Nanometer hard alloy material and preparation method thereof

Abstract

The invention discloses a nanometer hard alloy material and a preparation method thereof. The Vickers hardness of the nanometer hard alloy material ranges from 1000 HV10 to 3000 HV10, the bending strength ranges from 3000 MPa to 6000 MPa, and the grain size of tungsten carbide ranges from 0.1 micrometer to 0.5 micrometer. Two kinds of cobalt powder with different particle sizes and forms are combined to serve as a binding phase, gradient melting is achieved in the sintering process, a liquid phase is continuously provided, tungsten carbide grains are densified during low-temperature sintering, and meanwhile overgrowth does not occur. The nano hard alloy material is uniform in structure and excellent in comprehensive mechanical property, the problems that cutting edges of existing hard alloy material products are prone to breakage, the service life is short, and the precision in the machining process is poor can be solved, and the cost can be effectively controlled.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a nano-hard alloy material and its preparation method. Background Technology

[0002] Due to its excellent hardness, wear resistance, and impact resistance, cemented carbide is widely used in cutting tools, mining drilling, and wear-resistant components. Cemented carbide is formed by liquid-phase sintering and densification, using tungsten carbide (WC) as the hard phase and metallic cobalt (Co) as the binder phase. If nanoscale tungsten carbide (particle size <0.4 μm) is used as the hard phase, nano-cemented carbide can be obtained, which can significantly improve the hardness and strength of cemented carbide.

[0003] However, nano-tungsten carbide has extremely high surface energy, and grain coarsening easily occurs during densification at conventional sintering temperatures. Adding grain growth inhibitors such as vanadium carbide (VC), chromium carbide (Cr3C2), and tantalum carbide (TaC) can partially alleviate this grain coarsening. However, excessive addition of inhibitors can form brittle phases, impairing the alloy's fracture toughness and corrosion resistance. Therefore, the selection and dosage control of inhibitors during preparation are quite challenging.

[0004] In addition, the growth of nano-tungsten carbide grains can be directly suppressed by lowering the sintering temperature. However, the cobalt binder phase in the raw material is prone to excessive viscosity when melting at a lower sintering temperature, which will hinder the rearrangement of nano-tungsten carbide grains. Furthermore, insufficient solid-liquid interfacial energy and inadequate pore closure will easily lead to pore structure defects, ultimately affecting the mechanical properties of the alloy. Summary of the Invention

[0005] The purpose of this invention is to provide a nano-hard alloy material and its preparation method, so as to solve at least one aspect of the problems and defects mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A nano-hard alloy material with a Vickers hardness of 1000~3000HV10 and a bending strength of 3000MPa~6000MPa, wherein the tungsten carbide grain size is 0.1μm~0.5μm.

[0007] As a further aspect of the present invention: the Vickers hardness of the nano-hard alloy material is 1800~2200HV10.

[0008] As a further embodiment of the present invention, the bending strength of the nano-hard alloy material is 3900MPa~5000MPa.

[0009] As a further embodiment of the present invention, the carbide grain size in the nano-hard alloy material is 0.11μm~0.34μm.

[0010] As a further embodiment of the present invention: the raw material includes a binder phase, which includes spherical cobalt powder with a Fisher particle size of 0.2~2.0μm and flake cobalt powder with a Fisher particle size of 1.8~4.0μm.

[0011] This invention uses a combination of two cobalt powders with different physical properties as the binder phase, which can achieve step-by-step liquid phase generation during the sintering process: during the heating of the raw materials, the spherical fine cobalt powder melts preferentially and initiates the initial wetting; the flake coarse cobalt powder melts slowly and maintains the amount of liquid phase in the high-temperature stage.

[0012] As a further embodiment of the present invention, the raw materials also include tungsten carbide and an inhibitor.

[0013] As a further embodiment of the present invention, the mass percentage of the binder phase in the raw material is 7.0% to 13.0%, preferably 7.0% to 9.0%.

[0014] As a further embodiment of the present invention, the tungsten carbide content in the raw material is 86.5% to 93.0% by mass, preferably 90.0% to 92.6%.

[0015] As a further embodiment of the present invention, the mass percentage of the inhibitor in the raw material is 0-0.5%, preferably 0.3%-0.5%.

[0016] As a further embodiment of the present invention, the nano-hard alloy comprises the following components in weight percentage: 7.0%~13.0% binder phase, 86.5%~93.0% tungsten carbide and 0~0.5% inhibitor.

[0017] As a further embodiment of the present invention, the spherical cobalt powder has a Fisher particle size of 0.4~1.2μm.

[0018] As a further embodiment of the present invention, the Fisher particle size of the flake cobalt powder is 2.0~3.0μm.

[0019] As a further embodiment of the present invention, the mass ratio of the spherical cobalt powder to the flake cobalt powder is (1.5~3):1.

[0020] As a further embodiment of the present invention, the tungsten carbide has a Fisher particle size of 0.1~0.3μm.

[0021] As a further embodiment of the present invention, the inhibitor has a Fisher particle size of 1.1~1.5μm.

[0022] As a further embodiment of the present invention: the inhibitor includes at least one of chromium carbide, vanadium carbide, and tantalum carbide, preferably a mixture of chromium carbide and vanadium carbide.

[0023] As a further embodiment of the present invention: the inhibitor includes chromium carbide at a mass ratio of 2% to 95%, preferably 30% to 40%.

[0024] As a further aspect of the present invention, the carbon balance coefficient in the nano-hard alloy is controlled to be +0.05 to +0.10%.

[0025] The carbon balance mentioned in this invention refers to the ratio between the actual total carbon content and the theoretically required total carbon content in the mixed raw materials of cemented carbide materials, and is usually expressed as a carbon balance coefficient.

[0026] In the preparation of cemented carbide materials, the binder phase is fundamental to ensuring the alloy's good toughness and corrosion resistance. This invention selects two cobalt powders with different physical properties as raw materials to achieve a superimposed liquid-phase sintering effect resulting from the synergistic effect of spherical fine cobalt powder and flake-shaped coarse cobalt powder, which is compatible with tungsten carbide. Due to the difference in physical properties between the two types of cobalt powder, spherical fine cobalt powder melts completely first than flake coarse cobalt powder, and can obtain a flowing cobalt melt with lower viscosity and better fluidity at a lower sintering temperature, thus enabling it to be successfully combined with tungsten carbide. During the sintering process, as the raw material temperature rises, the flake-shaped cobalt powder gradually melts completely, continuing to provide a fluid liquid phase to fill the pores, achieving a full wetting effect between the cobalt phase and tungsten carbide, reducing the interfacial energy between tungsten carbide and cobalt, improving the capillary force-driven densification efficiency, and realizing the full densification of cemented carbide materials.

[0027] In this invention, spherical cobalt powder with a Fisher particle size of 0.4~1.2μm and flake-shaped cobalt powder with a Fisher particle size of 2.0~3.0μm are preferred as raw materials, and the mass ratio of the two cobalt powders is in the range of (1.5~3):1, which enables the raw materials to achieve full densification at a lower sintering temperature. Moreover, due to the lower sintering temperature, abnormal growth of nano-tungsten carbide is not caused, ensuring the uniformity of the alloy structure.

[0028] A method for preparing a nano-hard alloy material as described in any one of the above methods includes the following steps: ball milling, pressing and sintering the binder phase, tungsten carbide and inhibitor to obtain the nano-hard alloy material.

[0029] As a further embodiment of the present invention, a grinding aid and a forming agent are added during the ball milling process.

[0030] As a further embodiment of the present invention: the grinding aid is selected from at least one of ethanol and isopropanol, preferably ethanol.

[0031] As a further embodiment of the present invention: the grinding aid is added at a ratio of 100~450ml / kg to the liquid-solid ratio of the material.

[0032] As a further embodiment of the present invention: the molding agent is selected from at least one of polyethylene glycol and paraffin wax; the polyethylene glycol is selected from at least one of polyethylene glycol 2000, polyethylene glycol 3000, polyethylene glycol 4000, polyethylene glycol 6000 and polyethylene glycol 8000, preferably polyethylene glycol 4000.

[0033] As a further embodiment of the present invention, the amount of the molding agent added is 1.5% to 3.5% of the total mass of the raw materials.

[0034] As a further embodiment of the present invention, the ball milling time is 20-50 hours.

[0035] As a further embodiment of the present invention: the ball-to-material ratio during the ball milling process is (5~10):1.

[0036] As a further embodiment of the present invention, the rotation speed during the ball milling process is 30-40 revolutions per minute.

[0037] As a further embodiment of the present invention: the pressing molding is selected from one of compression molding, extrusion molding and isostatic pressing, preferably compression molding.

[0038] As a further embodiment of the present invention, the pressure sintering process is carried out in an inert gas atmosphere.

[0039] As a further embodiment of the present invention: the inert gas atmosphere is selected from nitrogen atmosphere, argon atmosphere, and helium atmosphere, preferably argon atmosphere.

[0040] As a further embodiment of the present invention: the gas pressure during the pressure sintering process is 30~100 bar, preferably 100 bar.

[0041] As a further embodiment of the present invention: the sintering temperature during the pressure sintering process is 1000~1500℃.

[0042] As a further embodiment of the present invention, the holding time during the pressure sintering process is 0.5~4.0h.

[0043] As a further embodiment of the present invention, the preparation method includes the following steps: S1: Add the grinding aid, then add the binder phase, tungsten carbide, inhibitor and forming agent, and perform wet grinding to obtain a mixed slurry; S2: The mixed slurry obtained in step S1 is pressed into shape and then pressure sintered to obtain the nano-hard alloy material.

[0044] The present invention has at least the following technical effects: 1. The cemented carbide material of the present invention achieves better coating of tungsten carbide by rationally applying the physical properties of cobalt powder and using a multi-level cobalt powder combination method, which combines "spherical cobalt powder to reduce melt viscosity" and "flaky cobalt powder to provide a continuous liquid phase". 2. By dynamically optimizing the wettability of combined cobalt powder, the sintering temperature can be reduced while the tungsten carbide / cobalt interface energy is lowered, thereby improving the capillary force-driven densification efficiency and achieving full densification of cemented carbide materials (>99.5%). 3. While reducing the amount of inhibitor added, abnormal growth of tungsten carbide grains is avoided. In the cemented carbide material prepared in the embodiments of the present invention, the average grain size of tungsten carbide is <0.4 μm, and the grain size increases by <0.05 μm compared with tungsten carbide raw material; 4. The Vickers hardness of the nano-hard alloy material prepared by this invention is 1850~2200HV10, and the bending strength is 3900~5000MPa, which has obvious performance advantages compared with alloy materials using cobalt powder as a single component. 5. Based on a thorough investigation and analysis of the physical and performance properties of existing cemented carbide materials, this invention fully utilizes cemented carbide design and sintering-related theories to solve the problems of incomplete densification and poor mechanical properties that occur in existing cemented carbide under low temperature and low inhibitor addition conditions. It provides a new nano-cemented carbide material with stable physical properties, controllable microstructure and defects, excellent processing performance, and longer service life. Attached Figure Description

[0045] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0046] Figure 1 Here is a scanning electron microscope image of the nano-hard alloy material prepared in Example 1 of this invention; Figure 2 This is a scanning electron microscope image of the nano-hard alloy material prepared in Comparative Example 1 of this invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0048] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0049] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0050] Example 1 This embodiment provides a nano-hard alloy material, the preparation method of which includes the following steps: S1: The raw materials are composed of 7.0% cobalt powder, 0.3% inhibitor powder, and 92.7% tungsten carbide powder by weight. The cobalt powder is composed of spherical cobalt powder with a Fisher particle size of 0.4 μm and flake cobalt powder with a Fisher particle size of 3.0 μm, with a mass ratio of spherical cobalt powder to flake cobalt powder of 3:1. The inhibitor powder is composed of chromium carbide powder and vanadium carbide powder. The chromium carbide powder has a Fisher particle size of 1.1 μm, the vanadium carbide powder has a Fisher particle size of 1.5 μm, and the mass ratio of chromium carbide powder to vanadium carbide powder is 1:2. The Fisher particle size of tungsten carbide powder is 0.3 μm; The carbon balance factor is controlled at +0.05%; The molding agent is polyethylene glycol 4000, and the amount of molding agent added is 3.5% of the total mass of the raw materials; S2: Add grinding aid ethanol and materials cobalt powder, tungsten carbide powder, chromium carbide powder, vanadium carbide powder and polyethylene glycol 4000 into a ball mill. The liquid-solid ratio of ethanol to materials is 100 ml / kg, the ball-to-material ratio is 5:1, the ball mill speed is 40 rpm, the ball milling time is 20 h, and after the ball milling is completed, spray drying is performed to obtain the mixture. S3: After the obtained mixture is molded and pressed, it is pressure sintered in a gas pressure sintering furnace at a temperature of 1300℃. During the sintering process, inert argon gas is introduced at a pressure of 100 bar and the sintering time is 0.5 h. After sintering, nano-hard alloy material is obtained.

[0051] Example 2 The difference from Example 1 is that the Fisher particle size of the tungsten carbide powder is replaced with 0.1 μm, while the other steps and parameters are the same as in Example 1, to obtain nano-hard alloy material.

[0052] Example 3 This embodiment provides a nano-hard alloy material, the preparation method of which includes the following steps: S1: The raw materials are composed of cobalt powder 13.0%, inhibitor powder 0.3%, and tungsten carbide powder 86.7% by weight. The cobalt powder is composed of spherical cobalt powder with a Fisher particle size of 0.4 μm and flake cobalt powder with a Fisher particle size of 3.0 μm, with a mass ratio of spherical cobalt powder to flake cobalt powder of 3:1. The inhibitor powder is composed of chromium carbide powder and vanadium carbide powder. The chromium carbide powder has a Fisher particle size of 1.1 μm, and the vanadium carbide powder has a Fisher particle size of 1.5 μm. The mass ratio of chromium carbide powder to vanadium carbide powder is 1:2. The Fisher particle size of tungsten carbide powder is 0.3 μm; The carbon balance factor is controlled at +0.05%; The molding agent is polyethylene glycol 4000, and the amount of molding agent added is 3.5% of the total mass of the raw materials; S2: Add grinding aid ethanol and materials cobalt powder, tungsten carbide powder, chromium carbide powder, vanadium carbide powder and polyethylene glycol 4000 into a ball mill. The liquid-solid ratio of ethanol to materials is 100 ml / kg, the ball-to-material ratio is 5:1, the ball mill speed is 40 rpm, the ball milling time is 20 h, and after the ball milling is completed, spray drying is performed to obtain the mixture. S3: After the obtained mixture is molded and pressed, it is pressure sintered in a gas pressure sintering furnace at a temperature of 1250℃. During the sintering process, inert argon gas is introduced at a pressure of 100 bar and the sintering time is 0.5 h. After sintering, nano-hard alloy material is obtained.

[0053] Example 4 This embodiment provides a nano-hard alloy material, the preparation method of which includes the following steps: S1: The raw materials are composed of 7.0% cobalt powder, 0.5% inhibitor powder, and 92.5% tungsten carbide powder by weight. The cobalt powder is composed of spherical cobalt powder with a Fisher particle size of 1.2 μm and flake-shaped cobalt powder with a Fisher particle size of 2.0 μm, with a mass ratio of spherical cobalt powder to flake-shaped cobalt powder of 1.5:1. The inhibitor powder is composed of chromium carbide powder and vanadium carbide powder. The chromium carbide powder has a Fisher particle size of 1.1 μm, the vanadium carbide powder has a Fisher particle size of 1.5 μm, and the mass ratio of chromium carbide powder to vanadium carbide powder is 3:7. The Fisher particle size of tungsten carbide powder is 0.2 μm; Control the carbon balance to +0.10%; The molding agent is paraffin wax, and the amount of molding agent added is 1.5% of the total mass of the raw materials; S2: Add grinding aid ethanol and materials cobalt powder, tungsten carbide powder, chromium carbide powder, vanadium carbide powder and paraffin wax into a ball mill. The liquid-solid ratio of ethanol to materials is 450 ml / kg, the ball-to-material ratio is 10:1, the ball mill speed is 30 rpm, the ball milling time is 50 h, and after the ball milling is completed, spray drying is performed to obtain the mixture. S3: After the obtained mixture is molded and pressed, it is pressure sintered in a gas pressure sintering furnace at a temperature of 1350℃. During the sintering process, inert argon gas is introduced at a pressure of 100 bar and the sintering time is 2.0 h. After sintering, nano-hard alloy material is obtained.

[0054] Comparative Example 1 This comparative example provides a nano-hard alloy material, the preparation method of which includes the following steps: S1: The raw material composition by weight percentage is 7.0% cobalt powder, 0.3% inhibitor, and 92.7% tungsten carbide powder; The cobalt powder is composed of spherical cobalt powder with a Fisher particle size of 0.4 μm; The inhibitor is composed of chromium carbide powder and vanadium carbide powder. The chromium carbide powder has a Fisher particle size of 1.1 μm, the vanadium carbide powder has a Fisher particle size of 1.5 μm, and the mass ratio of chromium carbide powder to vanadium carbide powder is 1:2. The Fisher particle size of tungsten carbide powder is 0.3 μm; The carbon balance is controlled at +0.05%; The molding agent is polyethylene glycol 4000, and the amount of molding agent added is 3.5% of the total mass of the raw materials; S2: Add grinding aid ethanol and materials cobalt powder, tungsten carbide powder, chromium carbide powder, vanadium carbide powder and polyethylene glycol 4000 into a ball mill. The liquid-solid ratio of ethanol to materials is 100 ml / kg, the ball-to-material ratio is 5:1, the ball mill speed is 40 rpm, the ball milling time is 20 h, and after the ball milling is completed, spray drying is performed to obtain the mixture. S3: After the obtained mixture is molded and pressed, it is pressure sintered in a gas pressure sintering furnace at a temperature of 1400℃. During the sintering process, inert argon gas is introduced at a pressure of 100 bar and the sintering time is 0.5 h. After sintering, nano-hard alloy material is obtained.

[0055] The physical properties of the nano-hard alloy materials obtained in Examples 1-4 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0056] Table 1

[0057] The results showed that the Vickers hardness and bending strength of the nano-hard alloy material obtained by using cobalt powder with a single composition in Comparative Example 1 were significantly lower than those of the nano-hard alloy materials obtained in Examples 1-4.

[0058] The average grain size of tungsten carbide in the nano-hard alloy material obtained in Example 1 was 0.33 μm, which increased by 0.03 μm compared to the 0.3 μm grain size of the tungsten carbide raw material, indicating that the tungsten carbide grains did not grow significantly during processing. Figure 1 As shown, the microstructure of the alloy material is normal, and there are no obvious pore defects.

[0059] The average grain size of tungsten carbide in the nano-hard alloy material obtained in Example 2 was 0.12 μm, which was 0.02 μm larger than that of the tungsten carbide raw material (0.1 μm). This indicates that the tungsten carbide grains did not grow significantly during the processing. The microstructure of the alloy material was normal and there were no obvious pore defects.

[0060] The average grain size of tungsten carbide in the nano-hard alloy material obtained in Example 3 was 0.31 μm, which was 0.01 μm larger than the 0.3 μm grain size of the tungsten carbide raw material. This indicates that the tungsten carbide grains did not grow significantly during processing; the microstructure of the alloy material was normal, and there were no obvious porosity defects.

[0061] Compared with Example 1, in Example 3, because the cobalt content was increased from 7% to 13%, more cobalt material participated in the closure process. Therefore, the change in tungsten carbide grain size in the nano-hard alloy obtained in Example 3 was less than that in Example 1.

[0062] The average grain size of tungsten carbide in the nano-hard alloy material obtained in Example 4 was 0.23 μm, which was 0.03 μm larger than that of the tungsten carbide raw material (0.2 μm). This indicates that the tungsten carbide grains did not grow significantly during the processing. The microstructure of the alloy material was normal and there were no obvious pore defects.

[0063] The average grain size of tungsten carbide in the nano-hard alloy material obtained in Comparative Example 1 was 0.48 μm, which was 0.18 μm larger than the 0.3 μm grain size of the tungsten carbide raw material, indicating that the tungsten carbide grains grew significantly during the processing.

[0064] like Figure 2 As shown, the nano-hard alloy material obtained in Comparative Example 1 exhibits blocky pore defects within the observation area. This indicates that the pores were not fully closed during the sintering process, resulting in defects. This ultimately affects the mechanical properties of the material, causing its Vickers hardness and flexural strength to be lower than those of the nano-hard alloy material obtained in Example 1.

[0065] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 60-90, in this specification it means specifically listing values ​​such as 61-89, 62-88, ..., 61-71, and 80-81. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0066] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A nano-hard alloy material, characterized in that, The nano-hard alloy material has a Vickers hardness of 1000~3000HV10 and a bending strength of 3000MPa~6000MPa, and the tungsten carbide grain size is 0.1μm~0.5μm.

2. The nano-hard alloy material according to claim 1, characterized in that, The raw materials include a binder phase, which comprises spherical cobalt powder with a Fisher particle size of 0.2~2.0μm and flake-shaped cobalt powder with a Fisher particle size of 1.8~4.0μm.

3. The nano-hard alloy material according to claim 2, characterized in that, The raw materials also include tungsten carbide and inhibitors, and the mass percentage of the binder phase in the raw materials is 7.0%~13.0%. And / or, the tungsten carbide content in the raw material is 86.5%~93.0% by mass; And / or, the mass percentage of the inhibitor in the raw material is 0~0.5%.

4. The nano-hard alloy material according to claim 3, characterized in that, The spherical cobalt powder in the binder phase has a Fisher particle size of 0.4~1.2μm; And / or, the Fisher particle size of the flaky cobalt powder in the binder phase is 2.0~3.0 μm; And / or, the mass ratio of spherical cobalt powder to flake cobalt powder in the binder phase is (1.5~3):1; And / or, the tungsten carbide has a Fisher particle size of 0.1~0.3 μm; And / or, the inhibitor has a Fisher particle size of 1.1~1.5 μm; And / or, the inhibitor includes at least one of chromium carbide, vanadium carbide, and tantalum carbide; And / or, the inhibitor comprises chromium carbide at a mass percentage of 2% to 95%.

5. The nano-hard alloy material according to any one of claims 2 to 4, characterized in that, The carbon balance coefficient of the raw materials is controlled at +0.05% to +0.10%.

6. A method for preparing the nano-hard alloy material as described in any one of claims 1 to 5, characterized in that, The process includes ball milling, pressing, and pressure sintering of raw materials to obtain the nano-hard alloy material.

7. The preparation method according to claim 6, characterized in that, Grinding aids and forming agents are added during the ball milling process; The grinding aid is selected from at least one of ethanol and isopropanol; And / or, the grinding aid is added at a ratio of 100~450ml / kg to the liquid-to-solid ratio of the material; And / or, the molding agent is selected from at least one of polyethylene glycol and paraffin wax; And / or, the amount of the molding agent added is 1.5% to 3.5% of the total mass of the raw materials.

8. The preparation method according to claim 6, characterized in that, During the ball milling process: The ball milling time is 20~50 hours; And / or, the ball-to-material ratio is (5~10):1; And / or, the rotation speed is 30~40 revolutions per minute.

9. The preparation method according to claim 6, characterized in that, The compression molding is selected from one of compression molding, extrusion molding, and isostatic pressing.

10. The preparation method according to claim 6, characterized in that, The pressure sintering process is carried out in an inert gas atmosphere; The inert gas atmosphere is selected from one of nitrogen atmosphere, argon atmosphere, and helium atmosphere; And / or, the gas pressure during the pressure sintering process is 30~100 bar; And / or, the sintering temperature during the pressure sintering process is 1000~1500℃; And / or, the sintering time during the pressure sintering process is 0.5~4.0h.

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