A nano-hard alloy, its preparation method and its application in milling cutters

Abstract

This invention provides a high-performance nano-cement alloy, its preparation method, and its application in milling cutters. By weight, it comprises the following components: 90.5-98.5 parts WC powder, 3-6 parts tungsten powder, 1-3 parts nano-nickel powder, 0.3-0.7 parts bismuth trioxide, 0.5-1.5 parts chromium boride, and 0.6-1.2 parts rare earth metal powder; the rare earth metal powder includes lanthanum, cerium, yttrium, and rubidium, with a mass ratio of 1:1.2-1.5:0.8-1.2:0.4-0.8; the WC powder has a particle size of 0.3-0.8 nm. The cemented carbide prepared by this invention possesses excellent toughness, hardness, and bending strength, making it better suited for use in milling cutter manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of cemented carbide technology, specifically relating to a nano-cemented carbide, its preparation method, and its application in milling cutters. Background Technology

[0002] Cemented carbide is a type of composite material composed of tungsten carbide (WC) and other metals (such as cobalt, nickel, and chromium). It possesses extremely high hardness, wear resistance, and heat resistance, and is widely used in cutting tools, wear-resistant parts, mining equipment, mold making, and other fields. The superior properties of cemented carbide make it an indispensable key material in modern industry.

[0003] Carbon content, as a key parameter of cemented carbide, plays a crucial role in its performance. Carbon content directly affects the hardness and wear resistance of cemented carbide products. The presence of carbon can refine the hard phase and enhance the bonding force between hard particles, thereby improving the wear resistance of the alloy. Traditional WC-Co cemented carbide suffers from deficiencies in high-temperature strength, fatigue resistance, and crack resistance during processing.

[0004] In this study, to simultaneously improve hardness, toughness, and strength, fine-grained strengthening and solid solution strengthening methods were employed. Compared with conventional grain WC-Co alloys, low-cobalt (≤6wt%Co) ultrafine-grained alloys exhibited higher comprehensive mechanical properties, including higher hardness, strength, and wear resistance. Because the WC grain size of this type of alloy is 0.3-0.5μm, the WC powder is extremely fine, resulting in a large specific surface area. Combined with the low cobalt content and narrow carbon range in the two-phase region, improper control during industrial production can easily lead to oxidation, decarburization, carburization, uneven dispersion, and abnormal grain growth, causing unstable product quality and ultimately affecting product performance. Therefore, developing a high-performance nano-hard alloy with excellent toughness, hardness, and bending strength is of practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance nano-hard alloy, its preparation method, and its application in milling cutters. By using self-made characteristic WC powder as the main component, and with the help of tungsten powder, nickel powder, bismuth trioxide, chromium boride, and rare earth metal powders, the prepared hard alloy simultaneously possesses excellent toughness, hardness, and bending strength, and can be better applied in milling cutter manufacturing.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high-performance nano-hard alloy comprises, by weight, the following components: 90.5-98.2 parts WC powder, 3-6 parts tungsten powder, 1-3 parts nano-nickel powder, 0.3-0.7 parts bismuth trioxide, 0.5-1.5 parts chromium boride, and 0.6-1.2 parts rare earth metal powder.

[0008] Preferably, the rare earth metal powder comprises lanthanum, cerium, yttrium and rubidium, and the mass ratio is 1:1.2-1.5:0.8-1.2:0.4-0.8.

[0009] Preferably, the WC powder has a particle size of 0.3-0.8 nm; the tungsten powder has a particle size of 40-60 nm; the nickel powder has a particle size of 2-6 nm; the bismuth trioxide has a particle size of 3-7 nm; the chromium boride has a particle size of 1-4 nm; and the rare earth metal has a particle size of 50-70 nm.

[0010] A method for preparing a high-performance nano-hard alloy includes the following steps:

[0011] S1; Weigh 90.5-98.5 parts of WC powder, 3-6 parts of tungsten powder, 1-3 parts of nano nickel powder, 0.3-0.7 parts of bismuth trioxide, 0.5-1.5 parts of chromium boride and 0.6-1.2 parts of rare earth metal powder and mix them to obtain a mixture;

[0012] S2: The mixture obtained in step S1 is put into a ball mill, and then ball milling media are added for ball milling treatment; after drying and pressing, a compact is obtained;

[0013] S3: The pressed blank obtained in step S2 is sintered in a sintering furnace to obtain cemented carbide.

[0014] Preferably, the preparation process of WC powder in step S1 is as follows: Based on the mass ratio of WC:V:Cr in the WC powder being 95-99:0.2-0.5:0.3-0.6, ammonium metatungstate, vanadium oxalate, and chromium acetate are taken and dissolved in deionized water at a solid-liquid ratio of 1g:10-15ml. After drying, a precursor is obtained. The calcination temperature is controlled at 650-750℃, the calcination time at 1.5-2.5h, the hydrogen flow rate at 3-5L / min, the carbonization temperature at 1350-1500℃, and the carbonization time at 1-3h. The precursor is calcined and then reduced and carbonized with hydrogen to obtain the WC powder.

[0015] Preferably, in step S2, the ball-to-material ratio is 7-12:1; the ball milling medium is alcohol; and the ball milling is carried out at a rate of 350-450 r / min for 10-14 h.

[0016] Preferably, step S2 also includes 1-4 parts of sodium hexametaphosphate.

[0017] Preferably, the pressing pressure in step S2 is 40-60 MPa, and the pressing time is 3-6 min; the molding agent is PEG 1000 or paraffin.

[0018] Preferably, the sintering temperature in step S3 is 1450-1550℃, and the sintering time is 1-3 hours.

[0019] Replacing modified nano-nickel powder with ordinary nickel powder results in the most significant decrease in product stability. Secondly, using commercially available WC powder directly also leads to a noticeable change in product performance stability. Using the raw materials of this invention results in the most significant improvement in product performance stability.

[0020] The nano-nickel powder has also undergone modification treatment, specifically the following modification method:

[0021] S11: Add 2-5 parts of hexagonal boron nitride nanosheets, 2-3 parts of fullerene powder and 3-4 parts of carbon nanotubes to 5-8 parts of sodium silicate solution with a mass fraction of 5% and stir thoroughly to obtain hexagonal boron nitride nanosheets.

[0022] S12: Subsequently, 1-2 parts of silane coupling agent KH550, 2-4 parts of TiC, 3-5 parts of hexagonal boron nitride nanoparticles, and 5-8 parts of 8% (w / w) dopamine hydrochloride solution are thoroughly mixed to obtain the modified solution.

[0023] S13: Irradiate the nano-nickel powder in a proton irradiation chamber for 10-15 minutes at an irradiation power of 350W. After irradiation, add the irradiated nano-nickel powder to the modification liquid at a weight ratio of 2:5 and stir to modify it. Then filter and dry it. The average particle size of the hexagonal boron nitride nanosheets is 100nm. The stirring speed for the stirring modification process is 450-500r / min, and the stirring time is 1h.

[0024] The inventors of this invention discovered that the performance of the product deteriorated significantly when hexagonal boron nitride nanoparticles were not added to the modified solution. Furthermore, the performance of the product also deteriorated to varying degrees when hexagonal boron nitride nanoparticles were not added during preparation, when fullerene powder and carbon nanotubes were not added, or when silane coupling agent KH550 and TiC were not added to the modified solution. Only the modified solution obtained by the specific method of this invention showed the most significant performance improvement, and other methods were not as effective as those of this invention.

[0025] Application of cemented carbide prepared by any of the above methods in end mills.

[0026] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0027] This invention utilizes ammonium metatungstate, vanadium oxalate, and chromium acetate through calcination followed by hydrogen reduction and carbonization. By precisely controlling the ratio of ammonium metatungstate, vanadium oxalate, and chromium acetate, the content of W, V, and Cr in the final WC powder can be adjusted, thereby obtaining WC powder with specific dimensions and physicochemical properties such as hardness, wear resistance, and corrosion resistance. Simultaneously, by incorporating tungsten powder, nickel powder, bismuth trioxide, chromium boride, and rare earth metal powders of appropriate particle size, catalytic densification during the sintering stage and interpenetration and solid solution between alloy materials, the grain structure of the cemented carbide is refined, resulting in an ultrafine cemented carbide that is uniform, free of inclusions and voids. This effectively improves the toughness and impact resistance of cemented carbide, enhances its machinability, makes it easier to form and cut, and improves the overall properties of cemented carbide. The oxidation resistance of the nano-nickel powder is particularly important when working in high-temperature environments, thereby improving the hardness, toughness, and bending strength of cemented carbide. Simultaneously, the nano-nickel powder undergoes specific process modifications, using a blend of hexagonal boron nitride nanosheets, fullerene powder, and carbon nanotubes with a 5% (w / w) sodium silicate solution, and a modifier solution co-modified with silane coupling agent KH550, TiC, and an 8% (w / w) dopamine hydrochloride solution. This specific modifier optimizes the nano-nickel powder, resulting in better synergy between the nano-nickel powder and the self-made nano-nickel powder in the system, optimizing the product's performance coordination. It also significantly improves the product's performance stability under harsh conditions of corrosion, scratching, and high temperatures. When applied to milling cutter manufacturing, it combines high hardness, high toughness, and high strength, resulting in a longer service life. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment provides a method for preparing high-performance nano-hard alloys, including the following steps:

[0031] S1; According to the mass ratio of W:V:Cr of 95:0.2:0.3, ammonium metatungstate, vanadium oxalate, and chromium acetate were taken and dissolved in deionized water at a solid-liquid ratio of 1g:10ml. After drying, a precursor was obtained. The calcination temperature was controlled at 650℃, the calcination time at 1.5h, the hydrogen flow rate at 3L / min, the carbonization temperature at 1350℃, and the carbonization time at 1h. The precursor was calcined and then reduced and carbonized with hydrogen to obtain the WC powder.

[0032] Lanthanum, cerium, yttrium and rubidium were mixed in a mass ratio of 1:1.2:0.8:0.4 and stirred at a rate of 200 r / min until homogeneous to obtain rare earth metal powder.

[0033] Weigh out 90.5g of WC powder, 3g of tungsten powder, 1g of nano nickel powder, 0.3g of bismuth trioxide, 0.5g of chromium boride and 0.6g of rare earth metal powder and mix them to obtain a mixture.

[0034] S2: According to the ball-to-material ratio of 7:1, the mixture obtained in step S1 is put into a ball mill, and then the ball milling media alcohol is added to it and ball milled at a rate of 350 r / min for 10 h; dried at 85℃ for 40 min; then 0.5 g of PEG 1000 is added, and the mixture is pressed at a pressure of 40 MPa for 3 min to obtain a compact.

[0035] S3: The pressed billet obtained in step S2 is heated to 1450°C in a sintering furnace at a rate of 5°C / min, and sintered at that temperature for 1 hour. After cooling, the cemented carbide can be obtained.

[0036] The nano-nickel powder also undergoes modification treatment, specifically the following modification methods:

[0037] S11: Add 2 parts of hexagonal boron nitride nanosheets, 2 parts of fullerene powder and 3 parts of carbon nanotubes to 5 parts of sodium silicate solution with a mass fraction of 5% and stir thoroughly to obtain hexagonal boron nitride nanosheets.

[0038] S12: Subsequently, 1 part of silane coupling agent KH550, 2 parts of TiC, 3 parts of hexagonal boron nitride nanoparticles and 5 parts of 8% (w / w) dopamine hydrochloride solution were thoroughly mixed to obtain the modified solution.

[0039] S13: First, irradiate the nano-nickel powder in a proton irradiation chamber for 10 minutes at an irradiation power of 350W. After irradiation, add the irradiated nano-nickel powder to the modification liquid at a weight ratio of 2:5 and stir to modify it. Then, filter and dry it. The average particle size of the hexagonal boron nitride nanosheets is 100nm. The stirring speed for the stirring modification process is 450r / min, and the stirring time is 1h.

[0040] Example 2

[0041] This embodiment provides a method for preparing high-performance nano-hard alloys, including the following steps:

[0042] S1; According to the mass ratio of W:V:Cr of 99:0.5:0.6, ammonium metatungstate, vanadium oxalate, and chromium acetate were taken and dissolved in deionized water at a solid-liquid ratio of 1g:15ml. After drying, the precursor was obtained. The calcination temperature was controlled at 750℃, the calcination time at 2.5h, the hydrogen flow rate at 5L / min, the carbonization temperature at 1500℃, and the carbonization time at 3h. The precursor was calcined and then reduced and carbonized with hydrogen to obtain the WC powder.

[0043] Lanthanum, cerium, yttrium and rubidium were mixed in a mass ratio of 1:1.5:1.2:0.8 and stirred at a rate of 300 r / min until homogeneous to obtain rare earth metal powder.

[0044] Weigh out 98.5g of WC powder, 6g of tungsten powder, 3g of nano nickel powder, 0.7g of bismuth trioxide, 1.5g of chromium boride and 1.2g of rare earth metal powder and mix them to obtain a mixture.

[0045] S2: According to the ball-to-material ratio of 12:1, the mixture obtained in step S1 is put into a ball mill, and then alcohol is added to it for ball milling at a rate of 450 r / min for 14 h; after drying at 85℃ for 40 min; then 1.5 g of paraffin is added, and the mixture is pressed at a pressure of 60 MPa for 6 min to obtain a compact.

[0046] S3: The pressed billet obtained in step S2 is heated to 1550°C in a sintering furnace at a rate of 10°C / min, and sintered at that temperature for 3 hours. After cooling, the cemented carbide can be obtained.

[0047] The nano-nickel powder also undergoes modification treatment, specifically the following modification methods:

[0048] S11: Add 5 parts of hexagonal boron nitride nanosheets, 3 parts of fullerene powder and 4 parts of carbon nanotubes to 8 parts of sodium silicate solution with a mass fraction of 5% and stir thoroughly to obtain hexagonal boron nitride nanosheets.

[0049] S12: Subsequently, 2 parts of silane coupling agent KH550, 4 parts of TiC, 5 parts of hexagonal boron nitride nanoparticles, and 8 parts of 8% (w / w) dopamine hydrochloride solution were thoroughly mixed to obtain the modified solution.

[0050] S13: First, irradiate the nano-nickel powder in a proton irradiation chamber for 15 minutes at an irradiation power of 350W. After irradiation, add the irradiated nano-nickel powder to the modification liquid at a weight ratio of 2:5 and stir to modify it. Then, filter and dry it. The average particle size of the hexagonal boron nitride nanosheets is 100nm. The stirring speed for the stirring modification process is 500r / min, and the stirring time is 1h.

[0051] Example 3

[0052] This embodiment provides a method for preparing high-performance nano-hard alloys, including the following steps:

[0053] S1; According to the mass ratio of W:V:Cr of 97:0.4:0.5, ammonium metatungstate, vanadium oxalate, and chromium acetate were taken and dissolved in deionized water at a solid-liquid ratio of 1g:13ml. After drying, the precursor was obtained. The calcination temperature was controlled at 700℃, the calcination time at 2h, the hydrogen flow rate at 4L / min, the carbonization temperature at 1450℃, and the carbonization time at 2h. The precursor was calcined and then reduced and carbonized with hydrogen to obtain the WC powder.

[0054] Lanthanum, cerium, yttrium and rubidium were mixed in a mass ratio of 1:1.4:1:0.7 and stirred at a rate of 250 r / min until homogeneous to obtain rare earth metal powder.

[0055] Weigh out 95g of WC powder, 5g of tungsten powder, 2g of nano-nickel powder, 0.5g of bismuth trioxide, 1.2g of chromium boride and 1g of rare earth metal powder and mix them to obtain a mixture.

[0056] S2: According to the ball-to-material ratio of 10:1, the mixture obtained in step S1 is put into a ball mill, and then the ball milling media alcohol is added to it and ball milled at a rate of 420 r / min for 12 h; dried at 85℃ for 40 min; then 1.3 g of PEG 1000 or paraffin is added, and the mixture is pressed at a pressure of 55 MPa for 5 min to obtain a compact.

[0057] S3: The pressed billet obtained in step S2 is heated to 1500°C in a sintering furnace at a rate of 8°C / min, and sintered at that temperature for 2 hours. After cooling, the cemented carbide can be obtained.

[0058] The nano-nickel powder also undergoes modification treatment, specifically the following modification methods:

[0059] S11: 3.5 parts of hexagonal boron nitride nanosheets, 2.5 parts of fullerene powder and 3.5 parts of carbon nanotubes are mixed and added to 6.5 parts of sodium silicate solution with a mass fraction of 5% and stirred thoroughly to obtain hexagonal boron nitride nanosheets.

[0060] S12: Subsequently, 1.5 parts of silane coupling agent KH550, 3 parts of TiC and 4 parts of hexagonal boron nitride nanoparticles and 6.5 parts of 8% (w / w) dopamine hydrochloride solution were thoroughly mixed to obtain the modified solution;

[0061] S13: First, irradiate the nano-nickel powder in a proton irradiation chamber for 12.5 min at an irradiation power of 350 W. After irradiation, add the irradiated nano-nickel powder to the modification liquid at a weight ratio of 2:5 and stir to modify it. Then, filter and dry it. The average particle size of the hexagonal boron nitride nanosheets is 100 nm. The stirring speed for the stirring modification process is 470 r / min, and the stirring time is 1 h.

[0062] Comparative Example 1

[0063] The difference from Example 3 is that the WC powder used in step S1 is commercially available and has a particle size of 30-40 nm, while the other steps remain unchanged.

[0064] Comparative Example 2

[0065] The difference from Example 3 is that step S1 does not contain rare earth metal powder, while the other steps remain unchanged.

[0066] Comparative Example 3

[0067] The difference from Example 3 is that bismuth trioxide is not added in step S1, while the other steps remain the same.

[0068] Comparative Example 4

[0069] The difference from Example 3 is that chromium boride is not added in step S1, while the other steps remain the same.

[0070] Comparative Example 5

[0071] The difference from Example 3 is that in step S1, ordinary nickel powder is used instead of modified nano-nickel powder, while the other steps remain unchanged.

[0072] Performance testing:

[0073] Rockwell hardness was tested according to GB5237-2004; toughness was tested according to GB / T 1817-2017 Test Method for Room Temperature Impact Toughness of Hard Alloys; and bending strength was tested according to GB / T 232-2010 Standard for Bending Test of Metallic Materials. The results are shown in the table below.

[0074]

[0075] The performance test results above show that the cemented carbide prepared in Examples 1-3 possesses good hardness, toughness, and bending resistance. Example 3, in particular, exhibits superior overall performance. Comparative Examples 1-5, however, failed to employ the necessary technical solutions, resulting in significantly inferior performance compared to the examples. These experimental results further demonstrate the importance of the technical solutions defined in this invention for its technical effectiveness. Furthermore, as seen in Comparative Examples 1 and 5, and Example 3, the use of commercially available WC powder and ordinary nickel powder leads to a significant deterioration in product performance. The use of the specific WC powder and modified nickel powder of this invention results in a significantly improved product performance.

[0076] Based on the above tests, the product was placed in a 5% hydrochloric acid mist environment for 24 hours, then heat-treated at 110°C for 12 hours, and finally scratched 10 times under a 10N load. This constituted one cycle, and the product was cycled 10 times to test its corrosion resistance, high temperature resistance, and scratch stability. The test results are as follows:

[0077]

[0078] The stability test results show that in Comparative Example 5, the product stability deteriorated most significantly when ordinary nickel powder was used instead of modified nano-nickel powder. In Comparative Example 1, the WC powder was directly used from the market, and the product performance stability changed significantly. The product performance stability was most significant when the raw materials of Example 3 of this invention were used.

[0079] Based on corrosion resistance, high temperature resistance, and scratch stability tests, this invention further investigates the impact of modified nano-nickel powder on the performance stability of the product:

[0080] The nano-nickel powder also undergoes modification treatment, specifically the following modification methods:

[0081] S11: 3.5 parts of hexagonal boron nitride nanosheets, 2.5 parts of fullerene powder and 3.5 parts of carbon nanotubes are mixed and added to 6.5 parts of sodium silicate solution with a mass fraction of 5% and stirred thoroughly to obtain hexagonal boron nitride nanosheets.

[0082] S12: Subsequently, 1.5 parts of silane coupling agent KH550, 3 parts of TiC and 4 parts of hexagonal boron nitride nanoparticles and 6.5 parts of 8% (w / w) dopamine hydrochloride solution were thoroughly mixed to obtain the modified solution;

[0083] S13: First, irradiate the nano-nickel powder in a proton irradiation chamber for 12.5 min at an irradiation power of 350 W. After irradiation, add the irradiated nano-nickel powder to the modification liquid at a weight ratio of 2:5 and stir to modify it. Then, filter and dry it. The average particle size of the hexagonal boron nitride nanosheets is 100 nm. The stirring speed for the stirring modification process is 470 r / min, and the stirring time is 1 h.

[0084] Comparative Example 6 differs from Example 3 in that the modified solution did not contain silane coupling agent KH550 or TiC.

[0085] Comparative Example 7 differs from Example 3 in that hexagonal boron nitride nanoparticles were not added to the modified solution.

[0086] Comparative Example 8 differs from Example 3 in that fullerene powder and carbon nanotubes were not added during the preparation of the hexagonal boron nitride nanoparticles.

[0087] Comparative Example 9 differs from Example 3 in that hexagonal boron nitride nanosheets were not added during the preparation of the hexagonal boron nitride nanosheets.

[0088] The effects of modified nickel powder on product performance under corrosion resistance, high temperature resistance, and scratch resistance conditions were tested. The test results are as follows:

[0089]

[0090] As can be seen from Comparative Examples 6-9, the performance of the product deteriorated significantly when hexagonal boron nitride nanoparticles were not added to the modified solution. Furthermore, the performance of the product deteriorated to varying degrees when hexagonal boron nitride nanoparticles were not added during preparation, when fullerene powder and carbon nanotubes were not added, or when silane coupling agent KH550 and TiC were not added to the modified solution. Only the modified solution obtained using the specific method of this invention showed the most significant performance improvement; other methods were not as effective as those of this invention.

[0091] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nanohardened cemented carbide, characterized in that, The WC powder, the tungsten powder, the nano-nickel powder, the bismuth trioxide, the chromium boride and the rare earth metal powder are respectively 90.5-98.5 parts, 3-6 parts, 1-3 parts, 0.3-0.7 parts, 0.5-1.5 parts and 0.6-1.2 parts by weight; The nano-nickel powder is also subjected to a modification treatment, and the specific modification method is as follows: S11: 2-5 parts of hexagonal boron nitride nanosheet, 2-3 parts of fullerene powder and 3-4 parts of carbon nanotube are blended into 5-8 parts of 5% sodium silicate solution and stirred fully to obtain a hexagonal boron nitride nanosheet agent; S12: 1-2 parts of silane coupling agent KH550, 2-4 parts of TiC and 3-5 parts of the hexagonal boron nitride nanosheet agent are blended fully into 5-8 parts of 8% dopamine hydrochloride solution to obtain a modified liquid; S13: the nano-nickel powder is first irradiated in a proton irradiation box for 10-15 min at an irradiation power of 350 W, and then the irradiated nano-nickel powder is added into the modified liquid in a weight ratio of 2:5 and stirred for modification treatment, and then is subjected to filtration and drying; The preparation process of the WC powder is as follows: According to the mass ratio of WC:V:Cr in the WC powder being 95-99:0.2-0.5:0.3-0.6, ammonium metatungstate, vanadium oxalate and chromium acetate are taken, and then the ammonium metatungstate, the vanadium oxalate and the chromium acetate are dissolved in deionized water at a solid-liquid ratio of 1g:10-15ml to obtain a precursor after drying; The precursor is calcined at a calcination temperature of 650-750℃ for 1.5-2.5h, and then is subjected to hydrogen reduction carbonization at a hydrogen flow rate of 3-5L / min and a carbonization temperature of 1350-1500℃ for 1-3h to obtain the WC powder.

2. The nanohard alloy according to claim 1, wherein The rare earth metal powder comprises lanthanum, cerium, yttrium and rubidium, and the mass ratio is 1:1.2-1.5:0.8-1.2:0.4-0.

8.

3. The nanohard alloy according to claim 1, wherein the nanohard alloy is characterized by The particle size of the WC powder is 0.3-0.8nm; the particle size of the tungsten powder is 40-60nm; the particle size of the nickel powder is 2-6nm; the particle size of the bismuth trioxide is 3-7nm; the particle size of the chromium boride is 1-4nm; and the particle size of the rare earth metal is 50-70nm.

4. A method for producing nanohard alloys, characterized by, The method comprises the following steps: S1: 90.5-98.5 parts of WC powder, 3-6 parts of tungsten powder, 1-3 parts of nano-nickel powder, 0.3-0.7 parts of bismuth trioxide, 0.5-1.5 parts of chromium boride and 0.6-1.2 parts of rare earth metal powder are weighed and mixed to obtain a mixture; S2: the mixture obtained in step S1 is put into a ball mill, and ball milling medium is added to the ball mill for ball milling treatment; and then the mixture is dried and pressed to form a green compact; S3: the green compact obtained in step S2 is sintered in a sintering furnace to obtain a hard alloy; The nano-nickel powder is also subjected to a modification treatment, and the specific modification method is as follows: S11: 2-5 parts of hexagonal boron nitride nanosheet, 2-3 parts of fullerene powder and 3-4 parts of carbon nanotube are blended into 5-8 parts of 5% sodium silicate solution and stirred fully to obtain a hexagonal boron nitride nanosheet agent; S12: Then 1-2 parts of silane coupling agent KH550, 2-4 parts of TiC and 3-5 parts of hexagonal boron nitride nanosheet agent and 5-8 parts of 8% mass fraction of dopamine hydrochloride solution were blended to obtain a modified liquid; S13: The nano-nickel powder was first irradiated in a proton irradiation box for 10-15 min at an irradiation power of 350 W, and after irradiation, the irradiated nano-nickel powder was added to the modified liquid in a weight ratio of 2:5 for stirring and modification treatment, and then was filtered and dried; The preparation process of the WC powder in step S1 is as follows: According to the mass ratio of WC:V:Cr in the WC powder being 95-99:0.2-0.5:0.3-0.6, ammonium metatungstate, vanadium oxalate and chromium acetate are taken, and the solid-liquid ratio is 1g:10-15ml, the ammonium metatungstate, vanadium oxalate and chromium acetate are dissolved in deionized water, and the precursor is obtained by drying; The calcination temperature is controlled at 650-750℃, the calcination time is 1.5-2.5h, the hydrogen flow rate is 3-5L / min, the carbonization temperature is 1350-1500℃, and the carbonization time is 1-3h, and the precursor is calcined and then reduced and carbonized by hydrogen, thereby obtaining the WC powder.

5. The method of claim 4, wherein the nanohard alloy is prepared by the steps of: The ball-to-material ratio in step S2 is 7-12:1, the ball milling medium is alcohol, and the ball milling rate is 350-450r / min for 10-14h; Step S2 also includes adding 1-4 parts of sodium hexametaphosphate; ​ The pressure for pressing in step S2 is 40-60Mpa, and the pressing time is 3-6min; the forming agent is PEG 1000 or paraffin; and the sintering temperature in step S3 is 1450-1550℃, and the sintering time is 1-3h.

6. The method of claim 4, wherein the nanohard alloy is prepared by the steps of: The average particle size of the hexagonal boron nitride nanosheet is 100nm. ​ 7. The method for preparing a nano-hard alloy according to claim 4, characterized in that, The stirring speed for stirring and modification treatment is 450-500r / min, and the stirring time is 1h.

8. The application of the nanometer cemented carbide according to any one of claims 1-3 or prepared by the preparation method according to any one of claims 4-7 in a milling cutter.

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