for 10 minutes to obtain the pretreated nickel-based alloy substrate.

[0042] Step 2: preparing a mixed powder of refractory high entropy alloy powder and hydride powder: WMoTaNb powder is weighed with corresponding elemental single substances according to atomic ratio, and a refractory high-entropy alloy ingot is prepared by vacuum suspension melting. The obtained refractory high-entropy alloy ingot is then cut into rods of actual required size using electric spark wire cutting technology. The rods are then prepared into refractory high-entropy alloy powder using a plasma rotating electrode method; the parameters of the plasma rotating electrode method are: electrode rotation speed of 45,000 r / min, plasma electrode power of 110-130 kW, and refractory high-entropy alloy powder with a particle size of 10-90 μm can be obtained.

[0043] The preparation of the hydride powder includes the following steps: acid-washing, alkali-washing, and drying metal chips. The metal chips are then placed in a hydrogenation furnace, where hydrogen is introduced at 700°C and a pressure of 1.0 MPa for 30-60 minutes. The metal chips are then cooled, ball-milled, subjected to secondary hydrogenation, and wet-milled for 1-6 hours to obtain a hydride powder with a particle size of 25-150 μm. The metal chips are titanium or vanadium.

[0044] WMoTaNb powder and VH2 and TiH2 powders are weighed according to the atomic ratio of W:Mo:Ta:Nb:V:Ti=1:1:1:1:1:1, and the powder purity is ≥99.99%. WMoTaNb powder and TiH2 are spherical powders, and VH3 powder is irregular powder. The mixing time of a V-type vacuum powder mixer is 6 hours, the mixer speed is 70 rpm, and the mixing is forward for 15 minutes and reverse for 15 minutes, and a pause of 5 minutes is made every 30 minutes of mixing to obtain the cladding powder.

[0045] Step 3, laser cladding: The refractory high-entropy alloy powder prepared in the above step 2 was dried and loaded into a powder tube. The laser cladding parameters were set as follows: synchronous powder feeding, laser power 2000 W, scanning speed 15 mm / s, cladding overlap rate 60%, nitrogen gas flow rate 10 L / min, and powder feeding speed 1.5 r / min. Under argon atmosphere, the refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a cladding layer.

[0046] Comparative Example 1 This comparative example provides a method for synergistically improving the quality of laser cladding refractory high entropy alloy coatings by solid solution strengthening and in-situ deoxidation as follows: Step 1, steel substrate surface pretreatment: a. Use 80#, 120#, and 240# sandpaper to polish the surface of the steel substrate in sequence. When the surface of the steel substrate reveals a metallic luster, the surface oxide film is considered to have been removed.

[0047] b. Spray anhydrous ethanol onto the surface of the polished steel substrate and wipe it with a dust-free cloth. Then, place the steel substrate in anhydrous ethanol and ultrasonically clean it for 20 minutes. Finally, place it in a 40°C oven and dry it for 10 minutes to obtain a pretreated steel substrate.

[0048] Step 2: preparing a mixed powder of refractory high entropy alloy powder and hydride powder: The preparation process of refractory high entropy alloy powder and hydride powder is the same as that in Example 1.

[0049] WMoTaNb powder and TiH2 powder are weighed according to the atomic ratio of W:Mo:Ta:Nb:Ti=1:1:1:1:1.5. The powder purity is ≥99.99%. WMoTaNb powder is spherical powder and TiH2 powder is irregular powder. The mixing time of a V-type vacuum powder mixer is 4 hours, the speed of the powder mixer is 20 rpm, and the mixing is forward for 15 minutes and reverse for 15 minutes, and a pause of 5 minutes is made every 30 minutes of mixing to obtain the cladding powder.

[0050] Step 3, laser cladding: The refractory high-entropy alloy powder prepared in the above step 2 was dried and loaded into a powder tube. The laser cladding parameters were set as follows: synchronous powder feeding, laser power of 1100 W, scanning speed of 5 mm / s, cladding overlap rate of 50%, nitrogen gas flow rate of 5 L / min, and powder feeding speed of 0.5 r / min. Under an argon atmosphere, the refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a cladding layer.

[0051] However, during the cladding process, the powder fluidity was poor and the powder flow was uneven.

[0052] Comparative Example 2 This comparative example provides a method for synergistically improving the quality of laser cladding refractory high entropy alloy coatings by solid solution strengthening and in-situ deoxidation as follows: Step 1, steel substrate surface pretreatment: a. Use 80#, 120#, and 240# sandpaper to polish the surface of the steel substrate in sequence. When the surface of the steel substrate is polished to reveal the metallic luster, the surface oxide film is considered to be removed.

[0053] b. Spray anhydrous ethanol onto the surface of the polished steel substrate and wipe it with a dust-free cloth. Then, place the steel substrate in anhydrous ethanol and ultrasonically clean it for 20 minutes. Finally, place it in a 40°C oven and dry it for 10 minutes to obtain a pretreated steel substrate.

[0054] Step 2: preparing a mixed powder of refractory high entropy alloy powder and hydride powder: The preparation process of the refractory high entropy alloy powder is the same as that of Example 1, and the preparation process of the hydride powder is the same as that of Example 1, except that titanium is replaced by chromium.

[0055] WMoTaNb powder and CrH3 powder are weighed according to the atomic ratio of W:Mo:Ta:Nb:Cr=1:1:1:1:1, and the powder purity is ≥99.99%. WMoTaNb powder is spherical powder, and CrH3 powder is irregular powder. The mixing time of a V-type vacuum powder mixer is 4 hours, the speed of the powder mixer is 20 rpm, and the mixing is forward for 15 minutes and reverse for 15 minutes, and a pause of 5 minutes is made every 30 minutes of mixing to obtain the cladding powder.

[0056] Step 3, laser cladding: The refractory high-entropy alloy powder prepared in the above step 2 was dried and loaded into a powder tube. The laser cladding parameters were set as follows: synchronous powder feeding, laser power of 1100 W, scanning speed of 5 mm / s, cladding overlap rate of 50%, nitrogen gas flow rate of 5 L / min, and powder feeding speed of 0.5 r / min. Under an argon atmosphere, the refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a cladding layer.

[0057] Comparative Example 3 This embodiment provides a method for synergistically improving the quality of laser cladding refractory high-entropy alloy coatings by solid solution strengthening and in-situ deoxidation as follows: Step 1, steel substrate surface pretreatment: a. Use 80#, 120#, and 240# sandpaper to polish the surface of the steel substrate in sequence. When the surface of the steel substrate is polished to reveal the metallic luster, the surface oxide film is considered to be removed.

[0058] b. Spray anhydrous ethanol onto the surface of the polished steel substrate and wipe it with a dust-free cloth. Then, place the steel substrate in anhydrous ethanol and ultrasonically clean it for 20 minutes. Finally, place it in a 40°C oven and dry it for 10 minutes to obtain a pretreated steel substrate.

[0059] Step 2: preparing a mixed powder of refractory high entropy alloy powder and hydride powder: The preparation process of the refractory high entropy alloy powder is the same as that of Example 1, and the preparation process of the hydride powder is the same as that of Example 1.

[0060] WMoTaNb powder and TiH2 powder are weighed according to the atomic ratio of W:Mo:Ta:Nb:Ti=1:1:1:1:1, and the powder purity is ≥99.99%. WMoTaNb powder is spherical powder, and TiH2 powder is irregular powder. The mixing time of a V-type vacuum powder mixer is 4 hours, the speed of the powder mixer is 20 rpm, and the mixing is forward for 15 minutes and reverse for 15 minutes, and a pause of 5 minutes is made every 30 minutes of mixing to obtain the cladding powder.

[0061] Step 3, laser cladding: The refractory high-entropy alloy powder prepared in the above step 2 was dried and loaded into a powder barrel. The laser cladding parameters were set as follows: synchronous powder feeding, laser power 4000 W, scanning speed 35 mm / s, cladding overlap rate 50%, nitrogen gas flow rate 5 L / min, and powder feeding speed 0.5 r / min. Under argon atmosphere, the refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a cladding layer.

[0062] Implementation Counterexample 1 This embodiment provides a laser cladding high-performance refractory high-entropy alloy powder, coating and preparation method thereof, and the preparation method is as follows: Step 1, substrate surface pretreatment: a. Use 80#, 120#, and 240# sandpaper to polish the substrate surface in sequence. When the metallic luster is exposed on the substrate surface, the surface oxide film is considered to be removed.

[0063] b. Spray anhydrous ethanol onto the polished surface of the substrate and wipe it with a dust-free cloth. Then, place the substrate in anhydrous ethanol and clean it ultrasonically for 20 minutes. Finally, place it in a 40°C oven and dry it for 10 minutes to obtain a pretreated substrate.

[0064] Step 2: Select refractory high entropy alloy powder: The preparation process of the refractory high entropy alloy powder is the same as that in Example 1. 200 g of WMoTaNb powder with a purity of ≥99.99% is used. The WMoTaNb powder is spherical.

[0065] Step 3, laser cladding: The refractory high entropy alloy powder prepared in step 2 was dried and loaded into a powder barrel. The laser cladding parameters were set as follows: synchronous powder feeding, laser power of 1400 W, scanning speed of 10 mm / s, cladding overlap rate of 50%, nitrogen gas flow rate of 15 L / min, and powder feeding speed of 1.2 r / min. Under an argon atmosphere, the refractory high entropy alloy powder was deposited on the pretreated substrate surface to form a cladding layer.

[0066] In this counterexample, since the refractory high-entropy alloy elements are easily combined with the O element during the laser cladding process, the prepared coating has defects such as cracks and pores, which reduces the performance of the coating and cannot solve the actual engineering problem.

[0067] The refractory high entropy alloy coatings prepared in the above examples and comparative examples were characterized and tested for performance, and the results are as follows: (1) XRD test Taking the refractory high entropy alloy powder prepared in Example 1 and the refractory high entropy alloy coating with high performance prepared in Example 1 as examples, XRD tests were performed on the surface layers of the refractory high entropy alloy powder prepared in Example 1 and the coating prepared in Example 1, and the test results were as follows: Figure 1 、 5 shown.

[0068] Figure 1 This is the XRD spectrum of the refractory high entropy alloy powder prepared in Example 1. It can be seen that the powder is composed of WMoTaNb and TiH2.

[0069] Figure 5This is the surface XRD spectrum of the refractory high entropy alloy coating prepared in Example 1. It can be seen that the refractory high entropy alloy coating is a single BCC phase.

[0070] (2) Morphology test The present invention conducted SEM tests on the cross-section and surface morphology of the refractory high entropy alloy powder prepared in Example 1 and the high entropy alloy coating prepared in Example 1, and the test results were as follows: Figure 2 、 3 shown.

[0071] Figure 2 This is an image of the refractory high entropy alloy powder prepared in Example 1. It can be seen that the refractory high entropy alloy powder prepared in Example 1 of the present invention is evenly mixed and has an average size of several tens of microns.

[0072] Figure 3 This is an SEM image of the cross section of the refractory high entropy alloy coating prepared in Example 1. It can be seen that most of the spherical particles in the coating are evenly distributed and well bonded to the substrate.

[0073] Figure 6 This is an SEM image of the cross section of the refractory high entropy alloy coating prepared in Comparative Example 3. It can be seen that using inappropriate laser power and scanning speed will cause penetrating cracks in the coating, significantly reducing the coating quality.

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for improving the quality of laser cladding refractory high entropy alloy coatings, characterized in that: The following steps are involved: (1) Pre-treating the substrate to remove the oxide film and impurities on the surface of the substrate to obtain a pre-treated substrate; (2) Preparing refractory high entropy alloy powder and hydride powder; the composition expression of the refractory high entropy alloy powder is W a Mo b Ta c Nb d ; wherein a, b, c, and d are the atomic percentages of W, Mo, Ta, and Nb, respectively; 0%≤a≤50%, 0%≤b≤50%, 0%≤c≤50%, and 0≤d≤50%; and a+b+c+d=100%; the hydride powder is any one or both of titanium hydride and vanadium hydride; (3) Mixing refractory high entropy alloy powder and hydride powder, using the mixed powder as a cladding coating material, and using laser cladding technology to clad the mixed powder on the surface of the pretreated substrate in an inert atmosphere in a synchronous powder feeding manner to obtain a refractory high entropy alloy coating.

2. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 1, characterized in that: In step (1), the substrate is any one of a steel substrate, a titanium alloy substrate or a nickel alloy substrate.

3. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 1, characterized in that: In step (2), the composition expression of the refractory high entropy alloy powder is W a Mo b Ta c Nb d In the equation (a), a:b:c:d=1:1:1:

1.

4. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 1, characterized in that: In step (3), the particle size of the mixed powder is 10-150 μm, and the molar ratio between the refractory high entropy alloy powder and the hydride powder in the mixed powder is 1:(1-2).

5. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 2, characterized in that: In step (3), the power of laser cladding is: 700W-3600W, the spot diameter is 1-10mm, the scanning speed is 5-30mm / s, the cladding overlap rate is 40%-70%, the powder feeding speed is 0.5-2.5r / min, and the gas flow rate is 5-15L / min.

6. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 1, characterized in that: In step (3), the refractory high entropy alloy powder and the rare earth hydride powder are mixed using a V-type vacuum powder mixer. The mixing time is 4-8 hours, the mixer speed is 20-100 rpm, and the mixer rotates forward for 15 minutes and reverse for 15 minutes during mixing, and pauses for 5 minutes every 30 minutes of mixing.

7. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 1, characterized in that: In step (2), the preparation of the refractory high entropy alloy powder includes the following steps: The corresponding elemental substances are weighed according to the atomic ratio, and a refractory high-entropy alloy ingot is prepared by vacuum levitation melting method, and then the obtained refractory high-entropy alloy ingot is cut into rods of actual required size by wire electric discharge cutting technology, and the rods are made into refractory high-entropy alloy powder by plasma rotating electrode method; The parameters of the plasma rotating electrode method are: electrode rotation speed of 45000-55000r / min, plasma electrode power of 110-130kW, and refractory high entropy alloy powder with a particle size of 10-90μm can be obtained.

8. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 1, characterized in that: In step (2), the preparation of the hydride powder includes the following steps: pickling, alkali washing, and drying the raw metal chips, placing them in a hydrogenation furnace, introducing hydrogen, and hydrogenating them at a pressure of 1.0-2.0 MPa for 30-60 minutes at a hydrogenation temperature of 450-700°C, cooling, ball milling, and secondary hydrogenation. The secondary hydrogenation temperature is 450-700°C, the hydrogenation pressure is 0.5-5 MPa, the hydrogenation time is 1-10 hours, and wet milling is performed for 1-6 hours to obtain a hydride powder with a particle size of 25-150 μm.

9. The method for improving the quality of laser cladding refractory high entropy alloy coating according to claim 1, characterized in that: The refractory high entropy alloy coating prepared in step (3) has a single BCC solid solution structure.

Images