A polycrystalline cubic boron nitride compact and a method for producing the same

Abstract

The application 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 coated with silicide; the silicide comprises at least one of silicon carbide, silicon nitride, silicon boride and silicon carbonitride; mixing the cubic boron nitride coated with silicide and a binder to obtain a mixture; and performing sintering treatment on the mixture and a hard alloy base body to obtain the polycrystalline cubic boron nitride composite sheet. The preparation method is simple and efficient, and the polycrystalline cubic boron nitride composite sheet prepared by the method has the characteristics of good corrosion resistance, good oxidation wear resistance, good diffusion wear resistance, good chemical wear resistance, good heat resistance and long service life.

Description

A polycrystalline cubic boron nitride composite sheet and its preparation method Technical Field

[0001] This invention relates to the field of superhard materials technology, and in particular to a polycrystalline cubic boron nitride composite sheet and its preparation method. Background Technology

[0002] Cubic boron nitride (CBN) exhibits high hardness, good thermal stability, excellent mechanical properties at high temperatures, and good chemical stability. Notably, it does not react with ferrous metals at high temperatures, making it suitable for machining ferrous metals. Polycrystalline cubic boron nitride can be prepared by sintering cubic boron nitride with a binder under high temperature and pressure. Polycrystalline cubic boron nitride overcomes the anisotropy of cubic boron nitride and plays a vital role in modern machining as a high-performance tool material, demonstrating significant potential in improving production efficiency, enhancing machining quality, and promoting sustainable manufacturing.

[0003] Although iron does not react with boron nitride under high-temperature conditions, during turning, the friction between the cubic boron nitride polycrystalline layer and the turning material generates high temperatures (above 700°C), and an oxidizing atmosphere (oxygen in the air) is also present. The initial oxidation temperature of cubic boron nitride is 650°C, oxidizing to boron oxide (B₂O₃) and nitrogen (N₂). At 1035°C, this oxidation reaction proceeds violently. The 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, leading to oxidative wear. Although Cubic boron nitride has strong chemical inertness with iron group metals, but not with other elements. Under the high-temperature environment of turning, interdiffusion between boron, nitrogen and the elements of the material being turned is inevitable, 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 reacts with the material being turned, forming oxides, carbides, nitrides and borides. These phenomena all reduce the life of polycrystalline cubic boron nitride tools and affect the improvement of production efficiency.

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

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a polycrystalline cubic boron nitride composite sheet and its preparation method, which aims to solve the problems of poor resistance to oxidation wear, diffusion wear and chemical wear of existing polycrystalline cubic boron nitride.

[0006] The technical solution of the present invention is 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] Cubic boron nitride is pretreated to obtain cubic boron nitride with a surface coated with silicide; the silicide includes at least one of silicon carbide, silicon nitride, silicon boride, and silicon carbonitride;

[0009] The cubic boron nitride with silicide coating on its surface is mixed with a binder to obtain a mixture;

[0010] The polycrystalline cubic boron nitride composite sheet is obtained by sintering the mixture with a cemented carbide matrix.

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

[0012] The silicon source, cubic boron nitride, and organic solvent are mixed, ultrasonicated to homogenize, and then evaporated to dryness to obtain the first mixture.

[0013] The first mixture 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 micrometers;

[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 silicon source accounts for 0.2% to 10% of the mass of cubic boron nitride.

[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 temperature of the heat treatment is 150–1200°C.

[0020] Optionally, in the mixture, the mass content of the cubic boron nitride with silicide coating 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] In a second aspect, the present invention provides a polycrystalline cubic boron nitride composite sheet, wherein the sheet is prepared by the preparation method described above.

[0023] Beneficial Effects: The preparation method provided by this 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 oxidizing and corrosive components and cubic boron nitride can be reduced or even isolated. This effectively prevents the interdiffusion of boron and nitrogen elements in cubic boron nitride with the elements of the material being machined, enhances the chemical inertness of cubic boron nitride, and reduces damage to cubic boron nitride. Consequently, it reduces the damage to polycrystalline cubic boron nitride caused by adverse factors during the cutting process, reduces wear on polycrystalline cubic boron nitride, and increases the tool life of polycrystalline cubic boron nitride. 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, and long service life. Attached Figure Description

[0024] Figure 1 is a flowchart of the preparation process of polycrystalline cubic boron nitride composite sheets. Detailed Implementation

[0025] This invention provides a polycrystalline cubic boron nitride composite sheet and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, the features, operations, or embodiments described in the specification are for illustrative purposes only and are not intended to limit the invention. The features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. Similarly, the steps or actions in the method description can be combined in any suitable manner to form various embodiments, and the steps or actions in the method description can be rearranged or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification are only for clearly describing a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed. Unless otherwise specified, all instruments and reagents used in this invention are commercially available products.

[0027] This invention provides a method for preparing a polycrystalline cubic boron nitride composite sheet, as shown in Figure 1, comprising the following steps:

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

[0029] S2. Mix the cubic boron nitride with silicide coating on the surface and the binder to obtain a mixture;

[0030] S3. After sintering the mixture with the cemented carbide matrix, the polycrystalline cubic boron nitride composite sheet is obtained.

[0031] The preparation method provided by this invention is simple and efficient. First, a high-melting-point, oxidation-resistant silicide, namely at least one of silicon carbide, silicon nitride, silicon boride, and silicon carbonitride, is coated onto the surface of cubic boron nitride. This reduces or even isolates the contact between oxidizing and corrosive components and cubic boron nitride, effectively preventing the interdiffusion of boron and nitrogen elements with the elements of the material being machined. This enhances the chemical inertness of cubic boron nitride, reduces damage to it, and thus reduces the damage to polycrystalline cubic boron nitride caused by adverse factors during cutting. This reduces the wear of polycrystalline cubic boron nitride (i.e., this invention reduces oxidative wear, diffusion wear, and chemical wear of polycrystalline cubic boron nitride by coating the surface of cubic boron nitride with silicide, thereby improving corrosion resistance) and extending 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 heat resistance, and long life.

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

[0033] S11. Mix the silicon source, cubic boron nitride and organic solvent, sonicate until homogeneous, and then evaporate to dryness to obtain the first mixture.

[0034] S12. The first mixture is heat-treated under a preset atmosphere to obtain cubic boron nitride with a surface coated with silicide.

[0035] This invention obtains cubic boron nitride with a silicide-coated surface by mixing a silicon source with cubic boron nitride and then heat-treating it under a certain atmosphere.

[0036] In step S11, the silicon source, cubic boron nitride, and organic solvent are mixed and ultrasonically homogenized. The silicon source and organic solvent can be mixed evenly first, and then cubic boron nitride is added and ultrasonically mixed evenly.

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

[0038] In some embodiments, the silicon source includes, but is not limited to, at least one of polycarbosilane, polymethylsilane, and polysilazane. These silicon sources are converted to at least one of silicon carbide, silicon nitride, silicon boride, and silicon carbonitride during 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 silicon source accounts for 0.2% to 10% of the mass of cubic boron nitride (e.g., 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%). This proportion ensures uniform coating of silicides on the surface of cubic boron nitride, improving its corrosion resistance, resistance to oxidative wear, diffusion wear, and chemical wear.

[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. The composition of the silicide coating on the surface of cubic boron nitride can be effectively controlled by controlling the atmosphere and the silicon source. Using polysilazane in a vacuum and argon atmosphere, the silicide coating on the surface of cubic boron nitride can be primarily silicon carbonitride; using polysilazane in a nitrogen atmosphere, the silicide coating on the surface of cubic boron nitride can be primarily silicon nitride; using polysilazane in a methane atmosphere, the silicide coating on the surface of cubic boron nitride can be primarily silicon carbide; using polycarbosilane and polymethylsilane in a vacuum, nitrogen atmosphere, argon atmosphere, and methane atmosphere, the silicide coating on the surface of cubic boron nitride can be primarily silicon carbide.

[0042] In some embodiments, the heat treatment temperature is 150–1200°C, for example, temperatures of 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 combined with different atmospheres can control the composition of the silicide formed on the surface of 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, it can be 45%, 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%, etc. This proportion is determined according to actual needs.

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

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

[0046] This invention also provides a polycrystalline cubic boron nitride composite sheet, which is prepared using the method described above. Specifically, the polycrystalline cubic boron nitride composite sheet of this invention is obtained by sintering cubic boron nitride with a surface-coated silicide, a binder, and a cemented carbide. The polycrystalline cubic boron nitride composite sheet provided by this invention has excellent corrosion resistance, oxidation wear resistance, diffusion wear resistance, chemical wear resistance, and heat resistance, resulting in a longer service life when used in the manufacture of cutting tools.

[0047] The present invention will be further described below through specific embodiments.

[0048] Example 1

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

[0050] (1) Add 5g of polycarbosilane to 200mL of toluene and stir evenly. Add 100g of cubic boron nitride with a particle size of 3 micrometers. After ultrasonic stirring for 30min, dry the mixture (i.e. evaporate it to dryness) to obtain the first mixture.

[0051] (2) The first mixture was heat-treated in a vacuum at 1200°C for 5 hours to obtain cubic boron nitride with silicon carbide coating on the surface.

[0052] (3) After ball milling 7.8g of metallic aluminum and 76g of titanium nitride until uniform, add the cubic boron nitride with silicon carbide coating on the surface, continue ball milling until uniform, and then dry to obtain a mixture.

[0053] (4) The above mixture and hard alloy substrate are placed in a metal cup and treated at 600°C for 2 hours (to remove adsorbed water vapor and other impurities). Then, the mixture is sintered at a pressure of 6 GPa and a temperature of 1400°C for 0.5 hours 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) Add 7g of polysilazane to 300mL of acetone and stir evenly. Add 141g of cubic boron nitride with a particle size of 2 micrometers. After ultrasonic stirring for 30min, dry the mixture (i.e. evaporate it to dryness) to obtain the first mixture.

[0057] (2) The first mixture was treated at 800°C for 5 hours in a nitrogen atmosphere to obtain cubic boron nitride with silicon nitride surface coating.

[0058] (3) After ball milling 7.7g of metallic aluminum and 17g of cobalt powder until uniform, add the cubic boron nitride coated with silicon nitride and continue ball milling until uniform. Then dry the mixture to obtain the mixture.

[0059] (4) The above mixture and hard alloy substrate are placed into a metal cup and treated at 600°C for 2 hours. Then, the mixture is sintered at a pressure of 6 GPa and a temperature of 1500°C for 0.5 hours 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 ball milling 7.8g of metallic aluminum and 76g of titanium nitride until uniform, add 100g of cubic boron nitride with a particle size of 3 micrometers, continue ball milling until uniform, and then dry to obtain a mixture;

[0064] (2) The above mixture and hard alloy substrate are placed in a metal cup and treated at 600°C for 2 hours. Then, the mixture is sintered at a pressure of 6 GPa and a temperature of 1400°C for 0.5 hours 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 7.7g of metallic aluminum and 17g of cobalt powder until uniform, add 141g of cubic boron nitride with a particle size of 2 micrometers, continue ball milling until uniform, and then dry to obtain a mixture;

[0069] (4) The above mixture and hard alloy substrate are placed into a metal cup and treated at 600°C for 2 hours. Then, the mixture is sintered at a pressure of 6 GPa and a temperature of 1500°C for 0.5 hours to obtain a polycrystalline cubic boron nitride composite sheet.

[0070] test:

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

[0072] The test results demonstrate that coating the surface of cubic boron nitride with silicon carbide can improve the wear resistance and lifespan of polycrystalline cubic boron nitride composite sheets.

[0073] (2) The polycrystalline cubic boron nitride composite sheets from Examples 2 and 2 were processed into cutting tools for cutting performance testing. The material being cut 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 depth of cut of 0.20 mm. Under the condition that the cutting stroke was 10000 m, the tool face wear of the polycrystalline cubic boron nitride composite sheet from Example 2 was 156 μm after the cutting test, while the tool face wear of the polycrystalline cubic boron nitride composite sheet from Comparative Example 2 was 231 μm. That is to say, the tool face wear of the polycrystalline cubic boron nitride composite sheet from Example 2 was 67.53% of that of the tool face wear of the polycrystalline cubic boron nitride composite sheet from Comparative Example 2.

[0074] This result demonstrates that coating the surface of cubic boron nitride with silicon nitride can improve the wear resistance and lifespan of polycrystalline cubic boron nitride composite sheets.

[0075] In summary, this invention provides a polycrystalline cubic boron nitride composite sheet and its preparation method. The preparation method provided by this 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 oxidizing and corrosive components and cubic boron nitride can be reduced or even isolated. This effectively prevents the interdiffusion of boron and nitrogen elements in cubic boron nitride with the elements of the material being machined, improves the chemical inertness of cubic boron nitride, and reduces damage to cubic boron nitride. This reduces the damage to polycrystalline cubic boron nitride caused by adverse factors during the cutting process, reduces wear on polycrystalline cubic boron nitride, and increases the tool life of polycrystalline cubic boron nitride. 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, and long service life.

[0076] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a polycrystalline cubic boron nitride composite sheet, characterized in that, The process includes the following steps: pretreating cubic boron nitride to obtain cubic boron nitride with a surface coated with silicide; the silicide includes at least one of silicon carbide, silicon nitride, silicon boride, and silicon carbonitride; mixing the cubic boron nitride with the silicide-coated surface with a binder to obtain a mixture; sintering the mixture with a cemented carbide substrate to obtain the polycrystalline cubic boron nitride composite sheet; the specific steps for pretreating cubic boron nitride to obtain cubic boron nitride with a surface coated with silicide are detailed below. The process includes: mixing a silicon source, cubic boron nitride, and an organic solvent, ultrasonically homogenizing the mixture, and then evaporating it to dryness to obtain a first mixture; heat-treating the first mixture under a preset atmosphere to obtain cubic boron nitride with a surface coated with silicide; wherein the silicon source includes at least one of polycarbosilane, polymethylsilane, and polysilazane; wherein the silicon source accounts for 0.2% to 10% of the mass of cubic boron nitride; and wherein the binder includes at least one of aluminum, silicon, aluminum-silicon alloy, titanium, titanium nitride, titanium carbide, titanium carbonitride, and cobalt.

2. The preparation method according to claim 1, characterized in that, The cubic boron nitride has a particle size of 0.1 to 20 micrometers.

3. The preparation method according to claim 1, characterized in that, The organic solvent includes at least one of toluene, acetone, and butyl acetate.

4. The preparation method according to claim 1, characterized in that, The preset atmosphere is a vacuum atmosphere; or the preset atmosphere is at least one of nitrogen atmosphere, argon atmosphere and methane atmosphere.

5. The preparation method according to claim 1, characterized in that, The heat treatment temperature is 150~1200℃.

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

7. A polycrystalline cubic boron nitride composite sheet, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

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