Cubic boron nitride sintered compact and tool

Abstract

Provided is a cubic boron nitride sintered compact comprising cubic boron nitride particles in the amount of 70-99 vol%, and a binder. The binder comprises: a first compound containing chromium, cobalt, and carbon; tungsten carbide; cobalt; and aluminum. In the first compound, the ratio NCr / (NCr+NCo) of the number of chromium atoms NCr to the total of the number of chromium atoms NCr and the number of cobalt atoms NCo is 0.10-0.90.

Description

Cubic boron nitride sintered body and tools

[0001] The present disclosure relates to cubic boron nitride sintered bodies and tools.

[0002] Cubic boron nitride (hereinafter referred to as "cBN") sintered bodies have extremely high hardness and excellent thermal and chemical stability, and are therefore used in cutting tools and wear-resistant tools. The content of cBN particles and the type of binder are being investigated to obtain the properties required for each application.

[0003] Patent Document 1 discloses a technique for suppressing the occurrence of sudden fractures in a tool using a cubic boron nitride sintered body by appropriately selecting a binder.

[0004] WO 2005 / 066381

[0005] The cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body comprising 70% by volume or more and 99% by volume or less of cubic boron nitride particles and a binder, wherein the binder contains: a first compound containing chromium, cobalt, and carbon; tungsten carbide; cobalt; and aluminum; and in the first compound, the number of chromium atoms, N, is 0.01; Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is a cubic boron nitride sintered body having a porosity of 0.10 or more and 0.90 or less.

[0006] [Problem to be Solved by the Present Disclosure] There is a demand for a cubic boron nitride sintered body that, when used as a tool material, can provide a tool with a long tool life even in machining sintered alloys.

[0007] Therefore, an object of the present disclosure is to provide a cubic boron nitride sintered body that, when used as a tool material, can provide a tool with a long tool life even when machining sintered alloys, and a tool including the cubic boron nitride sintered body.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cubic boron nitride sintered body that, when used as a tool material, can provide a tool having a long tool life even when machining sintered alloys, and a tool including the cubic boron nitride sintered body.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) A cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body comprising 70% by volume or more and 99% by volume or less of cubic boron nitride particles and a binder, wherein the binder contains: a first compound containing chromium, cobalt, and carbon; tungsten carbide; cobalt; and aluminum; and in the first compound, the number of chromium atoms, N, is 0.01 to 0.01; Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is a cubic boron nitride sintered body having a porosity of 0.10 or more and 0.90 or less.

[0010] According to the present disclosure, it is possible to provide a cubic boron nitride sintered body that, when used as a tool material, can provide a tool having a long tool life even when machining sintered alloys, and a tool including the cubic boron nitride sintered body.

[0011] (2) In the above (1), in a first graph showing the X-ray diffraction pattern of the cubic boron nitride sintered body in a coordinate system in which the horizontal axis is the diffraction angle 2θ and the vertical axis is the diffraction intensity cps, ＢＮ and the peak intensity I of the first compound ａ That is, 0.0010≦I ａ / I ＢＮ It may also show a relationship of ≦0.300.

[0012] This further improves the tool life.

[0013] (3) In the above (2), the peak intensity I ＢＮ and the peak intensity I ａ That is, 0.01≦I ａ / I ＢＮ It may also represent a relationship of ≦0.10.

[0014] This further improves the tool life.

[0015] (4) In any of the above (1) to (3), the N Ｃｒ / (N Ｃｒ +N Ｃｏ ) may be 0.20 or more and 0.90 or less. This further improves the tool life.

[0016] (5) In any of the above (1) to (4), the N Ｃｒ / (N Ｃｒ +N Ｃｏ ) may be 0.50 or more and 0.90 or less. This further improves the tool life.

[0017] (6) In any one of the above (1) to (5), in the first compound, the total content of chromium and cobalt may be 10 atomic % or more, the content of carbon may be 5 atomic % or more, and the total content of chromium, cobalt, and carbon may be 40 atomic % or more.

[0018] This further improves the tool life.

[0019] (7) In any one of the above (1) to (6), the content of the first compound in the cubic boron nitride sintered body may be 0.1% by volume or more and 29% by volume or less, thereby further improving the tool life.

[0020] (8) In any one of the above (1) to (7), the first compound may contain at least one first element selected from the group consisting of nitrogen, titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, rhenium, and silicon, thereby further improving tool life.

[0021] (9) In any of the above (1) to (8), the binder may further contain a second compound consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and aluminum, and at least one element selected from the group consisting of carbon, nitrogen, and oxygen, thereby further improving the fracture resistance of the cutting tool.

[0022] (10) In any one of the above (1) to (9), the binder may further contain silicon, which further improves the wear resistance of the cutting tool.

[0023] (11) A tool according to the present disclosure includes any one of the above (1) to (10). This makes it possible to provide a tool with a long tool life even when machining sintered alloys.

[0024] [Details of the embodiment of the present disclosure] In the present disclosure, the expression in the form of "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0025] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

[0026] In the present disclosure, when one or more numerical values ​​are listed as the lower limit and the upper limit of a numerical range, the combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit is also considered to be disclosed.

[0027] In this disclosure, "comprises," "includes," "has," and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even a configuration expressed in closed terms may include additional elements that are normally incidental impurities or unrelated to the subject technology.

[0028] In developing a cubic boron nitride sintered body that can provide a tool with a long tool life even when machining sintered alloys, the inventors first machined sintered alloys using a tool containing a conventional cubic boron nitride sintered body and observed the damage to the tool. As a result, they obtained the following findings: During machining, the metallic binder in the cubic boron nitride sintered body, which is lower in hardness than cBN, selectively wears away, and the cBN particles become visible. Next, the bonds between the cBN particles break, causing the cBN particles to fall off. As a result, the cutting edge of the tool becomes rounded, burrs form on the workpiece, and the tool reaches its end of life.

[0029] Based on the above findings, the present inventors have conducted extensive research, focusing particularly on wear resistance and the bonding strength between cBN particles, and have obtained the cubic boron nitride sintered body of the present disclosure. Specific examples of the cubic boron nitride sintered body and tool of the present disclosure are described below.

[0030] [Embodiment 1: Cubic boron nitride sintered body] A cubic boron nitride sintered body according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a cubic boron nitride sintered body including 70% by volume or more and 99% by volume or less of cubic boron nitride particles, and a binder, wherein the binder includes a first compound containing chromium, cobalt, and carbon, tungsten carbide, cobalt, and aluminum, and in the first compound, the number of chromium atoms N Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is a cubic boron nitride sintered body having a porosity of 0.10 or more and 0.90 or less.

[0031] When used as a tool material, the cubic boron nitride sintered body of the present disclosure can provide a tool with a long tool life even when machining sintered alloys. The reason for this is presumed to be as follows.

[0032] (i) The cubic boron nitride sintered body of the present disclosure contains 70% by volume or more and 99% by volume or less of cubic boron nitride particles that have excellent strength and toughness. Therefore, the cubic boron nitride sintered body also has excellent strength and toughness. Therefore, tools including the cubic boron nitride sintered body can have excellent wear resistance and chipping resistance even when machining sintered alloys.

[0033] (ii) The binder of the cubic boron nitride sintered body of the present disclosure includes a first compound containing chromium, cobalt, and carbon. In the first compound, the number of chromium atoms, N Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is 0.10 or more and 0.90 or less. Because the first compound has high hardness, a cubic boron nitride sintered body containing the first compound can also have high hardness. Therefore, a tool containing the cubic boron nitride sintered body can have excellent wear resistance even when machining sintered alloys.

[0034] (iii) The first compound contained in the cubic boron nitride sintered body of the present disclosure is derived from cobalt and chromium added to the raw material powder during production of the cubic boron nitride sintered body to promote the dissolution and crystallization of cubic boron nitride particles. Adding cobalt and chromium to the raw material powder promotes necking of cubic boron nitride particles during sintering, improving the thermal conductivity of the cubic boron nitride sintered body. Therefore, tools containing the resulting cubic boron nitride sintered body suppress the occurrence of thermal cracks even when machining sintered alloys.

[0035] <Composition of cubic boron nitride sintered body> The cubic boron nitride sintered body of embodiment 1 comprises 70 to 99 volume % cubic boron nitride particles and a binder. The binder contains a first compound containing chromium, cobalt, and carbon, tungsten carbide, cobalt, and aluminum. The cubic boron nitride sintered body of embodiment 1 may be composed of 70 to 99 volume % cubic boron nitride particles and a binder.

[0036] In the cubic boron nitride sintered body of embodiment 1, the content of cubic boron nitride particles is 70% by volume or more and 99% by volume or less. From the viewpoint of improving hardness, the lower limit of the content of cubic boron nitride particles in the cubic boron nitride sintered body is 70% by volume or more, or may be 80% by volume or more, or may be 90% by volume or more. From the viewpoint of improving toughness, the upper limit of the content of cubic boron nitride particles in the cubic boron nitride sintered body may be 99% by volume or less, or may be 95% by volume or less. The content of cubic boron nitride particles in the cubic boron nitride sintered body may be 80% by volume or more and 99% by volume or less, or may be 90% by volume or more and 95% by volume or less.

[0037] The binder content of the cubic boron nitride sintered body of embodiment 1 may be 1 vol % or more and 30 vol % or less, 1 vol % or more and 10 vol % or less, or 5 vol % or more and 10 vol % or less.

[0038] The total content of the cubic boron nitride particles and the binder in the cubic boron nitride sintered body of embodiment 1 may be 71 vol% or more and 99.9 vol% or less, 81 vol% or more and 99.9 vol% or less, or 95 vol% or more and 99.9 vol% or less.

[0039] The total content of the cubic boron nitride particles and the first compound in the cubic boron nitride sintered body of embodiment 1 may be 70.1 vol% or more and 99.1 vol% or less, 73 vol% or more and 99 vol% or less, 90.1 vol% or more and 95 vol% or less, or 91 vol% or more and 95 vol% or less.

[0040] The cubic boron nitride sintered body of embodiment 1 may contain inevitable impurities as long as the effects of the present disclosure are not impaired. The cubic boron nitride sintered body of embodiment 1 may be composed of cubic boron nitride particles, a binder, and inevitable impurities. Examples of inevitable impurities include nitrogen and oxygen. When the cubic boron nitride sintered body contains inevitable impurities, the content of the inevitable impurities in the cubic boron nitride sintered body can be 0.1 mass% or less. The content of inevitable impurities in the cubic boron nitride sintered body can be measured by secondary ion mass spectrometry (SIMS).

[0041] The cubic boron nitride sintered body of Embodiment 1 can be composed of cubic boron nitride particles, a first compound, tungsten carbide, cobalt, and aluminum. The cubic boron nitride sintered body of Embodiment 1 can contain, in addition to the first compound, tungsten carbide, cobalt, and aluminum, a second compound (described below), elemental silicon, and impurities resulting from raw materials, manufacturing conditions, and the like, as long as the effects of the present disclosure are not impaired. The cubic boron nitride sintered body of Embodiment 1 can be composed of cubic boron nitride particles, a first compound, tungsten carbide, cobalt, aluminum, one or both of the second compound and silicon, and inevitable impurities.

[0042] The cBN particle content (volume %) and binder content (volume %) in a cubic boron nitride sintered body can be confirmed by carrying out structural observation, elemental analysis, etc. of the cubic boron nitride sintered body using an energy dispersive X-ray analyzer (EDX) (Octane Elect EDS system) (hereinafter also referred to as "SEM-EDX") attached to a scanning electron microscope (SEM) ("JSM-7800F" (trade name) manufactured by JEOL Ltd.). Specific measurement methods are as follows.

[0043] The cubic boron nitride sintered body is cut at an arbitrary position to expose a cross section of the cubic boron nitride sintered body, and the cross section is polished. A focused ion beam device, a cross-section polisher device, or the like can be used to cut the cubic boron nitride sintered body. When the cubic boron nitride sintered body is used as part of a tool, a portion of the cubic boron nitride sintered body is cut out with a diamond grinding wheel, electrodeposited wire, or the like to expose a sample including a cross section of the cubic boron nitride sintered body.

[0044] Next, the cross section is observed under an SEM at 5000x magnification to obtain a backscattered electron image. In the backscattered electron image, for example, the areas where cBN particles are present appear as the darkest black areas, and the areas where the binder is present appear as gray or white areas.

[0045] Next, the backscattered electron image is binarized using image analysis software ("WinROOF 2018" by Mitani Corporation) so that only cBN particles are extracted. The binarization threshold varies depending on the contrast, so it is set for each image. From the binarized image, the area ratio of pixels originating from the dark field (pixels originating from cBN particles) to the area of ​​the measurement field is calculated. By regarding the calculated area ratio as volume %, the content (volume %) of cBN particles in the cubic boron nitride sintered body can be determined. The fact that the pixels originating from the dark field are originating from cBN particles can be confirmed by performing elemental analysis of the cubic boron nitride sintered body using SEM-EDX.

[0046] The binder content (volume %) in the cubic boron nitride sintered body can be determined by calculating the area ratio of pixels derived from the bright field (pixels derived from the binder) to the area of ​​the measurement field from the binarized image. The fact that the pixels derived from the bright field are derived from the binder can be confirmed by performing elemental analysis of the cubic boron nitride sintered body using SEM-EDX.

[0047] The area percentages of the cBN particles and binder are measured in five non-overlapping measurement fields, and the average of the area percentages of the cBN particles and binder for the five measurement fields is calculated. In the present disclosure, the average of the area percentages of the cBN particles for the five measurement fields corresponds to the content (volume %) of cubic boron nitride particles in the cubic boron nitride sintered body. In the present disclosure, the average of the area percentages of the binder for the five measurement fields corresponds to the content (volume %) of binder for the cubic boron nitride sintered body.

[0048] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results, even when five measurement fields are arbitrarily set for the same sample and the content of cubic boron nitride particles and binder in a cubic boron nitride sintered body is measured multiple times according to the above procedure.

[0049] In the cubic boron nitride sintered body of embodiment 1, the content of the first compound may be 0.1 volume % or more and 29 volume % or less. From the viewpoint of improving hardness, the lower limit of the content of the first compound in the cubic boron nitride sintered body may be 0.1 volume % or more, 0.15 volume % or more, 0.2 volume % or more, or 0.3 volume % or more. The upper limit of the content of the first compound in the cubic boron nitride sintered body may be 29 volume % or less, 15 volume % or less, 10 volume % or less, 9 volume % or less, or 3 volume % or less. The content of the first compound in the cubic boron nitride sintered body may be 0.15 volume % or more and 15 volume % or less, 0.2 volume % or more and 9 volume % or less, or 0.3 volume % or more and 3 volume % or less.

[0050] In the present disclosure, the content (vol %) of the first compound in a cubic boron nitride sintered body is measured using an energy dispersive X-ray analyzer (EDX) (a dual SSD system manufactured by JEOL Ltd.) (hereinafter also referred to as "TEM-EDX") attached to a transmission electron microscope (TEM) ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.) in the following manner.

[0051] (A1) A cubic boron nitride sintered body is sliced ​​to a thickness of 30 to 100 nm using an argon ion slicer ("Cryo-ion slicer IB-09060BCIS" (trademark) manufactured by JEOL Ltd.) under conditions of an acceleration voltage of 6 kV and a finishing voltage of 2 kV to prepare a measurement sample.

[0052] (B1) Next, the measurement sample is observed using a TEM at an acceleration voltage of 200 kV and a magnification of 20,000 to obtain a first image.

[0053] (C1) A rectangular measurement field of view of 10 μm x 10 μm is set in the first image. Element distribution analysis is performed in the measurement field of view using TEM-EDX. The measurement conditions are an acceleration voltage of 200 kV, a camera length of 10 cm, a pixel count of 512 x 512 pixels, and a dwell time of 0.5 ms / pixel. Based on the element distribution analysis results, a matrix consisting of 512 x 512 pixels (hereinafter also referred to as "512 x 512 pixels") is obtained, with each pixel indicating the atomic content (atomic %) of chromium, cobalt, and carbon.

[0054] (D1) For each pixel of the obtained matrix consisting of 512 × 512 pixels, the chromium content and the cobalt content are added, and then a binarization process is performed to obtain a first binarized image in which pixels containing at least one of chromium and cobalt are extracted. The threshold setting condition is applied to the "Otsu's binarization method," which is one of the well-known automatic threshold determination methods.

[0055] (E1) Next, binarization processing is performed on each pixel of the obtained matrix consisting of 512 x 512 pixels based on the carbon content, and a second binarized image is obtained in which pixels containing carbon are extracted. The threshold setting condition is "Otsu's binarization method."

[0056] (F1) Based on the first binarized image and the second binarized image, a pixel (hereinafter also referred to as a "first pixel") extracted from both the first binarized image and the second binarized image is identified from among the 512 x 512 pixels. Hereinafter, the region of the 512 x 512 pixels corresponding to the first pixel will also be referred to as region R1.

[0057] (G1) In each of the first pixels constituting the region R1, the number of chromium atoms N Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) of all the first pixels constituting the region R1. Ｃｒ / (N Ｃｒ +N Ｃｏ ) and calculate the median A.

[0058] (H1) The calculation of the median A is performed for five measurement fields that do not overlap each other, and N of the five measurement fields is Ｃｒ / (N Ｃｒ +N Ｃｏ In the present disclosure, when the average B is 0.10 or more and 0.90 or less, the region R1 in the five measurement visual fields is Ｃｒ / (N Ｃｒ +N Ｃｏ ) is determined to correspond to the first compound in which the value is 0.10 or more and 0.90 or less.

[0059] (I1) Calculate the percentage (N1 / NA) × 100 of the number N1 of first pixels constituting the region R1 corresponding to the first compound in all five measurement fields relative to the number NA of all pixels in the five measurement fields. In the present disclosure, the percentage (N1 / NA) × 100 corresponds to the content (volume %) of the first compound in the cubic boron nitride sintered body.

[0060] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the content of the first compound in a cubic boron nitride sintered body is measured multiple times according to the above procedure.

[0061] <Cubic Boron Nitride Particles> <Composition of Cubic Boron Nitride Particles> In embodiment 1, the cubic boron nitride particles are made of cubic boron nitride. The cubic boron nitride particles may contain impurities together with cubic boron nitride, as long as the effects of the present disclosure are not impaired. When the cubic boron nitride particles contain impurities, the impurity content of the cubic boron nitride particles may be 0.1 mass% or less. The impurity content of the cubic boron nitride particles can be measured by secondary ion mass spectrometry (SIMS).

[0062] <Average particle size of cubic boron nitride particles> In the cubic boron nitride sintered body of embodiment 1, the average particle size of the cubic boron nitride particles is not particularly limited and may be a general average particle size used in conventional cubic boron nitride sintered bodies. The particle size of the cubic boron nitride particles may be, for example, 0.1 μm or more and 10 μm or less.

[0063] In the present disclosure, the average particle size of cubic boron nitride particles is measured by the following procedure: A cross section of a cBN sintered body is exposed and polished using the same method as that used to measure the content of cubic boron nitride particles in a cubic boron nitride sintered body.

[0064] Next, the polished surface is observed at 10,000x magnification using an SEM to obtain an SEM image. A rectangular measurement field of view of 12 μm × 15 μm is set in the SEM image. The SEM image is processed using image analysis software ("WinROOF ver. 7.4.5" by Mitani Corporation) to obtain the circle-equivalent diameter of each cBN particle observed within the measurement field. The arithmetic mean of the circle-equivalent diameters of all cBN particles within the measurement field is calculated. This arithmetic mean corresponds to the average particle size of the cBN particles in the measurement field.

[0065] The above measurement is performed in five non-overlapping measurement fields. The arithmetic mean of the average particle diameters of the cBN particles in the five measurement fields is calculated. In the present disclosure, the arithmetic mean of the average particle diameters in the five measurement fields corresponds to the average particle diameter of the cubic boron nitride particles.

[0066] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the average particle size of cubic boron nitride particles is measured multiple times according to the above procedure.

[0067] <First Compound> The binder of the cubic boron nitride sintered body of the embodiment 1 contains a first compound. The first compound contains chromium, cobalt, and carbon, and in the first compound, the number of chromium atoms N Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is 0.10 or more and 0.90 or less. The first compound may be a compound represented by CrCoC.

[0068] N Ｃｒ / (N Ｃｒ +N Ｃｏ The lower limit of the ratio (ratio) of the cubic boron nitride particles to the total mass may be 0.20 or more and 0.90 or less, 0.30 or more and 0.90 or less, 0.50 or more and 0.90 or less, or 0.65 or more and 0.80 or less, from the viewpoint that the dissolution and crystallization of the cubic boron nitride particles are promoted and the growth of necking of the cubic boron nitride particles is promoted during the production of a cubic boron nitride sintered body.

[0069] In this disclosure, NＣｒ / (N Ｃｒ +N Ｃｏ ) is the N of five measurement fields determined according to the procedures (A1) to (H1) described in the method for measuring the content (volume %) of the first compound in the cubic boron nitride sintered body. Ｃｒ / (N Ｃｒ +N Ｃｏ ) corresponds to the median A and average B of the above.

[0070] In the first compound of the cubic boron nitride sintered body of Embodiment 1, the total content of chromium and cobalt may be 10 atomic % or more, the carbon content may be 10 atomic % or more, and the total content of chromium, cobalt, and carbon may be 40 atomic % or more.In the first compound of the cubic boron nitride sintered body of Embodiment 1, the total content of chromium and cobalt may be 10 atomic % or more, the carbon content may be 5 atomic % or more, and the total content of chromium, cobalt, and carbon may be 40 atomic % or more.

[0071] From the viewpoint of promoting the necking growth of cubic boron nitride particles, the total content of chromium and cobalt in the first compound may be 10 atomic % or more and 90 atomic % or less, 20 atomic % or more and 80 atomic % or less, or 30 atomic % or more and 70 atomic % or less.

[0072] The lower limit of the carbon content in the first compound may be 5 atomic % or more, 10 atomic % or more, or 15 atomic % or more, from the viewpoint of providing the first compound with high hardness as a carbide. The upper limit of the carbon content in the first compound may be 90 atomic % or less, 80 atomic % or less, or 70 atomic % or less, from the viewpoint of reducing the inhibition of necking growth of cubic boron nitride particles. The carbon content in the first compound may be 5 atomic % or more and 90 atomic % or less, 10 atomic % or more and 80 atomic % or less, or 15 atomic % or more and 70 atomic % or less.

[0073] From the viewpoint of fully exerting the effects of the present disclosure, the total content of chromium, cobalt, and carbon in the first compound may be 40 atomic % or more and 100 atomic % or less, 50 atomic % or more and 90 atomic % or less, or 60 atomic % or more and 80 atomic % or less.

[0074] In the cubic boron nitride sintered body of embodiment 1, the first compound may contain, in addition to chromium, cobalt, and carbon, at least one first element selected from the group consisting of nitrogen, titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, rhenium, and silicon. When the first element is nitrogen, the first element may be CrCoCN. Nitrogen is an element that may be mixed into the first compound during the manufacturing process of the first compound. Nitrogen may be solid-solved in CrCoC. When the first element is at least one element selected from the group consisting of titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, rhenium, and silicon, these elements may be solid-solved in CrCoC.

[0075] The total content of the first element in the first compound may be 0 atomic % or more and 25 atomic % or less, 3 atomic % or more and 15 atomic % or less, or 5 atomic % or more and 10 atomic % or less.

[0076] In the present disclosure, the respective contents (atomic %) of chromium, cobalt, carbon, and the first element in the first compound are measured by the following procedure: N is measured according to the procedures (A1) to (H1) described in the method for measuring the content (volume %) of the first compound in the cubic boron nitride sintered body. Ｃｒ / (N Ｃｒ +N Ｃｏ A region R1 corresponding to the first compound in which the value of σ is 0.10 or more and 0.90 or less is identified. Element distribution analysis is performed on all first pixels constituting the region R1 using TEM-EDX, and average values ​​of the contents (atomic %) of chromium, cobalt, carbon, and the first element in the region R1 are calculated based on the measurement results. The average values ​​of the contents (atomic %) of chromium, cobalt, carbon, and the first element in the region R1 correspond to the contents (atomic %) of chromium, cobalt, carbon, and the first element in the first compound.

[0077] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the contents of chromium, cobalt, carbon, and the first element in the first compound are measured multiple times according to the above-described procedure.

[0078] The first compound may contain elements other than chromium, cobalt, carbon, and the first element, as long as the effects of the present disclosure are not impaired. For example, the other elements may be boron, oxygen, or aluminum.

[0079] <Tungsten Carbide> The binder of the cubic boron nitride sintered body of embodiment 1 contains tungsten carbide. From the viewpoint of improving hardness, the lower limit of the tungsten carbide content of the cubic boron nitride sintered body of embodiment 1 may be 0.1 vol% or more, 0.2 vol% or more, or 0.3 vol% or more. The upper limit of the tungsten carbide content of the cubic boron nitride sintered body may be 29 vol% or less, 10 vol% or less, 7 vol% or less, 6 vol% or less, or 3 vol% or less. The tungsten carbide content of the cubic boron nitride sintered body may be 0.1 vol% or more to 29 vol% or less, 0.2 vol% or more to 10 vol% or less, 0.2 vol% or more to 7 vol% or less, 0.2 vol% or more to 6 vol% or less, or 0.3 vol% or more to 3 vol%.

[0080] In the present disclosure, the tungsten carbide content of a cubic boron nitride sintered body is measured by the following procedure.

[0081] (A2) Element distribution analysis is carried out according to the procedures (A1) to (C1) described in the method for measuring the content (volume %) of the first compound in the above-mentioned cubic boron nitride sintered body, and a matrix consisting of 512 × 512 pixels is obtained, in which the atomic content (atomic %) of carbon and tungsten is recorded in each pixel.

[0082] (B2) For each pixel of the obtained matrix consisting of 512 x 512 pixels, binarization processing is performed based on the carbon content to obtain a second binarized image in which pixels containing carbon are extracted. The threshold setting condition is "Otsu's binarization method."

[0083] (C2) For each pixel of the obtained matrix consisting of 512 × 512 pixels, binarization processing is performed based on the tungsten content to obtain a third binarized image in which pixels containing tungsten are extracted. The threshold setting condition is "Otsu's binarization method."

[0084] (D2) Based on the second binarized image and the third binarized image, pixels (hereinafter also referred to as "second pixels") extracted in both the second binarized image and the third binarized image are identified from among the 512 x 512 pixels.

[0085] (E2) Calculate the percentage (N2 / NA) of the number of second pixels N2 relative to the number NA of all pixels in the five measurement fields of view, that is, (N2 / NA) × 100. In the present disclosure, the percentage (N2 / NA) × 100 corresponds to the tungsten carbide content (volume %) of the cubic boron nitride sintered body.

[0086] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the tungsten carbide content of a cubic boron nitride sintered body is measured multiple times according to the above procedure.

[0087] <Cobalt> The cubic boron nitride sintered body of embodiment 1 contains cobalt. The cobalt exists as a cobalt phase consisting of simple cobalt, and is distinguished from the cobalt contained in the first compound.

[0088] From the viewpoint of improving toughness, the lower limit of the cobalt content of the cubic boron nitride sintered body of embodiment 1 may be 0.1 vol% or more, 0.5 vol% or more, or 1.0 vol% or more. The upper limit of the cobalt content of the cubic boron nitride sintered body may be 29 vol% or less, 17 vol% or less, 14 vol% or less, 5 vol% or less, or 3 vol% or less. The cobalt content of the cubic boron nitride sintered body may be 0.1 vol% or more to 29 vol% or less, 0.5 vol% or more to 17 vol% or less, 1.0 vol% or more to 14 vol% or less, 1.0 vol% or more to 5 vol% or less, or 1.0 vol% or more to 3 vol%. Here, the cobalt content is the content of simple cobalt.

[0089] In the present disclosure, the cobalt content of a cubic boron nitride sintered body is measured by the following procedure.

[0090] (A3) An element distribution analysis is carried out according to the procedures (A1) to (C1) described in the method for measuring the content (volume %) of the first compound in the cubic boron nitride sintered body, and pixels where only cobalt is present (hereinafter referred to as "third pixels") are identified in a matrix consisting of 512 x 512 pixels.

[0091] (B3) Calculate the percentage (N3 / NA) of the number of third pixels N3 relative to the number NA of all pixels in the five measurement fields of view, that is, (N3 / NA) × 100. In the present disclosure, the percentage (N3 / NA) × 100 corresponds to the cobalt content (volume %) of the cubic boron nitride sintered body.

[0092] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the cobalt content of a cubic boron nitride sintered body is measured multiple times according to the above procedure.

[0093] <Aluminum> The cubic boron nitride sintered body of embodiment 1 contains aluminum, which exists as an aluminum phase consisting of simple aluminum.

[0094] From the viewpoint of improving toughness, the lower limit of the aluminum content of the cubic boron nitride sintered body of embodiment 1 may be 0.1 vol% or more, 0.2 vol% or more, or 0.3 vol% or more. The upper limit of the aluminum content of the cubic boron nitride sintered body may be 29 vol% or less, 10 vol% or less, or 3 vol% or less. The aluminum content of the cubic boron nitride sintered body may be 0.1 vol% or more and 29 vol% or less, 0.2 vol% or more and 10 vol% or less, or 0.3 vol% or more and 3 vol% or less. Here, the aluminum content is the content of aluminum alone.

[0095] In the present disclosure, the aluminum content of a cubic boron nitride sintered body is measured by the following procedure.

[0096] (A4) An element distribution analysis is carried out according to the procedures (A1) to (C1) described in the method for measuring the content (volume %) of the first compound in the cubic boron nitride sintered body, and a pixel where only aluminum is present (hereinafter referred to as the "fourth pixel") is identified in a matrix consisting of 512 x 512 pixels.

[0097] (B4) Calculate the percentage (N4 / NA) of the number of fourth pixels N4 relative to the number NA of all pixels in the five measurement fields of view, that is, (N4 / NA) × 100. In the present disclosure, the percentage (N4 / NA) × 100 corresponds to the aluminum content (volume %) of the cubic boron nitride sintered body.

[0098] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the aluminum content of a cubic boron nitride sintered body is measured multiple times according to the above procedure.

[0099] <Second Compound> The binder of the cubic boron nitride sintered body of embodiment 1 may further contain a second compound consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and aluminum, and at least one element selected from the group consisting of carbon, nitrogen, and oxygen, which further improves the fracture resistance of the cutting tool.

[0100] The second compound is AlN, TiC, ZrC, HfC, VC, NbC, TaC, TiN, ZrN, HfN, VN, NbN, TaN, CrN, TiCN, ZrCN, HfCN, NbCN, TaCN, Al ２ O ３ , and ZrO ２ It may be at least one selected from the group consisting of:

[0101] <Other Components> The binder of the cubic boron nitride sintered body of embodiment 1 may contain silicon. Silicon exists as elemental silicon and is distinguished from silicon as the first element contained in the first compound. This further improves the wear resistance of the cutting tool.

[0102] The binder of the cubic boron nitride sintered body of embodiment 1 may contain nickel, which improves the toughness of the cubic boron nitride sintered body.

[0103] <X-ray diffraction pattern> In the first graph showing the X-ray diffraction pattern of the cubic boron nitride sintered body of embodiment 1 in a coordinate system in which the horizontal axis is the diffraction angle 2θ and the vertical axis is the diffraction intensity cps, the peak intensity I of cubic boron nitride ＢＮ and the peak intensity I of the first compound ａ That is, 0.0010≦I ａ / I ＢＮ ≦0.350, and 0.0010≦I ａ / I ＢＮ ≦0.300, and 0.01≦I ａ / I ＢＮ It may also represent a relationship of ≦0.10.

[0104] I ａ / I ＢＮ may be 0.01 or more and 0.300 or less, or may be 0.02 or more and 0.10 or less.

[0105] In the present disclosure, the X-ray diffraction pattern of a cubic boron nitride sintered body is obtained by the following procedure: The cubic boron nitride sintered body is cut with an electrodeposited diamond grinding wheel wire, and the cut surface is used as the observation surface.

[0106] An X-ray diffraction pattern of the cut surface of the cubic boron nitride sintered body is obtained using an X-ray diffractometer (Rigaku's "MiniFlex600" (trade name)). The conditions for the X-ray diffractometer are as follows: Characteristic X-ray: Cu-Kα (wavelength 1.54 Å) Tube voltage: 40 kV Tube current: 15 mA Filter: Multilayer mirror Optical system: Focusing method X-ray diffraction method: θ-2θ method

[0107] The obtained X-ray diffraction pattern is plotted on a coordinate system in which the horizontal axis represents the diffraction angle 2θ and the vertical axis represents the diffraction intensity cps, to obtain a first graph. In the first graph, the peak intensity I of cubic boron nitride is ＢＮ , and the peak intensity I of the first compound ａ The peak intensity I of cubic boron nitride is measured. ＢＮTheoretically, the peak representing the diffraction angle 2θ is present at 43.37°. However, due to variations in measurement and the atomic ratio of chromium to cobalt in the first compound, the peak intensity I ＢＮ The diffraction angle 2θ of the peak showing the peak intensity I may be shifted in the range of ±0.3° from 43.37°. ＢＮ The X-ray diffraction pattern on the first graph is normalized so that the diffraction angle 2θ of the peak showing

[0108] Cubic boron nitride peak intensity I ＢＮ is the intensity obtained by subtracting the background from the peak intensity at a diffraction angle 2θ of 43.37°. In the first graph after normalizing the X-ray diffraction pattern, the peak intensity I of the first compound ａ The peak intensity I of the first compound is at a diffraction angle 2θ of 39.08°±0.5°. ａ is the intensity obtained by subtracting the background from the peak intensity at a diffraction angle 2θ of 39.08°±0.5°.

[0109] <Method for manufacturing cubic boron nitride sintered body> A description will be given of a method for manufacturing the cubic boron nitride sintered body of embodiment 1. The method for manufacturing the cubic boron nitride sintered body of embodiment 1 can include a raw material powder preparation step, a mixing step, and a sintering step.

[0110] <<Raw Material Powder Preparing Step>> Cubic boron nitride powder, a first raw material powder, and a second raw material powder are prepared as raw material powders.

[0111] Cubic boron nitride powder is a raw material powder for cubic boron nitride particles contained in a cubic boron nitride sintered body. Cubic boron nitride powder may be produced by adding a catalyst (Li, Ca, Mg, or nitrides, borides, or boron nitrides of these elements) to hexagonal boron nitride powder and then heating and pressing the mixture, or commercially available cBN powder may be prepared.

[0112] The first raw material powder can be obtained, for example, by mixing a CoCr alloy produced by atomization with carbon powder and firing the mixture in a nitrogen atmosphere. Alternatively, the first element powder may be added to the CoCr alloy and carbon powder, mixed, and fired in a nitrogen atmosphere to obtain the first raw material powder.

[0113] The first element powder may be at least one selected from the group consisting of titanium powder, vanadium powder, zirconium powder, niobium powder, molybdenum powder, hafnium powder, tantalum powder, tungsten powder, rhenium powder, and silicon powder.

[0114] The first raw material powder is mixed using a ball mill, bead mill, planetary mill, jet mill, or the like. This allows for the production of a homogeneous first raw material powder. Each mixing and grinding method may be wet or dry. The average particle size of the first raw material powder may be, for example, 0.05 μm or more and 3 μm or less. In this disclosure, the average particle size of the raw material powder refers to the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. The average particle size is measured using a "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific. The particle size distribution of the raw material powder is measured using a particle size distribution measuring device manufactured by Microtrac (product name: MT3300EX).

[0115] The second raw material powder can be obtained by mixing tungsten carbide powder, cobalt powder, and aluminum powder, followed by firing and pulverization for homogenization. Alternatively, silicon powder, second compound raw material powder, nickel powder, etc. may be added to the tungsten carbide powder, cobalt powder, and aluminum powder, and the mixture may be mixed, followed by firing and pulverization to obtain the second raw material powder.

[0116] The second compound raw material powder includes AlN powder, TiC powder, ZrC powder, HfC powder, VC powder, NbC powder, TaC powder, TiN powder, ZrN powder, HfN powder, VN powder, NbN powder, TaN powder, CrN powder, TiCN powder, ZrCN powder, HfCN powder, NbCN powder, TaCN powder, Al ２ O ３ powder, and ZrO ２ It may be at least one selected from the group consisting of powders.

[0117] The mixing can be performed using a ball mill, a bead mill, a planetary mill, a jet mill, or the like. This allows for the production of a homogeneous second raw material powder. Each mixing and grinding method may be a wet method or a dry method. The average particle size of the second raw material powder may be, for example, 0.05 μm or more and 3 μm or less.

[0118] <Mixing Step> Cubic boron nitride powder, a first raw material powder, and a second raw material powder are mixed in a predetermined ratio to obtain a mixed powder. The mixing is performed by wet ball mill mixing using ethanol, acetone, or the like as a solvent. After preparing the mixed powder, the solvent is removed by natural drying or vacuum hot water drying. The mixed powder can then be subjected to a heat treatment (for example, at 200°C or higher under vacuum). This allows impurities such as moisture adsorbed on the surface to be removed.

[0119] <Sintering Step> The mixed powder is sintered to obtain the cubic boron nitride sintered body of the first embodiment. Specifically, the vacuum-sealed mixed powder is sintered using an ultra-high temperature and high pressure apparatus. The sintering temperature is 1600°C or higher and 1900°C or lower. The sintering pressure is 5.5 GPa or higher and 8.0 GPa or lower. The holding time is 10 minutes or higher and 50 minutes or lower.

[0120] [Embodiment 2: Tool] A tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a tool including the cubic boron nitride sintered body of Embodiment 1. Each tool may be entirely made of cubic boron nitride sintered body, or only a portion thereof (for example, the cutting edge portion in the case of a cutting tool) may be made of cubic boron nitride sintered body. Furthermore, a coating film may be formed on the surface of each tool. Examples of the tool include cutting tools and wear-resistant tools.

[0121] Examples of cutting tools include drills, end mills, indexable cutting tips for drills, indexable cutting tips for end mills, indexable cutting tips for milling, indexable cutting tips for turning, metal saws, gear cutting tools, reamers, taps, and cutting bits.

[0122] Examples of the wear-resistant tool include a die, a scriber, a scribing wheel, a dresser, etc. Examples of the grinding tool include a grinding wheel, etc.

[0123] [Supplementary Note 1] A cubic boron nitride sintered body comprising 70% by volume or more and 99% by volume or less of cubic boron nitride particles and a binder, wherein the binder contains: a first compound containing chromium, cobalt, and carbon; tungsten carbide; elemental cobalt; and elemental aluminum; and in the first compound, the number of chromium atoms N is Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is 0.10 or more and 0.90 or less.

[0124] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0125] <Preparation of Cubic Boron Nitride Sintered Body> Cubic boron nitride sintered bodies for each sample were prepared according to the following procedure.

[0126] <<Raw Material Powder Preparation Step>> Cubic boron nitride powder, a first raw material powder, and a second raw material powder were prepared as raw material powders.

[0127] The first raw material powder was obtained by mixing a CoCr alloy produced by atomization, carbon powder, and a first element powder in the ratios shown in the "CoCr," "C," and "First Element Powder" columns of "First Raw Material Powder" in Tables 1 and 2, and firing the mixture in a vacuum. However, only Sample 29 was fired in a nitrogen atmosphere. The ratio of the number of Co atoms to Cr atoms in the CoCr alloy used in each sample was the same as the ratio of the "Co content" to the "Cr content" of the "First Compound" in Tables 5 and 6. The first raw material powder was mixed in a wet ball mill. The average particle size of the first raw material powder was 0.1 μm or more and 3 μm or less. A "-" in the tables indicates that the corresponding powder was not used.

[0128] The second raw material powder was prepared with the composition shown in the "Second Raw Material Powder" column of Tables 1 and 2. For example, for Sample 1, tungsten carbide (WC) powder, cobalt (Co) powder, and aluminum (Al) powder were prepared. These powders were mixed, fired, and pulverized to obtain the second raw material powder. The second raw material powder was wet mixed using a ball mill. The average particle size of the second raw material powder was 0.1 μm or more and 3 μm or less.

[0129] <Mixing Step> A mixed powder was obtained by mixing cubic boron nitride powder, first raw material powder, and second raw material powder in the mass ratios shown in the "blending amount" columns of "cBN powder," "first raw material powder," and "second raw material powder" in Tables 1 and 2. Mixing was performed by wet ball mill mixing using ethanol as a solvent. After preparing the mixed powder, the solvent was removed by natural drying.

[0130] The mixed powder was sintered to obtain cubic boron nitride sintered bodies for each sample. Specifically, the vacuum-sealed mixed powder was sintered using an ultra-high temperature and pressure apparatus. The sintering temperature was 1700°C, the sintering pressure was 7 GPa, and the holding time was 15 minutes.

[0131]

[0132]

[0133] <Evaluation of cubic boron nitride sintered body> <Composition> In each sample of cubic boron nitride sintered body, the content (volume %) of cubic boron nitride particles was measured by SEM-EDX. The specific measurement method is as described in embodiment 1. The results are shown in the "cBN particles" column of "cBN sintered body" in Tables 3 and 4.

[0134] For each sample of cubic boron nitride sintered body, the content (volume %) of the first compound in the cBN sintered body, the chromium content (atomic %), cobalt content (atomic %), and carbon content (atomic %) of the first compound, and the type of first element contained in the first compound were measured using TEM-EDX. Specific measurement methods are as described in embodiment 1. The content of the first compound in the cBN sintered body is shown in the "First Compound" column of Tables 3 and 4. The chromium content, cobalt content, and carbon content of the first compound, and the type of first element contained in the first compound are shown in the "Cr," "Co," "C," and "First Element" columns of Tables 5 and 6.

[0135] In the first compound of each sample of cubic boron nitride sintered body, the number of chromium atoms N Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ The specific measurement method is as described in the first embodiment. The results are shown in Tables 5 and 6 under "N Ｃｒ / (N Ｃｒ +N Ｃｏ ) column.

[0136] In each sample of cubic boron nitride sintered body, the composition of components other than the cBN particles and the first compound was identified by TEM-EDX. The results are shown in the "Binder" column of Tables 3 and 4. The binder consists of the first compound and the components listed in the "Binder" column. All cubic boron nitride sintered bodies consist of cubic boron nitride particles and a binder consisting of the first compound and the components listed in the "Binder" column.

[0137] The tungsten carbide content (volume %), cobalt content (volume %), and aluminum content (volume %) of each sample of cubic boron nitride sintered body were measured. Here, the cobalt content is the content of simple cobalt, and the aluminum content is the content of simple aluminum. The specific measurement method is as described in embodiment 1. The results are shown in the "WC," "Co," and "Al" columns of Tables 3 and 4.

[0138] <X-ray Diffraction Pattern> The X-ray diffraction pattern of the cubic boron nitride sintered body of embodiment 1 was obtained, and a first graph was obtained by plotting this pattern on a coordinate system in which the horizontal axis represents the diffraction angle 2θ and the vertical axis represents the diffraction intensity cps. ａ / I ＢＮ The results are shown in Tables 5 and 6 under "I ａ / I ＢＮ " column.

[0139]

[0140]

[0141]

[0142]

[0143] <Cutting Test> The following cutting test was carried out using a tool (model number: 2NU-CNGA120408) made of the cubic boron nitride sintered body of each sample.

[0144] Workpiece: Sintered alloy equivalent to F-08C2 (150HV) Cutting speed: V = 205 m / min. Feed: f = 0.1 mm / rev. Depth of cut: ap = 0.2 mm Wet / dry: wet Cutting method: Continuous cutting The volume of the chipped cutting edge was measured over a cutting distance of 5.9 km. The chipped volume of the cutting edge was taken as the recession width from the position of the cutting edge ridgeline before cutting. In the "Cutting test" column of Tables 5 and 6, the chipped volume was 150,000 μm ３ The case where the volume of the fallen off is less than 150,000 μm is marked as "A". ３ More than 200000 μm ３ The case where the volume of the fallen off is less than 200,000 μm is marked as "B". ３ 300000 μm or more ３ The case where the volume of the fallen off is less than 300,000 μm is recorded as "C". ３ The smaller the volume of fallen off, the longer the tool life.

[0145] <Discussion> The cubic boron nitride sintered bodies and tools of Sample 1, Samples 3 to 4, Samples 7 to 11, Samples 13 to 27, and Samples 29 to 61 correspond to Examples. The cubic boron nitride sintered bodies and tools of Sample 2, Samples 5 to 6, Sample 12, and Sample 28 correspond to Comparative Examples. It was confirmed that the tools of the Examples had longer tool life than the tools of the Comparative Examples.

[0146] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

Claims

1. A cubic boron nitride sintered body comprising cubic boron nitride particles of 70% by volume or more and 99% by volume or less, and a binder, wherein the binder contains a first compound containing chromium, cobalt, and carbon, tungsten carbide, cobalt, and aluminum, and wherein the number of chromium atoms in the first compound is N. Ｃｒ and the number of cobalt atoms, N Ｃｏ The number of chromium atoms, N, Ｃｒ The proportion of N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is 0.10 or more and 0.90 or less.

2. In a first graph showing the X-ray diffraction pattern of the cubic boron nitride sintered body in a coordinate system in which the horizontal axis is the diffraction angle 2θ and the vertical axis is the diffraction intensity cps, the peak intensity I of cubic boron nitride ＢＮ and the peak intensity I of the first compound ａ That is, 0.0010≦I ａ / I ＢＮ 2. The cubic boron nitride sintered body according to claim 1, wherein the relationship is ≦0.

300.

3. The peak intensity I ＢＮ and the peak intensity I ａ That is, 0.01≦I ａ / I ＢＮ 3. The cubic boron nitride sintered body according to claim 2, wherein the relationship is ≦0.

10.

4. The above N Ｃｒ / (N Ｃｒ +N Ｃｏ 4. The cubic boron nitride sintered body according to claim 1, wherein the value of (a) is 0.20 or more and 0.90 or less.

5. The above N Ｃｒ / (N Ｃｒ +N Ｃｏ 5. The cubic boron nitride sintered body according to claim 4, wherein σ is 0.50 or more and 0.90 or less.

6. A cubic boron nitride sintered body according to any one of claims 1 to 5, wherein in said first compound, the total content of chromium and cobalt is 10 atomic % or more, the content of carbon is 5 atomic % or more, and the total content of chromium, cobalt and carbon is 40 atomic % or more.

7. A cubic boron nitride sintered body according to any one of claims 1 to 6, wherein the content of the first compound in the cubic boron nitride sintered body is 0.1% by volume or more and 29% by volume or less.

8. A cubic boron nitride sintered body according to any one of claims 1 to 7, wherein the first compound contains at least one first element selected from the group consisting of nitrogen, titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, rhenium, and silicon.

9. A cubic boron nitride sintered body according to any one of claims 1 to 8, wherein the binder further comprises a second compound consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and aluminum, and at least one element selected from the group consisting of carbon, nitrogen, and oxygen.

10. A cubic boron nitride sintered body according to any one of claims 1 to 9, wherein the binder further contains silicon.

11. A tool comprising the cubic boron nitride sintered body according to any one of claims 1 to 10.

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