High-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact and preparation method thereof

Abstract

The application discloses a high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet and a preparation method thereof, and belongs to the technical field of superhard materials. The polycrystalline cubic boron nitride composite sheet comprises a hard alloy base body, a transition composite coating arranged on the hard alloy base body, a powder transition layer arranged on the transition composite coating, and a polycrystalline cubic boron nitride layer arranged on the powder transition layer. The polycrystalline cubic boron nitride layer is composed of the following raw materials in percentage by weight: alumina-coated cubic boron nitride micropowder 40-55%, cubic boron nitride micropowder 25-30%, submicron cubic boron nitride micropowder 5-10%, graphyne 0.2-0.4%, fullerene 0.2-0.4% and a binder 14.6-19.2%. The transition composite coating is deposited on the surface of the hard alloy base body by using a magnetron sputtering method, and the powder transition layer is arranged between the transition composite coating and the polycrystalline cubic boron nitride layer, so that the interface stress between the polycrystalline cubic boron nitride layer and the hard alloy base body is reduced, the bonding strength of the polycrystalline cubic boron nitride layer and the hard alloy base body is improved, and the polycrystalline cubic boron nitride layer has excellent mechanical and thermal properties.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of superhard composite materials, and particularly relates to a high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet and a preparation method thereof. BACKGROUND

[0002] The polycrystalline cubic boron nitride composite sheet belongs to a polycrystalline cubic boron nitride-hard alloy layered structure composite material, which combines the high hardness and high wear resistance of the polycrystalline cubic boron nitride layer and the high toughness and high heat resistance of the hard alloy layer, and is widely used in the field of iron group metal processing as a superhard tool for high-speed cutting, high-efficiency and high-precision machining.

[0003] The interface bonding of the polycrystalline cubic boron nitride composite sheet is the mutual diffusion of the polycrystalline cubic boron nitride layer and the hard alloy layer to achieve the effect of mutual bonding. Such bonding is mostly physical bonding, accompanied by a small amount of chemical bonding. The hard alloy as a substrate has good toughness and certain hardness, and is weldable, but still has some problems. First, the hard alloy has a much larger thermal expansion coefficient than the cubic boron nitride composite phase, and generates mismatched thermal stress at the bonding interface. The existence of such interface mismatch residual stress causes cracks to form at the interface between the polycrystalline cubic boron nitride layer and the hard alloy layer, and in severe cases, delamination and peeling off. Second, the poor high-temperature resistance leads to a sharp decrease in the hardness, wear resistance and other properties of the polycrystalline cubic boron nitride composite sheet tool at high temperatures, thereby accelerating tool wear. SUMMARY

[0004] In order to overcome the deficiencies of the prior art, the present application aims to provide a high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet and a preparation method thereof, so as to improve the high-temperature wear resistance of the polycrystalline cubic boron nitride composite sheet and thereby prolong its service life.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet, comprising a hard alloy substrate and, sequentially arranged on the hard alloy substrate from inside to outside, a transition composite coating, a powder transition layer and a polycrystalline cubic boron nitride layer. The polycrystalline cubic boron nitride layer is composed of the following raw materials in weight percentage: alumina-coated cubic boron nitride micropowder 40-55%, cubic boron nitride micropowder 25-30%, submicron cubic boron nitride micropowder 5-10%, graphdiyne 0.2-0.4%, fullerene 0.2-0.4% and a binder 14.6-19.2%. The thickness of the polycrystalline cubic boron nitride layer is 1-1.2 mm.

[0007] Specifically, the transition composite coating is in the order of rare earth coating, TiCrN coating and TiSiN coating from inside to outside, wherein the rare earth coating is coated between the surface of the cemented carbide substrate and the TiCrN and TiSiN coatings; the material of the rare earth coating is selected from any one of rare earth elements Sm, Eu, Dd and Gd; the thickness of the rare earth coating is 2-4 μm; the thicknesses of the TiCrN and TiSiN coatings are 3-5 μm and 4-6 μm respectively; the cemented carbide substrate is a boronized cemented carbide substrate; and the thickness of the boronized layer on the surface of the cemented carbide substrate is 1-3 μm.

[0008] Specifically, the powder transition layer is composed of the following raw materials in weight percentage: 38-50% of alumina-coated cubic boron nitride micro powder, 36-40% of tungsten carbide powder, 5-10% of magnesium carbonitride powder, 0.3-0.5% of graphdiyne, 0.3-0.5% of fullerene and 8.4-11% of binder; the particle sizes of the tungsten carbide powder and the magnesium carbonitride powder are both 0.8-1.2 μm; and the thickness of the powder transition layer is 0.2-0.3 mm.

[0009] Specifically, the alumina-coated cubic boron nitride micro powder comprises cubic boron nitride micro powder and an aluminum alloy coating coated on the surface of the cubic boron nitride, and flaky alumina is in situ grown on the outer surface of the aluminum alloy coating, the thickness of the flaky alumina is 200-900 nm, the area coverage of the flaky alumina on the outer surface of the aluminum alloy coating is 1-30%, the thickness of the aluminum alloy coating is 10-100 nm, the particle size of the cubic boron nitride micro powder in the alumina-coated cubic boron nitride micro powder is 8-12 μm, and the cubic boron nitride micro powder is titanium ion implanted cubic boron nitride micro powder.

[0010] The alumina-coated cubic boron nitride micro powder can be prepared by using the prior art, for example, the preparation method disclosed in Chinese Patent CN201611122078.6 (Publication No. CN108179004 A, Cubic Boron Nitride Composite, Preparation and Application Thereof).

[0011] Specifically, the particle size of the cubic boron nitride micro powder is 4-6 μm; and the particle size of the sub-micron cubic boron nitride micro powder is 800-1000 nm.

[0012] Specifically, the particle size of the graphdiyne is 300-500 nm; and the particle size of the fullerene is 300-500 nm.

[0013] The graphdiyne and the fullerene can be directly purchased from ordinary commercial products, for example, from Beijing Deke Daojin Technology Co., Ltd.

[0014] Specifically, the binding agent is composed of the following raw materials in weight percentage: titanium 30-50%, aluminum 25-30%, tantalum-niobium solid solution (TaC:NbC=4:6 in mass ratio) 15-20%, oxide 5-10%, nitride 5-10%; the oxide includes one of aluminum oxide, zirconium oxide and magnesium oxide; the nitride includes one of lithium nitride, boron nitride and aluminum nitride. Each of the raw material powders involved in the present application is a common commercially available product that can be directly purchased.

[0015] More specifically, the particle size of the titanium, aluminum, tantalum-niobium solid solution, metal oxide and nitride is 40-50 nm. The above-mentioned method for preparing the high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet includes the following steps:

[0016] 1) Purification of the cemented carbide substrate: first, the cemented carbide substrate is ultrasonically cleaned in acetone for 10-30 min, then ultrasonically cleaned in a solution prepared by mixing K3Fe(CN)6:KOH:H2O in a mass ratio of 0.5:0.6-0.8:8-12 for 5-10 min, then immersed in a mixed solution prepared by mixing sulfuric acid with a concentration of 35-45 wt% and hydrochloric acid with a concentration of 30-38 wt% in a volume ratio of 1:4-6 for 1-2 min, and cleaned with deionized water, and then dried; the cleaned cemented carbide substrate is then fixed on a rotating shaft in an ion source / arc ion plating device, argon or hydrogen is introduced into the vacuum chamber, when argon is introduced, the argon flow rate is 300-500 sccm, the working pressure is 1-1.7 Pa, and the substrate bias is -500 to -700 V, the substrate is subjected to glow cleaning, and the cleaning time is 10-20 min; when hydrogen is introduced, the gas flow rate is 200-400 sccm, the working pressure is 0.8-1.6 Pa, and the substrate bias is -500 to -700 V, the surface of the cemented carbide substrate is subjected to glow cleaning, and the cleaning time is 10-20 min, to obtain a clean cemented carbide substrate;

[0017] 2) Boronizing the surface of the cemented carbide substrate: the clean cemented carbide substrate obtained in step 1) is placed in a vacuum tube-type drying furnace for boronizing treatment, wherein the boronizing treatment gas is a mixed gas of B2H6 with a volume fraction of 7-9% and H2 with a volume fraction of 91-93%, 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, to obtain a cemented carbide substrate with a boronized surface;

[0018] 3) Titanium ion implantation into cubic boron nitride: cubic boron nitride powder is placed in the vacuum working cavity of an ion implanter, monovalent titanium ions supplied by an ion source are separated by a mass spectrometer, and the titanium ions are implanted into the cubic boron nitride powder at a dose of 3×1015 ions / cm2. 15 ~ 3×10 17 ions / cm 2The surface of cubic boron nitride is implanted with titanium ions with an ion density of 1014-1015 ions / cm2 and an energy of 60-80 keV to obtain titanium ion implanted cubic boron nitride micro powder;

[0019] 4) Depositing transition composite coating: the surface boronized cemented carbide substrate in step 2) is used as a target material to deposit a 2-4 μm rare earth coating on the boronized surface of the cemented carbide substrate by magnetron sputtering, and then a TiCr composite target and a TiSi composite target are used as target materials to sequentially deposit a 3-5 μm TiCrN coating and a 4-6 μm TiSiN coating on the surface of the rare earth coating, to obtain the cemented carbide substrate with the transition composite coating;

[0020] 5) Powder transition layer mixing: Fullerene, graphyne, binder, tungsten carbide powder, magnesium carbonitride powder, and alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol, respectively, and are mechanically stirred and ultrasonically dispersed for 40-60 min, and the mass content of the powder is 0.2-0.5 g / ml; polyethylene glycol is weighed and added to the anhydrous ethanol dispersion, and is mechanically stirred and ultrasonically dispersed for 50-80 min, and the concentration of the polyethylene glycol is 1-3 g / L, and then is poured into a cemented carbide ball mill jar with cemented carbide balls, the ball-to-material mass ratio is 6-8:1, argon is filled as a protective gas, and then ball milling is performed for 35-40 h, and after mixing, is placed in a vacuum dryer and vacuum dried at 50-60°C for 3-5 h to obtain the powder transition layer mixed powder;

[0021] 6) Polycrystalline cubic boron nitride layer mixing: Fullerene, graphyne, binder, submicron cubic boron nitride micro powder, cubic boron nitride micro powder, and alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol, respectively, and are mechanically stirred and ultrasonically dispersed for 50-60 min, and the mass content of the powder is 0.5-1 g / ml; polyethylene glycol is weighed and added to the anhydrous ethanol dispersion, and is mechanically stirred and ultrasonically dispersed for 60-80 min, and the concentration of the polyethylene glycol is 2-5 g / L, and then is poured into a cemented carbide ball mill jar with cemented carbide balls, the ball-to-material mass ratio is 8-10:1, argon is filled as a protective gas, and then ball milling is performed for 40-45 h, and after mixing, is placed in a vacuum dryer and vacuum dried at 50-60°C for 4-6 h to obtain the polycrystalline cubic boron nitride layer mixed powder;

[0022] 7) Composite assembly: the polycrystalline cubic boron nitride layer mixed powder in step 6) and the powder transition layer mixed powder in step 5) are sequentially loaded into a metal cup, and are layered, compacted, and shaped, and then the cemented carbide substrate with the transition composite coating in step 4) is placed on the powder transition layer mixed powder with the coating facing down, and then two metal cups are respectively sleeved from the front and back directions to obtain the composite assembly, wherein the metal cup is composed of one or more of the following materials: Zr, Mo, Rb, Ta, Nb, and Sr.

[0023] 8) Pre-pressing of the composite: the composite assembly of step 7) is placed into a block of pyrophyllite, and the block of pyrophyllite is placed into a high-temperature high-pressure device, and the pressure is increased to 3.5-4.5 GPa without heating for 30-50 s, then the high-temperature high-pressure device is depressurized to standard atmospheric pressure, and the pressurization operation is repeated 1-3 times to obtain a pre-pressed composite assembly;

[0024] 9) Purification of the composite: the pre-pressed composite assembly of step 8) is placed into a vacuum sintering furnace for sintering, and during sintering, the furnace is first rough-pumped to a pressure of 5 x 10 -2 Pa or less, and heated to 250-350℃ for 10-15 min, and the vacuum is continued to be pumped to a pressure of 3 x 10 -5 Pa or less, and the temperature is increased to 650-750℃ for 10-15 min, and the vacuum is stopped, and a mixed gas of carbon monoxide, ammonia and argon is filled, and the carbon monoxide, ammonia and argon are uniformly mixed at a molar ratio of 0.5:0.5:1, and are maintained for 1.5-2 h, and the vacuum is again pumped to a pressure of 3 x 10 -5 Pa or less, to obtain a purified composite assembly;

[0025] 10) High-temperature high-pressure sintering: the purified composite assembly of step 9) is again assembled with a block of pyrophyllite, and is placed into a cubic press for high-temperature high-pressure sintering, and during sintering, the sintering pressure is first increased to 6.5-7.0 GPa at a rate of 0.2-0.7 GPa / min, and then the temperature is increased at a rate of 25-35℃ / S for high-temperature sintering, and the temperature is maintained at 1380-1400℃ for 120-150 s, and then the temperature is increased to 1480-1520℃ within 35-45 s, and the temperature is maintained at 1480-1520℃ for 120-150 s, and after sintering, the temperature is decreased at a rate of 15-20℃ / S to 500-600℃, and the temperature is maintained for 30-40 min, and then the temperature is decreased to room temperature, and the pressure is decreased to standard atmospheric pressure at a rate of 0.5-0.7 GPa / min, and the assembled block is removed from the cubic press, and the surface coating layer is removed, to obtain a sintered polycrystalline cubic boron nitride composite sheet blank;

[0026] 11) stress relief aging: the sintered polycrystalline cubic boron nitride compact blank of step 10) is assembled with the assembled block of step 1) again, and is placed in a cubic anvil press, and is pressed to 7.0 GPa, and the temperature is adjusted to 600-650 DEG C, and is kept for 20-30 min, and then the temperature of the block of step 1) is lowered to 500-550 DEG C, and is kept for 20-30 min, and then the temperature is continuously lowered to 400-500 DEG C, and is kept for 20-30 min, and then the temperature is lowered to 300-400 DEG C, and is kept for 20-30 min, and finally the temperature is lowered to room temperature at a rate of 10-20 DEG C / s, and the pressure is lowered to normal pressure at a rate of 0.5-0.6 GPa / min, and the polycrystalline cubic boron nitride compact blank after aging is taken out from the assembled block, and is processed to a required size by grinding equipment, and the high-temperature and wear-resistant polycrystalline cubic boron nitride compact is obtained.

[0027] Further, in step 4), the working pressure of the magnetron sputtering 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 DEG C, the vacuum degree is higher than 2*10 -3 Pa, the sputtering power is 120-200 W, and the sputtering time is 15-45 min; the surface area ratio of Ti element to Si element in the TiSi composite target is 10:6, and the surface area ratio of Ti element to Cr element in the TiCr composite target is 10:4.

[0028] Further, in step 1), the ultrasonic cleaning power is 50-70 W; in steps 5) and 6), the ultrasonic oscillation power is 40-60 W.

[0029] Further, in steps 5) and 6), the molecular weight of the polyethylene glycol is 1000-5000.

[0030] The cemented carbide substrate of the present application refers to tungsten-cobalt cemented carbide, such as YG11 (WC 89% and cobalt 11%).

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

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

[0033] (2) The present application uses alumina-coated cubic boron nitride micropowder, cubic boron nitride micropowder, and submicron cubic boron nitride micropowder of three particle sizes. Since the mixed particles of different particle sizes are mixed, the packing state of the cubic boron nitride particles can be effectively improved, and the connection between the cubic boron nitride particles is more compact. Reasonable gradation can make the cubic boron nitride particles arrange closely, and improve the density, hardness, wear resistance and thermal stability of the polycrystalline cubic boron nitride composite sheet. The alumina-coated cubic boron nitride micropowder is tightly combined with the cubic boron nitride micropowder, the mixture is uniform, the combination and wetting effect of alumina is fully utilized, and the bonding strength between cubic boron nitride and the binder is increased. The titanium ion implanted cubic boron nitride micropowder makes the crystal structure more compact due to the titanium atoms doped into the cubic boron nitride. A certain amount of submicron cubic boron nitride powder is added to the polycrystalline cubic boron nitride layer formula. On the one hand, the submicron cubic boron nitride has good orientation self-adjusting property and can fill the gap between the cubic boron nitride micropowder and the binder micropowder, improve the density of the polycrystalline cubic boron nitride composite sheet, and reduce or eliminate the "bridge" effect to make the pressure distribution uniform during synthesis. On the other hand, the submicron cubic boron nitride has high activity and can easily react with metals or non-metals in the binder to form alloy phase, which together with the residual submicron cubic boron nitride improves the strength and hardness of the polycrystalline cubic boron nitride. Therefore, the use of cubic boron nitride micropowder with three particle size distributions can effectively increase the wear resistance, heat resistance and impact resistance of the polycrystalline cubic boron nitride composite sheet, and prolong the service life of the cutting tool.

[0034] (3) The present invention adds fullerene and graphylene to the polycrystalline cubic boron nitride layer, which can activate the cubic boron nitride particles, so that the carbon atoms of the fullerene and graphylene and the alumina coated on the cubic boron nitride are connected together during the sintering process, promoting direct bonding between the cubic boron nitride particles and improving the bonding strength between cubic boron nitride particles. At the same time, the fullerene and graphylene materials exist in the interstices of cubic boron nitride, which can play a good lubricating role between the cubic boron nitride particles, reduce the frictional resistance between particles under high pressure, promote the filling of the fragmented cubic boron nitride space, improve the uniform distribution of the binder phase, increase the number of fine grains, and thus form a denser and more uniform structure in the polycrystalline diamond.

[0035] (4) The high-temperature wear-resistant polycrystalline cubic boron nitride composite sheet prepared by the present invention has a microhardness of 6000-6500 HV, a wear ratio of 12000-12500, and an impact count of 56-60. Attached Figure Description

[0036] Figure 1 A schematic diagram of the structure of a high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet;

[0037] Figure 2 This is a photograph of a high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet; in the picture:

[0038] 1. Polycrystalline cubic boron nitride layer; 2. Powder transition layer; 3. Transition composite coating; 4. Boronized layer on substrate surface; 5. Hard

[0039] High-strength alloy matrix. Detailed Implementation

[0040] The present invention will be further described below with reference to embodiments, but these are not intended to limit the invention. For the purpose of measurement and comparison...

[0041] The performance of the examples and comparative examples: The diameter of the polycrystalline cubic boron nitride composite sheets prepared in the following examples and comparative examples is φ55mm and the thickness is 3.2mm; the thickness of the polycrystalline cubic boron nitride layer is 1mm; the cemented carbide matrix refers to the tungsten-cobalt cemented carbide YG11 (WC 89% and cobalt 11%) matrix; the alumina-coated cubic boron nitride micropowder was prepared by replacing the 100μm cubic boron nitride with titanium ion implanted micropowder with a particle size of 8-12μm in Example 1 of CN108179004 A, according to the methods of Example 1 and Example 3 of CN108179004 A; the molecular weight of polyethylene glycol is 2000.

[0042] Example 1

[0043] The high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet of this embodiment, such as Figure 1As shown, it comprises a cemented carbide substrate 5 and, from inside to outside, a transition composite coating 3, a powder transition layer 2 and a polycrystalline cubic boron nitride layer 1 arranged on the cemented carbide substrate 5 in sequence; the polycrystalline cubic boron nitride layer 1 is composed of the following raw materials in weight percentage: alumina-coated cubic boron nitride micropowder 40%, cubic boron nitride micropowder 30%, submicron cubic boron nitride micropowder 10%, graphdiyne 0.4%, fullerene 0.4% and binder 19.2%; the transition composite coating 3, in order from inside to outside, is a rare earth coating, a TiCrN coating and a TiSiN coating, wherein the rare earth coating is coated between the surface of the cemented carbide substrate and the TiCrN and TiSiN coatings, the material of the rare earth coating is selected from rare earth element Sm; the thickness of the rare earth coating is 2 μm; the thickness of the TiCrN and TiSiN coatings is 3 μm and 4 μm respectively; 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: alumina-coated cubic boron nitride micropowder 38%, tungsten carbide powder 40%, magnesium carbonitride powder 10%, graphdiyne 0.5%, fullerene 0.5% and binder 11%; the particle size of the tungsten carbide powder and the magnesium carbonitride powder is 0.8-1.2 μm; the thickness of the powder transition layer 2 is 0.2 mm; the particle size of the cubic boron nitride micropowder is 4-6 μm; the particle size of the submicron cubic boron nitride micropowder is 800-1000 nm; the particle size of the graphdiyne is 300-500 nm; the particle size of the fullerene is 300-500 nm; the binder is composed of the following raw materials in weight percentage: titanium 30%, aluminum 30%, tantalum-niobium solid solution (TaC:NbC=4:6 by mass ratio) 20%, alumina 10% and lithium nitride 10%; the particle size of the titanium, aluminum, tantalum-niobium solid solution, alumina and lithium nitride is 40-50 nm.

[0044] The preparation method of the high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite piece described above, comprising the following steps:

[0045] 1) Cleaning of the cemented carbide substrate: First, ultrasonically clean the cemented carbide substrate in acetone (50W) for 30 minutes. Then, ultrasonically clean it for 5 minutes in a solution of K3Fe(CN)6:KOH:H2O mixed in a mass ratio of 0.5:0.6:8 (50W). Finally, soak it in a mixture of 40wt% sulfuric acid and commercially available concentrated hydrochloric acid (36-38wt%) in a volume ratio of 1:4. After cleaning with deionized water and drying, the cleaned cemented carbide substrate is fixed on a rotating frame in an ion source / arc ion plating device. Argon or hydrogen gas is introduced into the vacuum chamber. When argon gas is introduced, the argon gas flow rate is 300 sccm, the working pressure is 1 Pa, and the substrate bias voltage is -500 V. The substrate is then subjected to glow discharge cleaning for 10 minutes. When hydrogen gas is introduced, the gas flow rate is 200 sccm, the working pressure is 0.8 Pa, and the substrate bias voltage is -500 V. The surface of the cemented carbide substrate is then subjected to glow discharge cleaning for 10 minutes, resulting in a clean cemented carbide substrate.

[0046] 2) Boronizing the surface of cemented carbide substrate: The cleaned cemented carbide substrate from step 1) is placed in a vacuum tube drying furnace for boronizing treatment. The boronizing gas is a mixture of 7% B2H6 and 93% H2 by volume. The flow rate of the mixture is 9 sccm, the pressure is 8 kPa, and the reaction time is 3 h, to obtain a cemented carbide substrate with boronized surface.

[0047] 3) Titanium ion implantation into cubic boron nitride: Cubic boron nitride micropowder is placed in the vacuum working chamber of an ion implanter. The ions supplied by the ion source are separated into monovalent titanium ions using a mass spectrometer at a concentration of 3 × 10⁻⁶ ions. 15 ~3×10 17 ions / cm 2 Titanium ion implantation of cubic boron nitride micropowder was obtained by injecting titanium ion density and energy of 60 keV into the surface of cubic boron nitride.

[0048] 4) Deposition of transitional composite coating: Using magnetron sputtering, the boron-diffused cemented carbide substrate from step 2) is first deposited with a rare-earth coating on the boron-diffused surface of the cemented carbide substrate using rare-earth element Sm as the target. Then, TiCrN and TiSiN coatings are sequentially deposited on the rare-earth coating surface using TiCr and TiSi composite targets, respectively. The magnetron sputtering working pressure is 1.5 Pa, the nitrogen flow rate is 35 mL / min, the target-substrate distance is 50 ± 5 mm, the sputtering temperature is 500 °C, and the vacuum degree is higher than 2 × 10⁻⁶. -3Pa, sputtering power 120W, sputtering time of rare earth target material, TiCr composite target and TiSi composite target is 15min, 18min and 21min respectively; the surface area ratio of Ti element and Si element in the TiSi composite target is 10:6, the surface area ratio of Ti element and Cr element in the TiCr composite target is 10:4, to obtain the hard alloy substrate with the transition composite coating;

[0049] 5) Powder transition layer mixing: Fullerene, graphyne, binder, tungsten carbide powder, magnesium carbonitride powder and alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in turn, respectively, and are mechanically stirred and ultrasonic oscillation dispersed (power is 40W) for 40min, the mass content of the powder material is 0.2g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion liquid, and is mechanically stirred and ultrasonic oscillation dispersed (power is 40W) for 50min, the concentration of polyethylene glycol is 1g / L, then is poured into a hard alloy ball mill jar with hard alloy balls, the ball-to-material mass ratio is 6:1, argon is filled as a protective gas, and then ball milling is performed for 35h, after mixing, is placed in a vacuum dryer, and is vacuum dried at 50℃ for 3h, to obtain powder transition layer mixed powder;

[0050] 6) Polycrystalline cubic boron nitride layer mixing: Fullerene, graphyne, binder, submicron cubic boron nitride micro powder, cubic boron nitride micro powder, alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in turn, respectively, and are mechanically stirred and ultrasonic oscillation dispersed (power is 40W) for 50min, the mass content of the powder material is 0.5g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion liquid, and is mechanically stirred and ultrasonic oscillation dispersed (power is 40W) for 60min, the concentration of polyethylene glycol is 2g / L, then is poured into a hard alloy ball mill jar with hard alloy balls, the ball-to-material mass ratio is 8:1, argon is filled as a protective gas, and then ball milling is performed for 40h, after mixing, is placed in a vacuum dryer, and is vacuum dried at 50℃ for 4h, to obtain polycrystalline cubic boron nitride layer mixed powder;

[0051] 7) Composite assembly: the polycrystalline cubic boron nitride layer mixed powder of step 6) and the powder transition layer mixed powder of step 5) are sequentially loaded into a metal cup Zr, are layered, compacted and shaped, and then the hard alloy substrate with the transition composite coating of step 4) is placed on the powder transition layer mixed powder with the coating face downward, and then two metal cups Zr are respectively sleeved from the front and back directions to obtain a composite assembly;

[0052] 8) Composite pre-pressing: the composite assembly of step 7) is placed into a block of pyrophyllite, and the block of pyrophyllite is placed into a high-temperature and high-pressure device, the pressure is increased to 3.5GPa, and is maintained for 30s without heating, then the high-temperature and high-pressure device is depressurized to standard atmospheric pressure, and the pressurizing operation is repeated once to obtain a pre-pressed composite assembly;

[0053] 9) Complex purification: the pre-pressed complex assembly of step 8) is placed in a vacuum sintering furnace for sintering. During sintering, coarse vacuum is first applied to reach an internal pressure of 5x10 -2 Pa, and then the temperature is raised to 250°C for 10 min. Vacuum is continued to be applied to reach an internal pressure of 3x10 -5 Pa, and then the temperature is raised to 650°C for 10 min. Vacuum is stopped, and a mixed gas of carbon monoxide, ammonia and argon is filled in. The carbon monoxide, ammonia and argon are uniformly mixed in a molar ratio of 0.5:0.5:1, and maintained for 1.5 h. Vacuum is applied again to reach an internal pressure of 3x10 -5 Pa, and then the temperature is raised to 650°C for 10 min. Vacuum is stopped, and a mixed gas of carbon monoxide, ammonia and argon is filled in. The carbon monoxide, ammonia and argon are uniformly mixed in a molar ratio of 0.5:0.5:1, and maintained for 1.5 h. Vacuum is applied again to reach an internal pressure of 3x10

[0054] 10) High-temperature and high-pressure sintering: the purified complex assembly of step 9) is assembled again with the block of pyrophyllite, and placed in a cubic press for high-temperature and high-pressure sintering. During sintering, the sintering pressure is first raised to 6.5 GPa at a rate of 0.2 GPa / min, and then high-temperature sintering is performed at a temperature rising rate of 25°C / s. The temperature is maintained at 1380°C for 120 s, and then raised to 1480°C within 35 s, and maintained for 120 s. After sintering, the temperature is lowered to 500°C at a rate of 15°C / s, and maintained for 30 min. The temperature is then lowered to room temperature, and the pressure is lowered to normal pressure at a rate of 0.5 GPa / min. The assembled block is taken out of the cubic press, and the surface coating layer is removed to obtain a sintered polycrystalline cubic boron nitride composite blank;

[0055] 11) Stress relief aging: the sintered polycrystalline cubic boron nitride composite blank of step 10) is assembled again with the block of pyrophyllite, and placed in a cubic press. The pressure is raised to 7.0 GPa, and the temperature is adjusted to 600°C, and maintained for 20 min. The temperature of the block of pyrophyllite is then lowered to 500°C, and maintained for 20 min. The temperature is then lowered to 400°C, and maintained for 20 min. The temperature is then lowered to 300°C, and maintained for 20 min. The temperature is then lowered to room temperature at a rate of 10°C / s, and the pressure is lowered to normal pressure at a rate of 0.5 GPa / min. The aged polycrystalline cubic boron nitride composite blank is taken out of the assembled block, and processed to a desired size using grinding equipment to obtain the high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet. The finished product is shown in Figure 2

[0056] ​The high-temperature wear-resistant polycrystalline cubic boron nitride composite sheet prepared in this embodiment was tested for microhardness according to standard ASTM E384-2010; and for wear resistance according to standard JB / T3235-2013 "Test Method for Wear Ratio of Sintered Synthetic Diamond". The composite sheet sample was first placed in a tubular furnace and heated at 720°C for 1 minute. Then, the impact toughness was tested using a drop hammer impact method (i.e., a 1 kg hammer was dropped freely from a height of 35 cm, and the impact energy was used to impact the edges of the sample to obtain the impact toughness value when micro-cracks appeared on the surface). The test results showed that the microhardness was 6100 HV, the wear ratio was 12200, and the number of impacts was 58.

[0057] Example 2

[0058] The high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet of this embodiment, such as Figure 1 As shown, the system includes a cemented carbide substrate 5 and, from the inside out, a transition composite coating 3, a powder transition layer 2, and a polycrystalline cubic boron nitride layer 1 sequentially disposed on the cemented carbide substrate 5. The polycrystalline cubic boron nitride layer 1 is composed of the following raw materials in weight percentages: 55% alumina-coated cubic boron nitride micropowder, 25% cubic boron nitride micropowder, 5% submicron cubic boron nitride micropowder, 0.2% graphdiene, 0.2% fullerene, and 14.6% binder. The transition composite coating 3, from the inside out, consists of a rare earth coating, a TiCrN coating, and a TiSiN coating, wherein the rare earth coating is applied to the surface of the cemented carbide substrate and between the TiCrN and TiSiN coatings. The rare earth coating material is selected from the rare earth element Eu. The thickness of the rare earth coating is 4 μm. The thicknesses of the TiCrN and TiSiN coatings are 5 μm and 6 μm, respectively. The cemented carbide substrate 5 is a surface-boronized cemented carbide substrate. The surface-boronized layer 4 of the cemented carbide substrate... The thickness of the powder transition layer 2 is 3 μm; the powder transition layer 2 is composed of the following raw materials in weight percentages: 50% alumina-coated cubic boron nitride micro powder, 36% tungsten carbide powder, 5% magnesium carbonitride powder, 0.3% graphyne, 0.3% fullerene, and 8.4% binder; the particle size of the tungsten carbide powder and magnesium carbonitride powder is 0.8–1.2 μm; the thickness of the powder transition layer 2 is 0.3 mm; the particle size of the cubic boron nitride micro powder is 4–6 μm; the submicron cubic boron nitride... The boron nitride micro powder has a particle size of 800–1000 nm; the graphdiyne has a particle size of 300–500 nm; the fullerene has a particle size of 300–500 nm; the binder is composed of the following raw materials in weight percentages: 50% titanium, 25% aluminum, 15% tantalum-niobium solid solution (by mass ratio, TaC:NbC=4:6), 5% zirconium oxide, and 5% boron nitride; the particle size of titanium, aluminum, tantalum-niobium solid solution, zirconium oxide, and boron nitride is 40–50 nm.

[0059] The preparation method of the high-temperature resistant and wear-resistant polycrystalline cubic boron nitride composite sheet described above includes the following steps:

[0060] 1) Cleaning of the cemented carbide substrate: First, ultrasonically clean the cemented carbide substrate in acetone (70W) for 10 minutes. Then, ultrasonically clean it in a solution of K3Fe(CN)6:KOH:H2O in a mass ratio of 0.5:0.8:12 for 10 minutes. Next, soak it in a mixture of 40wt% sulfuric acid and commercially available concentrated hydrochloric acid (36-38wt%) in a volume ratio of 1:6 for 2 minutes. After rinsing with deionized water, dry it. Then, clean the cemented carbide substrate... The alloy substrate is fixed on a rotating frame in an ion source / arc ion plating device. Argon or hydrogen gas is introduced into the vacuum chamber. When argon gas is introduced, the argon gas flow rate is 500 sccm, the working pressure is 1.7 Pa, and the substrate bias voltage is -700 V. The substrate is then subjected to glow discharge cleaning for 20 min. When hydrogen gas is introduced, the gas flow rate is 400 sccm, the working pressure is 1.6 Pa, and the substrate bias voltage is -700 V. The surface of the cemented carbide substrate is then subjected to glow discharge cleaning for 20 min, resulting in a clean cemented carbide substrate.

[0061] 2) Boronizing the surface of the cemented carbide substrate: The cleaned cemented carbide substrate from step 1) is placed in a vacuum tube drying furnace for boronizing treatment. The boronizing gas is a mixture of 9% B2H6 and 91% H2 by volume. The flow rate of the mixture is 12 sccm, the pressure is 10 kPa, and the reaction time is 5 h, to obtain a cemented carbide substrate with boronized surface.

[0062] 3) Titanium ion implantation into cubic boron nitride: Cubic boron nitride micropowder is placed in the vacuum working chamber of an ion implanter. The ions supplied by the ion source are separated into monovalent titanium ions using a mass spectrometer at a concentration of 3 × 10⁻⁶ ions. 15 ~3×10 17 ions / cm 2 Titanium ion implantation of cubic boron nitride micropowder was obtained by injecting titanium ion density and energy of 80 keV into the surface of cubic boron nitride.

[0063] 4) Deposition of transitional composite coating: Using magnetron sputtering, the boron-diffused cemented carbide substrate from step 2) is first deposited with a rare-earth coating on the boron-diffused surface of the cemented carbide substrate using Eu as the target. Then, TiCrN and TiSiN coatings are sequentially deposited on the rare-earth coating surface using TiCr and TiSi composite targets, respectively. The magnetron sputtering working pressure is 2.0 Pa, the nitrogen flow rate is 50 mL / min, the target-substrate distance is 50 ± 5 mm, the sputtering temperature is 600 °C, and the vacuum degree is higher than 2 × 10⁻⁶. -3Pa, sputtering power 200W, sputtering time of rare earth target material, TiCr composite target and TiSi composite target is 41min, 43min and 45min respectively; the surface area ratio of Ti element and Si element in the TiSi composite target is 10:6, the surface area ratio of Ti element and Cr element in the TiCr composite target is 10:4, to obtain the hard alloy substrate with the transition composite coating;

[0064] 5) Powder transition layer mixing: Fullerene, graphyne, binder, tungsten carbide powder, magnesium carbonitride powder and alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in turn, mechanically stirred and ultrasonic oscillation (power is 60W) for 60min, the mass content of powder material is 0.5g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, mechanically stirred and ultrasonic oscillation (power is 60W) for 80min, the concentration of polyethylene glycol is 3g / L, then poured into a hard alloy ball mill jar with hard alloy balls, the ball-to-material mass ratio is 8:1, argon is filled as protective gas, and then ball milling is performed for 40h, after mixing, it is placed in a vacuum dryer and vacuum dried at 60℃ for 5h, to obtain powder transition layer mixed powder;

[0065] 6) Polycrystalline cubic boron nitride layer mixing: Fullerene, graphyne, binder, submicron cubic boron nitride micro powder, cubic boron nitride micro powder, alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in turn, mechanically stirred and ultrasonic oscillation (power is 60W) for 60min, the mass content of powder material is 1g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, mechanically stirred and ultrasonic oscillation (power is 60W) for 80min, the concentration of polyethylene glycol is 5g / L, then poured into a hard alloy ball mill jar with hard alloy balls, the ball-to-material mass ratio is 10:1, argon is filled as protective gas, and then ball milling is performed for 45h, after mixing, it is placed in a vacuum dryer and vacuum dried at 60℃ for 6h, to obtain polycrystalline cubic boron nitride layer mixed powder;

[0066] 7) Composite assembly: the polycrystalline cubic boron nitride layer mixed powder of step 6 and the powder transition layer mixed powder of step 5 are sequentially loaded into a metal Mo cup, layered, compacted and shaped, then the hard alloy substrate with transition composite coating of step 4 is placed on the powder transition layer mixed powder with the coating facing down, and then two metal Mo cups are respectively sleeved from the front and back directions to obtain a composite assembly;

[0067] 8) Composite pre-pressing: the composite assembly of step 7 is placed in a block of pyrophyllite, and the block of pyrophyllite is placed in a high-temperature and high-pressure device, the pressure is increased to 4.5GPa, and maintained for 50s without heating, then the high-temperature and high-pressure device is depressurized to standard atmospheric pressure, and the pressurizing action is repeated for 3 times, to obtain a pre-pressed composite assembly;

[0068] 9) Complex purification: the pre-pressed complex assembly of step 8) is placed in a vacuum sintering furnace for sintering. During sintering, coarse vacuum is first applied to reach an internal pressure of 5x10 -2 Pa, and heating is performed to 350℃ for 15 min. Vacuum is continuously applied to reach an internal pressure of 3x10 -5 Pa, and the temperature is raised to 750℃ for 15 min. Vacuum is then stopped, and a mixed gas of carbon monoxide, ammonia and argon is filled in. The carbon monoxide, ammonia and argon are uniformly mixed at a molar ratio of 0.5:0.5:1, and maintained for 2 h. Vacuum is then applied again to reach an internal pressure of 3x10 -5 Pa, and the temperature is raised to 750℃ for 15 min. Vacuum is then stopped, and a mixed gas of carbon monoxide, ammonia and argon is filled in. The carbon monoxide, ammonia and argon are uniformly mixed at a molar ratio of 0.5:0.5:1, and maintained for 2 h. Vacuum is then applied again to reach an internal pressure of 3x10

[0069] 10) High-temperature and high-pressure sintering: the purified complex assembly of step 9) is assembled again with the block of pyrophyllite, and placed in a cubic press for high-temperature and high-pressure sintering. During sintering, the sintering pressure is first raised to 7.0 GPa at a rate of 0.7 GPa / min, and then high-temperature sintering is performed at a temperature rising rate of 35℃ / S. The temperature is raised to 1400℃ for 150 S, and then raised to 1520℃ for 150 S within 45 S. After sintering, the temperature is lowered to 600℃ at a rate of 20℃ / S, and maintained for 40 min. The temperature is then lowered to room temperature, and the pressure is lowered to normal pressure at a rate of 0.7 GPa / min. The assembled block is taken out of the cubic press, and the surface coating layer is removed to obtain a sintered polycrystalline cubic boron nitride composite blank.

[0070] 11) Stress relief aging: the sintered polycrystalline cubic boron nitride composite blank of step 10) is assembled again with the block of pyrophyllite, and placed in a cubic press. The pressure is raised to 7.0 GPa, and the temperature is adjusted to 650℃ for 30 min. The temperature of the block of pyrophyllite is then lowered to 550℃ for 30 min, and then lowered to 500℃ for 30 min. The temperature is then lowered to 400℃ for 30 min, and finally lowered to room temperature at a rate of 20℃ / S. The pressure is lowered to normal pressure at a rate of 0.6 GPa / min. The aged polycrystalline cubic boron nitride composite blank is taken out of the assembled block, and processed to a desired size using grinding equipment to obtain the high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet, as shown in Figure 2

[0071] The high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet prepared in this example has a microhardness of 35.5 GPa, as measured according to the standard ASTM E384-2010.

[0072] ​Microhardness test; wear resistance test was conducted according to standard JB / T3235-2013 "Test Method for Wear Ratio of Sintered Synthetic Diamond". The composite sample was first placed in a tubular heating furnace and heated at 720℃ for 1 minute. Then, the impact toughness test was conducted using the drop hammer impact method (i.e., a 1kg hammer is dropped freely from a height of 35cm, and the impact energy is used to test the edges of the sample. When micro-cracks appear on the surface, the impact toughness value is obtained). The test results showed that the microhardness was 6300HV, the wear ratio was 12300, and the number of impacts was 60.

[0073] Example 3

[0074] The high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet of this embodiment, such as Figure 1 As shown, the system includes a cemented carbide substrate 5 and, from the inside out, a transition composite coating 3, a powder transition layer 2, and a polycrystalline cubic boron nitride layer 1 sequentially disposed on the cemented carbide substrate 5. The polycrystalline cubic boron nitride layer 1 is composed of the following raw materials in weight percentages: 47.5% alumina-coated cubic boron nitride micropowder, 27.5% cubic boron nitride micropowder, 7.5% submicron cubic boron nitride micropowder, 0.3% graphdiene, 0.3% fullerene, and 16.9% binder. The transition composite coating 3, from the inside out... The order of coating layers is rare earth coating, TiCrN coating, and TiSiN coating. The rare earth coating is applied to the surface of the cemented carbide substrate and between the TiCrN and TiSiN coatings. The rare earth coating material is selected from the rare earth element Dd. The thickness of the rare earth coating is 3 μm. The thicknesses of the TiCrN and TiSiN coatings are 4 μm and 5 μm, respectively. The cemented carbide substrate 5 is a boron-diffused cemented carbide substrate. The thickness of the boron-diffused layer 4 on the surface of the cemented carbide substrate is... 1.5μm; the powder transition layer 2 is composed of the following raw materials in weight percentages: 44% alumina-coated cubic boron nitride micro powder, 38% tungsten carbide powder, 7.5% magnesium carbonitride powder, 0.4% graphdiene, 0.4% fullerene, and 9.7% binder; the particle size of the tungsten carbide powder and magnesium carbonitride powder is 0.8–1.2μm; the thickness of the powder transition layer 2 is 0.25mm; the particle size of the cubic boron nitride micro powder is 4–6μm; the submicron cubic boron nitride micro powder... The particle size is 800-1000 nm; the particle size of the graphylene is 300-500 nm; the particle size of the fullerene is 300-500 nm; the binder is composed of the following raw materials in weight percentage: 40% titanium, 27.5% aluminum, 17.5% tantalum-niobium solid solution (by mass ratio, TaC:NbC=4:6), 7.5% magnesium oxide, and 7.5% aluminum nitride; the particle size of the titanium, aluminum, tantalum-niobium solid solution, magnesium oxide, and aluminum nitride is 40-50 nm.

[0075] The preparation method of the high-temperature resistant and wear-resistant polycrystalline cubic boron nitride composite sheet described above includes the following steps:

[0076] 1) Cleaning of the cemented carbide substrate: First, ultrasonically clean the cemented carbide substrate in acetone (60W) for 20 minutes. Then, ultrasonically clean it for 7.5 minutes in a solution of K3Fe(CN)6:KOH:H2O in a mass ratio of 0.5:0.7:10 (60W). Finally, soak it in a mixture of 40wt% sulfuric acid and commercially available concentrated hydrochloric acid (36-38wt%) in a volume ratio of 1:5 for 1.5 minutes. After cleaning with deionized water and drying, the cleaned cemented carbide substrate is fixed on a rotating frame in an ion source / arc ion plating device. Argon or hydrogen gas is introduced into the vacuum chamber. When argon gas is introduced, the argon gas flow rate is 400 sccm, the working pressure is 1.4 Pa, and the substrate bias voltage is -600 V. The substrate is then subjected to glow discharge cleaning for 15 minutes. When hydrogen gas is introduced, the gas flow rate is 300 sccm, the working pressure is 1.2 Pa, and the substrate bias voltage is -600 V. The surface of the cemented carbide substrate is then subjected to glow discharge cleaning for 15 minutes, resulting in a clean cemented carbide substrate.

[0077] 2) Boronizing the surface of cemented carbide substrate: The cleaned cemented carbide substrate from step 1) is placed in a vacuum tube drying furnace for boronizing treatment. The boronizing gas is a mixture of 8% B2H6 and 92% H2 by volume. The flow rate of the mixture is 10 sccm, the pressure is 9 kPa, and the reaction time is 4 h, to obtain a cemented carbide substrate with boronized surface.

[0078] 3) Titanium ion implantation into cubic boron nitride: Cubic boron nitride micropowder is placed in the vacuum working chamber of an ion implanter. The ions supplied by the ion source are separated into monovalent titanium ions using a mass spectrometer at a concentration of 3 × 10⁻⁶ ions. 15 ~3×10 17 ions / cm 2 Titanium ion implantation of cubic boron nitride micropowder was obtained by injecting titanium ion density and energy of 70 keV into the surface of cubic boron nitride.

[0079] 4) Deposition of transitional composite coating: Using magnetron sputtering, the boron-diffused cemented carbide substrate from step 2) is first deposited with a rare-earth coating on the boron-diffused surface of the cemented carbide substrate using rare-earth element Dd as the target. Then, TiCrN and TiSiN coatings are sequentially deposited on the rare-earth coating surface using TiCr and TiSi composite targets, respectively. The magnetron sputtering working pressure is 1.70 Pa, the nitrogen flow rate is 40 mL / min, the target-substrate distance is 50 ± 5 mm, the sputtering temperature is 550 °C, and the vacuum degree is higher than 2 × 10⁻⁶. -3Pa, sputtering power 160W, sputtering time of rare earth target material, TiCr composite target and TiSi composite target is 28min, 31min and 34min respectively; the surface area ratio of Ti element and Si element in the TiSi composite target is 10:6, the surface area ratio of Ti element and Cr element in the TiCr composite target is 10:4, to obtain the hard alloy substrate with the transition composite coating;

[0080] 5) Powder transition layer mixing: Fullerene, graphyne, binder, tungsten carbide powder, magnesium carbonitride powder and alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in turn, respectively, and are mechanically stirred and ultrasonic oscillation dispersed (power is 50W) for 50min, the mass content of the powder material is 0.3g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion liquid, and is mechanically stirred and ultrasonic oscillation dispersed (power is 50W) for 65min, the concentration of polyethylene glycol is 1.5g / L, then is poured into a hard alloy ball mill jar with hard alloy balls, the ball-to-material mass ratio is 7:1, argon is filled as a protective gas, and then ball milling is performed for 37h, after mixing, is placed in a vacuum dryer, and is vacuum dried at 55℃ for 4h, to obtain powder transition layer mixed powder;

[0081] 6) Polycrystalline cubic boron nitride layer mixing: Fullerene, graphyne, binder, submicron cubic boron nitride micro powder, cubic boron nitride micro powder, alumina coated cubic boron nitride micro powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in turn, respectively, and are mechanically stirred and ultrasonic oscillation dispersed (power is 50W) for 55min, the mass content of the powder material is 0.7g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion liquid, and is mechanically stirred and ultrasonic oscillation dispersed (power is 50W) for 70min, the concentration of polyethylene glycol is 3g / L, then is poured into a hard alloy ball mill jar with hard alloy balls, the ball-to-material mass ratio is 9:1, argon is filled as a protective gas, and then ball milling is performed for 42h, after mixing, is placed in a vacuum dryer, and is vacuum dried at 55℃ for 5h, to obtain polycrystalline cubic boron nitride layer mixed powder;

[0082] 7) Composite assembly: the polycrystalline cubic boron nitride layer mixed powder of step 6) and the powder transition layer mixed powder of step 5) are sequentially loaded into a metal cup Ta, are layered, compacted and shaped, and then the hard alloy substrate with the transition composite coating of step 4) is placed on the powder transition layer mixed powder with the coating facing down, and then two metal cups Ta are sleeved from the front and back directions respectively, to obtain a composite assembly;

[0083] 8) Composite pre-pressing: the composite assembly of step 7) is placed into a block of pyrophyllite, and the block of pyrophyllite is placed into a high-temperature and high-pressure device, the pressure is increased to 4GPa, and is maintained for 40s without heating, then the high-temperature and high-pressure device is depressurized to standard atmospheric pressure, and the pressurizing operation is repeated twice, to obtain a pre-pressed composite assembly;

[0084] 9) Complex purification: the pre-pressed complex assembly of step 8) is placed in a vacuum sintering furnace for sintering. During sintering, the furnace is first rough-pumped to a pressure of 5x10 -2 Pa, heated to 300℃ for 12 min, and then vacuum-pumped to a pressure of 3x10 -5 Pa, the temperature is raised to 700℃ for 12 min, and then vacuum-pumping is stopped. Carbon monoxide, ammonia, and argon are mixed at a molar ratio of 0.5:0.5:1, and the mixture is maintained for 1.7 h. Vacuum-pumping is then performed to a pressure of 3x10 -5 Pa, to obtain a purified complex assembly;

[0085] 10) High-temperature and high-pressure sintering: the purified complex assembly of step 9) is assembled with a block of pyrophyllite again, and placed in a cubic press for high-temperature and high-pressure sintering. During sintering, the sintering pressure is first increased to 6.8 GPa at a rate of 0.4 GPa / min, and then the temperature is increased at a rate of 30℃ / S for high-temperature sintering. The temperature is maintained at 1390℃ for 135 s, and then increased to 1500℃ within 40 s. The temperature is maintained at 1500℃ for 135 s, and then decreased to 550℃ at a rate of 17℃ / S. The temperature is maintained at 550℃ for 35 min, and then decreased to room temperature. The pressure is decreased to atmospheric pressure at a rate of 0.6 GPa / min. The assembled block is removed from the cubic press, and the surface coating is removed to obtain a sintered polycrystalline cubic boron nitride composite blank.

[0086] 11) Stress relief aging: the sintered polycrystalline cubic boron nitride composite blank of step 10) is assembled with a block of pyrophyllite again, and placed in a cubic press. The pressure is increased to 7.0 GPa, and the temperature is adjusted to 625℃ for 25 min. The temperature of the block of pyrophyllite is then decreased to 525℃ for 25 min, and then further decreased to 450℃ for 25 min. The temperature is then decreased to 350℃ for 25 min, and finally decreased to room temperature at a rate of 15℃ / S. The pressure is decreased to atmospheric pressure at a rate of 0.55 GPa / min. The aged polycrystalline cubic boron nitride composite blank is removed from the assembled block, and processed to the desired size using grinding equipment to obtain the high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet, as shown in Figure 2 .

[0087] The high-temperature and wear-resistant polycrystalline cubic boron nitride composite sheet prepared in this example has a microhardness of 35.5 GPa, as measured according to the standard ASTM E384-2010.

[0088] Microhardness test; wear resistance test was carried out according to standard JB / T3235-2013 "Abrasion ratio test method of sintered polycrystalline diamond"; the composite sheet sample was first placed in a tube furnace and heated at 720℃ for 1min, and then impact toughness test was carried out by drop hammer impact method (i.e. a 1kg mass of impact hammer was freely dropped from a height of 35cm, and the energy was used to impact the corners of the sample to test the impact toughness value when micro cracks appeared on the surface).

[0089] Comparative Example 1

[0090] The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet of the present comparative example comprises a cemented carbide substrate and a transition composite coating, a powder transition layer and a polycrystalline cubic boron nitride layer arranged on the cemented carbide substrate in sequence; the polycrystalline cubic boron nitride layer is composed of the following raw materials with the following weight percentages: alumina-coated cubic boron nitride micropowder 39.2%, cubic boron nitride micropowder 30.2%, submicron cubic boron nitride micropowder 10.2%, graphdiyne 0.5%, fullerene 0.5% and binder 19.4%.

[0091] The transition composite coating is in the order of rare earth coating, TiCrN coating and TiSiN coating from inside to outside, wherein the rare earth coating is coated on the surface of the cemented carbide substrate and between the TiCrN and TiSiN coatings; the material of the rare earth coating is selected from rare earth elements Dd; the thickness of the rare earth coating is 1.5μm; the thicknesses of the TiCrN and TiSiN coatings are 2.5μm and 3.5μm respectively; 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 0.5μm; the powder transition layer is composed of the following raw materials with the following weight percentages: alumina-coated cubic boron nitride micropowder 37.2%, tungsten carbide powder 40.2%, magnesium carbonitride powder 10.2%, graphdiyne 0.6%, fullerene 0.6% and binder 11.2%; the particle sizes of the tungsten carbide powder and the magnesium carbonitride powder are both 0.8-1.2μm; the thickness of the powder transition layer is 0.15mm; the particle size of the cubic boron nitride micropowder is 4-6μm; the particle size of the submicron cubic boron nitride micropowder is 800-1000nm; the particle size of the graphdiyne is 300-500nm; the particle size of the fullerene is 300-500nm; the binder is composed of the following raw materials with the following weight percentages: titanium 29.2%, aluminum 30.2%, tantalum-niobium solid solution (TaC:NbC=4:6 by mass ratio) 20.2%, magnesium oxide 10.2%, aluminum nitride 10.2%; the particle sizes of the titanium, aluminum, tantalum-niobium solid solution, magnesium oxide and aluminum nitride are all 40-50nm.

[0092] The preparation method of the high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet is the same as that in Example 3.

[0093] The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet prepared in the present comparative example is subjected to performance testing, and the testing method is the same as that in Example 3. After testing, the microhardness is 5000 HV, the wear ratio is 10000, and the impact number is 45. Compared with Example 3, the performance index is obviously reduced.

[0094] Comparative Example 2

[0095] The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet of the present comparative example comprises a cemented carbide substrate and, in sequence, a transition composite coating, a powder transition layer and a polycrystalline cubic boron nitride layer on the cemented carbide substrate; the polycrystalline cubic boron nitride layer is composed of the following raw materials in weight percentage: alumina-coated cubic boron nitride micropowder 55.8%, cubic boron nitride micropowder 24.8%, submicron cubic boron nitride micropowder 4.8%, graphdiyne 0.1%, fullerene 0.1% and binder 14.4%.

[0096] The transition composite coating is in the order of rare earth coating, TiCrN coating and TiSiN coating from inside to outside, wherein the rare earth coating is coated on the surface of the cemented carbide substrate and between the TiCrN and TiSiN coatings; the material of the rare earth coating is selected from rare earth elements Dd; the thickness of the rare earth coating is 4.5 μm; the thicknesses of the TiCrN and TiSiN coatings are 5.5 μm and 6.5 μm, respectively; 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 3.5 μm; the powder transition layer is composed of the following raw materials in weight percentage: alumina-coated cubic boron nitride micropowder 50.8%, tungsten carbide powder 35.8%, magnesium carbonitride powder 4.8%, graphdiyne 0.2%, fullerene 0.2% and binder 8.2%; the particle sizes of the tungsten carbide powder and the magnesium carbonitride are both 0.8-1.2 μm; the thickness of the powder transition layer is 0.35 mm; the particle size of the cubic boron nitride micropowder is 4-6 μm; the particle size of the submicron cubic boron nitride micropowder is 800-1000 nm; the particle size of the graphdiyne is 300-500 nm; the particle size of the fullerene is 300-500 nm; the binder is composed of the following raw materials in weight percentage: titanium 50.8%, aluminum 24.8%, tantalum-niobium solid solution (TaC:NbC=4:6 in mass ratio) 14.8%, magnesium oxide 4.8% and aluminum nitride 4.8%; the particle sizes of the titanium, aluminum, tantalum-niobium solid solution, magnesium oxide and aluminum nitride are all 40-50 nm.

[0097] The preparation method of the high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite sheet is the same as that in Example 3.

[0098] The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite piece prepared in the present comparative example was subjected to performance testing, and the testing method was the same as that in Example 3. The testing results were as follows: the microhardness was 5000 HV, the wear ratio was 10580, and the impact times were 50. Compared with Example 3, the performance indicators were obviously reduced.

[0099] Comparative Example 3

[0100] The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride composite piece of the present comparative example was prepared by using the same materials and their proportions as in Example 3. The preparation method included the following steps:

[0101] 1) Purification of the cemented carbide substrate: first, the cemented carbide substrate was cleaned in acetone by ultrasonic wave (power: 55 W) for 12 min, and then cleaned in a solution prepared by mixing K3Fe(CN)6, KOH and H2O at a mass ratio of 0.4:0.5:7.5 by ultrasonic wave (power: 55 W) for 7 min. Then, the cleaned cemented carbide substrate was immersed in a mixed solution prepared by mixing concentrated sulfuric acid (40 wt%) and commercially available concentrated hydrochloric acid (36-38 wt%) at a volume ratio of 1:3.5 for 0.5 min, and then cleaned with deionized water and dried. Then, the cleaned cemented carbide substrate was fixed on a rotating shaft in an ion source / arc ion plating film equipment, and argon or hydrogen was introduced into the vacuum chamber. When argon was introduced, the argon flow rate was 280 sccm, the working pressure was 0.8 Pa, and the substrate bias was -490 V. The substrate was subjected to glow cleaning, and the cleaning time was 9 min. When hydrogen was introduced, the gas flow rate was 190 sccm, the working pressure was 0.7 Pa, and the substrate bias was -490 V. The surface of the cemented carbide substrate was subjected to glow cleaning, and the cleaning time was 9 min. A clean cemented carbide substrate was obtained.

[0102] 2) Boronizing the surface of the cemented carbide substrate: the clean cemented carbide substrate obtained in step 1) was subjected to boronizing treatment in a vacuum tube-type drying furnace. The boronizing treatment gas was a mixed gas of B2H6 with a volume fraction of 6.8% and H2 with a volume fraction of 93.2%. The flow rate of the mixed gas was 8.5 sccm, the pressure was 7.5 kPa, and the reaction time was 2.5 h. A cemented carbide substrate with boronized surface was obtained.

[0103] 3) Titanium ion implantation into cubic boron nitride: cubic boron nitride powder was placed in the vacuum working cavity of an ion implanter. The ions supplied by the ion source were separated into monovalent titanium ions by a mass spectrometer. The titanium ions were implanted into the surface of the cubic boron nitride powder at an ion density of 3×1014 ions / cm2 and an energy of 55 keV. Cubic boron nitride powder with titanium ion implantation was obtained. 15 ~ 3×10 17 ions / cm 2

[0104] ​4) Depositing transition composite coating: using the surface boronized cemented carbide substrate of step 2) as the substrate, a rare earth coating is first deposited on the surface of the boronized cemented carbide substrate by magnetron sputtering method, then a TiCr composite target and a TiSi composite target are used as the target material to deposit a TiCrN coating and a TiSiN coating on the surface of the rare earth coating, respectively, the working pressure of the magnetron sputtering is 1.4 Pa, the nitrogen flow rate is 34 mL / min, the target-substrate distance is 50±5 mm, the sputtering temperature is 490℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 110 W, the sputtering time of the rare earth target, the TiCr composite target and the TiSi composite target is 6 min, 9 min and 12 min, respectively; the surface area ratio of Ti element and Si element in the TiSi composite target is 10:5, the surface area ratio of Ti element and Cr element in the TiCr composite target is 10:3, and the cemented carbide substrate with the transition composite coating is obtained;

[0105] 5) Powder transition layer mixing: according to the proportion, fullerene, graphyne, binder, tungsten carbide powder, magnesium carbonitride powder and alumina coated cubic boron nitride micro powder are weighed and dispersed into anhydrous ethanol, respectively, and mechanically stirred and ultrasonically (power 45W) oscillated for 45 min, the mass content of the powder is 0.15 g / ml; polyethylene glycol is weighed and added to the anhydrous ethanol dispersion, mechanically stirred and ultrasonically (power 45W) oscillated for 55 min, the concentration of polyethylene glycol is 0.8 g / L, then poured into a cemented carbide ball mill pot with cemented carbide balls, the ball-to-material mass ratio is 5:1, argon is filled as a protective gas, and then ball milling is performed for 34 h, after mixing, it is placed in a vacuum dryer and vacuum dried at 49℃ for 2.5 h, to obtain the powder transition layer mixed powder;

[0106] 6) Polycrystalline cubic boron nitride layer mixing: according to the proportion, fullerene, graphyne, binder, sub-micron cubic boron nitride micro powder, cubic boron nitride micro powder, alumina coated cubic boron nitride micro powder are weighed and dispersed into anhydrous ethanol, respectively, and mechanically stirred and ultrasonically (power 52W) oscillated for 47 min, the mass content of the powder is 0.4 g / ml; polyethylene glycol is weighed and added to the anhydrous ethanol dispersion, mechanically stirred and ultrasonically (power 52W) oscillated for 68 min, the concentration of polyethylene glycol is 1.8 g / L, then poured into a cemented carbide ball mill pot with cemented carbide balls, the ball-to-material mass ratio is 7:1, argon is filled as a protective gas, and then ball milling is performed for 39 h, after mixing, it is placed in a vacuum dryer and vacuum dried at 49℃ for 3.5 h, to obtain the polycrystalline cubic boron nitride layer mixed powder;

[0107] 7) Complex assembly: the polycrystalline cubic boron nitride layer mixed powder of step 6) and the powder transition layer mixed powder of step 5) are sequentially loaded into a metal cup Ta, and are layered, compacted and shaped, and then the cemented carbide substrate with a transition composite coating of step 4) is placed on the powder transition layer mixed powder with the coating facing down, and then two metal cups Ta are sleeved from the front and back directions respectively to obtain a complex assembly;

[0108] 8) Complex pre-pressing: the complex assembly of step 7) is placed in a block of talc, and the block of talc is placed in a high-temperature and high-pressure device, and is pressurized to 3 GPa without heating for 29 s, and then the high-temperature and high-pressure device is depressurized to standard atmospheric pressure, and the pressurizing operation is repeated 3 times to obtain a pre-pressing complex assembly;

[0109] 9) Complex purification: the pre-pressing complex assembly of step 8) is placed in a vacuum sintering furnace for sintering, and during sintering, vacuum is first coarsely extracted to a furnace internal air pressure of 5×10 -2 Pa, heating to 245℃ for 9 min, continuing to extract vacuum to a furnace internal air pressure of 3×10 -5 Pa, the temperature is raised to 655℃ for 9 min, and then the vacuum extraction is stopped, and a mixed gas of carbon monoxide, ammonia and argon is filled, and the carbon monoxide, ammonia and argon are uniformly mixed in a mole ratio of 0.5:0.5:1, and are maintained for 1.4 h, and then vacuum extraction is performed to a furnace internal air pressure of 3×10 -5 Pa to obtain a purified complex assembly;

[0110] 10) High-temperature and high-pressure sintering: the purified complex assembly of step 9) is assembled again with a talc assembly block, and is placed in a six-surface press for high-temperature and high-pressure sintering, and during sintering, the sintering pressure is first raised to 6 GPa at a rate of 0.15 GPa / min, and then high-temperature sintering is performed at a temperature rising rate of 24℃ / S, and the temperature is raised to 1475℃ for 118 s after being maintained at 1375℃ for 118 s, and then the temperature is lowered to 490℃ at a rate of 14℃ / S, and is maintained for 29 min, and then is lowered to room temperature, and is depressurized to normal pressure at a depressurizing rate of 0.4 GPa / min. The assembly block is taken out of the six-surface press, and the surface wrapping layer is removed to obtain a sintered polycrystalline cubic boron nitride composite sheet blank.

[0111] 11) stress relief aging: sinter the sintered polycrystalline cubic boron nitride compact blank of step 10) again, assemble with the assembled block of step 10), and place in a cubic anvil press, pressurize to 6.8 GPa, adjust the temperature to 590 °C, keep for 19 min, then lower the temperature of the block to 490 °C, keep for 19 min, then continue to lower the temperature to 390 °C, keep for 19 min, then lower the temperature to 290 °C, keep for 19 min, and finally lower the temperature to room temperature at a rate of 9 °C / s, and lower the pressure to normal pressure at a rate of 0.4 GPa / min. Take out the sintered polycrystalline cubic boron nitride compact blank from the assembled block, and process to the required size by grinding equipment to obtain the high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact.

[0112] The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact prepared in the present comparative example is tested for performance, and the testing method is the same as that of Example 3. The test results are as follows: the microhardness is 5500 HV, the wear ratio is 11000, and the impact times are 48. Compared with Example 3, the performance indicators are obviously reduced.

[0113] Comparative Example 4

[0114] The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact of the present comparative example has the same material and ratio as Example 3.

[0115] The preparation method thereof comprises the following steps:

[0116] 1) hard alloy substrate cleaning: first, clean the hard alloy substrate in acetone by ultrasonic wave (power 62 W) for 20 min, then clean in a solution prepared by mixing K3Fe(CN)6: KOH: H2O in a mass ratio of 0.5: 0.9: 13 by ultrasonic wave (power 62 W) for 8 min, then soak in a mixed solution prepared by mixing concentrated sulfuric acid (concentration 40 wt%) and commercially available concentrated hydrochloric acid (concentration 36-38 wt%) in a volume ratio of 1:7 for 3 min, and clean with deionized water, and then dry; then fix the cleaned hard alloy substrate on a rotating shaft in an ion source / arc ion plating film equipment, introduce argon or hydrogen into the vacuum chamber, when argon is introduced, the argon flow is 510 sccm, the working pressure is 1.8 Pa, and the substrate bias is -710 V, the substrate is cleaned by glow discharge, and the cleaning time is 21 min; when hydrogen is introduced, the gas flow is 410 sccm, the working pressure is 1.7 Pa, and the substrate bias is -710 V, the surface of the hard alloy substrate is cleaned by glow discharge, and the cleaning time is 21 min, to obtain a clean hard alloy substrate;

[0117] 2) boronizing the surface of the cemented carbide substrate: placing the clean cemented carbide substrate of step 1) in a vacuum tube drying furnace for boronizing treatment, wherein the boronizing treatment gas is a mixed gas of 9.2% by volume of B2H6 and 90.8% of H2, the flow rate of the mixed gas is 12.5sccm, the pressure is 10.5kPa, the reaction time is 5.5h, and a cemented carbide substrate with a boronized surface is obtained;

[0118] 3) titanium ion implantation into cubic boron nitride: placing cubic boron nitride powder in a vacuum working chamber of an ion implanter, separating monovalent titanium ions from ions supplied by an ion source through a mass spectrometer, and implanting the surface of the cubic boron nitride powder at an ion density of 3×1014 ions / cm2 and an energy of 81keV to obtain titanium ion implanted cubic boron nitride powder; 15 ~3×10 17 ions / cm 2 ;

[0119] 4) depositing a transition composite coating: using a magnetron sputtering method, first depositing a rare earth coating on the boronized surface of the cemented carbide substrate of step 2) using a rare earth element as a target material, then depositing a TiCrN coating and a TiSiN coating on the surface of the rare earth coating in sequence using a TiCr composite target and a TiSi composite target as target materials, wherein the magnetron sputtering working pressure is 2.1Pa, the flow rate of the nitrogen gas introduced is 51mL / min, the target-substrate distance is 50±5mm, the sputtering temperature is 610℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 210W, the sputtering time of the rare earth target, the TiCr composite target and the TiSi composite target is 48min, 51min and 54min respectively, the surface area ratio of Ti element to Si element in the TiSi composite target is 10:7, and the surface area ratio of Ti element to Cr element in the TiC composite target is 10:5, thereby obtaining the cemented carbide substrate with a transition composite coating;

[0120] 5) mixing the powder transition layer: weighing fullerene, graphyne, a binding agent, tungsten carbide powder, magnesium carbonitride powder and alumina-coated cubic boron nitride powder according to the proportion, respectively dispersing them into anhydrous ethanol in sequence, mechanically stirring and ultrasonic oscillation (power 48W) for 48min, and the mass content of the powder is 0.6g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanically stirring and ultrasonic oscillation (power 48W) for 70min, and the concentration of the polyethylene glycol is 3.5g / L, then pouring it into a cemented carbide ball milling tank with cemented carbide balls, ball milling for 41h after filling argon as a protective gas, and then placing it in a vacuum dryer for vacuum drying at 61℃ for 5.5h, thereby obtaining the mixed powder of the powder transition layer;

[0121] 6) Polycrystalline cubic boron nitride layer mixture: Fullerene, graphyne, binder, sub-micron cubic boron nitride powder, cubic boron nitride powder, and alumina-coated cubic boron nitride powder are weighed according to the proportion, and are dispersed into anhydrous ethanol in sequence, respectively, and are mechanically stirred and ultrasonically (power 48 W) oscillated and dispersed for 55 min, the mass content of the powder is 1.1 g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, and is mechanically stirred and ultrasonically (power 55 W) oscillated and dispersed for 75 min, the concentration of the polyethylene glycol is 5.5 g / L, then is poured into a hard alloy ball mill tank with hard alloy balls, the ball-to-material mass ratio is 11:1, argon is filled as a protective gas, and then ball milling is performed for 46 h, after mixing, the mixture is placed in a vacuum dryer, vacuum drying is performed at 61℃ for 5.5 h, and a polycrystalline cubic boron nitride layer mixed powder is obtained;

[0122] 7) Composite assembly: the polycrystalline cubic boron nitride layer mixed powder in step 6) and the powder transition layer mixed powder in step 5) are sequentially loaded into a metal cup Ta, are layered, compacted, and shaped, the hard alloy substrate with a transition coating in step 4) is placed on the transition powder layer mixed powder with the coating facing down, and then two metal cups Ta are sleeved from the front and back directions respectively, and a composite assembly is obtained;

[0123] 8) Composite pre-pressing: the composite assembly in step 7) is placed into a block of pyrophyllite, the block of pyrophyllite is placed into a high-temperature and high-pressure device, the pressure is increased to 4.6 GPa, and is maintained for 51 s without heating, then the high-temperature and high-pressure device is depressurized to standard atmospheric pressure, the pressurizing operation is repeated for 3 times, and a pre-pressed composite assembly is obtained;

[0124] 9) Composite purification: the pre-pressed composite assembly in step 8) is placed in a vacuum sintering furnace for sintering, during sintering, vacuum is first coarsely drawn until the furnace air pressure is below 5×10 -2 Pa, heating is performed until the temperature is 351℃, and is maintained for 16 min, vacuum is continuously drawn until the furnace air pressure is below 3×10 -5 Pa, the temperature is increased to 751℃, and is maintained for 10-15 min, then vacuum is stopped, a mixed gas of carbon monoxide, ammonia, and argon is filled, the carbon monoxide, ammonia, and argon are uniformly mixed in a mole ratio of 0.5:0.5:1, and are maintained for 2.1 h, vacuum is again drawn until the furnace air pressure is below 3×10 -5 Pa, and a purified composite assembly is obtained;

[0125] 10) high temperature and high pressure sintering: the assembly of step 9) is assembled again with the block of beryl, and is placed in a cubic press for high temperature and high pressure sintering. During sintering, the sintering pressure is first increased to 7.2 GPa at a rate of 0.8 GPa / min, and then the temperature is increased at a rate of 36 ℃ / S for high temperature sintering. After the temperature is kept at 1410 ℃ for 151 S, the temperature is increased to 1530 ℃ within 46 S, and then the temperature is kept at 1530 ℃ for 151 S. After sintering, the temperature is decreased to 610 ℃ at a rate of 21 ℃ / S, and then the temperature is kept at 610 ℃ for 41 min. After that, the temperature is decreased to room temperature, and the pressure is decreased to normal pressure at a rate of 0.8 GPa / min. The assembly block is taken out of the cubic press, and the surface coating layer is removed to obtain a sintered polycrystalline cubic boron nitride composite blank.

[0126] 11) stress relief aging: the sintered polycrystalline cubic boron nitride composite blank of step 10) is assembled again with the block of beryl, and is placed in a cubic press. The pressure is increased to 7.0 GPa, and the temperature is adjusted to 655 ℃, which is kept for 31 min. Then the temperature of the block of beryl is decreased to 555 ℃, which is kept for 31 min. Then the temperature is continuously decreased to 510 ℃, which is kept for 31 min. Then the temperature is decreased to 410 ℃, which is kept for 31 min. Finally, the temperature is decreased to room temperature at a rate of 21 ℃ / S, and the pressure is decreased to normal pressure at a rate of 0.7 GPa / min. The polycrystalline cubic boron nitride composite blank after aging is taken out of the assembly block, and is processed to a required size by grinding equipment to obtain the high temperature and wear resistant polycrystalline cubic boron nitride composite sheet.

[0127] The high temperature and wear resistant polycrystalline cubic boron nitride composite sheet prepared in the comparative example is tested for performance, and the testing method is the same as that in example 3. The test results are as follows: the microhardness is 4800 HV, the wear ratio is 9800, and the impact times are 46. Compared with example 3, the performance indexes are obviously reduced.

[0128] Through comparison and analysis of the technical performance indexes of the above examples and the comparative example, it can be obviously concluded that the high temperature and wear resistant polycrystalline cubic boron nitride composite sheet produced by the technical scheme of the present application has the advantages of high microhardness, wear resistance and impact toughness.

[0129] It should be noted that the materials used in the present application are commercially available if not mentioned by manufacturer and model. The manufacturers in the examples and the diameter, thickness, thickness of the polycrystalline cubic boron nitride layer of the composite sheet are not limitations of the present application.

[0130] Finally, it should be noted that the above examples are only used for illustration but not limitation of the technical scheme of the present application. Any equivalent replacement, 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 high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact, characterized in that, The cemented carbide substrate and transition composite coating, powder transition layer and polycrystalline cubic boron nitride layer arranged on the cemented carbide substrate from inside to outside; the polycrystalline cubic boron nitride layer is composed of the following raw materials with the weight percentage: alumina-coated cubic boron nitride micropowder 40-55%, cubic boron nitride micropowder 25-30%, submicron cubic boron nitride micropowder 5-10%, graphdiyne 0.2-0.4%, fullerene 0.2-0.4% and binder 14.6-19.2%, wherein the particle size of the cubic boron nitride micropowder in the alumina-coated cubic boron nitride micropowder is 8-12 μm, the particle size of the cubic boron nitride micropowder is 4-6 μm; the particle size of the submicron cubic boron nitride micropowder is 800-1000 nm; the transition composite coating from inside to outside is rare earth coating, TiCrN coating and TiSiN coating, wherein the rare earth coating is coated between the surface of the cemented carbide substrate and the TiCrN coating; the material of the rare earth coating is selected from any one of rare earth elements Sm, Eu, Dd and Gd; the thickness of the rare earth coating is 2-4 μm; the thickness of the TiCrN coating and the TiSiN coating is 3-5 μm and 4-6 μm respectively; 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 1-3 μm; the powder transition layer is composed of the following raw materials with the weight percentage: alumina-coated cubic boron nitride micropowder 38-50%, tungsten carbide powder 36-40%, magnesium carbonitride powder 5-10%, graphdiyne 0.3-0.5%, fullerene 0.3-0.5% and binder 8.4-11%; the particle size of the tungsten carbide powder and the magnesium carbonitride powder is 0.8-1.2 μm; the thickness of the powder transition layer is 0.2-0.3 mm.

2. The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact according to claim 1, characterized in that, The alumina-coated cubic boron nitride micropowder comprises cubic boron nitride micropowder and aluminum alloy coating coated on the surface of the cubic boron nitride micropowder, and flaky alumina is in situ grown on the outer surface of the aluminum alloy coating, the thickness of the flaky alumina is 200-900 nm, the area coverage of the flaky alumina on the outer surface of the aluminum alloy coating is 1-30%, the thickness of the aluminum alloy coating is 10-100 nm, and the cubic boron nitride micropowder in the alumina-coated cubic boron nitride micropowder is titanium ion implanted cubic boron nitride micropowder. 3.The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact according to claim 1, characterized in that, The particle size of the graphdiyne is 300-500 nm, and the particle size of the fullerene is 300-500 nm.

4. The high-temperature-resistant and wear-resistant polycrystalline cubic boron nitride compact according to claim 1, characterized in that, The binder is composed of the following raw materials with the weight percentage: titanium 30-50%, aluminum 25-30%, tantalum-niobium solid solution 15-20%, oxide 5-10% and nitride 5-10%, the tantalum-niobium solid solution is composed of TaC:NbC=4:6 in mass ratio, the oxide comprises one of aluminum oxide, zirconium oxide and magnesium oxide, the nitride comprises one of lithium nitride, boron nitride and aluminum nitride, and the particle size of the titanium, aluminum, tantalum-niobium solid solution, oxide and nitride is 40-50 nm.

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