A method for welding superhard material using a powder matrix at high temperature and high pressure

Abstract

The application discloses a method for welding superhard material by using powder matrix under high temperature and high pressure and belongs to the technical field of welding, and comprises the following steps: (1) adding a binder to the matrix powder material, uniformly mixing and pre-pressing to improve the compactness of the matrix powder material; (2) removing impurities on the surface of the superhard material, wrapping the superhard material after impurity removal with a lateral support ring and placing the superhard material on the matrix, placing a hard protective sheet on the superhard material and the lateral support ring, wrapping the formed assembly with a high-melting-point metal, placing soft protective sheets on the top and sides of the assembly, and performing high-temperature and high-pressure welding after the overall assembly is completed; (3) taking out the tool blank obtained by welding after temperature and pressure relief, removing the lateral support ring, the hard protective sheet and the soft protective sheet, and further processing to obtain a finished product. The application solves the problems of low welding strength, easy graphite of diamond, introduction of a solder layer by solder welding, and influence of the solder layer on the thermal stability of the tool in the welding of the matrix and the superhard material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of welding technology, in particular to a method for welding superhard materials using a powder matrix under high temperature and high pressure. BACKGROUND

[0002] Superhard materials are a general term for materials with a hardness exceeding 40 GPa, and currently only diamond and cubic boron nitride (cBN) are generally considered as superhard materials in the industry.

[0003] In industry, polycrystalline diamond (PCD) sintered under high temperature and high pressure is mostly used to eliminate the anisotropy of diamond single crystals. The most representative application of PCD is polycrystalline diamond cutter (PCDC), which is widely used in oil and gas drilling, so the performance of PCDC largely determines the depth and efficiency of drilling. As for cBN, the main form of use is polycrystalline cBN (PcBN), which mainly replaces PCD to cut iron group materials in industry.

[0004] In actual use, diamond / cBN is usually combined with a matrix of high hardness, high toughness and high thermal conductivity to prepare a cutter, which can reduce the use cost, but the existing technology still has the following problems in the combination method of the two:

[0005] 1. Diamond, cBN and matrix combination can usually be performed by means of glue bonding, laser welding, microwave welding, high-frequency welding and vacuum welding. Among them, the cutter with glue bonding has low bonding strength between the matrix part and the superhard material part, and the cutting and drilling effect is poor. Laser welding, high-frequency welding and vacuum welding can improve the bonding strength between the matrix and the superhard material, but the disadvantage is that the thermal response degree is large, which easily causes oxidation and graphitization of diamond, thereby reducing the physical and chemical properties of diamond; at the same time, the high-temperature environment introduced in the welding of diamond with binder will make the binder inside the diamond become a catalyst for the transformation of diamond particles to graphite, which will accelerate the transformation of diamond to graphite, and thus performance instability will occur; at the same time, the binder in PCD and PcBN with binder under high temperature has different thermal expansion coefficients from diamond and cBN, which will cause the binder to expand and extrude diamond and cBN, thereby causing cracks in diamond and cBN. Although the use of solder (iron, cobalt, nickel, silver, aluminum, silicon, etc.) to weld superhard materials and matrix can improve the bonding strength of the two, the presence of the solder layer will affect the heat transfer in use and the solder will be oxidized or melted under high temperature, so the solder layer will affect the performance of the cutter.

[0006] 2. The mainstream superhard material and substrate welding on the market can be mainly divided into the following ways: (1) diamond / cBN powder and substrate containing binder (sintered) are welded; (2) sintered high-performance PCD / PcBN is bonded by using glue, laser welding, microwave welding, high-frequency welding and vacuum welding. The tool made by method (1) cannot guarantee the uniform distribution of the binder in the PCD / PcBN after welding, resulting in obvious performance difference at the end of the PCD / PcBN; at the same time, the diamond / cBN powder and the substrate are bonded by using the binder in the substrate, so part of the superhard material contains binder, and the hardness and thermal stability of the superhard material end are far lower than those of PCD / PcBN without binder. For the (2) method of welding the tool, the listed several bonding methods need to ensure that the PCD / PcBN and the bonded substrate end remain parallel (ensure that the solder is evenly laid), and also need to ensure that there is no defect, such as notch, pore, crack, etc., between the PCD / PcBN end and the substrate end, otherwise the defects on the PCD / PcBN will crack under pressure, and the process requirement is high.

[0007] 3. When using bulk substrate material to weld superhard material, in order to ensure the quasi-static water pressure of welding, the sample part of all high-pressure assemblies is circular, and only cylindrical tools can be sintered. In real application, tools of different shapes (such as ellipse, square, frustum, etc.) are also needed, but if the bulk substrate is used for sintering in high-pressure assembly, the irregular substrate part will be damaged due to different pressures in high-pressure assembly, resulting in failure of tool welding, so irregular shaped tools cannot be directly sintered in high-pressure assembly. SUMMARY

[0008] The present application is to solve the technical problems of low bonding strength of diamond, cBN and substrate, easy oxidation and graphitization of diamond, influence of solder layer on tool thermal stability and utilization of damaged superhard material sample in the prior art; the purpose is to provide a method for welding superhard material by using powder substrate at high temperature and high pressure, which overcomes the problems of low welding strength, easy graphitization of diamond, introduction of solder layer affecting tool thermal stability and improving the utilization of damaged superhard material in the existing welding technology.

[0009] The present application is realized by the following technical scheme:

[0010] A method for welding superhard material by using powder substrate at high temperature and high pressure, comprising the following steps:

[0011] (1) adding binder to the substrate powder material, mixing uniformly and then pre-pressing to improve the density, the density of the pre-pressed substrate should be maintained above 60%;

[0012] (2) remove impurities on the surface of the superhard material by ultrasonic cleaning, after ultrasonic cleaning, immerse the superhard material in alcohol under ultrasonic cleaning, after immersion, dry, then wrap the superhard material after impurity removal with a lateral support ring and place it on the base, then place the hard protective sheet on the superhard material and the lateral support ring, wrap the formed assembly with a high-melting-point metal so that it does not contact the external material, then place the soft protective sheet on the top and side of the assembly, after the overall assembly is completed, perform high-temperature and high-pressure welding;

[0013] Since the compactness of the base powder after pre-pressing is generally between 50% and 90%, which means that the volume of the base part after sintering will be reduced by 10% to 50% compared to before pre-pressing, and the superhard material is sintered in advance, so its compactness is above 98%, in this case, the sintering and collapse of the base powder under high temperature and high pressure will cause a large stress gradient in the cavity, causing the superhard material to crack or generate many micro-cracks inside. In order to avoid this phenomenon, in step (2), the diameter of the base should be greater than the diameter of the superhard material layer (in the experiment, the diameter of the powder pre-pressed base should be maintained between 1 to 2 times the diameter of the superhard material to ensure that the base part has a corresponding processing size after sintering and collapse under high temperature and high pressure), the diameter difference is filled with material, that is, a lateral support ring is provided around the superhard material to provide lateral support, since the collapse of the base part under high pressure will also cause stress impact on the diamond / cBN surface not in contact with the base, therefore the end face also needs to be protected, so a hard protective sheet is provided to form a hard protection for the diamond / cBN and the lateral support ring, at the same time, the thickness of the diamond / cBN should be 1 to 10 times the thickness of the hard protective sheet, and a soft protective sheet is also provided on the hard protective sheet to improve the quasi-hydrostatic pressure environment of the diamond / cBN under high temperature and high pressure, reduce the stress accumulation of the diamond / cBN part, and the thickness of the soft protective sheet should also be 1 to 10 times the thickness of the diamond / cBN.

[0014] (3) After temperature and pressure relief, the tool blank obtained by welding is taken out, the lateral support ring, hard protective sheet and soft protective sheet are removed, and the finished product is further processed and handled.

[0015] The present application adopts the method of directly welding the superhard material and the base powder under high temperature and high pressure to prepare the tool, the advantages of welding the powder and the superhard material are that the process of base sintering and diamond welding can be carried out simultaneously under high temperature and high pressure, the powder can be more fully contacted with the superhard material in this process, thereby improving the bonding strength of the base and the diamond, and at the same time, the sintering process of the base can be omitted, reducing the process steps and reducing the tool manufacturing cost.

[0016] Further, the welding of the present application is carried out under high pressure, which can improve the thermal stability of superhard materials such as diamond, for example, the graphitization temperature of diamond under high pressure of 5 GPa is about 1400℃, which is about 500℃ higher than that under normal pressure; therefore, the welding of diamond and the substrate under high pressure can realize high-quality and high-strength combination of the diamond polycrystalline layer and the hard alloy substrate, and can avoid damage to the diamond polycrystalline layer, avoid large thermal response degree to cause oxidation and graphitization of diamond, thereby reducing the physical and chemical properties of diamond.

[0017] In addition, the welding method of the present application does not need to add solder, but directly uses the binder in the substrate powder to combine with the superhard material, so that the influence of the solder layer on the performance of the tool can be eliminated.

[0018] In summary, the present application overcomes the problems of low welding strength, easy to cause diamond graphitization, and the introduction of solder layer affecting the thermal stability of the tool during soldering in the prior art.

[0019] As a further aspect of the present application, the superhard material is diamond or cBN, wherein the diamond includes polycrystalline diamond without binder sintering, polycrystalline diamond with binder sintering, CVD polycrystalline diamond without binder, and the cBN includes polycrystalline cBN without binder sintering or polycrystalline cBN with binder sintering.

[0020] Since the binder in the diamond or cBN containing binder is different from the thermal expansion coefficient of diamond and cBN, it will cause the binder to expand and extrude the diamond and cBN grains at high temperature, thereby causing cracks in the two samples, therefore, the diamond or cBN without binder is preferred.

[0021] As a further aspect of the present application, the substrate powder material includes one or more of tungsten carbide, cBN, silicon carbide, silicon nitride and boron carbide, the binder includes one or more of iron, cobalt, nickel, aluminum, copper, silver and silicon, and the binder content is 1-20% of the mass of the substrate powder material.

[0022] As a further aspect of the present application, in step (1), the pre-pressing pressure is between 10-1200 MPa.

[0023] As a further aspect of the present application, in step (2), the lateral support ring material is selected from iron, cobalt, nickel, aluminum, aluminum oxide, magnesium oxide, cBN, diamond, silicon carbide or hBN.

[0024] As a further aspect of the present application, in step (2), the metal used for wrapping is tantalum, rhenium or molybdenum.

[0025] As a further scheme of the present application, in step (2), the hard protective sheet adopts alumina or magnesia ceramic material. In order to avoid the reaction between the hard protective sheet and diamond / cBN, ceramic material which does not react with diamond / cBN at 2-20 GPa and 1000-3000 ℃, such as alumina, magnesia, etc. is required.

[0026] As a further scheme of the present application, in step (2), the soft protective sheet material adopts sodium chloride, potassium chloride or calcium chloride. The soft protective sheet needs to adopt material which will melt at high temperature and high pressure.

[0027] As a further scheme of the present application, in step (2), the welding pressure is 2-20 GPa, the welding temperature is 1000-3000 ℃, and the welding time is 60-1200 s. The sintering temperature should be adjusted according to the high-pressure stability region of diamond and cBN, which needs to ensure good sintering of the substrate, good combination of the substrate powder with diamond and cBN, and non-graphitization of diamond at the temperature and pressure.

[0028] As a further scheme of the present application, the superhard material has defects or grooves;

[0029] For welding superhard material with defects, the binder-containing substrate powder is poured into the defect position for pre-pressing, and then welding is performed;

[0030] For welding superhard material with grooves, the grooves are laser processed on the superhard material, the superhard material with grooves is placed in the mold, the binder-containing substrate powder is poured into the annular groove for pre-pressing, and then welding is performed.

[0031] In order to further improve the bonding strength of diamond / cBN and the substrate, regular or irregular grooves can be processed on the surface, and the substrate powder is filled in the grooves for pre-pressing. Since the bonding surface of the substrate and diamond / cBN is not a plane, the substrate powder is embedded in the diamond / cBN, which can improve the bonding strength of the two, and a higher bonding strength cutter is obtained. The shear strength of ordinary commercial welded cutter is 240-260 MPa, and the bonding strength of the cutter welded with annular grooves is between 320-400 MPa. The present application finds that the bonding strength of the cutter welded with powder increases by at least 10 MPa for each groove, which indicates that the bonding strength of diamond / cBN and the substrate in the cutter welded with the sample with grooves is linearly related to the number of grooves on the sample.

[0032] In addition, in the industry, some defective samples are prepared in the process of preparing diamond and cBN, and the defective samples are generally classified as poor quality products, but the defective samples can still be used by using powder welding, which does not reduce the performance of the tool, but can improve the bonding strength of the tool and the matrix. Therefore, the use of powder matrix welding can improve the utilization rate of the sample and turn waste into treasure.

[0033] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0034] 1. The present application directly welds the superhard material and the matrix powder at high temperature and high pressure to prepare the tool. The advantage of welding the powder and the superhard material is that the process of sintering the matrix and welding the diamond can be carried out simultaneously at high temperature and high pressure. In this process, the powder can be more fully in contact with the superhard material, thereby improving the bonding strength of the matrix and the diamond. At the same time, the sintering process of the matrix can be omitted, the process steps are reduced, and the tool manufacturing cost is reduced.

[0035] 2. The welding of the present application is carried out at high pressure, which can improve the thermal stability of the superhard material such as diamond. For example, the graphitization temperature of diamond at 5GPa high pressure is about 1400℃, which is about 500℃ higher than that at normal pressure. Therefore, welding the diamond and the matrix at high pressure can realize high-quality and high-strength bonding of the diamond polycrystalline layer and the hard alloy matrix, and can avoid damage to the diamond polycrystalline layer, avoid the degree of thermal response, oxidation and graphitization of the diamond, thereby reducing the physical and chemical properties of the diamond.

[0036] 3. The welding method of the present application does not need to add solder, but directly uses the binder in the matrix powder to combine with the superhard material, thereby eliminating the influence of the solder layer on the performance of the tool, and the bonding strength of the matrix and the superhard material is high.

[0037] 4. In order to avoid the problem that the matrix powder collapses and generates a large stress gradient in the cavity at high temperature and high pressure, causing the superhard material to crack or many microcracks in the interior, a lateral support ring, a hard protective sheet and a soft protective sheet are provided to provide a hydrostatic pressure environment and a lateral support environment for the superhard material and the matrix powder, thereby avoiding stress accumulation and ensuring the performance of the welded tool.

[0038] 5. In the existing industry, when welding bulk substrate materials and superhard materials, irregular substrate parts will be damaged due to different pressures in high-pressure assembly, resulting in failure of tool welding, so irregular-shaped tools cannot be directly sintered in high-pressure assembly. In order to ensure the quasi-static water pressure of welding, the sample parts in the existing high-pressure assembly are circular, and only cylindrical tools can be sintered. The present application uses powder substrate to weld with diamond bulk or cBN bulk, which is not only suitable for cylindrical tool welding, but also can process the initial superhard material into a specific-shaped tool (such as square, oval, frustum, etc.). Compared with bulk substrate, powder substrate can collapse under high pressure to resist the non-hydrostatic pressure in the special-shaped assembly, thereby effectively avoiding the problem of fracture of special-shaped bulk substrate under non-hydrostatic pressure. The welding of special-shaped tools depends on the lateral support ring, hard protective sheet and soft protective sheet provided in the high-pressure assembly to provide a hydrostatic pressure environment and lateral support environment for superhard materials and substrate powder, thereby welding superhard tools with excellent performance.

[0039] 6. The current industry does not have in-depth research on the welding method of superhard material tools with defects and grooves. Generally, samples with defects cannot be prepared into tools. Using powder substrate to weld superhard materials with defects can improve the bonding strength of superhard materials and substrate, and turn waste into treasure. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the example embodiments of the present application, the following will briefly introduce the drawings needed to be used in the examples. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0041] Figure 1 It is a schematic diagram of the assembly structure of the cylindrical tool to be welded of the present application;

[0042] Figure 2 It is a schematic diagram of the assembly structure of the special-shaped tool to be welded of the present application;

[0043] Figure 3 It is a structure diagram of superhard material with annular groove;

[0044] Figure 4 It is a surface XRD pattern of PCD diamond with binder after high-temperature and high-pressure welding of example 2;

[0045] Figure 5 It is a surface XRD pattern of CVD diamond without binder after high-temperature and high-pressure welding of example 3;

[0046] Figure 6Post high temperature high pressure welding surface XRD pattern of binderless sintered polycrystalline diamond of Example 5;

[0047] Figure 7 Post welding diamond and substrate portion of weld scan electron micrograph of Example 6;

[0048] Figure 8 Post high temperature high pressure welding surface XRD pattern of binderless sintered polycrystalline cBN of Example 7.

[0049] Markings in the drawings and corresponding names of parts:

[0050] 1 - substrate, 2 - lateral support ring, 3 - superhard material, 301 - groove, 4 - hard protective sheet, 5 - soft protective sheet. DETAILED DESCRIPTION

[0051] In order to make the objects, technical solutions and advantages of the present application clearer, further detailed description will be given below in combination with examples and drawings, the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application.

[0052] Example 1

[0053] In this embodiment, no lateral support ring, hard protective sheet and soft protective sheet are arranged on the pieces to be welded. The specific method comprises the following steps:

[0054] (1) commercially available YG10 tungsten carbide powder (grain size 1 μm, cobalt binder content 10%wt) is pre-pressed using a die with an inner diameter of 10 mm, wherein the pre-pressing pressure of the tungsten carbide powder is 1.1 GPa, the compactness after pre-pressing is 65%, and the size of the tungsten carbide substrate after pre-pressing is Φ10*8 mm.

[0055] (2) then place the binderless CVD diamond with a size of Φ10*2 mm and a thickness of 2 mm on the substrate, and then wrap the substrate and the diamond with a high melting point metal such as tantalum, rhenium and molybdenum with a thickness of 0.05 mm. Perform powder welding work under the conditions of 5.5 GPa and 1250°C. In the high-pressure assembly, the diamond should be placed at the bottom of the tungsten carbide substrate, so that the binder cobalt in the tungsten carbide will melt at high temperature and weld the tungsten carbide and the diamond with high strength.

[0056] (3) after the experiment is completed, the wrapped body is taken out for cutting, polishing and other work, the surface of the powder welded diamond is polished, and the cutter is cut into a size of Φ8*8 mm, and then the welded cutter is tested for shear strength, scanning electron microscope and the like.

[0057] The shear strength of the CVD cutter welded by the powder is about 290 MPa, which is higher than that of the diamond cutter (280 MPa) welded by the solder under high temperature and high pressure.

[0058] The scanning electron microscope analysis shows that the diamond and the tungsten carbide substrate are tightly combined at the joint, there is no solder transition layer at the joint of the two layers, and there is a bonding layer of ≤2 μm between the diamond and the tungsten carbide, the thickness of the bonding layer is much smaller than that of the bonding layer (≥20 μm) in the cutter welded by the solder.

[0059] Meanwhile, the hardness test of the welded diamond shows that the hardness has no obvious change compared with that before welding; meanwhile, the hardness test of the tungsten carbide end shows that the hardness has no obvious difference with that of the commercially available sintered YG10 tungsten carbide block.

[0060] Example 2

[0061] In this embodiment, PCD diamond containing 10%wt binder is used. The specific method includes the following steps:

[0062] (1) Commercially available YG10 tungsten carbide powder (grain size 1 μm, cobalt binder content 10%wt) is pre-pressed by using a mold with an inner diameter of 10 mm, wherein the pre-pressing pressure of the tungsten carbide powder is 1.1 GPa, the density after pre-pressing is 65%, and the size of the tungsten carbide substrate after pre-pressing is Φ10*7 mm.

[0063] (2) Then, a PCD diamond piece with a size of Φ8.2*2 mm and a cobalt content of 10%wt is placed in a Φ10*8.2*2 mm alumina lateral support ring and placed on the substrate, then a hard protection piece (alumina piece, Φ10*1 mm) is placed on the diamond and the lateral support ring, and the above assembly is wrapped with 0.05 mm thick high melting point metals such as tantalum, rhenium and molybdenum. The wrapped whole sample is placed in a high pressure assembly, and then a layer of soft protection piece (sodium chloride, Φ10*1.5 mm) is placed on the diamond of the assembly. After the whole assembly is assembled, it is placed in a press, and a high temperature and high pressure condition of 5.5 GPa and 1200°C is applied.

[0064] (3) After unloading, the whole welded cutter is taken out and polished, etc. The size after polishing is Φ8*8 mm. Then the shear strength, scanning electron microscope, etc. of the welded cutter are tested, and the XRD pattern of the surface after welding is as shown in Figure 4 .

[0065] The shear strength of the PCD cutter welded by the powder is about 314 MPa, which is higher than that of the diamond cutter (280 MPa) welded by the solder under high temperature and high pressure.

[0066] The scanning electron microscope analysis found that the diamond and tungsten carbide substrate binding place is tight, there is no solder transition layer in the two layers, and there is a bonding layer of ≤2 μm between the diamond and tungsten carbide, and the thickness of the bonding layer is much smaller than that of the bonding layer in the soldered tool (≥20 μm).

[0067] Meanwhile, the hardness test of the welded diamond found that the hardness did not change significantly compared with the hardness before welding; at the same time, the hardness test of the tungsten carbide end found that the hardness had no obvious difference with the hardness of the commercially available sintered YG10 tungsten carbide block.

[0068] Example 3

[0069] In this embodiment, binderless doped CVD diamond sheet is used. The specific method includes the following steps:

[0070] (1) Commercially available YG10 tungsten carbide powder (grain size 1 μm, cobalt binder content 10%wt) is pre-pressed using a mold with an inner diameter of 10 mm. The pre-pressing pressure of the tungsten carbide powder is 1.1 GPa, and the density after pre-pressing is 65%. The size of the tungsten carbide substrate after pre-pressing is Φ10*7 mm.

[0071] (2) Then, a Φ8.2*2 mm thick, binderless doped CVD diamond sheet is placed in a Φ10*8.2*2 mm alumina lateral support ring and placed on the substrate. Then, a hard protective sheet (alumina sheet, Φ10*1 mm) is placed on the diamond and the lateral support ring, and the above assembly is wrapped with 0.05 mm thick high melting point metals such as tantalum, rhenium, molybdenum, etc. The wrapped whole sample is placed in a high pressure assembly, and then a layer of soft protective sheet (sodium chloride, Φ10*1.5 mm) is placed on the diamond of the assembly. After the whole assembly is assembled, it is placed in a press, and a high temperature and high pressure condition of 5.5 GPa and 1250°C is applied.

[0072] (3) After unloading, the whole welded tool is taken out and polished, etc. The size after polishing is Φ8*8 mm. Then, the shear strength, scanning electron microscope, etc. of the welded tool are tested, and the XRD pattern of the surface of the sample after welding is as shown in Figure 5 .

[0073] Through the shear strength test, it is found that the shear strength of the PCD tool welded by powder is about 301 MPa, which is higher than that of the diamond tool welded by solder under high temperature and high pressure (280 MPa).

[0074] The scanning electron microscope analysis found that the diamond and tungsten carbide substrate binding place is tight, there is no solder transition layer in the two layers, and there is a bonding layer of ≤2 μm between the diamond and tungsten carbide, and the thickness of the bonding layer is much smaller than that of the bonding layer in the soldered tool (≥20 μm).

[0075] Meanwhile, the hardness of the welded diamond was tested and found to have no significant change compared to the hardness before welding; at the same time, the hardness of the tungsten carbide end was tested and found to have no significant difference with the hardness of the commercially available sintered YG10 tungsten carbide block.

[0076] Example 4

[0077] In this example, a binderless doped sintered polycrystalline diamond sheet was used, and the compactness of the substrate after pre-pressing was 65%. The specific method includes the following steps:

[0078] (1) Commercially available YG10 tungsten carbide powder (grain size 1 μm, cobalt binder content 10% wt) was pre-pressed using a mold with an inner diameter of 10 mm. The pre-pressing pressure of the tungsten carbide powder was 1.1 GPa, and the compactness after pre-pressing was 65%. The size of the tungsten carbide substrate after pre-pressing was Φ10*7 mm.

[0079] (2) Then, a Φ8.2*2 mm thick, binderless doped sintered polycrystalline diamond sheet was placed in a Φ10*8.2*2 mm hBN lateral support ring and placed on the substrate, followed by placing a hard protective sheet (alumina sheet, Φ10*1 mm) on the diamond and the lateral support ring, and wrapping the above assembly with 0.05 mm thick high melting point metals such as tantalum, rhenium, molybdenum, etc. The wrapped whole sample was placed in a high pressure assembly, and then a layer of soft protective sheet (sodium chloride, Φ10*1.5 mm) was placed on the diamond of the assembly. After the whole assembly was assembled, it was placed in a press, and a high temperature and high pressure condition of 5.5 GPa and 1330°C was applied.

[0080] (3) After unloading, the entire welded cutter was taken out and polished, etc. The size after polishing was Φ8*8 mm. Then the shear strength, scanning electron microscope, etc. of the welded cutter were tested.

[0081] Through shear strength testing, it was found that the shear strength of the PCD cutter welded by powder was about 324 MPa, which was higher than that of the diamond cutter welded by solder under high temperature and high pressure (280 MPa).

[0082] Scanning electron microscope analysis found that the diamond and tungsten carbide substrate were tightly combined, and there was no solder transition layer at the two layers of the combination. There was a combination layer of ≤2 μm between the diamond and the tungsten carbide, and the thickness of the combination layer was much smaller than that of the combination layer in the cutter welded by solder (≥20 μm).

[0083] Meanwhile, the hardness of the welded diamond was tested and found to have no significant change compared to the hardness before welding; at the same time, the hardness of the tungsten carbide end was tested and found to have no significant difference with the hardness of the commercially available sintered YG10 tungsten carbide block.

[0084] Example 5

[0085] This example uses binderless doped sintered polycrystalline diamond compact, the matrix pre-pressed density is 83%. The specific method includes the following steps:

[0086] (1) commercially available YG10 tungsten carbide powder (grain size 1 μm, cobalt binder content 10% wt) is pre-pressed using a die with an inner diameter of 11.8 mm, the pre-pressed pressure on the tungsten carbide powder is 725 MPa, the pre-pressed density is 50%, and the size of the pre-pressed tungsten carbide matrix is Φ11.8*10 mm. The pre-pressed tungsten carbide matrix is wrapped with a 0.05 mm thick tantalum sheet and then pre-pressed again in the high-pressure assembly of the cubic press to increase the density of the matrix. A 5.5 GPa pressure is applied using the cubic press to obtain a tungsten carbide powder matrix with a density of 83%. The high-pressure pre-pressed matrix is ground to obtain a Φ10*7 mm tungsten carbide powder pre-pressed matrix.

[0087] (2) The Φ8.2*2 mm thick, binderless doped sintered polycrystalline diamond compact is placed in the Φ10*8.2*2 mm hBN lateral support ring and placed on the matrix, then the hard protective sheet (alumina sheet, Φ10*1 mm) is placed on the diamond and the lateral support ring, and the above assembly is wrapped with a 0.05 mm thick high-melting-point metal such as tantalum, rhenium, molybdenum, etc. The wrapped whole sample is placed in the high-pressure assembly, and a layer of soft protective sheet (sodium chloride, Φ10*1.5 mm) is placed on the side of the assembly close to the diamond. After the whole assembly is placed in the press, a high temperature and high pressure of 5.5 GPa and 1330°C is applied.

[0088] (3) After unloading, the entire welded tool is taken out and polished, etc. The size after polishing is Φ8*8 mm. Then the shear strength, scanning electron microscope, etc. of the welded tool are tested, and the XRD pattern of the surface of the sample after welding is as shown in Figure 6 .

[0089] Through shear strength testing, it is found that the shear strength of the PCD tool welded by powder is about 349 MPa, which is higher than that of the diamond tool welded by solder under high temperature and high pressure (280 MPa).

[0090] Scanning electron microscope analysis shows that the diamond and tungsten carbide matrix are tightly combined, there is no solder transition layer at the two layers of the combined layer, and there is a combined layer of ≤2 μm between the diamond and the tungsten carbide, the thickness of the combined layer is much smaller than that of the combined layer in the tool welded by solder (greater than or equal to 20 μm).

[0091] Meanwhile, hardness testing of the welded diamond revealed no significant change in hardness compared to its pre-welding hardness; and hardness testing of the tungsten carbide end showed no significant difference in hardness compared to commercially available sintered YG10 tungsten carbide blocks.

[0092] Example 6

[0093] This embodiment uses a PCD diamond sheet with a cobalt content of 10% wt and has grooves. The specific method includes the following steps:

[0094] (1) Commercially available YG10 tungsten carbide powder (grain size 1μm, cobalt binder content 10%wt) was used. The tungsten carbide powder was pre-pressed using a mold with an inner diameter of 11.8mm. The pre-pressing pressure was 725MPa, and the density after pre-pressing was 50%. The size of the tungsten carbide matrix after pre-pressing was Φ11.8*10mm. The pre-pressed tungsten carbide matrix was wrapped with a 0.05mm thick tantalum sheet and then placed in a six-sided top press for high-pressure assembly to further pre-press and improve the matrix density. After applying a pressure of 5.5GPa using the six-sided top press, a tungsten carbide powder matrix with a density of 83% was obtained. The high-pressure pre-pressed matrix was then ground to obtain a Φ10*7mm tungsten carbide powder pre-pressed matrix.

[0095] (2) Then, take a Φ8.2*2mm thick PCD diamond sheet with a cobalt content of 10%wt and annular grooves that has been laser-processed (the depth of the laser-processed grooves is 0.5mm, the width of a single groove is 0.3mm, and 4-5 concentric grooves are processed on the circular area of ​​Φ8.2). The structure of the grooved diamond is as follows: Figure 3 As shown. A diamond was placed in a Φ10mm diameter mold and pre-pressed with YG10 tungsten carbide powder, filling the grooves on the diamond surface with the tungsten carbide powder. The pre-pressing pressure was 1.1 GPa. After pre-pressing, the tungsten carbide around the diamond was removed, leaving only the tungsten carbide in the grooves. The pre-pressed diamond filled with tungsten carbide powder was then placed in a Φ10*8.2*2mm alumina lateral support ring and placed on the substrate. A hard protective sheet (alumina sheet, Φ10*1mm) was then placed on the diamond and the lateral support ring. The assembly was then wrapped with a 0.05mm thick layer of high-melting-point metals such as tantalum, rhenium, and molybdenum. The wrapped sample was placed in a high-pressure assembly, and a soft protective sheet (sodium chloride, Φ10*1.5mm) was placed on the side of the assembly closest to the diamond. After assembly, the sample was placed in a press and subjected to high-temperature and high-pressure conditions of 5.5 GPa and 1200℃.

[0096] (3) After depressurization and cooling, the entire welded tool was removed and polished. The size after polishing was Φ8*8mm. Subsequently, the welded tool was tested for shear strength and scanning electron microscopy.

[0097] The shear strength of the PCD cutter welded by powder is about 392 MPa, which is higher than that of the diamond cutter welded by solder under high temperature and high pressure (280 MPa).

[0098] As shown in Figure 7 FIG. 3 is a scanning electron microscope image of the weld, wherein a is a 100 times scanning electron microscope image (the arrow is the welding position), and b is a 3000 times scanning electron microscope image.

[0099] As shown in Figure 7 It can be seen that the diamond and the tungsten carbide substrate are combined tightly, and there is no solder transition layer at the two-layer combination position. The diamond and the tungsten carbide have a combination layer of ≤2 μm, and the maximum width of the combination layer is 2 μm. The thickness of the combination layer is much smaller than that of the combination layer in the cutter welded by solder (≥20 μm).

[0100] Meanwhile, the hardness test of the welded diamond shows that the hardness has no obvious change compared with the hardness before welding. Meanwhile, the hardness test of the tungsten carbide end shows that the hardness has no obvious difference with the hardness of the commercially available sintered YG10 tungsten carbide block.

[0101] Example 7

[0102] In this embodiment, a sintered polycrystalline cBN sheet without binder doping is used, and a groove is provided. The specific method comprises the following steps:

[0103] (1) Commercially available YG10 tungsten carbide powder (grain size 1 μm, cobalt binder content 10% wt) is pre-pressed using a mold with an inner diameter of 11.8 mm. The pre-pressing pressure of the tungsten carbide powder is 725 MPa, and the compactness after pre-pressing is 50%. The size of the pre-pressed tungsten carbide substrate is Φ11.8*10 mm. The pre-pressed tungsten carbide substrate is wrapped with a 0.05 mm thick tantalum sheet and then pre-pressed again in a high-pressure assembly of a cubic press to improve the compactness of the substrate. A compactness of 83% of the tungsten carbide powder substrate is obtained by applying a pressure of 5.5 GPa using the cubic press. The high-pressure pre-pressed substrate is ground to obtain a Φ10*7 mm tungsten carbide powder pre-pressed substrate.

[0104] (2) A Φ8.2*2 mm sintered polycrystalline cBN sheet without binder doping is placed in a Φ10*8.2*2 mm hBN lateral support ring and placed on the substrate, and then a hard protective sheet (alumina sheet, Φ10*1 mm) is placed on the cBN and the lateral support ring, and the above assembly is wrapped with a 0.05 mm thick high-melting-point metal such as tantalum, rhenium, molybdenum, etc. The wrapped whole sample is placed in a high-pressure assembly, and a layer of soft protective sheet (sodium chloride, Φ10*1.5 mm) is placed on the side of the assembly close to the diamond. After the whole assembly is placed in the press, a high temperature and high pressure of 5.5 GPa and 1500°C is applied.

[0105] (3) After the temperature and pressure are released, the entire welded cutter is taken out and polished, and the size of the polished cutter is Φ8*8mm. Then, the welded cutter is tested for shear strength, scanning electron microscopy, and the like, and the XRD pattern of the sample surface is as shown in Figure 8 .

[0106] It is found through shear strength testing that the shear strength of the PcBN cutter welded by powder is about 362MPa, which is much higher than that of the PcBN cutter welded by brazing.

[0107] It is found through scanning electron microscopy analysis that the combination of PcBN and tungsten carbide substrate is tight, and there is no solder transition layer at the two-layer combination. There is a combination layer of ≤2μm between PcBN and tungsten carbide, and the thickness of the combination layer is much smaller than that of the combination layer in the cutter welded by brazing (≥50μm).

[0108] At the same time, it is found through hardness testing of the welded PcBN that the hardness has no obvious change compared with the hardness before welding; at the same time, the hardness testing of the tungsten carbide end finds that the hardness has no obvious difference with the hardness of the commercially available sintered YG10 tungsten carbide block.

[0109] Example 8

[0110] This embodiment describes the assembly structure of the welding assembly involved in the preceding examples 2-7.

[0111] As shown in Figure 1 , the assembly structure of the cylindrical cutter is shown in the figure, and as shown in Figure 2 , the assembly structure of the special-shaped cutter is shown in the figure, and the structure is the same, including: a substrate 1, a lateral support ring 2, a superhard material 3, a hard protective sheet 4 and a soft protective sheet 5. Among them, the substrate 1 is arranged in the lowermost layer, the lateral support ring 2 is wrapped outside the superhard material 3, the lateral support ring 2 and the superhard material 3 are placed on the substrate 1, the hard protective sheet 4 is arranged on the lateral support ring 2 and the superhard material 3, and a layer of soft protective sheet 5 is further arranged on the hard protective sheet 4 and the outside of the assembly. Figure 3 As shown in

[0112] After the assembly structure of the above-mentioned welding assembly is welded at high temperature and high pressure, the lateral support ring 2, the hard protective sheet 4 and the soft protective sheet 5 need to be removed, and the welded product of the substrate 1 and the superhard material 3 is further processed.

[0113] The above detailed description of the specific embodiments of the present application has been given to understand the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for welding superhard materials using a powder matrix under high temperature and high pressure, characterized in that, Includes the following steps: (1) Add a binder to the matrix powder material, mix thoroughly and uniformly, and then pre-press to improve its density. The density of the matrix after pre-pressing should be maintained above 60%. The matrix powder material includes one or more of tungsten carbide, cBN, silicon carbide, silicon nitride and boron carbide. The binder includes one or more of iron, cobalt, nickel, aluminum, copper, silver and silicon. The binder content is 1-20% of the mass of the matrix powder material. (2) Remove impurities from the surface of the superhard material, wrap the superhard material after impurity removal with a lateral support ring and place it on the substrate, then place the hard protective sheet on the superhard material and the lateral support ring, wrap the formed component with a high melting point metal to prevent it from contacting the external material, then place soft protective sheets on the top and sides of the component, and perform high temperature and high pressure welding after the whole assembly is completed; the lateral support ring material is selected from iron, cobalt, nickel, aluminum, alumina, magnesium oxide, cBN, diamond, silicon carbide or hBN, the metal used for wrapping is tantalum, rhenium or molybdenum, the hard protective sheet is made of alumina or magnesium oxide ceramic material, and the soft protective sheet material is made of sodium chloride, potassium chloride or calcium chloride; (3) After the temperature and pressure are released, the welded tool blank is taken out, the lateral support ring, hard protective plate and soft protective plate are removed, and further processing is carried out to obtain the finished product.

2. The method for welding superhard materials using a powder matrix under high temperature and high pressure according to claim 1, characterized in that, The superhard material is diamond or cBN, wherein the diamond includes polycrystalline diamond without binder, polycrystalline diamond with binder, and CVD polycrystalline diamond without binder, and the cBN includes polycrystalline cBN without binder or polycrystalline cBN with binder.

3. The method for welding superhard materials using a powder matrix under high temperature and high pressure according to claim 1, characterized in that, In step (1), the pre-compression pressure is between 10 and 1200 MPa.

4. The method for welding superhard materials using a powder matrix under high temperature and high pressure according to claim 1, characterized in that, In step (2), the welding pressure is 2-20 GPa, the welding temperature is 1000-3000℃, and the welding time is 60-1200s.

5. The method for welding superhard materials using a powder matrix under high temperature and high pressure according to claim 1, characterized in that, The superhard material has defects or grooves; For welding ultra-hard materials with defects, it is necessary to pour a base powder containing binder into the defect area for pre-compression before welding. For welding ultra-hard materials with grooves, grooves need to be laser-machined into the ultra-hard material. The grooved ultra-hard material is then placed into a mold, and matrix powder containing binder is poured into the annular groove for pre-pressing before welding.

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