Superfine polycrystalline diamond compact and preparation method thereof

Abstract

The invention discloses a superfine polycrystalline diamond compact which sequentially comprises a hard alloy matrix, a polycrystalline diamond layer and a surface isolation layer. The invention also discloses a preparation method of the ultrafine polycrystalline diamond compact, which comprises the following steps: mixing diamond micro-powder, putting the mixed diamond micro-powder into a vacuum furnace for reduction, putting the hard alloy into an aerobic high-temperature furnace for surface oxidation treatment, and then rinsing, soaking and drying to obtain the hard alloy matrix; assembling the reduced mixed powder and a hard alloy matrix to form an assembly; and the combined piece is firstly placed in a cubic press for presintering, then assembled parts are placed in the cubic press for high-temperature and high-pressure sintering, and the superfine polycrystalline diamond compact is obtained. According to the superfine polycrystalline diamond compact and the preparation method thereof, the problem that in the prior art, the quality of the synthesized superfine polycrystalline diamond compact is not high due to the fact that mixing is not uniform and superfine particle diamond micro powder is prone to being squeezed and broken in the high-temperature and high-pressure synthesis process is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of superhard material preparation, and in particular relates to an ultrafine polycrystalline diamond composite sheet. The present invention also relates to a method for preparing the ultrafine polycrystalline diamond composite sheet. Background Art

[0002] Polycrystalline diamond (PCD) composites are synthesized using a high-temperature, high-pressure method using a metal catalyst as a binder. They exhibit excellent impact resistance, wear resistance, and processability. The precision machining and 3C industries are increasingly demanding higher precision and finer particle sizes for PCD composites. Many manufacturers require diamond powder particles ≤1µm, and even overseas manufacturers have achieved particle sizes below 0.5µm.

[0003] Ultrafine polycrystalline diamond compacts (PDCs) are technically challenging to manufacture due to their extremely fine particle size. Added binders tend to aggregate, resulting in defects in the resulting PDC. Direct sintering with a binder can lead to uneven mixing. When synthesizing PDCs using the melt infiltration method, binder cannot easily penetrate into diamond particles below a micron in size, making it difficult to evenly mix with other binders through other processing steps and conventional mixing methods. Furthermore, deviations from the normal growth process temperature can cause variations in product performance and abnormal particle growth, resulting in varying properties of the resulting PDC. Ultrafine diamond powders can be crushed and recrystallized during the high-temperature, high-pressure synthesis process, leading to significant shrinkage of the polycrystalline layer and significant impact on product quality. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultrafine polycrystalline diamond composite sheet, which solves the problem in the prior art that the synthesized ultrafine polycrystalline diamond composite sheet is of low quality due to uneven mixing and the ultrafine particle diamond powder is easily squeezed and broken during the high temperature and high pressure synthesis process.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned ultrafine polycrystalline diamond compact.

[0006] The technical solution adopted by the present invention is that the ultrafine polycrystalline diamond composite sheet includes a cemented carbide substrate, a polycrystalline diamond layer, and a surface insulation layer in sequence; the cemented carbide substrate includes cemented carbide and an oxide layer, and the oxide layer is connected to the polycrystalline diamond layer; the polycrystalline diamond layer is composed of diamond micropowder and a binder, and according to the mass percentage, the diamond micropowder accounts for 80-95% and the binder accounts for 5-20%; the surface insulation layer is a carbide layer or a diamond micropowder layer.

[0007] The present invention is also characterized in that: The particle size of diamond micropowder is 0.1~1.0um; The binder is any one or any two of nickel, cobalt and tungsten; The carbide layer is any one of a tungsten carbide layer, a titanium carbide layer, and a zirconium carbide layer.

[0008] Another technical solution of the present invention is a method for preparing an ultrafine polycrystalline diamond compact, which specifically comprises the following steps: Step 1: Weigh diamond micropowder and metal balls and place them into a catalyst pot, and mix them by a wet mixing process; place the mixed materials into a vacuum drying oven for drying, and sieve out the metal balls to obtain mixed diamond micropowder; Step 2: Place the mixed diamond powder into a vacuum furnace for reduction to obtain reduced mixed powder; Step 3: Place the cemented carbide in an oxygen high-temperature furnace for surface oxidation treatment; Step 4: Rinse, soak, and dry the cemented carbide processed in step 3 to obtain a cemented carbide substrate; Step 5: Assembling the reduced mixed powder with the cemented carbide substrate to form an assembly; Step 6: The assembly is first placed in a six-sided top press for pre-sintering, and then the assembled parts are placed in the press for high temperature and high pressure sintering to obtain an ultrafine polycrystalline diamond composite sheet.

[0009] Another technical solution of the present invention is also characterized in that: In step 1, the mass ratio of diamond powder to metal balls is 1:5-10; the metal balls are any one or any two of nickel balls, cobalt balls, and tungsten balls, and the metal purity of the metal balls is ≥99.9% and the diameter is 8-10 mm.

[0010] In step 1, the wet mixing process is specifically as follows: diamond micropowder and metal balls are mixed with alcohol for 50 to 150 hours, humidity ≤ 45%, and temperature 20-30°C; the alcohol is ethanol or propanol; and the mass ratio of diamond micropowder to alcohol is 3 to 5:1; In step 1, the mixed material is placed in a vacuum drying oven for drying. Specifically, the mixed material is placed in a vacuum drying oven, the vacuum oven is evacuated to -0.01 to -0.1 MPa; the temperature is raised to 100° C. to 200° C., and the mixture is dried for 2 to 6 hours.

[0011] In step 2, the mixed diamond powder is placed in a vacuum furnace for reduction as follows: First, the vacuum furnace was raised to 1×10 -3 ~5×10 -3 Pa vacuum, the mixed diamond powder is heated to reduce, the temperature is raised to 350-400 ° C within 15-20 min, and the temperature is kept for 30-40 min; Then, the temperature is raised to 700-800°C within 20-30 minutes and kept at this temperature for 30-40 minutes; Finally, the temperature is raised to 900-1000°C within 30-40 minutes and kept warm for 200-300 minutes. During the warming stage, hydrogen is introduced for 8-10 times for reduction. The mixture is cooled to room temperature with the furnace to obtain a reduced mixed powder.

[0012] In step 3, the cemented carbide is YG10, and the thickness is 3 to 6 times that of the polycrystalline diamond layer; the surface oxidation treatment of the cemented carbide is specifically as follows: the cemented carbide is placed in an oxygen high-temperature furnace, first the temperature is raised to 800 to 1000 ° C, kept warm for 0.5 to 1 hour, then the temperature is raised to 1200 to 1300 ° C, kept warm for 0.5 to 1 hour, and then the heating is stopped to room temperature to form an oxide layer on the surface of the cemented carbide.

[0013] Step 4 is specifically as follows: the oxidized cemented carbide is rinsed with clean water 2 to 3 times, then immersed in alcohol for 20 to 30 seconds, and dried in a vacuum furnace at 150 to 250° C. to obtain a cemented carbide substrate.

[0014] Step 5 is specifically as follows: a layer of carbide metal powder or pure diamond micropowder is laid on the bottom of the metal cup, and then the reduced mixed powder is spread flat in the metal cup using a tool, and then the cemented carbide substrate is buckled into the metal cup to form an assembly; the carbide metal powder is any one of tungsten carbide, titanium carbide, and zirconium carbide, and the particle size of the carbide metal powder is ≤1um and the purity is ≥99.5%; the particle size of the pure diamond micropowder is ≤2um and the purity is ≥99.9%; the mass ratio of the carbide metal powder or diamond micropowder to the reduced mixed powder is 1:5~10.

[0015] In step 6: Pre-sintering process: Increase the pressure to 1-4 GPa and the temperature to 800-1300°C, and keep it at this temperature for 3-8 minutes; High-temperature and high-pressure sintering process: First, increase the pressure to 2-3 GPa, maintain the pressure for 5-10 minutes, and then increase the pressure to 5-6 GPa; after increasing the pressure to 2-3 GPa, increase the temperature to 1300-1600 °C at a rate of 0.5-2 °C / s; maintain the temperature for 5-20 minutes.

[0016] The beneficial effects of the present invention are: 1. In the preparation method of the ultrafine polycrystalline diamond composite sheet of the present invention, the metal binder is derived from the wear of the diamond powder on the metal ball, which better ensures that the particle size of the metal binder is very fine and evenly distributed around the diamond differential particles, solves the problem that the ultrafine metal binder is difficult to mix with the ultrafine diamond particles, and better controls the content of the binder by controlling the mixing time, thereby avoiding the problem of binder addition deviation and ensuring consistent performance of the polycrystalline layer.

[0017] 2. In the preparation method of the ultrafine polycrystalline diamond composite sheet of the present invention, an oxide layer of a certain thickness is generated on the surface of the cemented carbide. The oxide layer can prevent the cobalt phase metal from penetrating into the diamond layer under high temperature environment, improve the stress concentration at the interface between the cemented carbide and the diamond layer, and better improve the impact resistance of the product.

[0018] 3. In the method for preparing the ultrafine polycrystalline diamond composite sheet of the present invention, the insulating layer formed by carbide or diamond powder effectively reduces the sintering temperature, thereby reducing the abnormal growth of diamond.

[0019] 4. In the preparation method of the ultrafine polycrystalline diamond composite sheet of the present invention, the assembly is first pre-sintered at low temperature and low pressure to ensure that the diamond powder is neatly arranged in the appropriate position, and the metal binder is melted at low temperature and evenly filled into the gaps between the diamond particles; then a secondary sintering is carried out at high temperature and high pressure. Under a stable high-pressure state, the temperature is increased to reduce the radial shrinkage of the polycrystalline layer, thereby better ensuring the transmission of pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the ultrafine polycrystalline diamond composite sheet of the present invention; FIG2 (a) is a schematic diagram of pressure and temperature lines in the pre-sintering process in the method for preparing the ultrafine polycrystalline diamond compact of the present invention; FIG2( b ) is a schematic diagram of pressure lines and temperature lines in the high temperature and high pressure process in the method for preparing the ultrafine polycrystalline diamond compact of the present invention; Figure 3 This is a microstructure diagram of the ultrafine polycrystalline diamond compact prepared in Example 2 of the present invention; Figure 4 is an ultrasonic scanning image of the ultrafine polycrystalline diamond compact prepared in Examples 2, 4, and 6 of the present invention; Figure 5 This is a microstructure diagram of the ultrafine polycrystalline diamond compact prepared in Example 4 of the present invention; Figure 6 This is a microstructure diagram of the ultrafine polycrystalline diamond composite sheet prepared in Example 6 of the present invention.

[0021] In the figure, 1. Surface isolation layer; 2. Polycrystalline diamond layer; 3. Oxide layer; 4. Cemented carbide. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] The ultrafine polycrystalline diamond composite sheet of the present invention is as follows Figure 1As shown, it includes a cemented carbide substrate, a polycrystalline diamond layer 2, and a surface isolation layer 1 in sequence; the cemented carbide substrate includes a cemented carbide 4 and an oxide layer 3, and the oxide layer 3 is connected to the polycrystalline diamond layer 2; the polycrystalline diamond layer is composed of diamond micropowder and a binder, and according to the mass percentage, the diamond micropowder accounts for 80-95%, and the binder accounts for 5-20%; the particle size of the diamond micropowder is 0.1-1.0um; the binder is any one or any two of nickel, cobalt, and tungsten; the surface isolation layer is a carbide layer or a diamond micropowder layer, and the carbide layer is any one of a tungsten carbide layer, a titanium carbide layer, and a zirconium carbide layer.

[0024] The method for preparing an ultrafine polycrystalline diamond composite sheet specifically comprises the following steps: Step 1: Weigh diamond micropowder and metal balls and place them into a catalyst pot, and mix them by a wet mixing process; place the mixed materials into a vacuum drying oven for drying, and sieve out the metal balls to obtain mixed diamond micropowder; Specifically, the mass ratio of diamond powder to metal balls is 1:5-10; the metal balls are any one or any two of nickel balls, cobalt balls, and tungsten balls, and the metal purity of the metal balls is ≥99.9% and the diameter is 8-10 mm.

[0025] Specifically, the wet mixing process involves mixing diamond powder and metal balls with an alcohol for 50-150 hours, at a humidity of ≤45%, and a temperature of 20-30°C. The alcohol is either ethanol or propanol, and the mass ratio of diamond powder to alcohol is 3-5:1. When two types of metal balls are used, the weight of metal lost due to wear is affected by the grinding time and the ratio of metal balls to diamond powder, based on the metal properties and production experience. Typically, the weight of metal lost due to wear of the two types of metal balls is consistent with the weight ratio of the added metal balls, and the dosage is related to the wear time.

[0026] Specifically, the mixed material is placed in a vacuum drying box for drying. Specifically, the mixed material is placed in a vacuum drying box, the vacuum box is evacuated to -0.01 to -0.1 MPa; the temperature is raised to 100° C. to 200° C., and the mixture is dried for 2 to 6 hours.

[0027] Step 2: Place the mixed diamond powder into a vacuum furnace for reduction to obtain reduced mixed powder; Specifically, the mixed diamond powder is placed in a vacuum furnace for reduction as follows: First, the vacuum furnace was raised to 1×10 -3 ~5×10 -3 Pa vacuum, the mixed diamond powder is heated to reduce, the temperature is raised to 350-400 ° C within 15-20 min, and the temperature is kept for 30-40 min; Then, the temperature is raised to 700-800°C within 20-30 minutes and kept at this temperature for 30-40 minutes; Finally, the temperature is raised to 900-1000°C within 30-40 minutes and kept warm for 200-300 minutes. During the warming stage, hydrogen is introduced for 8-10 times for reduction. The mixture is cooled to room temperature with the furnace to obtain a reduced mixed powder.

[0028] Step 3: Place the cemented carbide in an oxygen high-temperature furnace for surface oxidation treatment; Specifically, the cemented carbide is YG10, and its thickness is 3 to 6 times that of the polycrystalline diamond layer; the surface oxidation treatment of the cemented carbide is specifically as follows: the cemented carbide is placed in an oxygen high-temperature furnace, firstly the temperature is raised to 800 to 1000°C, kept warm for 0.5 to 1 hour, then the temperature is raised to 1200 to 1300°C, kept warm for 0.5 to 1 hour, and then the heating is stopped to room temperature to form an oxide layer on the surface of the cemented carbide.

[0029] Step 4: Rinse, soak, and dry the cemented carbide processed in step 3 to obtain a cemented carbide substrate; Specifically, the oxidized cemented carbide is rinsed with clean water for 2 to 3 times, then immersed in alcohol for 20 to 30 seconds, and dried in a vacuum furnace at 150 to 250° C. to obtain a cemented carbide substrate.

[0030] Step 5: Assembling the reduced mixed powder with the cemented carbide substrate to form an assembly; Specifically, a layer of carbide metal powder or pure diamond powder is placed on the bottom of a metal cup. The reduced mixed powder is then flattened inside the metal cup using a tool. The amount of reduced mixed powder is calculated based on the product thickness. A cemented carbide substrate is then added to form the assembly. The carbide metal powder can be any one of tungsten carbide, titanium carbide, and zirconium carbide, with a particle size of ≤1 μm and a purity of ≥99.5%. The pure diamond powder has a particle size of ≤2 μm and a purity of ≥99.9%. The mass ratio of the carbide metal powder or diamond powder to the reduced mixed powder is 1:5-10.

[0031] Step 6: The assembly is first placed in a six-sided top press for pre-sintering, and then the assembled parts are placed in the press for high temperature and high pressure sintering to obtain an ultrafine polycrystalline diamond composite sheet.

[0032] The pre-sintering process is shown in Figure 2 (a): the pressure is increased to 1-4 GPa, and the temperature is increased to 800-1300°C at the same time, and kept warm for 3-8 minutes; after the temperature drops to room temperature, the assembly is taken out and placed on a high-temperature and high-pressure pressure-transmitting part for secondary sintering.

[0033] The high-temperature and high-pressure sintering process is shown in Figure 2 (b): first, the pressure is increased to 2~3 GPa, and the pressure is maintained for 5~10 min, and then the pressure is increased to 5~6 GPa; after the pressure is increased to 2~3 GPa, the temperature is increased to 1300~1600℃ at a rate of 0.5~2℃ / s; and the temperature is maintained for 5~20 min.

[0034] All the parts and raw materials mentioned above are purchased from the market.

[0035] Example 1 This embodiment provides an ultrafine polycrystalline diamond composite sheet, comprising, in order, a cemented carbide YG10, an oxide layer, a polycrystalline diamond layer, and a surface insulation layer. The polycrystalline diamond layer is composed of diamond powder and a binder, in percentage by mass: 85% diamond powder and 15% binder; the diamond powder has a particle size of 0.5 µm; the binder comprises the following raw material components and weights: 10% Co powder and 5% W powder. The surface insulation layer is a tungsten carbide layer. The ultrafine polycrystalline diamond composite sheet provided in this embodiment has a diameter of Ø55 mm, a cemented carbide substrate thickness of 3.5 mm, and a polycrystalline diamond layer thickness of 0.5 mm.

[0036] Example 2 The preparation method of the ultrafine polycrystalline diamond compact in Example 1 specifically comprises the following steps: Step 1: Weigh diamond powder and metal balls and place them into a catalyst pot. The weight ratio of diamond powder to cobalt balls and tungsten balls is 1:6:3 respectively. Mix them by a wet mixing process, control the temperature and humidity. The temperature and humidity requirements are: ≤45%, temperature between 20-30°C, and mix for 120 hours. Place the mixed materials in a vacuum drying oven for drying, sieve out the metal balls, and calculate the binder content of 10% and 5% to obtain mixed diamond powder. Step 2: Place the mixed diamond powder into a vacuum furnace for reduction and raise the vacuum furnace temperature to 1×10 -3 The mixed diamond powder is heated and reduced under a vacuum of 1.5 Pa; the temperature is raised to 350°C within 20 minutes and kept at this temperature for 30 minutes; the temperature is then raised to 800°C within 30 minutes and kept at this temperature for 40 minutes; and finally the temperature is raised to 1000°C within 40 minutes and kept at this temperature for 200 minutes. During the holding period, hydrogen is introduced for 8-10 times for reduction, and the mixture is cooled in the furnace to obtain a reduced mixed powder; Step 3: Oxidation treatment of the surface of YG10 grade cemented carbide: Place the cemented carbide in an oxygen high-temperature furnace, first raise the temperature to 900°C, keep it warm for 0.5h, then raise the temperature to 1250°C, keep it warm for 1h, stop heating to room temperature, and form an oxide layer on the surface of the cemented carbide substrate.

[0037] Step 4: Clean the cemented carbide treated in step 3, rinse it twice with clean water, soak it in alcohol for 30 seconds, and dry it in a vacuum furnace at 200°C to obtain a cemented carbide substrate; Step 5: Place a layer of 99.9% pure 2um diamond powder (about 0.1mm thick) on the bottom of the metal cup. Then weigh the reduced mixed powder according to the thickness of the product specification and place it on the upper layer of the metal cup. Use a tool to flatten it inside the metal cup. Put the processed carbide substrate in to form an assembly. Step 6: Place the assembly into the assembled parts. First, place it in a six-sided press and use a pre-sintering process. The pressure is first increased to 2 GPa. Simultaneously, the temperature is raised to 900°C and held for 5 minutes for low-temperature, low-pressure pre-sintering. Once the assembly returns to room temperature, the assembled parts are placed into the press for high-temperature, high-pressure sintering. The pressure is first increased to 2 GPa and then held for 10 minutes. Once the pressure reaches 2 GPa, the temperature is simultaneously increased at a rate of 1°C / s to 1400°C. Finally, the pressure is increased to 5.5 GPa and held for 10 minutes. This results in an ultrafine polycrystalline diamond composite.

[0038] The ultrafine polycrystalline diamond composite sheet was ground and polished to perform plane processing. The microstructure of the ultrafine polycrystalline diamond composite sheet obtained in this embodiment was observed using a scanning electron microscope. Figure 3 As shown, the growth tissue is uniform, the particles are uniform, and there is no abnormal growth. Through ultrasonic scanning, as Figure 4 As shown, the internal growth structure is good, with no delamination or cracks.

[0039] Example 3 This embodiment provides an ultrafine polycrystalline diamond compact, comprising, in order, a cemented carbide YG10, an oxide layer, a polycrystalline diamond layer, and a surface insulation layer. The polycrystalline diamond layer is composed of diamond powder and a binder: by mass: 94% diamond powder and 6% binder; the diamond powder has a particle size of 0.5µm; the binder comprises the following raw material components and weights: 4% Co powder and 2% W powder. The surface insulation layer is a tungsten carbide layer. The ultrafine polycrystalline diamond compact provided in this embodiment has a diameter of Ø55mm, a cemented carbide substrate thickness of 3.5mm, and a polycrystalline diamond layer thickness of 0.5mm.

[0040] Example 4 The preparation method of the ultrafine polycrystalline diamond compact in Example 3 specifically comprises the following steps: Step 1: Weigh diamond powder and metal balls and place them into a catalyst pot. The weight ratio of diamond powder to cobalt balls and tungsten balls is 1:6:3 respectively. Mix them by wet mixing process, control the temperature and humidity. The temperature and humidity requirements are: ≤45%, temperature between 20-30℃, and mix for 50 hours. After mixing, place the mixed materials into a vacuum drying oven for drying, sieve out the metal balls, and calculate the binder content of 4% and 2% to obtain mixed diamond powder. Step 2: Place the mixed diamond powder into a vacuum furnace for reduction and raise the vacuum furnace temperature to 1×10 -3 The mixed diamond powder is heated and reduced under a vacuum of 1.5 Pa; the temperature is raised to 400°C within 20 minutes and kept at this temperature for 30 minutes; the temperature is then raised to 800°C within 30 minutes and kept at this temperature for 40 minutes; and finally the temperature is raised to 1000°C within 40 minutes and kept at this temperature for 200 minutes. During the holding period, hydrogen is introduced for 8-10 times for reduction, and the mixture is cooled in the furnace to obtain a reduced mixed powder; Step 3: Oxidation treatment of the surface of YG10 grade cemented carbide: Place the cemented carbide in an oxygen high-temperature furnace, first raise the temperature to 900°C, keep it warm for 0.5h, then raise the temperature to 1250°C, keep it warm for 1h, stop heating to room temperature, and form an oxide layer on the surface of the cemented carbide substrate.

[0041] Step 4: Clean the cemented carbide treated in step 3, rinse it with clean water three times, then soak it in alcohol for 20 seconds, and dry it in a vacuum furnace at 200°C to obtain a cemented carbide substrate; Step 5: Place a layer of tungsten carbide metal powder of about 0.1mm at the bottom of the metal cup, then weigh the reduced mixed powder according to the thickness of the product specification and place it on the upper layer of the metal cup. Use a tool to flatten it in the metal cup; buckle the processed cemented carbide substrate into it to form an assembly. Step 6: Place the assembly into the assembled parts. First, place it in a six-sided press and use a pre-sintering process to increase the pressure to 2 GPa. Simultaneously, raise the temperature to 800°C and hold for 5 minutes to perform low-temperature, low-pressure pre-sintering. Once the pressure reaches room temperature, place the assembled parts into the press for high-temperature, high-pressure sintering. Initially, increase the pressure to 2 GPa and hold for 10 minutes. Once the pressure reaches 2 GPa, simultaneously increase the temperature to 1400°C at a rate of 1°C / s. Finally, increase the pressure to 5.5 GPa and hold for 10 minutes. This results in an ultrafine polycrystalline diamond composite.

[0042] The ultrafine polycrystalline diamond composite sheet was ground and polished to perform plane processing. The microstructure of the ultrafine polycrystalline diamond composite sheet obtained in this embodiment was observed using a scanning electron microscope. Figure 5 As shown in the figure, the growth structure is uniform, the particles are uniform, and there is no abnormal growth. Through ultrasonic scanning, the internal growth structure is good, without delamination or cracks. Through ultrasonic scanning, as shown in the figure, the growth structure is uniform, the particles are uniform, and there is no abnormal growth. Through ultrasonic scanning, the internal growth structure is good, without delamination or cracks. Figure 4As shown, the internal growth structure is good, with no delamination or cracks.

[0043] Example 5 This embodiment provides an ultrafine polycrystalline diamond composite sheet, comprising, in order, a cemented carbide YG10, an oxide layer, a polycrystalline diamond layer, and a surface insulation layer. The polycrystalline diamond layer is composed of diamond powder and a binder, in percentage by mass: 80% diamond powder and 20% binder; the diamond powder has a particle size of 0.2 µm; the binder comprises the following raw material components and weights: 12% Co powder and 8% Ni powder. The surface insulation layer is a diamond powder layer. The ultrafine polycrystalline diamond composite sheet provided in this embodiment has a diameter of Ø55 mm, a cemented carbide substrate thickness of 3.5 mm, and a polycrystalline diamond layer thickness of 0.5 mm.

[0044] Example 6 The preparation method of the ultrafine polycrystalline diamond compact in Example 5 specifically comprises the following steps: Step 1: Weigh diamond powder and metal balls and place them into a catalyst pot, wherein the weight ratio of diamond powder to cobalt balls and nickel balls is 1:6:4 respectively, and mix them by a wet mixing process, controlling the temperature and humidity to ≤45% and between 20-30°C, and mix for 144 hours; the mixed materials are placed in a vacuum drying oven for drying, and the metal balls are sieved out. The binder content of the mixed materials is calculated to be 12% and 8%, respectively, to obtain mixed diamond powder; Step 2: Place the mixed diamond powder into a vacuum furnace for reduction and raise the vacuum furnace temperature to 1×10 -3 The mixed diamond powder is heated and reduced under a vacuum of 1.5 Pa; the temperature is raised to 400°C within 20 minutes and kept at this temperature for 30 minutes; the temperature is then raised to 800°C within 30 minutes and kept at this temperature for 40 minutes; and finally the temperature is raised to 1000°C within 40 minutes and kept at this temperature for 300 minutes. During the holding period, hydrogen is introduced for 8-10 times for reduction, and the mixture is cooled in the furnace to obtain a reduced mixed powder; Step 3: Oxidation treatment of the surface of YG10 grade cemented carbide: Place the cemented carbide in an oxygen high-temperature furnace, first raise the temperature to 900°C, keep it warm for 0.5h, then raise the temperature to 1250°C, keep it warm for 1h, stop heating to room temperature, and form an oxide layer on the surface of the cemented carbide substrate.

[0045] Step 4: Clean the cemented carbide treated in step 3, rinse it with clean water three times, then soak it in alcohol for 20 seconds, and dry it in a vacuum furnace at 200°C to obtain a cemented carbide substrate; Step 5: Place a layer of pure diamond powder (particle size 2um) about 0.1mm at the bottom of the metal cup, then weigh the reduced mixed powder according to the thickness of the product specification and place it on the upper layer of the metal cup. Use a tool to flatten it inside the metal cup; buckle the processed cemented carbide substrate into it to form an assembly. Step 6: Place the assembly into the assembled parts. First, place it in a six-sided press and use the pre-sintering process to increase the pressure to 4 GPa. Simultaneously, raise the temperature to 1000°C and hold for 8 minutes for low-temperature, low-pressure pre-sintering. Once it reaches room temperature, place the assembled parts into the press for high-temperature, high-pressure sintering. Initially, increase the pressure to 3 GPa and hold for 10 minutes. Once the pressure reaches 3 GPa, simultaneously increase the temperature to 1600°C at a rate of 1°C / s. Once the hold is complete, increase the pressure to 6 GPa over 30 minutes. Hold for 10 minutes. This results in an ultrafine polycrystalline diamond composite.

[0046] The ultrafine polycrystalline diamond composite sheet was ground and polished to perform plane processing. The microstructure of the ultrafine polycrystalline diamond composite sheet obtained in this embodiment was observed using a scanning electron microscope. Figure 6 As shown, the growth tissue is uniform, the particles are uniform, and there is no abnormal growth. Through ultrasonic scanning, as Figure 4 As shown, the internal growth structure is good, with no delamination or cracks.

[0047] Example 7 This embodiment provides an ultrafine polycrystalline diamond compact, comprising, in order, a cemented carbide YG10, an oxide layer, a polycrystalline diamond layer, and a surface insulation layer. The polycrystalline diamond layer is composed of diamond powder and a binder, in percentage by mass: 85% diamond powder and 15% binder; the diamond powder has a particle size of 0.5 µm; the binder is Co powder. The surface insulation layer is a tungsten carbide layer. The ultrafine polycrystalline diamond compact provided in this embodiment has a diameter of Ø55 mm, a cemented carbide substrate thickness of 3.5 mm, and a polycrystalline diamond layer thickness of 0.5 mm.

[0048] Example 8 This embodiment provides an ultrafine polycrystalline diamond compact, comprising, in order, a cemented carbide YG10, an oxide layer, a polycrystalline diamond layer, and a surface insulation layer. The polycrystalline diamond layer is composed of diamond powder and a binder, in percentage by mass: 85% diamond powder and 15% binder; the diamond powder has a particle size of 0.5 µm; the binder is tungsten powder. The surface insulation layer is a tungsten carbide layer. The ultrafine polycrystalline diamond compact provided in this embodiment has a diameter of Ø55 mm, a cemented carbide substrate thickness of 3.5 mm, and a polycrystalline diamond layer thickness of 0.5 mm.

Claims

1. Ultrafine polycrystalline diamond composite sheet, characterized in that: It includes a cemented carbide substrate, a polycrystalline diamond layer, and a surface isolation layer in sequence; the cemented carbide substrate includes cemented carbide and an oxide layer, and the oxide layer is connected to the polycrystalline diamond layer; the polycrystalline diamond layer is composed of diamond micropowder and a binder, and according to the mass percentage, the diamond micropowder accounts for 80-95%, and the binder accounts for 5-20%; the surface isolation layer is a carbide layer or a diamond micropowder layer.

2. The ultrafine polycrystalline diamond compact according to claim 1, characterized in that: The particle size of the diamond micropowder is 0.1 to 1.0 μm; The binder is any one or any two of nickel, cobalt, and tungsten; The carbide layer is any one of a tungsten carbide layer, a titanium carbide layer, and a zirconium carbide layer.

3. A method for preparing an ultrafine polycrystalline diamond composite sheet, characterized in that: The specific steps include: Step 1: Weigh diamond micropowder and metal balls and place them into a catalyst pot, and mix them by a wet mixing process; place the mixed materials into a vacuum drying oven for drying, and sieve out the metal balls to obtain mixed diamond micropowder; Step 2: Place the mixed diamond powder into a vacuum furnace for reduction to obtain reduced mixed powder; Step 3: Place the cemented carbide in an oxygen high-temperature furnace for surface oxidation treatment; Step 4: Rinse, soak, and dry the cemented carbide processed in step 3 to obtain a cemented carbide substrate; Step 5: Assembling the reduced mixed powder with the cemented carbide substrate to form an assembly; Step 6: The assembly is first placed in a six-sided top press for pre-sintering, and then the assembled parts are placed in the press for high temperature and high pressure sintering to obtain an ultrafine polycrystalline diamond composite sheet.

4. The method for preparing an ultrafine polycrystalline diamond compact according to claim 3, wherein: In step 1, the mass ratio of diamond powder to metal balls is 1:5-10; the metal balls are any one or any two of nickel balls, cobalt balls, and tungsten balls, and the metal purity of the metal balls is ≥99.9% and the diameter is 8-10 mm.

5. The method for preparing an ultrafine polycrystalline diamond compact according to claim 3, wherein: In step 1, the wet mixing process is specifically as follows: diamond micropowder and metal balls are mixed with alcohol for 50 to 150 hours, humidity ≤ 45%, and temperature 20-30° C.; the alcohol is ethanol or propanol; and the mass ratio of diamond micropowder to alcohol is 3 to 5:1; In step 1, the mixed material is placed in a vacuum drying oven for drying. Specifically, the mixed material is placed in a vacuum drying oven, the vacuum oven is evacuated to -0.01 to -0.1 MPa; the temperature is raised to 100° C. to 200° C., and the mixture is dried for 2 to 6 hours.

6. The method for preparing an ultrafine polycrystalline diamond compact according to claim 3, characterized in that: In step 2, the mixed diamond powder is placed in a vacuum furnace for reduction as follows: First, the vacuum furnace was raised to 1×10 -3 ~5×10 -3 Pa vacuum, the mixed diamond powder is heated to reduce, the temperature is raised to 350-400 ° C within 15-20 min, and the temperature is kept for 30-40 min; Then, the temperature is raised to 700-800°C within 20-30 minutes and kept at this temperature for 30-40 minutes; Finally, the temperature is raised to 900-1000°C within 30-40 minutes and kept warm for 200-300 minutes. During the warming stage, hydrogen is introduced for 8-10 times for reduction. The mixture is cooled to room temperature with the furnace to obtain a reduced mixed powder.

7. The method for preparing an ultrafine polycrystalline diamond compact according to claim 3, wherein: In step 3, the cemented carbide is YG10, and the thickness is 3 to 6 times that of the polycrystalline diamond layer; the surface oxidation treatment of the cemented carbide is specifically as follows: the cemented carbide is placed in an oxygen high-temperature furnace, first the temperature is raised to 800 to 1000 ° C, kept warm for 0.5 to 1 h, then the temperature is raised to 1200 to 1300 ° C, kept warm for 0.5 to 1 h, and then the heating is stopped to room temperature to form an oxide layer on the surface of the cemented carbide.

8. The method for preparing an ultrafine polycrystalline diamond compact according to claim 3, wherein: Step 4 is specifically as follows: the oxidized cemented carbide is rinsed with clean water 2 to 3 times, then immersed in alcohol for 20 to 30 seconds, and dried in a vacuum furnace at 150 to 250° C. to obtain a cemented carbide substrate.

9. The method for preparing an ultrafine polycrystalline diamond compact according to claim 3, wherein: Step 5 is specifically as follows: a layer of carbide metal powder or pure diamond micropowder is laid on the bottom of the metal cup, and then the reduced mixed powder is spread flat in the metal cup using a tool, and then the cemented carbide substrate is buckled into place to form an assembly; the carbide metal powder is any one of tungsten carbide, titanium carbide, and zirconium carbide, and the particle size of the carbide metal powder is ≤1um and the purity is ≥99.5%; the particle size of the pure diamond micropowder is ≤2um and the purity is ≥99.9%; the mass ratio of the carbide metal powder or diamond micropowder to the reduced mixed powder is 1:5~10.

10. The method for preparing an ultrafine polycrystalline diamond compact according to claim 3, characterized in that: In step 6: Pre-sintering process: Increase the pressure to 1-4 GPa and the temperature to 800-1300°C, and keep it at this temperature for 3-8 minutes; High-temperature and high-pressure sintering process: first increase the pressure to 2-3 GPa, maintain the pressure for 5-10 minutes, then increase the pressure to 5-6 GPa; after increasing the pressure to 2-3 GPa, increase the temperature to 1300-1600 °C at a rate of 0.5-2 °C / s; maintain the temperature for 5-20 minutes.

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