Cubic boron nitride sintered body, method for producing same, and tool

Abstract

Provided are: a cubic boron nitride sintered body having cubic boron nitride and a binder phase which is the remainder of the cubic boron nitride, in which the content of the cubic boron nitride is 50.0-90.0 vol%, the binder 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, and when the intensity of a diffraction peak attributed to the (111) plane of the cubic boron nitride is taken to be IA, the intensity of a diffraction peak attributed to the (211) plane of the W2B is taken to be IB, and the intensity of the diffraction peak of whichever of the diffraction peak attributed to the (211) plane and the diffraction peak attributed to the (310) plane of the W2CoB2 is stronger is taken to be Ic in the x-ray diffraction pattern of the cubic boron nitride with CuKα rays as the radiation source, the ratio [(IB+IC) / IA] of the total of IB and IC to IA is 0.25 or more; a method for producing the same; and a tool.

Description

Cubic boron nitride sintered body, its manufacturing method, and tool

[0001] The present embodiment relates to a cubic boron nitride sintered body, a method for producing the same, and a tool.

[0002] Cubic boron nitride (hereinafter also referred to as "cBN") is a substance with hardness comparable to that of diamond, and cBN sintered bodies, which are sintered using cBN particles as the main component, are materials that combine both wear resistance and chipping resistance. For this reason, cBN sintered bodies are mainly used in cutting tools for hard-to-cut materials such as high-hardness steel. Furthermore, improvements to cBN sintered bodies are being made to meet demands for further improved chipping resistance depending on the purpose of cutting and various usage modes of cutting tools.

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

[0004] WO 2000 / 047537

[0005] In recent years, work materials have become increasingly difficult to cut in order to reduce weight, and cutting speeds have increased significantly to reduce processing costs, so the performance requirements for tools using cBN sintered bodies (hereinafter also referred to as "cBN tools") have become increasingly strict.

[0006] In view of the current situation, an object of this embodiment is to provide a cBN sintered body having excellent chipping resistance, a method for manufacturing the same, and a tool.

[0007] The present inventors have conducted extensive research to solve the above problems, and have found that the above problems can be solved by the following embodiment: [1] A cubic boron nitride sintered body having cubic boron nitride and a binder phase which is the remainder of the cubic boron nitride, wherein the content of the cubic boron nitride is 50.0 to 90.0% by volume, and the binder phase is one or more selected from the group consisting of Ti carbide, Ti nitride, Ti carbonitride and Ti boride, and W.２ B and W ２ CoB ２ and one or more selected from the group consisting of: wherein, in an X-ray diffraction pattern of the cubic boron nitride sintered body using CuKα radiation as a radiation source, the intensity of a diffraction peak assigned to the (111) plane of the cubic boron nitride is I Ａ , the W ２ The intensity of the diffraction peak assigned to the (211) plane of B is I Ｂ , the W ２ CoB ２ The intensity of the diffraction peak attributable to the (211) plane and the diffraction peak attributable to the (310) plane, whichever has the greater intensity, is designated as I. ｃ When the above I Ａ For the above I Ｂ and the above I Ｃ The ratio of the sum of [(I Ｂ +I Ｃ ) / I Ａ [2] The cubic boron nitride sintered body according to the above [1], wherein the W content is 4.00 to 15.00 mass %. [3] The cubic boron nitride sintered body according to the above [1], wherein the I Ｃ The above I Ｂ The ratio [I Ｂ / I Ｃ ] is 0.20 to 1.00. [4] The cubic boron nitride sintered body according to the above [1] or [2]. ５０The cubic boron nitride sintered body according to any one of [1] to [3] above, containing two or more types of cubic boron nitride particles with different molecular weights. [5] The cubic boron nitride sintered body according to any one of [1] to [4] above, having a thermal conductivity of 50.0 W / m K or more. [6] A tool comprising the cubic boron nitride sintered body according to any one of [1] to [5] above as a constituent material. [7] The tool according to [6] above, which is used for cutting or grinding. [8] A method for producing the cubic boron nitride sintered body according to any one of [1] to [5] above, comprising: a binder crushing step of crushing a binder, which is a raw material for forming the binder phase, in a vessel containing a crushing medium; a mixing step of mixing the crushed binder and cubic boron nitride particles to obtain a raw material mixture; and a sintering step of pressurizing and heating the raw material mixture to obtain a cubic boron nitride sintered body, wherein the crushing medium used in the binder crushing step contains WC.

[0008] According to this embodiment, it is possible to provide a cBN sintered body having excellent chipping resistance, a method for manufacturing the same, and a tool.

[0009] 3 is an XRD pattern of the cBN sintered body obtained in Example 1. FIG. 4 is an XRD pattern of the cBN sintered body obtained in Comparative Example 2. FIG. 5 is a backscattered electron image (magnification: 5,000 times) of the cBN sintered body obtained in Example 1 by a scanning electron microscope (SEM). FIG. 6 is a binarized image of the backscattered electron image shown in FIG.

[0010] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. For example, a numerical range "X to Y" (X and Y are real numbers) means a numerical range that is equal to or greater than X and equal to or less than Y. In this specification, the term "X or greater" means X and a numerical value that exceeds X. In addition, the term "Y or less" in this specification means Y and a numerical value that is less than Y. The lower limit and upper limit of a numerical range described in this specification can be arbitrarily combined with the lower limit or upper limit of another numerical range. In the numerical ranges described in this specification, the lower limit or upper limit of that numerical range may be replaced with a value shown in the examples.

[0011] Unless otherwise specified, each of the components and materials exemplified in this specification may be used alone or in combination of two or more.

[0012] In this specification, when only one element symbol is written alone, such as "W," the valence and state of the element are not limited, and it refers to all elements that form compounds and elements in a metallic state. On the other hand, an element in a zero-valent metallic state has "metal" added before the element symbol, such as "metal W."

[0013] Unless otherwise specified, each of the components and materials exemplified in this specification may be used alone or in combination of two or more.

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

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

[0016] Any combination of the features described in this specification is also included in this embodiment.

[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 binder phase which is the remainder of the cubic boron nitride, wherein the content of the cubic boron nitride is 50.0 to 90.0% by volume, and the binder phase is one or more selected from the group consisting of Ti carbide, Ti nitride, Ti carbonitride and Ti boride, and W. ２ B and W ２ CoB ２ and one or more selected from the group consisting of: wherein, in an X-ray diffraction pattern of the cubic boron nitride sintered body using CuKα radiation as a radiation source, the intensity of a diffraction peak assigned to the (111) plane of the cubic boron nitride is I Ａ , the W ２ The intensity of the diffraction peak assigned to the (211) plane of B is I Ｂ , the W２ CoB ２ The intensity of the diffraction peak attributable to the (211) plane and the diffraction peak attributable to the (310) plane, whichever has the greater intensity, is designated as I. ｃ When the above I Ａ For the above I Ｂ and the above I Ｃ The ratio of the sum of [(I Ｂ +I Ｃ ) / I Ａ ] is 0.25 or more.

[0018] <cBN> The cBN content in the cBN sintered body of this embodiment is 50.0 to 90.0 vol%, preferably 55.0 to 89.0 vol%, more preferably 63.0 to 88.0 vol%, even more preferably 68.0 to 87.0 vol%, preferably 73.0 to 85.0 vol%, more preferably 75.0 to 82.0 vol%, and even more preferably 76.0 to 80.0 vol%. A cBN content of 50.0 vol% or more makes use of the excellent properties of cBN, such as high hardness, high oxidation resistance, and high thermal conductivity, while suppressing the propagation of microcracks into the cBN sintered body, thereby achieving good chipping resistance. Furthermore, a cBN content of 90.0 vol% or less suppresses aggregation of cBN particles, allowing the cBN to be easily sintered without falling off, thereby achieving good wear resistance. The content of cBN in the cBN sintered compact is a value obtained by regarding the area ratio of cBN as the volume content in an image of the polished surface of the cBN sintered compact observed with a scanning electron microscope (SEM), and specifically, can be determined by the method described in the examples.

[0019] The average Feret diameter of the cBN contained in the cBN sintered body of this embodiment, as measured from a cross-sectional SEM photograph, 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 Feret diameter of the cBN is equal to or greater than the lower limit, the cBN tends to be firmly held by the binder phase. Furthermore, when the average Feret diameter of the cBN is equal to or less than the upper limit, the cBN sintered body tends to have excellent fracture toughness. Note that, as used herein, "Feret diameter" refers to the longest distance among the straight lines connecting any two points on the periphery of the cBN cross section observed in a cross-sectional photograph of the cBN sintered body. The average Feret diameter of the cBN is determined by calculating the arithmetic average value of all measurable cBN Feret diameters in the entire field of view of a 5,000x magnification image of the polished surface of the cBN sintered body observed with a scanning electron microscope (SEM). Specifically, it can be determined by the method described in the Examples.

[0020] The cBN particles used to manufacture the cBN sintered body of this embodiment preferably have a small porosity, from the viewpoint of improving the thermal conductivity of the cBN sintered body and further improving the wear resistance and fracture resistance. In this specification, the "porosity of cBN particles" refers to the porosity calculated solely from the cBN particles used to manufacture the cBN sintered body. When only one type of cBN particle is used, it refers to the porosity of that one type of cBN particle. When two or more types of cBN particles are used, it refers to the porosity of a mixture of those two or more types of cBN particles. The porosity of the cBN particles can be calculated from the particle size distribution of the cBN particles using the following Ouchiyama formula. The Ouchiyama formula is described in detail in the following document: 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)

[0021]

[0022]

[0023]

[0024]

[0025]

[0026] The porosity of the cBN particles calculated using the Ouchiyama formula is preferably 50 vol% or less, more preferably 45 vol% or less, even more preferably 40 vol% or less, even more preferably 37 vol% or less, and particularly preferably 35 vol% or less. When the porosity of the cBN particles is equal to or less than the upper limit, the cBN sintered body of this embodiment tends to have better thermal conductivity, wear resistance, and fracture resistance. The smaller the porosity of the cBN particles, the better, but from the viewpoint of ease of production, it may be 10 vol% or more, 20 vol% or more, or 25 vol% or more. A more detailed method for calculating the porosity of the cBN particles using the Ouchiyama formula is described in the Examples.

[0027] From the viewpoint of reducing the 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 It is preferable that the cBN particles contain two or more types of cBN particles having different average particle diameters (D ５０ It is more preferable that the cBN sintered body of this embodiment contains three or more types of cBN particles having different average particle diameters (D ５０ The number of types of cBN particles having different average particle diameters (D) may be six or less, five or less, or four or less. ５０ ) means the particle size at 50% cumulative volume in the volume distribution of particle sizes measured by a laser diffraction scattering method. 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 having different average particle diameters (D５０ The difference between the average particle diameters (D ５０ The difference between the average particle diameter (D ５０ The largest average particle diameter (D) among two or more types of cBN particles having different average particle diameters ５０ ) and the smallest average particle size (D ５０ ) and an average particle diameter (D ５０ The difference between the thicknesses of the fibers 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 When the composite material contains two or more types of cBN particles having different average particle diameters (D ５０ ) are each 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 viewpoint of reducing the void ratio, the average particle diameter (D ５０ The two or more types of cBN particles having different average particle diameters (D ５０ cBN particles (1) having an average particle diameter (D ５０ cBN particles (2) having an average particle diameter (D ５０ ) preferably contains two or three types of cBN particles (3) having a size of 4.0 μm or more and less than 6.0 μm.

[0031] When the cBN particles (1), (2), and (3) are contained, the content of the 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 (100% by mass) of the cBN particles. When the cBN particles (1), (2), and (3) are contained, the content of the 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 (100% by mass) of the cBN particles. When the cBN particles (1), (2), and (3) are contained, the content of the 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 (100% by mass) of the cBN particles.

[0032] <Binder Phase> The binder phase corresponds to the remainder of the cBN in the cBN sintered body of this embodiment. The binder phase is composed of at least one selected from the group consisting of Ti carbide, Ti nitride, Ti carbonitride, and Ti boride, and W. ２ B and W ２ CoB ２ and one or more selected from the group consisting of:

[0033] The cBN sintered body of this embodiment has an X-ray diffraction pattern using CuKα radiation as a radiation source, in which the intensity of the diffraction peak assigned to the (111) plane of cBN is I Ａ , W ２ The intensity of the diffraction peak assigned to the (211) plane of B is I Ｂ , W ２ CoB ２ The diffraction peaks attributable to the (211) plane and W ２ CoB ２ The intensity of the diffraction peak with the larger intensity among the diffraction peaks attributed to the (310) plane is defined as I ｃ When this is done, I Ａ For I Ｂ and I Ｃ The ratio of the sum of [(I Ｂ +I Ｃ ) / I Ａ] is 0.25 or more. Ｂ +I Ｃ ) / I Ａ When the W content of the cBN sintered body of this embodiment is 0.25 or more, the fracture toughness is improved and the chipping resistance is excellent. The reason for this is not clear, but is presumed as follows. ２ B and W ２ CoB ２ Since it is easy to form from a fine W source, the above ratio [(I Ｂ +I Ｃ ) / I Ａ In the cBN sintered body of this embodiment, the value of ] is 0.25 or more. ２ B.W. ２ CoB ２ It is expected that a large amount of W is included. ２ B and W ２ CoB ２ Since cBN has the property of being difficult for cracks to propagate, the cBN sintered body of this embodiment has excellent fracture toughness, which is thought to result in excellent chipping resistance.

[0034] The intensity of the diffraction peak I Ａ , I Ｂ , I Ｃ and I, which will be described later. Ｄ The XRD pattern of the cBN sintered body for obtaining the above can be obtained by the method described in the Examples. The measured XRD pattern of the cBN sintered body can be collated with an inorganic material database to qualitatively identify the contained components, and the predetermined diffraction peak intensity of each component can be obtained. The qualitative analysis and the acquisition of the 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. It should be noted that the W in this embodiment ２ CoB ２ is W in the inorganic materials database ２ CoB ２ In addition, B ２ CoW ２ It may also be written as W. ２ CoB ２(211) plane and W ２ CoB ２ The (310) plane of W has a diffraction peak at a similar angle. ２ CoB ２ (211) plane and W ２ CoB ２ However, if it is not possible to determine which peak belongs to which, the peak is classified as "W ２ CoB ２ The diffraction peaks attributable to the (211) plane and W ２ CoB ２ The diffraction peak attributable to the (310) plane corresponds to the one having 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, ] is preferably 0.30 to 4.00, more preferably 0.40 to 3.00, even more preferably 0.50 to 2.50, still more preferably 0.60 to 2.00, still more preferably 0.70 to 1.60, still more preferably 0.80 to 1.40, and particularly preferably 0.90 to 1.20.

[0036] Intensity of the diffraction peak assigned to the cBN (111) plane I Ａ For W ２ Intensity of the diffraction peak assigned to the B(211) plane 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 of ] 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 of the diffraction peak assigned to the cBN (111) plane I Ａ For W ２ CoB ２ Diffraction peaks attributable to the (211) plane and W ２ CoB ２ The intensity I of the diffraction peak having the larger intensity among the diffraction peaks attributed to the (310) planeｃ 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 of ] is preferably 0.20 to 1.50, more preferably 0.30 to 1.00, and even more preferably 0.40 to 0.80.

[0038] W ２ CoB ２ Diffraction peaks attributable to the (211) plane and W ２ CoB ２ The intensity I of the diffraction peak having the larger intensity among the diffraction peaks attributed to the (310) plane ｃ For W ２ Intensity of the diffraction peak assigned to the B(211) plane 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 of ] 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 of the diffraction peak assigned to the cBN (111) plane I Ａ The intensity I of the diffraction peak assigned 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, ] 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 of this embodiment, the W content in the cBN sintered body 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 still more preferably 5.20 to 7.00 mass%. In this specification, the contents of W and elements such as Co, Ti, and Al described below are measured by energy dispersive X-ray spectroscopy (EDS), and specifically, can be measured by the method described in the examples.

[0041] The Co content in the cBN sintered body of this embodiment 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 still more preferably 0.50 to 0.80 mass%, from the viewpoint of further improving the wear resistance and fracture resistance of the cBN sintered body.

[0042] The content of one or more selected from the group consisting of Ti carbide, Ti nitride, Ti carbonitride, and Ti boride contained in the binder phase can be adjusted depending on the type of binder used. In this embodiment, it is preferable that the binder phase contains one or more selected from the group consisting of Ti nitride and Ti boride, and TiN and TiB ２ The content of Ti in the cBN sintered body of this embodiment 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%, from the viewpoint of further improving the wear resistance and fracture resistance of the cBN sintered body.

[0043] The binder phase preferably further contains one or more selected from the group consisting of Al nitride, Al boride, and Al oxide. The amount of one or more selected from the group consisting of Al nitride, Al boride, and Al oxide 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 nitride and Al oxide, and AlN and Al ２ O ３ The Al content in the cBN sintered body of this embodiment 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%, from the viewpoint of further improving the wear resistance and fracture resistance of the cBN sintered body.

[0044] Each compound constituting the bonded phase is ２ B.W. ２ CoB ２Similarly, it can be qualitatively determined from the XRD pattern of the cBN sintered body.

[0045] The binder phase may be the above-mentioned W ２ B.W. ２ CoB ２ The binder phase may contain compounds other than Ti compounds and Al compounds. Examples of the binder phase include a composite oxide of Al and Ti; ZrB ２ , ZrB １２ , HfB ２ , HfB, HfB １２ , V.B. ２ , V ３ B ４ , V ３ B １２ , VB, V ５ B ６ , V ２ B ２ , NbB ２ , Nb ３ B ２ , NbB, TaB ２ , Ta ２ B, Ta ３ B ２ , TaB, Ta ３ B ４ , CrB, CrB ４ , Cr ２ B, Cr ２ B ３ , Cr ５ B ３ , CrB ２ , MoB, Mo ２ B ５ , MoB ４ , Mo ２ B, MoB ２ , W.B., W.B. ４ Borides of transition metal elements of Groups 4 to 6, such as ZrN ｘ (0<x≦1), Hf ３ N ２ , HfN ｘ (0<x≦1), Hf ４ N ３ , V.N. ｘ (0<x≦1), V ２ N, NbN, Nb ４ N ３ , Nb ２ N, TaN ｘ (0<x≦1), Ta３ N ５ , Ta ４ N, Ta ２ N, Cr ２ N, CrN ｘ (0<x≦1), WN, W ２ The cBN sintered body may contain nitrides of Group 4 to 6 transition metal elements such as N; mutual solid solutions of the compounds, including the above-mentioned compounds; etc. However, it is preferable that the content of each Group 4 to 6 transition metal element other than Ti and W in the cBN sintered body is as low as possible. The content of each Group 4 to 6 transition metal element other than Ti and W is preferably 1,000 ppm by mass or less, more preferably 100 ppm by mass or less. In addition, the cBN sintered body of this embodiment may contain unavoidable impurities, for example, derived from the blended raw materials. Examples of the unavoidable impurities include Li, Mg, Ca, Al, Si, Ti, C, B, S, P, Ga, Co, Ni, Mn, Fe, Cl, W, and compounds thereof, and may also include those that overlap with the other compounds mentioned above.

[0046] <Vickers Hardness> From the viewpoint of suitable use in cutting high-hardness workpieces, the Vickers hardness of the cBN sintered body of this embodiment is preferably 3,000 HV or more, more preferably 3,200 HV or more, even more preferably 3,300 HV or more, still more preferably 3,400 HV or more, and particularly preferably 3,450 HV or more. The higher the Vickers hardness of the cBN sintered body of this embodiment, the better, but 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> From the viewpoint of further improving wear resistance and fracture resistance, the thermal conductivity of the cBN sintered body of this embodiment is preferably 50.0 W / m·K or more, more preferably 54.0 W / m·K or more, even more preferably 55.0 W / m·K or more, still more preferably 56.0 W / m·K or more, and particularly preferably 58.0 W / m·K or more. The higher the thermal conductivity of the cBN sintered body of this embodiment, the better, but from the viewpoint of ease of production, 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 body] The method for manufacturing a cBN sintered body of this embodiment includes: a binder crushing step in which a binder, which is a raw material for forming the binder phase, is crushed in a container containing crushing media, a mixing step in which the crushed binder and cubic boron nitride particles are mixed to obtain a raw material mixture, and a sintering step in which the raw material mixture is pressurized and heated to obtain a cubic boron nitride sintered body, wherein the crushing media used in the binder crushing step contain WC. Each step in the method for manufacturing a cBN sintered body of this embodiment will be described below.

[0049] <Binder Crushing Step> The binder crushing step is a step of crushing the binder in a container containing a crushing medium. The binder crushed in the binder crushing step preferably contains a raw material containing Ti, and may be only the raw material containing Ti, or may be a mixture of the raw material containing Ti and a raw material other than the raw material containing Ti.

[0050] The raw material containing Ti may be a simple element or a compound. Examples of the raw material containing Ti include TiN, TiAl, and the like. ３ are preferred, and TiN and TiAl ３ It is more preferable that the raw material containing Ti contains both TiN and TiAl. ３ By using TiN, AlN, Al in the binder phase ２ O ３ , TiB ２ etc. can be generated.

[0051] The average particle diameter (D ５０ From the viewpoint that a desired particle size can be easily obtained under appropriate pulverization conditions, the average particle size (D ５０ The average particle diameter (D) of TiN to be subjected to the binder crushing step may be 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. ５０ From the viewpoint that a desired particle size can be easily obtained under appropriate pulverization conditions, the average particle size (D) of TiN is preferably 2.5 μm or less, more preferably 2.0 μm or less, and even more preferably 1.5 μm or less. ５０ ) may be 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. ３ The average particle size (D ５０ ) is preferably 30.0 μm or less, more preferably 25.0 μm or less, and even more preferably 20.0 μm or less, from the viewpoint that a desired particle size can be easily obtained under appropriate pulverization conditions. ３ The average particle size (D ５０ ) may be 1.0 μm or more, 5.0 μm or more, or 10.0 μm or more.

[0052] In the binder crushing step, the binder is crushed in a container containing crushing media containing WC. In the method for producing a cBN sintered body of this embodiment, the binder is crushed using crushing media containing WC, so that WC derived from the crushing media is contained in the raw material. This WC is then converted into W through the subsequent sintering step. ２ B.W. ２ CoB ２ Thus, the cBN sintered body of this embodiment is obtained. ２ B and W ２ CoB ２For example, by making the grinding conditions in the binder grinding step more severe than before, a large amount of fine WC derived from the grinding medium is contained in the raw material, and W ２ B and W ２ CoB ２ is more likely to be formed.

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

[0054] The grinding method in the binder grinding step is not particularly limited as long as it uses a grinding medium, and examples include a ball mill and a rod mill. However, from the viewpoint of productivity, a ball mill is preferred. That is, the grinding medium is preferably the balls used in a ball mill. Note that the ball mill in this specification may be what is called a bead mill. The ball mill may be a rotary ball mill, a vibration ball mill, or a combination of rotation and vibration. However, from the viewpoint of productivity, a rotary ball mill is preferred. The rotary ball mill may be a conventional rotary ball mill or a planetary ball mill. When a ball mill is used, the material of the mill pot preferably contains WC, more preferably contains Co together with WC, and even more preferably is made of a cemented carbide containing WC and Co. The preferred contents of WC and Co in the mill pot material are the same as those 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] The grinding using a ball mill may be either a dry or wet method, but a wet method is preferred from the viewpoint of enabling more uniform grinding. Examples of dispersion media when performing the wet method include acetone, hexane, 2-propanol, ethanol, heptane, etc. Among these, acetone is preferred. One type of dispersion medium may be used alone, or two or more types may be used in combination. When grinding in the binder grinding step 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 mass%, more preferably 20 to 60 mass%, and even more preferably 30 to 50 mass%. Grinding may be performed in an air atmosphere, or in a N ２ The reaction may be carried out in an inert gas atmosphere such as a gas.

[0056] When a rotating ball mill is used in the binder crushing step, conditions such as crushing time, rotation speed, ball filling amount, and crushing target material filling amount are preferably determined appropriately depending on the crushing scale, the target particle size, etc. The crushing time of the ball mill in the binder crushing step using a rotating ball mill may be, for example, 3 to 7 hours. The rotation speed of the ball mill in the binder crushing step using a rotating ball mill may be, for example, 150 to 300 rpm. In the binder crushing step using a rotating ball mill, the filling amount of balls charged into the mill pot may be, for example, 15 to 35% by volume relative to the internal volume of the mill pot. In the binder crushing step using a rotating ball mill, the filling amount of the crushing target material charged into the mill pot may be, for example, 20 to 40% by volume relative to the internal volume of the mill pot. Crushing in the crushing step may be performed only once, or may be performed two or more times as necessary.

[0057] The average particle diameter (D ５０ ) 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, from the viewpoint of homogenizing the composition of the cBN sintered body.

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

[0059] The cBN particles are preferably prepared by finely pulverizing cBN with a purity of 99.9% or more obtained by ultra-high pressure, high temperature synthesis at 3 GPa or more and 1,200°C or more, and adjusting the particle size and particle shape. ５０ The amount of cBN particles blended is preferably an amount such that the cBN content in the resulting cBN sintered body falls within the above-mentioned preferred range.

[0060] In the mixing step, it is preferable to mix the raw materials containing the crushed binders and cBN particles in a container containing a crushing medium. The mixing method in the mixing step can be the same as the crushing method mentioned in the binder crushing step, and the preferred embodiments are also the same. That is, the mixing in the mixing step is preferably carried out using a rotary ball mill. When mixing using a rotary ball mill is carried out wet, the content of the raw materials in the slurry obtained by mixing the raw materials and the dispersion medium is preferably 50 to 80 mass%, more preferably 55 to 75 mass%, and even more preferably 60 to 70 mass%. Mixing may be carried out in an air atmosphere, or in a N ２ The reaction may be carried out in an inert gas atmosphere such as a gas.

[0061] When a rotating ball mill is used in the mixing step, conditions such as mixing time, rotation speed, ball filling amount, and filling amount of materials to be mixed are preferably determined appropriately depending on the mixing scale, etc. The mixing time of the ball mill in the mixing step using a rotating ball mill may be, for example, 2 to 6 hours. The rotation speed of the ball mill in the mixing step using a rotating ball mill may be, for example, 100 to 200 rpm. In the mixing step using a rotating ball mill, the filling amount of balls charged into the mill pot may be, for example, 25 to 40% by volume with respect to the internal volume of the mill pot. In the mixing step using a rotating ball mill, the filling amount of raw materials charged into the mill pot may be, for example, 40 to 60% by volume with respect to the internal volume of the mill pot.

[0062] <Heat Treatment Step> The raw material mixture obtained in the mixing step may be subjected to heat treatment for degassing as necessary to obtain a heat-treated raw material mixture. The temperature for the heat treatment for degassing is preferably 800°C or less from the viewpoints of uniform progress of reaction sintering of the binder phase and densification of the sintered body. Furthermore, from the viewpoints of sufficiently removing impurity components such as organic substances and densifying the cBN sintered body, the heat treatment temperature is preferably 500°C or more. From the above viewpoints, the heat treatment temperature is more preferably 550 to 750°C, and even more preferably 600 to 700°C. From the viewpoint of efficient degassing, the heat treatment is preferably performed in a vacuum atmosphere, and the pressure is 1.0 x 10 －３ The heat treatment time is appropriately set depending on the amount of the raw material mixture to be treated, the type of dispersion medium used in the mixing step, etc., but is usually 0.1 to 10 hours, and preferably 1 to 3 hours.

[0063] <Sintering Step> The sintering step is a step of subjecting the raw material mixture obtained in the mixing step to a pressure and heat treatment to obtain a cubic boron nitride sintered body. The raw material mixture obtained in the mixing step may be the raw material mixture after the heat treatment step, or may be a raw material mixture obtained without carrying out the heat treatment step.

[0064] The maximum temperature in the pressure and 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] From the viewpoint of densifying the cBN sintered body, the maximum pressure in the pressure and heat treatment is preferably 3.0 GPa or more, more preferably 3.5 GPa or more, and even more preferably 4.0 GPa or more. The maximum pressure in the pressure and heat treatment may be 7.0 GPa or less, 6.0 GPa or less, or 5.0 GPa or less.

[0066] In order to suppress oxidation of the raw material mixture during the heat-pressure treatment and to produce a desired cBN sintered body, it is preferable that the heat-pressure treatment be performed in an inert gas atmosphere. Examples of the inert gas include Ar gas and N２ These gases may be used alone or in combination of two or more.

[0067] [Tool] The tool of this embodiment contains the cBN sintered compact of this embodiment as a constituent material. As described above, the cBN sintered compact of this embodiment has high hardness and excellent wear resistance and chipping resistance, making it a suitable material for tools, particularly cutting or grinding tools.

[0068] Hereinafter, the present embodiment will be described based on examples, but the present embodiment is not limited to the examples.

[0069] [Average particle diameter (D ５０ ), 10% particle size (D １０ ) and 90% particle size (D ９０ The particle size distribution of particles was measured using a particle size analyzer (LA-920, manufactured by Horiba, Ltd.). In the obtained particle distribution, the 10% particle diameter (D １０ ), average particle diameter (D ５０ ), and the 90% particle diameter (D ９０ ) was measured.

[0070] [Method for calculating the porosity of cBN particles] The porosity of cBN particles was calculated using the above-mentioned Ouchiyama formula. ｉ ) is the same as the above [average particle diameter (D ５０ ) measurement method], and the average particle diameter (D with a bar above) is the particle size of the cBN particles obtained by the above [Measuring method of average particle diameter (D ５０ ) measurement method]. ５０ The ratio of the number of particles of each particle size (f ｉ ) and the mass ratio of particles of each particle size (w ｉ ) is a value obtained from the particle size distribution of cBN particles, and the porosity (ε ０ｉ ) are values ​​calculated assuming that the cBN particles having each particle size are spherical. When two or more types of cBN particles are mixed, the above parameters can be calculated from the particle size distribution and blending amount of each cBN particle.

[0071] [Method for measuring cBN content and Feret diameter] The cBN sintered body samples for evaluation obtained in each example were used as the measurement object, and backscattered electron images were taken at 5,000x magnification using a scanning electron microscope (SEM) ("S-5500", manufactured by Hitachi High-Tech Corporation). The captured image contained black, white, and gray areas. Energy dispersive X-ray spectroscopy (EDS) was performed on each area, confirming that the black areas were cBN and the white and gray areas were the binder phase. The captured image was binarized using image processing software, and the black areas representing cBN and the white areas representing the binder phase were identified. The area ratio of the black areas to the entire field of view of the binarized image was calculated, and the arithmetic average value for the three fields of view was considered to be the cBN content (unit: volume %). As a representative example, a backscattered electron image of the sintered body of Example 1 is shown in FIG. 3, and its binarized image is shown in FIG. 4. The size of one field of view is 25.0 μm in width and 17.4 μm in height, and the total area of ​​the three fields of view is 1305.0 μm ２ In addition, the Feret diameters of all measurable cBN particles were determined using image processing software in the entire field of view of a binarized image of a backscattered electron image taken at a magnification of 5,000 times, and the arithmetic mean value thereof was taken as the Feret diameter (unit: μm) of the cBN.

[0072] [Elemental Analysis] Energy dispersive X-ray spectroscopy (EDS) was performed on the cBN sintered body samples for evaluation obtained in each example, and the element concentrations of B, N, O, C, Al, Ti, Co, and W in the cBN sintered body were measured. The element concentrations were measured over the entire field of view observed under the following conditions, and the average values ​​for 10 fields of view were calculated. The EDS measurement conditions are as follows: Measurement device: JSM-6510LA (manufactured by JEOL Ltd.) EDS analysis software: Analysis Station (manufactured by JEOL Ltd.) Acceleration voltage: 20.0 kV (probe current: 1.00000 nA) Magnification: 2,000x Energy range: 0-20 keV

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

[0074] [Method for measuring diffraction peak intensity ratio] In the XRD pattern described in the above section [Method for analyzing sintered body composition], the diffraction peak intensity of the cBN (111) plane near 2θ = 43.30° was measured. Ａ , W around 2θ=40.90° ２ The intensity of the diffraction peak assigned to the B(211) plane is I Ｂ , W around 2θ=43.10° ２ CoB ２ Diffraction peaks attributable to the (211) plane and W ２ CoB ２ The intensity of the diffraction peak with the larger intensity among the diffraction peaks attributed to the (310) plane is designated as I ｃ , the diffraction peak intensity attributable to the (110) plane of metal W near 2θ = 40.30° is I Ｄ As the diffraction peak intensity ratio [I Ｂ / I Ａ ], [I Ｃ / I Ａ ], [I Ｂ / I Ｃ ], [I Ｄ / I Ａ ] and [(I Ｂ +I Ｃ ) / I Ａ As representative examples, the range of 2θ=39° to 44° of the XRD pattern of the cBN sintered compact obtained in Example 1 is shown in FIG. 1, and the range of 2θ=39° to 44° of the XRD pattern of the cBN sintered compact obtained in Comparative Example 2 is shown in FIG.

[0075] [Production of cubic boron nitride sintered body] Examples 1 to 3 (binder crushing step) TiN (average particle diameter (D ５０ ) = 1.2 μm) 7.7 g, TiAl ３ (Average particle diameter (D ５０ 2.6 g of the powder (particle size = 19.8 μm), 21 ml of a 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 pulverized under the following pulverization conditions. The mill pot and balls of the planetary ball mill were both made of cemented carbide (components: WC content of approximately 85% by mass, Co content of approximately 15% by mass), and the cylindrical mill pot had a height of 23 mm, an inner diameter of φ65 mm, and a ball diameter of 1.3 mm. <Binder pulverization conditions> - Raw material (slurry) filling amount: Approximately 32 vol% of the internal volume of the mill pot - Ball filling amount: Approximately 24 vol% of the internal volume of the mill pot - Atmosphere: Air - Rotation speed: 270 rpm - Pulverization time: 5 hours

[0076] (Step of mixing cBN particles and binder) After the binder crushing step, 31 g of the cBN particles shown in Table 1, 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 following mixing conditions to obtain a slurry of the raw material mixture. The material of the balls was the same as that used in the binder crushing step. <Mixing conditions for cBN particles and binder> - Raw material (slurry) filling amount: Approximately 54 vol% of the internal volume of the mill pot - Ball filling amount: Approximately 32 vol% of the internal volume of the mill pot - Atmosphere: N ２ Gas atmosphere 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 particles (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 particles (2): 10% particle diameter (D １０ ) = 1.92 μm, average particle diameter (D ５０ ) = 2.93 μm, 90% particle diameter (D ９０) = 4.31 μm cBN particles (3): 10% particle diameter (D １０ ) = 3.06 μm, average particle diameter (D ５０ ) = 4.60 μm, 90% particle diameter (D ９０ ) = 6.42 μm

[0078] (Heat Treatment Step) The slurry obtained above was heated in a nitrogen atmosphere. ２ After standing and drying for 5 hours at 70°C under a gas atmosphere, －３ The powder was degassed by heat treatment at 650° C. for 0.5 hours in a vacuum atmosphere of 100 Pa or less to obtain a heat-treated powder.

[0079] (Sintering process) N ２ The heat-treated powder was layered on a cemented carbide support plate in a gas atmosphere, and then pressurized and heated at 4.5 GPa and 1,500°C for 1 hour to produce a cBN sintered body (diameter: approximately 30 mm, thickness: approximately 4 mm). The upper surface of the cBN sintered body (the lower surface was in contact with the cemented carbide support plate) was ground with a #400 diamond grinding wheel to prepare a cBN sintered body sample for evaluation.

[0080] Example 4 (Binder Crushing Process) TiN (Average Particle Diameter (D ５０ ) = 1.2 μm) 0.9 g, TiC (average particle diameter (D ５０ ) = 0.70 μm) 5.8 g, TiAl ３ (Average particle diameter (D ５０ 3.6 g of the powder (particle size: 19.8 μm), 21 ml of a 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 GmbH), and pulverized under the same conditions as the binder pulverization conditions in Example 1. The specifications of the planetary ball mill and balls were the same as those in Example 1.

[0081] (Step of mixing cBN particles and binder) After the binder crushing step, 31 g of the cBN particles shown in Table 1, 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 those for mixing 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 that of the balls used in the binder crushing step.

[0082] (Heat Treatment Step and Firing Step) The slurry obtained above was subjected to a heat treatment step and a sintering step under the same conditions as in Example 1 to obtain a cBN sintered body sample for evaluation.

[0083] Example 5 (Binder Crushing Process) TiN (Average Particle Diameter (D ５０ ) = 1.2 μm) 9.3 g, TiAl ３ (Average particle diameter (D ５０ 3.1 g of the powder (particle size: 19.8 μm), 21 ml of a 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 GmbH), and pulverized under the same conditions as the binder pulverization conditions in Example 1. The specifications of the planetary ball mill and balls were the same as those in Example 1.

[0084] (Step of mixing cBN particles and binder) After the binder crushing step, 28.9 g of the cBN particles shown in Table 1, 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 those for mixing 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 that of the balls used in the binder crushing step.

[0085] (Heat Treatment Step and Firing Step) The slurry obtained above was subjected to a heat treatment step and a sintering step under the same conditions as in Example 1 to obtain a cBN sintered body sample for evaluation.

[0086] Example 6 (Binder Crushing Step) TiN (Average Particle Diameter (D ５０ )=1.2μm) 10.8g, TiAl ３ (Average particle diameter (D ５０ 3.7 g of the powder (particle size: 19.8 μm), 21 ml of a 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 GmbH), and pulverized under the same conditions as the binder pulverization conditions in Example 1. The specifications of the planetary ball mill and balls were the same as those in Example 1.

[0087] (Step of mixing cBN particles and binder) After the binder crushing step, 26.8 g of the cBN particles shown in Table 1, 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 those for mixing 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 that of the balls used in the binder crushing step.

[0088] (Heat Treatment Step and Firing Step) The slurry obtained above was subjected to a heat treatment step and a sintering step under the same conditions as in Example 1 to obtain a cBN sintered body sample for evaluation.

[0089] Example 7 (Binder Crushing Step) TiN (Average Particle Diameter (D ５０ )=1.2μm) 12.3g, TiAl ３ (Average particle diameter (D ５０ 4.2 g of the powder (particle size: 19.8 μm), 21 ml of a 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 GmbH), and pulverized under the same conditions as the binder pulverization conditions in Example 1. The specifications of the planetary ball mill and balls were the same as those in Example 1.

[0090] (Step of mixing cBN particles and binder) After the binder crushing step, 24.8 g of the cBN particles shown in Table 1, 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 those for mixing 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 that of the balls used in the binder crushing step.

[0091] (Heat Treatment Step and Firing Step) The slurry obtained above was subjected to a heat treatment step and a sintering step under the same conditions as in Example 1 to obtain a cBN sintered body sample for evaluation.

[0092] Comparative Example 1 In Example 1, the type of cBN particles was changed to the type shown in Table 1, the amount of cBN particles was changed to 26.1 g, the amount of TiN was changed to 9.1 g, and the amount of TiAl ３The cBN sintered body and the cBN sintered body sample for evaluation were obtained in the same manner as in Example 1, except that the compounding amount of was changed to 4.9 g, the amount of balls introduced in the binder crushing step was changed to 107 g, and the crushing time in the binder crushing step was changed to 4 hours.

[0093] Comparative Example 2 A cBN sintered body and a cBN sintered body sample for evaluation were obtained in the same manner as in Example 1, except that the amount of balls added in the binder crushing step was changed to 107 g, the ball diameter was changed to 3.0 mm, and the crushing time in the binder crushing step was changed to 4 hours, and no additional balls were added in the step of mixing the cBN particles and the binder.

[0094] Comparative Example 3 (Binder Crushing Process) TiN (Average Particle Diameter (D ５０ ) = 1.2 μm) 14.4 g, TiC (average particle diameter (D ５０ ) = 0.70 μm) 4.2 g, TiAl ３ (Average particle diameter (D ５０ 7.4 g of CBN particles (particle size = 19.8 μm), 15.3 g of cBN particles shown 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 GmbH), and 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 were the same as those in Example 1. <Grinding and mixing conditions> - Raw material (slurry) filling amount: Approximately 54 volume % of the internal volume of the mill pot - Ball filling amount: Approximately 24 volume % of the internal volume of the mill pot - Atmosphere: Air - Rotation speed: 190 rpm - Grinding and mixing time: 6 hours

[0095] (Heat Treatment Step and Firing Step) The slurry obtained above was subjected to a heat treatment step and a sintering step under the same conditions as in Example 1 to obtain a cBN sintered body sample for evaluation.

[0096] [Evaluation Method] The cBN sintered body samples for evaluation obtained in each example were subjected to the following various evaluations. 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 cBN sintered body samples for evaluation obtained in each example was measured using a measuring device with a product name "HMV-G21" (manufactured by Shimadzu Corporation) under 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 measuring thermal conductivity (thickness: 0.80 mm, diameter: 10.0 mmφ) was cut out from the cBN sintered compact sample for evaluation, 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 (manufactured by NETZSCH, product name "LFA457"), with the thickness direction of the sample as the heat flow direction. The specific heat of the sample was also measured using the same device, and the density of the sample was calculated from the dimensions and weight of the sample. From these results, the thermal conductivity of the cBN sintered compact sample for evaluation in the thickness direction was calculated using the following formula: Thermal conductivity (W / (m·K)) = Specific heat (J / (kg·K)) × Density (kg / m ３ ) × thermal diffusivity (m ２ / second)

[0099] <Method for Measuring Fracture Toughness Value> The fracture toughness value was determined by the IF method (indenter penetration method) in accordance with JIS R 1607:2015 "Room temperature fracture toughness test method for fine ceramics." A measuring device with the product name "HMV-G21" (manufactured by Shimadzu Corporation) was used, and a fracture toughness test was performed on 10 cBN sintered compact samples for evaluation under conditions of a maximum load of 9.8 N, an indenter penetration time of 5 seconds, and a temperature of 25°C. The arithmetic mean value was taken as the fracture toughness value.

[0100] <Cutting Evaluation 1> Cutting tools conforming to ISO standard CNGA120404 were produced from the cBN sintered bodies obtained in each example. Using the obtained cutting tools, cutting tests were conducted on workpiece materials 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 index of breakage resistance. In addition, for those that had cut 1,500 pieces, the amount of wear on the cutting tool after cutting 1,500 pieces was measured. (Cutting conditions) Cutting speed: 145 m / min. Machining allowance: φ0.33 mm. Feed rate: 0.20 (mm / rev). Type of workpiece: austenitic sintered alloy. Test environment temperature: 25°C

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

[0102] <Cutting Evaluation 3> Cutting tools conforming to ISO standard CNGA120404 (cutting edge shape: sharp edge) were produced from the cBN sintered bodies obtained in each example. Using the obtained cutting tools, cutting tests were conducted on workpiece materials 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 speed: 150 m / min Depth of cut: 0.2 mm Feed rate: 0.15 (mm / rev) Machining distance: 150 m / pass Type of workpiece material: SCM415 (8 grooves) (hardened steel, hardness HRC 62-60) Test environment temperature: 25°C

[0103] In Table 1, "ND" means that the result was at the detection limit. In Table 1, "NE" means that the evaluation was not performed.

[0104] It can be seen from Table 1 that the cBN sintered bodies of Examples 1 to 7 of this embodiment have excellent chipping resistance.

Claims

1. A cubic boron nitride sintered body having cubic boron nitride and a binder phase which is the remainder of the cubic boron nitride, wherein the content of the cubic boron nitride is 50.0 to 90.0% by volume, and the binder phase is one or more selected from the group consisting of Ti carbide, Ti nitride, Ti carbonitride and Ti boride, and W. ２ B and W ２ CoB ２ and one or more selected from the group consisting of: wherein, in an X-ray diffraction pattern of the cubic boron nitride sintered body using CuKα radiation as a radiation source, the intensity of a diffraction peak assigned to the (111) plane of the cubic boron nitride is I Ａ , the W ２ The intensity of the diffraction peak assigned to the (211) plane of B is I Ｂ , the W ２ CoB ２ The intensity of the diffraction peak attributable to the (211) plane and the diffraction peak attributable to the (310) plane, whichever has the greater intensity, is designated as I. ｃ When the above I Ａ For the above I Ｂ and the above I Ｃ The ratio of the sum of [(I Ｂ +I Ｃ ) / I Ａ ] is 0.25 or more.

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

3. I above Ｃ The above I Ｂ The ratio [I Ｂ / I Ｃ 3. The cubic boron nitride sintered body according to claim 1, wherein the value of [Ratio of Saturation of Nitride] is 0.20 to 1.

00.

4. Average particle diameter (D ５０ 3. The cubic boron nitride sintered body according to claim 1, wherein the cubic boron nitride sintered body contains two or more types of cubic boron nitride particles having different properties.

5. A cubic boron nitride sintered body according to claim 1 or 2, having a thermal conductivity of 50.0 W / m·K or more.

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

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

8. A method for producing a cubic boron nitride sintered body as defined in claim 1 or 2, comprising: a binder crushing step in which a binder, which is a raw material that forms the binder phase, is crushed in a vessel containing crushing media; a mixing step in which the crushed binder and cubic boron nitride particles are mixed to obtain a raw material mixture; and a sintering step in which the raw material mixture is pressurized and heated to obtain a cubic boron nitride sintered body, wherein the crushing media used in the binder crushing step contain WC.

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