Refractory high-entropy alloy spherical powder, preparation method and application

Abstract

The invention relates to the technical field of high-entropy alloy material preparation, in particular to refractory high-entropy alloy spherical powder and a preparation method and application thereof.The method comprises the steps that brand-new NbCrTiFeW alloy new components are designed, the NbCrTiFeW alloy new component raw materials are mixed and then alloyed in cooperation with mechanical alloying, and the refractory high-entropy alloy spherical powder is obtained through alloy powder drying, plasma melt-blowing and rapid condensation. And preparation of the single-phase body-centered cubic solid solution diagram high-entropy alloy spherical powder is achieved. The prepared refractory high-entropy alloy spherical powder is uniform in particle size distribution and good in sphericity degree, meanwhile, the wear resistance and corrosion resistance of the refractory high-entropy alloy spherical powder are guaranteed, and the problems that a refractory alloy spherical powder high-entropy alloy prepared in the prior art is thick in structure and segregated in composition are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of high-entropy alloy material preparation technology, specifically to a refractory high-entropy alloy spherical powder, its preparation method, and its application. Background Technology

[0002] In today's global wave of manufacturing transformation and upgrading, additive manufacturing (3D printing) technology, with its disruptive advantage of "design-manufacturing integration," has become a core engine driving innovation in high-end equipment, aerospace, biomedicine, and other fields. It achieves the direct molding of complex structural parts by layer-by-layer material deposition, breaking through the geometric constraints of traditional subtractive manufacturing, significantly shortening product development cycles, and reducing material waste and manufacturing costs. High-quality, low-cost refractory alloy spherical powders are the core support for the large-scale application of 3D printing technology in aerospace, high-end manufacturing, and other fields, directly determining the performance and reliability of the final components. Mastering its preparation technology is key to seizing the commanding heights of the additive manufacturing industry.

[0003] Currently, the mainstream preparation technologies for refractory alloy spherical powders are represented by gas atomization and rotating electrode atomization. Among them, gas atomization, as the most widely used powder preparation technology, works by using high-pressure gas (such as argon or nitrogen) to break up molten metal into tiny droplets, which then cool and solidify during flight to form spherical powder. The advantage of this technology lies in its wide applicability, capable of preparing powders for various alloy systems, and the ability to precisely control particle size through optimized nozzle structure and atomization parameters. In recent years, with the introduction of new technologies such as supersonic atomization and laminar flow atomization, the cooling rate of gas atomization has been significantly improved, optimizing the sphericity and oxygen content of the powder. Rotating electrode atomization uses the centrifugal force generated by electrode rotation as the breaking power. The electrode tip is melted by an electric arc or plasma beam, causing the molten metal to be ejected and solidified into powder under rotation. The unique feature of this technology is that it avoids gas intervention, reducing the oxygen content of the powder from the source, making it particularly suitable for chemically reactive materials such as titanium alloys. Furthermore, the powder prepared by the rotating electrode method has a narrower particle size distribution, excellent sphericity, smooth surface, and good flowability, significantly improving the uniformity and density of powder spreading during additive manufacturing. Despite significant progress in existing powder preparation technologies, a series of technical problems remain to be solved in the large-scale preparation of spherical powders of refractory alloys. While gas atomization improves powder performance through process optimization, its inherent principle leads to problems such as refractory element segregation, oxide inclusions, and hollow powder. During atomization, the rapid cooling of the molten metal prevents solute elements from diffusing evenly, easily leading to micro-segregation within the powder. This is particularly problematic for complex alloys containing refractory elements, such as nickel-based superalloys, where segregation significantly reduces the material's thermal strength and fatigue resistance, increasing the risk of cracking during use. Although gas atomization uses inert gas protection, the contact between the molten metal and the gas inevitably introduces oxidation reactions. Especially at high temperatures, reactive elements such as titanium and aluminum easily combine with oxygen to form oxide inclusions, becoming the source of crack initiation and seriously threatening the reliability of the components. During atomization, some of the gas trapped inside the molten metal droplets fails to escape in time, forming a hollow structure after solidification. This leads to a decrease in powder density and makes the powder prone to porosity defects during additive manufacturing, affecting the density and mechanical properties of the components. Furthermore, gas atomization requires extremely high equipment precision and process control. The maintenance costs of key components such as high-pressure gas systems and precision nozzles are high, and the atomization efficiency is relatively low, resulting in high powder production costs and making it difficult to meet the needs of large-scale applications. While the rotating electrode method performs well in terms of powder purity and sphericity, its powder preparation process requires the preparation of alloy electrodes through vacuum melting, forging, and machining. This process is complex and time-consuming, especially for small-batch, customized applications, where electrode preparation costs account for a higher proportion of the overall cost, significantly reducing its economic viability.At the same time, due to limitations in electrode rotation speed and melting power, the powder particle size prepared by the rotating electrode method is generally too large, which makes it difficult to meet the requirements of high-precision additive manufacturing processes for fine powders, thus limiting its application in the manufacturing of complex structural parts.

[0004] In summary, existing powder preparation technologies cannot simultaneously meet the industry's demands for "high quality, low cost, and large-scale production" of refractory alloy spherical powders. This has led to a long-term reliance on imports for high-end 3D printing powders, becoming a key bottleneck restricting the independent and controllable development of the additive manufacturing industry. Therefore, developing a new powder preparation technology that combines high purity, narrow particle size distribution, low oxygen content, and high production efficiency has become a core issue that the industry urgently needs to address. Summary of the Invention

[0005] To address the problems of coarse microstructure and compositional segregation in high-entropy spherical powders of refractory alloys prepared in existing technologies, this invention provides a spherical powder of refractory high-entropy alloys, a preparation method, and its application.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for preparing spherical powder of a refractory high-entropy alloy, characterized in that it comprises the following raw material components by mass fraction: 11.37%–33.9% Nb, 7.12%–9.54% Cr, 3.06%–4.10% Ti, 45.86%–61.50% Fe, and 10.06%–13.49% W; The preparation method includes the following steps: After Nb, Cr, Ti, Fe and W powders are mixed evenly, they are alloyed using a vibratory bar mill to obtain ultrafine high-entropy alloy powder. Ultrafine high-entropy alloy powder was melt-blown into spherical powder using plasma melt-blowing technology and then rapidly condensed to obtain refractory high-entropy alloy spherical powder.

[0007] Optionally, the raw material components include the following by mass fraction: 20.41%–27.7% Nb, 7.78%–8.57% Cr, 3.34%–3.68% Ti, 50.11%–55.22% Fe and 11%–12.12% W.

[0008] Optionally, the method for alloying the vibratory bar machine is as follows: The uniformly mixed Nb, Cr, Ti, Fe, and W powders were placed in a rod mill jar and evacuated to a vacuum of 0.8 × 10⁻⁶. -5 -1.2×10 -5 After Pa, argon gas is introduced, n-heptane is added, and argon gas is introduced again. The mixture is then alloyed in a vibratory rod mill for 4-6 hours. After alloying in the vibratory bar mill for 4-6 hours, the grinding jar is evacuated again to 0.8 × 10⁻⁶.-5 -1.2×10 -5 Pa, and then alloyed with anhydrous ethanol in a rod mill for 8-25 minutes using a vibrating rod mill to obtain a mixture of high-entropy alloy powder and anhydrous ethanol; The anhydrous ethanol in the mixture of high-entropy alloy powder and anhydrous ethanol was removed, and the mixture was then vacuum dried to obtain ultrafine high-entropy alloy powder.

[0009] Optionally, the ratio of n-heptane, anhydrous ethanol to Nb, Cr, Ti, Fe and W powder is (80-120 mL): (900-1100 mL): (350-420 g).

[0010] Optionally, the vacuum degree of vacuum drying is below -0.1 MPa, and the vacuum drying temperature is 60°C-80°C.

[0011] Optionally, the method of using plasma melt-blowing technology to melt-blown spheroidize ultrafine high-entropy alloy powder and then rapidly condensing it to obtain refractory high-entropy alloy spherical powder is as follows: Ultrafine high-entropy alloy powder is placed in a plasma melt-blown generator. Under nitrogen protection and stirring conditions, the ultrafine high-entropy alloy powder is heated to melt using the plasma melt-blown generator. As the molten ultrafine high-entropy alloy droplets fall, they rapidly solidify to form refractory high-entropy alloy spherical powder.

[0012] Optionally, the set current of the plasma meltblown generator is 70-80A, the air delivery speed of the plasma meltblown generator gun is 40-50L / min, the stirring speed is 5000-720-5500-1440r / min, and the powder feeding rate is 8.5-9.5g / min.

[0013] This invention also provides a refractory high-entropy alloy spherical powder, prepared using the above-described method for preparing refractory high-entropy alloy spherical powder. The self-corrosion potential of the refractory high-entropy alloy spherical powder reaches -0.49V, and the self-corrosion current reaches 1.323 x 10⁻⁶. - 5 uA·cm 2 .

[0014] The application of the above-mentioned refractory high-entropy alloy spherical powder in the preparation of protective coatings.

[0015] The application of the refractory high-entropy alloy spherical powder in the preparation of protective coatings includes the following steps: Under nitrogen protection, refractory high-entropy alloy spherical powder is printed into a protective coating using laser melting 3D printing technology; the laser power of the laser melting 3D printing is 900-1200W, the powder supply speed is 3-7g / s, and the scanning speed is 2.4-3.0m / min.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing spherical powders of refractory high-entropy alloys. This method involves designing a novel NbCrTiFeW alloy composition and employing a combined mechanical alloying and plasma-blowing process to mix and alloy the NbCrTiFeW alloy raw materials. After drying the alloy powder, plasma-blowing, and rapid condensation, single-phase body-centered cubic solid solution high-entropy alloy spherical powders are prepared. Mechanical alloying has unique advantages in promoting solid-state alloying of refractory systems, especially in preparing supersaturated solid solution alloy powders, yielding alloy powders with uniform composition. The mechanical alloying technology achieves homogenization of the high-entropy alloy powder composition through the combined effects of mechanical grinding (plastic deformation) and temperature enhancement (atomic diffusion). Then, the metal powder particles are rapidly heated to a molten state using a high-temperature plasma or other heat source. Under surface tension, the molten droplets shrink into spheres. Subsequently, during rapid condensation, the liquid metal gradually transforms into a solid state while maintaining its spherical shape. Due to the extremely rapid condensation rate, the droplets do not have time to form complex crystal structures or undergo segregation, thus ensuring the quality and performance of the spherical powder. This method, through a novel compositional design combined with a dual process of mechanical alloying and plasma melt-blowing, produces refractory high-entropy alloy spherical powders with uniform particle size distribution and excellent sphericity, while ensuring wear resistance and corrosion resistance. Furthermore, this preparation method is characterized by low cost and high flexibility, enabling small-batch, high-quality production of refractory high-entropy alloy spherical powders, providing a feasible technical solution for the industrial application of high-entropy alloys.

[0017] This invention also provides a refractory high-entropy alloy spherical powder, prepared using the above-described method for preparing refractory high-entropy alloy spherical powder. The self-corrosion potential of the refractory high-entropy alloy spherical powder reaches -0.49V, and the self-corrosion current reaches 1.323 x 10⁻⁶. - 5 uA·cm 2 This refractory high-entropy alloy spherical powder exhibits high thermodynamic stability in corrosive media, and from an energy perspective, it tends to maintain its structural stability, making it less susceptible to corrosion. The lower self-corrosion current reflects the alloy powder's ability to maintain stable performance over extended periods in corrosive environments, significantly extending the material's service life. With its excellent self-corrosion potential and current indicators, this refractory high-entropy alloy spherical powder effectively resists corrosion in various harsh corrosive environments, reducing material damage and equipment failure caused by corrosion, lowering maintenance costs and replacement frequency. Its strong environmental adaptability meets the stringent material requirements of high-end manufacturing fields such as aerospace, energy, and automotive.

[0018] The application of the aforementioned refractory high-entropy alloy spherical powder in the preparation of protective coatings. Compared to 316L substrates, the protective coating prepared using these refractory high-entropy alloy spherical powders exhibits superior corrosion resistance and a 2-3 times increase in hardness. The protective coating prepared from the refractory high-entropy alloy spherical powders effectively protects the substrate from corrosion, maintains the structural integrity of the equipment, and ensures safe and reliable operation under various working conditions. Simultaneously, the high hardness of this protective coating enhances the 316L substrate's resistance to external impacts, protecting the structural integrity of the equipment. This provides valuable experience and examples for the application of high-entropy alloys in the field of protection, and contributes to promoting the development of high-entropy alloy material technology and expanding its application scope. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of a method for preparing spherical powder of a refractory high-entropy alloy according to the present invention.

[0020] Figure 2 The XRD patterns are of the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention.

[0021] Figure 3 The images shown are SEM images of the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention. Specifically, a is the SEM image of the refractory high-entropy alloy spherical powder prepared in Example 1, b is the SEM image of the refractory high-entropy alloy spherical powder prepared in Example 2, c is the SEM image of the refractory high-entropy alloy spherical powder prepared in Example 3, and d is the SEM image of the refractory high-entropy alloy spherical powder prepared in Example 4.

[0022] Figure 4 The images show the SEM morphology and corresponding elemental distribution diagrams of the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention. Specifically, a is the SEM morphology and corresponding elemental distribution diagrams of Fe, Nb, Cr, W, and Ti for the refractory high-entropy alloy spherical powder prepared in Example 1; b is the SEM morphology and corresponding elemental distribution diagrams of Fe, Nb, Cr, W, and Ti for the refractory high-entropy alloy spherical powder prepared in Example 2; c is the SEM morphology and corresponding elemental distribution diagrams of Fe, Nb, Cr, W, and Ti for the refractory high-entropy alloy spherical powder prepared in Example 3; and d is the SEM morphology and corresponding elemental distribution diagrams of Fe, Nb, Cr, W, and Ti for the refractory high-entropy alloy spherical powder prepared in Example 4.

[0023] Figure 5 The XRD patterns are of the protective coatings prepared using the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention.

[0024] Figure 6 The images show the SEM morphology of the protective coatings prepared using the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention.

[0025] Figure 7 EDS image of the protective coating prepared using the refractory high-entropy alloy spherical powder prepared in Example 3 of this invention.

[0026] Figure 8 The graph shows the hardness variation of the protective coating prepared using the refractory high-entropy alloy spherical powder prepared in Examples 1-4 of this invention.

[0027] Figure 9 The graph shows the change in the tribological properties of the protective coating prepared using the refractory high-entropy alloy spherical powder prepared in Examples 1-4 of this invention.

[0028] Figure 10 The graphs show the electrochemical performance changes of the protective coatings prepared using the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention. In the graphs, a is the Tafel curve and b is the Nyquist curve. Detailed Implementation

[0029] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0030] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0031] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0032] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0033] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0034] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0035] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0036] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0037] This invention discloses a method for preparing spherical powder of refractory high-entropy alloy, comprising the following raw material components by mass fraction: 11.37%–33.9% Nb, 7.12%–9.54% Cr, 3.06%–4.10% Ti, 45.86%–61.50% Fe, and 10.06%–13.49% W; preferably, comprising 20.41%–27.7% Nb, 7.78%–8.57% Cr, 3.34%–3.68% Ti, 50.11%–55.22% Fe, and 11%–12.12% W.

[0038] See Figure 1 The preparation method includes the following steps: S1: After uniformly mixing Nb, Cr, Ti, Fe, and W powders, alloying is performed using a vibratory rod mill to obtain ultrafine high-entropy alloy powder, specifically: After uniformly mixing Nb, Cr, Ti, Fe, and W powders with a particle size of 50–100 μm, the mixture was placed into a rod mill jar and vacuumed to 0.8 × 10⁻⁶. -5 -1.2×10 -5 After Pa, argon gas is introduced, and this process is repeated twice. Then, a vacuum is created again, heptane is injected, and argon gas is introduced. Alloying is then performed in a vibratory rod mill for 2-3 hours. The mill jar is then evacuated to a vacuum level of 0.8 × 10⁻⁶. -5 -1.2×10 -5Pa, fill the rod mill jar with anhydrous ethanol, continue grinding for 8-25 minutes, then take out the mixture of alloy powder and ethanol, let it stand for more than 10 hours, filter off the supernatant, place it in a vacuum drying oven, keep the vacuum degree of the vacuum drying oven below -0.1 MPa, keep the temperature at 60°C-80°C, vacuum dry to obtain ultrafine high entropy alloy powder, and vacuum seal and store it.

[0039] S2: Ultrafine high-entropy alloy powder is melt-blown into spherical particles using plasma melt-blowing technology and then rapidly condensed to obtain refractory high-entropy alloy spherical powder, specifically: Ultrafine high-entropy alloy powder is placed in the powder feeder of a plasma melt-blown generator. The current is set to 70-80A, and the gas delivery rate of the plasma melt-blown generator is 40-50 L / min. Simultaneously, the switch is turned on to allow the plasma gun to spray flames. Under nitrogen protection and a stirring speed of 5000-720-5500-1440 r / min, the ultrafine high-entropy alloy powder is heated to melt using the plasma melt-blown generator. The molten ultrafine high-entropy alloy droplets are allowed to fall and rapidly solidify into refractory high-entropy alloy spherical powder. A cooling circulation system can be set up during the fall of the molten ultrafine high-entropy alloy droplets to facilitate rapid solidification and collection into a collecting device. Once all the refractory high-entropy alloy spherical powder has fallen into the collecting device, the powder feeder is turned off, followed by the plasma generator. After the temperature of the refractory high-entropy alloy spherical powder cools to room temperature, the collecting device is removed, and the powder is taken out. The powder is screened using sieves of different mesh sizes to remove large particles, ultimately obtaining ultrafine refractory high-entropy alloy spherical powder; wherein the powder feeding rate of the powder feeder is 8.5-9.5 g / min.

[0040] The application of the aforementioned refractory high-entropy alloy spherical powder in the preparation of protective coatings includes the following steps: Under nitrogen protection, refractory high-entropy alloy spherical powder is printed into a protective coating using laser melting 3D printing technology; the laser power of the laser melting 3D printing is 900-1200W, the powder supply speed is 3-7g / s, and the scanning speed is 2.4-3.0m / min.

[0041] Example 1 This invention provides spherical powders of refractory high-entropy alloys (Nb1Cr). 1.5 Ti 0.7 Fe9W 0.6 (Total weight 400g), Nb 11.37%, Cr 9.54%, Ti 4.10%, Fe 61.50% and W 13.49% powders were mixed evenly according to the mass fraction, and then loaded into a rod mill jar and evacuated to 1×10 -5After Pa, argon gas is introduced, and this process is repeated twice to prevent the elemental powder from being oxidized and forming intermetallic compounds during the alloying process under force-thermal coupling in the high-energy rod mill. 100 ml of n-heptane is added to reduce the mixing entropy of the powder during high-energy rod mill grinding, and at the same time reduce the ductility of the powder, so that the powder particle size can be significantly reduced. Argon gas is introduced again, and the mixed powder is alloyed in the high-energy vibratory rod mill for 5 hours. The rod mill jar is then evacuated to 1×10⁻⁶. -5 Pa, 1000 ml of anhydrous ethanol was added to the rod mill jar, and grinding was continued for 10 min. The mixture of high entropy alloy powder and ethanol was then removed, allowed to stand for 12 h, and the supernatant was filtered off. The mixture was then placed in a vacuum drying oven, with the vacuum level maintained below -0.1 MPa and the temperature maintained at 65°C. After drying for 8 h, ultrafine high entropy alloy powder was obtained and vacuum-sealed for storage.

[0042] Turn on the plasma meltblown generator, set the current to 70A, and the gas delivery rate of the gun body reaches 44L / min. Simultaneously, turn on the switch to allow the plasma gun body to spray flame. Load the ultrafine high-entropy alloy powder into the powder feeder, turn on the controller, and simultaneously introduce the protective gas argon. Turn on the motor to make the stirrer rotate, set the speed to 5400-960 r / min, and the actual powder delivery rate is 8.9 g / min. Heat the ultrafine high-entropy alloy powder to a molten state through the plasma flame, and allow the molten droplets to rapidly solidify during their fall from the flame due to the cooling circulation system, while simultaneously falling into the bottom collection device. After all the refractory high-entropy alloy spherical powder has fallen into the collection device, first turn off the powder feeder, and then turn off the plasma generator. After the temperature of the refractory high-entropy alloy spherical powder drops to room temperature, remove the collection device and take out the refractory high-entropy alloy spherical powder. Screen the refractory high-entropy alloy spherical powder using sieves of different mesh sizes to remove large particles, finally obtaining ultrafine spherical alloy powder, denoted as Nb1.

[0043] Example 2 This invention provides spherical powders of refractory high-entropy alloys (Nb2Cr). 1.5 Ti 0.7 Fe9W 0.6 (Total weight 400g), Nb 20.41%, Cr 8.57%, Ti 3.68%, Fe 55.22% and W 12.12% powders were mixed evenly according to the mass fraction, and then loaded into a rod mill jar and evacuated to 1×10 -5 After Pa, argon gas is introduced, and this process is repeated twice to prevent the elemental powder from being oxidized and forming intermetallic compounds during the alloying process under force-thermal coupling in the high-energy rod mill. 100 ml of n-heptane is added to reduce the mixing entropy of the powder during high-energy rod mill grinding, and at the same time reduce the ductility of the powder, so that the powder particle size can be significantly reduced. Argon gas is introduced again, and the mixed powder is alloyed in the high-energy vibratory rod mill for 5 hours. The rod mill jar is then evacuated to 1×10⁻⁶.-5 Pa, 1000 ml of anhydrous ethanol was added to the rod mill jar, and grinding was continued for 10 min. The mixture of high entropy alloy powder and ethanol was then removed, allowed to stand for 12 h, and the supernatant was filtered off. The mixture was then placed in a vacuum drying oven, with the vacuum level maintained below -0.1 MPa and the temperature maintained at 65°C. After drying for 8 h, ultrafine high entropy alloy powder was obtained and vacuum-sealed for storage.

[0044] Turn on the plasma meltblown generator, set the current to 70A, and ensure the gun body gas delivery rate reaches 44L / min. Simultaneously, turn on the switch to allow the plasma gun body to spray flame. Load the ultrafine high-entropy alloy powder into the powder feeder, turn on the controller, and simultaneously introduce the protective gas argon. Turn on the motor to rotate the stirrer, setting the speed to 5400-1200-960 r / min, with an actual powder delivery rate of 8.9 g / min. Heat the ultrafine high-entropy alloy powder to a molten state using the plasma flame, and allow the molten droplets to rapidly solidify during their fall from the flame due to the cooling circulation system, simultaneously falling into the bottom collection device. Once all the refractory high-entropy alloy spherical powder has fallen into the collection device, first turn off the powder feeder, then turn off the plasma generator. After the temperature of the refractory high-entropy alloy spherical powder has cooled to room temperature, remove the collection device and take out the refractory high-entropy alloy spherical powder. The spherical powder of refractory high-entropy alloy was screened with sieves of different mesh sizes to remove large particles, and finally ultrafine spherical alloy powder was obtained, denoted as Nb2.

[0045] Example 3 This invention provides spherical powder of refractory high-entropy alloy (Nb3Cr). 1.5 Ti 0.7 Fe9W 0.6 (Total weight 400g), Nb 27.78%, Cr 7.78%, Ti 3.34%, Fe 50.11% and W 11% powders were mixed evenly according to the mass fraction, and then loaded into a rod mill jar and evacuated to 1×10 -5 After Pa, argon gas is introduced, and this process is repeated twice to prevent the elemental powder from being oxidized and forming intermetallic compounds during the alloying process under force-thermal coupling in the high-energy rod mill. 100 ml of n-heptane is added to reduce the mixing entropy of the powder during high-energy rod mill grinding, and at the same time reduce the ductility of the powder, so that the powder particle size can be significantly reduced. Argon gas is introduced again, and the mixed powder is alloyed in the high-energy vibratory rod mill for 5 hours. The rod mill jar is then evacuated to 1×10⁻⁶. -5 Pa, 1000 ml of anhydrous ethanol was added to the rod mill jar, and grinding was continued for 10 min. The mixture of high entropy alloy powder and ethanol was then removed, allowed to stand for 12 h, and the supernatant was filtered off. The mixture was then placed in a vacuum drying oven, with the vacuum level maintained below -0.1 MPa and the temperature maintained at 65°C. After drying for 8 h, ultrafine high entropy alloy powder was obtained and vacuum-sealed for storage.

[0046] Turn on the plasma meltblown generator, set the current to 70A, and the gas delivery rate of the gun body reaches 44L / min. Simultaneously, turn on the switch to allow the plasma gun body to spray flame. Load the ultrafine high-entropy alloy powder into the powder feeder, turn on the controller, and simultaneously introduce the protective gas argon. Turn on the motor to make the stirrer rotate, set the speed to 960-5400 r / min, and the actual powder delivery rate is 8.9 g / min. Heat the ultrafine high-entropy alloy powder to a molten state through the plasma flame, and allow the molten droplets to rapidly solidify during their fall from the flame due to the cooling circulation system, while simultaneously falling into the bottom collection device. After all the refractory high-entropy alloy spherical powder has fallen into the collection device, first turn off the powder feeder, and then turn off the plasma generator. After the temperature of the refractory high-entropy alloy spherical powder drops to room temperature, remove the collection device and take out the refractory high-entropy alloy spherical powder. Screen the refractory high-entropy alloy spherical powder using sieves of different mesh sizes to remove large particles, finally obtaining ultrafine spherical alloy powder, denoted as Nb3.

[0047] Example 4 This invention provides spherical powders of refractory high-entropy alloy (Nb4Cr). 1.5 Ti 0.7 Fe9W 0.6 (Total weight 400g), Nb 33.91%, Cr 7.12%, Ti 3.06%, Fe 45.86% and W 10.06% powders were mixed evenly according to the mass fraction, and then loaded into a rod mill jar and evacuated to 1×10 -5 After Pa, argon gas is introduced, and this process is repeated twice to prevent the elemental powder from being oxidized and forming intermetallic compounds during the alloying process under force-thermal coupling in the high-energy rod mill. 100 ml of n-heptane is added to reduce the mixing entropy of the powder during high-energy rod mill grinding, and at the same time reduce the ductility of the powder, so that the powder particle size can be significantly reduced. Argon gas is introduced again, and the mixed powder is alloyed in the high-energy vibratory rod mill for 5 hours. The rod mill jar is then evacuated to 1×10⁻⁶. -5 Pa, 1000 ml of anhydrous ethanol was added to the rod mill jar, and grinding was continued for 10 min. The mixture of high entropy alloy powder and ethanol was then removed, allowed to stand for 12 h, and the supernatant was filtered off. The mixture was then placed in a vacuum drying oven, with the vacuum level maintained below -0.1 MPa and the temperature maintained at 65°C. After drying for 8 h, ultrafine high entropy alloy powder was obtained and vacuum-sealed for storage.

[0048] Turn on the plasma meltblown generator, set the current to 70A, and the gas delivery rate of the gun body reaches 44L / min. Simultaneously, turn on the switch to allow the plasma gun body to spray flame. Load the ultrafine high-entropy alloy powder into the powder feeder, turn on the controller, and simultaneously introduce the protective gas argon. Turn on the motor to make the stirrer rotate, set the speed to 960-5400 r / min, and the actual powder delivery rate is 8.9 g / min. Heat the ultrafine high-entropy alloy powder to a molten state through the plasma flame, and allow the molten droplets to rapidly solidify during their fall from the flame due to the cooling circulation system, while simultaneously falling into the bottom collection device. After all the refractory high-entropy alloy spherical powder has fallen into the collection device, first turn off the powder feeder, and then turn off the plasma generator. After the temperature of the refractory high-entropy alloy spherical powder drops to room temperature, remove the collection device and take out the refractory high-entropy alloy spherical powder. Screen the refractory high-entropy alloy spherical powder using sieves of different mesh sizes to remove large particles, finally obtaining ultrafine spherical alloy powder, denoted as Nb4.

[0049] See Figure 2 XRD analysis of the refractory high-entropy alloy spherical powders prepared in Examples 1-4 revealed that all elemental powders underwent an alloying process, forming a single-phase BCC solid solution. No second phase precipitated, indicating a high degree of alloying and demonstrating the rationality of the high-entropy alloy design composition and the feasibility of the process.

[0050] See Figure 3 SEM analysis of the refractory high-entropy alloy spherical powders prepared in Examples 1-4 showed that all high-entropy alloy powders with different Nb contents were spherical after plasma melt-blowing. Through in-depth mechanistic exploration and analysis, the sufficient heat environment provided by the plasma power source achieved the ideal heating conditions required for the complete melting of the alloy powder. After heating, the powder was in a molten state (quasi-spherical). During its descent, it was subjected to gravity and the tension of the protective argon gas, rapidly collapsing and solidifying into spherical powder in the cooling circulation system. The high degree of sphericity, smooth and intact surface, and uniform particle size distribution indicate that the process parameters were stable and controllable. With increasing Nb content, the sphericity of the powder decreased slightly, possibly related to the increased melting point of the element leading to reduced melt flowability. However, the overall powder still maintained good formability, meeting the morphological requirements of the raw material powder for subsequent additive manufacturing.

[0051] See Figure 4 SEM analysis and elemental analysis were performed on the refractory high-entropy alloy spherical powders prepared in Examples 1-4. The figures show that Nb, Cr, Ti, Fe, and W are uniformly distributed. Mechanical alloying has unique advantages in promoting solid-state alloying of refractory systems, especially in preparing supersaturated solid solution alloy powders, and can obtain alloy powders with uniform composition. Mechanical alloying technology achieves compositional homogenization of this type of high-entropy alloy metal powder through the combined effects of mechanical grinding (plastic deformation) and temperature increase (atomic diffusion).

[0052] The refractory high-entropy alloy spherical powders prepared in Examples 1-4 were loaded into ring-shaped powder feeders. Argon gas was introduced to provide a protective atmosphere and blow out the powder. The power switch and protective atmosphere valve of the powder feeder were turned on to fill the container with protective gas to prevent powder oxidation. The laser condenser circulating water system was turned on, and when the water temperature reached room temperature (greater than 21.5℃), the laser was turned on for positioning. The scanning path was set, the printer's processing accuracy was set to 0.1mm, and the parameters of the coaxial powder-feeding 3D printer were set as follows: laser power 1200W, powder supply speed 5g / s, scanning speed 2.6m / min. The 3D printer was debugged to execute the NH-1 command to print a 30×20mm high-entropy alloy coating on the pretreated 316L substrate. Finally, a 3-4mm refractory high-entropy alloy coating was obtained on the 316L substrate. After the coating printing was completed, the laser power was turned off, powder feeding was stopped, and the protective gas valve was closed. After the printed specimen cooled, samples were taken for processing, and the phase structure, microstructure, and properties were characterized and analyzed. The 316L substrate has dimensions of 100×100×20mm. After rust removal, it is cleaned in an ultrasonic cleaner for 30 minutes, and then its surface is polished smooth with 180-grit, 400-grit, and 800-grit sandpaper in sequence. Finally, it is dried in a drying oven at 30℃ for 10 minutes.

[0053] See Figure 5 XRD tests were performed on the protective coating prepared using the refractory high-entropy alloy spherical powder prepared in Examples 1-4 of this invention. It can be seen that the structure of the protective coating is almost the same as that of the powder, both being single-phase BCC structures with no second phase precipitation, indicating a high degree of alloying. This also proves that the prepared high-entropy alloy powder is energy stable and non-metastable.

[0054] See Figure 6 SEM analysis was performed on the protective coatings prepared using the refractory high-entropy alloy spherical powders from Examples 1-4 of this invention. It was observed that with increasing Nb content, the grain size gradually decreased due to grain refinement. Furthermore, the microstructure of the prepared protective coatings was almost entirely equiaxed crystals. In addition, some irregular particles aggregated within or along the grain boundaries. With increasing Nb content, the size of the white particles decreased significantly. The microstructure of the matrix became a non-uniform cellular structure. Moreover, a large number of Ti atoms dissolved in the crystals caused lattice distortion, leading to solid solution strengthening.

[0055] See Figure 7EDS analysis was performed on the protective coating prepared using the refractory high-entropy alloy spherical powder prepared in Example 3 of this invention. The results showed that the phase within the scanned region was rich in Fe, Cr, and Nb. EDS also revealed an abundance of Ti at grain boundaries and within the precipitated particles. This is mainly due to the atomic radii, and the close electronegativity among the four elements, resulting in an inter-element mixing ratio close to 0 kJ·mol⁻¹. -1 It easily forms an infinite solid solution.

[0056] See Figure 8 Hardness variation tests were conducted on the protective coatings prepared using the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention. It was observed that the average thickness of the cladding layer was approximately 1.2 mm, and the hardness values ​​were obtained as average values, thus the interference from defects was minimal. The average hardness of the substrate was only 192 HV. 0.2 When x=1 (Nb) x Cr 1.5 Ti 0.7 Fe9W 0.6 When x = 1, 2, 3, or 4, the hardness is three times that of the substrate. This increase in hardness is primarily due to the mutual solubility of atoms with size differences, causing lattice distortion and resulting in solid solution strengthening. When x = 4, the hardness of the cladding layer significantly increases, reaching 680 HV. 0.2 It is 3.5 times harder than the substrate.

[0057] See Figure 9 The tribological properties of the protective coatings prepared using the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention were tested. At the beginning of the friction test, it was clearly visible in the images that the friction coefficients of both the protective coating and the substrate increased sharply. This was due to certain roughness of the grinding material and the adhesion of the friction pair. As the friction process continued, the actual contact area expanded, ultimately leading to a sharp increase in the friction coefficient. When the friction process entered the stable wear zone, the stable friction coefficients of different samples continuously decreased with increasing Nb content. The protective coating exhibited a lower and more stable friction coefficient. For metallic materials, the lower the friction coefficient, the more stable the curve, and the better the wear resistance under friction conditions.

[0058] See Figure 10 Electrochemical performance tests were conducted on the protective coatings prepared using the refractory high-entropy alloy spherical powders prepared in Examples 1-4 of this invention. Generally, the smaller the self-corrosion current (icm) and the higher the self-corrosion potential (Eem), the stronger the corrosion resistance. In the initial stage of anodic polarization, the self-current density increases with the increase of the potential, and the cladding layer undergoes an anodic dissolution reaction. The anodic polarization curves within this range conform to Tafel's slope law. Figure 10As can be seen from 'a', Nb3 has the highest self-corrosion potential (-0.49V) and the lowest self-corrosion current (1.323x10⁻¹⁰). -5 uA·cm 2 ( ), cladding layers with different Nb contents all exhibited high positive self-corrosion potentials and low self-corrosion currents. In b, the Nyquist plots of all samples showed a concave semi-circular shape in the high-frequency region. The curve describes the impedance of the cladding layer. The wider impedance-capacitance loop further indicates the variation in corrosion resistance of all samples, suggesting improved corrosion resistance.

[0059] Example 5 Unlike Example 3, the ratio of n-heptane, anhydrous ethanol, and Nb, Cr, Ti, Fe, and W powders is 80 mL: 900 mL: 350 g; the set current of the plasma meltblown generator is 80 A, the gas delivery speed of the plasma meltblown generator gun is 50 L / min, the stirring speed is 1440-5500 r / min, and the powder delivery rate is 9.5 g / min.

[0060] Example 6 Unlike Example 3, the ratio of n-heptane, anhydrous ethanol, and Nb, Cr, Ti, Fe, and W powders is 120 mL: 1100 mL: 420 g; the set current of the plasma meltblown generator is 75 A, the gas delivery speed of the plasma meltblown generator gun is 40 L / min, the stirring speed is 5000 r / min to 720 r / min, and the powder delivery rate is 9 g / min.

[0061] Example 7 Unlike Example 3, the ratio of n-heptane, anhydrous ethanol, and Nb, Cr, Ti, Fe, and W powders is 100 mL: 1000 mL: 400 g; the set current of the plasma meltblown generator is 70 A, the gas delivery speed of the plasma meltblown generator gun is 42 L / min, the stirring speed is 1380-5300 r / min, and the powder delivery rate is 8.5 g / min.

[0062] In summary, this invention provides a method for preparing refractory high-entropy alloy spherical powder, its application, and a novel NbCrTiFeW alloy composition. By employing mechanical alloying, metals (niobium powder, chromium powder, titanium powder, iron powder, and tungsten powder) are uniformly mixed in a specific ratio and then alloyed. After drying the alloy powder, a single-phase body-centered cubic solid solution high-entropy alloy powder is successfully prepared. This method utilizes a dual process of mechanical alloying and plasma melt-blowing to explore a feasible solution for the flexible preparation of low-cost, high-quality, small-batch, specialized alloy spherical powders. High-entropy alloy coating materials were fabricated using laser melting deposition, exhibiting superior corrosion resistance and a 2-3 times increase in hardness compared to 316L substrates. Through process parameter optimization and powder characteristic research, this method yields refractory high-entropy alloy molded parts with fine microstructure, uniform composition, and excellent performance, effectively solving problems such as coarse microstructure and severe compositional segregation in high-entropy alloys containing refractory elements.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing spherical powder of a refractory high-entropy alloy, characterized in that, The raw material components, by mass fraction, include the following: 11.37%–33.9% Nb, 7.12%–9.54% Cr, 3.06%–4.10% Ti, 45.86%–61.50% Fe, and 10.06%–13.49% W; The preparation method includes the following steps: After Nb, Cr, Ti, Fe and W powders are mixed evenly, they are alloyed using a vibratory bar mill to obtain ultrafine high-entropy alloy powder. Ultrafine high-entropy alloy powder was melt-blown into spherical powder using plasma melt-blowing technology and then rapidly condensed to obtain refractory high-entropy alloy spherical powder.

2. The method for preparing refractory high-entropy alloy spherical powder according to claim 1, characterized in that, The raw material components, by mass fraction, include the following: 20.41%–27.7% Nb, 7.78%–8.57% Cr, 3.34%–3.68% Ti, 50.11%–55.22% Fe, and 11%–12.12% W.

3. The method for preparing refractory high-entropy alloy spherical powder according to claim 1, characterized in that, The method for alloying the vibratory rod machine is as follows: The uniformly mixed Nb, Cr, Ti, Fe, and W powders were placed in a rod mill jar and evacuated to a vacuum of 0.8 × 10⁻⁶. -5 -1.2×10 -5 After Pa, argon gas is introduced, n-heptane is added, and argon gas is introduced again. The mixture is then alloyed in a vibratory rod mill for 4-6 hours. After alloying in the vibratory bar mill for 4-6 hours, the grinding jar is evacuated again to 0.8 × 10⁻⁶. -5 -1.2×10 -5 Pa, and then alloyed with anhydrous ethanol in a rod mill for 8-25 minutes using a vibrating rod mill to obtain a mixture of high-entropy alloy powder and anhydrous ethanol; The anhydrous ethanol in the mixture of high-entropy alloy powder and anhydrous ethanol was removed, and the mixture was then vacuum dried to obtain ultrafine high-entropy alloy powder.

4. The method for preparing refractory high-entropy alloy spherical powder according to claim 3, characterized in that, The ratio of n-heptane, anhydrous ethanol, and Nb, Cr, Ti, Fe, and W powder is (80-120 mL): (900-1100 mL): (350-420 g).

5. The method for preparing refractory high-entropy alloy spherical powder according to claim 3, characterized in that, The vacuum degree of vacuum drying is below -0.1MPa, and the vacuum drying temperature is 60°C-80°C.

6. The method for preparing refractory high-entropy alloy spherical powder according to claim 1, characterized in that, The method for sphericalizing ultrafine high-entropy alloy powder using plasma melt-blowing technology and then rapidly condensing it to obtain refractory high-entropy alloy spherical powder is as follows: Ultrafine high-entropy alloy powder is placed in a plasma melt-blown generator. Under nitrogen protection and stirring conditions, the ultrafine high-entropy alloy powder is heated to melt using the plasma melt-blown generator. As the molten ultrafine high-entropy alloy droplets fall, they rapidly solidify to form refractory high-entropy alloy spherical powder.

7. The method for preparing refractory high-entropy alloy spherical powder according to claim 6, characterized in that, The set current of the plasma meltblown generator is 70-80A, the air delivery speed of the plasma meltblown generator gun is 40-50L / min, the stirring speed of the powder feeder is 5000-720-5500-1440r / min, and the powder delivery rate is 8.5-9.5g / min.

8. A spherical powder of a refractory high-entropy alloy, characterized in that, The refractory high-entropy alloy spherical powder is prepared using the method described in any one of claims 1-7, and the self-corrosion potential of the refractory high-entropy alloy spherical powder reaches -0.49V, and the self-corrosion current reaches 1.323x10⁻⁶. -5 uA·cm 2 .

9. The application of the refractory high-entropy alloy spherical powder according to claim 8 in the preparation of protective coatings.

10. The application of the refractory high-entropy alloy spherical powder according to claim 9 in the preparation of protective coatings, characterized in that, Includes the following steps: Under nitrogen protection, refractory high-entropy alloy spherical powder is printed into a protective coating using laser melting 3D printing technology; the laser power of the laser melting 3D printing is 900-1200W, the powder supply speed is 3-7g / s, and the scanning speed is 2.4-3.0m / min.

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