A method for preparing a polycrystalline diamond compact and its application in a drill bit

Abstract

This application relates to the field of superhard materials technology, specifically disclosing a method for preparing polycrystalline diamond composite sheets and their application in drill bits. The method for preparing the polycrystalline diamond composite sheet includes the following steps: S1, molding and sintering WC powder and Co to obtain a cemented carbide substrate; S2, grafting multi-walled carbon nanotubes with free radicals to obtain modified multi-walled carbon nanotubes; S3, surface-treating diamond micropowder to obtain modified diamond micropowder; S4, processing the modified diamond micropowder, modified multi-walled carbon nanotubes, N-rGO, Ti powder, etc., to obtain a powder, which is then combined with the cemented carbide substrate to obtain the polycrystalline diamond composite sheet. This application uses modified diamond and composite reinforcing phases to solve the problems of weak interfaces and thermal stress concentration within the polycrystalline diamond composite sheet, while simultaneously improving structural integrity and impact resistance at high temperatures.

Description

Technical Field

[0001] This application relates to the field of superhard materials technology, specifically to a method for preparing polycrystalline diamond composite sheets and drill bits. Background Technology

[0002] Polycrystalline diamond composite sheets are high-performance superhard composite materials, formed by sintering micron- or submicron-sized diamond powder with a cemented carbide substrate under ultra-high pressure and high temperature conditions with the aid of a metal catalyst. They employ a layered structure, with a high-purity, dense polycrystalline diamond layer on top and a cemented carbide substrate on the bottom. These two layers are metallurgically bonded to form a robust whole, possessing both the ultra-high hardness, excellent wear resistance, high thermal conductivity, and low coefficient of friction of diamond, and the strength, toughness, and weldability of cemented carbide, thus overcoming the anisotropy and fragility of natural diamond.

[0003] Polycrystalline diamond composite sheets possess self-sharpening properties during operation, maintaining a consistently sharp cutting edge and exhibiting wear resistance far exceeding that of conventional cemented carbide, significantly extending tool life and improving work efficiency. However, this material has limited stability at high temperatures and readily reacts with iron group elements, making it unsuitable for machining steel materials. Furthermore, its inherent brittleness results in relatively weak resistance to severe impacts. Due to its unique comprehensive properties, polycrystalline diamond composite sheets are widely used in drill bits for oil and gas drilling, geological exploration, and mining, as well as in the precision machining of non-ferrous metals and non-metallic materials.

[0004] The high-temperature stability defect of polycrystalline diamond stems from the fact that metal catalysts significantly lower the thermal stability temperature of diamond, accelerating its conversion to graphite at high temperatures. Therefore, it is necessary to reduce or remove metal catalysts at grain boundaries. Existing technologies, such as CN104532016A, disclose a cobalt removal method using a composite acid based on synthetic polycrystalline diamond composite sheets. This method efficiently, safely, and pollution-free removes metallic cobalt from the polycrystalline diamond composite sheets.

[0005] While acid washing can remove some metal catalysts such as cobalt, the process is time-consuming, inefficient, and may damage the cemented carbide substrate. Introducing reinforcing phases such as carbon nanotubes and graphene can improve performance to some extent, but their effect on improving thermal stability is limited. Furthermore, improving thermal stability through reinforcing phases requires ensuring compatibility between the reinforcing phase and the substrate.

[0006] Therefore, while ensuring the performance improvement of the reinforcing phase, solving the thermal stability defects of polycrystalline diamond composite sheets has become the key. Summary of the Invention

[0007] To address the issues of poor high-temperature stability and high brittleness of polycrystalline diamond composite sheets, this application provides a method for preparing polycrystalline diamond composite sheets and their application in drill bits.

[0008] This invention uses modified multi-walled carbon nanotubes and N-rGO (nitrogen-doped reduced graphene oxide) as a reinforcing phase. The complementary spatial structures of the two carbon nanomaterials form a three-dimensional network, which retains the fiber toughening and crack bridging effects of multi-walled carbon nanotubes, while the layered structure of N-rGO fills the gaps between diamond grains, improving density. At the same time, the active sites introduced by nitrogen doping can enhance the covalent bond with the modified diamond surface, avoiding the aggregation of the reinforcing phase.

[0009] Multi-walled carbon nanotubes are grafted with modified monomers containing double bonds under the action of an initiator and polymerized on the surface of carbon nanotubes. The functional groups of the resulting modified multi-walled carbon nanotubes can form chemical bonds with the ceramic layer on the surface of the modified diamond during sintering, resulting in a stronger interfacial bond.

[0010] This invention involves surface vapor-phase coating of diamond, where the precursor adsorption layer is pyrolyzed to transform into an amorphous binder layer containing silanol and aluminumol hydroxyl groups, yielding modified diamond micropowder. This binder layer has a loose structure and high activity, which is crucial for the in-situ formation of a composite ceramic coating on the diamond surface during subsequent high-temperature and high-pressure sintering. Functional groups on the surface of modified carbon nanotubes react with hydroxyl groups on the diamond surface to form preliminary chemical bonds. Subsequently, this initial interface structure evolves under high pressure and temperature, with the carbon source in the system and silicon, aluminum, and titanium in the interface region forming a covalently bonded ceramic transition layer mainly composed of SiC and TiC in situ. This transition layer forms a strong chemical and physical bond with both diamond and carbon nanotubes, thus constructing a complete diamond-ceramic layer-carbon nanomaterial continuous phase. The three-dimensional composite reinforcement phase solves the problems of weak interfaces and thermal stress concentration within polycrystalline diamond composite sheets, and the reinforcement between interfaces allows it to better maintain structural integrity under high temperature and impact.

[0011] In a first aspect, this application provides a method for preparing a polycrystalline diamond composite sheet, comprising the following steps:

[0012] S1. Add WC powder and Co powder into the mold, mold it at 200-300MPa, heat it to 1400-1500℃ at 5℃ / min, sinter it for 1-3h under vacuum degree ≤10Pa, spray corundum sand on the surface after sintering, ultrasonically clean it and dry it to obtain a cemented carbide substrate.

[0013] S2. Add multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate to a 5% ethanol aqueous solution, disperse evenly by ultrasonication, add modified monomer and initiator, heat to 60-70℃ and stir for 3-5 hours under nitrogen protection, cool to room temperature, centrifuge, wash and dry to obtain modified multi-walled carbon nanotubes.

[0014] S3. Add KH-560 and aluminum isopropoxide to ethanol to obtain a precursor solution. Vapor phase coating is carried out at 110-130℃ and vacuum degree ≤5Pa for 1-3h to uniformly coat the surface of diamond micro powder. Calcination and curing are carried out at 400-500℃ for 1-2h under argon atmosphere to obtain modified diamond micro powder.

[0015] S4. Modified diamond micro powder, modified multi-walled carbon nanotubes, N-rGO, Ti powder, and polyethylene glycol are added to ethanol, ultrasonically dispersed, ball-milled, dried and granulated. The resulting powder is loaded into a graphite mold, a cemented carbide substrate is placed at the bottom, and sintered at a constant temperature after gradient pressure increase. After cooling and depressurization, a preliminary blank is obtained. After vacuum annealing, dilute hydrochloric acid is added and ultrasonically washed for 10-20 minutes. The surface is polished to obtain a polycrystalline diamond composite sheet.

[0016] Furthermore, the mass ratio of WC powder to Co powder is 90-100:6.

[0017] Furthermore, the mass ratio of the multi-walled carbon nanotubes to sodium dodecylbenzenesulfonate and ethanol aqueous solution is 100:4-6:800-1000.

[0018] Furthermore, the modified monomer is one of hydroxyethyl methacrylate, glycidyl acrylate, monomethyl maleate, or monobutyl itaconic acid, and the mass ratio of the modified monomer to the initiator and multi-walled carbon nanotubes is 15-25:1-1.5:100.

[0019] Furthermore, the mass ratio of KH-560 to aluminum isopropoxide and ethanol is 10-20:6-10:100.

[0020] Furthermore, in step S3, the diamond micro powder is a mixture of two types of micro powder, 20-30μm and 1-3μm, in a mass ratio of 70:10-30.

[0021] Furthermore, the mass ratio of the modified diamond micro powder, modified multi-walled carbon nanotubes, N-rGO, Ti powder, polyethylene glycol, and ethanol is 85-95:0.4-0.6:0.1-0.3:0.2-0.4:0.05-0.1:5.

[0022] Furthermore, in step S4, the pressure is gradually increased to 3.0 GPa, and after holding at that temperature for 10 minutes, it is increased to 5-6 GPa.

[0023] Furthermore, in step S4, the isothermal sintering involves heating at 50°C / min to 1350°C-1450°C and holding at that temperature and pressure for 3-5 minutes. The cooling and depressurization involves holding at pressure while in the furnace and cooling down at 20°C / min to 550-650°C, and then depressurizing to atmospheric pressure.

[0024] Secondly, this application provides a polycrystalline diamond composite sheet prepared by the above-described preparation method.

[0025] Thirdly, this application provides the application of the polycrystalline diamond composite sheet prepared by the above preparation method in drill bits.

[0026] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0027] 1. By surface-treating diamond, the precursor adsorption layer is pyrolyzed into an amorphous binder layer containing silanol and aluminol hydroxyl groups, yielding modified diamond micropowder. This binder layer has a loose structure and high activity, which is crucial for the in-situ formation of a composite ceramic coating on the diamond surface during subsequent high-temperature and high-pressure sintering.

[0028] 2. Modified multi-walled carbon nanotubes and N-rGO composites are used as the reinforcing phase. The spatial structural complementarity of the two carbon nanomaterials is utilized to form a three-dimensional network, which can not only improve the density but also avoid the aggregation of the reinforcing phase, thus ensuring compatibility.

[0029] 3. The functional groups of modified multi-walled carbon nanotubes can form chemical bonds with the ceramic layer on the surface of modified diamond during the initial sintering. After sintering, a continuous interface of diamond-ceramic layer-carbon nanomaterial is finally formed, which together improves the structural integrity and impact resistance at high temperatures. Detailed Implementation

[0030] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0031] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0034] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0035] WC powder, particle size: 1-3μm, carbon content 6.1-6.2%;

[0036] Co powder, particle size: 0.5-1μm;

[0037] Multi-walled carbon nanotubes, diameter: 20-40 nm, aspect ratio: 50:1;

[0038] N-rGO, number of layers: 3-5 layers; nitrogen doping content: 10%;

[0039] Ti powder, average particle size: 50nm;

[0040] KH-560 is γ-glycidyl etheroxypropyltrimethoxysilane, CAS No.: 2530-83-8;

[0041] The number-average molecular weight of polyethylene glycol is 2000.

[0042] Example 1

[0043] A method for preparing a polycrystalline diamond composite sheet includes the following steps:

[0044] S1. Add 94 parts of WC powder and 6 parts of Co powder into a mold, mold it at 200 MPa, heat it to 1450℃ at 5℃ / min, sinter it at a vacuum of 5 Pa for 2 hours, spray corundum sand on the surface after sintering, ultrasonically clean it and dry it to obtain a cemented carbide substrate.

[0045] S2. Add 100 parts of multi-walled carbon nanotubes and 5 parts of sodium dodecylbenzenesulfonate to 1000 parts of 5% ethanol aqueous solution, disperse evenly by ultrasonication, add 20 parts of hydroxyethyl methacrylate and 1.2 parts of ammonium persulfate, heat to 65℃ and stir for 4 hours under nitrogen protection, cool to room temperature, centrifuge, wash and dry to obtain modified multi-walled carbon nanotubes.

[0046] S3. Add 1.5 parts KH-560 and 0.8 parts aluminum isopropoxide to 10 parts anhydrous ethanol to obtain a precursor solution. Vacuum-phase coating is carried out at 120℃ and 5Pa for 2 hours to uniformly coat the precursor onto the surface of diamond micro powder. The diamond micro powder is a mixture of 20-30μm and 1-3μm micro powders in a mass ratio of 70:20. Calcination and curing are carried out at 450℃ for 1.5 hours under an argon atmosphere to obtain modified diamond micro powder.

[0047] S4. 90 parts of modified diamond micro powder, 0.5 parts of modified multi-walled carbon nanotubes, 0.2 parts of N-rGO, 0.3 parts of Ti powder, and 0.07 parts of polyethylene glycol were added to 5 parts of anhydrous ethanol. After ultrasonic dispersion, the mixture was ball-milled, dried, and granulated. The powder obtained by passing through a 200-mesh sieve was loaded into a graphite mold, with a cemented carbide substrate placed at the bottom. The pressure was increased to 3.0 GPa and held for 10 min, then increased to 5.5 GPa and held for 10 min. At 5.5 GPa, the temperature was increased to 1400℃ at 50℃ / min and held for 3 min. The pressure was maintained while the furnace was cooled to 600℃ at 20℃ / min. The pressure was released to atmospheric pressure to obtain a blank. The blank was annealed at 600℃ under a vacuum of 10 Pa for 2 h. The blank was ultrasonically washed with 5% dilute hydrochloric acid for 15 min and the surface was polished until the surface roughness Ra ≤ 0.2 μm to obtain a polycrystalline diamond composite sheet.

[0048] Example 2

[0049] It is basically the same as Example 1, except that hydroxyethyl methacrylate is replaced with glycidyl acrylate.

[0050] Example 3

[0051] It is basically the same as Example 1, except that hydroxyethyl methacrylate is replaced with monomethyl maleate.

[0052] Example 4

[0053] It is basically the same as Example 1, except that hydroxyethyl methacrylate is replaced with itaconic acid monobutyl ester.

[0054] Example 5

[0055] It is basically the same as Example 1, except that the amount of hydroxyethyl methacrylate is 15 parts.

[0056] Example 6

[0057] It is basically the same as Example 1, except that the amount of hydroxyethyl methacrylate is 25 parts.

[0058] Comparative Example 1

[0059] A method for preparing a polycrystalline diamond composite sheet includes the following steps:

[0060] S1. Add 94 parts of WC powder and 6 parts of Co powder into a mold, mold it at 200 MPa, heat it to 1450℃ at 5℃ / min, sinter it at a vacuum of 5 Pa for 2 hours, spray corundum sand on the surface after sintering, ultrasonically clean it and dry it to obtain a cemented carbide substrate.

[0061] S2. Add 1.5 parts KH-560 and 0.8 parts aluminum isopropoxide to 10 parts anhydrous ethanol to obtain a precursor solution. Vapor phase coating treatment is carried out at 120℃ and 5Pa vacuum for 2 hours to uniformly coat the surface of diamond micro powder. Calcination and curing are carried out at 450℃ for 1.5 hours under argon atmosphere to obtain modified diamond micro powder.

[0062] S3. 90 parts modified diamond micro powder, 0.5 parts multi-walled carbon nanotubes, 0.2 parts N-rGO, 0.3 parts Ti powder, and 0.07 parts polyethylene glycol were added to 5 parts anhydrous ethanol. After ultrasonic dispersion, the mixture was ball-milled, dried, and granulated. The powder obtained by passing through a 200-mesh sieve was loaded into a graphite mold, with a cemented carbide substrate placed at the bottom. The pressure was increased to 3.0 GPa and held for 10 min, then increased to 5.5 GPa and held for 10 min. At 5.5 GPa, the temperature was increased to 1400℃ at 50℃ / min and held for 3 min. The pressure was maintained while the furnace was cooled to 600℃ at 20℃ / min. The pressure was released to atmospheric pressure to obtain a blank. The blank was annealed at 600℃ under a vacuum of 10 Pa for 2 h. The blank was ultrasonically washed with 5% dilute hydrochloric acid for 15 min and the surface was polished until the surface roughness Ra ≤ 0.2 μm to obtain a polycrystalline diamond composite sheet.

[0063] Comparative Example 2

[0064] A method for preparing a polycrystalline diamond composite sheet includes the following steps:

[0065] S1. Add 94 parts of WC powder and 6 parts of Co powder into a mold, mold it at 200 MPa, heat it to 1450℃ at 5℃ / min, sinter it at a vacuum of 5 Pa for 2 hours, spray corundum sand on the surface after sintering, ultrasonically clean it and dry it to obtain a cemented carbide substrate.

[0066] S2. Add 100 parts of multi-walled carbon nanotubes and 5 parts of sodium dodecylbenzenesulfonate to a 5% ethanol aqueous solution, disperse evenly by ultrasonication, then add 20 parts of monomethyl maleate and 1.2 parts of ammonium persulfate, heat to 65℃ and stir for 4 hours under nitrogen protection, cool to room temperature, centrifuge, wash and dry to obtain modified multi-walled carbon nanotubes.

[0067] S3. Diamond micro powder is prepared by mixing 20-30μm and 1-3μm micro powders at a mass ratio of 70:20. This mixture is then added to 5 parts of anhydrous ethanol along with 0.5 parts of modified multi-walled carbon nanotubes, 0.2 parts of N-rGO, 0.3 parts of Ti powder, and 0.07 parts of polyethylene glycol. After ultrasonic dispersion, the mixture is ball-milled, dried, granulated, and passed through a 200-mesh sieve. The resulting powder is then placed in a graphite mold, with a cemented carbide substrate at the bottom, and pressurized to 3.0G. Pa, hold for 10 min, raise to 5.5 GPa and hold for 10 min, at 5.5 GPa, raise to 1400℃ at 50℃ / min and hold for 3 min, hold pressure and lower to 600℃ at 20℃ / min in the furnace, release pressure to atmospheric pressure to obtain the initial billet, anneal at 600℃ for 2 h under 10 Pa vacuum, add 5% dilute hydrochloric acid and ultrasonically wash for 15 min, polish the surface to a surface roughness Ra≤0.2μm to obtain polycrystalline diamond composite sheet.

[0068] Test section

[0069] 1. The polycrystalline diamond composite sheets obtained in the examples and comparative examples were ground and chamfered into sheets with a diameter of φ16mm×13mm and a chamfer of 0.30mm. Impact resistance tests were then conducted by impacting an HRC58-60 steel block with a single impact energy of 80J until the composite sheet fractured. The cumulative impact energy was used as the impact resistance of the composite sheet.

[0070] 2. The high-temperature performance of the polycrystalline diamond composite sheets obtained in the examples and comparative examples was tested using a thermogravimetric analyzer. The sheets were heated in an air atmosphere at a temperature of 20-1000℃ with a heating rate of 10℃ / min. The thermogravimetric temperature was obtained by using the real-time weight at different temperatures as thermogravimetric curves to evaluate the thermal stability.

[0071] Table 1

[0072]

[0073] As shown in Table 1, compared with Comparative Examples 1-2, the polycrystalline diamond composite sheet samples obtained in the examples exhibit better impact resistance and thermal stability. In the examples, the modified diamond and the composite reinforcing phase form a continuous interface between diamond, ceramic layer, and carbon nanomaterials during sintering. The three-dimensional composite reinforcing phase addresses the issues of weak interfaces and thermal stress concentration within the polycrystalline diamond composite sheet, improving structural integrity and impact resistance at high temperatures.

[0074] Compared to Comparative Example 1, the multi-walled carbon nanotubes in this example underwent free radical grafting modification. Under the action of an initiator, free radicals initiated the polymerization of carbon nanotubes with monomers and between monomers. The resulting polymer chains on the surface of the modified multi-walled carbon nanotubes have different functional groups such as hydroxyl, carboxyl, or epoxy groups. During the initial sintering, these groups can form covalent bonds or chemical bonds with the Si-OH and Al-OH groups on the modified diamond surface. With continued sintering, the initial interface structure evolves under high pressure and high temperature. The carbon source in the system and the silicon, aluminum, titanium, etc. in the interface region generate a strongly covalently bonded ceramic transition layer mainly composed of SiC and TiC in situ. This transition layer forms a strong chemical and physical bond with both diamond and carbon nanotubes, resulting in a higher strength of the interface bond. The tighter the interface bond, the less likely the structure is to be damaged under impact, and the less likely the diamond is to be oxidized.

[0075] Compared to Comparative Example 2, the diamond surface in this example underwent vapor phase treatment, resulting in a uniform and reactive inorganic precursor layer. Therefore, during high-pressure, high-temperature sintering, the ceramization reaction proceeded uniformly and fully at the diamond interface, forming a ceramic interface with high bonding strength. This ceramic interface can further form strong chemical and physical bonds with both diamond and carbon nanotubes; therefore, the performance would decrease if this ceramic layer were absent.

[0076] Compared to Examples 2-4, Example 1 exhibits better impact resistance and thermal stability. This is likely because the hydroxyl groups in hydroxyethyl methacrylate (HME) polymerized after polymerization can directly condense with the silanol and aluminol groups of the modified diamond surface ceramic layer to form covalent bonds during the early stages of sintering. Furthermore, compared to other monomers, HME has a compact molecular structure and low steric hindrance, allowing for higher grafting density on the surface of multi-walled carbon nanotubes, thus providing more interfacial bonding points after sintering. During sintering, the polymer polymer undergoes pyrolysis, generating active carbon species that react fully with the titanium powder in the formulation, forming a strong and tough TiC transition layer in situ, further strengthening the interface.

[0077] The glycidyl acrylate used in Example 2 primarily forms ether bonds after ring-opening of its epoxy groups, resulting in relatively low bond energies. The monomers in Examples 3 and 4 contain carboxyl groups, exhibiting a tendency for decarboxylation during sintering, potentially generating carbon dioxide gas and introducing microdefects at the interface. Furthermore, the long-chain alkyl groups of itaconic acid monobutyl ester cause significant steric hindrance, reducing the effective grafting rate. The different monomers result in varying interfacial bonding strengths, ultimately manifesting as differences in impact resistance and thermal stability.

[0078] Compared with Examples 5 and 6, the dosage in Example 1 is better. This is because when the amount of monomer is small, the active sites on the surface of multi-walled carbon nanotubes cannot be fully grafted, resulting in a low grafting rate and insufficient interfacial bonding strength. On the other hand, when the amount of monomer is large, it may cause self-aggregation between monomers, resulting in a small amount of aggregation of multi-walled carbon nanotubes, which affects the final performance.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method of producing a polycrystalline diamond compact, characterized by, Includes the following steps: S1. Add WC powder and Co powder into the mold, mold it at 200-300MPa, heat it to 1400-1500℃ at 5℃ / min, sinter it for 1-3h under vacuum degree ≤10Pa, spray corundum sand on the surface after sintering, ultrasonically clean it and dry it to obtain a cemented carbide substrate. S2. Add multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate to a 5% ethanol aqueous solution, disperse evenly by ultrasonication, add modified monomer and initiator, heat to 60-70℃ and stir for 3-5 hours under nitrogen protection, cool to room temperature, centrifuge, wash and dry to obtain modified multi-walled carbon nanotubes. S3. Add KH-560 and aluminum isopropoxide to ethanol to obtain a precursor solution. At 110-130℃ and a vacuum degree ≤5Pa, the precursor is uniformly coated on the surface of diamond micro powder. The modified diamond micro powder is obtained by calcination and curing at 400-500℃ for 1-2 hours under an argon atmosphere. S4. Modified diamond micro powder, modified multi-walled carbon nanotubes, N-rGO, Ti powder, and polyethylene glycol are added to ethanol, ultrasonically dispersed, ball-milled, dried and granulated. The resulting powder is loaded into a graphite mold, a cemented carbide substrate is placed at the bottom, and sintered at a constant temperature after gradient pressure increase. After cooling and depressurization, a preliminary blank is obtained. After vacuum annealing, dilute hydrochloric acid is added and ultrasonically washed for 10-20 minutes. The surface is polished to obtain a polycrystalline diamond composite sheet.

2. The method of producing a polycrystalline diamond compact as claimed in claim 1, wherein, The mass ratio of WC powder to Co powder is 90-100:

6.

3. The method of producing a polycrystalline diamond compact as claimed in claim 1, wherein The mass ratio of the multi-walled carbon nanotubes to sodium dodecylbenzenesulfonate and ethanol aqueous solution is 100:4-6:800-1000.

4. The method of producing a polycrystalline diamond compact as claimed in claim 1, wherein The modified monomer is one of hydroxyethyl methacrylate, glycidyl acrylate, monomethyl maleate, or monobutyl itaconic acid, and the mass ratio of the modified monomer to the initiator and multi-walled carbon nanotubes is 15-25:1-1.5:

100.

5. The method of producing a polycrystalline diamond compact as claimed in claim 1, wherein The mass ratio of KH-560 to aluminum isopropoxide and ethanol is 10-20:6-10:

100.

6. The method of producing a polycrystalline diamond compact as claimed in claim 1, wherein In step S3, the diamond micro powder is a mixture of two types of micro powder, 20-30μm and 1-3μm, in a mass ratio of 70:10-30.

7. The method of producing a polycrystalline diamond compact as claimed in claim 1, wherein The mass ratio of the modified diamond micro powder, modified multi-walled carbon nanotubes, N-rGO, Ti powder, polyethylene glycol, and ethanol is 85-95:0.4-0.6:0.1-0.3:0.2-0.4:0.05-0.1:

5.

8. The method for preparing polycrystalline diamond composite sheets as described in claim 1, characterized in that, In step S4, the pressure is gradually increased to 3.0 GPa, and after holding for 10 minutes, it is increased to 5-6 GPa.

9. A polycrystalline diamond compact characterized by, Prepared by the method described in any one of claims 1-8.

10. The application of the polycrystalline diamond composite sheet as described in claim 9 in drill bits.

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