Cubic boron nitride sintered body, method for manufacturing the same, and tool

Abstract

Provided are a cBN sintered body excellent in resistance to chipping, a method for producing the same, and a tool. 【Solution means】A sintered body having cubic boron nitride and a binder phase as the remainder thereof, wherein the content of cubic boron nitride is 70.0 to 90.0% by volume, and the binder phase contains one or more selected from the group consisting of carbides, nitrides, carbonitrides, and borides of Ti, and one or more selected from the group consisting of W2B and W2CoB2. In the X-ray diffraction pattern of the sintered body using CuKα rays as a radiation source, the intensity of the diffraction peak attributed to the (111) plane of cubic boron nitride is I A , the intensity of the diffraction peak attributed to the (211) plane of W2B is I B , and among the intensity of the diffraction peak attributed to the (211) plane and the intensity of the diffraction peak attributed to the (310) plane of W2CoB2, the intensity of the diffraction peak with the greater intensity is I C . When this is the case, the ratio [(I A ) / I B and I C of the sum of I B + I C ) to I A is 0.25 or more.

Description

[Technical Field]

[0001] This embodiment relates to a cubic boron nitride sintered body, a method for manufacturing the same, and a tool. [Background technology]

[0002] Cubic boron nitride (hereinafter also referred to as "cBN") is a substance with hardness comparable to diamond, and cBN sintered bodies, which are sintered with cBN particles as the main component, are materials that possess both wear resistance and fracture resistance. For this reason, cBN sintered bodies are mainly used in cutting tools for difficult-to-machine materials such as high-hardness steel. Furthermore, improvements to cBN sintered bodies are being made to meet the demand for further improvements in fracture resistance, depending on the purpose of the cutting process and the various ways in which the cutting tools are used.

[0003] For example, Patent Document 1 describes that a cBN sintered body with excellent strength and heat resistance can be obtained by setting the ratio of the weight of W to the total weight of W, Co, and Ni to 0.2 to 0.6, and the ratio of the weight of Co to the total weight of Co and Ni to 0.6 to 0.95, for the metal components W, Co, and Ni present as compounds in the cBN sintered body. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2000 / 047537 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, in recent years, the difficulty of machining workpieces in order to reduce weight has increased significantly, and the cutting speed has increased dramatically in order to reduce processing costs, so the performance requirements for tools using cBN sintered bodies (hereinafter also referred to as "cBN tools") have also become stricter.

[0006] In view of such a current situation, an object of the present embodiment is to provide a cBN sintered body excellent in defect tolerance, a method for manufacturing the same, and a tool.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following present embodiment. [1] A cubic boron nitride sintered body having cubic boron nitride and a bonding phase which is the remainder of the cubic boron nitride, where the content of the cubic boron nitride is 50.0 to 90.0% by volume, the bonding phase contains one or more selected from the group consisting of carbides of Ti, nitrides of Ti, carbonitrides of Ti, and borides of Ti, and one or more selected from the group consisting of W2B and W2CoB2, in the X-ray diffraction pattern of the cubic boron nitride sintered body using CuKα rays as a radiation source, the intensity of the diffraction peak attributed to the (111) plane of the cubic boron nitride is I C , C , A , B , , C , <00ZZZ195>, A , B , B , c , C , B , , , the intensity of the diffraction peak attributed to the (211) plane of the W2B is I B , [[ID=2V]]the intensity of the diffraction peak attributed to the (211) plane or the (310) plane of the W2CoB2, whichever has the greater intensity, is I c when, the ratio [(I A +I B ) / I C of the total of the I B and the I C s to the I A is 0.25 or more, a cubic boron nitride sintered body. [2] The cubic boron nitride sintered body according to [1] above, wherein the content of W is 4.00 to 15.00% by mass. [3] The ratio [I C / I B of the I C to the I BA cubic boron nitride sintered body as described in [1] or [2] above, wherein ] is 0.20 to 1.00. [4] Average particle diameter (D 50 A cubic boron nitride sintered body according to any one of the above [1] to [3], comprising two or more cubic boron nitride particles of different types. [5] A cubic boron nitride sintered body according to any of [1] to [4] above, wherein the thermal conductivity is 50.0 W / m·K or higher. [6] A tool comprising a cubic boron nitride sintered body as described in any of [1] to [5] above as a constituent material. [7] The tool described in [6] above, which is for cutting or grinding. [8] A method for producing a cubic boron nitride sintered body as described in any of [1] to [5] above, A binder grinding step is performed in which the binder, which is a raw material for forming the binder phase, is ground in a container containing a grinding medium, A mixing step to obtain a raw material mixture by mixing the aforementioned crushed binder and cubic boron nitride particles, A sintering step is performed by pressurizing and heating the raw material mixture to obtain a cubic boron nitride sintered body. Includes, A method for producing a cubic boron nitride sintered body, wherein the grinding medium used in the binder grinding step contains WC. [Effects of the Invention]

[0008] According to this embodiment, it is possible to provide a cBN sintered body with excellent fracture resistance, a method for manufacturing the same, and a tool. [Brief explanation of the drawing]

[0009] [Figure 1] This is the XRD pattern of the cBN sintered body obtained in Example 1. [Figure 2] This is the XRD pattern of the cBN sintered body obtained in Comparative Example 2. [Figure 3] This is a scanning electron microscope (SEM) image (magnification 5,000x) of the cBN sintered body obtained in Example 1. [Figure 4]Figure 3 shows the binarized image of the backscattered electron image. [Modes for carrying out the invention]

[0010] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. For example, the notation "X~Y" (where X and Y are real numbers) means a range of numbers that are greater than or equal to X and less than or equal to Y. In this specification, the phrase "greater than or equal to X" means X and numbers greater than X. In this specification, the phrase "less than or equal to Y" means Y and numbers less than Y. The lower and upper limits of the numerical ranges described herein may be arbitrarily combined with the lower or upper limits of other numerical ranges. In the numerical ranges described herein, the lower or upper limits of those ranges may be replaced with the values ​​shown in the examples.

[0011] Unless otherwise specified, each component and material exemplified herein may be used alone or in combination of two or more.

[0012] In this specification, when only one element symbol is listed, such as "W," the valence and state of that element are not limited, and it refers to all elements that form compounds and elements that are in a metallic state. On the other hand, elements in a zero-valence metallic state are indicated by adding "metallic" before the element symbol, such as "metallic W."

[0013] Unless otherwise specified, each component and material exemplified herein may be used alone or in combination of two or more.

[0014] The expression "contains XX" as used herein includes both the meaning of containing XX in a reacted state if XX is capable of reacting, and simply the meaning of containing XX.

[0015] The mechanism of action described herein is speculative and does not limit the mechanism by which the effects of this embodiment are achieved.

[0016] Embodiments that combine any combination of the information described herein are also included.

[0017] [Cubic boron nitride sintered body] The cubic boron nitride sintered body of this embodiment is A cubic boron nitride sintered body having cubic boron nitride and a bonding phase which is the remainder of the cubic boron nitride, The content of the cubic boron nitride is 50.0 to 90.0 volume%, The bonded phase contains one or more selected from the group consisting of Ti carbides, Ti nitrides, Ti carbonitrides, and Ti borides, and one or more selected from the group consisting of W2B and W2CoB2. In the X-ray diffraction pattern of the cubic boron nitride sintered body using CuKα rays as the radiation source, The intensity of the diffraction peak attributed to the (111) plane of the cubic boron nitride is I A , The intensity of the diffraction peak attributed to the (211) plane of W2B is I B , Of the diffraction peaks attributed to the (211) plane and the (310) plane of the W2CoB2, the intensity of the diffraction peak with the greater intensity is determined to be I c In that case, I A The above I B and the above I C The ratio of the sum [(I B +I C ) / I A This is a cubic boron nitride sintered body in which the ratio is 0.25 or higher.

[0018] <cbn> The cBN content in the cBN sintered body of this embodiment is 50.0 to 90.0 volume%, preferably 55.0 to 89.0 volume%, more preferably 63.0 to 88.0 volume%, even more preferably 68.0 to 87.0 volume%, preferably 73.0 to 85.0 volume%, more preferably 75.0 to 82.0 volume%, and even more preferably 76.0 to 80.0 volume%. When the cBN content is 50.0 volume% or more, the excellent properties of cBN, such as high hardness, high oxidation resistance, and high thermal conductivity, are utilized, and even if minute cracks occur, the propagation of cracks into the interior of the cBN sintered body is suppressed, resulting in good fracture resistance. Furthermore, when the cBN content is 90.0 volume% or less, aggregation of cBN particles is suppressed, and sintering is easier without cBN falling off, resulting in good wear resistance. The cBN content in the cBN sintered body is determined by considering the percentage of cBN occupied by the surface area in a scanning electron microscope (SEM) image of the polished surface of the cBN sintered body as the volume content, and can be specifically determined by the method described in the examples.

[0019] The average value of the Ferret diameter measured from the cross-sectional SEM image of the cBN contained in the cBN sintered body of this embodiment is preferably 0.3 to 8.0 μm, more preferably 0.4 to 5.0 μm, and even more preferably 0.5 to 2.0 μm. When the average value of the Ferret diameter of the cBN is greater than or equal to the lower limit, the cBN tends to be more firmly held by the binding phase. Conversely, when the average value of the Ferret diameter of the cBN is less than or equal to the upper limit, the fracture toughness of the cBN sintered body tends to be superior. In this specification, "Ferret diameter" refers to the longest straight line connecting any two points on the outer circumference of the cBN cross-section observed in a cross-sectional photograph of the cBN sintered body. The average value of the Ferret diameter of cBN is determined by measuring the Ferret diameter of all measurable cBN within the entire field of view of a scanning electron microscope (SEM) image of the polished surface of the cBN sintered body at 5,000x magnification, and then taking the arithmetic mean of these values. Specifically, it can be determined by the method described in the examples.

[0020] In the production of the cBN sintered body of this embodiment, it is preferable that the cBN particles used have a small porosity, from the viewpoint of improving the thermal conductivity of the cBN sintered body and further improving its wear resistance and fracture resistance. In this specification, "porosity of cBN particles" refers to the porosity calculated solely from the cBN particles used in the manufacture of the cBN sintered body. If only one type of cBN particle is used, it refers to the porosity of that single type of cBN particle. If two or more types of cBN particles are used, it refers to the porosity of the mixture of those two or more types of cBN particles. The porosity of cBN particles can be calculated from the particle size distribution of the cBN particles using the following Ouchiyama formula. For more details on the Ouchiyama formula, please refer to the following literature. N. Ouchiyama and T. Tanaka, Ind. Eng. Chem. Fundam., 19, 338 (1980) N. Ouchiyama and T. Tanaka, Ind. Eng. Chem. Fundam., 20, 66 (1981) N. Ouchiyama and T. Tanaka, Ind. Eng. Chem. Fundam., 23, 490 (1984)

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[0026] The porosity of the cBN particles calculated using the above Ouchiyama formula is preferably 50 volume% or less, more preferably 45 volume% or less, even more preferably 40 volume% or less, even more preferably 37 volume% or less, and particularly preferably 35 volume% or less. When the porosity of the cBN particles is below the above upper limit, the cBN sintered body of this embodiment tends to have better thermal conductivity, wear resistance, and fracture resistance. While a small porosity is preferable for the above-mentioned cBN particles, from the viewpoint of ease of manufacture, it may be 10% by volume or more, 20% by volume or more, or 25% by volume or more. A more detailed method for calculating the porosity of cBN particles using the above Ouchiyama formula is described in the examples.

[0027] From the viewpoint of reducing the above-mentioned porosity and further improving the thermal conductivity, wear resistance, and fracture resistance of the cBN sintered body, the cBN sintered body of this embodiment has an average particle diameter (D 50 Preferably, it contains two or more cBN particles with different average particle diameters (D 50 It is more preferable that the mixture contains three or more different types of cBN particles. Furthermore, the average particle size (D) contained in the cBN sintered body of this embodiment 50 The types of cBN particles that are different from each other may be six or fewer, five or fewer, or four or fewer. In this specification, the average particle diameter (D 50 ) refers to the particle diameter at 50% of the cumulative volume in the volume distribution of particle diameters measured by laser diffraction scattering. 50 ) can be measured by the method described in the examples.

[0028] Average particle diameter (D 50 Among two or more types of cBN particles with different average particle diameters (D 50 The average particle diameter (D) of the two types of cBN particles with the smallest difference in ) 50 The difference between the two is preferably 0.5 to 3.0 μm, more preferably 1.0 to 2.0 μm, and even more preferably 1.4 to 1.8 μm. Also, the average particle diameter (D 50 Among two or more cBN particles that are different from each other, the one with the largest average particle diameter (D 50 cBN particles having ) and the minimum average particle diameter (D 50 cBN particles having ) and the average particle diameter (D 50 The difference between the two is preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.0 μm, and even more preferably 3.0 to 4.0 μm.

[0029] Average particle diameter (D 50 If the product contains two or more different types of cBN particles, the average particle diameter (D) of the two or more cBN particles is 50 Each of these is preferably selected from the range of 0.1 to 10.0 μm, more preferably 0.4 to 7.0 μm, and even more preferably 0.6 to 5.0 μm.

[0030] From the perspective of reducing the above porosity, the average particle diameter (D 50 Two or more types of cBN particles with different ) are, for example, average particle diameter (D 50 cBN particles (1) with a diameter of 0 μm or more and less than 2.0 μm, average particle size (D 50 cBN particles (2) with a diameter of 2.0 μm or more and less than 4.0 μm, and average particle diameter (D 50 It is preferable that the ) contains two or three types of cBN particles (3) that are 4.0 μm or larger and less than 6.0 μm in size.

[0031] When the above-mentioned cBN particles (1), cBN particles (2), and cBN particles (3) are included, the content of cBN particles (1) is preferably 5 to 35% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass, based on the total content of cBN particles (100% by mass). When the above-mentioned cBN particles (1), cBN particles (2), and cBN particles (3) are included, the content of cBN particles (2) is preferably 55 to 85% by mass, more preferably 60 to 80% by mass, and even more preferably 65 to 75% by mass, based on the total content of cBN particles (100% by mass). When the above-mentioned cBN particles (1), cBN particles (2), and cBN particles (3) are included, the content of cBN particles (3) is preferably 2 to 25% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, based on the total content of cBN particles (100% by mass).

[0032] <Binded phase> The bonding phase is the phase corresponding to the remainder of the cBN in the cBN sintered body of this embodiment. The bonded phase contains one or more materials selected from the group consisting of Ti carbides, Ti nitrides, Ti carbonitrides, and Ti borides, and one or more materials selected from the group consisting of W2B and W2CoB2.

[0033] In the cBN sintered body of this embodiment, in the X-ray diffraction pattern using CuKα rays as the source, The intensity of the diffraction peak attributed to the (111) plane of cBN is I A , The intensity of the diffraction peak attributed to the (211) plane of W2B is I B , Of the diffraction peaks attributed to the (211) plane of W2CoB2 and the diffraction peaks attributed to the (310) plane of W2CoB2, the intensity of the diffraction peak with the greater intensity is defined as I c In that case, I A I B and I C The ratio of the sum [(I B +I C ) / I A The value is 0.25 or higher. The cBN sintered body of this embodiment has the above ratio [(I B +I C ) / I A A value of 0.25 or higher improves fracture toughness and results in superior chipping resistance. The reason for this is not entirely clear, but it is presumed to be as follows. Since the W2B and W2CoB2 contained in the cBN sintered body of this embodiment are easily formed from a fine W source, the above ratio [(I B +I C ) / I A Since the cBN sintered body of this embodiment has a ratio of 0.25 or higher, it is expected that it contains a large amount of minute W2B and W2CoB2 particles. Furthermore, because W2B and W2CoB2 have properties that make them resistant to crack propagation, the cBN sintered body of this embodiment is thought to have excellent fracture toughness, and thereby excellent fracture resistance.

[0034] Intensity I of the above diffraction peak A , I B , I C and I, described later D The XRD pattern of the cBN sintered body can be obtained by the method described in the examples. The measured XRD pattern of the cBN sintered body can be compared with an inorganic material database to qualitatively determine the constituent components, and the diffraction peak intensity of each component can be obtained. This qualitative determination and acquisition of diffraction peak intensity can be performed using commercially available software. For example, the software "X' pert High Score Plus" manufactured by PANalytical can be used. In this embodiment, W2CoB2 may also be referred to as B2CoW2 in the inorganic materials database. Furthermore, since the diffraction peaks of the (211) plane and the (310) plane of W2CoB2 appear at similar angles, the peak is attributed to at least one of the (211) plane or the (310) plane of W2CoB2. However, if it is not possible to determine which plane a peak belongs to, the peak is considered to correspond to "the diffraction peak attributed to the (211) plane of W2CoB2 and the diffraction peak attributed to the (310) plane of W2CoB2, whichever has the greater intensity."

[0035] The above ratio [(I B +I C ) / I A From the viewpoint of further improving the fracture toughness, wear resistance and chipping resistance of the cBN sintered body, the value is preferably 0.30 to 4.00, more preferably 0.40 to 3.00, even more preferably 0.50 to 2.50, even more preferably 0.60 to 2.00, even more preferably 0.70 to 1.60, even more preferably 0.80 to 1.40, and particularly preferably 0.90 to 1.20.

[0036] Intensity I of the diffraction peak attributed to the cBN(111) plane A The intensity of the diffraction peak attributed to the W2B(211) plane for this value is I B The ratio [I B / I A From the viewpoint of further improving the fracture toughness, wear resistance, and chipping resistance of the cBN sintered body, the value is preferably 0.05 to 0.80, more preferably 0.10 to 0.60, and even more preferably 0.20 to 0.45.

[0037] Intensity I of the diffraction peak attributed to the cBN(111) plane A For the given value, the intensity of the diffraction peak with the greater intensity among the diffraction peaks attributed to the W2CoB2(211) plane and the diffraction peaks attributed to the W2CoB2(310) plane is I. c The ratio [I c / I A From the viewpoint of further improving the fracture toughness, wear resistance, and chipping resistance of the cBN sintered body, the value is preferably 0.20 to 1.50, more preferably 0.30 to 1.00, and even more preferably 0.40 to 0.80.

[0038] Of the diffraction peaks attributed to the W2CoB2(211) plane and the diffraction peaks attributed to the W2CoB2(310) plane, the intensity of the diffraction peak with the greater intensity is I. c The intensity of the diffraction peak attributed to the W2B(211) plane for this value is I B The ratio [I B / I C From the viewpoint of further improving the fracture toughness, wear resistance, and chipping resistance of the cBN sintered body, the value is preferably 0.20 to 1.00, more preferably 0.30 to 0.70, and even more preferably 0.40 to 0.50.

[0039] Intensity I of the diffraction peak attributed to the cBN(111) plane A The intensity of the diffraction peak I attributed to the (110) plane of metal W. D The ratio [I D / I A From the viewpoint of further improving the fracture toughness, wear resistance, and chipping resistance of the cBN sintered body, the value is preferably 0.10 or less, more preferably 0.01 or less, even more preferably 0.001 or less, and particularly preferably 0.

[0040] From the viewpoint of further improving the wear resistance and fracture resistance of the cBN sintered body in this embodiment, the W content is preferably 4.00 to 15.00 mass%, more preferably 4.50 to 10.00 mass%, even more preferably 5.00 to 8.50 mass%, and even more preferably 5.20 to 7.00 mass%. In this specification, the elemental content of W and other elements such as Co, Ti, and Al, as described later, is measured by energy-dispersive X-ray spectroscopy (EDS), and specifically can be measured by the method described in the examples.

[0041] From the viewpoint of further improving the wear resistance and fracture resistance of the cBN sintered body in this embodiment, the Co content is preferably 0.05 to 2.00 mass%, more preferably 0.10 to 1.50 mass%, even more preferably 0.30 to 1.00 mass%, and even more preferably 0.50 to 0.80 mass%.

[0042] The one or more substances selected from the group consisting of Ti carbides, Ti nitrides, Ti carbonitrides, and Ti borides contained in the binder phase can be adjusted depending on the type of binder used. In this embodiment, it is preferable to contain one or more substances selected from the group consisting of Ti nitrides and Ti borides, and it is more preferable to contain one or more substances selected from the group consisting of TiN and TiB2. From the viewpoint of further improving the wear resistance and fracture resistance of the cBN sintered body in this embodiment, the Ti content is preferably 4.00 to 15.00 mass%, more preferably 6.00 to 13.00 mass%, and even more preferably 8.00 to 12.00 mass%.

[0043] The bonding phase preferably further contains one or more selected from the group consisting of Al nitrides, Al borides, and Al oxides. The one or more selected from the group consisting of Al nitrides, Al borides, and Al oxides can be adjusted depending on the type of binder used. In this embodiment, it is preferable to contain one or more selected from the group consisting of Al nitrides and Al oxides, and more preferably to contain one or more selected from the group consisting of AlN and Al2O3. From the viewpoint of further improving the wear resistance and fracture resistance of the cBN sintered body in this embodiment, the Al content is preferably 1.00 to 6.00 mass%, more preferably 1.50 to 5.00 mass%, and even more preferably 2.00 to 4.00 mass%.

[0044] Each compound constituting the bonded phase can be qualitatively identified from the XRD pattern of the cBN sintered body, similar to the W2B, W2CoB2, etc. mentioned above.

[0045] The bonded phase may contain compounds other than those mentioned above, such as W2B, W2CoB2, Ti compounds, and Al compounds. Examples of bonded phases include Al-Ti composite oxides; ZrB2, ZrB 12 HfB2, HfB, HfB 12 VB2, V3B4, V3B 12 , borides of Group 4-6 transition metal elements such as VB, V5B6, V2B2, NbB2, Nb3B2, NbB, TaB2, Ta2B, Ta3B2, TaB, Ta3B4, CrB, CrB4, Cr2B, Cr2B3, Cr5B3, CrB2, MoB, Mo2B5, MoB4, Mo2B, MoB2, WB, WB4; ZrN x (0 < x ≤ 1), Hf3N2, HfN x (0 < x ≤ 1), Hf4N3, VN x (0 < x ≤ 1), V2N, NbN, Nb4N3, Nb2N, TaN x (0 < x ≤ 1), Ta3N5, Ta4N, Ta2N, Cr2N, CrN x (0 < x ≤ 1), nitrides of Group 4-6 transition metal elements such as WN, W2N; solid solutions of each compound including the above-mentioned compounds may also be included. However, in the cBN sintered body, the content of each Group 4-6 transition metal element other than Ti and W is preferably as low as possible. The content of each Group 4-6 transition metal element other than Ti and W is preferably 1,000 mass ppm or less, more preferably 100 mass ppm or less. In addition, the cBN sintered body of the present embodiment may contain, for example, inevitable impurities derived from the blending raw materials. Examples of the inevitable impurities include Li, Mg, Ca, Al, Si, Ti, C, B, S, P, Ga, Co, Ni, Mn, Fe, Cl, W, and their compounds, and those overlapping with the other compounds may also be included.

[0046] <Vickers hardness> From the viewpoint that the Vickers hardness of the cBN sintered body of the present embodiment can be suitably used for cutting processing of high-hardness workpieces, etc., it is preferably 3,000 HV or more, more preferably 3,200 HV or more, still more preferably 3,300 HV or more, even more preferably 3,400 HV or more, and particularly preferably 3,450 HV or more. Although the higher the Vickers hardness of the cBN sintered body of the present embodiment, the better, from the viewpoint of ease of manufacture, it may be 5,000 HV or less, 4,000 HV or less, or 3,800 HV or less. The Vickers hardness of the cBN sintered body can be measured by the method described in the examples.

[0047] <Thermal conductivity> The thermal conductivity of the cBN sintered body of this embodiment is preferably 50.0 W / m·K or higher, more preferably 54.0 W / m·K or higher, even more preferably 55.0 W / m·K or higher, even more preferably 56.0 W / m·K or higher, and particularly preferably 58.0 W / m·K or higher, from the viewpoint of further improving wear resistance and fracture resistance. In this embodiment, a higher thermal conductivity is preferable for the cBN sintered body, but from the viewpoint of ease of manufacturing, it may be 70.0 W / m·K or less, 67.0 W / m·K or less, or 65.0 W / m·K or less. The thermal conductivity of the cBN sintered body can be measured by the method described in the examples.

[0048] [Method for manufacturing cBN sintered bodies] The method for manufacturing the cBN sintered body of this embodiment is: A binder grinding step is performed in which the binder, which is a raw material for forming the binder phase, is ground in a container containing a grinding medium, A mixing step to obtain a raw material mixture by mixing the aforementioned crushed binder and cubic boron nitride particles, A sintering step is performed by pressurizing and heating the raw material mixture to obtain a cubic boron nitride sintered body. Includes, The method for producing a cubic boron nitride sintered body is one in which the grinding medium used in the binder grinding step contains WC. The following describes each step in the manufacturing method of the cBN sintered body according to this embodiment.

[0049] <Binding agent crushing process> The binder pulverization process is a process in which the binder is pulverized in a container containing a pulverization medium. The binder to be pulverized in the binder pulverization process preferably contains a raw material containing Ti, and may consist solely of a raw material containing Ti, or it may be a mixture of a raw material containing Ti and a raw material other than a raw material containing Ti.

[0050] The raw material containing Ti may be an elemental simple substance or a compound. As the raw material containing Ti, TiN and TiAl3 are preferable, and it is more preferable to contain both TiN and TiAl3. By using TiN and TiAl3 as the raw material containing Ti, TiN, AlN, Al2O3, TiB2, etc. can be generated in the bonding phase.

[0051] The average particle diameter (D 50 ) of the raw material containing Ti to be subjected to the binder pulverization step is preferably 30.0 μm or less, more preferably 25.0 μm or less, and still more preferably 20.0 μm or less from the viewpoint that a desired particle diameter can be easily obtained under appropriate pulverization conditions. The average particle diameter (D 50 ) of the raw material containing Ti may be 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. The average particle diameter (D 50 ) of TiN to be subjected to the binder pulverization step is preferably 2.5 μm or less, more preferably 2.0 μm or less, and still more preferably 1.5 μm or less from the viewpoint that a desired particle diameter can be easily obtained under appropriate pulverization conditions. The average particle diameter (D 50 ) of TiN may be 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. The average particle diameter (D 50 ) of TiAl3 to be subjected to the binder pulverization step is preferably 30.0 μm or less, more preferably 25. μm or less, and still more preferably 20.0 μm or less from the viewpoint that a desired particle diameter can be easily obtained under appropriate pulverization conditions. The average particle diameter (D 50 ) of TiAl3 may be 1.0 μm or more, 5.0 μm or more, or 10.0 μm or more.

[0052] In the binder pulverization step, the binder is pulverized in a container containing a pulverization medium containing WC. In the method for manufacturing the cBN sintered body of this embodiment, the binder is crushed using a crushing medium containing WC, thereby incorporating WC derived from the crushing medium into the raw material. This WC is then transformed into W2B, W2CoB2, etc., through the subsequent sintering process, yielding the cBN sintered body of this embodiment. Therefore, it is preferable to adjust the conditions of the binder crushing step in the manufacturing method of this embodiment so that a desirable amount of W2B and W2CoB2 is formed. For example, by making the crushing conditions in the binder crushing step more severe than conventional conditions, a large amount of minute WC derived from the crushing medium is incorporated into the raw material, making it easier to form W2B and W2CoB2.

[0053] The grinding medium may contain WC, but it is preferable that it contains Co along with WC, and more preferably that it is made of cemented carbide containing WC and Co. The WC content in the grinding medium is preferably 70-97% by mass, more preferably 76-92% by mass, and even more preferably 82-88% by mass. The Co content in the grinding medium is preferably 3 to 30% by mass, more preferably 8 to 24% by mass, and even more preferably 12 to 18% by mass.

[0054] The grinding method in the binder grinding process is not particularly limited as long as it uses a grinding medium, for example, a ball mill or a rod mill, but a ball mill is preferred from the viewpoint of productivity. That is, the grinding medium is preferably balls used in a ball mill. In this specification, a ball mill may also be called a bead mill. The ball mill may be a rotary ball mill, a vibrating ball mill, or a combination of rotary and vibrating, but from the viewpoint of productivity, a rotary ball mill is preferred. The rotary ball mill may be a conventional self-rotating ball mill or a planetary ball mill. When using a ball mill, the material of the mill pot preferably contains WC, more preferably contains Co along with WC, and even more preferably is made of a cemented carbide containing WC and Co. The preferred content of WC and Co in the material of the mill pot is the same as that for the grinding medium. The diameter of the balls used in the ball mill is preferably 0.1 to 20.0 mm, more preferably 0.5 to 10.0 mm, and even more preferably 1.0 to 5.0 mm.

[0055] Grinding with a ball mill may be done dry or wet, but wet grinding is preferred from the viewpoint of enabling more uniform grinding. Examples of dispersion media when using wet grinding include acetone, hexane, 2-propanol, ethanol, and heptane. Among these, acetone is preferred. One dispersion media may be used alone, or two or more may be used in combination. When the grinding of the binder is performed wet, the content of the material to be ground in the slurry obtained by mixing the material to be ground containing the binder with the dispersion medium is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 30 to 50% by mass. The grinding may be carried out in an air atmosphere or in an inert gas atmosphere such as N2 gas.

[0056] When using a rotary ball mill in the binder grinding process, it is preferable to appropriately determine conditions such as grinding time, rotation speed, ball filling amount, and filling amount of material to be ground, according to the grinding scale, the desired particle size, etc. In the binder grinding process using a rotary ball mill, the grinding time of the ball mill may be, for example, 3 to 7 hours. The rotational speed of the ball mill in the binder grinding process using a rotary ball mill may be, for example, 150 to 300 rpm. In a binder grinding process using a rotary ball mill, the amount of balls to be placed in the mill pot may be, for example, 15 to 35 volume percent of the internal volume of the mill pot. In a binder grinding process using a rotary ball mill, the amount of material to be ground into the mill pot may be, for example, 20 to 40% of the internal volume of the mill pot. The grinding process may be performed only once, or two or more times as necessary.

[0057] The average particle size (D) of the binder after grinding obtained by the binder grinding process. 50 From the viewpoint of homogenizing the composition of the cBN sintered body, the particle size is preferably 0.10 to 2.5 μm, more preferably 0.30 to 1.8 μm, and even more preferably 0.50 to 1.1 μm.

[0058] <Mixing process> The mixing step is a process of mixing the pulverized binder and cBN particles to obtain a raw material mixture.

[0059] For example, cBN particles obtained by finely grinding cBN with a purity of 99.9% or higher, which is synthesized under ultra-high pressure and high temperature of 3 GPa or higher and 1,200°C or higher, and adjusting the particle size and shape are preferably used. Preferred average particle size (D) of cBN particles 50 The explanation for ) is as described in the section on the explanation of [cBN] above. The amount of cBN particles added is preferably such that the cBN content in the resulting cBN sintered body falls within the preferred range described above.

[0060] In the mixing process, it is preferable to mix the raw materials, including each binder pulverized and cBN particles, in a container containing a grinding medium. The mixing method in the mixing step is the same as the grinding method mentioned in the binder grinding step, and the preferred embodiments are also the same. That is, mixing in the mixing step is preferably carried out by a rotary ball mill. When mixing by rotary ball mill is carried out wet, the content of the raw material in the slurry obtained by mixing the raw material and the dispersion medium is preferably 50 to 80% by mass, more preferably 55 to 75% by mass, and even more preferably 60 to 70% by mass. The mixing may be carried out in an air atmosphere or in an inert gas atmosphere such as N2 gas.

[0061] When using a rotary ball mill in the mixing process, it is preferable to determine conditions such as mixing time, rotation speed, ball filling amount, and filling amount of the material to be mixed as appropriate according to the mixing scale, etc. The mixing time in a ball mill in a mixing process using a rotary ball mill may be, for example, 2 to 6 hours. The rotational speed of the ball mill in a mixing process using a rotary ball mill may be, for example, 100 to 200 rpm. In a mixing process using a rotary ball mill, the amount of balls to be placed in the mill pot may be, for example, 25 to 40% of the internal volume of the mill pot. In a mixing process using a rotary ball mill, the amount of raw materials to be placed in the mill pot may be, for example, 40 to 60 volume percent of the internal volume of the mill pot.

[0062] <Heat treatment process> The raw material mixture obtained in the mixing process may be subjected to heat treatment for degassing as needed, and the heat-treated raw material mixture may be used as is. The temperature for the heat treatment for degassing is preferably 800°C or lower, from the viewpoint of uniform reaction sintering of the bonding phase and densification of the sintered body. Furthermore, from the viewpoint of thoroughly removing impurities such as organic matter and densifying the cBN sintered body, it is preferable that the heat treatment temperature be 500°C or higher. From the above viewpoint, the heat treatment temperature is more preferably 550 to 750°C, and even more preferably 600 to 700°C. The heat treatment is preferably carried out under a vacuum atmosphere from the viewpoint of efficiently removing gas, and the pressure is 1.0 × 10⁻⁶ -3 It is preferable to perform the procedure at Pa or below. The heat treatment time is set appropriately depending on the amount of raw material mixture to be treated, the type of dispersion medium used in the mixing process, etc., but is usually 0.1 to 10 hours, preferably 1 to 3 hours.

[0063] <Sintering process> The sintering process involves pressurizing and heating the raw material mixture obtained in the mixing process to obtain a cubic boron nitride sintered body. The raw material mixture obtained in the mixing process may be the raw material mixture obtained in the heat treatment process, or it may be the raw material mixture obtained without performing the heat treatment process.

[0064] The maximum temperature during the pressurized heat treatment is preferably 1,200 to 1,600°C, more preferably 1,250 to 1,550°C, and even more preferably 1,300 to 1,500°C, from the viewpoint of densifying the cBN sintered body.

[0065] The maximum pressure during the pressurized heat treatment is preferably 3.0 GPa or higher, more preferably 3.5 GPa or higher, and even more preferably 4.0 GPa or higher, from the viewpoint of densifying the cBN sintered body. The maximum pressure during the pressurized heat treatment may be 7.0 GPa or lower, 6.0 GPa or lower, or 5.0 GPa or lower.

[0066] From the viewpoint of suppressing oxidation of the raw material mixture during pressurized heat treatment and producing a desired cBN sintered body, it is preferable to use an inert gas atmosphere during pressurized heat treatment. Examples of inert gases include Ar gas and N2 gas. These gases may be used individually or in combination of two or more.

[0067] [tool] The tool of this embodiment includes the cBN sintered body of this embodiment as a constituent material. As described above, the cBN sintered body of this embodiment has high hardness and excellent wear resistance and fracture resistance, making it a suitable material for tools, especially cutting or grinding tools. [Examples]

[0068] The following description of this embodiment is based on examples, but this embodiment is not limited to these examples.

[0069] [Average particle diameter (D 50 ) Measurement method of 10% particle size (D 10 ) and 90% particle size (D 90 ) The particle size distribution of the particles was measured using a particle size analysis measuring device ("LA-920", manufactured by Horiba, Ltd.). And in the obtained particle distribution, the 10% particle size (D 10 ) where the cumulative volume is 10%, the average particle size (D 50 ), and the 90% particle size (D 90 ) where the cumulative volume is 90% were measured.

[0070] [Calculation method of porosity of cBN particles] The porosity of cBN particles was calculated from the above-mentioned Ouchi formula. Note that the particle size (D i ) in the Ouchi formula is the particle size of cBN particles obtained by the above [Measurement method of average particle size (D 50 ). The average particle size (D with overbar) is the average particle size (D 50 ) of cBN particles obtained by the above [Measurement method of average particle size (D 50 ). The number ratio (f i ) of particles with each particle size and the mass ratio (w i ) of particles with each particle size are values obtained from the particle size distribution of cBN particles. The porosity (ε 0i ) when the particle size is single is a value calculated assuming that cBN particles having each particle size are spheres. When mixing two or more kinds of cBN particles, the above parameters can be calculated from the particle size distribution and blending amount of each cBN particle.

[0071] [Measurement method of cBN content and Feret diameter] Taking the cBN sintered body sample for evaluation obtained in each example as the measurement object, a backscattered electron image was taken at a magnification of 5,000 times using a scanning electron microscope (SEM) ("S-5500", manufactured by Hitachi High-Tech Corporation). In the taken image, there are black parts, white parts and gray parts. When energy dispersive X-ray spectroscopy (EDS) was performed on each part, it was confirmed that the black part is cBN and the white part and the gray part are the bonding phases. The captured images were binarized using image processing software to identify the black areas representing cBN and the white areas representing the bonded phase. The area ratio of the black areas to the total field of view of the binarized images was calculated, and the arithmetic mean of the three fields of view was considered as the cBN content (in volume %). As a representative example, Figure 3 shows the backscattered electron image of the sintered body of Example 1, and Figure 4 shows its binarized image. The size of one field of view is 25.0 μm horizontally and 17.4 μm vertically, and the total area of ​​the three fields of view is 1305.0 μm. 2 That is the case. Furthermore, the Ferret diameters of all measurable cBNs were determined using image processing software within the entire field of view of the binarized image of backscattered electron images taken at a magnification of 5,000x, and the arithmetic mean of these values ​​was defined as the Ferret diameter of the cBN (unit: μm).

[0072] [Elemental analysis] Energy-dispersive X-ray spectroscopy (EDS) was performed on the evaluation cBN sintered body samples obtained in each example to measure the elemental concentrations of B, N, O, C, Al, Ti, Co, and W in the cBN sintered body. The elemental concentrations were measured across the entire field of view observed under the conditions described below, and the average value of 10 fields of view was used. The EDS measurement conditions are shown below. Measuring device: JSM-6510LA (manufactured by JEOL Ltd.) EDS analysis software: Analysis Station (manufactured by JEOL Ltd.) Acceleration voltage: 20.0kV (Irradiation current: 1.00000nA) Magnification: 2,000x Energy range: 0-20 keV

[0073] [Method for analyzing the composition of sintered bodies] XRD measurements were performed on evaluation cBN sintered body samples obtained in each example using an X-ray diffractometer ("X'pert PRO", manufactured by Panalytical). The measurements were performed under the following conditions: CuKα radiation, output voltage 40kV, output current 40mA, sampling width 0.0167°, scan speed 0.4178° / s, and measurement range 2θ = 10 to 80°. The measured XRD patterns were qualitatively analyzed by comparing them with an inorganic materials database using PANalytical's software "X' pert High Score Plus". The components detected by XRD analysis are shown in Table 1 under "Sintered Body Composition".

[0074] [Method for measuring diffraction peak intensity ratio] In the XRD pattern described in the section [Method for Analyzing Sintered Body Composition] above, the diffraction peak intensity of the cBN(111) plane around 2θ = 43.30° is I A The intensity of the diffraction peak attributed to the W2B(211) plane around 2θ=40.90° is I B Of the diffraction peaks attributed to the W2CoB2(211) plane and the W2CoB2(310) plane around 2θ=43.10°, the intensity of the diffraction peak with the greater intensity is defined as I c The diffraction peak intensity attributed to the (110) plane of metal W around 2θ = 40.30° is I D As, the ratio of each diffraction peak intensity [I B / I A ], [I C / I A ], [I B / I C ], [I D / I A ] and [(I B +I C ) / I A The values ​​for each were calculated. As representative examples, Figure 1 shows the range of 2θ = 39° to 44° for the XRD pattern of the cBN sintered body obtained in Example 1, and Figure 2 shows the range of 2θ = 39° to 44° for the XRD pattern of the cBN sintered body obtained in Comparative Example 2.

[0075] [Manufacturing of cubic boron nitride sintered bodies] Examples 1-3 (Binding agent crushing process) TiN (average particle diameter (D 50 )=1.2μm)7.7g, TiAl3(average particle diameter (D 50 ) = 19.8 μm) 2.6 g, dispersion medium (acetone) 21 ml, and balls 161 g were charged into a mill pot of a planetary ball mill (product name "Planetary Ball Mill", manufactured by Fritsch) and pulverized under the following pulverization conditions. The mill pot and balls of the planetary ball mill are both made of cemented carbide (constituent components: WC content is approximately 85% by mass, Co content is approximately 15% by mass). The height of the cylindrical mill pot is 23 mm, the inner diameter is φ65 mm, and the ball diameter of the balls is 1.3 mm. <Binder pulverization conditions> · Raw material (slurry) filling amount: Approximately 32% by volume based on the internal volume of the mill pot · Ball filling amount: Approximately 24% by volume based on the internal volume of the mill pot · Atmosphere: Air atmosphere · Rotation speed: 270 rpm · Pulverization time: 5 hours

[0076] (cBN particle and binder mixing step) After the above binder pulverization step, 31 g of cBN particles described in Table 1, 8 ml of dispersion medium (acetone), and 54 g of balls (ball diameter 3.0 mm) were additionally charged into the mill pot and mixed under the following mixing conditions to obtain a slurry of the raw material mixture. The material of the balls is the same as the material of the balls used in the binder pulverization step. <cBN particle and binder mixing conditions> · Raw material (slurry) filling amount: Approximately 54% by volume based on the internal volume of the mill pot · Ball filling amount: Approximately 32% by volume based on the internal volume of the mill pot · Atmosphere: N2 gas atmosphere [[ID=***]] · Rotation speed: 140 rpm · Mixing time: 4 hours

[0077] The details of the cBN particles (1) to (3) shown in Table 1 are as follows. cBN particle (1): 10% particle diameter (D 10 ) = 0.56 μm, average particle diameter (D 50 ) = 0.86 μm, 90% particle diameter (D 90 ) = 1.49 μm cBN particle (2): 10% particle diameter (D 10 It should be noted that there seems to be a missing item number in the provided text for the "Atmosphere" item in the "cBN particle and binder mixing conditions" section. I've marked it with "***" for your reference. If this is an error in the original text, it might need to be corrected for a more accurate translation.)=1.92μm, average particle diameter (D 50 )=2.93μm, 90% particle diameter (D 90 ) = 4.31 μm cBN particles (3): 10% particle size (D 10 )=3.06μm, average particle diameter (D 50 )=4.60μm, 90% particle diameter (D 90 ) = 6.42 μm

[0078] (Heat treatment process) The slurry obtained above was allowed to stand and dry in an N2 gas atmosphere at 70°C for 5 hours, and then divided into 1.0 × 10⁻⁶ units. -3 The heat-treated powder was obtained by degassing the powder at 650°C for 0.5 hours under a vacuum atmosphere of Pa or less.

[0079] (Sintering process) Under an N2 gas atmosphere, the above heat-treated powder was laminated onto a cemented carbide support plate, and then subjected to pressurized heat treatment at 4.5 GPa and 1,500°C for 1 hour to produce a cBN sintered body (approximately 30 mm in diameter and 4 mm in thickness). The upper surface of the cBN sintered body (the contact surface with the cemented carbide support plate was the lower surface) was ground with a #400 diamond grinding wheel to obtain a cBN sintered body sample for evaluation.

[0080] Example 4 (Binding agent crushing process) TiN (average particle diameter (D 50 )=1.2μm)0.9g, TiC(average particle diameter (D 50 )=0.70μm)5.8g, TiAl3(average particle diameter (D 50 3.6 g of (19.8 μm), 21 ml of dispersion medium (acetone), and 161 g of balls were placed in the mill pot of a planetary ball mill (product name "Planetary Ball Mill", manufactured by Fritsch) and ground under the same conditions as the binder grinding conditions in Example 1. The specifications of the planetary ball mill and balls were the same as in Example 1.

[0081] (Mixing process of cBN particles and binder) After the binder grinding process described above, 31 g of cBN particles, 8 ml of dispersion medium (acetone), and 54 g of balls (ball diameter 3.0 mm) were added to the mill pot and mixed under the same conditions as the mixing conditions for cBN particles and binder in Example 1 to obtain a slurry of raw material mixtures. The material of the balls was the same as the material of the balls used in the binder grinding process.

[0082] (Heat treatment process and firing process) Using the slurry obtained above, a cBN sintered body sample for evaluation was obtained by performing a heat treatment process and a sintering process under the same conditions as in Example 1.

[0083] Example 5 (Binding agent crushing process) TiN (average particle diameter (D 50 )=1.2μm)9.3g, TiAl3(average particle diameter (D 50 3.1 g of (19.8 μm), 21 ml of dispersion medium (acetone), and 161 g of balls were placed in the mill pot of a planetary ball mill (product name "Planetary Ball Mill", manufactured by Fritsch) and ground under the same conditions as the binder grinding conditions in Example 1. The specifications of the planetary ball mill and balls were the same as in Example 1.

[0084] (Mixing process of cBN particles and binder) After the binder grinding process described above, 28.9 g of cBN particles, 8 ml of dispersion medium (acetone), and 54 g of balls (ball diameter 3.0 mm) were added to the mill pot and mixed under the same conditions as the mixing conditions for cBN particles and binder in Example 1 to obtain a slurry of raw material mixtures. The material of the balls was the same as the material of the balls used in the binder grinding process.

[0085] (Heat treatment process and firing process) Using the slurry obtained above, a cBN sintered body sample for evaluation was obtained by performing a heat treatment process and a sintering process under the same conditions as in Example 1.

[0086] Example 6 (Binding agent crushing process) TiN (average particle diameter (D 50 )=1.2μm) 10.8g, TiAl3(average particle diameter (D 50 3.7 g of (19.8 μm), 21 ml of dispersion medium (acetone), and 161 g of balls were placed in the mill pot of a planetary ball mill (product name "Planetary Ball Mill", manufactured by Fritsch) and ground under the same conditions as the binder grinding conditions in Example 1. The specifications of the planetary ball mill and balls were the same as in Example 1.

[0087] (Mixing process of cBN particles and binder) After the binder grinding process described above, 26.8 g of cBN particles, 8 ml of dispersion medium (acetone), and 54 g of balls (ball diameter 3.0 mm) were added to the mill pot and mixed under the same conditions as the mixing conditions for cBN particles and binder in Example 1 to obtain a slurry of raw material mixtures. The material of the balls was the same as the material of the balls used in the binder grinding process.

[0088] (Heat treatment process and firing process) Using the slurry obtained above, a cBN sintered body sample for evaluation was obtained by performing a heat treatment process and a sintering process under the same conditions as in Example 1.

[0089] Example 7 (Binding agent crushing process) TiN (average particle diameter (D 50 )=1.2μm) 12.3g, TiAl3(average particle diameter (D 50 4.2 g of (19.8 μm), 21 ml of dispersion medium (acetone), and 161 g of balls were placed in the mill pot of a planetary ball mill (product name "Planetary Ball Mill", manufactured by Fritsch) and ground under the same conditions as the binder grinding conditions in Example 1. The specifications of the planetary ball mill and balls were the same as in Example 1.

[0090] (Mixing process of cBN particles and binder) After the binder grinding process described above was completed, 24.8 g of cBN particles, 8 ml of dispersion medium (acetone), and 54 g of balls (ball diameter 3.0 mm) were added to the mill pot and mixed under the same conditions as the mixing conditions for the cBN particles and binder in Example 1 to obtain a slurry of the raw material mixture. The material of the balls was the same as the material of the balls used in the binder grinding process.

[0091] (Heat treatment process and firing process) Using the slurry obtained above, a cBN sintered body sample for evaluation was obtained by performing a heat treatment process and a sintering process under the same conditions as in Example 1.

[0092] Comparative Example 1 In Example 1, the type of cBN particles was changed to the type listed in Table 1, the amount of cBN particles was changed to 26.1 g, the amount of TiN to 9.1 g, and the amount of TiAl3 to 4.9 g. In addition, the amount of balls added in the binder grinding process was changed to 107 g and the grinding time in the binder grinding process was changed to 4 hours. Except for these changes, a cBN sintered body and a cBN sintered body sample for evaluation were obtained in the same manner as in Example 1.

[0093] Comparative Example 2 In Example 1, the amount of balls added in the binder grinding step was changed to 107 g, the ball diameter to 3.0 mm, and the grinding time in the binder grinding step to 4 hours. Except for not adding any additional balls in the mixing step of cBN particles and binder, a cBN sintered body and a cBN sintered body sample for evaluation were obtained in the same manner as in Example 1.

[0094] Comparative Example 3 (Binding agent crushing process) TiN (average particle diameter (D 50 )=1.2μm) 14.4g, TiC(average particle diameter (D 50 )=0.70μm)4.2g, TiAl3(average particle diameter (D 50 7.4 g of (19.8 μm), 15.3 g of cBN particles as described in Table 1, 21 ml of dispersion medium (acetone), and 107 g of balls (ball diameter 3.0 mm) were placed in the mill pot of a planetary ball mill (product name "Planetary Ball Mill", manufactured by Fritsch), and the mixture was ground and mixed under the following conditions to obtain a slurry of the raw material mixture. The specifications of the planetary ball mill and balls are the same as those in Example 1. <Grinding and mixing conditions> • Raw material (slurry) filling amount: Approximately 54% of the internal volume of the mill pot • Ball filling amount: Approximately 24% of the internal volume of the mill pot • Atmosphere: Air and atmosphere • Rotation speed: 190 rpm • Grinding and mixing time: 6 hours

[0095] (Heat treatment process and firing process) Using the slurry obtained above, a cBN sintered body sample for evaluation was obtained by performing a heat treatment process and a sintering process under the same conditions as in Example 1.

[0096] [Evaluation Method] The following evaluations were performed on the cBN sintered body samples obtained for evaluation in each example. The evaluation results are summarized in Table 1.

[0097] <Method for measuring Vickers hardness> In accordance with JIS Z 2244:2009, the Vickers hardness of the evaluation cBN sintered body samples obtained in each example was measured using the "HMV-G21" measuring device (manufactured by Shimadzu Corporation) under the conditions of a load of 9.8 N, a holding time of 15 seconds, and a temperature of 25°C.

[0098] <Method for measuring thermal conductivity> A sample for thermal conductivity measurement (thickness: 0.80 mm, diameter: 10.0 mmφ) was cut from the evaluation cBN sintered body sample, and the surface of the obtained sample was blackened with black spray. The thermal diffusivity of this sample was measured using a laser flash analyzer (NETZSCH, product name "LFA457") with the thickness direction of the sample as the heat flow direction. In addition, the specific heat of the sample was measured using the same device, and the density of the sample was determined from the dimensions and weight of the sample. From these results, the thermal conductivity in the thickness direction of the evaluation cBN sintered body sample was determined using the following formula. Thermal conductivity (W / (m·K)) = Specific heat (J / (kg·K)) × Density (kg / m³) 3 ) × thermal diffusivity (m 2 / sec)

[0099] <Method for measuring fracture toughness> The fracture toughness value was determined by the IF method (indenter indentation method) in accordance with JIS R 1607:2015 "Test method for room temperature fracture toughness of fine ceramics". Using the "HMV-G21" measuring device (manufactured by Shimadzu Corporation), fracture toughness tests were performed on 10 cBN sintered body samples for evaluation under the conditions of a maximum load of 9.8 N, an indenter insertion time of 5 seconds, and a temperature of 25°C. The arithmetic mean of these results was taken as the fracture toughness value.

[0100] <Cutting Evaluation 1> Cutting tools conforming to ISO standard CNGA120404 were fabricated from the cBN sintered bodies obtained in each example. Using the obtained cutting tools, cutting tests were performed on the workpiece under the following cutting conditions. The maximum number of cuts was 1,500, and the number of cuts until the cutting tool broke was used as an indicator of fracture resistance. In addition, for tools that reached 1,500 cuts, the amount of wear of the cutting tool after 1,500 cuts was measured. (Cutting conditions) ·Cutting speed: 145m / min • Cutting area: φ0.33mm • Feed rate: 0.20 (mm / rev) • Type of workpiece material: Austenitic sintered alloy • Test environment temperature: 25℃

[0101] <Cutting Evaluation 2> Cutting tools conforming to ISO standard CNGA120404 (cutting edge shape: sharp edge) were fabricated from the cBN sintered bodies obtained in each example. Using the obtained cutting tools, cutting tests were performed on the workpiece under the following cutting conditions, and the VB wear amount (mm) of the cutting tool after the cutting evaluation was measured. (Cutting conditions) • Cutting method: Continuous cutting (dry cutting) ·Cutting speed: 400m / min • Cutting depth: 0.2mm • Feed rate: 0.2 (mm / rev) ·Processing distance: 330m / pass • Workpiece material type: FC250 (cast iron round bar, hardness HB190) • Test environment temperature: 25℃

[0102] <Cutting Evaluation 3> Cutting tools conforming to ISO standard CNGA120404 (cutting edge shape: sharp edge) were fabricated from the cBN sintered bodies obtained in each example. Using the obtained cutting tools, cutting tests were performed on the workpiece under the following cutting conditions, and the number of intermittent impacts until the cutting tool broke was measured. (Cutting conditions) • Cutting method: Intermittent cutting (dry cutting) ·Cutting speed: 150m / min • Cutting depth: 0.2mm Feed rate: 0.15 (mm / rev) ·Processing distance: 150m / pass • Workpiece material type: SCM415 (8 grooves) (hardened steel, hardness HRC62-60) • Test environment temperature: 25℃

[0103] [Table 1] In Table 1, "ND" indicates that the detection limit was reached. In Table 1, "NE" indicates that the evaluation was not conducted.

[0104] Table 1 shows that the cBN sintered bodies of Examples 1 to 7 of this embodiment exhibit excellent fracture resistance.< / cbn>

Claims

1. A cubic boron nitride sintered body having cubic boron nitride and a bonding phase which is the remainder of the cubic boron nitride, The content of the cubic boron nitride is 50.0 to 90.0 volume%, The bonding phase consists of one or more selected from the group consisting of Ti carbides, Ti nitrides, Ti carbonitrides, and Ti borides, and W ２ B and W ２ CoB ２ It contains one or more selected from the group consisting of, In the X-ray diffraction pattern of the cubic boron nitride sintered body with CuKα radiation as the source, The intensity of the diffraction peak attributed to the (111) plane of the cubic boron nitride is I Ａ , The aforementioned W ２ The intensity of the diffraction peak attributed to the (211) plane of B is I Ｂ , Said W ２ CoB ２ Of the diffraction peak attributed to the (211) plane and the diffraction peak attributed to the (310) plane of ２ CoB ２ , when the intensity of the diffraction peak with the greater intensity is I ｃ Then The above I Ａ The above I Ｂ and the above I Ｃ The ratio of the sum [(I Ｂ +I Ｃ ) / I Ａ A cubic boron nitride sintered body in which the ratio is 0.25 or higher.

2. The cubic boron nitride sintered body according to claim 1, wherein the W content is 4.00 to 15.00 mass%.

3. The above I Ｃ The above I Ｂ The ratio [I Ｂ / I Ｃ The cubic boron nitride sintered body according to claim 1 or 2, wherein [ ] is 0.20 to 1.

00.

4. Average particle diameter (D ５０ A cubic boron nitride sintered body according to claim 1 or 2, comprising two or more cubic boron nitride particles of different types.

5. A cubic boron nitride sintered body according to claim 1 or 2, wherein the thermal conductivity is 50.0 W / m·K or higher.

6. A tool comprising the cubic boron nitride sintered body described in claim 1 or 2 as a constituent material.

7. The tool according to claim 6, which is for cutting or grinding.

8. A method for producing a cubic boron nitride sintered body according to claim 1 or 2, A binder grinding step is performed in which the binder, which is a raw material for forming the binder phase, is ground in a container containing a grinding medium, A mixing step to obtain a raw material mixture by mixing the aforementioned crushed binder and cubic boron nitride particles, A sintering step is performed by pressurizing and heating the raw material mixture to obtain a cubic boron nitride sintered body. Includes, A method for producing a cubic boron nitride sintered body, wherein the grinding medium used in the binder grinding step contains WC.

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