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

Abstract

The application discloses a high-strength 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, a powder transition layer and a polycrystalline cubic boron nitride layer arranged on the hard alloy base body in sequence. The polycrystalline cubic boron nitride layer is prepared from cubic boron nitride micropowder containing nitrogen and titanium ions, alumina-coated cubic boron nitride micropowder, inorganic nonmetallic whiskers, fullerene, graphdiyne and a binder. The cubic boron nitride is combined with the cubic boron nitride by adding fullerene and graphdiyne materials and using cubic boron nitride micropowder containing nitrogen and titanium ions and alumina-coated cubic boron nitride micropowder in the polycrystalline cubic boron nitride layer. The transition composite coating is deposited on the surface of the hard alloy base body, and the powder transition layer is arranged between the coating and the polycrystalline cubic boron nitride layer, so that the combination strength between the polycrystalline cubic boron nitride layer and the hard alloy base body is greatly enhanced while the performance of the polycrystalline cubic boron nitride layer is ensured.

Description

TECHNICAL FIELD

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

[0002] The polycrystalline cubic boron nitride composite sheet is a superhard composite material sintered from cubic boron nitride micro powder and a hard alloy substrate as a backing under high temperature and high pressure conditions. It has high hardness, wear resistance and impact toughness of cubic boron nitride, high thermal stability, chemical stability, good thermal conductivity and low friction coefficient, and good chemical inertness to ferrous metals, and is therefore widely used in cutting of various high-hardness materials and some high-speed cutting fields.

[0003] With the progress of material science, higher requirements are put forward for the hardness, wear resistance, toughness and strength of tool materials. An ideal tool material should have extremely high hardness and wear resistance, be conducive to improving cutting efficiency and prolonging tool service life, and have good fracture toughness to withstand large cutting forces. In the process of high-speed cutting in precision machining, cubic boron nitride tools are particularly required to have high wear resistance to prevent premature wear and thus affect the machining accuracy of workpieces. The polycrystalline cubic boron nitride tools on the market are not strong and wear-resistant enough to completely meet the requirements of cutting machining. SUMMARY

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

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

[0006] A high-strength wear-resistant polycrystalline cubic boron nitride composite sheet comprises a hard alloy substrate and a transition composite coating, a powder transition layer and a polycrystalline cubic boron nitride layer arranged on the hard alloy substrate from inside to outside. The polycrystalline cubic boron nitride layer is composed of the following raw materials by weight percentage: cubic boron nitride micro powder containing nitrogen and titanium ions 38-46%, alumina-coated cubic boron nitride micro powder 32-35%, inorganic non-metallic whiskers 2-4%, fullerene 0.2-0.5%, graphdiyne 0.2-0.5% and a binder 19.6-22%. 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 layer, TiB coating and TiAl coating from inside to outside, wherein the rare earth coating is arranged between the boronized surface of the cemented carbide and the TiB coating and the TiAl coating; the material of the rare earth coating is selected from one of rare earth elements Dy, Ho and Er; the thickness of the rare earth coating is 2-4 μm; the thicknesses of the TiB coating and the TiAl coating are 4-6 μm and 5-10 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 1-4 μm.

[0008] Specifically, the powder transition layer is composed of the following raw materials in weight percentage: 30-45% of cemented carbide powder, 35-40% of alumina-coated cubic boron nitride powder, 6-10% of zirconium carbonitride powder, 5.6-9.2% of lithium boride powder, 4-5% of molybdenum powder, 4-5% of tungsten-titanium solid solution, 0.2-0.4% of fullerene and 0.2-0.4% of graphdiyne; the particle size of the zirconium carbonitride powder, the lithium boride powder, the molybdenum powder and the tungsten-titanium solid solution is 40-60 nm; the thickness of the powder transition layer is 0.2-0.4 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, and the particle size of the cubic boron nitride micro powder in the alumina-coated cubic boron nitride micro powder is 8-12 μm.

[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 containing nitrogen and titanium ions has two distributions, one in the range of 2-4 μm and the other in the range of 8-12 μm; the mass fraction of the two kinds of micro powder in the cubic boron nitride micro powder is as follows: the one in the range of 2-4 μm accounts for 10-20%, and the other in the range of 8-12 μm accounts for 80-90%.

[0012] Specifically, the inorganic non-metallic whisker is one or two kinds of whisker of alumina, zirconia and silicon nitride, the length of the whisker is in the range of 100 nm to 20 μm, and the diameter is not greater than 100 nm.

[0013] Specifically, the particle size of the fullerene is 300-500 nm; the particle size of the graphdiyne is 300-500 nm. The graphdiyne and the fullerene of the present application can be directly purchased from common commercially available products, such as from Beijing Deke Daojin Technology Co., Ltd.

[0014] Specifically, the binder is composed of the following raw materials in weight percentage: metal elements 20-45%, tungsten-titanium solid solution 15-20%, titanium disilicide 15-20%, lithium boron nitride 15-20%, nitride 5-10%, carbide 4.8-9.5%, and rare earth oxide 0.2-0.5%. The metal elements include one or more of aluminum, lithium, zirconium, and magnesium; the mass ratio of tungsten element to titanium element in the tungsten-titanium solid solution in the powder transition layer or the binder is 1:1; the nitride includes one or two of lithium nitride, boron nitride, and aluminum nitride; the carbide includes one or two of titanium carbide, tungsten carbide, and silicon carbide; the rare earth oxide includes one or two of lanthanum oxide, cerium oxide, and yttrium oxide; the particle size of the metal elements, the tungsten-titanium solid solution, the titanium disilicide, the lithium boron nitride, the nitride, the carbide, and the rare earth oxide is 60-80 nm.

[0015] Specifically, the cemented carbide powder is composed of the following raw materials in weight percentage: tungsten carbide powder 65-75%, cubic boron nitride micro powder 12-15%, cobalt powder 10-15%, calcium nitride carbide powder 1-2%, vanadium carbide powder 1-1.5%, and niobium carbide powder 1-1.5%; the particle size of the tungsten carbide powder is 1.0-1.2 µm; the particle size of the cubic boron nitride micro powder is 0.5-0.6 µm; the particle size of the cobalt powder, the calcium nitride carbide powder, the vanadium carbide powder, and the niobium carbide powder is 0.3-0.5 µm.

[0016] 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.

[0017] Further, in steps 5) and 6), the molecular weight of the polyethylene glycol is 1000-5000.

[0018] Each raw material powder involved in the present application is a common commercially available product that can be directly purchased.

[0019] The above-mentioned method for preparing a high-strength wear-resistant polycrystalline cubic boron nitride composite piece includes the following steps:

[0020] 1) substrate cleaning treatment: first, potassium ferricyanide, potassium hydroxide and deionized water are mixed according to the mass ratio of 0.4:0.5:10-12 to obtain an alkali cleaning solution, then the substrate is placed in the alkali cleaning solution for ultrasonic treatment for 15-20 min, taken out, placed in deionized water for ultrasonic treatment for 2-4 min for washing, then, 40% by mass of sulfuric acid and 40% by mass of hydrogen peroxide are mixed according to a volume ratio of 1:1 to obtain an acid cleaning solution, the alkali washed substrate is placed in the acid cleaning solution for immersion for 5-8 min, taken out, placed in deionized water for ultrasonic treatment for 10-15 min for washing, dried; then the hard alloy substrate is fixed on the rotating stand in the ion source / arc ion plating film equipment, the ion source is turned on to perform ion bombardment cleaning on the surface of the hard alloy substrate, wherein the ion source voltage is 50-70 V, the gas flow is 70-350 sccm, the working pressure is 0.5-1.5 Pa, the substrate bias is 100-600 V; the cleaning time is 10-25 min, and the cleaned hard alloy substrate is obtained;

[0021] 2) boronizing of hard alloy substrate: the cleaned hard alloy substrate of step 1) is placed in a vacuum tube type drying furnace for boronizing treatment, wherein the boronizing treatment gas is a mixed gas of 10-12% by volume of B2H6 and 88-90% of H2, the flow rate of the mixed gas is 10-12 sccm, the pressure is 9-11 kPa, and the reaction time is 3-6 h, to obtain a surface boronized hard alloy substrate;

[0022] 3) ion implantation of cubic boron nitride surface: cubic boron nitride powder is placed in the vacuum working cavity of the ion implanter, monovalent nitrogen ions are separated from the ions supplied by the ion source through the mass spectrometer, and the monovalent nitrogen ions are implanted into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 60-90 keV, then monovalent titanium ions are separated from the ions supplied by the ion source, and the monovalent titanium ions are implanted into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 60-90 keV, to obtain cubic boron nitride powder implanted with nitrogen and titanium ions;

[0023] 4) Depositing transition composite coating: using the boronized cemented carbide substrate of step 2) as the substrate, first depositing a rare earth coating on the boronized surface of the cemented carbide substrate using a magnetron sputtering method with a rare earth element as the target material, the coating thickness being 2-4 μm, then depositing a TiB coating and a TiAl coating on the rare earth coating surface in turn using a TiB composite target and a TiAl composite target as the target material, the TiB coating and the TiAl coating being 4-6 μm and 5-10 μm respectively, to obtain the cemented carbide substrate containing the transition composite coating;

[0024] 5) Powder transition layer mixing: weighing fullerene, graphyne, tungsten-titanium solid solution, molybdenum powder, lithium boride powder, zirconium carbonitride, alumina-coated cubic boron nitride micro powder and cemented carbide powder in proportion, respectively dispersing them into anhydrous ethanol in turn, mechanically stirring and ultrasonic oscillation dispersing for 30-50 min, the mass content of the powder being 0.3-1 g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanically stirring and ultrasonic oscillation dispersing for 50-60 min, the concentration of the polyethylene glycol being 1-5 g / L, then pouring into a cemented carbide ball mill jar containing cemented carbide balls, the ball-to-material mass ratio being 8-10:1, filling nitrogen as a protective gas, ball milling for 38-42 h, after mixing, placing in a vacuum dryer, vacuum drying at 50-60 °C for 3-5 h, to obtain the powder transition layer mixed powder;

[0025] 6) Polycrystalline cubic boron nitride layer mixing: weighing fullerene, graphyne, binder, inorganic non-metallic whisker, alumina-coated cubic boron nitride micro powder and nitrogen and titanium ion-containing cubic boron nitride micro powder in proportion, respectively dispersing them into anhydrous ethanol in turn, mechanically stirring and ultrasonic oscillation dispersing for 50-60 min, the mass content of the powder being 0.5-1 g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanically stirring and ultrasonic oscillation dispersing for 60-80 min, the concentration of the polyethylene glycol being 3-8 g / L, then pouring into a cemented carbide ball mill jar containing cemented carbide balls, the ball-to-material mass ratio being 8-12:1, filling nitrogen as a protective gas, ball milling for 40-45 h, after mixing, placing in a vacuum dryer, vacuum drying at 50-60 °C for 4-6 h, to obtain the polycrystalline cubic boron nitride layer mixed powder;

[0026] 7) Composite assembly: first, sequentially loading the polycrystalline cubic boron nitride layer mixed powder of step 6) and the powder transition layer mixed powder of step 5) into a metal cup, layering, compacting and shaping, then placing the cemented carbide substrate containing the composite transition coating of step 1) on the powder transition layer mixed powder with the coating facing down, then using a metal cup to cover from the opposite direction, to obtain the composite assembly, wherein the metal cup is composed of one or more of the following materials: Mo, Ta, Nb;

[0027] 8) Pre-pressing of the assembly: Put the assembly into a piece of talc, and put the talc into a high temperature and high pressure device,

[0028] Increase the pressure to 4.5-5.5 GPa, keep for 40-60 s without heating, decrease the pressure to standard atmospheric pressure, the temperature of the high temperature and high pressure device reaches room temperature, repeat the pressurizing action 1-2 times, and obtain a pre-pressed assembly;

[0029] 9) Purification treatment: Put the pre-pressed assembly of step 8) into a vacuum sintering furnace for sintering, during sintering, first rough vacuum to 6x10 -2 Pa in the furnace, heat to 250-350℃ for 10-15 min, continue to vacuum to 3x10 -5 Pa in the furnace, increase the temperature to 650-750℃ for 10-15 min, stop vacuuming, fill in reducing gas (70% CO and 30% N2 by volume), keep for 1.5-2 h, vacuum again to 3x10 -4 Pa in the furnace, and obtain a purified assembly;

[0030] 10) High temperature and high pressure sintering: Put the purified assembly of step 9) into a carbon heating tube, put the carbon heating tube into a piece of talc, put the talc into a high temperature and high pressure device, pressurize to 5.5 GPa, adjust the temperature to 1450-1480℃, then pressurize the talc to 6.0 GPa, keep for 150-250 s, then continue to pressurize to 6.5 GPa, keep for 300-500 s, then pressurize to 7.0 GPa, keep for 500-700 s, after sintering, decrease the temperature to 600℃ at a rate of 15-20℃ / s, keep for 15-20 min, then decrease the temperature to room temperature, decrease the pressure to normal pressure at a rate of 0.6-0.9 GPa / min, take out the assembly block from the cubic press, remove the surface coating layer, and obtain a sintered polycrystalline cubic boron nitride composite blank;

[0031] 11) Stress relief aging: Put the sintered polycrystalline cubic boron nitride composite blank of step 10) into a cubic press again, assemble with a talc block, pressurize to 7.0 GPa, adjust the temperature to 580-630℃, keep for 25-30 min, then decrease the temperature of the talc block to 480-530℃, keep for 25-30 min, then continue to decrease the temperature to 400-500℃, keep for 25-30 min, then decrease the temperature to 380-430℃, keep for 20-30 min, finally decrease the temperature to room temperature at a rate of 10-20℃ / s, decrease the pressure to normal pressure at a rate of 0.4-0.6 GPa / min, take out the aged polycrystalline cubic boron nitride composite blank from the assembly block, process to the required size by grinding equipment, and obtain the high-strength grinding polycrystalline cubic boron nitride composite sheet.

[0032] Further, in step 4), the magnetron sputtering working pressure is 1.5-1.8 Pa, the nitrogen or argon gas flow is 35-45 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 120-180 W, and the sputtering time is 15-40 min; the surface area ratio of Ti element to B element in the TiB composite target is 10:4, and the surface area ratio of Ti element to Al element in the TiAl composite target is 10:5.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] (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 and powder transition layer-polycrystalline cubic boron nitride layer gradually decrease in a gradient manner, the hard alloy substrate and the polycrystalline cubic boron nitride layer are gradually transitioned, so the interface stress is small, and the delamination problem of the polycrystalline cubic boron nitride composite sheet is improved. At the same time, the hard alloy substrate surface boronized layer and the transition composite coating can effectively block the diffusion of the metal cobalt in the hard alloy to the polycrystalline 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 with surface boronization and transition composite coating hard alloy substrate.

[0035] (2) The ion beam injection method is used to inject nitrogen ions and boron ions into the surface of cubic boron nitride, which makes up for the structural defects on the surface of ordinary cubic boron nitride particles, makes the structure more smooth, improves the strength of cubic boron nitride particles, and in addition, the polycrystalline layer of cubic boron nitride doped with nitrogen ions and titanium ions during the high-temperature and high-pressure sintering process, to some extent, weakens and softens the cubic boron nitride particles, so that these particles can be squeezed more tightly and have a larger contact area under high temperature and high pressure, enhancing their own binding ability and reducing the existence of pores, which helps to sinter and improve the volume ratio of the polycrystalline cubic boron nitride composite sheet, and is conducive to improving the strength, heat resistance and high-temperature fracture toughness of the polycrystalline cubic boron nitride composite sheet; the cubic boron nitride micropowder is coated with aluminum oxide, which achieves close combination with the cubic boron nitride micropowder, uniform mixing, fully plays the role of aluminum oxide in binding and wetting, and increases the bonding strength between cubic boron nitride and the binder.

[0036] (4) The present invention adds fullerene and graphylene to the polycrystalline cubic boron nitride layer, which can activate the cubic boron nitride particles and promote the direct bonding between the 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.

[0037] (5) The high-strength wear-resistant polycrystalline cubic boron nitride composite sheet prepared by the present invention has a microhardness of 5800-6300 HV, a wear ratio of 11800-12300, and an impact count of 58-62. Attached Figure Description

[0038] Figure 1 A schematic diagram of the structure of a high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet;

[0039] In the figure: 1. Polycrystalline cubic boron nitride layer; 2. Powder transition layer; 3. Transition composite coating; 4. Boronized layer on substrate surface; 5. Hard alloy substrate;

[0040] Figure 2 This is a photograph of a high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet. Detailed Implementation

[0041] 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...

[0042] The performance of the examples and comparative examples: the composite sheets prepared in the following examples and comparative examples all have a diameter of φ55mm and a thickness of 3.2mm; the thickness of the polycrystalline cubic boron nitride layer is 1mm. The cemented carbide matrix refers to a tungsten-cobalt cemented carbide YG10 (WC 90% and cobalt 10%) matrix; the alumina-coated cubic boron nitride micropowder was prepared by replacing the 100μm cubic boron nitride with cubic boron nitride micropowder with a particle size of 8-12μm, according to the methods of Examples 1 and 3 of CN108179004 A; the molecular weight of polyethylene glycol is 2000.

[0043] Example 1

[0044] This embodiment describes a high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet, 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 raw materials with the following weight percentage: nitrogen-containing, titanium ion cubic boron nitride micropowder 38%, alumina-coated cubic boron nitride micropowder 35%, alumina whisker 4%, fullerene 0.5%, graphdiyne 0.5% and binder 22%; the transition composite coating 3, from inside to outside, is in the order of rare earth coating, TiB coating and TiAl coating, wherein the rare earth layer is arranged between the surface of the cemented carbide and the TiB coating and the TiAl coating; the material of the rare earth coating is selected from rare earth element Dy; the thickness of the rare earth coating is 2 μm; the thickness of the TiB coating and the TiAl coating is 4 μm and 5 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 raw materials with the following weight percentage: cemented carbide powder 30%, alumina-coated cubic boron carbide powder 40%, zirconium carbonitride powder 10%, lithium boride powder 9.2%, molybdenum powder 5%, tungsten-titanium solid solution 5%, fullerene 0.4% and graphdiyne 0.4%; the particle size of the zirconium carbonitride powder, lithium boride powder, molybdenum powder and tungsten-titanium solid solution is 40-60 nm; the thickness of the powder transition layer 2 is 0.2 mm; the nitrogen-containing, titanium ion cubic boron nitride micropowder has two distributions, one in the range of 2-4 μm and the other in the range of 8-12 μm; the mass fraction of the two micropowders in the cubic boron nitride micropowder is 10% for the one in the range of 2-4 μm and 90% for the other in the range of 8-12 μm; the length of the alumina whisker is in the range of 100 nm to 20 μm and the diameter is not greater than 100 nm; the particle size of the fullerene is 300-500 nm; the particle size of the graphdiyne is 300-500 nm; the binder is composed of raw materials with the following weight percentage: metal element aluminum 20%, tungsten-titanium solid solution 20%, titanium disilicide 20%, lithium nitride boride 20%, lithium nitride 10%, titanium carbide 9.5% and rare earth lanthanum oxide 0.5%; the mass ratio of tungsten element to titanium element in the tungsten-titanium solid solution is 1:1; the particle size of the metal element aluminum, tungsten-titanium solid solution, titanium disilicide, lithium nitride boride, lithium nitride, titanium carbide and rare earth lanthanum oxide is 60-80 nm; the cemented carbide powder is composed of raw materials with the following weight percentage: tungsten carbide powder 65%, cubic boron nitride micropowder 15%, cobalt powder 15%, calcium nitride carbide powder 2%, vanadium carbide powder 1.5% and niobium carbide powder 1.5%; the particle size of the tungsten carbide powder is 1.0-1.2 μm; the particle size of the cubic boron nitride micropowder is 0.5-0.6 μm; the particle size of the cobalt powder, calcium nitride carbide powder, vanadium carbide powder and niobium carbide powder is 0.3-0.5 μm.

[0045] The above method for preparing the high-strength wear-resistant polycrystalline cubic boron nitride composite sheet comprises the following steps:

[0046] 1) Cemented carbide substrate purification: first, potassium ferricyanide, potassium hydroxide and deionized water are mixed in a mass ratio of 0.4:0.5:10 to obtain an alkali cleaning solution, then the substrate is placed in the alkali cleaning solution for ultrasonic treatment (power 50W) for 15 min, taken out, placed in deionized water for ultrasonic treatment (power 50W) for 2 min for washing, then 40% by mass sulfuric acid and 30% by mass hydrogen peroxide are mixed in a volume ratio of 1:1 to obtain an acid cleaning solution, the alkali-washed substrate is placed in the acid cleaning solution for immersion for 5 min, taken out, placed in deionized water for ultrasonic treatment (power 50W) for 10 min for washing, and dried; then the cemented carbide substrate is fixed on a rotating stand in an ion source / arc ion plating film equipment, and the ion source is turned on to perform ion bombardment cleaning on the surface of the cemented carbide substrate, wherein the ion source voltage is 50V, the gas flow is 70sccm, the working pressure is 0.5Pa, and the substrate bias is 100V; the cleaning time is 10 min, and a purified cemented carbide substrate is obtained;

[0047] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube drying oven for boronizing treatment, wherein the boronizing treatment gas is a mixed gas of 10% by volume B2H6 and 90% H2, the flow rate of the mixed gas is 10sccm, the pressure is 9kPa, and the reaction time is 3h, to obtain a surface-boronized cemented carbide substrate;

[0048] 3) Ion implantation of cubic boron nitride: cubic boron nitride powder is placed in the vacuum working cavity of an ion implanter, monovalent nitrogen ions are first separated from the ions supplied by the ion source by a mass spectrometer, and then implanted into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 60keV, and then monovalent titanium ions are separated from the ions supplied by the ion source, and implanted into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 60keV, to obtain cubic boron nitride powder implanted with nitrogen and titanium ions;

[0049] 4) Depositing transition composite coating: using the boronized cemented carbide substrate of step 2) as the target, depositing a rare earth coating on the boronized surface of the cemented carbide substrate by magnetron sputtering, then using TiB composite target and TiAl composite target as the target, depositing TiB coating and TiAl coating on the rare earth coating surface in turn; 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℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 120 W, the sputtering time of the rare earth target, TiB composite target and TiAl composite target is 16 min, 19 min and 21 min respectively; the surface area ratio of Ti element and B element in the TiB composite target is 10:4, and the surface area ratio of Ti element and Al element in the TiAl composite target is 10:5. The cemented carbide substrate with transition composite coating is obtained;

[0050] 5) Powder transition layer mixing: weighing fullerene, graphyne, tungsten-titanium solid solution, molybdenum powder, lithium boride powder, zirconium carbonitride, alumina-coated cubic boron nitride micro powder and cemented carbide powder according to the proportion, respectively dispersing them into anhydrous ethanol, mechanical stirring and ultrasonic (power 40W) oscillation dispersion for 30 min, the mass content of the powder is 0.3g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanical stirring and ultrasonic (power 40W) oscillation dispersion for 50 min, the concentration of polyethylene glycol is 1g / L, then pouring into a cemented carbide ball mill jar with cemented carbide balls, ball-to-material mass ratio is 8:1, filling nitrogen as protective gas, ball milling time is 38h, after mixing, placing in a vacuum dryer, vacuum drying at 50℃ for 3h, obtaining powder transition layer mixed powder;

[0051] 6) Polycrystalline cubic boron nitride layer mixing: weighing fullerene, graphyne, binder, inorganic non-metallic whisker, alumina-coated cubic boron nitride micro powder and nitrogen and titanium ion-containing cubic boron nitride micro powder according to the proportion, respectively dispersing them into anhydrous ethanol, mechanical stirring and ultrasonic (power 40W) oscillation dispersion for 50 min, the mass content of the powder is 0.5g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanical stirring and ultrasonic (power 40W) oscillation dispersion for 60 min, the concentration of polyethylene glycol is 3g / L, then pouring into a cemented carbide ball mill jar with cemented carbide balls, ball-to-material mass ratio is 8:1, filling nitrogen as protective gas, ball milling time is 40h, after mixing, placing in a vacuum dryer, vacuum drying at 50℃ for 4h, obtaining polycrystalline cubic boron nitride layer mixed powder;

[0052] 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 Mo cup, and are compacted and shaped layer by layer, and then the cemented carbide substrate with a composite transition coating of step 1) is placed on the powder transition layer mixed powder with the coating facing down, and then a metal Mo cup is sleeved from the opposite direction to obtain a complex assembly;

[0053] 8) Complex pre-pressing: the complex assembly is placed in a leaf spar block, and the leaf spar block is placed in a high-temperature and high-pressure device, and the pressure is increased to 4.5 GPa, maintained for 40 s without heating, and the pressure is reduced to standard atmospheric pressure, and the temperature of the high-temperature and high-pressure device reaches room temperature, and the pressurizing action is repeated once to obtain a pre-pressed complex assembly.

[0054] 9) Purification treatment: the pre-pressed complex assembly of step 8) is placed in a vacuum sintering furnace for sintering, and during sintering, vacuum is first rough-pumped to 6×10 -2 Pa below, heated to 250℃ for 10 min, vacuum is continuously pumped to 3×10 -5 Pa below, the temperature is increased to 650℃ for 10 min, vacuum is stopped, and reducing gas (70% CO and 30% N2 by volume ratio) is filled, and maintained for 1.5 h, vacuum is pumped again to 3×10 -4 Pa below to obtain a purified complex assembly.

[0055] 10) High-temperature and high-pressure sintering: the purified complex assembly of step 9) is placed in a carbon heating tube, the carbon heating tube is placed in a leaf spar block, the leaf spar block is placed in a high-temperature and high-pressure device, the pressure is increased to 5.5 GPa, the temperature is adjusted to 1450℃, the leaf spar block is then pressurized to 6.0 GPa, maintained for 150 s, and then pressurized to 6.5 GPa, maintained for 300 s, then pressurized to 7.0 GPa, maintained for 500 s, after sintering, the temperature is reduced to 600℃ at a rate of 15℃ / S, maintained for 15 min, and then reduced to room temperature, and the pressure is reduced to normal pressure at a rate of 0.6 GPa / min. The assembly block is taken out of the cubic press, the surface wrapping layer is removed, and a sintered polycrystalline cubic boron nitride composite sheet blank is obtained.

[0056] 11) stress relief aging: sinter the sintered polycrystalline cubic boron nitride compact blank of step 10) again with the assembled block of leaf spar, and place it in a cubic anvil press, pressurize to 7.0 GPa, adjust the temperature to 580℃, keep for 25 min, then lower the temperature of the leaf spar block to 480℃, keep for 25 min, then continue to lower the temperature to 400℃, keep for 25 min, then lower the temperature to 380℃, keep for 20 min, and finally lower the temperature to room temperature at a rate of 10℃ / S, and lower the pressure to normal pressure at a rate of 0.4 GPa / min. Take out the aged polycrystalline cubic boron nitride compact blank from the assembled block, and process it to the required size with grinding equipment to obtain the high-strength wear-resistant polycrystalline cubic boron nitride compact, which is shown in Figure 2 .

[0057] The high-strength wear-resistant polycrystalline cubic boron nitride compact prepared in this example is subjected to microhardness test according to standard ASTM E384-2010, wear resistance test according to standard JB / T3235-2013 "Test method for wear ratio of sintered artificial diamond", impact toughness test by the method of drop hammer impact (i.e. a 1kg mass of impact hammer is freely dropped from a height of 35cm, and the energy is used to impact the corners of the sample for testing, and the impact toughness value is obtained when micro cracks appear on the surface). The test results are as follows: microhardness is 6000HV, wear ratio is 12000, and impact times is 58.

[0058] Example 2

[0059] A high-strength wear-resistant polycrystalline cubic boron nitride compact of this example is shown in 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 raw materials with the following weight percentage: nitrogen-containing, titanium ion cubic boron nitride micropowder 46%, alumina-coated cubic boron nitride micropowder 32%, zirconia whisker 2%, fullerene 0.2%, graphdiyne 0.2% and binder 19.6%; the transition composite coating 3, from inside to outside, is a rare earth coating, a TiB coating and a TiAl coating, wherein the rare earth coating is arranged between the surface of the cemented carbide and the TiB coating and the TiAl coating; the material of the rare earth coating is selected from rare earth element Ho; the thickness of the rare earth coating is 4 μm; the thickness of the TiB coating and the TiAl coating is 6 μm and 10 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 4 μm; the powder transition layer 2 is composed of raw materials with the following weight percentage: cemented carbide powder 45%, alumina-coated cubic boron carbide powder 35%, zirconium carbonitride powder 6%, lithium boride powder 5.6%, molybdenum powder 4%, tungsten-titanium solid solution 4%, fullerene 0.2%, graphdiyne 0.2%; the particle size of the zirconium carbonitride powder, lithium boride powder, molybdenum powder and tungsten-titanium solid solution is 40-60 nm; the thickness of the powder transition layer 2 is 0.4 mm; the nitrogen-containing, titanium ion cubic boron nitride micropowder has two distributions, one in the range of 2-4 μm and the other in the range of 8-12 μm; the mass fraction of the two micropowders in the cubic boron nitride micropowder is 20% for the one in the range of 2-4 μm and 80% for the other in the range of 8-12 μm; the length of the zirconia whisker is in the range of 100 nm to 20 μm and the diameter is not greater than 100 nm; the particle size of the fullerene is 300-500 nm; the particle size of the graphdiyne is 300-500 nm; the binder is composed of raw materials with the following weight percentage: metal element lithium 45%, tungsten-titanium solid solution 15%, titanium disilicide 15%, lithium nitride boride 15%, boron nitride 5%, tungsten carbide 4.8%, rare earth cerium oxide 0.2%; the mass ratio of tungsten element to titanium element in the tungsten-titanium solid solution is 1:1; the particle size of the metal element lithium, tungsten-titanium solid solution, titanium disilicide, lithium nitride boride, boron nitride, tungsten carbide and rare earth cerium oxide is 60-80 nm; the cemented carbide powder is composed of raw materials with the following weight percentage: tungsten carbide powder 75%, cubic boron nitride micropowder 12%, cobalt powder 10%, calcium nitrocarbonate powder 1%, vanadium carbide powder 1%, niobium carbide powder 1%; the particle size of the tungsten carbide powder is 1.0-1.2 μm; the particle size of the cubic boron nitride micropowder is 0.5-0.6 μm; the particle size of the cobalt powder, calcium nitrocarbonate powder, vanadium carbide powder and niobium carbide powder is 0.3-0.5 μm.

[0060] The above method for preparing the high-strength wear-resistant polycrystalline cubic boron nitride composite sheet comprises the following steps:

[0061] 1) Cemented carbide substrate purification: first, potassium ferricyanide, potassium hydroxide and deionized water are mixed in a mass ratio of 0.4:0.5:12 to obtain an alkali cleaning solution, then the substrate is placed in the alkali cleaning solution for ultrasonic treatment (power 70W) for 20 min, taken out, placed in deionized water for ultrasonic treatment (power 70W) for 4 min for washing, then 40% by mass sulfuric acid and 35% by mass hydrogen peroxide are mixed in a volume ratio of 1:1 to obtain an acid cleaning solution, the alkali-washed substrate is placed in the acid cleaning solution for immersion for 8 min, taken out, placed in deionized water for ultrasonic treatment (power 70W) for 15 min for washing, and dried; then the cemented carbide substrate is fixed on a rotating stand in an ion source / arc ion plating film equipment, and the ion source is turned on to perform ion bombardment cleaning on the surface of the cemented carbide substrate, wherein the ion source voltage is 70V, the gas flow is 350sccm, the working pressure is 1.5Pa, and the substrate bias is 600V; the cleaning time is 25 min, and a purified cemented carbide substrate is obtained;

[0062] 2) Cemented carbide substrate boronizing: the clean cemented carbide substrate of step 1) is placed in a vacuum tube drying oven for boronizing treatment, wherein the boronizing treatment gas is a mixed gas of 12% by volume B2H6 and 88% H2, the flow rate of the mixed gas is 12sccm, the pressure is 11kPa, and the reaction time is 6h, to obtain a surface-boronized cemented carbide substrate;

[0063] 3) Ion implantation of cubic boron nitride: cubic boron nitride powder is placed in the vacuum working cavity of an ion implanter, monovalent nitrogen ions are first separated from the ions supplied by the ion source by a mass spectrometer, and then implanted into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 90keV, and then monovalent titanium ions are separated from the ions supplied by the ion source, and then implanted into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 90keV, to obtain cubic boron nitride powder implanted with nitrogen and titanium ions;

[0064] 4) Depositing transition composite coating: using the boronized cemented carbide substrate of step 2) as the target, depositing a rare earth coating on the boronized surface of the cemented carbide substrate by magnetron sputtering, then using TiB composite target and TiAl composite target as the target, depositing TiB coating and TiAl coating on the rare earth coating surface in turn; the magnetron sputtering working pressure is 1.8 Pa, the nitrogen flow rate is 45 mL / min, the target-substrate distance is 50±5 mm, the sputtering temperature is 600℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 180 W, the sputtering time of the rare earth target, TiB composite target and TiAl composite target is 35 min, 37 min and 40 min respectively; the surface area ratio of Ti element and B element in the TiB composite target is 10:4, and the surface area ratio of Ti element and Al element in the TiAl composite target is 10:5. The cemented carbide substrate with transition composite coating is obtained;

[0065] 5) Powder transition layer mixing: weighing fullerene, graphyne, tungsten-titanium solid solution, molybdenum powder, lithium boride powder, zirconium carbonitride, alumina-coated cubic boron nitride micro powder and cemented carbide powder according to the proportion, respectively dispersing them into anhydrous ethanol, mechanically stirring and ultrasonic (power 60 W) oscillation dispersing for 50 min, the mass content of the powder is 1 g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanically stirring and ultrasonic (power 60 W) oscillation dispersing for 60 min, the concentration of polyethylene glycol is 5 g / L, then pouring into a cemented carbide ball mill jar with cemented carbide balls, ball-to-material mass ratio is 10:1, filling nitrogen as protective gas, ball milling for 42 h, after mixing, placing in a vacuum dryer, vacuum drying at 60℃ for 5 h, obtaining powder transition layer mixed powder;

[0066] 6) Polycrystalline cubic boron nitride layer mixing: weighing fullerene, graphyne, binder, inorganic non-metallic whisker, alumina-coated cubic boron nitride micro powder and nitrogen and titanium ion-containing cubic boron nitride micro powder according to the proportion, respectively dispersing them into anhydrous ethanol, mechanically stirring and ultrasonic (power 60 W) oscillation dispersing for 60 min, the mass content of the powder is 1 g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanically stirring and ultrasonic (power 60 W) oscillation dispersing for 80 min, the concentration of polyethylene glycol is 8 g / L, then pouring into a cemented carbide ball mill jar with cemented carbide balls, ball-to-material mass ratio is 12:1, filling nitrogen as protective gas, ball milling for 45 h, after mixing, placing in a vacuum dryer, vacuum drying at 60℃ for 6 h, obtaining polycrystalline cubic boron nitride layer mixed powder;

[0067] 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 Ta cup, layered, compacted and shaped, and then the cemented carbide substrate with a composite transition coating of step 1) is placed on the powder transition layer mixed powder with the coating facing down, and then a metal Ta cup is sleeved from the opposite direction to obtain a composite assembly;

[0068] 8) Composite pre-pressing: the composite assembly is placed in a leaf spar block, the leaf spar block is placed in a high temperature and high pressure device, the pressure is increased to 5.5 GPa, maintained for 60 s without heating, the pressure is reduced to standard atmospheric pressure, the temperature of the high temperature and high pressure device reaches room temperature, and the pressurizing action is repeated 2 times to obtain a pre-pressed composite assembly.

[0069] 9) Purification treatment: the pre-pressed composite assembly of step 8) is placed in a vacuum sintering furnace for sintering. During sintering, the vacuum is first roughed to a furnace internal air pressure of 6×10 -2 Pa or less, heated to 350℃ for 15 min, the vacuum is continuously roughed to a furnace internal air pressure of 3×10 -5 Pa or less, the temperature is increased to 750℃ for 15 min, the vacuum is stopped, a reducing gas (70% CO and 30% N2 by volume) is filled, and the process is maintained for 2 h, the vacuum is again roughed to a furnace internal air pressure of 3×10 -4 Pa or less, and a purified composite assembly is obtained.

[0070] 10) High temperature and high pressure sintering: the purified composite assembly of step 9) is placed in a carbon heating tube, the carbon heating tube is placed in a leaf spar block, the leaf spar block is placed in a high temperature and high pressure device, the pressure is increased to 5.5 GPa, the temperature is adjusted to 1480℃, the leaf spar block is then increased to 6.0 GPa, maintained for 250 s, then further increased to 6.5 GPa, maintained for 500 s, then increased to 7.0 GPa, maintained for 700 s, after sintering, the temperature is decreased to 600℃ at a rate of 20℃ / S, maintained for 20 min, then decreased to room temperature, and the pressure is reduced to normal pressure at a rate of 0.9 GPa / min. The assembled block is taken out of the cubic press, the surface wrapping layer is removed, and a sintered polycrystalline cubic boron nitride composite sheet blank is obtained.

[0071] 11) stress relief aging: sinter the sintered polycrystalline cubic boron nitride compact blank of step 10) again with the assembled block of leaf spar, and place it in a cubic anvil press, pressurize to 7.0 GPa, adjust the temperature to 630℃, keep for 30 min, then lower the temperature of the leaf spar block to 530℃, keep for 30 min, then continue to lower the temperature to 500℃, keep for 30 min, then lower the temperature to 430℃, keep for 30 min, finally lower the temperature to room temperature at 20℃ / S, and lower the pressure to normal pressure at a pressure lowering rate of 0.6 GPa / min. Take out the sintered polycrystalline cubic boron nitride compact blank after aging from the assembled block, and process it to the required size with grinding equipment to obtain the high-strength wear-resistant polycrystalline cubic boron nitride compact, which is shown in Figure 2

[0072] The high-strength wear-resistant polycrystalline cubic boron nitride compact prepared in this example is subjected to microhardness test according to standard ASTM E384-2010, wear resistance test according to standard JB / T3235-2013 "Test method for wear ratio of sintered artificial diamond", impact toughness test by the method of drop hammer impact (i.e. a 1kg mass of impact hammer is freely dropped from a height of 35cm, and the energy is used to impact the corners of the sample for testing, and the impact toughness value is obtained when micro cracks appear on the surface). The test results are as follows: microhardness is 6000HV, wear ratio is 11900, and impact times is 59.

[0073] Example 3

[0074] A high-strength wear-resistant polycrystalline cubic boron nitride compact of this example is shown in Figure 1 ​As shown, it comprises a cemented carbide substrate 5, and 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 from inside to outside; the polycrystalline cubic boron nitride layer 1 is composed of the following raw materials with the weight percentage: nitrogen-containing, titanium ion cubic boron nitride micro powder 42%, alumina-coated cubic boron nitride micro powder 33.5%, silicon nitride whisker 3%, fullerene 0.35%, graphdiyne 0.35% and binder 20.8%; the transition composite coating 3 is in the order of rare earth coating, TiB coating and TiAl coating from inside to outside, wherein the rare earth coating is arranged between the surface of the cemented carbide and the TiB coating and the TiAl coating; the material of the rare earth coating is selected from rare earth element Er; the thickness of the rare earth coating is 3 μm; the thickness of the TiB coating and the TiAl coating is 5 μm and 7.5 μm respectively; the cemented carbide substrate is a 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 with the weight percentage: cemented carbide powder 37.5%, alumina-coated cubic boron carbide powder 37.5%, zirconium carbonitride powder 8%, lithium boride powder 7.4%, molybdenum powder 4.5%, tungsten-titanium solid solution 4.5%, fullerene 0.3%, graphdiyne 0.3%; the particle size of the zirconium carbonitride powder, lithium boride powder, molybdenum powder and tungsten-titanium solid solution is 40-60 nm; the thickness of the powder transition layer 2 is 0.3 mm; the nitrogen-containing, titanium ion cubic boron nitride micro powder has two distributions, one in the range of 2-4 μm and the other in the range of 8-12 μm; the mass fraction of the two kinds of micro powder in the cubic boron nitride micro powder is 15% and 85% respectively; the length of the silicon nitride whisker is in the range of 100 nm to 20 μm and the diameter is not greater than 100 nm; the particle size of the fullerene is 300-500 nm; the particle size of the graphdiyne is 300-500 nm; the binder is composed of the following raw materials with the weight percentage: metal element zirconium 32.5%, tungsten-titanium solid solution 17.5%, titanium disilicide 17.5%, lithium nitride boride 17.5%, aluminum nitride 7.5%, silicon carbide 7.15% and rare earth yttrium oxide 0.35%; the mass ratio of tungsten element and titanium element in the tungsten-titanium solid solution is 1:1; the particle size of the metal element zirconium, tungsten-titanium solid solution, titanium disilicide, lithium nitride boride, aluminum nitride, silicon carbide and rare earth yttrium oxide is 60-80 nm; the cemented carbide powder is composed of the following raw materials with the weight percentage: tungsten carbide powder 70%, cubic boron nitride micro powder 13.5%, cobalt powder 12.5%, calcium nitrocarbonate powder 1.5%, vanadium carbide powder 1.25% and niobium carbide powder 1.25%; the particle size of the tungsten carbide powder is 1.0-1.2 μm; the particle size of the cubic boron nitride micro powder is 0.5-0.6 μm; the particle size of the cobalt powder, calcium nitrocarbonate powder, vanadium carbide powder and niobium carbide powder is 0.3-0.5 μm.

[0075] The preparation method of the high-strength wear-resistant polycrystalline cubic boron nitride compact comprises the following steps:

[0076] 1) hard alloy substrate purification: first, mix potassium ferricyanide, potassium hydroxide and deionized water according to a mass ratio of 0.4:0.5:11 to obtain an alkali cleaning solution, then put the substrate into the alkali cleaning solution for ultrasonic treatment (power 60 W) for 17 min, take out, put into deionized water for ultrasonic treatment (power 60 W) for 3 min for washing, then mix 40% sulfuric acid and 35% hydrogen peroxide according to a volume ratio of 1:1 to obtain an acid cleaning solution, put the alkali-washed substrate into the acid cleaning solution for immersion for 6 min, take out, put into deionized water for ultrasonic treatment (power 60 W) for 12 min for washing and drying; then fix the hard alloy substrate on a rotating shaft in an ion source / arc ion plating film equipment, open the ion source to perform ion bombardment cleaning on the surface of the hard alloy substrate, wherein the ion source voltage is 60 V, the gas flow is 210 sccm, the working pressure is 1 Pa, and the substrate bias is 350 V; the cleaning time is 17 min, and a purified hard alloy substrate is obtained;

[0077] 2) hard alloy substrate boronizing: put the clean hard alloy substrate in step 1) into a vacuum tube-type drying furnace for boronizing treatment, wherein the boronizing treatment gas is a mixed gas of 11% B2H6 and 89% H2 by volume, the flow rate of the mixed gas is 11 sccm, the pressure is 10 kPa, and the reaction time is 4 h, and a hard alloy substrate with surface boronizing is obtained;

[0078] 3) ion implantation of cubic boron nitride: place cubic boron nitride powder in the vacuum working cavity of an ion implanter, first separate the ions supplied by the ion source into monovalent nitrogen ions by a mass spectrometer, implant the monovalent nitrogen ions into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 75 keV, then separate the ions supplied by the ion source into monovalent titanium ions, implant the monovalent titanium ions into the surface of the cubic boron nitride at an ion density of 3×10 15 ~ 3×10 17 ions / cm 2 and an energy of 75 keV, and obtain cubic boron nitride powder with nitrogen and titanium ion implantation;

[0079] 4) Depositing transition composite coating: using the boronized cemented carbide substrate of step 2) as the target, depositing a rare earth coating on the boronized surface of the cemented carbide substrate by magnetron sputtering, then using TiB composite target and TiAl composite target as the target, depositing TiB coating and TiAl coating on the rare earth coating surface in turn; the magnetron sputtering working pressure is 1.6 Pa, the nitrogen flow rate is 40 mL / min, the target-substrate distance is 50±5 mm, the sputtering temperature is 550℃, the vacuum degree is higher than 2×10 -3 Pa, the sputtering power is 150 W, the sputtering time of the rare earth target, TiB composite target and TiAl composite target is 25 min, 28 min and 31 min respectively; the surface area ratio of Ti element and B element in the TiB composite target is 10:4, and the surface area ratio of Ti element and Al element in the TiAl composite target is 10:5. The cemented carbide substrate with transition composite coating is obtained;

[0080] 5) Powder transition layer mixing: weighing fullerene, graphyne, tungsten-titanium solid solution, molybdenum powder, lithium boride powder, zirconium carbonitride, alumina-coated cubic boron nitride micro powder and cemented carbide powder according to the proportion, respectively dispersing them into anhydrous ethanol, mechanical stirring and ultrasonic (power 50 W) oscillation dispersion for 40 min, the mass content of the powder is 0.6 g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanical stirring and ultrasonic (power 50 W) oscillation dispersion for 55 min, the concentration of polyethylene glycol is 3 g / L, then pouring into a cemented carbide ball mill jar with cemented carbide balls, ball-to-material mass ratio is 9:1, filling nitrogen as protective gas, ball milling for 40 h, after mixing, placing in a vacuum dryer, vacuum drying at 55℃ for 4 h, obtaining powder transition layer mixed powder;

[0081] 6) Polycrystalline cubic boron nitride layer mixing: weighing fullerene, graphyne, binder, inorganic non-metallic whisker, alumina-coated cubic boron nitride micro powder and nitrogen and titanium ion-containing cubic boron nitride micro powder according to the proportion, respectively dispersing them into anhydrous ethanol, mechanical stirring and ultrasonic (power 50 W) oscillation dispersion for 55 min, the mass content of the powder is 0.7 g / ml; weighing polyethylene glycol and adding it into the anhydrous ethanol dispersion, mechanical stirring and ultrasonic (power 50 W) oscillation dispersion for 70 min, the concentration of polyethylene glycol is 5 g / L, then pouring into a cemented carbide ball mill jar with cemented carbide balls, ball-to-material mass ratio is 10:1, filling nitrogen as protective gas, ball milling for 42 h, after mixing, placing in a vacuum dryer, vacuum drying at 55℃ for 5 h, obtaining 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 Nb cup, layered, compacted and shaped, and then the cemented carbide substrate with a composite transition coating of step 1) is placed on the powder transition layer mixed powder with the coating facing down, and then a metal Nb cup is sleeved from the opposite direction to obtain a composite assembly;

[0083] 8) Composite pre-pressing: the composite assembly is placed in a leaf spar block, the leaf spar block is placed in a high temperature and high pressure device, the pressure is increased to 5 GPa, maintained for 50 s without heating, the pressure is reduced to standard atmospheric pressure, the temperature of the high temperature and high pressure device reaches room temperature, and the pressurizing action is repeated 2 times to obtain a pre-pressing composite assembly.

[0084] 9) Purification treatment: the pre-pressing composite assembly of step 8) is placed in a vacuum sintering furnace for sintering. During sintering, vacuum is first rough-pumped to 6×10 -2 Pa below, heated to 300℃ for 12 min, vacuum is continuously pumped to 3×10 -5 Pa below, the temperature is increased to 700℃ for 12 min, vacuum is stopped, reducing gas (70% CO and 30% N2 by volume ratio) is filled, and maintained for 1.7 h, vacuum is pumped again to 3×10 -4 Pa below to obtain a purified composite assembly.

[0085] 10) High temperature and high pressure sintering: the purified composite assembly of step 9) is placed in a carbon heating tube, the carbon heating tube is placed in a leaf spar block, the leaf spar block is placed in a high temperature and high pressure device, the pressure is increased to 5.5 GPa, the temperature is adjusted to 1465℃, the leaf spar block is then pressurized to 6.0 GPa, maintained for 200 s, then pressurized to 6.5 GPa, maintained for 400 s, then pressurized to 7.0 GPa, maintained for 600 s, after sintering, the temperature is reduced to 600℃ at a rate of 17℃ / S, maintained for 17 min, then reduced to room temperature, and the pressure is reduced to normal pressure at a rate of 0.7 GPa / min. The assembly block is taken out of the cubic press, the surface wrapping layer is removed, and a sintered polycrystalline cubic boron nitride composite sheet blank is obtained.

[0086] 11) Stress relief aging: sinter the sintered polycrystalline cubic boron nitride compact blank of step 10) again with the assembled block of leaf spar, and place it in a cubic anvil press, pressurize to 7.0 GPa, adjust the temperature to 600℃, keep for 27 min, then lower the temperature of the leaf spar block to 500℃, keep for 27 min, then continue to lower the temperature to 450℃, keep for 27 min, then lower the temperature to 400℃, keep for 25 min, and finally lower the temperature to room temperature at 15℃ / S, and lower the pressure to normal pressure at a rate of 0.5 GPa / min. Take out the aged polycrystalline cubic boron nitride compact blank from the assembled block, and process it to the required size with grinding equipment to obtain the high-strength wear-resistant polycrystalline cubic boron nitride compact, as shown in Figure 2

[0087] The high-strength wear-resistant polycrystalline cubic boron nitride compact prepared in this example is subjected to microhardness test according to standard ASTM E384-2010, wear resistance test according to standard JB / T3235-2013 "Test method for wear ratio of sintered artificial diamond", impact toughness test by the method of drop hammer impact (i.e. a 1kg mass of impact hammer is freely dropped from a height of 35cm, and the energy is used to impact the corners of the sample for testing, and the impact toughness value is obtained when micro cracks appear on the surface). The test results are as follows: microhardness is 6100HV, wear ratio is 12100, and impact times is 61.

[0088] Comparative Example 1

[0089] ​The high-strength wear-resistant polycrystalline cubic boron nitride compact of the 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 from inside to outside; the polycrystalline cubic boron nitride layer is composed of the following raw materials with the weight percentage: nitrogen and titanium ion cubic boron nitride micro powder 37.2%, alumina coated cubic boron nitride micro powder 35.2%, silicon nitride whisker 4.2%, fullerene 0.6%, graphdiyne 0.6% and binder 22.2%; the transition composite coating is in the order of rare earth coating, TiB coating and TiAl coating from inside to outside, wherein the rare earth coating is arranged between the surface of the cemented carbide and the TiB coating and the TiAl coating; the material of the rare earth coating is selected from rare earth element Er; the thickness of the rare earth coating is 1.8 μm; the thickness of the TiB coating and the TiAl coating is 3.8 μm and 4.8 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 0.8 μm; the powder transition layer is composed of the following raw materials with the weight percentage: cemented carbide powder 29%, alumina coated cubic boron carbide powder 40.2%, zirconium carbonitride powder 10.2%, lithium boride powder 9.4%, molybdenum powder 5.1%, tungsten-titanium solid solution 5.1%, fullerene 0.5% and graphdiyne 0.5%; the particle size of the zirconium carbonitride powder, lithium boride powder, molybdenum powder and tungsten-titanium solid solution is 40-60 nm; the thickness of the powder transition layer is 0.15 mm; the particle size of the nitrogen and titanium ion cubic boron nitride micro powder has two distributions, one in the range of 2-4 μm and the other in the range of 8-12 μm; the mass fraction of the two kinds of micro powder in the cubic boron nitride micro powder is 9% and 91% respectively; the length of the silicon nitride whisker is in the range of 100 nm to 20 μm and the diameter is not greater than 100 nm; the particle size of the fullerene is 300-500 nm; the particle size of the graphdiyne is 300-500 nm; the binder is composed of the following raw materials with the weight percentage: metal element zirconium 19%, tungsten-titanium solid solution 20.2%, titanium disilicide 20.2%, lithium nitride boride 20.2%, aluminum nitride 10.2%, silicon carbide 9.6% and rare earth yttrium oxide 0.6%; the mass ratio of tungsten element and titanium element in the tungsten-titanium solid solution is 1:1; the particle size of the metal element zirconium, tungsten-titanium solid solution, titanium disilicide, lithium nitride boride, aluminum nitride, silicon carbide and rare earth yttrium oxide is 60-80 nm; the cemented carbide powder is composed of the following raw materials with the weight percentage: tungsten carbide powder 64%, cubic boron nitride micro powder 15.2%, cobalt powder 15.2%, calcium nitrocarbonate powder 2.2%, vanadium carbide powder 1.7% and niobium carbide powder 1.7%; the particle size of the tungsten carbide powder is 1.0-1.2 μm; the particle size of the cubic boron nitride micro powder is 0.5-0.6 μm; the particle size of the cobalt powder, calcium nitrocarbonate powder, vanadium carbide powder and niobium carbide powder is 0.3-0.5 μm.

[0090] The preparation method of the high-strength wear-resistant polycrystalline cubic boron nitride compact is the same as that in Example 3.

[0091] The high-strength wear-resistant polycrystalline cubic boron nitride compact 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 5300HV, the wear ratio is 10000, and the impact number is 54 times. Compared with Example 3, the performance index is obviously reduced.

[0092] Comparative Example 2

[0093] The high-strength wear-resistant polycrystalline cubic boron nitride compact of the 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 weight percentage: nitrogen and titanium ion cubic boron nitride micro powder 47%, alumina coated cubic boron nitride micro powder 31.8%, silicon nitride whisker 1.8%, fullerene 0.1%, graphdiyne 0.1% and binder 19.2%; the transition composite coating is in the order of rare earth coating, TiB coating and TiAl coating from inside to outside, wherein the rare earth coating is arranged between the surface of the cemented carbide and the TiB coating and the TiAl coating; the material of the rare earth coating is selected from rare earth element Er; the thickness of the rare earth coating is 4.2 μm; the thickness of the TiB coating and the TiAl coating is 6.2 μm and 10.2 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 4.2 μm; the powder transition layer is composed of the following raw materials with the weight percentage: cemented carbide powder 46.2%, alumina coated cubic boron carbide powder 34.8%, zirconium carbonitride powder 5.8%, lithium boride powder 5.4%, molybdenum powder 3.8%, tungsten-titanium solid solution 3.8%, fullerene 0.1% and graphdiyne 0.1%; the particle size of the zirconium carbonitride powder, lithium boride powder, molybdenum powder and tungsten-titanium solid solution is 40-60 nm; the thickness of the powder transition layer is 0.45 mm; the nitrogen and titanium ion cubic boron nitride micro powder has two distributions, one in the range of 2-4 μm and the other in the range of 8-12 μm; the mass fraction of the two kinds of micro powder in the cubic boron nitride micro powder is 21% and 79% respectively; the length of the silicon nitride whisker is in the range of 100 nm to 20 μm and the diameter is not greater than 100 nm; the particle size of the fullerene is 300-500 nm; the particle size of the graphdiyne is 300-500 nm; the binder is composed of the following raw materials with the weight percentage: metal element zirconium 46%, tungsten-titanium solid solution 14.8%, titanium disilicide 14.8%, lithium nitride boride 14.8%, aluminum nitride 4.8%, silicon carbide 4.7% and rare earth yttrium oxide 0.1%; the mass ratio of tungsten element and titanium element in the tungsten-titanium solid solution is 1:1; the particle size of the metal element zirconium, tungsten-titanium solid solution, titanium disilicide, lithium nitride boride, aluminum nitride, silicon carbide and rare earth yttrium oxide is 60-80 nm; the cemented carbide powder is composed of the following raw materials with the weight percentage: tungsten carbide powder 76%, cubic boron nitride micro powder 11.8%, cobalt powder 9.8%, calcium nitrocarbonate powder 0.8%, vanadium carbide powder 0.8% and niobium carbide powder 0.8%; the particle size of the tungsten carbide powder is 1.0-1.2 µm; the particle size of the cubic boron nitride micro powder is 0.5-0.6 µm; the particle size of the cobalt powder, calcium nitrocarbonate powder, vanadium carbide powder and niobium carbide powder is 0.3-0.5 µm.

[0094] The preparation method of the high-strength wear-resistant polycrystalline cubic boron nitride composite sheet is the same as in Example 3.

[0095] The high-strength wear-resistant polycrystalline cubic boron nitride composite sheet prepared in this comparative example was subjected to performance testing. The testing method was the same as in Example 3. The results showed that the microhardness was 5200 HV, the wear ratio was 9800, and the number of impacts was 48. Compared with Example 3, its performance indicators were significantly reduced.

[0096] Comparative Example 3

[0097] The high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet used in this comparative example has the same materials and proportions as in Example 3. Its preparation method includes the following steps:

[0098] 1) Purification of cemented carbide substrate: First, potassium ferricyanide, potassium hydroxide, and deionized water are mixed in a mass ratio of 0.4:0.5:9 to obtain an alkaline cleaning solution. The substrate is then immersed in the alkaline cleaning solution and ultrasonically treated (55W power) for 16 min. After removal, it is immersed in deionized water and ultrasonically treated (55W power) for 3 min for washing. Subsequently, 40% sulfuric acid and 35% hydrogen peroxide are mixed in a volume ratio of 1:1 to obtain an acid cleaning solution. The alkaline-washed substrate is immersed in the acid cleaning solution for 4 min. After removal, it is immersed in deionized water and ultrasonically treated (55W power) for 12 min for washing and drying. Then, the cemented carbide substrate is fixed on the rotating frame in the ion source / arc ion plating equipment. The ion source is turned on to perform ion bombardment cleaning on the surface of the cemented carbide substrate. The ion source voltage is 49V, the gas flow rate is 69sccm, the working pressure is 0.4Pa, and the substrate bias voltage is 99V. The cleaning time is 9 min, resulting in a purified cemented carbide substrate.

[0099] 2) Boronizing 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 9 sccm, the pressure is 8 kPa, and the reaction time is 2 h, to obtain a surface-boronized cemented carbide substrate.

[0100] 3) Ion implantation of 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 first separated into monovalent nitrogen ions using a mass spectrometer at a concentration of 3 × 10⁻⁶ ppm. 15 ~3×10 17 ions / cm 2 The ion density and 59 keV energy were injected into the surface of cubic boron nitride, and then the ions supplied by the ion source were separated into monovalent titanium ions at a density of 3 × 10⁻⁶. 15 ~3×1017 ions / cm 2 a surface of cubic boron nitride with an ion density of 1.5 x 1016 ions / cm2 and an energy of 59 keV to obtain nitrogen and titanium ion implanted cubic boron nitride micro powder;

[0101] 4) depositing a transition composite coating: using a magnetron sputtering method, 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, then a TiB composite target and a TiAl composite target are used as target materials to sequentially deposit a TiB coating and a TiAl coating on the surface of the rare earth coating, the magnetron sputtering working pressure is 1.4 Pa, the nitrogen gas flow rate is 34 mL / min, the target-substrate distance is 50±5 mm, the sputtering temperature is 490°C, the vacuum degree is higher than 2x10 -3 Pa, the sputtering power is 118 W, and the sputtering time of the rare earth target, the TiB composite target and the TiAl composite target is 7 min, 10 min and 13 min respectively; the surface area ratio of Ti element to B element in the TiB target is 10:3, and the surface area ratio of Ti element to Al element in the TiAl target is 10:4. The cemented carbide substrate with the transition composite coating is obtained;

[0102] 5) powder transition layer mixing: according to the proportion, fullerene, graphyne, tungsten-titanium solid solution, molybdenum powder, lithium boride powder, zirconium carbonitride, alumina-coated cubic boron nitride micro powder and cemented carbide powder are weighed and dispersed into anhydrous ethanol respectively, mechanical stirring and ultrasonic (power 45W) oscillation dispersion for 32 min, the mass content of the powder is 0.2g / ml; then polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, mechanical stirring and ultrasonic (power 45W) oscillation dispersion for 53 min, the concentration of polyethylene glycol is 0.8g / L, then poured into a cemented carbide ball milling tank with cemented carbide balls, the ball-to-material mass ratio is 7:1, after filling nitrogen as protective gas, ball milling time is 37h, after mixing, placed in a vacuum dryer, vacuum drying at 49°C for 2.5h, to obtain powder transition layer mixed powder;

[0103] 6) polycrystalline cubic boron nitride layer mixing: according to the proportion, fullerene, graphyne, binder, inorganic non-metallic whisker, alumina-coated cubic boron nitride micro powder and nitrogen and titanium ion-containing cubic boron nitride micro powder are weighed and dispersed into anhydrous ethanol respectively, mechanical stirring and ultrasonic (power 45W) oscillation dispersion for 51 min, the mass content of the powder is 0.4g / ml; then polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, mechanical stirring and ultrasonic (power 45W) oscillation dispersion for 73 min, the concentration of polyethylene glycol is 2.5g / L, then poured into a cemented carbide ball milling tank with cemented carbide balls, the ball-to-material mass ratio is 7:1, after filling nitrogen as protective gas, ball milling time is 39h, after mixing, placed in a vacuum dryer, vacuum drying at 49°C for 3.5h, to obtain polycrystalline cubic boron nitride layer mixed powder;

[0104] 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 Nb cup, layered, compacted and shaped, and then the cemented carbide substrate with a composite transition coating of step 1) is placed on the powder transition layer mixed powder with the coating facing down, and then a metal Nb cup is sleeved from the opposite direction to obtain a composite assembly;

[0105] 8) Composite pre-pressing: the composite assembly is placed in a leaf spar block, the leaf spar block is placed in a high temperature and high pressure device, the pressure is increased to 4 GPa, maintained for 38 s without heating, the pressure is reduced to standard atmospheric pressure, the temperature of the high temperature and high pressure device reaches room temperature, and the pressurizing action is repeated 2 times to obtain a pre-pressed composite assembly.

[0106] 9) Purification treatment: the pre-pressed composite assembly of step 8) is placed in a vacuum sintering furnace for sintering. During sintering, vacuum is first rough-pumped to 6×10 -2 Pa below, heated to 249℃ for 9 min, vacuum is continuously pumped to 3×10 - 5 Pa below, the temperature is increased to 640℃ for 9 min, vacuum is stopped, reducing gas (70% CO and 30% N2 by volume ratio) is filled, and maintained for 1 h, vacuum is pumped again to 3×10 -4 Pa below to obtain a purified composite assembly.

[0107] 10) High temperature and high pressure sintering: the purified composite assembly of step 9) is placed in a carbon heating tube, the carbon heating tube is placed in a leaf spar block, the leaf spar block is placed in a high temperature and high pressure device, the pressure is increased to 5.5 GPa, the temperature is adjusted to 1440℃, the leaf spar block is then increased to 6.0 GPa, maintained for 140 s, then increased to 6.5 GPa, maintained for 290 s, then increased to 7.0 GPa, maintained for 490 s, after sintering, the temperature is decreased to 600℃ at a rate of 14℃ / S, maintained for 14 min, then decreased to room temperature, and the pressure is decreased to normal pressure at a rate of 0.5 GPa / min. The assembled block is taken out of the cubic press, the surface wrapping layer is removed, and a sintered polycrystalline cubic boron nitride composite sheet blank is obtained.

[0108] 11) stress relief aging: sinter the sintered polycrystalline cubic boron nitride compact blank of step 10) again with the assembled block of leaf spar, and place it in a cubic anvil press, pressurize to 7.0 GPa, adjust the temperature to 570℃, keep for 24 min, then lower the temperature of the leaf spar block to 470℃, keep for 24 min, then continue to lower the temperature to 390℃, keep for 24 min, then lower the temperature to 370℃, keep for 19 min, and finally lower the temperature to room temperature at a rate of 9℃ / S, and lower the pressure to normal pressure at a rate of 0.3 GPa / min. The sintered polycrystalline cubic boron nitride compact blank after aging is taken out of the assembled block, and processed to the required size by grinding equipment to obtain the high-strength abrasive polycrystalline cubic boron nitride compact.

[0109] The high-strength abrasive polycrystalline cubic boron nitride compact prepared in this comparative example is tested for performance, and the testing method is the same as that of Example 3. After testing, the microhardness is 5300HV, the wear ratio is 10800, and the impact frequency is 48 times. Compared with Example 3, the performance indicators are obviously reduced.

[0110] Comparative Example 4

[0111] The high-strength abrasive polycrystalline cubic boron nitride compact of this comparative example, the materials and their proportions are the same as those of Example 3.

[0112] The preparation method comprises the following steps:

[0113] 1) hard alloy substrate purification: first, mix potassium ferricyanide, potassium hydroxide and deionized water in a mass ratio of 0.4:0.5:13 to obtain an alkali cleaning solution, then place the substrate in the alkali cleaning solution for ultrasonic treatment (power 55W) for 17 min, take it out, and place it in deionized water for ultrasonic treatment (power 55W) for 3 min for washing, then mix 40% sulfuric acid and 35% hydrogen peroxide in a volume ratio of 1:1 to obtain an acid cleaning solution, and then place the alkali-washed substrate in the acid cleaning solution for immersion for 9 min, take it out, and place it in deionized water for ultrasonic treatment (power 55W) for 13 min for washing and drying; then fix the hard alloy substrate on the rotating shaft of the ion source / arc ion plating film equipment, and turn on the ion source to perform ion bombardment cleaning on the surface of the hard alloy substrate, wherein the ion source voltage is 71V, the gas flow is 352sccm, the working pressure is 1.6Pa, and the substrate bias is 610V; the cleaning time is 26 min, and the purified hard alloy substrate is obtained.

[0114] 2) Boronizing 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 13% B2H6 and 87% H2 by volume. The flow rate of the mixture is 13 sccm, the pressure is 12 kPa, and the reaction time is 7 h, to obtain a surface-boronized cemented carbide substrate.

[0115] 3) Ion implantation of 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 first separated into monovalent nitrogen ions using a mass spectrometer at a concentration of 3 × 10⁻⁶ ppm. 15 ~3×10 17 ions / cm 2 The ion density and 91 keV energy were injected into the surface of cubic boron nitride, and then the ions supplied by the ion source were separated into monovalent titanium ions at a density of 3 × 10⁻⁶. 15 ~3×10 17 ions / cm 2 Nitrogen and titanium ion implantation was performed on the surface of cubic boron nitride using ion density and 91 keV energy to obtain cubic boron nitride micro powder with nitrogen and titanium ion implantation.

[0116] 4) Deposition of transition composite coating: Using magnetron sputtering, the boron-diffused cemented carbide substrate from step 2) is first deposited with a rare earth element as the target material on the boron-diffused surface of the cemented carbide substrate. Then, TiB and TiAl coatings are sequentially deposited on the rare earth coating surface using TiB and TiAl composite targets, respectively. The magnetron sputtering working pressure is 1.9 Pa, the nitrogen flow rate is 46 mL / min, the target-substrate distance is 50 ± 5 mm, the sputtering temperature is 610 °C, and the vacuum degree is higher than 2 × 10⁻⁶. -3 The sputtering power was 190 W, and the sputtering times for the rare earth target, TiB composite target, and TiAl composite target were 43 min, 46 min, and 49 min, respectively. The surface area ratio of Ti to B in the TiB composite target was 10:5, and the surface area ratio of Ti to Al in the TiAl composite target was 10:6. The resulting cemented carbide substrate with the transition composite coating was obtained.

[0117] 5) Powder transition layer mixing: Fullerene, graphyne, tungsten-titanium solid solution, molybdenum powder, lithium boride powder, zirconium carbonitride, alumina-coated cubic boron nitride micro powder and cemented carbide powder are weighed according to the proportion, respectively dispersed into anhydrous ethanol, mechanically stirred and ultrasonic (power 45W) oscillation dispersed for 42min, the mass content of the powder is 1.1g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, mechanically stirred and ultrasonic (power 45W) oscillation dispersed for 54min, the concentration of polyethylene glycol is 6g / L, then poured into a cemented carbide ball mill tank with cemented carbide balls, the ball-to-material mass ratio is 11:1, nitrogen is filled as protective gas, the ball milling time is 43h, after mixing, placed in a vacuum dryer, vacuum dried at 61℃ for 6h, to obtain powder transition layer mixed powder;

[0118] 6) Polycrystalline cubic boron nitride layer mixing: Fullerene, graphyne, binder, inorganic non-metallic whisker, alumina-coated cubic boron nitride micro powder and nitrogen and titanium ion-containing cubic boron nitride micro powder are weighed according to the proportion, respectively dispersed into anhydrous ethanol, mechanically stirred and ultrasonic (power 45W) oscillation dispersed for 53min, the mass content of the powder is 1.1g / ml; polyethylene glycol is weighed and added into the anhydrous ethanol dispersion, mechanically stirred and ultrasonic (power 45W) oscillation dispersed for 72min, the concentration of polyethylene glycol is 9g / L, then poured into a cemented carbide ball mill tank with cemented carbide balls, the ball-to-material mass ratio is 13:1, nitrogen is filled as protective gas, the ball milling time is 46h, after mixing, placed in a vacuum dryer, vacuum dried at 61℃ for 7h, to obtain polycrystalline cubic boron nitride layer mixed powder;

[0119] 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 Nb cup, layered, compacted and shaped, then the cemented carbide substrate with a composite transition coating of step 1 is placed on the powder transition layer mixed powder with the coating facing down, and then a metal Nb cup is sleeved from the opposite direction to obtain a composite assembly;

[0120] 8) Composite pre-pressing: The composite assembly is placed in a leaf talc block, the leaf talc block is placed in a high-temperature and high-pressure device, the pressure is increased to 5.8GPa, kept for 65s without heating, the pressure is reduced to standard atmospheric pressure, the temperature of the high-temperature and high-pressure device reaches room temperature, the pressurizing action is repeated 2 times to obtain a pre-pressed composite assembly.

[0121] 9) Purification treatment: The pre-pressed composite assembly of step 8 is placed in a vacuum sintering furnace for sintering, during sintering, first rough vacuum to the furnace air pressure below 6×10 -2 Pa, heated to 360℃ for 16min, continue to vacuum to the furnace air pressure below 3×10 -5Pa, the temperature is raised to 760℃ for 16 min, then the vacuum is stopped, and the reducing gas (70% CO and 30% N2 by volume) is filled in, and kept for 2.2 h, and then the vacuum is extracted again to 3*10 -4 Pa, to obtain the purified composite assembly;

[0122] 10) High-temperature and high-pressure sintering: the purified composite assembly of step 9) is put into a carbon heating tube, the carbon heating tube is put into a block of beryl, the block of beryl is put into a high-temperature and high-pressure device, and the pressure is increased to 5.5 GPa, the temperature is adjusted to 1500℃, then the pressure of the block of beryl is increased to 6.0 GPa and kept for 260 s, then the pressure is continuously increased to 6.5 GPa and kept for 510 s, then the pressure is increased to 7.0 GPa and kept for 710 s, after the sintering is completed, the temperature is decreased to 600℃ at a rate of 21℃ / s, and kept for 21 min, then the pressure is decreased to normal pressure at a rate of 1 GPa / min. The assembled block is taken out of the cubic anvil press, and the surface wrapping layer is removed, to obtain a sintered polycrystalline cubic boron nitride composite sheet blank.

[0123] 11) Stress relief aging: the sintered polycrystalline cubic boron nitride composite sheet blank of step 10) is assembled again with the block of beryl, and is put into a cubic anvil press, and the pressure is increased to 7.0 GPa, the temperature is adjusted to 640℃, and kept for 31 min, then the temperature of the block of beryl is decreased to 540℃, and kept for 31 min, then the temperature is continuously decreased to 510℃, and kept for 31 min, then the temperature is decreased to 440℃, and kept for 31 min, and 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 aged polycrystalline cubic boron nitride composite sheet blank is taken out of the assembled block, and is processed to the required size by grinding equipment, to obtain the high-strength wear-resistant polycrystalline cubic boron nitride composite sheet.

[0124] The high-strength wear-resistant polycrystalline cubic boron nitride composite sheet produced by the comparative example is tested for performance, and the testing method is the same as that of example 3. After testing, the microhardness is 5200 HV, the wear ratio is 10200, and the impact frequency is 54 times. Compared with example 3, the performance indicators are obviously reduced.

[0125] Through the comparison and analysis of the technical performance indicators of the above examples and the comparative example, it can be obviously concluded that the high-strength 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.

[0126] 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 cubic boron nitride layer are not limitations of the present application.

[0127] 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 high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet, characterized in that, The system comprises a cemented carbide substrate and, from the inside out, a transition composite coating, a powder transition layer, and a polycrystalline cubic boron nitride layer sequentially disposed on the cemented carbide substrate. The polycrystalline cubic boron nitride layer is composed of the following raw materials in weight percentages: 38-46% nitrogen- and titanium-ion-containing cubic boron nitride micropowder, 32-35% alumina-coated cubic boron nitride micropowder, 2-4% inorganic non-metallic whiskers, 0.2-0.5% fullerene, 0.2-0.5% graphynylene, and 19.6-22% binder. The transition composite coating, from the inside out, consists of a rare earth coating, a TiB coating, and a TiAl coating, wherein the rare earth coating is applied to the surface of the cemented carbide substrate and the TiB coating... Between layers; the rare earth coating material is selected from one of the rare earth elements Dy, Ho, and Er; the thickness of the rare earth coating is 2-4 μm; the thicknesses of the TiB coating and the TiAl coating are 4-6 μm and 5-10 μm, respectively; the cemented carbide substrate is a surface-boronized cemented carbide substrate; the thickness of the surface-boronized layer of the cemented carbide substrate is 1-4 μm; the powder transition layer is composed of the following raw materials in weight percentages: cemented carbide powder 30-45%, alumina-coated cubic boron carbide powder 35-40%, zirconium carbonitride powder 6-10%, lithium boride powder 5.6-9.2%, molybdenum powder 4-5%, tungsten-titanium solid solution 4-5%. The powder comprises 0.2-0.4% fullerene and 0.2-0.4% graphyne; the particle size of the zirconium carbonitride powder, lithium boride powder, molybdenum powder, and tungsten titanium solid solution is 40-60 nm; the thickness of the powder transition layer is 0.2-0.4 mm; the inorganic non-metallic whiskers are one or two of alumina, zirconium oxide, and silicon nitride, with a whisker length ranging from 100 nm to 20 μm and a diameter not exceeding 100 nm; the binder is composed of the following raw materials in weight percentages: 20-45% metal elements, 15-20% tungsten titanium solid solution, 15-20% titanium disilicide, 15-20% lithium boride, and 5-10% nitrides. The composition includes 4.8–9.5% carbides and 0.2–0.5% rare earth oxides; the metal element includes one or more of aluminum, lithium, zirconium, and magnesium; the mass ratio of tungsten to titanium in the tungsten-titanium solid solution in the powder transition layer or binder is 1:1; the nitride includes one or two of lithium nitride, boron nitride, and aluminum nitride; the carbide includes one or two of titanium carbide, tungsten carbide, and silicon carbide; the rare earth oxide includes one or two of lanthanum oxide, cerium oxide, and yttrium oxide; the particle size of the metal element, tungsten-titanium solid solution, titanium disilicide, lithium boron nitride, nitride, carbide, and rare earth oxide is 60–80 nm.

2. The high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet according to claim 1, characterized in that, The alumina-coated cubic boron nitride micropowder comprises cubic boron nitride micropowder and an aluminum alloy coating coated on the surface of the cubic boron nitride. Alumina plates are grown in situ on the outer surface of the aluminum alloy coating. The thickness of the alumina plates is 200 nm to 900 nm, and the area coverage of the alumina plates on the outer surface of the aluminum alloy coating is 1% to 30%. The thickness of the aluminum alloy coating is 10 nm to 100 nm, and the particle size of the cubic boron nitride micropowder in the alumina-coated cubic boron nitride micropowder is 8 to 12 μm.

3. The high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet according to claim 1, characterized in that, The cubic boron nitride micropowder containing nitrogen and titanium ions has two particle size distributions: one in the range of 2–4 μm and the other in the range of 8–12 μm. The mass percentage of each type of micropowder in the cubic boron nitride micropowder is: 10–20% for the 2–4 μm range and 80–90% for the 8–12 μm range.

4. The high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet according to claim 1, characterized in that, The fullerene has a particle size of 300 nm to 500 nm; the graphdiyne has a particle size of 300 nm to 500 nm.

5. The high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet according to claim 1, characterized in that, The cemented carbide powder is composed of the following raw materials in weight percentages: 65-75% tungsten carbide powder, 12-15% cubic boron nitride micro powder, 10-15% cobalt powder, 1-2% calcium carbide nitride powder, 1-1.5% vanadium carbide powder, and 1-1.5% niobium carbide powder; the particle size of the tungsten carbide powder is 1.0-1.2µm; the particle size of the cubic boron nitride micro powder in the cemented carbide powder is 0.5-0.6µm; and the particle size of the cobalt powder, calcium carbide nitride powder, vanadium carbide powder, and niobium carbide powder is 0.3-0.5µm.

6. A method for preparing the high-strength, wear-resistant polycrystalline cubic boron nitride composite sheet according to any one of claims 1 to 5, characterized in that... The process includes the following steps: 1) Cleaning of the cemented carbide substrate: First, potassium ferricyanide, potassium hydroxide, and deionized water are mixed in a mass ratio of 0.4:0.5:10-12 to obtain an alkaline cleaning solution. The substrate is then immersed in the alkaline cleaning solution and ultrasonically treated for 15-20 minutes. After removal, it is immersed in deionized water and ultrasonically treated for 2-4 minutes for washing. Next, 40% sulfuric acid and 30-35 wt% hydrogen peroxide are mixed in a 1:1 volume ratio to obtain an acid cleaning solution. The alkaline-washed substrate is immersed in the acid cleaning solution for 5-8 minutes. After removal, it is immersed in deionized water and ultrasonically treated for 10-15 minutes, followed by drying. Then, the cemented carbide substrate is fixed on a rotating frame in an ion source or arc ion plating equipment. The ion source is turned on to perform ion bombardment cleaning on the surface of the cemented carbide substrate. The ion source voltage is 50–70V, the gas flow rate is 70–350 sccm, the working pressure is 0.5–1.5 Pa, the substrate bias voltage is 100–600V, and the cleaning time is 10–25 min, resulting in a purified cemented carbide substrate. 2) Boronizing the cemented carbide substrate: The purified cemented carbide substrate from step 1) is placed in a vacuum tube drying furnace for boronizing treatment. The boronizing gas is a mixture of 10-12% B2H6 and 88-90% H2 by volume. The flow rate of the mixture is 10-12 sccm, the pressure is 9-11 kPa, and the reaction time is 3-6 h, to obtain a surface-boronized cemented carbide substrate. 3) Ion implantation of 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 first separated into monovalent nitrogen ions using a mass spectrometer at a concentration of 3 × 10⁻⁶ ppm. 15 ~3×10 17 ions / cm 2 The ion density and energy of 60–90 keV are injected into the surface of cubic boron nitride, and then the ions supplied by the ion source are separated into monovalent titanium ions at a density of 3 × 10⁻⁶ keV. 15 ~3×10 17 ions / cm 2 The ion density and energy of 60-90 keV were injected into the surface of cubic boron nitride to obtain cubic boron nitride micro powder containing nitrogen ion and titanium ion implantation. 4) Deposition of transition composite coating: Using magnetron sputtering, the boron-dipped cemented carbide substrate from step 2) is first deposited with rare earth elements as the target material to form a rare earth coating with a thickness of 2-4 µm. Then, TiB and TiAl coatings are deposited sequentially on the rare earth coating surface using TiB and TiAl composite targets, respectively. The TiB and TiAl coatings are 4-6 µm and 5-10 µm thick, respectively, to obtain a cemented carbide substrate containing a transition composite coating. 5) Powder transition layer mixing: Weigh fullerene, graphylene, tungsten-titanium solid solution, molybdenum powder, lithium boride powder, zirconium carbonitride, alumina-coated cubic boron nitride micro powder and cemented carbide powder according to the proportion, and disperse them in anhydrous ethanol in sequence. Mechanically stir and ultrasonically vibrate for 30-50 min, and the mass content of the powder is 0.3-1 g / mL; then weigh polyethylene glycol and add it to the anhydrous ethanol dispersion, mechanically stir and ultrasonically vibrate for 50-60 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 added, with a ball-to-powder mass ratio of 8-10:

1. After filling with nitrogen as a protective gas, the ball milling time is 38-42 h. After mixing, place it in a vacuum dryer and vacuum dry at 50-60℃ for 3-5 h to obtain the powder transition layer mixed powder. 6) Polycrystalline cubic boron nitride layer mixture: Weigh fullerene, graphylene, binder, inorganic non-metallic whiskers, alumina-coated cubic boron nitride micro powder, and cubic boron nitride micro powder containing nitrogen and titanium ions according to the proportion, and disperse them in anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate for 50-60 min, and the mass content of the powder is 0.5-1 g / mL. Then weigh polyethylene glycol and add it to the anhydrous ethanol dispersion. Mechanically stir and ultrasonically vibrate for 60-80 min, and the concentration of polyethylene glycol is 3-8 g / L. Then pour it into a cemented carbide ball mill jar with cemented carbide balls. The mass ratio of ball to powder is 8-12:

1. After filling with nitrogen as a protective gas, the ball milling time is 40-45 h. After mixing, place it in a vacuum dryer and vacuum dry at 50-60℃ for 4-6 h to obtain polycrystalline cubic boron nitride layer mixed powder. 7) Composite assembly: First, the polycrystalline cubic boron nitride layer mixed powder described in step 6) and the powder transition layer mixed powder described in step 5) are sequentially loaded into a metal cup, layered and compacted to shape. Then, the hard alloy substrate containing the transition composite coating from step 4) is placed flat on the powder transition layer mixed powder with the coating side facing down. Then, a metal cup is inserted from the opposite direction to obtain the composite assembly. The metal cup is composed of one or more of the following materials: Mo, Ta, Nb. 8) Pre-compression of the composite: The composite component is placed in a pyrophyllite block, which is then placed in a high-temperature and high-pressure equipment. The pressure is increased to 4.5–5.5 GPa and held for 40–60 seconds without heating. The pressure is then reduced to standard atmospheric pressure. The temperature of the high-temperature and high-pressure equipment is brought to room temperature. The pressurization process is repeated 1 to 2 times to obtain the pre-compressed composite component. 9) Purification treatment: Place the pre-compressed composite component from step 8) into a vacuum sintering furnace for sintering. During sintering, first perform a rough vacuum evacuation until the furnace pressure reaches 6×10⁻⁶. -2 Below Pa, heat to 250–350℃ and hold for 10–15 minutes, then continue evacuating until the furnace pressure is 3 × 10⁻⁶. -5 Below Pa, raise the temperature to 650–750℃ and hold for 10–15 minutes, then stop evacuation and introduce reducing gas. The reducing gas should consist of 70% CO and 30% N2 by volume. Maintain this temperature for 1.5–2 hours, then evacuate again until the furnace pressure is 3 × 10⁻⁶. -4 Below Pa, a purification composite component is obtained; 10) High-temperature and high-pressure sintering: Place the purified composite component from step 9) into a carbon heating tube, place the carbon heating tube into a pyrophyllite block, place the pyrophyllite block into a six-sided press, pressurize to 5.5 GPa, adjust the temperature to 1450-1480℃, then pressurize the pyrophyllite block to 6.0 GPa and hold for 150-250 s, then continue to pressurize to 6.5 GPa and hold for 300-500 s; then pressurize to 7.0 GPa and hold for 500-700 s. After sintering, cool down to 600℃ at 15-20℃ / s, hold for 15-20 min, then cool down to room temperature, and depressurize to atmospheric pressure at a rate of 0.6-0.9 GPa / min. Remove the pyrophyllite block from the six-sided press, remove the surface coating layer, and obtain the sintered polycrystalline cubic boron nitride composite blank. 11) Stress-relief aging: The polycrystalline cubic boron nitride composite blank sintered in step 10) is reassembled with pyrophyllite blocks and placed in a six-sided press. The pressure is increased to 7.0 GPa, the temperature is adjusted to 580-630℃ and held for 25-30 min. The pyrophyllite blocks are then cooled to 480-530℃ and held for 25-30 min. The temperature is then further reduced to 400-500℃ and held for 25-30 min. The temperature is then reduced to 380-430℃ and held for 20-30 min. Finally, the temperature is reduced to room temperature at a rate of 10-20℃ / s and the pressure is reduced to atmospheric pressure at a rate of 0.4-0.6 GPa / min. The aged polycrystalline cubic boron nitride composite blank is removed from the pyrophyllite blocks and processed to the required dimensions using a grinding machine to obtain the high-strength wear-resistant polycrystalline cubic boron nitride composite sheet.

7. The method for preparing the high-strength wear-resistant polycrystalline cubic boron nitride composite sheet according to claim 6, characterized in that, In step 4), the magnetron sputtering working pressure is 1.5–1.8 Pa, the flow rate of nitrogen or argon gas is 35–45 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 120-180W, sputtering time 15-40 min; the surface area ratio of Ti to B in the TiB composite target is 10:4, and the surface area ratio of Ti to Al in the TiAl composite target is 10:5.

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