Cobalt-based tungsten carbide composite hard alloy and preparation method thereof

Abstract

The invention provides a cobalt-based tungsten carbide composite hard alloy material and a preparation method thereof. The hard alloy material is prepared by sintering a mixture of WC, A powder, B powder and optional C powder through a discharge plasma technology, and based on 100 wt.% of the total weight of the powder mixture, the content of the WC powder is 90.0 wt.%-94.5 wt.%; the sum of the content of the powder A, the content of the powder B and the content of the optional powder C is 5.5 wt.%-10.0 wt.%, A is Co, B is Cr3C2, and C is VC. The hard alloy material has high hardness, high strength and high toughness at the same time.

Description

Technical Field

[0001] The present invention belongs to the field of powder metallurgy and relates to a method for preparing a metal powder material, and more specifically, to a high-performance cobalt-based tungsten carbide composite cemented carbide and a method for preparing the same. Background Art

[0002] Due to their excellent hardness, wear resistance, and flexural strength, cemented carbide materials are widely used in cutting tools, mining, high-pressure scientific research, and superhard material synthesis. Cemented carbide materials are primarily made of tungsten carbide (WC) as the hard phase and cobalt (Co) as the binder phase, produced through a powder metallurgy process. However, traditional preparation methods (such as hot pressing and hot isostatic pressing) have problems such as high sintering temperatures, long holding times, high energy consumption, and the tendency to cause grain coarsening, which affect the overall performance of the material.

[0003] Spark plasma sintering (SPS) technology mainly prepares materials by introducing DC pulse current between powder particles. It is a new sintering technology that integrates plasma activation, pressurization and heating. It has the characteristics of rapid heating and short sintering time. It can effectively avoid grain coarsening caused by long sintering time, thereby reducing material performance. It has now become an effective method for preparing high-density, fine-grained cemented carbide.

[0004] However, in existing research, it is often difficult to achieve both toughness and strength when pursuing high hardness in cemented carbide materials. Although cemented carbide with high cobalt content has good toughness, it often suffers from insufficient hardness. For example, Sunil, BR et al. reported in the paper "Microwave sintering of nanocrystalline WC-12Co: Challenges and perspectives" that the fracture toughness of WC-12Co can reach up to 15.0MPa·m 1 / 2 , but its hardness is only 1466HV, and the hardness of the material edge area is even lower than 1000HV; CN102382997A discloses a WC-Co cemented carbide with a maximum bending strength of 3100MPa, while the hardness of the corresponding component alloy is less than 1300HV30. These low-hardness cemented carbides generally cannot meet the performance requirements of harsh working environments such as high temperature and high pressure (high-pressure testing, superhard material synthesis), high wear resistance, and corrosion resistance. High-hardness cemented carbide materials are also easily restricted in use due to reasons such as excessive brittleness and difficulty in processing.

[0005] Therefore, rationally controlling the binder phase content in cemented carbide is crucial for improving material properties. Furthermore, the selection and ratio of additives, powder processing methods, and sintering processes also play a crucial role in influencing material properties. Therefore, developing a cemented carbide material that maintains high hardness while also exhibiting good fracture toughness and flexural strength by optimizing the component ratio, improving the powder processing methods, and sintering processes is crucial for improving the performance of cemented carbide and broadening its application in harsh service environments. Summary of the Invention

[0006] The inventors of the present invention have discovered that in the prior art, simple ball milling is mostly performed using cemented carbide balls during the preliminary powder processing. The cemented carbide balls have a relatively large weight, while the cobalt powder has a relatively low density and a soft texture. When the heavy cemented carbide balls rotate in the ball mill, it is difficult to achieve flexible speed changes due to their large inertia. The centrifugal force and impact force generated cannot effectively drive the lightweight cobalt powder to participate in the movement, resulting in uneven distribution of the cobalt powder in the ball mill and prone to local accumulation. In addition, when there are many types of additives, due to density differences, it is also very easy for the additives to be unevenly distributed in the material. The advantages of the synergistic effect of ultrasonic resonance and zirconia ball milling are: ultrasonic resonance uses high-frequency vibration and cavitation effect to break up the agglomeration of additives with micro-flow impact and turbulence, eliminate phase boundary barriers, and achieve uniform mixing at the molecular level. At the same time, the high-temperature and high-pressure environment generated by the cavitation bubble burst accelerates the mutual diffusion of additives, greatly shortening the mixing time, which is especially suitable for multi-component complex systems; zirconia has a low relative density and light weight. On the one hand, it has low inertia and flexible movement during ball milling, and can collide with materials and additives at high frequency. On the other hand, using zirconia balls of various specifications for simultaneous ball milling can make the materials and additives more evenly distributed during the ball milling process, which is beneficial to improving the uniformity of material properties.

[0007] The purpose of the present invention is to make up for the deficiencies in the above-mentioned prior art and provide a high-performance cobalt-based tungsten carbide composite cemented carbide and a preparation method thereof. The cemented carbide material has the characteristics of high relative density and uniform structure. While maintaining high hardness, it has good fracture toughness and bending strength, and is suitable for high-pressure scientific research, superhard material synthesis and other fields.

[0008] According to a first aspect of the present invention, a cobalt-based tungsten carbide composite cemented carbide material is provided, wherein the cemented carbide material is prepared by sintering a mixture of WC, A powder, B powder and optional C powder by spark plasma technology, based on 100wt.% of the total weight of the powder mixture, the content of WC powder is 90.0wt.% to 94.5wt.%, preferably 92.0wt.% to 94.5wt.%; the sum of the contents of A powder, B powder and optional C powder is 5.5wt.% to 10.0wt.%, preferably 5.5wt.% to 8.0wt.%, wherein A is Co, B is Cr3C2, and C is VC.

[0009] Preferably, the content of A powder is 1.0 wt.% to 6.0 wt.%, more preferably 4.0 wt.% to 6.0 wt.%.

[0010] Preferably, the content of B powder is 0.5 wt.% to 2.0 wt.%, more preferably 0.5 wt.% to 1.5 wt.%.

[0011] Preferably, the content of C powder is 0.0 wt.% to 2.0 wt.%, more preferably 0.0 wt.% to 0.5 wt.%.

[0012] Preferably, the relative density of the cemented carbide material is not less than 99.9%.

[0013] Preferably, the cemented carbide material does not contain other impurity phases except the main phase.

[0014] Preferably, the hardness of the cemented carbide material is 1900HV30 to 2300HV30, preferably 2000HV30 to 2300HV30.

[0015] Preferably, the bending strength of the cemented carbide material is above 2000 MPa, more preferably above 2400 MPa.

[0016] Preferably, the fracture toughness of the cemented carbide material is 7.5 MPa·m 1 / 2 ~10.0MPa·m 1 / 2 , more preferably 7.9 MPa·m 1 / 2 ~10.0MPa·m 1 / 2 .

[0017] According to a second aspect of the present invention, there is provided a method for preparing the cobalt-based tungsten carbide composite cemented carbide according to the present invention, the steps comprising:

[0018] 1) Additive Mixing: Add powder A, powder B, and optionally powder C according to the ratio into an acoustic resonance device at room temperature, and mix the additive powders thoroughly in a nitrogen atmosphere to obtain a first powder mixture;

[0019] 2) Powder mixing: placing the WC powder, the first powder mixture obtained in step 1) and the ball milling medium into a cemented carbide ball mill for ball milling, and drying the obtained mixed powder to obtain a second powder mixture;

[0020] 3) Mold filling: The second powder mixture obtained in step 2) is placed in a graphite female mold and pre-pressed using a hydraulic press with a pre-pressing pressure of 5 to 20 MPa and a holding time of 5 minutes;

[0021] 4) Sintering: Place the assembled graphite mold in a spark plasma sintering system, set the axial pressure to 0-50 MPa, evacuate to below 5 Pa, and sinter with power on; set the heating rate to 5°C-30°C / min, the maximum sintering temperature to 1250°C-1450°C, preferably 1300°C-1400°C; and hold the temperature for 5-15 minutes;

[0022] 5) Sampling: The sample is taken out by using a hydraulic press, and the graphite on the surface of the sample is polished and removed to obtain a cobalt-based tungsten carbide composite cemented carbide material.

[0023] Preferably, the purity of the WC powder is not less than 99.9%, and the powder particle size is 0.1-0.6 μm.

[0024] Preferably, the purity of the Co powder is not less than 99.7%, and the powder particle size is 0.5-1.0 μm.

[0025] Preferably, the purity of the Cr3C2 powder is not less than 99.9%, and the powder particle size is 0.1-1.0 μm.

[0026] Preferably, the purity of the VC powder is not less than 99.5%, and the powder particle size is 0.1-1.0 μm.

[0027] For example, the WC powder, Co powder, Cr 3 C 2 powder and VC powder may be commercially available pure phase powders.

[0028] Preferably, the ball milling medium in step 2) is one or more selected from methanol, ethanol or acetone.

[0029] Preferably, the second powder mixture is placed at the center of the graphite mold, and the height difference between the exposed pressure heads at both ends of the graphite mold is no more than 5 mm.

[0030] Preferably, the graphite female mold and the second powder mixture are separated by a graphite bushing or graphite paper, and the graphite pressing head and the second powder mixture are separated by a graphite sheet or graphite paper; the assembled graphite mold is wrapped with a layer of graphite felt for thermal insulation.

[0031] Preferably, in step 2), the grinding balls used for powder mixing are zirconia balls, and the grinding ball specifications are 5 mm:10 mm:15 mm=5:3:2.

[0032] Preferably, in step 4), during the heating process, the temperature is kept at 50-80°C away from the maximum sintering temperature for 5-15 minutes; when the sintering temperature is less than 50°C away from the maximum sintering temperature, the heating rate is ≤10°C / min.

[0033] Preferably, in step 4), the axial pressure during the heating process is 5 to 20 MPa, and during the cooling process, when the temperature drops to 100 to 150°C from the maximum sintering temperature, the pressure is increased to 20 to 50 MPa, preferably 30 to 50 MPa, and the pressure is maintained at this temperature for 5 to 15 minutes; constant pressure sintering is performed at the target pressure until sintering is completed.

[0034] More preferably, the cooling method is controlled cooling, and the cooling rate is ≤50°C / min.

[0035] Preferably, the high-performance cobalt-based tungsten carbide composite hard alloy obtained by the method of the present invention has a relative density of not less than 99.9%, and contains no other impurity phases except the main phase.

[0036] Preferably, the high-performance cobalt-based tungsten carbide composite cemented carbide obtained according to the method of the present invention has a hardness of 1900HV30 to 2300HV30, preferably 2000HV30 to 2300HV30.

[0037] Preferably, the fracture toughness of the high-performance cobalt-based tungsten carbide composite hard alloy obtained by the method of the present invention is 7.5 MPa·m 1 / 2 ~10.0MPa·m 1 / 2 , more preferably 7.9 MPa·m 1 / 2 ~10.0MPa·m 1 / 2 .

[0038] The present invention has the following beneficial effects:

[0039] 1. The present invention provides a high-performance cobalt-based tungsten carbide composite hard alloy and its preparation method, which has significant advantages. The method uses commercial powder as raw material, which is widely available and cost-effective.

[0040] 2. The powder processing method provided by this invention, which combines ultrasonic resonance with zirconia ball milling, overcomes the problems of uneven cobalt powder distribution and multi-component additive mixing caused by the weight of the balls in traditional cemented carbide ball milling. Ultrasonic resonance breaks down additive agglomerates, achieving uniform mixing at the molecular level and accelerating additive diffusion. Zirconia balls have low density, low inertia, and flexible movement. The combination of various ball sizes allows for high-frequency collision and uniform dispersion of materials, significantly improving powder mixing uniformity.

[0041] 3. Through the innovative sintering process of precisely controlling the temperature and pressure fields, the binder phase is enabled to fully flow during the sintering process, achieving an effect similar to liquid phase sintering. This innovative method breaks through the limitations of traditional solid phase sintering.

[0042] 4. The prepared cemented carbide material has excellent comprehensive properties: the microstructure is uniform and dense, the relative density exceeds 99.9%; while maintaining a high hardness of 1900HV30~2300HV30, it also has a strength of 7.5MPa·m 1 / 2 -10.0MPa·m 1 / 2 The excellent fracture toughness and bending strength of more than 2000MPa have successfully solved the technical problem of balancing high hardness, high strength and high toughness in the field of cemented carbide.

[0043] 5. The process has good repeatability and high production efficiency, providing a reliable technical solution for the industrial production of high-performance cemented carbide. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is an energy spectrum diagram of the powder obtained in step 2) of Example 1 of the present invention after the synergistic effect of ultrasonic resonance and zirconia ball milling.

[0045] Figure 2 This is a microstructure diagram of the cemented carbide material prepared according to Example 1.

[0046] Figure 3 This is the energy spectrum of the cemented carbide material prepared according to Example 1.

[0047] Figure 4 This is the energy spectrum of the powder after simple ball milling using a cemented carbide ball according to step 1) of Comparative Example 2.

[0048] Figure 5 The microstructure photo and energy spectrum diagram of the cemented carbide material prepared according to Comparative Example 2 are shown. DETAILED DESCRIPTION

[0049] The present invention is further described below by way of examples, but the embodiments of the present invention are not limited thereto.

[0050] In the following examples, a graphite bushing / carbon paper is first assembled with a graphite die. A lower punch is then placed into the die, along with a graphite sheet, ensuring it fits snugly against the punch. A proportionally mixed powder is then loaded into the die. Finally, the graphite sheet / paper and upper punch are placed in sequence, and a hydraulic press applies preload and maintains pressure. After this is complete, the die is wrapped with high-temperature graphite felt. The dimensions of the graphite die and punch are determined by the desired sample size.

[0051] The spark plasma sintering systems used in the following examples are from SINTER LAND, Japan, and are model LABOX-350 and LABOX-6020. Spark plasma sintering (SPS) encompasses pulsed current pressure sintering, electric field-assisted sintering, and pulsed current rapid sintering. It should be noted that sintering cemented carbide materials using the methods described herein using equipment from other manufacturers and models falls within the scope of this invention.

[0052] The density results in the following examples were measured using the Archimedes displacement method;

[0053] The hardness test was obtained using a Vickers hardness tester, and the average value of 5 to 10 tests was taken as the final result; the fracture toughness test was in accordance with the international standard ISO 28079-2009 "Hardmetals-Palmqvist toughness test", measuring and calculating the total length of the four cracks at the indentation tip, and combining the Vickers hardness value of the sample under the indentation to calculate the fracture toughness K IC The bending strength test was carried out according to the national standard GB / T3851-2015 "Determination of transverse fracture strength of cemented carbide" for sample preparation and experiments.

[0054] Example 1

[0055] Prepare according to the following steps High-performance cobalt-based tungsten carbide composite hard alloy, wherein the composite powder mass ratio WC: Co: Cr3C2: VC = 94.5: 5: 0.5: 0

[0056] 1) Additive mixing: Co powder and Cr3C2 powder were weighed in proportion, placed in a Hummingbird HAM2000 ultrasonic resonance device, and reacted in a nitrogen atmosphere at room temperature for 2 hours.

[0057] 2) Powder Mixing: Place 120g of the WC weighed in the above mass ratio and the mixed additive powder obtained in step 1) into a carbide ball mill and ball mill. Zirconia balls are used for the milling, and the ball-to-material ratio is 2:1. To further promote uniform mixing of the powders, ethanol is added as the milling medium. The liquid-to-solid ratio is 0.7ml / g, and the milling speed is 1000 rpm for 24 hours. The milled powder is dried in a dryer at 70°C for 6-7 hours. The dried powder is then passed through a 160-mesh sieve and dried in a drying oven at 120°C for 4 hours.

[0058] 3) Mold filling: The alloy powder obtained after drying in step 2) is placed in a graphite female mold and pre-pressed using a manual hydraulic press with a pre-pressing pressure of 10 MPa and a holding time of 5 minutes.

[0059] 4) Sintering: Place the assembled graphite mold in the SPS sintering system, set the initial axial pressure to 10 MPa, evacuate to below 5 Pa, and turn on the power for sintering; heat to 1330°C at 20°C / min and keep warm for 10 minutes; after the insulation is completed, heat to 1380°C at 8°C / min, then cool to 1230°C at 40°C / min, pressurize to 50 MPa, hold the pressure for 5 minutes, and then continue to cool to 800°C at 40°C / min to end the sintering and cool with the furnace.

[0060] 5) Sampling: The sample is taken out using a hydraulic press, and the graphite on the sample surface is polished and removed to obtain a high-performance cobalt-based tungsten carbide composite cemented carbide. The specific performance parameters are shown in Table 1.

[0061] Table 1: Performance test results of cemented carbide materials prepared in Example 1

[0062]

[0063] Figure 2 is a microstructure diagram of the cemented carbide material prepared according to Example 1, and Figure 3 This is the energy spectrum of the cemented carbide material prepared according to Example 1. The WC grains are small, densely distributed, and micron-sized. There is no significant difference in grain size, and the overall grain size is small, with no obvious abnormal growth. The elements are relatively diffusely distributed throughout the field of view, with no obvious element aggregation or depletion areas. The elements are not distributed in isolation, but are intertwined and coordinated throughout the material.

[0064] Example 2

[0065] Prepare according to the following steps High-performance cobalt-based tungsten carbide composite hard alloy, wherein the composite powder mass ratio WC: Co: Cr3C2: VC = 93: 5: 1.5: 0.5

[0066] 1) Additive mixing: Co powder, Cr3C2 powder and VC powder were weighed in proportion, placed in a Hummingbird HAM2000 ultrasonic resonance device, and reacted in a nitrogen atmosphere at room temperature for 2 hours.

[0067] 2) Powder Mixing: Place 890g of the WC weighed in the above mass ratio and the mixed additive powder obtained in step 1) into a carbide ball mill and ball mill. Zirconia balls are used for the milling, with a ball-to-material ratio of 2:1. Acetone is added as the milling medium, with a liquid-to-solid ratio of 0.7ml / g. The milling speed is 1000 rpm, and the milling time is 24 hours. The milled powder is dried in a dryer at 70°C for 6-7 hours. The dried powder is then passed through a 160-mesh sieve and dried in a drying oven at 120°C for 4 hours.

[0068] 3) Mold filling: The alloy powder obtained after drying in step 2) is placed in a graphite female mold and pre-pressed using a manual hydraulic press with a pre-pressing pressure of 10 MPa and a holding time of 5 minutes.

[0069] 4) Sintering: Place the assembled graphite mold in the SPS sintering system, set the initial axial pressure to 10 MPa, evacuate to below 5 Pa, and turn on the power for sintering; heat to 1300°C at 20°C / min and keep warm for 10 minutes; after the insulation is completed, heat to 1350°C at 8°C / min, then cool to 1200°C at 40°C / min, pressurize to 40 MPa, hold the pressure for 5 minutes, and then continue to cool to 800°C at 40°C / min to end the sintering and cool with the furnace.

[0070] 5) Sampling: The sample is taken out using a hydraulic press, and the graphite on the sample surface is polished and removed to obtain high-performance cobalt-based tungsten carbide composite cemented carbide. The specific performance parameters are shown in Table 2.

[0071] Table 2: Performance test results of cemented carbide materials prepared in Example 2

[0072]

[0073] Example 3

[0074] Prepare according to the following steps Cobalt-based tungsten carbide composite hard alloy, wherein the composite powder mass ratio WC: Co: Cr3C2: VC = 92.5: 6: 1: 0.5

[0075] 1) Additive mixing: Co powder, Cr3C2 powder and VC powder were weighed in proportion, placed in a Hummingbird HAM2000 ultrasonic resonance device, and reacted in a nitrogen atmosphere at room temperature for 2 hours.

[0076] 2) Powder Mixing: Place 6000g of the WC weighed in the above mass ratio and the mixed additive powder obtained in step 1) into a carbide ball mill and ball mill. Zirconia balls are used for the milling, with a ball-to-material ratio of 2:1. Acetone is added as the milling medium, with a liquid-to-solid ratio of 0.7ml / g. The milling speed is 1000 rpm, and the milling time is 24 hours. The milled powder is dried in a dryer at 70°C for 6-7 hours. The dried powder is then passed through a 160-mesh sieve and dried in a drying oven at 120°C for 4 hours.

[0077] 3) Mold filling: The alloy powder obtained after drying in step 2) is placed in a graphite female mold and pre-pressed using a manual hydraulic press with a pre-pressing pressure of 10 MPa and a holding time of 5 minutes.

[0078] 4) Sintering: Place the assembled graphite mold in the SPS sintering system, set the initial axial pressure to 10 MPa, evacuate to below 5 Pa, and apply power for sintering; heat to 1320°C at 20°C / min and hold for 10 minutes; after the holding period, heat to 1400°C at 8°C / min, then cool to 1280°C at 40°C / min, apply pressure to 40 MPa, hold for 5 minutes, and then cool to 800°C at 40°C / min to terminate sintering and allow the mold to cool in the furnace.

[0079] 5) Sampling: The sample is taken out using a hydraulic press, and the graphite on the sample surface is polished and removed to obtain high-performance cobalt-based tungsten carbide composite cemented carbide. The specific performance parameters are shown in Table 3.

[0080] Table 3: Performance test results of cemented carbide materials prepared in Example 3

[0081]

[0082] Example 4

[0083] Prepare according to the following steps High-performance cobalt-based tungsten carbide composite hard alloy, wherein the composite powder mass ratio WC: Co: Cr3C2: VC = 92: 6: 1.5: 0.5

[0084] 1) Additive mixing: Co powder, Cr3C2 powder and VC powder were weighed in proportion, placed in a Hummingbird HAM2000 ultrasonic resonance device, and reacted in a nitrogen atmosphere at room temperature for 2 hours.

[0085] 2) Powder Mixing: Place 1200g of the WC weighed in the above mass ratio and the mixed additive powder obtained in step 1) into a carbide ball mill and ball mill. Zirconia balls are used for the milling, with a ball-to-material ratio of 2:1. Ethanol is used as the milling medium, with a liquid-to-solid ratio of 0.7ml / g. The milling speed is 1000 rpm, and the milling time is 24 hours. The milled powder is dried in a dryer at 70°C for 6-7 hours. The dried powder is then passed through a 160-mesh sieve and dried in a drying oven at 120°C for 4 hours.

[0086] 3) Mold filling: The alloy powder obtained after drying in step 2) is placed in a graphite female mold and pre-pressed using a manual hydraulic press with a pre-pressing pressure of 10 MPa and a holding time of 5 minutes.

[0087] 4) Sintering: Place the assembled graphite mold in the SPS sintering system, set the initial axial pressure to 10 MPa, evacuate to below 5 Pa, and apply power for sintering; heat to 1270°C at 20°C / min and hold for 10 minutes; after the holding period, heat to 1330°C at 8°C / min, then cool to 1230°C at 40°C / min, apply pressure to 50 MPa, hold for 5 minutes, and then cool to 800°C at 40°C / min to terminate sintering and allow the mold to cool in the furnace.

[0088] 5) Sampling: The sample is taken out using a hydraulic press, and the graphite on the sample surface is polished and removed to obtain high-performance cobalt-based tungsten carbide composite cemented carbide. The specific performance parameters are shown in Table 4.

[0089] Table 4: Performance test results of cemented carbide materials prepared in Example 4

[0090]

[0091] Example 5

[0092] Prepare according to the following steps High-performance cobalt-based tungsten carbide composite cemented carbide, wherein the composite powder mass ratio WC: Co: Cr3C2: VC = 93.5: 4: 1.5: 1

[0093] 1) Additive mixing: Co powder, Cr3C2 powder and VC powder were weighed in proportion, placed in a Hummingbird HAM2000 ultrasonic resonance device, and reacted in a nitrogen atmosphere for 2 hours at room temperature.

[0094] 2) Powder Mixing: Place 600g of the WC weighed in the above mass ratio and the mixed additive powder obtained in step 1) into a carbide ball mill and ball mill. Zirconia balls are used for the milling, with a ball-to-material ratio of 2:1. Alcohol is added as the milling medium, with a liquid-to-solid ratio of 0.7ml / g. The milling speed is 1000 rpm, and the milling time is 24 hours. The milled powder is dried in a dryer at 70°C for 6-7 hours. The dried powder is then passed through a 160-mesh sieve and dried in a drying oven at 120°C for 4 hours.

[0095] 3) Mold filling: The alloy powder obtained after drying in step 2) is placed in a graphite female mold and pre-pressed using a manual hydraulic press with a pre-pressing pressure of 10 MPa and a holding time of 5 minutes.

[0096] 4) Sintering: Place the assembled graphite mold in the SPS sintering system, set the initial axial pressure to 10 MPa, evacuate to below 5 Pa, and turn on the power for sintering; heat to 1300°C at 20°C / min and keep warm for 10 minutes; after the insulation is completed, heat to 1380°C at 8°C / min, then cool to 1250°C at 40°C / min, pressurize to 50 MPa, hold the pressure for 5 minutes, and then continue to cool to 800°C at 30-50°C / min, end sintering, and cool with the furnace.

[0097] 5) Sampling: The sample is taken out using a hydraulic press, and the graphite on the sample surface is polished and removed to obtain high-performance cobalt-based tungsten carbide composite cemented carbide. The specific performance parameters are shown in Table 5.

[0098] Table 5: Performance test results of cemented carbide materials prepared in Example 5

[0099]

[0100] Comparative Example 1

[0101] Prepare according to the following steps High-performance cobalt-based tungsten carbide composite hard alloy, wherein the composite powder mass ratio WC: Co: Cr3C2: VC = 94.5: 5: 0.5: 0

[0102] 1) Additive mixing: Co powder and Cr3C2 powder were weighed in proportion, placed in a Hummingbird HAM2000 ultrasonic resonance device, and reacted in a nitrogen atmosphere at room temperature for 2 hours.

[0103] 2) Powder Mixing: Place 890g of the WC weighed in the above mass ratio and the mixed additive powder obtained in step 1) into a carbide ball mill and ball mill. Zirconia balls are used for the milling, with a ball-to-material ratio of 2:1. Alcohol is added as the milling medium, with a liquid-to-solid ratio of 0.7ml / g. The milling speed is 1000 rpm, and the milling time is 24 hours. The milled powder is dried in a dryer at 70°C for 6-7 hours. The dried powder is then passed through a 160-mesh sieve and dried in a drying oven at 120°C for 4 hours.

[0104] 3) Mold filling: The alloy powder obtained after drying in step 2) is placed in a graphite female mold and pre-pressed using a manual hydraulic press with a pre-pressing pressure of 10 MPa and a holding time of 5 minutes.

[0105] 4) Sintering: Place the assembled graphite mold in the SPS sintering system, set the initial axial pressure to 10 MPa, evacuate to below 5 Pa, and apply power for sintering; heat to 1450°C at 20°C / min and hold for 10 minutes; after the holding period, heat to 1500°C at 8°C / min, then cool to 1400°C at 40°C / min, apply pressure to 30 MPa, hold for 5 minutes, and then cool to 800°C at 40°C / min to end sintering and cool with the furnace.

[0106] 5) Sampling: The sample is taken out using a hydraulic press, and the graphite on the surface of the sample is polished and removed to obtain a cemented carbide block material. The specific performance parameters are shown in Table 6.

[0107] Table 6: Performance test results of cemented carbide materials prepared in Comparative Example 1

[0108]

[0109] Comparative Example 2

[0110] Prepare according to the following steps High-performance cobalt-based tungsten carbide composite hard alloy, wherein the composite powder mass ratio WC: Co: Cr3C2: VC = 93: 5: 1.5: 0.5

[0111] 1) Powder Mixing: Place 120g of the WC and mixed additive powders weighed in the above mass ratios into a carbide ball mill and mill. The milling balls are all the same size, with a ball-to-material ratio of 3.5:1. Acetone is added as the milling medium, with a liquid-to-solid ratio of 0.7ml / g. The milling speed is 1000r / min and the milling time is 24h. The milled powder is dried in a dryer at 70°C for 6-7h. The dried powder is then passed through a 160-mesh sieve and dried in a drying oven at 120°C for 4h.

[0112] 2) Mold filling: The alloy powder obtained after drying in step 1) is placed in a graphite female mold and pre-pressed using a manual hydraulic press with a pre-pressing pressure of 10 MPa and a holding time of 5 minutes.

[0113] 3) Sintering: Place the assembled graphite mold in the SPS sintering system, set the initial axial pressure to 10 MPa, evacuate to below 5 Pa, and apply power for sintering; heat to 1330°C at 20°C / min and hold for 10 minutes; after the holding period, heat to 1380°C at 8°C / min, then cool to 1230°C at 40°C / min, apply pressure to 50 MPa, hold for 5 minutes, and then cool to 800°C at 40°C / min to terminate sintering and allow the mold to cool in the furnace.

[0114] 4) Sampling: The sample is taken out using a hydraulic press, and the graphite on the sample surface is polished and removed to obtain high-performance cobalt-based tungsten carbide composite cemented carbide. The specific performance parameters are shown in Table 7.

[0115] Table 7: Performance test results of cemented carbide materials prepared in Comparative Example 2

[0116]

[0117] Figure 5 The following are the microstructure and EDS results of the sample after simple ball milling with cemented carbide balls and sintering at 1380°C, 50 MPa, and 10 min of holding time, based on Comparative Example 2. It can be seen that the sample sintered after simple ball milling with cemented carbide balls exhibits obvious element aggregation.

[0118] Figure 1 This is the energy spectrum of the powder obtained in step 2) of Example 1 after the synergistic effect of ultrasonic resonance and zirconia ball milling. It can be seen from the figure that after the synergistic effect of ultrasonic resonance and zirconia ball milling, the powders are distributed more dispersedly and evenly. Figure 4 The energy spectrum of the powder after simple ball milling with a cemented carbide ball according to step 1) of comparative example 2. Figure 4 It can be seen that after simple ball milling of cemented carbide, obvious element aggregation was found in the powder energy spectrum, which will cause the elements to not fully diffuse in the subsequent sintering process. Figure 5 Microstructural defects in .

[0119] It can be seen from the above examples that according to the cemented carbide composition ratio and preparation method provided by the present invention, a cemented carbide material with high relative density, high hardness, good fracture toughness and bending strength can be obtained.

[0120] The above descriptions are only some embodiments of the present invention, not all embodiments. Obviously, the scope of protection of the present invention is not limited thereto. Practitioners in this field and related fields, based on the concept of the present invention, all other embodiments obtained through transformation, combination, etc., should be included in the scope of protection of the present invention.

Claims

1. A cobalt-based tungsten carbide composite cemented carbide material, wherein the cemented carbide material is prepared by sintering a mixture of WC, A powder, B powder and optional C powder by spark plasma technology, based on the total weight of 100wt.%, the content of WC powder is 90.0wt.% to 94.5wt.%, preferably 92.0wt.% to 94.5wt.%; the sum of the contents of A powder, B powder and optional C powder is 5.5wt.% to 10.0wt.%, preferably 5.5wt.% to 8.0wt.%, wherein A is Co, B is Cr3C2, and C is VC.

2. The cobalt-based tungsten carbide composite cemented carbide material according to claim 1, wherein: The content of A powder is 1.0 wt.% to 6.0 wt.%, preferably 4.0 wt.% to 6.0 wt.%; and / or The content of B powder is 0.5wt.% to 2.0wt.%, preferably 0.5wt.% to 1.5wt.%; and / or The content of C powder is 0.0 wt.% to 2.0 wt.%, preferably 0.0 wt.% to 0.5 wt.%.

3. The cobalt-based tungsten carbide composite cemented carbide material according to claim 1 or 2, wherein: The relative density of the cemented carbide material is not less than 99.9%; and / or The cemented carbide material does not contain any other impurity phases except the main phase; and / or The hardness of the cemented carbide material is 1900HV30 to 2300HV30, preferably 2000HV30 to 2300HV30; and / or The flexural strength of the cemented carbide material is above 2000 MPa; and / or The fracture toughness of the cemented carbide material is 7.5 MPa·m 1 / 2 ~10.0MPa·m 1 / 2 , preferably 7.9 MPa·m 1 / 2 ~10.0MPa·m 1 / 2 .

4. A method for preparing the cobalt-based tungsten carbide composite cemented carbide according to any one of claims 1 to 3, comprising the following steps: 1) Additive Mixing: Add powder A, powder B, and optionally powder C according to the ratio into an acoustic resonance device at room temperature, and mix the additive powders thoroughly in a nitrogen atmosphere to obtain a first powder mixture; 2) Powder mixing: placing the WC powder, the first powder mixture obtained in step 1) and the ball milling medium into a cemented carbide ball mill for ball milling, and drying the obtained mixed powder to obtain a second powder mixture; 3) Mold filling: The second powder mixture obtained in step 2) is placed in a graphite female mold and pre-pressed using a hydraulic press with a pre-pressing pressure of 5 to 20 MPa and a holding time of 5 minutes; 4) Sintering: Place the assembled graphite mold in a spark plasma sintering system, set the axial pressure to 0-50 MPa, evacuate to below 5 Pa, and sinter with power on; set the heating rate to 5°C-30°C / min, the maximum sintering temperature to 1250°C-1450°C, preferably 1300°C-1400°C; and hold the temperature for 5-15 minutes; 5) Sampling: The sample is taken out by using a hydraulic press, and the graphite on the surface of the sample is polished and removed to obtain a cobalt-based tungsten carbide composite cemented carbide material.

5. The method for preparing cobalt-based tungsten carbide composite hard alloy according to claim 4, wherein: The purity of WC powder is not less than 99.9%, and the powder particle size is 0.1 to 0.6 μm; and / or The purity of the Co powder is not less than 99.7%, and the powder particle size is 0.5 to 1.0 μm; and / or The purity of Cr3C2 powder is not less than 99.9%, and the powder particle size is 0.1 to 1.0 μm; and / or The purity of VC powder is not less than 99.5%, and the powder particle size is 0.1-1.0 μm.

6. The method for preparing cobalt-based tungsten carbide composite hard alloy according to claim 4 or 5, wherein: The ball milling medium in step 2) is one or more selected from methanol, ethanol or acetone; and / or The second powder mixture powder is placed at the center of the graphite mold, and the height difference between the exposed pressure heads at both ends of the graphite mold is no more than 5 mm.

7. The method for preparing a cobalt-based tungsten carbide composite hard alloy according to any one of claims 4 to 6, wherein: The graphite female mold and the second powder mixture are separated by a graphite bushing or graphite paper, and the graphite indenter and the second powder mixture are separated by a graphite sheet or graphite paper; the assembled graphite mold is wrapped with a layer of graphite felt for thermal insulation; and / or In step 2), the grinding balls used for powder mixing are zirconium oxide balls, and the grinding ball specifications are 5 mm:10 mm:15 mm=5:3:

2.

8. The method for preparing a cobalt-based tungsten carbide composite hard alloy according to any one of claims 4 to 7, wherein: In step 4), during the heating process, the temperature is kept at 50 to 80° C. away from the maximum sintering temperature for 5 to 15 minutes; when the sintering temperature is less than 50° C. away from the maximum sintering temperature, the heating rate is ≤10° C. / min.

9. The method for preparing a cobalt-based tungsten carbide composite hard alloy according to any one of claims 4 to 8, wherein: In step 4), the axial pressure during the heating process is 5 to 20 MPa, and during the cooling process, when the temperature drops to 100 to 150°C from the maximum sintering temperature, the pressure is increased to 20 to 50 MPa, preferably 30 to 50 MPa, and the pressure is maintained at this temperature for 5 to 15 minutes; constant pressure sintering is performed at the target pressure until sintering is completed.

10. The method for preparing cobalt-based tungsten carbide composite hard alloy according to any one of claims 4 to 9, wherein: The cooling method is controlled cooling, and the cooling rate is ≤50℃ / min.

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