Preparation method of superfine binding-phase-free hard alloy

Abstract

The material formula is WC-A% MC-B% M, WC refers to tungsten carbide, MC refers to one or more of crystal grain inhibitors including chromium carbide, vanadium carbide, titanium carbide, tantalum carbide and niobium carbide, M refers to one or more of metal binders including iron, cobalt, nickel, manganese and chromium, and in percentage by weight, A% is 0.5-3.0 wt%, B% is smaller than 0.5 wt%, and the balance is tungsten carbide; the WC-A% MC-B% M is split into X% WC-C% MC-D% M and (100-X)% WC, X is larger than or equal to 1 and smaller than or equal to 20, C is equal to 100A / X, D is equal to 100B / X, burdening is conducted according to the WC-C% MC-D% M, powder is subjected to ball milling, even mixing and drying, and a high-concentration raw material E is obtained; the WC powder is subjected to spray drying granulation treatment after ball milling, obtained powder is sieved, and a granulated WC powder raw material F with the particle size being 30-50 microns is obtained; the high-concentration raw material E and the WC powder raw material F are put into an acoustic resonance mixer according to the design proportion to be subjected to coating treatment, and sintering is conducted. The density of the superfine binding-phase-free hard alloy obtained through the method is larger than or equal to 99%, and the superfine binding-phase-free hard alloy is free of micro defects after being polished and can be used for aspheric glass lens molds, water jet nozzles and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of cemented carbide preparation, and in particular relates to a method for preparing ultrafine cemented carbide without a binder phase. Background Art

[0002] Due to its high hardness, high wear resistance, high hot hardness, good toughness and corrosion resistance, cemented carbide is widely used in mining, geotechnical exploration, oil and gas drilling, mold materials, rolling mills, wear-resistant parts, cutting tools and other fields. It has become an indispensable material for promoting the progress and development of various industries, plays a vital role in the national economy and social development, and is known as the "teeth" of modern industry.

[0003] Ultrafine binderless cemented carbide usually refers to WC cemented carbide with a grain size of less than 0.5μm and a binder content of less than 0.5wt%. Compared with traditional cemented carbide, it combines the advantages of high hardness and good toughness of ultrafine cemented carbide and excellent red hardness, corrosion resistance and oxidation resistance of binderless cemented carbide. This type of material is often used in aspherical glass lens molds, water jet nozzles, precision machining tools and hot processing molds. Traditional binder-phase cemented carbide often uses cobalt as a binder. The binder cobalt can effectively promote sintering densification, but it will also reduce the wear resistance, corrosion resistance and high temperature performance of the material. The binder content of ultrafine binderless cemented carbide is less than 0.5wt%, and it is difficult to achieve sintering densification using traditional sintering methods. The content of binder and grain inhibitor in the raw materials is low (especially the binder content is less than 0.5wt%), and the particle size of the raw material powder is less than 1μm. The traditional mixing method and mixing process flow are very likely to cause local powder agglomeration and inability to mix evenly. The unevenly mixed powder will form fine pores after sintering, which significantly affects the performance of the cemented carbide.

[0004] Patent CN09434122 uses high-energy ball milling to prepare TiC with vacancy energy 0.4 To reduce the sintering temperature of tungsten carbide without metal bonding phase and promote sintering; CN111996431A uses a rolling ball mill to mix tungsten carbide, chromium carbide, titanium carbide, zirconium carbide and other materials evenly, and uses a gas pressure sintering furnace to prepare a bonding phase-free cemented carbide; CN113897506A adds carbon powder during inert gas ball milling to avoid the performance deterioration caused by carbon deficiency in raw materials and oxidation and carbon deficiency during sintering; CN118703856A uses a magnetic stirring-ultrasonic dual mixing method to prepare rGO / G / Y 2 O 3 Composite powder, preparation of rGO / G / Y by dry mixing method 2 O 3 / WC pre-composite powder, high-energy ball milling method is used to prepare sintering raw materials, and nanocrystalline binderless cemented carbide is finally sintered. Patents for the preparation of ultrafine binderless cemented carbide using high-energy ball milling are often seen, but there are no related patents for the method of uniformly mixing ultrafine and low-content binders, grain inhibitors and ultrafine tungsten carbide powders in raw materials.

[0005] Therefore, how to provide a method for uniformly mixing ultrafine and low-content binder, grain inhibitor and ultrafine tungsten carbide powder to finally prepare ultrafine binder-free cemented carbide without micropores is a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art, and to provide a method for preparing ultrafine binderless cemented carbide in view of the problem that the existing ultrafine binderless cemented carbide is difficult to mix evenly using the traditional mixing method and process flow, and has some fine pores after sintering. The ultrafine binderless cemented carbide prepared by the method has a density of ≥99%, and has no fine defects after polishing, and can be used for aspheric glass lens molds, water jet nozzles, etc.

[0007] To achieve the above object, the present invention adopts the following technical solution: A method for preparing ultrafine binder-free cemented carbide comprises the following steps: 1) The formula of ultrafine binderless cemented carbide material is WC-A%MC-B%M, where WC refers to tungsten carbide, MC refers to one or more of the grain inhibitors chromium carbide, vanadium carbide, titanium carbide, tantalum carbide, niobium carbide, etc., and M refers to one or more of the metal binders iron, cobalt, nickel, manganese, chromium, etc., where, in terms of weight percentage, the grain inhibitor content A% is 0.5wt%~3.0wt%, the metal binder content B% is <0.5wt%, and the balance is tungsten carbide; 2) Split WC-A%MC-B%M into X%WC-C%MC-D%M and (100-X)%WC, where 1≤X≤20, C=100A÷X, D=100B÷X, and mix the powders evenly and achieve high-energy refining treatment in a planetary ball mill according to the WC-C%MC-D%M batching. After the ball milling, take out the slurry and dry it to obtain high-concentration raw material E; 3) The WC powder and alcohol are mixed evenly by a planetary ball mill, and the slurry obtained by ball milling is spray dried and granulated to obtain a granulated WC powder raw material F with a particle size of 30-50 μm after sieving; 4) According to the designed ratio, the high-concentration raw material E and the granulated WC powder raw material F are placed in an acoustic resonance mixer for coating treatment to obtain a sintering raw material G; 5) Place the sintering raw material G into a cemented carbide mold, cold-press the powder into a green body at a pressure of 100-300 MPa, place the green body into a graphite mold, adjust the graphite mold to ensure that the pressure heads at both ends are highly symmetrical, and then place the adjusted graphite mold into a spark plasma sintering press, evacuate to less than 10 Pa, and then sinter. After sintering, cool to room temperature, take out the graphite mold, and demold to obtain an ultrafine cemented carbide without a binder phase.

[0008] Specifically, in step 1), the particle size of the tungsten carbide powder is ≤400nm, the particle size of the grain inhibitor powder is ≤1μm, and the particle size of the metal binder powder is ≤500nm.

[0009] Specifically, in step 2), during ball milling, the mixing tank is a cemented carbide tank, the mass ratio of grinding balls to powder is 5:1-10:1, and the grinding ball materials include but are not limited to cemented carbide balls, ceramic balls, and metal balls; the ball milling process is: ball milling medium alcohol, ball-to-powder ratio 5:1-10:1, ball milling speed 300-400rpm, and ball milling time 50-70h.

[0010] Specifically, in step 3), during ball milling, the mixing tank is a carbide tank, the mass ratio of grinding balls to powder is 2:1~10:1, and the grinding ball materials include but are not limited to carbide balls, ceramic balls, and metal balls; the ball milling process is: ball milling medium alcohol, ball-to-powder ratio 2:1~10:1, ball milling speed 20~150rpm, ball milling time 2~5h. Further, in step 3), a spray drying granulation equipment is used for spray drying granulation treatment, with a feed pressure of 0.2~0.5MPa, an inlet temperature of 150~300℃, an outlet temperature of 80~120℃, and an atomizer speed of 5000~20000rpm.

[0011] Specifically, in step 4), the coating process is: mixing acceleration 60-100g, mixing time 5-20min.

[0012] When the vacuum degree of the vacuum chamber reaches less than 10Pa, the sintering of the material begins. Specifically, in step 5), the sintering process is as follows: the initial pressure of the material is 10MPa, the first stage is heated to 900℃ at 100℃ / min, and the pressure is increased from 10MPa to 25MPa; the second stage is kept at 900℃, 25MPa for 10min; the third stage is heated to 1100℃ at 100℃ / min, and the pressure is increased from 25MPa to 45MPa; the fourth stage is heated to 1500℃ at 80℃ / min, and the pressure remains unchanged; the fifth stage is heated to the final sintering temperature at 50℃ / min, the final temperature is 1600℃~1900℃, and the pressure is kept constant at 45MPa; the sixth stage is kept at the final temperature, 45MPa for 5~20min; the seventh stage is cooled to 800℃ at a cooling rate of 50℃ / min.

[0013] The invention provides an ultrafine binder-free hard alloy prepared by the preparation method.

[0014] The main innovations of the method of the present invention are: First, it is a method for obtaining sintering raw materials. The raw material formula is obtained in two steps. The first step is high-energy ball milling of high-concentration raw materials. On the one hand, it can improve the weighing accuracy and production efficiency. On the other hand, the sintering raw materials composed of the refined high-concentration raw materials and tungsten carbide have high sintering activity due to the differences in powder particle size and specific surface area, which can promote sintering densification; second, it is a method for uniformly mixing extremely trace binders and grain inhibitors. The high-concentration raw materials are refined by high-energy ball milling, and a large-particle WC powder is obtained by a spray drying granulation method. The two powders are coated in an acoustic resonance mixer. The nano-scale powder can be evenly coated on the large-size WC powder to avoid sintering pores caused by hard agglomeration of nano-powders and promote sintering densification.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1) The present invention divides the mixing and batching of ultrafine binderless cemented carbide raw materials into two steps. The high-concentration raw materials obtained in the first step can be directly mixed with tungsten carbide to obtain sintering raw materials. When using this method for production, high-concentration raw materials can be prepared first, which is convenient for subsequent production operations and improves production efficiency. The high-concentration raw materials have high content of grain inhibitors and metal binders, which is convenient for weighing and effectively improves the weighing accuracy.

[0016] 2) The present invention divides the mixing and batching of ultrafine binderless cemented carbide raw materials into two steps. The first step adopts a ball milling method with a high rotation speed and a high ball-to-material ratio to refine part of the powder grains in the raw materials. There is a particle size difference between the fine-grained high-concentration raw materials and the WC powder. After cold pressing, the porosity of the green body is reduced, the sintering activation energy is increased, and the sintering densification is effectively promoted.

[0017] 3) The present invention uses an acoustic resonance mixer to mix the high-concentration raw material obtained by ball milling with the large-particle WC powder obtained by spray drying and granulation. The nano-level high-concentration raw material is adsorbed on the large-particle WC powder by van der Waals force, achieving uniform coating of the high-concentration raw material on the WC powder. This method can achieve uniform mixing of trace binders and grain inhibitors, and avoid micropores caused by hard agglomeration of nano powders during sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a process flow chart for preparing the ultrafine binder-free cemented carbide; Figure 2 The ultrafine binder-free cemented carbide material prepared by the present invention; Figure 3The microstructure comparison between the ultrafine binderless cemented carbide material of the present invention (left) and the direct ball milling + spark plasma sintering material (right); Figure 4 The ultrafine binder-free cemented carbide material (left) and SEM image (right) prepared in Example 1 of the present invention; Figure 5 The ultrafine binderless cemented carbide material (left) and SEM image (right) prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0020] In the following examples, the raw materials used are all common commercial products that can be directly purchased, or can be prepared by conventional methods in the art.

[0021] Example 1 A method for preparing ultrafine cemented carbide material without binder phase, the material formula is WC-0.6%Cr 3 C 2 -0.2%Co. The specific preparation method is as follows (see Figure 1 ): (1) The raw material WC powder particle size is 300 nm, the grain inhibitor Cr 3 C 2 The powder particle size is 1 μm, and the metal binder Co powder particle size is 500 nm.

[0022] (2) Weigh 92g of WC powder and Cr 3 C 2 6g of powder, 2g of Co powder. Weigh 600g of 5mm carbide balls and 40ml of anhydrous ethanol, and put the weighed powder, carbide balls and anhydrous ethanol into a carbide tank. Set the ball milling process to: speed 400rpm, ball milling time 70h. After the ball milling is completed, sieve the powder and the grinding balls, and dry them to obtain a high-concentration raw material.

[0023] (3) Weigh 150g of WC powder, 360g of 5mm carbide balls, and 40ml of anhydrous ethanol. Place the weighed WC powder, carbide balls, and anhydrous ethanol into a carbide tank. Set the ball milling process to: speed 120rpm, ball milling time 2h. After ball milling, sieve the WC powder and grinding balls, and spray dry the slurry for granulation. The feed pressure is 0.3MPa, the inlet temperature is 220℃, the outlet temperature is 100℃, and the atomizer speed is 8000rpm. The granulated powder is sieved to obtain WC powder with a particle size of 30~50μm.

[0024] (4) According to the designed ratio, the high-concentration raw material accounts for 10%, 12 g of the high-concentration raw material obtained in step (2) and 108 g of the granulated WC powder obtained in step (3) are weighed, and the coating treatment is carried out in an acoustic resonance mixer. The coating process is: mixing acceleration 80 g, mixing time 10 min, to obtain uniformly coated sintering raw materials.

[0025] (5) Place 120 g of the sintering raw material obtained in step (4) into a carbide mold and cold press the powder into a green body at a pressure of 100 MPa. Place the green body into a φ30 mm graphite mold and adjust the graphite mold to ensure that the pressure heads at both ends are highly symmetrical. Place the adjusted graphite mold into a spark plasma sintering press and evacuate to within 10 Pa.

[0026] (6) When the vacuum degree of the vacuum chamber reaches less than 10Pa, the sintering of the material begins. The sintering process is as follows: the initial pressure of the material is 10MPa, the first stage of the process is heated to 900℃ at 100℃ / min, and the pressure is increased from 10MPa to 25MPa, and the second stage of the process is kept at 900℃ and 25MPa for 10min. The third stage of the process is heated to 1100℃ at 100℃ / min, and the pressure is increased from 25MPa to 45MPa. The fourth stage of the process is heated to 1500℃ at 80℃ / min, and the pressure remains unchanged. The fifth stage of the process is heated to the final sintering temperature at 50℃ / min, the final temperature is 1620℃, and the pressure is kept constant at 45MPa. The sixth stage of the process is kept at the final temperature and 45MPa for 10min. The seventh stage of the process is cooled to 800℃ at a cooling rate of 50℃ / min.

[0027] (7) After the material is cooled to room temperature, the graphite mold is removed and demolded to obtain an ultrafine cemented carbide material without a binder phase.

[0028] Example 2 A method for preparing ultrafine cemented carbide material without binder phase, the material formula is WC-0.6%Cr 3 C 2 -0.5%VC-0.1%Ni. The specific preparation method is as follows: (1) The raw material WC powder particle size is 300nm, the grain inhibitor Cr 3 C 2 The powder particle size is 1 μm, the grain inhibitor VC powder particle size is 1 μm, and the metal binder Ni powder particle size is 500 nm.

[0029] (2) Weigh 76g of WC powder, Cr 3 C 212g of powder, 10g of VC powder, and 2g of Ni powder. Weigh 500g of 5mm carbide balls and 40ml of anhydrous ethanol, and put the weighed powder, carbide balls, and anhydrous ethanol into a carbide tank. Set the ball milling process to: speed 350rpm, ball milling time 60h. After the ball milling is completed, sieve the powder and the grinding balls, and dry them to obtain a high-concentration raw material.

[0030] (3) Weigh 150g of WC powder, 360g of 5mm carbide balls, and 40ml of anhydrous ethanol, and put the weighed powder, carbide balls, and anhydrous ethanol into a carbide tank. Set the ball milling process to: speed 150rpm, ball milling time 5h. After the ball milling, the powder and the grinding balls are sieved, and the slurry is spray-dried and granulated with a feed pressure of 0.3MPa, an inlet temperature of 220℃, an outlet temperature of 100℃, and an atomizer speed of 10000rpm. The granulated powder is sieved to obtain WC powder with a particle size of 30~50μm.

[0031] (4) According to the designed ratio of high-concentration raw materials, the proportion of high-concentration raw materials is 5%. 6 g of the high-concentration raw materials obtained in step (2) and 114 g of the granulated WC powder obtained in step (3) are weighed and coated in an acoustic resonance mixer. The coating process is: mixing acceleration 70 g, mixing time 8 min, to obtain uniformly coated sintering raw materials.

[0032] (5) Place 120 g of the sintering raw material obtained in step (4) into a carbide mold and cold press the powder into a green body at a pressure of 100 MPa. Place the green body into a φ30 mm graphite mold and adjust the graphite mold to ensure that the pressure heads at both ends are highly symmetrical. Place the adjusted graphite mold into a spark plasma sintering press and evacuate to within 10 Pa.

[0033] (6) When the vacuum degree of the vacuum chamber reaches less than 10Pa, the sintering of the material begins. The sintering process is as follows: the initial pressure of the material is 10MPa, the first stage of the process is heated to 900℃ at 100℃ / min, and the pressure is increased from 10MPa to 25MPa, and the second stage of the process is kept at 900℃ and 25MPa for 10min. The third stage of the process is heated to 1100℃ at 100℃ / min, and the pressure is increased from 25MPa to 45MPa. The fourth stage of the process is heated to 1500℃ at 80℃ / min, and the pressure remains unchanged. The fifth stage of the process is heated to the final sintering temperature at 50℃ / min, the final temperature is 1700℃, and the pressure is kept constant at 45MPa. The sixth stage of the process is kept at the final temperature and 45MPa for 10 min. The seventh stage of the process is cooled to 800℃ at a cooling rate of 50℃ / min.

[0034] (7) After the material is cooled to room temperature, the graphite mold is removed and demolded to obtain an ultrafine cemented carbide material without a binder phase.

[0035] Comparative Example 1 A method for preparing ultrafine cemented carbide material without binder phase, the material formula is WC-0.6%Cr 3 C 2 -0.5%VC-0.1%Ni. The specific preparation method is as follows: (1) The raw material WC powder particle size is 300nm, the grain inhibitor Cr 3 C 2 The powder particle size is 1 μm, the grain inhibitor VC powder particle size is 1 μm, and the metal binder Ni powder particle size is 500 nm.

[0036] (2) Weigh 118.56 g of WC powder, Cr 3 C 2 0.72g of powder, 0.6g of VC powder, and 0.12g of Ni powder. Weigh 600g of 5mm carbide balls and 40ml of anhydrous ethanol, and put the weighed powder, carbide balls, and anhydrous ethanol into a carbide tank. Set the ball milling process to: speed 350rpm, ball milling time 30h. After the ball milling is completed, the powder and the grinding balls are sieved and dried to obtain the sintering raw materials.

[0037] (3) Place the sintering raw material obtained in step (2) into a cemented carbide mold and cold press the powder into a green body at a pressure of 100 MPa. Place the green body into a φ30 mm graphite mold and adjust the graphite mold to ensure that the pressure heads at both ends are highly symmetrical. Place the adjusted graphite mold into a spark plasma sintering press and evacuate to within 10 Pa.

[0038] (4) When the vacuum degree of the vacuum chamber reaches less than 10Pa, the sintering of the material begins. The sintering process is as follows: the initial pressure of the material is 10MPa, the first stage of the process is heated to 900℃ at 100℃ / min, and the pressure is increased from 10MPa to 25MPa, and the second stage of the process is kept at 900℃ and 25MPa for 10min. The third stage of the process is heated to 1100℃ at 100℃ / min, and the pressure is increased from 25MPa to 45MPa. The fourth stage of the process is heated to 1500℃ at 80℃ / min, and the pressure remains unchanged. The fifth stage of the process is heated to the final sintering temperature at 50℃ / min, the final temperature is 1700℃, and the pressure is kept constant at 45MPa. The sixth stage of the process is kept at the final temperature and 45MPa for 10 min. The seventh stage of the process is cooled to 800℃ at a cooling rate of 50℃ / min.

[0039] (5) After the material is cooled to room temperature, the graphite mold is removed and demolded to obtain an ultrafine cemented carbide material without a binder phase.

[0040] Table 1 Comparison of basic properties of different sintered materials It can be seen from the above table that the density of the ultrafine binderless cemented carbide material prepared by the present invention is ≥15.40g / cm 3 , Vickers microhardness ≥ 2500HV 5 The lower the binder content, the higher the microhardness. Under the same formula, the density and Vickers microhardness of the cemented carbide material prepared by direct ball milling and then spark plasma sintering are lower than those of the cemented carbide material prepared in the embodiment of the present invention.

[0041] Figure 2 The ultrafine binder-free cemented carbide material prepared by the present invention is given. Figure 3 The microstructure comparison of the ultrafine binderless cemented carbide material of the present invention (left) and the direct ball milling + spark plasma sintering material (right); it can be seen from the figure that after flat grinding and polishing, the cemented carbide material prepared by the present invention has a fine structure without microscopic pores under the optical microscope, while the cemented carbide material obtained by direct ball milling + spark plasma sintering has a large number of pores. The ultrafine binderless cemented carbide prepared by the method of the present invention has a density of ≥99%, and there are no microscopic defects after polishing, and can be used for aspheric glass lens molds, water jet nozzles, etc.

[0042] Figure 4 The ultrafine binderless cemented carbide material (left) and SEM image (right) prepared in Example 1 of the present invention. It can be seen from the figure that the cemented carbide material prepared in Example 1 of the present invention has a regular shape, and the grain size of the sample is ≤500nm after flat grinding, polishing and corrosion.

[0043] Figure 5 The ultrafine binderless cemented carbide material prepared in Example 2 of the present invention (left) and SEM image (right). It can be seen from the figure that the cemented carbide material prepared in Example 2 of the present invention has a regular shape, and the grain size of the sample is ≤500nm after flat grinding, polishing and corrosion.

Claims

1. A method for preparing ultrafine binder-free cemented carbide, characterized in that: The steps include: 1) The formula of ultrafine binderless cemented carbide material is WC-A%MC-B%M, where WC refers to tungsten carbide, MC refers to one or more of the grain inhibitors chromium carbide, vanadium carbide, titanium carbide, tantalum carbide, and niobium carbide, and M refers to one or more of the metal binders iron, cobalt, nickel, manganese, and chromium. In terms of weight percentage, the grain inhibitor content A% is 0.5wt%~3.0wt%, the metal binder content B% is less than 0.5wt%, and the balance is tungsten carbide; 2) Split WC-A%MC-B%M into X%WC-C%MC-D%M and (100-X)%WC, where 1≤X≤20, C=100A÷X, D=100B÷X, mix the powders evenly in a planetary ball mill according to the WC-C%MC-D%M batching, take out the slurry after the ball milling and dry it to obtain a high-concentration raw material E; 3) The WC powder and alcohol are mixed evenly by a planetary ball mill, and the slurry obtained by ball milling is spray dried and granulated to obtain a granulated WC powder raw material F with a particle size of 30-50 μm after sieving; 4) According to the designed ratio, the high-concentration raw material E and the granulated WC powder raw material F are placed in an acoustic resonance mixer for coating treatment to obtain a sintering raw material G; 5) Place the sintering raw material G into a cemented carbide mold, cold-press the powder into a green body at a pressure of 100-300 MPa, place the green body into a graphite mold, and then place it into a spark plasma sintering press, evacuate to less than 10 Pa, and then sinter. After sintering, cool to room temperature, take out the graphite mold, and demold to obtain an ultrafine cemented carbide without a binder phase.

2. The method for preparing the ultrafine binder-free cemented carbide according to claim 1, characterized in that: In step 1), the particle size of the tungsten carbide powder is ≤400nm, the particle size of the grain inhibitor powder is ≤1μm, and the particle size of the binder powder is ≤500nm.

3. The method for preparing the ultrafine binder-free cemented carbide according to claim 1, characterized in that: In step 2), during ball milling, the mixing tank is a cemented carbide tank, the mass ratio of grinding balls to powder is 5:1-10:1, and the grinding ball materials include but are not limited to cemented carbide balls, ceramic balls, and metal balls; the ball milling process is: ball milling medium alcohol, ball milling speed 300-400rpm, and ball milling time 50-70h.

4. The method for preparing the ultrafine binder-free cemented carbide according to claim 1, characterized in that: In step 3), during ball milling, the mixing tank is a cemented carbide tank, the mass ratio of grinding balls to powder is 2:1~10:1, and the grinding ball materials include but are not limited to cemented carbide balls, ceramic balls, and metal balls; the ball milling process is: ball milling medium alcohol, ball milling speed 20~150rpm, and ball milling time 2~5h.

5. The method for preparing ultrafine binder-free cemented carbide according to claim 1, characterized in that: In step 3), a spray drying granulation device is used for spray drying granulation treatment, with a feed pressure of 0.2-0.5 MPa, an inlet temperature of 150-300° C., an outlet temperature of 80-120° C., and an atomizer speed of 5000-20000 rpm.

6. The method for preparing ultrafine binder-free cemented carbide according to claim 1, characterized in that: In step 4), the coating process is: mixing acceleration 60~100g, mixing time 5~20min.

7. The method for preparing ultrafine binder-free cemented carbide according to claim 1, characterized in that: In step 5), the sintering process is as follows: the initial pressure of the material is 10MPa, the temperature is raised to 900°C at 100°C / min in the first stage, and the pressure is raised from 10MPa to 25MPa; the second stage is kept at 900°C and 25MPa for 10min; the third stage is heated to 1100°C at 100°C / min, and the pressure is raised from 25MPa to 45MPa; the fourth stage is heated to 1500°C at 80°C / min, and the pressure remains unchanged; The fifth process is to increase the temperature to the final sintering temperature at 50°C / min, with the final temperature ranging from 1600°C to 1900°C, and the pressure is kept constant at 45MPa; The sixth process is to maintain the final temperature at 45 MPa for 5 to 20 minutes; the seventh process is to cool the temperature to 800°C at a cooling rate of 50°C / min.

8. Ultrafine binder-free cemented carbide prepared by the preparation method according to any one of claims 1 to 7.

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