Preparation process of a high-performance polycrystalline diamond

Abstract

The present invention belongs to the technical field of diamond composite material preparation, and particularly relates to a preparation process of high-performance polycrystalline diamond. The preparation process includes processes such as purification treatment, mixing, ball milling, pressing, and sintering. Through formula optimization and process adjustment, the present invention uses diamond micropowders with different particle sizes, and etches the diamond surface by the molten salt method. On the one hand, the surface roughness of the diamond is increased. On the other hand, the small-particle-size diamonds can fill the voids between the large-particle diamonds, improving the contact area between diamond particles. During the preparation process, new derivatives will be obtained during the combination of diamond micropowders, boron carbide, and titanium powder, which can further promote the thermal stability and wear resistance of polycrystalline diamond, making up for the problems of poor thermal stability and insufficient toughness of traditional polycrystalline diamond.

Description

Technical Field

[0001] The present invention belongs to the technical field of diamond composite material preparation, and particularly relates to a preparation process of high-performance polycrystalline diamond. Background Art

[0002] Polycrystalline diamond has a wide range of applications due to its good wear resistance, corrosion resistance, high hardness, low friction coefficient, low adhesion, low machining roughness, isotropy, long service life, etc., and is an essential cutting tool in industrial production. However, common artificial diamond particles are generally used as abrasives and cannot be used as cutting tools. They need to be aggregated into blocks by a binder to be used. In the preparation process of traditional polycrystalline diamond, sintering aids such as Fe, Co, Ni, Si, ceramics, etc. are added. The addition of sintering aids can not only reduce the synthesis pressure and temperature, but also promote the combination of diamond carbon-carbon bonds to make diamond particles more tightly connected together. However, the presence of the binder also limits the improvement of the performance of polycrystalline diamond.

[0003] As a raw material and main component of cutting tools, various preparation methods of polycrystalline diamond have been disclosed in the prior art. For example, the Chinese patent with the publication number CN110625123A discloses a high-performance polycrystalline diamond composite sheet and its preparation method, including a cemented carbide substrate, and a silicon carbide-diamond transition layer and a polycrystalline diamond layer on the surface of the cemented carbide substrate. This patent injects nitrogen ions on the diamond surface by an ion beam implantation method to improve the thermal stability of the polycrystalline diamond composite sheet, and uses a chemical vapor deposition method to deposit a silicon carbide-diamond gradient transition layer on the surface of the cemented carbide substrate, which can inhibit the diffusion of cobalt elements to the polycrystalline diamond layer and extend the service life of the polycrystalline diamond layer.

[0004] Another example is the Chinese patent with the publication number CN112746814A, which discloses a high-temperature and wear-resistant polycrystalline diamond composite sheet and its preparation method. The polycrystalline diamond composite sheet is made of a mixed powder composed of diamond micro-powder coated with fullerene, boron-doped diamond micro-powder, boron carbide micro-powder and nano-diamond micro-powder as raw materials, and sintered with cemented carbide under the conditions of a pressure of 6.2 GPa to 7.2 GPa and a temperature of 1620 °C to 1780 °C. The polycrystalline diamond composite sheet of this patent can improve the density, hardness, wear resistance, thermal stability and other properties of the polycrystalline diamond composite sheet.

[0005] However, with the accelerating pace of industrial technology upgrading, some emerging industries have gradually emerged, and the requirements for cutting tools are getting higher and higher. The polycrystalline diamond prepared by traditional methods can no longer meet the needs of the industry. Therefore, a preparation process of high-performance polycrystalline diamond is sought.

[0006] The density of boron carbide (B4C) is 2.5 g / cm3 , with a melting point of 2450 °C, an elastic modulus of 450 GPa, and a coefficient of thermal expansion of 4.5×10 -6 / K -1 , and has the characteristics of low density, high strength, high temperature stability, and good chemical stability; the density of titanium powder is 4.5 g / cm 3 , with a melting point of 1668 °C, an elastic modulus of 450 GPa, and a coefficient of thermal expansion of 9.41 - 10.03×10 -6 / K -1 , and the thermal conductivity is 16.3 (W·m -1 ·K -1 ), and has the characteristics of low density, low thermal conductivity, small linear shrinkage rate, and active chemical properties.

[0007] Research shows that during the preparation of polycrystalline diamond, introducing boron carbide and titanium powder into diamond can increase the thermal stability and mechanical properties of polycrystalline diamond, including hardness, wear resistance, and impact toughness. At the same time, new derivatives obtained during the combination of the three can effectively enhance the strength and wear resistance of polycrystalline diamond.

[0008] Based on this, the present invention is improved on the basis of the existing technology. By adjusting the binder composition and process parameters of the preparation method during the preparation of polycrystalline diamond, it is expected to improve the thermal stability and toughness of polycrystalline diamond while also increasing its service life. Summary of the Invention

[0009] In view of the above problems, the present invention provides a preparation process for high-performance polycrystalline diamond through formula optimization and process adjustment. This process solves the problems of poor high-temperature stability and poor impact toughness of traditional polycrystalline diamond. By optimizing the ratio of each raw material and using high-temperature and high-pressure conditions, polycrystalline diamond with high hardness, good wear resistance, high impact toughness, and good thermal stability is obtained.

[0010] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0011] A preparation method for high-performance polycrystalline diamond, comprising the following steps:

[0012] I. Treatment of raw materials

[0013] 1) Purification treatment of raw materials: Take diamond micropowders with different particle sizes as the substrate, and use the microwave-molten salt method to purify the surface of the diamond micropowders. The specific steps are as follows:

[0014] First, take diamond micropowders with particle sizes of 20 - 25 μm and 4 - 10 μm respectively, stir and mix them evenly, and grind them. Then, fully mix the molten salt with the diamond micropowders of the two particle sizes (the mixing time is preferably 1 - 2 h) to obtain a mixed powder;

[0015] Then heat the mixed powder in a microwave tube furnace. During the heating process, introduce a protective gas, and after heating, cool it to room temperature (e.g., 25 ± °C) with the furnace; place the sample (mixed powder) in an ultrasonic cleaner for ultrasonic treatment for 1 - 3 h, with an ultrasonic power of 500 - 600 W and an ultrasonic temperature of 120 - 150 °C, clean it, and remove substances such as salts (molten salts) on the surface of the sample to obtain diamond micropowders of two particle sizes after purification treatment, dry them, and reserve for use;

[0016] 2) Mixing and ball milling: Mix and ball mill the diamond micropowders of two particle sizes after purification treatment in step 1) with boron carbide micropowder and titanium powder. The specific steps are as follows:

[0017] Mix the material obtained in step 1) (mainly diamond micropowders with particle sizes of 20 - 25 μm and 4 - 10 μm after purification treatment) with boron carbide micropowder and titanium powder to obtain a mixed material, place it in a ball mill tank for ball milling, dry it after ball milling, evacuate it, and perform vacuum heat treatment to obtain a solid powder; The purpose of vacuum heat treatment is mainly to remove impurities adsorbed on the surface of the powder during the grinding process and simultaneously activate the activity on the surface of the powder;

[0018] II. Pressing

[0019] 3) Pre - pressing: Place the solid powder after vacuum heat treatment in step 2) in a metal cup and perform pre - pressing in a mold with a hydraulic press to obtain a sample;

[0020] 4) Assembly and sintering: Assemble the sample obtained in step 3) with pyrophyllite, and then place it in a six - sided top press for high - temperature and high - pressure sintering to obtain a polycrystalline diamond blank;

[0021] Grind and polish the prepared polycrystalline diamond blank to finally obtain polycrystalline diamond with a dense and evenly distributed microstructure.

[0022] Furthermore, in step 1), the weight ratio of diamond micropowders with particle sizes of 20 - 25 μm and 4 - 10 μm is (65 - 70):(20 - 22).

[0023] Furthermore, in step 1), the molten salt is sodium chloride and potassium chloride, and the mass ratio of the two is (0.5 - 2):1; both sodium chloride and potassium chloride are of analytical purity, with a purity ≥ 99%.

[0024] Furthermore, in step 1), the ratio of the total mass of sodium chloride and potassium chloride to the total mass of diamond micropowders of two particle sizes is 1:1.

[0025] Furthermore, in step 1), during heating, the heating rate is 80 - 100 °C / min. After rising to 900 - 1100 °C, hold for 1 - 2 h.

[0026] Further, in step 1), the protective gas is argon or nitrogen.

[0027] Further, in step 2) during mixing and ball milling, by weight percentage, the proportions of the raw materials in the mixture are as follows: diamond micropowder with a particle size of 20 - 25 μm is 60 - 70 wt.%, diamond micropowder with a particle size of 4 - 10 μm is 20 - 25 wt.%, boron carbide micropowder is 5 - 10 wt.%, and titanium powder is 2 - 7 wt.%.

[0028] Further, in step 2), during ball milling, the ball - to - material ratio (mass ratio) of the ball milling medium (grinding balls) to the mixture is 1:1, the ball milling speed is 30 - 550 r / min, and the ball milling time is 6 - 10 h.

[0029] More preferably, anhydrous ethanol can be added as a lubricant during the ball milling process.

[0030] More preferably, when ball milling, two types of ball milling media (grinding balls) are selected, both made of YG8, with diameters of 8 - 12 mm and 4 - 6 mm respectively, and the weight ratio of the two is 1:1.

[0031] Further, in step 2), the vacuum heat treatment temperature is 700 - 900 °C, the time is 30 - 60 min, and the vacuum degree is (1 - 3)×10 -3 Pa.

[0032] Further, in step 3), the material of the metal cup is any one of tantalum, molybdenum, and niobium.

[0033] Further, in step 3), during pre - pressing, the pressure of the hydraulic press is 150 - 200 Mpa, and the pressure - holding time is 3 - 5 s.

[0034] Further, in step 4), the sintering pressure is 4 Gpa - 8 Gpa, the temperature is 1300 °C - 1700 °C, and the heat - preservation time is 0 - 600 s; after sintering, the temperature is reduced to 700 - 750 °C at a cooling rate of 80 - 90 °C / min, heat - preserved for 5 - 12 s, and finally reduced to room temperature, while the pressure is reduced to atmospheric pressure at a pressure - reducing rate of 0.3 - 0.5 GPa / min.

[0035] The above - mentioned method prepares high - performance polycrystalline diamond by ball milling, heat treatment, and pressing of diamond micropowder, boron carbide micropowder, and titanium powder with specific ratios.

[0036] Further, the present invention also provides the application of the high - performance polycrystalline diamond in manufacturing cutting tools and drilling tools.

[0037] The high-performance polycrystalline diamond prepared by the present invention is mainly used in the production of cutting tools, oil drilling tools, wire drawing dies, mining and wear-resistant components, etc. Since polycrystals have a polycrystalline structure, wear is non-directional, and grain gaps can store lubricating oil. When used in wire drawing dies, not only is the service life higher than that of natural single-crystal wire drawing dies, but also the surface quality of the drawn metal wire is good.

[0038] Specifically, the polycrystalline diamond of the present invention is used to manufacture various cutting tools, including turning tools, milling cutters, boring tools, etc., for processing high-hardness and wear-resistant metal and non-metal materials, and its performance is far higher than that of cemented carbide or single-crystal diamond tools.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The present invention uses diamond micropowders with different particle sizes to etch the surface of diamond by the molten salt method. On the one hand, it increases the surface roughness of diamond. On the other hand, small-particle-size diamonds can fill the voids between large-particle diamonds, improving the contact area between diamond particles.

[0041] The present invention introduces two binders, boron carbide and titanium powder. Boron carbide will release carbon and boron elements under high temperature and high pressure. When it comes into contact with diamond particles, chemical reactions can occur to generate borides and carbon-carbon chemical bonds, improving the bonding between the binder and diamond. At the same time, boron carbide has better high-temperature resistance and wear resistance than cobalt and silicon, acting as a skeleton in diamond particles and enhancing the high-temperature resistance and wear resistance of the embryo body. Moreover, strong nitride (titanium nitride) can generate stable compounds on the surface of diamond, further improving the density and wear resistance of polycrystalline diamond.

[0042] Titanium powder can combine with the carbon bonds on the surface of diamond and the free carbon bonds in boron carbide to form titanium carbide, thus tightly binding diamond and the binder together. Titanium powder can also combine with the oxygen and nitrogen adsorbed on the surface of diamond to form titanium dioxide and titanium nitride, reducing the porosity of diamond.

[0043] In the preparation method of the present invention, boron carbide and titanium powder are used as binders, and diamond micropowders with different particle sizes, doped boron carbide micropowders and titanium powder are used. Under high temperature and high pressure conditions, polycrystalline diamond with excellent performance is prepared. It can improve the heat resistance and toughness of the sintered body. At the same time, new derivatives will be obtained during the combination of diamond micropowders, boron carbide and titanium powder, which can further promote the thermal stability and wear resistance of polycrystalline diamond, making up for the problems of poor thermal stability and insufficient toughness of traditional polycrystalline diamond. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is an electron microscope picture of the polycrystalline diamond prepared in Example 1;

[0045] Figure 2 This is an electron microscope image of the polycrystalline diamond prepared in Example 2;

[0046] Figure 3 This is an electron microscope image of the polycrystalline diamond prepared in Example 3. DETAILED DESCRIPTION

[0047] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] In the following examples, the particle size of the boron carbide powder is 5-12 μm (purchased from Henan Sicheng Grinding Technology Co., Ltd.), the particle size of the titanium powder is 4-10 μm (purchased from Baoji Hengchuang Metal Products Co., Ltd.), and the diamond powder is single crystal purchased from Zhecheng Huifeng Diamond Technology Co., Ltd.

[0049] Example 1

[0050] Embodiment 1 provides a method for preparing high-performance polycrystalline diamond, and the specific steps are as follows:

[0051] 1. Raw material processing

[0052] 1) Raw material purification: Diamond powders of different particle sizes are used as the substrate, and the surface of the diamond powders is purified by microwave-molten salt method. The specific steps are as follows:

[0053] First, diamond micropowders with particle sizes of 20-25 μm and 4-10 μm were respectively taken in a mortar for stirring and grinding, and the weight ratio of the two particle sizes of diamond micropowders was 3.25:1 (65:20). Then, sodium chloride and potassium chloride with a mass ratio of 1:1 were placed in a mortar and fully mixed with the two particle sizes of diamond micropowders for 1 hour to obtain a mixed powder, wherein the ratio of the total mass of sodium chloride and potassium chloride to the total mass of the two particle sizes of diamond micropowders was 1:1;

[0054] Then the mixed powder was placed in a corundum crucible and heated in a microwave tube furnace. Argon gas was introduced for protection during the heating process. During heating, the heating rate was 90°C / min. After heating to 1100°C, the temperature was kept for 1 hour and then cooled to room temperature along with the furnace.

[0055] After cooling, the sample was taken out and placed in an ultrasonic cleaner for 1 hour, with an ultrasonic power of 600w and a temperature of 150°C. The sample was repeatedly cleaned with deionized water and alcohol, and salts (molten salt) and other substances on the surface of the sample were removed to obtain purified diamond micropowders of two particle sizes, which were dried and set aside.

[0056] 2) Mixing and ball milling: Mix and ball mill the diamond micropowders of two particle sizes, boron carbide micropowder, and titanium powder that have undergone purification treatment in step 1). The specific steps are as follows:

[0057] Mix the diamond micropowder with a particle size of 20 - 25 μm, diamond micropowder with a particle size of 4 - 10 μm, boron carbide micropowder, and titanium powder after purification treatment, and place them in a ball mill tank for ball milling; by weight percentage, the proportion of each raw material is: diamond micropowder with a particle size of 20 - 25 μm is 65 wt.%, diamond micropowder with a particle size of 4 - 10 μm is 20 wt.%, boron carbide micropowder is 10 wt.%, and titanium powder is 5 wt.%;

[0058] During ball milling, the ball - to - material ratio (mass ratio) of the ball milling medium to the material is 1:1. Anhydrous ethanol is added as a lubricant during the ball milling process. The ball milling speed is 300 r / min, and the ball milling time is 10 h; among them, when ball milling, two types of ball milling media (grinding balls) are selected, both with a material of YG8, diameters of 8 mm and 4 mm respectively, and the weight ratio of the two is 1:1;

[0059] After the ball milling stops, dry the stirred powder, place it in a graphite tank, evacuate, and conduct vacuum heat treatment. The heat treatment temperature is 700 °C, the holding time is 30 min, and the vacuum degree is 3×10 -3 Pa, and finally obtain the treated powder; the purpose of vacuum heat treatment is mainly to remove the impurities adsorbed on the surface of the powder during the grinding process and simultaneously activate the surface activity of the powder;

[0060] II. Pressing

[0061] 3) Pre - pressing: Put the powder obtained after vacuum heat treatment in step 2) into a metal cup and perform pre - pressing in a mold with a hydraulic press to obtain a sample; among them, the metal cup is a molybdenum cup; during pre - pressing, the pressure of the hydraulic press is 150 Mpa, and the pressure holding time is 5 s;

[0062] 4) Assembly and sintering: Assemble the sample obtained in step 3) with pyrophyllite, and then place it on a six - sided top press for high - temperature and high - pressure sintering; the sintering pressure is 5.5 Gpa, the temperature is 1400 °C, the holding time is 480 s. After the holding ends, lower the temperature to 700 °C at a cooling rate of 80 °C / min, hold for 10 s, and then lower it to room temperature. At the same time, lower the pressure to atmospheric pressure at a pressure reduction rate of 0.3 GPa / min to obtain a polycrystalline diamond blank;

[0063] Grind and polish the polycrystalline diamond blank prepared by the above method to finally obtain polycrystalline diamond with a dense and uniformly distributed microstructure. Its electron microscope image is as Figure 1 shown.

[0064] The prepared polycrystalline diamond sample was subjected to mechanical property tests (for the test method, refer to the patent document "202211116430.0 Polycrystalline Diamond and Its Preparation Method, Polycrystalline Diamond Composite Material and Its Preparation Method"). Its Vickers hardness is 7952 HV, the wear ratio is 302,000, the impact toughness is 80 J, and the initial oxidation temperature is 1120 °C (i.e., the heat-resistant temperature).

[0065] Example 2

[0066] Example 2 provides a preparation method of high-performance polycrystalline diamond, and the specific steps are as follows:

[0067] I. Treatment of raw materials

[0068] 1) Purification treatment of raw materials: Different particle size diamond micropowders were taken as the base materials, and the microwave-molten salt method was used to purify the surface of the diamond micropowders. The specific steps are as follows:

[0069] First, diamond micropowders with particle sizes of 20 - 25 μm and 4 - 10 μm were respectively taken in a mortar and stirred and ground. The weight ratio of the two particle size diamond micropowders was 10:3 (70:21). Then, sodium chloride and potassium chloride with a mass ratio of 2:1 and the two particle size diamond micropowders were placed in the mortar and mixed thoroughly for 1.5 h to obtain a mixed powder. Among them, the total mass ratio of sodium chloride and potassium chloride to the total mass of the two particle size diamond micropowders was 1:1;

[0070] Then, the mixed powder was put into a corundum crucible and heated in a microwave tube furnace. Argon was introduced for protection during the heating process; during heating, the heating rate was 100 °C / min. After rising to 1000 °C, it was kept warm for 1 h, and then cooled to room temperature with the furnace;

[0071] After cooling, the sample was taken out, placed in an ultrasonic cleaner and ultrasonically treated for 1 h. The ultrasonic power was 500 w, the temperature was 120 °C, and it was repeatedly washed with deionized water and alcohol, and substances such as salts (molten salts) on the surface of the sample were removed to obtain two particle size diamond micropowders after purification treatment, dried, and reserved;

[0072] 2) Mixing and ball milling: The two particle size diamond micropowders after purification treatment in step 1) were mixed and ball milled with boron carbide micropowder and titanium powder. The specific steps are as follows:

[0073] The diamond micropowder with a particle size of 20 - 25 μm, the diamond micropowder with a particle size of 4 - 10 μm after purification treatment, boron carbide micropowder, and titanium powder were mixed and placed in a ball mill tank for ball milling; calculated by weight percentage, the proportion of each raw material was: diamond micropowder with a particle size of 20 - 25 μm 70 wt.%, diamond micropowder with a particle size of 4 - 10 μm 21 wt.%, boron carbide micropowder 5 wt.%, and titanium powder 4 wt.%;

[0074] During ball milling, the ball-to-material ratio (mass ratio) of the ball milling medium to the material is 1:1. Anhydrous ethanol is added as a lubricant during the ball milling process. The ball milling speed is 500 r / min, and the ball milling time is 8 h. Among them, when ball milling, two types of ball milling media (grinding balls) are selected, both made of YG8, with diameters of 10 mm and 6 mm respectively, and the weight ratio of the two is 1:1;

[0075] After the ball milling stops, the stirred powder is dried, placed in a graphite crucible, evacuated, and subjected to vacuum heat treatment. The heat treatment temperature is 800 °C, the holding time is 30 min, and the vacuum degree is 3×10 -3 Pa, and finally the treated powder is obtained;

[0076] II. Pressing

[0077] 3) Pre-pressing: The powder obtained after the vacuum heat treatment in step 2) is put into a niobium cup and pre-pressed in a mold with a hydraulic press to obtain a sample. Among them, the metal cup is a niobium cup. When pre-pressing, the pressure of the hydraulic press is 180 Mpa, and the pressure holding time is 3 s;

[0078] 4) Assembly and sintering: The sample prepared in step 3) is assembled with pyrophyllite, and then placed on a six-sided top press for high-temperature and high-pressure sintering. The sintering pressure is 6.5 Gpa, the temperature is 1550 °C, the holding time is 500 s. After the holding is completed, the temperature is cooled to 725 °C at a cooling rate of 90 °C / min, held for 10 s, and then cooled to room temperature. At the same time, the pressure is reduced to atmospheric pressure at a pressure reduction rate of 0.4 GPa / min to obtain a polycrystalline diamond blank;

[0079] The polycrystalline diamond blank prepared by the above method is ground and polished to finally obtain polycrystalline diamond with a dense and evenly distributed microstructure. Its electron microscope image is as Figure 2 shown.

[0080] The mechanical properties of the prepared polycrystalline diamond sample are tested (the test method refers to the patent document "202211116430.0 Polycrystalline Diamond and Its Preparation Method, Polycrystalline Diamond Composite Material and Its Preparation Method"). Its Vickers hardness is 8590 HV, the wear ratio is 343,000, the impact toughness is 85 J, and the initial oxidation temperature is 1105 °C (i.e., the heat resistance temperature).

[0081] Example 3

[0082] Example 3 provides a method for preparing high-performance polycrystalline diamond, and the specific steps are as follows:

[0083] I. Treatment of raw materials

[0084] 1) Raw material purification: Diamond powders of different particle sizes are used as the substrate, and the surface of the diamond powders is purified by microwave-molten salt method. The specific steps are as follows:

[0085] First, diamond micropowders with particle sizes of 20-25 μm and 4-10 μm were respectively taken in a mortar for stirring and grinding, and the weight ratio of the two particle sizes of diamond micropowders was 34:11 (68:22). Then, sodium chloride and potassium chloride with a mass ratio of 1:2 were placed in a mortar and fully mixed with the two particle sizes of diamond micropowders for 2 hours to obtain a mixed powder, wherein the ratio of the total mass of sodium chloride and potassium chloride to the total mass of the two particle sizes of diamond micropowders was 1:1;

[0086] Then the mixed powder was placed in a corundum crucible and heated in a microwave tube furnace. Argon gas was introduced for protection during the heating process. During heating, the heating rate was 80°C / min. After heating to 900°C, the temperature was kept for 1 hour and then cooled to room temperature along with the furnace.

[0087] After cooling, the sample was taken out and placed in an ultrasonic cleaner for 1 hour, with an ultrasonic power of 550w and a temperature of 140°C. The sample was repeatedly cleaned with deionized water and alcohol, and salts (molten salt) and other substances on the surface of the sample were removed to obtain purified diamond micropowders of two particle sizes, which were dried and set aside.

[0088] 2) Mixing and ball milling: The diamond micropowders of two particle sizes after purification in step 1) are mixed with boron carbide micropowder and titanium powder and ball milled. The specific steps are as follows:

[0089] The diamond micropowder with a particle size of 20-25 μm and the diamond micropowder with a particle size of 4-10 μm after purification are mixed with boron carbide micropowder and titanium powder, and placed in a ball mill for ball milling; in terms of weight percentage, the proportion of each raw material is: diamond micropowder with a particle size of 20-25 μm 68wt.%, diamond micropowder with a particle size of 4-10 μm 22wt.%, boron carbide micropowder 7wt.%, titanium powder 3wt.%;

[0090] During ball milling, the ball-to-material ratio (mass ratio) of the ball milling medium to the material is 1:1, anhydrous ethanol is added as a lubricant during the ball milling process, the ball milling speed is 550r / min, and the ball milling time is 6h; during ball milling, two types of ball milling media (grinding balls) are selected, both made of YG8, with diameters of 12mm and 6mm respectively, and the weight ratio of the two is 1:1;

[0091] After the ball milling is stopped, the stirred powder is dried, placed in a graphite tank, evacuated, and vacuum heat treated at a temperature of 900°C, a holding time of 30 min, and a vacuum degree of 3*10 -3 Pa, the final processed powder is obtained;

[0092] II. Compression

[0093] 3) Pre - compression: Put the powder obtained after the vacuum heat treatment in step 2) into a tantalum cup, and perform pre - compression in a mold with a hydraulic press to obtain a sample. Among them, the tantalum cup is a metal cup. During pre - compression, the pressure of the hydraulic press is 200 Mpa, and the pressure - holding time is 3 s;

[0094] 4) Assembly and sintering: Assemble the sample obtained in step 3) with pyrophyllite, and then place it on a six - sided top press for high - temperature and high - pressure sintering. The sintering pressure is 7.0 Gpa, the temperature is 1700 °C, and the heat - preservation time is 500 s. After the heat - preservation is completed, cool the temperature to 750 °C at a cooling rate of 70 °C / min, keep it warm for 10 s, and then cool it to room temperature. At the same time, reduce the pressure to atmospheric pressure at a pressure - reducing rate of 0.5 GPa / min to obtain a polycrystalline diamond blank;

[0095] Grind and polish the polycrystalline diamond blank prepared by the above method to finally obtain polycrystalline diamond with a dense and evenly distributed microstructure. Its electron microscope image is as Figure 3 shown.

[0096] Perform mechanical property tests on the prepared polycrystalline diamond sample (the test method refers to the patent document "202211116430.0 Polycrystalline Diamond and Its Preparation Method, Polycrystalline Diamond Composite Material and Its Preparation Method"). Its Vickers hardness is 8027 HV, the wear - resistance ratio is 326,000, the impact toughness is 83 J, and the initial oxidation temperature is 1142 °C (i.e., the heat - resistant temperature).

[0097] The specific implementation cases of the present invention are described above. It should be understood that the present invention is not limited to the above - mentioned specific embodiments. Those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A high-performance polycrystalline diamond, characterized in that, It is prepared through the following steps: I. Treatment of raw materials 1) Purification treatment of raw materials: First, take diamond micropowders with particle sizes of 20 - 25 μm and 4 - 10 μm respectively, stir and mix them evenly, and grind them. Then, fully mix the molten salt with the diamond micropowders of the two particle sizes to obtain a mixed powder; Then heat the mixed powder, introduce a protective gas during the heating process, cool it to room temperature with the furnace after heating, and then perform ultrasonic treatment for 1 - 3 h, with an ultrasonic power of 500 - 600 W and an ultrasonic temperature of 120 - 150 °C. Clean and dry it for standby; 2) Mixing and ball milling: Mix the material obtained in step 1) with boron carbide micropowder and titanium powder to obtain a mixed material, ball mill it, dry it, evacuate it, and perform vacuum heat treatment to obtain a solid powder; II. Pressing 3) Pre-pressing: Place the solid powder after vacuum heat treatment in step 2) into a metal cup and perform pre-pressing in a mold to obtain a sample; 4) Assembly and sintering: Assemble the sample obtained in step 3) with pyrophyllite, and then place it in a six-sided press for high-temperature and high-pressure sintering to obtain a polycrystalline diamond blank; Grind and polish the prepared polycrystalline diamond blank to finally obtain polycrystalline diamond; In step 1), the molten salt is sodium chloride and potassium chloride, and the mass ratio of the two is (0.5 - 2):1; In step 1), the ratio of the total mass of sodium chloride and potassium chloride to the total mass of the diamond micropowders of the two particle sizes is 1:1; In step 1), during heating, the heating rate is 80 - 100 °C / min. After rising to 900 - 1100 °C, keep the temperature for 1 - 2 h; When mixing and ball milling in step 2), by weight percentage, the proportion of each raw material in the mixed material is: diamond micropowder with a particle size of 20 - 25 μm is 60 - 70 wt.%, diamond micropowder with a particle size of 4 - 10 μm is 20 - 25 wt.%, boron carbide micropowder is 5 - 10 wt.%, and titanium powder is 2 - 7 wt.%; In step 2), the vacuum heat treatment temperature is 700~900 °C, the time is 30 - 60 min, and the vacuum degree is (1~3)*10 -3 Pa; In step 3), during pre-pressing, the pressure is 150 - 200 Mpa and the pressure holding time is 3 - 5 s; In step 4), the sintering pressure is 4 Gpa - 8 Gpa, the temperature is 1300 °C - 1700 °C, and the heat preservation time is 0 - 600 s; After sintering, cool the temperature to 700 - 750 °C at a cooling rate of 80 - 90 °C / min, keep the temperature for 5 - 12 s, and finally cool it to room temperature, and at the same time reduce the pressure to atmospheric pressure at a pressure reduction rate of 0.3 - 0.5 GPa / min.

2. The high-performance polycrystalline diamond according to claim 1, characterized in that, In step 2), during ball milling, the mass ratio of the ball milling medium to the mixed material is 1:1, the ball milling speed is 30 - 550 r / min, and the ball milling time is 6 - 10 h.

3. The high-performance polycrystalline diamond according to claim 1, wherein During ball milling, anhydrous ethanol is added as a lubricant.

4. The high-performance polycrystalline diamond according to claim 1, wherein During ball milling, two types of ball milling media are selected, both with a material of YG8, diameters of 8 - 12 mm and 4 - 6 mm respectively, and the weight ratio of the two is 1:

1.

5. The high-performance polycrystalline diamond according to claim 1, characterized in that, In step 3), the material of the metal cup is any one of tantalum, molybdenum, and niobium.

6. Application of the high-performance polycrystalline diamond according to any one of claims 1 - 5 in manufacturing cutting tools and drilling tools.

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