Cubic boron nitride sintered body and tools

Abstract

A cubic boron nitride sintered body comprising cubic boron nitride particles of 70 volume % or more and 99 volume % or less, and a binder, the binder including 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, relative to the total Cr Proportion of N Cr / (N Cr +N Co ) is a cubic boron nitride sintered body having a modulus of elasticity of 0.10 or more and 0.90 or less.

Description

[Technical field]

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

[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 cBN particle content and type of binder for cubic boron nitride sintered bodies are being investigated to obtain properties suited to the application.

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

[0004] [Patent Document 1] International Publication No. 2005 / 066381 Summary of the Invention

[0005] The cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body comprising 70 volume % or more and 99 volume % or less of cubic boron nitride particles and a binder, The binder is a first compound comprising chromium, cobalt and carbon; Tungsten carbide, Cobalt and Aluminum, 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, relative to the total Cr Proportion of N Cr / (N Cr +N Co ) is a cubic boron nitride sintered body having a modulus of elasticity of 0.10 or more and 0.90 or less. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] There is a demand for cubic boron nitride sintered bodies which, when used as tool materials, can provide tools with 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 which, when used as a tool material, can provide a tool having a long tool life even in machining sintered alloys, and a tool including the cubic boron nitride sintered body.

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

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. (1) A cubic boron nitride sintered body according to the present disclosure is a cubic boron nitride sintered body comprising 70 volume % or more and 99 volume % or less of cubic boron nitride particles and a binder, The binder is a first compound comprising chromium, cobalt and carbon; Tungsten carbide, Cobalt and Aluminum, 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, relative to the total Cr Proportion of N Cr / (N Cr +N Co ) is a cubic boron nitride sintered body having a modulus of elasticity 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 which, when used as a tool material, can provide a tool having a long tool life even in 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, Cubic boron nitride peak intensity I BN and the peak intensity I of the first compound a That is, 0.0010≦I a / I BN A relationship of ≦0.300 may be indicated.

[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 A relationship of ≦0.10 may be indicated.

[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 of (1) to (5) above, In the first compound, The total content of chromium and cobalt is 10 atomic percent or more, The carbon content is 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 volume % or more and 29 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 the tool life.

[0021] (9) In any one 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 chipping 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 items (1) to (10). This makes it possible to provide a tool having a long tool life even in machining sintered alloys.

[0024] [Details of the embodiment of the present disclosure] In this disclosure, an expression in the form "A to B" means the upper and lower limits of a range (i.e., A or more and B or less). 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 in the lower limit and any one numerical value listed in the upper limit is also 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 "consists of" is a closed term. However, even if a configuration is expressed in a closed term, it may include additional elements that are usually associated with impurities or are unrelated to the subject technology.

[0028] In developing a cubic boron nitride sintered body capable of providing a tool with a long tool life even when machining a sintered alloy, the inventors first machined a sintered alloy using a tool containing a conventional cubic boron nitride sintered body and observed the damage state of the tool. As a result, the following findings were obtained. During machining, in the cubic boron nitride sintered body, the metal-based binder, which is lower in hardness than cBN, is selectively worn away, and the cBN particles are highlighted. Next, the bonds between the cBN particles are broken, and the cBN particles fall off. As a result, the cutting edge of the tool becomes rounded, burrs are generated on the workpiece, and the tool life is shortened.

[0029] Based on the above findings, the present inventors have conducted extensive research, focusing in particular 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 cubic boron nitride particles of 70 volume % or more and 99 volume % or less, and a binder, the binder including 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, relative to the total Cr Proportion of N Cr / (N Cr +N Co ) is a cubic boron nitride sintered body having a modulus of elasticity of 0.10 or more and 0.90 or less.

[0031] When the cubic boron nitride sintered body of the present disclosure is used as a tool material, it is possible to provide a tool having a long tool life even in machining a sintered alloy. The reason for this is presumably 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 having excellent strength and toughness. Therefore, the cubic boron nitride sintered body can also have excellent strength and toughness. Therefore, a tool including the cubic boron nitride sintered body can have excellent wear resistance and chipping resistance even when machining a sintered alloy.

[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, relative to the total Cr Proportion of N Cr / (NCr +N Co ) is 0.10 or more and 0.90 or less. Since 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 a sintered alloy.

[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 in order to promote the dissolution and crystallization of cubic boron nitride particles during the production of the cubic boron nitride sintered body. Adding cobalt and chromium to the raw material powder can promote the necking of cubic boron nitride particles during sintering, thereby improving the thermal conductivity of the cubic boron nitride sintered body. Therefore, in a tool containing the obtained cubic boron nitride sintered body, the occurrence of thermal cracks is suppressed even when machining a sintered alloy.

[0035] <Composition of cubic boron nitride sintered body> The cubic boron nitride sintered body of the first embodiment includes 70% to 99% by volume of cubic boron nitride particles and a binder. The binder includes a first compound including chromium, cobalt, and carbon, tungsten carbide, cobalt, and aluminum. The cubic boron nitride sintered body of the first embodiment may include 70% to 99% by volume of cubic boron nitride particles and a binder.

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

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

[0038] The total content of cubic boron nitride particles and binder in the cubic boron nitride sintered body of embodiment 1 may be 71 volume % or more and 99.9 volume % or less, 81 volume % or more and 99.9 volume % or less, or 95 volume % or more and 99.9 volume % 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 volume % or more and 99.1 volume % or less, 73 volume % or more and 99 volume % or less, 90.1 volume % or more and 95 volume % or less, or 91 volume % or more and 95 volume % or less.

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

[0041] The cubic boron nitride sintered body of the first embodiment can be composed of cubic boron nitride particles, a first compound, tungsten carbide, cobalt, and aluminum. The cubic boron nitride sintered body of the first embodiment can contain, in addition to the first compound, tungsten carbide, cobalt, and aluminum, a second compound described below, silicon alone, 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 the first embodiment 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 the cubic boron nitride sintered body can be confirmed by carrying out structural observation, elemental analysis, etc. on 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" (product name) manufactured by JEOL Ltd.). The specific measurement method is 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 a part of a tool, a portion of the cubic boron nitride sintered body is cut out with a diamond grindstone, an 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 at 5000x magnification using an SEM 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 (Mitani Shoji Co., Ltd.'s "WinROOF 2018") 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 obtained. 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 originating from the bright field (pixels originating from the binder) to the area of ​​the measurement field from the binarized image. The fact that the pixels originating from the bright field are originating from the binder can be confirmed by performing elemental analysis of the cubic boron nitride sintered body using SEM-EDX.

[0047] The above-mentioned measurement of the area percentage of the cBN particles and the binder is performed in five mutually non-overlapping measurement fields, and the average of the area percentages of the cBN particles and the binder in the five measurement fields is calculated. In the present disclosure, the average of the area percentages of the cBN particles in the five measurement fields corresponds to the content (volume %) of the cubic boron nitride particles in the cubic boron nitride sintered body. In the present disclosure, the average of the area percentages of the binder in the five measurement fields corresponds to the content (volume %) of the binder in 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 the content of cubic boron nitride particles and binder in a cubic boron nitride sintered body is measured multiple times by arbitrarily setting five measurement fields of view on the same sample and following the above procedure.

[0049] In the cubic boron nitride sintered body of the first embodiment, 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 of 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 of 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 of 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 (volume %) of the first compound in a cubic boron nitride sintered body is measured using a transmission electron microscope (TEM) ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.) with an attached energy dispersive X-ray analyzer (EDX) (dual SSD system manufactured by JEOL Ltd.) (hereinafter also referred to as "TEM-EDX") in the following manner.

[0051] (A1) The 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 at 20,000 magnifications using a TEM under conditions of an accelerating voltage of 200 kV 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. 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, in which the atomic content (atomic %) of chromium, cobalt, and carbon is recorded in each pixel.

[0054] (D1) For each pixel of the obtained matrix consisting of 512 x 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 is performed on each pixel of the obtained matrix consisting of 512 x 512 pixels based on the carbon content to obtain a second binarized image in which pixels containing carbon are extracted. The threshold setting condition is applied to "Otsu's binarization method".

[0056] (F1) Based on the first binarized image and the second binarized image, a pixel (hereinafter also referred to as "first pixel") extracted in both the first binarized image and the second binarized image is identified among the 512 x 512 pixels. Hereinafter, the region of the 512 x 512 pixels corresponding to the first pixel is also 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, relative to the total Cr Proportion of N Cr / (N Cr +N Co ) of all the first pixels constituting the region R1. Cr / (N Cr +N Co ) to calculate the median A.

[0058] (H1) The above median A is calculated for five non-overlapping measurement fields, and N of the five measurement fields is calculated. 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 N Cr / (N Cr +N Co ) is determined to be a first compound having a value of 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 of view relative to the number NA of all pixels in the five measurement fields of view. 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 the content of the first compound in a cubic boron nitride sintered body is measured multiple times by arbitrarily setting five measurement fields for the same sample and following the above procedure.

[0061] <Cubic boron nitride particles> <Composition of cubic boron nitride particles> In the first embodiment, 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 effect of the present disclosure is not impaired. When the cubic boron nitride particles contain impurities, the content of the impurities in the cubic boron nitride particles may be 0.1 mass% or less. The content of the impurities in the cubic boron nitride particles may 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 can 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 grain size of cubic boron nitride grains is measured by the following procedure: A cross section of a cBN sintered body is exposed and polished in the same manner as in the measurement procedure for the content of cubic boron nitride grains in a cubic boron nitride sintered body.

[0064] Next, the polished surface is observed at 10,000 times magnification with 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 Shoji Co., Ltd.) to obtain the circle equivalent diameter of each cBN particle observed in the measurement field of view. The arithmetic mean of the circle equivalent diameters of all cBN particles in the measurement field of view is calculated. The arithmetic mean corresponds to the average particle size of the cBN particles in the measurement field of view.

[0065] The above measurement is performed in five mutually non-overlapping measurement fields. The arithmetic mean of the average grain size of the cBN grains in the five measurement fields is calculated. In the present disclosure, the arithmetic mean of the average grain size in the five measurement fields corresponds to the average grain size of the cubic boron nitride grains.

[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 embodiment 1 includes a first compound. The first compound includes 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, relative to the total Cr Proportion of N Cr / (NCr +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 ) 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 dissolution and crystallization of cubic boron nitride particles are promoted and growth of necking of cubic boron nitride particles is promoted during production of a cubic boron nitride sintered body.

[0069] In this disclosure, N Cr / (N Cr +N Co ) is the N of five measurement fields obtained 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 the average B.

[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 growth of necking 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 the first compound having 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 the growth of necking 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 the first embodiment, 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 in addition to chromium, cobalt and carbon. 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-dissolved in CrCoC. When the first element is at least one selected from the group consisting of titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, rhenium and silicon, these elements may be solid-dissolved in CrCoC.

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

[0076] In the present disclosure, the contents (atomic %) of chromium, cobalt, carbon and the first element in the first compound are measured by the following procedure. Cr / (N Cr +N Co A region R1 corresponding to the first compound in which the ratio of chromium, cobalt, carbon, and the first element is 0.10 or more and 0.90 or less is identified. An element distribution analysis is performed by TEM-EDX for all first pixels constituting the region R1, and an average value of the respective contents (atomic %) of chromium, cobalt, carbon, and the first element in the region R1 is calculated based on the measurement results. The average value of the respective contents (atomic %) of chromium, cobalt, carbon, and the first element in the region R1 corresponds to the respective 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 on 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 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 the first embodiment includes tungsten carbide. The lower limit of the tungsten carbide content of the cubic boron nitride sintered body of the first embodiment may be 0.1 volume % or more, 0.2 volume % or more, or 0.3 volume % or more from the viewpoint of improving hardness. The upper limit of the tungsten carbide content of the cubic boron nitride sintered body may be 29 volume % or less, 10 volume % or less, 7 volume % or less, 6 volume % or less, or 3 volume % or less. The tungsten carbide content of the cubic boron nitride sintered body may be 0.1 volume % or more and 29 volume % or less, 0.2 volume % or more and 10 volume % or less, 0.2 volume % or more and 7 volume % or less, 0.2 volume % or more and 6 volume % or less, or 0.3 volume % or more and 3 volume % or less.

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

[0081] (A2) 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 above-mentioned cubic boron nitride sintered body, to obtain a matrix consisting of 512 x 512 pixels 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 applied to "Otsu's binarization method".

[0083] (C2) For each pixel of the obtained matrix consisting of 512 x 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 "Otsu's binarization method" is applied as the threshold setting condition.

[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 among the 512 x 512 pixels.

[0085] (E2) Calculate the percentage (N2 / NA) × 100 of the number of second pixels N2 relative to the number NA of all pixels in the five measurement fields of view. 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 the 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] The lower limit of the cobalt content of the cubic boron nitride sintered body of the first embodiment may be 0.1 volume% or more, 0.5 volume% or more, or 1.0 volume% or more from the viewpoint of improving toughness. The upper limit of the cobalt content of the cubic boron nitride sintered body may be 29 volume% or less, 17 volume% or less, 14 volume% or less, 5 volume% or less, or 3 volume% or less. The cobalt content of the cubic boron nitride sintered body may be 0.1 volume% or more and 29 volume% or less, 0.5 volume% or more and 17 volume% or less, 1.0 volume% or more and 14 volume% or less, 1.0 volume% or more and 5 volume% or less, or 1.0 volume% or more and 3 volume% or less. 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 steps (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 pixel (hereinafter referred to as the "third pixel") in which only cobalt is present is identified in a matrix consisting of 512 x 512 pixels.

[0091] (B3) Calculate the percentage (N3 / NA) × 100 of the number N3 of the third pixels relative to the number NA of all pixels in the five measurement fields of view. 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 the cobalt content of a cubic boron nitride sintered body is measured multiple times by arbitrarily setting five measurement fields for the same sample and following the above procedure.

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

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

[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 steps (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 pixel (hereinafter referred to as the "fourth pixel") in which only aluminum is present is identified in a matrix consisting of 512 x 512 pixels.

[0097] (B4) Calculate the percentage (N4 / NA) × 100 of the number N4 of the fourth pixel to the number NA of all pixels in the five measurement fields of view. 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 the embodiment 1 may further include 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 chipping resistance of the cutting tool.

[0100] The second compound may be at least one selected from the group consisting of AlN, TiC, ZrC, HfC, VC, NbC, TaC, TiN, ZrN, HfN, VN, NbN, TaN, CrN, TiCN, ZrCN, HfCN, NbCN, TaCN, Al2O3, and ZrO2.

[0101] <Other ingredients> The binder of the cubic boron nitride sintered body of the embodiment 1 may contain silicon. Silicon exists as a simple substance 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. According to this, the toughness of the cubic boron nitride sintered body is improved.

[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 where 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 satisfy the relationship of 0.0010 ≦ I a / I BN ≦ 0.350, or the relationship of 0.0010 ≦ I a / I BN ≦ 0.300, or the relationship of 0.01 ≦ I a / I BN ≦ 0.10 may be shown.

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

[0105] In the present disclosure, the X-ray diffraction pattern of the cubic boron nitride sintered body is obtained by the following procedure. The cubic boron nitride sintered body is cut with a diamond grinding wheel electrodeposited 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 of the X-ray diffractometer at this time 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: Convergent 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 is the diffraction angle 2θ and the vertical axis is the diffraction intensity cps to obtain a first graph. In the first graph, the peak intensity I BN , and the peak intensity I of the first compound a Measure the peak intensity I of cubic boron nitride. BN Theoretically, the peak with the diffraction angle 2θ of 43.37° exists. However, due to the measurement variation and the atomic ratio of chromium and cobalt in the first compound, the peak intensity I BN The diffraction angle 2θ of the peak showing the peak intensity I may shift from 43.37° by ±0.3°. BN The X-ray diffraction pattern on the first graph is normalized so that the diffraction angle 2θ of the peak showing is 43.37°.

[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 a The peak intensity of the first compound I is at a diffraction angle 2θ of 39.08°±0.5°. a is the peak intensity at a diffraction angle 2θ of 39.08°±0.5° minus the background.

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

[0110] ≪Raw material powder preparation process≫ As the raw material powders, a cubic boron nitride powder, a first raw material powder, and a second raw material powder are prepared.

[0111] Cubic boron nitride powder is a raw material powder of 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, and their nitrides, borides, and boronitride) to hexagonal boron nitride powder and then heating and pressing it, or commercially available cBN powder may be prepared.

[0112] The first raw powder can be obtained, for example, by mixing a CoCr alloy produced by an atomization method 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 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 powder is mixed in a ball mill, a bead mill, a planetary mill, a jet mill, or the like. This allows a homogeneous first raw powder to be obtained. Each mixing and grinding method may be wet or dry. The average particle size of the first raw 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 powder means 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 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. The second raw material powder may also be obtained by adding silicon powder, second compound raw material powder, nickel powder, etc. to the tungsten carbide powder, cobalt powder, and aluminum powder, mixing them, firing and pulverizing them.

[0116] The second compound raw material powder may be at least one selected from the group consisting of 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, Al2O3 powder, and ZrO2 powder.

[0117] The mixing can be performed using a ball mill, a bead mill, a planetary mill, a jet mill, or the like. This allows a homogeneous second raw material powder to be obtained. 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 process≫ A mixed powder is obtained by mixing cubic boron nitride powder, a first raw material powder, and a second raw material powder in a predetermined ratio. 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 drying in a vacuum water bath. The mixed powder can then be subjected to a heat treatment (for example, at 200°C or higher under vacuum). This makes it possible to remove impurities such as moisture adsorbed on the surface.

[0119] <Sintering process> 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 device. The sintering temperature is 1600°C or higher and 1900°C or lower. The sintering pressure is 5.5GPa or higher and 8.0GPa or lower. The holding time is 10 minutes or higher and 50 minutes or lower.

[0120] [Embodiment 2: Tools] 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 a cubic boron nitride sintered body, or only a part of the tool (for example, the cutting edge of a cutting tool) may be made of a 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, cutting bits, and the like.

[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] [Appendix 1] A cubic boron nitride sintered body comprising cubic boron nitride particles of 70 volume % or more and 99 volume % or less and a binder, The binder is a first compound comprising chromium, cobalt and carbon; Tungsten carbide, Cobalt alone, Aluminum itself, 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, relative to the total Cr Proportion of N Cr / (N Cr +N Co ) is 0.10 or more and 0.90 or less, cubic boron nitride sintered body. EXAMPLES

[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> The cubic boron nitride sintered bodies of the respective samples were prepared according to the following procedure.

[0126] ≪Raw material powder preparation process≫ As raw material powders, cubic boron nitride powder, a first raw material powder, and a second raw material powder were prepared.

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

[0128] The second raw powder was prepared with the composition shown in the "second raw 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, sintered, and pulverized to obtain the second raw powder. The second raw powder was mixed in a wet ball mill. The average particle size of the second raw powder was 0.1 μm or more and 3 μm or less.

[0129] ≪Mixing process≫ A mixed powder was obtained by mixing cubic boron nitride powder, the first raw powder, and the second raw powder in the mass ratios shown in the "blending amount" columns of "cBN powder," "first raw powder," and "second raw powder" in the "raw powder" of 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] <Sintering process> The mixed powder was sintered to obtain cubic boron nitride sintered bodies for each sample. Specifically, the mixed powder was sintered in a vacuum sealed container using an ultra-high temperature and pressure device. The sintering temperature was 1700°C, the sintering pressure was 7GPa, and the holding time was 15 minutes.

[0131] [Table 1]

[0132] [Table 2]

[0133] <Evaluation of cubic boron nitride sintered body> ≪Composition≫ The content (volume %) of cubic boron nitride particles in each sample of cubic boron nitride sintered body 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] In 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 the first element contained in the first compound were measured by TEM-EDX. The specific measurement method is as described in embodiment 1. The content of the first compound in the cBN sintered body is shown in the "First Compound" column in Tables 3 and 4. The chromium content, cobalt content and carbon content of the first compound, and the type of the first element contained in the first compound are shown in the "Cr", "Co", "C" and "First Element" columns in 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, relative to the total Cr Proportion of N Cr / (NCr +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] The composition of the components other than the cBN particles and the first compound in each sample of cubic boron nitride sintered body was identified by TEM-EDX. The results are shown in the "Binder" column of Tables 3 and 4. The binder is composed of the first compound and the components listed in the "Binder" column. All cubic boron nitride sintered bodies are composed of cubic boron nitride particles and a binder composed of the first compound and the components listed in the "Binder" column.

[0137] In each sample of cubic boron nitride sintered body, the tungsten carbide content (volume %), cobalt content (volume %), and aluminum content (volume %) 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 in Tables 3 and 4.

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

[0139] [Table 3]

[0140] [Table 4]

[0141] [Table 5]

[0142] [Table 6]

[0143] <Cutting test> The following cutting tests were carried out using tools (model number: 2NU-CNGA120408) made of sintered cubic boron nitride samples.

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

[0145] <Consideration> The cubic boron nitride sintered bodies and tools of Samples 1, 3 to 4, 7 to 11, 13 to 27, and 29 to 61 correspond to Examples. The cubic boron nitride sintered bodies and tools of Samples 2, 5 to 6, 12, and 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 outset 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 as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope.

Claims

1. A cubic boron nitride sintered body comprising 70% to 99% by volume of cubic boron nitride particles and a binder, The aforementioned bonding material is A first compound containing chromium, cobalt, and carbon, Tungsten carbide and Cobalt and, Contains aluminum, In the first compound, the number of chromium atoms is N. Ｃｒ and the number of cobalt atoms N Ｃｏ The number of chromium atoms N relative to the total Ｃｒ The proportion N Ｃｒ / (N Ｃｒ +N Ｃｏ ) is a cubic boron nitride sintered body having a coefficient of 0.10 or higher and 0.90 or lower.

2. In the first graph showing the X-ray diffraction pattern of the cubic boron nitride sintered body in a coordinate system where the horizontal axis is the diffraction angle 2θ and the vertical axis is the diffraction intensity cps, Peak intensity I of cubic boron nitride ＢＮ and the peak intensity I of the first compound ａ satisfy 0.0010 ≦ I ａ / I ＢＮ ≦ 0.300, and the cubic boron nitride sintered body according to claim 1

3. The aforementioned peak intensity I ＢＮ And the aforementioned peak intensity I ａ This means 0.01 ≤ I ａ / I ＢＮ A cubic boron nitride sintered body according to claim 2, which exhibits a relationship of ≤0.

10.

4. The aforementioned N Ｃｒ / (N Ｃｒ +N Ｃｏ The cubic boron nitride sintered body according to any one of claims 1 to 3, wherein the ratio is 0.20 or more and 0.90 or less.

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

6. In the first compound, The total content of chromium and cobalt is 10 atomic percent or more. The carbon content is 5 atomic percent or more, The cubic boron nitride sintered body according to claim 1 or claim 2, wherein the total content of chromium, cobalt, and carbon is 40 atomic percent or more.

7. The cubic boron nitride sintered body according to claim 1 or claim 2, wherein the content of the first compound in the cubic boron nitride sintered body is 0.1 volume% or more and 29 volume% or less.

8. The cubic boron nitride sintered body according to claim 1 or claim 2, wherein the first compound comprises at least one first element selected from the group consisting of nitrogen, titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, rhenium, and silicon.

9. The cubic boron nitride sintered body according to claim 1 or claim 2, wherein the binder further comprises a second compound comprising 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. The cubic boron nitride sintered body according to claim 1 or claim 2, wherein the binder further comprises silicon.

11. A tool comprising a cubic boron nitride sintered body according to claim 1 or claim 2.