A method for preparing high-strength high-toughness ultrafine grain cemented carbide containing carbonitride

Abstract

The application relates to a preparation method of high-strength high-toughness superfine-grain hard alloy containing carbonitride, and belongs to the technical field of hard alloy and powder metallurgy. Chromium oxide and carbon black or chromium oxide, vanadium pentoxide and carbon black are used as raw materials, are mixed by ball milling, and are subjected to heat treatment in a vacuum furnace to prepare carbonitride by using a nitriding reduction reaction. The prepared carbonitride powder is put into a ball milling tank with argon protection to be finely ground by ball milling, and carbonitride powder with an average particle size of 1-5 microns is obtained. Finally, the prepared carbonitride or the carbonitride after being finely ground is added into WC-Co composite powder in a proportion of 0.1wt.%-0.5wt.% according to the mass percentage content, and the superfine-grain WC-Co hard alloy with high strength and high toughness is prepared by using a low-pressure sintering method.

Description

Technical Field

[0001] This invention relates to a method for preparing a high-strength, high-toughness, ultrafine-grained cemented carbide containing carbonitrides, belonging to the fields of cemented carbide and powder metallurgy technology. Background Technology

[0002] WC-Co cemented carbide possesses a range of advantages, including high hardness, wear resistance, and good transverse fracture strength. Particularly noteworthy is its ability to maintain good hardness and strength even at high temperatures, leading to its widespread industrial application. WC-Co cemented carbide also exhibits good heat resistance and thermal conductivity, making it suitable for machining materials that are difficult to machine, such as heat-resistant alloys, titanium alloys, and superhard cast iron. Among these, ultrafine-grained WC-Co cemented carbide has become the mainstream matrix material for high-performance cutting tools. While ultrafine-grained cemented carbide exhibits significantly higher hardness than traditional tool materials, its lower toughness severely limits its application range.

[0003] To refine grain size and obtain ultrafine-grained cemented carbide, appropriate grain growth inhibitors are typically added during the preparation process to control WC grain growth during sintering and to make the WC grain size distribution more uniform, thereby improving the alloy's properties. Commonly used grain growth inhibitors include refractory metal carbides such as VC, Cr3C2, NbC, TaC, TiC, and ZrC. Among them, VC and Cr3C2 have the most significant effect on inhibiting grain growth and are also two commonly used grain growth inhibitors by enterprises and research institutions. However, adding refractory metal carbides as grain growth inhibitors often leads to a decrease in toughness, thus affecting the service life of cemented carbide tools. To address this problem, it is necessary to develop novel grain growth inhibitors that can improve hardness and strength without reducing fracture toughness, achieving a synergistic improvement in the fracture strength and toughness of WC-Co cemented carbide. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing methods of adding refractory metal carbide grain growth inhibitors cannot simultaneously improve the fracture strength and toughness of ultrafine-grained cemented carbides, and to provide a method for preparing high-strength, high-toughness, ultrafine-grained WC-Co cemented carbides containing carbonitrides. This invention first uses tungsten oxide, cobalt oxide, and carbon black as raw materials to synthesize WC-Co composite powder via in-situ reaction; then, using chromium oxide and carbon black, or chromium oxide, vanadium pentoxide, and carbon black as raw materials, the mixture is ball-milled and then heat-treated in a vacuum furnace to prepare carbonitrides via a nitriding reduction reaction; finally, the prepared carbonitrides are added to the WC-Co composite powder in a certain proportion, and an ultrafine-grained cemented carbide with both high strength and high toughness is prepared by low-pressure sintering.

[0005] The method for preparing carbonitride-containing ultrafine-grained cemented carbide provided by the present invention includes the following steps:

[0006] (1)With WO 2.9 Using Co3O4 and carbon black as raw materials, and according to the requirement that the mass ratio of Co in cemented carbide is 8-12%, the dosage ratio of the above three raw materials was calculated. WC-Co composite powder was prepared by in-situ reaction synthesis method. The in-situ reaction synthesis method for preparing WC-Co composite powder preferentially adopts the existing authorized patent technology (patent number CN200610165554.2, publication date 2007-06-27, publication number CN1986124).

[0007] (2) Using Cr2O3 and carbon black as raw materials, carbon black is added in the range of 16.48% to 24.00% by mass. The two raw materials (Cr2O3 and carbon black) are ball-milled and mixed. Anhydrous ethanol or hexane is used as the grinding medium. The mass ratio of grinding balls to powder (Cr2O3 and carbon black) is 1:1 to 3:1. The liquid-solid ratio of grinding medium to solid raw materials (Cr2O3 and carbon black) is 600 to 700 ml / kg. The ball mill speed is 500 to 600 r / min. The ball milling time is 20 to 30 hours. The mixed powder is placed in a vacuum furnace and reacted in the vacuum furnace using the following process parameters: heating rate 4 to 10℃ / min, reaction temperature 1200 to 1300℃, holding time 1 to 3 hours, and nitrogen gas is introduced throughout the process to make the pressure of the nitrogen atmosphere reach 0.02 to 0.04 MPa.

[0008] (3) Using Cr2O3, V2O5, and carbon black as raw materials, with a mass ratio of Cr2O3 to V2O5 of 10:1 to 12:1, and adding carbon black within a mass percentage range of 16.48% to 28.35%, the three raw materials (Cr2O3, V2O5, and carbon black) are ball-milled and mixed using anhydrous ethanol or hexane as the grinding medium. The mass ratio of grinding balls to powder (Cr2O3, V2O5, and carbon black) is 1:1 to 3:1. The mass ratio of grinding medium to solid raw material (Cr2O3, V2O5, and carbon black) is 1:1 to 3:1.

[0009] The liquid-to-solid ratio of V2O5 and carbon black was 600–700 ml / kg, the ball mill speed was 500–600 r / min, and the ball milling time was 20–30 hours. The mixed powder was then placed in a vacuum furnace, and the reaction was carried out in the vacuum furnace using the following process parameters: heating rate 4–10 °C / min, reaction temperature 1200–1300 °C.

[0010] The heat preservation time is 1 to 3 hours, and nitrogen gas is introduced throughout the process to make the pressure of the nitrogen atmosphere reach 0.02 to 0.04 MPa. (4) Refine the carbonitrides obtained in steps (2) and (3): First, dry mill in a ball mill, with Ar protective gas filling the ball mill jar. The mass ratio of grinding balls to powder (carbonitrides) is 10:1 to 30:1. The ball mill speed is 500 to 600 r / min, and the milling time is 10 to 50 hours. The powder is sieved once every 10 hours of milling. Then, wet mill with anhydrous ethanol or hexane as the grinding medium. The mass ratio of grinding balls to powder (carbonitrides) is 10:1 to 30:1. The liquid-solid ratio of the grinding medium to the solid raw material (carbonitrides) is 400 to 500 ml / kg. The ball mill speed is 500 to 600 r / min, and the milling time is 10 to 20 hours. After drying, carbonitride powder with an average particle size of 1 to 5 μm is obtained.

[0011] (5) Add the carbonitride powder prepared in step (2) or step (3) or refined in step (4) to the WC-Co composite powder prepared in step (1) at a mass percentage content of 0.1wt.% to 0.5wt.% (i.e., the mass percentage of carbonitride powder to WC-Co composite powder), and add the molding agent polyethylene glycol at a rate of 1 to 2 g of polyethylene glycol per 100 g of powder. Then, ball mill the mixture using anhydrous ethanol or hexane as the grinding medium. The mass ratio of grinding balls to powder (carbonitride, WC-Co composite powder, polyethylene glycol) is 1:1 to 3:1. The liquid-solid ratio of grinding medium to solid raw material (carbonitride, WC-Co composite powder, polyethylene glycol) is 400 to 500 ml / kg. The ball mill speed is 500 to 600 r / min, and the ball milling time is 20 to 30 hours. After drying, a mixed powder with added carbonitride is obtained. The mixed powder with added carbonitride is then pressed into shape. Low-pressure sintering is then carried out at a pressure of 5–8 MPa and a temperature of 1370–1470°C, with a holding time of 0.5–1.5 hours. After the holding time is completed, the furnace is cooled to room temperature.

[0012] This invention prepares carbonitrides from metal oxides and carbon black through a nitriding reaction, adds these carbonitrides to WC-Co composite powder obtained from metal oxides and carbon black through an in-situ reaction, and then prepares an ultrafine-grained WC-Co cemented carbide containing carbonitrides through low-pressure sintering. Compared with existing methods, this invention has the following advantages:

[0013] (1) Carbonitrides are prepared by nitriding reduction reaction using chromium oxide and carbon black as raw materials or chromium oxide, vanadium pentoxide and carbon black as raw materials. By designing ball milling process parameters, carbonitride powders with different particle sizes can be obtained, which can be used to regulate the microstructure and properties of ultrafine-grained cemented carbide.

[0014] (2) In this invention, carbonitrides of different particle sizes are uniformly mixed with WC-Co composite powder synthesized in situ using an existing authorized patent technology (patent number CN20061016554.2, publication date 2007-06-27, publication number CN1986124). By comprehensively designing the mass ratio of grinding balls to powder, mixing time and subsequent sintering process, an ultrafine-grained WC-Co cemented carbide containing carbonitrides is finally prepared. The WC phase, Co phase and carbonitrides are uniformly distributed in space, the WC grain size is small, and the ultrafine-grained cemented carbide has excellent comprehensive mechanical properties of hardness, strength and toughness. Attached Figure Description

[0015] Figure 1 The carbonitride powders prepared in the embodiments of the present invention are: (a) Cr2(C,N) powder in the prepared state; (b) Cr2(C,N) powder after dry milling for 50 h and then wet milling for 20 h; (c) powder with (Cr,V)2(C,N) as the main phase in the prepared state; and (d) powder with (Cr,V)2(C,N) as the main phase after dry milling for 50 h and then wet milling for 20 h.

[0016] Figure 2 The ultrafine-grained cemented carbide prepared in Example 1 of this invention: (a) microstructure morphology; (b) grain size distribution diagram.

[0017] Figure 3 The ultrafine-grained cemented carbide prepared in Example 2 of this invention: (a) microstructure morphology; (b) grain size distribution diagram.

[0018] Figure 4 The ultrafine-grained cemented carbide prepared in Example 3 of this invention: (a) microstructure morphology; (b) grain size distribution diagram.

[0019] Figure 5 The ultrafine-grained cemented carbide prepared in Example 4 of this invention: (a) microstructure morphology; (b) grain size distribution diagram. Detailed Implementation

[0020] Example 1: Using WO 2.9 Using Co3O4 and carbon black as raw materials, WC-12Co with a Co mass percentage of 12% is prepared. 2.9 The three powders (WO3O4:carbon black) were ball-milled in a mass ratio of 600:94.75:139.98 using anhydrous ethanol as the grinding medium. 2.9 The mass ratio of ethanol (Co3O4 and carbon black) is 3:1, and the mixture of anhydrous ethanol and solid raw material (WO3O4) is 1. 2.9The liquid-to-solid ratio of Cr2O3 and carbon black was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The dried powder underwent in-situ reduction carbonization in a vacuum furnace to obtain WC-12Co composite powder. The reaction temperature was 1050℃, and the holding time was 3 hours. Using Cr2O3 and carbon black as raw materials, they were ball-milled and mixed at a mass ratio of 50:9.87. Anhydrous ethanol was used as the grinding medium, the mass ratio of grinding balls to powder (Cr2O3 and carbon black) was 3:1, the liquid-to-solid ratio of anhydrous ethanol to solid raw materials (Cr2O3 and carbon black) was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The mixed powders (Cr2O3 and carbon black) were placed in a vacuum furnace and reacted using the following process parameters: heating rate of 10℃ / min, reaction temperature of 1200℃, holding time of 1 hour, and nitrogen gas was introduced throughout the process to achieve a nitrogen atmosphere pressure of 0.04MPa. The reaction yielded Cr2(C,N) powder. The obtained Cr2(C,N) powder was added to the WC-12Co composite powder synthesized in situ at an addition amount of 0.50 wt.% (i.e., the mass percentage of Cr2(C,N) powder to WC-12Co composite powder). Polyethylene glycol (PEG) was added as a molding agent at a rate of 1.5 g PEG per 100 g of powder (Cr2(C,N) powder and WC-12Co composite powder). The mixture was then ball-milled using anhydrous ethanol as the grinding medium. The mass ratio of grinding balls to powder (Cr2(C,N), WC-12Co composite powder, and PEG) was 3:1. The liquid-to-solid ratio of anhydrous ethanol to solid raw materials (Cr2(C,N), WC-12Co composite powder, and PEG) was 450 ml / kg. The ball mill speed was 560 r / min, and the ball milling time was 20 hours. After drying, WC-Co-0.5 wt.% Cr2(C,N) mixed powder was obtained. WC-Co-0.5wt.%Cr2(C,N) mixed powder was pressed into shape and then subjected to low-pressure sintering at a pressure of 5MPa and a temperature of 1410℃ for 1.3 hours. After holding, it was cooled to room temperature in the furnace. The microstructure of the final WC-12wt.%Co-0.5wt.%Cr2(C,N) cemented carbide is shown in the figure. Figure 2 Its mechanical properties are shown in Table 1.

[0021] Example 2: Using WO 2.9 Using Co3O4 and carbon black as raw materials, WC-12Co is prepared according to a composition ratio of 12% Co by mass, i.e., WO 2.9 The three powders (WO3O4:carbon black) were ball-milled in a mass ratio of 600:94.75:139.98 using anhydrous ethanol as the grinding medium. 2.9The mass ratio of ethanol (Co3O4 and carbon black) is 3:1, and the mixture of anhydrous ethanol and solid raw material (WO3O4) is 1. 2.9The liquid-to-solid ratio of Cr2O3 and carbon black was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The dried powder underwent in-situ reduction carbonization in a vacuum furnace to obtain WC-12Co composite powder. The reaction temperature was 1050℃, and the holding time was 3 hours. Using Cr2O3 and carbon black as raw materials, they were ball-milled and mixed at a mass ratio of 50:9.87. Anhydrous ethanol was used as the grinding medium, the mass ratio of grinding balls to powder (Cr2O3 and carbon black) was 3:1, the liquid-to-solid ratio of anhydrous ethanol to solid raw materials (Cr2O3 and carbon black) was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The mixed powders (Cr2O3 and carbon black) were placed in a vacuum furnace and reacted using the following process parameters: heating rate of 10℃ / min, reaction temperature of 1200℃, holding time of 1 hour, and nitrogen gas was introduced throughout the process to achieve a nitrogen atmosphere pressure of 0.04MPa. The reaction yielded Cr2(C,N) powder. The obtained Cr2(C,N) powder was first dry-milled in a ball mill with Ar protective gas filling the mill jar. The mass ratio of grinding balls to powder (Cr2(C,N)) was 30:1, the ball mill speed was 560 r / min, and the milling time was 50 hours. The powder was sieved once every 10 hours of milling using a 60-mesh sieve. Then, anhydrous ethanol was used as the grinding medium for wet milling. The mass ratio of grinding balls to powder (Cr2(C,N)) was 30:1, the liquid-solid ratio of anhydrous ethanol to solid raw material (Cr2(C,N)) was 450 ml / kg, the ball mill speed was 560 r / min, and the wet milling time was 20 hours. After drying, Cr2(C,N) powder with an average particle size of 1.7 μm was obtained. The obtained Cr2(C,N) powder with an average particle size of 1.7 μm was added to the WC-12Co composite powder synthesized in situ at an addition amount of 0.50 wt.% (i.e., the 1.7 μm Cr2(C,N) powder is the mass percentage of WC-12Co composite powder). Polyethylene glycol (PEG) was added as a molding agent at a rate of 1.5 g PEG per 100 g of powder (Cr2(C,N) powder and WC-12Co composite powder). The mixture was then ball-milled using anhydrous ethanol as the grinding medium. The mass ratio of grinding balls to powder (1.7 μm Cr2(C,N), WC-12Co composite powder, and PEG) was 3:1. The ratio of anhydrous ethanol to solid raw material (1.7 μm... The liquid-to-solid ratio of Cr2(C,N), WC-12Co composite powder, and polyethylene glycol was 450 ml / kg. The ball mill speed was 560 r / min, the ball milling time was 20 hours, and after drying, WC-Co-0.5 wt.%Cr2(C,N) mixed powder was obtained.WC-Co-0.5wt.%Cr2(C,N) mixed powder was pressed into shape and then subjected to low-pressure sintering at a pressure of 5MPa, a sintering temperature of 1410℃, and a holding time of 1.3 hours. After the holding time, the powder was cooled to room temperature in the furnace. The microstructure of the final WC-12wt.%Co-0.5wt.%Cr2(C,N) cemented carbide is shown in the figure. Figure 3 Its mechanical properties are shown in Table 1.

[0022] Example 3: Using WO 2.9 Using Co3O4 and carbon black as raw materials, WC-12Co is prepared according to a composition ratio of 12% Co by mass, i.e., WO 2.9 The three powders (WO3O4:carbon black) were ball-milled in a mass ratio of 600:94.75:139.98 using anhydrous ethanol as the grinding medium. 2.9 The mass ratio of ethanol (Co3O4 and carbon black) is 3:1, and the mixture of anhydrous ethanol and solid raw material (WO3O4) is 1. 2.9The liquid-to-solid ratio of Cr2O3, V2O5, and carbon black was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The dried powder underwent in-situ reduction carbonization in a vacuum furnace to obtain WC-12Co composite powder. The reaction temperature was 1050℃, and the holding time was 3 hours. Using Cr2O3, V2O5, and carbon black as raw materials, they were ball-milled and mixed at a mass ratio of 77:7:21. Anhydrous ethanol was used as the grinding medium, the mass ratio of grinding balls to powder (Cr2O3, V2O5, and carbon black) was 3:1, the liquid-to-solid ratio of anhydrous ethanol to solid raw materials (Cr2O3, V2O5, and carbon black) was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The mixed powders (Cr2O3, V2O5, and carbon black) were placed in a vacuum furnace and reacted using the following parameters: heating rate of 10℃ / min, reaction temperature of 1200℃, holding time of 1 hour, and nitrogen gas was introduced throughout the process to achieve a nitrogen atmosphere pressure of 0.04 MPa, resulting in (Cr,V)2(C,N) powder. The obtained (Cr,V)2(C,N) powder was added to the in-situ synthesized WC-12Co composite powder at a rate of 0.25 wt.% (i.e., the (Cr,V)2(C,N) powder is the mass percentage of the WC-12Co composite powder), along with a molding agent, polyethylene glycol, at a rate of 1.5 g of polyethylene glycol per 100 g of powder ((Cr,V)2(C,N) powder and WC-12Co composite powder). The mixture was then ball-milled using anhydrous ethanol as the grinding medium. The grinding media, with a mass ratio of grinding balls to powder ((Cr,V)₂(C,N), WC-12Co composite powder, and polyethylene glycol) of 3:1, and a liquid-to-solid ratio of anhydrous ethanol to solid raw materials ((Cr,V)₂(C,N), WC-12Co composite powder, and polyethylene glycol) of 450 ml / kg, were used. The ball mill speed was 560 r / min, and the ball milling time was 20 hours. After drying, a WC-Co-0.25wt.%(Cr,V)₂(C,N) mixed powder was obtained. The WC-Co-0.25wt.%(Cr,V)₂(C,N) mixed powder was pressed into shape and then subjected to low-pressure sintering at a pressure of 5 MPa, a sintering temperature of 1410℃, and a holding time of 1.3 hours. After the holding time, the powder was cooled to room temperature in the furnace. The microstructure of the final obtained WC-12wt.%Co-0.25wt.%(Cr,V)2(C,N) cemented carbide is shown in the figure. Figure 4 Its mechanical properties are shown in Table 1.

[0023] Example 4: Using WO 2.9 Using Co3O4 and carbon black as raw materials, WC-12Co is prepared according to a composition ratio of 12% Co by mass, i.e., WO 2.9The Co3O4 and carbon black powders were mixed by ball milling at a mass ratio of 600:94.75:139.98, using anhydrous ethanol as the grinding medium. The grinding balls were mixed with the three powders (WO3O4, CO2, and carbon black). 2.9 The mass ratio of ethanol (Co3O4 and carbon black) is 3:1, and the mixture of anhydrous ethanol and solid raw material (WO3O4) is 1. 2.9The liquid-to-solid ratio of Cr2O3, V2O5, carbon black, and grinding balls was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The dried powder underwent in-situ reduction carbonization in a vacuum furnace to obtain WC-12Co composite powder. The reaction temperature was 1050℃, and the holding time was 3 hours. Using Cr2O3, V2O5, and carbon black as raw materials, they were ball-milled and mixed at a mass ratio of 77:7:21. Anhydrous ethanol was used as the grinding medium, the mass ratio of grinding balls to powder (Cr2O3, V2O5, and carbon black) was 3:1, the liquid-to-solid ratio of anhydrous ethanol to solid raw materials (Cr2O3, V2O5, and carbon black) was 650 ml / kg, the ball mill speed was 560 r / min, and the ball milling time was 20 hours. The mixed powder (Cr2O3, V2O5 and carbon black) was placed in a vacuum furnace and reacted in the vacuum furnace using the following process parameters: heating rate of 10℃ / min, reaction temperature of 1200℃, holding time of 1 hour, and nitrogen gas was introduced throughout the process to make the nitrogen atmosphere pressure reach 0.04MPa, so as to obtain (Cr,V)2(C,N) powder. The obtained (Cr,V)₂(C,N) powder was first dry-milled in a ball mill with Ar protective gas filling the mill jar. The mass ratio of grinding balls to powder ((Cr,V)₂(C,N)) was 30:1, the ball mill speed was 560 r / min, and the milling time was 50 hours. The powder was sieved using a 60-mesh sieve every 10 hours of milling. Then, wet milling was performed using anhydrous ethanol as the grinding medium. The mass ratio of grinding balls to powder ((Cr,V)₂(C,N)) was 30:1, the liquid-to-solid ratio of anhydrous ethanol to solid raw material ((Cr,V)₂(C,N)) was 450 ml / kg, the ball mill speed was 560 r / min, and the milling time was 20 hours. After drying, (Cr,V)₂(C,N) powder with an average particle size of 1.4 μm was obtained. The obtained (Cr,V)₂(C,N) powder with an average particle size of 1.4 μm was added to the WC-12Co composite powder synthesized in situ at an addition amount of 0.25 wt.% (i.e., the 1.4 μm (Cr,V)₂(C,N) powder is the mass percentage of WC-12Co composite powder). Polyethylene glycol, a molding agent, was added at a rate of 1.5 g of polyethylene glycol per 100 g of powder ((Cr,V)₂(C,N) powder and WC-12Co composite powder). The mixture was then ball-milled and mixed with anhydrous ethylene glycol. Alcohol was used as the grinding medium. The mass ratio of grinding balls to powder (1.4μm(Cr,V)2(C,N), WC-12Co composite powder, and polyethylene glycol) was 3:1. The liquid-solid ratio of anhydrous ethanol to solid raw materials (1.4μm(Cr,V)2(C,N), WC-12Co composite powder, and polyethylene glycol) was 450 ml / kg. The ball mill speed was 560 r / min, and the ball milling time was 20 hours. After drying, WC-Co-0.25wt.%(Cr,V)2(C,N) mixed powder was obtained.WC-Co-0.25wt.%(Cr,V)2(C,N) mixed powder was pressed into shape and then subjected to low-pressure sintering at a pressure of 5MPa, a temperature of 1410℃, and a holding time of 1.3 hours. After holding, the powder was cooled to room temperature in the furnace. The microstructure of the final WC-12wt.%Co-0.25wt.%(Cr,V)2(C,N) cemented carbide is shown in the figure. Figure 5 Its mechanical properties are shown in Table 1.

[0024] Table 1. Properties of the ultrafine-grained cemented carbides prepared in different embodiments.

[0025]

Claims

1. A method for preparing a high-strength, high-toughness, ultrafine-grained cemented carbide containing carbonitrides, characterized in that... The steps are as follows: (1) With WO 2.9 Using Co3O4 and carbon black as raw materials, and according to the requirement of 8~12wt% Co mass ratio in cemented carbide, the dosage ratio of the above three raw materials was calculated, and WC-Co composite powder was prepared by in-situ reaction synthesis method. (2) Using Cr2O3 and carbon black as raw materials, carbon black is added in the range of 16.48%~24.00% by mass. The two raw materials, namely Cr2O3 and carbon black, are ball-milled and mixed. Anhydrous ethanol or hexane is used as the grinding medium. The mass ratio of grinding balls to Cr2O3 and carbon black is 1:1~3:

1. The liquid-solid ratio of grinding medium to solid raw materials, namely Cr2O3 and carbon black, is 600~700mL / kg. The ball mill speed is 500~600r / min. The ball milling time is 20~30 hours. The mixed powder is placed in a vacuum furnace and the reaction is carried out in the vacuum furnace using the following process parameters: heating rate 4~10℃ / min, reaction temperature 1200~1300℃, holding time 1~3 hours, and nitrogen gas is introduced throughout the process to make the pressure of the nitrogen atmosphere reach 0.02MPa~0.04MPa. (3) Using Cr2O3, V2O5, and carbon black as raw materials, with a mass ratio of Cr2O3 to V2O5 of 10:1 to 12:1, and adding carbon black within a mass percentage range of 16.48% to 28.35%, the three raw materials, namely Cr2O3, V2O5, and carbon black, are ball-milled and mixed. Anhydrous ethanol or hexane is used as the grinding medium, and the mass ratio of grinding balls to Cr2O3, V2O5, and carbon black powder is 1:1 to 3:

1. The grinding medium and the solid raw materials, namely Cr2O3, V2O5, and carbon black powder, are mixed by ball milling. The liquid-to-solid ratio of O2O5 and carbon black is 600-700 mL / kg, the ball mill speed is 500-600 r / min, and the ball milling time is 20-30 hours. The mixed powder is placed in a vacuum furnace and reacted in the vacuum furnace using the following process parameters: heating rate 4-10℃ / min, reaction temperature 1200-1300℃, holding time 1-3 hours, and nitrogen gas is introduced throughout the process to make the nitrogen atmosphere pressure reach 0.02MPa-0.04MPa. (4) Refine the carbonitrides obtained in steps (2) and (3): First, dry mill in a ball mill, with a mass ratio of grinding balls to carbonitrides of 10:1 to 30:1; then wet mill with anhydrous ethanol or hexane as the grinding medium, with a mass ratio of grinding balls to carbonitrides of 10:1 to 30:1 and a liquid-solid ratio of grinding medium to carbonitrides of 400 to 500 mL / kg; after drying, carbonitride powder with an average particle size of 1 to 5 μm is obtained. (5) Add the carbonitride powder prepared in step (2) or step (3) or refined in step (4) to the WC-Co composite powder prepared in step (1) at a mass percentage content of 0.1wt.%~0.5wt.%, that is, the mass percentage of carbonitride powder and WC-Co composite powder is 0.1wt.%~0.5wt.%, and add polyethylene glycol as a molding agent at a mass percentage of 1~2g of polyethylene glycol per 100g of powder. Then, ball mill the mixture using anhydrous ethanol or hexane as the grinding medium. The grinding balls and powder, i.e., carbonitride, WC-Co composite powder and... The mass ratio of polyethylene glycol is 1:1 to 3:

1. The liquid-to-solid ratio of the grinding media to the solid raw materials, namely carbonitride, WC-Co composite powder and polyethylene glycol, is 400 to 500 mL / kg. The ball mill speed is 500 to 600 r / min, and the ball milling time is 20 to 30 hours. After drying, a mixed powder with added carbonitride is obtained. The mixed powder with added carbonitride is pressed into shape. Then, low-pressure sintering is carried out. The sintering pressure is 5 to 8 MPa, the sintering temperature is 1370℃ to 1470℃, and the holding time is 0.5 to 1.5 hours. After the holding time is completed, the powder is cooled to room temperature in the furnace.

2. The preparation method according to claim 1, characterized in that: The specific process for refining carbonitrides in step (4) is as follows: First, dry grinding is carried out in a ball mill. Ar protective gas is introduced into the ball mill jar. The mass ratio of grinding balls to carbonitrides is 10:1 to 30:

1. The ball mill speed is 500 to 600 r / min. The ball milling time is 10 to 50 hours. The powder is sieved once every 10 hours of ball milling. Then, wet grinding is carried out using anhydrous ethanol or hexane as the grinding medium. The mass ratio of grinding balls to carbonitride powder is 10:1 to 30:

1. The liquid-solid ratio of grinding medium to solid raw material carbonitride is 400 to 500 mL / kg. The ball mill speed is 500 to 600 r / min. The ball milling time is 10 to 20 hours. After drying, carbonitride powder with an average particle size of 1 to 5 μm is obtained.

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