A high-toughness cubic boron nitride composite material and its preparation method and application

Abstract

The present invention provides a high-toughness cubic boron nitride composite material and its preparation method and application. The preparation method comprises the following steps: first, cubic boron nitride powder and silicon nitride powder are mixed in different proportions and pre-treated; then, the mixture is subjected to a synthesis process under high temperature and high pressure conditions, with a specific synthesis pressure of 5GPa and a temperature range of 1000°C-1800°C; then, after a period of heat preservation and pressure maintenance, the mixture is cooled and depressurized to obtain a composite material of cubic boron nitride and silicon nitride. By adjusting the ratio of silicon nitride and the transformation of its crystal phase (α phase to β phase), the method significantly improves its toughness without significantly reducing the hardness of cubic boron nitride, thereby effectively solving the contradiction between hardness and toughness in superhard materials. The method is simple in process and suitable for industrial production, and the resulting composite material has a wide range of application potentials in precision cutting and other high-demand industrial processing.

Description

Technical Field

[0001] The present invention relates to the field of superhard material preparation, and in particular to a high-toughness cubic boron nitride composite material and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern technology, superhard materials are increasingly used in industry, especially when processing hard materials, showing unparalleled superiority. Superhard materials mainly include diamond and cubic boron nitride (cBN). Although diamond has the highest hardness, it is prone to carburization reaction under high temperature conditions. In particular, its strength decreases rapidly when processing materials containing iron elements, which greatly limits the application range of diamond. In contrast, cubic boron nitride has become one of the ideal processing materials in industries such as automobiles, aerospace, mechanical electronics, and microelectronics because its hardness is second only to diamond and it has excellent thermal stability, wide band gap, high thermal conductivity, and chemical inertness to iron group metals and their alloys. Therefore, cubic boron nitride is considered to be a potential candidate material to replace diamond.

[0003] However, despite its extremely high hardness, cubic boron nitride's inherent brittleness limits its service life in high-impact environments, severely impacting its cutting efficiency and overall service life. To address this issue, various toughening solutions have been proposed. However, hardness and toughness are often mutually exclusive; increasing hardness typically results in a decrease in toughness. Developing a material with both high hardness and improved toughness remains a significant technical challenge.

[0004] At present, common toughening technologies include introducing metal binders (such as Ni, Co, Al, etc.) into polycrystalline cubic boron nitride materials and improving toughness through high temperature and high pressure sintering. Although this type of method can enhance toughness to a certain extent, it often leads to a decrease in hardness, and the commonly used metal binders are not strong enough at high temperatures and cannot cope with harsh industrial environments. For this reason, some researchers have tried to use non-metallic toughening materials such as titanium nitride, aluminum nitride and zirconium dioxide to improve toughness. Although certain results have been achieved, the high sintering temperature and equipment requirements required greatly increase the cost and process complexity.

[0005] In addition, using hard ceramics such as diamond instead of metal binders can further increase hardness, but the toughness improvement effect is still not ideal. In recent years, nano- and submicron-sized polycrystalline cubic boron nitride has provided a new direction for toughening, but its extremely high synthesis conditions and small sample size limit its practical industrial application.

[0006] In this context, silicon nitride (Si3N4) has become a promising binder material due to its high hardness and good toughness. The unique property of silicon nitride is that it can undergo a phase transformation from α phase to β phase under the action of force, consuming excess fracture energy and thus improving fracture toughness. For example, Chen Kexin and others achieved the transformation of α-Si3N4 to β-Si3N4 by precisely controlling the sintering parameters, preparing a dual-phase ceramic material with different ratios of α / β phase interfaces, which greatly improved the toughness of the material.

[0007] Therefore, using silicon nitride as a binder to dissipate the fracture energy of cubic boron nitride through its phase transition is expected to significantly improve the toughness of the material while maintaining its high hardness. By regulating the proportion of silicon nitride and its phase transition conditions, the overall performance of the material can be further optimized, providing an important technical path for the industrial production of cubic boron nitride. In order to improve the toughness while maintaining the hardness of cubic boron nitride, designing a new binder and preparation process is of great significance to promoting the industrial production of cubic boron nitride, improving the performance of this material, and promoting its application. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for preparing a high-toughness cubic boron nitride composite material, so as to solve the problems of short service life and poor impact resistance of the boron nitride composite materials prepared by conventional preparation methods in the prior art due to brittleness, and to provide a method for improving the toughness of cubic boron nitride through the phase transformation of the crystal structure of silicon nitride binder.

[0009] The present invention provides a method for preparing a high-toughness cubic boron nitride composite material, comprising the following steps:

[0010] S1: using cubic boron nitride powder as a raw material, pre-treating the raw material, and then mixing it with silicon nitride powder, wherein the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 1-10%;

[0011] S2: The raw materials mixed in step S1 are loaded into a synthesis chamber of a domestic six-sided top press, and subjected to high-temperature and high-pressure synthesis treatment, followed by heat and pressure maintenance treatment; the conditions of the high-temperature and high-pressure synthesis treatment are: synthesis pressure 5 GPa, synthesis temperature 1000-1800°C;

[0012] S3: Cooling and depressurizing the product after heat preservation in step S2 to obtain a composite material of cubic boron nitride and silicon nitride.

[0013] Compared with the prior art, the present invention provides a method for preparing a high-toughness cubic boron nitride composite material, which has the following advantages: the present invention replaces the traditional metal binder (such as Ni, Co, etc.) in the prior art with a silicon nitride binder. Compared with metal binders, silicon nitride consumes energy when the material is subjected to stress through its unique α-phase and β-phase crystal structure transformation, thereby enhancing the fracture toughness of the material, and absorbing impact force in the microstructure of the material through the crystal phase transformation of silicon nitride, thereby improving the impact resistance of the material; and the introduction of silicon nitride not only does not significantly reduce the hardness of cubic boron nitride, but on the contrary effectively improves the toughness of the material through its unique structural phase transformation mechanism. This improvement ensures that the material can withstand high impact. Under impact load, the material will not be as prone to brittle fracture as traditional cubic boron nitride, which significantly improves its service life and processing performance. Therefore, the material achieves excellent fracture toughness while maintaining ultra-high hardness; and in the above preparation method, the parameters of silicon nitride content, synthesis pressure, temperature and insulation and pressure holding time are closely related, and there is a synergistic effect between each other. By controlling the silicon nitride content (1-10%), synthesis temperature (1000-1800℃), synthesis pressure (5GPa), and precise setting of insulation and pressure holding time, the ideal phase change of the crystal structure of the composite material is ensured, thereby obtaining the ultimate perfect combination of high hardness and high toughness.

[0014] Traditional cubic boron nitride materials have a contradiction between high hardness and high toughness. The preparation method of the high-toughness cubic boron nitride composite material in the present invention uses silicon nitride as a binder and utilizes the α-phase and β-phase structural transformation mechanism of silicon nitride to successfully increase its toughness without reducing the hardness of cubic boron nitride, thereby significantly improving the overall performance of the composite material. This improvement not only overcomes the problem of material performance degradation at high temperatures caused by metal binders in traditional technologies, but also greatly extends the service life of the material, especially in industrial fine cutting and finishing applications; through the optimization design of material ratios, synthesis conditions and crystal structure phase transition processes, it successfully solves the technical problem of "it is difficult to balance high hardness and high toughness of materials" in the background technology, and significantly improves the fracture toughness and service life of cubic boron nitride materials. The core innovation of this technology lies in the introduction of the binder silicon nitride and the control of its phase transition process, which breaks through the limitations of existing superhard materials between high hardness and high toughness, and promotes the widespread promotion of materials in industrial applications.

[0015] In a possible embodiment, in step S1, the particle size of the cubic boron nitride powder is 450-550 nm.

[0016] Compared with the existing technology, the above technical solution can significantly improve the mechanical properties of the composite material by controlling the particle size of the cubic boron nitride powder at the nanometer level of 500nm. The cubic boron nitride powder with a smaller particle size can provide a higher specific surface area and a more uniform distribution, thereby forming a tighter bonding structure inside the material and reducing the generation of microscopic defects. Compared with materials with larger particle sizes, nano-scale powders can more fully react with silicon nitride under high temperature and high pressure synthesis conditions, ensuring that the crystal structure phase transition in the composite material is more complete, especially the transformation from α-Si3N4 to β-Si3N4 is more complete, thereby enhancing the fracture toughness of the material. Through the precise control of the cubic boron nitride particle size, it is ensured that the material has a higher reactivity and a more uniform structure during the synthesis process, thereby achieving an optimized balance between toughness and hardness and improving the overall performance of the material.

[0017] In a possible embodiment, in step S1, the pretreatment method is: before mixing the raw materials, heat-treating the cubic boron nitride powder at 300° C. for 2 hours.

[0018] Compared with the existing technology, the cubic boron nitride and silicon nitride composite material prepared by the above-mentioned technical solution through heat treatment at 300°C for 2 hours performs better in hardness and toughness, and the overall structure of the material is denser and more stable. The pretreated powder can better participate in the subsequent high-temperature and high-pressure synthesis reaction, avoiding possible material failure or performance inconsistency. Therefore, this material is suitable for application in harsh environments, such as industrial cutting, wear-resistant materials and other high-demand scenarios; the surface impurities and activated powder particles are removed through pretreatment, making the reaction in the subsequent synthesis process more complete, and ultimately achieving a significant improvement in material performance.

[0019] In a possible embodiment, in step S1, the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 3-7%.

[0020] Compared with the existing technology, using the above technical solution, when the addition amount of silicon nitride is controlled at 3%-10%, it is evenly distributed with cubic boron nitride under high temperature and high pressure conditions to form a stable composite material structure. Within this range, the phase change process of silicon nitride is more stable, ensuring its toughening effect, and the ratio of 3%-10% also avoids the situation where the hardness decreases due to excessive silicon nitride. Silicon nitride not only acts as a filling agent inside the material, but also effectively absorbs the fracture energy of the material under stress through its α-phase to β-phase crystal structure phase transition. Therefore, an appropriate proportion of silicon nitride powder can significantly improve the fracture toughness of the material. By controlling the addition amount of silicon nitride, the full play of the silicon nitride phase change toughening mechanism is ensured, while maintaining the high hardness of the material, and achieving optimization and improvement of the comprehensive performance of the material.

[0021] In a possible embodiment, in step S2, the conditions of the high temperature and high pressure synthesis treatment are: synthesis temperature 1300-1500° C., and synthesis pressure 5 GPa.

[0022] Compared with existing technologies, the above-mentioned technical solution can promote the phase transition of silicon nitride from the α phase to the β phase through optimized temperature range and high pressure conditions, thereby maximizing the overall performance of the composite material. Within the temperature range of 1300-1500°C, the crystal structure transformation process of silicon nitride can proceed more stably, avoiding uneven material properties or defects caused by excessively high or low temperatures. At the same time, the high pressure of 5GPa can ensure close bonding between the material particles, further improving the density and strength of the material. Through this combination of temperature and pressure, cubic boron nitride and silicon nitride powder can fully react, allowing the phase change of silicon nitride to effectively consume the material's fracture energy and enhance toughness. This synthesis condition can ensure that the material does not generate excessive internal stress during the formation process, thereby avoiding the problem of brittle fracture of the material.

[0023] In a possible implementation, in step S2, the heat preservation time is 15 minutes, and the pressure preservation time is 16 minutes.

[0024] Compared with the existing technology, the above technical solution precisely controls the holding time of heat and pressure in the key steps of material synthesis, so that the microstructure of the material undergoes stable changes. Under high temperature and high pressure, the reaction between cubic boron nitride and silicon nitride requires a certain amount of time to complete, especially the phase transition process from the α phase to the β phase of silicon nitride. The 15-minute holding time can ensure that the phase transition of silicon nitride is fully carried out, thereby improving the fracture toughness of the material. The 16-minute holding time ensures the close bonding of the material particles under high pressure, reduces internal voids, and increases the overall density of the material.

[0025] In a possible embodiment, in step S3, the cooling and pressure relief condition is: the product after the heat preservation treatment is naturally cooled to room temperature and then the pressure is relieved.

[0026] Compared with the existing technology, the above-mentioned technical solution is used to achieve a balance between hardness and toughness in the prepared cubic boron nitride and silicon nitride composite material by naturally cooling to room temperature and then unloading the pressure. Since the internal stress is greatly reduced, the material exhibits better structural stability and durability during use. This cooling method makes the material suitable for application scenarios with high requirements for impact resistance, fatigue resistance and long-term stability, such as high-strength cutting tools or industrial fine processing. The speed of the cooling process is controlled to ensure that the temperature inside and outside the material is consistent, thereby avoiding cracks or structural defects caused by stress concentration, and ultimately achieving a balance between high hardness and high toughness, extending the service life of the material.

[0027] Another technical problem to be solved by the present invention is to provide a high-toughness cubic boron nitride composite material to solve the problems of short service life and poor impact resistance caused by brittleness of conventional boron nitride composite materials.

[0028] In order to solve the above technical problems, the present invention provides a high-toughness cubic boron nitride composite material, wherein the cubic boron nitride and silicon nitride composite material is prepared by the above preparation method.

[0029] Compared with the prior art, the high-toughness cubic boron nitride composite material of the present application has the following advantages: the high-toughness cubic boron nitride composite material of the present invention replaces the metal binder (such as Ni, Co, etc.) in the prior art with silicon nitride as the binder, and during the crystal structure phase transition from the α phase to the β phase of silicon nitride, it can absorb and consume the energy of the material during fracture, thereby increasing the toughness of the material; at the same time, silicon nitride is a ceramic material with relatively high hardness. Its introduction not only does not significantly reduce the hardness of the composite material, but on the contrary, through close combination with cubic boron nitride, it enhances the impact resistance and wear resistance of the material, ultimately enabling the high-toughness cubic boron nitride composite material to further achieve the ultimate technical effect, that is, achieving high toughness and impact resistance of the material while maintaining high hardness.

[0030] Another technical problem to be solved by the present invention is to provide an application of the cubic boron nitride composite material, wherein the application includes application of the cubic boron nitride composite material in industrial fine cutting and finishing.

[0031] The application of a cubic boron nitride composite material in this application offers the following advantages over existing technologies: It replaces the traditional metal or ceramic cutting tool materials used in existing technologies with a composite material of cubic boron nitride and silicon nitride. This composite material simultaneously exhibits extremely high hardness and enhanced fracture toughness. The cubic boron nitride provides excellent wear resistance and hardness, while the introduction of silicon nitride, through the phase transition from α to β phase, can absorb and dissipate local stress during the cutting process, preventing the tool from breaking or failing under high stress or high temperature conditions. Due to the material's improved thermal stability, the composite material can maintain its mechanical properties at higher temperatures, reducing tool wear and deformation during processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is an X-ray diffraction pattern of the cubic boron nitride and silicon nitride composite material prepared in Example 1-5;

[0033] Figure 2 is an X-ray diffraction pattern of the cubic boron nitride and silicon nitride composite material prepared in Examples 6-10;

[0034] Figure 3is an X-ray diffraction pattern of the cubic boron nitride and silicon nitride composite material prepared in Examples 11-15;

[0035] Figure 4 is the X-ray diffraction pattern of the cubic boron nitride prepared in Comparative Examples 1-5;

[0036] Figure 5 is a graph showing the relationship between toughness and temperature of the cubic boron nitride and silicon nitride composite material prepared at a pressure of 5 GPa and a temperature of 1000° C. to 1800° C. in Examples 6-10;

[0037] Figure 6 This is a curve showing the relationship between hardness and temperature of the cubic boron nitride and silicon nitride composite material prepared at a pressure of 5 GPa and a temperature of 1000° C. to 1800° C. in Examples 6-10. DETAILED DESCRIPTION

[0038] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art may adjust them as needed to suit specific application scenarios.

[0039] The present invention provides a method for preparing a high-toughness cubic boron nitride composite material, comprising the following steps:

[0040] S1: using cubic boron nitride powder as a raw material, pre-treating the raw material, and then mixing it with silicon nitride powder, wherein the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 1-10%;

[0041] S2: The raw materials mixed in step S1 are loaded into a synthesis chamber of a domestic six-sided top press, and subjected to high-temperature and high-pressure synthesis treatment, followed by heat and pressure maintenance treatment; the conditions of the high-temperature and high-pressure synthesis treatment are: synthesis pressure 5 GPa, synthesis temperature 1000-1800°C;

[0042] S3: Cooling and depressurizing the product after heat preservation in step S2 to obtain a composite material of cubic boron nitride and silicon nitride.

[0043] As a preferred solution, in step S1, the particle size of the cubic boron nitride powder is 450-550 nm.

[0044] As a preferred solution, in step S1, the pretreatment method is: before mixing the raw materials, heat-treating the cubic boron nitride powder at 300° C. for 2 hours.

[0045] As a preferred solution, in step S1, the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 3-7%.

[0046] As a preferred solution, in step S2, the conditions of the high temperature and high pressure synthesis treatment are: synthesis temperature 1300-1500°C, synthesis pressure 5GPa.

[0047] As a preferred solution, in step S2, the heat preservation time is 15 minutes, and the pressure preservation time is 16 minutes.

[0048] As a preferred solution, in step S3, the cooling and pressure relief condition is: the product after the heat preservation treatment is naturally cooled to room temperature and then the pressure is relieved.

[0049] The present invention also provides a high-toughness cubic boron nitride composite material, wherein the cubic boron nitride and silicon nitride composite material is prepared by the above-mentioned preparation method.

[0050] The present invention also provides an application of the cubic boron nitride composite material, which includes application of the cubic boron nitride composite material in industrial fine cutting and finishing.

[0051] The following is a further description of the above scheme of the present invention in combination with specific data and experimental methods:

[0052] Example 1

[0053] Example 1 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0054] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 1%;

[0055] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1000°C for 15 minutes and 16 minutes, then stop heating.

[0056] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 1 .

[0057] Example 2

[0058] Example 2 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0059] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 1%;

[0060] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1200°C for 15 minutes and 16 minutes, then stop heating.

[0061] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 1 .

[0062] Example 3

[0063] Example 3 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0064] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 1%;

[0065] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1400°C for 15 minutes and 16 minutes, then stop heating.

[0066] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 1 .

[0067] Example 4

[0068] Example 4 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0069] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 1%;

[0070] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1600°C for 15 minutes and 16 minutes, then stop heating.

[0071] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 1 .

[0072] Example 5

[0073] Example 5 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0074] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 1%;

[0075] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1800°C for 15 minutes and 16 minutes, then stop heating.

[0076] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 1 .

[0077] Example 6

[0078] Example 6 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0079] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 5%;

[0080] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1000°C for 15 minutes and 16 minutes, then stop heating.

[0081] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 2 .

[0082] Example 7

[0083] Example 7 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0084] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 5%;

[0085] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1200°C for 15 minutes and 16 minutes, then stop heating.

[0086] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 2 .

[0087] Example 8

[0088] Example 8 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0089] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 5%;

[0090] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1400°C for 15 minutes and 16 minutes, then stop heating.

[0091] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 2 .

[0092] Example 9

[0093] Example 9 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0094] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 5%;

[0095] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1600°C for 15 minutes and 16 minutes, then stop heating.

[0096] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 2 .

[0097] Example 10

[0098] Example 10 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0099] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 5%;

[0100] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1800°C for 15 minutes and 16 minutes, then stop heating.

[0101] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 2 .

[0102] Example 11

[0103] Example 11 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0104] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 10%;

[0105] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1000°C for 15 minutes and 16 minutes, then stop heating.

[0106] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 3 .

[0107] Example 12

[0108] Example 12 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0109] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 10%;

[0110] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1200°C for 15 minutes and 16 minutes, then stop heating.

[0111] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 3 .

[0112] Example 13

[0113] Example 13 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0114] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 10%;

[0115] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1400°C for 15 minutes and 16 minutes, then stop heating.

[0116] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 3 .

[0117] Example 14

[0118] Example 14 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0119] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 10%;

[0120] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1600°C for 15 minutes and 16 minutes, then stop heating.

[0121] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 3 .

[0122] Example 15

[0123] Example 15 provides a high-toughness cubic boron nitride composite material and a preparation method thereof. The high-toughness cubic boron nitride composite material is prepared by the following method:

[0124] S1: Preheat cubic boron nitride powder at 300°C for 2 hours, add % silicon nitride powder and mix well, and then process into a cylinder with a diameter of 4 mm and a height of 2 mm; the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 10%;

[0125] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1800°C for 15 minutes and 16 minutes, then stop heating.

[0126] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 3 .

[0127] Comparative Example 1

[0128] Comparative Example 1 provides a boron nitride composite material and a preparation method thereof, the difference being that in step S1, the amount of silicon nitride powder added is 0 wt.%, i.e., no silicon nitride powder is added, and the boron nitride composite material is prepared by the following method:

[0129] S1: Preheat the cubic boron nitride powder at 300°C for 2 hours and process it into a cylinder with a diameter of 4 mm and a height of 2 mm;

[0130] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1000°C for 15 minutes and 16 minutes, then stop heating.

[0131] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 4 .

[0132] Comparative Example 2

[0133] Comparative Example 2 provides a boron nitride composite material and a preparation method thereof, the difference being that in step S1, the amount of silicon nitride powder added is 0 wt.%, i.e., no silicon nitride powder is added, and the boron nitride composite material is prepared by the following method:

[0134] S1: Preheat the cubic boron nitride powder at 300°C for 2 hours and process it into a cylinder with a diameter of 4 mm and a height of 2 mm;

[0135] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1200°C for 15 minutes and 16 minutes, then stop heating.

[0136] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 4 .

[0137] Comparative Example 3

[0138] Comparative Example 3 provides a boron nitride composite material and a preparation method thereof, the difference being that in step S1, the amount of silicon nitride powder added is 0 wt.%, i.e., no silicon nitride powder is added, and the boron nitride composite material is prepared by the following method:

[0139] S1: Preheat the cubic boron nitride powder at 300°C for 2 hours and process it into a cylinder with a diameter of 4 mm and a height of 2 mm;

[0140] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1400°C for 15 minutes and 16 minutes, then stop heating.

[0141] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 4 .

[0142] Comparative Example 4

[0143] Comparative Example 4 provides a boron nitride composite material and a preparation method thereof, the difference being that in step S1, the amount of silicon nitride powder added is 0 wt.%, i.e., no silicon nitride powder is added, and the boron nitride composite material is prepared by the following method:

[0144] S1: Preheat the cubic boron nitride powder at 300°C for 2 hours and process it into a cylinder with a diameter of 4 mm and a height of 2 mm;

[0145] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1600°C for 15 minutes and 16 minutes, then stop heating.

[0146] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 4 .

[0147] Comparative Example 5

[0148] Comparative Example 5 provides a boron nitride composite material and a preparation method thereof, the difference being that in step S1, the amount of silicon nitride powder added is 0 wt.%, i.e., no silicon nitride powder is added, and the boron nitride composite material is prepared by the following method:

[0149] S1: Preheat the cubic boron nitride powder at 300°C for 2 hours and process it into a cylinder with a diameter of 4 mm and a height of 2 mm;

[0150] S2: Place the raw materials processed in step S1 into a high-temperature and high-pressure synthesis block. Keep the temperature at 5 GPa and the synthesis temperature at 1800°C for 15 minutes and 16 minutes, then stop heating.

[0151] S3: The sample is naturally cooled to room temperature and then the pressure is released. The X-ray diffraction results of the composite materials of cubic boron nitride and silicon nitride prepared under different temperature conditions are shown in Figure 4 .

[0152] The experiments involved in the above embodiments were completed by experimental assembly of a domestic six-sided top press.

[0153] Figure 1 is the X-ray diffraction pattern of the cubic boron nitride and silicon nitride composite material prepared in Example 1, Example 2, Example 3, Example 4, and Example 5; Figure 2 is the X-ray diffraction pattern of the cubic boron nitride and silicon nitride composite material prepared in Example 6, Example 7, Example 8, Example 9, and Example 10; Figure 2 It can be seen from the XRD pattern that under the conditions of Example 8 of the present invention, that is, when the temperature is 1400°C, the silicon nitride α phase begins to transform into the β phase, and the sample is now a composite phase of silicon nitride dual phase and cubic boron nitride. Figure 3 is the X-ray diffraction pattern of the cubic boron nitride and silicon nitride composite material prepared in Example 11, Example 12, Example 13, Example 14, and Example 15; Figure 4 is the X-ray diffraction pattern of cubic boron nitride prepared in Comparative Examples 1-5; Figure 4The XRD patterns show that under the conditions of Comparative Example 5 of the present invention, at a temperature of 1800°C, cubic boron nitride is essentially completely converted to hexagonal boron nitride. Furthermore, due to the simple high-temperature and high-pressure sintering of cBN in the preparation methods of Comparative Examples 1-5, the samples are very brittle and have low toughness. However, the toughness of the examples of the present invention can be improved by adding a sintering aid.

[0154] The test results of the preparation methods of Examples 1-15 show that the effects of different addition amounts of silicon nitride (1 wt.%, 5 wt.%, 10 wt.%) in the composite material with cubic boron nitride are as follows:

[0155] 1% silicon nitride: At this addition, the amount of silicon nitride is small and the toughening effect is not significant. This is mainly because the silicon nitride content is insufficient to form a uniformly distributed bonding phase within the material or to fully transform the α phase to the β phase, resulting in limited improvement in the fracture toughness of the material.

[0156] 5% silicon nitride: Experiments have shown that at this content, the composite material exhibits an optimal balance between fracture toughness and hardness. 5wt.% silicon nitride is sufficient to induce a phase transition from α to β, which absorbs energy during fracture and effectively improves toughness. Furthermore, 5wt.% silicon nitride does not significantly reduce the material's hardness, achieving a balance between high hardness and toughness, making it the optimal addition ratio for technical results.

[0157] 10% Silicon Nitride: At 10wt.%, the toughening effect of silicon nitride is further enhanced, but this also affects the overall hardness of the material. Excessive silicon nitride may cause the composite material to slightly decrease in high hardness, not as good as the ideal balance of hardness and toughness achieved at 5wt.%.

[0158] Figure 5 1 is a curve showing the relationship between the fracture toughness and temperature of the cubic boron nitride and silicon nitride composite materials prepared at a pressure of 5 GPa and a temperature of 1000° C. to 1800° C. in Examples 6, 7, 8, 9, and 10;

[0159] Figure 6 is a curve showing the relationship between hardness and temperature of the cubic boron nitride and silicon nitride composite materials prepared at a pressure of 5 GPa and a temperature of 1000° C. to 1800° C. in Examples 6, 7, 8, 9, and 10;

[0160] Figure 5 、 Figure 6 It also shows that the composite material of cubic boron nitride and silicon nitride prepared by the present invention at a pressure of 5 GPa and a temperature of 1400 ° C can improve the fracture toughness to 9.58 MPa·m while retaining high hardness. 1 / 2, excellent mechanical properties and mechanical properties, with better comprehensive performance, provides a binder crystal structure phase change to increase the toughness of polycrystalline cubic boron nitride and its preparation method.

[0161] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

[0162] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a high-toughness cubic boron nitride composite material, characterized by: The following steps are involved: S1: using cubic boron nitride powder as a raw material, pre-treating the raw material, and then mixing it with silicon nitride powder, wherein the molar ratio of the silicon nitride powder to the cubic boron nitride powder is 5%; S2: The raw materials mixed in step S1 are loaded into a synthesis chamber of a domestic six-sided top press, and subjected to high-temperature and high-pressure synthesis treatment, followed by heat and pressure maintenance treatment; the conditions of the high-temperature and high-pressure synthesis treatment are: synthesis temperature 1400-1500° C., synthesis pressure 5 GPa; S3: Cooling and depressurizing the product after the heat preservation in step S2 to obtain a composite material of cubic boron nitride and silicon nitride, which is a composite phase having a dual phase of silicon nitride and cubic boron nitride; In step S1, the pretreatment method is: before mixing the raw materials, the cubic boron nitride powder is heat-treated at 300° C. for 2 hours; In step S2, the heat preservation time is 15 minutes, and the pressure preservation time is 16 minutes; In step S3, the cooling and pressure relief condition is: the product after the heat preservation treatment is naturally cooled to room temperature and then the pressure is relieved.

2. The method for preparing the high-toughness cubic boron nitride composite material according to claim 1, wherein: In the step S1, the particle size of the cubic boron nitride powder is 450-550 nm.

3. A high-toughness cubic boron nitride composite material, characterized by: The high-toughness cubic boron nitride composite material is prepared by the preparation method according to any one of claims 1-2.

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