High-performance polycrystalline diamond compact and method for manufacturing the same

Abstract

The application relates to a high-performance polycrystalline diamond compact and a preparation method thereof. The polycrystalline diamond compact comprises a cemented carbide base layer and a polycrystalline diamond layer superimposed on the cemented carbide base layer; the preparation raw material of the polycrystalline diamond layer comprises 75-95 wt% of diamond micro powder and 5-25 wt% of a binder, the binder comprises metal Co powder and nonmetal Si powder, and the mass ratio of the metal Co powder and the nonmetal Si powder is (1-3):(1-3). The binder in the polycrystalline diamond layer of the polycrystalline diamond compact comprises metal Co and nonmetal Si, the characteristics of Co and Si as PCD binders are fully utilized, the prepared PCD compact has toughness, electrical conductivity, wear resistance and temperature resistance, the comprehensive performance of the PCD material is greatly improved, and the PCD compact has greater market competitiveness.

Description

Technical Field

[0001] This application relates to the field of polycrystalline diamond composite materials technology, and in particular to a high-performance polycrystalline diamond composite sheet and its preparation method. Background Technology

[0002] Polycrystalline diamond (PCD) composite sheets are a type of composite material made by high-temperature and high-pressure sintering of diamond micron powder, binder, and cemented carbide matrix (WC-Co). It features high hardness and good wear resistance and is widely used in industries such as oil drilling, geological exploration, coalfield drilling bits and machining tools. In machining, it is mainly used for the finishing of materials such as aluminum alloys, copper alloys, titanium alloys, and wood.

[0003] Currently, the industry commonly uses cobalt (Co) as a metallic binder or silicon (Si) as a non-metallic binder to synthesize PCD composite sheets by mixing them with diamond micropowder under high temperature and high pressure conditions. However, the synthesis mechanisms of these two binders are somewhat different, resulting in significant differences in the performance of the synthesized PCD composite sheets. Diamond-Co composite sheets have high wear resistance and good toughness, but poor high-temperature resistance. When used as cutting tools, they are prone to oxidation at high temperatures (above 700℃), leading to performance degradation. Simultaneously, they have poor electrical conductivity, making them difficult to process using conventional wire electrical discharge machining (EDM), thus limiting their application range. Diamond-Si composite sheets, on the other hand, have good heat resistance and high electrical conductivity, but due to the presence of the ceramic material SiC, they are relatively brittle and have lower wear resistance, limiting their application in certain situations.

[0004] Therefore, there is a need to provide a high-performance polycrystalline diamond composite sheet with good toughness and conductivity, as well as high wear resistance and temperature resistance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a high-performance polycrystalline diamond composite sheet that combines toughness, conductivity, wear resistance, and temperature resistance, thereby significantly improving the overall performance of PCD materials and giving them greater market competitiveness.

[0006] To this end, the first aspect of this application provides a high-performance polycrystalline diamond composite sheet, the polycrystalline diamond composite sheet comprising a cemented carbide substrate layer and a polycrystalline diamond layer superimposed on the cemented carbide substrate layer; the polycrystalline diamond layer comprises 75-95 wt% diamond micro powder and 5-25 wt% binder based on the total weight of the raw materials for preparing the polycrystalline diamond layer, the binder comprising metallic Co powder and non-metallic Si powder, the mass ratio of metallic Co powder to non-metallic Si powder being (1-3):(1-3).

[0007] The polycrystalline diamond (PCD) composite sheet described in this application uses a binder comprising both metallic Co and non-metallic Si. Co is melted under high temperature and pressure, causing partial graphitization of the diamond surface. When the diamond stability region is reached, some graphite is converted back into diamond, forming strong diamond-diamond bonds, resulting in high wear resistance. Simultaneously, due to the formation of partial metallic solid solutions between diamonds, the toughness is also excellent. Furthermore, under high temperature and pressure, diamond reacts chemically with Si to form silicon carbide (SiC). During sintering, the Si content gradually decreases while the SiC content gradually increases. When the Si content is almost exhausted, slow graphitization begins on the diamond surface. The content of both graphite and silicon carbide increases with sintering time; graphite has better electrical conductivity, and SiC has high heat resistance. This application fully utilizes the above-mentioned characteristics of Co and Si, using them in a specific ratio as binders to synthesize a PCD composite sheet with excellent overall performance.

[0008] Furthermore, by controlling the mass ratio of metallic Co and non-metallic Si within the range of (1-3):(1-3), especially within 1:1, this application can improve the overall performance of the final PCD composite sheet.

[0009] In some embodiments, the diamond powder includes coarse-grained diamond powder with a particle size of 8-12 μm, medium-grained diamond powder with a particle size of 3-5 μm, and fine-grained diamond powder with a particle size of 1-3 μm.

[0010] The diamond micro powder used in this application is a mixed-size diamond micro powder, which includes three particle sizes: coarse, medium, and fine. Selecting diamond micro powder containing the above-mentioned particle size range can achieve the purpose of fine particles filling the gaps between coarse particles, thereby effectively increasing the density of the initial powder and ultimately increasing the density of the synthesized PCD composite sheet, resulting in a PCD composite sheet with superior performance.

[0011] In some embodiments, based on the total weight of the raw materials used to prepare the polycrystalline diamond layer, the content of the coarse-grained diamond powder is 50-65 wt%, the content of the medium-grained diamond powder is 10-25 wt%, and the content of the fine-grained diamond powder is 5-15 wt%.

[0012] By controlling the content of diamond microparticles of various particle sizes in polycrystalline diamond microparticles within the above-mentioned range, this application can further improve the density of the final synthesized PCD composite sheet, thus making its performance better.

[0013] In some embodiments, the particle size of the metal Co powder and the non-metal Si powder in the binder is independently 1 to 2 μm.

[0014] The particle size of the binder selected in this application has a significant impact on the final PCD composite sheet. Since the binder is always positioned between the diamond microparticles, its particle size must be smaller than the principal particle size of the diamond microparticles, ideally about 1 / 5 of the principal particle size. This ensures the binder can fully and uniformly coat the diamond microparticles and perform its optimal function. Choosing a smaller binder particle size can easily lead to uneven mixing, resulting in a high oxygen content in the overall microparticles. Conversely, choosing a coarser binder can lead to less contact between diamond microparticles, poor bonding between diamond particles, and ultimately reduced overall performance of the resulting PCD composite sheet.

[0015] In some of the most preferred embodiments, the raw materials for preparing the polycrystalline diamond layer, by weight of total weight, include 90 wt% diamond micropowder (60 wt% of coarse-grained diamond micropowder, 20 wt% of medium-grained diamond micropowder, and 10 wt% of fine-grained diamond micropowder) and 10 wt% binder, wherein the binder comprises metallic Co powder and non-metallic Si powder, both with a particle size of 1-2 μm, and the mass ratio of metallic Co to non-metallic Si is 1:1.

[0016] When the raw materials for preparing the polycrystalline diamond layer in the polycrystalline diamond composite sheet of this application are as described above, the overall performance of the final polycrystalline diamond composite sheet, such as toughness, conductivity, wear resistance, and temperature resistance, can be optimized, thereby maximizing the overall performance of the PCD material. When made into cutting tools, it can significantly improve the tool life, reduce the material processing cost, and have greater market competitiveness.

[0017] In some embodiments, the thickness ratio of the cemented carbide matrix layer to the polycrystalline diamond layer in the polycrystalline diamond composite sheet is (3-5):1.

[0018] In this application, the thickness of the cemented carbide matrix layer and the polycrystalline diamond layer in the polycrystalline diamond composite sheet can be adjusted according to actual needs. When the thickness ratio of the cemented carbide matrix layer to the polycrystalline diamond layer is controlled at (3~5):1, such as 4:1, the polycrystalline diamond composite sheet can be applied to a wider market.

[0019] The cemented carbide matrix used in this application is a cobalt-containing cemented carbide, and the cobalt content in the cemented carbide can range from 8 to 16 wt%.

[0020] The second aspect of this application provides a method for preparing polycrystalline diamond composite sheets as described in the first aspect of this application, the method comprising the following steps:

[0021] S1, the mixed powder of diamond micro powder and binder is dried and then placed in a vacuum furnace for reduction to obtain the reduced powder;

[0022] S2, the reduced mixed powder is encapsulated with the cemented carbide matrix and then composited under high temperature and high pressure conditions to obtain the polycrystalline diamond composite sheet.

[0023] The preparation method of the polycrystalline diamond composite sheet described in this application is simple. During the preparation process, by selecting a binder containing both metallic Co powder and non-metallic Si powder, and sintering under high temperature and high pressure conditions, the final PCD composite sheet can have toughness, conductivity, wear resistance and temperature resistance, resulting in a PCD composite sheet with better comprehensive performance.

[0024] In some embodiments, in step S1, the mixing method is wet mixing, the dispersant used in the wet mixing process is alcohol, and the ratio of the total mass of diamond micro powder and binder to the mass of dispersant is (2-3):1.

[0025] The wet mixing method used in this application can make the mixture more uniform. During the wet mixing process, controlling the amount of powder (diamond micro powder and binder) and dispersant (alcohol) within the above range helps to improve the uniformity of the mixture.

[0026] In some embodiments, the drying is carried out in a vacuum oven, and the drying conditions are: drying at 50-60°C for 1.5-2 hours, followed by drying at 130-150°C for 1-2 hours.

[0027] In this application, the vacuum degree inside the vacuum oven can be (1~5)×10⁻⁶. -2 Pa, such as 2×10 -2 Pa.

[0028] In some specific embodiments, the drying conditions are: drying at 50°C for 2 hours, and then drying at 150°C for 1 hour.

[0029] In some implementations, in step S1, the reduction process is as follows: in (1~5)×10 -3 The mixed powder is heated under a vacuum of Pa; the heating process is as follows: the temperature is raised to 350-400℃ within 15-20 minutes and held for 30-40 minutes; then the temperature is raised to 700-800℃ within 20-30 minutes and held for 120-150 minutes.

[0030] In some specific embodiments, the restoration process is as follows: at 2×10 -3 The mixed powder is heated under a vacuum of Pa; the heating process is as follows: heat up to 400°C for 20 minutes and hold for 30 minutes; then heat up to 800°C for 30 minutes and hold for 120 minutes.

[0031] In some embodiments, in step S2, the pressure during the compounding process is 5.2–5.8 GPa, the temperature is 1400–1600 °C, and the time is 5–15 min.

[0032] Under the above composite conditions, the packaged preforms can be effectively composited to obtain PCD composite sheets with better overall performance.

[0033] The beneficial technical effects of this application are as follows: The binder in the polycrystalline diamond layer of the polycrystalline diamond composite sheet described in this application includes both metallic Co and non-metallic Si. By fully utilizing the characteristics of Co and Si as PCD binders, a PCD composite sheet with excellent comprehensive performance is synthesized. Compared with the prior art, the PCD composite sheet obtained in this application combines toughness, conductivity, wear resistance, and temperature resistance, which can significantly improve the comprehensive performance of PCD materials. When made into cutting tools, it can significantly improve the tool life, reduce material processing costs, and have greater market competitiveness. Detailed Implementation

[0034] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0035] Example 1: Preparation of polycrystalline diamond composite sheet

[0036] The raw material composition of the polycrystalline diamond layer is as follows: 60wt% coarse diamond powder of 8-12µm; 20wt% medium-sized diamond powder of 3-5µm; 10wt% fine-sized diamond powder of 1-3µm; 5wt% metallic Co powder of 1-2µm; 5wt% non-metallic Si powder of 1-2µm; the content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0037] The cemented carbide matrix in the cemented carbide matrix layer is cemented carbide YG10 with a cobalt content of 10wt%.

[0038] Preparation process: The diamond micro powder and binder were mixed using a wet mixing method. Alcohol was used as the dispersant during the wet mixing process, and the mass ratio of powder (diamond micro powder and binder) to dispersant was 2:1. The wet-mixed powder was then placed in a vacuum oven for drying. The drying process involved first drying at 50°C for 2 hours, then increasing the temperature to 150°C for 1 hour. The vacuum degree of the oven was 2 × 10⁻⁶. -2Pa. The dried mixed powder is placed in a vacuum furnace for vacuum reduction to remove oxygen and moisture. The specific process is as follows: the vacuum pumps of each stage of the vacuum furnace are turned on sequentially to perform vacuuming until a vacuum level of 2 × 10⁻⁶ is reached. -3 The process involves heating to a high vacuum level of 5.5 GPa for 20 minutes, holding at 400°C for 30 minutes, then heating to 800°C for 120 minutes. The reduced mixed powder is then encapsulated with a cemented carbide substrate. The encapsulated preform is then calcined at 1500°C for 10 minutes to obtain a polycrystalline diamond composite sheet. The polycrystalline diamond layer in the composite sheet has a thickness of 1.0 mm, and the cemented carbide substrate layer has a thickness of 4.0 mm, with a thickness ratio of 4:1.

[0039] Example 2: Preparation of polycrystalline diamond composite sheet

[0040] The raw material composition of the polycrystalline diamond layer is as follows: 55wt% coarse diamond powder of 8-12µm; 25wt% medium diamond powder of 3-5µm; 10wt% fine diamond powder of 1-3µm; 5wt% metallic Co powder of 1-2µm; 5wt% non-metallic Si powder of 1-2µm; the content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0041] The rest is the same as in Example 1.

[0042] Example 3: Preparation of polycrystalline diamond composite sheet

[0043] The raw material composition of the polycrystalline diamond layer is as follows: 50wt% coarse diamond powder of 8-12µm; 25wt% medium-sized diamond powder of 3-5µm; 15wt% fine-sized diamond powder of 1-3µm; 5wt% metallic Co powder of 1-2µm; 5wt% non-metallic Si powder of 1-2µm; the content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0044] The rest is the same as in Example 1.

[0045] Example 4: Preparation of polycrystalline diamond composite sheet

[0046] The raw material composition of the polycrystalline diamond layer is as follows: 60wt% coarse diamond powder of 8-12µm; 20wt% medium-sized diamond powder of 3-5µm; 10wt% fine-sized diamond powder of 1-3µm; 7.5wt% metallic Co powder of 1-2µm; 2.5wt% non-metallic Si powder of 1-2µm; the content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 3:1.

[0047] The rest is the same as in Example 1.

[0048] Example 5: Preparation of polycrystalline diamond composite sheet

[0049] The raw material composition of the polycrystalline diamond layer is as follows: 60wt% coarse diamond powder of 8-12µm; 20wt% medium-sized diamond powder of 3-5µm; 10wt% fine-sized diamond powder of 1-3µm; 2.5wt% metallic Co powder of 1-2µm; and 7.5wt% non-metallic Si powder of 1-2µm. The content of diamond powder in the raw material is 90wt%, and the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:3.

[0050] The rest is the same as in Example 1.

[0051] Example 6: Preparation of polycrystalline diamond composite sheet

[0052] The raw material composition of the polycrystalline diamond layer is as follows: 55wt% coarse diamond powder of 8-12µm; 15wt% medium-sized diamond powder of 3-5µm; 10wt% fine-sized diamond powder of 1-3µm; 12wt% metallic Co powder of 1-2µm; and 8wt% non-metallic Si powder of 1-2µm. The content of diamond powder in the raw material is 80wt%, the content of binder is 20wt%, and the mass ratio of metallic Co powder to non-metallic Si powder in the binder is 1.5:1.

[0053] The rest is the same as in Example 1.

[0054] Example 7: Preparation of polycrystalline diamond composite sheet

[0055] The raw material composition of the polycrystalline diamond layer is as follows: 65wt% coarse diamond powder of 8-12µm, 25wt% medium diamond powder of 3-5µm, 5wt% metallic Co powder of 1-2µm, and 5wt% non-metallic Si powder of 1-2µm. The content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0056] The rest is the same as in Example 1.

[0057] Example 8: Preparation of polycrystalline diamond composite sheet

[0058] The raw material composition of the polycrystalline diamond layer is as follows: 50wt% medium-grained diamond powder of 3-5µm, 40wt% fine-grained diamond powder of 1-3µm; 5wt% metallic Co powder of 1-2µm; 5wt% non-metallic Si powder of 1-2µm; the content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0059] The rest is the same as in Example 1.

[0060] Example 9: Preparation of polycrystalline diamond composite sheet

[0061] The raw material composition of the polycrystalline diamond layer is as follows: 70wt% coarse diamond powder of 8-12µm, 20wt% fine diamond powder of 1-3µm, 5wt% metallic Co powder of 1-2µm, and 5wt% non-metallic Si powder of 1-2µm. The content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0062] The rest is the same as in Example 1.

[0063] Example 10: Preparation of polycrystalline diamond composite sheet

[0064] The raw material composition of the polycrystalline diamond layer is as follows: 60wt% coarse diamond powder of 8-12µm; 20wt% medium-sized diamond powder of 3-5µm; 10wt% fine diamond powder of 1-3µm; 5wt% metallic Co powder of 8-10µm; 5wt% non-metallic Si powder of 8-10µm; the content of diamond powder in the raw material is 90wt%, the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0065] The rest is the same as in Example 1.

[0066] Example 11: Preparation of polycrystalline diamond composite sheet

[0067] The raw material composition of the polycrystalline diamond layer is as follows: 60wt% coarse diamond powder of 8-12µm; 20wt% medium-sized diamond powder of 3-5µm; 10wt% fine diamond powder of 1-3µm; 5wt% metallic Co powder of 0.1-0.5µm; and 5wt% non-metallic Si powder of 0.1-0.5µm. The content of diamond powder in the raw material is 90wt%, and the content of binder is 10wt%, and the mass ratio of metallic Co powder and non-metallic Si powder in the binder is 1:1.

[0068] The rest is the same as in Example 1.

[0069] Example 12: Preparation of polycrystalline diamond composite sheet

[0070] The raw materials for the polycrystalline diamond layer and the cemented carbide matrix layer are the same as in Example 1.

[0071] Preparation process: The diamond micro powder and binder were mixed using a wet mixing method. Alcohol was used as the dispersant during the wet mixing process, and the mass ratio of powder (diamond micro powder and binder) to dispersant was 2:1. The wet-mixed powder was then placed in a vacuum oven for drying. The drying process involved drying at 150℃ for 2 hours, with a vacuum degree of 2×10⁻⁶. -2 Pa. The dried mixed powder is placed in a vacuum furnace for vacuum reduction to remove oxygen and moisture. The specific process is as follows: the vacuum pumps of each stage of the vacuum furnace are turned on sequentially to perform vacuuming until a vacuum level of 2 × 10⁻⁶ is reached. -3 The process involves heating to a high vacuum level of 5.5 GPa for 20 minutes, holding at 400°C for 30 minutes, then heating to 800°C for 120 minutes. The reduced mixed powder is then encapsulated with a cemented carbide substrate. The encapsulated preform is then calcined at 1500°C for 10 minutes to obtain a polycrystalline diamond composite sheet. The polycrystalline diamond layer in the composite sheet has a thickness of 1.0 mm, and the cemented carbide substrate layer has a thickness of 4.0 mm, with a thickness ratio of 4:1.

[0072] Example 13: Preparation of polycrystalline diamond composite sheet

[0073] The raw materials for the polycrystalline diamond layer and the cemented carbide matrix layer are the same as in Example 1.

[0074] Preparation process: The diamond micro powder and binder were mixed using a wet mixing method. Alcohol was used as the dispersant during the wet mixing process, and the mass ratio of powder (diamond micro powder and binder) to dispersant was 2:1. The wet-mixed powder was then placed in a vacuum oven for drying. The drying process involved first drying at 50°C for 2 hours, then increasing the temperature to 150°C for 1 hour. The vacuum degree of the oven was 2 × 10⁻⁶. -2 Pa. The dried mixed powder is placed in a vacuum furnace for vacuum reduction to remove oxygen and moisture. The specific process is as follows: the vacuum pumps of each stage of the vacuum furnace are turned on sequentially to perform vacuuming until a vacuum level of 2 × 10⁻⁶ is reached. -3The process involves heating to a high vacuum level of 5.5 GPa, followed by a 20-minute heating process to 350°C and a 40-minute holding period, then a 30-minute heating process to 700°C and a 150-minute holding period. The reduced mixed powder is then encapsulated with a cemented carbide substrate. The encapsulated preform is then calcined at 1500°C for 10 minutes to obtain a polycrystalline diamond composite sheet. The polycrystalline diamond layer in the composite sheet has a thickness of 1.0 mm, and the cemented carbide substrate layer has a thickness of 4.0 mm, with a thickness ratio of 4:1.

[0075] Test case

[0076] The toughness, conductivity, wear resistance, and temperature resistance of the polycrystalline diamond composite sheets prepared in Examples 1-13 were tested. The fracture toughness of the polycrystalline diamond composite sheets was calculated by measuring the length of the crack extending from the four corners of the indentation created by the Vickers hardness tester. Conductivity was characterized by the length of the cutting line per unit time using wire electrical discharge machining (EDM); a longer cutting line per unit time indicates better conductivity. Wear resistance was measured using a wear ratio tester. Temperature resistance was determined by heating the composite sheet at high temperature in a vacuum furnace to determine the graphitization temperature of the diamond layer. Specific test results are shown in Table 1.

[0077] Table 1

[0078]

[0079] As shown in Table 1, the fracture toughness of the polycrystalline diamond composite sheets synthesized in Examples 1-13 of this application is 8.4–11.2 MPa / m. 2 The unit time cutting line length used to characterize conductivity is 0.35 to 0.5 mm / min, the wear ratio is 501,000 to 605,000, and the heat resistance temperature is 701 to 739℃, indicating that the polycrystalline diamond composite sheet provided in this application has toughness, conductivity, wear resistance and temperature resistance.

[0080] The test results from Examples 1 and 7-9 show that when the diamond powder used includes coarse (8-12 μm), medium (3-5 μm), and fine (1-3 μm) diamond powders, the density of the initial powder can be effectively increased, resulting in superior performance of the obtained PCD composite sheet. The test results from Examples 1-3 show that when the content of coarse diamond powder is 60 wt%, the content of medium-sized diamond powder is 20 wt%, and the content of fine-sized diamond powder is 10 wt%, the overall performance of the PCD composite sheet can be further improved.

[0081] The test results from Examples 1 and 10-11 show that when the particle size of both the metal Co powder and the non-metal Si powder in the binder is controlled within 1 to 2 μm, it helps to improve the overall performance of the PCD composite sheet.

[0082] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. A high-performance polycrystalline diamond composite sheet, characterized in that, The polycrystalline diamond composite sheet includes a cemented carbide substrate layer and a polycrystalline diamond layer superimposed on the cemented carbide substrate layer; based on the total weight of the raw materials for preparing the polycrystalline diamond layer, the raw materials for preparing the polycrystalline diamond layer include 75~95wt% diamond micro powder and 5~25wt% binder, the binder includes metallic Co powder and non-metallic Si powder, and the mass ratio of metallic Co powder and non-metallic Si powder is (1~3):(1~3); The diamond micro powder comprises coarse-grained diamond micro powder with a particle size of 8-12 μm, medium-grained diamond micro powder with a particle size of 3-5 μm, and fine-grained diamond micro powder with a particle size of 1-3 μm. Based on the total weight of the raw materials used to prepare the polycrystalline diamond layer, the content of the coarse-grained diamond micro powder is 50-65 wt%, the content of the medium-grained diamond micro powder is 10-25 wt%, and the content of the fine-grained diamond micro powder is 5-15 wt%. The particle size of the metal Co powder and the non-metal Si powder in the binder is 1~2 μm, respectively.

2. The polycrystalline diamond composite sheet according to claim 1, characterized in that, The thickness ratio of the cemented carbide matrix layer to the polycrystalline diamond layer in the polycrystalline diamond composite sheet is (3~5):

1.

3. A method for preparing a polycrystalline diamond composite sheet as described in claim 1 or 2, characterized in that, The method includes the following steps: S1, the mixed powder of diamond micro powder and binder is dried and then placed in a vacuum furnace for reduction to obtain the reduced powder; S2, the reduced mixed powder is encapsulated with the cemented carbide matrix and then composited under high temperature and high pressure conditions to obtain the polycrystalline diamond composite sheet.

4. The method according to claim 3, characterized in that, In step S1, the mixing method is wet mixing, the dispersant used in the wet mixing process is alcohol, and the ratio of the total mass of diamond micro powder and binder to the mass of dispersant is (2~3):

1.

5. The method according to claim 3 or 4, characterized in that, The drying is carried out in a vacuum oven, and the drying conditions are: drying at 50~60℃ for 1.5~2 hours, and then drying at 130~150℃ for 1~2 hours.

6. The method according to claim 3 or 4, characterized in that, In step S1, the reduction process is as follows: in (1~5)×10 -3 The mixed powder is heated under a vacuum of Pa; the heating process is as follows: the temperature is raised to 350-400 °C within 15-20 min and held for 30-40 min; then the temperature is raised to 700-800 °C within 20-30 min and held for 120-150 min.

7. The method according to claim 3 or 4, characterized in that, In step S2, the pressure during the compounding process is 5.2~5.8 Gpa, the temperature is 1400~1600 ℃, and the time is 5~15 min.

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