Tungsten Carbide-Based Nanocrystalline Cemented Carbide and Its Preparation Method

Abstract

The present invention belongs to the technical field of nanocrystalline cemented carbides, and discloses a tungsten carbide-based nanocrystalline cemented carbide and a preparation method thereof. The preparation method comprises the following steps: soaking tungsten carbide powder in a modified solution containing soluble cobalt salt and soluble lanthanide metal salt, collecting, washing and drying the solid matter after soaking to obtain a first powder; calcining the first powder under a reducing atmosphere to obtain a second powder; mixing the second powder, high-entropy metal carbide powder or high-entropy metal carbonitride powder, and boron carbide powder, and then forming and sintering to obtain the tungsten carbide-based nanocrystalline cemented carbide. By utilizing the comprehensive action of lanthanide metals, high-entropy metal carbide powder or high-entropy metal carbonitride powder, and boron carbide and adopting a new introduction method, the present invention effectively inhibits the grain size of tungsten carbide, and successfully prepares a nanocrystalline cemented carbide with excellent hardness, toughness and high-temperature resistance, which has strong practicability.

Description

Technical Field

[0001] The present invention relates to the technical field of nanocrystalline cemented carbides, and more particularly to tungsten carbide-based nanocrystalline cemented carbides and their preparation methods. Background Art

[0002] Cemented carbides are widely used in the manufacture of cutting tools such as turning tools, milling cutters, and drills, dies such as wire drawing dies, bolt dies, and nut dies, and rock drilling tools, mining tools, drilling tools, etc. A system of cemented carbide materials is mainly a composite material composed of high-hardness tungsten carbide and a metallic cobalt binder phase. Among them, tungsten carbide provides hardness for the alloy material, and cobalt provides toughness for the alloy material, making the alloy material have excellent hardness, wear resistance, toughness, high temperature resistance, and corrosion resistance.

[0003] The size of tungsten carbide grains in cemented carbide materials directly affects the performance of the materials. As the size of tungsten carbide grains decreases, the hardness and flexural strength of cemented carbide materials continuously increase. In the technical field of this application, cemented carbides with an average tungsten carbide grain size in the range of 0.6 - 0.8 μm are generally defined as sub-micron cemented carbides, those with an average tungsten carbide grain size in the range of 0.2 - 0.6 μm are defined as ultra-fine cemented carbides, and those with an average tungsten carbide grain size below 0.2 μm are defined as nano-grained cemented carbides. Nano-grained cemented carbides have significantly higher hardness, wear resistance, red hardness, flexural strength, and impact toughness than ultra-fine cemented carbides.

[0004] In order to inhibit the growth of tungsten carbide grains, grain growth inhibitors are usually required. For example, in a superfine cemented carbide and its preparation method disclosed in Chinese invention patent CN117684036B and a superfine cemented carbide and its preparation method disclosed in CN111378886B, conventional carbides such as VC and Cr3C2 are used as grain growth inhibitors, making the grain size of tungsten carbide at the ultra-fine level. However, with the continuous development of the manufacturing industry, the requirements for the performance of cemented carbide tools are constantly increasing, and the performance of ultra-fine cemented carbides is difficult to meet the requirements of some special occasions. This requires the development and preparation of nano-grained cemented carbides to further improve the performance and service life of cemented carbides.

[0005] The applicant of this application has experimentally found that conventional carbides such as VC and Cr3C2 have a poor inhibitory effect on the growth of tungsten carbide grains with an average grain size below 0.2 μm, resulting in a relatively complex preparation process for existing nano-grained cemented carbides. Therefore, it is necessary to develop a new preparation process for nano-grained cemented carbides. Summary of the Invention

[0006] To solve the technical problem that the preparation process of nanocrystalline cemented carbide in the prior art is relatively complex, the present invention provides a tungsten carbide-based nanocrystalline cemented carbide and a preparation method thereof, and the technical solution is as follows:

[0007] A preparation method of tungsten carbide-based nanocrystalline cemented carbide, comprising the following steps:

[0008] Soak tungsten carbide powder in a modified solution containing soluble cobalt salt and soluble lanthanide metal salt, collect, wash and dry the solid matter after soaking to obtain a first powder;

[0009] Calcine the first powder under a reducing atmosphere to obtain a second powder;

[0010] Mix the second powder, high-entropy metal carbide powder or high-entropy metal carbonitride powder, and boron carbide powder, and then form and sinter to obtain tungsten carbide-based nanocrystalline cemented carbide.

[0011] As a further improvement of the above preparation method of tungsten carbide-based nanocrystalline cemented carbide: it also includes soaking tungsten carbide in a hydrofluoric acid solution before impregnation, and collecting, washing and drying tungsten carbide after soaking.

[0012] As a further improvement of the above preparation method of tungsten carbide-based nanocrystalline cemented carbide: the mass fraction of the hydrofluoric acid solution is 10-15%, the solid-liquid ratio of soaking is 1g:(20-50mL), the soaking time is 0.5-1 hour, the soaking temperature is 40-50°C, wash until neutral, and perform vacuum drying at 60-70°C.

[0013] As a further improvement of the above preparation method of tungsten carbide-based nanocrystalline cemented carbide: the lanthanide metal in the soluble lanthanide metal salt is at least one of lanthanum, cerium, praseodymium, dysprosium, neodymium, promethium, samarium, europium, terbium; in the modified solution, the concentration of cobalt ions is 0.1-0.5mol / L, and the concentration of lanthanide metal ions is 0.01-0.05mol / L; perform equal-volume soaking, the soaking time is 2-4 hours, the soaking temperature is 50-60°C, wash until neutral, and perform vacuum drying at 60-70°C.

[0014] As a further improvement of the above preparation method of tungsten carbide-based nanocrystalline cemented carbide: the soluble cobalt salt is cobalt nitrate; the soluble lanthanide metal salt includes at least dysprosium nitrate, and the molar fraction of dysprosium nitrate accounts for 40-60% of the total molar amount of the soluble lanthanide metal salt.

[0015] As a further improvement of the above preparation method of tungsten carbide-based nanocrystalline cemented carbide: the reducing atmosphere is a mixed gas of nitrogen and hydrogen, the volume fraction of hydrogen accounts for 20-30% of the total volume of the reducing atmosphere, the calcination temperature is 700-900°C, and the calcination time is 4-8 hours.

[0016] As a further improvement to the preparation method of the tungsten carbide-based nanocrystalline cemented carbide described above: the weight ratio of the second powder, the high-entropy metal carbide powder or the high-entropy metal carbonitride powder, and the boron carbide powder is 100: (0.2 - 1.5): (0.1 - 0.5); the metal occupancy in the high-entropy metal carbide powder or the high-entropy metal carbonitride powder is composed of at least five of vanadium, chromium, titanium, zirconium, hafnium, niobium, tantalum, and molybdenum in an equal atomic ratio; the average particle size of the tungsten carbide powder, the high-entropy metal carbide powder or the high-entropy metal carbonitride powder, and the boron carbide powder is 50 - 150 nm.

[0017] As a further improvement to the preparation method of the tungsten carbide-based nanocrystalline cemented carbide described above: the sintering temperature is 1500 - 1650 °C.

[0018] As a further improvement to the preparation method of the tungsten carbide-based nanocrystalline cemented carbide described above: first sinter in vacuum for 4 - 6 hours, and then sinter at 100 - 200 MPa for 1 - 2 hours.

[0019] The tungsten carbide-based nanocrystalline cemented carbide is prepared by the preparation method of the tungsten carbide-based nanocrystalline cemented carbide described above.

[0020] The tungsten carbide-based nanocrystalline cemented carbide and its preparation method of the present invention have the following advantages:

[0021] First, the lanthanide metals introduced in the present invention have strong deoxidizing properties, and oxygen is an important factor promoting grain growth in the alloy. Therefore, the addition of lanthanide metals can indirectly inhibit grain growth by reducing the oxygen content. Compounds of lanthanide metals can form particles at grain boundaries, which can fix the grain boundaries, enhance the strength of the grain boundaries, and prevent the free growth of grains under high temperature or long-term heat treatment. Lanthanide metals often form solid solutions in the matrix material. The formation of solid solutions can increase the lattice distortion, making the grains more stable at high temperatures and inhibiting grain growth. Lanthanide metals can enhance the creep resistance of the alloy at high temperatures and inhibit grain growth caused by high-temperature creep. Lanthanide metals can also change the phase diagram of the alloy, making more stable phases or refined structures appear in the alloy, especially enhancing phase stability in a high-temperature environment and preventing excessive coarsening of grains.

[0022] High-entropy alloys are alloys formed by five or more metals in equal or approximately equal amounts. The definition of an alloy is a substance with metallic properties synthesized from two or more metals and metals or non-metals. The present invention introduces high-entropy metal carbide powder or high-entropy metal carbonitride powder with high entropy and alloy properties as grain growth inhibitors, which can form stable grain boundaries in the tungsten carbide matrix, inhibit the excessive growth of grains, and further enhance the high-temperature strength and oxidation resistance of the alloy under extreme conditions, and enhance the wear resistance and toughness of the overall alloy. At the same time, high-entropy metal carbides or high-entropy metal carbonitrides are prone to form nanocrystalline structures, solid solutions and second-phase particles (such as metal compounds, metal oxides, carbides, etc.) during the preparation process, and can form a "pinning effect" under high-temperature or high-stress conditions, increasing the grain boundary density and strength, reducing the grain migration, and reducing the grain growth rate, thereby further restricting the growth of grains.

[0023] As a hard and chemically stable substance, boron carbide has a melting point as high as 2450 °C, can remain stable at high temperatures, forms a physical barrier during sintering, increases the strength of the interface, enhances the mutual binding between grains, hinders the migration of grains in the matrix material, reduces the diffusion rate, and thus effectively restricts the growth of grains. Boron carbide also has strong antioxidant ability, so it can effectively prevent the oxidation of the matrix material in a high-temperature environment, further avoid grain growth or changes in alloy composition caused by oxidation, and effectively improve the high-temperature performance, hardness, strength and other performance indicators of the alloy material.

[0024] Second, compared with the traditional powder mixing method of directly using cobalt powder and lanthanide metal oxide powder, the present invention introduces cobalt elements and lanthanide metal elements by impregnation and calcination, and has the following advantages:

[0025] (1) Direct addition of metal powders requires a long ball milling and mixing time, which easily leads to uneven distribution of cobalt and lanthanide metals. Especially in the case of larger particle powders, the metal elements may only act on the surface layer or local area, and it is difficult to achieve uniform distribution. However, the present invention introduces cobalt elements and lanthanide metal elements by soaking method, which can be more evenly attached to the surface of tungsten carbide, which is crucial for forming a stable nanocrystalline structure and can improve the overall performance of cemented carbide.

[0026] (2) For the physical addition method, if the particle size of the metal powder is relatively large, it is easy to result in poor density and performance of the final alloy due to insufficient interaction between particles or uneven sintering density during the sintering process. However, the smaller the particle size, the higher the cost. In the chemical reduction addition scheme of soaking + calcination used in the present invention, cobalt elements and lanthanide metal elements first contact tungsten carbide particles through a solution in the form of ions, and then are in-situ reduced to metals or oxides during the calcination process, reducing the risk of agglomeration of metal powders during sintering, thereby contributing to improving the sintering density and ultimately enhancing the mechanical properties and thermal stability of the cemented carbide.

[0027] (3) Metal powders are prone to oxidation in the air, and their activity will be greatly reduced after oxidation, affecting the performance of the final cemented carbide. The cobalt elements and lanthanide metal elements introduced by the soaking + calcination method in the present invention can directly form an alloy with tungsten carbide powder during the calcination process without being interfered by oxidation, effectively avoiding the oxidation problem of metal powders.

[0028] (4) Physical addition and mixing may lead to insufficient tight bonding between metal powder particles and tungsten carbide particles. Especially when the particle size of the metal powder is large, the bonding surface is small, which may affect the strength and toughness of the cemented carbide. The present invention directly reacts with the surface of tungsten carbide through the solution soaking method, which can more effectively form an interface bond between the metal and tungsten carbide. The calcination reduction process further ensures the uniform distribution and tight bonding of metal elements, enhancing the bonding force between tungsten carbide particles and the metal phase and optimizing the overall structure of the alloy.

[0029] (5) The direct physical addition of metal powders may cause agglomeration of larger particles, making it difficult to form fine nanocrystalline particles, thereby affecting the mechanical properties of the cemented carbide, especially its stability at high temperatures. The soaking + calcination scheme of the present invention introduces metal elements through chemical reactions and promotes grain refinement through the calcination process, which can effectively inhibit grain growth, thus forming a stable nanocrystalline structure, which is crucial for improving the properties such as hardness, wear resistance, and high-temperature strength of the alloy.

[0030] In summary, the present invention utilizes the combined action of lanthanide metals, high-entropy metal carbides or high-entropy metal carbonitrides, and boron carbide and adopts a new introduction method, effectively suppressing the particle size of tungsten carbide, successfully preparing a nanocrystalline cemented carbide with excellent hardness, strength and toughness, and high temperature resistance, effectively solving the technical problem of the relatively complex preparation process of nanocrystalline cemented carbide in the prior art, and having strong practicality.

[0031] The following further illustrates the present invention through specific embodiments. The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Detailed implementation mode

[0032] The present invention will be described clearly and completely below. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention, it should be particularly pointed out that:

[0033] In the present invention, the technical solutions and technical features provided in each part including the following description can be combined with each other without conflict.

[0034] In addition, the embodiments of the present invention involved in the following description are usually only some embodiments of the present invention, rather than all embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0035] Regarding the terms and units in the present invention. The terms "including", "having" and any variations thereof in the description, claims and relevant parts of the present invention are intended to cover non-exclusive inclusion.

[0036] Example 1: The preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example includes the following steps:

[0037] (1) Tungsten carbide is soaked in a hydrofluoric acid solution with a mass fraction of 13%, the solid-liquid ratio of soaking is 1 g:(40 mL), the soaking time is 1 hour, the soaking temperature is 40 °C. After soaking, the tungsten carbide is collected, washed to neutrality, and vacuum dried at 70 °C. By soaking with hydrofluoric acid, the oxides and impurities on the surface of the tungsten carbide powder can be removed, making the surface of the tungsten carbide more active and improving the adhesion and reactivity of the subsequent modification solution on the surface of the tungsten carbide.

[0038] (2) The tungsten carbide powder is put into a modification solution containing soluble cobalt salt and soluble lanthanide metal salt. The concentration of cobalt ions in the modification solution is 0.3 mol / L, and the concentration of lanthanide metal ions is 0.04 mol / L. Equal-volume soaking is adopted, the soaking temperature is 60 °C, and the soaking time is 3 hours. After soaking, the solid matter is collected, washed to neutrality, and vacuum dried at 70 °C to obtain the first powder.

[0039] Among them, the soluble cobalt salt is cobalt nitrate; the soluble lanthanide metal salts are neodymium nitrate, samarium nitrate and dysprosium nitrate, and the molar fraction of dysprosium nitrate accounts for 40% of the total molar amount of the soluble lanthanide metal salts.

[0040] (3) The first powder is calcined under a reducing atmosphere, the calcination temperature is 800 °C, and the calcination time is 6 hours to obtain the second powder.

[0041] (4) Weigh the second powder, high-entropy metal carbide powder or high-entropy metal carbonitride powder, and boron carbide powder according to a weight ratio of 100:1:0.3 to obtain the raw material powder. Then, use cemented carbide grinding balls with a diameter of 2 cm, and according to a ball-to-material mass ratio of 7:1, add the cemented carbide grinding balls, raw material powder, and a small amount of paraffin powder (2% of the mass of the raw material powder) into a horizontal ball mill and ball mill for 48 hours. Then, screen the powder with a particle size ≥ 140 mesh, and use a pressure of 2 T / cm 2 to press the powder into a green body.

[0042] Then sinter the green body at 1650 °C, with a heating rate of 10 °C / min. First, sinter under vacuum for 5 hours, and then sinter at 150 MPa for 1 hour to obtain tungsten carbide-based nanocrystalline cemented carbide.

[0043] Among them, the average particle size of the tungsten carbide powder is 126 nm, the average particle size of the high-entropy metal carbide powder or high-entropy metal carbonitride powder is 105 nm, and the average particle size of the boron carbide powder is 97 nm.

[0044] The metal occupancy in the high-entropy metal carbide powder or high-entropy metal carbonitride powder is composed of vanadium, chromium, titanium, zirconium, hafnium, niobium, tantalum, and molybdenum in equal atomic ratios. Mix the elemental powder or oxide powder of the occupancy metal with carbon powder evenly, and then react the mixed powder at 1400 °C under a reducing atmosphere to obtain the high-entropy metal carbide powder or high-entropy metal carbonitride powder.

[0045] After testing, the average particle size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 132 nm, the high-temperature Rockwell hardness is 93.5 HRA, the transverse rupture strength is 4150 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.11%.

[0046] Example 2: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that the molar fraction of dysprosium nitrate accounts for 60% of the total molar amount of soluble lanthanide metal salts.

[0047] After testing, the average particle size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 134 nm, the high-temperature Rockwell hardness is 93.3 HRA, the transverse rupture strength is 4180 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.11%.

[0048] Example 3: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that the soluble lanthanide metal salts are neodymium nitrate, samarium nitrate, and lanthanum nitrate.

[0049] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 141 nm, the high-temperature Rockwell hardness is 92.9 HRA, the transverse rupture strength is 4160 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.12%.

[0050] Example 4: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that the soluble lanthanide metal salt is neodymium nitrate and samarium nitrate.

[0051] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 148 nm, the high-temperature Rockwell hardness is 91.8 HRA, the transverse rupture strength is 4130 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.14%.

[0052] Example 5: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that the weight ratio of the second powder, the high-entropy metal carbide powder or the high-entropy metal carbonitride powder, and the boron carbide powder is 100:0.2:0.1.

[0053] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 135 nm, the high-temperature Rockwell hardness is 93.1 HRA, the transverse rupture strength is 4200 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.12%.

[0054] Example 6: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that the weight ratio of the second powder, the high-entropy metal carbide powder or the high-entropy metal carbonitride powder, and the boron carbide powder is 100:1.5:0.5.

[0055] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 131 nm, the high-temperature Rockwell hardness is 92.3 HRA, the transverse rupture strength is 4210 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.10%.

[0056] Control Example 1: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that the molar fraction of dysprosium nitrate accounts for 35% of the total molar amount of the soluble lanthanide metal salt.

[0057] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 132 nm, the high-temperature Rockwell hardness is 92.3 HRA, the transverse rupture strength is 4140 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.12%.

[0058] Comparative Example 2: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that the molar fraction of dysprosium nitrate accounts for 65% of the total molar amount of soluble lanthanide metal salts.

[0059] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 131 nm, the high-temperature Rockwell hardness is 94.2 HRA, the transverse rupture strength is 4040 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.13%.

[0060] Comparative Example 3: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that cobalt metal, neodymium oxide, samarium oxide and dysprosium oxide are directly physically added and mixed with tungsten carbide.

[0061] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 149 nm, the high-temperature Rockwell hardness is 91.6 HRA, the transverse rupture strength is 4100 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.15%.

[0062] Comparative Example 4: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that high-entropy metal carbide powder or high-entropy metal carbonitride powder is not used.

[0063] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 146 nm, the high-temperature Rockwell hardness is 92.1 HRA, the transverse rupture strength is 4050 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.15%.

[0064] Comparative Example 5: Compared with Example 1, the difference in the preparation method of the tungsten carbide-based nanocrystalline cemented carbide in this example is that boron carbide powder is not used.

[0065] After testing, the average grain size of the tungsten carbide-based nanocrystalline cemented carbide in this example is 145 nm, the high-temperature Rockwell hardness is 91.8 HRA, the transverse rupture strength is 3980 MPa, and the weight gain after oxidation in an air environment at 800 °C for 10 hours is 0.15%.

[0066] The examples of the tungsten carbide-based nanocrystalline cemented carbide of the present invention are prepared by the preparation method of the tungsten carbide-based nanocrystalline cemented carbide of any one of the above examples.

[0067] In the above examples and comparative examples, the reducing atmosphere is a mixture of nitrogen and hydrogen, and the volume fraction of hydrogen accounts for 20-30% of the total volume of the reducing atmosphere.

[0068] The average grain size of the tungsten carbide-based nanocrystalline cemented carbide is tested by a transmission electron microscope.

[0069] The high-temperature Rockwell hardness is tested by the method specified in Chinese National Standard GB / T 230.1-2018, and the test temperature is 760 °C.

[0070] The transverse rupture strength is tested by the method specified in Chinese National Standard GB / T 3851-2015.

[0071] The test method for "weight gain after oxidation in air at 800 °C for 10 hours" is as follows: First, the weight of the mold at room temperature is measured, then the mold is kept in an air environment at 800 °C for 10 hours. After the heat preservation is completed, its weight is measured again, and then the percentage change in weight gain before and after heat preservation is calculated, which is the weight gain after oxidation in air at 800 °C for 10 hours.

[0072] The above describes the relevant content of the present invention. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Based on the above content of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing tungsten carbide-based nanocrystalline cemented carbide, characterized in that: It includes the following steps: Before impregnation, soak tungsten carbide with a hydrofluoric acid solution. After soaking, collect, wash, and dry the tungsten carbide; Put tungsten carbide powder into a modified solution containing soluble cobalt salt and soluble lanthanide metal salt for soaking. After soaking, collect, wash, and dry the solid matter to obtain the first powder; In the said modified solution, the concentration of cobalt ions is 0.1 - 0.5 mol / L, and the concentration of lanthanide metal ions is 0.01 - 0.05 mol / L; Soak with equal volume, the soaking duration is 2 - 4 hours, the soaking temperature is 50 - 60 °C, wash until neutral, and perform vacuum drying at 60 - 70 °C; Calcine the first powder under a reducing atmosphere to obtain the second powder; Mix the second powder, high-entropy metal carbide powder or high-entropy metal carbonitride powder, and boron carbide powder, and then form and sinter to obtain tungsten carbide-based nanocrystalline cemented carbide; The average particle size of the tungsten carbide powder is 126 nm.

2. The preparation method of the tungsten carbide-based nanocrystalline cemented carbide according to claim 1, characterized in that: The mass fraction of the hydrofluoric acid solution is 10 - 15%, the solid-liquid ratio of soaking is 1 g:(20 - 50 mL), the soaking duration is 0.5 - 1 hour, the soaking temperature is 40 - 50 °C, wash until neutral, and perform vacuum drying at 60 - 70 °C.

3. The preparation method of the tungsten carbide-based nanocrystalline cemented carbide according to claim 1, characterized in that: The lanthanide metal in the said soluble lanthanide metal salt is at least one of lanthanum, cerium, praseodymium, dysprosium, neodymium, promethium, samarium, europium, and terbium.

4. The preparation method of the tungsten carbide-based nanocrystalline cemented carbide according to claim 3, characterized in that: The said soluble cobalt salt is cobalt nitrate; The said soluble lanthanide metal salt includes at least dysprosium nitrate, and the molar fraction of dysprosium nitrate accounts for 40 - 60% of the total molar amount of the soluble lanthanide metal salt.

5. The method for preparing tungsten carbide-based nanocrystalline cemented carbide according to claim 1, characterized in that: The said reducing atmosphere is a mixed gas of nitrogen and hydrogen, the volume fraction of hydrogen accounts for 20 - 30% of the total volume of the reducing atmosphere, the calcination treatment temperature is 700 - 900 °C, and the calcination treatment duration is 4 - 8 hours.

6. The preparation method of the tungsten carbide-based nanocrystalline cemented carbide according to claim 1, characterized in that: The weight ratio of the second powder, high-entropy metal carbide powder or high-entropy metal carbonitride powder, and boron carbide powder is 100:(0.2 - 1.5):(0.1 - 0.5); The metal occupancy in the high-entropy metal carbide powder or high-entropy metal carbonitride powder is composed of at least five of vanadium, chromium, titanium, zirconium, hafnium, niobium, tantalum, and molybdenum in equal atomic ratio; The average particle size of the high-entropy metal carbide powder or high-entropy metal carbonitride powder and boron carbide powder is 50 - 150 nm.

7. The method for preparing a tungsten carbide-based nanocrystalline cemented carbide according to claim 1, characterized in that: The sintering temperature is 1500 - 1650 °C.

8. The preparation method of the tungsten carbide-based nanocrystalline cemented carbide according to claim 7, characterized in that: First sinter under vacuum for 4 - 6 hours, and then sinter at 100 - 200 MPa for 1 - 2 hours.

9. Tungsten carbide-based nanocrystalline cemented carbide, characterized in that: Prepared by the preparation method of tungsten carbide-based nanocrystalline cemented carbide according to any one of claims 1 - 8.