Hard tungsten-based alloy material and preparation method thereof

Abstract

The invention relates to the technical field of hard alloy, and discloses a hard tungsten-based alloy material and a preparation method thereof.The hard tungsten-based alloy material comprises, by mass, 90-95 parts of tungsten carbide powder, 2-3 parts of cobalt powder, 2-3 parts of nickel powder, 1-2 parts of iron powder and 3-5 parts of modified carbon fibers. In the modified carbon fiber, the carbon fiber can be coated at a tungsten carbide grain boundary through a grain refiner, the compound grain refiner inhibits the growth of tungsten carbide grains, reduces the surface energy at the tungsten carbide grain boundary, realizes the grain refinement effect and improves the mechanical strength of the hard alloy, and the carbon fiber has an excellent length-diameter ratio and is inserted into a hard alloy system, so that the mechanical strength of the hard alloy is improved. And in addition, the nano carbon network generated by thermal decomposition grows by taking the carbon fiber as a template and is distributed at the grain boundary of the tungsten carbide, so that the situation that the mechanical property of the hard alloy is reduced due to agglomeration of the nano carbon network is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of cemented carbides, and specifically to a hard tungsten-based alloy material and a preparation method thereof. Background Art

[0002] Cemented carbide is a composite material prepared by powder metallurgy method with refractory metal carbides (such as tungsten carbide, titanium carbide, tantalum carbide, etc.) as hard phases and transition metal elements (such as cobalt, nickel, iron, etc.) as binder phases. It has excellent properties such as high hardness, high strength, high toughness, wear resistance, high temperature resistance and small expansion coefficient, and is widely used in fields such as cutting, drilling, mining, tool forming and wear-resistant parts. Among them, tungsten carbide cemented carbide with tungsten carbide as the hard phase and cobalt, nickel and iron as the bonding phases is the most widely used cemented carbide at present. Tungsten carbide cemented carbide needs to add grain growth inhibitors, which can inhibit the excessive growth of grains during the sintering process and further enhance the mechanical properties of the cemented carbide.

[0003] Adding grain refiners to tungsten carbide cemented carbide can effectively reduce the size of tungsten carbide grains. Fine grains can hinder the propagation of cracks, reduce the defects inside the alloy material, and improve the mechanical properties of the cemented carbide. However, the grain refiners are prone to agglomeration and difficult to be uniformly dispersed in the alloy matrix, unable to effectively prevent grain growth, resulting in a reduction in the grain refinement effect. Moreover, tungsten carbide cemented carbide has the problem of poor tissue uniformity, with low hardness, toughness and strength, which limits the application of tungsten carbide cemented carbide. Summary of the Invention

[0004] The present invention provides a hard tungsten-based alloy material and a preparation method thereof, which solve the problems of low mechanical strength and coarse grains of tungsten carbide cemented carbide.

[0005] The technical solution of the present invention: A hard tungsten-based alloy material, comprising the following raw materials in parts by mass: 90 - 95 parts of tungsten carbide powder, 2 - 3 parts of cobalt powder, 2 - 3 parts of nickel powder, 1 - 2 parts of iron powder, 3 - 5 parts of modified carbon fiber; The modified carbon fiber is prepared by surface-modifying carbon fiber with a silane coupling agent and then mixing it with a composite gel; The silane coupling agent is γ-aminopropyltriethoxysilane; The composite gel is prepared by mixing and reacting a grain refiner modified with microcrystalline cellulose, acrylamide, N,N-methylenebisacrylamide and an initiator; A preparation method of a hard tungsten-based alloy material, comprising the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and perform vacuum drying and ball milling to obtain a mixture; S2. Place the mixture in a pressure mold to press it into a preform, and then place the preform in a sintering furnace for primary sintering, secondary sintering, and cool it to room temperature to obtain a hard tungsten-based alloy material.

[0006] Further, in step S1, the vacuum drying process: the drying temperature is 90 - 110 °C, the vacuum degree is 4 - 6 Pa, and the drying time is 10 - 15 min.

[0007] Further, in step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is (8 - 10):1, the rotation speed is 150 - 200 r / min, and the ball milling time is 20 - 24 h.

[0008] Further, in step S2, the pressing pressure is 200 - 300 MPa, and the pressing time is 40 - 50 s.

[0009] Further, in step S2, the primary sintering temperature is 1050 - 1150 °C, and the sintering time is 1 - 2 h; the secondary sintering temperature is 1380 - 1480 °C, and the sintering time is 40 - 60 min.

[0010] Further, the modified carbon fiber is specifically prepared by the following steps: A1. Add a grain refiner and microcrystalline cellulose to ethanol, stir evenly, add ethylene glycol, stir at 70 - 80 °C for 3 - 5 h, cool to room temperature, filter, wash, and dry to obtain a grain refiner modified with microcrystalline cellulose; A2. Add acrylamide and N,N'-methylenebisacrylamide to deionized water, after ultrasonic treatment, add the grain refiner modified with microcrystalline cellulose, stir evenly, add an initiator, stir and react at 20 - 25 °C for 30 - 40 min, take out the gel, wash the gel, and dry to obtain a composite gel; A3. Add carbon fiber to ethanol and deionized water, stir evenly, add a silane coupling agent, stir and react at 65 - 75 °C for 1 - 2 h, cool to room temperature, filter, wash, and dry to obtain amino-functionalized carbon fiber; A4. Add the amino-functionalized carbon fiber and the composite gel to ethanol, stir evenly, heat to 60 - 70 °C, stir for 20 - 30 min, cool to room temperature, filter, wash, and dry to obtain the modified carbon fiber.

[0011] Further, during the reaction process of A1 above, the hydroxyl groups contained in microcrystalline cellulose can combine with the hydroxyl groups of ethylene glycol through strong hydrogen bonds to form a cross-linked network structure, and the hydroxyl groups contained in microcrystalline cellulose and ethylene glycol can also combine with the hydroxyl groups on the surface of the grain refiner through chemical bonds, so that microcrystalline cellulose is coated on the surface of the grain refiner to obtain a grain refiner modified with microcrystalline cellulose.

[0012] Further, in the above A2 reaction process, under the action of an initiator, acrylamide copolymerizes, and at the same time, N,N-methylenebisacrylamide crosslinks with the acrylamide molecular chain to form a three-dimensional network structure. Moreover, the active free radicals generated by the initiator enable acrylamide to also react with the hydroxyl groups on the surface of the grain refiner modified with microcrystalline cellulose, causing the grain refiner modified with microcrystalline cellulose to be embedded in the three-dimensional network structure to form a composite gel.

[0013] Further, in the above A3 reaction process, the silanol groups generated by the hydrolysis of the silane coupling agent can combine with the oxygen-containing functional groups on the surface of the carbon fiber through chemical bonds, causing the silane coupling agent to graft onto the surface of the carbon fiber, providing the carbon fiber with reactive functional groups amino groups, which is beneficial for coating the composite gel on the surface of the carbon fiber.

[0014] Further, in the above A4 reaction process, the amino groups carried on the surface of the amino-functionalized carbon fiber can combine with the hydroxyl groups and amine groups in the composite gel through chemical bonds, causing the composite gel to adhere to the surface of the carbon fiber to obtain modified carbon fiber, which is used as a composite grain refiner.

[0015] Further, in step A1, the dosage ratio of the grain refiner, microcrystalline cellulose, ethanol, and ethylene glycol is (4 - 5) g : (1.1 - 1.3) g : (90 - 110) mL : (0.4 - 0.6) mL.

[0016] Further, in step A2, the dosage ratio of acrylamide, N,N-methylenebisacrylamide, deionized water, the grain refiner modified with microcrystalline cellulose, and the initiator is (8 - 9) g : (3.6 - 3.8) g : (90 - 110) mL : (2.6 - 3) g : (5 - 7) mL.

[0017] Further, in step A3, the dosage ratio of the carbon fiber, ethanol, deionized water, and the silane coupling agent is (4 - 6) g : (25 - 35) mL : (8 - 12) mL : (1 - 2) g.

[0018] Further, in step A4, the dosage ratio of the amino-functionalized carbon fiber, the composite gel, and ethanol is (4.1 - 4.3) g : (2.2 - 2.4) g : (45 - 55) mL.

[0019] Further, the grain refiner is selected from any one of vanadium carbide, chromium carbide, niobium carbide, and tantalum carbide.

[0020] Further, the initiator is an ammonium persulfate solution with a mass fraction of 15 - 25%.

[0021] Further, the carbon fiber has a diameter of 1 - 2 µm and a length of 8 - 15 µm.

[0022] The present invention has the following beneficial effects: (1) In the technical solution of the present invention, microcrystalline cellulose coats the grain refiner through ethylene glycol. On the one hand, the grain refiner can precipitate at the grain boundaries of tungsten carbide, playing a role in pinning the grain boundaries, inhibiting the grain boundary diffusion and surface diffusion of tungsten carbide grains, and a stable solid solution thin layer is formed at the grain boundaries by the grain refiner, reducing the precipitation of tungsten carbide grains. On the other hand, microcrystalline cellulose coats the surface of the grain refiner, which is beneficial for the grain refiner to be embedded in the composite gel system, avoiding the easy agglomeration of small-sized grain refiners, which affects the inhibition of the growth of tungsten carbide grains by the grain refiner, resulting in coarse grains of the synthesized cemented carbide and a decline in the mechanical properties of the cemented carbide. In addition, microcrystalline cellulose can be thermally decomposed to form a carbon network structure, forming metal carbide strengthening phases with cobalt powder, nickel powder, and iron powder, producing a combined strengthening effect of solid solution strengthening and dispersion strengthening, and increasing the mechanical properties of the cemented carbide.

[0023] (2) In the technical solution of the present invention, the grain refiner modified by microcrystalline cellulose, acrylamide, N,N'-methylenebisacrylamide, and an initiator are mixed and reacted to form a composite gel with a three-dimensional network structure. On the one hand, during the preparation of the cemented carbide, the composite gel with a three-dimensional network structure is carbonized to form a dense nano-carbon network, and the grain refiner covers the surface of tungsten carbide grains, hindering grain boundary migration and atomic diffusion, and inhibiting the growth of tungsten carbide grains during sintering. On the other hand, the formed nano-carbon network serves as a bridge to connect adjacent tungsten carbide grains, strengthening the bonding between tungsten carbide grains. At the same time, the formed nano-carbon network can also absorb stress to avoid crack generation, improving the mechanical strength of the cemented carbide. In addition, the grain refiner modified by microcrystalline cellulose is embedded in the three-dimensional network structure, increasing the crosslinking density, which is beneficial for the formation of a denser nano-carbon network and improving the mechanical strength of the cemented carbide.

[0024] (3) In the technical solution of the present invention, the composite gel is coated on the surface of carbon fiber through a silane coupling agent to obtain modified carbon fiber, which is used as a composite grain refiner. On the one hand, during the preparation of the cemented carbide, the grain refiner contained in the composite gel plays a role in pinning the grain boundaries at the grain boundaries of tungsten carbide, enabling the carbon fiber to also be coated at the grain boundaries of tungsten carbide through the grain refiner. The compound grain refiner inhibits the growth of tungsten carbide grains, reduces the surface energy at the grain boundaries of tungsten carbide, realizes the function of grain refinement, and improves the mechanical strength of the cemented carbide. On the other hand, the carbon fiber has an excellent aspect ratio, interpenetrates into the cemented carbide system, improves the mechanical strength of the alloy, and the nano-carbon network generated by thermal decomposition grows with the carbon fiber as a template and is distributed at the grain boundaries of tungsten carbide, avoiding the decline of the mechanical properties of the cemented carbide caused by the agglomeration of the nano-carbon network. Specific embodiments

[0025] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] The raw materials used in the embodiments of the present invention are as follows, and all the reagents used are of analytical grade.

[0027] Among them, the Fisher particle size of tungsten carbide powder is 1.5 µm, and it is purchased from Xiamen Golden Egret Special Alloy Co., Ltd.

[0028] Cobalt powder: Fisher particle size 3.5 µm, purchased from Bohuasi Nano Technology (Ningbo) Co., Ltd.

[0029] Nickel powder: Fisher particle size 2.5 µm, purchased from Shanghai Shuitian Technology Co., Ltd.

[0030] Iron powder: average particle size 2.5 µm, purchased from Ultra-fine Nano Co., Ltd.

[0031] The carbon fiber has a diameter of 1.5 µm and a length of 10 µm.

[0032] The silane coupling agent is γ-aminopropyltriethoxysilane.

[0033] The initiator is an ammonium persulfate solution with a mass fraction of 20%.

[0034] Microcrystalline cellulose is purchased from Shandong Liaocheng Luxi Pharmaceutical Excipients Co., Ltd.

[0035] The grain refiner is selected from vanadium carbide, with the product number LF-VC-W001, a particle size of 1 µm, and is purchased from Ningbo Luofei Nano Technology Co., Ltd.

[0036] Example 1 A hard tungsten-based alloy material includes the following raw materials in parts by mass: 90 parts of tungsten carbide powder, 2 parts of cobalt powder, 2 parts of nickel powder, 1 part of iron powder, and 3 parts of modified carbon fiber; A preparation method of a hard tungsten-based alloy material includes the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and after vacuum drying and ball milling, obtain a mixed material; S2. Place the mixed material in a pressure mold to press into a preform, and then place the preform in a sintering furnace for primary sintering and secondary sintering, and cool to room temperature to obtain a hard tungsten-based alloy material.

[0037] Among them, in step S1, the vacuum drying process: the drying temperature is 90 °C, the vacuum degree is 4 Pa, and the drying time is 10 min; In step S1, ball milling is carried out using a ball mill, with a ball-to-material ratio of 8:1, a rotation speed of 150 r / min, and a ball milling time of 20 h; In step S2, the pressing pressure is 200 MPa and the pressing time is 40 s; In step S2, the primary sintering temperature is 1050 °C and the sintering time is 1 h; the secondary sintering temperature is 1380 °C and the sintering time is 40 min; The modified carbon fiber is specifically prepared by the following steps: A1. Add 4 g of vanadium carbide and 1.1 g of microcrystalline cellulose to 90 mL of ethanol, stir evenly, add 0.4 mL of ethylene glycol, stir at 70 °C for 3 h, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 80 °C for 10 min to obtain vanadium carbide modified with microcrystalline cellulose; A2. Add 8 g of acrylamide and 3.6 g of N,N-methylenebisacrylamide to 90 mL of deionized water, ultrasonicate at 40 KHz for 30 min, add 2.6 g of vanadium carbide modified with microcrystalline cellulose, stir evenly, add 5 mL of a 20% ammonium persulfate solution by mass fraction, stir and react at 20 °C for 30 min to form a gel, wash the gel 3 times with deionized water, and dry at room temperature for 24 h to obtain a composite gel; A3. Add 4 g of carbon fiber to 25 mL of ethanol and 8 mL of deionized water, stir evenly, add 1 g of γ-aminopropyltriethoxysilane, stir and react at 65 °C for 1 h, cool to room temperature, filter, wash 3 times with ethanol, wash 3 times with deionized water, and dry in an oven at 70 °C for 10 min to obtain amino-functionalized carbon fiber; A4. Add 4.1 g of amino-functionalized carbon fiber and 2.2 g of composite gel to 45 mL of ethanol, stir evenly, heat to 60 °C, stir and mix for 20 min, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 70 °C for 10 min to obtain modified carbon fiber.

[0038] Example 2 A hard tungsten-based alloy material, comprising the following raw materials in parts by mass: 93 parts of tungsten carbide powder, 2.5 parts of cobalt powder, 2.5 parts of nickel powder, 1.5 parts of iron powder, and 4 parts of modified carbon fiber; A preparation method of a hard tungsten-based alloy material, comprising the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, vacuum dry and ball mill to obtain a mixture; S2. Place the mixture in a pressure mold to press into a preform, and then place the preform in a sintering furnace for primary sintering and secondary sintering, and cool to room temperature to obtain a hard tungsten-based alloy material.

[0039] Among them, in step S1, the vacuum drying process: the drying temperature is 100 °C, the vacuum degree is 5 Pa, and the drying time is 13 min; In step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is 9:1, the rotation speed is 180 r / min, and the ball milling time is 22 h; In step S2, the pressing pressure is 250 MPa and the pressing time is 45 s; In step S2, the primary sintering temperature is 1100 °C and the sintering time is 1.5 h; the secondary sintering temperature is 1430 °C and the sintering time is 50 min.

[0040] The modified carbon fiber is specifically prepared by the following steps: A1. Add 4.5 g of vanadium carbide and 1.2 g of microcrystalline cellulose to 100 mL of ethanol, stir evenly, add 0.5 mL of ethylene glycol, stir at 75 °C for 4 h, cool to room temperature, filter, wash with deionized water 3 times, and dry in an oven at 80 °C for 10 min to obtain vanadium carbide modified by microcrystalline cellulose; A2. Add 8.5 g of acrylamide and 3.7 g of N,N'-methylenebisacrylamide to 100 mL of deionized water, ultrasonicate at 40 KHz for 30 min, add 2.8 g of vanadium carbide modified by microcrystalline cellulose, stir evenly, add 6 mL of a 20% ammonium persulfate solution by mass, stir and react at 23 °C for 35 min to form a gel, wash the gel with deionized water 3 times, and dry at room temperature for 24 h to obtain a composite gel; A3. Add 5 g of carbon fiber to 30 mL of ethanol and 10 mL of deionized water, stir evenly, add 1.5 g of γ-aminopropyltriethoxysilane, stir and react at 70 °C for 1.5 h, cool to room temperature, filter, wash with ethanol 3 times, wash with deionized water 3 times, and dry in an oven at 70 °C for 10 min to obtain amino-functionalized carbon fiber; A4. Add 4.2 g of amino-functionalized carbon fiber and 2.3 g of composite gel to 50 mL of ethanol, stir evenly, heat to 65 °C, stir and mix for 25 min, cool to room temperature, filter, wash with deionized water 3 times, and dry in an oven at 70 °C for 10 min to obtain modified carbon fiber.

[0041] Example 3 A hard tungsten-based alloy material, comprising the following raw materials in parts by mass: 95 parts of tungsten carbide powder, 3 parts of cobalt powder, 3 parts of nickel powder, 2 parts of iron powder, and 5 parts of modified carbon fiber; A preparation method of a hard tungsten-based alloy material, comprising the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and obtain a mixture through vacuum drying and ball milling; S2. Place the mixture in a pressure mold to press it into a preform, and then place the preform in a sintering furnace for primary sintering, secondary sintering, and cool it to room temperature to obtain a hard tungsten-based alloy material.

[0042] Among them, in step S1, the vacuum drying process: the drying temperature is 110 °C, the vacuum degree is 6 Pa, and the drying time is 15 min; In step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is 10:1, the rotation speed is 200 r / min, and the ball milling time is 24 h; In step S2, the pressing pressure is 300 MPa and the pressing time is 50 s; In step S2, the primary sintering temperature is 1150 °C and the sintering time is 2 h; the secondary sintering temperature is 1480 °C and the sintering time is 60 min.

[0043] The modified carbon fiber is specifically prepared by the following steps: A1. Add 5 g of vanadium carbide and 1.3 g of microcrystalline cellulose to 110 mL of ethanol, stir evenly, add 0.6 mL of ethylene glycol, stir at 80 °C for 5 h, cool to room temperature, filter, wash with deionized water 3 times, and dry in an 80 °C oven for 10 min to obtain vanadium carbide modified by microcrystalline cellulose; A2. Add 9 g of acrylamide and 3.8 g of N,N-methylenebisacrylamide to 110 mL of deionized water, ultrasonicate at 40 KHz for 30 min, add 3 g of vanadium carbide modified by microcrystalline cellulose, stir evenly, add 7 mL of a 20% ammonium persulfate solution by mass fraction, stir and react at 25 °C for 40 min to form a gel, wash the gel with deionized water 3 times, and dry at room temperature for 24 h to obtain a composite gel; A3. Add 6 g of carbon fiber to 35 mL of ethanol and 12 mL of deionized water, stir evenly, add 2 g of γ-aminopropyltriethoxysilane, stir and react at 75 °C for 2 h, cool to room temperature, filter, wash with ethanol 3 times, wash with deionized water 3 times, and dry in a 70 °C oven for 10 min to obtain amino-functionalized carbon fiber; A4. Add 4.3 g of amino-functionalized carbon fiber and 2.4 g of composite gel to 55 mL of ethanol, stir evenly, heat to 70 °C, stir and mix for 30 min, cool to room temperature, filter, wash with deionized water 3 times, and dry in a 70 °C oven for 10 min to obtain modified carbon fiber.

[0044] Comparative Example 1 A hard tungsten-based alloy material, including the following raw materials in parts by mass: 95 parts of tungsten carbide powder, 3 parts of cobalt powder, 3 parts of nickel powder, 2 parts of iron powder, and 5 parts of modified carbon fiber; A preparation method of a hard tungsten-based alloy material, including the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and obtain a mixed material through vacuum drying and ball milling. S2. Place the mixed material in a pressure mold to press it into a preform, and then place the preform in a sintering furnace for primary sintering and secondary sintering, and cool it to room temperature to obtain a hard tungsten-based alloy material.

[0045] Among them, in step S1, for the vacuum drying process: the drying temperature is 110 °C, the vacuum degree is 6 Pa, and the drying time is 15 min. In step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is 10:1, the rotation speed is 200 r / min, and the ball milling time is 24 h. In step S2, the pressing pressure is 300 MPa and the pressing time is 50 s. In step S2, the primary sintering temperature is 1150 °C and the sintering time is 2 h; the secondary sintering temperature is 1480 °C and the sintering time is 60 min.

[0046] The modified carbon fiber is specifically prepared by the following steps: A1. Add 9 g of acrylamide and 3.8 g of N,N'-methylenebisacrylamide to 110 mL of deionized water, ultrasonicate for 30 min at 40 KHz, add 3 g of vanadium carbide, stir evenly, add 7 mL of a 20% ammonium persulfate solution, and stir and react at 25 °C for 40 min to form a gel. Wash the gel 3 times with deionized water and dry it at room temperature for 24 h to obtain a composite gel. A2. Add 6 g of carbon fiber to 35 mL of ethanol and 12 mL of deionized water, stir evenly, add 2 g of γ-aminopropyltriethoxysilane, stir and react at 75 °C for 2 h, cool to room temperature, filter, wash 3 times with ethanol, wash 3 times with deionized water, and dry in an oven at 70 °C for 10 min to obtain amino-functionalized carbon fiber. A3. Add 4.3 g of amino-functionalized carbon fiber and 2.4 g of composite gel to 55 mL of ethanol, stir evenly, heat to 70 °C, stir and mix for 30 min, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 70 °C for 10 min to obtain modified carbon fiber.

[0047] Comparative Example 2 A hard tungsten-based alloy material, including the following raw materials in parts by mass: 95 parts of tungsten carbide powder, 3 parts of cobalt powder, 3 parts of nickel powder, 2 parts of iron powder, and 5 parts of modified carbon fiber. A preparation method of a hard tungsten-based alloy material, including the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and obtain a mixed material through vacuum drying and ball milling. S2. Place the mixture in a pressure mold to press it into a preform, and then place the preform in a sintering furnace for primary sintering, secondary sintering, and cool it to room temperature to obtain a hard tungsten-based alloy material.

[0048] Among them, in step S1, for the vacuum drying process: the drying temperature is 110 °C, the vacuum degree is 6 Pa, and the drying time is 15 min. In step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is 10:1, the rotation speed is 200 r / min, and the ball milling time is 24 h. In step S2, the pressing pressure is 300 MPa and the pressing time is 50 s. In step S2, the primary sintering temperature is 1150 °C and the sintering time is 2 h; the secondary sintering temperature is 1480 °C and the sintering time is 60 min.

[0049] The modified carbon fiber is specifically prepared by the following steps: A1. Add 5 g of vanadium carbide and 1.3 g of microcrystalline cellulose to 110 mL of ethanol, stir evenly, add 0.6 mL of ethylene glycol, stir at 80 °C for 5 h, cool to room temperature, filter, wash with deionized water 3 times, and dry in an 80 °C oven for 10 min to obtain vanadium carbide modified by microcrystalline cellulose. A2. Add 12.8 g of acrylamide to 110 mL of deionized water, ultrasonic for 30 min at 40 KHz, add 3 g of the grain refiner modified by microcrystalline cellulose, stir evenly, add 7 mL of a 20% ammonium persulfate solution by mass fraction, stir and react at 25 °C for 40 min to form a gel, wash the gel with deionized water 3 times, and dry at room temperature for 24 h to obtain a composite gel. A3. Add 6 g of carbon fiber to 35 mL of ethanol and 12 mL of deionized water, stir evenly, add 2 g of γ-aminopropyltriethoxysilane, stir and react at 75 °C for 2 h, cool to room temperature, filter, wash with ethanol 3 times, wash with deionized water 3 times, and dry in a 70 °C oven for 10 min to obtain amino-functionalized carbon fiber. A4. Add 4.3 g of amino-functionalized carbon fiber and 2.4 g of the composite gel to 55 mL of ethanol, stir evenly, heat to 70 °C, stir and mix for 30 min, cool to room temperature, filter, wash with deionized water 3 times, and dry in a 70 °C oven for 10 min to obtain the modified carbon fiber.

[0050] Comparative Example 3 A hard tungsten-based alloy material, including the following raw materials in parts by mass: 95 parts of tungsten carbide powder, 3 parts of cobalt powder, 3 parts of nickel powder, 2 parts of iron powder, and 5 parts of modified carbon fiber. A preparation method of a hard tungsten-based alloy material, including the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and obtain a mixture through vacuum drying and ball milling. S2. Place the mixture in a pressure mold to press it into a preform, and then place the preform in a sintering furnace for primary sintering and secondary sintering, and cool it to room temperature to obtain a hard tungsten-based alloy material.

[0051] Among them, in step S1, for the vacuum drying process: the drying temperature is 110°C, the vacuum degree is 6 Pa, and the drying time is 15 min. In step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is 10:1, the rotation speed is 200 r / min, and the ball milling time is 24 h. In step S2, the pressing pressure is 300 MPa, and the pressing time is 50 s. In step S2, the primary sintering temperature is 1150°C, and the sintering time is 2 h; the secondary sintering temperature is 1480°C, and the sintering time is 60 min.

[0052] The modified carbon fiber is specifically prepared by the following steps: A1. Add 5 g of vanadium carbide and 1.3 g of microcrystalline cellulose to 110 mL of ethanol, stir evenly, add 0.6 mL of ethylene glycol, stir at 80°C for 5 h, cool to room temperature, filter, wash 3 times with deionized water, and dry in an 80°C oven for 10 min to obtain vanadium carbide modified by microcrystalline cellulose. A2. Add 12.8 g of N,N-methylenebisacrylamide to 110 mL of deionized water, ultrasonically treat it at 40 KHz for 30 min, add 3 g of the grain refiner modified by microcrystalline cellulose, stir evenly, add 7 mL of a 20% ammonium persulfate solution by mass fraction, stir and react at 25°C for 40 min to form a gel, wash the gel 3 times with deionized water, and dry it at room temperature for 24 h to obtain a composite gel. A3. Add 6 g of carbon fiber to 35 mL of ethanol and 12 mL of deionized water, stir evenly, add 2 g of γ-aminopropyltriethoxysilane, stir and react at 75°C for 2 h, cool to room temperature, filter, wash 3 times with ethanol, wash 3 times with deionized water, and dry in a 70°C oven for 10 min to obtain amino-functionalized carbon fiber. A4. Add 4.3 g of amino-functionalized carbon fiber and 2.4 g of the composite gel to 55 mL of ethanol, stir evenly, heat up to 70°C, stir and mix for 30 min, cool to room temperature, filter, wash 3 times with deionized water, and dry in a 70°C oven for 10 min to obtain modified carbon fiber.

[0053] Comparative Example 4 A hard tungsten-based alloy material includes the following raw materials in parts by mass: 95 parts of tungsten carbide powder, 3 parts of cobalt powder, 3 parts of nickel powder, 2 parts of iron powder, and 5 parts of modified carbon fiber. A preparation method of a hard tungsten-based alloy material, comprising the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and obtain a mixture through vacuum drying and ball milling; S2. Place the mixture in a pressure mold to be pressed into a preform, and then place the preform in a sintering furnace for primary sintering and secondary sintering, and cool to room temperature to obtain the hard tungsten-based alloy material.

[0054] Among them, in step S1, the vacuum drying process: the drying temperature is 110 °C, the vacuum degree is 6 Pa, and the drying time is 15 min; In step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is 10:1, the rotation speed is 200 r / min, and the ball milling time is 24 h; In step S2, the pressing pressure is 300 MPa and the pressing time is 50 s; In step S2, the primary sintering temperature is 1150 °C and the sintering time is 2 h; the secondary sintering temperature is 1480 °C and the sintering time is 60 min.

[0055] The modified carbon fiber is specifically prepared by the following steps: A1. Add 5 g of vanadium carbide and 1.3 g of microcrystalline cellulose to 110 mL of ethanol, stir evenly, add 0.6 mL of ethylene glycol, stir at 80 °C for 5 h, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 80 °C for 10 min to obtain vanadium carbide modified by microcrystalline cellulose; A2. Add 6 g of carbon fiber to 35 mL of ethanol and 12 mL of deionized water, stir evenly, add 2 g of γ-aminopropyltriethoxysilane, stir and react at 75 °C for 2 h, cool to room temperature, filter, wash 3 times with ethanol, wash 3 times with deionized water, and dry in an oven at 70 °C for 10 min to obtain amino-functionalized carbon fiber; A3. Add 4.3 g of amino-functionalized carbon fiber and 2.4 g of vanadium carbide modified by microcrystalline cellulose to 55 mL of ethanol, stir evenly, heat up to 70 °C, stir and mix for 30 min, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 70 °C for 10 min to obtain the modified carbon fiber.

[0056] Comparative Example 5 A hard tungsten-based alloy material, comprising the following raw materials in parts by mass: 95 parts of tungsten carbide powder, 3 parts of cobalt powder, 3 parts of nickel powder, 2 parts of iron powder, and 5 parts of modified carbon fiber; A preparation method of a hard tungsten-based alloy material, comprising the following preparation steps: S1. Mix tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, and obtain a mixture through vacuum drying and ball milling; S2. Place the mixture in a pressure mold to press it into a preform, and then place the preform in a sintering furnace for primary sintering, secondary sintering, and cool it to room temperature to obtain a hard tungsten-based alloy material.

[0057] Among them, in step S1, the vacuum drying process: the drying temperature is 110°C, the vacuum degree is 6 Pa, and the drying time is 15 min. In step S1, ball milling is carried out using a ball mill, the ball-to-material ratio is 10:1, the rotation speed is 200 r / min, and the ball milling time is 24 h. In step S2, the pressing pressure is 300 MPa, and the pressing time is 50 s. In step S2, the primary sintering temperature is 1150°C, and the sintering time is 2 h; the secondary sintering temperature is 1480°C, and the sintering time is 60 min.

[0058] The modified carbon fiber is specifically prepared by the following steps: A1. Add 5 g of vanadium carbide and 1.3 g of microcrystalline cellulose to 110 mL of ethanol, stir evenly, add 0.6 mL of ethylene glycol, stir at 80°C for 5 h, cool to room temperature, filter, wash with deionized water 3 times, and dry in an 80°C oven for 10 min to obtain vanadium carbide modified by microcrystalline cellulose. A2. Add 9 g of acrylamide and 3.8 g of N,N-methylenebisacrylamide to 110 mL of deionized water, ultrasonicate at 40 KHz for 30 min, add 3 g of the grain refiner modified by microcrystalline cellulose, stir evenly, add 7 mL of a 20% ammonium persulfate solution by mass fraction, stir and react at 25°C for 40 min to form a gel, wash the gel with deionized water 3 times, and dry at room temperature for 24 h to obtain a composite gel. A3. Add 4.3 g of carbon fiber and 2.4 g of the composite gel to 55 mL of ethanol, stir evenly, heat up to 70°C, stir and mix for 30 min, cool to room temperature, filter, wash with deionized water 3 times, and dry in a 70°C oven for 10 min to obtain the modified carbon fiber.

[0059] Now, perform performance tests on the hard tungsten-based alloy materials prepared in Examples 1-3 and Comparative Examples 1-5.

[0060] Density test: Conduct the test according to the standard GB / T3850-2015, measure 3 different positions of the hard tungsten-based alloy material, and take the average value.

[0061] Hardness (HRA) test: Test the hardness value of the above-prepared hard tungsten-based alloy material according to the standard GB / T3849.1-2015.

[0062] Average grain size test: The average grain size of the prepared hard tungsten-based alloy material was tested in accordance with the standards GB / T3488.2-2018 and ISO4499-2:2008.

[0063] Mechanical property test: The flexural strength of the prepared hard tungsten-based alloy material was tested according to the standard GB / T6569-2006. The specimen size was 3mm×4mm×36mm, and the loading rate was 0.5mm / min. The impact toughness of the prepared hard tungsten-based alloy material was tested according to the standard GB / T1817-2017.

[0064] The test results are shown in Table 1.

[0065] Table 1 Performance detection of hard tungsten-based alloy materials prepared in Examples 1-3 and Comparative Examples 1-5

[0066] It can be seen from the data in Table 1 that the hard tungsten-based alloy materials prepared in Examples 1-3 have high mechanical strength and small grain size.

[0067] In Comparative Example 1, the modified carbon fiber prepared by replacing vanadium carbide modified with microcrystalline cellulose with vanadium carbide was added to the hard tungsten-based alloy material. Its mechanical properties decreased and the grain size increased, which proved that the microcrystalline cellulose coated on the surface of vanadium carbide was beneficial to the embedding of vanadium carbide into the composite gel system, avoiding the easy agglomeration of small-sized grain refiners, affecting the inhibition of the growth of tungsten carbide grains by the grain refiner, resulting in the decrease of the mechanical properties of the hard alloy. Moreover, the microcrystalline cellulose can be thermally decomposed to form a carbon network structure, forming metal carbide strengthening phases with cobalt powder, nickel powder, and iron powder, producing a combined strengthening effect of solid solution strengthening and dispersion strengthening, and increasing the mechanical properties of the hard alloy.

[0068] In Comparative Example 2, only acrylamide was selected, and in Comparative Example 3, only N,N-methylenebisacrylamide was selected to prepare the modified carbon fiber and added to the hard tungsten-based alloy material. Its mechanical properties decreased, which proved that the copolymerization of acrylamide and the cross-linking of the molecular chains of N,N-methylenebisacrylamide and acrylamide formed a three-dimensional network structure, which was beneficial to the formation of a dense nano-carbon network in the tungsten carbide alloy, inhibiting the growth of tungsten carbide grains during sintering and improving the mechanical strength of the hard alloy.

[0069] In Comparative Example 4, the modified carbon fiber prepared by replacing the composite gel with vanadium carbide modified by microcrystalline cellulose was added to the hard tungsten-based alloy material, and its mechanical properties decreased. This proved that the three-dimensional network carbonization formed by vanadium carbide modified by microcrystalline cellulose, acrylamide and N,N-methylenebisacrylamide could form a dense nano-carbon network covering the surface of tungsten carbide grains, hinder grain boundary migration and atomic diffusion, and inhibit the growth of tungsten carbide grains during sintering; the formed nano-carbon network served as a bridge to connect adjacent tungsten carbide grains, and absorbed stress to avoid crack generation, thus improving the mechanical strength of the hard alloy.

[0070] In Comparative Example 5, the modified carbon fiber prepared by replacing the aminated carbon fiber with carbon fiber was added to the hard tungsten-based alloy material, and its mechanical properties decreased. This proved that the composite gel was coated on the surface of the carbon fiber through a silane coupling agent, enabling the carbon fiber to coat at the grain boundaries of tungsten carbide, achieving the effect of grain refinement, improving the mechanical strength of the hard alloy, and the nano-carbon network generated by thermal decomposition grew with the carbon fiber as a template and was distributed at the grain boundaries of tungsten carbide, avoiding the decrease in the mechanical properties of the hard alloy caused by the agglomeration of the nano-carbon network.

[0071] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0072] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A hard tungsten-based alloy material, characterized in that: The raw materials include the following parts by weight: 90-95 parts of tungsten carbide powder, 2-3 parts of cobalt powder, 2-3 parts of nickel powder, 1-2 parts of iron powder, and 3-5 parts of modified carbon fiber; The modified carbon fiber is prepared by modifying the surface of the carbon fiber with a silane coupling agent and then mixing it with a composite gel; The silane coupling agent is γ-aminopropyltriethoxysilane; The composite gel is prepared by mixed reaction of a grain refiner modified by microcrystalline cellulose, acrylamide, N,N-methylenebisacrylamide and an initiator.

2. A hard tungsten-based alloy material according to claim 1, characterized in that: The modified carbon fiber is specifically prepared by the following steps: A1. Add the grain refiner and microcrystalline cellulose to ethanol, stir evenly, add ethylene glycol, stir at 70-80°C for 3-5h, cool to room temperature, filter, wash, and dry to obtain a grain refiner modified with microcrystalline cellulose; A2. Add acrylamide and N,N-methylenebisacrylamide to deionized water, add microcrystalline cellulose modified grain refiner after ultrasonication, stir evenly, add initiator, stir and react at 20-25°C for 30-40 minutes, take out the gel, wash the gel, and dry it to obtain a composite gel; A3. Add carbon fiber to ethanol and deionized water, stir evenly, add silane coupling agent, stir and react at 65-75°C for 1-2h, cool to room temperature, filter, wash and dry to obtain amino carbon fiber; A4. Add the amino carbon fiber and the composite gel into ethanol, stir evenly, heat to 60-70°C, stir for 20-30 minutes, cool to room temperature, filter, wash and dry to obtain modified carbon fiber.

3. A hard tungsten-based alloy material according to claim 2, characterized in that: In step A1, the ratio of the grain refiner, microcrystalline cellulose, ethanol and ethylene glycol is (4-5) g: (1.1-1.3) g: (90-110) mL: (0.4-0.6) mL.

4. A hard tungsten-based alloy material according to claim 2, characterized in that: In step A2, the amount ratio of acrylamide, N,N-methylenebisacrylamide, deionized water, microcrystalline cellulose modified grain refiner and initiator is (8-9) g: (3.6-3.8) g: (90-110) mL: (2.6-3) g: (5-7) mL.

5. A hard tungsten-based alloy material according to claim 2, characterized in that: In step A3, the ratio of the carbon fiber, ethanol, deionized water and silane coupling agent is (4-6) g: (25-35) mL: (8-12) mL: (1-2) g.

6. A hard tungsten-based alloy material according to claim 2, characterized in that: In step A4, the ratio of the amino carbon fiber, the composite gel and the ethanol is (4.1-4.3) g: (2.2-2.4) g: (45-55) mL.

7. The hard tungsten-based alloy material according to claim 1, characterized in that: The grain refiner is selected from any one of vanadium carbide, chromium carbide, niobium carbide and tantalum carbide.

8. The hard tungsten-based alloy material according to claim 1, characterized in that: The initiator is an ammonium persulfate solution with a mass fraction of 15-25%.

9. The hard tungsten-based alloy material according to claim 1, characterized in that: The carbon fiber has a diameter of 1-2µm and a length of 8-15µm.

10. A method for preparing a hard tungsten-based alloy material according to any one of claims 1 to 9, characterized in that: The method comprises the following preparation steps: S1, mixing tungsten carbide powder, cobalt powder, nickel powder, iron powder and modified carbon fiber, vacuum drying, and ball milling to obtain a mixture; S2. The mixed material is placed in a pressure mold and pressed into a preform, and the preform is placed in a sintering furnace for primary sintering, secondary sintering, and cooling to room temperature to obtain a hard tungsten-based alloy material.

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