JP2014055078A - Cubic boron nitride composition polycrystalline material and manufacturing method thereof, cutting tool and abrasion tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cubic boron nitride composite polycrystalline material having a surface to which a (111) surface having high abrasion resistance orients and having high hardness, to provide a cutting tool having abrasion resistance of a surface which wears at working, and to provide an abrasion tool.SOLUTION: A cubic boron nitride composite polycrystalline material is constituted by wurtzite type boron nitride, cubic boron nitride and inevitable impurities, and has alignment surface having a percentage content of wurtzite type boron nitride of 0.1 to 90 vol.%, an average particle diameter of the cubic boron nitride of 500 nm or less, a ratio of an X-ray diffraction strength Iof a (220) surface of the cubic boron nitride to the X-ray diffraction strength Iof a (111) surface of the cubic boron nitride, I/I, of less than 0.1.

Description

  The present invention relates to a cubic boron nitride composite polycrystal, a method for producing the same, a cutting tool, and an anti-abrasion tool, and more particularly, a cubic boron nitride composite polycrystal having a high orientation, a cutting tool including the polycrystal, and an anti-abrasion tool It is about.

  Cubic boron nitride (cBN) has hardness next to diamond and is excellent in thermal stability and chemical stability. Further, since iron-based materials are more stable than diamond, cBN sintered bodies have been used as processing tools for iron-based materials.

  However, this cBN sintered body contains about 10 to 40% of a binder, and this binder causes a decrease in strength, heat resistance, and thermal diffusibility of the sintered body. Therefore, especially when cutting iron-based materials at a high speed, the thermal load increases, the cutting edge is easily broken or cracked, and the tool life is shortened.

As a method for solving this problem, there is a method of manufacturing a sintered body using a catalyst without using a binder. In this method, hexagonal boron nitride (hBN) is used as a raw material, and magnesium boronitride (Mg ₃ BN ₃ ) or the like is used as a catalyst for reaction sintering. Since the cBN sintered body obtained by this method does not contain a binder, the cBNs are strongly bonded to each other, and the thermal conductivity is increased. Therefore, it is used for heat sink materials and TAB (Tape Automated Bonding) bonding tools. However, since some catalyst remains in the sintered body, when heat is applied, fine cracks due to a difference in thermal expansion between the catalyst and cBN are likely to occur. Further, since the particle size is as large as about 10 μm, the thermal conductivity is high, but the strength is weak and it cannot withstand heavy cutting.

  On the other hand, a cBN sintered body can also be obtained by converting normal pressure type BN such as hBN directly from hBN to cBN at the same time without using a catalyst under an ultra-high pressure and high temperature and simultaneously sintering it (direct conversion sintering method). For example, JP-A-47-34099 (Patent Document 1) and JP-A-3-159964 (Patent Document 2) show a method for obtaining a cBN sintered body by converting hBN to cBN under ultra-high pressure and high temperature. Has been. There is also a method for obtaining a cBN sintered body using pyrolytic boron nitride (pBN) as a raw material. This type of method is disclosed in, for example, Japanese Patent Publication No. 63-394 (Patent Document 3) and Japanese Patent Application Laid-Open No. 8-47801 (Patent Document 4).

  However, with the recent improvement in performance and efficiency of processing machines, the processing speed is increasing. Therefore, when the conventional cBN sintered body and polycrystalline cutting tool are used for high-speed cutting, the tool life is reached in a relatively short time.

  In order to solve the above-mentioned problem, a cutting tool in which a (111) plane of a cBN sintered body synthesized from normal pressure type h-BN at high temperature and high pressure is used as a rake face of a cutting blade is disclosed in Japanese Patent Application Laid-Open No. 8-336705. (Patent Document 5). The wear resistance on the rake face side is improved by producing the tool so that the (111) face of cBN faces the rake face side.

JP 47-34099 A JP-A-3-159964 Japanese Patent Publication No. 63-394 Japanese Patent Laid-Open No. 8-47801 JP-A-8-336705

  However, according to the cBN synthesis method described in JP-A-8-336705, hBN as a raw material is grown by heat treatment to improve crystallinity. In this case, unconverted hBN remains in the sintered body obtained under the sintering conditions of a pressure of 7 GPa and a sintering temperature of 2000 ° C., and the strength and durability are significantly reduced.

  The present invention has been made in view of the above problems, and a cubic boron nitride composite polycrystal having a surface having high wear resistance, a method for producing the same, a cutting tool provided with the polycrystal, and wear resistance The purpose is to provide a tool.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that pyrolytic boron nitride (pBN) and cubic boron nitride (hBN) and wurtzite boron nitride (wBN) under an ultra-high pressure and high temperature. It was found that a cubic boron nitride composite polycrystal having a plane in which cubic boron nitride is oriented in the [111] direction can be obtained.

The cubic boron nitride composite polycrystal according to the present invention is composed of wurtzite boron nitride, cubic boron nitride, and inevitable impurities, and the content of wurtzite boron nitride is 0.1 to 90% by volume. The average particle diameter of cubic boron nitride is 500 nm or less, and the X-ray diffraction intensity I of (220) plane of cubic boron nitride with respect to the X-ray diffraction intensity I ₍₁₁₁₎ of (111) plane of cubic boron nitride. _An orientation plane in which the ratio I ₍₂₂₀₎ / I _{(111) of (220 )} is less than 0.1 is provided.

  In the above cubic boron nitride composite polycrystal, the X-ray diffraction intensity of hexagonal boron nitride is preferably below the detection limit. Here, “below the detection limit” means that the X-ray diffraction intensity is below the detection limit when measured with a CuKα ray having a wavelength of 1.54 mm using an X-ray diffractometer X′Pert manufactured by PANalytical. Say.

  In the cubic boron nitride composite polycrystal, preferably, the Knoop hardness of the orientation plane is 55 GPa or more.

  In the above cubic boron nitride composite polycrystal, the cubic boron nitride preferably has an average particle size of 100 nm or less.

  The method for producing a cubic boron nitride composite polycrystal according to the present invention comprises a step of preparing pyrolytic boron nitride as a starting material, and pyrolytic boron nitride under conditions of a pressure of 8 GPa or more and a temperature of 1900 to 2300 ° C. Directly converting to cubic boron nitride and simultaneously sintering. Pyrolytic boron nitride has a (002) plane spacing of greater than 3.35 and less than or equal to 3.5.

  The cutting tool according to the present invention includes the above cubic boron nitride composite polycrystal, and uses the oriented surface as a rake face or flank face of the cutting edge. A wear-resistant tool according to the present invention includes the above cubic boron nitride composite polycrystal, and uses the above-mentioned orientation surface in a portion where wear resistance is required.

  According to the present invention, it is possible to produce a cubic boron nitride composite polycrystal having a plane in which the (111) plane of cubic boron nitride having high wear resistance is oriented. In addition, according to the present invention, it is possible to provide a cutting tool and an anti-abrasion tool having excellent characteristics provided with the composite polycrystal.

Hereinafter, this embodiment will be described.
(Embodiment)
The cubic boron nitride composite polycrystal according to the present embodiment includes a plurality of cubic boron nitrides (cBN) and a plurality of wurtzite boron nitrides (wBN). Cubic boron nitrides, wurtzite boron nitrides, and cubic boron nitride and wurtzite boron nitride are all firmly bonded and have a dense composite structure. Specifically, the polycrystal is composed of 0.1% by volume or more of wurtzite boron nitride, cubic boron nitride constituting the balance, and inevitable impurities. Inevitable impurities are, for example, nitrogen, hydrogen, oxygen and the like. At this time, the average particle diameter of cubic boron nitride is about 500 nm or less. The polycrystalline body substantially does not contain a binder, a sintering aid, a catalyst and the like.

The cubic boron nitride composite polycrystal of the present embodiment is such that the cubic boron nitride with respect to the X-ray diffraction intensity I ₍₁₁₁₎ of the (111) plane of the cubic boron nitride contained in the cubic boron nitride composite The ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ of the X-ray diffraction intensity I ₍₂₂₀₎ of the (220) plane is less than 0.1. That is, the cubic boron nitride composite polycrystal of the present embodiment includes a surface in which a plurality of cubic boron nitrides included in the cubic boron nitride composite polycrystal are oriented in the [111] direction (hereinafter referred to as “the cubic boron nitride composite polycrystal”). In the cubic boron nitride composite polycrystal, the plane in which the ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ of the X-ray diffraction intensity I _{(220 )} is less than 0.1 is a plane oriented in the [111] direction or (111) orientation plane).

From the examples described later, the content of the wurtzite boron nitride is 0.1% by volume or more, and the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is 0.04 to 0.09. It was confirmed that the cubic boron nitride composite polycrystal had a high hardness of 55 GPa or more in Knoop hardness at room temperature on the orientation plane. Further, from the examples described later, the cubic boron nitride composite having the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ of 0.05 to 0.09 has excellent wear resistance of the orientation plane. I was able to confirm. However, if the content of the wurtzite boron nitride is 0.1% by volume or more and the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is less than 0.1, the same effect can be obtained. It is considered a thing.

In the cubic boron nitride composite polycrystal of the present embodiment, the X-ray diffraction intensity of hexagonal boron nitride is preferably below the detection limit. Hexagonal boron nitride contained in the cubic boron nitride composite polycrystal causes a decrease in hardness of the cubic boron nitride composite polycrystal. From each Example described later, the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is 0.04 to 0.09, and the X-ray diffraction intensity of hexagonal boron nitride is below the detection limit. It was confirmed that the crystal boron nitride composite polycrystal had a high Knoop hardness of 55 GPa or higher at room temperature on the (111) orientation plane.

In addition, the average particle diameter of cubic boron nitride in the cubic boron nitride composite of the present embodiment is preferably about 150 nm or less. From each Example described later, the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is 0.04 to 0.09, and the average particle diameter of cubic boron nitride is about 31 nm or more and 148 nm or less. It was confirmed that the cubic boron nitride composite polycrystal had a high Knoop hardness of 55 GPa or more at room temperature in the (111) orientation plane. However, even if the X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ is less than 0.1 and the average particle diameter of cubic boron nitride is about 150 nm or less, the same effect can be obtained. it is conceivable that.

  Next, the manufacturing method of the cubic boron nitride composite polycrystal of this Embodiment is demonstrated. In the method for producing a cubic boron nitride composite polycrystal according to the present embodiment, a step of preparing pyrolytic boron nitride having a (002) plane spacing of 3.35 to 3.5 mm as a starting material (S01 ) And a step (S02) of directly converting the atmospheric boron nitride into cubic boron nitride at the same time as sintering under a pressure of 8 GPa or more and a temperature of 1300 to 2300 ° C. (S02).

First, in step (S01), pyrolytic boron nitride (pBN) having a (002) plane spacing of 3.35 mm to 3.5 mm is prepared. pBN is preferably highly oriented. The high orientation of pBN here refers to the X-ray diffraction intensity of the (100) plane relative to the X-ray diffraction intensity I ₍₀₀₂₎ of the (002) plane in the X-ray diffraction measurement perpendicular to the c-axis of the pBN crystal. refers to the ratio _{I (100) / I} of I _{(100) (002)} is 2.0 or more.

  Next, in the step (S02), the highly oriented pBN which is a starting material is converted into cubic boron nitride (cBN) and wurtzite boron nitride (wBN) using an ultrahigh pressure and high temperature generator. Sinter at the same time. Sintering is performed under conditions of a pressure of 8 GPa and a temperature of 1300 to 2300 ° C., and the cBN is held for a predetermined time under a pressure condition in which cBN is thermodynamically stable. Preferably, the sintering conditions are a pressure of about 8 GPa to 20 GPa and a temperature of 1300 to 2300 ° C. In the present embodiment, pBN is directly converted and sintered into cBN or wBN without adding a sintering aid or a catalyst under an ultra-high pressure and high temperature.

  In the method for producing a cubic boron nitride composite polycrystal, the sintering temperature is particularly important. When the sintering temperature is higher than 2300 ° C., the fine cBN crystal grows and its average particle size exceeds 500 nm. On the other hand, if the sintering temperature is low, unconverted starting materials remain. Unconverted starting material will be included in the cubic boron nitride composite polycrystal as hexagonal boron nitride. Therefore, in the method for producing a cubic boron nitride composite polycrystal, it is preferable that the sintering conditions are such that no unconverted starting material remains.

  The appropriate sintering temperature for synthesizing the cubic boron nitride composite polycrystal varies depending on the pressure applied during the simultaneous conversion of the starting material and the sintering in step (S02). A cubic boron nitride composite polycrystal can be synthesized at a high temperature when the pressure is low, and at a low temperature when the pressure is high. Further, the temperature and pressure conditions in the step (S02) also vary depending on the crystallinity and particle size of the starting material. For example, in the case of highly oriented pBN that satisfies the above conditions, unconverted starting material remains at a temperature of less than 1900 ° C. at 10 GPa, remains at a temperature of less than 1500 ° C. at 15 GPa, and remains at a temperature of less than 1300 ° C. at 20 GPa. .

  According to the method for producing a cubic boron nitride composite polycrystal of the present embodiment, the content of wBN is 0.1% by volume or more, is composed of wBN, cBN, and inevitable impurities, and the cBN is [111 ] A cubic boron nitride composite polycrystal having a plane oriented in the direction and having an average particle size of cBN of about 500 nm or less can be obtained.

  From the examples described later, in the step (S02), if the sintering conditions are a pressure of about 10 GPa or more and a temperature of about 1300 to 2300 ° C., the obtained cubic boron nitride composite polycrystal has a (111) orientation plane. It was confirmed that the Knoop hardness at room temperature of the (111) orientation plane was 55 GPa. However, it is considered that a cubic boron nitride composite polycrystal having similar characteristics can be obtained even under sintering conditions of a pressure of about 8 GPa or more and about 2300 ° C.

  As described above, the cubic boron nitride composite polycrystal of the present embodiment is composed of 0.1 vol% or more wurtzite boron nitride, cubic boron nitride having an average particle size of 500 nm or less, and inevitable impurities. Is done. Furthermore, the cubic boron nitride composite polycrystal of the present embodiment has a high hardness and excellent wear resistance by including a plane in which the (111) plane of cubic boron nitride having high hardness is oriented. The surface which has can be provided.

  Further, the cubic boron nitride composite polycrystal of the present embodiment can be made to have higher hardness by setting the X-ray diffraction intensity of hexagonal boron nitride to be below the detection limit.

  In addition, the cubic boron nitride composite polycrystal of the present embodiment is dense and has very few voids by setting the average particle size of the cubic boron nitride contained in the cubic boron nitride composite polycrystal to 150 nm or less. Since the crystal structure can be obtained, the hardness can be further increased.

  Furthermore, the cubic boron nitride composite polycrystal of the present embodiment can be used for cutting tools, wear-resistant tools, and the like. At this time, the surface (orientation surface) oriented in the [111] direction of the cubic boron nitride contained in the cubic boron nitride composite polycrystal of the present embodiment is in contact with the workpiece and faces the surface with a large amount of wear. Thus, by producing a tool, it can be set as the cutting tool or the wear-resistant tool excellent in abrasion resistance.

  For example, when cutting with a large feed amount (feed speed), friction with chips on the rake face of the cutting tool increases. Therefore, it is possible to extend the cutting tool life by making the tool so that the (111) -oriented surface of the cubic boron nitride composite polycrystal of the present embodiment faces the rake face.

  For example, when cutting with a small feed amount (feed speed), the flank face of the cutting tool wears from friction with the finished surface of the workpiece, so that the surface oriented in the [111] direction is directed to the flank face. It is possible to extend the life of the cutting tool by manufacturing the tool.

  Next, examples of the present invention will be described.

Cubic boron nitride composite polycrystals according to Examples 1 to 4 were produced by the following method. First, as a starting material, the (002) plane spacing is 3.36 mm, and in the X-ray diffraction measurement in the direction perpendicular to the c-axis, the (100) plane with respect to the (002) plane X-ray diffraction intensity I ₍₀₀₂₎ A highly oriented pBN having a ratio I ₍₁₀₀₎ / I ₍₀₀₂₎ of X-ray diffraction intensity I ₍₁₀₀₎ of 4.0 was prepared. Further, a cubic boron nitride composite polycrystal according to Example 5 was prepared by the following method. As a starting material, the (002) plane spacing is 3.47 mm, and in the X-ray diffraction measurement perpendicular to the c-axis, the (100) plane X with respect to the (002) plane X-ray diffraction intensity I ₍₀₀₂₎ A highly oriented pBN having a line diffraction intensity I ₍₁₀₀₎ ratio I ₍₁₀₀₎ / I ₍₀₀₂₎ of 3.4 was prepared. The starting material was put into a capsule made of a refractory metal, and held for 20 minutes under the pressure and temperature conditions shown in Table 1 using an ultrahigh pressure and high temperature generator to directly convert the starting material to cBN and wBN.

  A cubic boron nitride polycrystal according to Comparative Example 1 was produced by the following method. First, commercially available pelletized hBN was used as a starting material. The starting material was put into a capsule made of a refractory metal, and was held for 15 minutes under the pressure and temperature conditions shown in Table 1 using an ultrahigh pressure and high temperature generator to directly convert the starting material to cBN. In addition, as long as the holding time in the ultra-high pressure and high-temperature generator exceeds the time necessary for converting and sintering the starting material to cBN or wBN, the obtained cubic boron nitride composite Properties such as hardness and wear resistance of the polycrystal are not affected. That is, with regard to the present example and the comparative example, whether the holding time is 15 minutes or 20 minutes does not cause a difference in the characteristics of the cubic boron nitride composite polycrystal.

A cubic boron nitride composite polycrystal according to Comparative Example 2 was produced by the following method. First, as a starting material, the (002) plane spacing is 3.51 mm and the (100) plane with respect to the (002) plane X-ray diffraction intensity I ₍₀₀₂₎ in the X-ray diffraction measurement in the direction perpendicular to the c-axis. A low-orientation pBN having a ratio I ₍₁₀₀₎ / I ₍₀₀₂₎ of the X-ray diffraction intensity I ₍₁₀₀₎ of 1.0 was prepared. The starting material was put into a capsule made of a refractory metal, and held for 20 minutes under the pressure and temperature conditions shown in Table 1 using an ultrahigh pressure and high temperature generator to directly convert the starting material to cBN and wBN.

  In addition, X-ray diffraction performed to determine the orientation of pBN used an X-ray diffractometer (X'Pert) manufactured by Spectris.

  The composition, particle size, and hardness of the cubic boron nitride composite polycrystals of Examples 1 to 4 and Comparative Examples 1 and 2 obtained as described above were measured by the following methods.

  The composition of each phase was obtained by identifying each phase with an X-ray diffractometer (X′Pert manufactured by PANalytical). The X-ray source of this apparatus is Cu, which is a Kα ray with a wavelength of 1.54 mm.

  The average particle diameters of the samples listed in Table 1 were measured with a scanning electron microscope (ULTRA 55 manufactured by Carl Zeiss). A cutting method was used as a method for obtaining the average particle diameter. In this method, first, a circle is written on an image of a scanning electron microscope (SEM), eight straight lines are drawn radially from the center of the circle to the outer periphery of the circle, and the number of lines that cross the grain boundary in the circle is counted. Then, the average intercept length is obtained by dividing the length of the straight line by the number of crossing, and the average crystal grain size is obtained by multiplying the average intercept length by 1.128.

  The magnification of the SEM image used to use the cutting method is 30000 times. The reason for this is that at a magnification less than this, the number of grains in the circle increases, the grain boundaries are difficult to see, and counting mistakes occur, and the possibility of including a plate-like structure when drawing a line increases. is there. Further, when the magnification is higher than this, the number of grains in the circle is too small, and an accurate average particle diameter cannot be calculated.

  In this experiment, three SEM images obtained by photographing different locations were used for one sample. The average value was made into the average particle diameter using the cutting method with respect to each SEM image.

The orientation was evaluated using the X-ray diffractometer. The X-ray diffraction method, the ratio _I of the cubic boron complex polycrystalline body nitride cubic boron nitride (220) plane diffraction intensity _I and ₍₂₂₀₎ and (111) diffraction intensity of the plane _{I (111) (220 )} / I ₍₁₁₁₎ was calculated.

  In the cubic boron nitride composite polycrystal, Knoop hardness was measured as a measurement of the hardness at room temperature on the plane (orientation plane) in which the cubic boron nitride is oriented in the [111] direction. The Knoop hardness was measured using a micro Knoop indenter with a test load of 4.9 N. Nikon QM type was used as the measuring instrument.

Table 1 shows the composition, X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ , particle size, and hardness of the cubic boron nitride composite polycrystals of Examples 1 to 5 and Comparative Examples 1 and 2.

As shown in Table 1, Examples 1 to 5 were confirmed to contain 0.20 to 80.5% by volume of wurtzite boron nitride (wBN). Moreover, the average particle diameter of Examples 1-5 was 31-148 nm. At this time, the X-ray intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ in the (111) orientation plane of Examples 1 to 5 was 0.03 to 0.09. Furthermore, the Knoop hardness at room temperature on the (111) oriented surfaces of Examples 1 to 5 was 55 to 57 GPa under the condition of a test load of 4.9 N.

On the other hand, it was confirmed that Comparative Example 1 contained no wurtzite boron nitride (wBN) and contained 0.08% by volume of hexagonal boron nitride (hBN). Moreover, the average particle diameter of the comparative example 1 was 412 nm, and was large compared with Examples 1-5. The X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ was 0.05 and the same as in Examples 1 to 5, but the Knoop hardness in the (111) orientation plane of Comparative Example 1 was 47 GPa. Yes, compared with Examples 1-5.

Comparative Example 2 was confirmed to contain 1.1% wurtzite boron nitride (wBN). Moreover, the average particle diameter of the comparative example 1 was 99 nm, and was equivalent compared with Examples 1-5. The X-ray diffraction intensity ratio I ₍₂₂₀₎ / I ₍₁₁₁₎ was 0.22, which was higher than those of Examples 1 to 5, was not oriented in any plane, and was isotropic. . The Knoop hardness at room temperature was 50 GPa, which was low as compared with Examples 1-5.

  That is, the cubic boron nitride composite polycrystals of Examples 1 to 5 contain hexagonal boron nitride and do not contain wurtzite boron nitride, compared to the cubic boron nitride polycrystal of Comparative Example 1 ( It was confirmed that the 111) orientation plane had high hardness. In addition, it was confirmed that the cubic boron nitride composite polycrystals of Examples 1 to 5 had higher hardness than the cubic boron nitride composite polycrystal of Comparative Example 2.

Further, in order to compare the wear resistance of the face oriented in the [111] direction of the cubic boron nitride composite polycrystal, a wear test was conducted. The abrasion test was conducted by the following method. A sample of 2.0 × 2.0 mm size is placed on a diamond grinder with a particle size of # 800 with a metal bond, and the grinder is rotated at 1000 rpm with a load of 0.7 kg / mm ² applied to the sample. The surface in contact with the polishing machine was worn, and the amount of wear was compared. The test was performed on the cubic boron nitride composite polycrystals of Examples 1 to 5 and Comparative Examples 1 and 2.

  Examples 1 to 5 and Comparative Example 1 were tested by placing the surface oriented in the [111] direction in contact with the polishing disc. Since Comparative Example 2 is isotropic, the test was conducted with the randomly selected surface placed in contact with the polishing machine. The results are shown in Table 2. In Examples 1 to 5, the wear amount was 0.6 to 0.9 times that of Comparative Examples 1 and 2.

  In other words, the cubic boron nitride composite polycrystals of Examples 1 to 5 have wear resistance compared to the cubic boron nitride composite polycrystal of Comparative Example 2 by making the (111) -oriented surface wear. It was confirmed that there was an improvement. Further, the cubic boron nitride composite polycrystals of Examples 1 to 5 containing wurtzite boron nitride are more resistant to the cubic boron nitride composite polycrystal of Comparative Example 1 not containing wurtzite boron nitride. It was confirmed that the wearability was improved.

  Although the embodiments and examples of the present invention have been described above, various modifications can be made to the above-described embodiments and examples. Further, the scope of the present invention is not limited to the above-described embodiments and examples. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (8)

Consists of wurtzite boron nitride, cubic boron nitride and inevitable impurities,
The content of the wurtzite boron nitride is 0.1% by volume or more,
The cubic boron nitride has an average particle size of 500 nm or less,
The ratio of the X-ray diffraction intensity I ₍₂₂₀₎ of the (220) plane of the cubic boron nitride to the X-ray diffraction intensity I ₍₁₁₁₎ of the (111) plane of the cubic boron nitride I ₍₂₂₀₎ / I _{(111 )} Is a cubic boron nitride composite polycrystal having an orientation plane of less than 0.1.   The cubic boron nitride composite polycrystal according to claim 1, wherein the X-ray diffraction intensity of hexagonal boron nitride is below the detection limit.   The cubic boron nitride composite polycrystal according to claim 1 or 2, wherein the Knoop hardness in the orientation plane is 55 GPa or more.   The cubic boron nitride composite polycrystal according to any one of claims 1 to 3, wherein an average particle diameter of the cubic boron nitride is 150 nm or less.   A cutting tool comprising the cubic boron nitride composite polycrystal according to any one of claims 1 to 4, wherein the oriented surface is used as a rake face or flank face of a cutting edge.   A wear-resistant tool comprising the cubic boron nitride composite polycrystal according to any one of claims 1 to 4, wherein the oriented surface is used in a portion where wear resistance is required. Preparing pyrolytic boron nitride as a starting material;
A step of directly converting the pyrolytic boron nitride into cubic boron nitride and sintering at the same time under conditions of a pressure of 8 GPa or more and a temperature of 1300 to 2300 ° C. A method for producing a cubic boron nitride composite polycrystal having an interplanar spacing of 3.35 to 3.5 mm. The pyrolytic boron nitride, in the X-ray diffraction measurement in the direction perpendicular to the c axis, the ratio of the (002) plane of the X-ray diffraction intensity _{I (002),} (100) plane of the X-ray diffraction intensity _{I (100)} The method for producing a cubic boron nitride composite polycrystal according to claim 7, wherein I ₍₁₀₀₎ / I ₍₀₀₂₎ is 2.0 or more.