A multilayer gradient polycrystalline diamond compact and a method of making the same

Abstract

The present application belongs to the technical field of superhard material, and particularly relates to a multilayer gradient polycrystalline diamond compact and a preparation method thereof.The multilayer gradient polycrystalline diamond compact comprises polycrystalline diamond layers, transition layer A, hard alloy layers, transition layer B, polycrystalline diamond layers, transition layer C and hard alloy substrates arranged in sequence.Based on the adoption of a double-blade structure and the inheritance of the high wear resistance and impact resistance of traditional PDC compacts, the gradient structure design of multiple transition layers greatly reduces the residual stress between the hard alloy layers and the polycrystalline diamond layers, reduces the risk of the polycrystalline diamond layers from cracking, greatly improves the bonding strength between the hard alloy layers and the polycrystalline diamond layers, reduces the risk of the polycrystalline diamond layers and the hard alloy substrates from delaminating, is conducive to the improvement of the service life of the diamond compact, and is suitable for the application of PDC compacts.

Description

Technical Field

[0001] This invention belongs to the field of superhard materials technology, specifically relating to a multilayer gradient polycrystalline diamond composite sheet and its preparation method. Background Technology

[0002] Polycrystalline diamond compact (PDC) is an ultra-hard material made by sintering polycrystalline diamond powder and a cemented carbide substrate under high temperature and pressure. PDC combines the high hardness and wear resistance of diamond with the high impact resistance of cemented carbide (such as the polycrystalline diamond compact produced by the sintering method disclosed in Chinese invention patent CN106270883A). It is widely used in geological drilling, oil, natural gas, and coal mining industries.

[0003] However, due to the large difference in the coefficients of thermal expansion between diamond and cemented carbide, there is often a large residual stress at the interface between the two. In actual use, the huge residual stress at the interface can lead to the formation of interface cracks, causing the diamond layer to fail due to detachment and fracture, which greatly reduces the service life of the workpiece.

[0004] Currently, the preparation method of polycrystalline diamond composite sheets is disclosed in Chinese invention patent CN2632288Y, which discloses a double-edged artificial diamond composite sheet. The structure is arranged from bottom to top as a cemented carbide matrix, a polycrystalline diamond layer, a cemented carbide layer, and a polycrystalline diamond layer. In the actual use of the workpiece, it can form a double edge to improve the impact resistance and wear resistance of the workpiece. However, its structural design and preparation process cannot effectively reduce the residual stress between the two layers.

[0005] Chinese invention patent CN106735246A discloses a polycrystalline diamond composite sheet with a structure consisting of a cemented carbide substrate, a polycrystalline diamond layer, a tungsten carbide composite material layer, and a cemented carbide protective layer from bottom to top. It has excellent wear resistance and impact toughness and reduces the residual stress between the polycrystalline diamond layer and the cemented carbide protective layer. However, the polycrystalline diamond layer is still directly sintered on the cemented carbide substrate, which still does not solve the key problem of interfacial stress mismatch. Summary of the Invention

[0006] To address the aforementioned problems, the primary objective of this invention is to provide a multilayer gradient polycrystalline diamond composite sheet with low surface residual stress, excellent impact toughness and wear resistance, thereby improving the service life of the composite sheet.

[0007] The second objective of this invention is to provide a method for preparing multilayer gradient polycrystalline diamond composite sheets, which can effectively reduce the residual stress between cemented carbide and polycrystalline diamond and solve the problem of interface stress compatibility.

[0008] To achieve the above objectives, the technical solution adopted by the multilayer gradient polycrystalline diamond composite sheet of the present invention is as follows:

[0009] A multilayer gradient polycrystalline diamond composite sheet includes a polycrystalline diamond layer, a transition layer A, a cemented carbide layer, a transition layer B, a polycrystalline diamond layer, a transition layer C, and a cemented carbide matrix arranged sequentially.

[0010] The transition layers A, B, and C are obtained by sintering a transition layer mixture comprising diamond micron powder, tungsten carbide micron powder, and a binder. Transition layer A is obtained by sintering transition layer mixtures with different mass ratios in descending order of the mass ratio of diamond micron powder. Transition layer B is obtained by sintering transition layer mixtures with different mass ratios in ascending order of the mass ratio of diamond micron powder. Transition layer C is obtained by sintering transition layer mixtures with different mass ratios in descending order of the mass ratio of diamond micron powder.

[0011] The multi-layer gradient polycrystalline diamond composite sheet provided by this invention includes, in sequence, a polycrystalline diamond layer, a transition layer A, a cemented carbide layer, a transition layer B, another polycrystalline diamond layer, a transition layer C, and a cemented carbide matrix. It simultaneously possesses a double-edged structure and multiple transition gradient layers. Using this composite sheet during drilling, on the one hand, it generates a double-edged structure, reducing wear when drilling through harder formations and improving drilling efficiency. On the other hand, in geological exploration and oil and gas extraction, it can significantly improve the impact resistance and wear resistance of the polycrystalline diamond composite sheet, increasing drill bit lifespan and reducing drilling costs.

[0012] Preferably, the diamond micro powder has a particle size of 15-20 μm; the tungsten carbide micro powder has a particle size of 15-20 μm.

[0013] Furthermore, the binder is composed of the following components in weight percentage: Co 94-96%, Ni 2-4%, and Fe 1-2%. Using a binder with this composition improves the bonding strength of the materials, thereby enhancing the impact toughness and wear resistance of the composite sheet.

[0014] To simplify the process and effectively reduce residual stress between the cemented carbide layer and the polycrystalline diamond layer, preferably, the mass ratio of diamond powder to tungsten carbide powder in the transition layer mixtures of different mass ratios are 1:3, 1:1, and 3:1, respectively. Using these three specific mass ratios of diamond and tungsten carbide in the preparation of the transition layer mixture results in a reasonable gradient setting and material ratio, effectively reducing the residual stress of the PDC composite sheet and lowering its risk of breakage.

[0015] Furthermore, in the transition layer mixture, the combined mass percentage of diamond micro powder and tungsten carbide micro powder is 92-95%, and the mass percentage of binder is 5-8%.

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

[0017] A method for preparing a multilayer gradient polycrystalline diamond composite sheet includes the following steps:

[0018] (1) Mix diamond micro powder and binder to obtain diamond mixture;

[0019] In addition, diamond micro powder and tungsten carbide micro powder are mixed in different mass ratios to obtain diamond / tungsten carbide mixtures with different mass ratios. The diamond / tungsten carbide mixtures with different mass ratios are then mixed with binders to obtain transition layer mixtures with different mass ratios.

[0020] (2) From bottom to top, diamond mixture, transition layer mixture A, cemented carbide layer, transition layer mixture B, diamond mixture, transition layer mixture C, and cemented carbide matrix are laid in sequence to obtain the assembly. Then the assembly is sintered to obtain the final product.

[0021] The transition layer mixture A is obtained by laying transition layer mixtures with different mass ratios in descending order of the mass ratio of diamond micro powder; the transition layer mixture B is obtained by laying transition layer mixtures with different mass ratios in ascending order of the mass ratio of diamond micro powder; and the transition layer mixture C is obtained by laying transition layer mixtures with different mass ratios in descending order of the mass ratio of diamond micro powder.

[0022] As a further preferred embodiment, in step (2), the laying height of the diamond mixture is 2-4 mm; the laying height of the transition layer mixture A, transition layer mixture B, and transition layer mixture C is 3-6 mm; and the height of the cemented carbide layer and the cemented carbide substrate is 3-5 mm.

[0023] Preferably, in the diamond mixture, the mass percentage of diamond micro powder is 92-95%, and the mass percentage of binder is 5-8%.

[0024] The cemented carbide layer and cemented carbide substrate used in this invention can be made of the same material or different materials; no special limitation is made in this invention. The materials used for the cemented carbide layer and cemented carbide substrate can be independently selected from one or two of YG6, YG8, and YG16.

[0025] Preferably, the sintering pressure is 5 GPa to 8 GPa, the sintering temperature is 1100 to 1400℃, and the sintering time is 20 to 35 min.

[0026] More preferably, before sintering, the assembly is first kept at 500-700°C for 2-4 hours under vacuum conditions.

[0027] In the process of preparing multilayer gradient polycrystalline diamond composite sheets, this invention, while adopting a double-edged structure and inheriting the high wear resistance and impact resistance of traditional PDC composite sheets, significantly reduces the residual stress between the cemented carbide layer and the polycrystalline diamond layer through the gradient structure design of three transition layers. This reduces the risk of the polycrystalline diamond layer cracking and effectively improves the wear resistance and impact toughness between the cemented carbide layer and the polycrystalline diamond layer, reducing the risk of delamination between the polycrystalline diamond layer and the cemented carbide substrate, which is beneficial to improving the service life of the diamond composite sheet. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the multilayer gradient polycrystalline diamond composite sheet of the present invention;

[0029] Figure 2 These are the residual stress detection points for the multilayer gradient polycrystalline diamond composite sheet of the present invention;

[0030] in, Figure 1 In the diagram, 1-hard alloy, 2-transition layer C, 3-polycrystalline diamond, 4-transition layer B, and 5-transition layer A. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0032] In the following embodiments, the cemented carbide substrate and cemented carbide layer are both made of YG8; the particle size of the diamond micro powder is 15-20 μm; and the particle size of the tungsten carbide micro powder is 15-20 μm.

[0033] In other embodiments, the cemented carbide substrate and cemented carbide layer may also be made of other materials, such as YG6, YG16, etc.

[0034] A schematic diagram of the structure of the multilayer gradient polycrystalline diamond composite sheet of the present invention is shown below. Figure 1 As shown. Figure 1 In the multilayer gradient polycrystalline diamond composite sheet, the following layers are arranged sequentially from bottom to top: cemented carbide-1, transition layer C-2, polycrystalline diamond-3, transition layer B-4, cemented carbide-1, transition layer A-5, and polycrystalline diamond-3.

[0035] Example 1

[0036] The multilayer gradient polycrystalline diamond composite sheet of Example 1 is prepared using the following method: The multilayer gradient polycrystalline diamond composite sheet includes a polycrystalline diamond layer, a transition layer A, a cemented carbide layer, a transition layer B, another polycrystalline diamond layer, a transition layer C, and a cemented carbide substrate arranged sequentially. Transition layer A is formed by sintering transition layer mixture A, transition layer B is formed by sintering transition layer mixture B, transition layer C is formed by sintering transition layer mixture C, and the polycrystalline diamond layer is formed by sintering a diamond mixture.

[0037] The preparation method of the multilayer gradient polycrystalline diamond composite sheet in this embodiment includes the following steps:

[0038] (1) Wash diamond powder and tungsten carbide powder separately with concentrated sulfuric acid (70%), then wash them in pure water until neutral, and dry them for later use;

[0039] Diamond micro powder and binder are mixed using a three-dimensional planetary mixer to obtain a diamond mixture.

[0040] Diamond micro powder and tungsten carbide micro powder were mixed in a three-dimensional planetary mixer at mass ratios of 1:3, 1:1, and 3:1, respectively. Then, they were mixed with a binder to obtain three transition layer mixtures with different mass ratios.

[0041] The binder has the following mass percentage composition: Co 96%, Ni 2%, Fe 2%; in the diamond mixture, the mass percentage of diamond micro powder is 95%, and the mass percentage of binder is 5%; in the transition layer mixture, the mass percentage of diamond / tungsten carbide mixture is 95%, and the mass percentage of binder is 5%.

[0042] (2) Spread the diamond mixture evenly to the bottom of the metal cup, with a thickness of 3 mm; then, spread the three transition layer mixtures with different mass ratios in descending order of diamond powder mass ratio, i.e., diamond powder to tungsten carbide powder mass ratios of 3:1, 1:1, and 1:3, onto the diamond mixture in three layers, each layer being 1 mm high, forming transition layer mixture A; place the treated cemented carbide layer on the transition layer mixture A from the previous step, with a cemented carbide layer height of 3 mm; based on the previous step, spread the three transition layer mixtures with different mass ratios in ascending order of diamond powder mass ratio, i.e., diamond powder to tungsten carbide powder mass ratios of 1:1, 1:1, and 1:3, onto the diamond mixture in three layers, each layer being 1 mm high, forming transition layer mixture A. 3. Layer the diamond mixture in three ratios of 1:1 and 3:1 onto the cemented carbide layer, with each layer being 1 mm high, to form transition layer mixture B. Place the diamond mixture on top of the above steps and flatten it; this layer is the intermediate polycrystalline diamond layer, with a height of 2 mm. Then, layer the three transition layer mixtures with different mass ratios according to the diamond powder mass ratio from largest to smallest (i.e., diamond powder to tungsten carbide powder mass ratios of 3:1, 1:1, and 1:3) onto the diamond mixture obtained in the previous step, with each layer being 1 mm high, to form transition layer mixture C. Finally, place the cemented carbide substrate on top of the transition layer mixture C from the previous step and attach the metal cup lid to obtain the assembly.

[0043] (3) The assembly was placed in a vacuum furnace and dried at 600°C for 3 hours. The assembly was then placed in a six-sided press and kept under pressure of 6 GPa and 1400°C for 20 minutes to allow the structural layers in the assembly to be sintered and penetrated, thus obtaining the multilayer gradient polycrystalline diamond composite sheet of Example 1.

[0044] Example 2

[0045] The multilayer gradient polycrystalline diamond composite sheet of this embodiment is prepared using the following method: The multilayer gradient polycrystalline diamond composite sheet includes a polycrystalline diamond layer, a transition layer A, a cemented carbide layer, a transition layer B, another polycrystalline diamond layer, a transition layer C, and a cemented carbide substrate arranged sequentially. Transition layer A is formed by sintering transition layer mixture A, transition layer B is formed by sintering transition layer mixture B, transition layer C is formed by sintering transition layer mixture C, and the polycrystalline diamond layer is formed by sintering a diamond mixture.

[0046] The preparation method of the multilayer gradient polycrystalline diamond composite sheet in this embodiment includes the following steps:

[0047] (1) Wash diamond powder and tungsten carbide powder separately with concentrated sulfuric acid (70% concentration), then wash them in pure water until neutral, and dry them for later use;

[0048] Diamond micro powder and binder are mixed using a three-dimensional planetary mixer to obtain a diamond mixture.

[0049] Diamond micro powder and tungsten carbide micro powder were mixed in a three-dimensional planetary mixer at mass ratios of 1:3, 1:1, and 3:1, respectively. Then, they were mixed with a binder to obtain three transition layer mixtures with different mass ratios.

[0050] The binder has the following mass percentage composition: Co 96%, Ni 3%, Fe 1%; in the diamond mixture, the mass percentage of diamond micro powder is 94%, and the mass percentage of binder is 6%; in the transition layer mixture, the mass percentage of diamond / tungsten carbide mixture is 96%, and the mass percentage of binder is 6%.

[0051] (2) Spread the diamond mixture evenly to the bottom of the metal cup, with a thickness of 2 mm; then, spread three different mass ratio transition layer mixtures on the diamond mixture in three layers according to the diamond powder mass ratio from largest to smallest, i.e., diamond powder to tungsten carbide powder mass ratios of 3:1, 1:1, and 1:3, with each layer being 1.5 mm high, forming transition layer mixture A; place the treated cemented carbide layer on the transition layer mixture A from the previous step, with a cemented carbide layer height of 3 mm; based on the previous step, spread the three different mass ratio transition layer mixtures according to the diamond powder mass ratio from smallest to largest, i.e., diamond powder to tungsten carbide powder mass ratios of 1:1, 1:1, and 1:3, in three layers. Three layers of the diamond mixture (3:1, 1:1, and 3:1) are sequentially laid on the cemented carbide layer, each layer being 1 mm high, forming transition layer mixture B. Based on the above steps, a diamond mixture is placed and flattened; this layer is the intermediate polycrystalline diamond layer, with a height of 2 mm. Then, three transition layer mixtures with different mass ratios are sequentially laid on the diamond mixture obtained in the previous step, according to the diamond powder mass ratio from largest to smallest (i.e., diamond powder to tungsten carbide powder mass ratios of 3:1, 1:1, and 1:3), each layer being 1 mm high, forming transition layer mixture C. Finally, the cemented carbide substrate is placed on top of the transition layer mixture C from the previous step, and a metal cup lid is attached to obtain the assembly.

[0052] (3) Place the assembly in a vacuum furnace and dry it at 600℃ for 3 hours. Then, put the assembly into a six-sided press and keep it under pressure of 7GPa and 1100℃ for 35 minutes to allow the structural layers in the assembly to be sintered and penetrated, thus obtaining a multilayer gradient polycrystalline diamond composite sheet.

[0053] Example 3

[0054] The multilayer gradient polycrystalline diamond composite sheet of this embodiment is prepared using the following method: The multilayer gradient polycrystalline diamond composite sheet includes a polycrystalline diamond layer, a transition layer A, a cemented carbide layer, a transition layer B, another polycrystalline diamond layer, a transition layer C, and a cemented carbide substrate arranged sequentially. Transition layer A is formed by sintering transition layer mixture A, transition layer B is formed by sintering transition layer mixture B, transition layer C is formed by sintering transition layer mixture C, and the polycrystalline diamond layer is formed by sintering a diamond mixture.

[0055] The preparation method of the multilayer gradient polycrystalline diamond composite sheet in this embodiment includes the following steps:

[0056] (1) Wash diamond powder and tungsten carbide powder separately with concentrated sulfuric acid (70%), then wash them in pure water until neutral, and dry them for later use;

[0057] Diamond micro powder and binder are mixed using a three-dimensional planetary mixer to obtain a diamond mixture.

[0058] Diamond micro powder and tungsten carbide micro powder were mixed in a three-dimensional planetary mixer at mass ratios of 1:3, 1:1, and 3:1, respectively. Then, they were mixed with a binder to obtain three transition layer mixtures with different mass ratios.

[0059] The binder has the following mass percentage composition: Co 94%, Ni 4%, Fe 2%; in the diamond mixture, the mass percentage of diamond micro powder is 93%, and the mass percentage of binder is 7%; in the transition layer mixture, the mass percentage of diamond / tungsten carbide mixture is 93%, and the mass percentage of binder is 7%.

[0060] (2) Spread the diamond mixture evenly to the bottom of the metal cup, with a thickness of 4 mm; then, spread three different mass ratio transition layer mixtures on the diamond mixture in three layers according to the diamond powder mass ratio from largest to smallest, i.e., diamond powder to tungsten carbide powder mass ratios of 3:1, 1:1, and 1:3, with each layer having a height of 1.2 mm, forming transition layer mixture A; place the treated cemented carbide layer on the transition layer mixture A from the previous step, with a cemented carbide layer height of 3 mm; based on the previous step, spread the three different mass ratio transition layer mixtures according to the diamond powder mass ratio from smallest to largest, i.e., diamond powder to tungsten carbide powder mass ratios of 1:1, 1:1, and 1:3, in three layers. Three layers of the diamond mixture (3:1, 1:1, and 3:1) are sequentially laid on the cemented carbide layer, each layer being 1 mm high, forming transition layer mixture B. Based on the above steps, a diamond mixture is placed and flattened; this layer is the intermediate polycrystalline diamond layer, with a height of 2 mm. Then, three transition layer mixtures with different mass ratios are sequentially laid on the diamond mixture obtained in the previous step, according to the diamond powder mass ratio from largest to smallest (i.e., diamond powder to tungsten carbide powder mass ratios of 3:1, 1:1, and 1:3), each layer being 1 mm high, forming transition layer mixture C. Finally, the cemented carbide substrate is placed on top of the transition layer mixture C from the previous step, and a metal cup lid is attached to obtain the assembly.

[0061] (3) The assembly is placed in a vacuum furnace and dried at 600℃ for 3 hours. After being pressed into a sintered component, the component is placed in a six-sided press and kept under pressure of 8GPa and 1200℃ for 25 minutes to allow the structural layers in the assembly to be sintered and penetrated, thus obtaining a multi-layer gradient polycrystalline diamond composite sheet.

[0062] Comparative Example 1

[0063] The polycrystalline diamond composite sheet in this comparative example is structured with reference to the polycrystalline diamond composite sheet disclosed in prior art CN2632288Y. Its structure includes, from bottom to top, a cemented carbide substrate, a polycrystalline diamond layer, a cemented carbide layer, and a polycrystalline diamond layer.

[0064] The preparation method of the polycrystalline diamond composite sheet in this comparative example is the same as that in Example 1, except that the preparation step does not contain a transition layer.

[0065] Comparative Example 2

[0066] The polycrystalline diamond composite sheet in this comparative example is structurally designed with reference to the polycrystalline diamond composite sheet disclosed in prior art CN106735246A. Its structure includes, from bottom to top, a cemented carbide matrix, a polycrystalline diamond layer, a tungsten carbide composite material layer, and a cemented carbide layer. The compositions of the cemented carbide matrix, polycrystalline diamond layer, and cemented carbide layer are the same as in Example 1. In the tungsten carbide composite material layer, the mass percentage of tungsten carbide micropowder is 95%, and the mass percentage of binder is 5%. The compositions of the tungsten carbide micropowder and binder are the same as in Example 1.

[0067] The preparation method of the comparative polycrystalline diamond composite sheet is based on the structure of the polycrystalline diamond composite sheet described above. The preparation process and parameters of the cemented carbide matrix, polycrystalline diamond layer, and cemented carbide layer are the same as in Example 1. The thickness of the tungsten carbide composite material layer is 3 mm.

[0068] Comparative Example 3

[0069] The polycrystalline diamond composite sheet of this comparative example has a structure comprising, in sequence, a polycrystalline diamond layer, a transition layer A, a cemented carbide layer, a transition layer B, a polycrystalline diamond layer, a transition layer C, and a cemented carbide substrate.

[0070] Transition layers A, B, and C are all composed of tungsten carbide composite material, each with a height of 3 mm. In these tungsten carbide composite layers, tungsten carbide micropowder accounts for 95% of the mass, and the binder accounts for 5%. The preparation process, except for the composition and laying height of the transition layers, follows the same procedure as in Example 1.

[0071] Comparative Example 4

[0072] The polycrystalline diamond composite sheet and its preparation method in this comparative example are basically the same as those in Example 1, except that: transition layer A, transition layer B, and transition layer C are prepared by sintering a transition layer mixture with the same mass ratio.

[0073] In the transition layer mixture, the mass percentage of diamond / tungsten carbide mixture is 95%, and the mass percentage of binder is 5%. The mass ratio of diamond to tungsten carbide in the diamond / tungsten carbide mixture is 1:1.

[0074] Comparative Example 5

[0075] The polycrystalline diamond composite sheet and its preparation method in this comparative example are basically the same as those in Example 1, except that: transition layer A, transition layer B, and transition layer C are prepared by sintering a mixture of two transition layer materials in two mass ratios.

[0076] Transition layer A is prepared by sequentially laying transition layer mixtures of diamond powder and tungsten carbide powder in mass ratios of 3:1 and 1:3; transition layer B is prepared by sequentially laying transition layer mixtures of diamond powder and tungsten carbide powder in mass ratios of 1:3 and 3:1; transition layer C is prepared by sequentially laying transition layer mixtures of diamond powder and tungsten carbide powder in mass ratios of 3:1 and 1:3; the remaining steps are the same as in Example 1.

[0077] Experimental Example 1: Residual Stress Test

[0078] This experiment examines the residual stress of the polycrystalline diamond composite sheets from Examples 1-3 and Comparative Examples 1-5. The stress test points are as follows: Figure 2 As shown in Table 1, the residual stress was tested using X-ray diffraction with a copper target.

[0079] Table 1 Residual stress of polycrystalline diamond composite sheets

[0080]

[0081]

[0082] As shown in Table 1, the residual stress at each test point of the multilayer gradient polycrystalline diamond composite sheets prepared in Examples 1-3 of this invention is significantly lower than that in Comparative Examples 1 and 2, and also shows varying degrees of reduction compared to Comparative Examples 3-5. In practical applications, the residual stress of PDC composite sheets is a major factor affecting their failure. This invention employs a multi-transition layer gradient structure, which can effectively reduce the residual stress of PDC composite sheets and lower their risk of failure.

[0083] Experiment Example 2 Performance Test

[0084] This experiment examines the impact toughness, wear resistance, and maximum number of impacts that the polycrystalline diamond composite sheets of Examples 1-3 and Comparative Examples 1-5 can withstand before cracking and delamination. The specific test methods for each indicator are as follows:

[0085] Impact toughness test: A 10kg pendulum is used to impact the sample with an impact energy of 50J. The number of impacts the sample withstands before failure is recorded. The product of the number of impacts and the impact energy is the impact toughness.

[0086] Wear resistance test: Referring to the JB3235-2013 standard, PDC was installed on a machine tool to cut granite, and the wear ratio of PDC was tested. After the test, the mass difference of PDC composite sheet before and after cutting was measured as the wear amount, and the wear resistance of each sample was compared.

[0087] Maximum number of impacts before cracking and delamination: Record the number of impacts suffered by the polycrystalline diamond composite sheet when it cracks and delaminates during the impact resistance test.

[0088] The experimental results are shown in Table 2.

[0089] Table 2 Performance test results of the examples and polycrystalline diamond composite sheets

[0090]

[0091]

[0092] As can be seen from Table 2, compared with Comparative Examples 1 to 5, the impact toughness and wear resistance of Examples 1 to 3 of the present invention are significantly improved. Combined with the residual stress detection results of each test group, it can be shown that the present invention can effectively reduce residual stress and improve the impact toughness and wear resistance of the workpiece by preparing multilayer gradient polycrystalline diamond composite sheets, thereby extending the service life of the workpiece.

Claims

1. A multilayer gradient polycrystalline diamond composite sheet, characterized in that, It includes a polycrystalline diamond layer, a transition layer A, a cemented carbide layer, a transition layer B, a polycrystalline diamond layer, a transition layer C, and a cemented carbide substrate arranged sequentially. The transition layers A, B, and C are obtained by sintering a transition layer mixture comprising diamond micron powder, tungsten carbide micron powder, and a binder. Transition layer A is obtained by sequentially laying and sintering transition layer mixtures with different mass ratios according to the mass ratio of diamond micron powder in descending order. Transition layer B is obtained by sequentially laying and sintering transition layer mixtures with different mass ratios according to the mass ratio of diamond micron powder in ascending order. Transition layer C is obtained by sequentially laying and sintering transition layer mixtures with different mass ratios according to the mass ratio of diamond micron powder in descending order. In the transition layer mixtures with different mass ratios, the mass ratios of diamond micro powder to tungsten carbide micro powder are 1:3, 1:1, and 3:1, respectively. The binder is composed of the following components by mass percentage: Co 94~96%, Ni 2~4%, Fe 1~2%; In the transition layer mixture, the combined mass of diamond micro powder and tungsten carbide micro powder accounts for 92-95%, and the mass of binder accounts for 5-8%.

2. The multilayer gradient polycrystalline diamond composite sheet according to claim 1, characterized in that, The diamond micro powder has a particle size of 15~20μm; the tungsten carbide micro powder has a particle size of 15~20μm.

3. The method for preparing multilayer gradient polycrystalline diamond composite sheets as described in claim 1, characterized in that, Includes the following steps: (1) Mix diamond micro powder and binder to obtain diamond mixture; In addition, diamond micro powder and tungsten carbide micro powder are mixed in different mass ratios to obtain diamond / tungsten carbide mixtures with different mass ratios. The diamond / tungsten carbide mixtures with different mass ratios are then mixed with binders to obtain transition layer mixtures with different mass ratios. (2) From bottom to top, diamond mixture, transition layer mixture A, cemented carbide layer, transition layer mixture B, diamond mixture, transition layer mixture C, and cemented carbide matrix are laid in sequence to obtain the assembly. Then the assembly is sintered to obtain the final product. The transition layer mixture A is obtained by laying transition layer mixtures with different mass ratios in descending order of the mass ratio of diamond micro powder; the transition layer mixture B is obtained by laying transition layer mixtures with different mass ratios in ascending order of the mass ratio of diamond micro powder; and the transition layer mixture C is obtained by laying transition layer mixtures with different mass ratios in descending order of the mass ratio of diamond micro powder.

4. The method for preparing multilayer gradient polycrystalline diamond composite sheets according to claim 3, characterized in that, The diamond mixture is laid up to a height of 2-4 mm; the transition layer mixture A, transition layer mixture B, and transition layer mixture C are laid up to a height of 3-6 mm; and the cemented carbide layer and cemented carbide substrate are laid up to a height of 3-5 mm.

5. The method for preparing multilayer gradient polycrystalline diamond composite sheets according to claim 3, characterized in that, In the diamond mixture, the mass percentage of diamond micro powder is 92-95%, and the mass percentage of binder is 5-8%.

6. The method for preparing multilayer gradient polycrystalline diamond composite sheets according to any one of claims 3 to 5, characterized in that, The sintering pressure is 5 GPa to 8 GPa, the sintering temperature is 1100 to 1400℃, and the sintering time is 20 to 35 min.

7. The method for preparing multilayer gradient polycrystalline diamond composite sheets according to any one of claims 3 to 5, characterized in that, Before sintering, the assembly is held at 500-700°C for 2-4 hours under vacuum conditions.

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