Cubic boron nitride sintered compact and tool

Abstract

Disclosed is a cubic boron nitride sintered compact which comprises cubic boron nitride particles, a binder phase, and a first phase. The content of the cubic boron nitride particles in the cubic boron nitride sintered compact is 25% by volume to 80% by volume inclusive. The binder phase contains one or both of at least one first compound which is composed of at least one element that is selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, and silicon, and at least one element that is selected from the group consisting of nitrogen, carbon, boron, and oxygen, and a solid solution that is derived from the first compound. The first phase contains cobalt, tungsten, and at least one first element that is selected from the group consisting of the elements contained in the binder phase. The total content of cobalt and tungsten in the cubic boron nitride sintered compact is 1.0% by mass to 6.0% by mass inclusive. The binder phase is composed of a plurality of binder phase particles. The plurality of binder phase particles include 50% or more of first binder phase particles on the number basis. The surfaces of the first binder phase particles each comprise 50% by area or more of a first region, and the first region is in contact with the first phase.

Description

Cubic boron nitride sintered body and tools

[0001] The present disclosure relates to a cubic boron nitride sintered body and a tool. This application claims priority to Japanese Patent Application No. 2023-073631, filed on April 27, 2023. The entire contents of the Japanese patent application are incorporated herein by reference.

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

[0003] Patent Document 1 discloses a technology for improving crater wear resistance and chipping resistance in a cubic boron nitride sintered body containing cubic boron nitride particles and Ti compound particles as a binder phase by causing a W—Co phase to exist uninterruptedly between the cubic boron nitride particles.

[0004] Japanese Patent Application Laid-Open No. 2020-28929

[0005] The cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body comprising cubic boron nitride particles, a binder phase, and a first phase, wherein the cubic boron nitride particle content of the cubic boron nitride sintered body is 25% by volume or more and 80% by volume or less, the binder phase includes one or both of: one or more first compounds consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, and silicon, and at least one element selected from the group consisting of nitrogen, carbon, boron, and oxygen, and a solid solution derived from the first compound, and the first phase includes at least one first element selected from the group consisting of cobalt, tungsten, and the elements contained in the binder phase, The cubic boron nitride sintered body has a total content of cobalt and tungsten of 1.0 mass % or more and 6.0 mass % or less, the binder phase is composed of a plurality of binder phase particles, the plurality of binder phase particles contain first binder phase particles at 50% or more by number, the surfaces of the first binder phase particles contain first regions at 50% or more by area, and the first regions are regions in contact with the first phase.

[0006] The cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body comprising cubic boron nitride particles, a binder phase, and a first phase, wherein the cubic boron nitride sintered body has a content of the cubic boron nitride particles of 25% by volume or more and 80% by volume or less, the binder phase includes one or both of: one or more first compounds consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, and silicon, and at least one element selected from the group consisting of nitrogen, carbon, boron, and oxygen, and a solid solution derived from the first compound, and the first phase includes at least one first element selected from the group consisting of cobalt, tungsten, and the elements contained in the binder phase, The cubic boron nitride sintered body has a total content of cobalt and tungsten of 1.0 mass % or more and 6.0 mass % or less, the binder phase is composed of a plurality of binder phase particles, the plurality of binder phase particles contain first binder phase particles at 50% or more by number, the surfaces of the first binder phase particles contain first regions at 50% or more by area, and the first regions are regions in contact with the first phase.

[0007] [Problem to be Solved by the Present Disclosure] In recent years, there has been an increasing need for high-efficiency machining of high-hardness steel, and therefore there is a demand for a cubic boron nitride sintered body that, when used as a tool material, can provide a tool with a long tool life even in high-efficiency machining of high-hardness steel.

[0008] Therefore, an object of the present disclosure is to provide a cubic boron nitride sintered body that, when used as a tool material, can provide a tool with a long tool life even in high-efficiency machining of high-hardness steel, and a tool including the cubic boron nitride sintered body.

[0009] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cubic boron nitride sintered body that, when used as a tool material, can provide a tool having a long tool life even in high-efficiency machining of high-hardness steel, and a tool including the cubic boron nitride sintered body.

[0010] [Explanation of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) A cubic boron nitride sintered body of the present disclosure is a cubic boron nitride sintered body comprising cubic boron nitride particles, a binder phase, and a first phase, wherein the cubic boron nitride particle content of the cubic boron nitride sintered body is 25% by volume or more and 80% by volume or less, the binder phase includes one or both of: one or more first compounds each consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, and silicon, and at least one element selected from the group consisting of nitrogen, carbon, boron, and oxygen, and a solid solution derived from the first compound, and the first phase includes at least one first element selected from the group consisting of cobalt, tungsten, and the elements contained in the binder phase, The cubic boron nitride sintered body has a total content of cobalt and tungsten of 1.0 mass % or more and 6.0 mass % or less, the binder phase is composed of a plurality of binder phase particles, the plurality of binder phase particles contain first binder phase particles at 50% or more by number, the surfaces of the first binder phase particles contain first regions at 50% or more by area, and the first regions are regions in contact with the first phase.

[0011] According to the present disclosure, it is possible to provide a cubic boron nitride sintered body that, when used as a tool material, can provide a tool having a long tool life even in high-efficiency machining of high-hardness steel, and a tool including the cubic boron nitride sintered body.

[0012] (2) In the above (1), the plurality of binder phase particles may contain second binder phase particles in an amount of 50% or more by number, and the surfaces of the second binder phase particles may contain the first regions in an amount of 75% or more by area.

[0013] This further improves the life of the tool equipped with the cubic boron nitride sintered body.

[0014] (3) In the above (1) or (2), the binder phase may contain at least one element selected from the group consisting of titanium, chromium, aluminum, carbon, nitrogen, and boron, thereby further improving the life of a tool including the cubic boron nitride sintered body.

[0015] (4) In any one of the above (1) to (3), the first element may include at least one element selected from the group consisting of aluminum, carbon, nitrogen, boron, and silicon, thereby further improving the life of a tool including the cubic boron nitride sintered body.

[0016] (5) In any of the above (1) to (4), the first phase may be absent at the interface between the cubic boron nitride particles and the binder phase, which further improves the life of a tool including a cubic boron nitride sintered body, particularly in interrupted cutting under severe conditions.

[0017] (6) In any one of the above (1) to (5), the thickness of the first phase may be 20 nm or less, which further improves the life of a tool including the cubic boron nitride sintered body, particularly in interrupted cutting under severe conditions.

[0018] (7) In any one of the above (1) to (6), the tungsten content of the first phase may be greater than the cobalt content of the first phase, thereby further improving the life of a tool including the cubic boron nitride sintered body, particularly in interrupted cutting under severe conditions.

[0019] (8) A tool according to the present disclosure includes the cubic boron nitride sintered body according to any one of (1) to (7) above. The tool according to the present disclosure has a long tool life even in high-efficiency machining of high-hardness steel.

[0020] [Details of the embodiment of the present disclosure] Specific examples of the cubic boron nitride sintered body and tool of the present disclosure are described below. In this specification, the notation in the form of "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0021] In the present specification, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is understood to include any conventionally known atomic ratio, and is not necessarily limited to only those within the stoichiometric range.

[0022] In the present disclosure, when one or more numerical values ​​are recited as the lower limit and the upper limit of a numerical range, a combination of any one numerical value recited as the lower limit and any one numerical value recited as the upper limit is also considered to be disclosed. For example, when a1 or more, b1 or more, and c1 or more are recited as the lower limit and a2 or less, b2 or less, and c2 or less are recited as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are considered to be disclosed.

[0023] [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 comprising cubic boron nitride particles, a binder phase, and a first phase, wherein the cubic boron nitride sintered body has a cubic boron nitride particle content of 25% by volume or more and 80% by volume or less, the binder phase includes one or both of: one or more first compounds each consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, and silicon, and at least one element selected from the group consisting of nitrogen, carbon, boron, and oxygen, and a solid solution derived from the first compound, and the first phase includes at least one first element selected from the group consisting of cobalt, tungsten, and the elements contained in the binder phase, The cubic boron nitride sintered body has a total cobalt and tungsten content of 1.0 mass % or more and 6.0 mass % or less, the binder phase is composed of a plurality of binder phase particles, the plurality of binder phase particles contain first binder phase particles at 50% or more by number, the surfaces of the first binder phase particles contain first regions at 50% or more by area, and the first regions are regions in contact with the first phase.

[0024] When used as a tool material, the cubic boron nitride sintered body of the present disclosure can provide a tool with a long tool life even in high-efficiency machining of high-hardness steel. The reason for this is presumed to be as follows.

[0025] (i) The cubic boron nitride sintered body of the present disclosure contains 25% by volume or more and 80% by volume or less of cubic boron nitride particles that have excellent strength and toughness. Therefore, the cubic boron nitride sintered body also has excellent strength and toughness. Therefore, tools including this cubic boron nitride sintered body can have excellent wear resistance and chipping resistance even in high-efficiency machining of high-hardness steel.

[0026] (ii) In the cubic boron nitride sintered body of the present disclosure, the binder phase includes one or both of one or more first compounds consisting of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, and silicon, and at least one element selected from the group consisting of nitrogen, carbon, boron, and oxygen, and a solid solution derived from the first compound. The first compound itself has high strength and toughness and improves the bonding strength between cBN particles. Therefore, a tool including a cubic boron nitride sintered body containing the first compound as a binder phase can have excellent wear resistance and chipping resistance, even in high-efficiency machining of high-hardness steel.

[0027] (iii) The cubic boron nitride sintered body of the present disclosure contains a first phase containing cobalt, tungsten, and at least one first element selected from the elements contained in the binder phase. The first phase can improve the bonding strength between binder phase particles. In the cubic boron nitride sintered body of the present disclosure, the percentage of first binder phase particles with 50% or more of their surfaces in contact with the first phase is 50% or more, based on the number, and therefore the bonding strength between binder phase particles is improved. Therefore, tools containing the cubic boron nitride sintered body of the present disclosure can have excellent wear resistance and chipping resistance, even in high-efficiency machining of high-hardness steel.

[0028] In the present disclosure, examples of high-hardness steel include chromium-molybdenum steel (SCM415). While it has been described above that tools containing the cubic boron nitride sintered body of the present disclosure have a long tool life in highly efficient machining of high-hardness steel, the workpiece material is not limited to this. Examples of workpiece materials include high-strength cast iron (FCD700, etc.), carbon steel for machine construction (S50C, etc.), high-carbon chromium bearing steel (SUJ2, SUJ4, etc.), and alloy tool steel (SKD11, etc.).

[0029] <Composition of Cubic Boron Nitride Sintered Body> The cubic boron nitride sintered body of the first embodiment comprises cubic boron nitride particles, a binder phase, and a first phase.

[0030] In the cubic boron nitride sintered body of embodiment 1, the content of cubic boron nitride particles is 25 volume % or more and 80 volume % or less. From the viewpoint of improving hardness, the lower limit of the content of cubic boron nitride particles in the cubic boron nitride sintered body is 25 volume % or more, or may be 30 volume % or more, 35 volume % or more, or 40 volume % or more. From the viewpoint of improving toughness, the upper limit of the content of cubic boron nitride particles in the cubic boron nitride sintered body is 80 volume % or less, or may be 75 volume % or less, 70 volume % or less, or may be 65 volume % or less. The content of cubic boron nitride particles in the cubic boron nitride sintered body is 25 vol% or more and 80 vol% or less, or alternatively 25 vol% or more and 75 vol% or less, or 25 vol% or more and 70 vol% or less, or 30 vol% or more and 70 vol% or less, or 40 vol% or more and 65 vol% or less.

[0031] In the present disclosure, the content of cubic boron nitride particles in a cubic boron nitride sintered body is measured using an energy dispersive X-ray analyzer (EDX) ("Octane Elect EDS System" (trademark) manufactured by EDAX) attached to a scanning electron microscope (SEM) ("JSM-7800F" (trademark) manufactured by JEOL Ltd.) (hereinafter also referred to as "SEM-EDX") in the following manner.

[0032] The cubic boron nitride sintered body is cut at an arbitrary position to expose a cross section of the cubic boron nitride sintered body, and the cross section is polished. A focused ion beam device, a cross-section polisher device, or the like can be used to cut the cubic boron nitride sintered body. When the cubic boron nitride sintered body is used as part of a tool, a portion of the cubic boron nitride sintered body is cut out with a diamond grinding wheel, electrodeposited wire, or the like to expose a sample including a cross section of the cubic boron nitride sintered body.

[0033] Next, the cross section is observed under an SEM at 5000x magnification to obtain a backscattered electron image. In the backscattered electron image, the regions where the cBN particles exist appear as black regions, and the regions where the binder phase and the first phase exist appear as gray or white regions.

[0034] Next, the backscattered electron image is subjected to binarization processing using image analysis software ("WinROOF 2018" by Mitani Corporation) so that only the cBN particles are extracted. In the image after binarization processing, the cBN particles are shown in a dark field (black), and the binder phase and the first phase are shown in a bright field (white). In the image after binarization processing, the area percentage of pixels originating from the dark field (pixels originating from cBN particles) relative to the area of ​​the entire measurement field (hereinafter also referred to as "area percentage of cBN particles") is calculated.

[0035] The above-mentioned measurement of the area percentage of cBN particles is carried out in five measurement fields that do not overlap with one another, and the average of the area percentages of cBN particles in the five measurement fields is calculated. In the present disclosure, the average of the area percentages of cBN particles in the five measurement fields corresponds to the content (volume %) of cubic boron nitride particles in the cubic boron nitride sintered body.

[0036] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the content of cubic boron nitride particles in a cubic boron nitride sintered body is measured multiple times according to the above procedure.

[0037] The cubic boron nitride sintered body of embodiment 1 can be composed of cubic boron nitride particles, a binder phase, and a first phase. The cubic boron nitride sintered body of embodiment 1 can contain impurities resulting from raw materials, manufacturing conditions, etc., in addition to the cubic boron nitride particles, binder phase, and first phase, as long as the effects of the present disclosure are not impaired. The cubic boron nitride sintered body of embodiment 1 can be composed of cubic boron nitride particles, a binder phase, a first phase, and impurities. Examples of impurities include nickel. When the cubic boron nitride sintered body contains impurities, the impurity content of the cubic boron nitride sintered body can be 0.1 mass% or less. The impurity content of the cubic boron nitride sintered body can be measured by secondary ion mass spectrometry (SIMS).

[0038] <Cubic Boron Nitride Particles> <Composition of Cubic Boron Nitride Particles> In embodiment 1, the cubic boron nitride particles are made of cubic boron nitride. The cubic boron nitride particles may contain impurities together with cubic boron nitride, as long as the effects of the present disclosure are not impaired. When the cubic boron nitride particles contain impurities, the impurity content of the cubic boron nitride particles may be 0.1 mass% or less. The impurity content of the cubic boron nitride particles can be measured by secondary ion mass spectrometry (SIMS).

[0039] <Average particle size of cubic boron nitride particles> In the cubic boron nitride sintered body of embodiment 1, the average particle size of the cubic boron nitride particles is not particularly limited and may be a general average particle size used in conventional cubic boron nitride sintered bodies. The particle size of the cubic boron nitride particles may be, for example, 0.1 μm or more and 10 μm or less.

[0040] In the present disclosure, the average particle size of cubic boron nitride particles is measured by the following procedure: A cross section of a cBN sintered body is exposed and polished using the same method as that used to measure the content of cubic boron nitride particles in a cubic boron nitride sintered body.

[0041] Next, the polished surface is observed at 10,000x magnification using an SEM to obtain an SEM image. A rectangular measurement field of view of 12 μm × 15 μm is set in the SEM image. The SEM image is processed using image analysis software ("WinROOF ver. 7.4.5" by Mitani Corporation) to obtain the circle-equivalent diameter of each cBN particle observed within the measurement field. The arithmetic mean of the circle-equivalent diameters of all cBN particles within the measurement field is calculated. This arithmetic mean corresponds to the average particle size of the cBN particles in the measurement field.

[0042] The above measurement is performed in five non-overlapping measurement fields. The arithmetic mean of the average particle diameters of the cBN particles in the five measurement fields is calculated. In the present disclosure, the arithmetic mean of the average particle diameters in the five measurement fields corresponds to the average particle diameter of the cubic boron nitride particles.

[0043] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the average particle size of cubic boron nitride particles is measured multiple times according to the above procedure.

[0044] <Binder Phase> In the cubic boron nitride sintered body of embodiment 1, the binder phase contains one or both of one or more first compounds each consisting of at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum, chromium, molybdenum, aluminum, and silicon (hereinafter also referred to as "second element") and at least one element selected from the group consisting of nitrogen, carbon, boron, and oxygen, and a solid solution derived from the first compound.

[0045] The bonding phase can be in any of the following forms: (i) the bonding phase includes a first compound; (ii) the bonding phase consists of the first compound; (iii) the bonding phase includes a solid solution derived from the first compound; (iv) the bonding phase consists of a solid solution derived from the first compound; (v) the bonding phase includes the first compound and a solid solution derived from the first compound; or (vi) the bonding phase consists of the first compound and a solid solution derived from the first compound.

[0046] The binder phase may contain impurities together with one or both of the first compound and the solid solution derived from the first compound, as long as the effects of the present disclosure are not impaired. When the binder phase contains impurities, the impurity content of the binder phase may be 0.1 mass% or less. The impurity content of the binder phase can be measured by secondary ion mass spectrometry (SIMS).

[0047] Examples of the first compound (nitride) composed of the second element and nitrogen include titanium nitride (TiN), zirconium nitride (ZrN), hafnium nitride (HfN), vanadium nitride (VN), niobium nitride (NbN), tantalum nitride (TaN), and chromium nitride (CrN). ２ N), molybdenum nitride (MoN), AlN (aluminum nitride), silicon nitride (Si ３ N ４ ), titanium zirconium nitride (TiZrN), titanium hafnium nitride (TiHfN), titanium vanadium nitride (TiVN), titanium niobium nitride (TiNbN), titanium tantalum nitride (TiTaN), titanium chromium nitride (TiCrN), titanium molybdenum nitride (TiMoN), zirconium hafnium nitride (ZrHfN), zirconium vanadium nitride (ZrVN), zirconium niobium nitride (ZrNbN), zirconium tantalum nitride (ZrTaN), zirconium chromium nitride (ZrCrN), zirconium molybdenum nitride (ZrMoN), hafnium vanadium nitride (HfVN), hafnium nitride niobium nitride (HfNbN), hafnium tantalum nitride (HfTaN), hafnium chromium nitride (HfCrN), hafnium molybdenum nitride (HfMoN), vanadium niobium nitride (VNbN), vanadium tantalum nitride (VTaN), vanadium chromium nitride (VCrN), vanadium molybdenum nitride (VMoN), niobium tantalum nitride (NbTaN), niobium chromium nitride (NbCrN), niobium molybdenum nitride (NbMoN), tantalum chromium nitride (TaCrN), tantalum molybdenum nitride (TaMoN), chromium molybdenum nitride (CrMoN), or titanium aluminum nitride (TiAlN, Ti ２ AlN, Ti ３ AlN).

[0048] Examples of the first compound (carbide) composed of the second element and carbon include titanium carbide (TiC), zirconium carbide (ZrC), hafnium carbide (HfC), vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), and chromium carbide (Cr ２ C), molybdenum carbide (MoC), silicon carbide (SiC), titanium zirconium carbide (TiZrC), titanium hafnium carbide (TiHfC), titanium vanadium carbide (TiVC), titanium niobium carbide (TiNbC), titanium tantalum carbide (TiTaC), titanium chromium carbide (TiCrC), titanium molybdenum carbide (TiMoC), zirconium hafnium carbide (ZrHfC), zirconium vanadium carbide (ZrVC), zirconium niobium carbide (ZrNbC), zirconium tantalum carbide (ZrTaC), zirconium chromium carbide (ZrCrC), zirconium molybdenum carbide (ZrMoC), hafnium vanadium carbide ( HfVC), hafnium niobium carbide (HfNbC), hafnium tantalum carbide (HfTaC), hafnium chromium carbide (HfCrC), hafnium molybdenum carbide (HfMoC), vanadium niobium carbide (VNbC), vanadium tantalum carbide (VTaC), vanadium chromium carbide (VCrC), vanadium molybdenum carbide (VMoC), niobium tantalum carbide (NbTaC), niobium chromium carbide (NbCrC), niobium molybdenum carbide (NbMoC), tantalum chromium carbide (TaCrC), tantalum molybdenum carbide (TaMoC), chromium molybdenum carbide (CrMoC), or titanium aluminum carbide (TiAlC, Ti ２ AlC, Ti ３ AlC).

[0049] Examples of the first compound (carbonitride) consisting of the second element, carbon, and nitrogen include titanium carbonitride (TiCN), zirconium carbonitride (ZrCN), hafnium carbonitride (HfCN), and titanium aluminum carbonitride (TiAlCN, Ti ２ AlCN, Ti ３ AlCN).

[0050] The first compound (boride) consisting of the second element and boron is, for example, titanium boride (TiB ２), zirconium boride (ZrB ２ ), hafnium boride (HfB ２ ), vanadium boride (VB ２ ), niobium boride (NbB ２ ), tantalum boride (TaB ２ ), chromium boride (CrB ２ ), molybdenum boride (MoB ２ ), or silicon boride (SiB ４ ) can be mentioned.

[0051] Examples of the first compound (oxide) composed of the second element and oxygen include titanium oxide (TiO ２ ), zirconium oxide (ZrO ２ ), hafnium oxide (HfO ２ ), vanadium oxide (V ２ O ５ ), niobium oxide (Nb ２ O ５ ), tantalum oxide (Ta ２ O ５ ), chromium oxide (Cr ２ O ３ ), molybdenum oxide (MoO ３ ), aluminum oxide (Al ２ O ３ ), or silicon oxide (SiO ２ ) can be mentioned.

[0052] Examples of the first compound (oxynitride) composed of a second element, nitrogen, and oxygen include titanium oxynitride (TiON), zirconium oxynitride (ZrON), hafnium oxynitride (HfON), vanadium oxynitride (VON), niobium oxynitride (NbON), tantalum oxynitride (TaON), chromium oxynitride (CrON), molybdenum oxynitride (MoON), and SiAlON (sialon).

[0053] The binder phase may contain at least one element selected from the group consisting of titanium, chromium, aluminum, carbon, nitrogen and boron.

[0054] The first compound is selected from the group consisting of TiN, TiCN, TiC, CrN, AlCrN, and Al ２ O ３The first compound may be at least one selected from the group consisting of: One type of the first compound may be used, or two or more types may be used in combination.

[0055] The binder phase may contain a solid solution derived from the first compounds. Here, the solid solution derived from the first compounds means a state in which two or more types of first compounds are dissolved in each other's crystal structure, and refers to an interstitial solid solution or a substitutional solid solution.

[0056] In the present disclosure, the composition of the binder phase is identified using X-ray diffraction in the following procedure: A cross section of a cBN sintered body is exposed and polished in the same manner as in the procedure for measuring the content of cubic boron nitride particles in a cubic boron nitride sintered body.

[0057] An X-ray diffraction spectrum of the polished surface is obtained using an X-ray diffractometer (MiniFlex600 (trademark) manufactured by Rigaku Corporation). The conditions for the X-ray diffractometer are as follows:

[0058] Characteristic X-ray: Cu-Kα (wavelength 1.54 Å) Tube voltage: 45 kV Tube current: 40 mA Filter: Multilayer mirror Optical system: Focusing method X-ray diffraction method: θ-2θ method.

[0059] The composition of the binder phase is identified based on the obtained X-ray diffraction spectrum.

[0060] <First Phase> In the cubic boron nitride sintered body of embodiment 1, the first phase contains cobalt, tungsten, and at least one first element selected from the group consisting of elements contained in the binder phase. The first element is an element contained in the binder phase excluding tungsten. The first element is at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, silicon, nitrogen, carbon, boron, and oxygen, which is the same element as the element contained in the binder phase. For example, when the binder phase is TiCN, the first element is at least one element selected from the group consisting of Ti, C, and N. By containing at least one element that is the same as the element contained in the binder phase in addition to cobalt and tungsten, the first phase can improve the bonding strength between the binder phase particles.

[0061] The first element may include at least one element selected from the group consisting of aluminum, carbon, nitrogen, boron and silicon, which further improves the bonding strength between the binder phase particles.

[0062] In the present disclosure, whether a cubic boron nitride sintered body contains a first phase is confirmed by the following procedure.

[0063] (A1) A sample is taken from the cubic boron nitride sintered body, and sliced ​​into slices of 30 to 100 nm using an argon ion slicer. The slices are then observed at 10,000x magnification using a transmission electron microscope (TEM) (JEOL Ltd., "JEM-2100F / Cs" (trademark)) to obtain TEM images.

[0064] (A2) Based on the TEM image, an energy dispersive X-ray analyzer (EDX) attached to the TEM ("EDAX" (trademark) manufactured by AMETEK) is used to obtain an elemental mapping image of cobalt and an elemental mapping image of tungsten.

[0065] (A3) Using image analysis software ("WinROOF 2018" by Mitani Corporation), the elemental mapping image of cobalt and the elemental mapping image of tungsten are superimposed. In the superimposed image (hereinafter also referred to as "Image A"), a region where cobalt and tungsten continuously coexist (hereinafter also referred to as "W-Co region") is identified.

[0066] (A4) Based on the composition of the binder phase measured by X-ray diffraction, the elements constituting the binder phase are identified. Based on the TEM image of the same field of view as in (A1) above, elemental mapping analysis is performed using an electron energy loss spectrometer (EELS) attached to the TEM to obtain an elemental mapping image of each element (hereinafter also referred to as "Image B").

[0067] (A5) Using image analysis software, image A in (A3) and image B in (A4) are superimposed. If at least one of the elements constituting the binder phase identified in image B coexists in the W—Co region of image A in the superimposed image (hereinafter also referred to as “image C”), it is confirmed that the cubic boron nitride sintered body contains a first phase.

[0068] In the cubic boron nitride sintered body of embodiment 1, the total content of cobalt and tungsten in the cubic boron nitride sintered body is 1.0 mass% or more and 6.0 mass% or less. From the viewpoint of improving the bonding strength between binder phase particles, the lower limit of the total content of cobalt and tungsten in the cubic boron nitride sintered body is 1.0 mass% or more, or may be 1.4 mass% or more, 1.5 mass% or more, 1.8 mass% or more, 2.0 mass% or more, 2.5 mass% or more, or 3.0 mass% or more. The upper limit of the total cobalt and tungsten content of the cubic boron nitride sintered body is 6.0 mass% or less, from the viewpoint of suppressing a decrease in wear resistance due to coarsening of the first phase, and may be 5.8 mass% or less, 5.7 mass% or less, 5.5 mass% or less, 5.2 mass% or less, 5.0 mass% or less, 4.5 mass% or less, or 4.0 mass% or less. The total cobalt and tungsten content of the cubic boron nitride sintered body may be 1.4 mass% to 5.8 mass% or less, 1.5 mass% to 5.7 mass% or less, 1.8 mass% to 5.5 mass% or less, 2.0 mass% to 5.2 mass% or less, 2.5 mass% to 5.0 mass% or less, or 3.0 mass% to 4.5 mass%.

[0069] In the present disclosure, the total mass-based content of cobalt and tungsten in a cubic boron nitride sintered body is measured by ICP mass spectrometry.

[0070] <Thickness of First Phase> In the cubic boron nitride sintered body of the first embodiment, the thickness of the first phase may be 20 nm or less, 0.6 nm or more and 20 nm or less, or 5 nm or more and 10 nm or less.

[0071] In the present disclosure, the thickness of the first phase is confirmed by the following procedure. The first phase is identified by the same procedures as steps (A1) to (A5) of the method for confirming that a cubic boron nitride sintered body contains a first phase, and line analysis is performed using EDX in a direction perpendicular to the extending direction of the first phase in a TEM image. The half-width of the tungsten peak is taken as the thickness of the first phase. The thickness of the first phase is measured at 10 different arbitrary locations of the first phase, and the average value is calculated. However, if the thickness of the first phase is less than 0.5 nm, it is excluded from the calculation of the average value as noise. In the present disclosure, this average value corresponds to the thickness of the first phase. It has been confirmed that, as long as measurements are performed on the same cubic boron nitride sintered body, almost the same results can be obtained even if the measurement location is changed.

[0072] <Tungsten Content and Cobalt Content of First Phase> In the cubic boron nitride sintered body of the first embodiment, the tungsten content of the first phase may be higher than the cobalt content of the first phase.

[0073] In the present disclosure, the tungsten content and cobalt content of the first phase are measured by the following procedure. Line analysis of the first phase is performed using the same procedure as the method for measuring the thickness of the first phase. The content (atomic %) at the tungsten peak is considered to be the tungsten content of the first phase. The content (atomic %) at the cobalt peak is considered to be the cobalt content of the first phase. The tungsten content and cobalt content are measured at any 10 different locations in the first phase, and the respective averages are calculated. In the present disclosure, the average tungsten content corresponds to the tungsten content of the first phase. In the present disclosure, the average cobalt content corresponds to the cobalt content of the first phase. It has been confirmed that, as long as measurements are performed on the same cubic boron nitride sintered body, almost identical results can be obtained even if the measurement location is changed.

[0074] <Binder Phase Particles> In the cubic boron nitride sintered body of embodiment 1, the binder phase is composed of a plurality of binder phase particles. The plurality of binder phase particles contain first binder phase particles at a ratio of 50% or more by number. The surfaces of the first binder phase particles contain first regions at a ratio of 50% or more by area. The first regions are regions in contact with the first phase. In the cubic boron nitride sintered body of embodiment 1, the percentage by number of first binder phase particles whose surfaces are in contact with the first phase over 50% or more by area is 50% or more, relative to the total number of binder phase particles, and therefore the bonding strength between the binder phase particles is improved.

[0075] From the viewpoint of improving the bonding strength between the binder phase particles, the lower limit of the percentage of the first binder phase particles by number relative to the total binder phase particles is 50% or more, or may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, 95% or more, or even 95% or more. The percentage of the first binder phase particles by number relative to the total binder phase particles may even be 100%.

[0076] In the cubic boron nitride sintered body of the first embodiment, the plurality of binder phase particles may contain second binder phase particles in an amount of 50% or more by number, and the surfaces of the second binder phase particles may contain the first regions in an amount of 75% or more by area, thereby further improving the bonding strength between the binder phase particles.

[0077] From the viewpoint of improving the bonding strength between the binder phase particles, the lower limit of the percentage of the second binder phase particles by number relative to the total binder phase particles may be 50% or more, 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, 95% or more, or even 95% or more. The percentage of the second binder phase particles by number relative to the total binder phase particles may even be 100%.

[0078] In the present disclosure, the numerical content (percentage) of first binder phase particles in a plurality of binder phase particles of a cubic boron nitride sintered body and the numerical content (percentage) of second binder phase particles in a plurality of binder phase particles of a cubic boron nitride sintered body are measured using an energy dispersive X-ray analyzer (EDX) ("EDAX" (trademark) manufactured by AMETEK Corporation) attached to a transmission electron microscope (TEM) ("JEM-2100F / Cs" (trademark) manufactured by JEOL Ltd.) in the following manner.

[0079] (B1) A sample is taken from the cubic boron nitride sintered body, and sliced ​​into slices with a thickness of 30 to 100 nm using an argon ion slicer. The slices are then observed under a TEM at 10,000x magnification to obtain TEM images.

[0080] (B2) Based on the results of the composition of the binder phase measured by X-ray diffraction, the elements constituting the binder phase are identified. Elemental mapping analysis is performed using EDX for each element constituting the binder phase to obtain an elemental mapping image of each element. Furthermore, an elemental mapping image of cobalt is obtained in the same field of view.

[0081] (B3) Using image analysis software ("WinROOF 2018" by Mitani Corporation), elemental mapping images of the elements constituting the bonded phase are superimposed, and the overlapping region of each element is extracted. An elemental mapping image of cobalt is superimposed on the extracted region. Of the extracted regions, the region where cobalt does not overlap corresponds to the bonded phase.

[0082] (B4) In a TEM image of the same field of view as the element mapping image of (B2) above, the crystal orientation of the region corresponding to the binder phase identified in (B3) above is measured using a crystal orientation analyzer attached to the TEM ("ASTER (ACOM)" (trademark) manufactured by Nano Megas) and image analysis processing software ("DIM ver. 8" manufactured by TSL, attached to the TEM). A grain boundary is defined as a point where the crystal orientations of adjacent measurement points are separated by 5 degrees or more, and the portion other than the grain boundary is defined as a crystal grain. This allows the grain boundaries between binder phase particles to be identified.

[0083] Furthermore, in a TEM image of the same field of view as the element mapping image (B2) above, the grain boundaries between binder phase particles can also be identified by performing binarization processing and particle division processing using image analysis processing software ("WinROOF 2018" by Mitani Corporation). In the image obtained after the binarization processing (hereinafter also referred to as "Image 1A"), the pixel value of the grain boundary is 255, and the pixel value of the other regions is 0.

[0084] (B5) The image obtained in (B4) above, in which the grain boundaries between the binder phase particles have been identified, is subjected to a binarization process using image analysis software ("WinROOF 2018" by Mitani Corporation), to obtain an image in which the grain boundaries between the binder phase particles have been extracted (hereinafter also referred to as "first image"). In the first image, the pixel value of the grain boundary is 255, and the pixel value of the other areas is 0. Note that in the following steps, the first image A obtained in (B4) above may be used instead of the first image.

[0085] (B6) In a TEM image of the same field of view as the first image (or image 1A), an elemental mapping image of tungsten and an elemental mapping image of cobalt are obtained using EDX. The elemental mapping image of tungsten and the elemental mapping image of cobalt are each subjected to binarization processing using image analysis processing software. In the image obtained by binarizing the elemental mapping image of tungsten (hereinafter also referred to as the "second image"), the pixel value of the region where tungsten is present is 255, and the pixel value of the other regions is 0. In the image obtained by binarizing the elemental mapping image of cobalt (hereinafter also referred to as the "third image"), the pixel value of the region where cobalt is present is 255, and the pixel value of the other regions is 0.

[0086] (B7) Using image analysis software, the second and third images are superimposed. In the superimposed image (hereinafter also referred to as the "fourth image"), a region where the pixel value is 255 (hereinafter also referred to as the "W—Co phase") is identified.

[0087] Instead of the above (B6) and (B7), the observation magnification of the section of the above (B1) by TEM can be set to 10,000,000 times, thereby obtaining an image that identifies the W—Co phase (hereinafter also referred to as "4A image").

[0088] (B8) Using image analysis processing software, a rectangular measurement field of view of 12 μm × 15 μm is set in the first image (or the first-A image). For each of all binder phase particles within the measurement field, the length L1 of the grain boundary defining the outer edge of the binder phase particle is measured. The first image (or the first-A image) and the fourth image (or the fourth-A image, the magnification of which is adjusted to match that of the first image) are superimposed. A measurement field of view of the same region as above is set in the superimposed images. For each of all binder phase particles within the measurement field, the length L2 of the W—Co phase present at a position overlapping with the grain boundary defining the outer edge of the binder phase particle is measured. For each binder phase particle, the percentage of L2 relative to L1 (L2 / L1) × 100 is calculated. In the present disclosure, the percentage (L2 / L1) × 100 corresponds to the coverage rate of the surface of the binder phase particle by the first region. Binder phase particles for which the percentage (L2 / L1) × 100 is 50% or more are considered first binder phase particles. Binder phase particles for which the percentage (L2 / L1) × 100 is 75% or more are classified as second binder phase particles. Note that, in the vicinity of the outer edge of the measurement field, some of the binder phase particles may exist outside the measurement field. Only binder phase particles whose entirety exists inside the measurement field are measured. If some of the binder phase particles exist outside the measurement field, those binder phase particles are excluded from the measurement.

[0089] (B9) Calculate the percentage (N2 / N1) x 100 of the number N2 of first binder phase particles relative to the number N1 of all binder phase particles in the measurement field of view. Measure the percentage (N2 / N1) x 100 in three non-overlapping measurement fields. Calculate the arithmetic mean of the percentages (N2 / N1) x 100 of the three measurement fields of view. In the present disclosure, the arithmetic mean of the percentages (N2 / N1) x 100 of the three measurement fields of view corresponds to the number-based content (percentage) of first binder phase particles in the plurality of binder phase particles in the cubic boron nitride sintered body.

[0090] (B10) Calculate the percentage (N3 / N1) x 100 of the number N3 of second binder phase particles relative to the number N1 of all binder phase particles in the measurement field of view. The measurement of the percentage (N3 / N1) x 100 is performed in three measurement fields that do not overlap with each other. Calculate the arithmetic mean of the percentages (N3 / N1) x 100 of the three measurement fields of view. In the present disclosure, the arithmetic mean of the percentages (N3 / N1) x 100 of the three measurement fields of view corresponds to the number-based content (percentage) of second binder phase particles in the plurality of binder phase particles of the cubic boron nitride sintered body.

[0091] As far as the applicant has measured, it has been confirmed that there is almost no variation in the results even when the same cubic boron nitride sintered body is measured multiple times by arbitrarily setting the position of the measurement field.

[0092] <Average particle size of binder phase particles> In the cubic boron nitride sintered body of embodiment 1, the average particle size of the binder phase particles is not particularly limited and may be a general average particle size used in conventional cubic boron nitride sintered bodies. The particle size of the binder phase particles may be, for example, 50 nm or more and 200 μm or less.

[0093] In the present disclosure, the average particle size of the binder phase particles is measured by the following procedure: A first image in which the grain boundaries between the binder phase particles described in (B5) above are identified is obtained using the same method as the method for measuring the content (percentage) of first binder phase particles by number in a plurality of binder phase particles of a cubic boron nitride sintered body.

[0094] Next, a rectangular measurement field of view of 12 μm × 15 μm is set in the first image. The first image is processed using image analysis software ("WinROOF ver. 7.4.5" by Mitani Corporation) to obtain the circle-equivalent diameter of each binder phase particle observed in the measurement field of view. The arithmetic mean of the circle-equivalent diameters of all binder phase particles in the measurement field of view is calculated. This arithmetic mean corresponds to the average particle size of the binder phase particles in the measurement field of view.

[0095] The above measurement is performed in five measurement fields that do not overlap with each other. The arithmetic mean of the average particle diameters of the binder phase particles in the five measurement fields is calculated. In the present disclosure, the arithmetic mean of the average particle diameters in the five measurement fields corresponds to the average particle diameter of the binder phase particles.

[0096] As far as the applicant has measured, it has been confirmed that there is almost no variation in the measurement results even when five measurement fields are arbitrarily set for the same sample and the average particle size of the binder phase particles is measured multiple times according to the above procedure.

[0097] <Presence or absence of first phase at the interface between cubic boron nitride particles and binder phase> The first phase does not have to be present at the interface between the cubic boron nitride particles and binder phase.

[0098] In the present disclosure, whether or not a first phase exists at the interface between a cubic boron nitride particle and a binder phase is measured by the following procedure.

[0099] The binder phase and the W—Co phase (corresponding to the first phase) are identified in the TEM image using the same method as that used to measure the numerical content (percentage) of first binder phase particles in the plurality of binder phase particles of the cubic boron nitride sintered body.

[0100] Elemental mapping of boron and nitrogen is performed on the same TEM image as above. Using the image analysis software, the elemental mapping images of boron and nitrogen are superimposed, and the overlapping regions of each element are extracted and identified as cubic boron nitride particles. Elemental mapping images of each element constituting the binder phase are superimposed on the extracted regions to identify the regions where the cubic boron nitride particles and the binder phase exist.

[0101] Line analysis is performed using EDX at 10 positions, equally spaced along the length of the interface between any cubic boron nitride particle and its adjacent binder phase 1 particle, in a direction perpendicular to the direction of extension of the interface. If a first phase having a thickness of 0.5 nm or more does not exist between the cubic boron nitride particle and the binder phase 1 particle at 8 or more of the 10 positions, it is determined that no first phase exists at the interface between the cubic boron nitride particle and the binder phase. It has been confirmed that, as long as measurements are performed on the same cubic boron nitride sintered body, nearly identical results can be obtained even if the measurement position is changed.

[0102] <Method for manufacturing cubic boron nitride sintered body> A description will be given of a method for manufacturing the cubic boron nitride sintered body of embodiment 1. The method for manufacturing the cubic boron nitride sintered body of embodiment 1 can include, for example, a raw material preparation step, a mixing step, and a sintering step.

[0103] <<Raw Material Preparation Step (1)>> Cubic boron nitride powder (hereinafter also referred to as "cBN powder"), a binder phase raw material powder, is prepared as the raw material for the cubic boron nitride sintered body. There are no particular limitations on the cBN powder, and known cBN powders can be used. There are no particular limitations on the average particle size of the cBN powder, and it can be, for example, 0.1 to 12.0 μm.

[0104] As a binder phase raw material, binder phase raw material powder containing the elements that make up the binder phase is prepared. The binder phase raw material powder, acetone or ethanol as a solvent, and cemented carbide balls are placed in a cemented carbide container and mixed (hereinafter also referred to as "first mixture"). The cemented carbide contains tungsten carbide (WC) and cobalt (Co), for example, WC-6%Co. For the first mixture, at least one of the following conditions A to C is adopted: A. The mixing time is set to 120 hours or more and 240 hours or less. B. Cemented carbide balls with a surface coated with cobalt powder are used. C. Cemented carbide balls with a larger particle size than usual, measuring φ3 mm or more and φ10 mm or less, are used.

[0105] <Mixing Step (1)> Following the raw material preparation step (1), cBN powder, the binder raw material powder after ball mill mixing, acetone or ethanol, and balls are placed in a cemented carbide container and mixed (hereinafter also referred to as "second mixing"). In the second mixing, at least one of the following conditions D to F is adopted: D. Cemented carbide balls with a smaller particle size than usual, with a diameter of 0.5 mm or more and 3 mm or less are used. E. When cBN powders with different particle sizes are used as raw materials, the cBN powder with the smaller particle size and the binder raw material powder are mixed first, and after 3 to 12 hours, the cBN powder with the larger particle size is added and mixed. F. Balls other than cemented carbide are used. Examples of balls other than cemented carbide include balls made of silicon nitride or aluminum oxide.

[0106] After mixing, the solvent is removed by natural drying, and then heat treatment is performed to volatilize impurities such as moisture adsorbed on the surface of the mixed powder, thereby cleaning the surface of the mixed powder.

[0107] <<Raw Material Preparation Step (2)>> Instead of the raw material preparation step (1), the first mixing may be performed under the following condition G, and a coating process may be further performed to form a coating of the target composition on the powder after the first mixing under the conditions described in the coating process below. G. A 2.0 mm diameter cemented carbide ball is used. The mixing time is 24 to 90 hours. Coating Process Coating Device: Nanoparticle Formation Device APD-P, manufactured by Advance Riko Co., Ltd. Target: 30 to 60 atomic % W, 70 to 40 atomic % Co Introduced Gas: Ar Film Formation Pressure: 0.88 Pa Discharge Voltage: 150 V Discharge Frequency: 6 Hz Capacitor Capacity: 1080 μF Number of Shots: 1000 to 10000 Rotation Speed ​​of Powder Container: 50 rpm Amount of Powder Processed: 30 g

[0108] <Mixing Step (2)> Following the raw material preparation step (2), instead of the mixing step (1), a second mixing is carried out under the following condition H. H. A 2.0 mm diameter cemented carbide ball is used. The mixing time is 6 to 12 hours.

[0109] <Sintering Step> The mixed powder is placed in contact with a WC-6%Co cemented carbide disk and then filled into a Ta (tantalum) container and vacuum-sealed. The vacuum-sealed mixed powder is sintered using a belt-type ultra-high pressure and high temperature generator under conditions of 3 GPa to 12 GPa and 1100°C to 2200°C for 5 to 30 minutes. This produces the cubic boron nitride sintered body of embodiment 1.

[0110] In the manufacturing method of Patent Document 1, to form a W—Co phase in a cubic boron nitride sintered body, nano-W powder with an average particle size of 500 nm to 900 nm and nano-Co powder with an average particle size of 20 nm to 40 nm are added to cBN powder and Ti compound particle powder, and the mixed powder is then sintered to produce a cubic boron nitride sintered body. The inventors' investigations into the manufacturing method of Patent Document 1 revealed that when conditions were adopted such that the total content of cobalt and tungsten in the cubic boron nitride sintered body was small, the area where the surfaces of the binder phase particles contacted the W—Co phase was small, and the number-based content of binder phase particles in the cubic boron nitride sintered body in which 50 area% or more of their surfaces were in contact with the first phase was less than 50%. Furthermore, it was confirmed that the manufacturing method of Patent Document 1 did not contain any elements contained in the binder phase.

[0111] As a result of extensive research, the present inventors have found that by employing at least one of the above conditions A to C, and at least one of the conditions D to F, or the above conditions G and coating treatment, and H, the contact area between the surfaces of the binder phase particles and the first phase can be increased, the content by number of binder phase particles in a cubic boron nitride sintered body in which 50 area % or more of the surfaces are in contact with the first phase can be made 50% or more, and that the first phase contains elements contained in the binder phase together with tungsten and cobalt.

[0112] It is presumed that by adopting at least one of the above conditions A to C, the tungsten and cobalt contained in the cemented carbide container or the cemented carbide balls are more likely to come into contact with the surfaces of the binder phase particles, and the surfaces of the binder phase particles are more likely to react with the first phase.

[0113] By adopting at least one of the above conditions D to F, it is possible to suppress the crushing of cBN particles during mixing and to suppress the reactivity between the small crushed cBN particles and the tungsten and cobalt that make up the first phase during sintering, thereby enabling the binder phase particles to react more efficiently with tungsten and cobalt.

[0114] [Embodiment 2: Tool] A tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a tool including the cubic boron nitride sintered body of Embodiment 1. Each tool may be entirely made of a cubic boron nitride sintered body, or only a part of it (for example, the cutting edge in the case of a cutting tool) may be made of a cubic boron nitride sintered body. Furthermore, a coating film may be formed on the surface of each tool.

[0115] Examples of cutting tools include drills, end mills, indexable cutting tips for drills, indexable cutting tips for end mills, indexable cutting tips for milling, indexable cutting tips for turning, metal saws, gear cutting tools, reamers, taps, and cutting bits.

[0116] Examples of the wear-resistant tool include a die, a scriber, a scribing wheel, a dresser, etc. Examples of the grinding tool include a grinding wheel, etc.

[0117] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0118] <Preparation of Cubic Boron Nitride Sintered Body> Cubic boron nitride sintered bodies for each sample were prepared according to the following procedure.

[0119] <<Raw Material Preparation Step>> Cubic boron nitride powder and binder phase raw material powder were prepared. For samples employing Condition E in the mixing step described below, cubic boron nitride powders with two different average particle sizes were prepared. The composition of the binder phase raw material powder was selected so that the binder phase of the cubic boron nitride sintered body to be produced would contain the elements listed in the "Composition" column of "Binder Phase" in Table 2.

[0120] The binder phase raw material powder, acetone or ethanol as a solvent, and cemented carbide balls were placed in a cemented carbide container and mixed under one of the following conditions A to C or G. The conditions used for each sample are shown in the "First Mixing" column in Table 1. A. Mixing time: 120 hours or more and 240 hours or less. Cemented carbide balls with a diameter of 2.0 mm were used. B. Cemented carbide balls (diameter 2.0 mm) with cobalt powder coated on their surfaces were used. Mixing time: 96 hours. C. Cemented carbide balls with a diameter of 3 mm or more and 10 mm or less were used. Mixing time: 96 hours. G. Cemented carbide balls with a diameter of 2.0 mm were used. Mixing time: 24 to 90 hours.

[0121] Next, for samples 26 to 32, the powder after the first mixing was subjected to a coating treatment under the conditions described in the following treatment I or treatment J. Treatment I Coating device: Nanoparticle formation device APD-P manufactured by Advance Riko Co., Ltd. Target: 60 atomic % W, 40 atomic % Co Introduced gas: Ar Film formation pressure: 0.88 Pa Discharge voltage: 150 V Discharge frequency: 6 Hz Capacitor capacity: 1080 μF Number of shots: 1000 to 10000 Rotation speed of powder container: 50 rpm Amount of powder treated: 30 g Treatment J In treatment J, only the target of treatment I was changed as follows. Target: 30 atomic % W, 70 atomic % Co

[0122] <Mixing Step> cBN powder, binder raw material powder after ball mill mixing, acetone or ethanol, and balls were placed in a cemented carbide container and mixed under one of the following conditions D to F or H. The conditions used for each sample are shown in the "Second Mixing" column in Table 1. D. Cemented carbide balls with a diameter of 0.5 mm or more and 3 mm or less were used. The mixing time was 6 to 24 hours. E. Small particle size cBN powder and binder raw material powder were mixed first, and after 12 hours, large particle size cBN powder was added and mixed. Cemented carbide balls with a diameter of 2.0 mm were used. F. Balls other than cemented carbide balls with a diameter of 2.0 mm were used. The mixing time was 6 to 24 hours. H. Cemented carbide balls with a diameter of 2.0 mm were used. The mixing time was 6 to 12 hours.

[0123] The mixing ratio of each raw material powder was adjusted so that the content (volume %) of cubic boron nitride particles in the cubic boron nitride sintered body of each sample and the total content (mass %) of tungsten and cobalt in the cubic boron nitride sintered body would be as shown in the "cBN particle content" and "W+Co content" columns of "Cubic boron nitride sintered body" in Table 2.

[0124] The mixed powder was naturally dried and then heat-treated to volatilize impurities such as moisture adsorbed on the surface of the mixed powder, thereby cleaning the surface of the mixed powder.

[0125] <Sintering Step> The mixed powder was placed in contact with a WC-6%Co cemented carbide disk and filled into a Ta (tantalum) container, which was then vacuum-sealed. The vacuum-sealed mixed powder was sintered using a belt-type ultra-high pressure, high temperature generator under conditions of 3 GPa to 12 GPa and 1100°C to 2200°C for 5 minutes to 30 minutes. This produced cubic boron nitride sintered bodies for each sample. The tool shape of the cubic boron nitride sintered body was DNGA150408.

[0126]

[0127] <Evaluation of cubic boron nitride sintered body> <Content of cubic boron nitride particles> For each sample of cubic boron nitride sintered body, the content of cubic boron nitride particles in the cubic boron nitride sintered body was measured using SEM-EDX. The specific measurement method is as described in embodiment 1. The results are shown in the "cBN particle content" column of "Cubic boron nitride sintered body" in Table 2.

[0128] <Average Particle Size of Cubic Boron Nitride Particles> It was confirmed that the average particle size of the cubic boron nitride particles in all the sample cubic boron nitride sintered bodies was 0.1 μm or more and 10 μm or less.

[0129] <Composition of Binder Phase> The composition of the binder phase in each sample of cubic boron nitride sintered body was identified using X-ray diffraction. The specific identification method is as described in embodiment 1. The elements contained in the binder phase are shown in the "Binder Phase Composition" column of Table 2.

[0130] <Presence or Absence of First Phase and Type of First Element Contained in the First Phase> For each sample of cubic boron nitride sintered body, it was confirmed whether the cubic boron nitride sintered body contained a first phase. The specific confirmation method is as described in Embodiment 1. The results are shown in the "Presence / Absence" column of "First Phase" in Table 2. "Presence" indicates that the cubic boron nitride sintered body contains a first phase, and "Absence" indicates that the cubic boron nitride sintered body does not contain a first phase. For samples with a "Presence" of the first phase, the first element contained in the first phase is shown in the "First Element" column of "First Phase" in Table 2.

[0131] <<Content of First Binder Phase Particles and Content of Second Binder Phase Particles in Binder Phase Particles>> For each sample of cubic boron nitride sintered body, the content of first binder phase particles in the binder phase particles by number and the content of second binder phase particles in the binder phase particles by number were measured. The specific confirmation method is as described in Embodiment 1. The results are shown in the "First Binder Phase Particles" and "Second Binder Phase Particles" columns under "Binder Phase" in Table 2.

[0132] <<Total Content of Cobalt and Tungsten in Cubic Boron Nitride Sintered Body>> The total content of cobalt and tungsten was measured for each sample of cubic boron nitride sintered body. The specific measurement method is as described in Embodiment 1. The results are shown in the "W + Co Content" column in Table 2.

[0133]

[0134] <Tool Evaluation> <Samples 1 to 6, 103, 104> Tools (shape: DNGA150408) made of cubic boron nitride sintered bodies of Samples 1 to 6, 103, and 104, in which the cubic boron nitride particle content of the cubic boron nitride sintered body was 25% by volume or more and 45% by volume or less, were used to carry out the following cutting tests 1 and 2. The conditions for cutting tests 1 and 2 corresponded to high-efficiency machining of high-hardness steel.

[0135] Cutting Test 1: Evaluation of Fracture Resistance Workpiece: High-hardness steel SCM415H round bar, 5 grooves, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 150 m / min. Feed: f = 0.08 mm / rev. Depth of cut: ap = 0.1 mm Wet / dry: dry Cutting method: intermittent cutting The cutting edge was observed every 0.15 km of cutting distance, and the amount of shedding of the cutting edge was measured. The amount of shedding of the cutting edge was defined as the retreat width in the flank direction due to wear from the position of the cutting edge ridge before cutting. When chipping occurred, the size of the chipping was defined as the amount of shedding. When the amount of shedding of the cutting edge exceeded 0.04 mm or when the cutting distance was 5.0 km, the cutting evaluation was terminated, and the amount of shedding of the cutting edge was measured. A smaller amount of shedding indicates better fracture resistance and a longer tool life. In "Cutting Test 1" in Table 3, cases where the amount of cutting edge loss at a cutting distance of 5.0 km is 0.04 mm or less are marked as "A," and cases where the amount of cutting edge loss exceeds 0.04 mm before the cutting distance reaches 5.0 km or where the amount of cutting edge loss exceeds 0.04 mm at a cutting distance of 5.0 km are marked as "B." "A" indicates excellent fracture resistance and a long tool life. "B" indicates insufficient fracture resistance and a short tool life.

[0136] Cutting test 2: Wear resistance evaluation Workpiece: High-hardness steel SCM415H round bar, no groove, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 120 m / min. Feed: f = 0.1 mm / rev. Depth of cut: ap = 0.1 mm Wet / dry: wet Cutting method: continuous cutting The cutting edge was observed every 0.5 km of cutting distance, and the amount of shedding of the cutting edge was measured. The amount of shedding of the cutting edge was defined as the retreat width in the flank direction due to wear from the position of the cutting edge ridge before cutting. When the amount of shedding of the cutting edge exceeded 0.04 mm or when the cutting distance reached 10.0 km, the cutting evaluation was terminated, and the amount of shedding of the cutting edge was measured. A smaller amount of shedding indicates better wear resistance and a longer tool life. In "Cutting Test 2" in Table 3, cases where the amount of cutting edge loss at a cutting distance of 10.0 km was 0.04 mm or less were marked as "A," and cases where the amount of cutting edge loss exceeded 0.04 mm before the cutting distance reached 10.0 km, or where the amount of cutting edge loss at a cutting distance of 10.0 km was marked as "B." "A" indicates excellent wear resistance and a long tool life. "B" indicates insufficient wear resistance and a short tool life.

[0137] In this example, if the results of both Cutting Test 1 and Cutting Test 2 are "A," the tool life is determined to be long. If the results of either or both of Cutting Test 1 and Cutting Test 2 are "B," the tool life is determined to be insufficient.

[0138]

[0139] The cubic boron nitride sintered bodies and tools of Samples 1 to 6 correspond to Examples, while the cubic boron nitride sintered bodies and tools of Samples 103 and 104 correspond to Comparative Examples. It was confirmed that the tools of Samples 1 to 6 were excellent in fracture resistance and wear resistance and had long tool life. It was confirmed that the tools of Samples 103 and 104 were insufficient in either fracture resistance or wear resistance and had insufficient tool life.

[0140] <Samples 7 to 19, 101, 102, and 105> Using tools (shape: DNGA150408) made of cubic boron nitride sintered compacts of Samples 7 to 19, 101, 102, and 105, in which the cubic boron nitride particle content of the cubic boron nitride sintered compact was more than 45 volume % and not more than 65 volume %, the following cutting tests 3 and 4 were carried out. The conditions for cutting tests 3 and 4 corresponded to high-efficiency machining of high-hardness steel.

[0141] Cutting Test 3: Evaluation of Fracture Resistance Workpiece: High-hardness steel SCM415H round bar, 5 grooves, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 150 m / min. Feed: f = 0.15 mm / rev. Depth of cut: ap = 0.2 mm Wet / dry: dry Cutting method: intermittent cutting The cutting edge was observed every 0.15 km of cutting distance, and the amount of shedding of the cutting edge was measured. The amount of shedding of the cutting edge was defined as the retreat width in the flank direction due to wear from the position of the cutting edge ridge before cutting. When chipping occurred, the size of the chipping was defined as the amount of shedding. When the amount of shedding of the cutting edge exceeded 0.04 mm or when the cutting distance was 5.0 km, the cutting evaluation was terminated, and the amount of shedding of the cutting edge was measured. A smaller amount of shedding indicates better fracture resistance and a longer tool life. In "Cutting Test 3" in Table 4, cases where the amount of cutting edge loss at a cutting distance of 5.0 km was 0.04 mm or less were marked as "A," and cases where the amount of cutting edge loss exceeded 0.04 mm before the cutting distance reached 5.0 km, or cases where the amount of cutting edge loss at a cutting distance of 5.0 km was marked as "B." "A" indicates excellent fracture resistance and a long tool life. "B" indicates insufficient fracture resistance and a short tool life.

[0142] Cutting Test 4: Wear Resistance Evaluation Workpiece: High-hardness steel SCM415H round bar, no groove, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 120 m / min. Feed: f = 0.1 mm / rev. Depth of cut: ap = 0.15 mm Wet / dry: wet Cutting method: continuous cutting The cutting edge was observed every 0.5 km of cutting distance, and the amount of shedding of the cutting edge was measured. The amount of shedding of the cutting edge was defined as the retreat width in the flank direction due to wear from the position of the cutting edge ridge before cutting. When the amount of shedding of the cutting edge exceeded 0.04 mm or when the cutting distance reached 10.0 km, the cutting evaluation was terminated, and the amount of shedding of the cutting edge was measured. A smaller amount of shedding indicates better wear resistance and a longer tool life. In "Cutting Test 4" in Table 4, cases where the amount of cutting edge loss at a cutting distance of 10.0 km was 0.04 mm or less were marked as "A," and cases where the amount of cutting edge loss exceeded 0.04 mm before the cutting distance reached 10.0 km, or cases where the amount of cutting edge loss at a cutting distance of 10.0 km was marked as "B." "A" indicates excellent wear resistance and a long tool life. "B" indicates insufficient wear resistance and a short tool life.

[0143] In this example, if the results of both Cutting Test 3 and Cutting Test 4 are "A," the tool life is determined to be long. If the results of either or both of Cutting Test 3 and Cutting Test 4 are "B," the tool life is determined to be insufficient.

[0144]

[0145] The cubic boron nitride sintered bodies and tools of Samples 7 to 19 correspond to Examples, while the cubic boron nitride sintered bodies and tools of Samples 101, 102, and 105 correspond to Comparative Examples. It was confirmed that the tools of Samples 7 to 19 were excellent in fracture resistance and wear resistance and had long tool life. It was confirmed that the tools of Samples 101, 102, and 105 were insufficient in either fracture resistance or wear resistance and had insufficient tool life.

[0146] <Samples 20 to 25, Sample 106, Sample 107> Using tools (shape: DNGA150408) made of cubic boron nitride sintered compacts of Samples 20 to 25, Sample 106, and Sample 107, in which the cubic boron nitride particle content of the cubic boron nitride sintered compact was more than 65 volume % and not more than 80 volume %, the following cutting tests 5 and 6 were carried out. The conditions for cutting tests 5 and 6 corresponded to high-efficiency machining of high-hardness steel.

[0147] Cutting Test 5: Evaluation of Fracture Resistance Workpiece: High-hardness steel SCM415H round bar, 5 grooves, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 150 m / min. Feed: f = 0.2 mm / rev. Depth of cut: ap = 0.3 mm Wet / dry: dry Cutting method: intermittent cutting The cutting edge was observed every 0.15 km of cutting distance, and the amount of shedding of the cutting edge was measured. The amount of shedding of the cutting edge was defined as the retreat width in the flank direction due to wear from the position of the cutting edge ridge before cutting. When chipping occurred, the size of the chipping was defined as the amount of shedding. When the amount of shedding of the cutting edge exceeded 0.04 mm or when the cutting distance was 5.0 km, the cutting evaluation was terminated, and the amount of shedding of the cutting edge was measured. A smaller amount of shedding indicates better fracture resistance and a longer tool life. In "Cutting Test 5" in Table 5, cases where the amount of cutting edge loss at a cutting distance of 5.0 km is 0.04 mm or less are marked as "A," and cases where the amount of cutting edge loss exceeds 0.04 mm before the cutting distance reaches 5.0 km or where the amount of cutting edge loss at a cutting distance of 5.0 km is marked as "B." "A" indicates excellent fracture resistance and a long tool life. "B" indicates insufficient fracture resistance and a short tool life.

[0148] Cutting Test 6: Wear Resistance Evaluation Workpiece: High-hardness steel SCM415H round bar, no groove, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 120 m / min. Feed: f = 0.15 mm / rev. Depth of cut: ap = 0.2 mm Wet / dry: wet Cutting method: continuous cutting The cutting edge was observed every 0.5 km of cutting distance, and the amount of shedding of the cutting edge was measured. The amount of shedding of the cutting edge was defined as the retreat width in the flank direction due to wear from the position of the cutting edge ridge before cutting. When the amount of shedding of the cutting edge exceeded 0.04 mm or when the cutting distance reached 10.0 km, the cutting evaluation was terminated, and the amount of shedding of the cutting edge was measured. A smaller amount of shedding indicates better wear resistance and a longer tool life. In "Cutting Test 6" in Table 5, cases where the amount of cutting edge loss at a cutting distance of 10.0 km was 0.04 mm or less were marked as "A," and cases where the amount of cutting edge loss exceeded 0.04 mm before the cutting distance reached 10.0 km, or cases where the amount of cutting edge loss at a cutting distance of 10.0 km was marked as "B." "A" indicates excellent wear resistance and a long tool life. "B" indicates insufficient wear resistance and a short tool life.

[0149] In this example, if the results of both Cutting Test 5 and Cutting Test 6 are "A", the tool life is determined to be long. If the results of either or both of Cutting Test 5 and Cutting Test 6 are "B", the tool life is determined to be insufficient.

[0150]

[0151] The cubic boron nitride sintered bodies and tools of Samples 20 to 25 correspond to Examples, while the cubic boron nitride sintered bodies and tools of Samples 106 and 107 correspond to Comparative Examples. It was confirmed that the tools of Samples 20 to 25 were excellent in fracture resistance and wear resistance and had long tool life. It was confirmed that the tools of Samples 106 and 107 were insufficient in either fracture resistance or wear resistance and had insufficient tool life.

[0152] <Evaluation of Cubic Boron Nitride Sintered Body> Samples 6, 11, 22, 26 to 32, 101, 103, and 106 were evaluated as follows.

[0153] <Presence or absence of a first phase at the interface between cubic boron nitride particles and the binder phase> In each sample of cubic boron nitride sintered body, it was confirmed whether or not a first phase was present at the interface between the cubic boron nitride particles and the binder phase. The specific measurement method is as described in embodiment 1. The results are shown in the "Presence or absence of a first phase at the binder phase interface" column of "Cubic boron nitride sintered body" in Table 6. "Presence" indicates that a first phase is present at the interface between the cubic boron nitride particles and the binder phase. "Absence" indicates that a first phase is not present at the interface between the cubic boron nitride particles and the binder phase.

[0154] <<First Phase Thickness>> The thickness of the first phase was measured for each sample of cubic boron nitride sintered body. The specific measurement method is as described in embodiment 1. The results are shown in the "First Phase Thickness" column of "Cubic Boron Nitride Sintered Body" in Table 6.

[0155] <Tungsten Content and Cobalt Content in the First Phase> The tungsten content and cobalt content of each sample of cubic boron nitride sintered body were measured to determine which was larger. The results are shown in the "First Phase W, Co Content" column of "Cubic Boron Nitride Sintered Body" in Table 6. "W > Co" indicates that the tungsten content is greater than the cobalt content. "Co > W" indicates that the cobalt content is greater than the tungsten content.

[0156]

[0157] <Evaluation of Tools> <Cutting Test 5> Using tools (shape: DNGA150408) made of cubic boron nitride sintered bodies of Samples 6, 103, 27, and 28, Cutting Test 5 was carried out under the following conditions.

[0158] Workpiece: High-hardness steel SCM415H round bar, 5 grooves, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 150 m / min. Feed: f = 0.15 mm / rev. Depth of cut: ap = 0.2 mm Wet / dry: dry Cutting method: intermittent cutting The cutting edge was observed every 0.2 km of cutting distance, and the amount of shedding of the cutting edge was measured. The amount of shedding of the cutting edge was defined as the retreat width in the flank direction due to wear from the position of the cutting edge ridge before cutting. In the case of chipping, the size of the chipping was defined as the amount of shedding. When the amount of shedding of the cutting edge exceeded 0.03 mm or when the cutting distance was 2.0 km, the cutting evaluation was terminated and the amount of shedding of the cutting edge was measured. A smaller amount of shedding indicates better chipping resistance and a longer tool life. In "Cutting Test 5" in Table 7, when the amount of shedding of the cutting edge at a cutting distance of 2.0 km is 0.01 mm or less, it is marked as "A," when the amount of shedding of the cutting edge is more than 0.01 mm but not more than 0.02 mm, it is marked as "B," when the amount of shedding of the cutting edge is more than 0.02 mm but not more than 0.03 mm, it is marked as "C," and when the amount of shedding of the cutting edge is more than 0.03 mm or when the amount of shedding of the cutting edge exceeds 0.03 mm before reaching a cutting distance of 2.0 km, it is marked as "D." "A" indicates excellent fracture resistance and long tool life.

[0159]

[0160] <<Cutting Test 6>> Cutting test 6 was carried out under the following conditions using tools (shape: DNGA150408) made of cubic boron nitride sintered bodies of samples 11, 101, 26, 30, 31, and 32.

[0161] Workpiece: High-hardness steel SCM415H round bar, 5 grooves, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 150 m / min. Feed: f = 0.2 mm / rev. Depth of cut: ap = 0.3 mm Wet / dry: dry Cutting method: intermittent cutting Evaluation criteria A to D are the same as in Cutting Test 5. The results are shown in Table 8.

[0162] <<Cutting Test 7>> Cutting test 7 was carried out under the following conditions using tools (shape: DNGA150408) made of cubic boron nitride sintered bodies of sample 22, sample 106, and sample 29.

[0163] Workpiece: High-hardness steel SCM415H round bar, 5 grooves, HRC62, diameter 100 mm x length 300 mm Cutting speed: V = 150 m / min. Feed: f = 0.25 mm / rev. Depth of cut: ap = 0.4 mm Wet / dry: dry Cutting method: intermittent cutting Evaluation criteria A to D are the same as in Cutting Test 5. The results are shown in Table 9.

[0164]

[0165] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined and modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

Claims

1. A cubic boron nitride sintered body comprising cubic boron nitride particles, a binder phase, and a first phase, the content of the cubic boron nitride particles in the cubic boron nitride sintered body is 25 volume % or more and 80 volume % or less; The binder phase is one or more first compounds comprising at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, aluminum, and silicon, and at least one element selected from the group consisting of nitrogen, carbon, boron, and oxygen; and, A solid solution derived from the first compound; including one or both of the first phase includes at least one first element selected from the group consisting of cobalt, tungsten, and elements included in the binder phase; The total content of cobalt and tungsten in the cubic boron nitride sintered body is 1.0 mass% or more and 6.0 mass% or less, the binder phase comprises a plurality of binder phase particles; the plurality of binder phase particles include first binder phase particles in an amount of 50% or more by number; the surface of the first binder phase particle includes 50% or more by area of ​​a first region; A cubic boron nitride sintered body, wherein the first region is a region in contact with the first phase.

2. the plurality of binder phase particles include second binder phase particles in an amount of 50% or more by number; 2. The cubic boron nitride sintered body according to claim 1, wherein the surfaces of said second binder phase particles contain said first regions in an area ratio of 75% or more.

3. 3. The cubic boron nitride sintered body according to claim 1, wherein the binder phase contains at least one element selected from the group consisting of titanium, chromium, aluminum, carbon, nitrogen and boron.

4. 3. The cubic boron nitride sintered body according to claim 1, wherein the first element includes at least one element selected from the group consisting of aluminum, carbon, nitrogen, boron and silicon.

5. 3. The cubic boron nitride sintered body according to claim 1, wherein the first phase is not present at interfaces between the cubic boron nitride particles and the binder phase.

6. 3. The cubic boron nitride sintered body according to claim 1, wherein the first phase has a thickness of 20 nm or less.

7. 3. The cubic boron nitride sintered body according to claim 1, wherein the tungsten content of said first phase is greater than the cobalt content of said first phase.

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