Cubic boron nitride sintered body

Abstract

To provide a cubic boron nitride sintered body capable of extending a tool life.SOLUTION: A cBN sintered body comprises cBN and a binder phase, wherein: a content ratio of cBN is 80 to 94 vol% of the total volume of the sintered body and a content ratio of the binder phase is 6 to 20 vol% thereof; the binder phase comprises a metallic phase, a V compound, and an Al compound; the metallic phase comprises one or more selected from the group consisting of Ni, a Ni-containing alloy, and a solid solution; the Ni-containing alloy and the solid solution comprise Ni and one or more elements selected from the group consisting of Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, and Co; the V compounds comprises one or more selected from the group consisting of VN, VCN and VC; Al compounds comprise one or more selected from the group consisting of Al2O3, AlN and AlB2; a maximum peak position 2θ of a 200 plane of the metallic phase is less than 51.60°; and I1 / (I1+I2) is 0.40 to 0.80 when the peak intensity of a 220 plane of the V compound is I1 and that of the 200 plane of the metallic phase is I2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cubic boron nitride sintered body. [Background technology]

[0002] Cubic boron nitride (hereinafter referred to as "cBN") has a hardness second only to diamond and excellent thermal conductivity. Cubic boron nitride also has the characteristic of having a lower affinity with iron than diamond. Therefore, cubic boron nitride sintered bodies consisting of cubic boron nitride and a binder phase of metal or ceramic are used in cutting tools, wear-resistant tools, and the like.

[0003] In recent years, there has been an increasing demand for improved cutting tool performance for hard-to-cut materials such as heat-resistant alloys. In particular, when machining sintered metals, which have high formability, the workpiece often has a complex shape, which can easily cause tool damage due to thermal shock when machined with a tool. Furthermore, sintered metals can contain hard particles, which can easily cause tool wear. For this reason, cubic boron nitride is often used to machine sintered metals, and much research has been conducted on cubic boron nitride sintered bodies with a high cubic boron nitride content.

[0004] For example, Patent Document 1 discloses a sintered body containing hard particles made of one or more types selected from the group consisting of cubic boron nitride, Al2O3, AlON, SiAlON, TiC, TiCN, TiN, WC, and diamond, and a metal phase represented by (Co,Ni)3(Al,W,V,Ti). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-208889 Summary of the Invention [Problem to be solved by the invention]

[0006] In the sintered body described in Patent Document 1, when the hard particles are cubic boron nitride (also called cBN), the bonding strength between the cBN particles may be insufficient, leaving room for improvement in fracture resistance.

[0007] An object of the present invention is to provide a cubic boron nitride sintered body that can extend the tool life. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors discovered that a cubic boron nitride sintered body capable of extending tool life can be obtained by including a specific composition in a cBN sintered body, and have thus completed the present invention.

[0009] The gist of the present invention is as follows. [1] A cubic boron nitride sintered body comprising cubic boron nitride and a binder phase, the content of the cubic boron nitride is 80% by volume or more and 94% by volume or less with respect to the total amount of the sintered body, the content of the binder phase is 6% by volume or more and 20% by volume or less with respect to the total amount of the sintered body, the binder phase includes a metal phase, a V compound, and an Al compound; the metal phase comprises at least one selected from the group consisting of Ni metal, a Ni-containing alloy, and a Ni-containing solid solution; The Ni-containing alloy and the Ni-containing solid solution contain Ni and one or more elements selected from the group consisting of Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, and Co, the V compound includes one or more selected from the group consisting of VN, VCN, and VC; the Al compound includes one or more selected from the group consisting of Al2O3, AlN, and AlB2, The maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction is less than 51.60°, When the X-ray diffraction peak intensity of the (220) plane of the V compound is I1 and the X-ray diffraction peak intensity of the (200) plane of the metal phase is I2, A cubic boron nitride sintered body having I1 / (I1+I2) of 0.40 or more and 0.80 or less. [2] The cubic boron nitride sintered body according to [1], wherein the full width at half maximum (°) of the peak of the (200) plane of the metal phase in X-ray diffraction is 0.40° or more and 0.70° or less. [3] When the X-ray diffraction peak intensity of the (220) plane of the cubic boron nitride is I3, The cubic boron nitride sintered body according to [1] or [2], wherein I1 / I3 is 0.70 or more and 1.50 or less. [4] The cubic boron nitride sintered body according to any one of [1] to [3], wherein the maximum peak position 2θ (°) of the (220) plane of the V compound in X-ray diffraction is less than 63.40°. [5] The cubic boron nitride sintered body according to any one of [1] to [4], wherein the maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction is less than 51.40°. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a cubic boron nitride sintered body that can extend the tool life. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail, but the present invention is not limited to the following embodiment. The present invention can be modified in various ways without departing from the gist of the present invention.

[0012] [Cubic boron nitride sintered body] The cubic boron nitride sintered body of this embodiment is a cubic boron nitride sintered body containing cubic boron nitride and a binder phase, the content of cubic boron nitride being 80% by volume or more and 94% by volume or less with respect to the total amount of the sintered body, the content of the binder phase being 6% by volume or more and 20% by volume or less with respect to the total amount of the sintered body, the binder phase containing a metal phase, a V compound, and an Al compound, the metal phase containing one or more selected from the group consisting of Ni metal, Ni-containing alloys, and Ni-containing solid solutions, the Ni-containing alloys and Ni-containing solid solutions being Ni, Al, Ti, V, Cr, Zr, Nb, Mo, H and one or more elements selected from the group consisting of f, Ta, W, and Co, the V compound includes one or more elements selected from the group consisting of VN, VCN, and VC, the Al compound includes one or more elements selected from the group consisting of Al2O3, AlN, and AlB2, the maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction is less than 51.60°, and when the X-ray diffraction peak intensity of the (220) plane of the V compound is I1 and the X-ray diffraction peak intensity of the (200) plane of the metal phase is I2, I1 / (I1+I2) is 0.40 or more and 0.80 or less.

[0013] The cubic boron nitride sintered body of this embodiment can extend the tool life by including the above-mentioned structure.

[0014] The reason why the cubic boron nitride sintered body of this embodiment can extend the tool life is not clear in detail, but the present inventors believe that the reason is as follows, although the reason is not limited to this. The cubic boron nitride sintered body of this embodiment has a cubic boron nitride content of 80% by volume or more relative to the total volume of the sintered body, which improves the hardness of the cBN sintered body and provides excellent wear resistance. When the cubic boron nitride content is 94% by volume or less relative to the total volume of the sintered body, the binder phase content is relatively high, which suppresses the shedding of cBN particles and provides excellent wear resistance. When the binder phase content is 6% or more by volume relative to the total amount of the sintered body, the falling off of cBN particles is suppressed, resulting in excellent wear resistance. When the binder phase content is 20% or less by volume relative to the total amount of the sintered body, the cBN content becomes relatively high, improving the hardness of the cBN sintered body and resulting in excellent wear resistance. When the maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction is less than 51.60°, the heat resistance is improved and the wear resistance is excellent. When the X-ray diffraction peak intensity of the (220) plane of the V compound is I1 and the X-ray diffraction peak intensity of the (200) plane of the metal phase is I2, if I1 / (I1+I2) is 0.40 or more, the bond strength between the cBN particles is improved, resulting in excellent chipping resistance. In addition, the binder phase is more effective in preventing cBN particles from falling off, which also improves wear resistance. When I1 / (I1+I2) is 0.80 or less, the sinterability improves, and therefore the toughness of the sintered body improves and the fracture resistance is excellent. The cubic boron nitride sintered body of this embodiment has excellent chipping resistance as a result of the combined effects described above.

[0015] The cubic boron nitride sintered body of this embodiment contains cBN and a binder phase, and the total content of cBN and the binder phase in the cubic boron nitride sintered body of this embodiment is 100% by volume. The binder phase includes a metal phase, a V compound, and an Al compound.

[0016] The content (vol %) of the Al compound is preferably 0.5 vol % or more and 5.0 vol % or less, more preferably 0.8 vol % or more and 4.3 vol % or less, and even more preferably 0.8 vol % or more and 3.2 vol % or less, relative to the total amount of the sintered body.

[0017] The total content of the metal phase and the V compound is preferably 5.0 vol% or more and 18.0 vol% or less, more preferably 5.2 vol% or more and 16.3 vol% or less, and even more preferably 6.6 vol% or more and 12.5 vol% or less, relative to the total amount of the sintered body.

[0018] The metal phase includes one or more elements selected from the group consisting of Ni metal, a Ni-containing alloy, and a Ni-containing solid solution. The Ni-containing alloy and the Ni-containing solid solution include Ni and one or more elements selected from the group consisting of Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, and Co. The V compound includes one or more elements selected from the group consisting of VN, VCN, and VC. The Al compound includes one or more elements selected from the group consisting of Al2O3, AlN, and AlB2.

[0019] [Cubic boron nitride (cBN)] In the cubic boron nitride sintered body of this embodiment, the cubic boron nitride content is 80% by volume or more, which relatively reduces the proportion of the binder phase, resulting in improved hardness and excellent wear resistance. Meanwhile, the cubic boron nitride sintered body of this embodiment, the cubic boron nitride content is 94% by volume or less, which prevents cubic boron nitride particles from falling off and provides excellent wear resistance. Furthermore, in cutting, the surface roughness of the machined surface of the workpiece tends to be reduced, resulting in a better appearance after machining. From the same perspective, the cubic boron nitride content is preferably 80.5% by volume or more and 93.7% by volume or less, and more preferably 83.2% by volume or more and 92.3% by volume or less.

[0020] [Binded phase] The cubic boron nitride sintered body of this embodiment has a binder phase content of 6% or more by volume, which prevents cBN particles from falling off and provides excellent wear resistance. On the other hand, the cubic boron nitride sintered body has a binder phase content of 20% or less by volume, which increases the cBN content relatively, improving hardness and resulting in excellent wear resistance. From the same perspective, the binder phase content is preferably 6.3% to 19.5% by volume, and more preferably 7.7% to 16.8% by volume.

[0021] The cubic boron nitride sintered body of this embodiment contains a metal phase, a V compound, and an Al compound in the binder phase. The metal phase includes at least one selected from the group consisting of Ni metal, a Ni-containing alloy, and a Ni-containing solid solution, preferably at least one selected from the group consisting of a Ni-containing alloy and a Ni-containing solid solution, and more preferably a Ni-containing alloy. The Ni-containing alloy and Ni-containing solid solution contain Ni and one or more elements selected from the group consisting of Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, and Co, preferably Ni and one or more elements selected from the group consisting of Al and V, more preferably Ni and V, and even more preferably Ni3V. The V compound includes one or more selected from the group consisting of VN, VCN, and VC, and the Al compound includes one or more selected from the group consisting of Al2O3, AlN, and AlB2, preferably one or more selected from the group consisting of Al2O3 and AlN, and more preferably Al2O3.

[0022] When the maximum peak position 2θ(°) of the (200) plane of the metal phase in X-ray diffraction is less than 51.60°, heat resistance is improved and wear resistance is excellent. From the same viewpoint, the maximum peak position 2θ(°) of the (200) plane of the metal phase in X-ray diffraction is preferably less than 51.40°, and more preferably 50.80° or more and less than 51.30°. When the maximum peak position 2θ of the (200) plane of the metal phase in X-ray diffraction is within the following ranges, the metal phase is considered to be Ni3V or Ni, respectively. The crystal structure of Ni3V and Ni is cubic. Ni3V: 50.80° or more and less than 51.60° Ni: 51.60° or more and less than 52.2° Therefore, there is no particular limitation on the method for adjusting the maximum peak position 2θ (°) of the (200) plane of the metallic phase in X-ray diffraction to fall within the above range, but one example is a method of incorporating Ni3V into the metallic phase. Furthermore, for example, by increasing the content of Ni3V in the metallic phase, the maximum peak position 2θ (°) of the (200) plane of the metallic phase in X-ray diffraction tends to decrease.

[0023] In the cubic boron nitride sintered body of this embodiment, the full width at half maximum (°) of the peak of the (200) plane of the metal phase in X-ray diffraction is preferably 0.40° or more and 0.70° or less. The value of this full width at half maximum tends to increase as the structure becomes finer. When the metal structure becomes finer, the hardness improves, but the toughness tends to decrease. When the full width at half maximum (°) of the peak of the (200) plane of the metal phase in X-ray diffraction is 0.40° or more, the hardness of the metal phase is improved, resulting in excellent wear resistance. When the full width at half maximum (°) of the peak of the (200) plane of the metal phase in X-ray diffraction is 0.70° or less, the toughness of the metal phase is improved, resulting in excellent chipping resistance. From the same perspective, the full width at half maximum (°) of the peak of the (200) plane of the metal phase in X-ray diffraction is more preferably 0.42 to 0.67, and even more preferably 0.47 to 0.61.

[0024] In the cubic boron nitride sintered body of this embodiment, the maximum peak position 2θ (°) of the (220) plane of the V compound in X-ray diffraction is preferably 62.60° or more and less than 63.40°. When the maximum peak position 2θ(°) of the (220) plane of the V compound in X-ray diffraction is less than 63.40°, the wear resistance tends to be even better. From the same viewpoint, it is more preferable that the maximum peak position 2θ(°) of the (220) plane of the V compound in X-ray diffraction is less than 63.10°. When the maximum peak position 2θ of the (220) plane of a V compound in X-ray diffraction is in the following ranges, the V compound is considered to be VC, VCN, or VN, respectively. VC: 62.60° or more and less than 63.10° VCN: 63.10° or more and less than 63.40° VN: 63.40° or more and 63.90° or less Therefore, the method for adjusting the maximum peak position 2θ of the (220) plane of a V compound in X-ray diffraction to fall within the above range is not particularly limited, but examples thereof include a method in which the V compound contains a large amount of VCN and / or VC, which are superior in hardness to VN.

[0025] When the X-ray diffraction peak intensity of the (220) plane of the V compound is I1 and the X-ray diffraction peak intensity of the (200) plane of the metal phase is I2, if I1 / (I1+I2) is 0.40 or more, the bond strength between the cBN particles is improved, resulting in excellent chipping resistance. In addition, the binder phase is more effective in preventing cBN particles from falling off, which also improves wear resistance. When I1 / (I1+I2) is 0.80 or less, the sinterability is improved, and therefore the toughness of the sintered body is improved and the chipping resistance is excellent. From the same viewpoint, I1 / (I1+I2) is preferably 0.43 or more and 0.77 or less, and more preferably 0.53 or more and 0.64 or less.

[0026] In the cubic boron nitride sintered body of this embodiment, when the X-ray diffraction peak intensity of the (220) plane of cubic boron nitride is I3, it is preferable that I1 / I3 is 0.70 or more and 1.50 or less. When I1 / I3 is 0.70 or more, the bond strength between cBN molecules is improved, resulting in excellent fracture resistance. When I1 / I3 is 1.50 or less, sinterability is improved, resulting in improved toughness of the sintered body and excellent fracture resistance. From the same perspective, I1 / I3 is preferably 0.72 or more and 1.45 or less, and more preferably 0.76 or more and 1.32 or less. I1, I2, and I3 are the maximum intensities in the following ranges of 2θ, respectively. I1: 62.60° or more and 63.90° or less I2: 50.80° or more and 52.20° or less I3: 73.40° or more and 74.60° or less

[0027] In the cubic boron nitride sintered body of this embodiment, the binder phase may contain elements other than those constituting the metal phase, V compound, and Al compound. Specific examples include, but are not limited to, Mn, Fe, Si, etc. These elements may be unavoidably contained or may be intentionally added, for example, originating from the cylinders and balls used in the ball mill, the high-melting-point metal capsules used for filling, etc. The content of the other elements is not particularly limited, but may be, for example, 0% by mass or more and 10% by mass or less relative to 100% by mass of the total of all elements contained in the sintered body.

[0028] In the cubic boron nitride sintered body of this embodiment, the content (volume %) of cubic boron nitride and binder phase can be determined by analyzing a microstructure photograph of the cubic boron nitride sintered body taken with a scanning electron microscope (SEM) using commercially available image analysis software. More specifically, the cubic boron nitride sintered body is mirror-polished in a direction perpendicular to its surface. Next, a backscattered electron image of the mirror-polished surface of the cubic boron nitride sintered body revealed by mirror polishing is observed using an SEM. The mirror-polished surface of the cubic boron nitride sintered body is magnified at a magnification selected so that it contains 100 to 400 cubic boron nitride particles. Using an energy dispersive X-ray analyzer (EDS) attached to the SEM, the black areas can be identified as cubic boron nitride, and the gray and white areas as binder phase. Then, a structural photograph of the cross section of the cubic boron nitride is taken using an SEM. Using commercially available image analysis software, the areas occupied by the cubic boron nitride and the binder phase are determined from the obtained structural photograph, and the content (volume %) is calculated from the areas. For example, in the binder phase, the gray area may be an Al compound, and the white area may be a metal phase or a V compound. This image is analyzed, and the percentage of the gray area is calculated as the "content (volume %) of the Al compound." Also, the percentage of the white area is calculated as the "total content (volume %) of the metal phase and the V compound."

[0029] In this embodiment, the content (mass%) of each element in the binder phase can be determined by using an energy dispersive X-ray analyzer (EDS) in the same observation field as the structural photograph of the cubic boron nitride sintered body taken with a scanning electron microscope (SEM) to determine the content (volume%) of cubic boron nitride and the binder phase described above. More specifically, EDS analysis is performed over the entire observation field of the enlarged mirror-polished surface described above, and the content (mass%) of each element is calculated when the total of all elements contained in the cubic boron nitride sintered body is taken as 100 mass%.

[0030] Here, the mirror-polished surface of a cubic boron nitride sintered body is a cross-section of a cubic boron nitride sintered body obtained by mirror-polishing the surface or any cross-section of a cubic boron nitride sintered body. A method for obtaining a mirror-polished surface of a cubic boron nitride sintered body can be, for example, a method of polishing with diamond paste.

[0031] The composition of the binder phase can also be identified using a commercially available X-ray diffractometer. For example, the composition of the binder phase can be identified by X-ray diffraction measurement using a 2θ / θ focused optical system with Cu-Kα radiation using an X-ray diffractometer manufactured by Rigaku Corporation (product name "SmartLab"). Here, the measurement conditions are preferably, for example, those described in the examples below. Furthermore, analysis over a wide 2θ measurement range tends to enable detection of more peaks, making it possible to more reliably identify the materials contained in the sintered body. From this perspective, it is recommended to measure in the range of 2θ = 20 to 140°, for example. In this embodiment, the content ratios of cubic boron nitride and the binder phase, and the composition of the binder phase can also be measured by the methods described in the Examples below. Specifically, the composition of the binder phase can be identified by analyzing the results of measurement using an X-ray analyzer and the results of element mapping using EDS.

[0032] [Method for producing cubic boron nitride sintered body] The cubic boron nitride sintered body of this embodiment can be produced, for example, by the following method. cBN powder, VC powder, VN powder, Ni powder, and Al powder are prepared as raw material powders. By appropriately adjusting the average particle size of the raw material cBN powder, the average particle size of cBN in the resulting cubic boron nitride sintered body can be controlled within the above-mentioned specific range. Furthermore, by appropriately adjusting the ratio of each raw material powder, the content ratio of cBN and binder phase in the resulting cubic boron nitride sintered body can be controlled within the above-mentioned specific range. Next, the prepared raw material powders are mixed in a ball mill cylinder along with cemented carbide balls, a solvent, and paraffin. The raw material powders mixed in the ball mill are filled into a high-melting-point metal capsule made of Ta, and vacuum heat treatment is performed with the capsule open to remove moisture and other adhering components adsorbed on the powder surface. A cemented carbide substrate may be placed inside the capsule during filling. Next, the capsule is sealed, and the raw material powder filled in the capsule is sintered under high pressure, for example, under the conditions of a pressure of 6.0 to 9.0 GPa, a temperature of 1600 to 1900°C, and a sintering time of 15 to 60 minutes. Furthermore, after the high-pressure sintering, the temperature and / or pressure is reduced and maintained under the following conditions: pressure: 2.0 to 5.0 GPa, temperature: 600 to 1000° C., and maintenance time: 60 to 150 minutes.

[0033] In the present embodiment, the method for increasing the content ratio of cubic boron nitride is not particularly limited, but examples thereof include a method of increasing the content ratio of cBN in the composition in the manufacturing process of the above-mentioned cubic boron nitride sintered body.

[0034] In this embodiment, the method for increasing the above-mentioned I1 / (I1+I2) is not particularly limited, but examples thereof include a method of increasing the proportion of the total of V-containing compounds (e.g., VC, VN) relative to the total of Ni and V-containing compounds (e.g., VC, VN) in the blending composition in the manufacturing process of the above-mentioned cubic boron nitride sintered body.

[0035] In the present embodiment, the method for increasing the above-mentioned I1 / I3 is not particularly limited, but examples thereof include a method of reducing the proportion of cBN in the composition in the manufacturing process of the above-mentioned cubic boron nitride sintered body.

[0036] In this embodiment, the method for reducing the full width at half maximum (°) of the peak of the (200) plane of the metal phase in X-ray diffraction is not particularly limited, but examples thereof include a method of increasing the holding pressure in the manufacturing process of the above-mentioned cubic boron nitride sintered body.

[0037] In this embodiment, the method for reducing the maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction is not particularly limited, but examples thereof include a method of increasing the sintering temperature or the holding pressure in the manufacturing process of the above-mentioned cubic boron nitride sintered body.

[0038] In this embodiment, the method for making the metal phase Ni3V and the method for reducing the maximum peak position 2θ (°) of the (220) plane of the V compound in X-ray diffraction are not particularly limited, but examples thereof include a method of using VC as a raw material for the V compound in the manufacturing process of the above-mentioned cubic boron nitride sintered body.

[0039] The cubic boron nitride sintered body of this embodiment may be used as a coated cubic boron nitride sintered body having a coating layer on its surface. Forming a coating layer on the surface of the cubic boron nitride sintered body further improves wear resistance. The coating layer is not particularly limited, but may contain, for example, at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si, and at least one element selected from the group consisting of C, N, O, and B. The coating layer may have a single-layer structure or a laminated structure including two or more layers. When the coating layer has such a structure, the coated cubic boron nitride sintered body of this embodiment tends to have even more improved wear resistance.

[0040] Examples of compounds that form the coating layer include, but are not limited to, TiN, TiC, TiCN, TiAlN, TiSiN, and AlCrN. Among these, TiCN, TiAlN, and AlCrN are preferred. The coating layer may have a structure in which multiple layers with different compositions are stacked.

[0041] The thickness of each layer constituting the coating layer and the thickness of the entire coating layer can be measured from the cross-sectional structure of the coated cubic boron nitride sintered body using an optical microscope, SEM, transmission electron microscope (TEM), etc. The average thickness of each layer in the coated cubic boron nitride sintered body and the average thickness of the entire coating layer can be determined by measuring the thickness of each layer and the thickness of the entire coating layer from three or more cross sections in the vicinity of a position 50 μm from the cutting edge of the surface facing the metal evaporation source toward the center of said surface, and calculating the average value.

[0042] The composition of each layer constituting the coating layer can be measured from the cross-sectional structure of the coated cubic boron nitride sintered body using EDS or wavelength dispersive X-ray analyzer (WDS).

[0043] The method for producing the coating layer is not particularly limited, and examples thereof include chemical vapor deposition and physical vapor deposition methods such as ion plating, arc ion plating, sputtering, and ion mixing. Among these, the arc ion plating method is preferred because it provides superior adhesion between the coating layer and the cubic boron nitride sintered body.

[0044] The cubic boron nitride sintered body or coated cubic boron nitride sintered body of this embodiment can extend tool life, so it is preferably used as a cutting tool or a wear-resistant tool, and is particularly preferably used as a cutting tool. The cubic boron nitride sintered body or coated cubic boron nitride sintered body of this embodiment is more preferably used as a cutting tool for sintered metals or a cutting tool for cast iron. When the cubic boron nitride sintered body or coated cubic boron nitride sintered body of this embodiment is used as a cutting tool or a wear-resistant tool, it can extend tool life more than conventional tools. [Example]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0046] Example 1 [Preparation of raw powder] As the raw material for the cBN sintered body, raw material powders having the average particle diameters shown in Table 1 were prepared. The average particle size of the raw material powder was measured by the Fisher Sub-Sizer (FSSS) method according to the American Society for Testing and Materials (ASTM) standard B330.

[0047] [Table 1]

[0048] [Mixing process] Each raw material powder was weighed out to obtain the blending composition (volume %) shown in Table 2. The weighed raw material powder was placed in a cylinder for a ball mill together with alumina balls, hexane solvent, and paraffin, and mixed for 2 hours.

[0049] [Table 2]

[0050] [Filling process and drying process] The mixed raw material powder was filled into a disk-shaped capsule made of a high-melting-point metal, Ta. In order to remove moisture and organic components adsorbed on the surface of the filled raw material powder, the capsule was subjected to a vacuum heat treatment while left open, and after removing the moisture and other adhering components adsorbed on the surface of the powder, the capsule was sealed.

[0051] [Sintering process] The raw material powder packed in the capsule was then sintered under high pressure. The high-pressure sintering conditions are shown in Table 3.

[0052] [Holding process] Next, the temperature and pressure were lowered to the holding conditions shown in Table 3, and the temperature and pressure were held for the time shown in Table 3 to obtain a sintered body.

[0053] [Table 3]

[0054] [Measurement / Analysis] The cubic boron nitride and binder phase contents (volume %) of cubic boron nitride sintered bodies obtained by high-pressure sintering were determined by analyzing microstructure photographs of the cubic boron nitride sintered bodies taken with a scanning electron microscope (SEM) using commercially available image analysis software. More specifically, the cubic boron nitride sintered bodies were mirror-polished in a direction perpendicular to their surfaces. Next, backscattered electron images of the mirror-polished surfaces of the cubic boron nitride sintered bodies were observed using an SEM. The mirror-polished surfaces of the cubic boron nitride sintered bodies were magnified at a magnification selected to contain 100 to 400 cubic boron nitride particles. Using an energy dispersive X-ray analyzer (EDS) attached to the SEM, the black regions were identified as cubic boron nitride, and the gray and white regions were identified as binder phase. Then, a structural photograph of the mirror-polished surface of the cubic boron nitride was taken using an SEM. Using commercially available image analysis software, the areas occupied by the cubic boron nitride and the binder phase were determined from the obtained structural photograph, and the content (volume %) was calculated from the areas. Here, the mirror-polished surface of the cubic boron nitride sintered body was a cross-section of the cubic boron nitride sintered body obtained by mirror-polishing the surface or any cross-section of the cubic boron nitride sintered body. The mirror-polished surface (hereinafter also referred to as "cross-section") of the cubic boron nitride sintered body was obtained by polishing with diamond paste. In the binder phase, the gray areas were Al compounds, and the white areas were metal phases or V compounds. This was image-analyzed, and the proportion of the gray areas was calculated as the "content (volume %) of Al compounds." In addition, the proportion of the white areas was calculated as the "total content (volume %) of the metal phase and V compounds."

[0055] Furthermore, the composition of the binder phase was identified using an X-ray diffractometer (product name "SmartLab") manufactured by Rigaku Corporation. Specifically, the composition of the binder phase was identified by analyzing the results of X-ray diffraction measurement using a 2θ / θ focused optical system with Cu-Kα radiation under the conditions below and the element mapping results using EDS. <Measurement conditions> Output: 45kV, 200mA Entrance side Soller slit: 5° Divergence vertical slit: 2 / 3° Vertical divergence limiting slit: 5mm Scattering slit: 2 / 3° -Light receiving side solar slit: 5° Receiving slit: 0.3 mm Sampling width: 0.02° Scan speed: 1° / min 2θ measurement range: 30~90°

[0056] Specifically, the obtained cubic boron nitride sintered body was identified to contain the materials listed in Table 4 by the X-ray diffraction measurement using the method described above. Furthermore, because no clear peaks were obtained in X-ray diffraction measurements for compounds containing Al, they were identified by elemental mapping using EDS. As a result, it was found that all of the obtained cubic boron nitride sintered bodies contained Al compounds. In addition, there were materials that could not be identified by X-ray diffraction measurement but were identified only by the results of elemental mapping. Specifically, in invention product 16, no clear peak was detected by X-ray diffraction measurement, but a phase presumed to be AlB2 was confirmed from the results of elemental mapping. In other invention products and comparative products, AlB2 may also exist as a fine phase that cannot be identified at the magnification of this example. The measurement results obtained above are shown in Table 4.

[0057] Simultaneously with the above X-ray diffraction measurement, the X-ray diffraction peak intensity I1 of the (220) plane of the V compound, the X-ray diffraction peak intensity I2 of the (200) plane of the metallic phase, the X-ray diffraction peak intensity I3 of the (220) plane of cubic boron nitride, the maximum peak position 2θ (°) of the (200) plane of the metallic phase in X-ray diffraction, and the maximum peak position 2θ (°) of the (220) plane of the V compound in X-ray diffraction were obtained. In addition, I1 / (I1+I2), I1 / I3, and the full width at half maximum (°) of the peak on the (200) plane of the metal phase in X-ray diffraction were calculated from the X-ray diffraction peak intensity I1 of the (220) plane of the V compound, the X-ray diffraction peak intensity I2 of the (200) plane of the metal phase, the X-ray diffraction peak intensity I3 of the (220) plane of cubic boron nitride, and the maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction. The X-ray diffraction peaks of each crystal plane were identified based on the following ranges: The values obtained above are summarized in Table 5. When the maximum peak position 2θ in X-ray diffraction was in the following ranges, the V compounds were considered to be VC, VCN, and VN, respectively. VC: 62.60° or more and less than 63.10° VCN: 63.10° or more and less than 63.40° VN: 63.40° or more and 63.90° or less In addition, when the maximum peak position 2θ in X-ray diffraction was in the following ranges, the metallic phase was considered to be Ni3V and Ni, respectively. Ni3V: 50.80° or more and less than 51.60° Ni: 51.60° or more and less than 52.2°

[0058] [Table 4]

[0059] [Table 5]

[0060] [Cutting tool manufacturing] The obtained cubic boron nitride sintered body was cut using a wire electric discharge machine to fit the tool shape of the insert shape specified in ISO standard CNGA 120408. The cut cubic boron nitride sintered body was joined to a base metal made of cemented carbide by brazing.

[0061] [Cutting test] Using the obtained cutting tool, a cutting test was carried out under the following conditions. Workpiece: Carburized and quenched sintered metal (Material: JIS standard FD-08N4C-390, hardness: HRA70) Workpiece shape: Gear shape, φ45mm (tooth depth 8mm) x 30mm ·Cutting speed: 200m / min Feed: 0.10mm / rev Cutting depth: 0.30mm Coolant: None (dry cutting) Evaluation items: The tool life was determined when the tool flank wear width reached 0.15 mm or when chipping occurred, and the machining time until the tool life was reached was measured. The damage type at the end of the tool life was also confirmed. The measurement results are shown in Table 6.

[0062] [Table 6]

[0063] From the results shown in Table 6, it can be seen that the cubic boron nitride sintered body contains cubic boron nitride and a binder phase, the content of cubic boron nitride is 80% by volume or more and 94% by volume or less with respect to the total amount of the sintered body, the content of the binder phase is 6% by volume or more and 20% by volume or less with respect to the total amount of the sintered body, the binder phase contains a metal phase, a V compound, and an Al compound, the metal phase contains one or more elements selected from the group consisting of Ni metal, a Ni-containing alloy, and a Ni-containing solid solution, and the Ni-containing alloy and the Ni-containing solid solution contain Ni and one or more elements selected from the group consisting of Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, and Co. The V compound includes one or more compounds selected from the group consisting of VN, VCN, and VC, and the Al compound includes one or more compounds selected from the group consisting of Al2O3, AlN, and AlB2. The maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction is less than 51.60°, and when the X-ray diffraction peak intensity of the (220) plane of the V compound is I1 and the X-ray diffraction peak intensity of the (200) plane of the metal phase is I2, it has been found that the invention products in which I1 / (I1+I2) is 0.40 or more and 0.80 or less have superior wear resistance and fracture resistance and can extend tool life compared to comparative products in which this is not the case. [Industrial Applicability]

[0064] The cubic boron nitride sintered body of the present invention can extend the tool life compared to conventional ones, and in that respect has high industrial applicability.

Claims

1. A cubic boron nitride sintered body comprising cubic boron nitride and a binder phase, the content of the cubic boron nitride is 80% by volume or more and 94% by volume or less with respect to the total amount of the sintered body, the content of the binder phase is 6% by volume or more and 20% by volume or less with respect to the total amount of the sintered body, the binder phase includes a metal phase, a V compound, and an Al compound; the metal phase includes at least one selected from the group consisting of Ni metal, Ni-containing alloys, and Ni-containing solid solutions; The Ni-containing alloy and the Ni-containing solid solution contain Ni and one or more elements selected from the group consisting of Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, and Co, the V compound includes one or more selected from the group consisting of VN, VCN, and VC; The Al compound is Al 2 O 3 , AlN, and AlB 2 and The maximum peak position 2θ (°) of the (200) plane of the metal phase in X-ray diffraction is less than 51.60°, The X-ray diffraction peak intensity of the (220) plane of the V compound is expressed as I 1 , the X-ray diffraction peak intensity of the (200) plane of the metal phase is I 2 When I 1 / (I 1 +I 2 ) is 0.40 or more and 0.80 or less, the content of the Al compound is 5.0% by volume or less relative to the total amount of the sintered body, A cubic boron nitride sintered body, wherein the total content of the metal phase and the V compound is 5.0 volume % or more based on the total amount of the sintered body.

2. 2. The cubic boron nitride sintered body according to claim 1, wherein the full width at half maximum (°) of the peak of the (200) plane of said metallic phase in X-ray diffraction is 0.40° or more and 0.70° or less.

3. The X-ray diffraction peak intensity of the (220) plane of the cubic boron nitride is expressed as I 3 When I 1 / I 3 3. The cubic boron nitride sintered body according to claim 1, wherein the sintered body has a cubic boron nitride sintered body having ...

4. 3. The cubic boron nitride sintered body according to claim 1, wherein the maximum peak position 2θ (°) of the (220) plane of said V compound in X-ray diffraction is less than 63.40°.

5. 3. The cubic boron nitride sintered body according to claim 1, wherein the maximum peak position 2θ (°) of the (200) plane of said metal phase in X-ray diffraction is less than 51.40°.

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