Cubic boron nitride sintered body and cutting tool

Abstract

Disclosed is a cubic boron nitride sintered body which contains 75 vol% to 95 vol% inclusive of cubic boron nitride particles and 5 vol% to 25 vol% inclusive of a binder. The cubic boron nitride sintered body has a silicon content of 0.10 atom% to 7 atom% inclusive, and a cobalt content of 0.5 atom% to 13 atom% inclusive.

Description

Cubic boron nitride sintered body and cutting tool

[0001] The present disclosure relates to a cubic boron nitride sintered body and a cutting tool.

[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.

[0003] International Publication No. 2005 / 066381 International Publication No. 202! / 012858

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

[0005] FIG. 1 is a diagram for explaining plane defects intersecting at 90° with each other. FIG. 2 is a perspective view showing one aspect of the cutting tool according to Embodiment 2.

[0006] [Problems to be Solved by the Present Disclosure] Cutting tools using a cubic boron nitride sintered body containing a binder tend to experience wear progression due to the脱落 of cubic boron nitride particles and defects due to thermal cracks during use, leading to tool life. This tendency is particularly likely to occur when the workpiece is a sintered alloy, cast iron, or the like.

[0007] Patent Document 2 discloses that a cubic boron nitride sintered body containing silicon has excellent thermal conductivity. However, the use of the cubic boron nitride sintered body of Patent Document 2 is a heat sink, and since its strength and toughness are insufficient, it cannot be applied to a cutting tool.

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

[0009] [Effects of this disclosure] According to this disclosure, it is possible to provide a cubic boron nitride sintered body and a cutting tool equipped therewith, which, when used as a material for a cutting tool, can give the cutting tool a long tool life.

[0010] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described. (1) The cubic boron nitride sintered body of the Disclosure is a cubic boron nitride sintered body comprising 75 volume% to 95 volume% of cubic boron nitride particles and 5 volume% to 25 volume% of a binder, wherein the silicon content of the cubic boron nitride sintered body is 0.10 atomic% to 7 atomic%, and the cobalt content of the cubic boron nitride sintered body is 0.5 atomic% to 13 atomic%.

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

[0012] (2) In (1) above, the binder comprises silicon and cobalt, and the binder may also comprise a solid solution of silicon and cobalt, and a compound having silicon and cobalt, or both. This further improves the strength of the binder and further improves the tool life of the cutting tool using the cubic boron nitride sintered body.

[0013] (3) In (1) or (2) above, the 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 the first region in which silicon is present, and the atomic ratio of cobalt in the first region N Ｃｏ and the atomic ratio of silicon N Ｓｉ Ratio N Ｃｏ / N Ｓｉ It may be between 0.5 and 120.

[0014] N Ｃｏ / N Ｓｉ When the value is 0.5 or higher, the strength and wear resistance of the cubic boron nitride sintered body improve. Ｃｏ / N ＳｉWhen it is 120 or less, the bonding force between the cubic boron nitride particles is improved, the thermal conductivity of the cubic boron nitride sintered body is further improved, and the tool life of the 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. According to this, the thermal conductivity of the cubic boron nitride sintered body is further improved, and the tool life of the cutting tool using the cubic boron nitride sintered body is further improved.

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

[0017] (6) In any of the above (1) to (5), the binder contains tungsten, and in the X-ray diffraction pattern of the cubic boron nitride sintered body, the ratio IA / IB of the peak integrated intensity IA of the (420) plane of W ２ Co ２１ B ６ and the peak integrated intensity IB of the (111) plane of cubic boron nitride may be 0.05 or less.

[0018] W ２ Co ２１ B ６ is a by-product generated when synthesizing the cubic boron nitride sintered body. Since W ２ Co ２１ B ６ is a brittle compound, it becomes a factor for reducing the strength of the cubic boron nitride sintered body. When IA / IB is 0.05 or less, the amount of W ２ Co ２１ B ６ in the cubic boron nitride sintered body is suppressed. The cubic boron nitride sintered body maintains excellent strength, and the cutting tool using the cubic boron nitride sintered body as a material further suppresses the progress of wear due to the dropout of cubic boron nitride particles during use, and the tool life is further improved.

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

[0020] The presence of either or both cobalt and silicon in the first interface region of a cubic boron nitride sintered body improves the bonding force between cubic boron nitride particles. Cutting tools using this cubic boron nitride sintered body as a material further suppress wear progression due to the shedding of cubic boron nitride particles during use, thereby further improving tool life.

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

[0022] The presence of zirconium in the first interface region of a cubic boron nitride sintered body improves the bonding force between cubic boron nitride particles. Cutting tools using this cubic boron nitride sintered body as a material further suppress wear progression due to the shedding of cubic boron nitride particles during use, thereby further improving tool life.

[0023] (9) In any of (1) to (8) above, the cubic boron nitride sintered body has a second interface between adjacent cubic boron nitride particles and the binder, and when the silicon content is measured along a first direction toward the interior of the cubic boron nitride particles from the second interface, the width D of the region in which 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-mentioned amount exhibit strong bonding forces to binders and cubic boron nitride particles that do not contain silicon. Therefore, cutting tools using a cubic boron nitride sintered body containing these cubic boron nitride particles as a material further suppress wear progression due to the shedding of cubic boron nitride particles during use, thereby further improving tool life.

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

[0026] In cubic boron nitride sintered bodies obtained by ultra-high pressure sintering, cobalt typically has an fcc structure. Cobalt with an fcc structure is prone to the formation of {111} plane twinning defects (70.5°). Since the twinning defect plane is slippery, cobalt with {110} plane defects (90°) has higher strength than cobalt with twinning defects. Therefore, cutting tools made from cubic boron nitride sintered bodies containing a second region with 90° plane defects have further suppressed wear progression due to the shedding of cubic boron nitride particles during use, resulting in further improved tool life.

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

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

[0029] In this disclosure, the notation "A to B" means A or greater and B or less. If no unit is specified for A, and only a unit is specified for B, then the unit for A and the unit for B are the same.

[0030] In this disclosure, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

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

[0032] In this disclosure, “equipment,” “includes,” “possesses,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the subject technology.

[0033] [Embodiment 1: Cubic boron nitride sintered body] The cubic boron nitride sintered body of one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a cubic boron nitride sintered body comprising 75% to 95% by volume of cubic boron nitride particles and 5% to 25% by volume of a binder. The silicon content of the cubic boron nitride sintered body is 0.10 atomic% to 7 atomic%. The cobalt content of the cubic boron nitride sintered body is 0.5 atomic% to 13 atomic%.

[0034] <Composition of Cubic Boron Nitride Sintered Body> <Content of Cubic Boron Nitride Particles> The content of cubic boron nitride particles in the cubic boron nitride sintered body of Embodiment 1 is 75 volume% or more and 95 volume% or less, and may be 80 volume% or more and 95 volume% or less, or 85 volume% or more and 90 volume% or less. When the content of cubic boron nitride particles is 75 volume% or more, the cubic boron nitride particles come into contact with each other easily, and the effect of improving the bonding strength between cubic boron nitride particles by silicon is easily obtained. When the content of cubic boron nitride particles exceeds 95 volume%, it is not possible to manufacture a cubic boron nitride sintered body due to insufficient 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 10% by volume or more and 15% by volume or less. If the binder content is 5% by volume or more, the cubic boron nitride sintered body can have sufficient toughness. If 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% by volume or more and 100% by volume or less, 99% by volume or more and 99.99% by volume or less, or 99.90% by volume or more and 99.99% by volume or less.

[0037] The content of cubic boron nitride particles (volume %) and binder (volume %) in a cubic boron nitride sintered body can be confirmed by performing microstructural 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) (JEOL Ltd.'s "JSM-7800F" (product name)). The specific measurement method is as follows.

[0038] A sample containing the cross-section of a cubic boron nitride sintered body is prepared by cutting the body at an arbitrary position. A focused ion beam apparatus, a cross-section polisher apparatus, etc., can be used to prepare the cross-section. Next, the cross-section is observed with a scanning electron microscope (SEM) to obtain a backscattered electron image. In the backscattered electron image, the region where cubic boron nitride particles are present will be a black region, and the region where the binder is present will be a gray or white region. The magnification of the SEM is set appropriately according to the d50 of the equivalent circle diameter of the cubic boron nitride particles. If the d50 of the equivalent circle diameter of the cubic boron nitride particles is 5 μm or less, the magnification is 5000x; if it is greater than 5 μm and less than or equal to 20 μm, the magnification is 1000x; and if it is greater than 20 μm and about 100 μm, the magnification is 100x.

[0039] Next, the above backscattered electron image is subjected to binarization using image analysis software (WinROOF from Mitani Corporation). The binarization threshold changes depending on the contrast, so it is set for each image. From the image after binarization, the area ratio of pixels originating from the dark field (pixels originating from cubic boron nitride particles) to the area of ​​the measurement field of view is calculated. By considering the calculated area ratio as a volume percentage, the content (volume percentage) of cubic boron nitride particles in the cubic boron nitride sintered body can be determined.

[0040] By calculating the area ratio of pixels originating from the brightfield (pixels originating from the binder) to the area of ​​the measurement field of view from the binarized image, the binder content (volume %) in the cubic boron nitride sintered body can be determined.

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

[0042] It has been confirmed that even when measuring the content (volume %) of cubic boron nitride particles and the content (volume %) of binders multiple times in the same cubic boron nitride sintered body by changing the selected area of ​​the measurement field, there is almost no variation in the measurement results.

[0043] The cubic boron nitride sintered body of Embodiment 1 may consist of cubic boron nitride particles and a binder. The cubic boron nitride sintered body of Embodiment 1 may contain unavoidable impurities as long as the effects of the present disclosure are not impaired. The cubic boron nitride sintered body of Embodiment 1 may consist of cubic boron nitride particles, a binder and unavoidable impurities.

[0044] Inevitable impurities are components that are not present in the starting materials but are inevitably introduced as impurities during the manufacturing process. The content of unavoidable impurities may be 0.1% by mass or less. The content of unavoidable impurities can be measured by high-frequency induction plasma emission spectrometry (ICP analysis) and inert gas fusion spectrometry (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 force 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 method for measuring the silicon content of a cubic boron nitride sintered body is as follows: A sample is taken from the cubic boron nitride sintered body, and thin sections with a thickness of 30 to 100 nm are prepared from the sample using an argon ion slicer. Elemental analysis is performed on these test pieces using an energy-dispersive X-ray spectrometer (STEM-EDX) attached to a scanning transmission electron microscope to obtain an elemental mapping image. The observation magnification is 20,000x. The area for elemental analysis is the entire measurement field. For example, the "JEM-ARM300F2" (product name) manufactured by JEOL Ltd. is used. The above measurement is performed in five different, non-overlapping measurement fields. In this disclosure, the average of the 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 this disclosure, the cobalt content of the cubic boron nitride sintered body, as described later, is also measured by 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 between 50% and 99.9%.

[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. If the cobalt content is 0.5 atomic% or more, the cubic boron nitride sintered body can have sufficient toughness. If the cobalt content is 13 atomic% or less, the cubic boron nitride sintered body can have sufficient wear resistance. If the cobalt content is greater than 13 atomic%, the silicon content of the cubic boron nitride sintered body decreases, which reduces the bonding force between the cubic boron nitride particles and reduces 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. Of the cobalt contained in the cubic boron nitride sintered body, the cobalt present in the binder may be between 80% and 100%.

[0050] <Cubic boron nitride particles> In the cubic boron nitride sintered body of Embodiment 1, the cubic boron nitride particles mainly contain cubic boron nitride. The content of cubic boron nitride in the cubic boron nitride particles may be 99.9% by mass or more.

[0051] In the cubic boron nitride sintered body of Embodiment 1, the equivalent circle diameter d50 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 equivalent circle diameter d50 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 equivalent circle diameter d50 of the cubic boron nitride particles is 100 μm or less, the hardness of the cubic boron nitride sintered body is improved. In this disclosure, the equivalent circle diameter d50 of the cubic boron nitride particles means the equivalent circle diameter at which the cumulative frequency based on the number of particles reaches 50%.

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

[0053] A measurement field of view is set in the image after binarization. The size of the measurement field of view is set so that there are 500 to 800 cubic boron nitride particles within the measurement field of view. With the grain boundaries of the cubic boron nitride particles observed within the measurement field of view separated, the distribution of the equivalent circle diameter of the cubic boron nitride particles is measured using the image processing software described above. Five measurement fields of view 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 the cubic boron nitride particles is determined using the total number of cubic boron nitride particles in the measurement field as the denominator. The d50 of the equivalent circle diameter of the cubic boron nitride particles is determined for each of the five measurement fields, and their average value is calculated. This average value corresponds to the d50 of the equivalent circle diameter of the cubic boron nitride particles.

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

[0056] <Binding Agent> <Forms of Silicon and Cobalt> The binding agent of the cubic boron nitride sintered body of Embodiment 1 may contain silicon and cobalt. The binding agent may contain one or both of a solid solution of silicon and cobalt, and a compound having silicon and cobalt. As a compound having silicon and cobalt, Co ２ Si, CoSi, CoSi ２ These are some examples.

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

[0058] X-ray diffractometer: Product name "MiniFlex 600", manufactured by Rigaku Corporation. Characteristic X-ray: Cu-Kα (wavelength 1.54 Å) Tube voltage: 40 kV Tube current: 15 mA Filter: K-β filter Optical system: Focusing method X-ray diffraction method: θ-2θ method

[0059] In the X-ray diffraction spectrum, a compound peak (Co) containing silicon and cobalt is observed. ２ Si:2θ=45.5°±0.5°, CoSi:2θ=45.2°±0.5°, CoSi ２ If 2θ (48.3° ± 0.5°) is present, it is determined that a compound containing silicon and cobalt exists.

[0060] A STEM-EDX elemental mapping image is obtained using the same method as the method 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 exists.

[0061] In the cubic boron nitride sintered body of Embodiment 1, cobalt may exist as elemental cobalt.

[0062] In the cubic boron nitride sintered body of Embodiment 1, silicon may exist as elemental silicon, or as a silicon compound produced by the reaction of silicon with other elements contained in the cubic boron nitride sintered body. Examples of the silicon compound include silicon boride (SiB ６ ), silicon nitride (SiN), silicon oxide (SiO ２ Examples include 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 the cubic boron nitride particles. The zirconium content of the binder may be 0.00 atomic% to 2.0 atomic%, 0.01 atomic% to 1.5 atomic%, or 0.01 atomic% to 1.0 atomic%.

[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 also contain conventionally known components. 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 Embodiment 1 using an energy-dispersive X-ray spectrometer attached to a scanning transmission electron microscope may include a first region where silicon is present. The atomic ratio N of cobalt in the first region. Ｃｏ and the atomic ratio of silicon N Ｓｉ Ratio N Ｃｏ / N Ｓｉ It may be between 0.5 and 120, between 1 and 75, or between 1 and 25.

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

[0069] The area to be analyzed for elemental analysis is the entire measurement field of view. In the elemental mapping image (first image), identify the first region where silicon is present. In the first region, determine the atomic percentage N of cobalt. Ｃｏ and the atomic ratio of silicon N Ｓｉ Ratio N Ｃｏ / N Ｓｉ The N of the 10 measurement fields is measured. The above measurement is performed in 10 different measurement fields that do not overlap. In this disclosure, the N of the 10 measurement fields Ｃｏ / N Ｓｉ The average of the number of cobalt atoms in the first region N Ｃｏ and the atomic ratio of silicon N Ｓｉ Ratio N Ｃｏ / N Ｓｉ This applies.

[0070] As long as the measurement is performed on the same sample, the measurement field of view can be set arbitrarily, and the above procedure can be followed, N Ｃｏ / N Ｓｉ Even after performing the measurement multiple times, it was confirmed that there was almost no variation in the measurement results.

[0071] <W ２ Co ２１ B ６ The ratio IA / IB of the peak integral intensity IA of the (420) plane and the peak integral intensity IB of the (111) plane of the cubic boron nitride > The binder of the cubic boron nitride sintered body of Embodiment 1 contains tungsten, and in the X-ray diffraction pattern of the cubic boron nitride sintered body, W ２ Co ２１ B ６The ratio IA / IB of the peak integral intensity IA of the (420) plane of boron nitride to the peak integral intensity IB of the (111) plane of boron nitride may be 0.05 or less. IA / IB may also be between 0.01 and 0.04, or between 0.01 and 0.03.

[0072] The measurement method for IA / IB described above is as follows: First, a test piece with a thickness of approximately 1.0 to 2.0 mm is cut 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 (Rigaku Corporation's "MiniFlex 600" trademark). The measurement conditions are as follows.

[0073] X-ray diffractometer: Product name "MiniFlex 600", manufactured by Rigaku Corporation. Characteristic X-ray: Cu-Kα (wavelength 1.54 Å) Tube voltage: 40 kV Tube current: 15 mA Filter: K-β filter Optical system: Focusing method X-ray diffraction method: θ-2θ method

[0074] Based on the X-ray diffraction spectrum, W ２ Co ２１ B ６ The peak integrated intensity IA of the (420) plane and the peak integrated intensity IB of the (111) plane of cubic boron nitride are measured. In the X-ray diffraction spectrum, W ２ Co ２１ B ６ The peak of the (420) plane is observed at 2θ = 38.2° ± 0.15°. In the X-ray diffraction spectrum, the peak of the (111) plane of cubic boron nitride is observed at 2θ = 43.3° ± 0.15°. Based on the peak integrated intensities IA and IB, IA / IB is calculated.

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

[0076] <First Interface Region> The cubic boron nitride sintered body of Embodiment 1 may have a first interface region in which the distance from the first interface between adjacent cubic boron nitride particles is within 100 nm. At least a portion of the first interface region may contain one or both of cobalt and silicon.

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

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

[0079] In the second image, the first interface region is identified, where the distance from the first interface is within 100 nm. In other words, the first interface region consists of the region sandwiched between the first interface and a virtual line where the distance from the first interface to the first cubic boron nitride particle is 100 nm, and the region sandwiched between the first interface and a virtual line where the distance from the first interface to the second cubic boron nitride particle is 100 nm, assuming that the two cubic boron nitride particles forming the first interface are a first cubic boron nitride particle and a second cubic boron nitride particle.

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

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

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

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

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

[0085] In this disclosure, the fact that a cubic boron nitride sintered body includes the first interface region, and that at least a portion of the first interface region contains zirconium, is confirmed in the same manner as the method for confirming that at least a portion of the first interface region contains either or both 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 a binder. When the silicon content is measured along a first direction toward the interior of the cubic boron nitride particles from the second interface, the width D of the 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 there is a region around the cubic boron nitride particles where the silicon content is 0.1 atomic% or more and 1.5 atomic% or less, and the thickness of that region is 20 nm or more and 1000 nm.

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

[0088] In this 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, the 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 near the center of the image, and a third image is obtained by changing the observation magnification to 100,000 times and observing it.

[0089] In the third image, the direction of elongation of the second interface is confirmed, and elemental line analysis is performed along a direction approximately perpendicular to this elongation direction, and along the first direction toward the interior of the cubic boron nitride particles from the second interface. The beam diameter is set to 0.3 nm or less, and the scan interval is set to 0.1 to 0.7 nm.

[0090] From the results of elemental line analysis, the width D of the region where the silicon content is between 0.1 atomic% and 1.5 atomic% is calculated. Here, the silicon content is measured at each beam spot. The silicon content is determined by considering all elements measured at each peak spot as 100 atomic%.

[0091] The above analysis is repeatedly performed on the first image of the 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, it is determined that the cubic boron nitride sintered body has a region with a silicon content of 0.1 atomic% or more and 1.5 atomic% or less, and a width D of 20 nm or more and 1000 nm or less.

[0092] <Surface defects in the second region> The BF-STEM image of the cross-section of the cubic boron nitride sintered body of Embodiment 1 includes a second region in which cobalt is present, and surface defects intersecting each other at 90° angles may exist in the second region.

[0093] In this disclosure, the BF-STEM image of the cross-section of the cubic boron nitride sintered body includes a second region where cobalt is present, and the presence of planar defects intersecting each other at 90° within the second region is confirmed by the following procedure. Ｃｏ / N Ｓｉ An elemental mapping image (first image) is obtained using the same measurement method as above. In the first image, the second region where cobalt is present is identified. In the first image, an arbitrary location corresponding to the second region is selected, and the BF-STEM image, magnified 50,000 to 100,000 times so that the location is the center, is taken as the second image. In the second image, in the location corresponding to the second region, a streaky pattern that intersects each other at 90° is identified. The streaky pattern corresponds to a surface defect. Figure 1 is a diagram to illustrate the streaky pattern that intersects each other at 90°. In Figure 1, the streaky pattern 4 exists in the second region 5, intersecting each other at 90°. Based on the first image of 10 fields of view, the above observation is repeated, and if a streaky pattern that intersects each other at 90° is observed in the second region in 5 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 surface defects that intersect each other at 90° exist in the second region.

[0094] <Method for manufacturing a cubic boron nitride sintered body> The cubic boron nitride sintered body of Embodiment 1 can be manufactured, 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 powder means the median diameter d50 of the sphere equivalent diameter. The average particle size is measured using a particle size distribution analyzer (product name: MT3300EX) manufactured by Microtrac.

[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. One such method is the arc plasma powder method (APD method). The conditions for the APD method are as follows: Coating apparatus: Nanoparticle formation apparatus APD-P manufactured by Advance Engineering Co., Ltd. Target: Cobalt or silicon Introduced gas: 10 －４ After vacuuming the Pa system, argon gas is introduced to raise the internal pressure of the apparatus to 10. －１ Pa setting discharge voltage: 200V, discharge frequency: 6Hz, capacitor capacitance: 1080μF, shot count: 5000, processing powder amount: 25g, powder container rotation speed: 50rpm

[0098] As cobalt powder and silicon powder, powders obtained by pre-mixing and grinding cobalt powder and silicon powder in a ball mill can be used. The grinding time is 12 to 24 hours.

[0099] As a 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 a raw material powder other than the above, powders containing conventionally known components (Ni, Fe, Cr, Mo, Ti, V, Nb, Mo, Hf, Ta, Re) as binders may 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. The mass ratio of silicon powder to cobalt powder in the mixed 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 to a temperature of 1500 to 2000°C and a pressure of 5 to 8 GPa using a belt-type high-pressure high-temperature generator, 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 comprising 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 composed entirely of the cubic boron nitride sintered body, or only the cutting edge portion may be composed of the 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 means the portion involved in cutting. Specifically, the cutting edge means the region enclosed by the cutting edge ridge and a virtual plane at a distance of 0.5 mm from the cutting edge ridge to the cubic boron nitride sintered body side.

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

[0107] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0108] <Preparation of cubic boron nitride sintered body> <Raw material preparation process> The average particle size of cubic boron nitride (cBN) powder 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 where the temperature and time are listed in the "cBN Powder Heat Treatment" column of Tables 1 and 2, the cBN powder was heat-treated in a nitrogen atmosphere at the temperature and time indicated in the table. For samples marked with "-", no heat treatment was performed.

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

[0111] For samples where "Yes" is indicated in the "Co / Si Pre-Grinding" column of Tables 1 and 2, powder was used that was prepared by mixing cobalt powder and silicon powder in a ball mill and grinding them beforehand. The grinding time was 24 hours.

[0112] <Mixing Process> The raw material powders were mixed in the mass percentages listed in Tables 1 and 2 (with the total mixed powder being 100% by mass) to obtain the mixed powder. Mixing was performed 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 of each sample.

[0114]

[0115]

[0116] [Evaluation of Cubic Boron Nitride Sintered Bodies] <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 equivalent circular diameter d50 of the cubic boron nitride particles (cBN particles) were measured using 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, the amount of silicon present in the binder of the silicon contained in the cubic boron nitride sintered body was between 50% and 99.9%. In samples 1 to 33, the amount of cobalt present in the binder of the cobalt contained in the cubic boron nitride sintered body was between 80% and 100%. In each sample, the forms of silicon and cobalt present in the binder were confirmed by the method described in Embodiment 1. The results are shown in Tables 3 and 4. "Solid solution" refers to a solid solution of silicon and cobalt.

[0118] Elemental analysis was performed on the cubic boron nitride sintered body of each sample 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 of cobalt in the first region was N. Ｃｏ and the atomic ratio of silicon N Ｓｉ Ratio N Ｃｏ / N Ｓｉ The following measurements were taken. The results are shown in Tables 3 and 4.

[0119] <Thermal Diffusivity> The thermal diffusivity of cubic boron nitride sintered bodies of samples 1 to 18 and samples 1-1 to 1-6 was measured using the laser flash method. The measurement conditions were as follows: For the laser flash method, a NETZSCH "LFA467 Hyper Flash" (trademark) was used. The thermal diffusivity was calculated from the temperature history curve of the back surface of the test specimen when the surface of the test specimen was irradiated with a laser pulse (refer to JIS R1611:2010). The shape of the test specimen was a square with sides of 10 mm and a thickness of 1 to 2 mm, and the entire test specimen was treated to blackbody with graphite spray. Three measurements were taken for each sample, and the average values ​​are shown in Table 3. <Measurement Conditions> Laser voltage: 230 V Pulse width: 0.3 ms Measurement temperature: 25 °C

[0120] In sample 1-2, numerous voids were present in the cubic boron nitride sintered body, making it impossible to measure the thermal diffusivity. In sample 1-6, cracks were present in the cubic boron nitride sintered body, making it impossible to measure the thermal diffusivity. In Table 3, "Thermal Diffusivity" is indicated as "Unmeasurable".

[0121] <Cutting Test 1> Cutting tools (base material shape: SNGN090308, cutting edge treatment: T01225) were fabricated using cubic boron nitride sintered bodies of samples 1 to 18 and samples 1-1 to 1-6, and cutting test 1 was performed. The conditions for cutting test 1 were as follows: <Cutting conditions> Cutting speed: 1450 m / min. Feed rate: 0.11 mm / rev. Depth of cut: 0.3 mm Coolant: WET Coolant liquid: Emulsion 96 (diluted 20 times with water) Cutter: RM3080R (manufactured by Sumitomo Electric Industries, Ltd.) Cutting method: Intermittent cutting Lathe: NV5000 (manufactured by DMG Mori Seiki Co., Ltd.) Workpiece material: Simultaneous machining of two FC250 pearlite plates (cast iron).

[0122] <Evaluation Criteria> The cutting edge was observed every 0.5 km of cutting distance, and the amount of edge shedding was measured. The amount of edge shedding was defined as the recession due to wear from the position of the cutting edge ridge before cutting. In the case of chipping, the size of the chip was defined as the amount of shedding. The point at which the amount of edge shedding reached 0.1 mm or more was defined as the end of the cutting tool's lifespan, and the volume of cast iron removed by cutting at that point (unit: cm³) was defined. ３The volume of cast iron removed was measured. The results of ranking according to the following criteria are shown in Table 3. The larger the volume of cast iron removed by cutting, the longer the lifespan of the cutting tool can be considered to be. A: 90 cm ３ More than B:85cm ３ More than 90cm ３ Less than C: 70cm ３ 85cm or more ３ Less than D: 65cm ３ 70cm or more ３ Less than E: 45cm ３ less than

[0123]

[0124] <Discussion 1> The cubic boron nitride sintered bodies and cutting tools of Samples 1 to 18 correspond to the examples. The cubic boron nitride sintered bodies and cutting tools of Samples 1-1 to 1-6 correspond to the comparative examples. It was confirmed that the cutting tools of Samples 1 to 18 had a longer tool life than the cutting tools of Samples 1-1 to 1-6.

[0125] In the cubic boron nitride sintered bodies of samples 1-2, numerous voids were found within the microstructure. This is due to the low binder content.

[0126] The cubic boron nitride sintered bodies of samples 1-3 contain sufficient silicon, which improves the bonding strength between cubic boron nitride particles and thus improves thermal diffusivity. However, due to the low cobalt content, the toughness of the cubic boron nitride sintered bodies is low, resulting in a reduced lifespan for cutting tools.

[0127] Despite having a high cubic boron nitride particle content of 90% in samples 1-5, the cubic boron nitride sintered bodies exhibit low thermal diffusivity. This suggests weak bonding between cubic boron nitride particles, which reduces the cutting performance of the cutting tool.

[0128] Cracks were observed in the cubic boron nitride sintered bodies of samples 1-6. This is due to an excessive silicon content.

[0129] <Ratio IA / IB> In the cubic boron nitride sintered bodies of samples 19 to 33, X-ray diffraction patterns were obtained using the method described in Embodiment 1, and W ２ Co ２１ B ６The ratio IA / IB of the peak integral intensity IA of the (420) plane and the peak integral 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, the first interface region, in which the distance from the first interface between adjacent cubic boron nitride particles is within 100 nm, was identified using 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, or zirconium are present.

[0131] <Width D> In the cubic boron nitride sintered bodies of samples 19 to 33, the second interface between adjacent cubic boron nitride particles and the binder was identified using the method described in Embodiment 1. The silicon content was measured along the first direction toward the interior of the cubic boron nitride particles from the second interface, 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] <Surface defects in Co structure> In the cubic boron nitride sintered bodies of samples 19 to 33, BF-STEM images were obtained using the method described in Embodiment 1, and the maximum value of the angle (expressed as 0° to 90°) formed by the streaky patterns (corresponding to surface defects) in the second region was measured. The results are shown in Table 5. When the angle is 90°, the BF-STEM image of the cross-section of the cubic boron nitride sintered body includes the second region where cobalt is present, and it is determined that surface defects intersecting each other at 90° exist in the second region.

[0133]

[0134]

[0135] <Cutting Test 2> Cutting tools (base material shape: CNGA120408, cutting edge treatment: T01225) were fabricated using cubic boron nitride sintered bodies of samples 19 to 33 and samples 1-1 to 1-6, and cutting test 2 was performed. The conditions for cutting test 2 were as follows: <Cutting conditions> Cutting speed: 250 m / min. Feed rate: 0.1 mm / rev. Depth of cut: 0.25 mm Coolant: WET Cutting method: Continuous cutting Lathe: LB4000EX (manufactured by Okuma Corporation) Workpiece material: Sintered part (hardened sintered alloy D40 manufactured by Sumitomo Electric Industries, Ltd., 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 at which the amount of wear on the cutting edge reached 150 μm or more was measured. The above cutting distance was used as the lifespan 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 lifespan of the cutting tool can be evaluated. A: 5.0 km or more B: 4.5 km or more and less than 5.0 km C: 3.5 km or more and less than 4.5 km D: 3.0 km or more and less than 3.5 km E: 2.5 km or more and less than 3.0 km F: Less than 2.5 km

[0137]

[0138] <Discussion 2> The cubic boron nitride sintered bodies and cutting tools of Samples 19 to 33 correspond to the examples. The cubic boron nitride sintered bodies and cutting tools of Samples 1-1 to 1-6 correspond to the comparative examples. It was confirmed that the cutting tools of Samples 19 to 33 had a longer tool life than the cutting tools of Samples 1-1 to 1-6.

[0139] Comparing samples 19 to 22, samples 19 to 21, with an IA / IB of 0.05 or less, have longer tool life than sample 22, which has an IA / IB of 0.1. This is because the brittle phase W ２ Co ２１ B ６ The less of this substance there is, the stronger the binder becomes, which suppresses binder wear during cutting and the shedding of cubic boron nitride particles caused by binder wear.

[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 force between cubic boron nitride particles, suppressing wear progression due to the shedding of cubic boron nitride particles.

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

[0142] Comparisons between sample 19 and sample 32, and between sample 23 and sample 33, confirmed that samples with intersecting surface defects at 90° angles within the second region had longer tool life than samples without such surface defects. This is because the second region with {110} surface defects (90°) has higher strength than the second region with twinning defects, thus suppressing binder wear during cutting and the shedding of cubic boron nitride particles caused by binder wear.

[0143] While embodiments and examples of this disclosure have been described above, it is intended from the outset that the configurations of each of the embodiments and examples described above may be combined or modified in various ways as appropriate. The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalences.

[0144] 1. Rake face, 2. Relief face, 3. Edge ridge, 4. Striped pattern, 5. Second region

Claims

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

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

3. The 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 the first region where silicon is present, and the atomic ratio of cobalt in the first region N Ｃｏ and the atomic ratio of silicon N Ｓｉ Ratio N Ｃｏ / N Ｓｉ The cubic boron nitride sintered body according to claim 1 or claim 2, wherein the ratio is 0.5 or more and 120 or less.

4. The above N Ｃｏ / N Ｓｉ The cubic boron nitride sintered body according to claim 3, wherein the value is between 1 and 75.

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

6. The binder contains tungsten, and in the X-ray diffraction pattern of the cubic boron nitride sintered body, W ２ Co ２１ B ６ The ratio IA / IB of the peak integrated intensity IA of the (420) plane to the peak integrated intensity IB of the (111) plane of cubic boron nitride is 0.05 or less. The cubic boron nitride sintered body according to any one of claims 1 to 5.

7. The cubic boron nitride sintered body according to any one of claims 1 to 6, wherein the cubic boron nitride sintered body has a first interface region in which the distance from the first interface between adjacent cubic boron nitride particles is within 100 nm, and at least a portion of the first interface region contains one or both of cobalt and silicon.

8. The cubic boron nitride sintered body according to any one of claims 1 to 7, wherein the binder contains zirconium, the cubic boron nitride sintered body has a first interface region in which the distance from the first interface between adjacent cubic boron nitride particles is within 100 nm, and at least a portion of the first interface region contains zirconium.

9. The cubic boron nitride sintered body has a second interface between adjacent cubic boron nitride particles and the binder, and when the silicon content is measured along a first direction toward the interior of the cubic boron nitride particles from the second interface, the width D of the region in which 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, according to any one of claims 1 to 8.

10. The cubic boron nitride sintered body according to any one of claims 1 to 9, wherein the BF-STEM image of the cross-section of the cubic boron nitride sintered body includes a second region in which cobalt is present, and within the second region, there are surface defects that intersect each other at 90° angles.

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

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