Cutting Tools

Abstract

A cutting tool comprises: a substrate and a coating disposed on the substrate, wherein the coating includes a first layer composed of metal tungsten and hexagonal ditungsten carbide, and the elastic deformation rate of the first layer is not less than 43.0 and not more than 58.0.

Description

Technical Field

[0001] The present disclosure relates to a cutting tool. This application claims priority based on Japanese Patent Application No. 2020-208258 filed on December 16, 2020. All the contents described in the Japanese Patent Application are incorporated herein by reference. Background Art

[0002] Various studies have been conducted to extend the life of cutting tools. Japanese Patent Publication No. 06-262405 (Patent Document 1) discloses a coating component for a cutting tool or a grinding tool, characterized in that a coating having a thickness of 0.5 μm to 100 μm and containing 30% by volume or more of cubic tungsten carbide exists on the surface of a substrate.

[0003] Japanese Patent Application Laid-Open No. 54-152281 (Patent Document 2) discloses a surface-coated tool in the form of a coating layer composed of one or both of tungsten and tungsten carbide.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 06-262405

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 54-152281 Summary of the invention

[0008] The cutting tool disclosed in the present invention comprises: a substrate and a coating disposed on the substrate.

[0009] The coating includes a first layer composed of metallic tungsten and hexagonal tungsten carbide.

[0010] The elastic deformation rate of the first layer is 43.0 or more and 58.0 or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] [ Figure 1 ] Figure 1 A perspective view illustrating one approach to a cutting tool.

[0012] [ Figure 2 ] Figure 2 This is a schematic cross-sectional view of a cutting tool according to one form of the present embodiment.

[0013] [ Figure 3 ] Figure 3 This is a schematic cross-sectional view of another type of cutting tool according to the present embodiment.

[0014] [ Figure 4 ] Figure 4This is a schematic cross-sectional view of another type of cutting tool according to the present embodiment.

[0015] [ Figure 5 ] Figure 5 This is a schematic cross-sectional view of another type of cutting tool according to the present embodiment.

[0016] [ Figure 6 ] Figure 6 This is a schematic cross-sectional view of another type of cutting tool according to the present embodiment.

[0017] [ Figure 7 ] Figure 7 A coordinate system showing an example of a load-displacement curve drawn based on nanoindentation test results. DETAILED DESCRIPTION

[0018] [Problems to be Solved by the Present Disclosure]

[0019] For example, in the milling process of titanium alloy, a cutting tool having a long tool life is required even in an environment with a high thermal load.

[0020] Therefore, an object of the present disclosure is to provide a cutting tool having a long tool life even in an environment with a high thermal load such as during milling of titanium alloy.

[0021] [Effects of the present disclosure]

[0022] The cutting tool of the present disclosure can have a long tool life even in an environment with a high thermal load such as during milling of titanium alloy.

[0023] [Description of Embodiments of the Present Disclosure]

[0024] First, embodiments of the present disclosure will be listed and described.

[0025] (1) The cutting tool of the present disclosure comprises: a substrate and a coating disposed on the substrate;

[0026] The coating includes a first layer composed of metallic tungsten and hexagonal tungsten carbide.

[0027] The elastic deformation rate of the first layer is 43.0 or more and 58.0 or less.

[0028] The cutting tool of the present disclosure can have a long tool life even in an environment with a high thermal load such as during milling of titanium alloy.

[0029] (2) The thickness of the first layer is preferably 0.3 μm or more and 4.0 μm or less. This improves the defect resistance and wear resistance of the tool.

[0030] (3) Preferably, the coating further includes a second layer disposed on the first layer,

[0031] The second layer includes at least a first unit layer having a composition different from that of the first layer,

[0032] The first unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon in the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron.

[0033] This improves the defect resistance and wear resistance of the tool.

[0034] (4) Preferably, the second layer further comprises a second unit layer,

[0035] The second unit layer has a different composition from the first layer and the first unit layer,

[0036] The second unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon of the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron,

[0037] The first unit layer and the second unit layer form a multilayer structure in which one or more layers of each are alternately stacked.

[0038] This improves the defect resistance and wear resistance of the tool.

[0039] (5) Preferably, the thickness of the first unit layer is 1 nm to 100 nm, and the thickness of the second unit layer is 1 nm to 100 nm. This improves the defect resistance and wear resistance of the tool.

[0040] (6) Preferably, the coating further includes a third layer disposed below the first layer.

[0041] The third layer includes at least a 1A unit layer having a composition different from that of the first layer,

[0042] The 1A unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon in the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron.

[0043] This improves the defect resistance and wear resistance of the tool.

[0044] (7) Preferably, the third layer further comprises a 2A unit layer,

[0045] The 2A unit layer has a composition different from that of the first layer and the 1A unit layer,

[0046] The second A unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon of the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron,

[0047] The first A unit layer and the second A unit layer form a multilayer structure in which one or more layers of each are alternately stacked.

[0048] This improves the defect resistance and wear resistance of the tool.

[0049] (8) Preferably, the thickness of the first A unit layer is 1 nm to 100 nm, and the thickness of the second A unit layer is 1 nm to 100 nm. This improves the defect resistance and wear resistance of the tool.

[0050] (9) The substrate preferably includes at least one selected from the group consisting of cemented carbide, cermet, high-speed steel, ceramic, cBN sintered body, and diamond sintered body. This allows the tool to have excellent hardness and strength at high temperatures.

[0051] [Details of the embodiments of the present disclosure]

[0052] Hereinafter, a specific example of a cutting tool according to an embodiment of the present disclosure (hereinafter, also referred to as "the present embodiment") is described with reference to the accompanying drawings. In the drawings of the present disclosure, the same reference symbols represent the same parts or equivalent parts. In addition, in order to make the drawings clear and simple, the dimensional relationships of length, width, thickness, depth, etc. are appropriately changed, and do not necessarily represent the actual dimensional relationships.

[0053] In this specification, the expression of the form of "A to B" refers to the upper and lower limits of a range (i.e., greater than A and less than B). When the unit is not described for A but only the unit is described for B, the unit of A is the same as the unit of B.

[0054] In this specification, when a compound is represented by a chemical formula, when the atomic ratio is not particularly limited, it includes all atomic ratios known in the past, and should not be limited to the atomic ratio within the stoichiometric range. For example, when it is recorded as "TiN", the ratio of the number of atoms constituting TiN includes all atomic ratios known in the past.

[0055] [Embodiment 1: Cutting Tool]

[0056] The cutting tool of this embodiment includes: a substrate and a coating disposed on the substrate.

[0057] The coating includes a first layer composed of metallic tungsten and hexagonal tungsten carbide.

[0058] The elastic deformation rate of the first layer is 43.0 or more and 58.0 or less.

[0059] The cutting tool of this embodiment can have a long tool life even in a high heat load environment such as milling of titanium alloy. The reason is not clear, but it is presumed that the first layer contains metal tungsten and hexagonal tungsten carbide, thereby suppressing the diffusion reaction between the coating and the cut material.

[0060] The cutting tool of this embodiment can be, for example, a drill, an end mill, a cutting blade indexable cutting insert for a drill, a cutting blade indexable cutting insert for an end mill, a cutting blade indexable cutting insert for fraise processing, a cutting blade indexable cutting insert for milling processing, a metal saw, a gear cutting tool, a reamer, a tap, etc.

[0061] Figure 1 A perspective view of one embodiment of a cutting tool. A cutting tool having such a shape can be used, for example, as a cutting blade indexable cutting insert. The cutting tool 10 has: a front cutting face 1, a back cutting face 2, and a cutting edge ridge portion 3 where the front cutting face 1 and the back cutting face 2 intersect. That is, the front cutting face 1 and the back cutting face 2 are surfaces connected by clamping the cutting edge ridge portion 3. The cutting edge ridge portion 3 constitutes the front end portion of the cutting edge of the cutting tool 10. The shape of such a cutting tool 10 can also be understood as the shape of the substrate of the cutting tool. That is, the above-mentioned substrate has: a front cutting face, a back cutting face, and a cutting edge ridge portion connecting the front cutting face and the back cutting face.

[0062] <Base material>

[0063] The substrate of the present embodiment can use a substrate known in the past as the substrate. For example, the substrate preferably includes at least one selected from the group consisting of cemented carbide (e.g., tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide with carbonitrides of Cr, Ti, Ta, Nb, etc. added in addition to WC, etc.), cermet (materials with TiC, TiN, TiCN, etc. as main components), high-speed steel, ceramic (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body (cBN sintered body) and diamond sintered body, more preferably includes at least one selected from the group consisting of cemented carbide, cermet and cBN sintered body.

[0064] It should be noted that, when cemented carbide is used as the substrate, even if the cemented carbide contains free carbon or an abnormal phase called η phase in the texture, the effect of the present embodiment can be exhibited. It should be noted that even if the surface of the substrate used in the present embodiment is modified, it will not be affected. For example, in the case of cemented carbide, a de-β layer can be formed on its surface; or in the case of metal ceramics, a surface hardening layer can be formed, and even if the surface is modified in this way, the effect of the present embodiment can be exhibited.

[0065] In the case where the cutting tool is a cutting blade indexable cutting insert (a cutting blade indexable cutting insert for milling (fraise) processing, etc.), the substrate may have a chip breaker or may not have one. The shape of the ridgeline portion of the cutting edge may include any of the following shapes: a sharp edge (a ridge formed by the intersection of the front cutting surface and the back cutting surface), a honed edge (a shape obtained by giving a rounded corner to the sharp edge), a negative land (a chamfered shape), or a shape obtained by combining a honed edge and a negative land.

[0066] <Lamination>

[0067] The "film" involved in this embodiment has the function of improving the defect resistance, wear resistance and other characteristics of the cutting tool by covering at least a portion of the above-mentioned substrate (for example, the portion in contact with the cut material during cutting). The above-mentioned film can also cover the entire surface of the above-mentioned substrate. It should be noted that even if a part of the above-mentioned substrate is not covered by the above-mentioned film, or the composition of the film is partially different, it does not deviate from the scope of this embodiment.

[0068] The thickness of the coating is preferably 0.1 μm to 10 μm, more preferably 0.3 μm to 10 μm, further preferably 0.5 μm to 10 μm, further preferably 1 μm to 6 μm, and particularly preferably 1.5 μm to 4 μm. When the thickness is less than 0.1 μm, the wear resistance tends to decrease. When the thickness exceeds 10 μm, for example, when a large stress is applied between the coating and the substrate during intermittent processing, the coating tends to be peeled off or broken at a high frequency.

[0069] In this specification, the thickness of the coating refers to the sum of the thicknesses of the layers constituting the coating, such as the first layer, the second layer (the first unit layer, the second unit layer) and the third layer (the 1A unit layer, the 2A unit layer) described later. The thickness of the above coating can be obtained, for example, by the following method: using a transmission electron microscope (TEM), measuring any three points in a cross-section sample parallel to the normal direction of the surface of the substrate, and calculating the average value of the thickness of the three measured points. The same is true for measuring the thickness of the first layer, the second layer (the first unit layer, the second unit layer) and the third layer (the 1A unit layer, the 2A unit layer) described later. As a transmission electron microscope, for example, the spherical aberration correction device "JEM-2100F (trademark)" manufactured by JEOL Ltd. can be cited.

[0070] (First floor)

[0071] The coating includes a first layer composed of metal tungsten and hexagonal tungsten carbide. The first layer may contain inevitable impurities within the scope of the effect obtained by the cutting tool involved in the present embodiment without damaging it. As the inevitable impurities, for example, iron (Fe), calcium (Ca), zinc (Zn), sodium (Na), fluorine (F), nickel (Ni), molybdenum (Mo), chromium (Cr) can be listed. Relative to the total mass of the first layer, the content ratio of the inevitable impurities is preferably 0 mass% or more and 0.2 mass% or less. The content ratio of the inevitable impurities is determined by glow discharge mass spectrometry. The description of the "second layer", "first unit layer", "second unit layer", "third layer", "1A unit layer", "2A unit layer" and "other layers" described later is also the same, and inevitable impurities may be contained within the scope of the effect obtained by the cutting tool involved in the present embodiment without damaging it.

[0072] The situation that the first layer is composed of metal tungsten and hexagonal tungsten carbide (W2C) can be confirmed by the following method: irradiating the surface on the opposite side of the substrate of the measurement sample with X-rays to perform X-ray diffraction measurement (XRD measurement) and analyze any area of ​​the above-mentioned first layer. In the case where the first layer contains metal tungsten, peaks from crystal planes such as the (110) plane and the (220) plane of metal tungsten are observed in the XRD measurement. In the case where the first layer has hexagonal tungsten carbide, peaks from crystal planes such as the (011) plane of hexagonal tungsten carbide are observed in the XRD measurement. Specifically, in the X-ray diffraction pattern, peaks from the (110) plane of metal tungsten and the (011) plane of hexagonal tungsten carbide are observed at 2θ=39.6~40.1°, and peaks from the (220) plane of metal tungsten are observed at 2θ=86.0~86.5°.

[0073] In XRD measurement, in addition to the peaks of the metal tungsten and hexagonal tungsten carbide from the first layer, peaks from other layers or substrates such as the second layer, the third layer, and the intermediate layer (hereinafter also referred to as "other peaks") may be detected. In this case, the peak from the first layer is identified by the following method.

[0074] The measuring method when there are other layers on the surface side closer to the coating than the first layer is as follows. First, the surface of the measuring sample on the opposite side of the substrate is irradiated with X-rays to perform XRD measurement to obtain a diffraction pattern A. Then, the layer (other layer) closer to the surface side (X-ray irradiation side) than the first layer of the measuring sample is mechanically removed to expose the first layer. The surface of the exposed first layer is irradiated with X-rays to perform XRD measurement to obtain a diffraction pattern B. Then, in the measuring sample in which the above-mentioned first layer is exposed, the first layer is mechanically removed to expose the substrate or a layer closer to the substrate side than the first layer. The surface of the exposed substrate or a layer closer to the substrate side than the first layer is irradiated with X-rays to perform XRD measurement to obtain a diffraction pattern C. The peak from the first layer is identified by comparing diffraction pattern A, diffraction pattern B and diffraction pattern C.

[0075] The first layer is arranged at the outermost side of the coating, and the measurement method when no other layer exists on the surface side closer to the coating than the first layer is as follows. First, the surface of the measurement sample on the opposite side of the substrate, that is, the surface of the first layer, is irradiated with X-rays to perform XRD measurement to obtain a diffraction pattern B. Next, in the above-mentioned measurement sample, the first layer is mechanically removed to expose the substrate or the layer closer to the substrate side than the first layer. The surface of the exposed substrate or the layer closer to the substrate side than the first layer is irradiated with X-rays to perform XRD measurement to obtain a diffraction pattern C. The peak from the first layer is identified by comparing the diffraction pattern B and the diffraction pattern C.

[0076] In addition, when the thickness of the first layer is 1 μm or more, the peak derived from the first layer can also be identified by performing thin-film X-ray measurement in a state where the first layer is exposed.

[0077] Examples of an apparatus used for the X-ray diffraction measurement include “SmartLab” (trade name) manufactured by Rigaku Corporation and “X'Pert” (trade name) manufactured by PANalytical.

[0078] In this specification, the conditions for XRD measurement are as follows.

[0079] (XRD measurement conditions)

[0080] Scanning axis: 2θ-θ

[0081] X-ray source: Cu-Kα line

[0082] Detector: 0-dimensional detector (scintillation counter)

[0083] Tube voltage: 45kV

[0084] Tube current: 40mA

[0085] Incident optical system: using a reflector

[0086] Light receiving optical system: using spectroscopic crystal (PW3098 / 27)

[0087] Step length: 0.03°

[0088] Cumulative time: 2 seconds

[0089] Scanning range (2θ): 10° or more and 120° or less

[0090] It should be noted that, according to the measurements made by the applicant, it can be confirmed that as long as the above analysis is performed on the same sample, there is almost no deviation in the analysis result even if the measurement area is changed and the above analysis is performed multiple times, and the analysis result is not arbitrary even if the measurement area is set arbitrarily.

[0091] The elastic deformation rate of the above-mentioned first layer is greater than 43.0 and less than 58.0. When the elastic deformation rate of the first layer is greater than 43.0, the hardness of the coating is high, and the cutting tool can have excellent wear resistance. The lower limit of the elastic deformation rate of the first layer can be set to greater than 43.0, greater than 44.0, or greater than 45.0. When the elastic deformation rate of the first layer is less than 58.0, it is difficult for cracks to occur inside the coating when the cutting tool is used, so that the cutting tool can have excellent defect resistance. The upper limit of the elastic deformation rate of the first layer can be set to less than 58.0, less than 53.0, or less than 48.5. The elastic deformation rate of the first layer is preferably greater than 44.0 and less than 53.0, and more preferably greater than 45.0 and less than 48.5.

[0092] In this specification, the elastic deformation rate of the first layer is measured by a nanoindentation test in accordance with ISO 14577. Specifically, the measurement is performed under the following conditions using a nanoindenter ("ENT1100a" (trademark) manufactured by Elionix Corporation).

[0093] (Nanoindenter Measurement Conditions)

[0094] Indenter material: Diamond

[0095] Indenter shape: Berkovich indenter

[0096] Test load: 20mN

[0097] Measurement points: 10 points

[0098] If there are other layers on the surface side closer to the coating than the first layer, the other layers are removed by mechanical grinding or the like to expose the first layer and then measured. The elastic deformation rate is determined by measuring 10 points of the first layer, and the average value of the elastic deformation rate of the 10 points is taken as the elastic deformation rate of the first layer. The elastic deformation rate of the first layer is calculated based on the theory of Oliver and Pharr and the load displacement curve. Figure 7 A coordinate system showing an example of a load-displacement curve drawn based on nanoindentation test results. Figure 7 In the coordinate system, the X-axis represents displacement and the Y-axis represents load. Figure 7 In the coordinate system of Figure 7 W elast represents the area) and plastic deformation work ( Figure 7 W plast The sum of the deformation work W total That is, W total =W elast +W plast Elastic deformation rate η IT It is represented by the following formula (1).

[0099] η IT =(W elast / W total )×100

[0100] It should be noted that, as far as the applicant has measured, it can be confirmed that as long as the above-mentioned measurement is performed on the same sample, there is almost no deviation in the measurement result even if the measurement position is changed and the above-mentioned measurement is performed multiple times, and the measurement result is not arbitrary even if the measurement position is set arbitrarily.

[0101] Figure 2 Schematic cross-sectional view of a cutting tool according to one embodiment of the present invention. Figure 2 As shown, the first layer 12 may be in contact with the substrate 11. In other words, the first layer 12 may be disposed directly above the substrate 11.

[0102] The lower limit of the thickness of the first layer is preferably greater than 0.3 μm. Thus, the diffusion reaction between the first layer and the cut material is suppressed. The lower limit of the thickness of the first layer is preferably greater than 0.3 μm, greater than 0.5 μm, and greater than 0.7 μm. The upper limit of the thickness of the first layer is preferably less than 4.0 μm. Thus, the coating has high hardness and good wear resistance. The upper limit of the thickness of the first layer is preferably less than 4.0 μm, less than 2.0 μm, and less than 1.5 μm. The thickness of the first layer is preferably greater than 0.3 μm and less than 4.0 μm, preferably greater than 0.5 μm and less than 2.0 μm, and preferably greater than 0.7 μm and less than 1.5 μm.

[0103] (Second floor)

[0104] The coating preferably further includes a second layer disposed on the first layer. Here, "the second layer disposed on the first layer" means that the second layer is disposed on the upper side of the first layer (the side opposite to the substrate), and does not need to be in contact with each other. In other words, other layers may be disposed between the first layer and the second layer. In addition, Figure 3 As shown, the second layer 13 may also be disposed directly above the first layer 12. The second layer may be the outermost layer (surface layer).

[0105] The second layer preferably includes at least a first unit layer having a composition different from that of the first layer.

[0106] (First unit layer)

[0107] Preferably, the first unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum (Al) and silicon (Si) of the periodic table, or a compound consisting of at least one of the above elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron. As the Group 4 element of the periodic table, titanium (Ti), zirconium (Zr), hafnium (Hf) and the like can be listed. As the Group 5 element of the periodic table, vanadium (V), niobium (Nb), tantalum (Ta) and the like can be listed. As the Group 6 element of the periodic table, chromium (Cr), molybdenum (Mo), tungsten (W) and the like can be listed. More preferably, the first unit layer is composed of at least one element selected from the group consisting of Cr, Al, Ti and Si; or a compound consisting of at least one of the above elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron.

[0108] As the compound constituting the above-mentioned first unit layer, for example, there can be listed: TiAlN, TiAlSiN, TiCrSiN, TiAlCrSiN, AlCrN, AlCrO, AlCrSiN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, AlCrTaN, AlTiVN, TiB2, TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlCrCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TiAlBN, TiAlCrSiBCNO, ZrN, ZrCN, CrWCN, AlTiCrN, TiN, TiBN and the like.

[0109] In the case where the second layer is composed only of the first unit layer (for example, Figure 3 ), the thickness of the first unit layer (ie, the second layer) is preferably not less than 0.1 μm and not more than 10 μm, and more preferably not less than 0.5 μm and not more than 7 μm.

[0110] (Second unit layer)

[0111] Preferably, the second layer includes a second unit layer in addition to the first unit layer, and the second unit layer has a composition different from that of the first layer and the first unit layer.

[0112] Preferably, the second unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum (Al) and silicon (Si) of the periodic table; or a compound consisting of at least one of the above elements and at least one of the elements selected from the group consisting of carbon, nitrogen, oxygen and boron. More preferably, the second unit layer is composed of at least one element selected from the group consisting of Cr, Al, Ti and Si; or a compound consisting of at least one of the above elements and at least one of the elements selected from the group consisting of carbon, nitrogen, oxygen and boron. As specific examples of each of the Group 4 elements, Group 5 elements and Group 6 elements of the periodic table, the above-mentioned elements can be listed.

[0113] Examples of the compound constituting the second unit layer include the compounds exemplified in the first unit layer.

[0114] In addition, the first unit layer and the second unit layer preferably form a multilayer structure in which one or more layers are alternately stacked. Figure 4As shown, the second layer 13 preferably includes a multilayer structure consisting of a first unit layer 131 and a second unit layer 132. Here, the multilayer structure can be stacked starting from any one of the first unit layer or the second unit layer. That is, the interface on the first layer side of the multilayer structure can be composed of any one of the first unit layer or the second unit layer. In addition, the interface on the side opposite to the first layer side of the multilayer structure can also be composed of any one of the first unit layer or the second unit layer.

[0115] When the second layer includes the multilayer structure, the thickness of the second layer is preferably 0.1 μm to 10 μm, and more preferably 0.5 μm to 7 μm.

[0116] In the case where the second layer includes the multilayer structure, the thickness of the first unit layer is preferably from 1 nm to 100 nm, more preferably from 2 nm to 25 nm. In addition, the thickness of the second unit layer is preferably from 1 nm to 100 nm, more preferably from 2 nm to 25 nm. In one embodiment of the present invention, in the case where the second layer includes the multilayer structure, it is preferred that the thickness of the first unit layer is from 1 nm to 100 nm, and the thickness of the second unit layer is from 1 nm to 100 nm. Here, the "thickness of the first unit layer" refers to the thickness of each layer of the first unit layer. The "thickness of the second unit layer" refers to the thickness of each layer of the second unit layer.

[0117] In addition, as long as the number of layers stacked in the multilayer structure makes the overall thickness of the second layer within the above range, the first unit layer and the second unit layer may be stacked by one layer each, and preferably, the two layers are stacked by more than 20 layers and less than 2500 layers each.

[0118] (Third floor)

[0119] The coating preferably further includes a third layer disposed below the first layer. Here, "the third layer disposed below the first layer" means that the third layer can be disposed on the lower side (substrate side) of the first layer without contacting each other. In other words, other layers can be disposed between the first layer and the third layer. Figure 5 As shown, the third layer 14 may be disposed directly below the first layer 12 .

[0120] The third layer preferably includes at least a 1A unit layer having a composition different from that of the first layer.

[0121] (Unit 1A layer)

[0122] Preferably, the first unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum (Al) and silicon (Si) of the periodic table; or a compound consisting of at least one of the above elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron. As the Group 4 element of the periodic table, titanium (Ti), zirconium (Zr), hafnium (Hf) and the like can be listed. As the Group 5 element of the periodic table, vanadium (V), niobium (Nb), tantalum (Ta) and the like can be listed. As the Group 6 element of the periodic table, chromium (Cr), molybdenum (Mo), tungsten (W) and the like can be listed. More preferably, the first unit layer is composed of at least one element selected from the group consisting of Cr, Al, Ti and Si; or a compound consisting of at least one of the above elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron.

[0123] As the compounds constituting the above-mentioned 1A unit layer, for example, there can be listed: TiAlN, TiAlSiN, TiCrSiN, TiAlCrSiN, AlCrN, AlCrO, AlCrSiN, TiZrN, TiAlMoN, TiAlNbN, TiSiN, AlCrTaN, AlTiVN, TiB2, TiCrHfN, CrSiWN, TiAlCN, TiSiCN, AlZrON, AlCrCN, AlHfN, CrSiBON, TiAlWN, AlCrMoCN, TiAlBN, TiAlCrSiBCNO, ZrN, ZrCN, CrWCN, AlTiCrN, TiN, TiBN and the like.

[0124] When the third layer is composed of only the 1A unit layer, the thickness of the 1A unit layer (ie, the third layer) is preferably 0.1 μm to 10 μm, and more preferably 0.5 μm to 7 μm.

[0125] (Unit 2A layer)

[0126] Preferably, the third layer includes a second A unit layer in addition to the first A unit layer, and the second A unit layer has a composition different from that of the first layer and the first A unit layer.

[0127] Preferably, the 2A unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum (Al) and silicon (Si) of the periodic table; or a compound consisting of at least one of the above elements and at least one of the elements selected from the group consisting of carbon, nitrogen, oxygen and boron. More preferably, the 2A unit layer is composed of at least one element selected from the group consisting of Cr, Al, Ti and Si; or a compound consisting of at least one of the above elements and at least one of the elements selected from the group consisting of carbon, nitrogen, oxygen and boron. As specific examples of each of the Group 4 elements, Group 5 elements and Group 6 elements of the periodic table, the above-mentioned elements can be listed.

[0128] Examples of the compound constituting the second A unit layer include the compounds exemplified in the first A unit layer.

[0129] In addition, the 1A unit layer and the 2A unit layer preferably form a multilayer structure in which one or more layers are alternately stacked. Figure 6 As shown, the third layer 14 preferably includes a multilayer structure composed of a 1A unit layer 141 and a 2A unit layer 142. Here, the multilayer structure can be stacked starting from any one of the 1A unit layer or the 2A unit layer. That is, the interface on the side opposite to the first layer (i.e., the substrate side) in the multilayer structure can be composed of any one of the 1A unit layer or the 2A unit layer. In addition, the interface on the first layer side in the multilayer structure can also be composed of any one of the 1A unit layer or the 2A unit layer.

[0130] When the third layer includes the multilayer structure, the thickness of the third layer is preferably 0.1 μm to 10 μm, and more preferably 0.5 μm to 7 μm.

[0131] In the case where the third layer includes the multilayer structure, the thickness of the 1A unit layer is preferably from 1 nm to 100 nm, more preferably from 2 nm to 25 nm. In addition, the thickness of the 2A unit layer is preferably from 1 nm to 100 nm, more preferably from 2 nm to 25 nm. In one mode of the present embodiment, in the case where the third layer includes the multilayer structure, it is preferred that the thickness of the 1A unit layer is from 1 nm to 100 nm, and the thickness of the 2A unit layer is from 1 nm to 100 nm. Here, the "thickness of the 1A unit layer" refers to the thickness of each layer of the 1A unit layer. The "thickness of the 2A unit layer" refers to the thickness of each layer of the 2A unit layer.

[0132] In addition, as long as the number of layers stacked in the multilayer structure makes the overall thickness of the third layer within the above range, the 1A unit layer and the 2A unit layer may be stacked by one layer each, and preferably the two layers are stacked by more than 20 layers and less than 2500 layers each.

[0133] (Other layers)

[0134] The coating may further include other layers within the scope of not impairing the effect of the present embodiment. The composition of the other layers may be different from or the same as that of the first layer and the second layer. As other layers, for example, a TiN layer, a TiWCN layer, etc. may be listed. It should be noted that the order of the stacking is not particularly limited. For example, as other layers, an intermediate layer provided between the first layer and the second layer, a surface layer provided on the outermost surface of the tool, etc. may be listed. Within the scope of not impairing the effect of the present embodiment, there is no particular limitation on the thickness of the other layers, for example, it may be listed as 0.1 μm or more and 2 μm or less.

[0135] [Embodiment 2: Method for manufacturing cutting tool]

[0136] The manufacturing method of the cutting tool of the first embodiment is described below. It should be noted that the following manufacturing method is an example, and the cutting tool of the first embodiment can also be made by other methods. The manufacturing method of the cutting tool involved in this embodiment includes a substrate preparation step and a first layer coating step. Each step is described below.

[0137] <Base material preparation process>

[0138] In the substrate preparation step, the above-mentioned substrate is prepared. As the above-mentioned substrate, as described above, any substrate can be used as the substrate as long as it is a substrate known in the past. For example, in the case where the above-mentioned substrate is composed of cemented carbide, first, a commercially available attritor is used to uniformly mix the raw material powder composed of a predetermined combination composition (mass %). Subsequently, the mixed powder is press-formed into a predetermined shape (for example, SEET13T3AGSN, CNMG120408, etc.). Then, by sintering the mixed powder after the above-mentioned press-forming in a predetermined sintering furnace at a temperature of more than 1300° C. and less than 1500° C. for more than 1 hour and less than 2 hours, the above-mentioned substrate composed of cemented carbide can be obtained. In addition, the substrate can also directly use a commercially available product.

[0139] <First layer coating process>

[0140] In the first layer coating step, at least a portion of the surface of the substrate is coated with the first layer. Here, "at least a portion of the surface of the substrate" includes a portion that contacts a workpiece during cutting.

[0141] As a method of covering at least a part of the substrate with the first layer, for example, a physical vapor deposition method (PVD method) can be cited.

[0142] As physical vapor deposition methods, for example, sputtering, ion plating, arc ion plating, electron ion beam evaporation, etc. can be cited. In particular, when using cathode arc ion plating or sputtering with a high ion rate of the raw material element, the substrate surface can be subjected to metal or gas ion bombardment treatment before forming the film, thereby significantly improving the adhesion between the film and the substrate, and therefore it is preferred.

[0143] When the first layer is formed by arc ion plating, the following conditions can be cited, for example. First, a WC target (for example, a sintered target having a composition of binderless WC containing 93% or more of WC and a C content of 3% or more and 6.1% or less of WC) is set in two arc evaporation sources facing each other in the device. The substrate (base material) temperature is set to 400°C or more and 550°C or less, and the gas pressure in the device is set to 1.0Pa or more and 4.0Pa or less.

[0144] As the gas, only argon gas or a mixed gas of methane gas and argon gas as a hydrocarbon-based gas is introduced. Here, as the hydrocarbon-based gas, for example, acetylene gas, methane gas, etc. can be cited.

[0145] By supplying an arc current of 80A to 150A to the cathode electrode while maintaining the substrate (negative) bias voltage at 10V to 150V and DC or pulsed DC (frequency 20kHz to 350kHz), metal ions etc. are generated from an arc evaporation source, thereby forming the first layer. During film formation, the tungsten filament is also discharged (the emission current is 10A to 25A). Thus, the ions in the plasma can be increased. As an apparatus used in the arc ion plating method, for example, AIP (trade name) manufactured by Kobe Steel, Ltd. can be cited.

[0146] By forming the first layer under the above conditions, the first layer can be made of metal tungsten and hexagonal ditungsten carbide, and the elastic deformation rate of the first layer can be 43.0 to 58.0. The above conditions are newly discovered as a result of repeated experiments by the inventors.

[0147] <Second layer coating process>

[0148] The manufacturing method of the cutting tool involved in this embodiment preferably further includes a second layer coating step after the first layer coating step. There is no particular limitation on the method for forming the second layer, and a conventional method can be used. Specifically, for example, the second layer can be formed by the above-mentioned PVD method.

[0149] <Third layer coating process>

[0150] The manufacturing method of the cutting tool involved in this embodiment preferably further includes a third layer coating step before the first layer coating step. There is no particular limitation on the method for forming the third layer, and a conventional method can be used. Specifically, for example, the third layer can be formed by the above-mentioned PVD method.

[0151] <Other Process>

[0152] In the manufacturing method involved in the present embodiment, in addition to the above-mentioned process, it is also possible to appropriately perform: an intermediate layer coating process of forming an intermediate layer between the above-mentioned first layer and the above-mentioned second layer, a surface layer coating process of forming a surface layer on the outermost surface of the coating, and a process of performing surface treatment, etc. When forming other layers such as the above-mentioned intermediate layer and the surface layer, other layers can be formed by conventional methods. Specifically, for example, the above-mentioned other layers can be formed by the above-mentioned PVD method. As a process for performing surface treatment, for example, a surface treatment of a medium loaded with diamond powder on an elastic material can be listed. As a device for performing the above-mentioned surface treatment, for example, SIRIUS-Z manufactured by Fuji Seisakusho Co., Ltd. can be listed.

[0153] Example

[0154] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0155] 《Manufacturing of cutting tools》

[0156] [Sample 1 to Sample 27, Sample 1-3, Sample 1-4]

[0157] <Base material preparation process>

[0158] First, as a substrate preparation step, a JIS standard K10 hard material (shape: JIS standard RCMT1204) was prepared as a substrate. Next, the substrate was set at a predetermined position in an arc ion plating device (manufactured by Kobe Steel, Ltd., trade name: AIP).

[0159] <First layer coating process>

[0160] As the first layer coating process, the first layer is formed on the above-mentioned substrate by arc ion plating. Specifically, it is carried out by the following method. First, a WC target (a sintered target having a composition of binderless WC containing more than 93% by mass of WC and a C content of more than 3% by mass and less than 6.1% by mass) is set in two arc evaporation sources facing each other in the device. The substrate (substrate) temperature is set to more than 400°C and less than 550°C, and the gas pressure in the device is set to more than 1.0Pa and less than 4.0Pa.

[0161] As the gas, only argon gas or a mixed gas of methane gas and argon gas, which are hydrocarbon-based gases, is introduced.

[0162] In samples 1 to 27, while the substrate (negative) bias voltage was maintained at 10 V to 150 V and DC or pulsed DC (frequency 20 kHz to 350 kHz), an arc current of 80 A to 150 A was supplied to the cathode electrode to generate metal ions from an arc evaporation source, thereby forming the first layer. During film formation, the tungsten filament was also discharged (the emission current was 10 A to less than 25 A).

[0163] In samples 1-3 and 1-4, the substrate (negative) bias voltage was maintained at 160 V and the first layer was formed by supplying an arc current of 80 A to 150 A to the cathode electrode to generate metal ions from an arc evaporation source while maintaining DC or pulsed DC (frequency 20 kHz to 350 kHz). During film formation, the tungsten filament was also discharged (radiation current 5 A to 9.5 A).

[0164] <Third layer coating process>

[0165] For the samples (samples 18 to 23) in which the third layer is provided between the substrate and the first layer, the third layer is formed on the substrate by the following steps before the first layer coating process is performed. First, a target (sintered target or smelted target) containing the metal composition in the composition column of the third layer described in Tables 1 and 2 is set in an arc evaporation source of an arc ion plating device. Next, the substrate temperature is set to be above 400°C and below 650°C, and the gas pressure in the device is set to be above 0.8Pa and below 5Pa. In the case where the third layer is a nitride, a mixed gas of nitrogen and argon is introduced as a reaction gas. In the case where the third layer is a carbonitride, a mixed gas of nitrogen, methane gas and argon is introduced as a reaction gas. Then, an arc current of 80A or more and 150A or less is supplied to the cathode electrode. By supplying an arc current to generate metal ions, etc. from the arc evaporation source, a third layer having a thickness as described in Tables 1 and 2 is formed. In the case of forming the third layer of the multilayer structure (sample 21), the 1A unit layer and the 2A unit layer were repeatedly stacked in order from the layer described on the left side of Table 1 until the target thickness was reached, thereby forming the third layer.

[0166] <Second layer coating process>

[0167] In addition, for the samples (samples 22 and 23) in which the second layer was provided on the first layer, after the first layer covering step, the second layer was formed on the first layer by the following steps, thereby producing the cutting tool according to the present embodiment.

[0168] In sample 22, a TiB2 layer as the second layer was produced by the HiPIMS method. First, a TiB2 target was set in a HiPIMS evaporation source of a composite device of an arc ion plating device and a HiPIMS device. Next, the chamber was evacuated and an inert gas (Ar) was introduced. Next, a bias voltage was applied to the substrate via a bias power supply, and pulse power was supplied to the target via a HiPIMS power supply, thereby starting a film forming operation relative to the HiPIMS device. The film forming conditions are as follows.

[0169] (film forming conditions)

[0170] Target: TiB2

[0171] Ar pressure: 0.4Pa

[0172] Average power: 5kW

[0173] Output frequency: 800Hz

[0174] Duty ratio: 5%

[0175] Bias voltage: 50V

[0176] Substrate temperature: 450°C

[0177] As a result, plasma is generated in the chamber, and ions collide with the TiB2 target, releasing Ti atoms, Bi atoms, Ti ions, and Bi ions from the TiB2 target, thereby forming a TiB2 layer having a thickness described in Table 1 on the substrate.

[0178] In sample 23, first, a target material (sintered target material or smelted target material) containing a metal composition in the composition column of the second layer described in Table 2 is set in an arc evaporation source of an arc ion plating device. Next, the substrate temperature is set to be greater than 500°C and less than 650°C, and the gas pressure in the device is set to be greater than 0.8Pa and less than 5.0Pa. In the case where the second layer is a nitride, a mixed gas of nitrogen and argon is introduced as a reaction gas. Then, an arc current of greater than 80A and less than 150A is supplied to the cathode electrode. By supplying an arc current to generate metal ions, etc. from the arc evaporation source, the first unit layer and the second unit layer are repeatedly stacked in sequence starting from the layer described on the left side of Table 2 until the target thickness is reached, thereby forming the second layer.

[0179] [Sample 1-1]

[0180] <Base material preparation process>

[0181] In the substrate preparation step, the same substrate as that of the above-mentioned sample 1 was prepared, and the substrate was set at a predetermined position in an arc ion plating apparatus (manufactured by Kobe Steel, Ltd., trade name: AIP).

[0182] <First layer coating process>

[0183] As the first layer coating process, a first layer is formed on the above-mentioned substrate by arc ion plating. Specifically, it is carried out by the following method. First, a WC target (a sintered target having a composition of binder-free WC containing more than 93% by mass of WC and a C content of more than 3% by mass and less than 6.1% by mass) is set in two arc evaporation sources facing each other in the device. The substrate (substrate) temperature is set to more than 400°C and less than 550°C, and the gas pressure in the device is set to more than 0.3Pa and less than 1.5Pa. As the above-mentioned gas, only argon gas is introduced.

[0184] While the substrate (negative) bias voltage was maintained at 40 V and DC, an arc current of 130 A was supplied to the cathode electrode to generate metal ions and the like from an arc evaporation source, thereby forming a first layer.

[0185] [Sample 1-2]

[0186] <Base material preparation process>

[0187] In the substrate preparation step, the same substrate as that of the above-mentioned sample 1 was prepared, and the substrate was set at a predetermined position in an arc ion plating apparatus (manufactured by Kobe Steel, Ltd., trade name: AIP).

[0188] <First layer coating process>

[0189] As the first layer coating process, the first layer is formed on the above-mentioned substrate by arc ion plating. Specifically, it is carried out by the following method. First, a WC target (for example, a sintered target having a composition of binderless WC containing more than 93% by mass of WC and a C content of more than 3% by mass and less than 6.1% by mass) is set in two arc evaporation sources facing each other in the device. The substrate (substrate) temperature is set to more than 400°C and less than 550°C, and the gas pressure in the device is set to more than 0.3Pa and less than 1.5Pa.

[0190] As the gas, a mixed gas of methane gas and argon gas, which are hydrocarbon-based gases, is introduced.

[0191] While the substrate (negative) bias voltage was maintained at 20 V and DC, a pulse arc current of 120 A (frequency 0.25 Hz) was supplied to the cathode electrode to generate metal ions and the like from an arc evaporation source, thereby forming a first layer.

[0192] [Sample 1-5]

[0193] <Base material preparation process>

[0194] In the substrate preparation step, the same substrate as that of the above-mentioned sample 1 was prepared, and the substrate was set at a predetermined position in an arc ion plating apparatus (manufactured by Kobe Steel, Ltd., trade name: AIP).

[0195] <First layer coating process>

[0196] As the first layer coating process, the first layer is formed on the above-mentioned substrate by arc ion plating. Specifically, it is carried out by the following method. First, a WC target (for example, a sintered target composed of WC and a C content of 3 mass % or more and 6.1 mass % or less) is set in two arc evaporation sources facing each other in the device. The substrate (substrate) temperature is set to 450°C, and the gas pressure in the device is set to 1.0 Pa or more and 1.5 Pa or less.

[0197] As the above-mentioned gas, only argon gas was introduced.

[0198] The substrate (negative) bias voltage was set to 30 V pulse DC (alternating application frequencies of 30 kHz and 200 kHz), and an arc current of 150 A was supplied to the cathode electrode to generate metal ions and the like from an arc evaporation source, thereby forming a first layer.

[0199] 《Evaluation of cutting tool characteristics》

[0200] Using the cutting tools of the samples (Samples 1 to 27, Samples 1-1 to 1-5) prepared as described above, various characteristics of the cutting tools were evaluated as follows.

[0201] (Composition of the first layer)

[0202] By irradiating X-rays to the surface of each sample on the opposite side of the substrate, the first layer is subjected to XRD measurement to determine the composition and crystal structure of the first layer. It should be noted that when the second layer and / or the third layer are formed, the measurement is performed after these layers are mechanically removed. The specific measurement method is described in Embodiment 1, so its description will not be repeated.

[0203] The results are shown in the "Composition" column of the "First Layer" in Tables 1 and 2. In the "Composition" column, "W+hW2C" means that the first layer is composed of metal tungsten and hexagonal tungsten carbide, "W" means that the first layer is composed of metal tungsten, "W+cWC+hW2C" means that the first layer is composed of metal tungsten, cubic tungsten carbide and hexagonal tungsten carbide, and "hW2C" means that the first layer is composed of hexagonal tungsten carbide.

[0204] (Elastic deformation rate)

[0205] The surface of each sample was polished with diamond paper or diamond paste to expose the first layer, and the elastic deformation rate of the first layer was measured. The specific measurement method is described in Embodiment 1, so the description thereof will not be repeated. The results are shown in Tables 1 and 2.

[0206] (Thickness of each layer)

[0207] The thickness of the first layer, the third layer, the second layer (the first unit layer, the second unit layer) and the coating was determined as follows. First, a transmission electron microscope (TEM) (manufactured by JEOL Ltd., trade name: JEM-2100F) was used to measure at any three points in the cross-section sample parallel to the normal direction of the surface of the substrate. Then, the thickness was determined by taking the average value of the thickness of the three points measured. The results are shown in the "Thickness" column of each layer in Tables 1 and 2.

[0208] In Tables 1 and 2, the expression "-" in "third layer" and "second layer" indicates that the layer does not exist in the coating. The expression "TiAlBN (8nm) / TiAlCrN (14nm)" in "third layer" indicates that the third layer is formed by a multilayer structure (total thickness of 2.0μm) in which a TiAlBN layer with a thickness of 8nm and a TiAlCrN layer with a thickness of 14nm are alternately stacked up and down. The expression "TiN (10nm) / TiBN (2nm)" in "second layer" indicates that the second layer is formed by a multilayer structure (total thickness of 1.5μm) in which a TiN layer with a thickness of 10nm (first unit layer) and a TiBN layer with a thickness of 2nm (second unit layer) are alternately stacked up and down.

[0209] [Table 1]

[0210]

[0211] [Table 2]

[0212]

[0213] 《Cutting Test》

[0214] Using each cutting tool produced as described above, the cutting time (tool life) until the cutting tool was broken was measured under the following cutting conditions. The results are shown in the "Tool Life" column of "Cutting Test" in Table 2.

[0215] (Cutting conditions)

[0216] Cutting material (material): Ti-6Al-4V

[0217] Speed: V50m / min

[0218] Feed: 0.1mm / edge

[0219] Cutting amount: ad10mm, ae10mm

[0220] The above-mentioned cutting conditions correspond to the milling process of titanium alloy, and a high thermal load is applied to the cutting tool during the machining.

[0221] The cutting tools of samples 1 to 27 correspond to the examples, and the cutting tools of samples 1-1 to 1-5 correspond to the comparative examples. From the results of the above cutting tests, it can be seen that the cutting tools of samples 1 to 27 have excellent defect resistance and long tool life compared with the cutting tools of samples 1-1 to 1-5. This suggests that the cutting tools of samples 1 to 27 are suitable for use in an environment with high heat load during processing.

[0222] As mentioned above, although the embodiment and the example of the present disclosure have been described, it is initially intended that the configurations of the above-mentioned respective embodiments and the examples can be appropriately combined.

[0223] The embodiments and examples disclosed herein are illustrative in all aspects and are not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0224] Explanation of symbols

[0225] 1 rake face, 2 flank face, 3 cutting edge ridge, 10 cutting tool, 11 substrate, 12 first layer, 13 second layer, 131 first unit layer, 132 second unit layer, 14 third layer, 141 1A unit layer, 142 2A unit layer.

Claims

1. A cutting tool comprising: A substrate and a coating disposed on the substrate, The coating includes a first layer composed of metallic tungsten and hexagonal tungsten carbide. In the first layer, the content ratio of unavoidable impurities is not less than 0 mass % and not more than 0.2 mass % relative to the total mass of the first layer, The elastic deformation rate of the first layer is 43.0 or more and 58.0 or less, The thickness of the first layer is not less than 0.3 μm and not more than 4.0 μm, The elastic deformation rate is measured by a nanoindentation test according to ISO14577 with a test load of 20 mN.

2. The cutting tool according to claim 1, wherein: The coating further includes a second layer disposed on the first layer, The second layer includes at least a first unit layer having a composition different from that of the first layer, The first unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon in the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron.

3. The cutting tool according to claim 2, wherein: The second layer further comprises a second unit layer, The second unit layer has a different composition from the first layer and the first unit layer, The second unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon of the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron, The first unit layer and the second unit layer form a multilayer structure in which one or more layers of each are alternately stacked.

4. The cutting tool according to claim 3, wherein: The thickness of the first unit layer is greater than or equal to 1 nm and less than or equal to 100 nm, and the thickness of the second unit layer is greater than or equal to 1 nm and less than or equal to 100 nm.

5. The cutting tool according to claim 1, wherein: The coating further includes a third layer disposed below the first layer, The third layer includes at least a 1A unit layer having a composition different from that of the first layer, The 1A unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon in the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron.

6. The cutting tool according to claim 5, wherein: The third layer further comprises a 2A unit layer, The 2A unit layer has a composition different from that of the first layer and the 1A unit layer, The second A unit layer is composed of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum and silicon of the periodic table; or a compound composed of at least one of the elements and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron, The first A unit layer and the second A unit layer form a multilayer structure in which one or more layers of each are alternately stacked.

7. The cutting tool according to claim 6, wherein: The thickness of the first A unit layer is greater than or equal to 1 nm and less than or equal to 100 nm, and the thickness of the second A unit layer is greater than or equal to 1 nm and less than or equal to 100 nm.

8. The cutting tool according to claim 1, wherein The substrate includes at least one selected from the group consisting of cemented carbide, cermet, high-speed steel, ceramic, cBN sintered body, and diamond sintered body.

9. The cutting tool according to claim 2, wherein The second layer is composed only of the first unit layer, The thickness of the second layer is not less than 0.1 μm and not more than 10 μm.

10. The cutting tool according to claim 3 or claim 4, wherein The thickness of the second layer is not less than 0.1 μm and not more than 10 μm.

11. The cutting tool according to claim 5, wherein The third layer is composed only of the 1A unit layer, The thickness of the third layer is not less than 0.1 μm and not more than 10 μm.

12. The cutting tool according to claim 6 or claim 7, wherein The thickness of the third layer is not less than 0.1 μm and not more than 10 μm.

13. The cutting tool according to claim 2, wherein The compound is at least one compound selected from the group consisting of TiB 2 , TiN and TiBN.

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