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

Abstract

The application relates to a polycrystalline cubic boron nitride composite sheet and a preparation method thereof. The polycrystalline cubic boron nitride composite sheet comprises a hard alloy base layer and a polycrystalline cubic boron nitride layer superimposed on the hard alloy base layer; the preparation raw material of the polycrystalline cubic boron nitride layer comprises 55-70 wt% cubic boron nitride micropowder and 30-45 wt% ceramic binder micropowder, and the particle size of the ceramic binder micropowder is 50-180 nm. The ceramic binder in the polycrystalline cubic boron nitride composite sheet is a nano ceramic binder (the particle size is 50-180 nm), the ceramic binder with the size has the characteristics of small size and high activity, can easily fill the gap in the material, can not only significantly increase the density of the composite material, reduce or eliminate the "bridge effect", make the stress distribution in the material more uniform, but also can inhibit the crack propagation, and further improve the toughness of the PCBN composite sheet.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite superhard material, in particular to a polycrystalline cubic boron nitride compact and a preparation method thereof. BACKGROUND

[0002] The polycrystalline cubic boron nitride (PCBN) compact is a composite superhard material synthesized by cubic boron nitride powder, a binder and a hard alloy substrate under high temperature and high pressure. The PCBN compact has excellent properties such as high hardness, high wear resistance and high chemical stability, and is mainly used for machining various quenched steels, thermal spraying materials, chilled cast iron and difficult-to-cut materials such as cobalt-based and nickel-based materials with HRC 35 or above.

[0003] Currently, the binders for sintering PCBN mainly include metals in groups IVB, VB and VIB of the periodic table of elements and their nitrides, carbides or carbonitrides, and aluminum, cobalt, nickel or their alloys. The PCBN compact can be divided into ceramic binder type PCBN compact and metal binder type PCBN compact according to the binder. Generally, the ceramic binder type PCBN compact has high heat resistance and is mainly used for cutting high-hardness metals such as quenched steel, while the metal binder type PCBN compact has good toughness and is mainly used for cutting cast iron metals. According to the content of cubic boron nitride powder, the PCBN compact can be divided into high-content PCBN compact and low-content PCBN compact. Cubic boron nitride powder with a content higher than 80% is generally referred to as high-content PCBN compact, while cubic boron nitride powder with a content lower than 80% is generally referred to as low-content PCBN compact.

[0004] For low-content PCBN compact, although it has high temperature resistance and high hardness and has great advantages in machining quenched steel, low-content PCBN is generally synthesized by using a ceramic binder, which makes it generally have greater brittleness and is prone to collapse during machining of quenched steel, thereby affecting the service life.

[0005] Therefore, it is urgent to solve the problem of poor toughness of low-content PCBN compact and improve the cutting life. SUMMARY

[0006] In order to solve the problems in the prior art, the present application provides a polycrystalline cubic boron nitride compact. The PCBN compact has a more compact and fine microstructure by using a nano ceramic binder, thereby solving the problem of poor toughness of low-content PCBN compact to a certain extent and improving the cutting life.

[0007] To this end, the first aspect of the present application provides a polycrystalline cubic boron nitride compact, which comprises a cemented carbide substrate layer and a polycrystalline cubic boron nitride layer superimposed on the cemented carbide substrate layer; the polycrystalline cubic boron nitride layer is prepared from raw materials, which comprise 55-70 wt% cubic boron nitride micropowder and 30-45 wt% ceramic binder micropowder, and the particle size of the ceramic binder micropowder is 50-180 nm.

[0008] The prior art often uses micron-sized ceramic binder as the binder of low-content PCBN compact, which has poor activity and poor affinity with cubic boron nitride micropowder, and the two are mechanically combined together at high temperature and high pressure. In addition, the use of coarse-grained ceramic binder leads to obvious "bridging effect" of the synthesized PCBN, and cracks are easily generated. The binder in the polycrystalline cubic boron nitride layer of the polycrystalline cubic boron nitride compact described in the present application creatively uses nanometer ceramic binder with a particle size of 50-180 nm. The ceramic binder with this size has the characteristics of small size and high activity, and can easily fill the gaps in the material, not only can significantly increase the density of the composite material, reduce or eliminate the "bridging effect", make the stress distribution in the material more uniform, but also can inhibit the propagation of cracks, and further improve the toughness of the PCBN compact.

[0009] In some embodiments, the particle size of the ceramic binder micropowder can be 50 nm, 80 nm, 100 nm, 120 nm, 150 nm or 180 nm, etc.

[0010] In some preferred embodiments, the particle size of the ceramic binder micropowder is 80-120 nm. In some most preferred embodiments, the particle size of the ceramic binder micropowder is 100 nm.

[0011] By further controlling the particle size of the ceramic binder micropowder to be 80-120 nm, especially 100 nm, the polycrystalline cubic boron nitride compact obtained by the present application has a more compact and fine microstructure, and the toughness of the PCBN compact is further improved.

[0012] In some embodiments, the ceramic binder is selected from at least one of TiN, TiCN, TiC, Al2O3, TiB2, AlN and HfB2.

[0013] In some preferred embodiments, the ceramic binder is selected from at least one of TiN, TiCN and TiC. For example, the ceramic binder can be TiN, a mixture of TiN and TiCN, a mixture of TiCN and TiC, a mixture of TiN and TiC, and a mixture of TiN, TiCN and TiC.

[0014] In some further preferred embodiments, the ceramic binder is a mixture of TiN and TiCN, a mixture of TiCN and TiC, a mixture of TiN and TiC, or a mixture of TiN, TiCN and TiC.

[0015] The binder plays an important role in the process of synthesizing polycrystalline cubic boron nitride, and the addition of an appropriate amount of binder can reduce the sintering temperature and pressure, and improve the performance of the prepared polycrystalline cubic boron nitride; and different binders have different effects on the performance of the PCBN composite sheet. The selection of the above-mentioned types of ceramic binders can improve the performance of the PCBN composite sheet, and further improve the toughness of the PCBN composite sheet.

[0016] In some embodiments, the cubic boron nitride micropowder includes coarse-grained cubic boron nitride micropowder with a particle size of 2-5 um and fine-grained cubic boron nitride micropowder with a particle size of 0-1 um.

[0017] The particle size of the cubic boron nitride micropowder directly determines the density and microstructure of the PCBN composite sheet. The selection of the above-mentioned mixed particle size of the cubic boron nitride micropowder in the range of particle size can achieve the purpose of filling the gaps between coarse particles with fine particles, thereby effectively improving the density of the initial powder and ultimately improving the density and uniformity of the microstructure of the synthesized PCBN composite sheet, and obtaining a PCBN composite sheet with better toughness.

[0018] In some embodiments, the mass ratio of the coarse-grained cubic boron nitride micropowder to the fine-grained cubic boron nitride micropowder is (2-3):1.

[0019] In some specific embodiments, the mass ratio of the coarse-grained cubic boron nitride micropowder to the fine-grained cubic boron nitride micropowder can be, for example, 2:1, 2.5:1 or 3:1, etc.

[0020] In some preferred embodiments, the mass ratio of the coarse-grained cubic boron nitride micropowder to the fine-grained cubic boron nitride micropowder is 2.5:1.

[0021] By controlling the mass ratio of the coarse-grained cubic boron nitride micropowder to the fine-grained cubic boron nitride micropowder within the above range, especially when the mass ratio is 2.5:1, the density and uniformity of the microstructure of the PCBN composite sheet can be further improved, thereby making the toughness of the PCBN composite sheet better.

[0022] In some embodiments, the thickness of the cemented carbide substrate layer in the polycrystalline cubic boron nitride compact is 1.0-6.0 mm, and the thickness of the polycrystalline cubic boron nitride layer is 0.5-1.5 mm.

[0023] The cemented carbide substrate used in the present application is a cobalt-containing cemented carbide, and the content of cobalt in the cemented carbide can be 8-16 wt%. For example, commercially available cemented carbides YG8-YG16 can be used.

[0024] The second aspect of the present application provides a method for preparing the polycrystalline cubic boron nitride compact as described in the first aspect of the present application, which comprises the following steps:

[0025] S1, drying the mixed powder of the polycrystalline cubic boron nitride micropowder and the ceramic binder micropowder and then placing it in a vacuum furnace for reduction to obtain a reduced powder;

[0026] S2, encapsulating the reduced mixed powder with the cemented carbide substrate and then sintering under high temperature and high pressure to obtain the polycrystalline cubic boron nitride compact.

[0027] The method for preparing the polycrystalline cubic boron nitride compact described in the present application is simple, and during the preparation process, by adding nano ceramic binder, the prepared PCBN compact has the characteristics of high density, good toughness and strong impact resistance, the proportion of cracks generated during laser cutting processing is greatly reduced, the impact resistance during cutting processing of quenched steel is also significantly improved, and the service life is much higher than that of other materials of the same type on the market.

[0028] In some embodiments, in step S1, the mixing method is wet mixing, and the dispersing agent used in the wet mixing process is alcohol, and the mass ratio of the total mass of the cubic boron nitride micropowder and the ceramic binder micropowder to the mass of the dispersing agent is (2-3):1.

[0029] The use of wet mixing in the present application can make the mixing of the mixed material more uniform, and the use amount of the powder (cubic boron nitride micropowder and ceramic binder micropowder) and the dispersing agent (alcohol) in the wet mixing process is controlled within the above range, which is more helpful to improve the uniformity of the mixed material.

[0030] In some embodiments, the drying is carried out in a vacuum oven, and the drying conditions are as follows: drying at 50-60°C for 1.5-2 hours, and then drying at 130-150°C for 1-2 hours.

[0031] In some specific embodiments, the drying conditions are as follows: drying at 50°C for 2 hours, and then drying at 150°C for 1 hour.

[0032] In the present application, the vacuum degree in the vacuum oven can be (1-5) x 10-2 Pa, such as 3x10 -2 Pa.

[0033] In some embodiments, in step S1, the reduction process is: heating the mixed powder under a vacuum degree of (3-8) x 10 -3 Pa; the heating process is: increasing the temperature to 550-600℃ within 25-30 min, and maintaining the temperature for 120-150 min.

[0034] In some specific embodiments, the reduction process is: heating the mixed powder under a vacuum degree of 5x10 -3 Pa; the heating process is: increasing the temperature to 600℃ within 30 min, and maintaining the temperature for 120 min.

[0035] In some embodiments, in step S2, the sintering pressure is 4.0-5.5 Gpa, the temperature is 1300-1600℃, and the time is 5-20 min.

[0036] Under the above sintering conditions, the encapsulated green body can be effectively compounded, and a PCBN composite sheet with better comprehensive performance can be prepared.

[0037] The poly crystalline cubic boron nitride composite sheet has the following beneficial technical effects: the ceramic binder in the poly crystalline cubic boron nitride layer is a nano ceramic binder (particle size is 50-180 nm), which has the characteristics of small size and high activity, can easily fill the gaps in the material, can significantly increase the density of the composite material, reduce or eliminate the "bridging effect", make the stress distribution in the material more uniform, inhibit the expansion of cracks, and thus improve the toughness of the PCBN composite sheet. At the same time, the preparation method of the poly crystalline cubic boron nitride composite sheet is simple, and the obtained PCBN composite sheet has the characteristics of high density, good toughness, and strong impact resistance. The proportion of cracks generated in the laser cutting process is greatly reduced, the impact resistance in the cutting process of quenched steel is obviously improved, and the service life is much higher than that of other materials of the same type on the market. DETAILED DESCRIPTION

[0038] In order to make the present application easier to understand, the present application will be further described in detail below in combination with embodiments, which only serve an illustrative purpose and do not limit the application scope of the present application. The raw materials or components used in the present application can be prepared by commercial channels or conventional methods if not specifically stated.

[0039] Example 1: Preparation of a poly crystalline cubic boron nitride composite sheet

[0040] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder with a particle size of 2-5um; 20wt% of fine-grained cubic boron nitride powder with a particle size of 0-1um; and 30wt% of TiN ceramic binder powder with a particle size of 100nm. The content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0041] The hard alloy substrate in the hard alloy substrate layer is hard alloy YG12 with a cobalt content of 12wt%.

[0042] The preparation process is as follows: the above-mentioned polycrystalline cubic boron nitride powder and ceramic binder powder are mixed by wet mixing method, and the dispersing agent used in the wet mixing process is alcohol. The mass ratio of the powder (polycrystalline cubic boron nitride powder and ceramic binder powder) to the dispersing agent is 2:1. The mixed powder after wet mixing is placed in a vacuum oven for drying. The drying process is as follows: first, drying at 50℃ for 2 hours, then heating to 150℃ for 1 hour. The vacuum degree of the oven is 3×10 -2 Pa. The mixed powder after drying is placed in a vacuum furnace for vacuum reduction to remove oxygen and water in the mixed powder. The specific process is as follows: sequentially start the vacuum pumps of the vacuum furnace for vacuum treatment until the high vacuum degree of 5×10 -3 Pa is reached; heating is carried out at the above-mentioned vacuum degree. The heating process is as follows: heating to 600℃ for 30min and holding for 120min. The reduced mixed powder is packaged with the hard alloy substrate. The packaged blank is sintered at a pressure of 5.0Gpa and a temperature of 1500℃ for 20min for compounding to obtain a polycrystalline cubic boron nitride composite sheet. The thickness of the polycrystalline cubic boron nitride layer in the polycrystalline cubic boron nitride composite sheet is 1.0mm, and the thickness of the hard alloy substrate layer is 3.0mm.

[0043] Example 2: Preparation of a polycrystalline cubic boron nitride composite sheet

[0044] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder with a particle size of 2-5um; 20wt% of fine-grained cubic boron nitride powder with a particle size of 0-1um; and 30wt% of TiC ceramic binder powder with a particle size of 100nm. The content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0045] The rest is the same as in Example 1.

[0046] Example 3: Preparation of a polycrystalline cubic boron nitride composite sheet

[0047] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of 2-5um coarse-grained cubic boron nitride powder; 20wt% of 0-1um fine-grained cubic boron nitride powder; 30wt% of 100nm TiNC ceramic binder powder; the content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0048] The rest is the same as in Example 1.

[0049] Example 4: Preparation of polycrystalline cubic boron nitride composite sheet

[0050] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of 2-5um coarse-grained cubic boron nitride powder; 20wt% of 0-1um fine-grained cubic boron nitride powder; 30wt% of 100nm TiB2 ceramic binder powder; the content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0051] The rest is the same as in Example 1.

[0052] Example 5: Preparation of polycrystalline cubic boron nitride composite sheet

[0053] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of 2-5um coarse-grained cubic boron nitride powder; 20wt% of 0-1um fine-grained cubic boron nitride powder; 15wt% of 100nm TiN ceramic binder powder; 15wt% of 100nm TiC ceramic binder powder; the content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1, and the mass ratio of TiN ceramic binder powder to TiC ceramic binder powder is 1:1.

[0054] The rest is the same as in Example 1.

[0055] Example 6: Preparation of polycrystalline cubic boron nitride composite sheet

[0056] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder of 2-5um; 20wt% of fine-grained cubic boron nitride powder of 0-1um; 10wt% of TiN ceramic binder powder of 100nm; 10wt% of TiC ceramic binder powder of 100nm; 10wt% of TiNC ceramic binder powder of 100nm; the content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1, and the mass ratio of TiN ceramic binder powder, TiC ceramic binder powder and TiNC ceramic binder powder is 1:1:1.

[0057] The rest is the same as in Example 1.

[0058] Example 7: Preparation of polycrystalline cubic boron nitride composite sheet

[0059] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder of 2-5um; 20wt% of fine-grained cubic boron nitride powder of 0-1um; 30wt% of TiC ceramic binder powder of 50nm; the content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0060] The rest is the same as in Example 1.

[0061] Example 8: Preparation of polycrystalline cubic boron nitride composite sheet

[0062] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder of 2-5um; 20wt% of fine-grained cubic boron nitride powder of 0-1um; 30wt% of TiC ceramic binder powder of 180nm; the content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0063] The rest is the same as in Example 1.

[0064] Example 9: Preparation of polycrystalline cubic boron nitride composite sheet

[0065] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder with a particle size of 2-5um; 20wt% of fine-grained cubic boron nitride powder with a particle size of 0-1um; and 30wt% of TiC ceramic binder powder with a particle size of 250nm. The content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0066] The rest is the same as in Example 1.

[0067] Example 10: Preparation of a polycrystalline cubic boron nitride composite sheet

[0068] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder with a particle size of 2-5um; 20wt% of fine-grained cubic boron nitride powder with a particle size of 0-1um; and 30wt% of TiC ceramic binder powder with a particle size of 250nm. The content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0069] The rest is the same as in Example 1.

[0070] Example 11: Preparation of a polycrystalline cubic boron nitride composite sheet

[0071] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder with a particle size of 2-5um; 20wt% of fine-grained cubic boron nitride powder with a particle size of 0-1um; and 30wt% of TiC ceramic binder powder with a particle size of 250nm. The content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0072] The rest is the same as in Example 1.

[0073] Example 12: Preparation of a polycrystalline cubic boron nitride composite sheet

[0074] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 50wt% of coarse-grained cubic boron nitride powder with a particle size of 2-5um; 20wt% of fine-grained cubic boron nitride powder with a particle size of 0-1um; and 30wt% of TiC ceramic binder powder with a particle size of 250nm. The content of cubic boron nitride powder in the raw material is 70wt%, the content of ceramic binder powder is 30wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 2.5:1.

[0075] The rest is the same as in Example 1.

[0076] Example 13: Preparation of polycrystalline cubic boron nitride compact

[0077] The raw material composition of the polycrystalline cubic boron nitride layer is as follows: 45 wt% of coarse-grained cubic boron nitride powder of 2-5 um; 15 wt% of fine-grained cubic boron nitride powder of 0-1 um; and 40 wt% of TiC ceramic binder powder of 100 nm. The content of cubic boron nitride powder in the raw material is 60 wt%, the content of ceramic binder powder is 40 wt%, and the mass ratio of coarse-grained cubic boron nitride powder to fine-grained cubic boron nitride powder in the cubic boron nitride powder is 3:1.

[0078] The rest is the same as Example 11.

[0079] Example 14: Preparation of polycrystalline cubic boron nitride compact

[0080] The raw materials of the polycrystalline cubic boron nitride layer and the cemented carbide substrate layer are the same as Example 1.

[0081] Preparation process: The above polycrystalline cubic boron nitride powder and ceramic binder powder are mixed by wet mixing method, and the dispersing agent used in the wet mixing process is alcohol. The mass ratio of the powder (polycrystalline cubic boron nitride powder and ceramic binder powder) to the dispersing agent is 2:1. The mixed powder after wet mixing is placed in a vacuum oven for drying. The drying process is as follows: drying at 150°C for 2 hours, and the vacuum degree of the oven is 3x10 -2 Pa. The mixed powder after drying is placed in a vacuum furnace for vacuum reduction to remove oxygen and water in the mixed powder. The specific process is as follows: sequentially start the vacuum pumps of the vacuum furnace for vacuum treatment until the high vacuum degree of 2x10 -3 Pa is reached; heating is carried out at the above vacuum degree. The heating process is as follows: 20 min to 400°C, holding for 30 min, then 30 min to 800°C, holding for 120 min. The reduced mixed powder is packaged with the cemented carbide substrate. The green body after packaging is sintered at a pressure of 5.0 Gpa and a temperature of 1500°C for 20 min for compounding to obtain a polycrystalline cubic boron nitride compact. The thickness of the polycrystalline cubic boron nitride layer in the polycrystalline cubic boron nitride compact is 1.0 mm, and the thickness of the cemented carbide substrate layer is 3.0 mm.

[0082] Example 15: Preparation of polycrystalline cubic boron nitride compact

[0083] The raw materials of the polycrystalline cubic boron nitride layer and the cemented carbide substrate layer are the same as Example 1.

[0084] Preparation process: the above polycrystalline cubic boron nitride powder and ceramic binder powder are mixed by wet mixing method, and the dispersing agent used in the wet mixing process is alcohol, and the mass ratio of the powder (polycrystalline cubic boron nitride powder and ceramic binder powder) to the dispersing agent is 2:1. The mixed powder after wet mixing is placed in a vacuum oven for drying, and the drying process is as follows: first, 50℃ for 2 hours, then 150℃ for 1 hour, and the vacuum degree of the oven is 3×10 -2 Pa. The mixed powder after drying is placed in a vacuum furnace for vacuum reduction to remove oxygen and water in the mixed powder, and the specific process is as follows: sequentially start the vacuum pumps of the vacuum furnace for vacuum treatment until the high vacuum degree of 2×10 -3 Pa is reached; heating is carried out at the above vacuum degree, and the heating process is as follows: 30min to 500℃, and holding for 140min. The reduced mixed powder is packaged with a hard alloy substrate, and the packaged blank is compounded at a pressure of 5.0Gpa and a temperature of 1500℃ for 20min to prepare a polycrystalline cubic boron nitride composite sheet. The thickness of the polycrystalline cubic boron nitride layer in the polycrystalline cubic boron nitride composite sheet is 1.0mm, and the thickness of the hard alloy substrate layer is 3.0mm.

[0085] Test example

[0086] The density, fracture toughness and impact toughness of the polycrystalline cubic boron nitride composite sheet prepared in examples 1-15 are detected, wherein the density is tested by drainage method, the fracture toughness is calculated by the four-corner crack length of the pressure pit pressed by the indenter of the Vickers hardness tester, and the impact toughness is tested by the bending strength through three-point bending method. The specific detection results are shown in Table 1.

[0087] Table 1: performance test results of polycrystalline cubic boron nitride composite sheet

[0088]

[0089]

[0090] From the detection results in Table 1, the density of the polycrystalline cubic boron nitride composite sheet synthesized in examples 1-15 is 3.78-4.12g / m 3 , the fracture toughness is 5.3-6.7MPa / m 2 , and the impact toughness is 36-50KJ / m 2 , which shows that the polycrystalline cubic boron nitride composite sheet provided by the application has high density and excellent fracture toughness and impact toughness.

[0091] From the test results of Examples 1-6, it can be seen that when the ceramic binder used is selected from at least one of TiN, TiCN and TiC, especially at least two of TiN, TiCN and TiC, the density and toughness of the polycrystalline cubic boron nitride compact prepared can be better.

[0092] From the test results of Examples 1, 7-10, it can be seen that when the particle size of the ceramic binder powder used is 50-180 nm, especially 100 nm, the density and toughness of the polycrystalline cubic boron nitride compact can be further improved, and thus its performance can be improved.

[0093] From the test results of Examples 1, 11-12, it can be seen that when the mass ratio of coarse cubic boron nitride powder to fine cubic boron nitride powder in the cubic boron nitride powder used is (2-3): 1, especially 2.5, the density and toughness of the polycrystalline cubic boron nitride compact can be more favorably improved.

[0094] It should be noted that the above-described examples are only used to explain the present application and do not constitute any limitation on the present application. The present application has been described by referring to typical examples, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. The present application can be modified within the scope of the claims, and the present application can be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and examples, it does not mean that the present application is limited to the specific examples disclosed therein, on the contrary, the present application can be extended to all other methods and applications having the same function.

Claims

1. A polycrystalline cubic boron nitride compact, characterized by, The polycrystalline cubic boron nitride compact comprises a cemented carbide substrate layer and a polycrystalline cubic boron nitride layer stacked on the cemented carbide substrate layer; the polycrystalline cubic boron nitride layer is prepared from raw materials including 55-70 wt% cubic boron nitride micropowder and 30-45 wt% ceramic binder micropowder, and the particle size of the ceramic binder micropowder is 100-180 nm; The ceramic binder is a mixture of TiN, TiCN and TiC; The cubic boron nitride micropowder includes coarse cubic boron nitride micropowder with a particle size of 2-5 um and fine cubic boron nitride micropowder with a particle size of 0-1 um, and the mass ratio of the coarse cubic boron nitride micropowder to the fine cubic boron nitride micropowder is (2-3):

1.

2. The polycrystalline cubic boron nitride compact according to claim 1, wherein The thickness of the cemented carbide substrate layer in the polycrystalline cubic boron nitride compact is 1.0-6.0 mm, and the thickness of the polycrystalline cubic boron nitride layer is 0.5-1.5 mm.

3. A method of producing a polycrystalline cubic boron nitride compact as claimed in claim 1 or 2, characterized by, The method comprises the following steps: S1, after drying the mixed powder of the polycrystalline cubic boron nitride micropowder and the ceramic binder micropowder, the mixed powder is placed in a vacuum furnace for reduction to obtain a reduced powder; S2, after packaging the reduced mixed powder and the cemented carbide substrate, sintering is performed under high temperature and high pressure conditions to obtain the polycrystalline cubic boron nitride compact.

4. The method of claim 3, wherein, In step S1, the mixing method is wet mixing, and the dispersing agent used in the wet mixing process is alcohol, and the mass ratio of the total mass of the cubic boron nitride micropowder and the ceramic binder micropowder to the mass of the dispersing agent is (2-3):1; The drying is performed in a vacuum oven, and the drying conditions are as follows: drying at 50-60℃ for 1.5-2 hours, and then drying at 130-150℃ for 1-2 hours.

5. The method according to claim 3 or 4, characterized in that, In step S1, the reduction process is heating the mixed powder under a vacuum degree of (3-8) x 10 -3 Pa; the heating process is: increasing the temperature to 550-600 ℃ within 25-30 min, and maintaining the temperature for 120-150 min.

6. The method according to claim 3 or 4, characterized in that, In step S2, the pressure during sintering is 4.0-5.5 Gpa, the temperature is 1300-1600℃, and the time is 5-20 min.

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