Cubic boron nitride sintered body and cutting tool

Abstract

A cubic boron nitride sintered body comprising 75% by volume or more and 95% by volume or less of cubic boron nitride particles and 5% by volume or more and 25% by volume or less of a binder, wherein the cubic boron nitride sintered body has a silicon content of 0.10 atomic % or more and 7 atomic % or less, and a cobalt content of 0.5 atomic % or more and 13 atomic % or less.

Description

[Technical Field]

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

[0002] Cubic boron nitride sintered bodies are used as materials for cutting tools. For example, Patent Document 1 discloses a cubic boron nitride sintered body containing 70% to 98% by volume of cubic boron nitride particles and a binder containing a cobalt compound or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2005 / 066381 [Patent Document 2] International Publication No. 2023 / 012858 Summary of the Invention

[0004] The cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body containing 75 volume % or more and 95 volume % or less of cubic boron nitride particles and 5 volume % or more and 25 volume % or less of a binder, wherein the cubic boron nitride sintered body has a silicon content of 0.10 atomic % or more and 7 atomic % or less, and a cobalt content of 0.5 atomic % or more and 13 atomic % or less. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a diagram for explaining planar defects that intersect with each other at 90°. [Figure 2] FIG. 2 is a perspective view showing one aspect of a cutting tool according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] Cutting tools made of cubic boron nitride sintered bodies containing binders tend to experience wear progression due to the shedding of cubic boron nitride particles and fracture due to thermal cracking, leading to the end of the tool's life, particularly when the workpiece material is sintered alloy or cast iron.

[0007] Patent Document 2 discloses that cubic boron nitride sintered bodies containing silicon have excellent thermal conductivity. However, the cubic boron nitride sintered body of Patent Document 2 is intended for use as a heat sink, and because it has insufficient strength and toughness, the cubic boron nitride sintered body cannot be applied to cutting tools.

[0008] Therefore, an object of the present disclosure is to provide a cubic boron nitride sintered body that, when used as a material for a cutting tool, enables the cutting tool to have a long tool life, and a cutting tool including the same.

[0009] [Effects of this disclosure] According to the present disclosure, it is possible to provide a cubic boron nitride sintered body that, when used as a material for a cutting tool, enables the cutting tool to have a long tool life, and a cutting tool including the same.

[0010] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) The cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body containing 75 volume % or more and 95 volume % or less of cubic boron nitride particles and 5 volume % or more and 25 volume % or less of a binder, wherein the cubic boron nitride sintered body has a silicon content of 0.10 atomic % or more and 7 atomic % or less, and a cobalt content of 0.5 atomic % or more and 13 atomic % or less.

[0011] According to the present disclosure, it is possible to provide a cubic boron nitride sintered body that, when used as a material for cutting tools, enables the cutting tools to have a long tool life.

[0012] (2) In the above (1), the binder contains silicon and cobalt, and may contain one or both of a solid solution of silicon and cobalt and a compound containing silicon and cobalt, which further improves the strength of the binder and further extends the tool life of a cutting tool using a cubic boron nitride sintered body.

[0013] (3) In the above (1) or (2), the cubic boron nitride sintered body is subjected to elemental analysis using an energy dispersive X-ray spectrometer attached to a scanning transmission electron microscope, and the first image obtained includes a first region where the silicon is present, and the atomic ratio N of cobalt in the first region is Co and the atomic ratio of silicon, N Si Ratio to N Co / N Si may be 0.5 or more and 120 or less.

[0014] N Co / N Si When the ratio is 0.5 or more, the strength of the cubic boron nitride sintered body is improved, and the wear resistance is also improved. Co / N Si When the σ is 120 or less, the bonding strength between cubic boron nitride particles is improved, the thermal conductivity of the cubic boron nitride sintered body is further improved, and the tool life of a cutting tool using the cubic boron nitride sintered body is further improved.

[0015] (4) In the above (3), the N Co / N Si may be 1 or more and 75 or less. This further improves the thermal conductivity of the cubic boron nitride sintered body, and further improves the tool life of a cutting tool using the cubic boron nitride sintered body.

[0016] (5) In the above (4), the N Co / N Si may be 1 or more and 25 or less. This further improves the thermal conductivity of the cubic boron nitride sintered body, and further improves the tool life of a cutting tool using the cubic boron nitride sintered body.

[0017] (6) In any one of the above (1) to (5), the binder contains tungsten, and the X-ray diffraction pattern of the cubic boron nitride sintered body is WCo 21 The ratio IA / IB of the peak integrated intensity IA of the (420) plane of B6 to the peak integrated intensity IB of the (111) plane of cubic boron nitride may be 0.05 or less.

[0018] W2Co 21 B6 is a by-product produced during the synthesis of cubic boron nitride sintered bodies. 21 Since B6 is a brittle compound, it reduces the strength of the cubic boron nitride sintered body. If the IA / IB ratio is 0.05 or less, the W2Co in the cubic boron nitride sintered body 21 The amount of B6 is suppressed. The cubic boron nitride sintered body maintains excellent strength, and cutting tools using the cubic boron nitride sintered body as a material further suppress the progression of wear due to the shedding of cubic boron nitride particles during use, further improving the tool life.

[0019] (7) In any one of the above (1) to (6), the cubic boron nitride sintered body may have a first interface region that is located at a distance of 100 nm or less from a first interface between adjacent cubic boron nitride particles, and at least a portion of the first interface region may contain one or both of cobalt and silicon.

[0020] The presence of either or both of cobalt and silicon in the first interface region of the cubic boron nitride sintered body improves the bonding strength between the cubic boron nitride particles, and cutting tools made from this cubic boron nitride sintered body are further inhibited from wear progression due to shedding of cubic boron nitride particles during use, further improving the tool life.

[0021] (8) In any one of the above (1) to (7), the binder may contain zirconium, and the cubic boron nitride sintered body may have a first interface region that is located at a distance of 100 nm or less from a first interface between adjacent cubic boron nitride particles, and at least a portion of the first interface region may contain zirconium.

[0022] The presence of zirconium in the first interface region of the cubic boron nitride sintered body improves the bonding strength between the cubic boron nitride particles, and cutting tools made from this cubic boron nitride sintered body are further inhibited from wear progression due to shedding of cubic boron nitride particles during use, further improving the tool life.

[0023] (9) In any of the above (1) to (8), the cubic boron nitride sintered body may have a second interface between the cubic boron nitride particles and the binder adjacent to each other, and when the silicon content is measured along a first direction from the second interface toward the inside of the cubic boron nitride particle, a width D of a region where the silicon content is 0.1 atomic % or more and 1.5 atomic % or less may be 20 nm or more and 1000 nm or less.

[0024] Cubic boron nitride particles containing silicon in the above amount have a strong bonding force to binders and cubic boron nitride particles not containing silicon. Therefore, cutting tools made from a cubic boron nitride sintered body containing such cubic boron nitride particles are further inhibited from wear progression due to shedding of cubic boron nitride particles during use, further improving tool life.

[0025] (10) In any of the above (1) to (9), a BF-STEM image of a cross section of the cubic boron nitride sintered body may include a second region where cobalt is present, and planar defects intersecting each other at 90° may be present in the second region.

[0026] In cubic boron nitride sintered bodies obtained by ultra-high pressure sintering, the cobalt usually has an fcc structure. Cobalt with an fcc structure is prone to twin defects (70.5°) on the {111} plane. Because twin defect planes are slippery, cobalt with planar defects (90°) on the {110} plane is stronger than cobalt with twin defects. Therefore, cutting tools made from cubic boron nitride sintered bodies containing second regions with 90° planar defects are further inhibited from wearing out due to the shedding of cubic boron nitride particles during use, further improving tool life.

[0027] (11) A cutting tool according to the present disclosure is a cutting tool comprising the cubic boron nitride sintered body according to any one of (1) to (10) above. The cutting tool according to the present disclosure can have a long tool life.

[0028] [Details of the embodiments of the present disclosure] Specific examples of the cubic boron nitride sintered body and cutting tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0029] In the present disclosure, the notation in the form "A to B" means greater than or equal to A and less than or equal to B, and when no unit is specified for A and only a unit is specified for B, the unit of A and the unit of B are the same.

[0030] 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.

[0031] In this disclosure, when one or more numerical values ​​are listed as the lower and upper limits of a numerical range, the combination of any one numerical value listed in the lower limit with any one numerical value listed in the upper limit is also disclosed.

[0032] 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.

[0033] [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 containing 75 to 95 volume % cubic boron nitride particles and 5 to 25 volume % binder. The silicon content of the cubic boron nitride sintered body is 0.10 to 7 atomic %. The cobalt content of the cubic boron nitride sintered body is 0.5 to 13 atomic %.

[0034] <Composition of cubic boron nitride sintered body> <Cubic boron nitride particle content> The cubic boron nitride particle content of the cubic boron nitride sintered body of embodiment 1 is 75% by volume or more and 95% by volume or less, or may be 80% by volume or more and 95% by volume or less, or may be 85% by volume or more and 90% by volume or less. When the cubic boron nitride particle content is 75% by volume or more, the cubic boron nitride particles are more likely to come into contact with each other, and the effect of improving the bonding strength between the cubic boron nitride particles by silicon is more likely to be obtained. When the cubic boron nitride particle content is more than 95% by volume, a cubic boron nitride sintered body cannot be produced due to a lack of binder.

[0035] <Binder content> The binder content of the cubic boron nitride sintered body of embodiment 1 is 5% by volume or more and 25% by volume or less, and may be 5% by volume or more and 20% by volume or less, or may be 10% by volume or more and 15% by volume or less. When the binder content is 5% by volume or more, the cubic boron nitride sintered body can have sufficient toughness. When the binder content is 25% by volume or less, the cubic boron nitride sintered body can have sufficient wear resistance.

[0036] The total content of cubic boron nitride and binder in the cubic boron nitride sintered body may be 99 volume % or more and 100 volume % or less, 99 volume % or more and 99.99 volume % or less, or 99.90 volume % or more and 99.99 volume % or less.

[0037] The cubic boron nitride particle content (volume %) and binder content (volume %) of 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.). The specific measurement method is as follows.

[0038] A cubic boron nitride sintered body is cut at an arbitrary position to prepare a sample containing a cross section of the cubic boron nitride sintered body. A focused ion beam device, a cross-section polisher, or the like can be used to prepare the cross section. The cross section is then observed using an SEM to obtain a backscattered electron image. In the backscattered electron image, areas where cubic boron nitride particles exist appear as black regions, and areas where the binder exists appear as gray or white regions. The magnification of the SEM is appropriately set according to the d50 of the equivalent circle diameter of the cubic boron nitride particles. The magnification is 5000x when the d50 of the equivalent circle diameter of the cubic boron nitride particles is 5 μm or less, 1000x when it is greater than 5 μm and less than 20 μm, and 100x when it is greater than 20 μm and approximately 100 μm.

[0039] Next, the backscattered electron image is binarized using image analysis software ("WinROOF" by Mitani Corporation). 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 cubic boron nitride particles) to the area of ​​the measurement field is calculated. By regarding the calculated area ratio as volume %, the content (volume %) of cubic boron nitride particles in the cubic boron nitride sintered body can be determined.

[0040] 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 image after binarization processing.

[0041] In the image after binarization, the pixels derived from the dark field are derived from cubic boron nitride particles, and the pixels derived from the bright field are derived from the binder. This can be confirmed by performing elemental analysis by SEM-EDX on the same field of view as the image after binarization on the cross section of the cubic boron nitride sintered body to obtain an elemental mapping image.

[0042] It has been confirmed that there is almost no variation in the measurement results even when the cubic boron nitride particle content (volume %) and binder content (volume %) of the same cubic boron nitride sintered body are measured multiple times by changing the selected location of the measurement field.

[0043] The cubic boron nitride sintered body of embodiment 1 may be composed of cubic boron nitride particles and a binder. 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.

[0044] Inevitable impurities are components not contained in the starting materials that are inevitably mixed in as impurities during the manufacturing process. The content of inevitable impurities may be 0.1% by mass or less. The content of inevitable impurities can be measured by inductively coupled plasma emission spectrometry (ICP analysis) and inert gas fusion analysis (gas analysis).

[0045] <Silicon content> The silicon content of the cubic boron nitride sintered body of embodiment 1 is 0.10 atomic % or more and 7 atomic % or less, and may be 0.10 atomic % or more and 7.0 atomic % or less, 0.5 atomic % or more and 6.6 atomic % or less, 0.7 atomic % or more and 3.0 atomic % or less, or 0.75 atomic % or more and 3.0 atomic % or less. When the silicon content is 0.10 atomic % or more, the bonding strength between cubic boron nitride particles is improved, and the cubic boron nitride sintered body can have high thermal conductivity. When the silicon content is 7 atomic % or less, the cubic boron nitride sintered body can have sufficient toughness.

[0046] The silicon content of a cubic boron nitride sintered body is measured as follows. A sample is taken from the cubic boron nitride sintered body, and a thin slice with a thickness of 30 to 100 nm is prepared from the sample using an argon ion slicer. Elemental analysis is performed on the test piece using an energy dispersive X-ray spectrometer (STEM-EDX) attached to a scanning transmission electron microscope to obtain an element mapping image. The observation magnification is 20,000 times. The area subjected to elemental analysis is the entire measurement field. For example, a JEOL Ltd. "JEM-ARM300F2" (product name) is used. The above measurement is performed in five different, non-overlapping measurement fields. In the present disclosure, the average silicon content of the cubic boron nitride sintered body in the five measurement fields corresponds to the silicon content of the cubic boron nitride sintered body. In the present disclosure, the cobalt content of the cubic boron nitride sintered body described below is also measured using the same method.

[0047] At least a portion of the silicon contained in the cubic boron nitride sintered body may be present in the binder. Of the silicon contained in the cubic boron nitride sintered body, the silicon present in the binder may be 50% or more and 99.9% or less.

[0048] <Cobalt content> The cobalt content of the cubic boron nitride sintered body of embodiment 1 is 0.5 atomic % or more and 13 atomic % or less, and may be 1.0 atomic % or more and 12 atomic % or less, or 1.5 atomic % or more and 7 atomic % or less. When the cobalt content is 0.5 atomic % or more, the cubic boron nitride sintered body can have sufficient toughness. When the cobalt content is 13 atomic % or less, the cubic boron nitride sintered body can have sufficient wear resistance. When the cobalt content is more than 13 atomic %, the silicon content of the cubic boron nitride sintered body decreases, thereby reducing the bonding strength between cubic boron nitride particles and reducing the strength of the cubic boron nitride sintered body.

[0049] At least a portion of the cobalt contained in the cubic boron nitride sintered body may be present in the binder, and the proportion of cobalt present in the binder may be 80% or more and 100% or less of the cobalt contained in the cubic boron nitride sintered body.

[0050] <Cubic boron nitride particles> In the cubic boron nitride sintered body of embodiment 1, the cubic boron nitride particles contain cubic boron nitride as a main component. The cubic boron nitride content of the cubic boron nitride particles may be 99.9 mass % or more.

[0051] In the cubic boron nitride sintered body of embodiment 1, the d50 of the equivalent circle diameter of the cubic boron nitride particles may be 0.1 μm or more and 100 μm or less, 0.2 μm or more and 15 μm or less, or 0.3 μm or more and 5 μm or less. When the d50 of the equivalent circle diameter of the cubic boron nitride particles is 0.1 μm or more, the thermal conductivity of the cubic boron nitride sintered body is further improved. When the d50 of the equivalent circle diameter of the cubic boron nitride particles is 100 μm or less, the hardness of the cubic boron nitride sintered body is improved. In the present disclosure, the d50 of the equivalent circle diameter of the cubic boron nitride particles means the equivalent circle diameter at which the cumulative frequency based on number is 50%.

[0052] The circle-equivalent diameter d50 of cubic boron nitride particles is measured by the following procedure, in which a binarized image is obtained using the same method as for measuring the cubic boron nitride content of a cubic boron nitride sintered body.

[0053] A measurement field of view is set in the image after binarization processing. The size of the measurement field of view is set so that the number of cubic boron nitride particles within the measurement field of view is 500 to 800. With the grain boundaries of the cubic boron nitride particles observed within the measurement field of view separated, the distribution of the circle-equivalent diameters of the cubic boron nitride particles is measured using the image processing software described above. Five measurement fields are set arbitrarily.

[0054] Based on the distribution of the equivalent circle diameters of cubic boron nitride particles, the d50 of the equivalent circle diameter of cubic boron nitride particles is calculated using the number of all cubic boron nitride particles in the measurement field of view as the denominator. The d50 of the equivalent circle diameter of cubic boron nitride particles is calculated for each of the five measurement fields of view, and the average value of these is calculated. This average value corresponds to the d50 of the equivalent circle diameter of cubic boron nitride particles.

[0055] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even when the measurement field of view is arbitrarily set and the measurement of the equivalent-circle diameter d50 of cubic boron nitride particles is performed multiple times according to the above procedure.

[0056] <Binding material> <Forms of silicon and cobalt> The binder of the cubic boron nitride sintered body of embodiment 1 may contain silicon and cobalt. The binder may contain one or both of a solid solution of silicon and cobalt and a compound containing silicon and cobalt. Examples of compounds containing silicon and cobalt include Co2Si, CoSi, and CoSi2.

[0057] The fact that the binder of the cubic boron nitride sintered body contains one or both of a solid solution of silicon and cobalt and a compound containing silicon and cobalt is confirmed using X-ray diffraction and STEM-EDX. First, a test piece with a thickness of approximately 1.0 to 2.0 mm is cut out from the cubic boron nitride sintered body. An X-ray diffraction spectrum is obtained by performing XRD analysis on the test piece using an X-ray diffractometer. The measurement conditions are as follows:

[0058] X-ray diffraction equipment: Product name "MiniFlex600", manufactured by Rigaku Corporation Characteristic X-ray: Cu-Kα (wavelength 1.54Å) Tube voltage: 40kV Tube current: 15mA Filter: K-beta filter Optics: Concentration method X-ray diffraction method: θ-2θ method

[0059] When peaks of a compound having silicon and cobalt (Co2Si: 2θ=45.5°±0.5°, CoSi: 2θ=45.2°±0.5°, CoSi2: 2θ=48.3°±0.5°) are present in the X-ray diffraction spectrum, it is determined that a compound having silicon and cobalt is present.

[0060] A STEM-EDX elemental mapping image is obtained using the same method as for measuring the silicon content of the cubic boron nitride sintered body described above. If silicon and cobalt are present in the same location in the STEM-EDX elemental mapping image, it is determined that a solid solution of silicon and cobalt is present.

[0061] In the cubic boron nitride sintered body of the first embodiment, cobalt may be present as simple cobalt.

[0062] In the cubic boron nitride sintered body of embodiment 1, silicon may exist as elemental silicon or as a silicon compound formed by reaction of silicon with other elements contained in the cubic boron nitride sintered body. Examples of the silicon compound include silicon boride (SiB), silicon nitride (SiN), silicon oxide (SiO), and silicon carbide (SiC).

[0063] In the cubic boron nitride sintered body of embodiment 1, the cobalt content of the binder may be 2 atomic % or more and 99 atomic % or less, 10 atomic % or more and 99 atomic % or less, or 15 atomic % or more and 99 atomic % or less.

[0064] In the cubic boron nitride sintered body of embodiment 1, the silicon content of the binder may be 0.5 atomic % or more and 80 atomic % or less, 1.0 atomic % or more and 70 atomic % or less, or 1.0 atomic % or more and 60 atomic % or less.

[0065] In the cubic boron nitride sintered body of embodiment 1, the binder may contain zirconium. This improves the bonding strength between cubic boron nitride particles. The zirconium content of the binder may be 0.00 atomic % or more and 2.0 atomic % or less, 0.01 atomic % or more and 1.5 atomic % or less, or 0.01 atomic % or more and 1.0 atomic % or less.

[0066] In the cubic boron nitride sintered body of embodiment 1, the binder contains cobalt and silicon. In addition to cobalt and silicon, the binder may contain components conventionally known as binders. Examples of such components include aluminum, nickel, iron, chromium, manganese, titanium, vanadium, niobium, molybdenum, hafnium, tantalum, and rhenium.

[0067] <N Co / N Si > The first image obtained by performing elemental analysis on the cubic boron nitride sintered body of the first embodiment using an energy dispersive X-ray spectrometer attached to a scanning transmission electron microscope may include a first region where silicon is present. Co and the atomic ratio of silicon, N Si Ratio to N Co / N Si may be 0.5 or more and 120 or less, 1 or more and 75 or less, or 1 or more and 25 or less.

[0068] Cobalt atomic fraction in the first region, N Co and the atomic ratio of silicon, N Si Ratio to N Co / N Si The measurement method is as follows. First, a sample is taken from the cubic boron nitride sintered body, and a thin slice with a thickness of 30 to 100 nm is prepared from the sample using an argon ion slicer. Elemental analysis is performed on the test piece using an energy dispersive X-ray spectrometer (STEM-EDX) attached to a scanning transmission electron microscope, and an elemental mapping image is obtained. The elemental mapping image corresponds to the first image. The observation magnification is 20,000 times. If the particle size of the cubic boron nitride particles is large and the binder does not fit into the measurement field of view at 20,000 times, the magnification is reduced until approximately 10 cubic boron nitride particles are included in the measurement field of view.

[0069] The region for elemental analysis is the entire measurement field of view. In the element mapping image (first image), a first region where silicon exists is identified. In the first region, the atomic ratio N of cobalt is Co and the atomic ratio of silicon, NSi Ratio to N Co / N Si The above measurement is performed in 10 different non-overlapping measurement fields. In the present disclosure, N of the 10 measurement fields is Co / N Si The average of the cobalt atom number ratio N in the first region Co and the atomic ratio of silicon, N Si Ratio to N Co / N Si This applies to:

[0070] As long as measurements are made on the same sample, the measurement field can be arbitrarily set and N Co / N Si It was confirmed that there was almost no variation in the measurement results even when measurements were performed multiple times.

[0071] <W2Co 21 The ratio IA / IB of the peak integrated intensity IA of the (420) plane of B6 to the peak integrated intensity IB of the (111) plane of cubic boron nitride The binder of the cubic boron nitride sintered body of the first embodiment contains tungsten, and in the X-ray diffraction pattern of the cubic boron nitride sintered body, WCo 21 The ratio IA / IB of the peak integrated intensity IA of the (420) plane of B6 to the peak integrated intensity IB of the (111) plane of cubic boron nitride may be 0.05 or less, or may be 0.01 or more and 0.04 or less, or 0.01 or more and 0.03 or less.

[0072] The IA / IB ratio is measured as follows. First, a test piece having a thickness of approximately 1.0 to 2.0 mm is cut out from a cubic boron nitride sintered body. An XRD analysis is performed on the test piece using an X-ray diffractometer (MiniFlex600 (trademark) manufactured by Rigaku Corporation) to obtain an X-ray diffraction spectrum. The measurement conditions are as follows:

[0073] X-ray diffraction equipment: Product name "MiniFlex600", manufactured by Rigaku Corporation Characteristic X-ray: Cu-Kα (wavelength 1.54Å) Tube voltage: 40kV Tube current: 15mA Filter: K-beta filter Optics: Concentration method X-ray diffraction method: θ-2θ method

[0074] Based on the X-ray diffraction spectrum, W2Co 21 The peak integrated intensity IA of the (420) plane of B6 and the peak integrated intensity IB of the (111) plane of cubic boron nitride are measured. 21 The peak of the (420) plane of B6 is confirmed at 2θ=38.2°±0.15°. In the X-ray diffraction spectrum, the peak of the (111) plane of cubic boron nitride is confirmed at 2θ=43.3°±0.15°. IA / IB is calculated based on the peak integrated intensity IA and the peak integrated intensity IB.

[0075] As long as measurements were performed on the same sample, it was confirmed that there was almost no variation in the measurement results even when IA / IB measurements were performed multiple times according to the above procedure.

[0076] <First interface area> The cubic boron nitride sintered body of embodiment 1 may have a first interface region that is located within 100 nm of the first interface between adjacent cubic boron nitride particles, and at least a portion of the first interface region may contain one or both of cobalt and silicon.

[0077] In the present disclosure, it is confirmed using STEM-EDX by the following procedure that the cubic boron nitride sintered body includes the first interface region, and that at least a portion of the first interface region includes one or both of cobalt and silicon.

[0078] A sample is taken from the cubic boron nitride sintered body, and sliced ​​to a thickness of 30 to 100 nm using an argon ion slicer to prepare a slice. The slice is then observed at 50,000x magnification using a STEM (scanning transmission electron microscope) to obtain a first image. An example of the transmission electron microscope used here is the "JEM-ARM300F2" (product name) manufactured by JEOL Ltd. In the first image, a first interface between adjacent cubic boron nitride particles is arbitrarily selected. The selected first interface is then positioned so that it passes through the center of the image, and the magnification is changed to 100,000x to obtain a second image.

[0079] In the second image, a first interface region that is within 100 nm of the first interface is identified. In other words, when the two cubic boron nitride particles that form the first interface are a first cubic boron nitride particle and a second cubic boron nitride particle, the first interface region comprises a region sandwiched between the first interface and an imaginary line that is 100 nm away from the first interface toward the first cubic boron nitride particle, and a region sandwiched between the first interface and an imaginary line that is 100 nm away from the first interface toward the second cubic boron nitride particle.

[0080] The extension direction of the first interface is confirmed in the second image. Element line analysis is performed in the first interface region in a direction approximately perpendicular to the extension direction using an energy dispersive X-ray spectrometer (STEM-EDX) attached to a scanning transmission electron microscope. The beam diameter is 0.3 nm or less, and the scan interval is 0.1 to 0.7 nm.

[0081] The results of the elemental line analysis confirm that when one or both of cobalt and silicon are present in the first interface region, the cubic boron nitride sintered body includes a first interface region, and at least a portion of the first interface region includes one or both of cobalt and silicon.

[0082] The above analysis is repeatedly performed on the first images in six fields of view. If it is confirmed that at least a portion of the first interface region contains one or both of cobalt and silicon in at least one field of view, the cubic boron nitride sintered body is determined to have a first interface region that is located within 100 nm of the first interface between adjacent cubic boron nitride particles, and that at least a portion of the first interface region contains one or both of cobalt and silicon.

[0083] As long as measurements were made on the same sample, it was confirmed that there was almost no variation in the results even when the measurement field was arbitrarily set and the above confirmation was performed multiple times according to the above procedure.

[0084] The binder of the cubic boron nitride sintered body of embodiment 1 may contain zirconium. The cubic boron nitride sintered body may have a first interface region that is located within 100 nm of the first interface between adjacent cubic boron nitride particles. At least a portion of the first interface region may contain zirconium.

[0085] In the present disclosure, the cubic boron nitride sintered body includes the first interface region, and the fact that at least a portion of the first interface region contains zirconium is confirmed by a method similar to the method for confirming that at least a portion of the first interface region contains one or both of cobalt and silicon.

[0086] <Second interface> The cubic boron nitride sintered body of embodiment 1 may have a second interface between adjacent cubic boron nitride particles and the binder. When the silicon content is measured along a first direction from the second interface toward the inside of the cubic boron nitride particle, the width D of a region where the silicon content is 0.1 atomic % or more and 1.5 atomic % or less may be 20 nm or more and 1000 nm or less. This indicates that a region where the silicon content is 0.1 atomic % or more and 1.5 atomic % or less exists in the periphery of the cubic boron nitride particle, and that the thickness of this region is 20 nm or more and 1000 nm or less.

[0087] When the width D of the region with a silicon content of 0.1 atomic % or more is 20 nm or more, the bonding force between the binder and the silicon-free cubic boron nitride particles is strong. If the silicon content in the cubic boron nitride particles is too high, defects tend to occur in the cubic boron nitride particles, reducing their strength. Taking this into consideration, when the silicon content is 1.5 atomic % or less and the width D is 1000 nm or less, the cubic boron nitride sintered body can have excellent strength.

[0088] In the present disclosure, the width D is measured by STEM-EDX. The specific measurement method is as follows: A first image is obtained using the same method as the STEM-EDX measurement of the first interface region described above. In the first image, a second interface between adjacent cubic boron nitride particles and the binder is arbitrarily selected. Next, the selected second interface is positioned so that it passes through the vicinity of the center of the image, and the observation magnification is changed to 100,000 times to obtain a third image.

[0089] In the third image, the extension direction of the second interface is confirmed, and element line analysis is performed along a direction substantially perpendicular to the extension direction and along a first direction extending from the second interface toward the interior of the cubic boron nitride particle, with a beam diameter of 0.3 nm or less and a scan interval of 0.1 to 0.7 nm.

[0090] From the results of the elemental line analysis, the width D of the region where the silicon content is 0.1 atomic % or more and 1.5 atomic % or less is calculated. Here, the silicon content is measured at each beam spot. The silicon content is calculated assuming that the total of all elements measured at each peak spot is 100 atomic %.

[0091] The above analysis is repeated for the first images of six fields of view, and if the width D is 20 nm or more and 1000 nm or less in one or more fields of view, the cubic boron nitride sintered body is determined to have a region where the silicon content is 0.1 atomic % or more and 1.5 atomic % or less, with a width D of 20 nm or more and 1000 nm or less.

[0092] <Planar defects in the second region> The BF-STEM image of the cross section of the cubic boron nitride sintered body of the first embodiment includes a second region where cobalt is present, and planar defects that intersect with each other at 90° may be present in the second region.

[0093] In the present disclosure, the BF-STEM image of the cross section of a cubic boron nitride sintered body contains a second region where cobalt is present, and it is confirmed by the following procedure that there are planar defects in the second region that intersect with each other at 90°. Co / N Si An element mapping image (first image) is obtained using the same method as the measurement method in step 1. A second region where cobalt is present is identified in the first image. A location corresponding to the second region is arbitrarily selected in the first image, and a BF-STEM image magnified 50,000 to 100,000 times with that location as the center is used as the second image. A streak-like pattern intersecting each other at 90° is identified in the location corresponding to the second region in the second image. The streak-like pattern corresponds to a planar defect. FIG. 1 is a diagram illustrating streak-like patterns intersecting each other at 90°. In FIG. 1, streak-like patterns 4 exist in second region 5, intersecting each other at 90°. The above observation is repeated based on 10 first images. If streak-like patterns intersecting each other at 90° are observed in the second region in five or more fields of view, it is determined that the BF-STEM image of the cross section of the cubic boron nitride sintered body includes the second region where cobalt is present, and that planar defects intersecting each other at 90° are present in the second region.

[0094] <Method for manufacturing cubic boron nitride sintered body> The cubic boron nitride sintered body of the first embodiment can be produced, for example, by the following method.

[0095] ≪Raw material preparation process≫ Cubic boron nitride powder (hereinafter also referred to as "cBN powder"), silicon powder, cobalt powder, and tungsten carbide powder (hereinafter also referred to as "WC powder") are prepared as raw materials. The average particle size of the cubic boron nitride powder is 0.2 to 100 μm. The average particle size of the silicon powder is 0.5 to 10 μm. The average particle size of the cobalt powder is 0.2 to 5 μm. The average particle size of the WC powder is 0.2 to 5 μm. In this specification, the average particle size of the raw material powders refers to the median diameter d50 of the equivalent sphere diameter. The average particle size is measured using a particle size distribution analyzer manufactured by Microtrac (product name: MT3300EX).

[0096] The cBN powder may be heat-treated in a nitrogen atmosphere at 1400 to 1600° C. for 30 to 300 minutes.

[0097] Cobalt or silicon may be deposited on the surface of the heat-treated cBN powder. This can be done by the arc plasma powder deposition (APD) method. The conditions for the APD method are as follows: Coating device: Nanoparticle forming device APD-P manufactured by Advance Riko Co., Ltd. Target: Cobalt or silicon Intake gas: 10 -4 After evacuation to 10 Pa, argon gas was introduced to increase the pressure inside the device to 10 -1 Set to Pa Discharge voltage: 200V Discharge frequency: 6Hz Capacitor capacity: 1080μF Number of shots: 5000 Processing powder amount: 25g Powder container rotation speed: 50 rpm

[0098] The cobalt powder and silicon powder may be prepared by mixing and grinding the cobalt powder and silicon powder in a ball mill in advance. The grinding time is 12 to 24 hours.

[0099] As the zirconium source, zirconium carbide powder, zirconium nitride powder, etc. can be prepared. The average particle size of the zirconium carbide powder and zirconium nitride powder is 1 to 5 μm. As raw material powders other than those mentioned above, powders containing conventionally known components as binders (Ni, Fe, Cr, Mo, Ti, V, Nb, Mo, Hf, Ta, Re) may also be prepared.

[0100] ≪Mixing process≫ A mixed powder is obtained by mixing cBN powder, silicon powder, cobalt powder, WC powder, and optionally other raw material powders, in which the mass ratio of silicon powder to cobalt powder is silicon powder:cobalt powder=5:1 to 1:275.

[0101] The mixing method is not particularly limited. From the viewpoint of efficient and homogeneous mixing, ball mill mixing, bead mill mixing, planetary mill mixing, or jet mill mixing may be used. Each mixing method may be wet or dry.

[0102] <Sintering process> Next, the mixed powder is sealed in a tantalum capsule, and the mixed powder is heated and pressurized using a belt-type high-pressure and high-temperature generator to a temperature of 1500 to 2000°C and a pressure of 5 to 8 GPa, and held for 5 to 50 minutes to obtain a cubic boron nitride sintered body.

[0103] [Embodiment 2: Cutting Tool] A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a cutting tool including the cubic boron nitride sintered body of Embodiment 1.

[0104] The cutting tool comprising the cubic boron nitride sintered body of embodiment 1 may be entirely made of cubic boron nitride sintered body, or only the cutting edge portion may be made of cubic boron nitride sintered body. Furthermore, a coating film may be formed on the surface of the cutting tool. In this disclosure, the cutting edge portion refers to the portion involved in cutting. Specifically, the cutting edge refers to the region surrounded by the cutting edge ridge and an imaginary plane 0.5 mm away from the cutting edge ridge toward the cubic boron nitride sintered body.

[0105] Examples of cutting tools include drills, end mills, indexable cutting inserts for drills, indexable cutting inserts for end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metal saws, gear cutting tools, reamers, taps, and cutting tools. FIG. 2 is a perspective view showing one aspect of a cutting tool according to a second embodiment. The cutting tool 10 has a rake face 1, a flank face 2, and a cutting edge ridge 3 where the rake face 1 and the flank face 2 intersect. The cutting tool 10 is used, for example, as an indexable cutting insert.

[0106] The cubic boron nitride sintered body of embodiment 1 may be used as a material for wear-resistant tools or grinding tools. Examples of wear-resistant tools include dies, scribers, scribing wheels, and dressers. Examples of grinding tools include grinding wheels. [Example]

[0107] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0108] <Preparation of cubic boron nitride sintered body> ≪Raw material preparation process≫ Cubic boron nitride (cBN) powder (average particle size is shown in Tables 1 and 2), silicon (Si) powder (average particle size 1 μm), cobalt (Co) powder (average particle size 0.5 μm), WC powder (average particle size 0.5 μm), and ZrC powder (average particle size 2.5 μm) were prepared.

[0109] For samples with the temperature and time listed in the "cBN powder heat treatment" column in Tables 1 and 2, the cBN powder was heat treated in a nitrogen atmosphere at the temperature and time listed in the table. Samples marked with "-" were not heat treated.

[0110] For samples marked with "APD" in the "cBN powder surface treatment" column in Tables 1 and 2, cobalt or silicon was deposited on the surface of the cBN powder by the APD method. The specific method is as described in embodiment 1. For samples marked with "-", the APD method was not performed.

[0111] For samples marked "Yes" in the "Co / Si Pre-milling" column in Tables 1 and 2, the powder used was made by mixing cobalt powder and silicon powder in a ball mill and milling them in advance. The milling time was 24 hours.

[0112] ≪Mixing process≫ Mixed powders were obtained by mixing the raw material powders in the mass percentages (the total mixed powder is taken as 100 mass%) shown in Tables 1 and 2. Mixing was carried out for 10 minutes using a planetary mill (bead diameter φ0.3 mm).

[0113] <Sintering process> Next, the mixed powder was sealed in a tantalum capsule, and the mixed powder was pressurized to 6.5 GPa using a belt-type high-pressure, high-temperature generator at the sintering temperatures shown in Tables 1 and 2, and held for 30 minutes to obtain cubic boron nitride sintered bodies for each sample.

[0114] [Table 1]

[0115] [Table 2]

[0116] [Evaluation of cubic boron nitride sintered body] <Composition and structure> For each sample of cubic boron nitride sintered body, the content of cubic boron nitride particles (cBN particles), the content of binder, the content of silicon (Si), the content of cobalt (Co), and the d50 of the equivalent circle diameter of the cubic boron nitride particles (cBN particles) were measured by the method described in embodiment 1. The results are shown in Tables 3 and 4.

[0117] In all samples, the binder of the cubic boron nitride sintered body contained silicon and cobalt. In Samples 1 to 33, of the silicon contained in the cubic boron nitride sintered body, the silicon present in the binder was 50% or more and 99.9% or less. In Samples 1 to 33, of the cobalt contained in the cubic boron nitride sintered body, the cobalt present in the binder was 80% or more and 100% or less. For each sample, the presence form of silicon and cobalt in the binder was confirmed by the method described in embodiment 1. The results are shown in Tables 3 and 4. "Solid solution" means a solid solution of silicon and cobalt.

[0118] The cubic boron nitride sintered body of each sample was subjected to elemental analysis using an energy dispersive X-ray spectrometer attached to a scanning transmission electron microscope according to the method described in embodiment 1, and a first image was obtained. In all samples, the first image included a first region where silicon was present. In each sample, the atomic ratio N of cobalt in the first region was Co and the atomic ratio of silicon, N Si Ratio to N Co / N Si The results are shown in Tables 3 and 4.

[0119] <Thermal diffusivity> The thermal diffusivities of the cubic boron nitride sintered bodies of Samples 1 to 18 and Samples 1-1 to 1-6 were measured by the laser flash method. The measurement conditions were as follows. For the laser flash method, an "LFA467 Hyper Flash" (trademark) manufactured by NETZSCH was used. The thermal diffusivity was calculated from the temperature history curve of the back surface of the test piece when a laser pulse was irradiated onto the front surface (see JIS R1611:2010). The test piece had a square main surface with sides of 10 mm and a thickness of 1 to 2 mm, and the entire test piece was blackened with graphite spray. Three measurements were performed for each sample, and the average values ​​are shown in Table 3. <Measurement conditions> Laser voltage: 230V Pulse width: 0.3 ms Measurement temperature: 25℃

[0120] For sample 1-2, numerous voids were generated in the structure of the cubic boron nitride sintered body, making it impossible to measure the thermal diffusivity. For sample 1-6, cracks were generated in the cubic boron nitride sintered body, making it impossible to measure the thermal diffusivity. The "Thermal diffusivity" column in Table 3 shows "Unmeasurable."

[0121] <Cutting test 1> Cutting tools (substrate shape: SNGN090308, cutting edge treatment: T01225) were fabricated using the cubic boron nitride sintered bodies of Samples 1 to 18 and Samples 1-1 to 1-6, and cutting test 1 was carried out under the following conditions. <Cutting conditions> Cutting speed: 1450m / min. Feed rate: 0.11 mm / rev. Depth of cut: 0.3 mm Coolant:WET Coolant: Emulsion 96 (diluted 20 times with water) Cutter: RM3080R (Sumitomo Electric Industries, Ltd.) Cutting method: Intermittent cutting Lathe: NV5000 (DMG Mori Seiki Co., Ltd.) Workpiece: Two FC250 pearlite plates (cast iron) are machined simultaneously.

[0122] <Evaluation criteria> The cutting edge was observed every 0.5 km of cutting distance, and the amount of cutting edge loss was measured. The amount of cutting edge loss was the retreat distance due to wear from the position of the cutting edge ridge before cutting. In the case of chipping, the size of the chipping was taken as the amount of loss. The time when the amount of chipping of the cutting edge reached 0.1 mm or more was considered to be the end of the cutting tool life, and the volume of cast iron (unit: cm) cut and removed at that time was taken as the amount of loss. 3 The results were ranked according to the following criteria and are shown in Table 3. The larger the volume of cast iron removed by cutting, the longer the cutting tool's life can be evaluated. A:90cm 3 End B:85cm 3 More than 90cm 3 less than C:70cm 3 Over 85cm 3 less than D:65cm 3 More than 70cm 3 less than E:45cm 3 less than

[0123] [Table 3]

[0124] <Consideration 1> The cubic boron nitride sintered bodies and cutting tools of Samples 1 to 18 correspond to Examples. The cubic boron nitride sintered bodies and cutting tools of Samples 1-1 to 1-6 correspond to Comparative Examples. It was confirmed that the cutting tools of Samples 1 to 18 had longer tool lives than the cutting tools of Samples 1-1 to 1-6.

[0125] In the cubic boron nitride sintered body of Sample 1-2, many voids were generated in the structure, due to the low content of binder.

[0126] The cubic boron nitride sintered body of sample 1-3 contains a sufficient amount of silicon, which strengthens the bonding strength between cubic boron nitride particles and improves thermal diffusivity. However, because the cobalt content is low, the cubic boron nitride sintered body has low toughness, which reduces the life of cutting tools.

[0127] The cubic boron nitride sintered body of Sample 1-5 has a low thermal diffusivity despite having a high cubic boron nitride particle content of 90%, which suggests that the bonding strength between the cubic boron nitride particles is weak, resulting in poor cutting performance of the cutting tool.

[0128] The cubic boron nitride sintered body of Sample 1-6 had cracks due to the excessive silicon content.

[0129] <Comparison IA / IB> For the cubic boron nitride sintered bodies of Samples 19 to 33, X-ray diffraction patterns were obtained by the method described in Embodiment 1, and WCo 21The ratio IA / IB of the peak integration intensity IA of the (420) plane of B6 to the peak integration intensity IB of the (111) plane of cubic boron nitride was measured. The results are shown in Table 5.

[0130] <First interface region> In the cubic boron nitride sintered bodies of Samples 19 to 33, a first interface region where the distance from the first interface between adjacent cubic boron nitride particles is within 100 nm was specified by the method described in Embodiment 1, and it was confirmed whether cobalt, silicon, and zirconium were present in the first interface region. The elements present in the first interface region are shown in Table 5. "-" indicates that none of cobalt, silicon, and zirconium are present.

[0131] <Width D> In the cubic boron nitride sintered bodies of Samples 19 to 33, the second interface between the cubic boron nitride particles and the binder was specified by the method described in Embodiment 1. The silicon content was measured along the first direction from the second interface toward the inside of the cubic boron nitride particles, and the width D of the region where the silicon content is 0.1 atomic% or more and 1.5 atomic% or less was measured. The results are shown in Table 5.

[0132] <Planar defects in Co structure> In the cubic boron nitride sintered bodies of Samples 19 to 33, a BF-STEM image was acquired by the method described in Embodiment 1, and the maximum value of the angle (expressed in the range of 0° to 90°) formed by the linear patterns (corresponding to planar defects) in the second region was measured. The results are shown in Table 5. When the angle is 90°, it is determined that the BF-STEM image of the cross-section of the cubic boron nitride sintered body includes the second region where cobalt is present, and there are planar defects intersecting at 90° with each other in the second region.

[0133] <000057,3>

Table 4

[0134]

Table 5

[0135] <Cutting test 2> Cutting tools (substrate shape: CNGA120408, cutting edge treatment: T01225) were fabricated using the cubic boron nitride sintered bodies of Samples 19 to 33 and Samples 1-1 to 1-6, and cutting test 2 was carried out under the following conditions. <Cutting conditions> Cutting speed: 250m / min. Feed rate: 0.1 mm / rev. Depth of cut: 0.25 mm Coolant:WET Cutting method: Continuous cutting Lathe: LB4000EX (Okuma Corporation) Workpiece: Sintered parts (Sumitomo Electric Industries, Ltd. hardened sintered alloy D40, hardness of hardened cutting part: HRB75)

[0136] <Evaluation criteria> The cutting edge was observed every 0.5 km of cutting distance, and the amount of wear on the cutting edge was measured. The cutting distance was measured when the amount of wear on the cutting edge reached 150 μm or more. The cutting distance was taken as the life of the cutting tool, and it was ranked according to the following criteria. The results are shown in Table 6. The longer the cutting distance, the longer the cutting tool's life can be evaluated. A: 5.0km or more B: 4.5km or more and less than 5.0km C: 3.5km or more but less than 4.5km D: 3.0km or more and less than 3.5km E: 2.5km or more but less than 3.0km F: Less than 2.5km

[0137] [Table 6]

[0138] <Consideration 2> The cubic boron nitride sintered bodies and cutting tools of Samples 19 to 33 correspond to Examples. The cubic boron nitride sintered bodies and cutting tools of Samples 1-1 to 1-6 correspond to Comparative Examples. It was confirmed that the cutting tools of Samples 19 to 33 had longer tool lives than the cutting tools of Samples 1-1 to 1-6.

[0139] Comparing Samples 19 to 22, Samples 19 to 21, which have an IA / IB ratio of 0.05 or less, have a longer tool life than Sample 22, which has an IA / IB ratio of 0.1. This is due to the brittle phase W2Co 21 This is because the smaller the amount of B6, the stronger the binder, and the more effectively binder wear during cutting and the falling off of cubic boron nitride particles caused by binder wear are suppressed.

[0140] Comparing Sample 19 with Samples 23 to 27, Samples 23 to 27, which have at least one of Co, Si, and Zr in the first interface region, have a longer tool life than Sample 19, which does not have these elements in the first interface region. This is because the presence of at least one of Co, Si, and Zr in the first interface region improves the bonding strength between cubic boron nitride particles, suppressing the progression of wear due to the shedding of cubic boron nitride particles.

[0141] Comparing Sample 19 with Samples 28 to 31, Samples 28 to 30 with width D of 20 to 1000 nm had longer tool life than Sample 19 with width D of 0 nm and Sample 31 with width D of 1050 nm. This is because cubic boron nitride particles containing silicon in an amount that results in width D of 20 to 1000 nm have a strong bonding force with the binder and cubic boron nitride particles that do not contain silicon, thereby suppressing the progression of wear due to the cubic boron nitride particles falling off.

[0142] Comparisons between Sample 19 and Sample 32, and between Sample 23 and Sample 33, confirmed that samples with planar defects in the second region that intersect at 90° to each other have longer tool life than samples without such planar defects. This is because the second region with planar defects (90°) in the {110} plane is stronger than the second region with twin defects, thereby suppressing binder wear during cutting and the shedding of cubic boron nitride particles caused by binder wear.

[0143] Although the embodiments and examples of the present disclosure have been described above, it is originally intended 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 embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0144] 1 rake face, 2 flank face, 3 cutting edge ridge, 4 streak pattern, 5 second area

Claims

1. A cubic boron nitride sintered body comprising 75% by volume or more and 95% by volume or less of cubic boron nitride particles and 5% by volume or more and 25% by volume or less of a binder, the silicon content of the cubic boron nitride sintered body is 0.10 atomic % or more and 7 atomic % or less; The cubic boron nitride sintered body has a cobalt content of 0.5 atomic % or more and 13 atomic % or less.

2. the binder comprises silicon and cobalt; 2. The cubic boron nitride sintered body according to claim 1, wherein the binder comprises one or both of a solid solution of the silicon and the cobalt and a compound containing the silicon and the cobalt.

3. a first image obtained by performing elemental analysis on the cubic boron nitride sintered body using an energy dispersive X-ray spectrometer attached to a scanning transmission electron microscope includes a first region where the silicon is present; The atomic ratio N of the cobalt in the first region Ｃｏ and the atomic ratio N of silicon Ｓｉ Ratio to N Ｃｏ / N Ｓｉ 3. The cubic boron nitride sintered body according to claim 1, wherein is 0.5 or more and 120 or less.

4. The N Ｃｏ / N Ｓｉ 4. The cubic boron nitride sintered body according to claim 3, wherein is 1 or more and 75 or less.

5. The N Ｃｏ / N Ｓｉ The cubic boron nitride sintered body according to claim 4, wherein is 1 or more and 25 or less.

6. the binder comprises tungsten; In the X-ray diffraction pattern of the cubic boron nitride sintered body, W ２ Co ２１ B ６ 3. The cubic boron nitride sintered body according to claim 1, wherein the ratio IA / IB of the peak integrated intensity IA of the (420) plane of cubic boron nitride to the peak integrated intensity IB of the (111) plane of cubic boron nitride is 0.05 or less.

7. the cubic boron nitride sintered body has a first interface region that is located within 100 nm of a first interface between adjacent cubic boron nitride particles, 3. The cubic boron nitride sintered body according to claim 1, wherein at least a portion of the first interface region contains one or both of the cobalt and the silicon.

8. the binder comprises zirconium; the cubic boron nitride sintered body has a first interface region that is located within 100 nm of a first interface between adjacent cubic boron nitride particles, 3. The cubic boron nitride sintered body according to claim 1, wherein at least a portion of the first interface region contains zirconium.

9. the cubic boron nitride sintered body has second interfaces between the cubic boron nitride particles and the binder adjacent to each other, 3. The cubic boron nitride sintered body according to claim 1, wherein, when the silicon content is measured along a first direction from the second interface toward the inside of the cubic boron nitride particle, a width D of a region where the silicon content is 0.1 atomic % or more and 1.5 atomic % or less is 20 nm or more and 1000 nm or less.

10. a BF-STEM image of a cross section of the cubic boron nitride sintered body includes a second region in which the cobalt is present; 3. The cubic boron nitride sintered body according to claim 1, wherein planar defects intersecting at 90° with each other are present in said second region.

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

Images