Polycrystalline cubic boron nitride composite sheet and preparation method thereof

Abstract

The invention discloses a polycrystalline cubic boron nitride composite sheet and a preparation method thereof, and relates to the technical field of superhard materials. The preparation method of the polycrystalline cubic boron nitride composite sheet comprises the following steps: pretreating cubic boron nitride to obtain cubic boron nitride of which the surface is coated with silicide; the silicide comprises at least one of silicon carbide, silicon nitride, silicon boride and silicon carbonitride; mixing the cubic boron nitride of which the surface is coated with the silicide with a binder to obtain a mixture; and sintering the mixture and a hard alloy matrix to obtain the polycrystalline cubic boron nitride composite sheet. The preparation method provided by the invention is simple and efficient, and the polycrystalline cubic boron nitride composite sheet with the characteristics of good corrosion resistance, good oxidative wear resistance, good diffusion wear resistance, good chemical wear resistance, good heat resistance, long service life and the like is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of superhard materials, and in particular to a polycrystalline cubic boron nitride composite sheet and a preparation method thereof. Background Art

[0002] Cubic boron nitride (CBN) offers high hardness, excellent thermal stability, superior mechanical properties at high temperatures, and excellent chemical stability. Its non-reactive nature at high temperatures makes it particularly suitable for ferrous metal processing. Polycrystalline CBN can be produced by sintering CBN with a binder under high temperature and high pressure. Polycrystalline CBN overcomes the anisotropic nature of CBN and, as a high-performance tool material, plays a vital role in the modern machining industry, demonstrating significant potential for improving production efficiency, enhancing machining quality, and promoting sustainable manufacturing.

[0003] Under high temperature conditions, although iron will not react with boron nitride, under turning conditions, the friction between the cubic boron nitride polycrystalline layer and the turning material generates high temperature (greater than 700°C). At the same time, there is an oxidizing atmosphere (oxygen in the air). The initial oxidation temperature of cubic boron nitride is 650°C, and it is oxidized into boron oxide (B2O3) and nitrogen (N2). At 1035°C, the oxidation reaction proceeds violently. Boron oxide is peeled off during the friction between the cubic boron nitride polycrystalline layer and the turning material, exposing a new surface and forming a new surface oxide layer, which leads to oxidative wear. Although Cubic boron nitride has strong chemical inertness towards iron group metals, but not towards other elements. In the high temperature environment generated by turning, mutual diffusion between boron, nitrogen and the elements of the material being turned will inevitably occur, reducing the chemical inertness of cubic boron nitride. At the same time, under the high temperature, high speed friction and oxidation conditions of turning, the working layer of polycrystalline cubic boron nitride will react with the material being turned to form oxides, carbides, nitrides and borides, etc. The occurrence of these situations will reduce the life of polycrystalline cubic boron nitride tools and affect the improvement of production efficiency.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] Based on the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a polycrystalline cubic boron nitride composite sheet and a preparation method thereof, aiming to solve the problem that the existing polycrystalline cubic boron nitride has poor resistance to oxidation wear, diffusion wear and chemical wear.

[0006] The technical solutions of the present invention are as follows:

[0007] A first aspect of the present invention provides a method for preparing a polycrystalline cubic boron nitride composite sheet, comprising the following steps:

[0008] Pre-treating cubic boron nitride to obtain cubic boron nitride with a surface coated with silicide; the silicide comprises at least one of silicon carbide, silicon nitride, silicon boride and silicon carbonitride;

[0009] Mixing the cubic boron nitride with the silicide coated on the surface with a binder to obtain a mixture;

[0010] The polycrystalline cubic boron nitride composite sheet is obtained by sintering the mixed material and the cemented carbide matrix.

[0011] Optionally, the step of pre-treating the cubic boron nitride to obtain the cubic boron nitride with the surface coated with silicide specifically includes:

[0012] The silicon source, cubic boron nitride and organic solvent are mixed, ultrasonically homogenized, and evaporated to dryness to obtain a first mixed material;

[0013] The first mixed material is heat-treated under a preset atmosphere to obtain cubic boron nitride with a surface coated with silicide.

[0014] Optionally, the particle size of the cubic boron nitride is 0.1 to 20 microns;

[0015] The silicon source includes at least one of polycarbosilane, polymethylsilane and polysilazane.

[0016] Optionally, the organic solvent includes at least one of toluene, acetone and butyl acetate.

[0017] Optionally, the mass ratio of the silicon source to the cubic boron nitride is 0.2% to 10%.

[0018] Optionally, the preset atmosphere is a vacuum atmosphere; or the preset atmosphere is at least one of a nitrogen atmosphere, an argon atmosphere and a methane atmosphere.

[0019] Optionally, the heat treatment temperature is 150-1200°C.

[0020] Optionally, in the mixture, the mass content of the cubic boron nitride with the surface coated with silicide is 45% to 95%.

[0021] Optionally, the binder includes at least one of aluminum, silicon, aluminum-silicon alloy, titanium, titanium nitride, titanium carbide, titanium carbonitride and cobalt.

[0022] A second aspect of the present invention provides a polycrystalline cubic boron nitride composite sheet, which is prepared using the preparation method of the present invention as described above.

[0023] Beneficial effects: The preparation method provided by the present invention is simple and efficient. First, by coating the surface of cubic boron nitride with a layer of high-melting-point, oxidation-resistant silicide, namely at least one of silicon carbide, silicon nitride, silicon boride and silicon carbonitride, the contact between components with oxidation and corrosion and cubic boron nitride can be reduced or even isolated, and the mutual diffusion between boron and nitrogen elements in cubic boron nitride and elements of the turned material can be effectively prevented, the chemical inertness of cubic boron nitride is improved, and the damage to cubic boron nitride is reduced, thereby reducing the damage to polycrystalline cubic boron nitride caused by adverse factors during the cutting process, reducing the wear of polycrystalline cubic boron nitride, and improving the life of polycrystalline cubic boron nitride tools; then the cubic boron nitride coated with silicide and the binder are sintered with a cemented carbide substrate to prepare a polycrystalline cubic boron nitride composite sheet with good corrosion resistance, good oxidation wear resistance, good diffusion wear resistance, good chemical wear resistance, good heat resistance, long life and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart for the preparation of polycrystalline cubic boron nitride composite sheets. DETAILED DESCRIPTION

[0025] The present invention provides a polycrystalline cubic boron nitride composite sheet and a method for preparing the same. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0026] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In addition, the features, operations or embodiments described in the specification are only used to explain the present invention and are not intended to limit the present invention. The features, operations or characteristics described in the specification can be combined in any appropriate manner to form various embodiments. At the same time, the steps or action features in the method description can be combined in any appropriate manner to form various embodiments, and the steps or actions in the method description can also be swapped or adjusted in order in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary sequence, unless otherwise specified that a certain sequence must be followed. Unless otherwise specified, the instruments and reagents used in the present invention are all commercially available products that can be obtained through commercial channels.

[0027] The embodiment of the present invention provides a method for preparing a polycrystalline cubic boron nitride composite sheet, wherein, Figure 1 As shown, the following steps are included:

[0028] S1. Pretreating cubic boron nitride to obtain cubic boron nitride having a surface coated with a silicide, wherein the silicide comprises at least one of silicon carbide, silicon nitride, silicon boride, and silicon carbonitride;

[0029] S2, mixing the cubic boron nitride having the silicide coated on the surface and a binder to obtain a mixture;

[0030] S3. Sintering the mixture and the cemented carbide substrate to obtain the polycrystalline cubic boron nitride composite sheet.

[0031] The preparation method provided by the present invention is simple and efficient. First, a layer of high-melting-point, oxidation-resistant silicide, namely at least one of silicon carbide, silicon nitride, silicon boride and silicon carbonitride, is coated on the surface of cubic boron nitride to reduce or even isolate the contact between components with oxidation and corrosion and the cubic boron nitride, effectively prevent the mutual diffusion between boron and nitrogen elements and the elements of the turned material, improve the chemical inertness of the cubic boron nitride, reduce damage to the cubic boron nitride, thereby reducing the damage to the polycrystalline cubic boron nitride caused by adverse factors during the cutting process, reduce the wear of the polycrystalline cubic boron nitride (that is, the present invention reduces the oxidation wear, diffusion wear and chemical wear of the polycrystalline cubic boron nitride by coating the silicide on the surface of the cubic boron nitride, and improves the corrosion resistance), thereby improving the life of the polycrystalline cubic boron nitride tool; then, the cubic boron nitride coated with the silicide and the binder are sintered with a cemented carbide substrate to prepare a polycrystalline cubic boron nitride composite sheet with good corrosion resistance, good heat resistance and long service life.

[0032] In step S1, in some embodiments, the step of pre-treating the cubic boron nitride to obtain the cubic boron nitride with the surface coated with silicide specifically includes:

[0033] S11, mixing the silicon source, cubic boron nitride and the organic solvent, ultrasonically homogenizing them, and evaporating them to dryness to obtain a first mixture;

[0034] S12. Heat-treating the first mixed material under a preset atmosphere to obtain cubic boron nitride with a surface coated with silicide.

[0035] The invention obtains cubic boron nitride with silicide coated on the surface by mixing silicon source with cubic boron nitride and then performing heat treatment under a certain atmosphere.

[0036] In step S11, the silicon source, cubic boron nitride and organic solvent are mixed. During the ultrasonic homogenization process, the silicon source and the organic solvent are first mixed evenly, and then the cubic boron nitride is added and ultrasonicated to mix evenly.

[0037] In some embodiments, the particle size of the cubic boron nitride is 0.1 to 20 microns. The present invention can adjust the particle size according to actual needs. The particle size of the cubic boron nitride can be 0.1 micron, 1 micron, 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns or 20 microns, etc.

[0038] In some embodiments, the silicon source includes at least one of polycarbosilane, polymethylsilane, and polysilazane, but is not limited thereto. These silicon sources are converted into at least one of silicon carbide, silicon nitride, silicon boride, and silicon carbonitride during the heat treatment.

[0039] In some embodiments, the organic solvent includes at least one of toluene, acetone, and butyl acetate, but is not limited thereto.

[0040] In some embodiments, the mass ratio of the silicon source to the cubic boron nitride is 0.2% to 10% (e.g., 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%). This ratio can ensure uniform silicide coating on the surface of the cubic boron nitride, thereby improving the corrosion resistance, oxidation wear resistance, diffusion wear resistance, and chemical wear resistance of the cubic boron nitride.

[0041] In step S12, in some embodiments, the preset atmosphere is a vacuum; or the preset atmosphere is at least one of a nitrogen atmosphere, an argon atmosphere, and a methane atmosphere. By controlling the atmosphere and the silicon source, the composition of the silicide coated on the surface of the cubic boron nitride can be effectively controlled. By using polysilazane in a vacuum and argon atmosphere, the silicide coated on the surface of the cubic boron nitride can be mainly silicon carbonitride; by using polysilazane in a nitrogen atmosphere, the silicide coated on the surface of the cubic boron nitride can be mainly silicon nitride; by using polysilazane in a methane atmosphere, the silicide coated on the surface of the cubic boron nitride can be mainly silicon carbide; by using polycarbosilane and polymethylsilane in a vacuum, nitrogen atmosphere, argon atmosphere, and methane atmosphere, the silicide coated on the surface of the cubic boron nitride can be mainly silicon carbide.

[0042] In some embodiments, the heat treatment temperature is 150-1200° C., for example, the heat treatment temperature is 150° C., 200° C., 300° C., 400° C., 500° C., 600° C., 700° C., 800° C., 900° C., 1000° C., 1100° C., or 1200° C. Different temperatures and different atmospheres can be used to control the composition of the silicide formed on the surface of the cubic boron nitride.

[0043] In step S2, in some embodiments, the mass content of the cubic boron nitride coated with silicide in the mixture is 45% to 95%, for example, 45%, 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. This ratio is determined according to actual needs.

[0044] In some embodiments, the binder includes at least one of aluminum, silicon, aluminum-silicon alloy, titanium, titanium nitride, titanium carbide, titanium carbonitride, and cobalt, but is not limited thereto.

[0045] In step S3, in some embodiments, the mixture and the cemented carbide substrate are sintered at a temperature of 1200-1500°C (for example, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C or 1500°C, etc.) and a pressure of 4-8GPa (for example, 4GPa, 5GPa, 6GPa, 7GPa or 8GPa, etc.) to obtain the polycrystalline cubic boron nitride composite sheet.

[0046] The present invention also provides a polycrystalline cubic boron nitride (PCBN) composite sheet, prepared using the aforementioned preparation method. Specifically, the PCBN composite sheet is obtained by sintering cubic boron nitride (CBN) coated with a silicide, a binder, and a cemented carbide. The PCBN composite sheet exhibits excellent corrosion resistance, oxidative wear resistance, diffusion wear resistance, chemical wear resistance, and heat resistance. When used in the manufacture of cutting tools, the cutting tools exhibit a long service life.

[0047] The present invention will be further described below with reference to specific examples.

[0048] Example 1

[0049] This embodiment provides a method for preparing a polycrystalline cubic boron nitride composite sheet, comprising the following steps:

[0050] (1) 5 g of polycarbosilane was added to 200 mL of toluene and stirred uniformly, 100 g of cubic boron nitride with a particle size of 3 μm was added, ultrasonically stirred for 30 min, and then dried (i.e., evaporated to dryness) to obtain a first mixture;

[0051] (2) heat treating the first mixture at 1200° C. in vacuum for 5 h to obtain cubic boron nitride coated with silicon carbide;

[0052] (3) After 7.8g of aluminum and 76g of titanium nitride were evenly mixed by ball milling, the above-mentioned cubic boron nitride coated with silicon carbide was added, and the ball milling was continued to mix evenly, and then dried to obtain a mixture;

[0053] (4) The mixture and the carbide substrate were placed in a metal cup, treated at 600°C for 2 h (to remove adsorbed water vapor and other impurities), and then sintered at a pressure of 6 GPa and a temperature of 1400°C for 0.5 h to obtain a polycrystalline cubic boron nitride composite sheet.

[0054] Example 2

[0055] This embodiment provides a method for preparing a polycrystalline cubic boron nitride composite sheet, comprising the following steps:

[0056] (1) 7 g of polysilazane was added to 300 mL of acetone and stirred uniformly, 141 g of cubic boron nitride with a particle size of 2 μm was added, and after ultrasonic stirring for 30 min, drying (i.e., evaporation) was performed to obtain a first mixed material;

[0057] (2) treating the first mixture at 800° C. for 5 h in a nitrogen atmosphere to obtain cubic boron nitride with a surface coated with silicon nitride;

[0058] (3) After 7.7 g of metallic aluminum and 17 g of cobalt powder were ball-milled and mixed uniformly, the above-mentioned cubic boron nitride coated with silicon nitride was added, and the ball milling was continued to mix uniformly, and then dried to obtain a mixture;

[0059] (4) The mixture and the cemented carbide substrate were placed in a metal cup, treated at 600°C for 2 h, and then sintered at a pressure of 6 GPa and a temperature of 1500°C for 0.5 h to obtain a polycrystalline cubic boron nitride composite sheet.

[0060] Comparative Example 1

[0061] This comparative example provides a method for preparing a polycrystalline cubic boron nitride composite sheet, which differs from Example 1 only in that silicon carbide is not coated on the surface of the cubic boron nitride.

[0062] Specifically, the preparation method of the polycrystalline cubic boron nitride composite sheet in this comparative example includes the following steps:

[0063] (1) After 7.8g of aluminum and 76g of titanium nitride were ball-milled and mixed uniformly, 100g of cubic boron nitride with a particle size of 3 μm was added, and the mixture was further ball-milled and mixed uniformly, and then dried to obtain a mixture;

[0064] (2) The mixture and the cemented carbide substrate were placed in a metal cup, treated at 600°C for 2 h, and then sintered at a pressure of 6 GPa and a temperature of 1400°C for 0.5 h to obtain a polycrystalline cubic boron nitride composite sheet.

[0065] Comparative Example 2

[0066] This comparative example provides a method for preparing a polycrystalline cubic boron nitride composite sheet, which differs from Example 2 only in that silicon nitride is not coated on the surface of the cubic boron nitride.

[0067] Specifically, the preparation method of the polycrystalline cubic boron nitride composite sheet in this comparative example includes the following steps:

[0068] (1) After ball milling 7.7 g of aluminum and 17 g of cobalt powder, 141 g of cubic boron nitride with a particle size of 2 μm was added, and the mixture was further ball milled and then dried to obtain a mixture;

[0069] (4) The mixture and the cemented carbide substrate were placed in a metal cup, treated at 600°C for 2 h, and then sintered at a pressure of 6 GPa and a temperature of 1500°C for 0.5 h to obtain a polycrystalline cubic boron nitride composite sheet.

[0070] test:

[0071] (1) The polycrystalline cubic boron nitride composite sheets in Example 1 and Comparative Example 1 were processed into cutting tools for cutting performance testing. The cutting material was hardened steel GCr15, and the cutting parameters were cutting speed 150 m / min, feed rate 0.10 mm / r, and back cutting depth 0.20 mm. Under the condition that the cutting stroke was 7000 m, the tool made from the polycrystalline cubic boron nitride composite sheet in Example 1 had a flank wear of 105 μm after the cutting test, while the tool made from the polycrystalline cubic boron nitride composite sheet in Comparative Example 1 had a flank wear of 168 μm after the cutting test. In other words, the tool flank wear of the tool made from the polycrystalline cubic boron nitride composite sheet in Example 1 was 62.50% of the tool flank wear of the tool made from the polycrystalline cubic boron nitride composite sheet in Comparative Example 1.

[0072] The test results show that coating silicon carbide on the surface of cubic boron nitride can improve the wear resistance of polycrystalline cubic boron nitride composite sheets and increase the life of polycrystalline cubic boron nitride composite sheets.

[0073] (2) The polycrystalline cubic boron nitride composite sheets in Example 2 and Comparative Example 2 were processed into cutting tools for cutting performance testing. The cut material was gray cast iron HT200. The cutting parameters were a cutting speed of 300 m / min, a feed rate of 0.10 mm / r, and a back cut of 0.20 mm. Under the condition that the cutting stroke was 10,000 m, the tool made from the polycrystalline cubic boron nitride composite sheet in Example 2 had a flank wear of 156 μm, while the tool made from the polycrystalline cubic boron nitride composite sheet in Comparative Example 2 had a flank wear of 231 μm. In other words, the tool flank wear of the tool made from the polycrystalline cubic boron nitride composite sheet in Example 2 was 67.53% of the tool flank wear of the tool made from the polycrystalline cubic boron nitride composite sheet in Comparative Example 2.

[0074] This result shows that coating silicon nitride on the surface of cubic boron nitride can improve the wear resistance of polycrystalline cubic boron nitride composite sheets and increase the life of polycrystalline cubic boron nitride composite sheets.

[0075] In summary, the present invention provides a polycrystalline cubic boron nitride composite sheet and a preparation method thereof. The preparation method provided by the present invention is simple and efficient. First, by coating a layer of high-melting-point, oxidation-resistant silicide, namely at least one of silicon carbide, silicon nitride, silicon boride and silicon carbonitride, on the surface of cubic boron nitride, the contact between components with oxidation and corrosion and cubic boron nitride can be reduced or even isolated, and the mutual diffusion between the boron and nitrogen elements in the cubic boron nitride and the elements of the turned material can be effectively prevented, the chemical inertness of the cubic boron nitride is improved, and the damage to the cubic boron nitride is reduced, thereby reducing the damage to the polycrystalline cubic boron nitride caused by adverse factors during the cutting process, reducing the wear of the polycrystalline cubic boron nitride, and improving the life of the polycrystalline cubic boron nitride tool; then the cubic boron nitride coated with the silicide and the binder are sintered with a cemented carbide substrate to prepare a polycrystalline cubic boron nitride composite sheet with good corrosion resistance, good oxidation wear resistance, good diffusion wear resistance, good chemical wear resistance, good heat resistance, and long life.

[0076] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a polycrystalline cubic boron nitride composite sheet, characterized in that: The steps include: Pre-treating cubic boron nitride to obtain cubic boron nitride with a surface coated with silicide; the silicide comprises at least one of silicon carbide, silicon nitride, silicon boride and silicon carbonitride; Mixing the cubic boron nitride with the silicide coated on the surface with a binder to obtain a mixture; The polycrystalline cubic boron nitride composite sheet is obtained by sintering the mixed material and the cemented carbide matrix.

2. The preparation method according to claim 1, characterized in that The steps of pre-treating cubic boron nitride to obtain cubic boron nitride with a surface coated with silicide specifically include: The silicon source, cubic boron nitride and organic solvent are mixed, ultrasonically homogenized, and evaporated to dryness to obtain a first mixed material; The first mixed material is heat-treated under a preset atmosphere to obtain cubic boron nitride with a surface coated with silicide.

3. The preparation method according to claim 2, characterized in that The particle size of the cubic boron nitride is 0.1 to 20 microns; The silicon source includes at least one of polycarbosilane, polymethylsilane and polysilazane.

4. The preparation method according to claim 2, characterized in that The organic solvent includes at least one of toluene, acetone and butyl acetate.

5. The preparation method according to claim 2, characterized in that The mass ratio of the silicon source to the cubic boron nitride is 0.2% to 10%.

6. The preparation method according to claim 2, characterized in that The preset atmosphere is a vacuum atmosphere; or the preset atmosphere is at least one of a nitrogen atmosphere, an argon atmosphere, and a methane atmosphere.

7. The preparation method according to claim 2, characterized in that The temperature of the heat treatment is 150-1200°C.

8. The preparation method according to claim 1, characterized in that In the mixture, the mass content of the cubic boron nitride with the silicide coated on the surface is 45% to 95%.

9. The preparation method according to claim 1, characterized in that The binder includes at least one of aluminum, silicon, aluminum-silicon alloy, titanium, titanium nitride, titanium carbide, titanium carbonitride, and cobalt.

10. A polycrystalline cubic boron nitride composite sheet, characterized in that: The preparation method is described in any one of claims 1 to 9.

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