High-toughness polycrystalline cubic boron nitride composite sheet and preparation method thereof

Abstract

The invention relates to a high-toughness polycrystalline cubic boron nitride composite sheet which is prepared from the following raw materials in parts by weight: 70-95% of a main crystal phase and 5-30% of a binding agent, the main crystal phase is cubic boron nitride powder, the grain size of the cubic boron nitride powder is smaller than 4 microns, the binding agent is MaAbXc, and M is Ti; a is composed of at least one of Al, Cr and Si; x is composed of at least one of C and N. The prepared polycrystalline cubic boron nitride composite sheet has excellent wear resistance, high toughness and impact resistance.

Description

Technical Field

[0001] The invention relates to a high-toughness polycrystalline cubic boron nitride composite sheet and a preparation method thereof, and belongs to the field of superhard composite materials. Background Art

[0002] Polycrystalline cubic boron nitride (PCBN) is a composite formed by sintering numerous finely divided cubic boron nitride particles, with or without additives, under high temperature and high pressure. PCBN perfectly addresses the challenges inherent in single crystals. Its grains are randomly arranged, resulting in macroscopically isotropic material properties and the absence of cleavage planes. Furthermore, its large size makes it easier to process and shape, thus facilitating a wide range of applications. Due to the excellent thermal stability, chemical inertness, and high hardness of PCBN cutting tools, PCBN not only achieves high precision and low surface roughness when machining high-hardness (HRC>50) and low-thermal-conductivity ferrous metals and their alloys, but also enables high- and ultra-high-speed cutting, long tool life, and relatively low processing costs. PCBN cutting tools have a wide range of applications, primarily in advanced CNC machine tools, multi-purpose fully automatic machine tools, and specialized high-speed automated production lines. They are also used in flexible production systems for machining hardened steel, chilled cast iron, die steel, and hardened forged steel.

[0003] Polycrystalline cubic boron nitride (PCBN) cutting tools experience physical wear during use, and their quality affects their service life and replacement frequency. Current research and development focuses on improving the toughness, strength, and hardness of cutting tools. For example, the PCBN cutting tool material disclosed in patent CN201710709833 has a bending strength of 2.8-3.1 MPa, a fracture toughness of 4.6-5.4 MPa.m1 / 2, and a hardness of 37-45 GPa. The PCBN composite sheet disclosed in patent CN202411549079.3 has a hardness of 26±1.5 GPa. Therefore, it is of great practical significance to produce high-strength and high-toughness PCBN cutting tool materials by improving the raw material formula and regulating the production process. Summary of the Invention

[0004] The object of the present invention is to provide a polycrystalline cubic boron nitride composite sheet having excellent high temperature resistance, impact resistance and wear resistance, as well as excellent toughness. The specific solution is: A high-toughness polycrystalline cubic boron nitride composite sheet is prepared from the following raw materials in parts by weight: 70%-95% main crystal phase and 5%-30% binder; the main crystal phase is cubic boron nitride powder, the grain size of the cubic boron nitride powder is less than 4 μm, and the binder is M a A b X c , M is Ti; A is composed of at least one of Al, Cr, and Si; and X is composed of at least one of C and N.

[0005] In this scheme, by adopting a new sintering aid, AlCN, AlN, AlxCy, SiC, TiCx, etc. are generated on the surface of cubic boron nitride powder through in-situ reaction, which promotes the densification of polycrystalline cubic boron nitride while reducing the difficulty of sintering during material preparation. In addition, the mechanism of in-situ reaction promoting the densification of polycrystalline cubic boron nitride is revealed, solving the problems of difficult sintering and poor toughness of polycrystalline cubic boron nitride.

[0006] Preferably, the grain size of the cubic boron nitride powder is 0.5-1 μm.

[0007] In Examples 1-4 disclosed in patent CN201710709833, and in Example 1 of patent CN202411549079.3, the particle size of the cubic boron nitride powder used was all above 1 μm. The smaller the grain size of the cubic boron nitride, the greater the hardness and toughness, and the better the wear resistance. However, the smaller the grain size, the more difficult it is to sinter. Based on the use of a new binder to solve the problem of difficult sintering, this solution uses cubic boron nitride powder below 1 μm, which can significantly improve the strength and toughness of polycrystalline cubic boron nitride.

[0008] Preferably, a:b:c=1-3:1:1-2.

[0009] Preferably, the binder is TiAlN, TiAlC2 or Ti3SiC2. When Ti3SiC2 is used as the binder, the hardness value reaches 3900-4000 Hv and the bending strength reaches 1.20-1.35 GPa.

[0010] The present invention also discloses a method for preparing the above high-toughness polycrystalline cubic boron nitride composite sheet, comprising the following steps: S1. Select raw materials, which include the following components in mass percentage: 70%-95% main crystal phase and 5%-30% binder; wherein the main crystal phase is cubic boron nitride powder, and the constituent elements of the binder are selected from at least three of Ti, Al, Cr, Si, C, and N.

[0011] S2. Evenly mix the binder and cubic boron nitride powder, and obtain a mixed powder by drying; S3. The mixed parts are loaded into a synthesis mold and assembled into a synthesis block, which is then sintered at high temperature and high pressure in a six-sided top press according to the set process parameters, with a pressure of 4-8 GPa, a temperature of 1200-1600°C, and a sintering time of 10-50 min to obtain a polycrystalline cubic boron nitride composite sheet.

[0012] Furthermore, in step S2, the binder is first ball-milled, and then mixed with cubic boron nitride powder and then ball-milled.

[0013] Based on the existing technology, the present invention can further improve the strength and hardness of polycrystalline cubic boron nitride materials. DETAILED DESCRIPTION

[0014] The following describes the solution of the present invention in detail with reference to specific examples.

[0015] Example 1 This embodiment provides a polycrystalline cubic boron nitride composite sheet, whose raw materials include binder TiAlC2 powder and cubic boron nitride powder, the binder particle size is 2-3 μm, the cubic boron nitride powder particle size is 0.5-1 μm, and the mass ratio of the binder to the cubic boron nitride powder is 2:8.

[0016] This embodiment also provides a method for preparing the above-mentioned polycrystalline cubic boron nitride composite sheet, which includes the following steps: The binder was first ball-milled in a ball mill at a speed of 400 r / min and a mass ratio of grinding balls to binder of 3.5:1 for 16 hours; the ball-milled binder and cubic boron nitride powder were then mixed uniformly at a speed of 200 r / min, and dried to obtain a mixed powder; The mixed powder is loaded into a synthesis mold and assembled into a synthesis block, which is then sintered at high temperature and high pressure in a six-sided top press according to the set process parameters: pressure 5.0 GPa, temperature 1300°C, and sintering time 30 minutes to obtain a polycrystalline cubic boron nitride composite sheet.

[0017] Example 2 This embodiment provides a polycrystalline cubic boron nitride composite sheet, whose raw materials include binder Ti3SiC2 powder and cubic boron nitride powder, the binder particle size is 2-3 μm, the cubic boron nitride powder particle size is 0.5-1 μm, and the mass ratio of the binder to the cubic boron nitride powder is 1.5:8.5.

[0018] This embodiment also provides a method for preparing the above-mentioned polycrystalline cubic boron nitride composite sheet, which includes the following steps: The binder was first ball-milled in a ball mill at a rotation speed of 400 r / min in a mass ratio of grinding balls to the binder of 3.5:1 for 16 hours; the ball-milled binder and cubic boron nitride powder were then mixed uniformly at a rotation speed of 200 r / min, and dried to obtain a mixed powder; The mixed powder is loaded into a synthesis mold and assembled into a synthesis block, which is then sintered at high temperature and high pressure in a six-sided top press according to the set process parameters: pressure 5.5 GPa, temperature 1400°C, and sintering time 30 minutes to obtain a polycrystalline cubic boron nitride composite sheet.

[0019] Example 3 This embodiment provides a polycrystalline cubic boron nitride composite sheet, whose raw materials include binder TiAlN powder and cubic boron nitride powder, the binder particle size is 2-3 μm, the cubic boron nitride powder particle size is 0.5-1 μm, and the mass ratio of the binder to the cubic boron nitride powder is 1:9.

[0020] This embodiment also provides a method for preparing the above-mentioned polycrystalline cubic boron nitride composite sheet, which includes the following steps: The binder was first ball-milled in a ball mill at a speed of 400 r / min and a mass ratio of grinding balls to binder of 3.5:1 for 16 h. The ball-milled binder and cubic boron nitride powder were then mixed uniformly at a speed of 200 r / min and dried to obtain a mixed powder. The mixed powder is loaded into a synthesis mold and assembled into a synthesis block, which is then sintered at high temperature and high pressure in a six-sided top press according to the set process parameters: pressure 6 GPa, temperature 1500°C, and sintering time 30 minutes to obtain a polycrystalline cubic boron nitride composite sheet.

[0021] Example 4 This embodiment provides a polycrystalline cubic boron nitride composite sheet, whose raw materials include binder Ti3SiC2 powder and cubic boron nitride powder, the binder particle size is 2-3 μm, the cubic boron nitride powder particle size is 2-3 μm, and the mass ratio of the binder to the cubic boron nitride powder is 1.5:8.5.

[0022] This embodiment also provides a method for preparing the above-mentioned polycrystalline cubic boron nitride composite sheet, which includes the following steps: The binder was first ball-milled in a ball mill at a rotation speed of 400 r / min in a mass ratio of grinding balls to the binder of 3.5:1 for 16 hours; the ball-milled binder and cubic boron nitride powder were then mixed uniformly at a rotation speed of 200 r / min, and dried to obtain a mixed powder; The mixed powder is loaded into a synthesis mold and assembled into a synthesis block, which is then sintered at high temperature and high pressure in a six-sided top press according to the set process parameters: pressure 6 GPa, temperature 1500°C, and sintering time 30 minutes to obtain a polycrystalline cubic boron nitride composite sheet.

[0023] Comparative Example 1 This comparative example provides a polycrystalline cubic boron nitride composite sheet. This sheet differs from Example 2 in that the binder comprises titanium powder, aluminum powder, and cubic boron nitride powder in a mass ratio of 3:1:1. The remaining process parameters and preparation method are consistent with those of Example 2. The primary crystal phase has a particle size of 0.5-1 μm.

[0024] Performance Characterization The polycrystalline cubic boron nitride composite sheets prepared in Examples 1 to 4 and Comparative Example 1 were tested. The test results are shown in Table 1. Table 1 Performance parameters of polycrystalline cubic boron nitride composite sheets prepared in Examples 1 to 4 and Comparative Example 1

[0025] As can be seen from Table 1, the polycrystalline cubic boron nitride composite sheets obtained in Examples 1 to 4 have high hardness and high flexural strength. Among them, Example 2 uses Ti3SiC2 as a binder, and the main crystal phase particle size is 0.5-1μm. The hardness of the obtained polycrystalline cubic boron nitride composite sheet reaches 3900~4000Hv, and the flexural strength reaches 1.20~1.35GPa. Compared with Example 2, Example 4 uses the same binder, but the main crystal phase particle size is larger. The hardness and flexural strength of the obtained polycrystalline cubic boron nitride composite sheet are lower than those of Example 2. While Control Example 1 uses a ratio of elemental metal powder and ceramic powder as a binder, compared with Example 2, although a smaller main crystal phase particle size is also used, the hardness and flexural strength of the obtained polycrystalline cubic boron nitride composite sheet are lower.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the present invention. They should all be included in the scope of the technical solutions for which protection is sought in the present invention.

Claims

1. A high-toughness polycrystalline cubic boron nitride composite sheet, characterized in that: It is prepared from the following raw materials in parts by weight: 70%-95% main crystal phase, 5%-30% binder; the main crystal phase is cubic boron nitride powder, the grain size of the cubic boron nitride powder is less than 4 μm, and the binder is M a A b X c , M is Ti; A is composed of at least one of Al, Cr, and Si; and X is composed of at least one of C and N.

2. The high-toughness polycrystalline cubic boron nitride composite sheet according to claim 1, characterized in that: The grain size of cubic boron nitride powder is 0.5-1 μm.

3. The high-toughness polycrystalline cubic boron nitride composite sheet according to claim 1, characterized in that: a:b:c=1-3:1:1-2.

4. The high-toughness polycrystalline cubic boron nitride composite sheet according to claim 1, characterized in that: The binder is TiAlN, TiAlC2 or Ti3SiC2.

5. A method for preparing a high-toughness polycrystalline cubic boron nitride composite sheet according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Select raw materials, which include the following components by mass percentage: 70%-95% main crystalline phase and 5%-30% binder; wherein the main crystalline phase is cubic boron nitride powder, and the constituent elements of the binder are selected from at least three of Ti, Al, Cr, Si, C, and N; S2. Evenly mix the binder and cubic boron nitride powder, and obtain a mixed powder by drying; S3. The mixed powder is loaded into a synthesis mold and assembled into a synthesis block, which is then sintered at high temperature and high pressure in a six-sided top press according to the set process parameters, with a pressure of 4-8 GPa, a temperature of 1200-1600°C, and a sintering time of 10-50 min to obtain a polycrystalline cubic boron nitride composite sheet.

6. The method for preparing a high-toughness polycrystalline cubic boron nitride composite sheet according to claim 5, characterized in that: In step S2, the binder is first ball-milled, and then mixed with cubic boron nitride powder and then ball-milled.

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