An external synthesis mold structure for a polycrystalline diamond compact

Abstract

The present application provides a kind of diamond compact outer synthesis mold structure, the outer synthesis mold structure is set to diamond layer and cemented carbide substrate layer, the outer synthesis mold structure includes two layers of equalizing material layer, wherein, equalizing material A layer is set to one end close to diamond layer, equalizing material B layer is set to one end close to cemented carbide substrate layer, the thermal conductivity of uniform material used in equalizing material A layer is greater than the thermal conductivity of uniform material used in equalizing material B layer.The diamond compact outer synthesis mold structure of the present application makes diamond layer and cemented carbide substrate layer in high temperature sintering process, effectively reduce the phenomenon of " free carbon " of matrix interface caused by diamond to matrix carburizing, improve the impact resistance of compact;At the same time, it is beneficial to the pre-graphitization of diamond grain surface and the full migration of cobalt, and it is beneficial to the nucleation and growth of diamond and the dense bonding, so as to improve the comprehensive performance of compact, especially the impact resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of superhard materials, in particular to a diamond compact outer synthesis mold structure. BACKGROUND

[0002] The polycrystalline diamond compact is composed of a polycrystalline diamond layer and a cemented carbide substrate, and is usually sintered from diamond powder and a cemented carbide substrate under high temperature and high pressure (5-9 GPa, 1400-1600 ℃), and has high wear resistance of the diamond layer and high toughness of the cemented carbide substrate. As a key cutting element of the diamond PDC drill bit, the comprehensive performance (wear resistance, impact resistance and thermal stability) and sintering stability of the diamond compact play a key decisive role in the use effect of the drill bit.

[0003] The existing diamond compact synthesis structure diagram is shown in Figure 1 : which includes an inner synthesis mold assembly arranged at the center, the inner synthesis mold assembly includes diamond powder, cemented carbide substrate and metal shielding cup for wrapping and assembling the two materials together, and mainly serves to form the diamond layer and the cemented carbide substrate. Outside the inner synthesis mold is an outer synthesis mold assembly, which includes pressure equalizing material (such as salt pipe + salt sheet) wrapped outside the inner synthesis mold, heating element (such as carbon pipe + carbon sheet), pressure transmission material and heat preservation material (such as dolomite and pyrophyllite), conductive steel ring and other fillers (various gaskets, rings), and mainly serves to heat and transmit pressure to provide suitable pressure field and temperature field for the synthesis of the diamond compact. Among them, the main function of the pressure equalizing material is to form a molten state at high temperature and high pressure, so that the pressure transmitted from the six external directions to the inner synthesis mold forms a more uniform isostatic pressure field, and also has a heat preservation effect; the main function of the heating element is to form a temperature field in the electrically conductive state by means of side heating; the main function of the pressure transmission material and heat preservation material is to transmit pressure, seal the synthesis cavity and preserve heat.

[0004] In the synthesis process of the diamond compact, high temperature is obtained by electric heating of the heating element, and the temperature field is mainly constructed by the outer synthesis mold structure. The uniformity of the temperature field of the compact synthesis, the formation and maintenance of the necessary temperature gradient are necessary conditions for obtaining good sintering quality. The temperature field formed by the conventional outer synthesis mold structure has the following problems:

[0005] First, the peripheral heating element warms up by conduction and radiation, which will inevitably form a situation that the center temperature is lower and the edge temperature is higher, resulting in insufficient penetration of the center cobalt liquid, and the problem of loose defects in the diamond layer center, as shown in Figure 2 , which further leads to the reduction of the impact resistance of the compact;

[0006] Secondly, the conventional symmetrical outer synthetic mold assembly structure causes the cemented carbide substrate to also be in a high temperature environment of 1400-1600 DEG C, thereby causing the diamond layer to be carburized to different degrees at the end of the substrate and the substrate "free carbon" phenomenon, as shown in Figure 3 , which causes the substrate brittleness to increase and the impact resistance of the composite sheet to decrease;

[0007] Thirdly, various assembly elements of the outer synthetic mold will be deformed to a certain degree under high temperature and high pressure, especially the heating element which is easily deformed under high pressure into a "horn" shape with a thin middle and thick ends, as shown in Figure 4 . The deformation causes the heating element to be in poor contact with the pressure transmission and conductive material, causing "series current", "temperature mutation" and other phenomena, which causes the sintering temperature to be unstable, thereby causing the sintering stability and comprehensive performance of the product to decrease, and even causing defects such as notches and cracks to be scrapped. SUMMARY

[0008] In view of the defects in the prior art, the technical problem to be solved by the present application is to provide an outer synthetic mold structure of a diamond composite sheet, which can effectively improve the comprehensive performance of the diamond composite sheet, especially the impact resistance.

[0009] To achieve the above object, the present application provides an outer synthetic mold structure of a diamond composite sheet, which is arranged outside the diamond layer and the cemented carbide substrate layer, and comprises two layers of pressure equalizing material, wherein the pressure equalizing material A layer is arranged at one end close to the diamond layer, the pressure equalizing material B layer is arranged at one end close to the cemented carbide substrate layer, and the thermal conductivity of the pressure equalizing material used in the pressure equalizing material A layer is greater than the thermal conductivity of the pressure equalizing material used in the pressure equalizing material B layer.

[0010] Preferably, the thermal conductivity of the pressure equalizing material used in the pressure equalizing material A layer is greater than or equal to 4.80 W / m·K, and the thermal conductivity of the pressure equalizing material used in the pressure equalizing material B layer is less than or equal to 4.00 W / m·K.

[0011] Preferably, the pressure equalizing material used in the pressure equalizing material A layer is a salt added with graphite, and the pressure equalizing material used in the pressure equalizing material B layer is a salt added with zirconium oxide.

[0012] Preferably, the thickness of the pressure equalizing material A layer is greater than the thickness of the pressure equalizing material B layer.

[0013] Preferably, the thickness difference between the pressure equalizing material A layer and the pressure equalizing material B layer is 1mm to 3mm.

[0014] Preferably, the outer synthetic mold structure further comprises a center auxiliary heating material layer arranged at one end close to the diamond layer, the center auxiliary heating material layer is composed of an insulating ring piece and a heating piece and two high-temperature metal pieces filled in the center of the insulating ring piece, and the heating piece is clamped between the two high-temperature metal pieces.

[0015] Preferably, the insulating ring piece is made of one or more materials of Al2O3, ZrO2 and TiO2.

[0016] Preferably, the high-temperature metal piece is made of one or more materials of molybdenum, titanium, tantalum and zirconium.

[0017] Preferably, the outer synthetic mold structure further comprises a heating pipe arranged at the periphery of the diamond layer and the cemented carbide substrate layer, and both ends of the heating pipe are provided with a high-temperature metal ring or a high-temperature metal cup.

[0018] Preferably, 2% of the height of the heating pipe ≤ the height of the high-temperature metal ring or the high-temperature metal cup ≤ 10% of the height of the heating pipe.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] (1) The present application adopts low-thermal-conductivity pressure-equalizing materials close to the cemented carbide substrate and high-thermal-conductivity pressure-equalizing materials close to the diamond layer, so that the temperature at the end of the cemented carbide substrate is relatively low during high-temperature sintering, effectively reducing the phenomenon of "free carbon" at the interface of the substrate caused by the carburization of the diamond to the substrate end, and improving the impact resistance of the composite sheet; at the same time, the temperature at the end of the diamond layer is higher, which is conducive to the pre-graphitization of the diamond grain surface and the sufficient migration of cobalt, thereby constructing a temperature field more suitable for the nucleation and growth of diamond, which is conducive to the nucleation and growth of diamond and the formation of bonds, thereby improving the comprehensive performance of the composite sheet, especially the impact resistance.

[0021] (2) The pressure-equalizing material close to the end of the cemented carbide substrate is thinner, and the pressure-equalizing material close to the end of the diamond layer is thicker, because the thicker pressure-equalizing material at the end of the diamond layer can make the diamond layer closer to the heating area at the center of the heating element, and the temperature is higher, which meets the conditions for the full sintering and bonding of the diamond; the thinner pressure-equalizing material at the end of the cemented carbide substrate can make the substrate farther away from the heating area at the center of the heating element, and the temperature is relatively lower. The functional design of the pressure-equalizing material can break the original "balance" and "symmetry" of the conventional outer synthetic mold, meet the different needs of the diamond layer and the cemented carbide substrate for the temperature field, and further improve the comprehensive performance of the composite sheet.

[0022] (3) The center auxiliary heating material layer with special structure has a "sandwich" structure of "insulating ring piece + high-temperature metal piece + heating piece + high-temperature metal piece", which can solve the problem of insufficient sintering heat at the center of the composite sheet, form a temperature field suitable for sintering of the composite sheet, and significantly improve the sintering quality and performance of the product. Moreover, the heating amount can be adjusted by adjusting the thickness of the heating piece, so that the heating amount of the structure can be flexibly controlled.

[0023] (4) The center auxiliary heating material layer is arranged near one end of the diamond, which can also make the diamond layer closer to the heating area at the center of the heating element, greatly improve the temperature of the diamond, meet the condition of fully sintering the diamond into a bond, and further improve the comprehensive performance of the composite sheet.

[0024] (5) The high-temperature metal ring or high-temperature metal cup is wrapped at both ends of the heating pipe, so that the high-temperature metal ring or high-temperature metal cup forms a surface contact with the pressure-conducting and electrically-conducting material instead of a point contact. Thus, even under high pressure, the problem of poor contact caused by deformation of the heating pipe can be effectively avoided, so that the sintering stability and comprehensive performance of the composite sheet are greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 The structure diagram of a conventional diamond composite sheet synthesis mold in the embodiment of the present application;

[0027] Figure 2 The diagram of loose diamond layer center caused by a conventional diamond composite sheet synthesis structure mold in the embodiment of the present application;

[0028] Figure 3 The diagram of carburization phenomenon of hard alloy substrate at high temperature caused by a conventional diamond composite sheet synthesis structure mold in the embodiment of the present application;

[0029] Figure 4 The diagram of the heating element (pipe) in a conventional diamond composite sheet synthesis structure mold in the embodiment of the present application being deformed into a horn under high pressure;

[0030] Figure 5 The structure diagram of the pressure equalizing material layer in the outer synthesis mold in the embodiment of the present application;

[0031] Figure 6The structural schematic diagram of the outer synthesis mold in the embodiment of the present application is shown in the figure.

[0032] Figure 7 The structural schematic diagram of the high-temperature metal cup or high-temperature metal ring fixed at the two ends of the heating pipe in the embodiment of the present application is shown in the figure.

[0033] In the figure: 100-diamond layer, 101-hard alloy substrate layer, 102-pressure equalizing material (pipe), 103-pressure equalizing material (sheet), 104-conductive filler material layer, 105-heating element (pipe), 106-pressure transmission sealing and heat preservation layer, 500-axis of the outer synthesis mold, 503-pressure equalizing material A layer, 504-pressure equalizing material B layer, 600-inner synthesis mold, 602-insulating ring sheet, 603-high-temperature metal sheet, 604-heating sheet, 605-heating pipe, 606-high-temperature metal ring (or high-temperature metal cup). DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiment of the present application more clear, the technical scheme in the embodiment of the present application will be described clearly and completely below in combination with the drawings in the embodiment of the present application. Obviously, the described embodiment is a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiment in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0035] Referring to Figure 1 As shown in the figure, the synthesis structure of the diamond composite sheet in the prior art includes an outer synthesis mold structure and an inner synthesis mold structure, and the outer synthesis mold structure is arranged outside the inner synthesis mold structure. The inner synthesis mold structure includes a diamond layer 100 and a hard alloy substrate layer 101, and a metal shielding cup (not shown in the figure) for wrapping and assembling the diamond layer and the hard alloy substrate layer together. The outer synthesis mold structure includes a pressure equalizing material layer 103, a heating element 105, a conductive filler material layer 104 and a pressure transmission sealing and heat preservation layer 106. The pressure equalizing material layer 103 is provided with two layers, one layer is arranged at one end close to the diamond layer 100, and the other layer is arranged at one end close to the hard alloy substrate layer 101. The two layers of the pressure equalizing material layer 103 adopt the same material and the same thickness, which leads to a higher temperature of the hard alloy substrate layer 101, and thus the diamond layer 100 appears different degrees of carbon penetration and substrate “free carbon” phenomenon (as shown in the figure) at the end of the hard alloy substrate layer 101, which further leads to an increase in the brittleness of the substrate and a decrease in the impact resistance of the composite sheet. Figure 3 As shown in the figure), the diamond layer center loose defect problem (as shown in the figure) appears due to the insufficient penetration of the center cobalt liquid.Figure 2 The diamond layer is in contact with the hard alloy substrate, and the diamond layer is in contact with the hard alloy substrate.

[0036] In order to solve the above technical defects caused by the synthesis structure of the diamond compact in the prior art, the embodiment of the present application provides a diamond compact outer synthesis mold structure, which can make the temperature of the hard alloy substrate end relatively low during high-temperature sintering, effectively reduce the carbon penetration of the diamond layer to the substrate end, cause the substrate interface "free carbon" phenomenon, improve the impact resistance of the compact, and make the diamond layer end temperature higher, which is conducive to the pre-graphitization of the diamond grain surface and the migration of cobalt, thereby constructing a temperature field more suitable for the nucleation and growth of diamond, thereby effectively improving the comprehensive performance of the compact.

[0037] In order to achieve the above technical effects, the general idea of the present application is as follows:

[0038] As shown in Figure 5 The present application provides a diamond compact synthesis mold structure, which is arranged outside the diamond layer 100 and the hard alloy substrate layer 101, and comprises two layers of pressure equalizing material, wherein the pressure equalizing material A layer 503 is arranged at one end close to the diamond layer 100, the pressure equalizing material B layer 504 is arranged at one end close to the hard alloy substrate layer 101, and the thermal conductivity of the uniform material used in the pressure equalizing material A layer 503 is greater than that of the uniform material used in the pressure equalizing material B layer 504.

[0039] In the embodiment of the present application, low-thermal-conductivity pressure equalizing material is used at one end close to the hard alloy substrate layer 101, and high-thermal-conductivity pressure equalizing material is used at one end close to the diamond layer 100, so that during high-temperature sintering, the temperature of the hard alloy substrate end is relatively low, effectively reducing the carbon penetration of the diamond to the substrate end, causing the substrate interface "free carbon" phenomenon, improving the impact resistance of the compact, and at the same time, the diamond end temperature is higher, which is conducive to the pre-graphitization of the diamond grain surface and the migration of cobalt, thereby constructing a temperature field more suitable for the nucleation and growth of diamond, which is conducive to the nucleation and growth of diamond and the formation of dense bonds, thereby improving the comprehensive performance of the compact.

[0040] Preferably, the thermal conductivity of the pressure equalizing material used in the pressure equalizing material A layer 503 is ≥4.80 W / m·K, and the pressure equalizing material with a thermal conductivity of ≥4.80 W / m·K can accelerate the heat transfer of diamond, which is conducive to the nucleation and growth of diamond; the thermal conductivity of the pressure equalizing material used in the pressure equalizing material B layer 504 is ≤4.00 W / m·K, and the pressure equalizing material with a thermal conductivity of ≤4.00 W / m·K can prevent the carbon penetration phenomenon caused by the high temperature of the hard alloy substrate end.

[0041] Preferably, the pressure equalizing material A layer 503 adopts pressure equalizing material with graphite added, wherein the amount of graphite added is 5-10% (mass percentage); the pressure equalizing material B layer 504 adopts pressure equalizing material with zirconium oxide added, wherein the amount of zirconium oxide added is 15-20% (mass percentage), and Table 1 shows the thermal conductivity of different types of pressure equalizing material at room temperature.

[0042] Table 1 Thermal conductivity of different types of pressure equalizing material at room temperature

[0043]

[0044] Preferably, the thickness of the pressure equalizing material A layer 503 is greater than the thickness of the pressure equalizing material B layer 504.

[0045] The present application adopts thinner pressure equalizing material at one end close to the cemented carbide substrate layer 101 and adopts thicker pressure equalizing material at one end close to the diamond layer 100, because the thickness of the diamond layer 100 is less than that of the cemented carbide substrate layer 101, and setting the pressure equalizing material at the diamond layer 100 end to be thicker can make the diamond closer to the heating area at the center of the heating element, with higher temperature, meeting the condition for the diamond to be fully sintered into a bond; adopting thinner pressure equalizing material at the end of the cemented carbide substrate layer 101 can make the cemented carbide substrate farther away from the heating area at the center of the heating element, with relatively lower temperature. The functional design of the pressure equalizing material can break the "balance" and "symmetry" of the conventional outer synthesis mold, meet the different needs of the diamond and the cemented carbide substrate for the temperature field, and further improve the comprehensive performance of the composite sheet.

[0046] Preferably, 1mm≤ the thickness difference between the pressure equalizing material A layer 503 and the pressure equalizing material B layer 504 ≤3mm. Setting the thickness difference between the pressure equalizing material A layer 503 and the pressure equalizing material B layer 504 in the above range is mainly to make the inner synthesis mold structure (the diamond layer 100 and the cemented carbide substrate layer 101, and the metal shielding cup wrapping and assembling the diamond layer and the cemented carbide substrate layer together) as close as possible to the center of the heating element, which is conducive to the uniformity of the entire temperature field.

[0047] Preferably, referring to the accompanying drawings, Figure 6 Preferably, the outer synthesis mold structure further comprises a center auxiliary heating material layer, which is arranged at one end close to the diamond layer 100, and is composed of an insulating ring piece 602, a heating piece 604 and two high-temperature metal pieces 603 filled in the center of the insulating ring piece 602, and the heating piece is clamped between the two high-temperature metal pieces.

[0048] Since the center auxiliary heating material layer comprises two high-temperature metal discs and the heating disc clamped between the two high-temperature metal discs, the heating disc generates heat to transfer heat to the local area of the center of the composite disc, and the problem of insufficient energy in the center caused by the side heating type heating mode can be compensated, and at the same time, the insulating ring disc of the center auxiliary heating material layer can make the current pass through a smaller area of the center auxiliary heating material layer "high-temperature metal disc + heating disc + high-temperature metal disc" through the insulation effect, so as to concentrate heat in a small local area, and further solve the problem of insufficient sintering heat in the center of the composite disc.

[0049] Therefore, the center auxiliary heating material layer with a special structure is adopted in the present application, and the center auxiliary heating material layer has a "sandwich" structure of "insulating ring disc + high-temperature metal disc + heating disc + high-temperature metal disc", which can solve the problem of insufficient sintering heat in the center of the composite disc, form a temperature field suitable for sintering of the composite disc, and significantly improve the sintering quality and performance of the product, and the heating capacity of the structure can be flexibly controlled by adjusting the thickness of the heating disc.

[0050] At the same time, the center auxiliary heating material layer is arranged at one end close to the diamond layer, so that the diamond layer is closer to the heating area in the center of the heating element, the temperature of the diamond is greatly improved, the condition of fully sintering the diamond into a bond is met, and the comprehensive performance of the composite disc is further improved.

[0051] Preferably, the insulating ring disc 602 is made of one or more materials of Al2O3, ZrO2 and TiO2.

[0052] Preferably, the high-temperature metal disc 603 is made of one or more materials of molybdenum, titanium, tantalum and zirconium.

[0053] Preferably, the heating disc 604 is made of high-purity flake or microcrystalline graphite.

[0054] Preferably, the outer synthetic mold structure further comprises a heating pipe 605 arranged at the periphery of the diamond layer and the cemented carbide substrate layer, and high-temperature metal rings or high-temperature metal cups 606 are arranged at both ends of the heating pipe.

[0055] The heating tube is easily transformed from a cylindrical shape into a "bell mouth" shape with a thin middle and thick ends under high pressure, and the pressure-conducting and electrically-conducting material in contact with the heating tube 605 is mostly metal material, which has a much smaller deformation than the heating element, which will cause poor contact between the heating element and the pressure-conducting and electrically-conducting material during sintering of the composite sheet, thereby causing sintering temperature fluctuations, resulting in unstable quality and performance of the composite sheet, and even defects such as notches and cracks. To solve this defect, the high-temperature metal ring or high-temperature metal cup 606 is wrapped around both ends of the heating tube 605, so that the high-temperature metal ring or high-temperature metal cup 606 forms a surface contact with the pressure-conducting and electrically-conducting material instead of a point contact, which effectively avoids the problem of poor contact caused by deformation of the heating element under high pressure, thereby greatly improving the sintering stability and comprehensive performance of the composite sheet.

[0056] Preferably, the high-temperature metal ring or high-temperature metal cup 606 is made of one or more of molybdenum, titanium, tantalum, and zirconium.

[0057] Preferably, the height of the high-temperature metal ring or high-temperature metal cup 606 is 2% of the height of the heating tube 605 to 10% of the height of the heating tube, and the height of the high-temperature metal ring or high-temperature metal cup is limited to prevent the heating capacity of the carbon tube from being affected when electrified, and if the height of the metal cup or metal ring is too high, the heating capacity of the carbon tube at both ends will be reduced when the current passes through.

[0058] In summary, the composite sheet outer synthesis module assembly material and structure proposed by the present application has different material and thickness of the pressure-equalizing material layer, a special structure of the center auxiliary heating material layer, and a structure of the high-temperature metal ring for fixing both ends of the heating tube, which makes the composite sheet obtain a stable asymmetric temperature field, solves the problem of loose center and under-sintering, and improves the sintering stability and comprehensive performance of the composite sheet. The specific principle is as follows:

[0059] The application adopts low-thermal-conductivity pressure-equalizing material (such as salt added with zirconium oxide) near the end of the cemented carbide substrate, and due to the thermal barrier effect of zirconium oxide, the temperature of the substrate end is relatively lower, thereby effectively reducing the phenomenon of "free carbon" at the substrate interface caused by the carbonization of the diamond layer to the substrate end, and improving the impact resistance of the composite sheet; high-thermal-conductivity pressure-equalizing material (such as salt added with graphite) is used near the end of the diamond layer, and due to the higher thermal conductivity of the pressure-equalizing material, heat can be conducted to the diamond layer more quickly, so that the temperature of the diamond layer is higher, which is beneficial to the pre-graphitization of the surface of the diamond grain and the migration of cobalt, thereby constructing a temperature field more suitable for the nucleation and growth of the diamond. At the same time, the thicker pressure-equalizing material at the end of the diamond layer can make the diamond layer closer to the heating area at the center of the heating element, and the temperature is higher, which meets the condition of fully sintering the diamond into a bond; the thinner pressure-equalizing material at the end of the cemented carbide substrate can make the substrate farther away from the heating area at the center of the heating element, and the temperature is relatively lower. The functional design of the pressure-equalizing material can break the "balance" and "symmetry" of the conventional outer synthesis mold, and meet the different needs of the diamond layer and the cemented carbide substrate for the temperature field. Research shows that polycrystalline diamond needs a relatively "high temperature and low pressure" synthesis environment during synthesis, which is more beneficial to the nucleation, growth and dense bonding of the diamond; and the cemented carbide substrate needs a relatively "low temperature and high pressure" synthesis environment during the synthesis of the composite sheet, which can reduce the carbonization phenomenon at the end of the cemented carbide substrate at high temperature, so the application improves the pressure-equalizing material to meet the different needs of the diamond layer and the cemented carbide substrate for the temperature field, thereby ensuring the comprehensive performance of the composite sheet.

[0060] The application also adopts a special structure of the center auxiliary heating material layer, and a "sandwich" structure of "insulating ring piece + high-temperature metal piece + heating element + high-temperature metal piece" is used at the end near the diamond layer. The inherent radiation heating mechanism of the heating element leads to insufficient heating at the center of the composite sheet, and the center is loose and under-sintered. The three-layer center auxiliary heating structure solves the problem of insufficient sintering heat at the center of the composite sheet, forms a temperature field suitable for the sintering of the composite sheet, and significantly improves the sintering quality and performance of the product. The characteristics and advantages of the structure are that the heating amount can be adjusted by adjusting the thickness of the heating element, thereby flexibly controlling the heating amount of the structure.

[0061] The application also adopts the structure of fixing high-temperature metal cups (or high-temperature metal rings) at both ends of the heating element. The heating element is easy to be transformed from a cylindrical shape into a "bell mouth" shape with thin middle and thick ends under high pressure. The pressure-transmitting conductive material in contact with the heating element is mostly metal material, which has much smaller deformation than the heating element. This will cause poor contact between the heating element and the pressure-transmitting conductive material during sintering of the composite sheet, thereby causing sintering temperature fluctuation, resulting in unstable quality and performance of the composite sheet, and even defects such as notches and cracks. To solve this situation, the high-temperature metal cups (rings) are wrapped at both ends of the heating element, so that the high-temperature metal cups (rings) form surface contact with the pressure-transmitting conductive material instead of point contact. In this way, even under high pressure, the problem of poor contact caused by deformation of the heating element can be effectively avoided, thereby greatly improving the sintering stability and comprehensive performance of the composite sheet.

[0062] The structure of the diamond composite sheet outer synthesis mold of the application will be described below through specific examples.

[0063] Example 1

[0064]

[0065] Example 2

[0066]

[0067] Example 3

[0068]

[0069] Example 4

[0070]

[0071] Example 5

[0072]

[0073] Comparative Example 1

[0074]

[0075] Table 2 Comparison of comprehensive performance of products of Examples 1-5 and Comparative Example 1

[0076]

[0077] From the above table, it can be seen that the application of the molding assembly material and structure solves the problem of loose defects in the center of the diamond layer caused by the conventional synthesis mold, and also avoids the problem of unstable temperature field and large product quality fluctuation caused by deformation of the heating element during high temperature and high pressure process, improves the synthesis mold temperature field and sintering stability, and improves the comprehensive performance of the composite sheet to some extent.

[0078] It should be noted that, in the present application, the relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0079] The present application is not limited to the above-described embodiments, and various improvements and modifications can be made thereto without departing from the principles of the present application, which are to be considered within the scope of the present application. The contents not described in detail in the present specification are the existing technologies known to those skilled in the art.

Claims

1. A diamond composite sheet external molding structure, wherein the external molding structure is disposed outside the diamond layer and the cemented carbide substrate layer, characterized in that, The external composite mold structure includes two layers of equalizing material, wherein equalizing material A is disposed at one end near the diamond layer; equalizing material B is disposed at one end near the cemented carbide substrate layer, and the thermal conductivity of the uniform material used in equalizing material A is greater than the thermal conductivity of the uniform material used in equalizing material B. The external composite mold structure also includes a central auxiliary heating material layer, which is disposed at one end near the diamond layer. The central auxiliary heating material layer consists of an insulating ring, a heating element filled in the center of the insulating ring, and two high-temperature metal sheets, with the heating element sandwiched between the two high-temperature metal sheets.

2. The diamond composite sheet external molding structure as described in claim 1, characterized in that, The thermal conductivity of the equalizing material used in layer A is ≥4.80 W / m·K; the thermal conductivity of the equalizing material used in layer B is ≤4.00 W / m·K.

3. The diamond composite sheet external molding structure as described in claim 2, characterized in that, The equalizing material A layer uses a salt with added graphite; the equalizing material B layer uses a salt with added zirconium oxide.

4. The diamond composite sheet external molding structure as described in claim 1, characterized in that, The thickness of the equalizing material A layer is greater than the thickness of the equalizing material B layer.

5. The diamond composite sheet external molding structure as described in claim 1, characterized in that, 1mm≤thickness difference between the equalizing material A layer and the equalizing material B layer≤3mm.

6. The diamond composite sheet external molding structure as described in claim 1, characterized in that, The insulating ring is made of one or more materials selected from Al2O3, ZrO2, and TiO2.

7. The diamond composite sheet external molding structure as described in claim 1, characterized in that, The high-temperature metal sheet is made of one or more materials selected from molybdenum, titanium, tantalum, and zirconium.

8. The diamond composite sheet external molding structure as described in claim 1, characterized in that, The external composite mold structure also includes a heating tube disposed around the diamond layer and the cemented carbide substrate layer, and both ends of the heating tube are provided with a high-temperature metal ring or a high-temperature metal cup.

9. The diamond composite sheet external molding structure as described in claim 8, characterized in that, The height of the heating element is 2% ≤ the height of the high-temperature metal ring or high-temperature metal cup is ≤ 10% of the height of the heating element.

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