A BN reinforced high-entropy alloy composite coating and a preparation method thereof

Abstract

This invention provides a BN-reinforced high-entropy alloy composite coating and its preparation method, relating to the field of surface strengthening. The preparation method includes: ball milling of B powder, including ball milling while simultaneously filling the milling jar with high-temperature nitrogen; mixed ball milling, where Al powder, Cr powder, Fe powder, and Ni powder are loaded into the milling jar and dry-milled to obtain a mixed powder; preheating of the substrate; laser cladding: loading the mixed powder into a powder feeder, then sealing the feeder and filling it with a powder-feeding gas and a protective gas, setting various laser cladding parameters, performing laser cladding every 3-5 passes to form a cladding cycle, and performing n cladding cycles; and cooling. The BN-reinforced high-entropy alloy composite coating prepared by this method exhibits a nearly 50% or even more reduction in high-temperature oxidative wear volume loss compared to commonly used Stellite alloy coatings, while the material cost is only about 75%-80% of that of Stellite alloy coatings. In other words, it offers better wear resistance and lower cost, providing a potential alternative to Stellite alloy coatings.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening technology, and more specifically, to a BN-reinforced high-entropy alloy composite coating and its preparation method. Background Technology

[0002] In existing technologies, the preparation of high-temperature wear-resistant coatings or materials using laser cladding has made significant progress and yielded many beneficial results. However, the performance of the wear-resistant coatings obtained using existing technologies still needs further improvement, and the cost needs further reduction. Therefore, the preparation of wear-resistant coatings with better performance and lower cost to replace commonly used coatings such as Stellite alloy coatings has important innovative value and engineering application significance, and has become one of the research directions for engineering users and researchers both domestically and internationally. Summary of the Invention

[0003] The first objective of this invention is to provide a method for preparing a BN-reinforced high-entropy alloy composite coating, in order to solve the technical problems in the prior art where the performance of wear-resistant coatings needs to be further improved and the cost needs to be further reduced.

[0004] The method for preparing BN-reinforced high-entropy alloy composite coatings provided by this invention includes the following steps:

[0005] Ball milling of B powder: The B powder weighed at a ball-to-powder ratio of 1:10 is loaded into the ball milling jar and ball milled for 5 to 10 hours. Then, while filling the ball milling jar with high-temperature nitrogen gas, ball milling continues for 15 to 30 hours. After stopping the machine and cutting off the gas supply, the ball milling jar is kept sealed and cooled.

[0006] Mixed ball milling: Al powder, Cr powder, Fe powder and Ni powder with a molar ratio of 1:1:1:1 and a total weight of 15 to 30 times that of B powder are loaded into the ball mill jar and dry milled for 2 to 5 hours. After stopping the machine, the ball mill jar is kept sealed and cooled to obtain mixed powder.

[0007] Preheating the substrate: Preheat the surface of the substrate to be melted to 200-300℃;

[0008] Laser cladding: The mixed powder is loaded into the powder feeder of the laser cladding equipment, then the powder feeder is sealed and filled with powder-feeding gas and protective gas. The laser power is set to 0.5-2kW, the defocusing amount is 18-22mm, the powder feeding rate is controlled to be 20-25g / min, the cladding speed is 100-200mm / min, and the protective gas flow rate is 0.5-1ml / min. Every 3-5 laser cladding passes form a cladding cycle, and a total of n cladding cycles are performed, where n is a natural number and 1≤n≤6.

[0009] Cooling: After laser cladding is completed, the coating is cooled to room temperature to obtain the BN-reinforced high-entropy alloy composite coating.

[0010] Optionally, the purity of the nitrogen gas is not less than 99.5%, the heating temperature is 800-950℃, and it is kept at this temperature for 1-3 minutes before being introduced into the ball mill jar.

[0011] Optionally, after each deposition cycle, the resulting coating is subjected to induction heat treatment at a temperature of 750–900°C.

[0012] Optionally, after the last laser cladding pass, the resulting coating is annealed at a heating temperature of 200–400°C.

[0013] Optionally, the purity of the B powder is not less than 99%, and the average particle size is not higher than 100 μm.

[0014] Optionally, the purity of the Al powder, the Cr powder, the Fe powder, and the Ni powder is not less than 99.5%, and the average particle size is not higher than 200 μm.

[0015] Optionally, in the step of ball milling B powder, after the B powder is loaded into the ball milling jar, the ball milling jar is subjected to vacuum treatment, and the vacuum degree is not less than 0.01 Pa;

[0016] And / or, in the step of mixing and ball milling, after the high-entropy alloy powder is loaded into the ball milling jar, the ball milling jar is subjected to vacuum treatment, and the vacuum degree is not less than 0.01 Pa.

[0017] Optionally, both the powder feeding gas and the protective gas are argon, and their purity is not less than 99.5%.

[0018] Optionally, the surface of the substrate is cleaned with anhydrous ethanol before preheating.

[0019] The method for preparing BN-reinforced high-entropy alloy composite coatings provided by this invention can produce the following beneficial effects:

[0020] The method for preparing BN-reinforced high-entropy alloy composite coatings provided by this invention, through laser cladding, produces a BN-reinforced high-entropy alloy composite coating with excellent bonding between BN and the high-entropy alloy substrate. The B element generates molten boron oxide at high temperatures, exhibiting significant friction reduction and oxidation corrosion resistance. Compared to commonly used Stellite alloy coatings, the prepared BN-reinforced high-entropy alloy composite coating reduces volume loss during high-temperature oxidative wear (e.g., wear at 800°C for 2 hours) by nearly half or even more, while the material cost is only about 75% to 80% of that of Stellite alloy coatings. In other words, the BN-reinforced high-entropy alloy composite coating preparation method provided by this invention produces a composite coating with superior wear and corrosion resistance and lower cost, demonstrating significant cost-effectiveness and providing a potential alternative to the currently used, more expensive Stellite alloy coatings.

[0021] The second objective of this invention is to provide a BN-reinforced high-entropy alloy composite coating to address the technical problems in the prior art where the performance of wear-resistant coatings needs further improvement and the cost needs further reduction.

[0022] The BN-reinforced high-entropy alloy composite coating provided by this invention is prepared using the above-described method for preparing BN-reinforced high-entropy alloy composite coatings.

[0023] The BN-reinforced high-entropy alloy composite coating provided by this invention exhibits excellent bonding between BN and the high-entropy alloy substrate. The B element generates molten boron oxide at high temperatures, demonstrating significant friction reduction and resistance to oxidation and corrosion. Compared to commonly used Stellite alloy coatings, the volume loss during high-temperature oxidative wear (e.g., 2 hours of wear at 800°C) is reduced by nearly half or even more, while the material cost is only about 75% to 80% of that of Stellite alloy coatings. In other words, the BN-reinforced high-entropy alloy composite coating provided by this invention offers superior wear and corrosion resistance at a lower cost, demonstrating a significantly high cost-performance ratio and providing a potential alternative to the currently used, more expensive Stellite alloy coating. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a photograph of the BN-reinforced high-entropy alloy composite coating obtained in Embodiment 1 of the present invention. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] This embodiment provides a method for preparing a BN-reinforced high-entropy alloy composite coating, including the following steps:

[0028] Ball milling of B powder: Weigh the B powder according to the ball-to-powder ratio of 1:10 and put it into the ball milling jar and ball mill for 5 to 10 hours. Then, while filling the ball milling jar with high-temperature nitrogen gas, ball mill for 15 to 30 hours. After stopping the machine and cutting off the gas supply, keep the ball milling jar sealed and cool it down. Furthermore, in the first stage of ball milling B powder, namely the ball milling stage without nitrogen gas, the ball milling time can be 5h, 6h, 7h, 8h, 9h, 10h, or any time between two points. In this stage, the longer the ball milling time, the finer and more uniform the B powder grains become. In the stage of ball milling while purging high-temperature nitrogen gas, the ball milling time can be 15h, 20h, 25h, 30h, or any time between two points. In this stage, the longer the ball milling time, the more fully the B powder and nitrogen react and combine, which is beneficial to improving the performance of the final composite coating. As for the degree of cooling, preferably, after the machine is stopped and the gas is cut off, the ball milling jar is cooled to room temperature, usually for 8 to 12 hours, for example, about 10 hours.

[0029] Mixed ball milling: Al powder, Cr powder, Fe powder, and Ni powder, with a molar ratio of 1:1:1:1 and a total weight of 15 to 30 times that of B powder, are loaded into a ball mill jar and dry-milled for 2 to 5 hours. After stopping the mill, the ball mill jar is kept sealed and cooled to obtain a mixed powder. Further, the total weight of the high-entropy alloy powder can be 20 to 25 times that of B powder. Specifically, the ratio of the total weight of the high-entropy alloy powder to the weight of B powder can be 15, 20, 25, 30, or any multiple between two values. Further, the mixing ball milling time can be 2.5 to 5 hours. Specifically, the mixing ball milling time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or any time between two values. As the mixing ball milling time increases, the resulting mixed powder becomes finer and more uniform. Regarding the degree of cooling, preferably, after shutdown, the mill jar is allowed to cool to room temperature, typically for 1.5 to 3 hours, for example, about 2 hours.

[0030] Preheating the substrate: Preheat the surface of the substrate to be melted to 200–300°C. Further, the surface of the substrate to be melted can be preheated to 220–280°C, and even further, to 240–260°C. Specifically, it can be preheated to 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, or any temperature between two of these values.

[0031] Laser cladding: The mixed powder is loaded into the powder feeder of the laser cladding equipment, then the powder feeder is sealed and filled with powder-feeding gas and protective gas. The laser power is set to 0.5–2 kW, the defocusing distance to 18–22 mm, the powder feed rate to 20–25 g / min, the cladding speed to 100–200 mm / min, and the protective gas flow rate to 0.5–1 ml / min. Each cladding cycle consists of 3–5 passes, and a total of n cladding cycles are performed, where n is a natural number and 1 ≤ n ≤ 6. Specifically, each cladding cycle can include 3, 4, or 5 passes, and the number of cladding cycles, n, can be 1, 2, 3, 4, 5, or 6.

[0032] Furthermore, the laser power can be 0.5kW, 1kW, 1.5kW, 2kW, or any power between two points; the defocus amount can be 18mm, 19mm, 20mm, 21mm, 22mm, or any defocus amount between two points, preferably, the defocus amount is 20mm.

[0033] Furthermore, the powder feeding rate can be 20g / min, 21g / min, 22g / min, 23g / min, 24g / min, 25g / min, or any powder feeding rate between two points; the deposition rate can be 120-180mm / min, and even further, the deposition rate can be 140-160mm / min. Specifically, the deposition rate can be 100mm / min, 110mm / min, 120mm / min, 130mm / min, 140mm / min, 150mm / min, 160mm / min, 170mm / min, 180mm / min, 180mm / min, 200mm / min, or any deposition rate between two points.

[0034] Further, the protective gas flow rate can be 0.5 ml / min, 0.6 ml / min, 0.7 ml / min, 0.8 ml / min, 0.9 ml / min, 1 ml / min, or any flow rate between two values. Preferably, in this embodiment, both the powder feeding gas and the protective gas are argon, and the purity is not less than 99.5%, more preferably, the purity is not less than 99.9%. Furthermore, it should be noted that in other embodiments of this application, other inert gases, such as krypton, can also be used for the powder feeding gas and the protective gas.

[0035] Cooling: After laser cladding is completed, the coating is cooled to room temperature to obtain a BN-reinforced high-entropy alloy composite coating.

[0036] This embodiment provides a method for preparing a BN-reinforced high-entropy alloy composite coating. The BN-reinforced high-entropy alloy composite coating, prepared by laser cladding, exhibits excellent bonding between BN and the high-entropy alloy substrate. The B element generates molten boron oxide at high temperatures, demonstrating significant friction reduction and oxidation corrosion resistance. Compared to commonly used Stellite alloy coatings, the prepared BN-reinforced high-entropy alloy composite coating reduces volume loss during high-temperature oxidative wear (e.g., wear at 800°C for 2 hours) by nearly half or even more, while the material cost is only about 75% to 80% of that of Stellite alloy coatings. In other words, the BN-reinforced high-entropy alloy composite coating preparation method provided in this embodiment produces a composite coating with superior wear and corrosion resistance at a lower cost, demonstrating significant cost-effectiveness and offering a potential alternative to the currently used, more expensive Stellite alloy coating.

[0037] Specifically, in this embodiment, the nitrogen gas has a purity of not less than 99.5%, the heating temperature is 800–950°C, and it is held at this temperature for 1–3 minutes before being introduced into the ball mill jar. Preferably, the nitrogen gas is high-purity nitrogen with a purity of not less than 99.9%. High nitrogen purity is beneficial for the full bonding of nitrogen atoms with B powder, thereby ensuring the BN content in the composite coating. The heating temperature of the nitrogen gas can be 800°C, 850°C, 900°C, 950°C, or any temperature between two values, and the holding time can be 1 minute, 2 minutes, 3 minutes, or any time between two values.

[0038] More specifically, in this embodiment, before charging the ball mill jar with high-temperature nitrogen, the nitrogen cylinder is first connected to the heating vessel, and the nitrogen flow rate is controlled at 0.1–0.5 ml / min to heat and maintain the nitrogen at that temperature. Then, the high-temperature nitrogen is charged into the ball mill jar from another port of the heating vessel. The specific flow rate of nitrogen flowing into the heating vessel can be 0.1 ml / min, 0.2 ml / min, 0.3 ml / min, 0.4 ml / min, 0.5 ml / min, or any flow rate value between two values.

[0039] Preferably, in this embodiment, after each deposition cycle, the resulting coating is subjected to induction heat treatment at a heating temperature of 750–900°C. Induction heat treatment enables better bonding between BN and the high-entropy alloy substrate, thereby improving the wear and corrosion resistance of the composite coating. The heating temperature during heat treatment can specifically be 750°C, 800°C, 850°C, 900°C, or any temperature value between two of these values.

[0040] Preferably, in this embodiment, after the last laser cladding pass is completed, the resulting coating is annealed to remove stress; the heating temperature is 200-400℃, further, the heating temperature can be 250-350℃, specifically, the heating temperature can be 200℃, 250℃, 300℃, 350℃, 400℃, or any temperature between two temperature values.

[0041] Preferably, in this embodiment, the purity of powder B is not less than 99%, and the average particle size is not higher than 100 μm. Specifically, the purity of powder B can be 99.5% or 99.9%, etc. The higher the purity, the higher the purity of the final composite coating, which is beneficial to ensuring the performance of the final composite coating. The average particle size of powder B can be further 50-100 μm, specifically 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or any particle size value between two points. The smaller and more uniform the particle size, the more conducive it is to the reaction and combination with nitrogen.

[0042] Preferably, in this embodiment, the purity of Al powder, Cr powder, Fe powder, and Ni powder is not less than 99.5%. The higher the purity, the higher the purity of the final composite coating, which is more beneficial to improving the performance of the final composite coating. The average particle size of the above-mentioned high-entropy alloy powder is not higher than 200 μm, further, it can be 50-200 μm, and even further, it can be 50-150 μm. The average particle size of the above-mentioned high-entropy alloy powder can specifically be 50 μm, 100 μm, 150 μm, 200 μm, or any particle size value between two particle size values. The smaller and more uniform the particle size of the powder, the more conducive it is to mixing and bonding, and the better the performance of the prepared composite coating.

[0043] Preferably, in this embodiment, in the step of ball milling powder B, after the powder B is loaded into the ball mill jar, the ball mill jar is subjected to vacuum treatment, and the vacuum degree is not less than 0.01 Pa; in the step of mixing and ball milling, after the high-entropy alloy powder is loaded into the ball mill jar, the ball mill jar is also subjected to vacuum treatment, and the vacuum degree is also not less than 0.01 Pa. Vacuuming can effectively prevent the powder in the ball mill jar from reacting with components in the air, such as effectively preventing powder oxidation, thereby improving the purity of the obtained composite coating and ensuring its performance.

[0044] Preferably, in this embodiment, before preheating the substrate, anhydrous ethanol is used to clean the surface of the substrate to remove surface oxides, oil stains, and other impurities. Of course, in other embodiments of this application, other cleaning solvents can also be used to clean the surface of the substrate to be melted, as long as the surface cleanliness can be guaranteed.

[0045] Specifically, in this embodiment, a stainless steel ball mill jar is used, but in other embodiments of this application, it is not limited to this, as long as the requirements of the ball milling process described above can be met.

[0046] This embodiment also provides a BN-reinforced high-entropy alloy composite coating, which is prepared using the above-described method for preparing BN-reinforced high-entropy alloy composite coatings.

[0047] The BN-reinforced high-entropy alloy composite coating provided in this embodiment exhibits excellent bonding between BN and the high-entropy alloy substrate. The B element generates molten boron oxide at high temperatures, demonstrating significant friction reduction and resistance to oxidation and corrosion. Compared to commonly used Stellite alloy coatings, the volume loss during high-temperature oxidative wear (e.g., 2 hours of wear at 800°C) is reduced by nearly half or even more, while the material cost is only about 75% to 80% of that of Stellite alloy coatings. In other words, the BN-reinforced high-entropy alloy composite coating provided in this embodiment offers superior wear and corrosion resistance at a lower cost, demonstrating significant cost-effectiveness and providing a potential alternative to the currently used, more expensive Stellite alloy coating.

[0048] To further illustrate the present invention, the preparation method of BN-reinforced high-entropy alloy composite coating and the BN-reinforced high-entropy alloy composite coating provided by the present invention will be described in more detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] S110: Weigh B powder with a particle size of 100μm and a purity of not less than 99% at a ball-to-powder ratio of 1:10 and load it into a vacuum-capable stainless steel ball mill jar. Then, evacuate the ball mill jar to a vacuum level of 0.01Pa. After ball milling for 10 hours, stop the machine without reducing the vacuum level.

[0051] In step S120, high-purity nitrogen gas with a purity of 99.9% is connected from the nitrogen cylinder to the heating vessel. The nitrogen flow rate is controlled at 0.5 ml / min. When the temperature reaches 950°C, it is held for 3 minutes. Then, the gas is introduced into the ball mill jar through another port of the heating vessel (the ball mill is stopped before the gas is introduced) to achieve ball milling while introducing high-temperature nitrogen gas. Then, in step S110, the ball milling is carried out for 30 hours. Finally, the machine is stopped and the gas supply is cut off. The ball mill jar is allowed to cool to room temperature for 10 hours, and the ball mill jar is kept sealed.

[0052] S130: Weigh Al powder, Cr powder, Fe powder and Ni powder with a purity of 99.5% and an average particle size of 200μm in a molar ratio of 1:1:1:1 (total weight is 15 times that of B powder). Open the ball mill jar and load the weighed composite powder. Vacuum the ball mill jar again and dry mix for 2 hours. After stopping the machine for 2 hours, take out the mixed powder.

[0053] S140: Before fusion, clean the surface of the P92 steel substrate to be fused with anhydrous ethanol to remove surface oxides, oil stains and other impurities, and preheat to 200℃.

[0054] S150: The prepared mixed powder is placed into the powder feeder of the laser cladding equipment. The powder feeder is then sealed and filled with protective gas. The laser cladding parameters are: laser power 2kW; powder feed rate 20g / min; defocusing distance 20mm; cladding speed 200mm / min; protective gas flow rate 1ml / min. Both the powder feeder gas and the protective gas are argon gas with a purity of 99.9%.

[0055] S160, perform multiple cladding passes according to step S150. After each 3-pass cladding pass, perform induction heat treatment on the coating at a temperature of 750℃ to enable better bonding between BN and the high-entropy alloy substrate. Then, perform the next 3-pass cladding cycle. After each cladding cycle, perform heat treatment. Perform a total of 5 cladding cycles, for a total of 15 passes.

[0056] S170, after the final deposition, undergoes stress-relief annealing at 400℃, followed by cooling to room temperature to obtain the desired result. Figure 1 The image shows a BN-reinforced high-entropy alloy composite coating. In the photo, the bright white spots are BN particles, and the dark areas are the high-entropy alloy substrate.

[0057] After a 2-hour high-temperature wear test at 800℃, the volume loss due to oxidation wear of each sample is shown in Table 1. As can be seen from the data in Table 1, the volume loss of the BN-reinforced high-entropy alloy composite coating is nearly half that of the Stellite alloy coating, indicating a significant improvement in high-temperature wear resistance.

[0058] Table 1

[0059] Stellite alloy coating BN-reinforced high-entropy alloy composite coating <![CDATA[Volume loss (mm 3 / h)]]> 1.82 0.96

[0060] Example 2

[0061] S210: Weigh B powder with a particle size of 50μm and a purity of not less than 99% at a ball-to-powder ratio of 1:10 and load it into a vacuum-capable stainless steel ball mill jar. Then, evacuate the ball mill jar to a vacuum level of 0.01Pa. After ball milling for 5 hours, stop the machine without reducing the vacuum level.

[0062] In step S220, high-purity nitrogen gas with a purity of 99.9% is connected from the nitrogen cylinder to the heating vessel, and the nitrogen flow rate is controlled at 0.1 ml / min. When the temperature is raised to 800℃, it is held for 1 minute. Then, the gas is introduced into the ball mill jar through another port of the heating vessel (the ball mill is stopped before the gas is introduced) to achieve ball milling while introducing high-temperature nitrogen gas. Then, in step S210, the ball mill is milled for 20 hours. Finally, the machine is stopped and the gas supply is cut off. The ball mill jar is allowed to cool to room temperature for 10 hours, and the ball mill jar is kept sealed.

[0063] S230: Weigh Al powder, Cr powder, Fe powder and Ni powder with a purity of 99.5% and an average particle size of 50μm in a molar ratio of 1:1:1:1 (total weight is 20 times that of B powder). Open the ball mill jar and load the weighed composite powder. Vacuum the ball mill jar again and dry mix for 3.5 hours. After stopping the machine for 2 hours, take out the mixed powder.

[0064] S240: Before fusion, clean the surface of the P92 steel substrate to be fused with anhydrous ethanol to remove surface oxides, oil stains and other impurities, and preheat to 250℃.

[0065] S250: The prepared mixed powder is placed into the powder feeder of the laser cladding equipment. The powder feeder is then sealed and filled with protective gas. The laser cladding parameters are: laser power 1kW; powder feed rate 25g / min; defocusing distance 20mm; cladding speed 100mm / min; protective gas flow rate 0.75ml / min. Both the powder feeder gas and the protective gas are argon gas with a purity of 99.9%.

[0066] S260, perform multiple cladding passes according to step S250. After each 5-pass cladding pass, perform induction heat treatment on the coating at a temperature of 850℃ to achieve better bonding between BN and the high-entropy alloy substrate. Then, perform the next 5-pass cladding cycle. After each cladding cycle, perform heat treatment. Perform a total of 4 cladding cycles, for a total of 20 passes.

[0067] After the final annealing of S270, stress-relief annealing is performed at a heating temperature of 300℃. After cooling to room temperature, a BN-reinforced high-entropy alloy composite coating is obtained.

[0068] After a 2-hour high-temperature wear test at 800℃, the volume loss due to oxidation wear of each sample is shown in Table 2. The data in Table 2 show that the volume loss of the BN-reinforced high-entropy alloy composite coating is reduced by more than half compared to the Stellite alloy coating, indicating a significant improvement in high-temperature wear resistance.

[0069] Table 2

[0070] Stellite alloy coating BN-reinforced high-entropy alloy composite coating <![CDATA[Volume loss (mm 3 / h)]]> 1.82 0.89

[0071] Example 3

[0072] S310: Weigh B powder with a particle size of 100μm and a purity of not less than 99% at a ball-to-powder ratio of 1:10 and load it into a vacuum-capable stainless steel ball mill jar. Then, evacuate the ball mill jar to a vacuum level of 0.01Pa. After ball milling for 7 hours, stop the machine without reducing the vacuum level.

[0073] In step S320, high-purity nitrogen gas with a purity of 99.9% is connected from the nitrogen cylinder to the heating vessel. The nitrogen flow rate is controlled at 0.3 ml / min. When the temperature reaches 850°C, it is held for 2 minutes. Then, the nitrogen gas is introduced into the ball mill jar through another port of the heating vessel (the ball mill is stopped before introducing the nitrogen gas). This allows for ball milling while simultaneously introducing high-temperature nitrogen gas. Then, in step S310, the ball mill is milled for 15 hours. Finally, the machine is stopped and the gas supply is cut off. The ball mill jar is allowed to cool to room temperature for 10 hours, ensuring that the ball mill jar remains sealed.

[0074] S330: Weigh Al powder, Cr powder, Fe powder and Ni powder with a purity of 99.5% and an average particle size of 200μm in a molar ratio of 1:1:1:1 (total weight is 30 times that of B powder). Open the ball mill jar and load the weighed composite powder. Vacuum the ball mill jar again and dry mix for 5 hours. After stopping the machine for 2 hours, take out the mixed powder.

[0075] S340: Before fusion, clean the surface of the P92 steel substrate to be fused with anhydrous ethanol to remove surface oxides, oil stains and other impurities, and preheat to 300℃.

[0076] S350: The prepared mixed powder is placed into the powder feeder of the laser cladding equipment. The powder feeder is then sealed and filled with protective gas. The laser cladding parameters are: laser power 0.5kW; powder feed rate 22g / min; defocusing distance 20mm; cladding speed 150mm / min; protective gas flow rate 0.5ml / min. Both the powder feeder gas and the protective gas are argon with a purity of 99.9%.

[0077] S360, proceed with multiple cladding passes according to step S350. After each 4-pass cladding pass, perform induction heat treatment on the coating at a temperature of 900℃ to achieve better bonding between BN and the high-entropy alloy substrate. Then proceed with the next 4-pass cladding cycle. After each cladding cycle, perform heat treatment. Perform a total of 6 cladding cycles, for a total of 24 passes.

[0078] After the final annealing of S370, stress-relief annealing is performed at a heating temperature of 200℃. After cooling to room temperature, a BN-reinforced high-entropy alloy composite coating is obtained.

[0079] After a 2-hour high-temperature wear test at 800℃, the volume loss due to oxidation wear of each sample is shown in Table 3. The data in Table 3 show that the volume loss of the BN-reinforced high-entropy alloy composite coating is reduced by more than half compared to the Stellite alloy coating, indicating a significant improvement in high-temperature wear resistance.

[0080] Table 3

[0081] Stellite alloy coating BN-reinforced high-entropy alloy composite coating <![CDATA[Volume loss (mm 3 / h)]]> 1.82 0.79

[0082] Example 4

[0083] S410: Weigh B powder with a particle size of 50μm and a purity of 99.9% at a ball-to-powder ratio of 1:10 and load it into a vacuum-capable stainless steel ball mill jar. Then, evacuate the ball mill jar to a vacuum level of 0.01Pa. After ball milling for 8 hours, stop the machine without reducing the vacuum level.

[0084] In step S420, high-purity nitrogen gas with a purity of 99.9% is connected from the nitrogen cylinder to the heating vessel, and the nitrogen flow rate is controlled at 0.3 ml / min. When the temperature is raised to 900℃, it is held for 3 minutes. Then, the gas is introduced into the ball mill jar through another port of the heating vessel (the ball mill is stopped before the gas is introduced) to achieve ball milling while introducing high-temperature nitrogen gas. Then, in step S410, the ball milling is carried out for 25 hours. Finally, the machine is stopped and the gas supply is cut off. The ball mill jar is allowed to cool to room temperature for 10 hours, and the ball mill jar is kept sealed.

[0085] S430: Weigh Al powder, Cr powder, Fe powder and Ni powder with a purity of 99.5% and an average particle size of 200μm in a molar ratio of 1:1:1:1 (total weight is 20 times that of B powder). Open the ball mill jar and load the weighed composite powder. Vacuum the ball mill jar again and dry mix for 2.5 hours. After stopping the machine for 2 hours, take out the mixed powder.

[0086] S440: Before welding, clean the surface of the substrate (P92 steel) to be welded with anhydrous ethanol to remove surface oxides, oil stains and other impurities, and preheat to 300°C.

[0087] S450: The prepared mixed powder is placed into the powder feeder of the laser cladding equipment. The powder feeder is then sealed and filled with protective gas. The laser cladding parameters are: laser power 1kW; powder feed rate 20g / min; defocusing distance 20mm; cladding speed 15mm / min; protective gas flow rate 1ml / min. Both the powder feeder gas and the protective gas are argon gas with a purity of 99.9%.

[0088] S460, perform multiple cladding passes according to step S450. After each 5-pass cladding pass, perform induction heat treatment on the coating at a temperature of 800℃ to achieve better bonding between BN and the high-entropy alloy substrate. Then, perform the next 5-pass cladding cycle. After each cladding cycle, perform heat treatment. Perform 2 cladding cycles in total, for a total of 10 passes.

[0089] After the final annealing of S470, stress-relief annealing is performed at a heating temperature of 350℃. After cooling to room temperature, a BN-reinforced high-entropy alloy composite coating is obtained.

[0090] After a 2-hour high-temperature wear test at 800℃, the volume loss due to oxidation wear of each sample is shown in Table 4. The data in Table 4 show that the volume loss of the BN-reinforced high-entropy alloy composite coating is reduced by half compared to the Stellite alloy coating, indicating a significant improvement in high-temperature wear resistance.

[0091] Table 4

[0092] Stellite alloy coating BN-reinforced high-entropy alloy composite coating <![CDATA[Volume loss (mm 3 / h)]]> 1.82 0.91

[0093] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0094] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a BN-strengthened high-entropy alloy composite coating, characterized in that, Includes the following steps: Ball milling of B powder: The B powder weighed at a ball-to-powder ratio of 1:10 is loaded into the ball milling jar and ball milled for 5-10 hours. Then, while filling the ball milling jar with high-temperature nitrogen gas, ball milling continues for 15-30 hours. After stopping the machine and cutting off the gas supply, the ball milling jar is kept sealed and cooled. Mixed ball milling: Weigh Al powder, Cr powder, Fe powder and Ni powder with a molar ratio of 1:1:1:1 and a total weight of 15 to 30 times that of B powder, load them into the ball mill jar and dry mill for 2 to 5 hours. After stopping the machine, keep the ball mill jar sealed and cool it to obtain mixed powder. Preheating the substrate: Preheat the surface of the substrate to be melted to 200~300℃; Laser cladding: The mixed powder is loaded into the powder feeder of the laser cladding equipment, then the powder feeder is sealed and filled with powder gas and protective gas. The laser power is set to 0.5~2kW, the defocusing amount is 18~22mm, the powder feeding rate is controlled to be 20~25g / min, the cladding speed is 100~200mm / min, and the protective gas flow rate is 0.5~1ml / min. Every 3~5 laser cladding passes form a cladding cycle, and a total of n cladding cycles are performed, where n is a natural number and 1≤n≤6. Cooling: After laser cladding is completed, the coating is cooled to room temperature to obtain the BN-reinforced high-entropy alloy composite coating.

2. The method for preparing BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, The nitrogen gas has a purity of not less than 99.5%, and the heating temperature is 800~950℃. After holding at this temperature for 1~3 minutes, it is then filled into the ball mill jar.

3. The method for preparing a BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, After each deposition cycle, the resulting coating is subjected to induction heat treatment at a temperature of 750~900℃.

4. The method for preparing a BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, After the last laser cladding pass, the resulting coating is annealed at a temperature of 200~400℃.

5. The method for preparing a BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, The purity of the B powder is not less than 99%, and the average particle size is not higher than 100μm.

6. The method for preparing a BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, The purity of the Al powder, Cr powder, Fe powder, and Ni powder is not less than 99.5%, and the average particle size is not higher than 200 μm.

7. The method for preparing a BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, In the step of ball milling B powder, after the B powder is loaded into the ball milling jar, the ball milling jar is vacuumed and the vacuum degree is not less than 0.01 Pa. And / or, in the step of mixing and ball milling, after the high-entropy alloy powder is loaded into the ball milling jar, the ball milling jar is subjected to vacuum treatment, and the vacuum degree is not less than 0.01 Pa.

8. The method for preparing a BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, Both the powder feeding gas and the protective gas are argon, and their purity is not less than 99.5%.

9. The method for preparing a BN-reinforced high-entropy alloy composite coating according to claim 1, characterized in that, Before preheating the substrate, the surface of the substrate is cleaned with anhydrous ethanol.

10. A BN-reinforced high-entropy alloy composite coating, characterized in that, The coating was prepared using the method described in any one of claims 1-9 for preparing BN-reinforced high-entropy alloy composite coatings.

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