A multi-scale cemented carbide friction stir welding tool and a method for manufacturing the same

Abstract

This invention discloses a multi-scale cemented carbide friction stir welding head and its preparation method, which is made from the following raw materials: 10-25wt% of 0-25μm Al 0.5 CoCrFeNiTi 0.5 High-entropy alloy and 75-90 wt% WC; the total WC weight is 100%, including 50-80 wt% ultrafine-grained WC (0.2-0.4 μm), 10-30 wt% extra-coarse-grained WC (6-10 μm), and the balance being medium-grained WC (1-3 μm). Multi-scale WC is used as the matrix, and Al is added. 0.5 CoCrFeNiTi 0.5 High-entropy alloys are novel binder phases. Multiscale WC-Al was prepared using a two-step ball milling method and rapid hot pressing sintering technology. 0.5 CoCrFeNiTi 0.5 Hard alloys will be used to prepare multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 A multi-scale cemented carbide friction stir welding head is fabricated by machining and heat treatment of cemented carbide. This invention uses multi-scale WC as the matrix and Al... 0.5 CoCrFeNiTi 0.5 High-entropy alloys were used as binders to replace Co, and multi-scale WC-Al was prepared by optimizing ball milling and sintering processes. 0.5 CoCrFeNiTi 0.5 Hard alloys achieve a balance of hardness and toughness, meeting the requirements for friction stir welding.

Description

Technical Field

[0001] This invention belongs to the field of cemented carbide preparation technology, specifically relating to a multi-scale cemented carbide friction stir welding head and its preparation method. Background Technology

[0002] Friction stir welding (FSW) is a green and pollution-free solid-state welding technology widely used in aerospace, aviation, high-speed rail, and other rail transportation production fields. Its core welding tool is considered the "heart" of the FSW technology. During operation, the welding tool experiences high-temperature friction and wear due to high-speed rotation, shear forces between the stirring material and the tool as it advances, and must also withstand the axial force of the spindle. Therefore, FSW tools face higher requirements. Hard alloy, an important metal-ceramic material developed and used since 1923, is suitable for use as a material in friction stir welding tools due to its high specific strength, corrosion resistance, and high-temperature resistance.

[0003] Traditional cemented carbide exhibits high hardness but low fracture toughness, making it unsuitable for friction stir welding of high-melting-point materials. To address the contradiction between high fracture toughness and high hardness in traditional cemented carbide, a dual-crystal synergistic reinforcement and toughening strategy is employed. This involves using fine-grained tungsten carbide to ensure high hardness, strength, and wear resistance, while coarse-grained tungsten carbide ensures toughness, resulting in a dual-crystal WC-Co cemented carbide with excellent overall performance. Since abnormal tungsten carbide grain growth is prone to occur during sintering, grain growth inhibitors are added to inhibit this abnormal growth behavior. For example, Chinese authorized patent CN111041320B—"A cemented carbide with a mixed crystal structure and its preparation method"—is prepared by mixing a mixture A with a mass percentage of 5-20% and a mixture B with a mass percentage of 80-95%. Mixture A includes the following raw materials by mass percentage: tungsten carbide (Fishler particle size of 0.4-0.8μm) 89.3-93.7%, cobalt 6-10%, and chromium carbide 0.3-0.7%. Mixture B (Fishler particle size of 2.5-4.5μm) includes the following raw materials by mass percentage: tungsten carbide 90-94% and cobalt 6-10%. The mixed crystal structure cemented carbide is obtained by ball milling, drying, pressing, and sintering. Chinese patent CN112359241B, entitled "A Bicrystalline Non-uniform Cemented Carbide and Its Preparation Method," describes a method for preparing a bicrystalline non-uniform cemented carbide by mixing a fine-grained precursor prepared by spray drying and calcination with coarse WC powder, cobalt powder, and paraffin wax in a ratio of 14wt%:70wt%:12wt%:2wt%. The mixture is then ball-milled, pressed into shape, and subjected to pressure holding at 1440℃. After cooling, a bicrystalline non-uniform cemented carbide is obtained. All of the above patents use cobalt as a binder. Given the scarcity and high price of cobalt resources, finding new binders to replace cobalt is of great significance for reducing the cost of cemented carbide and promoting the sustainable development of the cemented carbide industry.

[0004] High-entropy alloys are formed from five or more main elements and possess higher hardness, strength, toughness, wear resistance, high-temperature resistance, and oxidation resistance compared to single-phase alloys. High-entropy alloys exhibit thermodynamic high-entropy effects, kinetic slow diffusion effects, structural lattice distortion effects, a "cocktail effect" in performance, and high microstructure stability, making them suitable as novel binders for cemented carbides used in friction stir welding tools. Related research indicates that high-entropy alloys, as a binder phase in WC, can inhibit abnormal WC grain growth and improve the overall performance of cemented carbides. For example, Chinese authorized patent CN114058893B—"A method for preparing a WC-Y2O3-ZrO2 matrix cemented carbide with AlCoCrFeNi as a binder"—uses a WC matrix doped with Y2O3 and ZrO2, and uses AlCoCrFeNi high-entropy alloy powder as a binder instead of Co, employing ball milling and spark plasma sintering techniques to prepare the alloy.

[0005] The WCY2O3ZrO210AlCoCrFeNi cemented carbide exhibits superior overall performance compared to cemented carbides using Co as a binder. However, cemented carbides are brittle materials, and excessively rapid cooling rates increase brittleness. This patent employs an unsuitable preparation process, including a long ball milling time and a cooling rate of 100℃ / min, resulting in significant brittleness and substantial time costs. Summary of the Invention

[0006] In view of the above-mentioned shortcomings and defects of the prior art, the purpose of this invention is to provide a multi-scale cemented carbide friction stir welding head and its preparation method, which solves the problems of the existing stirring head not being able to have both hardness and toughness, as well as the high cost and environmental pollution in the preparation process.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A multi-scale cemented carbide friction stir welding head, by weight, is made from the following raw materials: 10-25 wt% of 0-25 μm Al. 0.5 CoCrFeNiTi 0.5 The total weight percentage of the raw materials is 100%, consisting of high-entropy alloys and 75-90 wt% WC.

[0009] The WC mentioned herein is made from the following raw materials by weight: 50-80 wt% of ultrafine WC with a diameter of 0.2-0.4 μm, 10-30 wt% of extra-coarse WC with a diameter of 6-10 μm, and the balance being medium-grained WC with a diameter of 1-3 μm, the sum of the parts by weight of the raw materials being 100%.

[0010] The multi-scale cemented carbide friction stir welding head consists of a shoulder and a stirring pin. The shoulder is cylindrical, and the connection point with the stirring pin is concave in an arc. The connection between the edge of the shoulder and the side is a rounded transition. The stirring pin is frustum-shaped, and the connection with the shoulder is a rounded transition. The bottom diameter of the stirring pin is 1 / 2-3 / 4 of the shoulder diameter, the top diameter is 1 / 2-2 / 3 of the bottom diameter, and the length is ≤1 / 4 of the shoulder diameter.

[0011] This invention also provides a method for preparing a multi-scale cemented carbide friction stir welding head.

[0012] The following steps are used:

[0013] Using multi-scale WC as the matrix and Al 0.5 CoCrFeNiTi 0.5 High-entropy alloys, as novel binder phases replacing Co, were prepared using a two-step ball milling method and rapid hot-pressing sintering technology to create multi-scale alloys.

[0014] WC-Al 0.5 CoCrFeNiTi 0.5 cemented carbide will be used to prepare multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 Multi-scale cemented carbide friction stir welding heads are produced by machining and heat treatment of cemented carbide.

[0015] The multi-scale WC refers to ultrafine WC of 0.2-0.4 μm, extra-coarse WC of 6-10 μm, and medium-sized WC of 1-3 μm.

[0016] Step 1, the first step of ball milling:

[0017] Al with a particle size of 0-25μm 0.5 CoCrFeNiTi 0.5 High-entropy alloy powder and ultrafine WC powder with a particle size of 0.2-0.4μm were placed in a ball mill jar and wet-milled to obtain a first solid-liquid mixture.

[0018] Step 2, the second step of ball milling:

[0019] The first solid-liquid mixture, medium-grained WC powder with a particle size of 1-3 μm and extra-coarse-grained WC powder with a particle size of 6-10 μm are mixed and wet-milled to obtain the final solid-liquid mixture.

[0020] Step 3, Drying:

[0021] The final solid-liquid mixture obtained in step 2 was dried in a vacuum drying oven, and then the dried powder was ground to obtain multi-scale WC-Al. 0.5 CoCrFeNiTi 0.5 Mixed powders;

[0022] Step 4, Pre-compression:

[0023] The multiscale WC-Al obtained in step 3 0.5 CoCrFeNiTi 0.5 The mixed powder is loaded into a graphite mold, and the powder is pre-pressed using a hydraulic press to obtain a pre-pressed blank;

[0024] Step 5, sintering:

[0025] The pre-pressed billet and mold obtained in step 4 are placed into a rapid hot pressing sintering furnace for sintering to obtain multi-scale cemented carbide.

[0026] Step 6, Machining:

[0027] The multi-scale cemented carbide prepared in step 5 is machined to obtain a friction stir welding tool.

[0028] Step 7, Heat treatment:

[0029] The friction stir welding tool machined in step 6 is heat-treated to produce a multi-scale cemented carbide friction stir welding head.

[0030] In step 1, the ball mill speed is set to 300-400 r / min, the ball milling time is 12-24 h, the ball milling medium is anhydrous ethanol, the mass ratio of grinding balls, material and anhydrous ethanol is 10:1:1, and the mass ratio of large, medium and small cemented carbide grinding balls is 5:3:2.

[0031] The grinding balls are made of cemented carbide, and they come in three sizes: 20g large balls, 5g medium balls, and 1g small balls.

[0032] In step 2, the ball mill speed is set to 100-200 r / min, the ball milling time is 8-24 h, the mass ratio of grinding balls, material and anhydrous ethanol is 5:1:1, and the mass ratio of large and medium balls is 5:3.

[0033] In step 3, the drying conditions are: vacuum degree greater than or equal to 0.085 MPa, heating temperature of 60-80℃, and drying time of 6-8 hours.

[0034] In step 4, the pre-compression is performed once for every 1 / 5 to 1 / 10 of the mass of the added mixture, with a pressure of 50-60 MPa, and the pressure is maintained for 30 seconds. Finally, the entire mixture is maintained under pressure for 3 minutes.

[0035] In step 5, the heating rate is set to 100-150℃ / min, the temperature is held at 900℃ for 5-20 min, the temperature is held at the final sintering temperature of 1100-1250℃ for 10-120 min, the cooling rate is 10-30℃ / min, the initial pre-pressure is set to 0MPa, the pressure increase rate is 0.5-4MPa / min, the pressure is further increased during the degassing holding at 850-950℃, the pressure is increased to 30-50MPa at the final sintering temperature, and the pressure is maintained during the holding stage at the final sintering temperature. Then the pressure is slowly reduced to 0MPa at a rate of 0.15-0.3MPa / min.

[0036] In step 6, the machined friction stir welding tool is divided into a shoulder and a stirring pin. The shoulder is cylindrical, and the connection with the stirring pin is concave in an arc. The connection between the edge of the shoulder and the side is a rounded transition. The stirring pin is frustum-shaped, and the connection with the shoulder is a rounded transition. The diameter of the bottom of the stirring pin (near the shoulder) is 1 / 2-3 / 4 of the shoulder diameter, the diameter of the top is 1 / 2-2 / 3 of the bottom diameter, and the length is ≤1 / 4 of the shoulder diameter.

[0037] In step 7, the processed friction stir welding tool is subjected to surface quenching treatment at a temperature of 850-1000℃ for 10-20 minutes.

[0038] Compared with the prior art, the beneficial technical effects of this invention are:

[0039] (I) This invention uses multi-scale WC as the matrix, Al 0.5 CoCrFeNiTi 0.5 High-entropy alloys were used as binders to replace Co, and multi-scale WC-Al was prepared by optimizing ball milling and sintering processes. 0.5 CoCrFeNiTi 0.5 Hard alloys achieve a balance of hardness and toughness, meeting the requirements for friction stir welding.

[0040] (II) The method of this invention uses a combination of ultrafine, medium-grained, and extra-coarse WC. Ultrafine WC, due to its fine-grain strengthening effect, ensures the strength, hardness, and wear resistance of the cemented carbide. Extra-coarse WC, due to its crack propagation stress relaxation strengthening effect, ensures the toughness of the cemented carbide. Medium-grained WC acts as an intermediate bridge between ultrafine and extra-coarse WC, avoiding the generation of microcracks during sintering due to its large gradation difference. The combination of ultrafine, medium-grained, and extra-coarse WC, combined with Al... 0.5 CoCrFeNiTi 0.5 High-entropy alloys and optimized preparation processes have improved the comprehensive mechanical properties of cemented carbides, resulting in the preparation of multi-scale WC-Al alloys. 0.5 CoCrFeNiTi 0.5The hardness of the cemented carbide is 1817.48 HV, and its fracture toughness is 15.5 MPa·m. 1 / 2 (Ultrafine WC-Al) 0.5 CoCrFeNiTi 0.5 The hardness and fracture toughness of the cemented carbide are 1974.07 HV and 8.17 MPa·m, respectively. 1 / 2 ).

[0041] (III) This invention uses Al 0.5 CoCrFeNiTi 0.5 High-entropy alloys, as the binder phase of hard alloys, Al 0.5 CoCrFeNiTi 0.5 High-entropy alloys offer advantages over traditional alloys, including higher strength, hardness, toughness, and excellent wear resistance. They can replace Co as a novel binder phase in hard alloys, reducing the use of Co resources, lowering costs, and minimizing environmental pollution. Furthermore, the inherent hysteresis diffusion effect of high-entropy alloys effectively inhibits abnormal WC grain growth, thus avoiding the need for grain growth inhibitors and further reducing costs.

[0042] (IV) This invention optimizes the ball milling process, employing a two-step ball milling method for ultrafine, medium-grained, and extra-coarse-grained WC and Al. 0.5 CoCrFeNiTi 0.5 High-entropy alloy powder undergoes comprehensive planetary wet milling. The first step, ball milling, performs three-dimensional wet milling of the ultrafine-grained WC and high-entropy alloy. High-speed wet milling reduces the particle size of the high-entropy alloy, achieving thorough and uniform mixing of the ultrafine-grained WC and the high-entropy alloy. The high milling energy provides the driving force for the powder during sintering, promoting the uniform dispersion of the high-entropy alloy at the WC grain boundaries. The second step, ball milling, mixes all materials. Low-speed milling avoids damaging the medium- and extra-coarse-grained WC particles. Appropriate milling time, combined with ball and milling ball gradation, ensures uniform mixing of all powders. Simultaneously, suitable milling balls, material, and anhydrous ethanol ratios are selected based on the desired effects of the first and second milling steps, significantly improving milling efficiency.

[0043] (V) This invention optimizes the preparation process by improving the pre-pressing before powder sintering. Pre-pressing is performed once for every 1 / 5-1 / 10 of the added material mass, at a pressure of 50-60 MPa for 30 seconds, followed by a final overall pressure hold of 3 minutes. This avoids uneven density of the billet leading to delamination during sintering. Advanced sintering technology, namely DC rapid hot pressing sintering, is employed, reducing abnormal grain growth. Compared to other processes (such as vacuum hot pressing sintering), it saves time and energy and is simple and safe to operate. Sintering parameters are optimized. Rapid heating is used during the heating stage to reduce abnormal grain growth. The temperature is raised to 900℃ and held for 5-20 minutes for degassing. Pressure is applied during degassing to reduce voids caused by gas release. Pressure is maintained during the sintering temperature holding stage. The cooling rate is reduced during the cooling stage to avoid microcracks in the hard alloy caused by excessively rapid cooling, thus improving density and fracture toughness. Attached Figure Description

[0044] Figure 1 The image shows the powder morphology of multi-scale cemented carbide after two-step ball milling.

[0045] WC powder particles are white, Al 0.5 CoCrFeNiTi 0.5 The high-entropy alloy powder is gray. The WC and high-entropy alloy powders exhibit significant morphological deformation, appearing as irregular shapes, and are uniformly mixed.

[0046] Figure 2 This is the optimized sintering process curve;

[0047] The classic three-stage sintering process is adopted, and the process of each stage is optimized. The rapid heating and pressurization stage achieves rapid densification in the initial densification stage, and degassing is carried out at 950℃ to avoid abnormal growth of WC in the heating stage. The constant temperature and pressure stage eliminates the thermal stress of the rapid stage. The slow cooling and depressurization stage combines heat treatment concepts to reduce brittleness and thermal stress.

[0048] The upper curve is the sintering temperature process curve optimized based on experimental data and differential scanning calorimetry analysis, while the lower curve is the pressure process curve optimized based on thermogravimetric analysis and experimental data.

[0049] Figure 3 The multiscale WC-Al prepared in Example 1 0.5 CoCrFeNiTi 0.5 Scanning electron microscope image of cemented carbide;

[0050] WC grains are gray, while face-centered cubic high-entropy alloys are dark gray. The facets of extra-coarse, medium-coarse, and ultra-fine WC grains are distinct and uniformly distributed. Due to the low content of high-entropy alloys, high-entropy alloys exist between extra-coarse WC grains, and some ultra-fine WC grains are in grain boundary contact.

[0051] Figure 4 The multi-scale WC-Al prepared in Example 2 0.5 CoCrFeNiTi 0.5 Scanning electron microscope image of cemented carbide;

[0052] WC grains are gray, face-centered cubic high-entropy alloys are dark gray, and body-centered cubic high-entropy alloys are black. Ultrafine and medium-grained WC have a spherical morphology, while very coarse grains are faceted.

[0053] Figure 5 The multi-scale WC-Al prepared in Example 3 0.5 CoCrFeNiTi 0.5 Scanning electron microscope image of cemented carbide;

[0054] WC grains are gray, face-centered cubic high-entropy alloys are dark gray, and body-centered cubic high-entropy alloys are black. Both ultrafine and coarse-grained WC grains are spherical and uniformly distributed, while high-entropy alloys are uniformly distributed between WC grains.

[0055] Figure 6 The multi-scale WC-Al prepared in Example 4 0.5 CoCrFeNiTi 0.5 Scanning electron microscope image of cemented carbide;

[0056] WC grains are gray, face-centered cubic high-entropy alloys are dark gray, and body-centered cubic high-entropy alloys are black. Ultrafine, medium, and extra-coarse WC grains all exhibit faceted morphologies and are uniformly distributed across multiple scales. High-entropy alloys are uniformly distributed between WC grains.

[0057] Figure 7 This is a dimensional drawing of friction stir welding tools.

[0058] The specific content of the present invention will be further explained in detail below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0059] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0060] Unless otherwise specified, all components in this invention are components known in the prior art.

[0061] This invention aims to address the existing problems with material composition and processing by providing a method for preparing multi-scale cemented carbide friction stir welding tools. This invention uses multi-scale WC as the matrix and Al... 0.5 CoCrFeNiTi 0.5 High-entropy alloys were used as binders to replace Co, and multi-scale WC-Al was prepared by optimizing ball milling and sintering processes. 0.5 CoCrFeNiTi 0.5 Hard alloy achieves a balance of hardness and toughness, meeting the requirements for use in friction stir welding tools.

[0062] By employing a reasonable tungsten carbide gradation and a high-entropy alloy as a binder, and through a suitable preparation process, high-performance cemented carbide can be prepared. Furthermore, by designing the geometry and heat treatment according to the material properties, high-performance multi-scale cemented carbide friction stir welding tools can be obtained.

[0063] The preferred materials of this invention include ultrafine-grained WC with a particle size of 0.2-0.4 μm, medium-grained WC with a particle size of 1-3 μm, extra-coarse-grained WC with a particle size of 6-10 μm, and Al with a particle size of 0-25 μm. 0.5 CoCrFeNiTi 0.5 High-entropy alloy powder. The cemented carbide of this invention utilizes the fine-grained strengthening effect of ultrafine WC to improve the alloy's strength, hardness, and wear resistance. The crack propagation stress relaxation strengthening effect of extra-coarse WC improves the alloy's fracture toughness. Medium-grained WC serves as an intermediate transition phase, preventing microcracks from forming during sintering due to the large gradation of ultrafine and extra-coarse WC, which could negatively impact performance. The body-centered cubic AlCoCrFeNi high-entropy alloy possesses a stable microstructure and good mechanical properties, often used as a reinforcing phase in metal matrix composites. Ti has low density, high melting point, high specific strength, and high high- and low-temperature performance. Combining Ti with AlCoCrFeNi high-entropy alloys can achieve higher hardness, toughness, strength, melting point, and high- and low-temperature performance. However, AlCoCrFeNi high-entropy alloys have a stable body-centered cubic structure; therefore, the Al atomic ratio needs to be reduced to 0.5 to transform the high-entropy alloy from a stable state to a metastable state, making it easier to combine with the remaining Ti atomic ratio to form a metastable body-centered cubic Al structure. 0.5 CoCrFeNiTi 0.5 High-entropy alloys. High-strength and high-toughness Al. 0.5 CoCrFeNiTi 0.5 High-entropy alloys replace Co as a binder phase, utilizing its retarded diffusion effect to avoid abnormal grain growth, and its phase transformation equilibrium interface stress concentration to achieve coordinated distribution of interface strain. Combined with multi-scale WC synergistically, the overall performance of cemented carbide is improved.

[0064] The optimized preparation process of this invention includes optimization of the ball milling process, optimization of the sintering process, optimization of tool geometry, and heat treatment. The optimization of the ball milling process lies in adjusting the WC and Al content... 0.5 CoCrFeNiTi 0.5The high-entropy alloys were ball-milled in two steps to determine their respective properties and required powder states, with optimized ball milling parameters, ball material gradation, and grinding ball quality gradation. The first ball milling process involved ultrafine-grained WC and the high-entropy alloys, using high rotation speed and appropriate ball material and grinding ball gradation. The aim was to refine the high-entropy alloy, form a thin film on the surface of the ultrafine-grained WC, alter the WC particle morphology, introduce surface defects such as dislocations and stacking faults, and impart stored energy to the high-entropy alloy and WC to enhance the sintering activation energy during sintering, thus promoting the flow of the high-entropy alloy between WC crystals. The second ball milling process involved the materials from the first step, as well as medium- and coarse-grained WC, using low rotation speed and appropriate ball material and grinding ball gradation, while removing small grinding balls from the first step. The aim was to minimize damage to the medium- and coarse-grained crystal sizes, modify the WC surface, increase internal energy, achieve multi-scale gradation, uniform mixing, improve sintering activity, and balance the strain distribution at the cemented carbide interface to achieve strain coordination in the cemented carbide process. The optimization of the sintering process lies in improving the pre-pressing and sintering processes based on the powder state after high-energy ball milling. Since the powder is multi-scale, soft agglomeration occurs after drying due to van der Waals forces. To avoid excessively large pores between agglomerates during overall pressing, uneven distribution of loosely packed particles in the mold cavity, leading to uneven elastic internal stress and excessive elastic tension in the compact, which in turn results in numerous residual pores and delamination in the sintered body, this invention proposes layered pressing. This involves layer-by-layer pressing and multiple pressurization processes to reduce the internal porosity of the compact, increase the loose density of the material, regulate internal elastic internal stress, and reduce elastic tension. The sintering process optimization also involves adopting a "rapid heating and pressurization - constant temperature and pressure - slow cooling and pressurization" sintering strategy, based on the brittleness and hardness of WC and the sensitivity of powder sintering temperature, combined with the powder activation effect of high-energy ball milling and the layered pressing effect. Since ball milling activates the WC and high-entropy alloy powders, the high-entropy alloy does not exist as a liquid phase at the WC interface during the initial sintering stage. Some of the WC particles in contact with each other are prone to coalescence and growth. Therefore, a rapid heating and pressurization method is adopted, along with rapid densification during the initial densification stage, followed by degassing at 900℃. During this stage, a slow pressurization method is used to ensure densification. The isothermal and pressure-controlled stage ensures that the high-entropy alloy flows as a liquid phase between WC particles and undergoes metallurgical bonding with WC to form a good interface structure, eliminating the internal stress introduced by the initial rapid sintering stage. Due to the brittle nature of WC, an excessively rapid cooling rate will increase its brittleness. Therefore, a slow cooling and pressurization method is chosen to improve its toughness and avoid different shrinkage rates due to the different thermal expansion coefficients of WC and the high-entropy alloy, thus increasing the degree of densification. Tool geometry optimization involves selecting rounded transitions at all contact points with the workpiece. Due to the high hardness and low toughness of WC cemented carbide and the significant differences between WC and high-entropy alloys, rounded transitions are chosen at all contact points to avoid tool failure caused by stress concentration at the facet tips in actual working conditions. Surface hardening is also applied to the tool to improve its surface hardness and wear resistance.

[0065] Example 1:

[0066] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 Hard alloy is prepared by a two-step ball milling method and rapid hot pressing sintering, wherein the Al 0.5 CoCrFeNiTi 0.5 The multi-scale WC-based cemented carbide material, acting as the binder phase, comprises 15 wt% Al by mass percentage. 0.5 CoCrFeNiTi 0.5 And 85 wt% WC (of which 51 wt% ultrafine WC, 12.75 wt% extra-coarse WC and 21.25 wt% medium-grained WC). WC and Al 0.5 CoCrFeNiTi 0.5 The purity of the powder is 99.9%, and the purity of the anhydrous ethanol is 99.7%. (Based on a total weight of 100% WC, it comprises 60 wt% ultrafine WC, 15 wt% extra-coarse WC, and 25 wt% medium-grained WC.)

[0067] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 The preparation method of cemented carbide composite materials is as follows:

[0068] Step 1: Ball milling: according to 15wt% Al 0.5 CoCrFeNiTi 0.5 The design incorporates 51 wt% ultrafine WC powder, with grinding balls, materials, and anhydrous ethanol in a mass ratio of 10:1:1 and large, medium, and small grinding balls in a mass ratio of 5:3:2, to prepare ultrafine WC powder and Al. 0.5 CoCrFeNiTi 0.5 The powder, cemented carbide balls, and anhydrous ethanol were weighed and mixed, and then placed in a cemented carbide ball milling jar for packaging. Finally, the mixture was placed in an all-around planetary ball mill for wet grinding, with the ball milling speed set at 400 r / min and the grinding time at 24 h.

[0069] The second step is ball milling: The first material milled in the first step is weighed and mixed with 12.75 wt% extra coarse crystal WC and 21.25 wt% medium crystal WC according to the designed composition. The mass ratio of grinding balls, material and anhydrous ethanol is 5:1:1 and the mass ratio of large and medium balls is 5:3. The mixture is then placed in a carbide ball mill jar and sealed. Finally, it is placed in an all-around planetary ball mill for wet milling. The ball milling speed is set to 100 r / min and the ball milling time is 24 h.

[0070] Drying: The final solid-liquid mixture obtained after the second ball milling step is placed in an evaporating dish and then placed in a vacuum drying oven for drying. The vacuum degree is greater than or equal to 0.085 MPa (0.085 MPa refers to the vacuum degree display of the vacuum drying oven -0.085 MPa, the same below), the heating temperature is 80℃, and the drying time is 4 hours.

[0071] Pre-pressing: Drying and grinding multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 The mixed powder, at a ratio of 1 / 10 of its total sintering mass, was placed in a graphite mold with the same height of upper and lower pressure heads for pre-pressing once at a pressure of 60 MPa and held for 30 seconds. This process was repeated 10 times, and finally, the entire mixture was held under pressure for 3 minutes.

[0072] Sintering: A graphite mold filled with pre-pressed powder is placed in a rapid hot-press sintering furnace. A vacuum is applied at room temperature, with a vacuum level below 8.5 Pa (this refers to a pressure below 8.5 Pa in the rapid hot-press sintering furnace, the same below). The temperature is increased from room temperature to 750℃ at a rate of 150℃ / min, while the pressure increases from 0 MPa to 10 MPa. The temperature is then increased to 900℃ at a rate of 50℃ / min and held for 20 min, while the pressure is increased to 30 MPa. The temperature is then increased to the final sintering temperature of 1180℃ and held for 30 min, while the pressure increases to 40 MPa. This is followed by holding at both temperatures and pressures. Finally, the temperature is reduced to room temperature at a rate of 10℃ / min, yielding multi-scale WC-Al. 0.5 CoCrFeNiTi 0.5 Hard alloy.

[0073] Machining: The prepared multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 Hard alloy is machined to obtain friction stir welding tools;

[0074] Heat treatment: The friction stir welding tool is heat treated to produce a multi-scale cemented carbide friction stir welding head.

[0075] Multiscale WC-Al after sintering 0.5 CoCrFeNiTi 0.5 The Vickers hardness and fracture toughness of the cemented carbide composite material reached 1991.8 HV and 13.06 MPa·m, respectively. 1 / 2 .

[0076] The nano-WC-Co cemented carbide prepared according to the method described in Chinese authorized patent CN115044795A—"A Nano-WC-Co Cemented Carbide and Its Preparation Method" has a hardness of 1820 HV and a fracture toughness of 12.1 MPa·m. 1 / 2 Compared to that patent, the multi-scale WC-Al of this embodiment... 0.5CoCrFeNiTi 0.5 The hardness and fracture toughness of cemented carbide were increased by 9.4% and 8%, respectively.

[0077] In this embodiment: the WC powder, Al 0.5 CoCrFeNiTi 0.5 The purity of the high-entropy alloy powder is 99.9%.

[0078] The ball milling method is an all-around planetary ball mill, the ball mill model is PMQW2 all-around planetary ball mill, the grinding jar is made of cemented carbide, the grinding balls are made of cemented carbide, and the cemented carbide grinding balls are divided into 20g large balls, 5g medium balls and 1g small balls.

[0079] The vacuum drying oven is model DZF-6050.

[0080] The graphite mold has a diameter of 20-40mm, and the height of the upper and lower graphite pressure heads is consistent.

[0081] The rapid hot pressing sintering furnace mentioned is model FHP-858 DC rapid hot pressing sintering furnace, the same below.

[0082] Example 2:

[0083] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 Hard alloy is prepared by a two-step ball milling method and rapid hot pressing sintering, wherein the Al 0.5 CoCrFeNiTi 0.5 The multi-scale WC-based cemented carbide material, acting as the binder phase, comprises 20 wt% Al by mass percentage. 0.5 CoCrFeNiTi 0.5 And 80 wt% WC (of which 48 wt% is ultrafine WC, 8 wt% is extra-coarse WC and 24 wt% is medium-grained WC). (The total weight of WC is 100%, of which 60 wt% is ultrafine WC, 10 wt% is extra-coarse WC and 30 wt% is medium-grained WC)

[0084] WC and Al 0.5 CoCrFeNiTi 0.5 The purity of the powder is 99.9%, and the purity of the anhydrous ethanol is 99.7%.

[0085] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 The preparation method of cemented carbide composite materials is as follows:

[0086] Step 1: Ball milling: according to 20wt% Al 0.5 CoCrFeNiTi0.5 The design incorporates 48 wt% ultrafine WC components. Ultrafine WC powder and Al are prepared by mixing grinding balls, materials, and anhydrous ethanol in a mass ratio of 10:1:1 and large, medium, and small grinding balls in a mass ratio of 5:3:2. 0.5 CoCrFeNiTi 0.5 The powder, cemented carbide balls, and anhydrous ethanol were weighed and mixed, and then placed in a cemented carbide ball milling jar for packaging. Finally, the mixture was placed in an all-around planetary ball mill for wet grinding, with the ball milling speed set at 400 r / min and the grinding time at 24 h.

[0087] The second step is ball milling: The first material after the first ball milling is weighed and mixed with 8 wt% extra coarse WC and 24 wt% medium WC according to the designed composition. The mass ratio of grinding balls, material and anhydrous ethanol is 5:1:1 and the mass ratio of large and medium balls is 5:3. The mixture is then placed in a carbide ball mill jar and sealed. Finally, it is placed in an all-around planetary ball mill for wet milling. The ball milling speed is set to 100 r / min and the ball milling time is 24 h.

[0088] Drying: The final solid-liquid mixture obtained after the second step of ball milling is placed in an evaporating dish and then placed in a vacuum drying oven for drying. The vacuum degree is greater than or equal to 0.085 MPa, the heating temperature is 80℃, and the drying time is 4 hours.

[0089] Pre-compression: This involves drying and grinding multi-scale WC-Al... 0.5 CoCrFeNiTi 0.5 The mixed powder, at a ratio of 1 / 5 of its total sintering mass, was placed in a graphite mold with the same height of upper and lower pressure heads for pre-pressing once at a pressure of 60 MPa and held for 30 seconds. This process was repeated 10 times, and finally, the entire mixture was held under pressure for 3 minutes.

[0090] Sintering: A graphite mold filled with pre-pressed powder is placed in a rapid hot-pressing sintering furnace. A vacuum is applied at room temperature (lower than 8.5 Pa). The temperature is increased from room temperature to 750℃ at a rate of 150℃ / min, while the pressure increases from 0 MPa to 10 MPa. The temperature is then increased to 900℃ at a rate of 50℃ / min and held for 20 min, while the pressure is increased to 30 MPa. The temperature is then increased to the final sintering temperature of 1150℃ and held for 30 min, while the pressure is increased to 40 MPa. The temperature and pressure are then maintained. Finally, the temperature is decreased to room temperature at a rate of 10℃ / min, yielding multi-scale WC-Al. 0.5 CoCrFeNiTi 0.5 Hard alloy.

[0091] Machining: The prepared multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 Hard alloy is machined to obtain friction stir welding tools;

[0092] Heat treatment: The friction stir welding tool is heat treated to produce a multi-scale cemented carbide friction stir welding head.

[0093] Multiscale WC-Al after sintering 0.5 CoCrFeNiTi 0.5 The Vickers hardness and fracture toughness of the cemented carbide composite material reached 2109.60 HV and 12.18 MPa·m, respectively. 1 / 2 .

[0094] The dual-morphology WC-Co cemented carbide prepared according to the method described in Chinese authorized patent CN114836642B—"A Dual-Modal Cemented Carbide and Its Preparation Method" has a hardness of 1786 HV and a fracture toughness of 10.34 MPa·m. 1 / 2 Compared to that patent, the multi-scale WC-Al of this embodiment... 0.5 CoCrFeNiTi 0.5 The hardness and fracture toughness of cemented carbide were increased by 18.1% and 17.8%, respectively.

[0095] Example 3:

[0096] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 Hard alloy is prepared by a two-step ball milling method and rapid hot pressing sintering, wherein the Al 0.5 CoCrFeNiTi 0.5 The multi-scale WC-based cemented carbide material, acting as the binder phase, comprises 25 wt% Al by mass. 0.5 CoCrFeNiTi 0.5 And 75 wt% WC, of ​​which 60 wt% is ultrafine-grained WC and 15 wt% is extra-coarse-grained WC. (The total weight of WC is 100%, of which 80 wt% is ultrafine-grained WC and 20 wt% is extra-coarse-grained WC.)

[0097] WC and l 0.5 CoCrFeNiTi 0.5 The purity of the powder is 99.9%, and the purity of the anhydrous ethanol is 99.7%.

[0098] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 The preparation method of cemented carbide composite materials is as follows:

[0099] Step 1: Ball milling: according to 25wt% Al 0.5 CoCrFeNiTi 0.5The design incorporates 60 wt% ultrafine WC components, with grinding balls, materials, and anhydrous ethanol in a mass ratio of 10:1:1 and large, medium, and small grinding balls in a mass ratio of 5:3:2 to prepare ultrafine WC powder and Al. 0.5 CoCrFeNiTi 0.5 The powder, cemented carbide balls, and anhydrous ethanol were weighed and mixed, and then placed in a cemented carbide ball milling jar for packaging. Finally, the mixture was placed in an all-around planetary ball mill for wet grinding, with the ball milling speed set at 400 r / min and the grinding time at 24 h.

[0100] The second step is ball milling: The first material after the first ball milling is weighed and mixed with 16wt% extra coarse WC according to the designed composition. The mass ratio of grinding balls, material and anhydrous ethanol is 5:1:1 and the mass ratio of large and medium balls is 5:3. The mixture is then placed in a carbide ball mill jar and sealed. Finally, it is placed in an all-around planetary ball mill for wet milling. The ball milling speed is set to 200 r / min and the ball milling time is 24 h.

[0101] Drying: The final solid-liquid mixture obtained after the second step of ball milling is placed in an evaporating dish and then placed in a vacuum drying oven for drying. The vacuum degree is greater than or equal to 0.085 MPa, the heating temperature is 80℃, and the drying time is 4 hours.

[0102] Pre-compression: This involves drying and grinding multi-scale WC-Al... 0.5 CoCrFeNiTi 0.5 The mixed powder, at a ratio of 1 / 5 of its total sintering mass, was placed in a graphite mold with the same height of upper and lower pressure heads for pre-pressing once at a pressure of 60 MPa and held for 30 seconds. This process was repeated 10 times, and finally, the entire mixture was held under pressure for 3 minutes.

[0103] Sintering: A graphite mold filled with pre-pressed powder is placed in a rapid hot-pressing sintering furnace. A vacuum is applied at room temperature (lower than 8.5 Pa). The temperature is increased from room temperature to 750℃ at a rate of 150℃ / min, while the pressure increases from 0 MPa to 10 MPa. The temperature is then increased to 900℃ at a rate of 50℃ / min and held for 20 min, while the pressure is increased to 30 MPa. The temperature is then increased to the final sintering temperature of 1200℃ and held for 30 min, while the pressure is increased to 40 MPa. This process is repeated, and the temperature and pressure are maintained. Finally, the temperature is decreased to room temperature at a rate of 10℃ / min to obtain multi-scale WC-Al. 0.5 CoCrFeNiTi 0.5 Hard alloy.

[0104] Machining: The prepared multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 Hard alloy is machined to obtain friction stir welding tools;

[0105] Heat treatment: The friction stir welding tool is heat treated to produce a multi-scale cemented carbide friction stir welding head.

[0106] Multiscale WC-Al after sintering 0.5 CoCrFeNiTi 0.5 The Vickers hardness and fracture toughness of the cemented carbide composite material reached 1593.97 HV and 15.96 MPa·m, respectively. 1 / 2 .

[0107] A bicrystalline WC-Co cemented carbide was prepared according to the method described in Chinese authorized patent CN111088449B—"A Bicrystalline WC Structure Cemented Carbide and Its Preparation Method"—with a hardness of 1466 HV and a fracture toughness of 15.3 MPa·m. 1 / 2 Compared to that patent, this embodiment features multi-scale...

[0108] WC-Al 0.5 CoCrFeNiTi 0.5 The hardness and fracture toughness of cemented carbide were increased by 8.7% and 4.3%, respectively.

[0109] Example 4:

[0110] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 Hard alloy is prepared by a two-step ball milling process and rapid hot pressing sintering. The Al... 0.5 CoCrFeNiTi 0.5 The multi-scale WC-based cemented carbide material, acting as the binder phase, comprises 25 wt% Al by mass. 0.5 CoCrFeNiTi 0.5 And 75 wt% WC (of which 45 wt% ultrafine WC, 7.5 wt% extra-coarse WC and 22.5 wt% medium-grained WC). (The total weight of WC is 100%, of which 60 wt% ultrafine WC, 10 wt% extra-coarse WC and 30 wt% medium-grained WC)

[0111] WC and Al 0.5 CoCrFeNiTi 0.5 The purity of the powder is 99.9%, and the purity of the anhydrous ethanol is 99.7%.

[0112] The multi-scale WC-Al in this embodiment 0.5 CoCrFeNiTi 0.5 The preparation method of cemented carbide composite materials is as follows:

[0113] Step 1: Ball milling: according to 25wt% Al 0.5 CoCrFeNiTi0.5 The design incorporates 45 wt% ultrafine WC components. The ultrafine WC powder and Al are prepared by mixing grinding balls, materials, and anhydrous ethanol in a mass ratio of 10:1:1 and large, medium, and small grinding balls in a mass ratio of 5:3:2. 0.5 CoCrFeNiTi 0.5 The powder, cemented carbide balls, and anhydrous ethanol were weighed and mixed, and then placed in a cemented carbide ball milling jar for packaging. Finally, the mixture was placed in an all-around planetary ball mill for wet grinding, with the ball milling speed set at 400 r / min and the grinding time at 24 h.

[0114] The second step is ball milling: The first material after the first ball milling is weighed and mixed with 7.5 wt% extra coarse crystal WC and 22.5 wt% medium crystal WC according to the designed composition. The mass ratio of grinding balls, material and anhydrous ethanol is 5:1:1 and the mass ratio of large and medium balls is 5:3. The mixture is then placed in a carbide ball mill jar and sealed. Finally, it is placed in an all-around planetary ball mill for wet milling. The ball milling speed is set to 100 r / min and the ball milling time is 24 h.

[0115] Drying: The final solid-liquid mixture obtained after the second ball milling step is placed in an evaporating dish and then placed in a vacuum drying oven for drying. The vacuum degree is greater than or equal to 0.085 MPa, the heating temperature is 70℃, and the drying time is 4 hours.

[0116] Pre-compression: This involves drying and grinding multi-scale WC-Al... 0.5 CoCrFeNiTi 0.5 The mixed powder, at a ratio of 1 / 5 of its total sintering mass, was placed in a graphite mold with the same height of upper and lower pressure heads for pre-pressing once at a pressure of 55 MPa and held for 30 seconds. This process was repeated 10 times, and finally, the entire mixture was held under pressure for 3 minutes.

[0117] Sintering: A graphite mold filled with pre-pressed powder is placed in a rapid hot-pressing sintering furnace. A vacuum is applied at room temperature (lower than 8.5 Pa). The temperature is increased from room temperature to 750℃ at a rate of 150℃ / min, while the pressure increases from 0 MPa to 10 MPa. The temperature is then increased to 900℃ at a rate of 50℃ / min and held for 20 min, while the pressure is increased to 30 MPa. The temperature is then increased to the final sintering temperature of 1180℃ and held for 30 min, while the pressure is increased to 45 MPa. This is followed by holding at both temperatures and pressures. Finally, the temperature is reduced to room temperature at a rate of 10℃ / min to obtain multi-scale WC-Al. 0.5 CoCrFeNiTi 0.5 Hard alloy.

[0118] Machining: The prepared multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 Hard alloy is machined to obtain friction stir welding tools;

[0119] Heat treatment: The friction stir welding tool is heat treated to produce a multi-scale cemented carbide friction stir welding head.

[0120] Multiscale WC-Al after sintering 0.5 CoCrFeNiTi 0.5 The Vickers hardness and fracture toughness of the cemented carbide composite material reached 1817.48 HV and 15.5 MPa·m, respectively. 1 / 2 .

[0121] A WC-based cemented carbide with a high-entropy alloy as the binder phase, prepared according to the method described in Chinese authorized patent CN112647006B—"A Tungsten Carbide-Based Cemented Carbide and Its Preparation Method Thereof," has a hardness of 1392 HV and a fracture toughness of 14.1 MPa·m. 1 / 2 Compared to that patent, the multi-scale WC-Al of this embodiment... 0.5 CoCrFeNiTi 0.5 The hardness and fracture toughness of cemented carbide were increased by 30.6% and 9.9%, respectively.

[0122]

[0123] (The content in parentheses is the total weight of WC measured at 100%)

[0124] The above descriptions are merely embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for preparing a multi-scale cemented carbide friction stir welding head, characterized in that, The following steps were adopted: multi-scale WC was used as the matrix, and Al was used as the substrate. 0.5 CoCrFeNiTi 0.5 High-entropy alloys were used as the binder phase, and multi-scale WC-Al was prepared using a two-step ball milling method and rapid hot pressing sintering technology. 0.5 CoCrFeNiTi 0.5 cemented carbide will be used to prepare multi-scale WC-Al 0.5 CoCrFeNiTi 0.5 Multi-scale cemented carbide friction stir welding heads are produced by machining and heat treatment of cemented carbide. The multi-scale WC refers to ultrafine-grained WC of 0.2-0.4 μm, extra-coarse-grained WC of 6-10 μm, and medium-grained WC of 1-3 μm. The multi-scale cemented carbide friction stir welding head is made from the following raw materials by weight: 10-25 wt.% of 0-25 μm Al. 0.5 CoCrFeNiTi 0.5 The high-entropy alloy and 75-90 wt.% WC, the sum of the weight parts of the raw materials is 100%; The WC mentioned herein, by weight, is made from the following raw materials: 50-80 wt.% of ultrafine WC (0.2-0.4 μm), 10-30 wt.% of extra-coarse WC (6-10 μm), and the balance being medium-grained WC (1-3 μm), with the sum of the raw material parts being 100%. The multi-scale hard alloy friction stir welding head is divided into a shoulder and a stirring pin. The shoulder is cylindrical, and the connection with the stirring pin is concave in an arc. The connection between the edge of the shoulder and the side is a rounded transition. The stirring pin is frustum-shaped, and the connection with the shoulder is a rounded transition. The bottom diameter of the stirring pin is 1 / 2-3 / 4 of the shoulder diameter, the top diameter is 1 / 2-2 / 3 of the bottom diameter, and the length is ≤1 / 4 of the shoulder diameter. The preparation method of the multi-scale cemented carbide friction stir welding head specifically includes the following steps: Step 1, First step ball milling: Milling Al particles with a particle size of 0-25 μm... 0.5 CoCrFeNiTi 0.5 High-entropy alloy powder and ultrafine WC powder with a particle size of 0.2-0.4 μm were placed in a ball mill jar and wet-milled to obtain a first solid-liquid mixture. Step 2, second ball milling: The first solid-liquid mixture, medium-grained WC powder with a particle size of 1-3 μm and extra-coarse WC powder with a particle size of 6-10 μm are mixed and wet-milled to obtain the final solid-liquid mixture. Step 3, Drying: The final solid-liquid mixture obtained in Step 2 is dried in a vacuum drying oven, and then the dried powder is ground to obtain multi-scale WC-Al. 0.5 CoCrFeNiTi 0.5 Mixed powders; Step 4, Pre-compression: The multi-scale WC-Al obtained in Step 3 is pre-compressed. 0.5 CoCrFeNiTi 0.5 The mixed powder is loaded into a graphite mold, and the powder is pre-pressed using a hydraulic press to obtain a pre-pressed blank; Step 5, Sintering: The pre-pressed billet and mold obtained in Step 4 are placed in a rapid hot pressing sintering furnace for sintering to obtain multi-scale WC-Al. 0.5 CoCrFeNiTi 0.5 cemented carbide; Step 6, Machining: The multi-scale WC-Al prepared in Step 5 is then machined. 0.5 CoCrFeNiTi 0.5 Hard alloy is machined to obtain friction stir welding tools; Step 7, heat treatment: The friction stir welding tool machined in step 6 is heat treated to produce a multi-scale cemented carbide friction stir welding head.

2. The method as described in claim 1, characterized in that, In step 1, the ball mill speed is set to 300-400 r / min, the ball milling time is 12-24 h, the ball milling medium is anhydrous ethanol, the mass ratio of grinding balls, material and anhydrous ethanol is 10:1:1, and the mass ratio of large, medium and small cemented carbide grinding balls is 5:3:

2. The grinding balls are made of cemented carbide and consist of 20g large balls, 5g medium balls, and 1g small balls, with a mass ratio of 5:3:

2.

3. The method as described in claim 2, characterized in that, In step 2, the ball mill speed is set to 100-200 r / min, the ball milling time is 8-24 h, the mass ratio of grinding balls, material and anhydrous ethanol is 5:1:1, and the mass ratio of large and medium balls is 5:

3. The grinding balls are made of cemented carbide and are divided into 20g large balls and 5g medium balls, with a mass ratio of 5:

3.

4. The method as described in claim 1, characterized in that, In step 3, the drying conditions are: vacuum degree greater than or equal to 0.085 MPa, heating temperature of 60-80℃, and drying time of 6-8 h.

5. The method as described in claim 1, characterized in that, In step 4, the pre-compression is performed once for every 1 / 5 to 1 / 10 of the mass of the added mixture, with a pressure of 50-60 MPa, and the pressure is maintained for 30 seconds. Finally, the entire mixture is maintained under pressure for 3 minutes.

6. The method as described in claim 1, characterized in that, In step 5, the heating rate is set to 100-150℃ / min, the holding temperature is 900℃ for 5-20 min, the holding temperature is 1100-1250℃ for 10-120 min, the cooling rate is 10-30℃ / min, the initial pre-pressure is set to 0 MPa, the pressure increase rate is 0.5-4 MPa / min, the pressure is further increased during degassing holding at 850-950℃, the pressure is increased to 30-50 MPa at the final sintering temperature, and the pressure is maintained during the holding stage at the final sintering temperature. Subsequently, the pressure is slowly reduced to 0 MPa at a rate of 0.15-0.3 MPa.

7. The method as described in claim 1, characterized in that, In step 7, the processed friction stir welding tool is subjected to surface quenching treatment at a temperature of 850-1000℃ for 10-20 minutes.

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