Method for inhibiting cracks of laser cladding refractory high-entropy alloy coating

Abstract

The invention relates to a method for inhibiting cracks of a laser cladding refractory high-entropy alloy coating and the coating, and the method comprises the following steps: carrying out surface polishing and cleaning treatment on a matrix to remove an oxidation film and impurities; the method comprises the steps that refractory high-entropy alloy powder is prepared, the expression of refractory high-entropy alloy is WaMobTacXd, nickel powder, chromium powder and the refractory high-entropy alloy powder are mixed according to the mass percent to obtain mixed powder, the content of the refractory high-entropy alloy powder is 30-70 wt.%, and the ratio of the nickel powder to the chromium powder is 53: 19; a laser cladding technology is adopted to prepare the composite coating with coexistence of a gamma phase and a BCC hard phase. A series of experiments prove that the method effectively inhibits coating cracks, and the application prospect of the method in the fields of aerospace and military industry is widened.

Description

Technical Field

[0001] This invention relates to the field of refractory high-entropy alloy technology, and in particular to a method and coating for suppressing cracks in laser cladding refractory high-entropy alloy coatings. Background Technology

[0002] High-entropy alloys, as a new and popular metallic material, possess unique design concepts and characteristics such as high entropy, lattice distortion, slow diffusion, and cocktail effect, which give them high hardness, strong oxidation resistance, outstanding mechanical properties, excellent wear resistance, and corrosion resistance.

[0003] Refractory high-entropy alloys are a new type of multi-principal element alloy developed on the basis of high-entropy alloys. They are mainly composed of refractory metal elements (melting points above 1650℃, such as Nb, Ta, Mo, W, V, etc.) and have excellent properties such as high strength, high specific strength, high temperature resistance and radiation resistance. They have a very broad application prospect in aerospace, nuclear reactors and other fields.

[0004] Laser cladding technology offers several advantages in processing refractory alloys: 1) Localized heating: During laser cladding, the heat input from the laser is relatively concentrated, enabling localized heating, reducing the heat-affected zone, and thus avoiding substrate deformation and performance degradation; 2) High material utilization: Due to minimal material loss during laser cladding, alloy powder or welding wire can be utilized more effectively, reducing costs; 3) High control precision: Laser cladding technology possesses excellent control capabilities, allowing for precise control of coating thickness and composition to meet specific application requirements; 4) Diverse material selection: Laser cladding can be combined with various refractory alloy materials, providing customized solutions for different applications; 5) Large coating thickness: The thickness of laser cladding coatings can generally be controlled between 50μm and 1500μm. However, for refractory, high-melting-point, high-entropy alloys (such as WMoTaNb) coatings, significant thermal stress is generated during rapid solidification, leading to defects such as cracking and peeling, severely impacting their application under actual working conditions. Meanwhile, coatings obtained by cladding with pure high-entropy alloy powder are hard and brittle with poor toughness, requiring optimization of their microstructure and properties through alloy composition design.

[0005] Based on this, the present invention provides a method for suppressing cracks in laser cladding of refractory high-entropy alloy coatings, wherein Ni powder, Cr powder and high-entropy alloy powder are mixed and laser cladding is performed to introduce a tough phase (γ phase), thereby improving the toughness and high-temperature performance of the cladding layer.

[0006] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] This invention provides a method and coating for suppressing cracks in laser cladding refractory high-entropy alloy coatings, solving defects such as cracking and peeling in laser cladding refractory high-entropy alloy coatings. Ni powder, Cr powder and high-entropy alloy powder are mixed for laser cladding, introducing a tough phase (γ phase), thereby improving the toughness and high-temperature performance of the cladding layer.

[0008] A method for suppressing cracks in laser cladding of refractory high-entropy alloy coatings includes, The substrate is subjected to surface grinding and cleaning to remove oxide film and impurities; 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%.

[0009] Nickel powder, chromium powder and the refractory high entropy alloy powder are mixed in a mass percentage to obtain a mixed powder, wherein the content of the refractory high entropy alloy powder is 30~70 wt.% and the ratio of nickel powder to chromium powder is 53:19; Laser cladding technology is used to deposit mixed powders onto the substrate surface under inert gas protection, forming a composite coating with the coexistence of γ toughening phase and BCC hard phase.

[0010] The method described above includes preparing refractory high-entropy alloy powder, comprising: According to the atomic ratio of refractory high-entropy alloys, the corresponding elemental substances are weighed and melted into ingots by vacuum induction. The ingots are processed into bars by wire electrical discharge machining. Spherical refractory high-entropy alloy powders with particle sizes of 15-50 μm and oxygen content ≤200 ppm were prepared by plasma rotating electrode method.

[0011] In the method described, the elemental particles are placed into a vacuum induction levitation furnace in order of increasing melting point, and then subjected to a 5×10⁻⁶ kcal / kg heat treatment process. -3 Under a vacuum of Pa, the alloy is repeatedly melted into a homogeneous melt and then cooled in the furnace to obtain an ingot of a refractory high-entropy alloy with a BCC structure, an impurity content of ≤0.1%, and an oxygen content of ≤100ppm.

[0012] The laser cladding parameters described herein include: laser power of 1000~2200W, scanning speed of 5~30mm / s, powder feeding speed of 1~5g / min, spot diameter of 2~5mm, overlap rate of 50~60%, protective gas of argon, and flow rate of 10~25L / min.

[0013] In the method described, the substrate is a steel substrate, and the laser cladding is carried out in a closed atmosphere chamber to isolate O and N elements in the air.

[0014] In the method described, the composite coating comprises a γ phase and a BCC hard phase, the ratio of which is controlled according to the content of the refractory high-entropy alloy powder.

[0015] In the method described, the surface of the steel alloy substrate is polished with sandpaper until the surface shows a metallic luster, which is considered to remove the surface oxide film. Anhydrous ethanol is used as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, the cleaning agent on the substrate surface is removed by drying, and the pretreated substrate is obtained.

[0016] In the method described, the refractory high-entropy alloy contains 25 at.%, 25 at.%, 25 at.%, and 25 at.% of W, Mo, Ta, and Nb.

[0017] In the method described, the nickel powder, chromium powder and refractory high-entropy alloy powder are mixed in a vacuum mixer at a speed of 60~120 r / min for 6~12 hours to ensure uniform composition; the mixed powder is then dried at 90~120℃ for 4~8 hours.

[0018] A composite coating, which is made according to the method described above.

[0019] Compared with existing technologies, this invention has the following advantages: Ni is an important component of the γ matrix (FCC) and δ (Ni3Nb) precipitates. By introducing Ni and combining it with Nb in the WMoTaNb high-entropy system, Ni3Nb precipitates can be formed in the cladding layer, significantly improving the coating's toughness and high-temperature strengthening ability. Cr easily forms solid solution strengthening, significantly affecting the hot cracking sensitivity of the molten pool. High Cr content at grain boundaries can enhance oxidation resistance and creep resistance, and also assist in the formation of the FCC-BCC dual-phase system, reducing thermal stress concentration and lowering the tendency for crack formation. The ratio of tough phase and high-entropy alloy phase in the coating can be controlled, balancing cladding performance and high-temperature performance. Different WMoTaNb content gradients (from 30% to 70%) were designed, and while maintaining the Ni:Cr ratio at approximately 53:19, the controllable adjustment of the toughening phase and high-entropy hardening phase in the coating was achieved: Lower WMoTaNb content (approximately 30%-40%): This composition has relatively high Ni and Cr content, providing a sufficient compositional basis for the γ phase (face-centered cubic solid solution) and the δ phase (Ni3Nb precipitates). At this level, the proportion of the strengthening phase in the coating structure is higher, which is conducive to the formation of fine and dispersed precipitates, significantly improving the high-temperature strength of the coating and making it suitable for applications under high-temperature and high-load conditions. Increased WMoTaNb content (approximately 60%-70%): At this level, Ni / Cr is relatively balanced with the high-entropy main elements, and the coating simultaneously contains γ phase and BCC phase solid solution structures, achieving synergistic optimization of toughness and hardness. While maintaining high-temperature mechanical properties, the structural stability and crack resistance of the cladding layer are also improved, making it suitable for medium- and high-temperature conditions that balance load-bearing capacity and wear resistance. By adjusting the content gradient of WMoTaNb and keeping the Ni:Cr ratio constant, a synergistic control strategy of "γ phase-BCC phase" was constructed to realize the controllable conversion between the strengthening phase and the toughening phase of the coating. This effectively solved the problems of insufficient strengthening or easy cracking in traditional high-entropy cladding systems, and improved the application adaptability and engineering reliability of the coating. Attached Figure Description

[0020] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0021] In the attached diagram: Figure 1 The XRD pattern of the mixed powder of elemental metal powder and refractory high-entropy alloy powder prepared in Example 1; Figure 2 The image shows the flaw detection photograph of the refractory high-entropy alloy with a metallic element powder coating prepared in Example 1. According to the national standard GB_T 42401-2023 "Classification of Defect Quality of Laser Cladding Repair", it reached Level I (strict). Figure 3 The image shows a cross-section of the refractory high-entropy alloy coating with metallic elemental powder prepared in Example 1. The cross-section of the refractory high-entropy alloy coating prepared in Example 1 shows that the coating has formed a dense refractory high-entropy alloy coating structure and no cracks have been generated, indicating that the coating quality has been improved. Figure 4 The image shows the elemental distribution of the cross-section of the refractory high-entropy alloy coating with metallic elemental powder prepared in Example 1. As can be seen from the elemental distribution of the middle part of the cross-section of the refractory high-entropy alloy coating prepared in Example 1, the Ni and Cr elements in the coating are uniformly distributed without obvious segregation. Figure 5 The XRD pattern of the refractory high-entropy alloy with a metallic elemental powder coating prepared in Example 1 is shown below. Figure 6 Flaw detection photographs of a refractory high-entropy alloy coating prepared for comparison. Figure 7 Flaw detection photographs of the refractory high-entropy alloy coating prepared for counterexample 1; Figure 8 Flaw detection photographs of the refractory high-entropy alloy coating prepared for counterexample 2.

[0022] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0023] 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.

[0024] 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.

[0025] 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.

[0026] like Figures 1 to 8 As shown, a method for suppressing cracks in laser cladding refractory high-entropy alloy coatings includes, Step 1: Process the surface of the laser cladding substrate by grinding, polishing and ultrasonic cleaning to remove oxide film and impurities; Step 2: 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%; Step 3: Mix nickel powder, chromium powder and the refractory high entropy alloy powder according to the mass percentage to obtain a mixed powder, wherein the content of refractory high entropy alloy powder is 30~70 wt.% and the ratio of nickel powder to chromium powder is 53:19; Step 4: Using laser cladding technology, the mixed powder is clad onto the substrate surface in a synchronous powder feeding manner under inert gas protection, and a composite coating with γ tough phase and BCC hard phase coexisting is formed on the substrate surface.

[0027] In a preferred embodiment of the method, step 2, preparing the refractory high-entropy alloy powder, includes: According to the atomic ratio of refractory high-entropy alloys, the corresponding elemental substances are weighed and melted into ingots by vacuum induction. The ingots are processed into bars by wire electrical discharge machining. Spherical refractory high-entropy alloy powders with particle sizes of 15-50 μm and oxygen content ≤200 ppm were prepared by plasma rotating electrode method.

[0028] In a preferred embodiment of the method, the elemental particles are placed into a vacuum induction levitation furnace in order of increasing melting point, and then subjected to a 5×10⁻⁶ kcal / kg heat treatment process. -3 Under a vacuum of Pa, the alloy is repeatedly melted into a homogeneous melt and then cooled in the furnace to obtain an ingot of a refractory high-entropy alloy with a BCC structure, an impurity content of ≤0.1%, and an oxygen content of ≤100ppm.

[0029] In a preferred embodiment of the method, in step 4, the laser cladding parameters include: laser power of 1000~2200W, scanning speed of 5~30mm / s, powder feeding speed of 1~5g / min, spot diameter of 2~5mm, overlap rate of 30~70%, protective gas of argon, and flow rate of 10~25L / min.

[0030] In a preferred embodiment of the method, the substrate is a steel substrate, and the laser cladding is performed in a closed atmosphere chamber to isolate O and N elements in the air.

[0031] In a preferred embodiment of the method, the composite coating comprises a γ phase and a BCC hard phase, the ratio of which is controlled according to the content of the refractory high-entropy alloy powder.

[0032] In a preferred embodiment of the method, the surface of the steel alloy substrate is polished with sandpaper until the surface shows a metallic luster, which is considered to remove the surface oxide film. Anhydrous ethanol is used as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, the cleaning agent on the substrate surface is removed by drying, and the pretreated substrate is obtained.

[0033] In a preferred embodiment of the method, the nickel powder, chromium powder and refractory high-entropy alloy powder are mixed in a vacuum mixer at a speed of 60-120 r / min for 6-12 hours to ensure uniform composition; the mixed powder is then dried at 90-120°C for 4-8 hours.

[0034] A composite coating, which is made according to the method described above.

[0035] Example 1 A method for suppressing cracks in laser cladding of refractory high-entropy alloy coatings includes the following steps: Step 1, Pretreatment of substrate surface: (1) Use 1000# SiC sandpaper to polish the surface of the steel alloy substrate until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0036] (2) Use anhydrous ethanol as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0037] Step 2, 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 25at.%, Mo 25at.%, Ta 25at.%, Nb 25at.%.

[0038] (2) The weighed elemental particles are placed into a vacuum induction levitation melting furnace in order of increasing melting point. The furnace is repeatedly melted 6 times under a vacuum of 5×10-3Pa. Each time, the melting is carried out until a uniform melt is obtained. The furnace is then cooled to obtain a refractory high entropy alloy ingot with BCC structure, impurity content ≤0.1% and oxygen content ≤100ppm.

[0039] (3) Using wire electrical discharge machining, the refractory high entropy alloy ingot obtained above is cut into round bars with a diameter of 30 mm and a length of 150 mm. Then, the surface oxide layer is removed by grinding with 1000# SiC sandpaper, and the oil is removed by ultrasonic cleaning with alcohol and acetone.

[0040] (4) The rod obtained above is clamped in a plasma rotating electrode device, vacuum plasma melting and high speed rotation at 50000 r / min and vacuum degree of 5×10-3 Pa to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder is then sieved using a vibrating screen and selected with a particle size of 200 mesh to obtain refractory high entropy alloy powder.

[0041] Step 3: Prepare a mixed powder of elemental nickel powder, chromium powder, and refractory high-entropy alloy powder: 45 wt.% nickel powder, 15 wt.% Cr powder, and 40 wt.% refractory high-entropy alloy powder were added to a V-type vacuum powder mixer, and the nickel powder, chromium powder, and refractory high-entropy alloy powder were mixed at 60 r / min for 8 h to obtain a mixed powder. The mixed powder was dried in a vacuum drying oven at 90 ℃ for 6 h to be used as a deposition coating material.

[0042] Step 4, laser cladding: The mixed powder prepared in step 4 above is loaded into a powder feeder. The parameters for laser cladding are set as follows: synchronous powder feeding, laser power of 1000W-2200W (200W as a gradient), scanning speed of 10mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.6r / min. Under Ar2 atmosphere, the dried refractory high entropy alloy powder is deposited on the pretreated substrate surface to form a single-phase refractory high entropy alloy coating on the pretreated substrate surface.

[0043] Example 2 A method for suppressing cracks in laser cladding of refractory high-entropy alloy coatings includes the following steps: Step 1, Pretreatment of substrate surface: (1) Use 1000# SiC sandpaper to polish the surface of the steel alloy substrate until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0044] (2) Use anhydrous ethanol as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0045] Step 2, 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 25at.%, Mo 25at.%, Ta 25at.%, Nb 25at.%.

[0046] (2) The weighed elemental particles are placed into a vacuum induction levitation melting furnace in order of increasing melting point. The furnace is repeatedly melted 6 times under a vacuum of 5×10-3Pa. Each time, the melting is carried out until a uniform melt is obtained. The furnace is then cooled to obtain a refractory high entropy alloy ingot with BCC structure, impurity content ≤0.1% and oxygen content ≤100ppm.

[0047] (3) Using wire electrical discharge machining, the refractory high entropy alloy ingot obtained above is cut into round bars with a diameter of 30 mm and a length of 150 mm. Then, the surface oxide layer is removed by grinding with 1000# SiC sandpaper, and the oil is removed by ultrasonic cleaning with alcohol and acetone.

[0048] (4) The rod obtained above is clamped in a plasma rotating electrode device, vacuum plasma melting and high speed rotation at 50000 r / min and vacuum degree of 5×10-3 Pa to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder is then sieved using a vibrating screen and selected with a particle size of 200 mesh to obtain refractory high entropy alloy powder.

[0049] Step 3: Prepare a mixed powder of elemental nickel powder, chromium powder, and refractory high-entropy alloy powder: 50 wt.% nickel powder, 20 wt.% chromium powder, and 30 wt.% refractory high-entropy alloy powder were added to a V-type vacuum mixer, and the nickel powder, chromium powder, and refractory high-entropy alloy powder were mixed at 60 r / min for 8 h to obtain a mixed powder. The mixed powder was dried in a vacuum drying oven at 90 ℃ for 6 h to be used as a deposition coating material.

[0050] Step 4, laser cladding: The mixed powder prepared in step 4 above is loaded into a powder feeder. The parameters for laser cladding are set as follows: synchronous powder feeding, laser power of 1000W-2200W (200W as a gradient), scanning speed of 10mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.6r / min. Under Ar2 atmosphere, the dried refractory high entropy alloy powder is deposited on the pretreated substrate surface to form a single-phase refractory high entropy alloy coating on the pretreated substrate surface.

[0051] Example 3 A method for suppressing cracks in laser cladding of refractory high-entropy alloy coatings includes the following steps: Step 1, Pretreatment of substrate surface: (1) Use 1000# SiC sandpaper to polish the surface of the steel alloy substrate until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0052] (2) Use anhydrous ethanol as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0053] Step 2, 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 25at.%, Mo 25at.%, Ta 25at.%, Nb 25at.%.

[0054] (2) The weighed elemental particles are placed into a vacuum induction levitation melting furnace in order of increasing melting point. The furnace is repeatedly melted 6 times under a vacuum of 5×10-3Pa. Each time, the melting is carried out until a uniform melt is obtained. The furnace is then cooled to obtain a refractory high entropy alloy ingot with BCC structure, impurity content ≤0.1% and oxygen content ≤100ppm.

[0055] (3) Using wire electrical discharge machining, the refractory high entropy alloy ingot obtained above is cut into round bars with a diameter of 30 mm and a length of 150 mm. Then, the surface oxide layer is removed by grinding with 1000# SiC sandpaper, and the oil is removed by ultrasonic cleaning with alcohol and acetone.

[0056] (4) The rod obtained above is clamped in a plasma rotating electrode device, vacuum plasma melting and high speed rotation at 50000 r / min and vacuum degree of 5×10-3 Pa to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder is then sieved using a vibrating screen and selected with a particle size of 200 mesh to obtain refractory high entropy alloy powder.

[0057] Step 3: Prepare a mixed powder of elemental nickel powder, chromium powder, and refractory high-entropy alloy powder: 22 wt.% nickel powder, 8 wt.% chromium powder, and 70 wt.% refractory high-entropy alloy powder were added to a V-type vacuum mixer, and the nickel powder, chromium powder, and refractory high-entropy alloy powder were mixed at 60 r / min for 8 h to obtain a mixed powder. The mixed powder was dried in a vacuum drying oven at 90 ℃ for 6 h to be used as a deposition coating material.

[0058] Step 4, laser cladding: The mixed powder prepared in step 3 above is loaded into a powder feeder. The parameters for laser cladding are set as follows: synchronous powder feeding, laser power of 1200W-2200W (in increments of 200W), scanning speed of 10mm / s, cladding overlap rate of 60%, Ar2 gas flow rate of 15L / min, powder feeding speed of 1.2 r / min, and preheating temperature of 400℃. Under Ar2 atmosphere, the dried refractory high entropy alloy powder is deposited on the pretreated substrate surface to form a refractory high entropy alloy coating on the pretreated substrate surface.

[0059] Comparative Example 1 A laser cladding method for a refractory high-entropy alloy coating includes the following steps: Step 1, Pretreatment of substrate surface: (1) Use 1000# SiC sandpaper to polish the substrate surface until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0060] (2) Use anhydrous ethanol as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0061] Step 2, 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 25at.%, Mo 25at.%, Ta 25at.%, Nb 25at.%.

[0062] (2) The weighed elemental particles are placed into a vacuum induction levitation melting furnace in order of increasing melting point. The furnace is repeatedly melted 6 times under a vacuum of 5×10-3Pa. Each time, the melting is carried out until a uniform melt is formed. The furnace is then cooled to obtain a refractory high entropy alloy ingot with a single-phase BCC structure, impurity content ≤0.1%, and oxygen content ≤100ppm.

[0063] (3) Using wire electrical discharge machining, the refractory high entropy alloy ingot obtained above is cut into round bars with a diameter of 30 mm and a length of 150 mm. Then, the surface oxide layer is removed by grinding with 1000# SiC sandpaper, and the oil is removed by ultrasonic cleaning with alcohol and acetone.

[0064] (4) The rod obtained above is clamped in a plasma rotating electrode device, vacuum plasma melting and high speed rotation at 50000 r / min and vacuum degree of 5×10-3 Pa to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder is then sieved using a vibrating screen and selected with a particle size of 200 mesh to obtain refractory high entropy alloy powder.

[0065] Step 3, laser cladding: The mixed powder prepared in step 2 above is loaded into a powder feeder. The parameters for laser cladding are set as follows: synchronous powder feeding, laser power of 1200W-2200W (200W as a gradient), scanning speed of 10mm / s, cladding overlap rate of 60%, Ar2 gas flow rate of 15L / min, powder feeding speed of 1.2 r / min, and preheating temperature of 400℃. Under Ar2 atmosphere, the dried refractory high entropy alloy powder is deposited on the pretreated substrate surface to form a refractory high entropy alloy coating on the pretreated substrate surface.

[0066] It can be seen that the coating prepared in Comparative Example 1 has cracks in its macroscopic flaw detection. Figure 6 ) Counterexample 1 A laser cladding method for a refractory high-entropy alloy coating includes the following steps: Step 1, Pretreatment of substrate surface: (1) Use 1000# SiC sandpaper to polish the surface of the steel alloy substrate until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0067] (2) Use anhydrous ethanol as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0068] Step 2, Preparation of Refractory High-Entropy Alloy Powder: (1) Weigh out the corresponding high-purity metal particles with a purity ≥99.99% according to the following atomic percentage composition, and set aside: W 25at.%, Mo 25at.%, Ta 25at.%, Nb 25at.%.

[0069] (2) The weighed elemental particles are placed into a vacuum induction levitation melting furnace in order of increasing melting point. The furnace is repeatedly melted 6 times under a vacuum of 5×10-3Pa. Each time, the melting is carried out until a uniform melt is obtained. The furnace is then cooled to obtain a refractory high entropy alloy ingot with BCC structure, impurity content ≤0.1% and oxygen content ≤100ppm.

[0070] (3) Using wire electrical discharge machining, the refractory high entropy alloy ingot obtained above is cut into round bars with a diameter of 30 mm and a length of 150 mm. Then, the surface oxide layer is removed by grinding with 1000# SiC sandpaper, and the oil is removed by ultrasonic cleaning with alcohol and acetone.

[0071] (4) The rod obtained above is clamped in a plasma rotating electrode device, vacuum plasma melting and high speed rotation at 50000 r / min and vacuum degree of 5×10-3 Pa to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder is then sieved using a vibrating screen and selected with a particle size of 200 mesh to obtain refractory high entropy alloy powder.

[0072] Step 3: Prepare a mixed powder of elemental nickel powder, chromium powder, and refractory high-entropy alloy powder: 5 wt.% nickel powder, 2 wt.% chromium powder, and 93 wt.% refractory high-entropy alloy powder were added to a V-type vacuum powder mixer, and the nickel powder, chromium powder, and refractory high-entropy alloy powder were mixed at 60 r / min for 8 h to obtain a mixed powder. The mixed powder was dried in a vacuum drying oven at 90 ℃ for 6 h to be used as a deposition coating material.

[0073] Step 4, laser cladding: The mixed powder prepared in step 4 above was loaded into a powder feeder. The laser cladding parameters were set as follows: synchronous powder feeding, laser power of 1800W, scanning speed of 10mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.2r / min. Under an Ar2 atmosphere, the dried refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a refractory high-entropy alloy coating on the pretreated substrate surface. It can be seen that the refractory high-entropy alloy coating prepared in this counterexample has cracks on macroscopic flaw detection. Figure 7 ).

[0074] Counterexample 2 (Ni powder to Cr powder ratio is not 53:19, coating cracks).

[0075] A laser cladding method for a refractory high-entropy alloy coating includes the following steps: Step 1, Pretreatment of substrate surface: (1) Use 1000# SiC sandpaper to polish the surface of the steel alloy substrate until the surface shows a metallic luster, which can be considered as removing the surface oxide film.

[0076] (2) Use anhydrous ethanol as a cleaning agent to clean the polished substrate. After ultrasonic cleaning for 10 minutes, dry the substrate surface to remove the cleaning agent and obtain the pretreated substrate.

[0077] Step 2, Preparation of Refractory High-Entropy Alloy Powder: (1) Weigh out the corresponding high-purity metal particles with a purity ≥99.99% according to the following atomic percentage composition, and set aside: W 25at.%, Mo 25at.%, Ta 25at.%, Nb 25at.%.

[0078] (2) The weighed elemental particles are placed into a vacuum induction levitation melting furnace in order of increasing melting point. The furnace is repeatedly melted 6 times under a vacuum of 5×10-3Pa. Each time, the melting is carried out until a uniform melt is obtained. The furnace is then cooled to obtain a refractory high entropy alloy ingot with BCC structure, impurity content ≤0.1% and oxygen content ≤100ppm.

[0079] (3) Using wire electrical discharge machining, the refractory high entropy alloy ingot obtained above is cut into round bars with a diameter of 30 mm and a length of 150 mm. Then, the surface oxide layer is removed by grinding with 1000# SiC sandpaper, and the oil is removed by ultrasonic cleaning with alcohol and acetone.

[0080] (4) The rod obtained above is clamped in a plasma rotating electrode device, vacuum plasma melting and high speed rotation at 50000 r / min and vacuum degree of 5×10-3 Pa to prepare powder with sphericity ≥90% and oxygen content ≤200ppm. The powder is then sieved using a vibrating screen and selected with a particle size of 200 mesh to obtain refractory high entropy alloy powder.

[0081] Step 3: Prepare a mixed powder of elemental nickel powder, chromium powder, and refractory high-entropy alloy powder: 15 wt.% nickel powder, 25 wt.% chromium powder, and 60 wt.% refractory high-entropy alloy powder were added to a V-type vacuum powder mixer, and the nickel powder, chromium powder, and refractory high-entropy alloy powder were mixed at 60 r / min for 8 h to obtain a mixed powder. The mixed powder was dried in a vacuum drying oven at 90 ℃ for 6 h to be used as a deposition coating material.

[0082] Step 4, laser cladding: The mixed powder prepared in step 4 above was loaded into a powder feeder. The laser cladding parameters were set as follows: synchronous powder feeding, laser power of 2200W, scanning speed of 10mm / s, cladding overlap rate of 50%, Ar2 gas flow rate of 15L / min, and powder feeding speed of 1.2r / min. Under an Ar2 atmosphere, the dried refractory high-entropy alloy powder was deposited on the pretreated substrate surface to form a refractory high-entropy alloy coating on the pretreated substrate surface. It can be seen that the refractory high-entropy alloy coating prepared in this counterexample has cracks on macroscopic flaw detection. Figure 8 ).

[0083] Furthermore, it can be seen that the present invention forms a γ-tough phase by adding Ni and Cr to the Fe element in the matrix through solid solution: during the cladding process, Ni, Cr and Fe elements in the matrix undergo solid solution to form a face-centered cubic (FCC) γ phase. This γ phase has good plasticity and toughness, and can effectively absorb and alleviate thermal stress and mechanical impact during the cladding-service process, thereby improving the overall crack resistance and fatigue resistance of the coating; Synergistic effect of multiple elements: Adding Ni as the main element of the γ tough phase lays the foundation for high-temperature stability; adding Cr to form a dense Cr2O3 oxide film enhances the high-temperature oxidation resistance and corrosion resistance of the coating; adding Mo to strengthen the γ tough phase through solid solution, hinder grain boundary diffusion, and improve the coating's creep resistance. The dual-phase structure can effectively disperse thermal stress, improve structural toughness and stability, further reduce the risk of crack initiation, and protect the surface integrity of the cladding layer. The ratio of the tough phase and the high-entropy alloying phase in the coating can be controlled, balancing cladding crack susceptibility and high-temperature performance. This invention designed different WMoTaNb content gradients (from 30% to 70%), and while maintaining the Ni:Cr ratio at approximately 53:19, achieved controllable adjustment of the tough phase and the high-entropy hardening phase in the coating. With a low WMoTaNb content (approximately 30%-40%), the relatively high Ni and Cr content provides a sufficient compositional basis for the γ phase (face-centered cubic solid solution) and δ phase (Ni3Nb precipitates). This results in a higher proportion of reinforcing phases in the coating microstructure, which is conducive to the formation of fine and dispersed precipitates, significantly improving the high-temperature strength of the coating and making it suitable for applications under high-temperature and high-load conditions.

[0084] With an increased WMoTaNb content (approximately 60%-70%), Ni, Cr, and the high-entropy main elements are in relative equilibrium. The coating simultaneously contains both a γ-phase and a BCC solid solution structure, achieving synergistic optimization of toughness and hardness. While maintaining high-temperature mechanical properties, the structural stability and crack resistance of the cladding layer are also improved, making it suitable for medium- and high-temperature applications requiring both load-bearing capacity and wear resistance. By adjusting the WMoTaNb content gradient and maintaining a constant Ni:Cr ratio, this invention constructs a synergistic control strategy of "γ-phase-BCC phase," enabling controllable conversion between the strengthening and toughening phases in the coating. This effectively solves the problems of insufficient strengthening or easy cracking in traditional high-entropy cladding systems, improving the coating's application adaptability and engineering reliability.

[0085] 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 suppressing cracks in laser cladding of refractory high-entropy alloy coatings, characterized in that, It includes, The substrate is subjected to surface grinding and cleaning to remove oxide film and impurities; Prepare refractory high-entropy alloy powder. The expression for 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%; Nickel powder, chromium powder and the refractory high entropy alloy powder are mixed in a mass percentage to obtain a mixed powder, wherein the content of the refractory high entropy alloy powder is 30~70 wt.% and the ratio of nickel powder to chromium powder is 53:19; Laser cladding technology is used to deposit mixed powders onto the substrate surface under inert gas protection, forming a composite coating with the coexistence of γ tough phase and BCC hard phase.

2. The method according to claim 1, characterized in that, Preferably, the preparation of refractory high-entropy alloy powder includes, According to the atomic ratio of refractory high-entropy alloys, the corresponding elemental substances are weighed and melted into ingots by vacuum induction. The ingots are processed into bars by wire electrical discharge machining. Spherical refractory high-entropy alloy powders with particle sizes of 15-50 μm and oxygen content ≤200 ppm were prepared by plasma rotating electrode method.

3. The method according to claim 2, characterized in that, Elemental particles, in order of increasing melting point, are placed into a vacuum induction levitation furnace and smelted at 5 × 10⁻⁶ ℃. -3 Under a vacuum of Pa, the alloy is repeatedly melted into a homogeneous melt and then cooled in the furnace to obtain an ingot of a refractory high-entropy alloy with a BCC structure, an impurity content of ≤0.1%, and an oxygen content of ≤100ppm.

4. The method according to claim 1, characterized in that, The laser cladding parameters include: laser power of 1000~2200W, scanning speed of 5~30mm / s, powder feeding speed of 1~5g / min, spot diameter of 2~5mm, overlap rate of 30~70%, protective gas of argon, and flow rate of 10~25L / min.

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

6. The method according to claim 1, characterized in that, The composite coating comprises a γ phase and a BCC hard phase, the ratio of which is controlled according to the content of the refractory high-entropy alloy powder.

7. The method according to claim 1, characterized in that, The surface of the steel alloy substrate was polished with sandpaper until the surface showed a metallic luster, which was considered to remove the surface oxide film. The polished substrate was then cleaned with anhydrous ethanol as a cleaning agent. After ultrasonic cleaning for 10 minutes, the cleaning agent on the substrate surface was removed by drying, and the pretreated substrate was obtained.

8. The method according to claim 1, characterized in that, The thickness of the refractory high-entropy alloy coating is 0.4~1.5mm.

9. The method according to claim 1, characterized in that, The nickel powder, chromium powder, and refractory high-entropy alloy powder are mixed in a vacuum mixer at a speed of 60-120 r / min for 6-12 hours to ensure uniform composition; the mixed powder is then dried at 90-120℃ for 4-8 hours.

10. A composite coating, characterized in that, It is made by the method according to any one of claims 1-8.

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