Cutting tool

Abstract

This cutting tool includes a rake face and a flank face. The cutting tool includes a base material and a coating film provided on the base material. The coating film includes a MAlN layer. The MAlN layer includes crystal grains of a cubic crystal type MxAl1-xN. An atomic ratio x of the metal element M in MxAl1-xN is 0.2 to 0.8. M in the MAlN layer indicates a metal element containing titanium, chromium, or a combination thereof. In a cross section obtained by cutting the MAlN layer in a plane including a normal to the rake face, the number nR of voids per 50 µm length of the MAlN layer on the rake face is 3 or less. The cross-sectional area of each void is 1.0×10-4µm2 to 0.5 µm2.

Description

cutting tools

[0001] The present disclosure relates to cutting tools.

[0002] Cubic boron nitride (hereinafter referred to as "cBN") has hardness second only to diamond and also 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.

[0004] International Publication No. 2021 / 024737 International Publication No. 2022 / 230182

[0005] A cutting tool according to the present disclosure is a cutting tool including a rake face and a flank face, the cutting tool including a substrate and a coating provided on the substrate, the coating including an MAlN layer, the MAlN layer being a cubic MAlN layer. ｘ Al １－ｘ The 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 n of voids 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 0.5 μm ２ The following is the result.

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

[0007] [Problem to be Solved by the Present Disclosure] For example, International Publication No. 2021 / 024737 (Patent Document 1) discloses a cutting tool including a rake face and a flank face, the cutting tool including a substrate made of a cubic boron nitride sintered body and a coating provided on the substrate, the cubic boron nitride sintered body including cubic boron nitride, the coating including an MAlN layer, M in the MAlN layer representing a metal element including titanium, chromium, or both, and the MAlN layer including a cubic M ｘ Al １－ｘ 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 with respect to the cubic boron nitride sintered body, and in a cross section obtained by cutting the MAlN layer along a plane including a normal line of the flank, the number of voids per 100 μm length of the MAlN layer on the flank is n Ｆ In a cross section of the MAlN layer cut along a plane including a normal to the cutting face, the number of voids per 100 μm length of the MAlN layer on the cutting face is defined as n Ｒ In this case, n Ｆ <n ＲIn a cross section of the MAlN layer cut along a plane including a normal to the flank, the number n of droplets per 100 μm length of the MAlN layer on the flank satisfies Ｄ A cutting tool is disclosed in which the .gtoreq..times ...

[0008] Furthermore, WO 2022 / 230182 (Patent Document 2) discloses a cutting tool including a rake face and a flank face, the cutting tool including a substrate and a coating provided on the substrate, the coating including a TiMAlN layer, and the TiMAlN layer including a cubic Ti ｘ M ｙ Al ｚ containing N crystal grains, ｘ M ｙ Al ｚ The atomic ratio x of titanium element in N is 0.4 or more and 0.79 or less, 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, 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 of them, and the number n of voids per 100 μm length of the TiMAlN layer located on the flank surface in a cross section obtained by cutting the TiMAlN layer along a plane including a normal line of the flank surface is Ｆ and the number n of voids per 100 μm length of the TiMAlN layer located on the rake face in a cross section obtained by cutting the TiMAlN layer along a plane including a normal line to the rake face. Ｒ That is, n Ｆ <n Ｒ 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 line of the flank surface satisfies the relationship: Ｄ is 3 or less.

[0009] However, the MAlN layer 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 cutting tools to highly efficient cutting processes (such as cutting processes with high feed rates), further improvement in performance (e.g., chipping resistance) is 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] Effect of the Present Disclosure According to the present disclosure, it is possible to provide a cutting tool with excellent fracture resistance.

[0012] [Summary of the embodiment] First, the embodiments of the present disclosure will be listed and described. [1] A cutting tool according to the present disclosure is 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 an MAlN layer, the MAlN layer being a cubic MAlN layer. ｘ Al １－ｘ 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 n of voids 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 0.5 μm ２ The following is the result.

[0013] The number of voids n per 50 μm length of the MAlN layer on the rake face Ｒ The cutting tool has excellent chipping resistance when the value of the tensile strength 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 a normal to the flank, the number n of voids 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] The cutting edge further includes a cutting edge surface connecting the rake face and the flank, and in a cross section when the MAlN layer is cut along a plane including a normal to the cutting edge surface, the number n of voids per 50 μm length of the MAlN layer on the cutting edge surface Ｃ may be not more 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 n Ｒ is 3 or less, and the 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 excellent 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 substrate ｍａｘ By specifying the thickness in this way, the cutting tool has even better fracture resistance.

[0020] [8] The coating may further include an underlayer provided 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 may further include a surface layer provided on the MAlN layer, and the composition of the surface layer may be different from the composition of the MAlN layer. By specifying in this way, the cutting tool has excellent versatility in machining conditions and excellent visibility of a used cutting edge.

[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 chipping resistance.

[0024] [Details of the embodiment] Hereinafter, one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described. However, the present 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 a unit is not described for A and a unit is described only 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", the 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 the stoichiometric composition "Ti １ N １ " as well as, for example, "Ti １ N ０．８ This also applies to compounds other than "TiN."

[0025] <<Surface-Coated Cutting Tool>> A cutting tool according to the present disclosure is a cutting tool including a rake face and a flank face, the cutting tool including a substrate and a coating provided on the substrate, the coating including an MAlN layer, the MAlN layer being a cubic MAlN layer. ｘ Al １－ｘ The 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 n of voids 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 0.5 μm 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 showing an example of a cutting tool 10. The cutting tool 10 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 of 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 partly contacts the workpiece. The cutting edge face is included in the part that constitutes 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 (a ridge where the rake face and flank intersect) (e.g., Fig. 3) and a negative land (a 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 , but the same terms as above will be used for the shape and names of the components of the substrate of the cutting tool according to this embodiment that correspond to cutting tool 10. That is, the substrate of the cutting tool 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 an MAlN layer 12 provided on the substrate 11 ( FIG. 4 ). In addition to the MAlN layer 12, the cutting tool 10 may further include an underlayer 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 ). Other layers, such as the underlayer 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 covering 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] <Substrate> The substrate of this embodiment can be any conventionally known substrate of this kind.For example, the substrate can comprise at least one selected from the group consisting of cemented carbide (for example, tungsten carbide (WC)-based cemented carbide, cemented carbide that contains Co in addition to WC, cemented carbide that contains Cr, Ti, Ta, Nb, etc. carbonitride in addition to WC), cermet (mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), 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, particularly 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 its surface modified. For example, a β-free 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] The surface roughness R of the 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 the present embodiment, the base material may be a cubic boron nitride sintered body (cBN sintered body). The cubic boron nitride sintered body contains cubic boron nitride. In one aspect of the present embodiment, the cubic boron nitride sintered body may further contain 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 or more to 97% by volume or less, or 20% by volume or more to 80% by volume or less, relative to the cubic boron nitride sintered body. The content (volume %) of cubic boron nitride and the content (volume %) of the binder (binding phase) described below in the cubic boron nitride sintered body 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) ("JSM-7800F" (trademark) manufactured by JEOL Ltd.).

[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 areas where the binder is present appear 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 determined 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 determined 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 cubic boron nitride ５０ 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 is 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, the circle equivalent diameters are arranged in ascending order from the minimum to the maximum 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 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 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, and TiB ２ , AlB ２ Borides such as Al ２ O ３ or TiCN, AlON, SiAlON, SiTiAlON, and the like.

[0049] (Inevitable Impurities) The cubic boron nitride sintered body may contain inevitable impurities to the extent that the effects of the present disclosure are not impaired. Inevitable impurities refer 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 inevitable impurity may be 0% to 5% by volume, and the sum of these (i.e., the total content of trace impurities) may be 0% to 5% by volume. Therefore, inevitable impurities may or may not be contained in the cubic boron nitride sintered body. Examples of inevitable impurities include Li, Mg, Ca, Sr, Ba, Be, Si, Ga, La, Fe, and Cu.

[0050] <Coating> The coating according to this embodiment includes an 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, this does not depart from the scope of this embodiment.

[0051] The thickness of the coating may be 0.1 μm or more and 2.5 μm or less, 0.3 μm or more and 2.5 μm or less, or 0.5 μm or more and 1.5 μm or less. 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, 10,000 times. 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 MAlN layer. ｘ Al １－ｘ In other words, the MAlN layer contains polycrystalline M ｘ Al １－ｘ It 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 usually considered to be a semimetal that exhibits properties intermediate between metallic elements and non-metallic elements, but 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 Ti and N crystal grains. ｘ Al １－ｘ This is a layer containing 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－ｘ The 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 energy dispersive X-ray spectroscopy (SEM-EDX) attached to a 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 value of the determined 10 points is defined as the x value in the MAlN layer. Here, when the metal element M includes multiple metal elements, the sum of the atomic ratios of the respective metal elements is the atomic ratio x of the metal element M. Furthermore, 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 more than 0 and not more than 0.8, or may be 0.4 or more 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－ｘThe atomic ratio y of chromium in N may be more than 0 and not more than 0.8, or may be 0.25 or more and 0.5 or less. It goes without saying that when the metal atom M is chromium only, 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 described below, the thickness of the MAlN layer means the thickness per 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, to be described later, to form a multilayer structure. In one aspect of this embodiment, the MAlN layer itself may form a multilayer structure.

[0061] (Number of voids in 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 when the MAlN layer is cut. －４ μm２ More than 0.5 μm 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 present 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 ２ Even 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 repeatedly subjected to 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 exceeding 0 may be zero.

[0063] The number of voids is counted by 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, a backscattered electron composition image (BSE image) is 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., FIG. 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., FIGS. 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, this range may be 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.). Thereafter, shape analysis is performed on the part that stands out in the binarization, and a 1.0 x 10 －４ μm ２ More than 0.5 μm ２ Portions 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 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 film structure, and 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 was counted in at least three "continuous ranges of 50 μm length," and the average of these was taken as the number of voids.

[0066] The above-described method for counting voids is, in principle, applicable to all of the flank, rake, and cutting edge surfaces (see, for example, Figures 2 and 3). However, if a "continuous 50 μm range" cannot be ensured on the cutting edge surface, etc., the number of voids is counted within the maximum length range that can be ensured, and converted into the number of voids per 50 μm length to determine the number of voids. For example, if the maximum length range that can be ensured is 20 μm, the number of voids within the 20 μm length range is counted, and the counted number of voids is 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 in a cross section obtained by cutting the MAlN layer on a plane including a normal to the cutting edge surface is defined as n Ｃ In this case, n Ｃ may be 3 or less.

[0068] The above n Ｒ may be 3 or less, 2 or less, or 1 or less. 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] The above n Ｆ may be 3 or less, 2 or less, or 1 or less. It is thought that the presence of voids on the flank face reduces the wear resistance against abrasive wear during cutting, and flank wear progresses. In other words, reducing the number of voids in the MAlN layer on the flank face improves the wear resistance.

[0070] The 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 n Ｒ is 3 or less, and the n Ｃ In another aspect of this embodiment, the n Ｆ is 2 or less, and the n Ｒ is 2 or less, and the n Ｃ In another aspect of the present embodiment, the n Ｆ is 1 or less, and the n Ｒ is 1 or less, and the n Ｃ may be 1 or less.

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

[0073] (Number of droplets in 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 n of droplets 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, "droplets" refer to metal particles present in a layer constituting the coating (for example, an MAlN layer such as a TiAlN layer) and having a predetermined size, as will be described later. The number of droplets is determined by the following method. That is, the cross section of the cutting tool is observed at a magnification of 30,000 times using an SEM to obtain an SEM image. At this time, 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 paid to a white, approximately circular portion present in the MAlN layer (for example, in the layer shown in light gray in FIG. 10). Next, the length L of the long side of a 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. ａ and L ｂ If the following condition is satisfied, 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 "continuous ranges of 50 μm length," 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 may be, for example, 0.1 μm or more and 2 μm or less.

[0076] <Method for manufacturing cutting tool> The method for manufacturing a cutting tool according to this embodiment includes the steps of preparing the substrate (hereinafter, sometimes referred to as the "first step"), and forming the MAlN layer on the substrate using a high-power pulse sputtering method (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 electric power is applied and atoms of a target (raw material) are ejected by discharge and deposited on a substrate or the like.

[0078] In the HiPIMS method, a substrate and a target are placed in the apparatus, and then a negative voltage is applied to the target to generate a discharge. The apparatus is filled with an inert gas (e.g., Ar gas) under reduced pressure. The discharge ionizes the inert gas inside the apparatus, causing the inert gas ions to collide with the target surface at high speed. This collision ejects target atoms, which are then deposited on the substrate to form a coating. Because the HiPIMS method forms films based on the above-described 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 an 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. Since the voids are believed 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] <Step 1: Preparing a Substrate> In step 1, a substrate is prepared. Examples of the substrate include cemented carbide, cermet, and cubic boron nitride sintered body. A commercially available substrate may be used. Alternatively, the substrate may be manufactured by a general powder metallurgy method. For example, when manufacturing a cemented carbide using 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 compact. The compact is then sintered to obtain a WC—Co-based 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-based cemented carbide. Depending on the cutting edge processing method, a substrate including a cutting edge surface ( FIG. 2 ) or a substrate not including a cutting edge surface ( FIG. 3 ) can be manufactured. In step 1, 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 MAlN Layer> In the second step, the MAlN layer is formed on the substrate by high-power pulse sputtering, for example, by using a target in which the amounts of metal element M (e.g., Ti, Cr, etc.) and Al are 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 then 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 the 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 be within a predetermined range. In the second step, the MAlN layer may be formed on the surface of the substrate other than the portion involved in the cutting process, in addition to the portion involved in the cutting process (e.g., the rake face and flank near the cutting edge).

[0082] (Raw materials for the MAlN layer) In the second step, the raw materials for the MAlN layer include metal elements M and Al. When the MAlN layer is a TiAlN layer, the raw materials for the TiAlN layer include Ti and Al. Examples of raw materials for the TiAlN layer include a powder sintered alloy of Ti and Al. When the MAlN layer is a CrAlN layer, the raw materials for the CrAlN layer include Cr and Al. Examples of raw materials for the CrAlN layer include a powder sintered alloy of Cr and Al.

[0083] In this embodiment, the reactive gas is appropriately set depending on the composition of the MAlN layer, and may be, for example, 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 may be, for example, as follows: Inert gas: Ar gas Temperature: 500° C. Pressure: 350 mPa Voltage: Pulse DC voltage (500 V, frequency 200 kHz) Processing time: 5 minutes

[0085] <Other Steps> In addition to the steps described above, 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 described above, 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.

[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] <<Preparation of Cutting Tools>> <Step 1: Preparation of Substrate>> Substrates of cemented carbide, cermet, or cubic boron nitride sintered body were prepared in 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, and the like were mixed using a ball mill or the like to obtain a mixed powder. After drying the mixed powder, it 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. That is, raw cermet 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 a raw binder powder. Next, the raw binder powder was mixed with cubic boron nitride powder (cBN powder) to obtain a mixed powder. The resulting mixed powder was filled 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 a shape conforming to ISO standard CNGA 120408 to obtain a cubic boron nitride sintered body substrate. Samples 20 and 21 were substrates including a cutting edge surface (Figure 2). Samples 1-19 and 22-34 were substrates without a cutting edge surface (Figure 3).

[0091] (Surface roughness of substrate) Surface roughness R of the obtained substrateｍａｘ 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] <Coating Production> (Second Step: Production of MAlN Layer) On the substrate obtained in the first step, a MAlN layer was formed by HiPIMS so as to have the composition shown in Table 1 or 2. That is, multiple targets were placed in a film-forming apparatus, and the substrate was attached to a rotary substrate auxiliary jig provided at the center of these targets, and film formation was performed in the following manner. At this time, 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 interior of the film-forming apparatus was first reduced in pressure to 3 mPa and then heated to approximately 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, and the surface of the substrate was etched (for 5 minutes).

[0094] Next, Ar gas and N ２ Gas was added to the inside of the film-forming apparatus until the total pressure reached 750 mPa (partial pressure: Ar 350 mPa, N ２ The pressure was adjusted to 400 mPa. Then, a bias voltage of -50 V (pulse width 50 μs) was 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), and the target metal was sputtered to form an MAlN layer. The thickness of the MAlN layer was adjusted by the film formation time. In this manner, cutting tools of Samples 7 to 20 and Samples 22 to 34 were produced.

[0095] Samples 1 to 6 and 21 were formed 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 way, cutting tools for Samples 1 to 6 and 21 were fabricated. (Sample 1) Bias power supply voltage: -50 V Bias power supply pulse width: 50 μs (Sample 2) Bias power supply voltage: -30 V Bias power supply pulse width: 50 μs (Sample 3) Bias power supply voltage: -70 V Bias power supply pulse width: 50 μs (Sample 4) Bias power supply voltage: -50 V Bias power supply pulse width: 70 μs (Sample 5) Bias power supply voltage: -50 V Bias power supply pulse width: 70 μs (Sample 6) Bias power supply voltage: -50 V Bias power supply pulse width: 70 μs (Sample 21) Bias power supply voltage: -50 V Bias power supply pulse width: 40 μs

[0096] (Preparation of Underlayer 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] <Evaluation of Cutting Tool Properties> Using the cutting tools of Samples 1 to 34 prepared as described above, the properties 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 cubic boron nitride sintered body 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 by 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 Thickness of Each Layer Constituting 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 arbitrary points on a cross-sectional sample parallel to the normal direction of the surface of the substrate using an SEM (manufactured by JEOL Ltd., product name: JEM-2100F) and calculating the average value of the thicknesses measured at 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 on 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 Table 1 and Table 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 was 0.45 and the atomic ratio of Cr was 0.1.

[0102] <Measurement of Composition of Underlayer 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]

[0104]

[0105] <Measurement of the Number of Voids> The number of voids per 50 μm length of the MAlN layer was determined by the method described above. Specifically, the cross-sectional sample was observed at 30,000x magnification using an SEM to obtain an SEM image. A backscattered electron image (BSE image) was obtained so that the MAlN layer was continuously included within a 50 μm length range (see, e.g., FIGS. 6 and 8 ). The obtained BSE image was converted into a 256-level monochrome image within a range excluding the vicinity of the substrate and 30 nm from the film surface (hereinafter, sometimes referred to as the "evaluation range"). Within the evaluation range, binarization processing was performed using image analysis software ("WinROOF" manufactured by Mitani Shoji Co., Ltd.) with the 80th level counting from black as the threshold. Subsequently, shape analysis was performed on the portions highlighted by the binarization, and a 1.0×10 －４ μm ２ More than 0.5 μm ２ Portions with the following cross-sectional areas were counted as voids (Figure 7). If a portion of a void was outside the 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 by the method described above. That is, the above-mentioned cross-sectional sample was observed using an SEM at a magnification of 30,000 times to obtain an SEM image (e.g., FIG. 10). At this time, the SEM image was acquired so that the MAlN layer was included in a continuous range of 50 μm length. The obtained SEM image was visually inspected, and the number of droplets in a continuous range of 50 μm length was counted. The results are shown in Tables 3 and 4.

[0107]

[0108]

[0109] <Cutting Test> (Heavy Intermittent 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 whose substrate was a cBN sintered compact, samples with a pass number of 20 or more were evaluated as cutting tools with excellent fracture resistance. For samples whose substrate was a cemented carbide, samples with a pass number of 15 or more were evaluated as cutting tools with excellent fracture resistance. For samples whose substrate was a cermet, 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 test Workpiece: SCr420H U-groove end face round bar Cutting speed (Vc): 100 m / min Feed rate (f): 0.1 mm / rev Depth of cut (ap): 0.2 mm Cutting oil: dry

[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) exhibited a PASS number before chipping equal to or greater than the standard value, and thus achieved favorable results. On the other hand, the cutting tools of the comparative examples (Samples 3-7, 11, 12, and 16) exhibited a PASS number before chipping less than the standard value. These results demonstrate that the cutting tools of the examples have excellent chipping 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.

[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 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 The 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 n of voids 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 0.5 μm ２ Below are cutting tools.

2. In a cross section of the MAlN layer cut along a plane including a normal to the flank, the number n of voids per 50 μm length of the MAlN layer on the flank Ｆ The cutting tool according to claim 1 , wherein is 3 or less.

3. The cutting edge further includes a cutting edge surface connecting the rake face and the flank, and in a cross section when the MAlN layer is 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 is Ｃ The cutting tool according to claim 2 , wherein is 3 or less.

4. The above n Ｆ is 3 or less, and said n Ｒ is 3 or less, and said n Ｃ The cutting tool of claim 3 , wherein is 3 or less.

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

6. A cutting tool according to any one of claims 1 to 5, wherein the substrate comprises 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.

7. Surface roughness R of the substrate ｍａｘ The cutting tool according to claim 1 , wherein the thickness of the surface roughness is 1 μm or less.

8. A cutting tool according to any one of claims 1 to 7, wherein the coating further includes an underlayer provided between the substrate and the MAlN layer, and the composition of the underlayer is different from the composition of the MAlN layer.

9. A cutting tool according to any one of claims 1 to 8, wherein the coating further includes a surface layer provided on the MAlN layer, and the composition of the surface layer is different from the composition of the MAlN layer.

10. A cutting tool according to any one of claims 1 to 9, wherein the thickness of the MAlN layer is 0.1 μm or more and 2.0 μm or less.

11. A cutting tool according to any one of claims 1 to 10, wherein the coating has a thickness of 0.1 μm or more and 2.5 μm or less.

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