Method for preparing pure phase polycrystalline diamond drill bit by high pressure welding technology

Abstract

The method for preparing pure phase polycrystalline diamond drill teeth by high pressure welding technology, which takes cemented carbide block, pure phase polycrystalline diamond block and welding agent as raw materials, and the process steps are as follows: the processed cemented carbide drill tooth base, welding agent and processed pure phase polycrystalline diamond working layer are sequentially placed into a metal package, and then the opening end of the metal package is folded and closed to form a package; the obtained package is pre-pressed, and then the pre-pressed package is placed into a large cavity static high pressure device for welding under a pressure of 3.5-7 GPa and a temperature of 1000-1300 DEG C, to obtain a pure phase polycrystalline diamond drill tooth blank; and the obtained pure phase polycrystalline diamond drill tooth blank is processed to obtain a pure phase polycrystalline diamond drill tooth. The pure phase polycrystalline diamond drill teeth prepared by the above method have obviously improved heat resistance and wear resistance compared with commercial PDC drill teeth.

Description

Technical Field

[0001] This invention belongs to the field of drill bits for oil and gas exploration and development, and relates to a method for preparing drill bits for oil and gas exploration and development. Background Technology

[0002] Currently, drill bits used in oil and gas exploration and development are mainly commercial polycrystalline diamond (PDC) composite drill bits, consisting of a PDC working layer and a cemented carbide matrix. During the industrial synthesis of the PDC working layer, metallic materials such as iron, cobalt, and nickel, or non-metallic materials such as silicon carbide and boron carbide, are typically added as binders or sintering aids. This is because adding binders or sintering aids can reduce the high-temperature and high-pressure conditions during the sintering process of PDC and improve the yield of the polycrystalline diamond sintered body. However, during oil and gas drilling, as the drilling depth continues to increase, the cutting edge of the drill bit generates a large amount of heat and localized high stress due to cutting / friction with the rock. In the deep well environment, the heat cannot be dissipated in time and accumulates, causing thermal expansion of the working layer of the drill bit made of polycrystalline diamond. Since the binder or sintering aid has a different coefficient of thermal expansion than polycrystalline diamond, microcracks are generated in the polycrystalline diamond drill bit during thermal expansion, greatly shortening its service life. In addition, the binder or sintering aid can also promote the graphitization of polycrystalline diamond or react with polycrystalline diamond in a high-temperature environment, thereby affecting the cutting performance and wear resistance of the drill bit.

[0003] To address the issues associated with commercially available polycrystalline diamond (PDC) due to the presence of binders or sintering aids, existing technology discloses a method for high-temperature, high-pressure, integral, one-time sintering of PDC drill teeth. This method involves pre-pressing pure diamond micropowder with a tungsten carbide-cobalt cemented carbide matrix, followed by sintering under high temperature and pressure to obtain a drill tooth blank, which is then machined to produce the drill teeth. The problem with this method is that during the high-temperature, high-pressure sintering process, the cobalt in the cemented carbide dissolves the tungsten carbide to form a solid solution γ-phase, which penetrates and sweeps into the diamond powder layer in a molten state. The cobalt in the γ-phase causes the diamond particles to recrystallize, forming a strong polycrystalline diamond layer with D-D bonds on the cemented carbide matrix, which is tightly bonded to the matrix through the γ-phase. During use, residual stress at the interface can lead to fracture and detachment of the diamond layer, and the cobalt penetrating into the diamond layer can affect the diamond's wear resistance and thermal stability. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing pure phase polycrystalline diamond drill teeth by high pressure welding technology, so as to improve the heat resistance and wear resistance of the drill teeth.

[0005] The method for preparing pure-phase polycrystalline diamond drill bits using high-pressure welding technology described in this invention uses cemented carbide blocks, pure-phase polycrystalline diamond blocks, and flux as raw materials, and the process steps are as follows: (1) Process the pure phase polycrystalline diamond block into a drill tooth working layer of the required shape and size, process the cemented carbide block into a drill tooth matrix of the required shape and size, and then put the processed cemented carbide drill tooth matrix, flux, and processed pure phase polycrystalline diamond drill tooth working layer into the metal package in sequence, so that the flux is located on the end face of the cemented carbide drill tooth matrix and the pure phase polycrystalline diamond drill tooth working layer is located on the flux, and then fold the open end of the metal package to close it to form a package; (2) The package obtained in step (1) is pre-compressed to make the cemented carbide drill base, flux and pure phase polycrystalline diamond drill working layer tightly bonded. (3) Place the pre-compressed package from step (2) into a large-cavity static high-pressure device, and apply it at a pressure of 3.5–7 GPa and a temperature of 1000–1300 °C. 0 Welding is performed at C for 10-2000s to obtain a blank of pure phase polycrystalline diamond drill bit; the obtained blank of pure phase polycrystalline diamond drill bit is then processed to obtain pure phase polycrystalline diamond drill bit.

[0006] The method for preparing pure phase polycrystalline diamond drill bits by high-pressure welding technology described in this invention preferably uses Co-containing WC cemented carbide blocks, which are purchased from the market; the pure phase polycrystalline diamond blocks are prepared using diamond micro powder with a carbon purity greater than 99% as raw material, in accordance with the method described in CN 202010508137.3.

[0007] The method for preparing pure-phase polycrystalline diamond drill teeth using high-pressure welding technology described in this invention allows the welding surface between the working layer of the pure-phase polycrystalline diamond drill tooth and the cemented carbide drill tooth substrate to be planar (see...). Figure 1 Figure a in the diagram can also be non-planar (see Figure a). Figure 1 (See Figures b and c). A flat welding surface is easier to process, while a non-planar welding surface can increase the contact area between the two, which is beneficial to improving the mechanical bonding strength of the weld and can alleviate stress concentration at the weld to a certain extent.

[0008] The method for preparing pure-phase polycrystalline diamond drill bits using high-pressure welding technology described in this invention uses a flux primarily composed of Ni, Ag, Al, or Co. Preferably, the flux is AgCuTi or Al. 88 Si, BNi-2~13 or BCo-1, wherein the AgCuTi contains more than 68 wt% Ag. The amount of flux is determined by the area of ​​the welding surface between the cemented carbide drill bit matrix and the working layer of the pure polycrystalline diamond drill bit, and the preferred amount of flux per square millimeter of welding surface is... ~ gram.

[0009] The method for preparing pure phase polycrystalline diamond drill teeth by high-pressure welding technology described in this invention, wherein the metal coating material in step (1) is tantalum, rhenium, molybdenum, niobium or platinum.

[0010] The method for preparing pure phase polycrystalline diamond drill teeth by high pressure welding technology described in this invention, in step (2), the pressure of pre-compressing the inclusion body is 10~1000MPa and the time is 10~120s.

[0011] The method for preparing pure phase polycrystalline diamond drill teeth by high pressure welding technology described in this invention has the following steps: In step (3), the pressure increase rate from atmospheric pressure to welding pressure and the pressure decrease rate from welding pressure to atmospheric pressure are 9-18 GPa / h, and the temperature increase rate from room temperature to welding temperature and the temperature decrease rate from welding temperature to room temperature are 50-200℃ / min.

[0012] Compared with the prior art, the present invention has the following beneficial technical effects: 1. The method of the present invention obtains drill teeth by high-pressure welding a drill tooth working layer made of pure phase polycrystalline diamond block and a drill tooth base made of cemented carbide block. Compared with existing commercial PDC drill teeth, the heat resistance and wear resistance are significantly improved (see...). Figure 9 and Figure 10 ).

[0013] 2. The method of the present invention forms a drill tooth by high-pressure welding a drill tooth working layer made of pure polycrystalline diamond block and a drill tooth matrix made of cemented carbide block. Compared with preparing drill teeth by pre-pressing pure diamond powder and cemented carbide matrix and then sintering at high temperature and high pressure, the high-pressure welding temperature is lower and the structure of the pure polycrystalline diamond drill tooth working layer is different from that of pure diamond powder. Therefore, alloying elements (such as Co) and impurities in the cemented carbide matrix are difficult to diffuse into the pure polycrystalline diamond drill tooth working layer, which is beneficial to improving the wear resistance and thermal stability of the drill tooth.

[0014] 3. Diamond begins to oxidize at approximately 600°C and graphitize at approximately 900°C under normal or low pressure. However, the graphitization temperature increases under high pressure (for example, the graphitization temperature of diamond at 5 GPa is approximately 1400°C). Therefore, compared with laser welding, high-frequency welding, and vacuum welding, the method described in this invention can achieve a high-quality and high-strength bond between the pure phase polycrystalline diamond drill bit working layer and the cemented carbide drill bit matrix, while avoiding damage to the physical and chemical properties of the pure phase polycrystalline diamond drill bit working layer.

[0015] 4. Because the method described in this invention selects a suitable flux, the shear strength of the weld can reach 350 MPa. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a pure polycrystalline diamond drill bit prepared by the method described in this invention. In Figure a, the welding surface between the cemented carbide drill bit substrate and the pure polycrystalline diamond drill bit working layer is a plane; in Figure b, the welding surface between the cemented carbide drill bit substrate and the pure polycrystalline diamond drill bit working layer is a tooth-shaped surface; in Figure c, the welding surface between the cemented carbide drill bit substrate and the pure polycrystalline diamond drill bit working layer is an annular surface and a cylindrical surface. In the figures, 1—cemented carbide drill bit substrate, 2—welding layer, 3—pure polycrystalline diamond drill bit working layer.

[0017] Figure 2 An optical photograph of the pure phase polycrystalline diamond drill bit prepared in Example 2.

[0018] Figure 3 An optical photograph of the pure phase polycrystalline diamond drill bit prepared in Example 3.

[0019] Figure 4 An optical photograph of the pure phase polycrystalline diamond drill bit prepared in Example 4.

[0020] Figure 5 An optical photograph of the pure phase polycrystalline diamond drill bit prepared in Example 5.

[0021] Figure 6 The X-ray diffraction patterns are of five randomly selected blocks from the pure phase polycrystalline diamond blocks prepared in Example 1.

[0022] Figure 7 This is a scanning electron microscope image of the working layer surface of the pure phase polycrystalline diamond drill bit prepared in Example 2.

[0023] Figure 8 This is a cross-sectional scanning electron microscope image of the weld joint of the pure phase polycrystalline diamond drill bit prepared in Example 4.

[0024] Figure 9 Figure 1 shows the wear resistance test results of the pure phase polycrystalline diamond drill bit prepared in Example 2 and the commercial PDC drill bit. Figure 2 shows the wear resistance test results of the commercial PDC drill bit and the wear resistance test results of the pure phase polycrystalline diamond drill bit prepared in Example 2.

[0025] Figure 10 Figure 1 shows the room temperature and high temperature in-situ X-ray diffraction patterns of the pure phase polycrystalline diamond drill bit prepared in Example 5 and the commercial PDC drill bit. Figure 2 shows the room temperature and high temperature in-situ X-ray diffraction patterns of the commercial PDC drill bit and the pure phase polycrystalline diamond drill bit prepared in Example 5.

[0026] Figure 11The shear strength test results of the weld are shown in the figure, which shows the working layer of pure phase polycrystalline diamond drill teeth and the WC cemented carbide drill tooth matrix containing Co, which are welded in different ways.

[0027] Figure 12 The X-ray diffraction patterns of the working layer of the pure phase polycrystalline diamond block and the pure phase polycrystalline diamond drill tooth working layer prepared in Example 1, and the working layer of the drill tooth obtained by welding the WC cemented carbide drill tooth matrix containing Co in different ways are shown in Figure (2), which is an enlarged view of the 20~40° range in Figure (1). Detailed Implementation

[0028] The method of the present invention will be further described below through embodiments and in conjunction with the accompanying drawings. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] In the following examples, the large-cavity static high-pressure device for preparing pure phase polycrystalline diamond blocks in Example 1 is a domestically produced hinged six-sided top press, model DS 6×25 MN; the large-cavity static high-pressure device used for high-temperature and high-pressure welding in Examples 2-5 is a domestically produced hinged six-sided top press, model DS 6×14 MN.

[0030] In the following embodiments, diamond powder, Co-containing WC cemented carbide bulk, flux BNi-2, and Ag are used. 72 CuTi is purchased from the market.

[0031] Example 1 In this embodiment, the working layer of pure phase polycrystalline diamond drill bits is prepared using the following process steps: (1) Diamond powder with an average particle size of 10 μm and hydrofluoric acid with a mass concentration of 30% were added to a purification vessel at a mass ratio of 1:4. The mixture was stirred and heated to 60°C in a water bath, and then stirred at this temperature for 48 hours. After the powder settled, the liquid was discarded, and the powder was washed with deionized water until the wash water was neutral. The above operation was repeated twice. The acid-washed diamond powder was dried, and then the dried diamond powder was placed in a vacuum sintering furnace at a vacuum degree of 5×10 -3 The diamond powder was treated at 800℃ for 8 hours to remove agglomerates and impurities such as oxygen, nitrogen, and water vapor adsorbed on the surface of the diamond powder. (2) Using tantalum foil as the wrapping material, the surface of the tantalum foil is first polished, degreased, ultrasonically cleaned and infrared dried. The diamond powder treated in step (1) is placed into two tantalum foil wrappers and pre-pressed for 60s under a pressure of 400MPa to obtain two tantalum foil wrappers. (3) Place the two tantalum foil-wrapped blanks obtained in step (2) into a large-cavity static high-pressure device and sinter for 20 min at a pressure of 16 GPa and a temperature of 2300 °C. The loading and unloading methods and process conditions are as follows: pressurize to 16 GPa at a pressurization rate of 3.6 GPa / h and keep it constant, then heat to 2300 °C at a heating rate of 100 °C / min and hold for sintering for 20 min. After the sintering time is reached, first cool down at a cooling rate of 100 °C / min. The pressure was reduced to room temperature and then reduced to atmospheric pressure at a rate of 3.6 GPa / h. The resulting sample was placed in a mixed acid solution (volume ratio of hydrofluoric acid to nitric acid 1:1) consisting of 40% hydrofluoric acid and 40% nitric acid to remove the tantalum encapsulating material. After washing with deionized water and drying, two pure phase polycrystalline diamond blocks were obtained. The two pure phase polycrystalline diamond blocks were then processed by cutting, grinding, and polishing to obtain two pure phase polycrystalline diamond drill bit working layers with a size of Φ10mm×2mm.

[0032] Thirty-six pure-phase polycrystalline diamond drill bit working layers with dimensions of Φ10mm×2mm were prepared using the above method.

[0033] Five pure-phase polycrystalline diamond blocks were randomly selected from the prepared blocks and tested using X-ray diffraction. The test results are shown in [Figure number missing]. Figure 6 ,from Figure 6 It can be seen that the pure phase polycrystalline diamond bulk prepared in this embodiment contains only the diamond phase.

[0034] One layer was randomly selected from the prepared pure-phase polycrystalline diamond drill bit working layer, and its surface was analyzed by scanning electron microscopy. The scanning electron micrograph is shown below. Figure 7 ,from Figure 7 It can be seen that a large area of ​​tightly bonded, high-strength diamond-diamond interface is formed between the diamond grains, with few pores and high density.

[0035] Example 2 This embodiment uses a pure phase polycrystalline diamond drill bit working layer with dimensions of Φ10mm×2mm prepared in Example 1, a drill bit matrix with dimensions of Φ10mm×3mm machined from a Co-containing WC cemented carbide (YG10) block, and flux BNi-2 (Ni>82%) as raw materials to prepare pure phase polycrystalline diamond drill bits. The process steps are as follows: (1) Place the Co-containing WC cemented carbide drill base, 0.1g BNi-2, and pure phase polycrystalline diamond drill working layer into a tantalum foil package in sequence, so that the flux is located on the end face of the cemented carbide drill base and the pure phase polycrystalline diamond drill working layer is located on the flux. Then fold the open end of the tantalum foil package to close it to form a package. (2) The inclusion obtained in step (1) is pre-pressed at a pressure of 200 MPa for 60s to tightly bond the Co-containing WC cemented carbide drill tooth matrix, flux BNi-2, and pure phase polycrystalline diamond drill tooth working layer. (3) Place the pre-compressed package from step (2) into a large-cavity static high-pressure device, increase the pressure from atmospheric pressure to welding pressure of 5.5 GPa at a pressurization rate of 10 GPa / h and maintain it, then increase the temperature from room temperature to welding temperature of 1200℃ at a heating rate of 100℃ / min for welding, and weld for 600s. After the welding time is reached, first reduce the temperature to room temperature at a cooling rate of 100℃ / min, and then reduce the pressure to atmospheric pressure at a depressurization rate of 10GPa / h. Then take out the welded package, grind it to remove the tantalum foil wrapping, and obtain a pure phase polycrystalline diamond drill bit blank. Process the pure phase polycrystalline diamond drill bit blank to obtain pure phase polycrystalline diamond drill bit.

[0036] Repeat the above process steps to prepare 5 pure phase polycrystalline diamond drill teeth.

[0037] Optical photographs of the pure-phase polycrystalline diamond drill bits prepared in this embodiment are shown below. Figure 2 As shown, five pure-phase polycrystalline diamond drill bits were tested for hardness and shear strength. The average Vickers hardness of the working layer of the pure-phase polycrystalline diamond drill bits was about 120 GPa, and the shear strength of the weld joint was 310~332 MPa.

[0038] The wear resistance of the pure phase polycrystalline diamond drill bits prepared in this embodiment and commercial PDC drill bits was tested. The wear resistance test involved cutting a marble column with both types of drill bits on a CNC lathe at a cutting speed of 100 m / min and a cutting depth of 0.5 mm. The test results are shown below. Figure 9 ,from Figure 9 It can be seen that after cutting 3000m, the defect area of ​​the working layer of the commercial PDC drill tooth is 3.05*1.04mm, while the defect area of ​​the working layer of the pure phase polycrystalline diamond drill tooth prepared in this embodiment is 2.34*0.49mm. Therefore, compared with the commercial PDC drill tooth, the wear resistance of the pure phase polycrystalline diamond drill tooth prepared in this embodiment is significantly improved.

[0039] Example 3

[0040] This embodiment uses a pure phase polycrystalline diamond drill bit working layer with dimensions of Φ10mm×2mm prepared in Example 1, a drill bit matrix with dimensions of Φ10mm×3mm machined from a Co-containing WC cemented carbide (YG12) block, and flux BNi-2 (Ni>82%) as raw materials to prepare pure phase polycrystalline diamond drill bits. The process steps are as follows: (1) Place the Co-containing WC cemented carbide drill base, 0.2g BNi-2, and pure phase polycrystalline diamond drill working layer into a tantalum foil package in sequence, so that the flux is located on the end face of the cemented carbide drill base and the pure phase polycrystalline diamond drill working layer is located on the flux. Then fold the open end of the tantalum foil package to close it to form a package. (2) The inclusion obtained in step (1) is pre-pressed at a pressure of 200MPa for 60s to make the Co-containing WC cemented carbide drill tooth matrix, flux BNi-2, and pure phase polycrystalline diamond drill tooth working layer tightly bonded together. (3) Place the pre-compressed package from step (2) into a large-cavity static high-pressure device, increase the pressure from atmospheric pressure to welding pressure of 5.5 GPa at a pressurization rate of 10 GPa / h and maintain it, then increase the temperature from room temperature to welding temperature of 1300℃ at a heating rate of 100℃ / min for welding, and weld for 900s. After the welding time is reached, first reduce the temperature to room temperature at a cooling rate of 100℃ / min, and then reduce the pressure to atmospheric pressure at a depressurization rate of 10 GPa / h. Then take out the welded package, grind it to remove the tantalum foil wrapping, and obtain a pure phase polycrystalline diamond drill bit blank. Process the pure phase polycrystalline diamond drill bit blank to obtain pure phase polycrystalline diamond drill bit.

[0041] Repeat the above process steps to prepare 5 pure phase polycrystalline diamond drill teeth.

[0042] Optical photographs of the pure-phase polycrystalline diamond drill bits prepared in this embodiment are shown below. Figure 3 As shown, five pure-phase polycrystalline diamond drill bits were tested for hardness and shear strength. The average Vickers hardness of the working layer of the pure-phase polycrystalline diamond drill bits was about 120 GPa, and the shear strength of the weld was 327~350 MPa.

[0043] Example 4 This embodiment uses a pure phase polycrystalline diamond drill bit working layer with dimensions of Φ10mm×2mm prepared in Example 1, a drill bit base with dimensions of Φ10mm×3mm machined from a Co-containing WC cemented carbide (YG10) block, and flux Ag. 72 Pure-phase polycrystalline diamond drill bits were prepared using CuTi as raw material. The process steps are as follows: (1) Take a Co-containing WC cemented carbide drill bit matrix and 0.1g Ag 72 CuTi and pure phase polycrystalline diamond drill bit working layers are sequentially placed in a tantalum foil package, with the flux located on the end face of the cemented carbide drill bit matrix and the pure phase polycrystalline diamond drill bit working layer located on the flux. Then, the open end of the tantalum foil package is folded to close and form a package. (2) The inclusion obtained in step (1) is pre-compressed at a pressure of 200 MPa for 60 s to make the Co-containing WC cemented carbide drill bit matrix and flux Ag 72The CuTi and pure polycrystalline diamond drill bit working layer are tightly bonded together; (3) Place the pre-compressed package from step (2) into a large-cavity static high-pressure device, increase the pressure from atmospheric pressure to welding pressure of 5.5 GPa at a pressurization rate of 10 GPa / h and maintain it, then increase the temperature from room temperature to welding temperature of 1000℃ at a heating rate of 100℃ / min for welding, and weld for 600s. After the welding time is reached, first reduce the temperature to room temperature at a cooling rate of 100℃ / min, and then reduce the pressure to atmospheric pressure at a depressurization rate of 10 GPa / h. Then take out the welded package, grind it to remove the tantalum foil wrapping, and obtain a pure phase polycrystalline diamond drill bit blank. Process the pure phase polycrystalline diamond drill bit blank to obtain pure phase polycrystalline diamond drill bit.

[0044] Repeat the above process steps to prepare 5 pure phase polycrystalline diamond drill teeth.

[0045] Optical photographs of the pure-phase polycrystalline diamond drill bits prepared in this embodiment are shown below. Figure 4 As shown. A cross-sectional scanning electron microscope image of the weld joint of the pure-phase polycrystalline diamond drill bit prepared in this embodiment is shown below. Figure 8 ,from Figure 8 It can be seen that the weld layer is about 20μm thick.

[0046] Five pure-phase polycrystalline diamond drill bits were tested for hardness and shear strength. The average Vickers hardness of the working layer of the pure-phase polycrystalline diamond drill bits was about 120 GPa, and the shear strength of the weld was 280~307 MPa.

[0047] Example 5 This embodiment uses a pure phase polycrystalline diamond drill bit working layer with dimensions of Φ10mm×2mm prepared in Example 1, a drill bit base with dimensions of Φ10mm×3mm machined from a Co-containing WC cemented carbide (YG12) block, and flux Ag. 72 Pure-phase polycrystalline diamond drill bits were prepared using CuTi as raw material. The process steps are as follows: (1) Take a Co-containing WC cemented carbide drill bit matrix and 0.2g Ag 72 CuTi and pure phase polycrystalline diamond drill bit working layers are sequentially placed in a tantalum foil package, with the flux located on the end face of the cemented carbide drill bit matrix and the pure phase polycrystalline diamond drill bit working layer located on the flux. Then, the open end of the tantalum foil package is folded to close and form a package. (2) The inclusion obtained in step (1) is pre-compressed at a pressure of 200 MPa for 60 s to compress the Co-containing WC cemented carbide drill bit matrix and the flux Ag. 72 The CuTi and pure polycrystalline diamond drill bit working layer are tightly bonded together; (3) Place the pre-compressed package from step (2) into a large-cavity static high-pressure device, increase the pressure from atmospheric pressure to welding pressure of 5.5 GPa at a pressurization rate of 10 GPa / h and maintain it, then increase the temperature from room temperature to welding temperature of 1100℃ at a heating rate of 100℃ / min for welding, and weld for 900s. After the welding time is reached, first reduce the temperature to room temperature at a cooling rate of 100℃ / min, and then reduce the pressure to atmospheric pressure at a depressurization rate of 10 GPa / h. Then take out the welded package, grind it to remove the tantalum foil wrapping, and obtain a pure phase polycrystalline diamond drill bit blank. Process the pure phase polycrystalline diamond drill bit blank to obtain pure phase polycrystalline diamond drill bit.

[0048] Repeat the above process steps to prepare 5 pure phase polycrystalline diamond drill teeth.

[0049] Optical photographs of the pure-phase polycrystalline diamond drill bits prepared in this embodiment are shown below. Figure 5 As shown, five pure-phase polycrystalline diamond drill bits were tested for hardness and shear strength. The average Vickers hardness of the working layer of the pure-phase polycrystalline diamond drill bits was about 120 GPa, and the shear strength of the weld joint was 298~319 MPa.

[0050] The pure-phase polycrystalline diamond drill bits prepared in this embodiment were subjected to in-situ X-ray diffraction tests at room temperature and high temperature, and commercial PDC drill bits were compared with those tested. The test structures are shown in the figure. Figure 10 ,from Figure 10 As can be seen from Figure (1), commercial PDC drill bits contain diamond phase, Co3O4, and Co from 22℃ to 800℃, and graphite phase appears in addition to diamond phase, Co3O4, and Co at 1000℃. Figure 10 As can be seen from Figure (2), the pure-phase polycrystalline diamond drill bit prepared in this embodiment exhibits only the diamond phase from 22℃ to 1200℃, with the graphite phase appearing only at 1400℃. Therefore, compared with commercial PDC drill bits, the heat resistance of the pure-phase polycrystalline diamond drill bit prepared in this embodiment is significantly improved.

[0051] Comparative Example 1. Comparison of shear strength at weld joints (1) Five pure-phase polycrystalline diamond drill bit working layers with dimensions of Φ10mm×2mm prepared in Example 1 were vacuum welded to five YG10 cemented carbide drill bit substrates with dimensions of Φ10mm×3mm. The flux was BNi-2. The vacuum welding process parameters were: vacuum degree of 2×10 -4 The welding temperature was 900℃, the heating / cooling rate was 100℃ / h, and the holding time was 30min. Shear strength tests were performed on the five welded drill teeth, and the shear strength ranged from 180 to 230 MPa (see...). Figure 11 ).

[0052] (2) Five pure-phase polycrystalline diamond drill bit working layers with dimensions of Φ10mm×2mm prepared in Example 1 were respectively subjected to high-frequency welding to five YG10 cemented carbide drill bit substrates with dimensions of Φ10mm×3mm. The flux was BNi-2, and the high-frequency welding process parameters were: welding frequency of 400KHz and welding time of 10s. The shear strength of the welded joints of the five drill bits was tested, and the shear strength was 160~220MPa (see...). Figure 11 ).

[0053] (3) Five pure-phase polycrystalline diamond drill bit working layers with dimensions of Φ10mm×2mm prepared in Example 1 were laser-welded to five YG10 cemented carbide drill bit substrates with dimensions of Φ10mm×3mm. The flux was BNi-2, and the laser welding process parameters were: laser frequency 20Hz, power 800W, and laser action time 30s. The shear strength of the five drill bit welds was tested, and the shear strength was 170~240MPa (see...). Figure 11 ).

[0054] (4) The 20 drill teeth prepared by high-pressure welding in Examples 2 to 5 of the present invention were tested and found to have a shear strength of 280-350 MPa at the weld (see Examples 2 to 5 and Figure 11 ).

[0055] From the test results ( Figure 11 As can be seen, the high-pressure welding described in this invention significantly improves the shear strength at the weld compared to vacuum welding, high-frequency welding, and laser welding.

[0056] 2. The appearance of graphite phase X-ray diffraction tests were performed on the pure phase polycrystalline diamond drill bit working layer (also known as the initial sample) prepared in Example 1, the drill bits obtained by vacuum welding, high-frequency welding, laser welding, and high-pressure welding in Examples 2-5. The test results are shown in […]. Figure 12 ,from Figure 12 As can be seen, the drill teeth obtained by high-pressure welding in this embodiment are the same as the initial sample, with no graphite phase in the 20~40° range; the drill teeth obtained by vacuum welding, high-frequency welding, and laser welding all showed graphite phase in the 20~40° range. Therefore, compared with vacuum welding, high-frequency welding, and laser welding, the high-pressure welding described in this invention can improve the strength, wear resistance, and thermal stability of the drill teeth.

Claims

1. A method for preparing pure-phase polycrystalline diamond drill bits using high-pressure welding technology, characterized in that... Using cemented carbide blocks, pure-phase polycrystalline diamond blocks, and flux as raw materials, the process steps are as follows: (1) Process the pure phase polycrystalline diamond block into a drill tooth working layer of the required shape and size, process the cemented carbide block into a drill tooth matrix of the required shape and size, and then put the processed cemented carbide drill tooth matrix, flux, and processed pure phase polycrystalline diamond drill tooth working layer into the metal package in sequence, so that the flux is located on the end face of the cemented carbide drill tooth matrix and the pure phase polycrystalline diamond drill tooth working layer is located on the flux, and then fold the open end of the metal package to close it to form a package; (2) The package obtained in step (1) is pre-compressed to make the cemented carbide drill base, flux and pure phase polycrystalline diamond drill working layer tightly bonded. (3) Place the pre-compressed package from step (2) into a large-cavity static high-pressure device and weld it at a pressure of 3.5 to 7 GPa and a temperature of 1000 to 1300℃ for 10 to 2000 s to obtain a blank of pure phase polycrystalline diamond drill bit; process the obtained blank of pure phase polycrystalline diamond drill bit to obtain pure phase polycrystalline diamond drill bit; The flux is AgCuTi or BNi-2~13, wherein the Ag content in AgCuTi is greater than 68wt%; the amount of flux is determined by the area of ​​the welding surface between the cemented carbide drill bit matrix and the working layer of the pure phase polycrystalline diamond drill bit, and the amount of flux per square millimeter of welding surface is... ~ gram.

2. The method for preparing pure-phase polycrystalline diamond drill bits by high-pressure welding technology according to claim 1, characterized in that... In step (1), the metal wrapping material is tantalum, rhenium, molybdenum, niobium or platinum.

3. The method for preparing pure-phase polycrystalline diamond drill bits by high-pressure welding technology according to claim 1 or 2, characterized in that... In step (2), the pressure of the package is 10~1000MPa and the time is 10~120s.

4. The method for preparing pure-phase polycrystalline diamond drill bits by high-pressure welding technology according to claim 1 or 2, characterized in that... In step (3), the pressure increase rate from atmospheric pressure to welding pressure and the pressure decrease rate from welding pressure to atmospheric pressure are 9 to 18 GPa / h, and the temperature increase rate from room temperature to welding temperature and the temperature decrease rate from welding temperature to room temperature are 50 to 200℃ / min.

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