Tungsten carbide hard alloy and preparation method thereof

Abstract

The invention discloses a tungsten carbide hard alloy and a preparation method thereof, and belongs to the technical field of hard alloys. The tungsten carbide hard alloy provided by the invention comprises the following preparation raw materials: WC, Co, Ni, Cu, Fe and Mn. The tungsten carbide hard alloy provided by the invention is composite material powder prepared by adopting a one-step method, and the high-entropy alloy is used as a binder, so that the preparation process is simplified, and the tungsten carbide hard alloy has good hardness and fracture toughness. The result of the embodiment shows that the hardness of the tungsten carbide composite material is 1109-1552 HV30, the fracture toughness of the tungsten carbide composite material is 8.35-12.89 MPa / m < 1 / 2 >, and the tungsten carbide composite material has good fracture toughness.

Description

Technical Field

[0001] The invention relates to the technical field of cemented carbides, and in particular to a tungsten carbide cemented carbide and a preparation method thereof. Background Art

[0002] WC cemented carbide is an alloy material made of WC, a compound of transition refractory metals, and bonding metals (such as Co, Ni, Fe) through powder metallurgy. Cemented carbide has a series of excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance, and corrosion resistance. In particular, its high hardness and wear resistance remain basically unchanged even at a temperature of 500 ℃, and it still has a high hardness at 1000 ℃. In view of its excellent properties, cemented carbide is widely used as a tool material.

[0003] High entropy alloys have excellent friction and wear properties, corrosion resistance, high temperature resistance and other properties, which improve the comprehensive performance of cemented carbide. In addition, the sintering process of WC-HEA cemented carbide is similar to that of WC-Co, making it an ideal material for the bonding phase in WC cemented carbide and capable of synthesizing WC cemented carbide that meets higher requirements. Luo et al. prepared a 10wt.% Al-containing high entropy alloy by spark plasma sintering. x Ultrafine WC cemented carbide combined with CoCrCuFeNi (x is the molar content of aluminum, ranging from 0-1.5) high entropy alloy. Due to the slow diffusion effect of HEA binder, the WC grain growth activation energy of WC-HEA cemented carbide is significantly higher than that of WC-Co alloy. Therefore, the WC grain growth is inhibited during the sintering process, and an ultrafine microstructure can be obtained. The obtained 10 wt.% Al addition 0.5 WC-HEA cemented carbide with CoCrCuFeNi high entropy alloy binder exhibits the best Vickers hardness and fracture toughness, which are 2071±6 HV, respectively. 30 and 10.3±0.1 MPa·m 1 / 2 However, the current process of preparing WC-HEA cemented carbide is relatively complicated, with a long cycle, low efficiency and high energy consumption. Therefore, in order to promote the sustainable development of the cemented carbide industry, it is particularly important to explore a simpler and more environmentally friendly preparation method. Summary of the invention

[0004] The main purpose of the present invention is to provide a tungsten carbide hard alloy and a preparation method thereof. The tungsten carbide hard alloy provided by the present invention is directly mixed with a metal binder under air conditions, wherein the metal binder synthesizes a high entropy alloy during the ball milling process, plays a role in toughening WC and inhibiting its grain growth.

[0005] In order to solve the above technical problems, the present invention discloses a tungsten carbide cemented carbide. The raw materials for preparing the tungsten carbide cemented carbide include: WC, Co, Ni, Cu, Fe and Mn, wherein Co, Ni, Cu, Fe and Mn are synthesized into a high entropy alloy binder during the preparation process.

[0006] According to one embodiment of the present invention, the mass ratio of the high entropy alloy synthesized by the above-mentioned WC and Co, Ni, Cu, Fe, and Mn is 10:1, and the molar ratio of Co, Ni, Cu, Fe, and Mn is 1:1:1:1:1.

[0007] According to one embodiment of the present invention, the preparation method of the above-mentioned tungsten carbide cemented carbide comprises: ball milling and sintering WC, Co, Ni, Cu, Fe and Mn to obtain tungsten carbide cemented carbide.

[0008] According to one embodiment of the present invention, the ball milling comprises: mixing WC and Co, Ni, Cu, Fe and Mn and ball milling them to obtain WC-CoNiCuFeMn composite powder.

[0009] According to one embodiment of the present invention, the ball-to-material ratio of the mixed ball milling is 2:1.

[0010] According to one embodiment of the present invention, the rotation speed of the mixing ball mill is 300 r / min, and the mixing ball milling time is 2 h.

[0011] According to one embodiment of the present invention, the sintering pressure is 30-50 MPa, the sintering temperature is 600-1400° C., and the sintering time is 5-30 min.

[0012] According to one embodiment of the present invention, the sintering includes a first sintering and a second sintering performed sequentially; the first sintering is performed at a temperature of 600°C for 5 to 10 min; the second sintering is performed at a temperature of 1200 to 1400°C for 10 to 20 min.

[0013] According to one embodiment of the present invention, the atmosphere of the mixing material is air atmosphere.

[0014] According to one embodiment of the present invention, the sintering atmosphere is a vacuum atmosphere. Compared with the prior art, the present application can obtain the following technical effects: 1) The present invention provides a tungsten carbide cemented carbide and a preparation method thereof, wherein the raw materials for preparing the tungsten carbide cemented carbide include: WC, Co, Ni, Cu, Fe and Mn. The tungsten carbide cemented carbide provided by the present invention is directly mixed with a metal binder under air conditions, wherein the metal binder synthesizes a high entropy alloy during the ball milling process, which plays a role in toughening WC and inhibiting the growth of WC grains, thereby ensuring the hardness of the material while also being beneficial to improving the toughness of the composite material; secondly, mixing the materials in the air simplifies the process flow and greatly improves work efficiency. The results of the embodiment show that the hardness of the tungsten carbide composite material of the present invention is 1109-1552 HV 30 , fracture toughness is 8.35~12.89 MPa / m 1 / 2 , indicating that the tungsten carbide composite material of the present invention has good fracture toughness.

[0015] Of course, any product implementing the present invention does not necessarily need to achieve all of the above technical effects at the same time. DETAILED DESCRIPTION

[0016] The following examples are used to explain the implementation methods of the present application in detail, so that the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0017] The invention provides a tungsten carbide hard alloy. The raw materials for preparing the tungsten carbide hard alloy include: WC, Co, Ni, Cu, Fe and Mn, wherein Co, Ni, Cu, Fe and Mn are synthesized into a high entropy alloy binder during the preparation process.

[0018] The raw materials for preparing tungsten carbide cemented carbide provided by the present invention include WC, Co, Ni, Cu, Fe and Mn. In the present invention, the particle sizes of the WC, Co, Ni, Cu, Fe and Mn are independently preferably 1~3 μm. In the present invention, the ball milling time is 2~30 h; in an embodiment of the present invention, the ball milling time is specifically 2, 10, 20, 30 h. In a specific embodiment of the present invention, the mass ratio of WC to (Co, Ni, Cu, Fe and Mn) is 1:1, wherein the molar ratio of Co, Ni, Cu, Fe and Mn is 1:1:1:1:1. In the present invention, the atmosphere during the ball milling process is in an air environment. The present invention has no special requirements on the sources of the WC, Co, Ni, Cu, Fe and Mn, and WC, Co, Ni, Cu, Fe and Mn from sources familiar to those skilled in the art are used or prepared by themselves.

[0019] In the present invention, the particle size of the tungsten carbide powder is preferably 1-3 μm, and the purity of the tungsten carbide is preferably ≥99.5%; the present invention has no special requirements on the source of the tungsten carbide powder, and commercially available products familiar to those skilled in the art can be used. The particle size of the cobalt powder, copper powder, nickel powder, iron powder and manganese powder is preferably 1-5 μm, and the purity of the tungsten carbide is preferably ≥99.0%. The present invention has no special requirements on the source of the titanium powder, and commercially available products familiar to those skilled in the art can be used. In the present invention, the mass ratio of the tungsten carbide powder to the cobalt powder, copper powder, nickel powder, iron powder and manganese powder is 10:1.

[0020] In the present invention, the ball milling is preferably carried out in the presence of a dispersant; the dispersant is preferably ethanol, and the purity of the ethanol is preferably ≥99.7%. In the present invention, the amount of the ethanol is preferably 0.5 mL / 10g raw material, based on the total mass of the raw materials of tungsten carbide powder, cobalt powder, copper powder, nickel powder, iron powder and manganese powder. The dispersant of the present invention plays a role in assisting ball milling, which is conducive to the uniform dispersion of the final product WC-CoNiCuFeMn composite powder. In the present invention, the atmosphere of the ball milling is preferably an inert atmosphere and air, and is further preferably an air atmosphere. In the present invention, the purity of the argon gas is preferably ≥99.9%.

[0021] In the present invention, the rotation speed of the ball mill is preferably 300-450 r / min, and further preferably 300 r / min; the ball-to-material ratio is preferably 2:1. In the invention, the equipment used for the ball mill is preferably a high-energy planetary ball mill, the ball mill jar used is preferably a stainless steel ball mill jar, and the grinding balls used are preferably stainless steel balls. In the present invention, the grinding balls are preferably stainless steel balls with diameters of 6 mm, 8 mm and 10 mm, and the mass ratio of the stainless steel balls with diameters of 6 mm, 8 mm and 10 mm is preferably 6:3:1. The present invention has no special requirements on the sources of the high-energy planetary ball mill, stainless steel ball mill jar and stainless steel balls, and high-energy planetary ball mills, stainless steel ball mill jars and stainless steel balls with sources familiar to those skilled in the art can be used. In the process of ball milling described in the present invention, cobalt powder, copper powder, nickel powder, iron powder and manganese powder synthesize high entropy alloys and toughen WC cemented carbide.

[0022] In the present invention, the ball mill preferably adopts the method of forward and reverse ball milling, and the forward ball milling and reverse ball milling are stopped for 30 minutes; specifically: first forward ball milling for 1 to 2 hours, stop for 30 minutes, then reverse ball milling for 1 to 2 hours, and repeat this process; the present invention adopts the method of forward and reverse ball milling to prevent agglomeration during the ball milling process. In the present invention, the ball milling time is preferably 2 to 30 hours, and more preferably 2 hours; the ball milling time does not include the downtime. The present invention adopts the method of forward and reverse ball milling to make the structure of the WC composite powder more uniform.

[0023] In the present invention, the ball milling atmosphere is preferably argon and air atmosphere, and more preferably air atmosphere. In the present invention, the purity of the argon is preferably ≥99.9%.

[0024] In the present invention, the sintering pressure is preferably 30-50 MPa, and more preferably 35-45 MPa; the sintering temperature is preferably 600-1400 °C. In the present invention, the sintering preferably includes a first sintering and a second sintering performed sequentially; the temperature of the first sintering is preferably 600 °C, and the time is preferably 5-10 min; the temperature of the second sintering is preferably 1200-1400 °C, and the time is preferably 10-30 min. In the present invention, the sintering time refers to the insulation time at the sintering temperature. The present invention first sintered the ball mill mixture at 600 °C for 5-10 min to allow surface gas to be resolved, which is beneficial to later densification.

[0025] The present invention preferably heats from room temperature to the first sintering temperature; the present invention preferably first heats to 571°C at a rate of 110°C / min, and then heats to 600°C at a rate of 20-30°C / min. The heating rate of the present invention is first high and then low in order to improve the sintering efficiency, while ensuring the accuracy of the sintering temperature, which is conducive to sintering densification.

[0026] After the first sintering, the present invention preferably heats up from the first sintering temperature to the second sintering temperature. The present invention preferably first heats up to 1100 ° C at a heating rate of 80-100 ° C / min, and then heats up from 1100 ° C to the second sintering temperature at a heating rate of 15-70 ° C / min. The present invention first heats up to 1100 ° C at a larger heating rate, and then heats up to the final set temperature at a smaller heating rate, which is beneficial to improving the sintering efficiency, while ensuring the accuracy of the sintering temperature, which is beneficial to the densification of the sintering. In the present invention, the sintering atmosphere is preferably a vacuum atmosphere or an inert atmosphere, and the inert atmosphere is preferably an argon atmosphere.

[0027] The present invention preferably places the ball-milled mixture into a graphite mold with a diameter of 10 mm for sintering. The present invention has no special requirements for the equipment used for sintering, and sintering equipment familiar to those skilled in the art can be used; in a specific embodiment of the present invention, a spark plasma sintering furnace is preferably used for sintering.

[0028] After sintering, the sintered product is preferably cooled under a protective atmosphere. In the present invention, the protective atmosphere is preferably an argon atmosphere. The present invention uses a protective atmosphere for cooling in order to prevent oxidation during the cooling process and to accelerate the cooling time.

[0029] During the sintering process of the present invention, WC, Co, Ni, Cu, Fe and Mn undergo atomic interdiffusion to form a WC-CoNiCuFeMn composite powder. CoNiCuFeMn is a high entropy alloy. Compared with traditional alloys, it has excellent mechanical properties, corrosion resistance, high temperature resistance, and friction and wear properties. It can not only toughen WC cemented carbide, but also inhibit the growth of WC grains during the sintering process. Therefore, the obtained composite material has good fracture toughness.

[0030] The tungsten carbide hard alloy and the preparation method thereof provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention. Example 1

[0031] According to the raw material ratio and reaction conditions in Tables 1 and 2, the weighed WC, Co, Ni, Cu, Fe and Mn raw materials were placed in a stainless steel ball mill with a capacity of 125 mL. Stainless steel balls with diameters of 6 mm, 8 mm and 10 mm were used, with a mass ratio of 6:3:1 and a ball-to-material ratio of 2:1. 30 g of cemented carbide balls and 15 g of raw materials were added each time. After repeated gas washing in the transition chamber of the glove box, the raw materials were placed in the operating chamber (the gas used was argon), and the sealing cover was covered to ensure that the argon environment in the tank was taken out and placed in the ball mill. The ball mill speed was 300 r / min, and the ball milling was carried out for 2 h. The forward and reverse rotations were alternately operated, and the forward rotation was stopped for 30 min and then reversed for 1 h. Finally, the WC-CoNiCuFeMn composite powder was obtained by filtration through a sieve.

[0032] SPS sintering is carried out in a SPS-3.20MK-IV spark plasma machine. In a glove box, the mixed powder is filled into a graphite mold with a diameter of 20 mm for spark plasma sintering. The mold is placed on a sintering table, filled with argon protective gas, pressurized, and the sintering pressure is adjusted. The pressure is set to 30 MPa, and the temperature is increased from room temperature to 571 °C at a heating rate of 110 °C / min, and from 571 °C to 600 °C at a heating rate of 30 °C / min. Keep it at 600 °C for 10 min, and from 600 °C to 1100 °C at a heating rate of 100 °C / min, and then from 1100 °C to 1200 °C at a heating rate of 25-50 °C / min. After reaching the sintering temperature, keep it warm for 5 min, then flush with protective gas, and after cooling, tungsten carbide cemented carbide is obtained. Example 2

[0033] Except for the loading and unloading, which were all carried out in air, the remaining operations were carried out according to the method of Example 1 to prepare tungsten carbide cemented carbide. The specific reaction conditions are shown in Table 2. Example 3

[0034] Except that the loading and unloading were all carried out in air and the ball milling time was 10 h, the remaining operations were carried out according to the method of Example 1 to prepare tungsten carbide cemented carbide. The specific reaction conditions are shown in Table 2. Example 4

[0035] Except that the loading and unloading were all carried out in air and the ball milling time was 20 h, the remaining operations were carried out according to the method of Example 1 to prepare tungsten carbide cemented carbide. The specific reaction conditions are shown in Table 2. Example 5

[0036] Except for charging and taking materials, the ball milling time is 2 h, the mold is placed on the sintering table, filled with argon protective gas, pressurized, and the sintering pressure is regulated. The pressure is set to 30 MPa, and the temperature is increased from room temperature to 571 ° C at a heating rate of 110 ° C / min, and from 571 ° C to 600 ° C at a heating rate of 30 ° C / min, and kept at 600 ° C for 10 min, and from 600 ° C to 1150 ° C at a heating rate of 100 ° C / min, and then from 1150 ° C to 1250 ° C at a heating rate of 25-50 ° C / min, and kept for 5 min after reaching the sintering temperature, and then the protective gas is rushed into, and after cooling, tungsten carbide cemented carbide is obtained. The remaining operations are performed according to the method of Example 1 to prepare tungsten carbide cemented carbide, and the specific reaction conditions are shown in Table 2. Example 6

[0037] Except for charging and taking materials, the ball milling time is 2 h, the mold is placed on the sintering table, filled with argon protective gas, pressurized, and the sintering pressure is regulated. The pressure is set to 30 MPa, and the temperature is increased from room temperature to 571 ° C at a heating rate of 110 ° C / min, and from 571 ° C to 600 ° C at a heating rate of 30 ° C / min, and kept at 600 ° C for 10 min, and from 600 ° C to 1200 ° C at a heating rate of 100 ° C / min, and then from 1200 ° C to 1300 ° C at a heating rate of 25-50 ° C / min, and kept for 5 min after reaching the sintering temperature, and then the protective gas is rushed into, and after cooling, tungsten carbide cemented carbide is obtained. The remaining operations are performed according to the method of Example 1 to prepare tungsten carbide cemented carbide, and the specific reaction conditions are shown in Table 2.

[0038] The specific raw material ratios in Examples 2 to 6 are shown in Table 1.

[0039]

[0040] The sintered tungsten carbide hard alloys of Examples 1 to 6 were ground and polished for microstructure and performance testing. The performance testing was performed using a nanohardness tester. The performance is shown in Table 3.

[0041]

[0042] From the results in Table 2 and Table 3, it can be seen that the fracture toughness of the tungsten carbide hard alloy prepared by using WC as raw material in the present invention is 8.35~10.81 MPa / m 1 / 2 , hardness is 1109.6~1552.0 HV 30 , indicating that the tungsten carbide cemented carbide of the present invention has higher toughness and hardness.

[0043] The above description shows and describes several preferred embodiments of the present application, but as before, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the present application through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present application, and shall be within the scope of protection of the claims attached to the present application.

Claims

1. A tungsten carbide hard alloy, characterized in that: The raw materials for preparing the tungsten carbide hard alloy include: WC, Co, Ni, Cu, Fe and Mn, wherein Co, Ni, Cu, Fe and Mn are synthesized into a high entropy alloy binder during the preparation process.

2. The tungsten carbide cemented carbide according to claim 1, characterized in that: The mass ratio of the high entropy alloy synthesized by WC and Co, Ni, Cu, Fe and Mn is 10:1, wherein the molar ratio of Co, Ni, Cu, Fe and Mn is 1:1:1:1:

1.

3. The method for preparing tungsten carbide cemented carbide according to any one of claims 1 to 2, characterized in that: include: WC, Co, Ni, Cu, Fe and Mn are ball-milled and sintered to obtain tungsten carbide cemented carbide.

4. The method for preparing tungsten carbide cemented carbide according to claim 3, characterized in that: include: The ball milling comprises: mixing WC with Co, Ni, Cu, Fe and Mn and ball milling them to obtain WC-CoNiCuFeMn composite powder.

5. The method for preparing tungsten carbide cemented carbide according to claim 3, characterized in that: The ball-to-material ratio of the mixed ball mill is 2:

1.

6. The method for preparing tungsten carbide cemented carbide according to claim 3 or 5, characterized in that: The rotating speed of the mixing ball mill is 300 r / min, and the mixing ball milling time is 2 h.

7. The method for preparing tungsten carbide cemented carbide according to claim 4, characterized in that: The sintering pressure is 30-50 MPa, the sintering temperature is 600-1400°C, and the sintering time is 5-30 min.

8. The method for preparing tungsten carbide cemented carbide according to claim 7, characterized in that: The sintering includes a first sintering and a second sintering performed sequentially; the temperature of the first sintering is 600°C and the time is 5-10 min; the temperature of the second sintering is 1200-1400°C and the time is 10-20 min.

9. The method for preparing tungsten carbide cemented carbide according to claim 2 or 3, characterized in that: The atmosphere of the mixture is air atmosphere.

10. The method for preparing tungsten carbide cemented carbide according to claim 7 or 8, characterized in that: The sintering atmosphere is a vacuum atmosphere.

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