A polycrystalline diamond compact with high thermal stability and a method of making the same

Abstract

The application discloses a polycrystal diamond compact with high thermal stability and a preparation method thereof, and belongs to the technical field of diamond and hard alloy composite materials. The polycrystal diamond compact comprises a hard alloy base body and a rare earth composite coating, a powder transition layer and a polycrystal diamond layer which are sequentially arranged on the hard alloy base body from inside to outside. In the polycrystal diamond layer, graphdiyne and fullerene materials are added, and diamond micro-powder is coated with graphene, carbon nanotubes and fullerene, so that the combination of diamond and diamond is promoted. The transition composite coating is deposited on the surface of the hard alloy base body by adopting a magnetron sputtering method, and the powder transition layer is arranged between the rare earth composite coating and the polycrystal diamond layer, so that the interface stress between the polycrystal diamond layer and the hard alloy base body is reduced, the bonding strength of the polycrystal diamond layer and the hard alloy base body is improved, and the polycrystal diamond compact has excellent mechanical and thermal properties.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of diamond and hard alloy composite materials, and particularly relates to a polycrystalline diamond compact with high thermal stability and a preparation method thereof. BACKGROUND

[0002] The polycrystalline diamond compact is sintered from diamond micro powder and hard alloy substrate under super high pressure and high temperature. That is, the polycrystalline diamond compact has high hardness, high wear resistance and thermal conductivity of diamond, and strength and impact toughness of hard alloy, and is an ideal material for manufacturing cutting tools, drilling bits and other wear-resistant tools.

[0003] In the prior art, the polycrystalline diamond compact prepared from ordinary diamond micro powder has a series of advantages of diamond single crystal, but has deficiencies in heat resistance, oxidation resistance and chemical inertness in practical application. In order to protect the original strength of diamond particles and prevent oxidation, people usually perform metal or ceramic treatment (such as titanium plating or titanium carbide) on the surface of the diamond micro powder. However, the polycrystalline diamond compact prepared from the diamond micro powder with metal or ceramic treatment has no direct bonding between diamond particles, but has a diamond-transition phase-diamond structure. Therefore, the polycrystalline diamond compact prepared from the surface metalized diamond micro powder has certain thermal stability to a certain extent by overcoming the surface structural defects of ordinary diamond grains, but the polycrystalline diamond compact has poor wear resistance and no direct diamond-diamond bonding. In the increasingly developing oil drilling and cutting tool industry, higher requirements are put forward for the heat resistance, wear resistance and comprehensive performance of the polycrystalline diamond compact, and the improvement of the polycrystalline diamond compact prepared from the surface metalized diamond micro powder in high-temperature wear resistance is limited. SUMMARY

[0004] In order to overcome the problems in the prior art, the present application provides a polycrystalline diamond compact with high thermal stability and a preparation method thereof, which can solve the problem of low thermal stability of the polycrystalline diamond compact, so as to improve the service life and performance of the tool.

[0005] To achieve the above-mentioned purposes, the technical solutions of the present application are as follows:

[0006] The application discloses a polycrystalline diamond compact with high thermal stability, which comprises a hard alloy base and a rare earth composite coating, a powder transition layer and a polycrystalline diamond layer arranged on the hard alloy base from inside to outside, wherein the polycrystalline diamond layer is composed of the following raw materials in percentage by weight: graphene-coated diamond micro powder 55-70%, carbon nanotube-coated diamond micro powder 15-20%, fullerene-coated diamond micro powder 10-15%, graphdiyne 0.3-0.5%, fullerene 0.2-0.5% and a binder 4.5-9%. The thickness of the polycrystalline diamond layer is 0.5-0.7 mm.

[0007] Specifically, the rare earth composite coating is arranged in the order of a rare earth coating and a TiB coating from inside to outside, wherein the rare earth coating is arranged between the surface of the hard alloy base and the TiB coating; the material of the rare earth coating is selected from one of rare earth elements Pr, Nd and Pm; the thickness of the rare earth coating is 3-5 mu m; the thickness of the TiB coating is 4-8 mu m; the hard alloy base is a boronized hard alloy base; and the thickness of the boronized layer on the surface of the hard alloy base is 1-4 mu m.

[0008] Specifically, the powder transition layer is composed of the following raw materials in percentage by weight: fullerene-coated diamond micro powder 39-50%, tungsten carbide powder 37-40%, magnesium carbonitride powder 5-10%, graphdiyne 0.25-0.5%, fullerene 0.25-0.5% and a binder 7.5-10%; the particle size of the tungsten carbide powder and the magnesium carbonitride powder in the powder transition layer is 0.8-1.2 mu m; and the thickness of the powder transition layer is 0.2-0.3 mm.

[0009] Specifically, the particle size of the graphene-coated diamond micro powder is 20-30 mu m; the particle size of the carbon nanotube-coated diamond micro powder is 10-20 mu m; and the particle size of the fullerene-coated diamond micro powder is 5-10 mu m.

[0010] Specifically, the particle size of the graphdiyne is 400-600 nm; and the particle size of the fullerene is 300-500 nm. The fullerene and the graphdiyne in the application can be directly purchased from common market products, such as from Beijing Deke Dao Gold Technology Co., Ltd.

[0011] Specifically, the binder is composed of the following raw materials in percentage by weight: cobalt powder 95-98%, tungsten-titanium solid solution 1-2%, tantalum-niobium solid solution 0.5-1%, lithium nitride-boronide powder 0.25-1% and magnesium carbonitride powder 0.25-1%; the mass ratio of tungsten and titanium in the tungsten-titanium solid solution is 1:1; and the mass ratio of TaC and NbC in the tantalum-niobium solid solution is 4:6. The raw material powders in the application are common market products that can be directly purchased.

[0012] Further, the particle size of the cobalt, tungsten-titanium solid solution, tantalum-niobium solid solution, lithium boron nitride powder, and magnesium carbonitride in the binding agent is 30-40 nm.

[0013] The graphene and carbon nanotube coated diamond micro powder of the present application is graphene chemically vapor deposited on the catalytic layer provided on the surface of the diamond; the graphene is a single-layer structure or a multi-layer structure. The graphene or carbon nanotube coated diamond micro powder can be prepared by using the existing technology, such as referring to Chinese patent CN201610161233.9 (publication number CN105803420A, graphene and / or carbon nanotube coated diamond composite material and its preparation method and application) for preparation. Specifically, a layer of nickel catalytic layer can be sputtered on the surface of the diamond by using a magnetron sputtering technology, and the thickness of the nickel film is 80-100 nm; then graphene or carbon nanotube can be deposited on the diamond containing the catalytic layer by using a chemical vapor deposition technology. During the deposition process, a plasma auxiliary growth is applied to the surface of the diamond, and a magnetic field is added at the bottom of the diamond to confine the plasma on the surface of the diamond, so as to strengthen the bombardment of the plasma on the surface of the diamond, and make the graphene or carbon nanotube grow vertically to the surface of the diamond, i.e. to obtain the graphene or carbon nanotube coated diamond micro powder. The deposition parameters are as follows: the percentage of carbon-containing gas in the total gas mass flow in the furnace is 0.5-80%, the temperature is 400-1200°C, the gas pressure is 5-10 Pa, and the plasma current density is 0-30 mA / cm 5 . 2 The magnetic field strength in the deposition area is 100 Gauss-30 Tesla.

[0014] The fullerene coated diamond micro powder of the present application can be prepared by using the existing technology, such as referring to Chinese patent CN202011526764.6 (publication number CN112746814 A, a high-temperature-resistant diamond composite sheet and its preparation method) for preparation. Specifically, a fullerene layer can be plated on the surface of the diamond by using a magnetron sputtering technology to obtain the fullerene coated diamond micro powder, and the particle size of the diamond micro powder is 5-10 μm, and the thickness of the fullerene layer is 0.1 μm-0.2 μm; the process parameters of the reaction magnetron sputtering are as follows: the cathode target material is a graphite target with a purity of 99.9%, the sputtering gas is argon with a purity of 99.9%, the reaction gas is nitrogen with a purity of 99.9%, the power of the graphite target is 1250 W, the substrate bias is -100 V, the argon flow rate is 36 mL / min, and the nitrogen flow rate is 18 mL / min.

[0015] The preparation method of the polycrystalline diamond composite sheet with high thermal stability comprises the following steps:

[0016] 1) Cemented carbide substrate purification: first, the cemented carbide substrate is placed in anhydrous ethanol for ultrasonic cleaning for 8-12 min, then placed in a solution mixed with NaOH:K3Fe(CN)6:H2O in a mass ratio of 0.5:0.5:12-15 for ultrasonic cleaning for 5-10 min, then immersed in a mixed solution of concentrated nitric acid with a concentration of 35-45 wt% and hydrochloric acid with a concentration of 30-38 wt% in a volume ratio of 1:2-3 for 2-3 min, and then cleaned with deionized water and dried; then the cleaned cemented carbide substrate is fixed on the rotating stand in the ion source / arc ion plating film equipment, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow is 300-400 sccm, the working pressure is 1-1.5 Pa, and the substrate bias is -500 to -700 V, the surface of the cemented carbide substrate is glow cleaned, and the cleaning time is 8-12 min; when hydrogen is introduced, the gas flow is 200-300 sccm, the working pressure is 0.8-1.5 Pa, and the substrate bias is -500 to -700 V, the surface of the cemented carbide substrate is glow cleaned, and the cleaning time is 8-12 min, to obtain the clean cemented carbide substrate;

[0017] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube drying oven for boronizing treatment to obtain a surface boronized cemented carbide substrate;

[0018] 3) Depositing rare earth composite coating: the surface boronized cemented carbide substrate of step 2) is deposited with a rare earth coating on the boronized surface of the cemented carbide substrate by a magnetron sputtering method using a rare earth element as a target material, and the thickness of the rare earth coating is 3-5 µm; then a TiB composite target is used as a target material to deposit a TiB coating on the surface of the rare earth coating, and the thickness of the TiB coating is 4-8 µm, to obtain the cemented carbide substrate containing a rare earth composite coating;

[0019] 4) Powder transition layer mixing: graphite yne, fullerene, binder, tungsten carbide powder, magnesium carbonitride powder, and fullerene-coated diamond micro powder are weighed according to the proportion, respectively dispersed into anhydrous ethanol, mechanically stirred and ultrasonically dispersed for 50-60 min, and the mass content of the powder is 0.3-0.5 g / ml; polyethylene glycol is weighed and added to the anhydrous ethanol dispersion, mechanically stirred and ultrasonically dispersed for 50-80 min, and the concentration of polyethylene glycol is 1-3 g / L, then poured into a cemented carbide ball milling jar with cemented carbide balls, the ball-to-material mass ratio is 8-12:1, argon is filled as a protective gas, and then ball milled for 30-40 h, and after mixing, placed in a vacuum dryer and vacuum dried at 50-60°C for 2-5 h to obtain the powder transition layer mixed powder;

[0020] 5) Polycrystalline diamond layer mixing: Weigh fullerene, graphylene, binder, fullerene-coated diamond powder, carbon nanotube-coated diamond powder, and graphene-coated diamond powder according to the proportions, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate for 45-50 min, and the mass content of the powder is 0.2-1 g / ml. Then weigh polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate for 60-70 min, and the concentration of polyethylene glycol is 1-5 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 8-10:1. After purging with nitrogen as a protective gas, ball mill for 45-50 h. After mixing, place it in a vacuum dryer and vacuum dry at 50-60℃ for 3-5 h to obtain polycrystalline diamond layer mixed powder.

[0021] 6) Composite assembly: First, the polycrystalline diamond layer mixed powder described in step 5) and the powder transition layer mixed powder described in step 4) are sequentially loaded into a metal cup, layered and compacted for shaping. Then, the cemented carbide substrate containing the rare earth transition layer from step 3) is placed flat on the powder transition layer mixed powder with the coated side facing down. Then, two metal cups are inserted from the front and back directions respectively to obtain the composite assembly. The metal cups are composed of one or more of the following materials: Zr, Mo, Rb, Ta, Nb, Sr.

[0022] 7) Composite preloading: Place the composite component from step 6) into the pyrophyllite block, and then place the pyrophyllite block into a high-temperature, high-pressure apparatus.

[0023] During preparation, the pressure is increased to 5-6 GPa and held for 80-100 seconds without heating. Then, the pressure is reduced to standard atmospheric pressure using a high-temperature and high-pressure equipment to obtain a pre-compressed composite component.

[0024] 8) Composite purification: Place the pre-compressed composite assembly from step 7) into a vacuum sintering furnace for sintering. During sintering, first perform a rough vacuum evacuation until the furnace pressure reaches 7×10⁻⁶. -2 Below Pa, heat to 245-300℃ and hold for 5-10 minutes, then continue evacuating until the furnace pressure is 3×10⁻⁶. -5 Below Pa, raise the temperature to 1200–1300℃ and hold for 5–10 minutes, then stop evacuation and fill with reducing gas (by volume: 40% carbon monoxide, 30% ammonia, and 30% nitrogen), maintaining this temperature for 1.0–1.5 hours. Then evacuate again until the furnace pressure is 3 × 10⁻⁶. -5 Below Pa, a purification composite component is obtained;

[0025] 9) High-temperature and high-pressure sintering: Assemble the purification composite component from step 8) with the pyrophyllite assembly block, and place it in a six-sided press for sintering. First, raise the pressure to 6.5–6.8 GPa at a rate of 0.5–5 GPa / min, and then perform high-temperature sintering at a rate of 30–40 °C / s. After holding at 1360–1410 °C for 120–150 s, raise the temperature to 1470–1490 °C within 30–40 s and hold for 120–150 s. After sintering, lower the temperature to 550–600 °C at a rate of 15–20 °C / s, hold for 15–20 min, and then lower to room temperature. Finally, depressurize to atmospheric pressure at a rate of 0.5–0.6 GPa / min. Remove the assembly block from the six-sided press, remove the surface coating layer, and obtain the sintered polycrystalline diamond composite sheet blank.

[0026] 10) Stress-relief aging: The sintered polycrystalline diamond composite blank from step 9) is reassembled with the pyrophyllite assembly block and placed in a six-sided press. The pressure is increased to 6.5–6.8 GPa, and the temperature is adjusted to 650–700 °C, held for 20–25 min. The pyrophyllite block is then cooled to 550–600 °C, held for 20–25 min, and then further cooled to 400–500 °C, held for 20–25 min. The temperature is then further reduced to 300–400 °C, held for 20–25 min, and finally cooled to room temperature at a rate of 15–20 °C / s, and then depressurized to atmospheric pressure at a rate of 0.5–0.8 GPa / min. The aged polycrystalline diamond composite blank is removed from the assembly block, machined to the required dimensions using a grinding machine, and then surface polished to obtain the polycrystalline diamond composite sheet with high thermal stability.

[0027] In step 2), the boronizing gas is a mixture of 6-8% B2H6 and 92-94% H2 by volume, with a flow rate of 9-12 sccm, a pressure of 8-10 kPa, and a reaction time of 3-5 h.

[0028] In step 3, the magnetron sputtering working pressure is 1.5–2.0 Pa, the flow rate of nitrogen or argon gas is 35–50 mL / min, the target-substrate distance is 50 ± 5 mm, the sputtering temperature is 500–600 °C, and the vacuum degree is higher than 2 × 10⁻⁶. -3 Pa, sputtering power 120-200W, sputtering time 15-45 min, and the surface area ratio of Ti to B in the TiB composite target is 10:5.

[0029] In step 1), the ultrasonic power is 30-50W.

[0030] In steps 4) and 5), the ultrasonic power is 40-50W. The molecular weight of the polyethylene glycol is 1000-5000.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] 1) The present application deposits a rare earth composite coating on the boronized surface of the cemented carbide substrate and sets a powder transition layer between the rare earth composite coating and the polycrystalline diamond layer. Since the thermal expansion coefficients of the cemented carbide substrate-surface boronized layer-rare earth composite coating-powder transition layer-polycrystalline diamond layer gradually decrease in gradient, the gradient transition between the cemented carbide substrate and the polycrystalline diamond layer is achieved, so the interface stress is small, and the delamination problem of the polycrystalline diamond compact is improved. At the same time, the boronized layer on the surface of the cemented carbide substrate and the rare earth composite coating can effectively block the diffusion of cobalt metal in the cemented carbide to the polycrystalline diamond layer during the high-temperature and high-pressure sintering process of the polycrystalline diamond compact, reduce the metal content of the polycrystalline diamond layer, and improve the thermal stability and reduce the delamination probability of the polycrystalline diamond compact.

[0033] 2) The diamond of the polycrystalline diamond layer of the present application is composed of graphene-coated diamond micro powder with relatively coarse particle size, carbon nanotube-coated diamond micro powder with intermediate particle size, and fullerene-coated diamond micro powder with relatively fine particle size. By pre-mixing the powders and optimizing the reasonable addition amount of graphdiyne powder, fullerene powder and binder, the purpose of improving the diamond packing density is achieved, and the volume ratio of the diamond of the polycrystalline diamond layer is improved. Since the graphene-coated diamond micro powder with diamond and graphite dual characteristics is selected, the wettability, thermal conductivity and lubricity of the diamond particles and the binder are improved, the contact area between the diamond and the binder is effectively increased, the interparticle friction resistance is reduced, and the strength, density, heat dissipation and wear resistance of the polycrystalline diamond are improved. The carbon nanotube-coated diamond micro powder with diamond and carbon nanotube dual characteristics is selected. Since the carbon nanotube is a fibrous nanomaterial, it exists in the interstitial space of the diamond and is distributed in a three-dimensional network in space, which can enhance the toughness and reduce the residual stress, thereby improving the impact resistance of the polycrystalline diamond compact. The fullerene-coated diamond micro powder with diamond and fullerene dual characteristics is selected. Due to the unique spherical structure of fullerene, it has strong compression resistance, strong intramolecular force, relatively weak intermolecular force and low surface energy, etc. It can be used as a super heat-resistant and wear-resistant material, or made into a more excellent lubricant, which can achieve good lubrication and friction reduction effect. Therefore, the density, hardness, wear resistance and thermal stability of the polycrystalline diamond compact are comprehensively improved.

[0034] 3) The present application adds graphdiyne and fullerene materials in the polycrystalline diamond layer, which can activate diamond particles and promote the direct bonding between diamond particles. At the same time, due to the addition of a certain proportion of graphdiyne and fullerene, good lubrication can be achieved between diamond particles, reducing the frictional resistance between particles under high pressure conditions, promoting the filling of fragmented diamond space, improving the uniform distribution of binder phase, and increasing fine grains, so that a more dense and uniform structure is formed in the polycrystalline diamond. In the process of preparing polycrystalline diamond, it is divided into carbon atom phase change process and diamond dissolution and precipitation process. In the sintering process, graphdiyne and fullerene are filled between diamond particles, forming a uniform pressure field inside. When the pressure reaches the stable interval of diamond precipitation, the carbon in the solvent-carbon system will precipitate in the form of diamond in these gaps, so that fine particles and powders grow up and lap together with the surrounding particles, reducing the surface free energy of the particles, forming a stable and dense polycrystalline sintered body, and improving the strength and wear resistance of the polycrystalline diamond composite sheet.

[0035] 4) The polycrystalline diamond composite sheet with high thermal stability prepared by the present application has the following performance indicators: wear ratio is 440-470 million, impact toughness is 62-66 times, and thermal stability characterization temperature is 750-780℃. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a structure diagram of the polycrystalline diamond composite sheet with high thermal stability.

[0037] In the figure: 1, polycrystalline diamond layer; 2, powder transition layer; 3, rare earth composite coating; 4, substrate surface boronizing layer; 5, hard alloy substrate.

[0038] Figure 2 It is a real object diagram of the polycrystalline diamond composite sheet with high thermal stability prepared in Example 1. DETAILED DESCRIPTION

[0039] The application is further described below with reference to examples, but is not limited to the examples. In order to determine and compare the performance of the composite plates prepared in the examples and the comparative examples, the diameter of the composite plates in the following examples and comparative examples is φ55mm, and the thickness is 4mm; the thickness of the polycrystalline diamond layer is 0.5mm. The cemented carbide substrate refers to a tungsten-cobalt cemented carbide YG12 (WC 88% and cobalt 12%) substrate. The preparation of graphene-coated diamond powder uses diamond powder with a particle size of 20-30μm instead of 0.3mm diamond material in Example 3 of CN105803420A, and is prepared according to the process of Example 3 of CN105803420A. The preparation of carbon nanotube-coated diamond powder uses diamond powder with a particle size of 10-20μm as raw material, first magnetron sputters a 100nm nickel film, and then uses the diamond powder with the nickel film instead of the diamond sheet in Example 2 of CN105803420A to prepare the carbon nanotube-coated diamond powder. The molecular weight of polyethylene glycol is 2000.

[0040] Example 1

[0041] The polycrystalline diamond composite plate with high thermal stability of the present embodiment, such as Figure 1As shown, it comprises a cemented carbide substrate 5 and, from inside to outside, a rare earth composite coating 3, a powder transition layer 2 and a polycrystalline diamond layer 1 arranged on the cemented carbide substrate, the polycrystalline diamond layer 1 is composed of the following raw materials in weight percentage: graphene-coated diamond micro powder 55%, carbon nanotube-coated diamond micro powder 20%, fullerene-coated diamond micro powder 15%, graphdiyne 0.5%, fullerene 0.5% and binder 9%; the rare earth composite coating 3, from inside to outside, is a rare earth coating and a TiB coating, wherein the rare earth coating is arranged between the surface of the cemented carbide substrate and the TiB coating; the material of the rare earth coating is selected from rare earth element Pr; the thickness of the rare earth coating is 3 μm; the thickness of the TiB coating is 4 μm; the cemented carbide substrate 5 is a boronized cemented carbide substrate; the thickness of the boronized layer 4 on the surface of the cemented carbide substrate is 1 μm; the powder transition layer 2 is composed of the following raw materials in weight percentage: fullerene-coated diamond micro powder 39%, tungsten carbide powder 40%, magnesium carbonitride powder 10%, graphdiyne 0.5%, fullerene 0.5% and binder 10%; the particle size of the tungsten carbide powder and the magnesium carbonitride powder in the powder transition layer 2 is 0.8-1.2 μm; the thickness of the powder transition layer 2 is 0.2 mm; the particle size of the fullerene-coated diamond micro powder is 5-10 μm; the particle size of the graphdiyne is 400-600 nm; the particle size of the fullerene is 300-500 nm; the binder is composed of the following raw materials in weight percentage: cobalt powder 95%, tungsten-titanium solid solution 2%, tantalum-niobium solid solution 1%, lithium boron nitride powder 1%, magnesium carbonitride powder 1%; the mass ratio of tungsten element to titanium element in the tungsten-titanium solid solution is 1:1; the mass ratio of TaC to NbC in the tantalum-niobium solid solution is 4:6; the particle size of cobalt, tungsten-titanium solid solution, tantalum-niobium solid solution, lithium boron nitride powder and magnesium carbonitride in the binder is 30-40 nm.

[0042] The preparation method of the polycrystalline diamond compact with high thermal stability, comprising the following steps:

[0043] 1) Cemented carbide substrate cleaning: first, the cemented carbide substrate is placed in anhydrous ethanol and cleaned by ultrasonic wave (power 30W) for 8 min, then placed in a solution mixed by NaOH:K3Fe(CN)6:H2O in a mass ratio of 0.5:0.5:12 and cleaned by ultrasonic wave (power 30W) for 5 min, then immersed in a mixed solution of 40wt% nitric acid and commercially available concentrated hydrochloric acid (36-38wt%) in a volume ratio of 1:2 for 2 min, and cleaned with deionized water, and then dried; then the cleaned cemented carbide substrate is fixed on a rotating stand in an ion source / arc ion plating film equipment, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow is 300sccm, the working pressure is 1Pa, the substrate bias is -500V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 8min; when hydrogen is introduced, the gas flow is 200sccm, the working pressure is 0.8Pa, the substrate bias is -500V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 8min, to obtain the clean cemented carbide substrate;

[0044] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube drying oven for boronizing treatment; the boronizing treatment gas is a mixed gas of 6% B2H6 and 94% H2 by volume, the flow rate of the mixed gas is 9sccm, the pressure is 8kPa, and the reaction time is 3h, to obtain a surface boronized cemented carbide substrate;

[0045] 3) Depositing rare earth composite coating: the surface boronized cemented carbide substrate of step 2) is deposited with a rare earth coating on the boronized surface of the cemented carbide substrate by a magnetron sputtering method using a rare earth element as a target material, and then a TiB composite target as a target material to deposit a TiB coating on the surface of the rare earth coating, the magnetron sputtering working pressure is 1.5Pa, the nitrogen flow rate introduced is 35mL / min, the target-to-substrate distance is 50±5mm, the sputtering temperature is 500℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 120W, the sputtering time is 15min and 17min respectively, the surface area ratio of Ti element and B element in the TiB composite target is 10:5, to obtain the cemented carbide substrate containing a rare earth composite coating;

[0046] 4) Powder transition layer mixing: Weigh out graphylene, fullerene, binder, tungsten carbide powder, magnesium carbonitride powder, and fullerene-coated diamond micro powder according to the proportion, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 40W) for 50 min. The mass content of the powder is 0.3 g / ml. Then weigh out polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate (power 40W) for 50 min. The concentration of polyethylene glycol is 1 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 8:1. After filling with argon as a protective gas, ball mill for 30 h. After mixing, place it in a vacuum dryer and vacuum dry at 50℃ for 2 h to obtain the powder transition layer mixed powder.

[0047] 5) Polycrystalline diamond layer mixing: Weigh fullerene, graphylene, binder, fullerene-coated diamond powder, carbon nanotube-coated diamond powder, and graphene-coated diamond powder according to the proportion, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 40W) for 45 min. The mass content of the powder is 0.2 g / ml. Then weigh polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate (power 40W) for 60 min. The concentration of polyethylene glycol is 1 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 8:1. After filling with nitrogen as a protective gas, ball mill for 45 h. After mixing, place it in a vacuum dryer and vacuum dry at 50℃ for 3 h to obtain polycrystalline diamond layer mixed powder.

[0048] 6) Composite assembly: First, the polycrystalline diamond layer mixed powder described in step 5) and the powder transition layer mixed powder described in step 4) are sequentially loaded into a metal Zr cup, layered and compacted to shape. Then, the cemented carbide substrate containing the rare earth transition layer from step 3) is placed flat on the powder transition layer mixed powder with the coated side facing down. Then, two metal Zr cups are inserted from the front and back directions respectively to obtain the composite assembly.

[0049] 7) Composite preloading: Place the composite component from step 6) into the pyrophyllite block, and then place the pyrophyllite block into a high-temperature, high-pressure apparatus.

[0050] During preparation, the pressure is increased to 5 GPa and held for 80 seconds without heating. Then, the pressure is reduced to standard atmospheric pressure using a high-temperature and high-pressure equipment to obtain a pre-compressed composite component.

[0051] 8) Composite purification: Place the pre-compressed composite assembly from step 7) into a vacuum sintering furnace for sintering. During sintering, first perform a rough vacuum evacuation until the furnace pressure reaches 7×10⁻⁶. -2 Below Pa, heat to 245℃ and hold for 5 minutes, then continue evacuating until the furnace pressure is 3×10⁻⁶. -5Pa, the temperature was raised to 1200℃ for 5 min, vacuum was stopped, and reducing gas (40% carbon monoxide, 30% ammonia, and 30% nitrogen by volume) was filled into the furnace for 1.0 h, and then vacuum was applied again to a pressure of 3 x 10 -5 Pa, to obtain a purified composite assembly;

[0052] 9) High-temperature and high-pressure sintering: the purified composite assembly of step 8) and a block of beryl were assembled and placed in a cubic press for sintering. The sintering pressure was raised to 6.5 GPa at a rate of 0.5 GPa / min, and high-temperature sintering was performed at a temperature rising rate of 30℃ / S. After being kept at 1360℃ for 120 S, the temperature was raised to 1470℃ within 30 S, and the sintering was kept at 1470℃ for 120 S. After sintering, the temperature was lowered to 550℃ at a rate of 15℃ / S, and the sintering was kept at 550℃ for 15 min. Then the temperature was lowered to room temperature, and the pressure was lowered to normal pressure at a rate of 0.5 GPa / min. The assembled block was taken out of the cubic press, and the surface wrapping layer was removed to obtain a sintered polycrystalline diamond compact blank.

[0053] 10) Stress relief aging: the sintered polycrystalline diamond compact blank of step 9) was assembled with a block of beryl again, and placed in a cubic press. The pressure was raised to 6.5 GPa, and the temperature was adjusted to 650℃ for 20 min. Then the temperature of the beryl block was lowered to 550℃ for 20 min, and then lowered to 400℃ for 20 min. Then the temperature was lowered to 300℃ for 20 min, and finally lowered to room temperature at a rate of 15℃ / S. The pressure was lowered to normal pressure at a rate of 0.5 GPa / min. The aged polycrystalline diamond compact blank was taken out of the assembled block, and processed to the required size using grinding equipment. Then the surface was polished to obtain the polycrystalline diamond compact with high thermal stability, as shown in Figure 2 .

[0054] The polycrystalline diamond compact with high thermal stability prepared in this example was tested for wear resistance according to the standard JB / T3235-2013 "Abrasion Resistance Test Method for Artificial Diamond Sintered Body". The compact sample was placed in a tube furnace and heated at 690℃ for 1 min. Then the impact toughness was tested by the falling weight impact method (i.e. a 1 kg weight was dropped from a height of 30 cm to impact the corners of the sample, and the impact toughness value was obtained when micro cracks appeared on the surface). The thermal stability was tested by thermogravimetric analysis, and the initial oxidation temperature of the differential thermal curve was used as the thermal stability characterization temperature. The higher the initial oxidation temperature, the better the thermal stability. The test results were as follows: the abrasion ratio was 450,000, the impact toughness was 63 times, and the thermal stability characterization temperature was 760℃. The polycrystalline diamond compact had excellent heat resistance, wear resistance, and impact toughness.

[0055] Example 2

[0056] The polycrystalline diamond composite sheet with high thermal stability in this embodiment, such as... Figure 1 As shown, the system includes a cemented carbide substrate 5 and a rare earth composite coating 3, a powder transition layer 2, and a polycrystalline diamond layer 1 sequentially disposed on the cemented carbide substrate 5. The polycrystalline diamond layer 1 is composed of the following raw materials in weight percentage: 70% graphene-coated diamond powder, 15% carbon nanotube-coated diamond powder, 10% fullerene-coated diamond powder, 0.3% graphyne, 0.2% fullerene, and 4.5% binder. The rare earth composite coating 3 consists of a rare earth coating and a TiB coating in the order from the inside to the outside, wherein the rare earth coating is disposed on the surface of the cemented carbide substrate and between the TiB coating. The material of the rare earth coating is selected from the rare earth element Nd. The thickness of the rare earth coating is 5 μm. The thickness of the TiB coating is 8 μm. The cemented carbide substrate 5 is a surface-boronized cemented carbide substrate. The thickness of the boronized layer 4 on the surface of the cemented carbide substrate is 4 μm. The powder transition layer 2 is composed of the following raw materials in weight percentage: fullerene-coated diamond powder, 70% graphene-coated diamond powder, 15% carbon nanotube-coated diamond powder, 10% fullerene-coated diamond powder, 0.3% graphyne, 0.2% fullerene, and 4.5% binder. The rare earth composite coating 3 consists of a rare earth coating and a TiB coating in the order from the inside to the outside, wherein the rare earth coating is disposed on the surface of the cemented carbide substrate and between the TiB coating. The rare earth coating is selected from the rare earth element Nd. The thickness of the rare earth coating is 5 μm. The thickness of the TiB coating is 8 μm. The cemented carbide substrate 5 is a surface-boronized cemented carbide substrate. The thickness of the boronized layer 4 on the surface of the cemented carbide The powder consists of 50% tungsten carbide powder, 37% tungsten carbide powder, 5% magnesium carbonitride powder, 0.25% graphyne, 0.25% fullerene, and 7.5% binder; the particle size of the tungsten carbide powder and magnesium carbonitride powder in the powder transition layer 2 is 0.8–1.2 μm; the thickness of the powder transition layer 2 is 0.3 mm; the particle size of the fullerene-coated diamond micropowder is 5–10 μm; the particle size of the graphyne is 400–600 nm; and the particle size of the fullerene is 300–500 nm. m; the binder is composed of the following raw materials in weight percentage: 98% cobalt powder, 1% tungsten-titanium solid solution, 0.5% tantalum-niobium solid solution, 0.25% lithium boride powder, and 0.25% magnesium carbonitride powder; the mass ratio of tungsten to titanium in the tungsten-titanium solid solution is 1:1; the mass ratio of TaC to NbC in the tantalum-niobium solid solution is 4:6; the particle size of cobalt, tungsten-titanium solid solution, tantalum-niobium solid solution, lithium boride powder, and magnesium carbonitride in the binder is 30-40 nm.

[0057] The preparation method of the above-mentioned polycrystalline diamond composite sheet with high thermal stability includes the following steps:

[0058] 1) Cemented carbide substrate cleaning: first, the cemented carbide substrate is placed in anhydrous ethanol and cleaned by ultrasonic wave (power 50W) for 12 min, then placed in a solution mixed by NaOH:K3Fe(CN)6:H2O in a mass ratio of 0.5:0.5:15 and cleaned by ultrasonic wave (power 50W) for 10 min, then immersed in a mixed solution of 40wt% nitric acid and commercially available concentrated hydrochloric acid (36-38wt%) in a volume ratio of 1:3 for 3 min, cleaned by deionized water and dried; then the cleaned cemented carbide substrate is fixed on a rotating stand in an ion source / arc ion plating film equipment, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow is 400sccm, the working pressure is 1.5Pa, the substrate bias is -700V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 12 min; when hydrogen is introduced, the gas flow is 300sccm, the working pressure is 1.5Pa, the substrate bias is -700V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 12 min, to obtain the clean cemented carbide substrate;

[0059] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate in step 1) is placed in a vacuum tube drying furnace for boronizing treatment; the boronizing treatment gas is a mixed gas of 8% B2H6 and 92% H2 by volume, the flow of the mixed gas is 12sccm, the pressure is 10kPa, and the reaction time is 5h, to obtain a cemented carbide substrate with surface boronizing;

[0060] 3) Depositing rare earth composite coating: the cemented carbide substrate with surface boronizing in step 2) is deposited with a rare earth coating on the boronized surface of the cemented carbide substrate by a magnetron sputtering method using a rare earth element as a target material, and then deposited with a TiB coating on the surface of the rare earth coating using a TiB composite target as a target material, the magnetron sputtering working pressure is 2.0Pa, the nitrogen flow introduced is 50mL / min, the target-to-substrate distance is 50±5mm, the sputtering temperature is 600℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 200W, the sputtering time is 43min and 45min respectively, the surface area ratio of Ti element to B element in the TiB composite target is 10:5, to obtain the cemented carbide substrate with rare earth composite coating;

[0061] 4) Powder transition layer mixing: Weigh out graphylene, fullerene, binder, tungsten carbide powder, magnesium carbonitride powder, and fullerene-coated diamond micro powder according to the proportion, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 50W) for 60 min, and the mass content of the powder is 0.5 g / ml. Then weigh out polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate (power 50W) for 80 min, and the concentration of polyethylene glycol is 3 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 12:1. After filling with argon as a protective gas, ball mill for 40 h. After mixing, place it in a vacuum dryer and vacuum dry at 60℃ for 5 h to obtain the powder transition layer mixed powder.

[0062] 5) Polycrystalline diamond layer mixing: Weigh fullerene, graphylene, binder, fullerene-coated diamond powder, carbon nanotube-coated diamond powder, and graphene-coated diamond powder according to the proportions, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 50W) for 50 min, and the mass content of the powder is 1g / ml. Then weigh polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate (power 50W) for 70 min, and the concentration of polyethylene glycol is 5g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 10:1. After filling with nitrogen as a protective gas, ball mill for 50 h. After mixing, place it in a vacuum dryer and vacuum dry at 60℃ for 5 h to obtain polycrystalline diamond layer mixed powder.

[0063] 6) Composite assembly: First, the polycrystalline diamond layer mixed powder described in step 5) and the powder transition layer mixed powder described in step 4) are sequentially loaded into a metal Mo cup, layered and compacted to shape. Then, the cemented carbide substrate containing the rare earth transition layer from step 3) is placed flat on the powder transition layer mixed powder with the coated side facing down. Then, two metal Mo cups are inserted from the front and back directions respectively to obtain the composite component.

[0064] 7) Composite preloading: Place the composite component from step 6) into the pyrophyllite block, and then place the pyrophyllite block into a high-temperature, high-pressure apparatus.

[0065] During preparation, the pressure is increased to 6 GPa and held for 100 seconds without heating. Then, the pressure is reduced to standard atmospheric pressure using a high-temperature and high-pressure equipment to obtain a pre-compressed composite component.

[0066] 8) Composite purification: Place the pre-compressed composite assembly from step 7) into a vacuum sintering furnace for sintering. During sintering, first perform a rough vacuum evacuation until the furnace pressure reaches 7×10⁻⁶. -2 Below Pa, heat to 300℃ and hold for 10 minutes, then continue evacuating until the furnace pressure is 3×10⁻⁶. -5Pa, the temperature was raised to 1300℃ for 10 min, vacuum was stopped, and reducing gas (40% carbon monoxide, 30% ammonia, and 30% nitrogen by volume) was filled in for 1.5 h, and vacuum was again applied to 3 x 10 -5 Pa, to obtain a purified composite assembly;

[0067] 9) High-temperature and high-pressure sintering: the purified composite assembly of step 8) and a block of beryl were assembled and placed in a cubic press for sintering. The sintering pressure was raised to 6.8 GPa at a rate of 5 GPa / min, and high-temperature sintering was performed at a temperature rising rate of 40℃ / S. After holding at 1410℃ for 150 S, the temperature was raised to 1490℃ within 40 S, and the sintering was held for 150 S. After sintering, the temperature was lowered to 600℃ at a rate of 20℃ / S, and the temperature was held for 20 min before being lowered to room temperature. The pressure was lowered to normal pressure at a rate of 0.6 GPa / min. The assembled block was removed from the cubic press, and the surface wrapping layer was removed to obtain a sintered polycrystalline diamond compact blank.

[0068] 10) Stress relief aging: the sintered polycrystalline diamond compact blank of step 9) was again assembled with a block of beryl, and placed in a cubic press. The pressure was raised to 6.8 GPa, and the temperature was adjusted to 700℃ and held for 25 min. The beryl block was then cooled to 600℃ and held for 25 min, and then further cooled to 500℃ and held for 25 min. Then, the temperature was further lowered to 400℃ and held for 25 min, and finally cooled to room temperature at a rate of 20℃ / S, and the pressure was lowered to normal pressure at a rate of 0.8 GPa / min. The aged polycrystalline diamond compact blank was removed from the assembled block, and processed to the desired size using grinding equipment, and then surface polished to obtain the polycrystalline diamond compact with high thermal stability.

[0069] The polycrystalline diamond compact with high thermal stability prepared in this example was tested for wear resistance according to the standard JB / T3235-2013 "Abrasion Resistance Test Method for Artificial Diamond Sintered Body". The compact sample was first placed in a tube furnace and heated at 690℃ for 1 min, and then tested for impact toughness using a drop hammer impact method (i.e., a 1 kg hammer was dropped from a height of 30 cm to impact the corners of the sample, and the impact toughness value was obtained when a micro crack appeared on the surface). The thermal stability test was performed using a thermogravimetric-differential thermal analysis method, and the initial oxidation temperature of the differential thermal curve was used as the thermal stability characterization temperature. The higher the initial oxidation temperature, the better the thermal stability. The test results were as follows: the abrasion ratio was 470,000, the impact toughness was 65 times, and the thermal stability characterization temperature was 755℃. The polycrystalline diamond compact had excellent heat resistance, wear resistance, and impact toughness.

[0070] Example 3

[0071] The polycrystalline diamond composite sheet with high thermal stability in this embodiment, such as... Figure 1 As shown, the structure includes a cemented carbide substrate 5 and, from the inside out, a rare earth composite coating 3, a powder transition layer 2, and a polycrystalline diamond layer 1 sequentially disposed on the cemented carbide substrate 5. The polycrystalline diamond layer 1 is composed of the following raw materials in weight percentages: 62.5% graphene-coated diamond powder, 17.5% carbon nanotube-coated diamond powder, 12.5% ​​fullerene-coated diamond powder, 0.4% graphyne, 0.4% fullerene, and 6.7% binder; the rare earth composite coating 3 is arranged in the following order from the inside out. The coating consists of a rare earth coating and a TiB coating. The rare earth coating is disposed on the surface of the cemented carbide substrate and between the TiB coating. The rare earth coating material is selected from the rare earth element Pm. The thickness of the rare earth coating is 4 μm. The thickness of the TiB coating is 6 μm. The cemented carbide substrate 5 is a surface-boronized cemented carbide substrate. The thickness of the boronized layer 4 on the surface of the cemented carbide substrate is 2.5 μm. The powder transition layer 2 is composed of the following raw materials in weight percentage: fullerene-coated diamond micropowder 4... The powder transition layer 2 comprises 4.5% tungsten carbide powder, 38.5% magnesium carbonitride powder, 7.5% graphyne powder, 0.375% fullerene, and 8.75% binder; the particle size of the tungsten carbide powder and magnesium carbonitride powder in the powder transition layer 2 is 0.8–1.2 μm; the thickness of the powder transition layer 2 is 0.25 mm; the particle size of the fullerene-coated diamond micropowder is 5–10 μm; the particle size of the graphyne powder is 400–600 nm; and the particle size of the fullerene powder is 300–500 nm. m; the binder is composed of the following raw materials in weight percentage: 96.5% cobalt powder, 1.5% tungsten-titanium solid solution, 0.75% tantalum-niobium solid solution, 0.625% lithium boron nitride powder, and 0.625% magnesium carbonitride powder; the mass ratio of tungsten to titanium in the tungsten-titanium solid solution is 1:1; the mass ratio of TaC to NbC in the tantalum-niobium solid solution is 4:6; the particle size of cobalt, tungsten-titanium solid solution, tantalum-niobium solid solution, lithium boron nitride powder, and magnesium carbonitride in the binder is 30-40 nm.

[0072] The preparation method of the above-mentioned polycrystalline diamond composite sheet with high thermal stability includes the following steps:

[0073] 1) Cemented carbide substrate cleaning: first, the cemented carbide substrate is placed in anhydrous ethanol and cleaned by ultrasonic wave (power 40W) for 10 min, then placed in a solution mixed by NaOH:K3Fe(CN)6:H2O with a mass ratio of 0.5:0.5:13 and cleaned by ultrasonic wave (power 40W) for 7.5 min, then immersed in a mixed solution of 40wt% nitric acid and commercially available concentrated hydrochloric acid (36-38wt%) with a volume ratio of 1:2.5 for 2.5 min, and cleaned with deionized water, and then dried; then the cleaned cemented carbide substrate is fixed on a rotating stand in an ion source / arc ion plating film equipment, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow is 350sccm, the working pressure is 1.2Pa, the substrate bias is -600V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 10 min; when hydrogen is introduced, the gas flow is 250sccm, the working pressure is 1.2Pa, the substrate bias is -600V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 10 min, to obtain the clean cemented carbide substrate;

[0074] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube drying oven for boronizing treatment; the boronizing treatment gas is a mixed gas of 7% B2H6 and 93% H2 by volume, the flow of the mixed gas is 10.5sccm, the pressure is 9kPa, and the reaction time is 4h, to obtain a surface boronized cemented carbide substrate;

[0075] 3) Depositing rare earth composite coating: the surface boronized cemented carbide substrate of step 2) is deposited with a rare earth element as a target material on the boronized surface of the cemented carbide substrate by a magnetron sputtering method, and then a TiB composite target is used as a target material to deposit a TiB coating on the surface of the rare earth coating, the magnetron sputtering working pressure is 1.75Pa, the nitrogen flow introduced is 42.5mL / min, the target-to-substrate distance is 50±5mm, the sputtering temperature is 550℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 160W, and the sputtering time is 29min and 31min respectively, the surface area ratio of Ti element and B element in the TiB composite target is 10:5, to obtain the cemented carbide substrate with rare earth composite coating;

[0076] 4) Powder transition layer mixing: Weigh out graphylene, fullerene, binder, tungsten carbide powder, magnesium carbonitride powder, and fullerene-coated diamond micro powder according to the proportion, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 45W) for 55 min. The mass content of the powder is 0.4 g / ml. Then weigh out polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate (power 45W) for 65 min. The concentration of polyethylene glycol is 2 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 10:1. After filling with argon as a protective gas, ball mill for 35 h. After mixing, place it in a vacuum dryer and vacuum dry at 55℃ for 3.5 h to obtain the powder transition layer mixed powder.

[0077] 5) Polycrystalline diamond layer mixing: Weigh fullerene, graphylene, binder, fullerene-coated diamond powder, carbon nanotube-coated diamond powder, and graphene-coated diamond powder according to the proportions, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 45W) for 47.5 min, and the mass content of the powder is 0.6 g / ml; then weigh polyethylene glycol and add it to the anhydrous ethanol dispersion, mechanically stir and ultrasonically vibrate (power 45W) for 65 min, and the concentration of polyethylene glycol is 3 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls added, with a ball-to-powder mass ratio of 9:1. After filling with nitrogen as a protective gas, ball mill for 47.5 h. After mixing, place it in a vacuum dryer and vacuum dry at 55℃ for 4 h to obtain polycrystalline diamond layer mixed powder.

[0078] 6) Composite assembly: First, the polycrystalline diamond layer mixed powder described in step 5) and the powder transition layer mixed powder described in step 4) are sequentially loaded into a metal Rb cup, layered and compacted to shape. Then, the cemented carbide substrate containing the rare earth transition layer from step 3) is placed flat on the powder transition layer mixed powder with the coated side facing down. Then, two metal Rb cups are inserted from the front and back directions respectively to obtain the composite assembly.

[0079] 7) Composite preloading: Place the composite component from step 6) into the pyrophyllite block, and then place the pyrophyllite block into a high-temperature, high-pressure apparatus.

[0080] During preparation, the pressure is increased to 5.5 GPa and held for 90 seconds without heating. Then, the pressure is reduced to standard atmospheric pressure using a high-temperature and high-pressure equipment to obtain a pre-compressed composite component.

[0081] 8) Composite purification: Place the pre-compressed composite assembly from step 7) into a vacuum sintering furnace for sintering. During sintering, first perform a rough vacuum evacuation until the furnace pressure reaches 7×10⁻⁶. -2 Below Pa, heat to 272℃ and hold for 7.5 minutes, then continue evacuating until the furnace pressure is 3×10⁻⁶. -5Pa, the temperature was raised to 1250℃ for 7.5 min, then the vacuum was stopped and the reducing gas (40% carbon monoxide, 30% ammonia, 30% nitrogen by volume) was filled in for 1.2 h, and then the vacuum was extracted to 3 x 10 -5 Pa, to obtain the purified composite assembly;

[0082] 9) High temperature and high pressure sintering: the purified composite assembly of step 8) and the block of beryl were assembled and placed in a cubic press for sintering. The sintering pressure was first raised to 6.6 GPa at a rate of 2.7 GPa / min, and then the temperature was raised at a rate of 35℃ / S for high temperature sintering. After being kept at 1385℃ for 135 S, the temperature was raised to 1480℃ for 135 S, and then the temperature was lowered to 575℃ at a rate of 17℃ / S. After being kept at 575℃ for 17 min, the temperature was lowered to room temperature, and then the pressure was lowered to normal pressure at a rate of 0.55 GPa / min. The assembled block was taken out of the cubic press, and the surface wrapping layer was removed to obtain the sintered polycrystalline diamond compact blank.

[0083] 10) Stress relief aging: the sintered polycrystalline diamond compact blank of step 9) was assembled with the block of beryl again, and placed in a cubic press. The pressure was raised to 6.6 GPa, and the temperature was adjusted to 675℃ for 22 min. Then the temperature of the beryl block was lowered to 575℃ for 22 min, and then lowered to 450℃ for 22 min. Then the temperature was lowered to 350℃ for 22 min, and finally lowered to room temperature at a rate of 17℃ / S. The pressure was lowered to normal pressure at a rate of 0.65 GPa / min. The aged polycrystalline diamond compact blank was taken out of the assembled block, and processed to the required size using grinding equipment, and then surface polished to obtain the polycrystalline diamond compact with high thermal stability.

[0084] The polycrystalline diamond compact with high thermal stability prepared in this example was tested for wear resistance according to the standard JB / T3235-2013 "Abrasion Resistance Test Method for Artificial Diamond Sintered Body". The compact sample was first placed in a tube furnace and heated at 690℃ for 1 min, and then the impact toughness was tested by the falling weight impact method (i.e. a 1 kg weight hammer was dropped freely from a height of 30 cm to impact the corners of the sample, and the impact toughness value was obtained when micro cracks appeared on the surface). The thermal stability test was performed by thermogravimetric-differential thermal analysis method, and the initial oxidation temperature of the differential thermal curve was used as the thermal stability characterization temperature. The higher the initial oxidation temperature, the better the thermal stability. The test results showed that the abrasion ratio was 460,000, the impact toughness was 66 times, and the thermal stability characterization temperature was 770℃. The polycrystalline diamond compact had excellent heat resistance, wear resistance and impact toughness.

[0085] Comparative Example 1

[0086] The polycrystalline diamond compact with high thermal stability of the comparative example comprises a cemented carbide substrate and a rare earth composite coating, a powder transition layer and a polycrystalline diamond layer arranged on the cemented carbide substrate from inside to outside, the polycrystalline diamond layer is composed of the following raw materials in percentage by weight: graphene-coated diamond powder 54.2%, carbon nanotube-coated diamond powder 20.2%, fullerene-coated diamond powder 15.2%, graphyne 0.6%, fullerene 0.6% and binder 9.2%; the rare earth composite coating is in the order of rare earth coating, TiB coating from inside to outside, wherein the rare earth coating is arranged between the surface of the cemented carbide substrate and the TiB coating; the material of the rare earth coating is selected from rare earth element Pm; the thickness of the rare earth coating is 2.5 μm; the thickness of the TiB coating is 3.5 μm; the cemented carbide substrate is a boronized cemented carbide substrate; the thickness of the boronized layer on the surface of the cemented carbide substrate is 0.8 μm; the powder transition layer is composed of the following raw materials in percentage by weight: fullerene-coated diamond powder 38.2%, tungsten carbide powder 40.2%, magnesium carbonitride powder 10.2%, graphyne 0.6%, fullerene 0.6% and binder 10.2%; the particle size of the tungsten carbide powder and the magnesium carbonitride powder in the powder transition layer is 0.8-1.2 μm; the thickness of the powder transition layer is 0.18 mm; the particle size of the fullerene-coated diamond powder is 5-10 μm; the particle size of the graphyne is 400-600 nm; the particle size of the fullerene is 300-500 nm; the binder is composed of the following raw materials in percentage by weight: cobalt powder 94.6%, tungsten-titanium solid solution 2.1%, tantalum-niobium solid solution 1.1%, lithium nitride-boronide powder 1.1%, magnesium carbonitride powder 1.1%; the mass ratio of tungsten element to titanium element in the tungsten-titanium solid solution is 1:1; the mass ratio of TaC to NbC in the tantalum-niobium solid solution is 4:6; the particle size of cobalt, tungsten-titanium solid solution, tantalum-niobium solid solution, lithium nitride-boronide powder and magnesium carbonitride in the binder is 30-40 nm.

[0087] The preparation method of the polycrystalline diamond compact with high thermal stability is the same as that of Example 3.

[0088] The polycrystalline diamond compact with high thermal stability prepared in the comparative example is tested for performance, and the testing method is the same as that of Example 3. The test result is that the abrasion ratio is 320,000, the impact toughness is 55 times, the thermal stability characterization temperature is 650℃, and the performance index is obviously reduced compared with Example 3.

[0089] Comparative Example 2

[0090] The polycrystalline diamond compact with high thermal stability of the embodiment comprises a cemented carbide substrate and, sequentially from inside to outside, a rare earth composite coating, a powder transition layer and a polycrystalline diamond layer on the cemented carbide substrate, the polycrystalline diamond layer is composed of the following raw materials in percentage by weight: graphene-coated diamond micro powder 70.8%, carbon nanotube-coated diamond micro powder 14.8%, fullerene-coated diamond micro powder 9.8%, graphyne 0.2%, fullerene 0.1% and binder 4.3%; the rare earth composite coating sequentially from inside to outside is a rare earth coating and a TiB coating, wherein the rare earth coating is arranged between the surface of the cemented carbide substrate and the TiB coating; the material of the rare earth coating is selected from rare earth element Pm; the thickness of the rare earth coating is 5.5 μm; the thickness of the TiB coating is 9 μm; the cemented carbide substrate is a boronized cemented carbide substrate; the thickness of the boronized layer on the surface of the cemented carbide substrate is 4.5 μm; the powder transition layer is composed of the following raw materials in percentage by weight: fullerene-coated diamond micro powder 50.7%, tungsten carbide powder 36.8%, magnesium carbonitride powder 4.8%, graphyne 0.2%, fullerene 0.2% and binder 7.3%; the particle size of the tungsten carbide powder and the magnesium carbonitride powder in the binder is 0.8-1.2 μm; the thickness of the powder transition layer is 0.35 mm; the particle size of the fullerene-coated diamond micro powder is 5-10 μm; the particle size of the graphyne is 400-600 nm; the particle size of the fullerene is 300-500 nm; the binder is composed of the following raw materials in percentage by weight: cobalt powder 98.4%, tungsten-titanium solid solution 0.9%, tantalum-niobium solid solution 0.4%, lithium nitride-boronide powder 0.15% and magnesium carbonitride powder 0.15%; the mass ratio of tungsten element to titanium element in the tungsten-titanium solid solution is 1:1; the mass ratio of TaC to NbC in the tantalum-niobium solid solution is 4:6; the particle size of cobalt, tungsten-titanium solid solution, tantalum-niobium solid solution, lithium nitride-boronide powder and magnesium carbonitride in the binder is 30-40 nm.

[0091] The preparation method of the polycrystalline diamond compact with high thermal stability is the same as that in Embodiment 3.

[0092] The polycrystalline diamond compact with high thermal stability prepared in the comparative example is tested for performance, and the testing method is the same as that in Embodiment 3. The test result is that the abrasion ratio is 360,000, the impact toughness is 55 times, the thermal stability characterization temperature is 680℃, and the performance index is obviously reduced compared with Embodiment 3.

[0093] Comparative Example 3

[0094] The polycrystalline diamond compact with high thermal stability of the comparative example is composed of the same materials and in the same proportion as in Embodiment 3.

[0095] The preparation method thereof comprises the following steps:

[0096] 1) Cemented carbide substrate cleaning: first, the cemented carbide substrate is placed in anhydrous ethanol and cleaned by ultrasonic wave (power 35 W) for 12 min, then placed in a solution mixed by NaOH: K3Fe(CN)6: H2O in a mass ratio of 0.5: 0.5: 11 and cleaned by ultrasonic wave (power 35 W) for 6 min, then immersed in a mixed solution of 40wt% nitric acid and commercially available concentrated hydrochloric acid (36-38wt%) in a volume ratio of 1:1.5 for 2 min, and cleaned with deionized water, and then dried; then the cleaned cemented carbide substrate is fixed on a rotating stand in an ion source / arc ion plating film equipment, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow is 295 sccm, the working pressure is 0.8 Pa, the substrate bias is -495 V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 7.5 min; when hydrogen is introduced, the gas flow is 195 sccm, the working pressure is 0.7 Pa, the substrate bias is -495 V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 7.5 min, to obtain the clean cemented carbide substrate;

[0097] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube drying furnace for boronizing treatment; the boronizing treatment gas is a mixed gas of 5.5% B2H6 and 94.5% H2 by volume, the flow rate of the mixed gas is 8 sccm, the pressure is 7 kPa, and the reaction time is 2.5 h, to obtain a surface boronized cemented carbide substrate;

[0098] 3) Depositing rare earth composite coating: the surface boronized cemented carbide substrate of step 2) is subjected to a magnetron sputtering method, first, a rare earth element is used as a target material to deposit a rare earth coating on the boronized surface of the cemented carbide substrate, the thickness of the rare earth coating is 2.5 µm, then a TiB composite target is used as a target material to deposit a TiB coating on the surface of the rare earth coating, the thickness of the TiB coating is 3.5 µm; the magnetron sputtering working pressure is 1.0 Pa, the nitrogen flow rate introduced is 34 mL / min, the target-to-substrate distance is 50±5 mm, the sputtering temperature is 495℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 118 W, and the sputtering time is 12 min and 14 min respectively, the surface area ratio of Ti element to B element in the TiB composite target is 10:4, to obtain the cemented carbide substrate containing a rare earth composite coating;

[0099] 4) Powder transition layer mixing: Weigh out graphylene, fullerene, binder, tungsten carbide powder, magnesium carbonitride powder, and fullerene-coated diamond micro powder according to the proportion, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 43W) for 54 min. The mass content of the powder is 0.2 g / ml. Then weigh out polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate (power 43W) for 54 min. The concentration of polyethylene glycol is 0.8 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 7:1. After filling with argon as a protective gas, ball mill for 29 h. After mixing, place it in a vacuum dryer and vacuum dry at 49℃ for 1.5 h to obtain the powder transition layer mixed powder.

[0100] 5) Polycrystalline diamond layer mixing: Fullerene, graphylene, binder, fullerene-coated diamond powder, carbon nanotube-coated diamond powder, and graphene-coated diamond powder were weighed according to the proportions and dispersed in anhydrous ethanol in sequence. The mixture was mechanically stirred and ultrasonically dispersed (power 43W) for 48 min, and the mass content of the powder was 0.4 g / ml. Polyethylene glycol was then weighed and added to the anhydrous ethanol dispersion. The mixture was mechanically stirred and ultrasonically dispersed (power 43W) for 64 min, and the concentration of polyethylene glycol was 0.8 g / L. The mixture was then poured into a cemented carbide ball mill jar with cemented carbide balls added. The mass ratio of the balls to the powder was 7:1. Nitrogen gas was introduced as a protective gas and the mixture was ball-milled for 44 h. After mixing, the mixture was placed in a vacuum dryer and vacuum dried at 49℃ for 2.5 h to obtain polycrystalline diamond layer mixed powder.

[0101] 6) Composite assembly: First, the polycrystalline diamond layer mixed powder described in step 5) and the powder transition layer mixed powder described in step 4) are sequentially loaded into a metal Rb cup, layered and compacted to shape. Then, the cemented carbide substrate containing the rare earth transition layer from step 3) is placed flat on the powder transition layer mixed powder with the coated side facing down. Then, two metal Rb cups are inserted from the front and back directions respectively to obtain the composite assembly.

[0102] 7) Composite preloading: Place the composite component from step 6) into the pyrophyllite block, and then place the pyrophyllite block into a high-temperature, high-pressure apparatus.

[0103] During preparation, the pressure is increased to 4.8 GPa and held for 75 seconds without heating. Then, the pressure is reduced to standard atmospheric pressure using a high-temperature and high-pressure equipment to obtain a pre-compressed composite component.

[0104] 8) Composite purification: Place the pre-compressed composite assembly from step 7) into a vacuum sintering furnace for sintering. During sintering, first perform a rough vacuum evacuation until the furnace pressure reaches 7×10⁻⁶. -2 Below Pa, heat to 240℃ and hold for 4.5 minutes, then continue evacuating until the furnace pressure is 3×10⁻⁶. -5Pa, the temperature is raised to 1180℃ and kept for 4.5 min, then the vacuum is stopped and the reducing gas (40% carbon monoxide, 30% ammonia, 30% nitrogen by volume) is filled in, and kept for 0.5 h, then the vacuum is extracted again to 3x10 -5 Pa, to obtain the purified composite assembly;

[0105] 9) High temperature and high pressure sintering: the purified composite assembly of step 8) and the block of beryl are assembled and placed in a cubic press for sintering, first raised to a sintering pressure of 6.4 GPa at a rate of 0.4 GPa / min, then raised to a sintering temperature of 1460℃ at a rate of 28℃ / S, and kept for 118 S, then raised to 1350℃ within 28 S, and kept for 118 S, then cooled to 545℃ at a rate of 14℃ / S, kept for 14 min, and then cooled to room temperature, and then reduced to normal pressure at a rate of 0.4 GPa / min. The assembled block is taken out of the cubic press, and the surface wrapping layer is removed, to obtain a sintered polycrystalline diamond compact blank.

[0106] 10) Stress relief aging: the sintered polycrystalline diamond compact blank of step 9) is assembled with the block of beryl again, and placed in a cubic press, pressurized to 6.0 GPa, and the temperature is adjusted to 640℃, kept for 19 min, then the block of beryl is cooled to 540℃, kept for 18 min, then further cooled to 390℃, kept for 18 min, then further cooled to 290℃, kept for 18 min, and finally cooled to room temperature at a rate of 14℃ / S, and reduced to normal pressure at a rate of 0.4 GPa / min. The aged polycrystalline diamond compact is taken out of the assembled block, processed to the required size with grinding equipment, and then surface polished, to obtain the polycrystalline diamond compact with high thermal stability.

[0107] The polycrystalline diamond compact with high thermal stability prepared in this comparative example is tested for performance, and the testing method is the same as in example 3. The test results show that the wear ratio is 350,000, the impact toughness is 51 times, and the thermal stability characterization temperature is 690℃. Compared with example 3, the performance indicators are significantly reduced.

[0108] Comparative example 4

[0109] The polycrystalline diamond compact with high thermal stability in this comparative example is prepared from the same materials and in the same proportions as in example 3.

[0110] The preparation method comprises the following steps:

[0111] 1) Cemented carbide substrate cleaning: first, the cemented carbide substrate is placed in anhydrous ethanol and cleaned by ultrasonic wave (power 34 W) for 10 min, then placed in a solution mixed by NaOH: K3Fe(CN)6: H2O in a mass ratio of 0.5: 0.5: 15.5 and cleaned by ultrasonic wave (power 34 W) for 9 min, then immersed in a mixed solution of 40% nitric acid and commercially available concentrated hydrochloric acid (36-38 wt%) in a volume ratio of 1:3.5 for 2 min, and cleaned with deionized water, and then dried; then the cleaned cemented carbide substrate is fixed on a rotating stand in an ion source / arc ion plating film equipment, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow is 410 sccm, the working pressure is 1.6 Pa, the substrate bias is -710 V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 13 min; when hydrogen is introduced, the gas flow is 305 sccm, the working pressure is 1.6 Pa, the substrate bias is -705 V, the surface of the cemented carbide substrate is cleaned by glow discharge, and the cleaning time is 13 min, to obtain the clean cemented carbide substrate;

[0112] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube drying oven for boronizing treatment; the boronizing treatment gas is a mixed gas of 8.5% B2H6 and 92.5% H2 by volume, the flow rate of the mixed gas is 13 sccm, the pressure is 11 kPa, and the reaction time is 5.5 h, to obtain a surface boronized cemented carbide substrate;

[0113] 3) Depositing rare earth composite coating: the surface boronized cemented carbide substrate of step 2) is subjected to a magnetron sputtering method, first, a rare earth element is used as a target material to deposit a rare earth coating on the boronized surface of the cemented carbide substrate, the thickness of the rare earth coating is 5.5 µm, then a TiB composite target is used as a target material to deposit a TiB coating on the surface of the rare earth coating, the thickness of the TiB coating is 8.5 µm; the magnetron sputtering working pressure is 2.1 Pa, the nitrogen flow rate introduced is 51 mL / min, the target-to-substrate distance is 50±5 mm, the sputtering temperature is 605℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 205 W, and the sputtering time is 46 min and 48 min respectively, the surface area ratio of Ti element to B element in the TiB composite target is 10:6, to obtain the cemented carbide substrate containing a rare earth composite coating;

[0114] 4) Powder transition layer mixing: Weigh out graphylene, fullerene, binder, tungsten carbide powder, magnesium carbonitride powder, and fullerene-coated diamond micro powder according to the proportion, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate (power 44W) for 54 min. The mass content of the powder is 0.6 g / ml. Then weigh out polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate (power 44W) for 54 min. The concentration of polyethylene glycol is 3.5 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of balls to powder is 12.5:1. After filling with argon as a protective gas, ball mill for 41 h. After mixing, place it in a vacuum dryer and vacuum dry at 61℃ for 5.5 h to obtain the powder transition layer mixed powder.

[0115] 5) Polycrystalline diamond layer mixing: Fullerene, graphylene, binder, fullerene-coated diamond powder, carbon nanotube-coated diamond powder, and graphene-coated diamond powder were weighed according to the proportions and dispersed in anhydrous ethanol in sequence. The mixture was mechanically stirred and ultrasonically dispersed (power 44W) for 48 min, and the mass content of the powder was 1.1 g / ml. Polyethylene glycol was then weighed and added to the anhydrous ethanol dispersion. The mixture was mechanically stirred and ultrasonically dispersed (power 44W) for 64 min, and the concentration of polyethylene glycol was 5.5 g / L. The mixture was then poured into a cemented carbide ball mill jar with cemented carbide balls added. The mass ratio of the balls to the powder was 10.5:1. Nitrogen gas was introduced as a protective gas and the mixture was ball-milled for 51 h. After mixing, the mixture was placed in a vacuum dryer and vacuum dried at 61℃ for 5.5 h to obtain the polycrystalline diamond layer mixed powder.

[0116] 6) Composite assembly: First, the polycrystalline diamond layer mixed powder described in step 5) and the powder transition layer mixed powder described in step 4) are sequentially loaded into a metal Rb cup, layered and compacted to shape. Then, the cemented carbide substrate containing the rare earth transition layer from step 3) is placed flat on the powder transition layer mixed powder with the coated side facing down. Then, two metal Rb cups are inserted from the front and back directions respectively to obtain the composite assembly.

[0117] 7) Composite preloading: Place the composite component from step 6) into the pyrophyllite block, and then place the pyrophyllite block into a high-temperature, high-pressure apparatus.

[0118] During preparation, the pressure is increased to 6.2 GPa and held for 105 seconds without heating. Then, the pressure is reduced to standard atmospheric pressure using a high-temperature and high-pressure equipment to obtain a pre-compressed composite component.

[0119] 8) Composite purification: Place the pre-compressed composite assembly from step 7) into a vacuum sintering furnace for sintering. During sintering, first perform a rough vacuum evacuation until the furnace pressure reaches 7×10⁻⁶. -2 Below Pa, heat to 305℃ and hold for 11 minutes, then continue evacuating until the furnace pressure is 3×10⁻⁶. -5Pa, the temperature is raised to 1310℃ for 11 min, then the vacuum is stopped, and the reducing gas (40% carbon monoxide, 30% ammonia, 30% nitrogen by volume) is filled in for 1.6 h, and then the vacuum is extracted to 3*10 -5 Pa, to obtain the purified composite assembly;

[0120] 9) High-temperature and high-pressure sintering: the purified composite assembly of step 8) and the block of beryl are assembled, and are placed in a cubic press for sintering. The sintering pressure is raised to 7.0 GPa at a rate of 5.5 GPa / min, and the temperature is raised at a rate of 42℃ / S for high-temperature sintering. After being kept at 1420℃ for 155 S, the temperature is raised to 1500℃ within 42 S, and is kept at 1500℃ for 155 S. After sintering, the temperature is lowered to 605℃ at a rate of 21℃ / S, and is kept at 605℃ for 21 min, and then is lowered to room temperature. The pressure is lowered to normal pressure at a rate of 0.7 GPa / min. The block is taken out of the cubic press, and the surface wrapping layer is removed, to obtain the sintered polycrystalline diamond compact blank.

[0121] 10) Stress relief aging: the sintered polycrystalline diamond compact blank of step 9) is assembled with the block of beryl again, and is placed in a cubic press. The pressure is raised to 7.0 GPa, and the temperature is adjusted to 705℃, and is kept for 26 min. The temperature of the block of beryl is lowered to 605℃, and is kept for 26 min. Then the temperature is lowered to 510℃, and is kept for 26 min. Then the temperature is lowered to 410℃, and is kept for 26 min. Finally, the temperature is lowered to room temperature at a rate of 21℃ / S, and the pressure is lowered to normal pressure at a rate of 0.9 GPa / min. The aged polycrystalline diamond compact is taken out of the block, and is processed to the required size by grinding equipment. Then surface polishing treatment is performed, to obtain the polycrystalline diamond compact with high thermal stability.

[0122] The polycrystalline diamond compact with high thermal stability prepared in the comparative example is subjected to performance testing. The testing method is the same as that of example 3. The test abrasion ratio is 350,000, the impact toughness is 56 times, and the thermal stability characterization temperature is 665℃. Compared with example 3, the performance indexes are obviously reduced.

[0123] Through comparison and analysis of the technical performance indexes of the above examples and the comparative example, it can be obviously concluded that the polycrystalline diamond compact with high thermal stability produced by the technical scheme of the present application has the advantages of high heat resistance, wear resistance and impact toughness.

[0124] It should be noted that the materials used in the present application are commercially available, and the manufacturers and models are not mentioned. The manufacturers in the examples and the diameter, thickness and thickness of the polycrystalline diamond layer of the compact are not limitations of the present application.

[0125] Finally, it should be noted that the above examples are only used for illustration and not to limit the technical solutions of the present application, any equivalent replacement and modification or partial replacement of the present application without departing from the spirit and scope of the present application should be covered within the scope of protection of the claims of the present application.

Claims

1. A polycrystalline diamond compact having high thermal stability, characterized in that, The cemented carbide substrate and the rare earth composite coating, the powder transition layer and the polycrystalline diamond layer arranged on the cemented carbide substrate from inside to outside are composed of the following raw materials in percentage by weight: graphene-coated diamond micro powder 55-70%, carbon nanotube-coated diamond micro powder 15-20%, fullerene-coated diamond micro powder 10-15%, graphdiyne 0.3-0.5%, fullerene 0.2-0.5% and binder 4.5-9%; the powder transition layer is composed of the following raw materials in percentage by weight: fullerene-coated diamond micro powder 39-50%, tungsten carbide powder 37-40%, magnesium carbonitride powder 5-10%, graphdiyne 0.25-0.5%, fullerene 0.25-0.5% and binder 7.5-10%; the particle size of the tungsten carbide powder and the magnesium carbonitride powder in the powder transition layer is 0.8-1.2 μm; the thickness of the powder transition layer is 0.2-0.3 mm; the rare earth composite coating is arranged in the order of rare earth coating, TiB coating from inside to outside, wherein the rare earth coating is arranged between the surface of the cemented carbide substrate and the TiB coating; the material of the rare earth coating is selected from one of the rare earth elements Pr, Nd and Pm; the thickness of the rare earth coating is 3-5 μm; the thickness of the TiB coating is 4-8 μm; the cemented carbide substrate is a boronized cemented carbide substrate; the thickness of the boronized layer on the surface of the cemented carbide substrate is 1-4 μm; the binder is composed of the following raw materials in percentage by weight: cobalt powder 95-98%, tungsten-titanium solid solution 1-2%, tantalum-niobium solid solution 0.5-1%, lithium nitride boride powder 0.25-1% and magnesium carbonitride powder 0.25-1%; the mass ratio of tungsten and titanium in the tungsten-titanium solid solution is 1:1; the mass ratio of TaC and NbC in the tantalum-niobium solid solution is 4:6; the particle size of the cobalt powder, the tungsten-titanium solid solution, the tantalum-niobium solid solution, the lithium nitride boride powder and the magnesium carbonitride powder in the binder is 30-40 nm.

2. The PDC with high thermal stability according to claim 1, wherein, The particle size of the graphene-coated diamond micro powder is 20-30 μm; the particle size of the carbon nanotube-coated diamond micro powder is 10-20 μm; the particle size of the fullerene-coated diamond micro powder is 5-10 μm; the particle size of the graphdiyne is 400-600 nm; the particle size of the fullerene is 300-500 nm.

3. The method of producing a PCD compact having high thermal stability according to claim 1 or 2, characterized in that, The method comprises the following steps: 1) Cemented carbide substrate purification: first, the cemented carbide substrate is placed in anhydrous ethanol for ultrasonic cleaning for 8-12 min, then placed in a solution mixed with NaOH: K3Fe(CN)6:H2O in a mass ratio of 0.5:0.5:12-15 for ultrasonic cleaning for 5-10 min, then immersed in a mixed solution of concentrated nitric acid with a concentration of 35-45 wt% and hydrochloric acid with a concentration of 30-38 wt% in a volume ratio of 1:2-3 for 2-3 min, and then cleaned with deionized water and dried; then the cleaned cemented carbide substrate is fixed on the rotating shaft in the ion source or arc ion plating film equipment, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow is 300-400 sccm, the working pressure is 1-1.5 Pa, and the substrate bias is -500 to -700 V, the surface of the cemented carbide substrate is glow cleaned, and the cleaning time is 8-12 min; when hydrogen is introduced, the gas flow is 200-300 sccm, the working pressure is 0.8-1.5 Pa, and the substrate bias is -500 to -700 V, the surface of the cemented carbide substrate is glow cleaned, and the cleaning time is 8-12 min, to obtain a clean cemented carbide substrate; 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube type drying oven for boronizing treatment to obtain a cemented carbide substrate with a boronized surface; 3) Depositing rare earth composite coating: the cemented carbide substrate with a boronized surface of step 2) is deposited with a rare earth coating on the boronized surface of the cemented carbide substrate by a magnetron sputtering method using a rare earth element as a target material, and the thickness of the rare earth coating is 3-5 µm; then a TiB composite target is used as a target material to deposit a TiB coating on the surface of the rare earth coating, and the thickness of the TiB coating is 4-8 µm, to obtain a cemented carbide substrate with a rare earth composite coating; 4) Powder transition layer mixing: graphiteyne, fullerene, binder, tungsten carbide powder, magnesium carbonitride powder and fullerene-coated diamond micro powder are weighed according to the proportion, dispersed into anhydrous ethanol respectively, mechanically stirred and ultrasonically dispersed for 50-60 min, and the mass content of the powder is 0.3-0.5 g / mL; polyethylene glycol is weighed and added to the anhydrous ethanol dispersion, mechanically stirred and ultrasonically dispersed for 50-80 min, and the concentration of polyethylene glycol is 1-3 g / L, then poured into a cemented carbide ball milling jar with cemented carbide balls, the ball-to-material mass ratio is 8-12:1, argon is filled as a protective gas, and then ball milled for 30-40 h, and the mixed powder is placed in a vacuum dryer and vacuum dried at 50-60°C for 2-5 h to obtain a powder transition layer mixed powder; 5) Poly-crystal diamond layer mixing: Fullerene, graphyne, binder, fullerene-coated diamond micro-powder, carbon nanotube-coated diamond micro-powder and graphene-coated diamond micro-powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in turn, and are mechanically stirred and ultrasonically dispersed for 45-50 min, the mass content of the powder is 0.2-1 g / mL; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, and is mechanically stirred and ultrasonically dispersed for 60-70 min, the concentration of the polyethylene glycol is 1-5 g / L, then the mixture is poured into a hard alloy ball mill tank with hard alloy balls, the ball-to-material mass ratio is 8-10:1, nitrogen is filled as a protective gas, and then ball milling is performed for 45-50 h, the mixture is placed in a vacuum dryer and vacuum dried at 50-60°C for 3-5 h, and a poly-crystal diamond layer mixed powder is obtained; 6) Composite assembly: the poly-crystal diamond layer mixed powder of step 5) and the powder transition layer mixed powder of step 4) are sequentially loaded into a metal cup, are layered, compacted and shaped, and then the hard alloy substrate with the rare earth composite coating of step 3) is placed on the powder transition layer mixed powder with the coating facing down, and then two metal cups are sleeved from the front and back directions respectively to obtain a composite assembly, wherein the metal cup is composed of one or more of the following materials: Zr, Mo, Rb, Ta, Nb and Sr; 7) Composite pre-pressing: the composite assembly of step 6) is placed in a pyrophyllite block, the pyrophyllite block is placed in a high-temperature and high-pressure device, the pressure is increased to 5-6 GPa, and is maintained for 80-100 s without heating, then the high-temperature and high-pressure device is depressurized to standard atmospheric pressure, and a pre-pressed composite assembly is obtained; 8) Complex purification: the pre-pressing complex assembly of step 7) is placed in a vacuum sintering furnace for sintering, during which, first, rough vacuum is applied to reach a furnace pressure of 7x10 -2 Pa, then heating is performed to 245-300°C for 5-10 min, and vacuum is continuously applied to reach a furnace pressure of 3x10 -5 Pa, the temperature is raised to 1200-1300°C for 5-10 min, vacuum is then stopped, and reducing gas is filled, the reducing gas is composed of 40% carbon monoxide, 30% ammonia, and 30% nitrogen by volume, and is maintained for 1.0-1.5 h, vacuum is then applied again to reach a furnace pressure of 3x10 -5 Pa, and a purified complex assembly is obtained; 9) High-temperature and high-pressure sintering: the purified composite assembly of step 8) and the pyrophyllite assembly block are assembled and placed in a cubic anvil press for sintering, the sintering pressure is increased to 6.5-6.8 GPa at a rate of 0.5-5 GPa / min, the temperature is increased at a rate of 30-40°C / s for high-temperature sintering, and then the temperature is increased to 1470-1490°C within 30-40 s, and the temperature is maintained for 120-150 s, then the temperature is decreased to 550-600°C at a rate of 15-20°C / s, and the temperature is maintained for 15-20 min, and then the temperature is decreased to room temperature, the pressure is decreased to normal pressure at a rate of 0.5-0.6 GPa / min, the pyrophyllite assembly block is taken out of the cubic anvil press, the surface coating layer is removed, and a sintered poly-crystal diamond composite blank is obtained. 10) stress relief aging: the sintered polycrystalline diamond compact blank of step 9) is assembled with the beryl assembly block again, and is placed in a cubic press, is pressed to 6.5-6.8 GPa, is adjusted to 650-700 DEG C, is kept for 20-25 min, is then cooled to 550-600 DEG C, is kept for 20-25 min, then is continuously cooled to 400-500 DEG C, is kept for 20-25 min, is then cooled to 300-400 DEG C, is kept for 20-25 min, is finally cooled to room temperature at 15-20 DEG C / s, is reduced to normal pressure at 0.5-0.8 GPa / min, the polycrystalline diamond compact blank after aging is taken out from the beryl assembly block, is processed to the required size by grinding equipment, is then subjected to surface polishing treatment, and the polycrystalline diamond compact with high thermal stability is obtained.

4. The method of claim 3, wherein the high-thermal-stability PDC is prepared by the steps of: In step 2), the boronizing treatment gas is a mixed gas of 6-8% B2H6 and 92-94% H2 by volume fraction, the flow rate of the mixed gas is 9-12 sccm, the pressure is 8-10 kPa, and the reaction time is 3-5 h. ​ 5. The method of claim 3, wherein the high-thermal-stability PDC is prepared by the steps of: In step 3), the magnetron sputtering working pressure is 1.5-2.0 Pa, the nitrogen or argon flow is 35-50 mL / min, the target-to-substrate distance is 50±5 mm, the sputtering temperature is 500-600℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 120-200 W, the sputtering time is 15-45 min, and the surface area ratio of Ti element to B element in the TiB composite target is 10:

5. ​

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