Cutting tools

Abstract

A cutting tool including a rake face and a flank face, the cutting tool comprising a substrate and a coating provided on the substrate, the coating including a MAlN layer, the MAlN layer being a cubic M x Al 1-x Contains N crystal grains, and the above M x Al 1-x The atomic ratio x of the metal element M in N is 0.2 or more and 0.8 or less, M in the MAlN layer represents a metal element containing titanium, chromium, or both, and in a cross section of the MAlN layer cut along a plane including a normal to the rake face, the number of voids n per 50 μm length of the MAlN layer on the rake face is R is 3 or less, and the cross-sectional area of ​​the void is 1.0 × 10 -4 μm 2 More than 0.5μm 2 Below are cutting tools.

Description

[Technical Field]

[0001] The present disclosure relates to cutting tools. [Background technology]

[0002] Cubic boron nitride (hereinafter referred to as "cBN") is second only to diamond in hardness and has excellent thermal and chemical stability. Furthermore, because it is more stable than diamond when used on ferrous materials, cBN sintered compacts have been used as cutting tools for machining ferrous materials.

[0003] Furthermore, in order to improve the wear resistance of cutting tools made of sintered cBN, it has been considered to provide a coating on the base material of the sintered cBN. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 024737 [Patent Document 2] International Publication No. 2022 / 230182 Summary of the Invention

[0005] The cutting tool according to the present disclosure comprises: 1. A cutting tool including a rake face and a flank face, the cutting tool comprises a substrate and a coating provided on the substrate; the coating comprises a MAlN layer; The MAlN layer is a cubic M x Al 1-x Contains N crystal grains, Said M x Al 1-x the atomic ratio x of the metal element M in N is 0.2 or more and 0.8 or less; M in the MAlN layer represents a metal element including titanium, chromium, or both; In a cross section of the MALN layer cut along a plane including a normal to the rake face, the number of voids n per 50 μm length of the MALN layer on the rake face R is less than or equal to 3, The cross-sectional area of ​​the void is 1.0×10 -4 μm 2 More than 0.5μm 2 The following is the result. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view illustrating an embodiment of a cutting tool. [Figure 2] FIG. 2 is a schematic cross-sectional view of a cutting tool according to one aspect of the present embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view of a cutting tool according to another aspect of the present embodiment. [Figure 6] FIG. 6 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment. [Figure 7] FIG. 7 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment. [Figure 8] FIG. 8 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment. [Figure 9] FIG. 9 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment. [Figure 10] FIG. 10 is an enlarged BSE image of a cross section of the cutting tool according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by this disclosure] For example, in International Publication No. 2021 / 024737 (Patent Document 1), 1. A cutting tool including a rake face and a flank face, the cutting tool comprises a substrate made of a cubic boron nitride sintered body and a coating provided on the substrate; The cubic boron nitride sintered body contains cubic boron nitride, the coating comprises a MAlN layer; M in the MAlN layer represents a metal element including titanium, chromium, or both; The MAlN layer is a cubic M x Al 1-x Contains N crystal grains, The above M x Al 1-x the atomic ratio x of the metal element M in N is 0.3 or more and 0.7 or less; the content of the cubic boron nitride is 20% by volume or more relative to the cubic boron nitride sintered body, In a cross section of the MALN layer cut along a plane including the normal to the flank, the number of voids per 100 μm length of the MALN layer on the flank is defined as n F year, In the cross section of the MALN layer cut along a plane including the normal to the rake face, the number of voids per 100 μm length of the MALN layer on the rake face is defined as n R In this case, n F <n R Fulfilling In a cross section of the MALN layer cut along a plane including the normal to the flank, the number of droplets n per 100 μm length of the MALN layer on the flank D A cutting tool is disclosed in which the .gtoreq..times.3 ...

[0008] In addition, in International Publication No. 2022 / 230182 (Patent Document 2), 1. A cutting tool including a rake face and a flank face, The cutting tool includes a substrate and a coating provided on the substrate, the coating comprises a TiMAlN layer; The TiMAlN layer is a cubic Ti x My Al z Contains N crystal grains, The above Ti x M y Al z the atomic ratio x of titanium element in N is 0.4 or more and 0.79 or less, The above Ti x M y Al z the atomic ratio y of the element M in N is 0.01 or more and 0.1 or less; The above Ti x M y Al z The atomic ratio z of aluminum element in N is 0.2 or more and 0.5 or less, the sum of x, y, and z is 1, the element M is at least one of boron and silicon, or both; The number n of voids per 100 μm length of the TiMAlN layer located on the flank in a cross section of the TiMAlN layer cut along a plane including a normal to the flank. F and the number n of voids per 100 μm length of the TiMAlN layer located on the rake face in a cross section of the TiMAlN layer cut along a plane including a normal to the rake face. R What is that? n F <n R Fulfilling the relationship, The number n of droplets per 100 μm length of the TiMAlN layer located on the flank surface in a cross section of the TiMAlN layer cut along a plane including a normal to the flank surface. D is 3 or less.

[0009] However, the MAlN or TiMAlN layer in the cutting tools of Patent Documents 1 and 2 contains minute voids that are not counted in these documents, and these minute voids can cause chipping of the coating and substrate during cutting. Therefore, when applying these to highly efficient cutting (such as cutting with a high feed rate), further improvements in performance (e.g., chipping resistance) are required.

[0010] The present disclosure has been made in view of the above circumstances, and has an object to provide a cutting tool with excellent fracture resistance.

[0011] [Effects of this disclosure] According to the present disclosure, it is possible to provide a cutting tool with excellent chipping resistance.

[0012] [Outline of the embodiment] First, embodiments of the present disclosure will be listed and described. [1] The cutting tool according to the present disclosure comprises: 1. A cutting tool including a rake face and a flank face, The cutting tool includes a substrate and a coating provided on the substrate, the coating comprises a MAlN layer; The MAlN layer is a cubic M x Al 1-x Contains N crystal grains, The above M x Al 1-x the atomic ratio x of the metal element M in N is 0.2 or more and 0.8 or less; M in the MAlN layer represents a metal element including titanium, chromium, or both; In a cross section of the MALN layer cut along a plane including the normal to the rake face, the number of voids n per 50 μm length of the MALN layer on the rake face R is less than or equal to 3, The cross-sectional area of ​​the void is 1.0 x 10 -4 μm 2 More than 0.5μm 2 The following is the result.

[0013] The number of voids per 50 μm length of the MALN layer on the rake face, n R The cutting tool has excellent chipping resistance when the value of the cross section is 3 or less. Here, "chip resistance" means resistance to chipping of the MAlN layer from the substrate.

[0014] [2] In a cross section of the MALN layer cut along a plane including the normal to the flank, the number of voids n per 50 μm length of the MALN layer on the flank F may be 3 or less. By specifying it in this way, the cutting tool has excellent wear resistance in addition to excellent chipping resistance. Here, "wear resistance" means resistance to wear of the MALN layer during cutting.

[0015] [3] Further including a cutting edge surface connecting the rake face and the flank face, In a cross section of the MALN layer cut along a plane including a normal to the cutting edge surface, the number of voids n per 50 μm length of the MALN layer on the cutting edge surface C may be equal to or less than 3. By specifying it in this way, the cutting tool has even better fracture resistance.

[0016] [4] The above n F is 3 or less, and the above n R is 3 or less, and the above n C may be equal to or less than 3. By specifying it in this way, the cutting tool has excellent wear resistance in addition to excellent fracture resistance.

[0017] [5] The metal element M may further include at least one element selected from the group consisting of boron, silicon, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. By specifying this, the cutting tool has excellent heat resistance and lubricity in addition to excellent fracture resistance.

[0018] [6] The substrate may include at least one material selected from the group consisting of cemented carbide, cermet, high-speed steel, ceramics, cubic boron nitride sintered body, and diamond sintered body. By specifying the substrate in this manner, the cutting tool has excellent versatility in terms of machining conditions.

[0019] [7] Surface roughness R of the above substrate maxBy specifying the thickness in this way, the cutting tool has even better fracture resistance.

[0020] [8] The coating may further include an underlayer disposed between the substrate and the MAlN layer, and the composition of the underlayer may be different from the composition of the MAlN layer. By specifying in this way, the cutting tool has excellent versatility in terms of machining conditions.

[0021] [9] The coating further includes a surface layer formed on the MAlN layer, and the composition of the surface layer may be different from that of the MAlN layer. By specifying in this way, the cutting tool has excellent versatility in machining conditions and excellent visibility of used cutting edges.

[0022]

[10] The thickness of the MAlN layer may be 0.1 μm or more and 2.0 μm or less. By specifying it in this way, the cutting tool has even better chipping resistance.

[0023]

[11] The thickness of the coating may be 0.1 μm or more and 2.5 μm or less. By specifying it in this way, the cutting tool has even better fracture resistance.

[0024] [Details of the embodiment] Hereinafter, one embodiment of the present disclosure (hereinafter referred to as "this embodiment") will be described. However, this embodiment is not limited to this. In this specification, the notation in the format "A to Z" means the upper and lower limits of a range (i.e., A or more and Z or less), and when no unit is specified for A and only a unit is specified for Z, the unit of A and the unit of Z are the same. Furthermore, in this specification, when a compound is expressed by a chemical formula in which the composition ratio of the constituent elements is not limited, such as "TiN", this chemical formula is considered to include all conventionally known composition ratios (element ratios). In this case, the above chemical formula is considered to include not only stoichiometric compositions but also non-stoichiometric compositions. For example, the chemical formula of "TiN" includes not only the stoichiometric composition "Ti1N1", but also other compositions such as "Ti1N 0.8This also applies to descriptions of compounds other than "TiN."

[0025] ≪Surface coated cutting tools≫ The cutting tool according to the present disclosure comprises: 1. A cutting tool including a rake face and a flank face, the cutting tool comprises a substrate and a coating provided on the substrate; the coating comprises a MAlN layer; The MAlN layer is a cubic M x Al 1-x Contains N crystal grains, Said M x Al 1-x the atomic ratio x of the metal element M in N is 0.2 or more and 0.8 or less; M in the MAlN layer represents a metal element including titanium, chromium, or both; In a cross section of the MALN layer cut along a plane including a normal to the rake face, the number of voids n per 50 μm length of the MALN layer on the rake face R is less than or equal to 3, The cross-sectional area of ​​the void is 1.0×10 -4 μm 2 More than 0.5μm 2 The following is the result.

[0026] The surface-coated cutting tool according to this embodiment (hereinafter, sometimes simply referred to as "cutting tool") may be, for example, a drill, an end mill, an indexable cutting tip for a drill, an indexable cutting tip for an end mill, an indexable cutting tip for milling, an indexable cutting tip for turning, a metal saw, a gear cutting tool, a reamer, a tap, etc.

[0027] 1 is a perspective view illustrating one embodiment of a cutting tool 10. A cutting tool 10 having such a shape is used as an indexable cutting insert for turning.

[0028] 1 has a surface including an upper surface, a lower surface, and four side surfaces, and has an overall rectangular prism shape that is slightly thin in the vertical direction. Furthermore, the cutting tool 10 has a through-hole that penetrates the upper and lower surfaces, and adjacent side surfaces are connected at the boundaries between the four side surfaces by arcuate surfaces.

[0029] In the cutting tool 10, the upper and lower surfaces usually form the rake face 1a, the four side surfaces (and the arc surfaces connecting them) form the flank face 1b, and the surface connecting the rake face 1a and the flank face 1b forms the cutting edge face 1c. The "rake face" refers to the surface that scoops out chips cut from the workpiece. The "flank face" refers to the surface that contacts the workpiece. The cutting edge face is included in the part that makes up the cutting edge of the cutting tool.

[0030] When the cutting tool is an indexable cutting insert, the cutting tool 10 may have a shape with or without a chip breaker. In Fig. 1, the shape of the cutting edge of the cutting tool is shown as a flat surface (cutting edge surface 1c), but the shape of the cutting edge is not limited to this. In other words, the shape of the cutting edge includes a sharp edge (the ridge where the rake face and flank intersect) (e.g., Fig. 3) and a negative land (chamfered shape) (e.g., Fig. 2).

[0031] The shape and names of the components of cutting tool 10 have been described above using FIG. 1 . However, the same terms as above will be used for the shape and names of the components of the cutting tool substrate according to this embodiment that correspond to cutting tool 10. That is, the cutting tool substrate has a rake face and a flank. The substrate may also have a cutting edge surface connecting the rake face and the flank.

[0032] The cutting tool 10 includes a substrate 11 and a MAlN layer 12 provided on the substrate 11 (FIG. 4). In addition to the MAlN layer 12, the cutting tool 10 may further include a base layer 13 provided between the substrate 11 and the MAlN layer 12 (FIG. 5). The cutting tool 10 may further include a surface layer 14 provided on the MALN layer 12 (FIG. 5). The other layers, such as the base layer 13 and the surface layer 14, will be described later. The above-described layers provided on the substrate may be collectively referred to as a "coating." That is, the cutting tool 10 includes a coating 20 that covers the substrate 11 (FIGS. 2 and 3). The coating 20 includes the MAlN layer 12 (FIG. 4). The coating 20 may further include the underlayer 13 or the surface layer 14 (FIG. 5).

[0033] <Base material> The substrate of this embodiment can be any known substrate of this type. For example, the substrate may include at least one selected from the group consisting of cemented carbide (for example, tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide containing Cr, Ti, Ta, Nb, or other carbonitrides in addition to WC), cermet (mainly composed of TiC, TiN, TiCN, or the like), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, or the like), cubic boron nitride sintered body (cBN sintered body), and diamond sintered body.

[0034] Among these various substrates, cemented carbide (particularly WC-based cemented carbide), cermet (particularly TiCN-based cermet), and cubic boron nitride sintered body may be selected because these substrates have an excellent balance between hardness and strength, especially at high temperatures, and have excellent properties as substrates for cutting tools for the above-mentioned applications.

[0035] When a cemented carbide is used as the substrate, the effect of this embodiment is exhibited even if the cemented carbide contains free carbon or an abnormal phase called the η phase in its structure. The substrate used in this embodiment may have a modified surface. For example, a de-β layer may be formed on the surface of a cemented carbide, or a surface-hardened layer may be formed on the surface of a cBN sintered compact. The effect of this embodiment is exhibited even if the surface is modified in this way.

[0036] Surface roughness R of the above substrate max The surface roughness R of the substrate may be 1 μm or less, or may be 0.5 μm or less. max The lower limit of the surface roughness is not particularly limited, but may be, for example, 0.1 μm or more. The surface roughness can be measured in accordance with JIS B06012001 using a stylus surface roughness measuring instrument with a cutoff value of 0.3 mm, a reference length of 0.8 mm, and a scanning speed of 0.06 mm / sec.

[0037] (cubic boron nitride sintered body) In one aspect of this embodiment, the substrate may be a cubic boron nitride sintered body (cBN sintered body). The cubic boron nitride sintered body includes cubic boron nitride. In one aspect of this embodiment, the cubic boron nitride sintered body may further include a binder.

[0038] (cubic boron nitride) In this embodiment, "cubic boron nitride" refers to cubic boron nitride crystal grains. That is, the cubic boron nitride sintered body contains polycrystalline cubic boron nitride.

[0039] The content of the cubic boron nitride may be 20% by volume or more, 20% by volume to 97% by volume or less, or 20% by volume to 80% by volume, relative to the cubic boron nitride sintered body. The content (volume %) of the cubic boron nitride in the cubic boron nitride sintered body and the content (volume %) of the binder (binding phase) described below can be confirmed by performing structural observation, elemental analysis, etc. on the cubic boron nitride sintered body using an energy dispersive X-ray analyzer (EDX) "Octane Elect EDS System" (trademark) attached to a scanning electron microscope (SEM) ("JEOL Ltd. JSM-7800F" (trademark)).

[0040] Specifically, the cubic boron nitride content (volume %) can be determined as follows. First, a cubic boron nitride sintered body is cut at an arbitrary position to prepare a sample containing a cross section of the cubic boron nitride sintered body. A focused ion beam device, a cross-section polisher device, or the like can be used to prepare the cross section. Next, the cross section is observed at 5000x magnification using an SEM to obtain a backscattered electron image. In the backscattered electron image, cubic boron nitride particles appear black (dark field), and the area where the binder is present appears gray or white (bright field).

[0041] Next, the backscattered electron image is binarized using image analysis software (for example, "WinROOF" by Mitani Corporation). From the binarized image, the area ratio of pixels originating from the dark field (pixels originating from cubic boron nitride) to the area of ​​the measurement field is calculated. By regarding the calculated area ratio as volume %, the content (volume %) of cubic boron nitride can be determined.

[0042] The ratio obtained by the above method is the area ratio of cubic boron nitride in the field of view, but in this embodiment, this area ratio is treated as a volume ratio. That is, if the area ratio of cubic boron nitride obtained by the above method is 20%, the content of cubic boron nitride is considered to be 20 volume% with respect to the cubic boron nitride sintered body.

[0043] The median diameter D of the above cubic boron nitride 50 The thickness may be 0.1 μm or more and 5 μm or less, or 0.2 μm or more and 3 μm or less.

[0044] Cubic boron nitride D 50 can be determined as follows. First, a sample containing a cross section of a cubic boron nitride sintered body is prepared in accordance with the method for determining the cubic boron nitride content described above, and a backscattered electron image is obtained. Next, image analysis software ("WinROOF (ver. 7.4.5)" by Mitani Corporation) is used to calculate the equivalent circle diameter of each dark field (equivalent to cBN) in the backscattered electron image. It is preferable to calculate the equivalent circle diameter of 100 or more cubic boron nitride particles by observing five or more fields of view.

[0045] Next, arrange each circle equivalent diameter in ascending order from the smallest to the largest value to determine the cumulative distribution. The particle diameter at which the cumulative area reaches 50% in the cumulative distribution is D 50 The circle equivalent diameter means the diameter of a circle having the same area as the measured area of ​​a particle of cubic boron nitride.

[0046] (binder) In this embodiment, the term "binder" refers to a substance that binds the crystal grains of the cubic boron nitride together. The binder may contain a compound consisting of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al (aluminum), and Si (silicon) in the periodic table of the elements, and at least one element selected from the group consisting of C (carbon), N (nitrogen), B (boron), and O (oxygen).

[0047] Examples of the Group 4 elements include Ti (titanium), Zr (zirconium), and Hf (hafnium). Examples of the Group 5 elements include V (vanadium), Nb (niobium), and Ta (tantalum). Examples of the Group 6 elements include Cr (chromium), Mo (molybdenum), and W (tungsten). The components contained in the binder can be determined by analyzing a region corresponding to the binder of a sample including the cut surface of the cutting tool using an energy dispersive X-ray spectroscopy (SEM-EDX) attached to an SEM. The observation magnification is, for example, 10,000 times.

[0048] Examples of compounds consisting of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, Al and Si in the periodic table of the elements, and at least one element selected from the group consisting of C, N, B and O include nitrides such as TiN and AlN, carbides such as TiC and WC, borides such as TiB2 and AlB2, oxides such as Al2O3, and the like, as well as TiCN, AlON, SiAlON, SiTiAlON, etc.

[0049] (unavoidable impurities) The cubic boron nitride sintered body may contain unavoidable impurities to the extent that the effects of the present disclosure are not impaired. "Avoidable impurities" refers to elements and compounds that may be contained in trace amounts in the raw materials of the cubic boron nitride sintered body or during its production. The content (volume %) of each element and compound contained as an unavoidable impurity may be 0% to 5% by volume, and the sum of these elements and compounds (i.e., the total content of trace impurities) may be 0% to 5% by volume. Therefore, the cubic boron nitride sintered body may or may not contain unavoidable impurities. Examples of unavoidable impurities include Li, Mg, Ca, Sr, Ba, Be, Si, Ga, La, Fe, and Cu.

[0050] <Coating> The coating according to this embodiment includes a MAlN layer. M in the MAlN layer represents a metal element including titanium, chromium, or both. The "coating" has the effect of improving various properties of the cutting tool, such as chipping resistance and wear resistance, by covering at least a portion of the substrate (e.g., a portion of the rake face and a portion of the flank face). The coating may cover the entire surface of the substrate. However, even if a portion of the substrate is not covered with the coating or the coating has a partially different configuration, it does not deviate from the scope of this embodiment.

[0051] The thickness of the coating may be 0.1 μm to 2.5 μm, 0.3 μm to 2.5 μm, or 0.5 μm to 1.5 μm. Here, the thickness of the coating refers to the sum of the thicknesses of the layers constituting the coating. Examples of "layers constituting the coating" include the MAlN layer, the intermediate layer described below, and other layers such as the base layer and surface layer described above. The thickness of the coating can be determined, for example, by measuring 10 arbitrary points on a cross-sectional sample parallel to the normal direction of the substrate surface using an SEM and averaging the thicknesses measured at the 10 points. The measurement magnification is, for example, 10,000x. The same applies when measuring the thickness of the MALN layer, the intermediate layer, the base layer, and the surface layer described above. Examples of SEMs include the JSM-7600F (product name) and JSM-7800 (product name) manufactured by JEOL Ltd.

[0052] (MAlN layer) The MAlN layer is a cubic M x Al 1-x In other words, the MAlN layer contains polycrystalline M x Al 1-x This is a layer containing N. Cubic M x Al 1-x N crystal grains can be identified, for example, by the diffraction peak pattern obtained by X-ray diffraction.

[0053] In the MAlN layer, M represents a metal element. The metal element M includes titanium, chromium, or both. In one aspect of this embodiment, the metal element M may further include at least one element (hereinafter sometimes referred to as a "third element") selected from the group consisting of boron, silicon, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. Note that boron is generally considered to be a semimetal that exhibits properties intermediate between metallic elements and non-metallic elements. However, in the MAlN layer of this embodiment, elements having free electrons are considered to be metals, and boron is included in the range of metallic elements.

[0054] In one aspect of this embodiment, the metal element M may be titanium. That is, the coating includes a TiAlN layer as the MAlN layer, and the TiAlN layer is a cubic Ti x Al 1-x The TiAlN layer may contain polycrystalline TiN crystal grains. x Al 1-x This layer contains N. Cubic Ti x Al 1-x N crystal grains can be identified, for example, by the diffraction peak pattern obtained by X-ray diffraction.

[0055] The above M x Al 1-xThe atomic ratio x of the metal element M in N is 0.2 or more and 0.8 or less, and may be 0.4 or more and 0.65 or less. The x can be determined by performing elemental analysis of the entire MAlN layer on the cross-sectional sample using an energy dispersive X-ray spectroscopy (SEM-EDX) attached to an SEM. The observation magnification is, for example, 5000x. Specifically, the x value is determined by measuring 10 arbitrary points on the MAlN layer of the cross-sectional sample, and the average of the values ​​determined at the 10 points is defined as the x value of the MAlN layer. Here, when the metal element M contains multiple metal elements, the sum of the atomic ratios of the respective metal elements is the atomic ratio x of the metal element M. The "arbitrary 10 points" are selected from different crystal grains in the MAlN layer. An example of the EDX device is the JED-2300 (product name) manufactured by JEOL Ltd.

[0056] When the metal element M contains titanium, the M x Al 1-x The atomic ratio w of titanium in N may be greater than 0 and not greater than 0.8, or may be 0.4 or greater and 0.65 or less. It goes without saying that when the metal atom M is titanium only, the atomic ratio x of the metal element M and the atomic ratio w of titanium will be the same.

[0057] When the metal element M contains chromium, the M x Al 1-x The atomic ratio y of chromium in N may be greater than 0 and not greater than 0.8, or may be 0.25 or greater and 0.5 or less. When the metal atom M is chromium only, it goes without saying that the atomic ratio x of the metal element M and the atomic ratio y of chromium will be the same.

[0058] When the metal element M contains a third element, the M x Al 1-x The atomic ratio z of the third element in N may be more than 0 and not more than 0.8, or may be 0.01 or more and 0.4 or less. When a plurality of metal elements are contained as the third element, the sum of the atomic ratios of the respective metal elements is the atomic ratio z of the third element.

[0059] The thickness of the MAlN layer may be 0.1 μm or more and 2.0 μm or less, or 0.3 μm or more and 1.4 μm or less. When the MAlN layer forms a multilayer structure as described below, the thickness of the MALN layer refers to the thickness of one layer. The thickness can be measured, for example, by observing the cross section of the cutting tool as described above using an SEM at a magnification of 10,000 times.

[0060] The coating may contain one or more MAlN layers (e.g., 2 to 50 layers). The MAlN layers may be alternately stacked together with other layers such as intermediate layers described below to form a multilayer structure. In one aspect of this embodiment, the MALN layers themselves may form a multilayer structure.

[0061] (Number of voids in the MALN layer) In this embodiment, in a cross section of the MALN layer cut along a plane including a normal to the cutting face, the number of voids n per 50 μm length of the MALN layer on the cutting face is R In this embodiment, in a cross section of the MALN layer cut along a plane including a normal to the flank, the number of voids n per 50 μm length of the MALN layer on the flank is F may be 3 or less.

[0062] In this embodiment, the term "void" refers to a gap having a cross-sectional area of ​​1.0×10 -4 μm 2 More than 0.5μm 2 The voids may extend in the thickness direction of the coating. In this embodiment, the cross-sectional area is 1.0×10 -4 μm 2 The inventors have confirmed that voids having a cross-sectional area of ​​less than 1.0 × 10 are not generated in the cutting tool manufacturing method described below, or even if generated, they are very few. -4 μm 2 There may be voids with a cross-sectional area of ​​less than 1.0×10 -4 μm 2Even if voids having a cross-sectional area of ​​less than 0.5 μm exist, the inventors believe that they cannot become the origin of chipping when subjected to repeated impacts during cutting. 2 The present inventors have confirmed that voids exceeding the cross-sectional area of ​​0.5 μm are not generated in the cutting tool manufacturing method described below. 2 The number of voids in excess of 0 may be zero.

[0063] The number of voids is counted using the following procedure. First, a cross section of the cutting tool as described above is observed at a magnification of 30,000 times using an SEM to obtain an SEM image. At this time, backscattered electron composition images (BSE images) are acquired so that the MAlN layer is continuously included within a range of 50 μm in length (the length in the direction perpendicular to the thickness direction of the MAlN layer) (e.g., Figure 6). The number of BSE images to be acquired is not particularly limited as long as the MALN layer is included within the above-mentioned 50 μm length range, and may be one field of view or multiple fields of view. When BSE images are acquired from multiple fields of view, the BSE images may be stitched together (e.g., Figures 8 and 9) and the number of voids, as described below, may be counted. The size of one field of view may be, for example, 3.7 μm × 2.6 μm.

[0064] The obtained BSE image is converted into a monochrome image of 256 levels within a range excluding the vicinity of the substrate and 30 nm from the film surface (hereinafter referred to as the "evaluation range"). In the evaluation range, the 80th level counted from black is used as the threshold, and binarization processing is performed using image analysis software (for example, "WinROOF" manufactured by Mitani Shoji Co., Ltd.). Then, shape analysis is performed on the part that stands out in the binarization, and a 1.0 x 10 -4 μm 2 More than 0.5μm 2Portions with the following cross-sectional areas are counted as voids (see, for example, Figure 7). Here, if a portion of a void is outside the evaluation range, that void is not counted. The inventors believe that the number of voids is a parameter that reflects the properties of the entire MAlN layer. Note that a void is counted as one whether it penetrates the target MAlN layer or not. For example, in the SEM image (BSE image) shown in Figure 6, the light gray layer is the MAlN layer, and the black dots within that layer are voids. In this case, the number of voids is counted as three (see Figure 7).

[0065] It is believed that some voids are generated starting from the surface of the substrate, while others are generated independently within the membrane structure. The inventors believe that the voids observed in the MAlN layer in the SEM image of the cross-sectional sample are one of these types of voids. The number of such voids is counted in at least three "continuous ranges of 50 μm length," and the average value is taken as the number of voids.

[0066] In principle, the above-mentioned method of counting voids applies to all surfaces, including the flank, rake face, and cutting edge (see, for example, Figures 2 and 3). However, if a "50-μm continuous range" cannot be ensured on the cutting edge, etc., the number of voids is counted within the maximum possible range and converted to the number of voids per 50 μm length to determine the number of voids. For example, if the maximum possible range is 20 μm, the number of voids is counted within the 20-μm range and multiplied by 2.5 to calculate the number of voids per 50 μm length.

[0067] In the cutting tool according to this embodiment, when a cutting edge surface connecting the rake face and the flank is further included, the number of voids per 50 μm length of the MAlN layer on the cutting edge surface is defined as n C In this case, n C may be 3 or less.

[0068] Above n R may be 3 or less, 2 or less, or 1 or less. The voids present on the rake face act as chipping origins when subjected to repeated impacts during cutting. In other words, reducing the number of voids in the MALN layer on the rake face improves chipping resistance.

[0069] Above n F may be 3 or less, 2 or less, or 1 or less. The presence of voids on the flank face may reduce the wear resistance against abrasive wear during cutting, and may accelerate flank wear. In other words, reducing the number of voids in the MALN layer on the flank face improves the wear resistance.

[0070] Above n C may be 3 or less, 2 or less, or 1 or less. Voids present on the cutting edge surface act as chipping origins when repeatedly subjected to impacts during cutting. In other words, reducing the number of voids in the MALN layer on the cutting edge surface further improves chipping resistance.

[0071] In one aspect of this embodiment, the n F is 3 or less, and the above n R is 3 or less, and the above n C In another aspect of this embodiment, the n F is 2 or less, and the above n R is 2 or less, and the above n C may be 2 or less. In another aspect of this embodiment, F is 1 or less, and the above n R is 1 or less, and the above n C may be less than or equal to 1.

[0072] When a coating contains multiple MAlN layers, it is sufficient that at least one of the multiple MAlN layers satisfies the above-mentioned condition regarding the number of voids, because it is believed that the effects of the present disclosure are achieved in the MAlN layer.

[0073] (Number of droplets in the MALN layer) In this embodiment, in a cross section of the MALN layer cut along a plane including a normal to the flank, the number of droplets n per 50 μm length of the MALN layer on the flank is D may be 1 or less, or may be 0.

[0074] In this embodiment, the term "droplet" refers to a metal particle present in a layer constituting the coating (for example, a MAlN layer such as a TiAlN layer) and having a predetermined size, as will be described later. The number of droplets is determined as follows: The cross section of the cutting tool is observed at a magnification of 30,000 times using an SEM to obtain an SEM image. The SEM image is acquired so that the MAlN layer is continuously included within a length of 50 μm. The obtained SEM image is visually inspected, and attention is focused on a white, approximately circular portion present in the MAlN layer (for example, in the layer shown in light gray in Figure 10). Next, the length L of the long side of the rectangle circumscribing this approximately circular portion is calculated. a (μm) and the length of the short side L b (μm). Here, the rectangle is set so that the long side or the short side is parallel to the main surface of the substrate. In this embodiment, "parallel" is not limited to geometric parallel, but also includes the concept of approximately parallel. The calculated L a and L b If the following conditions are met, the approximately circular portion is counted as a droplet. 0.25 <L b / L a ≦1 and 0.1 <L a The number of droplets is counted in at least three locations in a "range of 50 μm in length, consecutively," and the average value is taken as the number of droplets.

[0075] (other layers) The coating may further include other layers as long as the effects of this embodiment are not impaired. Examples of such other layers include a base layer provided between the substrate and the MAlN layer, a surface layer provided on the MAlN layer, and an intermediate layer provided between the base layer and the MAlN layer or between the MAlN layer and the surface layer. The base layer, surface layer, and intermediate layer may have the same or different compositions as the MAlN layer, as long as they are distinguishable from the MAlN layer. The base layer may be, for example, a layer made of a compound represented by TiN. The surface layer may be, for example, a layer made of a compound represented by AlCrN. The intermediate layer may be, for example, a layer made of a compound represented by CrN. The thickness of the other layers is not particularly limited as long as the effects of this embodiment are not impaired, and examples include a range of 0.1 μm to 2 μm.

[0076] <Cutting tool manufacturing method> The method for manufacturing a cutting tool according to this embodiment includes the steps of: A step of preparing the substrate (hereinafter sometimes referred to as "first step"); and forming the MAlN layer on the substrate by high-power pulse sputtering (hereinafter, sometimes referred to as the "second step").

[0077] High-power pulse sputtering (HiPIMS) is a type of sputtering method. Unlike conventional sputtering, HiPIMS is a film formation method in which pulsed power is applied, and atoms of the target (raw material) ejected by discharge are deposited on a substrate or other material.

[0078] In the HiPIMS method, a substrate is placed inside the device, and a target is placed as a cathode. A negative voltage is then applied to the target to generate a discharge. At this time, the device is filled with an inert gas (e.g., Ar gas) under reduced pressure. The discharge ionizes the inert gas inside the device, and the inert gas ions collide with the surface of the target at high speed. This collision ejects atoms from the target, which are then deposited on the substrate to form a coating. Because the HiPIMS method forms films based on the above-mentioned principle, droplets are less likely to be generated than with the arc cathode ion plating method. Furthermore, the inventors believe that by using the HiPIMS method to form a MAlN layer, such as a TiAlN layer, on a substrate made of cubic boron nitride sintered body, some of the voids are generated from the surface of the substrate, while others are generated independently within the film structure. Because the voids are considered to be due to the film formation method, the inventors believe that the voids are also generated when forming layers other than the MAlN layer (e.g., an underlayer, an intermediate layer, etc.).

[0079] <First step: Preparing the substrate> In the first step, a substrate is prepared. Examples of the substrate include cemented carbide, cermet, and cubic boron nitride sintered body. Commercially available substrates may be used. Alternatively, the substrate may be manufactured by a general powder metallurgy method. For example, when manufacturing cemented carbide by a general powder metallurgy method, WC powder and Co powder are first mixed using a ball mill or the like to obtain a mixed powder. The mixed powder is then dried and molded into a predetermined shape to obtain a green body. The green body is then sintered to obtain a WC-Co cemented carbide (sintered body). The sintered body is then subjected to a predetermined cutting edge processing, such as honing, to produce a substrate made of a WC-Co cemented carbide. Depending on the cutting edge processing method, either a substrate with a cutting edge surface (FIG. 2) or a substrate without a cutting edge surface (FIG. 3) can be manufactured. In the first step, any substrate other than those described above can be prepared as long as it is a conventionally known substrate of this type.

[0080] <Second step: Step of forming a MALN layer> In the second step, the MAlN layer is formed on the substrate by high-power pulse sputtering, which may involve using a target containing metal elements M (e.g., Ti, Cr, etc.) and Al in amounts adjusted according to the composition of the MAlN layer to be formed.

[0081] For example, the second step can be performed as follows. First, a chip of any desired shape is placed as a substrate in the chamber of a film-forming apparatus. The substrate is positioned so that its flank faces the target. For example, the substrate is attached to a substrate holder on a turntable rotatably installed in the center of the chamber of the film-forming apparatus. A bias power supply is connected to the substrate holder. With the turntable rotating in the center of the chamber, Ar gas and nitrogen gas are introduced. Furthermore, while maintaining the substrate temperature at 500 to 800°C, the Ar gas pressure at 300 mPa to 600 mPa, the nitrogen gas pressure at 300 mPa to 800 mPa, the bias power supply voltage at -200 to -30 V, and the bias power supply pulse width at 50 to 100 μs, sputtering power (e.g., average power 10 kW, frequency 2000 to 4000 Hz, pulse width 50 to 100 μs) is applied to the target for forming the MAlN layer. This causes metal atoms to be sputtered from the target for forming the MAlN layer, and after a predetermined time has elapsed, the application of sputtering power is stopped to form a MAlN layer on the surface of the substrate. At this time, the deposition time is adjusted to adjust the thickness of the MAlN layer to fall within a predetermined range. In the second step, the MAlN layer may be formed on the surface of the substrate other than the part involved in the cutting process, in addition to the part involved in the cutting process (e.g., the rake face and flank near the cutting edge).

[0082] (raw material for MALN layer) In the second step, the raw material of the MAlN layer contains metal elements M and Al. When the MAlN layer is a TiAlN layer, the raw material of the TiAlN layer contains Ti and Al. An example of the raw material of the TiAlN layer is a powder sintered alloy of Ti and Al. When the MAlN layer is a CrAlN layer, the raw material of the CrAlN layer contains Cr and Al. An example of the raw material of the CrAlN layer is a powder sintered alloy of Cr and Al.

[0083] In this embodiment, the above-mentioned reactive gas is appropriately set depending on the composition of the MAlN layer. For example, the reactive gas may be a mixed gas of nitrogen gas and an inert gas.

[0084] In one aspect of this embodiment, the surface of the substrate may be etched before the MAlN layer is formed. The etching conditions include, for example, the following conditions. Etching conditions Inert gas: Ar gas Temperature: 500℃ Pressure: 350mPa Voltage: Pulse DC voltage (500V, frequency 200kHz) Processing time: 5 minutes

[0085] <Other processes> In addition to the above-described steps, the manufacturing method according to this embodiment may also include other steps, such as forming a base layer on the substrate, forming an intermediate layer on the base layer or the MAlN layer, forming a surface layer on the MAlN layer, and performing a surface treatment. When forming other layers, such as the base layer, intermediate layer, and surface layer, the other layers may be formed by conventional methods. Specifically, for example, the other layers may be formed by a physical vapor deposition (PVD) method other than the HiPIMS method. Examples of surface treatment steps include surface treatment using a medium in which diamond powder is supported on an elastic material. [Example]

[0086] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0087] <Cutting tool manufacturing> <Step 1: Preparing the substrate> Substrates of cemented carbide, cermet, or cubic boron nitride sintered body were prepared according to the following procedure. The substrates used for each sample are shown in Tables 1 and 2. In Tables 1 and 2, items listed across multiple samples mean that the items are the same for those multiple samples. For example, with regard to the composition of the substrate in Table 1, Samples 1 to 4 all indicate that they are cBN.

[0088] (Cemented carbide) The cemented carbide substrate was manufactured by a general powder metallurgy method. That is, WC powder, Co powder, etc. were mixed using a ball mill or the like to obtain a mixed powder. After drying, the mixed powder was molded into a predetermined shape (the shape specified in ISO standard CNGA120408) to obtain a green body. The green body was then sintered to obtain a WC-Co based cemented carbide (sintered body) substrate.

[0089] (cermet) The cermet substrate was manufactured by a general powder metallurgy method. Specifically, cermet raw material powders such as TiC powder were mixed using a ball mill or the like to obtain a mixed powder. The mixed powder was dried and then molded into a predetermined shape (the shape specified in ISO standard CNGA120408) to obtain a green body. The green body was then sintered to obtain a cermet (sintered body) substrate.

[0090] (cubic boron nitride sintered body) First, the binders TiN, Ti, and Al were mixed using a cemented carbide pot and cemented carbide balls to obtain raw binder powder. Next, the raw binder powder was mixed with cubic boron nitride (cBN) powder to obtain a mixed powder. The resulting mixed powder was then loaded into a molybdenum container. The mixed powder in the container was sintered for 20 minutes under conditions of 5 GPa pressure and 1400°C temperature to obtain a cubic boron nitride sintered body. The resulting cubic boron nitride sintered body was processed into the shape specified in ISO standard CNGA120408 to obtain a cubic boron nitride sintered body substrate. Samples 20 and 21 were substrates that included the cutting edge surface (Figure 2). Samples 1 to 19 and 22 to 34 were substrates that did not include the cutting edge surface (Figure 3).

[0091] (Surface roughness of the substrate) The surface roughness R of the obtained substrate max was measured using a stylus surface roughness measuring instrument in accordance with JIS B06012001, with a cutoff value of 0.3 mm, a reference length of 0.8 mm, and a scanning speed of 0.06 mm / sec. The results are shown in Tables 1 and 2.

[0092] <Creating the coating> (Second step: Preparation of MALN layer) On the substrate obtained in the first step, a MAlN layer was formed by the HiPIMS method to have the composition shown in Table 1 or 2. That is, multiple targets were placed in the film-forming apparatus, and the substrate was attached to a rotary substrate auxiliary jig installed at the center of these targets, and film formation was carried out according to the following procedure. The substrate was placed so that the flank of the substrate faced the target.

[0093] For Samples 7 to 20 and Samples 22 to 34, the inside of the film-forming apparatus was first reduced in pressure to 3 mPa and then heated to around 500°C. Ar gas was then introduced. A pulsed DC voltage of 500 V (frequency 200 kHz) was then applied to the substrate in an atmosphere of 350 mPa to generate Ar plasma, which etched the surface of the substrate (for 5 minutes).

[0094] Next, Ar gas and N2 gas were added to the inside of the deposition apparatus, and the total pressure was adjusted to 750 mPa (partial pressure: Ar 350 mPa, N2 400 mPa). A bias voltage of -50 V (pulse width 50 μs) was then applied to the substrate, and sputtering power (average power 10 kW, frequency 3000 Hz, pulse width 100 μs) was applied to the cathode (target metal, a sintered alloy composed of metal M and Al), sputtering the target metal to form a MAlN layer. The thickness of the MAlN layer was adjusted by the deposition time. In this manner, cutting tools for Samples 7 to 20 and Samples 22 to 34 were fabricated.

[0095] Samples 1 to 6 and 21 were deposited under the same conditions as described above, except that the voltage and pulse width of the bias power supply were changed as follows: In this manner, cutting tools for Samples 1 to 6 and 21 were fabricated. (Sample 1) Bias power supply voltage: -50V Bias power pulse width: 50 μs (Sample 2) Bias power supply voltage: -30V Bias power pulse width: 50 μs (Sample 3) Bias power supply voltage: -70V Bias power pulse width: 50 μs (Sample 4) Bias power supply voltage: -50V Bias power pulse width: 70 μs (Sample 5) Bias power supply voltage: -50V Bias power pulse width: 70 μs (Sample 6) Bias power supply voltage: -50V Bias power pulse width: 70 μs (Sample 21) Bias power supply voltage: -50V Bias power pulse width: 40 μs

[0096] (Creating the base layer and surface layer) For samples 26 and 28, an underlayer was formed between the substrate and the MAlN layer by HiPIMS. The composition and thickness of the underlayer are shown in Table 2. For samples 27 and 28, a surface layer was formed on the MAlN layer by conventional sputtering. The composition and thickness of the surface layer are shown in Table 2.

[0097] <Cutting tool characteristic evaluation> Using the cutting tools of Samples 1 to 34 prepared as described above, the characteristics of the cutting tools were evaluated as follows.

[0098] <Median diameter D of cubic boron nitride 50 > Median diameter D of cubic boron nitride in sintered cubic boron nitride 50 was determined by the above-mentioned cross-section method using a scanning electron microscope (SEM). 50 was 1 μm.

[0099] <Cubic boron nitride content> The cubic boron nitride content in the cubic boron nitride sintered bodies of Samples 1 to 4, Samples 7 to 21, and Samples 24 to 34 was determined by the method described above. Specifically, cross-sectional samples of the cubic boron nitride sintered bodies were photographed with an SEM, and the photographed images were subjected to image analysis to determine the content. As a result, the cubic boron nitride content in the cubic boron nitride sintered bodies of Samples 1 to 4, Samples 7 to 21, and Samples 24 to 34 was 65% by volume. The binder content in the cubic boron nitride sintered bodies was also measured using the same method. The binder content in the cubic boron nitride sintered bodies of Samples 1 to 4, Samples 7 to 21, and Samples 24 to 34 was 35% by volume.

[0100] <Measurement of the thickness of each layer that makes up the coating> The thickness of each layer constituting the coating (i.e., the thickness of each of the underlayer, MALN layer, and surface layer) was determined by measuring 10 random points on a cross-sectional sample parallel to the normal direction of the substrate surface using an SEM (manufactured by JEOL Ltd., product name: JEM-2100F) and calculating the average thickness of the 10 measured points. The observation magnification was 10,000 times. The results are shown in Tables 1 and 2.

[0101] <M x Al 1-x Measurement of atomic ratio x of M in N> M x Al 1-x The atomic ratio x of M in N was determined by the method described above. That is, ten arbitrary points in the MAlN layer of the cross-sectional sample were measured with an SEM-EDX device to determine the value of x, and the average of the values ​​determined at the ten points was taken as M. x Al 1-x The atomic ratio x in N was taken as x. The results are shown in Tables 1 and 2. In Table 1, for Samples 17 to 19, the "atomic ratio x" is listed in the order of the "element M" column. For example, Sample 17 shows that the atomic ratio of Ti is 0.45 and the atomic ratio of Cr is 0.1.

[0102] <Measurement of the composition of the base layer and surface layer> The compositions of the underlayer and surface layer were determined by analyzing the entire layer of the cross-sectional sample described above using an SEM-EDX device. The results are shown in Table 2.

[0103] [Table 1]

[0104] [Table 2]

[0105] <Measurement of the number of voids> The number of voids per 50 μm length of the MAlN layer was determined using the method described above. Specifically, the above-mentioned cross-sectional sample was observed using an SEM at a magnification of 30,000 times, and an SEM image was obtained. At this time, a backscattered electron composition image (BSE image) was obtained so that the above-mentioned MAlN layer was continuously included within a 50 μm length range (Figures 6, 8, etc.). The obtained BSE image was converted into a monochrome image with 256 levels within a range excluding the vicinity of the substrate and 30 nm near the film surface (hereinafter referred to as the "evaluation range"). Within the evaluation range, the 80th level counting from black was used as the threshold, and binarization processing was performed using image analysis software ("WinROOF" manufactured by Mitani Shoji Co., Ltd.). Subsequently, shape analysis was performed on the parts that emerged in the binarization, and a 1.0 × 10 -4 μm 2 More than 0.5μm 2 Portions with the following cross-sectional areas were counted as voids (Fig. 7). If a portion of a void was outside the above evaluation range, that void was not counted. The number of voids was counted on the flank, rake face, and cutting edge face. The results are shown in Tables 3 and 4.

[0106] <Measurement of droplet number> The number of droplets per 50 μm length of the MAlN layer was determined using the method described above. Specifically, the cross-sectional sample was observed at 30,000x magnification using an SEM, and an SEM image was obtained (e.g., Figure 10). The SEM image was acquired so that the MAlN layer was included within a continuous 50 μm length range. The obtained SEM image was visually inspected, and the number of droplets within a continuous 50 μm length range was counted. The results are shown in Tables 3 and 4.

[0107] [Table 3]

[0108] [Table 4]

[0109] <Cutting test> (Heavy interrupted cutting test: fracture life) Using the cutting tools of the samples (Samples 1 to 34) prepared as described above, intermittent cutting of workpieces was performed under the following cutting conditions. The number of passes until the cutting tools fractured was measured. The results are shown in Tables 3 and 4. For samples with a cBN sintered body substrate, samples with a pass number of 20 or more were evaluated as cutting tools with excellent fracture resistance. For samples with a cemented carbide substrate, samples with a pass number of 15 or more were evaluated as cutting tools with excellent fracture resistance. For samples with a cermet substrate, samples with a pass number of 10 or more were evaluated as cutting tools with excellent fracture resistance. In this cutting test, Samples 1, 2, 8 to 10, 13 to 15, and 17 to 34 correspond to Examples. Samples 3 to 7, 11, 12, and 16 correspond to Comparative Examples. Conditions for heavy interrupted cutting tests Work material: SCr420H U-groove end round bar Cutting speed (Vc): 100m / min Feed rate (f): 0.1 mm / rev Depth of cut (ap): 0.2 mm Cutting oil: dry type

[0110] From the results in Tables 3 and 4, the cutting tools of the examples (Samples 1, 2, 8-10, 13-15, and 17-34) showed a pass count of more than the standard value before the cutting tool fractured, and thus obtained good results. On the other hand, the cutting tools of the comparative examples (Samples 3-7, 11, 12, and 16) showed a pass count of less than the standard value before the cutting tool fractured. From these results, it was found that the cutting tools of the examples have excellent fracture resistance.

[0111] Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined.

[0112] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0113] 1a rake face, 1b flank face, 1c cutting edge face, 10 cutting tool, 11 substrate, 12 MAlN layer, 13 underlayer, 14 surface layer, 20 coating

Claims

1. A cutting tool including a rake face and a flank face, The cutting tool consists of a base material and a coating provided on the base material. The aforementioned coating includes a MAlN layer, The aforementioned MAlN layer is a cubic M ｘ Al １－ｘ Contains N crystal grains, Said M ｘ Al １－ｘ The atomic ratio x of the metal element M in N is between 0.2 and 0.

8. In the MAlN layer, M represents a metallic element including titanium, chromium, or both. In the cross-section obtained when the MAlN layer is cut by a plane including the normal to the scoop face, the number of voids per 50 μm length of the MAlN layer on the scoop face is n. Ｒ is 3 or less, The cross-sectional area of ​​the aforementioned void is 1.0 × 10 －４ μm ２ The above 0.5 μm ２ The following: The number of voids is the average value of the number of voids per 50 μm length of the MAlN layer in at least three locations. Gaps with a cross-sectional area of ​​less than 1.0 × 10⁻⁴ μm² may exist. A cutting tool in which the number of gaps with a cross-sectional area exceeding 0.5 μm² is zero.

2. In a cross-section obtained by cutting the MAlN layer with a plane including the normal line of the relief surface, the number n of voids per 50 μm length of the MAlN layer on the relief surface Ｆ The cutting tool according to claim 1, wherein the number is 3 or less.

3. It further includes a cutting edge surface connecting the rake face and the relief face, In the cross-section obtained by cutting the MAlN layer with a plane including the normal to the cutting edge surface, the number of voids per 50 μm length of the MAlN layer on the cutting edge surface is n. Ｃ The cutting tool according to claim 2, wherein the ratio is 3 or less.

4. The aforementioned n Ｆ is 3 or less, and the n Ｒ is 3 or less, and the n Ｃ The cutting tool according to claim 3, wherein the value is 3 or less.

5. The cutting tool according to any one of claims 1 to 4, wherein the metal element M further comprises at least one element selected from the group consisting of boron, silicon, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten.

6. The cutting tool according to any one of claims 1 to 4, wherein the base material includes at least one selected from the group consisting of cemented carbide, cermet, high-speed steel, ceramics, cubic boron nitride sintered body, and diamond sintered body.

7. Surface roughness R of the aforementioned substrate ｍａｘ The cutting tool according to any one of claims 1 to 4, wherein the diameter is 1 μm or less.

8. The coating further includes an underlayer provided between the substrate and the MAlN layer, The cutting tool according to any one of claims 1 to 4, wherein the composition of the underlayer is different from the composition of the MAlN layer.

9. The coating further includes a surface layer provided on the MAlN layer, The cutting tool according to any one of claims 1 to 4, wherein the composition of the surface layer is different from the composition of the MAlN layer.

10. The cutting tool according to any one of claims 1 to 4, wherein the thickness of the MAlN layer is 0.1 μm or more and 2.0 μm or less.

11. The cutting tool according to any one of claims 1 to 4, wherein the thickness of the coating is 0.1 μm or more and 2.5 μm or less.

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