Uniform heat-stable polycrystalline diamond compact and preparation method thereof

Abstract

The invention discloses a uniform thermostable polycrystalline diamond compact and a preparation method thereof, the diamond compact comprises a hard alloy matrix, a diamond layer and a transition layer arranged between the hard alloy matrix and the diamond layer, the diamond layer is a modified diamond micro powder layer, the modified diamond micro-powder is boron-doped diamond micro-powder uniformly coated with metal cobalt; the transition layer is a metal layer and is deposited on the hard alloy matrix, and the hard alloy matrix and the diamond layer are sintered at high temperature and high pressure to form the polycrystalline diamond compact. According to the composite sheet, cobalt metal is evenly distributed, cobalt-rich and cobalt-poor areas can be avoided, the thermal stability of the composite sheet is excellent, and the composite sheet is more wear-resistant.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of superhard materials. More particularly, the present application relates to a uniform thermal stability type polycrystalline diamond compact and a preparation method thereof. BACKGROUND

[0002] A polycrystalline diamond compact (PDC) is a composite material formed by sintering a polycrystalline diamond layer with a metal or non-metal binder and a cemented carbide substrate. The synthesized compact has both the high wear resistance and high hardness of polycrystalline diamond, and also has the high impact toughness and weldability of cemented carbide. It has a wide range of applications, mainly in oil drilling, coal mining, geological drilling, etc.

[0003] For a compact used in oil drilling, there are many reasons for the failure of the polycrystalline diamond compact during use, including wear failure, impact failure and thermal failure, etc. Therefore, in addition to having strong wear resistance and impact resistance, the compact should also have excellent thermal stability. From the perspective of thermal failure, the main reasons for the thermal failure of the compact are as follows: firstly, the thermal expansion coefficients of diamond and sintering aid cobalt do not match, and when the drilling time is too long and the temperature rises sharply, the expansion of cobalt will greatly exceed that of diamond, thereby generating local deformation stress at the junction between diamond and cobalt, and further generating microcracks, causing micro or macro cracks; secondly, cobalt has a certain catalytic effect on the graphitization of diamond at high temperatures, which causes the diamond in contact with cobalt to be converted into graphite, thereby greatly reducing the valence binding force between diamond and diamond, and further causing thermal failure.

[0004] The cobalt content of the conventional compact polycrystalline diamond layer is in the range of 11-16wt%, and this part of cobalt is from the cobalt migrated and swept from the cemented carbide substrate to the polycrystalline diamond layer during the sintering process of the compact. Since the temperature field and pressure field during the sintering process are difficult to control very uniformly, the cobalt and carbide in the substrate are very easy to appear in the rich / poor cobalt and rich / poor tungsten carbide regions in the diamond layer during the sweeping migration process, thereby adversely affecting the performance of the PDC. In order to improve the uniformity of cobalt in the diamond layer during the sweeping process, the prior art uses the method of directly adding cobalt powder to the diamond powder to improve the uniformity, but the uniform dispersion of cobalt powder and diamond powder is also a technical problem.

[0005] In order to improve the thermal stability of the composite sheet, in 2001, ReedHycalog Company of the United States launched a trademark TREX of the thermal stability composite sheet and applied for a patent, the key technology of the TREX composite sheet is to dissolve and remove the cobalt on the surface of the composite sheet by acid corrosion and the like, so that the service life is greatly improved. But the thickness of the decobalt layer of the decobalt composite sheet is only 1 / 3~2 / 3 of the thickness of the diamond layer, the thermal stability is limited: and the decobalt speed is extremely slow, a single piece needs 20 days or even longer, in addition, the cemented carbide substrate is also easy to be corroded by acid in the decobalt process. SUMMARY

[0006] Another object of the present application is to provide a uniform thermal stability type polycrystalline diamond composite sheet which can solve the problems of uneven distribution of cobalt metal in the diamond layer of the composite sheet, low heat resistance and poor stability of the composite sheet in the prior art.

[0007] In order to achieve these objects and other advantages according to the present application, a uniform thermal stability type polycrystalline diamond composite sheet is provided, comprising a cemented carbide substrate, a diamond layer and a transition layer arranged between the cemented carbide substrate and the diamond layer, the diamond layer is a modified diamond micro powder layer, the modified diamond micro powder is boron-doped diamond micro powder uniformly coated with cobalt metal; the transition layer is a metal layer deposited on the cemented carbide substrate, and the cemented carbide substrate and the diamond layer are sintered under high temperature and high pressure to form a polycrystalline diamond composite sheet.

[0008] Preferably, the boron source of the boron-doped diamond micro powder is amorphous boron element, and the doping amount of boron element is 0.001~1wt%.

[0009] Preferably, the plating amount of the cobalt metal is 2.5~3.5wt%, and the plating thickness is 50~65nm.

[0010] Preferably, the modified diamond micro powder layer comprises a plurality of different particle size powders, and the average particle size of the plurality of different powders is 15μm.

[0011] A preparation method of a uniform thermal stability type polycrystalline diamond composite sheet, comprising the following steps: S1, by high temperature and high pressure in-situ growth method, amorphous boron element is used as boron source and doped into diamond micro powder in the growth process of the diamond micro powder to obtain boron-doped diamond micro powder; metal cobalt is plated on the boron-doped diamond micro powder by vacuum evaporation method to obtain modified diamond micro powder; S2, a plurality of different particle size modified diamond micro powder powders are mixed by acoustic resonance mixing process; S3, the transition layer is deposited on the cemented carbide substrate by PVD technology; S4, the mixed uniform modified diamond micro powder and the cemented carbide substrate with the deposited transition layer are assembled into a synthesis mold. S5, put the synthetic mold into the cavity of a cubic press, sinter under the condition of 7-8 GPa and 1400-1600 DEG C, and obtain the uniform and heat-stable polycrystalline diamond compact.

[0012] Preferably, in step S1, the vacuum degree of vacuum evaporation is not more than 2*10 -5 The thickness of the coating film of the metal cobalt formed on the boron-doped diamond powder is 50-65 nm, and the mass ratio is 2.5-3.5%.

[0013] Preferably, in step S2, the acceleration of the acoustic resonance mixing process is 10-100 g, and the mixing time is 10-60 min.

[0014] The diamond layer of the present application adopts boron-doped diamond powder, and the heat-resistant temperature of the boron-doped diamond powder is 200 DEG C higher than that of conventional diamond powder, so that the heat-resistant temperature of the compact obtained by pressing is also correspondingly improved, and the thermal stability of the compact is greatly improved. The boron-doped diamond powder coated with cobalt uniformly can ensure the required cobalt metal in the sintering process, and the cobalt metal is uniformly distributed, which can avoid the occurrence of cobalt-rich / poor and tungsten carbide-rich / poor regions. The plating amount of cobalt is set to 2.5-3.5 wt%, which can significantly reduce the content of cobalt element in the diamond layer, improve the wear resistance and thermal stability of the compact; the transition layer separates the hard alloy substrate and the diamond layer, which can reduce the stress at the interface between the substrate and the diamond layer, prevent the uneven penetration of cobalt and carbide in the substrate to the diamond layer, and avoid the influence of cobalt and tungsten carbide in the substrate on the sintering of the diamond layer. The microstructure of the polycrystalline diamond compact finally obtained is highly uniform, the compact product has controllable pressing stability, and has excellent thermal stability and wear resistance, which meets the demand for heat resistance and wear resistance of the compact under the enhanced drilling parameters.

[0015] Other advantages, objects and features of the present application will be apparent from the following description, and will be understood by those skilled in the art through practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a structure diagram of the uniform and heat-stable polycrystalline diamond compact of the present application; Figure 2 It is a phase transition temperature curve diagram of the diamond powder; Figure 3 It is a phase transition temperature curve diagram of the boron-doped diamond powder of the present application; Figure 4 It is an SEM diagram of the uniform and heat-stable polycrystalline diamond compact of the present application; Figure 5 It is an SEM diagram of the cobalt-rich region in the comparative example one compact; Figure 6 SEM image of the cobalt-depleted region produced in the comparative example composite film. Explanation of reference numerals in the instruction manual: 1. Matrix, 2. Transition layer, 3. Diamond layer. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0018] It should be noted that in the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] like Figures 1-4 As shown, the present invention provides a uniform, thermally stable polycrystalline diamond composite sheet, such as... Figure 1 As shown, the structure includes a cemented carbide substrate, a diamond layer, and a transition layer disposed between the cemented carbide substrate and the diamond layer. The diamond layer is a modified diamond micropowder layer, wherein the modified diamond micropowder is boron-doped diamond micropowder uniformly coated with metallic cobalt. The boron source of the boron-doped diamond micropowder is amorphous elemental boron, and the boron doping amount is 0.001~1wt%. The metallic cobalt doping amount is 2.5~3.5wt%, and the coating thickness is 50~65nm. The transition layer is a metal layer deposited on the cemented carbide substrate. The cemented carbide substrate and the diamond layer are sintered under high temperature and high pressure to form a polycrystalline diamond composite sheet. The modified diamond micro powder layer comprises various powders of different particle sizes, with an average particle size of 15 μm.

[0020] The boron-doped diamond powder is used in the diamond layer of the present application, and the heat-resistant temperature of the boron-doped diamond powder is 200°C higher than that of the conventional diamond powder, so that the heat-resistant temperature of the composite sheet obtained by pressing is also correspondingly improved, and the thermal stability of the composite sheet is greatly improved. The boron-doped diamond powder coated with cobalt can ensure the required cobalt metal during the sintering process, and the cobalt metal is uniformly distributed, so that the rich / poor cobalt and rich / poor tungsten carbide regions can be avoided. The plating amount of cobalt is set to 2.5-3.5wt%, which can significantly reduce the content of cobalt element in the diamond layer and improve the wear resistance and thermal stability of the composite sheet. The transition layer separates the hard alloy substrate and the diamond layer, which can reduce the stress at the interface between the substrate and the diamond layer, prevent the uneven penetration of cobalt and carbide in the substrate to the diamond layer, and avoid the influence of cobalt and tungsten carbide in the substrate on the sintering of the diamond layer. The microstructure of the final polycrystalline diamond compact is highly uniform, the pressing stability of the finished composite sheet is controllable, and the composite sheet has excellent thermal stability and wear resistance. The problems of uneven distribution of cobalt metal in the diamond layer of the composite sheet, low heat resistance and poor stability of the composite sheet in the prior art are solved, the demand for heat resistance and wear resistance of the composite sheet under the strengthened drilling parameters is met, and the quality stability of the polycrystalline diamond compact is ensured. The interface of the hard alloy substrate is a plane or a protrusion, and the transition layer metal can be titanium, molybdenum, tungsten sheet, etc.

[0021] A preparation method of a uniform thermal stability type polycrystalline diamond compact, comprising the following steps: S1, by high temperature and high pressure in-situ growth method, amorphous boron is used as boron source and doped into diamond powder during the growth process of diamond powder to obtain boron-doped diamond powder; vacuum evaporation method is used to coat metal cobalt on the boron-doped diamond powder to obtain modified diamond powder; the vacuum degree of vacuum evaporation is not more than 2*10 -5 ; the plating film thickness of the metal cobalt generated on the boron-doped diamond powder is 50-65nm, and the mass ratio is 2.5-3.5%; S2, a plurality of different particle sizes of modified diamond powder are mixed by using acoustic resonance mixing process, and the type of particle size is preferably 2-3; the acceleration of acoustic resonance mixing process is 10-100g, and the mixing time is 10-60min, which can prevent the damage of the plating layer metal and ensure the purity of the powder, and obtain uniformly mixed modified diamond powder; S3, the transition layer metal is deposited on the hard alloy substrate by PVD technology, and the deposition thickness is 50μm; S4, the uniformly mixed modified diamond powder and the hard alloy substrate with deposited transition layer are assembled into a synthesis mold; S5, the synthesis mold is placed in the cavity of a six-surface press, and sintered under the conditions of 7-8GPa and 1400-1600°C to obtain a uniform thermal stability type polycrystalline diamond compact.

[0022] <Embodiment One> A uniform thermal stability type polycrystalline diamond compact is prepared by the following method: F1, using amorphous boron as the boron source, through high-temperature and high-pressure in-situ growth method, doping into the growth process of diamond powder, the doping amount of boron element is 0.1%, obtaining boron-doped diamond powder, obtaining the phase transition temperature curve of boron-doped diamond powder as shown in Figure 3 ; the diamond powder is a single layer of powder, and the main particle size range of the powder is 10-20 microns; the metal cobalt is plated on the boron-doped diamond powder in a vacuum chamber with a vacuum degree of 1*10 -5 The mass ratio of the metal cobalt is 3.1%, and the generated plating film thickness is 60 nm, obtaining modified diamond powder; F2, after the preparation of the modified diamond powder, the gradation of the three different particle sizes of the modified diamond powder is designed to have an average particle size of 15 microns, and then the acoustic resonance process is used to uniformly mix the three different particle sizes of the modified diamond powder, the acoustic resonance process acceleration is 80g, and the mixing time is 30 minutes; after mixing, the impurity content of the powder is measured to be 15 ppm; F3, the transition layer is deposited on the hard alloy substrate by PVD technology, the transition layer is a titanium layer with a thickness of 50 microns; F4, the modified diamond powder, the transition layer and the hard alloy substrate are assembled into a synthesis mold, and the synthesis mold is placed in the cavity of a cubic press, and sintered under the conditions of 8GPa and 1500°C to obtain a uniform thermal stability type polycrystalline diamond compact, the cobalt content in the diamond compact is measured to be 3.1%, and the SEM picture of the uniform thermal stability type polycrystalline diamond compact is shown in Figure 4 , and the cobalt is uniformly and densely distributed.

[0023] <Comparative Example One> A diamond compact is composed of a hard alloy substrate and a diamond layer, and the diamond layer is a diamond powder layer, and the phase transition temperature curve of the diamond powder is shown in Figure 2 ; the diamond compact is prepared by the following method: The gradation of the three different particle sizes of the diamond powder is designed to have an average particle size of 15 microns, and then the mixing process is used to uniformly mix the three different particle sizes of the diamond powder, and the impurity content of the powder is measured to be 30 ppm after mixing; The diamond powder and the hard alloy substrate are assembled into a synthesis mold, and the synthesis mold is placed in the cavity of a cubic press, and sintered under the conditions of 8GPa and 1500°C to obtain a diamond compact, and the cobalt content in the diamond compact is measured to be 13%; the SEM pictures of the cobalt-rich and cobalt-poor regions generated in the diamond compact are shown in Figure 5 , respectively.Figure 6 As shown, it is illustrated that the composite sheet of Comparative Example 1 has rich / poor cobalt regions, which will seriously affect the performance of the composite sheet and affect the drilling efficiency.

[0024] [Comparative Example 2] A uniform thermal stability type of polycrystalline diamond composite sheet, which is different from Example 1 in that the thickness of the film generated in step F1 is 70 nm, and the rest is the same as Example 1. The cobalt content in the diamond composite sheet prepared is 3.6%, which is higher than that in the composite sheet of Example 1, and the wear resistance and heat resistance are reduced by 2% compared with Example 1.

[0025] According to Figure 2 , Figure 3 It can be known that the phase transition starting temperature of the boron-doped diamond powder of Example 1 of the present application is 1224.66°C, which is 140.48°C higher than the phase transition starting temperature of the diamond powder of Comparative Example 1 1084.18°C, and the powder mixed by the acoustic resonance mixing process used in Example 1 is more uniform and has less impurities. The thermal stability of the boron-doped diamond powder of the present application is good, and according to Figure 4 It can be known that the cobalt distribution of the composite sheet prepared in the present application is uniform and dense, therefore, the present application can ensure the cobalt metal required in the sintering process, and the cobalt metal is uniformly distributed, avoiding the occurrence of rich cobalt and poor cobalt regions, and the heat resistance of the present application is improved by 80% compared with Comparative Example 1, and the wear resistance is improved by 22%.

[0026] According to Example 1 and Comparative Example 2, as the plating thickness of cobalt on the modified diamond powder increases (60→70 nm), the cobalt content in the composite sheet increases, and the wear resistance and heat resistance slightly decrease, therefore, the composite sheet of the present application has excellent thermal stability and wear resistance.

[0027] Although the embodiments of the present application have been disclosed as above, it is not limited to the application listed in the specification and the embodiments, it can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, therefore, the present application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A uniform, thermally stable polycrystalline diamond composite sheet, characterized in that, The composite material includes a cemented carbide substrate, a diamond layer, and a transition layer disposed between the cemented carbide substrate and the diamond layer. The diamond layer is a modified diamond powder layer, wherein the modified diamond powder is boron-doped diamond powder uniformly coated with metallic cobalt. The transition layer is a metal layer deposited on the cemented carbide substrate. The cemented carbide substrate and the diamond layer are sintered under high temperature and high pressure to form a polycrystalline diamond composite sheet.

2. The uniform, thermally stable polycrystalline diamond composite sheet as described in claim 1, characterized in that, The boron source of the boron-doped diamond micropowder is amorphous boron, and the boron doping amount is 0.001~1wt%.

3. The uniform, thermally stable polycrystalline diamond composite sheet as described in claim 1, characterized in that, The amount of cobalt metal plating is 2.5~3.5wt%, and the plating thickness is 50~65nm.

4. The uniform, thermally stable polycrystalline diamond composite sheet as described in claim 1, characterized in that, The modified diamond micro powder layer comprises powders of various particle sizes, with an average particle size of 15 μm.

5. A method for preparing a uniform, thermally stable polycrystalline diamond composite sheet as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Amorphous boron is used as the boron source and incorporated into the diamond powder during the growth process by high temperature and high pressure in situ growth method to obtain boron-doped diamond powder; metallic cobalt is deposited on the boron-doped diamond powder by vacuum evaporation method to obtain modified diamond powder. S2. Mix various modified diamond micro powders of different particle sizes using an acoustic resonance mixing process; S3. The transition layer is deposited on the cemented carbide substrate using PVD technology; S4. Assemble the uniformly mixed modified diamond micro powder with the cemented carbide matrix with the deposited transition layer into a synthetic mold. S5. Place the composite mold into the cavity of a six-sided press and sinter it under conditions of 7-8 GPa and 1400-1600°C to obtain a uniform, thermally stable polycrystalline diamond composite sheet.

6. The method for preparing a uniform, thermally stable polycrystalline diamond composite sheet as described in claim 5, characterized in that, In step S1, the vacuum degree of vacuum evaporation is no greater than 2*10. -5 The thickness of the cobalt coating formed on boron-doped diamond powder ranges from 50 to 65 nm, with a mass ratio of 2.5 to 3.5%.

7. The method for preparing a uniform, thermally stable polycrystalline diamond composite sheet as described in claim 5, characterized in that, In step S2, the acceleration of the acoustic resonance mixing process is 10~100g, and the mixing time is 10~60min.

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