High-uniformity nanocrystalline WC-Co hard alloy and preparation method thereof

Abstract

The invention relates to the technical field of tungsten-carbon hard alloy, and particularly discloses a high-uniformity nanocrystalline WC-Co hard alloy and a preparation method thereof.The high-uniformity nanocrystalline WC-Co hard alloy is prepared from tungsten carbide powder, cobalt powder, a composite inhibitor and a forming agent; the preparation method of the composite inhibitor comprises the following steps: dissolving a vanadium-chromium inhibition raw material in a solvent, and heating until spontaneous combustion reaction to obtain a precursor; and placing the precursor in a protective gas atmosphere, heating to 650-1200 DEG C, and reacting for 1-3 hours to obtain the composite inhibitor. The high-specific-surface-area nano composite inhibitor with the fluffy porous structure characteristic is adopted, a polyethylene acid solution is introduced to conduct surface treatment on hard alloy raw material powder such as tungsten carbide, grain coarsening can be effectively inhibited, generation of a grain boundary brittle phase is avoided, and finally the nanocrystalline WC-Co hard alloy with excellent strength, hardness, toughness and the like is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of tungsten carbide hard alloys, and more specifically, to a nanocrystalline WC-Co hard alloy with high uniformity and a preparation method thereof. Background Art

[0002] Tungsten carbide-cobalt hard alloy, which can be abbreviated as WC-Co hard alloy, refers to a hard alloy material mainly using tungsten carbide as the hard phase and cobalt as the bonding phase. Due to its high strength, high hardness and other characteristics, it is made into various tools and widely used in fields such as machining, mining, road milling, and mold processing. With the acceleration of the industrialization process, the booming development of the electronic information industry, and the enhancement of people's environmental protection awareness, various new materials and products have emerged continuously, and hard alloys have gradually developed towards the direction of near-nano or even nano-crystalline size.

[0003] The preparation principle of nanocrystalline hard alloy is to use tungsten carbide powder with a smaller particle size, and during the mixing and sintering processes, add grain growth inhibitors such as chromium carbide or vanadium carbide. By inhibiting the excessive growth of the hard phase principle, the finally obtained hard alloy product presents a nano-scale crystal structure. For example, the patent with the publication number CN115044795A provides a nano WC-Co hard alloy and its preparation method. Using nano tungsten carbide, cobalt powder, inhibitor, etc. as the mixed raw materials, nano-structured WC-Co hard alloy can be prepared, and metal organic salts are used instead of metal carbides to act as inhibitors to alleviate the problem of inhibitor aggregation.

[0004] However, the existing methods for solving the problem of uneven dispersion of inhibitors, although they can improve the degree of uniform dispersion of product grains, the metal organic salts acting as inhibitors have poor thermal stability, resulting in low precision of composition control during the sintering process, and the metal organic salts may cause carbides to accumulate at grain boundaries, increasing the risk of brittleness of the hard alloy. Therefore, there is an urgent need for a measure that can improve the uniform dispersion of grain growth inhibitors and tungsten carbide grains on the basis of better maintaining the performance of hard alloy materials. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of low hardness and low strength caused by poor uniformity of tungsten carbide grains in existing nanocrystalline tungsten carbide-cobalt hard alloys.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention provides a nanocrystalline WC-Co cemented carbide with high uniformity. The preparation raw materials include tungsten carbide powder, cobalt powder, a composite inhibitor, and a forming agent. The preparation method of the composite inhibitor includes the following steps: taking vanadium-chromium inhibition raw materials, dissolving them in a solvent, heating to an autoignition reaction to obtain a precursor; then placing the precursor in an atmosphere of a protective gas, heating to 650 - 1200 °C, and reacting for 1 - 3 h to obtain the composite inhibitor.

[0008] Preferably, the particle size of the composite inhibitor is < 150 nm, and the specific surface area is 30 - 35 m 2 / g.

[0009] Preferably, in the preparation method of the composite inhibitor, by mass fraction, the vanadium-chromium inhibition raw materials include 0.5 - 2 parts of a vanadium source, 0.5 - 2 parts of a chromium source, 2 - 5 parts of a carbon source, 2 - 5 parts of a combustion aid, and 5 - 10 parts of an oxidant.

[0010] Preferably, the average particle size of the tungsten carbide powder is < 400 nm, and the specific surface area is 3.0 - 3.2 m 2 / g.

[0011] Preferably, by mass fraction, it includes 85 - 90% tungsten carbide powder, 8 - 10% cobalt powder, 0.5 - 2.0% composite inhibitor, 1.0 - 5.0% forming agent, and 0 - 1.5% tungsten powder.

[0012] The present invention also provides a preparation method of the above-mentioned nanocrystalline WC-Co cemented carbide with high uniformity, including the following steps:

[0013] S1 Raw material mixing:

[0014] Weigh the tungsten carbide powder, cobalt powder, composite inhibitor, and forming agent, mix them, perform ball milling with a ball-to-material ratio of 2 - 10:1 and a ball milling temperature of 25 - 40 °C, then add polyethylene glycol and stir evenly to obtain a premix.

[0015] S2 Surface modification treatment of the premix:

[0016] Immerse the premix in a polyvinyl acid solution, perform impregnation treatment, drain, and heat to 70 - 90 °C for drying to obtain a pre-sintered material.

[0017] S3 Sintering treatment:

[0018] Press the pre-sintered material into a green compact, place it in a sintering furnace, and then successively perform dewaxing at 350 - 580 °C, vacuum sintering at 1050 - 1350 °C, and low-pressure sintering treatment at 1300 - 1500 °C, and then cool to room temperature at 5 - 8 °C / min to obtain the nanocrystalline WC-Co cemented carbide.

[0019] Preferably, in step S1, the addition amount of polyethylene glycol accounts for 0.5-1.0 wt% of the total mass of the premix.

[0020] Preferably, in step S3, the specific steps of dewaxing include: placing the green compact in a sintering furnace, first heating from room temperature to 350-380 °C at a rate of 1-4 °C / min and holding for 2.5-3.5 h; then heating to 420-480 °C at a rate of 2-3 °C / min and holding for 20-40 min; and then heating to 520-580 °C at a rate of 3-4 °C / min and holding for 20-40 min.

[0021] Preferably, in step S3, the specific steps of vacuum sintering include: based on the temperature after dewaxing, heating to 1050-1150 °C at a rate of 3-5 °C / min, while adjusting the vacuum degree in the furnace to less than 30 Pa and holding for 0.75-1.5 h; then heating to 1200-1250 °C at a rate of 4-5 °C / min and holding for 0.75-1.5 h; and then heating to 1300-1350 °C at a rate of 4-5 °C / min and holding for 0.75-1.5 h.

[0022] Preferably, in step S3, the specific steps of low-pressure sintering include: based on the temperature after vacuum sintering, continuing to heat to 1400-1450 °C at a rate of 0.5-2 °C / min, holding for 5-15 min, then closing the vacuum, and subsequently reducing the temperature to 1300-1500 °C while applying a pressure of 9-10 Mpa and holding for 20-50 min.

[0023] Preferably, in step S3, during cooling, first cool with the furnace to below 1200 °C, and then rapidly reduce the temperature to room temperature by air cooling at a rate of 5-8 °C / min.

[0024] The technical solution of the present invention has the following beneficial effects:

[0025] The nanocrystalline WC-Co cemented carbide and its preparation method proposed by the present invention adopt a high-specific-surface-area nanocomposite inhibitor with a fluffy and porous structure, which can be fully contacted and mixed with cemented carbide base materials such as tungsten carbide. During the sintering process, it uniformly acts on the grains, hinders the dissolution-precipitation process, inhibits grain coarsening, and at the same time avoids the generation of brittle phases at grain boundaries, that is, ultimately improves the dispersion uniformity and inhibition efficiency. In addition, introducing a polyvinyl alcohol solution to coat the surface of cemented carbide raw materials such as tungsten carbide can improve the surface activity of the raw materials and inhibit grain boundary migration that occurs during the sintering process, thereby inhibiting grain coarsening and reducing their agglomeration during the mixed sintering process, and ultimately realizing the high uniformity characteristics of the nanocrystalline WC-Co cemented carbide. The nanocrystalline WC-Co cemented carbide and its preparation method of the present invention can be applied to almost all WC-xCo (x = 6-12 wt%) alloys, can effectively improve the grain uniformity of the cemented carbide, and have higher material strength, hardness, and toughness, etc. Description of the Drawings

[0026] Figure 1 SEM image of the nanocrystalline WC-Co cemented carbide in Example 1 magnified 5000 times;

[0027] Figure 2 SEM image of the nanocrystalline WC-Co cemented carbide in Comparative Example 1 magnified 5000 times;

[0028] Figure 3 SEM image of the nanocrystalline WC-Co cemented carbide in Comparative Example 2 magnified 5000 times. Detailed Description of the Invention

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Among them, for those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer; for those instrument devices, reagent raw materials, etc. not specified for the manufacturer, they are all conventional products that can be obtained by purchasing in the market.

[0030] The present invention provides a nanocrystalline WC-Co cemented carbide with high uniformity, and its preparation method includes the following steps:

[0031] (1) Raw material mixing:

[0032] By mass fraction, 85-90% of nanoscale tungsten carbide powder, 0-1.5% of tungsten powder, 8-10% of cobalt powder, 0.5-2.0% of composite inhibitor, and 1.0-5.0% of forming agent are mixed to obtain a preliminary mixed raw material; using ethane as the ball milling medium, controlling the ball-to-material ratio of ball milling to be 2-10:1, adopting a cooling ball mill, controlling the temperature during ball milling to be 25-40°C to avoid affecting the alloy strength due to excessive oxidation of raw materials such as cobalt powder, wet milling the preliminary mixed raw material for 30-80h to make the composite inhibitor fully dispersed in raw materials such as tungsten carbide powder, and then adding polyethylene glycol, stirring evenly to obtain a premixed material.

[0033] Among them, the average particle size of the tungsten carbide powder is less than 400nm, the specific surface area is 3.0-3.2m 2 / g, the average particle size of the cobalt powder is less than 1.5μm; preferably, controlling the total carbon content in the preliminary mixed raw material to be 6.10-6.15wt%, the addition amount of the composite inhibitor to be 0.5-2.0wt% of the total mass of the preliminary mixed raw material, the addition amount of the forming agent to be 0.5-3.5wt% of the total mass of the preliminary mixed raw material; the addition amount of polyethylene glycol accounts for 0.5-1.0wt% of the total mass of the premixed material, which can reduce the agglomeration between raw material powders.

[0034] The present invention adopts a moderate ball-to-material ratio and wet milling time. The reason is as follows: Extending the wet milling time and increasing the ball-to-material ratio during ball milling can improve the uniformity of wet milling, but both will increase the grinding activity of nano-WC, resulting in carbide lattice distortion and surface potential barriers, thus causing abnormal grain growth during sintering, that is, the finally obtained nanocrystalline cemented carbide still exhibits poor grain uniformity.

[0035] (2) Surface modification treatment of the premix:

[0036] The premix is subjected to surface modification treatment. The specific treatment process is as follows: The premix is immersed in a polyvinyl alcohol solution with a mass fraction of 2.0 - 4.0%, impregnated for 10 - 60 min, drained, and dried at 70 - 90 °C for 10 - 25 min to obtain the pre-sintered material. Through the surface modification treatment of polyethylene, the surface activity of the raw materials can be improved, and the grain boundary migration that occurs during sintering can be inhibited, thereby inhibiting grain coarsening.

[0037] (3) Sintering treatment:

[0038] The pre-sintered material is pressed at 3.5 - 8 MPa to obtain a green compact, and the green compact is subjected to multi-step sintering treatment including dewaxing, vacuum sintering, low-pressure sintering, and cooling in sequence. The specific treatment process is as follows:

[0039] 3.1 Dewaxing:

[0040] Take the green compact and place it in a sintering furnace. First, heat it from room temperature to 350 - 380 °C at a rate of 1 - 4 °C / min and hold for 2.5 - 3.5 h; then heat it to 420 - 480 °C at a rate of 2 - 3 °C / min and hold for 20 - 40 min; then heat it to 520 - 580 °C at a rate of 3 - 4 °C / min and hold for 20 - 40 min, thus completing the dewaxing treatment.

[0041] 3.2 Vacuum sintering:

[0042] After dewaxing, based on its temperature, heat it to 1050 - 1150 °C at a rate of 3 - 5 °C / min, and at the same time adjust the vacuum degree in the furnace to less than 30 Pa and hold for 0.75 - 1.5 h; then heat it to 1200 - 1250 °C at a rate of 4 - 5 °C / min and hold for 0.75 - 1.5 h; then heat it to 1300 - 1350 °C at a rate of 4 - 5 °C / min and hold for 0.75 - 1.5 h, thus completing the vacuum sintering.

[0043] 3.3 Low-pressure sintering:

[0044] After vacuum sintering, based on its temperature, continue to heat it to 1400 - 1450 °C at a rate of 0.5 - 2 °C / min, hold for 5 - 15 min, then turn off the vacuum, and then reduce the temperature to 1300 - 1500 °C, and at the same time apply a pressure of 9 - 10 Mpa and hold for 20 - 50 min, thus completing the low-pressure sintering.

[0045] 3.4 Cooling

[0046] The sintered compact after the above multi-step heating and sintering is cooled in the furnace to below 1200 °C, taken out, and rapidly air-cooled to reduce the temperature to room temperature at a rate of 5-8 °C / min, thus obtaining the nanocrystalline WC-Co cemented carbide.

[0047] In the present invention, the composite inhibitor is prepared from a vanadium-chromium inhibitor raw material. Through the low-temperature combustion synthesis method, a nanometer particulate material with a high specific surface area is prepared and used as the composite inhibitor for the nanocrystalline WC-Co cemented carbide of the present invention. Its high specific surface area characteristic can effectively improve the dispersion uniformity and the grain growth inhibition efficiency.

[0048] Among them, the vanadium-chromium inhibitor raw material includes a vanadium source, a chromium source, a carbon source, urea, and ammonium nitrate in a mass ratio of 0.5-2:0.5-2:2-5:2-5:5-10. Urea and ammonium nitrate act as a combustion aid and an oxidant respectively. Those skilled in the art can also select other existing combustion aids and oxidants;

[0049] The treatment process of the low-temperature combustion synthesis method is as follows: First, dissolve the vanadium-chromium inhibitor raw material in deionized water and heat it until a self-combustion reaction occurs to form a fluffy precursor; then place the precursor in a nitrogen protection atmosphere and heat it to 650-1200 °C for 1-3 h to obtain the composite inhibitor, whose particle size is less than 150 nm and specific surface area is 30-35 m 2 / g.

[0050] In the present invention, the above composite inhibitor is used to control the grain growth. In the finally obtained nanocrystalline WC-Co cemented carbide, the preferred chromium carbide content is 0.30-0.90 wt%, and the preferred vanadium carbide content is 0.30-0.50 wt%. This nanocrystalline WC-Co cemented carbide and its preparation method can be applied to almost all WC-xCo (x = 6-12%) alloys, can effectively improve the grain uniformity of the cemented carbide, and have higher material strength, hardness, and toughness, etc.

[0051] Example 1

[0052] Step 1: Take ammonium metavanadate, chromium nitrate, glucose, urea, and ammonium nitrate in a mass ratio of 1:1:3:3.5:8.5, mix them, dissolve them in an equal volume of deionized water, and heat until a self-combustion reaction occurs to form a precursor; then place the precursor in a nitrogen protection atmosphere and heat it to 820 ± 20 °C for 2 h to obtain the composite inhibitor for standby.

[0053] Step 2: Weigh the raw materials by mass parts, specifically including 88.7 parts of ultrafine tungsten carbide powder, 0.6 parts of ultrafine tungsten powder, 7.5 parts of ultrafine cobalt powder, 1.2 parts of composite inhibitor, and 2 parts of paraffin. The average particle size of the ultrafine tungsten carbide powder is 0.25 ± 0.05 μm, the average particle size of the ultrafine tungsten powder is 0.3 ± 0.05 μm, and the average particle size of the ultrafine cobalt powder is 0.85 ± 0.05 μm. Mix them to obtain the preliminarily mixed raw materials.

[0054] Step 3: Put the preliminarily mixed raw materials into a cooling ball milling tank. Use alloy balls with a diameter of 3.2 mm as the ball grinding media, control the ball-to-material ratio to be 8:1, add 500 mL / kg of ethane, and control the ambient temperature to be maintained at 30 ± 5 °C. Ball mill at a speed of 72 r / min for 40 h, then pass through a 300-mesh sieve, and then add 1.0% of polyethylene glycol based on the mass of the preliminarily mixed raw materials and mix well to obtain the pre-mixed materials.

[0055] Step 4: Immerse the pre-mixed materials in a polyvinyl alcohol solution with a mass fraction of 3.0% and a volume twice that of the pre-mixed materials for 40 min, drain, and place them in a vacuum dryer at 75 °C for 20 min to obtain the pre-sintered materials; then press them under 5 MPa to obtain the green compact.

[0056] Step 5: Place the green compact in a sintering furnace. First, heat it from room temperature to 250 ± 10 °C at a rate of 4 °C / min, then heat it to 320 ± 10 °C at a rate of 1.2 °C / min, then heat it to 370 ± 10 °C at a rate of 0.3 °C / min, and hold for 3 h; then heat it to 450 ± 10 °C at a rate of 2.6 °C / min and hold for 30 min; then heat it to 550 ± 10 °C at a rate of 3.3 °C / min and hold for 30 min to complete the dewaxing process; heat it to 650 ± 10 °C at a rate of 3.3 °C / min, then heat it to 1100 ± 10 °C at a rate of 4.5 °C / min, and at the same time adjust the vacuum degree in the furnace to be less than 30 Pa and hold for 1 h; then heat it to 1230 ± 10 °C at a rate of 4 - 5 °C / min and hold for 1 h; then heat it to 1320 ± 10 °C at a rate of 4.5 °C / min and hold for 1 h to complete the vacuum sintering; continue to heat it to 1420 ± 10 °C at a rate of 1 °C / min, hold for 10 min, then turn off the vacuum, and then reduce the temperature to 1400 ± 10 °C, and at the same time apply pressure below 10 Mpa and hold for 30 min to complete the low-pressure sintering; finally, cool it in the furnace to below 1200 °C, take it out, and quickly air-cool it to room temperature at a rate of 6 °C / min to obtain the nanocrystalline WC-Co cemented carbide.

[0057] Example 2

[0058] The difference between this example and Example 1 is that in Step 2, the raw materials specifically include 88.7 mass parts of ultrafine tungsten carbide powder, 0.6 mass parts of ultrafine tungsten powder, 7.5 mass parts of ultrafine cobalt powder, 0.6 mass parts of composite inhibitor, and 2 parts of paraffin.

[0059] Example 3

[0060] The difference between this example and Example 1 is that the processing in Step 3 is as follows: Put the preliminarily mixed raw materials into a cooling ball mill tank, use alloy balls with a diameter of 3.2 mm as nodularizers, control the ball-to-material ratio to be 3:1, add 500 mL / kg of ethane, and control the ambient temperature to be maintained at 30 ± 5 °C. Ball mill at a speed of 72 r / min for 40 h, then pass through a 300-mesh sieve, and then add 0.5% of polyethylene glycol based on the mass of the preliminarily mixed raw materials and mix evenly to obtain a premixed material.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that in Step 2, the raw materials specifically include 88.7 parts by mass of ultrafine tungsten carbide powder, 0.6 parts by mass of ultrafine tungsten powder, 7.5 parts by mass of ultrafine cobalt powder, 0.6 parts by mass of chromium carbide, 0.6 parts by mass of vanadium carbide, and 2 parts of paraffin.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Comparative Example 1 is that in Step 4, the premixed material is directly laid, pressed into a green compact at 5 MPa, and then sintered.

[0065] Test Example

[0066] (1) Respectively take the WC-Co cemented carbides prepared in Example 1 and Comparative Examples 1 to 2 as samples. After surface polishing treatment, use an electron scanning microscope to observe the surface morphology of the above samples. The observed sample morphologies are as Figures 1 to 3 shown, Figures 1 to 3 They are SEM images of the WC-Co cemented carbides in Example 1, Comparative Example 1, and Comparative Example 2 magnified 5000 times respectively.

[0067] It can be found from the observed situation that for the nanocrystalline WC-Co cemented carbide prepared in Example 1, the grain morphology uniformity and dispersibility are significantly better than those of the WC-Co cemented carbide grain morphologies in Comparative Example 1 and Comparative Example 2. Moreover, large-sized grains formed by aggregation can be clearly observed in the samples of Comparative Example 1 and Comparative Example 2. Therefore, it can be shown that the proposed nanocrystalline WC-Co cemented carbide and its preparation method can effectively solve the problem of poor grain dispersibility and uniformity of the currently nanoscale-structured WC-Co cemented carbide.

[0068] (2) Respectively take the WC-Co cemented carbides prepared in Examples 1 to 3 and Comparative Examples 1 to 2 as samples. According to the test methods in Table 1 below, measure the material property parameters such as the hardness of the samples, and the results are summarized as shown in Table 1 below:

[0069] Table 1 Material Property Measurement Results of Different Samples

[0070]

[0071] As can be seen from Table 1 above, the WC-Co cemented carbide samples prepared in Examples 1 to 3 have a smaller average particle size as a whole. Combining with the observation of the scanning electron microscope, this is because the WC-Co cemented carbide obtained by the preparation method proposed in the present invention has better dispersion uniformity of grains, avoiding the aggregation of a large number of grains; on this basis, the WC-Co cemented carbides in Examples 1 to 3 are significantly superior to the WC-Co cemented carbides in Comparative Example 1 and Comparative Example 2 in terms of Rockwell hardness, Vickers hardness, flexural strength and fracture toughness. Thus, it can be shown that the nanocrystalline WC-Co cemented carbide and its preparation method proposed in the present invention can improve the performance of the cemented carbide material in terms of strength and hardness by enhancing the dispersion uniformity of grains.

[0072] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A nanocrystalline WC-Co cemented carbide with high uniformity, characterized in that, The preparation raw materials include tungsten carbide powder, cobalt powder, composite inhibitor and binder; The preparation method of the composite inhibitor comprises the following steps: taking vanadium-chromium inhibition raw materials, dissolving them in a solvent, heating to self-ignition reaction to obtain a precursor; then placing the precursor in an atmosphere of protective gas, heating to 650 - 1200 °C, and reacting for 1 - 3 h to obtain the composite inhibitor.

2. The high-uniformity nanocrystalline WC-Co cemented carbide according to claim 1, wherein The particle size of the composite inhibitor is < 150 nm, and the specific surface area is 30 - 35 m 2 / g.

3. The nanocrystalline WC-Co cemented carbide with high uniformity according to claim 1, characterized in that, In the preparation method of the composite inhibitor, by mass fraction, the vanadium-chromium inhibition raw materials include 0.5 - 2 parts of vanadium source, 0.5 - 2 parts of chromium source, 2 - 5 parts of carbon source, 2 - 5 parts of combustion promoter and 5 - 10 parts of oxidant.

4. The high-uniformity nanocrystalline WC-Co cemented carbide according to claim 1, wherein The average particle size of the tungsten carbide powder is < 400 nm, and the specific surface area is 3.0 - 3.2 m 2 / g.

5. The nanocrystalline WC-Co cemented carbide with high uniformity according to claim 1, characterized in that, By mass fraction, it includes 85 - 90% tungsten carbide powder, 8 - 10% cobalt powder, 0.5 - 2.0% composite inhibitor, 1.0 - 5.0% binder and 0 - 1.5% tungsten powder.

6. A preparation method of a nanocrystalline WC-Co cemented carbide with high uniformity as described in any one of claims 1 to 5, characterized in that, It includes the following steps: S1 Raw material mixing: Weigh tungsten carbide powder, cobalt powder, composite inhibitor and binder according to the amount, mix them, perform ball milling with a ball-to-material ratio of 2 - 10:1 and a ball milling temperature of 25 - 40 °C, then add polyethylene glycol and stir evenly to obtain a premix. S2 Surface modification treatment of the premix: Immerse the premix in a polyvinyl alcohol solution, perform impregnation treatment, drain, and heat to 70 - 90 °C for drying to obtain a pre-sintered material. S3 Sintering treatment: Press the pre-sintered material into a green compact, place it in a sintering furnace, and then successively perform dewaxing at 350 - 580 °C, vacuum sintering at 1050 - 1350 °C, and low-pressure sintering at 1300 - 1500 °C, and then cool to room temperature at 5 - 8 °C / min to obtain the nanocrystalline WC-Co cemented carbide.

7. The preparation method of the nanocrystalline WC-Co cemented carbide with high uniformity according to claim 6, characterized in that, In step S1, the addition amount of polyethylene glycol accounts for 0.5 - 1.0 wt% of the total mass of the premix.

8. The preparation method of the nanocrystalline WC-Co cemented carbide with high uniformity according to claim 6, characterized in that, In step S3, the specific steps of dewaxing include: Place the green compact in the sintering furnace, first heat from room temperature to 350 - 380 °C at 1 - 4 °C / min and hold for 2.5 - 3.5 h; then heat to 420 - 480 °C at 2 - 3 °C / min and hold for 20 - 40 min; then heat to 520 - 580 °C at 3 - 4 °C / min and hold for 20 - 40 min.

9. The preparation method of the nanocrystalline WC-Co cemented carbide with high uniformity according to claim 8, characterized in that, In step S3, the specific steps of vacuum sintering include: Based on the temperature after dewaxing, heat to 1050 - 1150 °C at 3 - 5 °C / min, and at the same time adjust the vacuum degree in the furnace to less than 30 Pa, hold for 0.75 - 1.5 h; then heat to 1200 - 1250 °C at 4 - 5 °C / min and hold for 0.75 - 1.5 h; then heat to 1300 - 1350 °C at 4 - 5 °C / min and hold for 0.75 - 1.5 h.

10. The preparation method of the nanocrystalline WC-Co cemented carbide with high uniformity according to claim 9, characterized in that, In step S3, the specific steps of low-pressure sintering include: Based on the temperature after vacuum sintering, continue to heat to 1400 - 1450 °C at 0.5 - 2 °C / min, hold for 5 - 15 min, then close the vacuum, and then reduce the temperature to 1300 - 1500 °C, and at the same time apply pressure to 9 - 10 Mpa and hold for 20 - 50 min.

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