A WC-Ni3Al cemented carbide with coating phase reinforcement and preparation method thereof

Abstract

The present invention belongs to the technical field of cemented carbide preparation and discloses a WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening and a preparation method thereof. By mass fraction, the hard phase is 84.7% to 94.98% WC, the bonding phase is 5% to 15% Ni3Al, and the reinforcing phase is 0.01% to 0.15% multilayer graphene-coated hexagonal boron nitride and 0.01% to 0.2% boron. After the multilayer graphene powder and hexagonal boron nitride are combined, the multilayer graphene-coated hexagonal boron nitride formed can produce nanoscale pores in the cemented carbide. These nanoscale pores can absorb the energy required for fracture toughness, significantly improving the fracture toughness of the WC-Ni3Al cemented carbide.

Description

Technical Field

[0001] The invention belongs to the technical field of cemented carbide preparation, and particularly relates to a WC-Ni3Al cemented carbide strengthened and toughened by adding a coating phase and a preparation method thereof. Background Art

[0002] WC cemented carbide is widely used in cutting tools, mining equipment, metallurgy, and wear-resistant parts of engineering machinery due to its high hardness, high wear resistance, and high toughness. As the application range of WC-based cemented carbide tools increases, cutting processes have also put forward more and higher performance requirements for them. Many researchers have developed a series of new cemented carbide tools with high toughness and high wear resistance by adjusting WC grain size, optimizing binder phase composition, surface coating, and functional gradient design. The intermetallic compound Ni3Al has excellent properties such as high temperature resistance, corrosion resistance, and low density. It has great potential as a high-temperature structural material and is considered to be an excellent material for use as a new binder for cemented carbide. However, cemented carbide with Ni3Al as the binder phase still has the disadvantages of insufficient fracture toughness and easy failure of the material. Therefore, it is necessary to strengthen the WC-Ni3Al cemented carbide.

[0003] Chinese patent application document CN105907997A discloses an in-situ Al2O3 toughened WC-Ni3Al composite material and its preparation method. This method strengthens and toughens WC-Ni3Al cemented carbide by directly adding a reinforcing phase, but the improvement in the fracture toughness performance of the cemented carbide is limited. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a WC-Ni3Al cemented carbide with a coating phase added to strengthen and toughen it and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A WC-Ni3Al cemented carbide strengthened and toughened by adding a coating phase, wherein, by mass fraction, the hard phase is 84.7%-94.98% WC, the bonding phase is 5%-15% Ni3Al, and the reinforcing phase is 0.01%-0.15% multilayer graphene-coated hexagonal boron nitride and 0.01%-0.2% B.

[0007] The above-mentioned WC-Ni3Al cemented carbide with added coating phase strengthening and toughening, further, the number of layers of the multilayer graphene is 3 to 10 layers; the multilayer graphene-coated hexagonal boron nitride is obtained by wet ball milling multilayer graphene powder and hexagonal boron nitride powder in a mass ratio of 3 to 7:1.

[0008] Multilayer graphene (MLG) and hexagonal boron nitride (h-BN) exhibit friction-reducing and wear-resistant properties at different temperature levels due to their unique physicochemical properties. However, MLG exhibits excellent interfacial compatibility with a tungsten carbide (WC) matrix, while h-BN exhibits poor interfacial bonding with WC. The present invention utilizes a multilayer graphene-coated hexagonal boron nitride (h-BN@MLG) core-shell structure material, prepared through a coating process, to induce the formation of uniformly distributed nanoscale pores in WC cemented carbide. This unique microstructural design significantly improves the alloy's fracture toughness while maintaining the material's hardness.

[0009] Based on a general inventive concept, the present invention also provides a method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0010] (1) The multilayer graphene powder and hexagonal boron nitride powder after ultrasonic dispersion are wet ball milled, dried, and crushed to obtain multilayer graphene-coated hexagonal boron nitride powder, i.e., h-BN@MLG powder;

[0011] (2) wet-ball milling the h-BN@MLG powder, WC powder, Ni3Al powder, B powder and paraffin wax debris obtained in step (1) in a vacuum environment, drying, crushing and sieving to obtain WC-Ni3Al-Bh-BN@MLG powder;

[0012] (3) pressing the WC-Ni3Al-Bh-BN@MLG powder obtained in step (2) to obtain a molded sample;

[0013] (4) placing the molded sample obtained in step (3) into a vacuum sintering furnace, heating and keeping the temperature under vacuum for a period of time, stopping heating and keeping the vacuum in the furnace until cooling to obtain a pre-sintered sample;

[0014] (5) The pre-sintered sample obtained in step (4) is placed in a microwave sintering furnace, subjected to microwave heating and heat preservation under a nitrogen environment, and then cooled to obtain the product.

[0015] The above preparation method further comprises the following steps: in step (1), the mass ratio of the multilayer graphene to the hexagonal boron nitride is 3 to 7:1; the number of layers of the multilayer graphene is 3 to 10, the diameter of the flakes is 5 μm to 50 μm, and the thickness is 3 nm to 10 nm; and the hexagonal boron nitride is a granular powder with a single flake diameter of 100 nm to 500 nm.

[0016] Furthermore, the conditions for wet ball milling in step (1) are as follows: the ball milling is carried out in a carbide ball mill, the organic solvent used for ball milling is anhydrous ethanol, the grinding balls are carbide grinding balls, the grinding ball diameter is 1-10 mm, the ball-to-material mass ratio is 20-30:1, the ball mill speed is 300 r / min-400 r / min, and the ball milling time is 40 h-55 h.

[0017] Furthermore, in step (2), the particle size of the WC powder is 200 nm to 1 μm, the particle size of the Ni3Al powder is 200 nm to 1 μm, and the particle size of the B powder is 200 nm to 1 μm; the drying temperature is 70 to 80°C, and the mesh size of the standard sieve is 70 to 300 mesh.

[0018] Furthermore, the conditions for wet ball milling in step (2) are as follows: the process is carried out in a carbide ball milling jar with a vacuum of ≤1Pa, the organic solvent is anhydrous ethanol, the grinding balls are carbide grinding balls, the grinding balls are arranged in a number ratio of 1:2~3:4~9 according to the diameter specification of 10mm:5mm:2mm, the ball-to-material mass ratio is 3~5:1, the ball mill speed is 250r / min~350r / min, and the ball milling time is 20h~30h.

[0019] Furthermore, in step (3), the pressing pressure is 280 MPa to 300 MPa, and the holding time is 2 min to 10 min.

[0020] Furthermore, in step (4), the vacuum sintering furnace is evacuated to ≤0.1 Pa and maintained, and the molded sample is heated to 400~650℃ at a heating rate of 6℃ / min~10℃ / min and kept warm for 20~80min.

[0021] Furthermore, in step (5), the microwave frequency of the microwave sintering furnace is 2.45 GHZ, and the nitrogen pressure filled is 300 Pa~800 Pa; microwave heating is performed to a temperature of 1380°C~1550°C and kept warm for 10 min~20 min, wherein the heating rate in the room temperature~350°C stage is 20°C / min~35°C / min, the heating rate in the 350°C~1250°C stage is 10°C / min~20°C / min, and the heating rate in the 1250°C~1550°C stage is 5°C / min~10°C / min.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. In the WC-Ni3Al cemented carbide of the present invention, the multilayer graphene powder and hexagonal boron nitride have friction-reducing and wear-resistant effects at different temperature stages, which can improve the wear resistance of the WC-Ni3Al cemented carbide; the multilayer graphene powder and hexagonal boron nitride also have very good thermal conductivity, which can improve the thermal conductivity of the WC-Ni3Al cemented carbide material and promote its uniform temperature distribution during microwave sintering; after the multilayer graphene powder and hexagonal boron nitride are combined, the multilayer graphene-coated hexagonal boron nitride formed can generate nano-scale pores in the cemented carbide. These nano-scale pores can absorb the energy required for fracture toughness to occur, thereby significantly improving the fracture toughness of the WC-Ni3Al cemented carbide.

[0024] 2. In the WC-Ni3Al cemented carbide of the present invention, graphene is distributed in Ni3Al, which can isolate hexagonal boron nitride from direct contact with WC and pinning with WC, thereby avoiding the problem of poor wettability between hexagonal boron nitride and WC, hindering the movement of WC grains during bending, and helping to improve the overall wettability, hardness and strength of the alloy.

[0025] 3. In the WC-Ni3Al cemented carbide of the present invention, the B element can cause lattice distortion in the Ni3Al binder phase, thereby achieving a solid solution strengthening effect and effectively improving the strength of the WC-Ni3Al cemented carbide. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 TEM image of the coating phase h-BN@MLG prepared in Example 4.

[0028] Figure 2 This is the surface TEM image of the WC-Ni3Al cemented carbide with coating phase toughening prepared in Example 4.

[0029] Figure 3 This is a BSE image of the surface morphology of the WC-Ni3Al cemented carbide with coating phase toughening prepared in Example 4.

[0030] Figure 4 This is the SEM image of the fracture morphology of the WC-Ni3Al cemented carbide with coating phase strengthening and toughening prepared in Example 4.

[0031] Figure 5This is the SEM image of the indentation test of the WC-Ni3Al cemented carbide with coating phase strengthening and toughening prepared in Example 4. DETAILED DESCRIPTION

[0032] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0034] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0035] In the present invention, MLG represents multilayer graphene, and h-BN represents hexagonal boron nitride.

[0036] The present invention will be further described in detail below with reference to Examples (Table 1), but the embodiments of the present invention are not limited thereto.

[0037] Table 1: Composition of WC-Ni3Al cemented carbide in the examples

[0038]

[0039] Example 1:

[0040] A method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0041] (1) Ultrasonic dispersed MLG and h-BN powders were weighed in a mass fraction ratio of 5:1. Taking the preparation of 20g composite powder as an example, 16.67g MLG and 3.33g h-BN were weighed respectively using a precision balance. The number of graphene layers was 3 to 10, the sheet diameter was 5μm to 50μm, and the thickness was 3nm to 10nm. The h-BN was a granular powder with a single sheet diameter of 100nm to 500nm. The powder was then poured into a carbide ball mill and carbide grinding balls were added. The mass ratio of carbide grinding balls to composite powder was 20:1. Anhydrous ethanol was then added to 3 / 4 of the volume of the ball mill. The mill was milled at a speed of 400r / min for 48h. After the milling was completed, the powder was dried in a drying oven at 80℃ and crushed in a stainless steel mortar to obtain graphene-coated hexagonal boron nitride powder, i.e., h-BN@MLG powder.

[0042] (2) Weigh the raw material powders according to the mass fraction of 84.7% WC, 15% Ni3Al, 0.15% h-BN@MLG and 0.15% B, and then weigh 3% of the total mass of the raw materials as paraffin chips (sintering aid), and pour all of them into a carbide ball mill. After adding carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the filled ball mill is tightly closed. The mass ratio of carbide grinding balls to composite powder is 5:1, and the grinding balls are arranged in a ratio of 1:2:4 with a diameter of 10mm:5mm:2mm. The speed is 250r / min and the ball mill is used for 24h. The ball milled mixture is then poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material is then poured into a stainless steel mortar and crushed. It is sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN@MLG powder.

[0043] (3) Weigh 9 g of the WC-Ni3Al-Bh-BN@MLG powder prepared in step (2) and put it into a molding die. Use a press to press and mold it at a pressure of 300 MPa. After holding the pressure for 2 minutes, release the pressure and remove the mold to obtain a molded sample.

[0044] (4) Place the molded sample in a vacuum sintering furnace, evacuate the vacuum sintering furnace to ≤1Pa and maintain it, then heat the molded sample to 550℃ at a heating rate of 8℃ / min and keep it warm for 1h. Pre-sinter to remove the molding agent paraffin. Then turn off the heating system and maintain the vacuum in the furnace. Keep the cooling water circulating and let the sample cool to room temperature with the furnace.

[0045] (5) The molded sample obtained after pre-sintering was placed in a microwave sintering furnace with a microwave frequency of 2.45 GHZ. The microwave sintering furnace was evacuated to a vacuum of ≤1 Pa, and then 600 Pa of nitrogen was introduced. The water circulation was turned on, and the microwave heating system was started to heat the sample to 1500 °C and keep it warm for 15 minutes. The heating rate from room temperature to 350 °C was 30 °C / min, the heating rate from 350 °C to 1250 °C was 15 °C / min, and the heating rate from 1250 °C to 1550 °C was 8 °C / min. After that, the microwave heating system was turned off, the water circulation was maintained, and the sample was cooled to room temperature with the furnace, thereby preparing a WC-Ni3Al cemented carbide with coating phase strengthening and toughening.

[0046] The hardness, toughness, strength, and friction coefficient of the WC-Ni3Al cemented carbide were measured using a Vickers hardness tester, a universal material mechanical testing machine, and a high-speed reciprocating friction testing machine (grinding ball material Gcr15). The WC-Ni3Al cemented carbide reinforced with the coating phase obtained in this example had a hardness of 1050 HV and a fracture toughness of 22 MPa·mm 1 / 2 , the bending strength is 853MPa and the average friction coefficient is 0.76.

[0047] Example 2:

[0048] A method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0049] Steps (1), (3), (4), and (5) are the same as in Example 1, except that step (2) is as follows:

[0050] The raw material powders were weighed according to the mass fraction of 87.3% WC, 12.5% Ni3Al, 0.1% h-BN@MLG and 0.1% B, and then 3% paraffin chips (sintering aid) of the total mass of the raw materials were weighed and poured into a cemented carbide ball mill. After adding cemented carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the ball mill filled with materials was tightly closed. The mass ratio of cemented carbide grinding balls to composite powder was 5:1, and the grinding balls were configured with a diameter of 10mm:5mm:2mm in a ratio of 1:2:4. The speed was 250r / min and the ball milling was carried out for 24h. The ball-milled mixture was then poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material was then poured into a stainless steel mortar and crushed. It was sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN@MLG powder.

[0051] The WC-Ni3Al cemented carbide with the coating phase strengthened and toughened in this embodiment has a hardness of 1125HV and a fracture toughness of 18.5MPa·mm 1 / 2 , the bending strength is 1095MPa and the average friction coefficient is 0.65.

[0052] Example 3:

[0053] A method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0054] Steps (1), (3), (4), and (5) are the same as in Example 1, except that step (2) is as follows:

[0055] The raw material powders were weighed according to the mass fraction of 89.85% WC, 10% Ni3Al, 0.05% h-BN@MLG and 0.1% B, and then 3% paraffin chips (sintering aid) of the total mass of the raw materials were weighed and poured into a cemented carbide ball mill. After adding cemented carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the ball mill filled with materials was tightly closed. The mass ratio of cemented carbide grinding balls to composite powder was 5:1, and the grinding balls were configured with a diameter of 10mm:5mm:2mm in a ratio of 1:2:4. The speed was 250r / min and the ball milling was carried out for 24h. The ball-milled mixture was then poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material was then poured into a stainless steel mortar and crushed. It was sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN@MLG powder.

[0056] The WC-Ni3Al cemented carbide with the coating phase strengthened and toughened in this embodiment has a hardness of 1382HV and a fracture toughness of 76.5MPa·mm 1 / 2 , the bending strength is 1195MPa and the average friction coefficient is 0.36.

[0057] Example 4:

[0058] A method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0059] Steps (1), (3), (4), and (5) are the same as in Example 1, except that step (2) is as follows:

[0060] The raw material powders were weighed according to the mass fraction of 89.8% WC, 10% Ni3Al, 0.1% h-BN@MLG and 0.1% B, and then 3% paraffin chips (sintering aid) of the total mass of the raw materials were weighed and poured into a cemented carbide ball mill. After adding cemented carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the ball mill filled with the materials was tightly closed. The mass ratio of cemented carbide grinding balls to composite powder was 5:1, and the grinding balls were configured with a diameter of 10mm:5mm:2mm in a ratio of 1:2:4. The speed was 250r / min and the ball milling was carried out for 24h. The ball-milled mixture was then poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material was then poured into a stainless steel mortar and crushed. It was sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN@MLG powder.

[0061] The WC-Ni3Al cemented carbide with coating phase toughening obtained in this embodiment has a hardness of 1399HV and a fracture toughness of 93.5MPa·mm 1 / 2 , the bending strength is 1387MPa and the average friction coefficient is 0.28.

[0062] Depend on Figure 1-5 It can be seen that the h-BN@MLG composite powder was successfully prepared ( Figure 1 ) can form a uniformly distributed nanoscale pore structure in situ after being introduced into the WC-Ni3Al based cemented carbide system ( Figure 2 ). This material significantly improves the fracture toughness of WC-Ni3Al based cemented carbide while maintaining the original hardness of the alloy. Microstructural analysis shows that the surface of the alloy ( Figure 3 ) and fracture morphology ( Figure 4 ) showed good density, no obvious pore defects were observed, and the indentation test ( Figure 5 ) further showed that its crack propagation resistance was significantly enhanced.

[0063] Compared with other embodiments, when the mass fraction of the binder phase is 10% and the mass fraction of the coating phase is 0.1%, the relative density, hardness and strength performance of the alloy are optimal, and the improvement in the fracture toughness effect is most obvious at this time.

[0064] Example 5:

[0065] A method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0066] Steps (1), (3), (4), and (5) are the same as in Example 1, except that step (2) is as follows:

[0067] The raw material powders were weighed according to the mass fraction of 89.75% WC, 10% Ni3Al, 0.15% h-BN@MLG and 0.1% B, and then 3% paraffin chips (sintering aid) of the total mass of the raw materials were weighed and poured into a cemented carbide ball mill. After adding cemented carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the ball mill filled with the materials was tightly closed. The mass ratio of cemented carbide grinding balls to composite powder was 5:1, and the grinding balls were configured with a diameter of 10mm:5mm:2mm in a ratio of 1:2:4. The speed was 250r / min and the ball milling was carried out for 24h. The ball-milled mixture was then poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material was then poured into a stainless steel mortar and crushed. It was sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN@MLG powder.

[0068] The WC-Ni3Al cemented carbide with coating phase toughening obtained in this embodiment has a hardness of 1386HV and a fracture toughness of 88.9MPa·mm 1 / 2 , the bending strength is 1295MPa and the average friction coefficient is 0.33.

[0069] Example 6:

[0070] A method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0071] Steps (1), (3), (4), and (5) are the same as in Example 1, except that step (2) is as follows:

[0072] The raw material powders were weighed according to the mass fraction of 92.3% WC, 7.5% Ni3Al, 0.1% h-BN@MLG and 0.1% B, and then 3% paraffin chips (sintering aid) of the total mass of the raw materials were weighed and poured into a cemented carbide ball mill. After adding cemented carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the ball mill filled with materials was tightly closed. The mass ratio of cemented carbide grinding balls to composite powder was 5:1, and the grinding balls were configured with a diameter of 10mm:5mm:2mm in a ratio of 1:2:4. The speed was 250r / min and the ball milling was carried out for 24h. The ball-milled mixture was then poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material was then poured into a stainless steel mortar and crushed. It was sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN@MLG powder.

[0073] The WC-Ni3Al cemented carbide with the coating phase strengthened and toughened in this embodiment has a hardness of 1475HV and a fracture toughness of 24.3MPa·mm 1 / 2 , the bending strength is 1451MPa and the average friction coefficient is 0.26.

[0074] Example 7:

[0075] A method for preparing WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, comprising the following steps:

[0076] Steps (1), (3), (4), and (5) are the same as in Example 1, except that step (2) is as follows:

[0077] The raw material powders were weighed according to the mass fraction of 94.98% WC, 5% Ni3Al, 0.01% h-BN@MLG and 0.01% B, and then 3% of the total mass of the raw materials was weighed as paraffin chips (sintering aid), all of which were poured into a cemented carbide ball mill. After adding cemented carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the ball mill filled with materials was tightly closed. The mass ratio of cemented carbide grinding balls to composite powder was 5:1, and the grinding balls were configured with a diameter of 10mm:5mm:2mm in a ratio of 1:2:4. The speed was 250r / min and the ball milling was carried out for 24h. The ball-milled mixture was then poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material was then poured into a stainless steel mortar and crushed. It was sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN@MLG powder.

[0078] The WC-Ni3Al cemented carbide with the coating phase strengthened and toughened in this embodiment has a hardness of 1605HV and a fracture toughness of 13.6MPa·mm 1 / 2 , the bending strength is 1497MPa and the average friction coefficient is 0.36.

[0079] Comparative Example 1:

[0080] A method for preparing WC-Ni3Al cemented carbide reinforced with MLG and h-BN comprises the following steps:

[0081] (1) The raw material powders were weighed according to the mass fractions of 89.78% WC, 10% Ni3Al, 0.1% MLG, 0.02% h-BN and 0.1% B. The number of graphene layers is 3 to 10, the diameter of the flakes is 5 μm to 50 μm, and the thickness is 3 nm to 10 nm. The h-BN is a granular powder with a single flake diameter of 100 nm to 500 nm. 3% of the total mass of the raw materials is weighed as paraffin chips (sintering aid) and poured into a carbide ball mill. Carbide grinding balls and 3 / 4 of anhydrous ethanol are added and the filled ball mill is tightly covered. The mass ratio of the carbide grinding balls to the composite powder is 5:1, and the grinding balls are arranged in a ratio of 1:2:4 with diameters of 10 mm:5 mm:2 mm. The milling is carried out at a speed of 250 r / min for 24 h. The milled mixture is then poured into a stainless steel plate and dried in a drying oven at 80°C. The dried material is then crushed in a stainless steel mortar and sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN / MLG powder.

[0082] (2) Weigh 9 g of the WC-Ni3Al-Bh-BN / MLG powder prepared in step (2) and put it into a molding die. Use a press to press and mold it at a pressure of 300 MPa. After holding the pressure for 2 minutes, release the pressure and remove the mold to obtain a molded sample.

[0083] (3) Same as step (4) of embodiment (1);

[0084] (4) Same as step (5) of embodiment (1);

[0085] The WC-Ni3Al cemented carbide with the coating phase strengthened and toughened in this comparative example has a hardness of 1405HV and a fracture toughness of 12.7MPa·mm 1 / 2 , the bending strength is 1375MPa and the average friction coefficient is 0.37.

[0086] Comparative Example 2:

[0087] A method for preparing WC-Ni3Al cemented carbide reinforced with MLG, comprising the following steps:

[0088] (1) Weigh the raw material powders according to the mass fraction of 89.8% WC, 10% Ni3Al, 0.1% MLG and 0.1% B. The number of graphene layers is 3 to 10, the diameter of the layer is 5 μm to 50 μm, and the thickness is 3 nm to 10 nm. Then weigh 3% of the total mass of the raw materials as paraffin chips (sintering aid) and pour them all into a carbide ball mill. After adding carbide grinding balls and 3 / 4 of anhydrous ethanol, the filled ball mill is tightly closed. The mass ratio of carbide grinding balls to composite powder is 5:1, and the grinding balls are arranged in a ratio of 1:2:4 with a diameter of 10 mm:5 mm:2 mm. The speed is 250 r / min and the ball mill is milled for 24 h. The ball milled mixture is then poured into a stainless steel plate and placed in a drying oven for drying at 80 ° C. The dried material is then poured into a stainless steel mortar and crushed. It is sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-B-MLG powder.

[0089] (2) Weigh 9 g of the WC-Ni3Al-B-MLG powder prepared in step (2) and put it into a molding die. Use a press to press and mold it at a pressure of 300 MPa. After holding the pressure for 2 minutes, release the pressure and remove the mold to obtain a molded sample.

[0090] (3) Same as step (4) of embodiment (1);

[0091] (4) Same as step (5) of embodiment (1);

[0092] The WC-Ni3Al cemented carbide with the coating phase strengthened and toughened in this comparative example has a hardness of 1387HV and a fracture toughness of 13.3MPa·mm 1 / 2 , the bending strength is 1383MPa and the average friction coefficient is 0.32.

[0093] Comparative Example 3:

[0094] A method for preparing h-BN-reinforced WC-Ni3Al cemented carbide comprises the following steps:

[0095] (1) Weigh the raw material powders according to the mass fraction of 89.88% WC, 10% Ni3Al, 0.02% h-BN and 0.1% B. Among them, h-BN is a granular powder with a single piece diameter of 100nm~500nm. Then weigh 3% of the total mass of the raw materials as paraffin chips (sintering aid) and pour all of them into a carbide ball mill. After adding carbide grinding balls and 3 / 4 of the can of anhydrous ethanol, the filled ball mill is tightly closed. The mass ratio of carbide grinding balls to composite powder is 5:1, and the grinding balls are arranged in a ratio of 1:2:4 with a diameter of 10mm:5mm:2mm. The speed is 250r / min and the ball mill is used for 24h. Then the ball milled mixture is poured into a stainless steel plate and placed in a drying oven for drying at 80℃. The dried material is then poured into a stainless steel mortar and crushed. It is sieved with a 100-mesh standard sieve to obtain WC-Ni3Al-Bh-BN powder.

[0096] (2) Weigh 9 g of the WC-Ni3Al-Bh-BN powder prepared in step (2) and put it into a molding die. Use a press to press and mold it at a pressure of 300 MPa. After holding the pressure for 2 minutes, release the pressure and remove the mold to obtain a molded sample.

[0097] (3) Same as step (4) of embodiment (1);

[0098] (4) Same as step (5) of embodiment (1);

[0099] The WC-Ni3Al cemented carbide with the coating phase strengthened and toughened in this comparative example has a hardness of 1334HV and a fracture toughness of 11.6MPa·mm 1 / 2 , the bending strength is 1279MPa and the average friction coefficient is 0.65.

Claims

1. A WC-Ni3Al cemented carbide with a coating phase for strengthening and toughening, characterized in that: Calculated by mass fraction, the hard phase is 89.75% to 89.85% WC, the bonding phase is 10% Ni3Al, and the reinforcing phase is 0.05% to 0.15% hexagonal boron nitride coated with multilayer graphene and 0.1% B; the number of layers of the multilayer graphene is 3 to 10; the multilayer graphene-coated hexagonal boron nitride is obtained by wet ball milling multilayer graphene powder and hexagonal boron nitride powder in a mass ratio of 3 to 7:

1.

2. A method for preparing WC-Ni3Al cemented carbide with added coating phase for strengthening and toughening as claimed in claim 1, characterized in that: The steps include: (1) Wet-ball milling, drying, and crushing the ultrasonically dispersed multilayer graphene powder and hexagonal boron nitride powder to obtain multilayer graphene-coated hexagonal boron nitride powder, i.e., h-BN@MLG powder; the mass ratio of the multilayer graphene to the hexagonal boron nitride is 3-7:1; and the number of layers of the multilayer graphene is 3-10; (2) wet-ball milling the h-BN@MLG powder, WC powder, Ni3Al powder, B powder and paraffin wax debris obtained in step (1) in a vacuum environment, drying, crushing and sieving to obtain WC-Ni3Al-Bh-BN@MLG powder; (3) pressing the WC-Ni3Al-Bh-BN@MLG powder obtained in step (2) to obtain a molded sample; (4) placing the molded sample obtained in step (3) into a vacuum sintering furnace, heating and keeping the temperature under vacuum, stopping heating and maintaining the vacuum in the furnace until cooling to obtain a pre-sintered sample; (5) The pre-sintered sample obtained in step (4) is placed in a microwave sintering furnace, subjected to microwave heating and heat preservation under a nitrogen environment, and then cooled to obtain the product.

3. The preparation method according to claim 2, characterized in that In step (1), the diameter of the flake is 5 μm to 50 μm, and the thickness is 3 nm to 10 nm; the hexagonal boron nitride is a granular powder, and the diameter of a single flake is 100 nm to 500 nm.

4. The preparation method according to claim 2, characterized in that The conditions for wet ball milling in step (1) are as follows: the milling is carried out in a carbide ball mill, the organic solvent used for the ball milling is anhydrous ethanol, the grinding balls are carbide grinding balls, the grinding ball diameter is 1-10 mm, the ball-to-material mass ratio is 20-30:1, the ball mill speed is 300 r / min-400 r / min, and the ball milling time is 40 h-55 h.

5. The preparation method according to claim 2, characterized in that In step (2), the particle size of the WC powder is 200 nm to 1 μm, the particle size of the Ni3Al powder is 200 nm to 1 μm, and the particle size of the B powder is 200 nm to 1 μm; the drying temperature is 70 to 80°C, and the mesh size of the standard sieve is 70 to 300 mesh.

6. The preparation method according to claim 2, characterized in that The conditions for wet ball milling in step (2) are as follows: the milling is carried out in a carbide ball milling jar with a vacuum of ≤1Pa, the organic solvent is anhydrous ethanol, the grinding balls are carbide grinding balls, the grinding balls are arranged in a number ratio of 1:2~3:4~9 according to the diameter specifications of 10mm:5mm:2mm, the ball-to-material mass ratio is 3~5:1, the ball mill speed is 250r / min~350r / min, and the ball milling time is 20h~30h.

7. The preparation method according to claim 2, characterized in that In step (3), the pressing pressure is 280 MPa to 300 MPa, and the holding time is 2 min to 10 min.

8. The preparation method according to claim 2, characterized in that In step (4), the vacuum sintering furnace is evacuated to ≤0.1 Pa and maintained, and the molded sample is heated to 400~650℃ at a heating rate of 6℃ / min~10℃ / min and kept warm for 20~80min.

9. The preparation method according to any one of claims 2 to 8, characterized in that In step (5), the microwave frequency of the microwave sintering furnace is 2.45 GHZ, and the nitrogen pressure filled is 300 Pa~800 Pa; microwave heating is performed to a temperature of 1380°C~1550°C and kept warm for 10 min~20 min, wherein the heating rate in the room temperature~350°C stage is 20°C / min~35°C / min, the heating rate in the 350°C~1250°C stage is 10°C / min~20°C / min, and the heating rate in the 1250°C~1550°C stage is 5°C / min~10°C / min.

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