Cubic boron nitride sintered body tool

Abstract

The cubic boron nitride sintered body tool has at least a first sintered body at the tool tip, and the first sintered body contains a plurality of cBN particles. The cBN particles located on the surface of the tool tip include a cubic boron nitride phase composed of the crystal structure of cBN and a hexagonal boron nitride phase composed of the crystal structure of hBN. For the cBN particles on the surface of the tool tip, by the TEM-EELS method, the energy loss associated with the excitation of the K-shell electrons of boron is measured, and thus the ratio I of the intensity of the π* peak derived from the π bond of hBN in the hexagonal boron nitride phase to the intensity of the σ* peak derived from the σ bond of hBN in the hexagonal boron nitride phase and the σ bond of cBN in the cubic boron nitride phase is obtained. π* / I σ* In the case of, the ratio I of the cBN particles in the surface of the tool tip π* / I σ* is 0.1 to 2, and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is 0.001 to 0.1.

Description

Technical Field

[0001] The present disclosure relates to a cubic boron nitride sintered body tool. This application claims priority based on International Patent Application PCT / JP2020 / 037533 filed on October 2, 2020. All the descriptions recorded in this international patent application are incorporated herein by reference. Background Art

[0002] Cubic boron nitride (hereinafter, also referred to as "cBN") has both hardness second only to diamond and excellent thermal conductivity. Further, cBN has the characteristic of low affinity with iron. Based on these physical properties, after obtaining a mixture by mixing cBN with a binder material, a cBN sintered body obtained by sintering the above mixture, and a binderless cBN sintered body obtained by directly converting hexagonal boron nitride or the like into cBN and simultaneously sintering it (hereinafter, these are also collectively referred to as "cBN-based sintered bodies") are used as base materials for cutting tools and wear-resistant tools, etc. As an example of such a cBN-based sintered body, for example, Japanese Patent Application Laid-Open No. 2016-145131 (Patent Document 1) discloses a cubic boron nitride polycrystal characterized by toughness.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-145131 Summary of the Invention

[0006] The cubic boron nitride sintered body tool according to the present disclosure is a cubic boron nitride sintered body tool having at least a first sintered body at a tool tip, the first sintered body including a plurality of cubic boron nitride particles, at least a part of the plurality of cubic boron nitride particles being located on the surface of the tool tip, the cubic boron nitride particles located on the surface of the tool tip including a cubic boron nitride phase composed of a crystal structure of cubic boron nitride and a hexagonal boron nitride phase composed of a crystal structure of hexagonal boron nitride, for the cubic boron nitride particles located on the surface of the tool tip, by using electron energy loss spectroscopy of a transmission electron microscope, the energy loss associated with the excitation of the K-shell electrons of boron is measured, and thereby the ratio I of the intensity of the π* peak derived from the π bond of the hexagonal boron nitride in the hexagonal boron nitride phase to the intensity of the σ* peak of the σ bond of the hexagonal boron nitride in the hexagonal boron nitride phase and the σ bond of the cubic boron nitride in the cubic boron nitride phase is obtained. π* / I σ* In the case of, the ratio I of the cubic boron nitride particles in the surface of the tool tip π* / Iσ* is 0.1 to 2, and the ratio I of the cubic boron nitride particles at a depth of 5 μm from the surface of the blade tip along the normal direction of the surface of the blade tip is π* / I σ* It is 0.001~0.1. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a perspective schematic diagram showing an example of the structure of a cubic boron nitride sintered body tool according to the present embodiment.

[0008] Figure 2 This is an explanatory diagram for explaining a part of a cross section obtained by cutting cubic boron nitride grains located on the surface of a cutting edge of a cubic boron nitride sintered body tool according to the present embodiment along a plane parallel to the normal direction of the surface of the cutting edge. DETAILED DESCRIPTION

[0009] [Problems to be Solved by the Present Disclosure]

[0010] In order to use cBN-based sintered bodies as substrates for cutting tools and wear-resistant tools, a tool shape has been formed from a block of cBN-based sintered bodies by using lasers, and the shape of the blade tip has been finely processed. However, the surface of the cBN-based sintered body becomes very high due to laser processing, so the cBN present on the above surface sometimes undergoes a large amount of phase transformation into hexagonal boron nitride (hereinafter also referred to as "hBN"). In this case, in a cutting tool having a cBN-based sintered body containing a large amount of hBN after phase transformation at the blade tip, since hBN is softer than cBN, the blade tip frequently cracks and defects due to reduced strength, and there is a tendency for the tool life to be shortened. On the other hand, by grinding a block of cBN-based sintered bodies with a grindstone, a tool that does not contain hBN on the surface of the blade tip can also be formed. However, in this case, since the surface of the blade tip is composed of cBN, crater wear is easily generated due to the progress of reactive wear during cutting, and cracks and defects frequently occur, so there is a tendency for the tool life to be shortened. Therefore, in cubic boron nitride sintered body tools using a cBN-based sintered body as a base material, sufficient defect resistance has not yet been achieved, and its development is urgently desired.

[0011] In view of the above-mentioned actual situation, an object of the present disclosure is to provide a cubic boron nitride sintered body tool having improved defect resistance.

[0012] [Effects of the present disclosure]

[0013] According to the present disclosure, a cubic boron nitride sintered body tool having improved defect resistance can be provided.

[0014] [Description of Embodiments of the Present Disclosure]

[0015] The inventors of the present invention conducted intensive research repeatedly to solve the above problems, and thus completed the present disclosure. Specifically, in the process of forming a tool shape from a massive cBN-based sintered body using a laser and performing finish machining on the cutting edge shape, an appropriate amount of hBN that does not adversely affect the strength of the cutting edge is generated on the surface of the cutting edge. In this case, the inventors of the present invention found that the hBN on the surface of the cutting edge acts like a lubricant based on its softness, thereby improving the slidability of the tool and thus enhancing the chipping resistance, and thus completed the present disclosure.

[0016] First, embodiments of the present disclosure will be described by way of example.

[0017] [1] The cubic boron nitride sintered body tool according to one aspect of the present disclosure is a cubic boron nitride sintered body tool having at least a first sintered body at the cutting edge. The first sintered body includes a plurality of cubic boron nitride particles, and at least a part of the plurality of cubic boron nitride particles are located on the surface of the cutting edge. The cubic boron nitride particles located on the surface of the cutting edge include a cubic boron nitride phase composed of the crystal structure of cubic boron nitride and a hexagonal boron nitride phase composed of the crystal structure of hexagonal boron nitride. For the cubic boron nitride particles located on the surface of the cutting edge, by using electron energy loss spectroscopy of a transmission electron microscope, the energy loss associated with the excitation of the K-shell electrons of boron is measured, and thus the intensity ratio I of the π* peak derived from the π bond of the hexagonal boron nitride in the hexagonal boron nitride phase to the intensity of the σ* peak of the σ bond of the hexagonal boron nitride in the hexagonal boron nitride phase and the σ bond of the cubic boron nitride in the cubic boron nitride phase is obtained. π* / I σ* In the case of, the ratio I of the cubic boron nitride particles on the surface of the cutting edge π* / I σ* is 0.1 to 2, and the ratio I of the cubic boron nitride particles at a depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge π* / I σ* is 0.001 to 0.1. The cubic boron nitride sintered body tool having such characteristics can enhance the chipping resistance.

[0018] [2] Preferably, the ratio I of the cubic boron nitride particles at a depth position of 1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge π* / I σ* is 0.001 to 0.1. Thereby, the chipping resistance of the cubic boron nitride sintered body tool can be further enhanced.

[0019] [3] Preferably, the ratio I of the cubic boron nitride particles at a depth position of 0.2 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge is π* / I σ* from 0.001 to 0.1. Thereby, the chipping resistance of the cubic boron nitride sintered body tool can be further improved.

[0020] [4] Preferably, the cubic boron nitride sintered body tool includes a rake face, a flank face, and a ridge line where the rake face intersects with the flank face. The rake face is connected to the flank face via the ridge line. The cutting edge of the cubic boron nitride sintered body tool is composed of a part of the rake face, a part of the flank face, and the ridge line. The surface of the cutting edge is the surface of at least a part of the cutting edge. Thereby, the chipping resistance of the cutting edge of the cubic boron nitride sintered body tool can be improved.

[0021] [Details of the embodiments of the present disclosure]

[0022] Hereinafter, embodiments of the present disclosure (hereinafter, also referred to as "the present embodiment") will be described in detail. In the following description, an expression in the form of "A to B" means the upper and lower limits of a range (that is, A or more and B or less). When there is no unit notation in A and only a unit is recorded in B, the unit of A is the same as the unit of B.

[0023] [Cubic boron nitride sintered body tool]

[0024] The cubic boron nitride sintered body tool according to the present embodiment is a cubic boron nitride sintered body tool having at least a first sintered body at the cutting edge. Based on the characteristics of a part of the cubic boron nitride particles in the first sintered body on the surface of the cutting edge, the cubic boron nitride sintered body tool according to the present embodiment can at least improve the chipping resistance compared with such a conventionally known cubic boron nitride sintered body tool. Therefore, the cubic boron nitride sintered body tool according to the present embodiment is suitable for uses such as drills, end mills, indexable insert cutting blades for drills, indexable insert cutting blades for end mills, indexable insert cutting blades for milling, indexable insert cutting blades for turning, hacksaws, gear cutting tools, reamers, taps, etc. as cutting tools. Further, the cubic boron nitride sintered body tool is also suitable for uses as wear-resistant tools such as dies, scribers, scribe wheels, trimmers, etc., and grinding tools such as grinding wheels.

[0025] In the present specification, "blade tip" refers to the portion of the cutting edge of a cubic boron nitride sintered body tool that is directly related to the processing of the cut piece. Furthermore, the surface of the above-mentioned "blade tip" is defined as the "surface of the blade tip". The position of the "surface of the blade tip" is a depth position of 0 μm along the normal direction of the surface of the blade tip from the surface of the blade tip. In the present specification, "front cutting edge" refers to the surface from which chips removed from the above-mentioned cut piece are discharged during cutting, and "rear cutting edge" refers to the surface opposite to the cut surface of the above-mentioned cut piece during cutting. The above-mentioned cubic boron nitride sintered body tool preferably includes a front cutting edge, a rear cutting edge, and a ridgeline where the above-mentioned front cutting edge and the above-mentioned rear cutting edge intersect. In this case, the above-mentioned front cutting edge is connected to the above-mentioned rear cutting edge via the above-mentioned ridgeline. Further, preferably, the blade tip of the cubic boron nitride sintered body tool is composed of a part of the rake face, a part of the flank face, and the ridgeline, and the surface of the blade tip is the surface of at least a part of the blade tip (the surface of a part of the rake face, the surface of a part of the flank face, and at least any one of the ridgeline). The blade tip of the cubic boron nitride sintered body tool involved in this embodiment is sometimes composed of the ridgeline and a region separated from the ridgeline by 0.5 mm toward the rake face side and the flank face side, respectively.

[0026] Here, the shape of the tool tip includes a sharp edge (a ridge where the front cutting surface and the back cutting surface intersect), honing (rounding the sharp edge), a negative land (chamfering), a shape formed by combining honing and a negative land, and the like. Therefore, when the tool tip is formed into a sharp edge shape, it has a ridgeline at the boundary where the front cutting surface and the back cutting surface intersect, but when it has a honed shape or a negative land shape, it does not have the ridgeline. However, in this specification, even in these cases, it is considered that there are a virtual front cutting surface formed by extending the front cutting surface of the cubic boron nitride sintered body tool, a virtual back cutting surface formed by extending the back cutting surface, and a virtual ridgeline where the virtual front cutting surface and the back cutting surface intersect in the honed shape portion and the negative land shape portion, and the following description is given.

[0027] The cubic boron nitride sintered body tool involved in the present embodiment has a first sintered body at least at the tip of the tool as described above. The above-mentioned cubic boron nitride sintered body tool preferably has a structure in which the first sintered body and the substrate are combined and integrated by an adhesive layer. The substrate can use any of the substrates known as the substrate used in such a tool. As the raw material of such a substrate, for example, it is preferably any of cemented carbide (for example, WC-based cemented carbide, also including cemented carbide containing Co or carbonitrides added with Ti, Ta, Nb, etc. on the basis of WC), metal ceramics (metal ceramics with TiC, TiN, TiCN, etc. as the main components), high-speed steel and ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.).

[0028] As a raw material for the substrate, cemented carbide (especially WC-based cemented carbide) or cermet (especially TiCN-based cermet) is preferably selected. The above-mentioned raw materials have excellent balance between hardness and strength at high temperatures, and thus have preferable characteristics for applications using cubic boron nitride sintered body tools. When using WC-based cemented carbide as the substrate, free carbon and abnormal layers such as η-phase or ε-phase can be included in its structure. Further, the substrate can also be a substrate whose surface is modified. For example, in the case of cemented carbide, a decarburized β-layer can be formed on its surface, or a surface hardened layer can be formed in the case of cermet. The substrate shows the desired effect even if its surface is modified. When the cubic boron nitride sintered body tool is a drill bit or an end mill, etc., the substrate is sometimes called a shank, etc. Further, when the cubic boron nitride sintered body tool is an indexable insert type cutting blade, etc., the substrate includes a substrate with a chip breaker and also includes a substrate without a chip breaker. In addition, the cubic boron nitride sintered body tool according to the present embodiment can be in a form that does not include a substrate. For example, it can have a form consisting only of a first sintered body. The above-mentioned cubic boron nitride sintered body tool can also include a coating film that covers at least a part of the cutting edge including the rake face, the flank face, and the ridge line where the above-mentioned rake face and the above-mentioned flank face intersect.

[0029] Here, an example of the structure of the above-mentioned cubic boron nitride sintered body tool will be described with reference to the drawings. Figure 1 is a perspective schematic view showing an example of the structure of the cubic boron nitride sintered body tool according to the present embodiment. As Figure 1 shown, the cubic boron nitride sintered body tool 100 according to the present embodiment is, for example, an end mill, and is composed of a cutting edge portion 90, a joint portion 8, and a shank portion 3. The cutting edge portion 90 has a first rake face 10, a first flank face 31, a second rake face 15, a second flank face 33, an outer peripheral cutting edge 20, a bottom cutting edge 21, and a front end. The shank portion 3 has a rear end. The cutting edge portion 90 is fixed to the shank portion 3 through the joint portion 8. The joint portion 8 is, for example, a brazing material. The first rake face 10 and the second rake face 15 correspond to the rake faces involved in the present disclosure, and the first flank face 31 and the second flank face 33 correspond to the flank faces involved in the present disclosure.

[0030] The first flank face 31 is connected to the first rake face 10. The ridge line of the first rake face 10 and the first flank face 31 constitutes the outer peripheral cutting edge 20. The second flank face 33 is connected to the second rake face 15. The ridge line of the second rake face 15 and the second flank face 33 constitutes the bottom cutting edge 21. In addition, the first rake face 10 is connected to the second rake face 15. The first rake face 10 is located behind the second rake face 15 in the axial direction. The first flank face 31 is connected to the second flank face 33. The first flank face 31 is located behind the second flank face 33 in the axial direction. In addition, Figure 1The end mill is merely an example of the constitution of the cubic boron nitride sintered body tool involved in this embodiment. This embodiment is not limited to this end mill. As described above, as a cutting tool, it includes drills, indexable insert cutting blades for drills, indexable insert cutting blades for end mills, indexable insert cutting blades for milling, indexable insert cutting blades for turning, hacksaws, gear cutting tools, reamers, taps, etc. It also includes wear-resistant tools such as dies, scribers, scribe wheels, and trimmers, and also includes grinding tools such as grinding wheels.

[0031] <The first sintered body>

[0032] The first sintered body contains a plurality of cubic boron nitride particles. Specifically, preferably, the first sintered body contains a plurality of cubic boron nitride particles (hereinafter, also referred to as "cBN particles") and has the same composition as the above-mentioned cBN-based sintered body (the above-mentioned cBN sintered body or the above-mentioned binderless cBN sintered body).

[0033] For example, the first sintered body may be a cBN sintered body (cBN-based sintered body) produced by sintering a mixture obtained by mixing cBN particles and a bonding material. In this case, the content of cBN particles in the first sintered body is preferably 40% by volume or more and 95% by volume or less with respect to the total amount (100% by volume) of the first sintered body, and the total content of the bonding material and inevitable impurities is preferably 5% by volume or more and 60% by volume or less.

[0034] When the content of cBN particles is 40% by volume or more with respect to the total amount of the first sintered body, based on the physical properties of the cBN particles, the strength of the first sintered body is maintained at a relatively high level, so the defect resistance is improved. On the other hand, when the content of cBN particles is 95% by volume or less with respect to the total amount of the first sintered body, the amount of the bonding material required for bonding between cBN particles can be ensured, so the increase in defects can be suppressed. Thus, the generation of defects starting from defects can be prevented, so the defect resistance is improved. When the first sintered body is a cBN-based sintered body produced by sintering a mixture obtained by mixing cBN particles and a bonding material, the content of cBN particles is preferably 50% by volume or more and 95% by volume or less with respect to the total amount of the first sintered body.

[0035] The above-mentioned bonding material preferably contains at least one element selected from the group consisting of Group 4 elements (Ti, Zr, Hf, etc.), Group 5 elements (V, Nb, Ta, etc.), Group 6 elements (Cr, Mo, W, etc.), Al, Co, Ni, and Si in the periodic table, and at least one compound selected from the group consisting of nitrides, carbonitrides, borides, oxides, and their solid solutions containing the above elements. Specifically, the bonding material more preferably has at least one composition selected from the group consisting of Ti, Co, Cr, Ni, Al, AlN, Al2O3, AlB2, TiN, TiC, TiCN, TiB2, Cr2N, WC, ZrO2, ZrO, ZrN, ZrB2, and Si3N4. In this case, the strength of the first sintered body can be improved.

[0036] Furthermore, the first sintered body may be a binderless cBN sintered body (cBN-based sintered body) produced by directly converting low-pressure phase boron nitride under high temperature and high pressure while sintering without mixing the above-mentioned bonding material. In this case, the content of cBN particles in the first sintered body is substantially 100% by volume except for inevitable impurities. Here, low-pressure phase boron nitride (hereinafter also referred to as "low-pressure phase BN") refers to boron nitride that is thermodynamically stable in the low-pressure region. Specifically, it includes hexagonal boron nitride (hBN) similar to the hexagonal graphite-type structure, rhombohedral boron nitride (rBN), turbostratic boron nitride (tBN), and amorphous boron nitride (aBN). Such low-pressure phase BN can be prepared by reducing a compound containing boron and oxygen with a compound containing carbon and nitrogen. The first sintered body can be produced, for example, by directly converting the above-mentioned low-pressure phase BN under high temperature and high pressure of 1500 to 2100 °C and 6 to 10 GPa while sintering. In addition, the lower the content of inevitable impurities, the more preferable it is. Ideally, it is 0% by volume, but inevitable impurities sometimes contain a few percent relative to the total amount of the first sintered body. The types and contents of elements contained as inevitable impurities can be determined, for example, by using secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry).

[0037] The direct conversion to cBN is preferably carried out using heated low-pressure phase BN under conditions above the boiling point of the compound containing boron and oxygen and in a non-oxidizing atmosphere. In this case, since the compound containing boron and oxygen and the adsorbed gas volatilize by heating, the compound containing boron and oxygen and the adsorbed gas do not remain in the low-pressure phase BN. As a result, the bonding strength between cBN particles becomes larger, and a cBN-based sintered body (first sintered body) with excellent strength, hardness, heat resistance, and heat dissipation can be obtained.

[0038] In the case where the first sintered body is a cBN sintered body (cBN-based sintered body) produced by sintering a mixture obtained by mixing cBN particles and a binder, the contents (volume %) of the cBN particles and the binder in the first sintered body can be determined by analyzing a micrograph of the first sintered body taken by a scanning electron microscope (SEM, trade name: "JSM-7800F", manufactured by JEOL Ltd.) using commercially available image analysis software (trade name: "WinROOF", manufactured by Mitani Corporation). More specifically, first, a sample of the first sintered body is collected from the surface of the tip of a cubic boron nitride sintered body tool manufactured according to the manufacturing method described below, and the surface of the sample of the first sintered body is mirror-polished. Then, the backscattered electron image of the mirror-polished surface of the sample is observed using the above SEM at a magnification of 5000 to 20000 times. Further, by using an energy dispersive X-ray analyzer (EDS, trade name: "Octane Elect", manufactured by AMETEK Inc.) attached to the SEM, the black regions in the backscattered electron image are identified as cubic boron nitride, and the gray and white regions are identified as the binder. On this basis, a micrograph of the mirror-polished surface is taken using the SEM, and by using the above image analysis software for this micrograph, the occupied areas of cubic boron nitride (black regions) and the binder (gray and white regions) can be determined from the micrograph, and the respective contents (volume %) of cubic boron nitride and the binder can be determined from the occupied areas.

[0039] Furthermore, the D 50 (average particle size) of the cBN particles is not particularly limited, and can be set to, for example, 0.5 to 10.0 μm. Generally, when D 50 is small, the hardness of the cBN sintered body tends to be high, and when the deviation in particle size is small, the properties of the cBN sintered body tend to be homogeneous. The D 50 of the cBN particles is preferably 1 to 5.0 μm, for example.

[0040] The D 50 of the cBN particles is determined as follows. First, a specimen including a cross-section of the cBN sintered body is prepared according to the above method for measuring the content of the cBN particles, and a backscattered electron image is obtained. Then, the equivalent circle diameter of each black region in the backscattered electron image is calculated using the above image analysis software. It is preferable to calculate the equivalent circle diameters of 100 or more cBN particles by observing five or more fields of view.

[0041] Next, the equivalent circle diameters are arranged in ascending order from the minimum value to the maximum value to obtain a cumulative distribution. The particle size at which the cumulative area is 50% in the cumulative distribution is D 50In addition, the equivalent circle diameter refers to the diameter of a circle having the same area as the area of the measured cBN particle.

[0042] (The presence ratio of hBN in the first sintered body (ratio I π* / I σ* ))

[0043] As described above, the first sintered body contains a plurality of cBN particles. At least a part of the cBN particles among the plurality of cBN particles are located on the surface of the cutting edge. The cBN particles located on the surface of the cutting edge include a cubic boron nitride phase (hereinafter, also referred to as "cBN phase") composed of the crystal structure of cBN and a hexagonal boron nitride phase (hereinafter, also referred to as "hBN phase") composed of the crystal structure of hBN. For the cBN particles located on the surface of the cutting edge, by using electron energy loss spectroscopy of a transmission electron microscope (hereinafter, also referred to as "TEM-EELS method"), the energy loss associated with the excitation of the K-shell electrons of boron is measured, and thus the π of the π bond of hBN derived from hBN in the hBN phase is obtained. * The intensity ratio I of the peak to the intensity of the σ bond of hBN in the hBN phase and the σ bond of cBN in the cBN phase * / I π* / I σ* In the case of, the ratio I of the cBN particles in the surface of the cutting edge π* / I σ* is 0.1 to 2, and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge π* / I σ* is 0.001 to 0.1. Thereby, the chipping resistance of the cubic boron nitride sintered body tool can be improved.

[0044] As described above, in the cubic boron nitride sintered body tool according to the present embodiment, the ratio I of the cBN particles in the surface of the cutting edge π* / I σ* is 0.1 to 2, and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge π* / I σ* is 0.001 to 0.1. Thereby, the above cubic boron nitride sintered body tool can have hBN at a moderate ratio that does not adversely affect its strength in the cutting edge. In this case, the hBN on the surface of the cutting edge acts as a lubricant based on its softness, thereby improving the sliding property of the tool and thus improving the chipping resistance. In particular, the ratio I of the cBN particles at a depth position of 1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge π* / Iσ* Preferably 0.001 to 0.1, the ratio I of cBN particles at a depth position of 0.2 μm from the surface of the cutting edge along the normal direction of the surface of the cutting edge π* / I σ* Preferably 0.001 to 0.1. In this case, the chipping resistance of the cubic boron nitride sintered body tool can be further improved.

[0045] Here, use Figure 2 to illustrate the cBN particles located on the surface of the cutting edge. Figure 2 is an explanatory diagram for explaining a part of a cross-section obtained by cutting the cubic boron nitride particles located on the surface of the cutting edge of the cubic boron nitride sintered body tool according to the present embodiment with a plane parallel to the normal direction of the surface of the cutting edge. In Figure 2 one (a single grain) of the cBN particles A located on a part of the surface of the cutting edge among the plurality of cBN particles constituting the first sintered body in the cutting edge is focused on and shown. Figure 2 The cBN particle A of

[0046] The cBN particle A integrally and inseparably has a first region 11, a second region 12, and a tool tip inner region 13. In this specification, "integrally and inseparably" means that the crystal lattice constituting the cBN particle A is continuous at the interfaces between the first region 11 and the second region 12 and between the second region 12 and the tool tip inner region 13, and does not crack at the interfaces between the first region 11 and the second region 12 and between the second region 12 and the tool tip inner region 13. That is, in this specification, both the interface between the first region 11 and the second region 12 and the interface between the second region 12 and the tool tip inner region 13 refer to the interfaces provided for convenience on the cross-section of the cBN particle A for measuring the ratio I π* / I σ* indicating the existence ratio of hBN at the depth positions 11a which is 0.2 μm from the surface of the tool tip of the cBN particle A along the normal direction of the surface of the tool tip, 12a which is 1 μm from the surface of the tool tip of the cBN particle A along the normal direction of the surface of the tool tip, and 13a which is 5 μm from the surface of the tool tip of the cBN particle A along the normal direction of the surface of the tool tip, respectively. Hereinafter, the method for measuring the ratio I π* / I σ* indicating the existence ratio of hBN using the TEM-EELS method will be described.

[0047] (Measurement method of the existence ratio of hBN (ratio I π* / I σ* ) using the TEM-EELS method)

[0048] First, a cubic boron nitride sintered body tool is manufactured according to the manufacturing method described later. Then, a sample of the first sintered body is collected from the surface of the tool tip of the cubic boron nitride sintered body tool, and the sample is cut with an argon ion milling machine in a plane parallel to the normal direction of the surface of the tool tip to produce a slice with a thickness of 3 to 100 nm. Further, the slice is observed with a transmission electron microscope (TEM, trade name: "JEM-2100F / Cs", manufactured by JEOL Ltd.) at a magnification of 100,000 to 1,000,000 to obtain a cross-sectional transmission image of the cBN particle A located on the surface of the tool tip in the sample.

[0049] Next, in the above-mentioned cross-sectional transmission image, the surface position of the cutting edge in the cBN particle A, the depth position 11a of the cBN particle A at a depth of 0.2 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, the depth position 12a of the cBN particle A at a depth of 1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, and the depth position 13a of the cBN particle A at a depth of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge are respectively determined. Further, by applying electron energy loss spectroscopy (EELS method), at the surface position of the cutting edge in the cBN particle A, the depth position 11a at a depth of 0.2 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, the depth position 12a at a depth of 1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, and the depth position 13a at a depth of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, for example, a 10-nm scan is performed on observation points of 1 nm in a direction parallel to the surface of the cutting edge, thereby observing the energy loss (K edge) associated with the excitation of the K-shell electrons of boron. Based on the above, it is possible to respectively depict the energy loss (K edge) curves near 200 eV associated with the excitation of the K-shell electrons of boron at the surface position of the cutting edge in the cBN particle A, the depth position 11a at a depth of 0.1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, the depth position 12a at a depth of 0.2 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, and the depth position 13a at a depth of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge.

[0050] Finally, based on the energy loss curve depicted by the observation at the surface position of the cutting edge of the cBN particle A, the π * peak intensity (I π* ) derived from the π bond of hBN in the hBN phase and the σ * peak intensity (I σ* ) derived from the σ bond of hBN in the hBN phase and the σ bond of cBN in the cBN phase are obtained. Then, by dividing I π* by I σ* , the ratio I π* / I σ* can be obtained. Based on the energy loss curve depicted by the observation at the depth position 11a at a depth of 0.2 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, the energy loss curve depicted by the observation at the depth position 12a at a depth of 1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, and the energy loss curve depicted by the observation at the depth position 13a at a depth of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, the ratio I π* / Iσ* .

[0051] In this case, in the cubic boron nitride sintered body tool according to this embodiment, the ratio I of the cBN particles A in the surface of the tool tip π* / I σ* is 0.1 to 2, and the ratio I of the cBN particles A at a depth position of 5 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is 0.001 to 0.1. Further, the ratio I of the cBN particles A at a depth position of 1 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is preferably 0.001 to 0.1, and the ratio I of the cBN particles A at a depth position of 0.2 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is preferably 0.001 to 0.1.

[0052] The cubic boron nitride sintered body tool according to this embodiment is more preferably such that the ratio I of the cBN particles A in the surface of the tool tip π* / I σ* is 0.6 to 1, and more preferably the ratio I of the cBN particles A at a depth position of 5 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is 0.005 to 0.01. Further, the ratio I of the cBN particles A at a depth position of 1 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is preferably 0.001 to 0.2, and the ratio I of the cBN particles A at a depth position of 0.2 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is preferably 0.001 to 0.9. The ratio I of the cBN particles A at a depth position of 1 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is further preferably 0.005 to 0.01, and the ratio I of the cBN particles A at a depth position of 0.2 μm along the normal direction of the surface of the tool tip from the surface of the tool tip π* / I σ* is further preferably 0.005 to 0.01.

[0053] Here, in the above measurement method, it is preferable to prepare one cross-sectional transmission photograph (a total of two) of the cBN particles on the rake face side and the flank face side of the cutting edge, respectively, which are located on the surface of the cutting edge. In the two cross-sectional transmission photographs of the cBN particles related to the present embodiment, the ratio I of the cBN particles in the surface of the cutting edge is obtained. π* / I σ* and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge. π* / I σ* In the case of, by satisfying the above ratio in at least any one of the cross-sectional transmission photographs, the defect resistance of the cubic boron nitride sintered body tool to be measured can be improved. The above ratio I π* / I σ* refers to the ratio of the peak value of the π * peak to the peak value of the σ * peak. In addition, the π * peak and the σ * peak can be obtained as follows: For measurement sites such as the surface position of the cutting edge and the depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, the results measured by scanning 1 nm observation points, for example, 10 nm in the direction parallel to the surface of the cutting edge are accumulated, and it is depicted as an energy loss curve. Here, the 10 nm as the length of the above scanning can be arbitrarily changed between 1 and 100 nm.

[0054] In addition, in the cubic boron nitride sintered body tool related to the present embodiment, there may be other cBN particles different from the cBN particles located on the surface of the cutting edge at a depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge, or at a depth position of 1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge. However, even in this case, as long as it is the case of measuring the ratio I π* / I σ* indicating the existence ratio of hBN, the above other cBN particles are regarded as cBN particles located on the surface of the cutting edge, and the above TEM-EELS method is applied, and the ratio I π* / I σ* at those depth positions is obtained.

[0055] <Function and Effect>

[0056] In the cubic boron nitride sintered body tool related to the present embodiment, as described above, the ratio I π* / I σ* of the cBN particles in the surface of the cutting edge is 0.1 to 2, and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge.π* / I σ* is 0.001 to 0.1. Thus, among the cBN particles on the surface of the tool tip, hBN can be present at a moderate ratio that does not adversely affect the strength of the tool tip. In this case, the hBN on the surface of the tool tip acts like a lubricant due to its softness, thereby improving the slidability of the tool and enhancing the chipping resistance. In particular, in the cubic boron nitride sintered body tool according to the present embodiment, the ratio I of the cBN particles at a depth position of 1 μm from the surface of the tool tip along the normal direction of the surface of the tool tip π* / I σ* is preferably 0.001 to 0.1, and the ratio I of the cBN particles at a depth position of 0.2 μm from the surface of the tool tip along the normal direction of the surface of the tool tip π* / I σ* is preferably 0.001 to 0.1. In this case, the chipping resistance can be further improved.

[0057] [Manufacturing method of cubic boron nitride sintered body tool]

[0058] The cubic boron nitride sintered body tool according to the present embodiment can be manufactured by performing a method for manufacturing a conventional cubic boron nitride sintered body tool, except for the step of finishing the tool tip described later. For example, it is preferable to manufacture the cubic boron nitride sintered body tool according to the present embodiment by using the following manufacturing method. Hereinafter, a method for manufacturing the cubic boron nitride sintered body tool according to the present embodiment using a cBN sintered body (cBN-based sintered body) obtained by sintering a mixture of cBN particles and a binder material as a material will be described as an example, but the above manufacturing method is not limited thereto. For example, the cubic boron nitride sintered body tool according to the present embodiment may be manufactured using a binderless cBN sintered body (cBN-based sintered body) as a material. In this case, based on the conventional manufacturing method using a binderless cBN sintered body as a material, the same steps as the step of finishing the tool tip described later are also performed on the tool tip including the binderless cBN sintered body, whereby the cubic boron nitride sintered body tool according to the present embodiment can be manufactured.

[0059] The manufacturing method of the cubic boron nitride sintered body tool according to this embodiment preferably includes at least: a process of preparing a cBN-based sintered body (the first process); a process of cutting the cBN-based sintered body into a predetermined tool shape (the second process); a process of joining the sintered body cut into the tool shape to a substrate by brazing (the third process); and a process of finishing the tip of the sintered body joined to the substrate by performing laser processing on the tip (the fourth process). In addition, in the case where the cubic boron nitride sintered body tool is in a form composed only of a cBN-based sintered body, since no substrate is used, there is also a case where the fourth process of finishing the tip of the sintered body cut into a predetermined tool shape in the second process is performed without performing the above third process.

[0060] <The first process>

[0061] The first process is a process of preparing a cBN-based sintered body. The first process can be carried out by a conventionally known method. For example, first, a powder of cubic boron nitride particles having an average particle size of 1 to 5 μm in an amount of 15 to 90% by volume and a powder of an average particle size of 0.05 to 8 μm in an amount of 10 to 85% by volume, which contains at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Co, Ni, and Si or a compound of the above elements and at least one element selected from the group consisting of C, N, O, and B (wherein the total of them is set to 100% by volume) is mixed to obtain a raw material powder. Then, the above raw material powder is mixed by wet ball milling using a cemented carbide ball or the like for 5 to 24 hours to prepare a mixture. Further, a compact is obtained by shaping the above mixture into a predetermined shape. Finally, the above compact is placed in a conventionally known ultra-high pressure generating device and held for a predetermined time at a sintering temperature of 1300 to 1500 °C under a pressure of 4 to 7 GPa. Thus, a cBN-based sintered body can be prepared.

[0062] <The second process>

[0063] The second process is a process of cutting the cBN-based sintered body into a predetermined tool shape. The second process can also be carried out by a conventionally known method. For example, by at least any one of conventionally known electrical discharge machining using an electrical discharge machine, grinding using a grinding machine, and laser machining using a laser machine, the cBN-based sintered body can be cut into a predetermined tool shape. In other words, the second process can be said to be a process of cutting the cBN-based sintered body into a predetermined tool shape by performing rough machining and precision machining on the cBN-based sintered body using a predetermined means.

[0064] <The third process>

[0065] The third process is a process of joining the sintered body cut into the above-mentioned tool shape to the base body by brazing. Regarding the third process, it can also be carried out by a conventionally well-known method. Specifically, it can be joined by brazing the base body to the end face on the side opposite to the side where the cutting edge is formed of the sintered body cut into the above-mentioned tool shape. As brazing, for example, brazing using a silver solder is preferably used. Thereby, in the next process (the fourth process), it becomes convenient to irradiate the laser toward the cutting edge of the sintered body, and it is easy to subject the cutting edge of the above-mentioned sintered body to finishing.

[0066] <Fourth Process>

[0067] The fourth process is a process of finishing the cutting edge by performing laser processing on the cutting edge of the sintered body joined to the base body. Through the fourth process, an hBN phase having the above-mentioned characteristics can be formed on the cBN particles located on the surface of the cutting edge. In the fourth process, as long as an hBN phase having the above-mentioned characteristics can be formed on the cBN particles located on the surface of the cutting edge, the conditions of the laser processing and the like should not be particularly limited. For example, by performing laser processing under the conditions described below, an hBN phase having the above-mentioned characteristics can be formed with a good yield rate in the cBN particles located on the surface of the cutting edge.

[0068] For example, in the fourth process, it is preferable to use a picosecond laser. Under the laser irradiation conditions where the laser wavelength is 532 nm or more and 1064 nm or less, the laser spot diameter is 5 μm or more and 70 μm or less in terms of the full width at half maximum, the laser focus depth is 0.5 mm or more and 20 mm or less, the laser output at the processing point is 1 W or more and 20 W or less, and the laser scanning speed is 5 mm / second or more and 100 mm / second or less, the cutting edge of the sintered body is finished. In this case, in order to avoid excessive heating on the surface of the cutting edge, it is preferable to blow compressed air to the processing part for cooling. For example, when using a vortex tube (manufactured by Koji Corporation) to blow compressed air to the processing part, cold air with a temperature lower than room temperature can be obtained through the vortex effect, and cooling can be carried out more effectively. Thereby, the phase change from cBN to hBN in the region near the surface of the cutting edge (for example, within 1 μm from the surface, preferably within 0.2 μm) can be controlled to an appropriate amount that does not adversely affect the strength of the cutting edge. The cooling conditions used in combination with the above-mentioned laser processing can be set by appropriately adjusting the operating conditions of the vortex tube.

[0069] Furthermore, as the above-mentioned laser irradiation conditions, it is preferable to specify a laser pulse width of 1 femtosecond or more and 1 microsecond or less and a laser repetition frequency of 10 Hz or more and 1 MHz or less as needed.

[0070] Under the above laser irradiation conditions, when the laser spot diameter is less than 5 μm in terms of the full width at half maximum, since the laser power is low, there is a tendency that the finish machining of the tool tip becomes difficult. When the laser spot diameter is more than 70 μm in terms of the full width at half maximum, since the laser power is high, there is a tendency that the cBN-based sintered body breaks. When the laser focus depth is less than 0.5 mm, there is a tendency that the finish machining of the tool tip becomes difficult due to defocusing. When the laser output is less than 1 W at the machining point, since the laser power is low, there is a tendency that the finish machining of the tool tip becomes difficult. When the laser output is more than 20 W at the machining point, since the laser power is high, there is a tendency that the cBN-based sintered body breaks.

[0071] When the laser scanning speed is less than 5 mm / second, there is a tendency that the laser penetrates too deeply into the tool tip and the cBN-based sintered body breaks. When it exceeds 100 mm / second, there is a tendency that almost no laser-based machining is performed. When the laser pulse width is less than 1 fs, there is a tendency that the laser-based machining takes an excessive amount of time, and there is a tendency that the laser device becomes extremely expensive. When the laser pulse width exceeds 1 μs, thermal processing becomes dominant, and there is a tendency that the phase change from cBN to hBN becomes excessive. When the laser repetition frequency is less than 10 Hz, thermal processing becomes dominant, and there is a tendency that the phase change from cBN to hBN becomes excessive. When the laser repetition frequency exceeds 1 MHz, the next laser pulse arrives before the energy of the irradiated laser pulse is consumed at the machining point. Therefore, there is a tendency that the thermal load at the machining point becomes large and the phase change from cBN to hBN becomes excessive.

[0072] <Other processes>

[0073] The cubic boron nitride sintered body tool according to the present embodiment may include a coating film covering at least a part of the rake face, the flank face, and the ridge line where the rake face and the flank face intersect. In this case, as a manufacturing method of the cubic boron nitride sintered body tool according to the present embodiment, it preferably includes a process of coating the cubic boron nitride sintered body tool with a coating film. This process can use a conventionally well-known method. For example, physical vapor deposition methods such as ion plating method, arc ion plating method, sputtering method, and ion mixing method can be cited. Further, the cubic boron nitride sintered body tool can also be coated with a coating film by chemical vapor deposition method.

[0074] <Function and effect>

[0075] Based on the above, it is possible to manufacture the cubic boron nitride sintered body tool according to this embodiment. In the above cubic boron nitride sintered body tool, the phase transformation from cBN to hBN in the surface of the cutting edge is suppressed during the finish machining of the cutting edge. Therefore, in the above cubic boron nitride sintered body tool, for the cBN particles located on the surface of the cutting edge, by using the TEM-EELS method, the energy loss associated with the excitation of the K-shell electrons of boron is measured, and thus the π of the π bond of hBN derived from the hBN phase in the hBN phase is obtained. * The intensity ratio I of the peak of the σ bond of hBN and cBN in the σ bond of hBN derived from the hBN phase and the cBN phase in the hBN phase * In the case of π* / I σ* For the cBN particles on the surface of the cutting edge, the ratio I of I π* / I σ* is 0.1 to 2, and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge π* / I σ* is 0.001 to 0.1. Therefore, by the above manufacturing method, a cubic boron nitride sintered body tool with improved chipping resistance can be obtained.

[0076] 〔Supplementary Note〕

[0077] The above description includes the following embodiments described in the supplementary notes.

[0078] <Supplementary Note 1>

[0079] A cubic boron nitride sintered body tool, which is a cubic boron nitride sintered body tool having at least a first sintered body at the cutting edge, wherein

[0080] The first sintered body contains a plurality of cubic boron nitride particles,

[0081] At least a part of the plurality of cubic boron nitride particles of the cubic boron nitride particles is located on the surface of the cutting edge,

[0082] The cubic boron nitride particles located on the surface of the cutting edge contain a cubic boron nitride phase composed of the crystal structure of cubic boron nitride and a hexagonal boron nitride phase composed of the crystal structure of hexagonal boron nitride,

[0083] For the cubic boron nitride particles located on the surface of the cutting edge, by using the electron energy loss spectroscopy of a transmission electron microscope, the energy loss associated with the excitation of the K-shell electrons of boron is measured, and thus the π of the π bond of the hexagonal boron nitride in the hexagonal boron nitride phase is obtained. *The intensity of the peak is related to the σ bonds of hexagonal boron nitride in the hexagonal boron nitride phase and the σ bonds of cubic boron nitride in the cubic boron nitride phase. * The ratio I π* / I σ* In the case of, the ratio I π* / I σ* of the cubic boron nitride particles in the surface of the tool tip is 0.1 to 2, and the ratio I π* / I σ* of the cubic boron nitride particles at a depth position of 5 μm along the normal direction of the tool tip surface from the tool tip surface is 0.001 to 0.1.

[0084] <Appendix 2>

[0085] The cubic boron nitride sintered body tool according to Appendix 1, wherein, when the first sintered body is a cBN sintered body produced by sintering a mixture obtained by mixing cubic boron nitride particles and a bonding material, the content of cubic boron nitride particles in the first sintered body is 40% by volume or more and 95% by volume or less with respect to the total amount (100% by volume) of the first sintered body.

[0086] <Appendix 3>

[0087] The cubic boron nitride sintered body tool according to Appendix 1, wherein the first sintered body is a binderless cBN sintered body produced by directly converting low-pressure phase boron nitride at high temperature and high pressure while sintering without mixing a bonding material.

[0088] Examples

[0089] Hereinafter, examples will be listed to explain the present disclosure in more detail, but the present disclosure is not limited to these examples. In the following description, Specimens 1 to 9 are examples, and Specimen 10 is a comparative example.

[0090] [Manufacture of cubic boron nitride sintered body tool]

[0091] <Specimen 1>

[0092] (First step)

[0093] Prepare cBN particles with an average particle size of 1 μm (trade name: "SBN", manufactured by Showa Denko K.K.). Then, the diameter A hard spherical medium with a diameter of 3 mm, TiN particles with an average particle size of 1 μm (trade name: "titanium nitride powder", manufactured by Nippon New Metal Co., Ltd.), and Al2O3 particles with an average particle size of 200 nm (trade name: "high-purity alumina", manufactured by Sumitomo Chemical Co., Ltd.) are placed in a hard container together with ethanol, and mixing and pulverization are performed for 20 hours by a ball milling method to obtain a raw material powder for the composite material. Further, the above cBN particles are added to the raw material powder for the composite material in the above hard container, and mixing and pulverization are performed for 10 hours by a ball milling method to obtain a mixed powder. Then, the above mixed powder is filled into a capsule made of molybdenum (Mo), and sintered at a pressure of 7.0 GPa and a temperature of 1600 °C for 30 minutes using a ultra-high pressure generating device to prepare a cBN-based sintered body.

[0094] (Second process)

[0095] In order to manufacture an end mill specified in the catalog number "BNES1120" (Sumitomo Electric Industries, Ltd.), the above cBN-based sintered body is cut into a rectangular sintered body using a commercially available wire electrical discharge machining machine. In addition, the shape of the above end mill includes a rake face, a flank face, and a cutting edge where the above rake face intersects with the above flank face, and the above rake face is connected to the above flank face via the above cutting edge. Further, in the above end mill shape, a cutting tip is formed by a part of the above rake face, a part of the above flank face, and the above cutting edge. Specifically, in the above end mill shape, the cutting tip is formed by the cutting edge and regions that are 0.5 mm away from the cutting edge toward the rake face side and the flank face side, respectively.

[0096] (Third process)

[0097] A shank as a substrate is prepared by processing IGETALLOY (registered trademark, material type: G10E), which is a cemented carbide, manufactured by Sumitomo Electric Industries, Ltd. The shank is joined to the sintered body cut into the above rectangle by brazing.

[0098] (Fourth process)

[0099] After forming a cutting tip by grinding the sintered body joined to the above shank, only the surface on the flank face side of the cutting tip is subjected to laser processing under the following irradiation conditions to finish the above cutting tip.

[0100] 〈Irradiation conditions〉

[0101] Laser wavelength: 1064 nm

[0102] Laser spot diameter: 40 μm (half-width)

[0103] Laser focus depth: 1.5 mm

[0104] Laser output: 5 W (at the processing point)

[0105] Laser scanning speed: 10 mm / min

[0106] Laser pulse width: 10 ps (picoseconds)

[0107] Laser repetition frequency: 200 kHz.

[0108] Based on the above, a milling cutter (cubic boron nitride sintered body tool) of Specimen 1 was obtained. The milling cutter of Specimen 1 has at least a first sintered body composed of a cBN-based sintered body at the tool tip. The first sintered body contains a plurality of cubic boron nitride particles, and at least a part of the plurality of cubic boron nitride particles are located on the surface of the tool tip. The cubic boron nitride particles located on the surface of the tool tip form a cubic boron nitride phase composed of the crystal structure of cubic boron nitride and a hexagonal boron nitride phase composed of the crystal structure of hexagonal boron nitride through the above-mentioned fourth process.

[0109] <Specimen 2>

[0110] In the fourth process, laser processing was only performed on the rake face side of the tool tip of the sintered body. Except for this, the same method as that of Specimen 1 was used, and thus a milling cutter (cubic boron nitride sintered body tool) of Specimen 2 was obtained.

[0111] <Specimen 3>

[0112] In the fourth process, laser processing was performed on both the flank face side and the rake face side of the tool tip of the sintered body. Except for this, the same method as that of Specimen 1 was used, and thus a milling cutter (cubic boron nitride sintered body tool) of Specimen 3 was obtained.

[0113] <Specimen 4>

[0114] In the fourth process, when laser processing was performed on the flank face side of the tool tip of the sintered body, compressed air was blown to the processing part for cooling using a vortex tube (manufactured by Hongji Co., Ltd.) on the flank face side of the tool tip, and the laser output was set to 10 W. Except for this, the same method as that of Specimen 1 was used, and thus a milling cutter (cubic boron nitride sintered body tool) of Specimen 4 was obtained.

[0115] <Specimen 5>

[0116] In the fourth process, when laser processing was performed on the rake face side of the tool tip of the sintered body, compressed air was blown to the processing part for cooling using a vortex tube (manufactured by Hongji Co., Ltd.) on the rake face side of the tool tip, and the laser output was set to 10 W. Except for this, the same method as that of Specimen 2 was used, and thus a milling cutter (cubic boron nitride sintered body tool) of Specimen 5 was obtained.

[0117] <Specimen 6>

[0118] In the fourth process, when laser processing is performed on the flank side and rake face side of the tip of the sintered body, compressed air is blown to the processing part using a vortex tube (manufactured by Koji Co., Ltd.) for cooling on the flank side and rake face side of the above tip, and the laser output is set to 10 W. Other than this, the same method as that for Specimen 3 is used, whereby a end mill (cubic boron nitride sintered body tool) of Specimen 6 is obtained.

[0119] <Specimen 7>

[0120] In the fourth process, when laser processing is performed on the flank side of the tip of the sintered body, compressed air is blown to the processing part using a vortex tube (manufactured by Koji Co., Ltd.) for cooling on the flank side of the above tip, and the laser output is set to 3 W. Other than this, the same method as that for Specimen 1 is used, whereby a end mill (cubic boron nitride sintered body tool) of Specimen 7 is obtained.

[0121] <Specimen 8>

[0122] In the fourth process, when laser processing is performed on the rake face side of the tip of the sintered body, compressed air is blown to the processing part using a vortex tube (manufactured by Koji Co., Ltd.) for cooling on the rake face side of the above tip, and the laser output is set to 3 W. Other than this, the same method as that for Specimen 2 is used, whereby a end mill (cubic boron nitride sintered body tool) of Specimen 8 is obtained.

[0123] <Specimen 9>

[0124] In the fourth process, when laser processing is performed on the flank side and rake face side of the tip of the sintered body, compressed air is blown to the processing part using a vortex tube (manufactured by Koji Co., Ltd.) for cooling on the flank side and rake face side of the above tip, and the laser output is set to 3 W. Other than this, the same method as that for Specimen 3 is used, whereby a end mill (cubic boron nitride sintered body tool) of Specimen 9 is obtained.

[0125] <Specimen 10>

[0126] In the fourth process, instead of performing laser processing on both the flank side and rake face side of the tip of the sintered body, grinding is performed using a grindstone. Other than this, the same method as that for Specimen 3 is used, whereby a end mill (cubic boron nitride sintered body tool) of Specimen 10 is obtained.

[0127] 〔Measurement of the existence ratio of hBN (ratio I π* / I σ* )〕

[0128] The cBN particles on the surfaces of the end mills of Specimens 1 to 10 at the tool tips (both on the flank face side and the rake face side) were respectively subjected to the measurement method using the above TEM-EELS method, and thereby the ratio I of the cBN particles in the surface of the tool tip was respectively obtained. π* / I σ* The ratio I of the cBN particles at a depth position of 0.2 μm along the normal direction of the surface of the tool tip from the surface of the tool tip. π* / I σ* The ratio I of the cBN particles at a depth position of 1 μm along the normal direction of the surface of the tool tip from the surface of the tool tip. π* / I σ* The ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the surface of the tool tip from the surface of the tool tip. π* / I σ* . The results are shown in Table 1.

[0129] 〔Cutting Test (Chipping Resistance Test)〕

[0130] Using the end mills of Specimens 1 to 10, carburized and quenched steel (SCM415 (size: 200 mm × 200 mm × thickness 5 mm), hardness: HRC60) was prepared as the workpiece to be cut, and the workpiece was cut under the following cutting conditions. In this cutting test, cutting was terminated when the size of either chipping or cracking at the tool tip exceeded 0.1 mm, and the time (in minutes) from the start of the test to this time point was evaluated. The longer this time, the higher the chipping resistance can be evaluated. The results are shown in the item of "Chipping Resistance (min)" in Table 1.

[0131] <Cutting Conditions>

[0132] Machine tool: Machining center

[0133] Cutting speed Vc: 100 m / min

[0134] Feed rate f: 0.05 mm / rev

[0135] Axial depth of cut ap: 5 mm / rev

[0136] Radial depth of cut ae: 0.1 mm / rev

[0137] Cutting oil (coolant): None.

[0138] Table I

[0139]

[0140] 〔Discussion〕

[0141] Examples of cubic boron nitride sintered body tools in which the end mills of Specimen 1, Specimen 2, Specimen 4, Specimen 5, Specimen 7, and Specimen 8 are manufactured by the above-described fourth process: In any of the cBN particles on the rake face side and the flank face side of the tool tip surface, the ratio I of the cBN particles in the tool tip surface π* / I σ* is 0.1 to 2, and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the tool tip surface from the tool tip surface π* / I σ* is 0.001 to 0.1. Examples of cubic boron nitride sintered body tools in which the end mills of Specimen 3, Specimen 6, and Specimen 9 are manufactured by the above-described fourth process: In both of the cBN particles on the rake face side and the flank face side of the tool tip surface, the ratio I of the cBN particles in the tool tip surface π* / I σ* is 0.1 to 2, and the ratio I of the cBN particles at a depth position of 5 μm along the normal direction of the tool tip surface from the tool tip surface π* / I σ* is 0.001 to 0.1. The end mill of Specimen 10 is an example of a cubic boron nitride sintered body tool manufactured by using conventional grinding with a grindstone.

[0142] As can be understood from Table 1, the end mills of Specimens 1 to 9 have improved chipping resistance compared to the end mill of Specimen 10. It can be understood that, in particular, the end mill of Specimen 3 has further improved chipping resistance compared to Specimens 1 to 2, the end mill of Specimen 6 has further improved chipping resistance compared to Specimens 4 to 5, and the end mill of Specimen 9 has further improved chipping resistance compared to Specimens 7 to 8. Based on the above, it can be evaluated that the end mills (cubic boron nitride sintered body tools) of Specimens 1 to 9 have improved chipping resistance compared to the prior art.

[0143] As described above, the embodiments and examples of the present disclosure have been described. However, it is also contemplated from the beginning to appropriately combine the configurations of the above-described embodiments and examples or to make various modifications.

[0144] It should be considered that the embodiments and examples disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is not represented by the above-described embodiments and examples, but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0145] Description of Reference Numerals

[0146] A: Cubic boron nitride particles (cBN particles); 3: Shank; 8: Joint portion; 10: First rake face; 11: First region; 11a: Depth position of 0.2 μm from the surface of the tool tip along the normal direction of the surface of the tool tip; 12: Second region; 12a: Depth position of 1 μm from the surface of the tool tip along the normal direction of the surface of the tool tip; 13: Inner region of the tool tip; 13a: Depth position of 5 μm from the surface of the tool tip along the normal direction of the surface of the tool tip; 15: Second rake face; 20: Peripheral cutting edge; 21: Bottom cutting edge; 31: First flank face; 33: Second flank face; 90: Cutting edge portion; 100: Cubic boron nitride sintered body tool.

Claims

1. A cubic boron nitride sintered body tool, which is a cubic boron nitride sintered body tool having at least a first sintered body at the cutting edge, wherein, the first sintered body contains a plurality of cubic boron nitride particles, at least a part of the cubic boron nitride particles among the plurality of cubic boron nitride particles are located on the surface of the cutting edge, the cubic boron nitride particles located on the surface of the cutting edge contain a cubic boron nitride phase composed of the crystal structure of cubic boron nitride and a hexagonal boron nitride phase composed of the crystal structure of hexagonal boron nitride, For the cubic boron nitride particles located on the surface of the tool tip, by using electron energy loss spectroscopy with a transmission electron microscope, the energy loss associated with the excitation of the K-shell electrons of boron is measured, and thereby the ratio I of the intensity of the π* peak derived from the π bond of hexagonal boron nitride in the hexagonal boron nitride phase to the intensity of the σ* peak derived from the σ bond of hexagonal boron nitride in the hexagonal boron nitride phase and the σ bond of cubic boron nitride in the cubic boron nitride phase is obtained. π* / I σ* In the case where, for the cubic boron nitride particles on the surface of the tool tip, the ratio I π* / I σ* is 0.1 to 2, and at a depth position of 5 μm along the normal direction of the surface of the tool tip from the surface of the tool tip, the ratio I π* / I σ* is 0.001 to 0.

1.

2. The cubic boron nitride sintered body tool according to claim 1, wherein, The ratio I of the cubic boron nitride particles in the surface of the cutting edge π* / I σ* is 0.6 to 1, and the ratio I of the cubic boron nitride particles at a depth position of 5 μm from the surface of the cutting edge along the normal direction of the surface of the cutting edge π* / I σ* is 0.005 to 0.

01.

3. The cubic boron nitride sintered body tool according to claim 1 or 2, wherein, The ratio I of the cubic boron nitride particles at a depth position of 1 μm from the surface of the tool tip along the normal direction of the surface of the tool tip π* / I σ* is 0.001 to 0.

1.

4. The cubic boron nitride sintered body tool according to claim 3, wherein, The ratio I of the cubic boron nitride particles at a depth position of 1 μm along the normal direction of the surface of the cutting edge from the surface of the cutting edge π* / I σ* is 0.005 to 0.

01.

5. The cubic boron nitride sintered body tool according to claim 1 or 2, wherein, The ratio I of the cubic boron nitride particles at a depth position of 0.2 μm along the normal direction of the surface of the cutting edge starting from the surface of the cutting edge π* / I σ* is 0.001 to 0.

1.

6. The cubic boron nitride sintered body tool according to claim 5, wherein, The ratio I of the cubic boron nitride particles at a depth position of 0.2 μm along the normal direction of the surface of the cutting edge starting from the surface of the cutting edge π* / I σ* is 0.005 to 0.

01.

7. The cubic boron nitride sintered body tool according to claim 1 or 2, wherein, the cubic boron nitride sintered body tool includes a rake face, a flank face, and a cutting edge where the rake face intersects with the flank face, the rake face is connected to the flank face via the cutting edge, the cutting edge of the cubic boron nitride sintered body tool is composed of a part of the rake face, a part of the flank face, and the cutting edge, the surface of the cutting edge is the surface of at least a part of the cutting edge.

8. The cubic boron nitride sintered body tool according to claim 1 or 2, wherein, the cubic boron nitride sintered body tool has a substrate and an adhesive layer that binds the first sintered body to the substrate, the substrate is cemented carbide or cermet.

9. The cubic boron nitride sintered body tool according to claim 1 or 2, wherein, the first sintered body contains 40 vol% or more and 95 vol% or less of cBN particles, and 5 vol% or more and 60 vol% or less of a bonding material and inevitable impurities.

10. The cubic boron nitride sintered body tool according to claim 9, wherein, the bonding material contains at least one element selected from the group consisting of elements of Group 4, Group 5, Group 6, Al, Co, Ni, and Si in the periodic table, and at least one compound selected from the group consisting of nitrides, carbonitrides, borides, oxides, and their solid solutions containing the elements.

11. The cubic boron nitride sintered body tool according to claim 10, wherein, the bonding material has at least one or more selected from the group consisting of Ti, Co, Cr, Ni, Al, AlN, Al2O3, AlB2, TiN, TiC, TiCN, TiB2, Cr2N, WC, ZrO2, ZrO, ZrN, ZrB2, and Si3N4.

12. The cubic boron nitride sintered body tool according to claim 1 or 2, wherein, the first sintered body is a binderless cBN sintered body.

13. The cubic boron nitride sintered body tool according to claim 1 or 2, wherein the average particle size of the cubic boron nitride particles is 0.5 to 10.0 μm.

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