Polycrystalline diamond composite material, preparation method thereof and application of polycrystalline diamond composite material in preparation of wire-drawing die blank

Abstract

The invention provides a polycrystalline diamond composite material, a preparation method thereof and application of the polycrystalline diamond composite material in preparation of a wire-drawing die blank. The polycrystalline diamond composite material comprises a fine-grained polycrystalline diamond cobalt-removed sintered body located at the core part and a large-grained polycrystalline diamond sintered body located at the outer part, the fine-grained polycrystalline diamond cobalt-removed sintered body and the large-grained polycrystalline diamond sintered body both have the synergistic effect of a special formula and a special process, and particularly, a binder for preparing the fine-grained polycrystalline diamond cobalt-removed sintered body is composed of metal Co and metal W, in the high-temperature and high-pressure sintering process, W and diamond are carbonized to form WC, and the phenomenon that the diamond grows up abnormally due to the fact that micro-nano-scale diamond micro-powder is subjected to high-temperature and high-pressure sintering treatment twice, and consequently the uniformity of a fine-grained polycrystalline diamond cobalt-removed sintered body is affected is effectively avoided; meanwhile, through two times of high-temperature and high-pressure treatment, the internal structure is more compact, and the bonding degree is higher; therefore, the polycrystalline diamond composite material can be used as a wire-drawing die blank to draw a wire with better roundness and smoothness, and meanwhile, the service life is longer.

Description

Technical Field

[0001] This invention belongs to the field of superhard materials, specifically relating to a polycrystalline diamond composite material, its preparation method, and its application in the preparation of wire drawing die blanks. Background Technology

[0002] Polycrystalline diamond (PCD) is an example of a superhard material, also known as a superhard abrasive, consisting of a large number of intergrowth diamond grains forming a framework defining the spaces between them. PCD materials contain at least about 80% diamond by volume and can be prepared by subjecting the aggregated mass of the diamond grains to pressures greater than about 5 GPa and temperatures of at least about 1200 °C in the presence of sintering aids. Components containing PCD are used in a variety of tools for cutting, machining, drilling, wire drawing, or degrading hard or abrasive materials such as rock, metals, ceramics, composites, wire drawing, and wood-based materials. Due to its extreme hardness and wear resistance, PCD is a preferred tool material for some wire drawing and drilling conditions, as well as for applications requiring high productivity. A disadvantage of PCD containing certain catalyst materials as fillers for diamond may be its relatively poor thermal stability above about 400 °C. Catalyst materials can promote the degradation of PCD at elevated temperatures, particularly above about 750 °C.

[0003] Currently, in the wire drawing industry, polycrystalline diamond is widely used in the drawing process of metal wires, tubes, and profiles. It possesses characteristics such as high hardness, wear resistance, impact resistance, and high precision, making the wire drawing process more efficient, stable, and reliable. As a high-performance, high-efficiency wire drawing tool, polycrystalline diamond wire drawing dies have become an indispensable part of modern metal wire drawing production. With technological advancements and industrial development, polycrystalline diamond wire drawing dies will play an important role in more fields. For example, Chinese patent CN 210059364 U describes a polycrystalline diamond wire drawing die with a cobalt removal layer on the inner surface of the hole, which can effectively improve the cobalt removal production efficiency of large-diameter dies. Another example is Chinese patent CN110102585 A, which describes a die blank comprising at least two integrally connected polycrystalline diamond stacked layers, with each polycrystalline diamond stacked layer having a different diamond grain size structure. However, the multi-layered diamond structure increases internal stress during product operation, while also increasing the risk of cracking.

[0004] In the wire drawing die industry, most diamond particles are currently larger than 1µm, with no reports on diamond particles between 50 nm and 1000 nm. However, fine-grained polycrystalline diamond composites mean that wires with better roundness and surface finish can be drawn, along with a longer service life. Maintaining uniformity during the preparation of ultrafine diamond particles is a difficult aspect to control; furthermore, the wire drawing die industry almost always requires inserts, which introduces additional processing steps. Inserts are typically made of steel or cemented carbide, which have poor heat dissipation, increasing the risk of drill bit loss and cracking due to high temperatures in the die core. This is because the wire drawing and the channel have an interference fit structure, resulting in poor cooling effect of the coolant at the channel location. A significant amount of heat is conducted through the diamond. If the insert is made of steel or cemented carbide, the heat conduction is even worse. Starting from 700 degrees Celsius, the diamond gradually graphitizes, and at 900 degrees Celsius, it graphitizes rapidly, accelerating the damage to the diamond core. No technical solution to this problem has been found in the existing technology. Summary of the Invention

[0005] In view of this, the present invention provides a polycrystalline diamond composite material containing different particle sizes, a method for preparing the same, and its application in the preparation of wire drawing die blanks, in order to solve the above problems.

[0006] Specifically, the present invention provides a polycrystalline diamond composite material, comprising a fine-grained polycrystalline diamond decobalt-removed sintered body located in the middle and a large-grained polycrystalline diamond sintered body surrounding the fine-grained polycrystalline diamond decobalt-removed sintered body; wherein, the fine-grained polycrystalline diamond decobalt-removed sintered body is mainly obtained by high-temperature and high-pressure sintering and decobalt removal treatment of a first mixed powder composed of fine-grained diamond micro powder and a first binder, wherein the fine-grained diamond micro powder is micro-nano-level diamond micro powder and accounts for 75-98 wt% of the mass in the first mixed powder, and the first binder is composed of a uniform mixture of metals Co and W in a mass ratio of 1:1 to 4:1; the large-grained polycrystalline diamond sintered body is mainly obtained by high-temperature and high-pressure sintering of a second mixed powder composed of large-grained diamond micro powder and a second binder, wherein the particle size of the large-grained diamond micro powder is larger than that of the fine-grained diamond micro powder, and the mass percentage of the large-grained diamond micro powder in the second mixed powder is 70-95 wt%.

[0007] To achieve optimal performance design for the wire drawing product, preferably, the fine-grained diamond powder has a particle size of 50-1000 nm, and the large-grained diamond powder has a particle size of 0.1-100 μm.

[0008] In one specific embodiment, the fine-grained polycrystalline diamond decobaltized sintered body is cylindrical, polygonal, conical, or pyramidal in shape.

[0009] This invention provides a method for preparing the above-mentioned polycrystalline diamond composite material, comprising the following steps: Preparation of fine-grained polycrystalline diamond decobaltized sintered body: First, the fine-grained diamond micro powder and the first binder are uniformly mixed to form the first mixed powder; then, the first mixed powder is subjected to a first high-temperature and high-pressure treatment under a pressure of 5-7 GPa and a temperature of 1500-1600℃ to obtain a fine-grained polycrystalline diamond sintered body; then, the fine-grained polycrystalline diamond sintered body is subjected to a decobalt treatment to obtain the fine-grained polycrystalline diamond decobaltized sintered body; Preparation of large-particle-size polycrystalline diamond sintered body: First, large-particle-size diamond micro powder and a second metal binder are uniformly mixed to obtain the second mixed powder; then, the second mixed powder is placed around the fine-particle-size polycrystalline diamond decobalt-free sintered body, so that the second mixed powder surrounds the fine-particle-size polycrystalline diamond decobalt-free sintered body; then, a second high-temperature and high-pressure sintering treatment is performed under a pressure of 7-10 GPa and a temperature of 1600-1800℃, so that the second mixed powder is transformed into the large-particle-size polycrystalline diamond sintered body, and the height of the fine-particle-size polycrystalline diamond decobalt-free sintered body is not higher than that of the large-particle-size polycrystalline diamond sintered body, thus obtaining the polycrystalline diamond composite material.

[0010] Furthermore, the method for removing cobalt includes: removing the first binder in the fine-grained polycrystalline diamond sintered body by electrolysis or acid immersion to obtain the cobalt-removed fine-grained polycrystalline diamond sintered body, wherein the content of the residual first binder in the cobalt-removed fine-grained polycrystalline diamond sintered body does not exceed 3 wt%.

[0011] Furthermore, between the steps of preparing the fine-grained polycrystalline diamond decobalt-free sintered body and preparing the large-grained polycrystalline diamond sintered body, a step of cutting and processing the fine-grained polycrystalline diamond decobalt-free sintered body into a predetermined shape is included; this simplifies the subsequent preparation process of the wire drawing die blank. The predetermined shape includes, but is not limited to, cylindrical, polygonal prism, conical, and pyramidal shapes.

[0012] Furthermore, the step of preparing the large-particle-size polycrystalline diamond sintered body includes: firstly, uniformly mixing the large-particle-size diamond micro powder and the second binder using a ball milling method to obtain the second mixed powder; then, placing the fine-particle-size polycrystalline diamond decobalt-removed sintered body in the middle of the second mixed powder, so that the second mixed powder uniformly surrounds the fine-particle-size polycrystalline diamond decobalt-removed sintered body; then, performing a second high-temperature and high-pressure sintering treatment under a pressure of 7-10 GPa and a temperature of 1600-1800℃, so that the obtained large-particle-size polycrystalline diamond sintered body and the fine-particle-size polycrystalline diamond decobalt-removed sintered body are coaxially arranged, and the height of the fine-particle-size polycrystalline diamond decobalt-removed sintered body is not higher than that of the large-particle-size polycrystalline diamond sintered body, thereby obtaining the polycrystalline diamond composite material.

[0013] This invention provides an application of the above-mentioned polycrystalline diamond composite material in the preparation of wire drawing die blanks.

[0014] The present invention provides a wire drawing die blank composed of the above-mentioned polycrystalline diamond composite material, including an inlet region, a compression region, a sizing region and an outlet region, wherein the sizing region and / or the compression region are composed of the fine-grained polycrystalline diamond decobaltized sintered body.

[0015] Furthermore, at least one of the inlet region, compression region, and outlet region is composed of the large-particle polycrystalline diamond sintered body.

[0016] Therefore, compared with the prior art, the technical solution provided by the present invention has the following technical effects: 1) The fine-grained polycrystalline diamond decobalt-free sintered body and the large-grained polycrystalline diamond sintered body in the above-mentioned polycrystalline diamond composite material provided by the present invention both have the synergistic effect of special formulation and special process. In particular, the binder prepared for the fine-grained polycrystalline diamond decobalt-free sintered body is composed of metallic Co and W. During the high-temperature and high-pressure sintering process, W and diamond carbonize to form WC, which effectively avoids the phenomenon of abnormal diamond growth in micro-nano-level diamond powder after two high-temperature and high-pressure sintering treatments, thus affecting the uniformity of the fine-grained polycrystalline diamond decobalt-free sintered body. At the same time, after two high-temperature and high-pressure treatments, the internal structure is more compact and the bonding degree is higher. Therefore, the above-mentioned polycrystalline diamond composite material can be used as a wire drawing die blank to draw wires with better roundness and smoothness, and at the same time, the service life is longer.

[0017] 2) The polycrystalline diamond composite material provided by the present invention is composed of polycrystalline diamond sintered bodies with different particle size structures. The sizing region and / or compression region use fine-grained polycrystalline diamond decobalt-free sintered bodies formed by fine-grained diamond, which can improve the drawing quality. The inlet region, compression region and outlet region use large-grained polycrystalline diamond sintered bodies made of coarse-grained diamond, which can improve the compression speed and effectively utilize the characteristics of polycrystalline diamonds with different particle sizes, thereby improving the service life and wear resistance of the wire drawing die, and improving the roundness and smoothness of the drawn wire.

[0018] 3) This invention utilizes the above-mentioned polycrystalline diamond composite material to make a wire drawing die blank, which uses two layers of polycrystalline diamond sintered bodies with different particle sizes. Through multiple high-temperature and high-pressure sintering processes, it can be used directly without the need for additional cemented carbide inserts. At the same time, the coarse-grained polycrystalline diamond sintered body on the outside can also provide a holding force for the cobalt-free polycrystalline diamond sintered body inside. In terms of heat conduction, the coarse-grained polycrystalline diamond sintered body has a better effect, which is conducive to the timely removal of heat and reduces the probability of internal graphitization. It can avoid the phenomenon of high temperature during wire drawing not being able to dissipate heat, which can lead to the wire drawing die core falling off or cracking. When drawing fine wires, the wire accuracy, roundness, and surface finish are better.

[0019] 4) The wire drawing die blank provided by the present invention uses the above-mentioned polycrystalline diamond composite material as raw material. In the preparation process of the polycrystalline diamond composite material, only the diamond sintered body in the core needs to be decobaltized, and the large-particle polycrystalline diamond sintered body on the outside does not need to be decobaltized, which greatly shortens the decobaltization cycle of the wire drawing die blank. At the same time, the two wire drawing dies are more compact and have a higher degree of bonding after two high temperature and high pressure sintering treatments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the polycrystalline diamond composite material (left) and the wire drawing die blank (right) provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the polycrystalline diamond composite material (left) and the wire drawing die blank (right) provided in Embodiment 2 of the present invention; Figure 3 This is a SEM image of the fine-grained polycrystalline diamond decobalt-free sintered body in the polycrystalline diamond composite material provided in Example 1 of the present invention.

[0021] Figure 4 SEM images of fine-grained polycrystalline diamond decobalt-free sintered bodies in polycrystalline diamond composite materials provided for Comparative Example 1 (left) and Comparative Example 2 (right); in the left image, diamond particles in the dashed area grow abnormally.

[0022] In the figure, the component symbols are: 101 - large-grained polycrystalline diamond sintered body, 201 - fine-grained polycrystalline diamond decobaltized sintered body. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0024] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0025] All terms used in this invention are common terms in the relevant field. Unless otherwise specified, the raw materials, equipment, preparation processes, testing methods, etc., used are all existing technologies in the relevant field.

[0026] The polycrystalline diamond composite material provided by this invention is mainly prepared by using two high-pressure and high-temperature sintering processes with different parameters to prepare a sintered body of nano- and micron-sized polycrystalline diamonds, and then removing the binder from the inner sintered body. This ensures that the diamond particles in the core of the polycrystalline diamond composite material have a particle size of no more than 1 μm and also exhibit good thermal stability. This method optimizes the overall performance of the polycrystalline diamond composite material by combining macroscopic and microscopic approaches, minimizing the complexity of the preparation process and solving, to some extent, the problem of preparing fine-grained diamond wire drawing dies. Furthermore, using this polycrystalline diamond composite material as a wire drawing die blank provides good heat dissipation performance and can be used for drawing high-strength tungsten wire, molybdenum wire, stainless steel wire, and other metal wires, resulting in better wire accuracy, roundness, and surface finish when drawing fine wires. The specific implementation scheme is as follows: This invention provides a method for preparing the above-mentioned polycrystalline diamond composite material, comprising the following steps: Preparation of fine-grained polycrystalline diamond decobaltized sintered body: Fine-grained diamond micropowder and a first binder are mixed by wet ball milling to obtain a first mixed powder, wherein the fine-grained diamond micropowder is micro-nano-sized diamond micropowder and accounts for 75-98 wt% of the mass in the first mixed powder; the first mixed powder is packaged into a six-sided press and subjected to a first high-temperature and high-pressure (HTHP) sintering treatment under a pressure of 5-7 GPa and a temperature of 1500-1600℃ to obtain the fine-grained polycrystalline diamond sintered body; the first binder in the fine-grained polycrystalline diamond sintered body is removed by existing electrolysis or acid leaching methods to obtain the fine-grained polycrystalline diamond decobaltized sintered body, and the content of the residual first binder in the fine-grained polycrystalline diamond decobaltized sintered body does not exceed 3 wt% to avoid obvious diamond graphitization during subsequent wire drawing.

[0027] Preparation of large-particle-size polycrystalline diamond sintered bodies: First, large-particle-size diamond micro powder and a second binder are uniformly mixed using a dry ball milling method to obtain the second mixed powder. The particle size of the large-particle-size diamond micro powder is larger than that of the fine-particle-size diamond micro powder, and the mass percentage of the large-particle-size diamond micro powder in the second mixed powder is 70-95 wt%. Then, the cobalt-free sintered body of the fine-particle-size polycrystalline diamond is placed in the middle of the second mixed powder, so that the second mixed powder uniformly surrounds the cobalt-free sintered body. Next, a second high-temperature and high-pressure sintering treatment is performed under a pressure of 7-10 GPa and a temperature of 1600-1800℃, so that the obtained large-particle-size polycrystalline diamond sintered body and the cobalt-free sintered body are coaxially arranged, and the height of the cobalt-free sintered body is not higher than that of the large-particle-size polycrystalline diamond sintered body, thus producing a polycrystalline diamond composite material.

[0028] In the step of preparing the cobalt-free sintered body of fine-grained polycrystalline diamond, the formulation and preparation process parameters of the fine-grained polycrystalline diamond sintered body have a significant impact on its performance. If the particle size of the fine-grained diamond powder is too small, abnormal diamond growth is likely to occur during subsequent high-temperature and high-pressure sintering processes, making it difficult to effectively control the diamond particle size in the fine-grained polycrystalline diamond sintered body, thus making it difficult to obtain high-quality, high-strength metal wires. If the particle size of the fine-grained diamond powder is too large, it will cause excessively large pores to form inside the sintered body, affecting the physical properties of the fine-grained polycrystalline diamond sintered body, thereby affecting the service life and drawing quality of the wire drawing die blank. Therefore, the particle size of the fine-grained diamond powder is 50-1000 nm, such as 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc.; preferably 50-500 nm.

[0029] Because the particle size of fine-grained diamond powder is less than 1 μm, abnormal diamond particle growth is prone to occur during high-temperature and high-pressure sintering. Therefore, metallic W is introduced into the first binder, so that some W is converted into WC during high-temperature and high-pressure sintering, effectively preventing abnormal diamond growth. If the mass proportion of metallic W in the first binder is small, it cannot effectively prevent abnormal diamond growth; if the mass proportion of W is large, it will lead to a decrease in the bonding strength of the diamond, increase porosity, and make the matrix brittle, which not only reduces its own strength but also fails to effectively "hold" the diamond. Therefore, the first binder is composed of Co metal powder with a particle size of 50-500 nm and W metal powder with a particle size of 50-500 nm, uniformly mixed in a mass ratio of 1:1 to 4:1.

[0030] If the content of fine-grained diamond powder is high, a large amount of diamond will transform into the graphite phase during high-temperature sintering. During the process of diamond re-precipitation, abnormal diamond growth is likely to occur, thus failing to produce qualified wire drawing die blanks. If the content is low, the wear resistance of the wire drawing die blank will be reduced, and the insufficient C-C bonds will result in weak internal bonding strength, affecting the drawing quality and service life of the wire drawing die. Therefore, the mass percentage of fine-grained diamond powder in the first mixed material is limited to 70-98 wt%, preferably 80-95%.

[0031] During the first high-temperature and high-pressure sintering process, if the sintering pressure is too high or the sintering temperature is too high, abnormal diamond growth is likely to occur; if the sintering pressure is too low or the sintering temperature is too low, a large amount of graphite inside will not be completely converted, making wire drawing impossible. Therefore, the process parameters for the first high-temperature and high-pressure sintering process are limited to: pressure 5-7 GPa, temperature 1500-1600℃, and sintering time 10-30 min. This helps to ensure the uniformity and density of diamond particle distribution in the sintered body, thereby improving strength. It also ensures that the fine-grained polycrystalline diamond sintered body serves as the sizing zone for the wire drawing die blank, which can improve the drawing quality of high-strength tungsten wire, molybdenum wire, stainless steel wire, and other metal wires, giving the wire drawing die a better service life and wear resistance.

[0032] The cobalt removal treatment method for the fine-grained polycrystalline diamond sintered body is an existing technology; for example, an acid solution composed of nitric acid and hydrochloric acid is used to soak the fine-grained polycrystalline diamond sintered body at 100°C for 100-720 h to remove the metal binder therein, so that the content of the residual first binder in the cobalt-removed fine-grained polycrystalline diamond sintered body does not exceed 3wt%.

[0033] Furthermore, between the steps of preparing the fine-grained polycrystalline diamond decobalt-free sintered body and preparing the large-grained polycrystalline diamond sintered body, a step of cutting and processing the fine-grained polycrystalline diamond decobalt-free sintered body into a predetermined shape is included; this simplifies the subsequent preparation process of the wire drawing die blank. The predetermined shape includes, but is not limited to, cylindrical, polygonal prism, conical, and pyramidal shapes.

[0034] In the process of preparing large-particle polycrystalline diamond sintered bodies, if the particle size of the large-particle diamond micro powder is too small, it will result in poor heat dissipation during use and insufficient holding force for the fine-particle diamond decobaltized sintered body. If the particle size of the large-particle diamond micro powder is too large, there will be a large difference in particle size between it and the fine-particle diamond decobaltized sintered body, which will cause stress and thus easily lead to cracks. Therefore, the particle size of the large-particle diamond micro powder is smaller than that of the fine-particle diamond micro powder. Preferably, the particle size of the large-particle diamond micro powder is 0.1-100 μm; more preferably, it is 0.1-25 μm.

[0035] If the content of large-particle diamond micro powder is too high, it will be brittle and lack toughness, making it prone to cracking; if the content is too low, the temperature in the core will not be able to diffuse outward, resulting in high core temperature and diamond graphitization. Therefore, the mass ratio of the large-particle diamond micro powder in the second mixture is limited to 70-95 wt%; preferably 80-90 wt%.

[0036] The composition of the second binder is the existing composition, which can be at least one of the metallic elements such as Co, Si, Ni, Ti, and Cr.

[0037] In the second high-temperature and high-pressure sintering process, the sintering pressure and temperature are higher than those in the first high-temperature and high-pressure sintering process. The main reason is that the second sintered body does not participate in wire drawing, so appropriately increasing the synthesis pressure and temperature can improve the internal density and bonding strength. However, if the sintering pressure and temperature are too high in the second high-temperature and high-pressure sintering process, it is easy for too much binder to re-enter the first sintered body. Therefore, the process parameters for the second high-temperature and high-pressure sintering process are limited to: pressure 7-10 GPa, temperature 1600-1800℃, and sintering time 20-40 min.

[0038] Since the large-particle polycrystalline diamond sintered body does not participate in wire drawing, it does not require cobalt removal treatment. That is, in the preparation process of the polycrystalline diamond composite material, only the fine-particle polycrystalline diamond sintered body serving as the core layer needs to undergo cobalt removal treatment, without needing to perform cobalt removal treatment on the large-particle polycrystalline diamond sintered body, which greatly shortens the cobalt removal cycle of the wire drawing die.

[0039] This invention also provides a polycrystalline diamond composite material prepared by the above-described method, comprising a fine-grained polycrystalline diamond decobalt-removed sintered body located in the inner core and a large-grained polycrystalline diamond sintered body located in the outer layer, wherein the two polycrystalline diamond sintered bodies surround the fine-grained polycrystalline diamond decobalt-removed sintered body. Since this polycrystalline diamond composite material is mainly composed of diamond, it has good heat dissipation performance. Simultaneously, the fine-grained polycrystalline diamond decobalt-removed sintered body undergoes secondary sintering, resulting in a denser internal structure and a higher degree of bonding; moreover, the diamond particle size therein does not exceed 1 μm, so it can serve as the sizing region and / or compression region of the wire drawing die blank. The large-grained polycrystalline diamond sintered body, as the outer layer, with its larger diamond particle size, provides a holding force for the internal diamonds. The coarse-grained diamonds are more effective in heat conduction, facilitating timely heat removal, reducing the probability of internal graphitization, and decreasing phenomena such as drill bit loss and cracking. This results in better wire accuracy, roundness, and surface finish when drawing fine wires.

[0040] Therefore, the present invention also provides an application of the above-mentioned polycrystalline diamond composite material in the preparation of wire drawing die blanks.

[0041] Furthermore, the application includes: laser drilling the fine-grained polycrystalline diamond decobalt-free sintered body in the polycrystalline diamond composite material, so that the drilled fine-grained polycrystalline diamond decobalt-free sintered body is located in the sizing region and / or compression region of the wire drawing die blank; thereby improving the drawing quality.

[0042] Furthermore, the application further includes: laser drilling the large-particle polycrystalline diamond sintered body in the polycrystalline diamond composite material, such that the drilled large-particle polycrystalline diamond sintered body is located in at least one of the inlet region, compression region, or outlet region of the wire drawing die blank, so as to improve the quality of the wire.

[0043] The present invention also provides a wire drawing die blank composed of the aforementioned polycrystalline diamond composite material, comprising an inlet region, a compression region, a sizing region, and an outlet region, wherein the sizing region and / or the compression region are composed of the fine-grained polycrystalline diamond decobaltized sintered body. Further, at least one of the inlet region, compression region, and outlet region is composed of the large-grained polycrystalline diamond sintered body.

[0044] The technical solution provided by the present invention will be further explained and illustrated below through specific embodiments.

[0045] Example 1 like Figure 1 As shown in the left, this embodiment provides a polycrystalline diamond composite material, which includes a large-particle polycrystalline diamond sintered body 101 and a fine-particle polycrystalline diamond decobalt-removed sintered body 201 from the outside to the inside, wherein the fine-particle polycrystalline diamond decobalt-removed sintered body 201 is a quadrangular prism.

[0046] This embodiment also provides a method for preparing the above-mentioned polycrystalline diamond composite material, including: Preparation of fine-grained polycrystalline diamond sintered body: Using a three-dimensional mixer at a ball-to-particle ratio of 3:1, fine-grained diamond powder with a particle size of 50-100 nm and a first binder were uniformly mixed at a mass ratio of 82:18 using wet ball milling (with alcohol as a dispersant) to obtain a first mixed powder. The first binder was composed of Co metal powder and W metal powder with a particle size of 50-100 nm uniformly mixed at a mass ratio of 5:4, meaning that the Co metal powder accounted for 10% wt and the W metal powder accounted for 8% wt in the first mixed powder. The first mixed powder was placed in a shielded cup and sealed in a six-sided press. Under conditions of 6 GPa and 1550 °C, the first mixed powder underwent a first high-temperature and high-pressure sintering for 25 min to obtain the fine-grained polycrystalline diamond sintered body. Figure 3 As shown in (left), the fine-grained polycrystalline diamond sintered body was immersed in an acid solution composed of concentrated nitric acid and concentrated hydrochloric acid in a volume ratio of 1:3 at 100°C for 720 h to remove the metal binder, resulting in the following: Figure 3 The fine-grained polycrystalline diamond decobalt-free sintered body shown on the right has a residual first binder content of no more than 3 wt%; the fine-grained polycrystalline diamond decobalt-free sintered body is cut into quadrangular prisms using laser cutting method; Preparation of large-particle-size polycrystalline diamond sintered body: First, using a three-dimensional mixer, large-particle-size diamond micro powder with a particle size of 5-10 μm and a second binder are uniformly mixed at a mass ratio of 85:15 using a dry ball milling method at a ball-to-particle ratio of 3:1 to obtain the second mixed powder. The second binder is composed of 10% wt of Co metal powder with a particle size of 1-3 μm and 5% wt of W metal powder with a particle size of 1-3 μm. Then, a square-prism-shaped fine-particle-size polycrystalline diamond cobalt-removed sintered body 201 is placed in the middle of the second mixed powder, so that the second mixed powder is uniformly wrapped around the square-prism-shaped fine-particle-size polycrystalline diamond cobalt-removed sintered body 201. Then, a second high-temperature and high-pressure sintering is carried out at 8 GPa and 1700℃ for 35 min to obtain the polycrystalline diamond composite material provided in this embodiment.

[0047] This embodiment also provides an application of the above-mentioned polycrystalline diamond composite material in the preparation of wire drawing die blanks.

[0048] like Figure 1 As shown on the right, this embodiment provides a wire drawing die blank composed of the aforementioned polycrystalline diamond composite material, including an inlet region, a compression region, a sizing region, and an outlet region. The sizing region and compression region are composed of the fine-grained polycrystalline diamond decobalt-removed sintered body 201; the inlet region and outlet region are composed of the large-grained polycrystalline diamond sintered body 101. The preparation method of this wire drawing die blank includes: first, laser drilling is performed on the fine-grained polycrystalline diamond decobalt-removed sintered body 201, so that the drilled fine-grained polycrystalline diamond decobalt-removed sintered body 201 is located in the sizing region of the wire drawing die blank, thereby improving the drawing quality; then, laser drilling is performed on the large-grained polycrystalline diamond sintered body 101, so that the drilled large-grained polycrystalline diamond sintered body is located in the inlet region, compression region, and outlet region of the wire drawing die blank, thereby increasing the drawing compression speed. The polycrystalline diamond drawing die blank provided in this embodiment can be made into a drawing die for drawing high-strength tungsten and molybdenum wires.

[0049] Example 2 like Figure 2 As shown on the left, this embodiment provides a polycrystalline diamond composite material, which includes, from the outside to the inside, a large-particle polycrystalline diamond sintered body 101 and a second polycrystalline diamond decobaltized sintered body 201. The fine-particle polycrystalline diamond decobaltized sintered body 201 is drum-shaped.

[0050] This embodiment also provides a method for preparing the above-mentioned polycrystalline diamond composite material, including: Preparation of fine-grained polycrystalline diamond sintered body: Fine-grained diamond micropowder with a particle size of 500 nm and a first binder were uniformly mixed at a mass ratio of 85:15 using the same wet ball milling method as in Example 1 to obtain a first mixed powder. The first binder was composed of Co metal powder and W metal powder with a particle size of 300-600 nm, uniformly mixed at a mass ratio of 2:1, i.e., Co metal powder accounted for 10% wt and W metal powder accounted for 5% wt in the first mixed powder. The first mixed powder was placed in a shielded cup and sealed in a six-sided press. Under conditions of 6 GPa and 1550℃, the first mixed powder underwent a first high-temperature and high-pressure sintering for 30 min to obtain the fine-grained polycrystalline diamond sintered body. The fine-grained polycrystalline diamond sintered body was then immersed in an acid solution composed of concentrated nitric acid and concentrated hydrochloric acid at a volume ratio of 1:3 at 100℃ for 650 minutes. h, to remove the metal binder therein, so that the content of the residual first binder in the fine-grained polycrystalline diamond decobalt-free sintered body does not exceed 3 wt%; the fine-grained polycrystalline diamond decobalt-free sintered body is cut into the following shapes using laser cutting: Figure 2 The waist drum shape shown on the left; Preparation of large-particle-size polycrystalline diamond sintered body: First, using the same dry ball milling method as in Example 1, 15 wt% of diamond micro powder with a particle size of 5-10 μm, 70 wt% of diamond micro powder with a particle size of 20-25 μm, and 15 wt% of a second binder are uniformly mixed to obtain the second mixed powder. The second binder is composed of 5 wt% Co metal powder with a particle size of 1-3 μm and 10 wt% Si powder with a particle size of 1-3 μm. Then, a drum-shaped fine-particle-size polycrystalline diamond decobalt-removed sintered body 201 is placed in the middle of the second mixed powder, so that the second mixed powder uniformly surrounds the quadrangular prism-shaped fine-particle-size polycrystalline diamond decobalt-removed sintered body 201. Then, a second high-temperature and high-pressure sintering is performed at 7 GPa and 1600℃ for 40 min to obtain the polycrystalline diamond composite material provided in this example.

[0051] This embodiment also provides an application of the above-mentioned polycrystalline diamond composite material in the preparation of wire drawing die blanks.

[0052] like Figure 2 As shown on the right, this embodiment provides a wire drawing die blank composed of the aforementioned polycrystalline diamond composite material, including an inlet region, a compression region, a sizing region, and an outlet region. The inlet region, compression region, sizing region, and outlet region are composed of the fine-grained polycrystalline diamond decobalt-removed sintered body 201. The preparation method of this wire drawing die blank includes: laser drilling the fine-grained polycrystalline diamond decobalt-removed sintered body 201, and creating a hole in the middle of the fine-grained polycrystalline diamond decobalt-removed sintered body 201. Figure 2The drum-shaped through-hole shown ensures that the core layer of the entire wire drawing die blank is composed of fine-grained polycrystalline diamond decobaltized sintered body. Thus, this polycrystalline diamond wire drawing die blank can be manufactured into a wire drawing die for drawing high-strength stainless steel wire and molybdenum wire.

[0053] Example 3 This embodiment provides a wire drawing die blank, the preparation method of which is basically the same as that of the wire drawing die blank provided in Example 1. The main difference is that the formulations and processes of the fine-grained polycrystalline diamond sintered body and the large-grained polycrystalline diamond sintered body in the polycrystalline diamond composite material used in both are different. The specific differences are as follows, while other steps and parameters are the same: Preparation of fine-grained polycrystalline diamond sintered body: The first mixed powder is obtained by uniformly mixing fine-grained diamond micro powder with a particle size of 200-300 nm and the first binder at a mass ratio of 90:10. The sintering pressure is 7 GPa, the sintering temperature is 1500 ℃, and the sintering time is 15 min. Preparation of large-particle-size polycrystalline diamond sintered body: The second mixed powder is obtained by uniformly mixing large-particle-size diamond micro powder with a particle size of 20-25 μm and the second binder at a mass ratio of 70:30. The sintering pressure is 10 GPa, the sintering temperature is 1800 ℃, and the sintering time is 20 min.

[0054] Comparative Example 1—W content is too low This comparative example provides a wire drawing die blank, the preparation method of which is basically the same as that of the wire drawing die blank provided in Example 1. The main difference is that the formulation of the fine-grained polycrystalline diamond sintered body used in this comparative example is different from that in Example 1. In this comparative example, the mass ratio of Co metal powder to W metal powder in the first binder is 5:1, and the resulting fine-grained polycrystalline diamond sintered body is as follows: Figure 4 As shown on the left, the other steps and parameters are the same.

[0055] Comparative Example 2 - Excessive W content This comparative example provides a wire drawing die blank, the preparation method of which is basically the same as that of the wire drawing die blank provided in Example 1. The main difference is that the formulation of the fine-grained polycrystalline diamond sintered body used in this comparative example is different from that in Example 1. In this comparative example, the mass ratio of Co metal powder to W metal powder in the first binder is 0.5:1, and the resulting fine-grained polycrystalline diamond sintered body is as follows: Figure 4 As shown on the right, the other steps and parameters are the same.

[0056] contrast Figure 3 and Figure 4It can be seen that the diamond particles in the fine-grained polycrystalline diamond sintered body in Example 1 are basically the same before and after cobalt removal; while in Comparative Examples 1-2, there are obviously abnormally grown diamond particles. The main reason is that adding an appropriate amount of W to the binder can effectively inhibit the abnormal growth of fine-grained diamond. The excessive amount or lack thereof of W added in Comparative Examples 1-2 makes the diamond particle size distribution in the diamond sintered body uneven, making it difficult to use as a wire drawing die blank.

[0057] Comparative Example 3 – The inner layer is coarse-grained, and the outer layer is fine-grained. This comparative example provides a wire drawing die blank, the preparation method of which is basically the same as that of the wire drawing die blank provided in Example 1. The main difference is that the inner layer of this comparative example is a large-particle polycrystalline diamond decobalt-free sintered body, and the outer layer is a fine-particle polycrystalline diamond sintered body. The formula of the large-particle polycrystalline diamond decobalt-free sintered body in this comparative example is the same as the formula of the large-particle polycrystalline diamond sintered body in Example 1, and the formula of the fine-particle polycrystalline diamond sintered body in this comparative example is the same as the formula of the fine-particle polycrystalline diamond sintered body in Example 1. Other steps and parameters are the same.

[0058] Comparative Example 4—Different Sintering Process Parameters This comparative example provides a wire drawing die blank, the preparation method of which is basically the same as that of the wire drawing die blank provided in Example 1. The main difference is that in this comparative example, the process parameters for the first high-temperature and high-pressure sintering treatment are: pressure 7.5 GPa, temperature 1650℃, and sintering time 30 min; the process parameters for the second high-temperature and high-pressure sintering treatment are: pressure 10 GPa, temperature 1900℃, and sintering time 45 min; other steps and parameters are the same. Comparative Example 5—Different Process Parameters This comparative example provides a wire drawing die blank, the preparation method of which is basically the same as that of the wire drawing die blank provided in Example 1. The main difference is that the formulations and processes of the fine-grained polycrystalline diamond sintered body and the large-grained polycrystalline diamond sintered body in the polycrystalline diamond composite material used in both are different. The specific differences are as follows, while other steps and parameters are the same: Preparation of fine-grained polycrystalline diamond sintered body: The first mixed powder is obtained by uniformly mixing fine-grained diamond micro powder with a particle size of 200-400 nm and the first binder at a mass ratio of 95:5. The sintering pressure is 7 GPa, the sintering temperature is 1700 ℃, and the sintering time is 30 min. Preparation of large-particle-size polycrystalline diamond sintered body: The second mixed powder is obtained by uniformly mixing large-particle-size diamond micro powder with a particle size of 25-30 μm and the second binder at a mass ratio of 60:40. The sintering pressure is 7 GPa, the sintering temperature is 1700 ℃, and the sintering time is 30 min.

[0059] Comparative Example 6—Multi-layer Stacking Setup This comparative example provides a wire drawing die blank, comprising three integrally stacked polycrystalline diamond sintered layers arranged from top to bottom. The specific preparation method includes: pre-pressing diamond micropowders of three different particle size ranges (5-10 μm, 100 nm, and 10-15 μm) into cylinders, then placing the three cylinders into sealed containers, with cobalt positioned between the cylinders and the inner wall of the sealed container. The amount of cobalt is 15 wt% of the diamond micropowder. Then, the mixture is heated at 1550℃ for 7... The polycrystalline diamond sintered body was sintered for 1800s in a sealed container under a pressure of 7 GPa to obtain a three-layer stacked polycrystalline diamond sintered body. After removing cobalt from the three-layer stacked polycrystalline diamond sintered body using the same method as in Example 1, the layers were stacked sequentially from top to bottom and placed in a sealed container, with the cobalt positioned between the polycrystalline diamond sintered body and the inner wall of the sealed container. The amount of cobalt was 10 wt% of the polycrystalline diamond sintered body. The layers were then sintered for 1800s in a sealed container at 1550°C and a pressure of 7 GPa to obtain the three-layer stacked polycrystalline diamond sintered body wire drawing die blank.

[0060] The wire drawing die blanks provided in Examples 1-2 and Comparative Examples 1-6 were subjected to molybdenum wire drawing. The surface finish was detected by a white light interferometer, while the core temperature was collected by the change in electromotive force of the thermocouple wire. The results are shown in Table 1.

[0061] Table 1. Performance Test Results of Each Wire Drawing Die Blank As can be seen from the table above, compared with Comparative Examples 1-6, the molybdenum wires drawn in Examples 1-3 of the present invention have better surface finish, and the core temperature does not exceed 550 ℃, avoiding the risk of diamond loss due to graphitization. Furthermore, even after drawing for 40 kilometers, the surface finish remains good, not exceeding 0.1 μm. The main reason is that the raw material formulation, process, and parameters of the polycrystalline diamond composite material used in the drawing die blanks provided in Examples 1-3 work synergistically to homogenize the diamond particles in both the cobalt-free sintered body of fine-grained polycrystalline diamond and the sintered body of large-grained polycrystalline diamond, resulting in better quality of the drawn filaments. Moreover, due to the high thermal conductivity of diamond, the maximum core temperature of the drawing die blanks provided in the embodiments of the present invention is lower, resulting in lower heat dissipation capacity, especially lower than that of existing diamond drawing die blanks with externally nested stainless steel or cemented carbide.

[0062] Therefore, the preparation method of the polycrystalline diamond composite material and wire drawing die blank provided in this embodiment of the invention is simpler to operate and saves more steps. Simultaneously, the addition of nano-sized polycrystalline diamond cobalt-free sintered bodies and secondary sintering results in a denser internal structure and higher bonding. Fine-grained diamond is used in the sizing zone to improve drawing quality. Coarse-grained diamond is used in the inlet, compression, and outlet regions to increase compression speed and effectively utilize the characteristics of polycrystalline diamonds of different particle sizes, thereby improving the service life and wear resistance of the wire drawing die, while also improving the roundness and surface finish of the drawn wire. Furthermore, the coarse-grained diamond on the outside can provide a holding force to the internal diamond, and its superior heat conduction facilitates timely heat removal, reduces the probability of internal graphitization, and decreases phenomena such as drill bit loss and cracking. This results in better wire accuracy, roundness, and surface finish when drawing fine wires.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A polycrystalline diamond composite material, characterized in that, The system comprises a fine-grained polycrystalline diamond sintered body with cobalt removal located in the middle and a large-grained polycrystalline diamond sintered body surrounding the fine-grained polycrystalline diamond sintered body. The fine-grained polycrystalline diamond sintered body is mainly prepared by high-temperature and high-pressure sintering and cobalt removal treatment of a first mixed powder composed of fine-grained diamond micropowder and a first binder. The fine-grained diamond micropowder is micro-nano-level diamond micropowder and accounts for 75-98 wt% of the mass in the first mixed powder. The first binder is composed of a uniform mixture of metallic Co and W in a mass ratio of 1:1 to 4:

1. The large-grained polycrystalline diamond sintered body is mainly prepared by high-temperature and high-pressure sintering of a second mixed powder composed of large-grained diamond micropowder and a second binder. The large-grained diamond micropowder has a larger particle size than the fine-grained diamond micropowder and accounts for 70-95 wt% of the mass in the second mixed powder.

2. The polycrystalline diamond composite material according to claim 1, characterized in that, The fine-grained diamond powder has a particle size of 50-1000 nm, and the large-grained diamond powder has a particle size of 0.1-100 μm.

3. The polycrystalline diamond composite material according to claim 1, characterized in that, The fine-grained polycrystalline diamond decobaltized sintered body is cylindrical, prismatic, conical, or pyramidal in shape.

4. A method for preparing the polycrystalline diamond composite material according to any one of claims 1-3, comprising the steps of: Preparation of fine-grained polycrystalline diamond decobaltized sintered body: First, the fine-grained diamond micro powder and the first binder are uniformly mixed to form the first mixed powder; then, the first mixed powder is subjected to a first high-temperature and high-pressure treatment under a pressure of 5-7 GPa and a temperature of 1500-1600℃ to obtain a fine-grained polycrystalline diamond sintered body; then, the fine-grained polycrystalline diamond sintered body is subjected to a decobalt treatment to obtain the fine-grained polycrystalline diamond decobaltized sintered body; Preparation of large-particle-size polycrystalline diamond sintered body: First, large-particle-size diamond micro powder and a second metal binder are uniformly mixed to obtain the second mixed powder; then, the second mixed powder is placed around the fine-particle-size polycrystalline diamond decobalt-free sintered body, so that the second mixed powder surrounds the fine-particle-size polycrystalline diamond decobalt-free sintered body; then, under the conditions of pressure 7-10 GPa and temperature 1600-1800℃, a second high-temperature and high-pressure sintering treatment is performed, so that the second mixed powder is transformed into the large-particle-size polycrystalline diamond sintered body, and the height of the fine-particle-size polycrystalline diamond decobalt-free sintered body is not higher than that of the large-particle-size polycrystalline diamond sintered body, thus obtaining the polycrystalline diamond composite material.

5. The preparation method according to claim 4, characterized in that, Between the steps of preparing fine-grained polycrystalline diamond decobalt-free sintered bodies and preparing large-grained polycrystalline diamond sintered bodies, there is also a step of cutting and processing the fine-grained polycrystalline diamond decobalt-free sintered bodies into a predetermined shape.

6. The preparation method according to claim 4 or 5, characterized in that, The steps for preparing the large-particle-size polycrystalline diamond sintered body include: firstly, uniformly mixing the large-particle-size diamond micro powder and the second binder using a ball milling method to obtain the second mixed powder; then, placing the fine-particle-size polycrystalline diamond decobalt-removed sintered body in the middle of the second mixed powder, so that the second mixed powder uniformly surrounds the fine-particle-size polycrystalline diamond decobalt-removed sintered body; then, performing a second high-temperature and high-pressure sintering treatment under a pressure of 7-10 GPa and a temperature of 1600-1800℃, so that the obtained large-particle-size polycrystalline diamond sintered body and the fine-particle-size polycrystalline diamond decobalt-removed sintered body are coaxially arranged, and the height of the fine-particle-size polycrystalline diamond decobalt-removed sintered body is not higher than that of the large-particle-size polycrystalline diamond sintered body, thereby obtaining the polycrystalline diamond composite material.

7. The application of the polycrystalline diamond composite material according to any one of claims 1-3 in the preparation of wire drawing die blanks.

8. The application according to claim 7, characterized in that, include: Laser drilling is performed on the fine-grained polycrystalline diamond decobalt-free sintered body in the polycrystalline diamond composite material, so that the drilled fine-grained polycrystalline diamond decobalt-free sintered body is located in the sizing region and / or compression region of the wire drawing die blank.

9. A wire drawing die blank, characterized in that, Composed of the polycrystalline diamond composite material according to any one of claims 1-3, comprising an inlet region, a compression region, a sizing region, and an outlet region, wherein the sizing region and / or the compression region are composed of the fine-grained polycrystalline diamond decobaltized sintered body.

10. The wire drawing die blank according to claim 9, characterized in that, At least one of the inlet region, compression region, and outlet region is composed of the large-particle polycrystalline diamond sintered body.

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