Method for preparing polycrystalline diamond compact, method for preparing polycrystalline diamond

Abstract

This invention relates to a method for preparing polycrystalline diamond (PCD) preforms and a method for preparing PCD, belonging to the field of PCD technology. The method for preparing PCD preforms of this invention involves isostatic pressing of PCD raw material powder, which effectively reduces porosity within the PCD preform, improves the uniformity of density distribution within the preform, and reduces residual stress within the preform. When using the PCD preform prepared by this invention to prepare PCD, defects such as cracks and fissures on the surface of the PCD can be effectively reduced, improving the surface quality of the PCD and thus increasing the production yield. Furthermore, it can improve the wear resistance and impact toughness of the PCD.

Description

Technical Field

[0001] This invention relates to a method for preparing polycrystalline diamond preforms and a method for preparing polycrystalline diamond, belonging to the field of polycrystalline diamond technology. Background Technology

[0002] Polycrystalline diamond (PCD) is produced by sintering diamond micropowder with a catalyst (metal catalyst) under high temperature and pressure. It possesses the high hardness and wear resistance of diamond and is widely used in industries such as oil drill bits and cutting tools. The sintering temperature for synthesizing PCD is generally not less than 1200℃, and the pressure is not less than 5 GPa. During sintering, the metal catalyst catalyzes the formation of DD bonds between diamond particles, forming PCD. Currently, when using high-temperature and high-pressure sintering (HTHS) processes to prepare PCD, the HTHS sintering equipment is becoming increasingly larger, and the size of the synthesis chamber is also becoming an inevitable trend. The larger the space of the synthesis chamber, the larger the product volume, and the higher the requirement for the pre-forming density of the product. Existing technologies mainly use cold pressing to increase the density of PCD preforms (PCD preforms), that is, using a double-sided press to pre-press the raw material powder in the synthesis chamber to obtain the PCD preform. Pre-pressing with a double-sided press can increase the pre-forming density of the material axially. However, the pressure provided by the double-sided press is limited, and the effect on increasing the density of the polycrystalline diamond preform is limited. Furthermore, during pre-pressing, the radial stress strength and uniformity of the material are significantly lower than those in the axial direction. Therefore, pre-pressing introduces residual stress, causing anisotropy, which makes the polycrystalline diamond preform prone to defects such as cracks or even ruptures during high-temperature and high-pressure sintering. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing polycrystalline diamond preforms, which can solve the problem that uneven density distribution of the preforms, which leads to cracks in the prepared polycrystalline diamonds, when using the pre-pressing process to prepare them.

[0004] Another objective of this invention is to provide a method for preparing polycrystalline diamond that can solve the problem of cracks easily occurring during the current preparation of polycrystalline diamond.

[0005] To achieve the above objectives, the technical solution adopted in the preparation method of the polycrystalline diamond preform of the present invention is as follows:

[0006] A method for preparing a polycrystalline diamond blank includes the following steps: isostatic pressing of polycrystalline diamond raw material powder to obtain a polycrystalline diamond blank; the polycrystalline diamond raw material powder is mainly composed of diamond micro powder and catalyst; the pressure used in the isostatic pressing is 30-250 MPa.

[0007] The method for preparing polycrystalline diamond preforms according to the present invention uses isostatic pressing to process polycrystalline diamond raw material powder, which can effectively reduce the porosity within the polycrystalline diamond preform, improve the uniformity of density distribution within the preform, and reduce residual stress within the preform. When polycrystalline diamond is prepared using the polycrystalline diamond preform prepared according to the present invention, defects such as cracks and fissures on the surface of the polycrystalline diamond can be effectively reduced, improving the surface quality of the polycrystalline diamond, thereby increasing the production qualification rate, and also improving the wear resistance and impact toughness of the polycrystalline diamond.

[0008] Isostatic pressing (IPC) involves placing the sample (powder) in a high-pressure container. Utilizing the incompressibility and uniform pressure transmission properties of the liquid medium, pressure is uniformly applied to the sample from all directions. When the liquid medium is injected into the pressure container via a pressure pump, according to fluid mechanics principles, its pressure remains constant and is uniformly transmitted in all directions. At this point, the powder in the high-pressure container experiences uniform and consistent pressure in all directions. IPC includes the following stages: initial stage with low forming pressure, characterized by powder particle migration and recombination; intermediate stage with increasing pressure, characterized by localized powder flow and fragmentation; and final stage with maximum pressure, characterized by powder volume compression, expulsion of pores, and densification. To avoid contact between the liquid medium and the powder, during IPC, the powder is placed in an elastic mold. The deformation of the elastic mold under liquid pressure is transmitted to the powder within the mold. This results in low friction between the powder and the mold wall, uniform stress on the blank, and a uniform density distribution, effectively preventing uneven density distribution within the blank. Isostatic pressing is divided into cold isostatic pressing and hot isostatic pressing. Cold isostatic pressing is an isostatic pressing method that shapes the powder to be pressed at room temperature; hot isostatic pressing is a method that shapes the powder to be pressed under high temperature and high pressure.

[0009] To reduce costs, the isostatic pressing process of this invention employs cold isostatic pressing, and the liquid medium can be a chemically stable liquid. To avoid increased costs due to high temperatures, the isostatic pressing temperature is preferably between 10 and 100°C. To further reduce costs, the isostatic pressing temperature is preferably room temperature.

[0010] Preferably, the particle size of the diamond micro powder is 0.1–100 μm. More preferably, the particle size of the diamond micro powder is 0.1–60 μm. More preferably, the particle size of the diamond micro powder is 1–60 μm. If the particle size of the diamond micro powder is too small, the impact performance of the polycrystalline diamond obtained by sintering will be poor. If the particle size of the diamond micro powder is too large, it will be difficult for DD bonds to form between the diamond micro powder particles, making it impossible to obtain tightly bonded polycrystalline diamond, thereby reducing the wear resistance of the polycrystalline diamond.

[0011] Preferably, the catalyst is selected from one or any combination of iron powder, cobalt powder, and nickel powder.

[0012] Preferably, the particle size of the catalyst is 0.1–10 μm. More preferably, the particle size of the catalyst is 1–7 μm. If the particle size of the catalyst is too small, it is prone to agglomeration, which is not conducive to the uniform dispersion of the catalyst in the raw material powder; if the particle size of the catalyst is too large, it will cause the catalyst to be unable to be fully activated during sintering, affecting the graphitization of diamond micron powder and the formation of DD bonds.

[0013] To ensure that the diamond micropowder can fully form DD bonds under the action of the catalyst, preferably, the mass ratio of the diamond micropowder to the catalyst is (7-10):(1-3). More preferably, the mass ratio of the diamond micropowder to the catalyst is (8-9):(1-2). If the mass ratio of the diamond micropowder to the catalyst is too large, it will make it difficult for the diamond micropowder to sinter; if the mass ratio is too small, it will result in poor wear resistance of the sintered product.

[0014] More preferably, the diamond micropowder comprises fine diamond micropowder and coarse diamond micropowder, wherein the fine diamond micropowder has a particle size of 1–5 μm; the coarse diamond micropowder has a particle size greater than 5 μm and not greater than 60 μm; and the mass ratio of the fine diamond micropowder to the coarse diamond micropowder is (2–5):(5–8). More preferably, the catalyst comprises small-particle catalyst and large-particle catalyst, wherein the small-particle catalyst has a particle size of 1–5 μm; the large-particle catalyst has a particle size greater than 5 μm and not greater than 7 μm; and the mass ratio of the small-particle catalyst to the large-particle catalyst is (3–5):(5–7). By using a combination of fine and coarse diamond powder, the fine diamond powder can fill the gaps between the coarse diamond powder during isostatic pressing, effectively reducing the voids between the diamond powder particles and improving the density of the polycrystalline diamond preform. Similarly, by using a combination of small and large-particle catalysts, the catalysts can fill the voids between diamond powder particles of different sizes during isostatic pressing, further reducing the void volume and increasing the density of the polycrystalline diamond preform. This also ensures close contact and uniform distribution of the catalyst around the fine and coarse diamond powder particles, thus contributing to improved performance of the finished polycrystalline diamond product.

[0015] In this invention, there are no particular limitations on the mold used for isostatic pressing, as long as it has sufficient elasticity and shape retention and does not react with the diamond raw material powder; for example, a rubber mold. During isostatic pressing, the polycrystalline diamond raw material powder is first loaded into the mold, ensuring uniform filling and avoiding air pockets. Then, pressure is applied and held for isostatic pressing, followed by depressurization to obtain the polycrystalline diamond preform. Stable pressure application and an appropriate pressurization rate are crucial to avoid incomplete gas removal from the powder voids due to excessively rapid pressurization. Simultaneously, to prevent structural damage to the polycrystalline diamond preform in high-speed gas flow due to excessively rapid depressurization, a suitable depressurization rate must be selected. Preferably, the isostatic pressing process involves first pressurizing the polycrystalline diamond raw material powder to 30–250 MPa at a pressurization rate of 0.1–5 MPa / min, then holding the pressure for 1–20 minutes, and finally depressurizing at a depressurization rate of 0.1–5 MPa / min. More preferably, the isostatic pressing process involves first pressurizing the polycrystalline diamond raw material powder to 30-250 MPa at a pressurization rate of 2-4 MPa / min, then holding the pressure for 5-10 minutes, and finally depressurizing at a depressurization rate of 2-4 MPa / min.

[0016] The technical solution adopted in the preparation method of polycrystalline diamond of the present invention is as follows:

[0017] A method for preparing polycrystalline diamond includes the following steps: subjecting the polycrystalline diamond blank prepared by the method described above to high-temperature and high-pressure sintering to obtain polycrystalline diamond.

[0018] The polycrystalline diamond preparation method of the present invention uses isostatic pressing to prepare a polycrystalline diamond blank and then sintering it. The sintered polycrystalline diamond is less prone to defects such as cracks and fissures, thereby improving the surface quality of the polycrystalline diamond, increasing the production qualification rate, and improving the wear resistance and impact toughness of the polycrystalline diamond.

[0019] In this invention, the temperature and pressure used for high-temperature and high-pressure sintering of polycrystalline diamond blanks can refer to the temperature and pressure used in the prior art for high-temperature and high-pressure sintering of raw material powder composed of diamond micron powder and catalyst. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0021] I. Specific embodiments of the method for preparing the polycrystalline diamond preform of the present invention are as follows:

[0022] Example 1

[0023] The method for preparing the polycrystalline diamond preform in this embodiment specifically includes the following steps:

[0024] Diamond micro powder and catalyst are mixed evenly using a three-dimensional mixer to obtain polycrystalline diamond raw material powder. The polycrystalline diamond raw material powder is then loaded into a niobium cup, which is then placed in a rubber mold to seal the niobium cup. Finally, isostatic pressing is performed to obtain a polycrystalline diamond blank.

[0025] In this embodiment, the diamond micro powder includes fine diamond micro powder and coarse diamond micro powder. The particle size of the fine diamond micro powder is 1-2 μm, the particle size of the coarse diamond micro powder is 50-60 μm, and the mass ratio of fine diamond micro powder to coarse diamond micro powder is 2:8.

[0026] The catalyst is iron powder, which includes small-particle catalyst and large-particle catalyst. The particle size of the small-particle catalyst is 1-2 μm, and the particle size of the large-particle catalyst is 6-7 μm. The mass ratio of small-particle catalyst to large-particle catalyst is 3:7.

[0027] The mass ratio of diamond micron powder to catalyst is 8:2;

[0028] Isostatic pressing involves increasing the pressure of polycrystalline diamond raw material powder to 30 MPa at a pressurization rate of 2 MPa / min, holding the pressure for 5 minutes, and then depressurizing at a depressurization rate of 2 MPa / min.

[0029] Example 2

[0030] The method for preparing the polycrystalline diamond preform in this embodiment specifically includes the following steps:

[0031] Diamond micro powder and catalyst are mixed evenly using a three-dimensional mixer to obtain polycrystalline diamond raw material powder. The polycrystalline diamond raw material powder is then loaded into a niobium cup, which is then placed in a rubber mold to seal the niobium cup. Finally, isostatic pressing is performed to obtain a polycrystalline diamond blank.

[0032] In this embodiment, the diamond micro powder includes fine diamond micro powder and coarse diamond micro powder. The particle size of the fine diamond micro powder is 4-5 μm, the particle size of the coarse diamond micro powder is 5-10 μm, and the mass ratio of fine diamond micro powder to coarse diamond micro powder is 5:5.

[0033] The catalyst is nickel powder, which includes small-particle catalyst and large-particle catalyst. The particle size of the small-particle catalyst is 2-4 μm, and the particle size of the large-particle catalyst is 5-6 μm. The mass ratio of small-particle catalyst to large-particle catalyst is 4:6.

[0034] The mass ratio of diamond powder to catalyst is 9:1;

[0035] Isostatic pressing involves increasing the pressure of polycrystalline diamond raw material powder to 250 MPa at a pressurization rate of 4 MPa / min, holding the pressure for 8 minutes, and then depressurizing at a depressurization rate of 4 MPa / min.

[0036] Example 3

[0037] The method for preparing the polycrystalline diamond preform in this embodiment specifically includes the following steps:

[0038] Diamond micro powder and catalyst are mixed evenly using a three-dimensional mixer to obtain polycrystalline diamond raw material powder. The polycrystalline diamond raw material powder is then loaded into a niobium cup, which is then placed in a rubber mold to seal the niobium cup. Finally, isostatic pressing is performed to obtain a polycrystalline diamond blank.

[0039] In this embodiment, the diamond micro powder includes fine diamond micro powder and coarse diamond micro powder. The particle size of the fine diamond micro powder is 2-4 μm, the particle size of the coarse diamond micro powder is 20-40 μm, and the mass ratio of fine diamond micro powder to coarse diamond micro powder is 4:6.

[0040] The catalyst is cobalt powder, which includes small-particle catalyst and large-particle catalyst. The particle size of the small-particle catalyst is 3-5 μm, and the particle size of the large-particle catalyst is 5-6 μm. The mass ratio of small-particle catalyst to large-particle catalyst is 5:5.

[0041] The mass ratio of diamond powder to catalyst is 9:1;

[0042] Isostatic pressing involves increasing the pressure of polycrystalline diamond raw material powder to 100 MPa at a pressurization rate of 3 MPa / min, holding the pressure for 10 minutes, and then depressurizing at a depressurization rate of 3 MPa / min.

[0043] Comparative Example 1

[0044] The only difference between the preparation method of the polycrystalline diamond blank in this comparative example and the preparation method of the polycrystalline diamond blank in Example 1 is that the particle size of the diamond powder in this comparative example is the same as that of the fine diamond powder in Example 1, and the particle size of the catalyst is the same as that of the small particle catalyst in Example 1.

[0045] Comparative Example 2

[0046] The difference between the preparation method of the polycrystalline diamond blank in this comparative example and the preparation method of the polycrystalline diamond blank in Example 1 is that the particle size of the diamond powder in this comparative example is the same as that of the coarse diamond powder in Example 1, and the particle size of the catalyst is the same as that of the large-particle catalyst in Example 1.

[0047] Comparative Example 3

[0048] The only difference between the preparation method of the polycrystalline diamond blank in this comparative example and the preparation method of the polycrystalline diamond blank in Example 1 is that the particle size of the diamond powder in this comparative example is the same as that of the fine diamond powder in Example 1, and the particle size of the catalyst is the same as that of the large-particle catalyst in Example 1.

[0049] Comparative Example 4

[0050] The only difference between the preparation method of the polycrystalline diamond blank in this comparative example and the preparation method of the polycrystalline diamond blank in Example 1 is that the particle size of the diamond powder in this comparative example is the same as that of the coarse diamond powder in Example 1, and the particle size of the catalyst is the same as that of the small-particle catalyst in Example 1.

[0051] Comparative Example 5

[0052] The only difference between the preparation method of the polycrystalline diamond blank in this comparative example and the preparation method of the polycrystalline diamond blank in Example 1 is that the mass ratio of fine diamond powder to coarse diamond powder is 1:5 in the preparation method of the polycrystalline diamond blank in this comparative example.

[0053] Comparative Example 6

[0054] The only difference between the preparation method of the polycrystalline diamond blank in this comparative example and the preparation method of the polycrystalline diamond blank in Example 1 is that the mass ratio of fine diamond powder to coarse diamond powder is 5:9 in the preparation method of the polycrystalline diamond blank in this comparative example.

[0055] Comparative Example 7

[0056] The only difference between the preparation method of the polycrystalline diamond preform in this comparative example and the preparation method of the polycrystalline diamond preform in Example 1 is that the mass ratio of small-particle catalyst to large-particle catalyst is 2:5 in the preparation method of the polycrystalline diamond preform in this comparative example.

[0057] Comparative Example 8

[0058] The only difference between the preparation method of the polycrystalline diamond preform in this comparative example and the preparation method of the polycrystalline diamond preform in Example 1 is that the mass ratio of small-particle catalyst to large-particle catalyst is 5:8 in the preparation method of the polycrystalline diamond preform in this comparative example.

[0059] Comparative Example 9

[0060] The preparation method of the polycrystalline diamond preform in this comparative example specifically includes the following steps: the polycrystalline diamond raw material powder prepared in Example 1 is used to prepare the polycrystalline diamond preform using a double-sided press (the pressure of the double-sided press is 15 MPa and the pressing time is 15 s).

[0061] The polycrystalline diamond preforms prepared in Examples 1-3 and Comparative Examples 1-9 were all cylindrical, with a diameter of 50 mm and a height of 5 mm.

[0062] II. Specific embodiments of the polycrystalline diamond preparation method of the present invention are as follows:

[0063] Example 4

[0064] The preparation method of polycrystalline diamond in this embodiment specifically includes the following steps: the polycrystalline diamond blank prepared in Example 1 is placed into the synthesis cavity, then assembled into a synthesis block, and then subjected to high temperature and high pressure sintering using a six-sided top press. The high temperature and high pressure sintering temperature is 1300℃, the pressure is 5GPa, and the time is 60min.

[0065] Example 5

[0066] The preparation method of polycrystalline diamond in this embodiment specifically includes the following steps: the polycrystalline diamond blank prepared in Example 2 is placed into the synthesis cavity, then assembled into a synthesis block, and then subjected to high temperature and high pressure sintering using a six-sided top press. The high temperature and high pressure sintering temperature is 1400℃, the pressure is 6GPa, and the time is 50min.

[0067] Example 6

[0068] The preparation method of polycrystalline diamond in this embodiment specifically includes the following steps: the polycrystalline diamond blank prepared in Example 3 is placed into the synthesis cavity, then assembled into a synthesis block, and then subjected to high temperature and high pressure sintering using a six-sided top press. The high temperature and high pressure sintering temperature is 1200℃, the pressure is 4.5GPa, and the time is 60min.

[0069] Experimental Example 1

[0070] To investigate the effect of different methods on the appearance of the prepared polycrystalline diamond preforms, polycrystalline diamond preforms were prepared according to the methods of Examples 1-3 and Comparative Examples 1-9, with 100 preforms prepared by each method. Each preform was then prepared into a polycrystalline diamond using the method of Example 6. The surface of the prepared polycrystalline diamond was then observed. If cracks or fissures appeared on the surface, the test result was considered unqualified. The pass rate of polycrystalline diamonds prepared by each method was calculated, and the results are shown in Table 1.

[0071] Table 1. Qualification rate of polycrystalline diamond prepared by different methods

[0072] processing method Pass rate (%) Example 1 98 Example 2 99 Example 3 100 Comparative Example 1 84 Comparative Example 2 77 Comparative Example 3 74 Comparative Example 4 66 Comparative Example 5 47 Comparative Example 6 46 Comparative Example 7 55 Comparative Example 8 56 Comparative Example 9 44

[0073] Experiment Example 2

[0074] To investigate the performance of polycrystalline diamonds obtained by sintering polycrystalline diamond preforms prepared by different methods, polycrystalline diamond preforms prepared in Examples 1-3 and Comparative Examples 1-9 were prepared into polycrystalline diamonds according to the method in Example 6. The wear ratio and impact toughness of the polycrystalline diamonds prepared by each method were then tested. For ease of comparison, the wear ratio and impact toughness of the polycrystalline diamonds obtained from the polycrystalline diamond preforms prepared in Comparative Example 9 were set to 1. The ratios of the wear ratio and impact toughness of the polycrystalline diamonds obtained from the polycrystalline diamond preforms prepared in Examples 1-3 and Comparative Examples 1-8 to those obtained from the polycrystalline diamond preforms prepared in Comparative Example 9 were then calculated. The relative values ​​of the wear ratio and impact toughness of the polycrystalline diamonds obtained from the polycrystalline diamond preforms prepared in each example and comparative example were obtained, and the results are shown in Table 2.

[0075] Table 2. Relative values ​​of wear ratio and impact toughness of polycrystalline diamond obtained from polycrystalline diamond preforms prepared by different methods.

[0076] processing method Relative value of wear ratio Relative value of impact toughness Example 1 0.3 7 Example 2 0.2 6.6 Example 3 0.3 6.8 Comparative Example 1 0.6 3.2 Comparative Example 2 0.7 4.1 Comparative Example 3 0.7 3.4 Comparative Example 4 0.8 3.0 Comparative Example 5 0.8 2.9 Comparative Example 6 0.8 3.0 Comparative Example 7 0.9 1.6 Comparative Example 8 0.9 1.5 Comparative Example 9 1 1

[0077] To further investigate the influence of isostatic pressing (OSP) on the experimental results, based on Example 1, the pressure increase rate, holding time, and depressurization rate during OSP were adjusted. When the pressure increase rate was adjusted from 2 MPa / min to 0.1 MPa / min or 5 MPa / min, or the holding time was adjusted from 5 min to 1 min or 20 min, or the depressurization rate was adjusted from 2 MPa / min to 0.1 MPa / min or 5 MPa / min, the polycrystalline diamond preforms obtained were similar in performance to those prepared using the method described in Example 4. Therefore, when the pressure increase rate during OSP is 0.1–5 MPa / min, the holding time is 1–20 min, and the depressurization rate is 0.1–5 MPa / min, high-performance polycrystalline diamond can be obtained.

Claims

1. A method of producing a polycrystalline diamond compact, characterized by, Includes the following steps: Polycrystalline diamond raw material powder is isostatically pressed to obtain a polycrystalline diamond blank; the polycrystalline diamond raw material powder is mainly composed of diamond micro powder and catalyst in a mass ratio of (7~10):(1~3); the pressure used in the isostatic pressing is 30~250MPa; the diamond micro powder includes fine diamond micro powder and coarse diamond micro powder, the particle size of the fine diamond micro powder is 1~5μm; the particle size of the coarse diamond micro powder is greater than 5μm and not greater than 60μm; the mass ratio of the fine diamond micro powder to the coarse diamond micro powder is (2~5):(5~8); the catalyst includes small-particle catalyst and large-particle catalyst, the particle size of the small-particle catalyst is 1~5μm; the particle size of the large-particle catalyst is greater than 5μm and not greater than 7μm; the mass ratio of the small-particle catalyst to the large-particle catalyst is (3~5):(5~7).

2. The method of producing a polycrystalline diamond compact as claimed in claim 1, wherein, The isostatic pressing process is performed at a temperature of 10~100℃.

3. The method for preparing polycrystalline diamond preform as described in claim 2, characterized in that, The isostatic pressing process is performed at room temperature.

4. The method for preparing polycrystalline diamond preform as described in claim 1, characterized in that, The catalyst is selected from one or any combination of iron powder, cobalt powder, and nickel powder.

5. The method for preparing a polycrystalline diamond preform as described in any one of claims 1-4, characterized in that, The mass ratio of the diamond micro powder to the catalyst is (8~9):(1~2).

6. The method for preparing a polycrystalline diamond preform as described in any one of claims 1-4, characterized in that, The isostatic pressing process involves first increasing the pressure of polycrystalline diamond raw material powder to 30-250 MPa at a pressurization rate of 0.1-5 MPa / min, then holding the pressure for 1-20 minutes, and finally depressurizing at a depressurization rate of 0.1-5 MPa / min.

7. The method for preparing a polycrystalline diamond preform as described in claim 6, characterized in that, The isostatic pressing process involves first increasing the pressure of polycrystalline diamond raw material powder to 30-250 MPa at a pressurization rate of 2-4 MPa / min, then holding the pressure for 5-10 minutes, and finally depressurizing at a depressurization rate of 2-4 MPa / min.

8. A method for preparing polycrystalline diamond, characterized in that, Includes the following steps: The polycrystalline diamond preform prepared by the method described in any one of claims 1-7 is subjected to high-temperature and high-pressure sintering to obtain polycrystalline diamond.