Micro-nano heterogeneous polycrystalline diamond compact and preparation method thereof, drill bit

Abstract

The present application provides a kind of micro-nano heterogeneous polycrystalline diamond compact and its preparation method, drill bit.The micro-nano heterogeneous polycrystalline diamond compact includes hard alloy substrate and micro-nano heterogeneous polycrystalline diamond layer arranged on the hard alloy substrate;Wherein, micro-nano heterogeneous polycrystalline diamond layer includes micron diamond microcrystal and nanometer polycrystalline diamond microcrystal.The micro-nano heterogeneous polycrystalline diamond compact introduces the internal structure for nanometer polycrystalline diamond into the traditional polycrystalline diamond layer to replace the original part of micron diamond, can reduce the cobalt content in polycrystalline layer, improve the heat resistance of compact, in addition, since the nanometer polycrystalline diamond with higher hardness, toughness than traditional micron diamond is added, the hardness, wear resistance and impact resistance of polycrystalline diamond compact are improved.

Description

Technical Field

[0001] This invention relates to the field of superhard materials technology, and in particular to a micro / nano heterogeneous polycrystalline diamond composite sheet, its preparation method, and a drill bit. Background Technology

[0002] Polycrystalline diamond compact (PDC) drill bits are key tools in the oil and gas industry, widely used for their high cutting efficiency and wear resistance. As the application of PDC drill bits in oil drilling increases, the requirements for wear resistance, impact resistance, and thermal stability of PDC composite bits are also gradually rising.

[0003] The existing PDC composite sheet is synthesized by combining a hard alloy substrate and micron-sized diamond powder under high temperature and high pressure. After synthesis, the cobalt element in the PDC composite sheet is removed by a cobalt removal process.

[0004] If the synthesized diamond layer contains too much cobalt or if the pores are not backfilled after cobalt removal, the quality of the PDC composite sheet will be affected to some extent, especially its impact resistance. This will cause the PDC composite sheet to delaminate and break easily after being impacted, affecting its normal use. Summary of the Invention

[0005] This invention provides a micro / nano heterogeneous polycrystalline diamond composite sheet, its preparation method, and a drill bit, which solves the problems of poor heat resistance, impact resistance, and wear resistance caused by the high cobalt volume fraction in the polycrystalline layer of the polycrystalline diamond composite sheet.

[0006] In one aspect, the present invention provides a micro / nano heterogeneous polycrystalline diamond composite sheet, comprising: a cemented carbide substrate and a micro / nano heterogeneous polycrystalline diamond layer disposed on the cemented carbide substrate; wherein the micro / nano heterogeneous polycrystalline diamond layer comprises micron-sized diamond microcrystals and nano-sized polycrystalline diamond microcrystals.

[0007] According to one embodiment of the present invention, the mass percentage content of the nano-polycrystalline diamond microcrystals is 1wt% to 70wt%.

[0008] According to one embodiment of the present invention, the polycrystalline diamond layer further includes a carbide-forming element, wherein the mass percentage content of the carbide-forming element is 2wt% to 5wt%.

[0009] According to one embodiment of the present invention, the macroscopic particle size of the nanocrystalline polycrystalline diamond is in the micrometer range, and the microscopic grain size is in the nanometer range; furthermore, the hardness of the nanocrystalline polycrystalline diamond is 100~200 GPa, and the fracture toughness is 6~11 MPa•m. 0.5 .

[0010] In a second aspect, the present invention provides a method for preparing a micro / nano heterogeneous polycrystalline diamond composite sheet, for preparing the micro / nano heterogeneous polycrystalline diamond composite sheet according to any of the above-mentioned methods. The preparation method includes the following steps: obtaining nano-polycrystalline diamond microcrystals by ultra-high temperature and high pressure synthesis and ball milling; weighing micron-sized diamond powder and nano-polycrystalline diamond microcrystals in a predetermined proportion, mixing them to obtain a powder to be synthesized; and subjecting the powder to be synthesized and a cemented carbide substrate to high temperature and high pressure sintering treatment to obtain a micro / nano heterogeneous polycrystalline diamond composite sheet.

[0011] According to one embodiment of the present invention, the macroscopic particle size range of the nano-polycrystalline diamond microcrystals is 1~50μm, and the internal micro-grain size range is 1~500nm; the grain size range of the micron-sized diamond powder is 1~30μm.

[0012] According to one embodiment of the present invention, nano-polycrystalline diamond microcrystals and micron-sized diamond powder are weighed in a predetermined proportion to obtain a powder to be synthesized, including: weighing nano-polycrystalline diamond microcrystals with a mass percentage content of 1wt% to 70wt%, carbide-forming element with a mass percentage content of 2wt% to 5wt%, and micron-sized diamond powder, and mixing them to obtain a powder to be synthesized.

[0013] According to one embodiment of the present invention, obtaining nanocrystalline polycrystalline diamond through ultra-high temperature and high pressure synthesis and ball milling includes: synthesizing nanocrystalline polycrystalline diamond using spherical graphite, carbon nanotubes, and fullerene as raw materials under preset conditions; and screening the nanocrystalline polycrystalline diamond to obtain those with a target hardness of 100~200 GPa and a fracture toughness of 6~11 MPa•m. 0.5 The raw material to be crushed is subjected to mechanical ball milling to obtain nano-polycrystalline diamond microcrystals.

[0014] According to one embodiment of the present invention, mechanical ball milling is performed on the raw material to be crushed to obtain nano-polycrystalline diamond microcrystals, comprising: placing the raw material to be crushed and cemented carbide grinding balls in a cemented carbide ball milling jar for high-energy ball milling; performing laser particle size detection after high-energy ball milling to obtain target nano-polycrystalline diamond; purifying by acid-base treatment to remove cemented carbide mixed in with the target nano-polycrystalline diamond during high-energy ball milling; and sequentially performing natural sedimentation, repeated centrifugation, filtration and drying treatments to obtain nano-polycrystalline diamond microcrystals.

[0015] A third aspect of the present invention provides a drill bit comprising a drill bit body and the aforementioned micro / nano heterogeneous polycrystalline diamond composite sheet fixed to the surface of the drill bit body, or a micro / nano heterogeneous polycrystalline diamond composite sheet prepared according to the aforementioned method for preparing the micro / nano heterogeneous polycrystalline diamond composite sheet.

[0016] The present invention provides a micro / nano heterogeneous polycrystalline diamond composite sheet, its preparation method, and a drill bit. The micro / nano heterogeneous polycrystalline diamond composite sheet includes a cemented carbide substrate and a polycrystalline diamond layer disposed on the cemented carbide substrate. Furthermore, the polycrystalline diamond layer includes micron-sized diamond microcrystals and nano-sized polycrystalline diamond microcrystals.

[0017] Replacing traditional micron-sized diamond powder with nano-polycrystalline diamond allows for the direct realization of more carbon atoms and cobalt-free catalytic bonding between carbon atoms in the polycrystalline layer, resulting in higher grain boundary density. Furthermore, nano-polycrystalline diamond exhibits superior hardness and fracture toughness compared to traditional micron-sized diamond. By introducing nano-polycrystalline diamond with a tightly integrated internal structure to replace some of the original micron-sized diamond in the polycrystalline diamond composite sheet, the amount of cobalt required in the cemented carbide substrate during the synthesis of the micro / nano heterogeneous polycrystalline diamond composite sheet can be reduced, and the heat resistance of the polycrystalline diamond composite sheet can be improved. In addition, the addition of components with higher hardness and toughness improves the wear resistance and impact resistance of the composite sheet. Attached Figure Description

[0018] Figure 1 Flowchart of the preparation method of the micro / nano heterogeneous polycrystalline diamond composite sheet provided by the present invention Figure 1 ;

[0019] Figure 2 Flowchart of the preparation method of the micro / nano heterogeneous polycrystalline diamond composite sheet provided by the present invention Figure 2 ;

[0020] Figure 3 Flowchart of the preparation method of the micro / nano heterogeneous polycrystalline diamond composite sheet provided by the present invention Figure 3 ;

[0021] Figure 4 A graph showing the relationship between the content of nano-polycrystalline diamond and hardness and impact resistance in the micro-nano heterogeneous polycrystalline diamond composite sheet provided by the present invention.

[0022] Figure 5 A graph showing the relationship between the content of nano-polycrystalline diamond and the wear ratio performance in the micro-nano heterogeneous polycrystalline diamond composite sheet provided by the present invention.

[0023] Figure 6 The graph shows the relationship between the content of nano-polycrystalline diamond and the initial expansion temperature and cobalt content in the micro-nano heterogeneous polycrystalline diamond composite sheet provided by the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Polycrystalline diamond composite sheets are a type of ultra-hard composite material made from diamond micron powder as raw material and cemented carbide as matrix, sintered under high temperature and high pressure conditions through a specific synthesis process. Due to its excellent hardness and wear resistance, polycrystalline diamond composite sheets are widely used in various fields such as oil and gas drilling, mining, geological exploration, and machining.

[0026] In related technologies, the traditional preparation of polycrystalline diamond composite sheets typically involves synthesizing a cemented carbide substrate and diamond micropowder under high temperature and pressure (5-6 GPa, 1300-1500℃). After synthesis, a cobalt removal process is then used to remove cobalt from the polycrystalline diamond layer. According to the inventors' research, if the cobalt content in the diamond layer is too high during synthesis or if pore backfilling is not performed after cobalt removal, it will negatively impact the quality of the polycrystalline diamond composite sheet, particularly its impact resistance. This makes the polycrystalline diamond composite sheet prone to delamination and breakage upon impact, leading to a reduced service life.

[0027] In general drilling environments, traditional polycrystalline diamond composite sheets can meet drilling requirements. However, in some construction environments where the impact resistance of polycrystalline diamond composite sheets is required to be high, such as in soft and hard interlayer formations, traditional cobalt-free polycrystalline diamond composite sheets often cannot meet the requirements.

[0028] In view of this, embodiments of the present invention provide a micro / nano heterogeneous polycrystalline diamond composite sheet, comprising: a cemented carbide substrate and a micro / nano heterogeneous polycrystalline diamond layer disposed on the cemented carbide substrate. The micro / nano heterogeneous polycrystalline diamond layer comprises micron-sized diamond crystals and nano-sized polycrystalline diamond crystals. The cemented carbide substrate is a composite material composed of metal carbide particles and a metal binder, widely used in cutting tools, molds, and wear-resistant parts. Its main components are cobalt and tungsten. Tungsten typically exists in the form of tungsten carbide (WC), imparting extremely high hardness and wear resistance to the cemented carbide, enabling it to maintain good mechanical properties under high temperature and high pressure conditions. Cobalt exists as a binder in the cemented carbide. It is a metallic binder phase, typically existing in a metallic state.

[0029] During the synthesis of polycrystalline diamond, cobalt can disperse around the diamond powder particles under the influence of capillary force and synthesis pressure difference, playing a role in dissolving diamond and then precipitating it. The newly precipitated diamond then fuses with the existing diamond to form polycrystalline diamond.

[0030] Because nano-polycrystalline diamond can directly achieve cobalt-free catalytic bonding between carbon atoms, and it possesses superior hardness and fracture toughness compared to traditional micron-sized diamond, a micro-nano heterogeneous polycrystalline diamond composite sheet is formed by introducing nano-polycrystalline diamond with a tightly integrated internal structure to replace some of the original micron-sized diamond. This reduces the amount of cobalt required from the cemented carbide substrate and improves the heat resistance of the polycrystalline diamond composite sheet. Simultaneously, it introduces components with higher hardness and fracture toughness. Therefore, it improves the wear resistance and impact resistance of the composite sheet.

[0031] In some embodiments, the mass percentage content of the nano-polycrystalline diamond microcrystals can be from 1wt% to 70wt%, for example, the mass percentage content of the nano-polycrystalline diamond microcrystals can be 1wt%, 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, or any combination thereof.

[0032] Since cobalt's primary function is to dissolve diamond particles and then re-precipitate diamond, and to promote bonding between particles, introducing an excessively high proportion of already sintered ultra-high-performance nanocrystalline diamond, while mitigating the problems of low hardness, poor heat resistance, impact resistance, and wear resistance caused by a high cobalt volume fraction in the polycrystalline layer, may also negatively impact the bonding strength between diamond particles if the cobalt volume fraction is too low. Furthermore, insufficient cobalt diffusion can lead to localized areas of excessively high or low cobalt content, creating regions of uneven performance, which could negatively affect the material's heat resistance, impact resistance, and wear resistance.

[0033] In other words, insufficient cobalt content may lead to inadequate bonding between nanodiamond particles and microdiamond particles, thereby reducing the material's mechanical strength and wear resistance. Therefore, controlling the mass percentage of polycrystalline diamond crystals within a suitable range can improve the impact resistance of the composite sheet without hindering polycrystalline formation due to insufficient cobalt content and diffusion capacity, or conversely, causing poor composite sheet performance due to excessively low cobalt content resulting in insufficient synergistic deformation and impact load bearing capacity. Furthermore, since the manufacturing cost of polycrystalline diamond is high, excessively high content of polycrystalline diamond would lead to excessively high composite sheet costs; therefore, it is not advisable to use it if there is no significant difference in performance.

[0034] In some embodiments, the mass percentage content of nano-polycrystalline diamond microcrystals can be 1wt% to 12wt%, for example, a range of 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, 12wt or any two of these, which is beneficial for further improving the impact resistance and hardness of micro-nano heterogeneous polycrystalline diamond composite sheets while controlling costs.

[0035] According to further research by the inventors, the polycrystalline diamond layer may also include carbide-forming elements. The mass percentage content of the carbide-forming elements can be 2wt% to 5wt%, for example, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any combination thereof.

[0036] For example, the carbide-forming elements may consist of any one or more of silicon, boron, titanium, aluminum, vanadium, chromium, molybdenum, tantalum and tungsten.

[0037] Carbide-forming elements can react with carbon in nanodiamond particles and micron-diamond particles to form a very hard carbide phase. These carbides can form between diamond particles or between diamond and cobalt, enhancing the bonding strength between particles. Furthermore, the formation of the carbide phase can significantly improve the wear resistance of the composite sheet, giving it a longer service life in cutting and drilling applications. In addition, the presence of the carbide phase can slow down the graphitization process of diamond at high temperatures, thereby improving the stability of the material in high-temperature applications.

[0038] Therefore, by introducing carbide-forming elements as a binder in the composite sheet synthesis process, it is possible to ensure that the surface of nanocrystalline diamond can be bonded to micron-sized diamond powder through the carbide-forming elements. Simultaneously, controlling the mass percentage content of the carbide-forming elements within the range of 2wt% to 5wt% avoids weakening the overall strength of the material due to excessive carbide content. Furthermore, it also reduces the adverse effects of the carbide-forming elements themselves, due to their different coefficients of thermal expansion compared to diamond, on the heat resistance and wear resistance of the composite sheet.

[0039] In some embodiments, the macroscopic particle size of the nanocrystalline polycrystalline diamond is in the micrometer range, and the microscopic grain size is in the nanometer range. Furthermore, the nanocrystalline polycrystalline diamond has a hardness of 100~200 GPa and a fracture toughness of 6~11 MPa•m. 0.5 For example, the hardness of nano-polycrystalline diamond microcrystals can be in the range of 100 GPa, 110 GPa, 120 GPa, 130 GPa, 140 GPa, 150 GPa, 160 GPa, 170 GPa, 180 GPa, 190 GPa, 200 GPa, or any combination thereof.

[0040] The fracture toughness of nanocrystalline polycrystalline diamond can reach 6 MPa•m. 0.5 6.5 MPa•m 0.5 7MPa•m 0.5 7.5 MPa•m 0.5 8MPa•m 0.5 8.5 MPa•m 0.5 9MPa•m 0.5 9.5 MPa•m 0.5 10MPa•m 0.5 10.5 MPa•m 0.5 11 MPa•m 0.5 or a range consisting of any two of them.

[0041] By screening the hardness and fracture toughness of the introduced nano-polycrystalline diamond microcrystals, the hardness and toughness of the synthesized micro-nano heterogeneous polycrystalline diamond composite sheet can be enhanced, thereby improving its overall performance.

[0042] Figure 1 Flowchart of the preparation method of the micro / nano heterogeneous polycrystalline diamond composite sheet provided by the present invention Figure 1 . Figure 2 Flowchart of the preparation method of the micro / nano heterogeneous polycrystalline diamond composite sheet provided by the present invention Figure 2 . Figure 3 Flowchart of the preparation method of the micro / nano heterogeneous polycrystalline diamond composite sheet provided by the present invention Figure 3 .like Figures 1-3 As shown, this embodiment of the invention also provides a method for preparing micro / nano heterogeneous polycrystalline diamond composite sheets, used to prepare any of the above-mentioned micro / nano heterogeneous polycrystalline diamond composite sheets. The preparation method includes the following steps:

[0043] S100, nano-polycrystalline diamond microcrystals are obtained by ultra-high temperature and high pressure synthesis and ball milling;

[0044] Specifically, nanocrystalline diamond can be synthesized by ultra-high temperature and high pressure synthesis, and nanocrystalline diamond microcrystals can be obtained by ball milling.

[0045] S200: Weigh out micron-sized diamond powder and nano-polycrystalline diamond microcrystals in a predetermined ratio, mix them to obtain the powder to be synthesized.

[0046] It is understandable that the preset ratio can be set according to specific performance parameter requirements, and no restrictions are imposed here.

[0047] S300: The powder to be synthesized and the hard alloy substrate are subjected to high temperature and high pressure sintering to obtain micro-nano heterogeneous polycrystalline diamond composite sheets.

[0048] Specifically, the powder to be synthesized and the hard alloy substrate can be placed in a metal container (such as a metal cup), and then high-pressure components such as pyrophyllite blocks can be placed in it for high-temperature and high-pressure sintering.

[0049] Through the inventors' research, although nanocrystalline diamond can directly bond carbon atoms under ultra-high pressure of 20-30 GPa, thus achieving cobalt-free catalytic bonding, the sample size is only 1-5 mm in diameter and height. Under industrial conditions, the diamond composite sheets required for synthetic petroleum need to have a diameter of at least 13 mm and a thickness of 5 mm. Therefore, the synthesis pressure of the composite sheets cannot exceed 7 GPa, and can only be achieved through cobalt-catalyzed sintering. Based on this, nanocrystalline diamond can serve as a substitute for diamond. Because its internal structure and strength are already formed, its volume occupied by the polycrystalline diamond layer can reduce the use of traditional diamond, thereby reducing the use of cobalt.

[0050] By introducing nano-polycrystalline diamond with a tight internal structure, which has superior hardness and fracture toughness compared to traditional diamond, the demand for cobalt can be reduced, and components with higher hardness and toughness can be added, thus improving the performance of the composite sheet.

[0051] In some embodiments, nano-polycrystalline diamond microcrystals and micron-sized diamond powder are weighed in a predetermined ratio to obtain the powder to be synthesized, comprising:

[0052] Weigh out 1 wt% to 70 wt% of nano-polycrystalline diamond microcrystals, 2 wt% to 5 wt% of carbide-forming elemental substances, and micron-sized diamond powder, and mix them to obtain the powder to be synthesized.

[0053] Replacing a portion of the micron-sized diamond powder with nano-polycrystalline diamond microcrystals by a certain mass percentage can reduce the cobalt requirement during the synthesis of polycrystalline diamond composite sheets, thereby improving the impact resistance of the composite sheets. Simultaneously, adding appropriate carbide-forming elements to the powder to be synthesized is beneficial for the bonding between nano-polycrystalline diamond and micron-sized polycrystalline diamond, thus improving the overall integrity of the composite sheet.

[0054] This solves, on the one hand, the long-standing problem of limited application due to the high brittleness, small sheet size, and processing difficulties of nano-polycrystalline diamond. On the other hand, it also achieves the combination of nano-polycrystalline diamond microcrystals and micron-sized diamond particles in traditional polycrystalline diamond composite sheets through the catalytic recrystallization of cobalt and the bonding effect of carbide-forming elements.

[0055] Meanwhile, since nano-polycrystalline diamond has achieved cobalt-free catalytic bonding of diamond particles, the addition of nano-polycrystalline diamond can reduce the cobalt content required for sintering polycrystalline diamond composite sheets, reduce the content of residual cobalt after decobalt removal in the polycrystalline layer, and reduce the number of weak structures caused by decobalt removal. Compared with traditional polycrystalline diamond composite sheets, it has significant improvements in strength, heat resistance, impact resistance and wear resistance.

[0056] In some embodiments, the mass percentage content of the nano-polycrystalline diamond microcrystals may also be 3% to 70%, for example, a range consisting of 3wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, or any two of these.

[0057] In some embodiments, obtaining nano-polycrystalline diamond microcrystals through ultra-high temperature and high pressure synthesis and ball milling may include the following steps:

[0058] S110, using spherical graphite, carbon nanotube onion, and fullerene as raw materials, synthesizes nano-polycrystalline diamond under preset conditions.

[0059] Specifically, the spherical graphite can include micron-sized and nano-sized spherical graphite. The preset conditions can be ultra-high temperature and high pressure synthesis conditions with a pressure range of 7–25 GPa and a temperature range of 1800–2500°C. For example, the pressure can be any combination of 7 GPa, 9 GPa, 11 GPa, 13 GPa, 15 GPa, 17 GPa, 19 GPa, 21 GPa, 23 GPa, 25 GPa, or any combination thereof, and the temperature can be any combination of 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, 2500°C, or any combination thereof. Under the above ultra-high temperature and high pressure synthesis conditions, nano-polycrystalline diamond with millimeter-sized and centimeter-sized nanoscale polycrystalline diamond can be synthesized.

[0060] In some embodiments, since the pressure and heat transfer materials of the synthesis chamber may adhere to the surface of the nano-polycrystalline diamond during conventional synthesis, which may interfere with performance testing, in order to avoid performance differences caused by size differences, the nano-polycrystalline diamond may be machined after removing impurities from its surface to make the material into a standard-sized sample.

[0061] S120. Select nano-polycrystalline diamond that meets the target hardness of 100~200 GPa and fracture toughness of 6~11 MPa•m. 0.5 The raw materials to be crushed.

[0062] Screening the raw materials for crushing is beneficial to improving the hardness and fracture toughness of the synthesized micro-nano heterogeneous polycrystalline diamond composite sheets.

[0063] S130. The raw material to be crushed is subjected to mechanical ball milling to obtain nano-polycrystalline diamond microcrystals.

[0064] In some embodiments, the raw material to be pulverized is subjected to mechanical ball milling to obtain nano-polycrystalline diamond microcrystals, which may specifically include:

[0065] S131. Place the raw material to be crushed and the cemented carbide grinding balls into a cemented carbide ball milling jar for high-energy ball milling.

[0066] Specifically, the ball milling speed of the high-energy ball mill can be 300~1000 rpm, for example, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, or any combination thereof. The ball-to-material ratio can be 4:1~10:1, for example, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, or any combination thereof. The ball milling medium can be anhydrous ethanol, and the ball milling time can be 0.5~2 hours, for example, 0.5, 1 hour, 1.5 hours, 2 hours, or any combination thereof. This allows large-particle polycrystalline diamond nanoparticles to be pulverized into micron-sized polycrystalline diamond nanoparticles.

[0067] S132. After high-energy ball milling, laser particle size detection is performed to obtain the target nano-polycrystalline diamond.

[0068] Specifically, the target nanocrystalline diamond has a particle size range of 1–50 μm. Laser particle size analysis and screening facilitate the subsequent synthesis of polycrystalline diamond composite sheets.

[0069] S133. The hard alloy mixed in the target nano-polycrystalline diamond during the high-energy ball milling process is removed by acid and alkali treatment purification.

[0070] Acid-base purification primarily involves using hydrofluoric acid and nitric acid to remove cemented carbide impurities introduced during ball milling. The acid solution is then removed using alkaline substances such as sodium hydroxide. This process reduces the impact of mixed cemented carbide on the performance of the final synthesized composite sheet.

[0071] S134. The mixture is subjected to natural sedimentation, repeated centrifugation, filtration and drying in sequence to obtain nano-polycrystalline diamond microcrystals.

[0072] The nanocrystalline polycrystalline diamond obtained through the above steps can be used as raw materials to participate in the synthesis of micro / nano heterogeneous polycrystalline diamond composite sheets.

[0073] In some embodiments, the macroscopic particle size range of the weighed polycrystalline diamond nanocrystals can be 1~50 μm, and the internal microscopic grain size ranges from 1~500 nm. The grain size range of the micron-sized diamond powder is 1~30 μm.

[0074] For example, the size of polycrystalline diamond nanocrystals can be in the range of 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 45 μm, 50 μm, or any combination thereof. The grain size of polycrystalline diamond nanocrystals can be in the range of 1 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, or any combination thereof.

[0075] The grain size of micron-sized diamond powder can be 1μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, or any combination thereof.

[0076] By controlling the size range of nano-polycrystalline diamond crystals and their grain size range, as well as the grain size range of micron-sized diamond powder, it is beneficial to improve the polycrystalline bonding between nano-polycrystalline diamond crystals and micron-sized diamond powder during the preparation process.

[0077] In some embodiments, to improve the uniformity of the powder to be synthesized, ensure that each component is evenly distributed in the powder to be synthesized, and improve the sintering performance of the powder to be synthesized, the weighed mixture of nano-polycrystalline diamond microcrystals, carbide-forming elemental substances, and micron-sized diamond powder can be ball-milled. This can promote densification by refining the particles and increasing surface activity, increase the surface energy of the particles, and make their surface more active.

[0078] Specifically, the ball milling process may include placing 1 wt% to 70 wt% of nano-polycrystalline diamond microcrystals (internal micro-grain size 1 to 500 nm, macro-particle size 1 to 50 μm), 2 wt% to 5 wt% of carbide-forming elemental (silicon, boron, titanium, aluminum, etc.), and micron-sized diamond powder of different particle sizes (grain size 1 to 30 μm) in a cemented carbide ball milling jar. The mass ratio of cemented carbide balls to the above mixed powder can be 4:1, and the ball milling speed can be 100 to 500 rpm, for example, it can be a range of 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, or any combination thereof.

[0079] The ball milling time can be 0.5 to 1 hour, for example, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1 hour or any combination thereof.

[0080] After ball milling, the mixed powder after ball milling can be screened through a metal sieve to obtain a uniform powder to be synthesized.

[0081] In some embodiments, the high-temperature and high-pressure sintering treatment of the powder to be synthesized and the cemented carbide substrate can specifically be performed with a sintering pressure range of 7 to 10 GPa, for example, a range consisting of 7 GPa, 7.5 GPa, 8 GPa, 8.5 GPa, 9 GPa, 9.5 GPa, 10 GPa or any two of these.

[0082] And a sintering temperature range of 1600~1900℃, for example, 1600℃, 1650℃, 1700℃, 1750℃, 1800℃, 1850℃, 1900℃ or any combination thereof.

[0083] This invention also provides a drill bit, comprising a drill bit body and a micro / nano heterogeneous polycrystalline diamond composite sheet fixed to the surface of the drill bit body. The micro / nano heterogeneous polycrystalline diamond composite sheet can be the micro / nano heterogeneous polycrystalline diamond composite sheet as described in the above embodiments, or a micro / nano heterogeneous polycrystalline diamond composite sheet prepared according to the above-described preparation method. The technical effects achievable are the same as those achieved by the aforementioned micro / nano heterogeneous polycrystalline diamond composite sheet, and will not be elaborated upon here.

[0084] The present invention will be further described below through specific embodiments.

[0085] Example 1:

[0086] Nano-onion carbon was synthesized into nano-polycrystalline diamond with a diameter of 1.8 mm, a height of 2.0 mm, and a hardness of 160~170 GPa under ultra-high temperature and pressure conditions of 20 GPa, 1700℃, and 15 minutes using a two-sided press.

[0087] Nanocrystalline diamond was placed in a cemented carbide ball mill jar for high-energy ball milling at a speed of 600 rpm, a ball-to-material ratio of 10:1, anhydrous ethanol as the milling medium, and a milling time of 2 h. After laser particle size analysis, the material was purified by acid-base treatment, followed by natural sedimentation, repeated centrifugation, filtration and drying to obtain nanocrystalline diamond powder with an average particle size of 3~5 μm.

[0088] 2 wt% nano-titanium and 0.5 wt% nano-polycrystalline diamond powder were added to a mixture of 90 wt% diamond powder with an average particle size of 14 μm and 10 wt% diamond powder with an average particle size of 1 μm.

[0089] The above powders were mixed and placed in a cemented carbide ball mill jar with a cemented carbide ball to powder mass ratio of 4:1. The milling speed was 500 rpm, and the milling time was 0.5 h. The resulting powder was then passed through a metal sieve. The powder and cemented carbide substrate were placed in a metal cup and then placed in a high-pressure element such as a pyrophyllite block. Sintering was completed at 7.3 GPa and 1600°C to obtain a micro / nano heterogeneous polycrystalline diamond composite sheet.

[0090] Examples 2 to 7: The difference from Example 1 is the mass fraction of the nano-polycrystalline diamond powder, as shown in Table 1. The other conditions are the same as in Example 1.

[0091] Comparative Example 1: The difference from Example 1 is that no nano-polycrystalline diamond powder was added to the powder to be synthesized, while the other conditions were the same as in Example 1.

[0092] The hardness, impact resistance, initial expansion temperature, wear ratio, and cobalt content of the micro-nano heterogeneous polycrystalline diamond composite sheets synthesized in Examples 1-7 and Comparative Example 1 were tested respectively, and the results are shown in Table 1.

[0093] It is understood that, in the embodiments of the present invention, the hardness, impact resistance, initial expansion temperature, and wear ratio of the micro / nano heterogeneous polycrystalline diamond composite sheet can be obtained using conventional methods in the art, such as measuring the hardness of the composite sheet using a Vickers hardness test. The impact resistance of the material is evaluated through an impact test. The initial expansion temperature is determined using a thermal expansion tester. And the wear ratio is obtained through a VTL vertical lathe test.

[0094] The cobalt content of the synthesized polycrystalline diamond composite sheet can be semi-quantitatively determined using an energy dispersive spectroscopy (EDS) analyzer within a scanning electron microscope.

[0095] Table 1

[0096]

[0097] Figure 4 The graph shows the relationship between the content of nano-polycrystalline diamond and the hardness and impact resistance in the micro-nano heterogeneous polycrystalline diamond composite sheet provided by the present invention. Figure 5 The graph shows the relationship between the content of nano-polycrystalline diamond and the wear ratio performance in the micro-nano heterogeneous polycrystalline diamond composite sheet provided by the present invention. Figure 6 The graph shows the relationship between the content of nano-polycrystalline diamond and the initial expansion temperature and cobalt content in the micro-nano heterogeneous polycrystalline diamond composite sheet provided by the present invention.

[0098] according to Figures 4-6As can be seen from Table 1, compared to Comparative Example 1, Examples 1 to 14 introduced nano-polycrystalline diamond particles to replace some micron-sized diamond particles, which can reduce the cobalt content in the polycrystalline layer and improve the hardness, impact resistance, initial expansion temperature and wear ratio of the synthesized composite sheet.

[0099] Among them, compared with Examples 1 and 2, the micro / nano heterogeneous polycrystalline diamond composite sheets in Examples 3-14 showed further improvements in impact resistance, hardness, initial expansion temperature, and wear ratio. It is understood that when the mass percentage content of nano-polycrystalline diamond microcrystals is greater than or equal to 1 wt%, the impact resistance, hardness, initial expansion temperature, and wear ratio of the micro / nano heterogeneous polycrystalline diamond composite sheets are significantly improved.

[0100] Furthermore, compared to Examples 1-3 and Examples 13-14, the micro-nano heterogeneous polycrystalline diamond composite sheets in Examples 4-12 exhibit superior performance.

[0101] However, as the mass percentage content of nano-polycrystalline diamond crystals gradually increases, the cobalt content in the polycrystalline layer will gradually decrease, and its diffusion ability will decrease accordingly. This will affect the polycrystalline bonding between nano-polycrystalline diamond and micron-sized diamond, resulting in a gradual decrease in the impact resistance, initial expansion temperature, and wear ratio of the composite sheet.

[0102] Considering the high production cost and long production cycle of nano-polycrystalline diamond, introducing excessively high amounts of nano-polycrystalline diamond would significantly increase economic costs, and its main performance would begin to decline after reaching a peak. As shown in Examples 3-8, when the mass percentage content of nano-polycrystalline diamond is in the range of 1wt% to 12wt%, the impact resistance of the micro / nano heterogeneous polycrystalline diamond composite sheet gradually improves. Subsequently, the impact resistance value decreases due to the insufficient cobalt content and its diffusion ability affecting the impact resistance.

[0103] Understandably, within this range, while reducing cobalt content and improving impact resistance, it is possible to maintain an appropriate cobalt content within the polycrystalline layer and ensure that cobalt has sufficient diffusion capacity. This helps to form a dense polycrystalline structure, allowing the nano-polycrystalline diamond microcrystals and micron-polycrystalline diamond grains to stably form a polycrystalline structure during the synthesis process. This prevents the impact resistance of the micro / nano heterogeneous polycrystalline diamond composite sheet from being affected by excessively low cobalt content.

[0104] Furthermore, when the mass percentage content of nano-polycrystalline diamond is 10wt%, the initial expansion temperature and wear resistance of the micro-nano heterogeneous polycrystalline diamond composite sheet both reach optimal performance.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A micro / nano heterogeneous polycrystalline diamond composite sheet, characterized in that, include: A cemented carbide substrate and a micro / nano heterogeneous polycrystalline diamond layer disposed on the cemented carbide substrate; The micro / nano heterogeneous polycrystalline diamond layer includes micron-sized diamond crystals and nano-sized polycrystalline diamond crystals.

2. The micro / nano heterogeneous polycrystalline diamond composite sheet according to claim 1, characterized in that, The mass percentage content of the nano-polycrystalline diamond microcrystals is 1wt%~70wt%.

3. The micro / nano heterogeneous polycrystalline diamond composite sheet according to claim 1, characterized in that, The polycrystalline diamond layer also includes a carbide-forming element, wherein the mass percentage of the carbide-forming element is 2wt% to 5wt%.

4. The micro / nano heterogeneous polycrystalline diamond composite sheet according to claim 1, characterized in that, The macroscopic particle size of the nano-polycrystalline diamond crystals is in the micrometer range, and the microscopic grain size is in the nanometer range; furthermore, the hardness of the nano-polycrystalline diamond crystals is 100~200 GPa, and the fracture toughness is 6~11 MPa•m. 0.5 .

5. A method for preparing a micro / nano heterogeneous polycrystalline diamond composite sheet, characterized in that, The method for preparing the micro / nano heterogeneous polycrystalline diamond composite sheet according to any one of claims 1-4 includes the following steps: Nano-polycrystalline diamond microcrystals were obtained by ultra-high temperature and high pressure synthesis and ball milling. Weigh out micron-sized diamond powder and nano-polycrystalline diamond microcrystals in a predetermined ratio, mix them to obtain the powder to be synthesized; The powder to be synthesized and the cemented carbide substrate are subjected to high temperature and high pressure sintering to obtain micro-nano heterogeneous polycrystalline diamond composite sheets.

6. The method for preparing the micro / nano heterogeneous polycrystalline diamond composite sheet according to claim 5, characterized in that, The macroscopic particle size range of the nano-polycrystalline diamond microcrystals is 1~50μm, and the internal microscopic grain size ranges from 1~500nm. The grain size of the micron-sized diamond crystals ranges from 1 to 30 μm.

7. The method for preparing micro / nano heterogeneous polycrystalline diamond composite sheets according to claim 5, characterized in that, The process involves weighing out nano-polycrystalline diamond microcrystals and micron-sized diamond microcrystals in a predetermined ratio to obtain the powder to be synthesized, comprising: Weigh out 1wt%~70wt% of nano-polycrystalline diamond microcrystals, 2wt%~5wt% of carbide-forming elemental substances, and micron-sized diamond powder, and mix them to obtain the powder to be synthesized.

8. The method for preparing micro / nano heterogeneous polycrystalline diamond composite sheets according to claim 5, characterized in that, The process of obtaining nano-polycrystalline diamond microcrystals through ultra-high temperature and high pressure synthesis and ball milling includes: Nanocrystalline diamond was synthesized using spherical graphite, carbon nanotube onion, and fullerene as raw materials under preset conditions. Selected nanocrystalline diamonds with a target hardness of 100-200 GPa and a fracture toughness of 6-11 MPa•m were chosen. 0.5 The raw materials to be crushed; The raw material to be crushed is subjected to mechanical ball milling to obtain the nano-polycrystalline diamond microcrystals.

9. The method for preparing micro / nano heterogeneous polycrystalline diamond composite sheets according to claim 8, characterized in that, The process of mechanically ball-milling the raw material to be pulverized to obtain nano-polycrystalline diamond microcrystals includes: The raw material to be crushed and the cemented carbide grinding balls are placed in a cemented carbide ball mill jar for high-energy ball milling; After high-energy ball milling, laser particle size analysis was performed to obtain the target nano-polycrystalline diamond. The hard alloy mixed in the target nano-polycrystalline diamond during the high-energy ball milling process is removed by acid and alkali treatment purification. The nanocrystalline polycrystalline diamond was obtained by sequentially subjecting the processes of natural sedimentation, repeated centrifugation, filtration, and drying.

10. A drill bit, characterized in that, The micro / nano heterogeneous polycrystalline diamond composite sheet as described in any one of claims 1-4, which includes a drill bit body and a micro / nano heterogeneous polycrystalline diamond composite sheet fixed to the surface of the drill bit body, or a micro / nano heterogeneous polycrystalline diamond composite sheet prepared according to the preparation method of the micro / nano heterogeneous polycrystalline diamond composite sheet as described in any one of claims 5-9.

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