Cutting Tools

Abstract

A cutting tool comprising a substrate and a coating provided on the substrate, the coating including a first layer and a second layer, the second layer being provided closer to the substrate than the first layer, the first layer having a multilayer structure in which a first unit layer and a second unit layer are alternately laminated, the average thickness of the first unit layer being 2 nm or more and 50 nm or less, the average thickness of the second unit layer being 2 nm or more and 50 nm or less, the first unit layer being composed of Ti a Al 1-a-b B b N, where 0.30 ≤ a ≤ 0.50, 0 < b ≤ 0.10 are satisfied, the second unit layer being composed of Ti c Al 1-c N, where 0.70 ≤ c ≤ 1.00 is satisfied, in the first layer, the percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number of titanium and aluminum atoms T1 is 60% or more, the second layer having a multilayer structure in which a third unit layer and a fourth unit layer are alternately laminated, the average thickness of the third unit layer being 2 nm or more and 100 nm or less, the average thickness of the fourth unit layer being 2 nm or more and 100 nm or less, the third unit layer being composed of Ti d Al 1-d-e B e N, the fourth unit layer being composed of Ti f Al 1-f-g B g N, where 0.25 ≤ d < 0.45, 0

Description

Technical Field

[0001] The present disclosure relates to a cutting tool.

Background Art

[0002] Conventionally, in order to improve the performance of cutting tools, the development of coatings for coating the surfaces of substrates made of cemented carbide, cubic boron nitride sintered bodies, etc. has been promoted (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The cutting tool of the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, the coating includes a first layer and a second layer, the second layer is provided closer to the substrate than the first layer, the first layer has a multilayer structure in which a first unit layer and a second unit layer are alternately laminated, the average thickness of the first unit layer is 2 nm or more and 50 nm or less, the average thickness of the second unit layer is 2 nm or more and 50 nm or less, the first unit layer is composed of Ti a Al 1-a-b B b N, where 0.30 ≦ a ≦ 0.50, 0 < b ≦ 0.10 is satisfied, the second unit layer is composed of Ti c Al 1-c N, where 0.70 ≦ c ≦ 1.00 is satisfied, In the first layer, a percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number T1 of titanium and aluminum atoms is 60% or more; the second layer has a multilayer structure in which third unit layers and fourth unit layers are alternately laminated; the average thickness of the third unit layer is 2 nm or more and 100 nm or less; the fourth unit layer has an average thickness of 2 nm or more and 100 nm or less; The third unit layer is Ti d Al 1-d-e B e It consists of N, The fourth unit layer is made of Ti f Al 1-f-g B g It consists of N, Where: 0.25≦d<0.45, 0 <e≦0.10、 0.35≦f<0.55, 0 <g≦0.10、 0.05≦fd≦0.20 is satisfied, In the X-ray diffraction spectrum of the second layer, a ratio I(200) / I(002) of a peak intensity I(200) originating from the (200) plane to a peak intensity I(002) originating from the (002) plane is 2 or more, and a half-width of the peak originating from the (002) plane is 2 degrees or more. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a cutting tool according to a first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of a film forming apparatus. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing an example of the configuration of a film forming apparatus. [Figure 4] FIG. 4 is a diagram for explaining a measurement region when measuring the diameter of the maximum inscribed circle of a crystal grain in the first layer. [Diagram 5]FIG. 5 is a diagram for explaining a method of measuring the diameter of the largest inscribed circle of crystal grains in the first layer, and is a diagram schematically showing a bright-field image of a measurement field of view. [Figure 6] FIG. 6 is a diagram for explaining the positional relationship between crystal grains, the first unit layer, and the second unit layer.

Embodiments for Carrying Out the Invention

[0006] [Problems to be Solved by the Present Disclosure] In recent years, the demand for cost reduction has been increasing, and a longer tool life is required. For example, even in the turning of stainless steel, cutting tools with a long tool life are required.

[0007] Therefore, an object of the present disclosure is to provide a cutting tool having a long tool life.

[0008] [Effects of the Present Disclosure] The cutting tool of the present disclosure can have a long tool life.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) The cutting tool of the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, the coating includes a first layer and a second layer, the second layer is provided at a position closer to the substrate than the first layer, the first layer has a multilayer structure in which a first unit layer and a second unit layer are alternately laminated, the average thickness of the first unit layer is 2 nm or more and 50 nm or less, the average thickness of the second unit layer is 2 nm or more and 50 nm or less, the first unit layer is Ti a Al 1-a-b B b N, where 0.30 ≦ a ≦ 0.50, 0 < b ≦ 0.10, is satisfied, The second unit layer is Ti c Al 1-c It consists of N, Where: 0.70≦c≦1.00 is satisfied, In the first layer, a percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number T1 of titanium and aluminum atoms is 60% or more; the second layer has a multilayer structure in which third unit layers and fourth unit layers are alternately laminated; the average thickness of the third unit layer is 2 nm or more and 100 nm or less; the fourth unit layer has an average thickness of 2 nm or more and 100 nm or less; The third unit layer is Ti d Al 1-d-e B e It consists of N, The fourth unit layer is made of Ti f Al 1-f-g B g It consists of N, Where: 0.25≦d<0.45, 0 <e≦0.10、 0.35≦f<0.55, 0 <g≦0.10、 0.05≦fd≦0.20 is satisfied, In the X-ray diffraction spectrum of the second layer, a ratio I(200) / I(002) of a peak intensity I(200) originating from the (200) plane to a peak intensity I(002) originating from the (002) plane is 2 or more, and a half-width of the peak originating from the (002) plane is 2 degrees or more.

[0010] The cutting tools of the present disclosure can have long tool life.

[0011] (2) In the above (1), the first layer may have a nanoindentation hardness of 30 GPa or more at 25° C. This improves the wear resistance of the cutting tool.

[0012] (3) In the above (1) or (2), the first layer may have an average thickness of 1.0 μm or more and 20 μm or less. This increases the number of first unit layers and second unit layers in the first layer, further improving the effect of suppressing the progress of cracks. This makes it possible to suppress large-scale damage to the coating, and extends the tool life of the cutting tool.

[0013] (4) In any of the above (1) to (3), the second layer may have an average thickness of 0.5 μm to 10 μm. This increases the number of third and fourth unit layers in the second layer, further improving the effect of suppressing the progression of cracks. This makes it possible to suppress large-scale damage to the coating, and extends the tool life of the cutting tool.

[0014] [Details of the embodiment of the present disclosure] Specific examples of the cutting tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0015] In this disclosure, an expression in the form "A to B" means the upper and lower limits of a range (i.e., A or more and B or less). When no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0016] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

[0017] In the present disclosure, when one or more numerical values are described as the lower limit and upper limit of a numerical range, combinations of any one numerical value described as the lower limit and any one numerical value described as the upper limit are also considered to be disclosed. For example, when the lower limit is described as a1 or more, b1 or more, c1 or more, and the upper limit is described as a2 or less, b2 or less, c2 or less, then a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, c1 or more and c2 or less are considered to be disclosed.

[0018] [Embodiment 1: Cutting Tool] A cutting tool according to an embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") includes a substrate and a coating provided on the substrate. The coating includes a first layer and a second layer. The second layer is provided closer to the substrate than the first layer. The first layer has a multilayer structure in which first unit layers and second unit layers are alternately laminated. The average thickness of the first unit layer is 2 nm or more and 50 nm or less. The average thickness of the second unit layer is 2 nm or more and 50 nm or less. The first unit layer consists of Ti a Al 1-a-b B b N, Here, 0.30 ≦ a ≦ 0.50, 0 < b ≦ 0.10, is satisfied. The second unit layer consists of Ti c Al 1-c N, Here, 0.70 ≦ c ≦ 1.00, is satisfied. In the first layer, the percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number of titanium and aluminum atoms T1 is 60% or more. The second layer has a multilayer structure in which third unit layers and fourth unit layers are alternately laminated. The average thickness of the third unit layer is 2 nm or more and 100 nm or less, The average thickness of the fourth unit layer is 2 nm or more and 100 nm or less, The third unit layer is composed of Ti d Al 1-d-e B e N, The fourth unit layer is composed of Ti f Al 1-f-g B g N, Here, 0.25 ≤ d < 0.45, 0 < e ≤ 0.10, 0.35 ≤ f < 0.55, 0 < g ≤ 0.10, 0.05 ≤ f - d ≤ 0.20 is satisfied, In the X-ray diffraction spectrum of the second layer, the ratio I(200) / I(002) of the peak intensity I(200) derived from the (200) plane to the peak intensity I(002) derived from the (002) plane is 2 or more, and the half-value width of the peak derived from the (002) plane is 2 degrees or more. It is a cutting tool.

[0019] The cutting tool of the present disclosure can have a long tool life. The reason is presumed as follows.

[0020] (i) The coating of the cutting tool of the present disclosure includes a first layer having a multilayer structure in which the first unit layer and the second unit layer are alternately laminated. The first unit layer and the second unit layer have different compositions. Therefore, near the interface between the first unit layer and the second unit layer, the progress of cracks from the surface of the coating generated during the use of the cutting tool can be suppressed.

[0021] (ii) The first unit layer is Ti a Al 1-a-b B b N (where 0.30 ≤ a ≤ 0.50 and 0 < b ≤ 0.10 are satisfied). The first unit layer has improved hardness due to the addition of a small amount of boron (B) to TiAlN. The second unit layer is Ti c Al 1-cN (where 0.70≦c≦1.00 is satisfied). The second unit layer has a high titanium (Ti) content and has excellent high-temperature stability. In the present disclosure, the first layer has a multilayer structure in which high-hardness first unit layers and second unit layers with excellent high-temperature stability are alternately stacked, so that stable hardness is obtained even at high temperatures and crater wear resistance is improved. Crater wear is wear that occurs mainly on the rake face of the cutting tool due to frictional heat between the cutting tool and the cutting chips. Furthermore, the first layer has a multilayer structure in which high-hardness first unit layers and second unit layers with lower hardness than the first unit layers are alternately stacked, so that chipping resistance is also improved. Therefore, the crater wear resistance and chipping resistance of the coating are improved in a well-balanced manner, and the tool life of the cutting tool is extended.

[0022] (iii) The first unit layer and the second unit layer have different Ti and Al contents. Therefore, the first unit layer and the second unit layer have different crystal lattices, which causes distortion of the crystal lattice in the first layer, and the first layer can have high hardness. Therefore, the coating including the first layer can have excellent wear resistance.

[0023] (iv) In the first layer, the percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number T1 of titanium and aluminum atoms is 60% or more. This allows the first layer to have excellent crater wear resistance, and extends the tool life of the cutting tool.

[0024] (v) The coating of the cutting tool of the present disclosure includes a second layer having a multilayer structure in which third unit layers and fourth unit layers are alternately stacked. The third unit layers and the fourth unit layers have different compositions. This makes it possible to suppress the growth of cracks from the surface of the coating that occur during use of the cutting tool near the interface between the third unit layer and the fourth unit layer.

[0025] (vi) The second layer has a higher aluminum (Al) content and higher toughness than the first layer, and therefore the coating having the second layer can have excellent chipping resistance.

[0026] (vii) The third unit layer and the fourth unit layer have different Ti contents. Therefore, the third unit layer and the fourth unit layer have different crystal lattices, which causes distortion of the crystal lattice in the second layer, and the second layer can have high hardness. Therefore, the coating including the second layer can have excellent wear resistance.

[0027] <Cutting tools> The cutting tool of the first embodiment is not particularly limited in shape, use, etc., as long as it is a cutting tool. The cutting tool of the first embodiment may be, for example, a drill, an end mill, a milling cutting insert, a turning cutting insert, a metal saw, a gear cutting tool, a reamer, a tap, or a crankshaft pin milling insert.

[0028] 1 is a schematic partial cross-sectional view showing an example of the configuration of a cutting tool of embodiment 1. The cutting tool 100 includes a substrate 10 and a coating 20 provided on the substrate 10. The coating 20 includes a first layer 21 and a second layer 22. The second layer 22 is provided at a position closer to the substrate 10 than the first layer 21. The first layer 21 has a multilayer structure in which a first unit layer 1 and a second unit layer 2 are alternately laminated. The second layer 22 has a multilayer structure in which a third unit layer 3 and a fourth unit layer 4 are alternately laminated.

[0029] ≪Base material≫ The substrate 10 is not particularly limited. The substrate 10 may be made of, for example, cemented carbide, cermet, high speed steel, ceramics, cubic boron nitride sintered body, diamond sintered body, etc. The substrate 10 is preferably made of cemented carbide. This is because cemented carbide has excellent wear resistance.

[0030] The cemented carbide is a sintered body mainly composed of WC (tungsten carbide) particles. The cemented carbide includes a hard phase and a binder phase. The hard phase contains WC particles. The binder phase bonds the WC particles together. The binder phase contains, for example, Co (cobalt) and the like. The binder phase may further contain, for example, TiC (titanium carbide), TaC (tantalum carbide), NbC (niobium carbide), and the like.

[0031] The cemented carbide may contain impurities that are inevitably mixed in during the manufacturing process. The cemented carbide may also contain free carbon or an abnormal layer called an "η layer" in its structure. Furthermore, the cemented carbide may be one that has been subjected to a surface modification treatment. For example, the cemented carbide may include a de-β layer on its surface.

[0032] The cemented carbide may contain 85% to 98% by mass of WC particles and 2% to 15% by mass of Co. The WC particles may have an average particle size of 0.2 μm to 4 μm.

[0033] Co is softer than WC particles. As described later, when the surface of the substrate 10 is subjected to ion bombardment treatment, the soft Co can be removed. Since the cemented carbide has the above composition and the WC particles have the above average particle size, appropriate irregularities are formed on the surface after the Co is removed. It is believed that by forming the coating 20 on such a surface, an anchor effect is exerted, and the adhesion between the coating 20 and the substrate 10 is improved.

[0034] Here, the particle size of the WC particles refers to the diameter of a circle circumscribing a two-dimensional projection image of the WC particles. The particle size is measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). That is, the cemented carbide is cut and the cut surface is observed with an SEM or a TEM. In the observed image, the diameter of the circle circumscribing the WC particles is regarded as the particle size of the WC particles. In the observed image, the particle sizes of 10 or more (preferably 50 or more, more preferably 100 or more) WC particles randomly selected are measured, and the arithmetic average value is regarded as the average particle size of the WC particles. When observing, it is desirable to process the cut surface by a cross section polisher (CP) or a focused ion beam (FIB), etc.

[0035] ≪Coating≫ The coating 20 is provided on the substrate 10. The coating 20 may be provided on a part of the surface of the substrate 10, or may be provided on the entire surface. However, the coating 20 is provided on at least a part of the surface of the substrate 10 that corresponds to the cutting edge. In the present disclosure, the part of the surface of the substrate 10 that corresponds to the cutting edge means an area of ​​the surface of the substrate 10 that is within 0.5 mm or 2 mm away from the cutting edge. As long as the effect of the present disclosure is not impaired, the scope of the present disclosure does not deviate even if a coating is not formed on at least a part of the part that corresponds to the cutting edge.

[0036] The coating 20 includes a first layer 21 and a second layer 22. The second layer 22 may be provided directly on the substrate 10. The first layer 21 may be the outermost layer of the coating 20. The coating 20 may be composed of a second layer 22 provided directly on the substrate 10 and a first layer 21 provided directly on the second layer 22. The coating 20 may include other layers in addition to the first layer 21 and the second layer 22, as long as the effects of the present disclosure are not impaired. For example, the coating 20 may include one or both of a base layer provided between the substrate 10 and the second layer 22 and a surface layer provided on the outermost surface of the coating 20. The base layer may include at least one layer selected from the group consisting of a TiCN layer, a TiN layer, and a TiCNO layer. The surface layer may include at least one layer selected from the group consisting of a TiC layer, a TiN layer, and a TiCN layer.

[0037] The layered structure of the coating 20 does not need to be uniform over the entire coating 20, and the layered structure may differ partially.

[0038] The thickness of the coating 20 may be 1.5 μm or more and 30 μm or less. When the thickness of the coating 20 is 1.5 μm or more, the wear resistance is improved. When the thickness of the coating 20 is 30 μm or less, the chipping resistance is improved. The thickness of the coating 20 may be 2.0 μm or more and 25 μm or less, or 3.0 μm or more and 20 μm or less. Here, the thickness of the coating means the sum of the thicknesses of the layers constituting the coating. Examples of the "layers constituting the coating" include a first layer, a second layer, a base layer, a surface layer, etc.

[0039] The thickness of each layer constituting the coating is measured by obtaining a thin section sample (hereinafter also referred to as a "cross-sectional sample") of a cross section parallel to the normal direction of the surface of the cutting tool, and observing the cross-sectional sample with a scanning transmission electron microscope (STEM). An example of a scanning transmission electron microscope is JEM-2100F (product name) manufactured by JEOL Ltd. The observation magnification of the cross-sectional sample is 5000 to 10000 times, and the thickness of each layer is measured at five points, and the arithmetic average value is taken as the "thickness of each layer."

[0040] It has been confirmed that as long as the measurements are performed using the same cutting tool, there is no variation in the measurement results even if the measurement points are selected arbitrarily.

[0041] ≪First layer≫ The first layer 21 has a multilayer structure in which the first unit layer 1 and the second unit layer 2 are alternately laminated. The number of layers is not particularly limited as long as the average thickness of each of the first unit layer 1 and the second unit layer 2 is 2 nm or more and 50 nm or less. The number of layers indicates the number of the first unit layer 1 and the second unit layer 2 included in the first layer 21. The number of layers may be 10 or more and 5000 or less, 200 or more and 5000 or less, 400 or more and 2000 or less, or 500 or more and 1000 or less. In the first layer 21, the layer closest to the substrate 10 may be the first unit layer 1 or the second unit layer 2. In the first layer 21, the layer farthest from the substrate 10 may be the first unit layer 1 or the second unit layer 2.

[0042] The average thickness of the first layer can be 1.0 μm or more and 20 μm or less. When the average thickness of the first layer is 1.0 μm or more, the wear resistance is improved. When the average thickness of the first layer is 20 μm or less, the chipping resistance is improved. The lower limit of the average thickness of the first layer may be 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more. The upper limit of the average thickness of the first layer may be 20 μm or less, 18 μm or less, 16 μm or less, or 12 μm or less. The average thickness of the first layer may be 1.0 μm or more and 20 μm or less, 2.0 μm or more and 16 μm or less, or 3.0 μm or more and 12 μm or less.

[0043] ≪Average thickness of the first and second unit layers≫ The average thickness of the first unit layer 1 is 2 nm or more and 50 nm or less, and the average thickness of the second unit layer 2 is 2 nm or more and 50 nm or less. In the first layer, such thin layers are alternately stacked, thereby suppressing the progress of cracks. If the average thickness of one or both of the first unit layer 1 and the second unit layer 2 is less than 2 nm, the compositions of the first unit layer 1 and the second unit layer 2 may be mixed, and the effect of suppressing the progress of cracks may be reduced. If the average thickness of one or both of the first unit layer 1 and the second unit layer 2 exceeds 50 nm, the effect of suppressing delamination between layers may be reduced. The average thickness of the first unit layer and the average thickness of the second unit layer may be the same or different.

[0044] The lower limit of the average thickness of the first unit layer is 2 nm or more, may be 4 nm or more, may be 6 nm or more, or may be 8 nm or more. The upper limit of the average thickness of the first unit layer is 50 nm or less, may be 46 nm or less, may be 40 nm or less, or may be 30 nm or less. The average thickness of the first unit layer is 2 nm or more and 50 nm or less, may be 4 nm or more and 40 nm or less, or may be 6 nm or more and 30 nm or less.

[0045] The lower limit of the average thickness of the second unit layer is 2 nm or more, may be 4 nm or more, may be 6 nm or more, or may be 8 nm or more. The upper limit of the average thickness of the second unit layer is 50 nm or less, may be 46 nm or less, may be 40 nm or less, or may be 30 nm or less. The average thickness of the second unit layer is 2 nm or more and 50 nm or less, may be 4 nm or more and 40 nm or less, or may be 6 nm or more and 30 nm or less.

[0046] The method for measuring the average thickness of each of the first unit layer and the second unit layer is as follows. A thin section sample (hereinafter also referred to as a "cross-sectional sample") of the cutting tool cross section parallel to the normal direction of the surface of the cutting tool is obtained. The cross-sectional sample is observed with a scanning transmission electron microscope (STEM). An example of a scanning transmission electron microscope is JEM-2100F (product name) manufactured by JEOL Ltd. The observation magnification of the cross-sectional sample is appropriately adjusted according to the thickness of the first unit layer 1 and the second unit layer 2. For example, the observation magnification can be about 1 million times. The thickness is measured at five points in one first unit layer. The arithmetic mean value of the thicknesses of the five points of the first unit layer is calculated, and the arithmetic mean value is set to the average thickness of the first unit layer. The thickness is measured at five points in one second unit layer.

[0047] For each of five different first unit layers, the average thickness of the first unit layer is measured using the above procedure. The arithmetic average value of the average thicknesses of the five first unit layers is determined. In the present disclosure, this arithmetic average value is referred to as the average thickness of the first unit layer. For each of five different second unit layers, the average thickness of the second unit layer is measured using the above procedure. The arithmetic average value of the average thicknesses of the five second unit layers is determined. In the present disclosure, this arithmetic average value is referred to as the average thickness of the second unit layer. The average thicknesses of the third and fourth unit layers described below are also measured in the same manner as above.

[0048] It has been confirmed that as long as the measurements are performed using the same cutting tool, there is no variation in the measurement results even if the measurement points are selected arbitrarily.

[0049] <Composition of the first and second unit layers> In the cutting tool of the present disclosure, the first unit layer is Ti a Al 1-a-b B b N, where 0.30 ≤ a ≤ 0.50 and 0 < b ≤ 0.10 are satisfied, and the second unit layer is Ti c Al 1-c N, where 0.70 ≤ c ≤ 1.00 is satisfied. As long as the effects of the present disclosure are not impaired, the first unit layer can contain impurities together with Ti a Al 1-a-b B b N. The first unit layer can consist of Ti a Al 1-a-b B b N and impurities. As long as the effects of the present disclosure are not impaired, the second unit layer can contain impurities together with Ti c Al 1-c N. The second unit layer can consist of Ti c Al 1-c N and impurities. Examples of the impurities include carbon (C) and oxygen (O).

[0050] In the first unit layer, the lower limit of a is 0.30 or more, and may be 0.36 or more, 0.37 or more, or 0.39 or more. The upper limit of a is 0.50 or less, and may be 0.48 or less, 0.45 or less. a may be 0.36 ≤ a ≤ 0.48 or 0.37 ≤ a ≤ 0.45.

[0051] In the first unit layer, the lower limit of b is more than 0, and may be 0.01 or more, 0.02 or more, or 0.05 or more. The upper limit of b is 0.10 or less, and may be 0.08 or less, 0.07 or less. b may be 0.01 ≤ b ≤ 0.08 or 0.02 ≤ b ≤ 0.07.

[0052] In the second unit layer, the lower limit of c is 0.70 or more, and may be 0.75 or more, 0.80 or more, or 0.87 or more. The upper limit of c is 1.00 or less, and may be 0.95 or less, 0.92 or less. c may be 0.75 ≤ d ≤ 0.95 or 0.80 ≤ d ≤ 0.92.

[0053] Ti of the first unit layer a Al 1-a-b B b Ti in a, b and second unit layers in N c Al 1-c The c in N is determined by measuring the composition of each layer using Energy Dispersive X-ray spectrometry (EDX). e An EDX (TEM-DEX) attached to a TEM is used. An example of the EDX device is JED-2300 (trademark) manufactured by JEOL Ltd.

[0054] The composition analysis is performed as follows: A thin section sample (hereinafter also referred to as a "cross-sectional sample") of a cross section parallel to the normal direction of the surface of the cutting tool is obtained. While observing the cross-sectional sample with a TEM, EDX analysis is performed at five arbitrarily selected points in one first unit layer or one second unit layer. The first unit layer and the second unit layer can be distinguished by the difference in contrast. Here, the "five arbitrarily selected points" are selected from crystal grains that are different from each other. The composition ratios of each element obtained by the measurements at the five points are arithmetically averaged to identify the compositions of the first unit layer and the second unit layer.

[0055] For each of the five different first unit layers, the composition of the first unit layer is determined using the above procedure. In the present disclosure, the average of the compositions of the five first unit layers is taken as the composition of the first unit layer, and a and b are determined based on this. For each of the five different second unit layers, the composition of the second unit layer is determined using the above procedure. In the present disclosure, the average of the compositions of the five second unit layers is taken as the composition of the second unit layer, and c is determined based on this. The compositions of the third and fourth unit layers described below, as well as the Ti of the third unit layer, are also determined. d Al 1-d-e B e d and e in N, Ti in the fourth unit layer f Al 1-f-g B gf and g in N are also measured in the same manner as above.

[0056] It has been confirmed that as long as measurements are taken with the same cutting tool, there is no variation in the measurement results even if the measurement points are selected arbitrarily.

[0057] <Composition of the first layer> In the first layer, the percentage (T2 / T1)×100 of the number of titanium atoms T2 relative to the total number T1 of the atoms of titanium and aluminum is 60% or more (hereinafter, also referred to as "percentage (T2 / T1)×100"). This allows the first layer to have excellent crater wear resistance. From the viewpoint of improving crater wear resistance, the lower limit of the percentage (T2 / T1)×100 is 60% or more, may be 60.0% or more, may be 62.2% or more, may be 62.5% or more, may be 63% or more, may be 63.5% or more, or may be 66% or more. From the viewpoint of improving oxidation resistance, the upper limit of the percentage (T2 / T1)×100 may be 80% or less, may be 77% or less, may be 76.9% or less, or may be 75% or less. The percentage (T2 / T1)×100 may be 60% or more and 80% or less, 63% or more and 77% or less, or 66% or more and 75% or less.

[0058] The percentage (T2 / T1)×100 in the first layer is measured by TEM-EDX. An example of an EDX device is JED-2300 (product name) manufactured by JEOL Ltd. The percentage (T2 / T1)×100 is measured by the following procedure.

[0059] A thin section sample (hereinafter also referred to as "cross-sectional sample") of a cross section parallel to the normal direction of the cutting tool surface is obtained. While observing the cross-sectional sample with a TEM, EDX analysis is performed in five arbitrarily selected fields of view in the first layer, and the percentage (T2 / T1)×100 of the number of titanium atoms T2 relative to the total number T1 of titanium and aluminum atoms is measured. Here, the "five arbitrarily selected fields of view" are set so as not to overlap with each other. The range of one field of view is 200×200 nm. In the present disclosure, the arithmetic average of the percentages (T2 / T1)×100 obtained by measuring the five fields of view is defined as the percentage (T2 / T1)×100 in the first layer.

[0060] It has been confirmed that as long as measurements are taken with the same cutting tool, there is no variation in the measurement results even if the measurement points are selected arbitrarily.

[0061] <Nano indentation hardness of the first layer> The nanoindentation hardness of the first layer at 25°C may be 30 GPa or more. This improves the wear resistance of the cutting tool. The lower limit of the nanoindentation hardness may be 32 GPa or more, or 34 GPa or more. The upper limit of the nanoindentation hardness H is not particularly limited, but may be 60 GPa or less, 40 GPa or less, or 36 GPa or less from the viewpoint of manufacturing. The nanoindentation hardness H may be 30 GPa or more and 60 GPa or less, 32 GPa or more and 60 GPa or less, or 34 GPa or more and 60 GPa or less.

[0062] The nanoindentation hardness of the first layer at 25°C is measured by the nanoindentation method in accordance with the standard procedure defined in "ISO 14577-1: 2015 Metallic materials-Instrumented indentation test for hardness and materials parameters-". The measuring instrument used is "ENT-1100a" manufactured by Elionix. The indenter pressing load is 1g. In a cross section parallel to the normal direction of the cutting tool surface, the indenter is pressed against the first layer in the direction perpendicular to the cross section (i.e., parallel to the cutting tool surface).

[0063] The above measurement is performed at five points on one measurement sample. The average value of the nanoindentation hardness at the five points is regarded as the nanoindentation hardness of the first layer. Note that data that appears to be abnormal at first glance is to be excluded.

[0064] It has been confirmed that as long as measurements are taken with the same cutting tool, there is no variation in the measurement results even if the measurement points are selected arbitrarily.

[0065] <Diameter of the maximum inscribed circle of the grains in the first layer> The first layer may be composed of a plurality of crystal grains, and the diameter of the maximum inscribed circle of the crystal grains may be 5 nm or more and 500 nm or less. This improves the crater wear resistance of the cutting tool. The first layer of the present disclosure may include, together with the plurality of crystal grains, a region that does not constitute crystal grains (a region in which the atomic arrangement is random) within a range that does not impair the effects of the present disclosure.

[0066] The upper limit of the diameter of the maximum inscribed circle of the crystal grain may be 500 nm or less, 450 nm or less, or 400 nm or less from the viewpoint of improving wear resistance and chipping resistance. The lower limit of the diameter of the maximum inscribed circle of the crystal grain may be 5 nm or more, 7 nm or more, or 10 nm or more from the viewpoint of suppressing a decrease in film hardness due to excessive grain refinement. The diameter of the maximum inscribed circle of the crystal grain may be 5 nm or more and 500 nm or less, 7 nm or more and 450 nm or less, or 10 nm or more and 400 nm or less.

[0067] The method for measuring the diameter of the maximum inscribed circle of the crystal grain is as follows. A thin section sample (thickness: about 10 to 100 nm, hereinafter also referred to as "cross-sectional sample") of the cutting tool cross section parallel to the normal direction of the cutting tool surface is obtained. The cross-sectional sample is observed with a transmission electron microscope (TEM) to obtain a bright-field image. The observation magnification is 1 million to 5 million times. The bright-field image is obtained so as to include an area A sandwiched between a line L2 that is 0.2 μm away from a line L1 indicating the center in the average thickness direction of the first layer toward the substrate side, and a line L3 that is 0.2 μm away from the line L1 toward the surface side of the coating, as shown in FIG. 4. A rectangular measurement field of view of 150 nm × 150 nm is arbitrarily set in the area A.

[0068] In the above-mentioned measurement field of view, a region where the atomic arrangement is within ±0.5° is specified, and the region is defined as a crystal grain. The method of specifying the region where the atomic arrangement is within ±0.5° and the crystal grain will be described with reference to FIG.

[0069] FIG. 5 is a schematic diagram showing an example of a bright-field image of the above-mentioned measurement field. In FIG. 5, atoms are indicated by black dots with the reference numeral 50. Note that FIG. 5 shows only a portion of the atoms. In the bright-field image, atoms 50 that are regularly arranged are connected by line segments that provide the shortest interatomic distance. In FIG. 5, the line segments are indicated by L10 to L14, L20 to L22, and L30 to L34. Regions where the angle between the line segments is ±0.5° or less (i.e., −0.5° or more and 0.5° or less) are defined as crystal grains.

[0070] 5, the angle between line segments L10 to L14 is ±0.5° or less, and the area including these line segments corresponds to crystal grain 24a. The angle between line segments L20 to L22 is ±0.5° or less, and the area including these line segments corresponds to crystal grain 24b. The angle between line segments L30 to L34 is ±0.5° or less, and the area including these line segments corresponds to crystal grain 24c.

[0071] The diameter of the maximum inscribed circle of each crystal grain in the above measurement field is determined. The diameter of the maximum inscribed circle means the diameter of the largest inscribed circle that can be drawn inside the crystal grain and that contacts at least a part of the outer edge of the crystal grain.

[0072] In Fig. 5, the diameter of the maximum inscribed circle 25a of crystal grain 24a is D1. The diameter of the maximum inscribed circle 25b of crystal grain 24b is D2. The diameter of the maximum inscribed circle 25c of crystal grain 24c is D3. When D1, D2, and D3 are all 50 nm or less, it is confirmed that the first layer shown in Fig. 5 is composed of a plurality of crystal grains, and the diameters of the maximum inscribed circles of the crystal grains are 50 nm or less.

[0073] It has been confirmed that as long as the measurements are performed using the same cutting tool, there is no variation in the measurement results of the diameter of the maximum inscribed circle of the crystal grains even if the above measurement field of view is set arbitrarily.

[0074] In FIG. 5, there are spaces between the crystal grains 24a, 24b, and 24c, but in reality, the crystal grains are present in the spaces. Since the thickness of the cross-sectional sample for TEM is about 10 to 100 nm, the bright-field image also reflects information in the depth direction. In the region where multiple crystal grains overlap in the thickness direction of the sample, a regular atomic arrangement cannot be confirmed in the bright-field image. Therefore, the region where multiple crystal grains overlap is not identified as a crystal grain by the above-mentioned identification method.

[0075] <Positional relationship between crystal grains and the first and second unit layers> The positional relationship between the crystal grains and the first and second unit layers will be described with reference to FIG. 6. FIG. 6 is a diagram showing a schematic cross section along the film thickness direction of the first layer of the first embodiment. As shown in FIG. 6, the first layer 21 has a multilayer structure in which the first unit layers 1 and the second unit layers 2 are alternately stacked. FIG. 6 shows a plurality of crystal grains 24, and the boundaries between the crystal grains 24 are shown as crystal grain boundaries 25. Each crystal grain 24 can be made of only the first unit layer or the second unit layer. Also, each crystal grain 24 can exist across one or more first unit layers and one or more second unit layers. That is, each crystal grain 24 can have a lamellar structure in which the first unit layers and the second unit layers are alternately stacked.

[0076] ≪Second layer≫ The second layer 22 has a multilayer structure in which the third unit layer 3 and the fourth unit layer 4 are alternately laminated. The number of layers is not particularly limited as long as the average thickness of each of the third unit layer 3 and the fourth unit layer 4 is 2 nm or more and 50 nm or less. The number of layers indicates the number of the third unit layer 3 and the fourth unit layer 4 included in the second layer 22. The number of layers may be 10 or more and 5000 or less, 200 or more and 5000 or less, 400 or more and 2000 or less, or 500 or more and 1000 or less. In the second layer 22, the layer closest to the substrate 10 may be the third unit layer 3 or the fourth unit layer 4. In the second layer 22, the layer farthest from the substrate 10 may be the third unit layer 3 or the fourth unit layer 4.

[0077] The average thickness of the second layer can be 0.5 μm or more and 10 μm or less. When the average thickness of the second layer is 0.5 μm or more, the wear resistance is improved. When the average thickness of the second layer is 10 μm or less, the chipping resistance is improved. The lower limit of the average thickness of the second layer may be 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more. The upper limit of the average thickness of the second layer may be 10 μm or less, 9 μm or less, 8 μm or less, or 7 μm or less. The average thickness of the second layer may be 1.0 μm or more and 9 μm or less, 2.0 μm or more and 8 μm or less, or 3.0 μm or more and 7 μm or less.

[0078] <Average thickness of the third and fourth unit layers> The average thickness of the third unit layer 3 is 2 nm or more and 100 nm or less, and the average thickness of the fourth unit layer 4 is 2 nm or more and 100 nm or less. In the second layer, such thin layers are alternately stacked, thereby suppressing the progress of cracks. If the average thickness of one or both of the third unit layer 3 and the fourth unit layer 4 is less than 2 nm, the compositions of the third unit layer 3 and the fourth unit layer 4 may be mixed, reducing the effect of suppressing the progress of cracks. If the average thickness of one or both of the third unit layer 3 and the fourth unit layer 4 exceeds 100 nm, the effect of suppressing delamination between layers may be reduced. The average thickness of the third unit layer and the average thickness of the fourth unit layer may be the same or different.

[0079] The lower limit of the average thickness of the third unit layer is 2 nm or more, and may be 5 nm or more, 10 nm or more, 15 nm or more, or 20 nm or more. The upper limit of the average thickness of the third unit layer is 100 nm or less, 80 nm or less, 75 nm or less, 65 nm or less, or 64 nm or less. The average thickness of the third unit layer is 2 nm or more and 100 nm or less, and may be 5 nm or more and 75 nm or less, or 10 nm or more and 65 nm or less.

[0080] The lower limit of the average thickness of the fourth unit layer is 2 nm or more, and may be 5 nm or more, 10 nm or more, 15 nm or more, or 20 nm or more. The upper limit of the average thickness of the fourth unit layer is 100 nm or less, 80 nm or less, 75 nm or less, 65 nm or less, 52 nm or less, or 50 nm or less. The average thickness of the fourth unit layer is 2 nm or more and 100 nm or less, and may be 5 nm or more and 75 nm or less, or 10 nm or more and 50 nm or less.

[0081] The average thickness of each of the third and fourth unit layers is measured in the same manner as the average thickness of each of the first and second unit layers described above. It has been confirmed that there is no variation in the measurement results even if the measurement points are arbitrarily selected, as long as the measurements are performed using the same cutting tool.

[0082] ≪Composition of the Third Unit Layer and the Fourth Unit Layer≫ In the cutting tool of the present disclosure, the third unit layer is composed of Ti d Al 1-d-e B e N, where 0.25 ≤ d < 0.45 and 0 < e ≤ 0.10 are satisfied. The fourth unit layer is composed of Ti f Al 1-f-g B g N, where 0.35 ≤ f < 0.55, 0 < g ≤ 0.10, and 0.05 ≤ f - d ≤ 0.2 are satisfied. As long as the effects of the present disclosure are not impaired, the third unit layer can contain impurities together with Ti d Al 1-d-e B e N. The third unit layer can consist of Ti d Al 1-d-e B e N and impurities. As long as the effects of the present disclosure are not impaired, the fourth unit layer can contain impurities together with Ti f Al 1-f-g B g N. The fourth unit layer can consist of Ti f Al 1-f-g B g N and impurities. Examples of the impurities include carbon (C) and oxygen (O).

[0083] In the third unit layer, the lower limit of d is 0.25 or more, and may be 0.30 or more, 0.31 or more, 0.32 or more, 0.33 or more, 0.34 or more. The upper limit of d is less than 0.45, and may be 0.40 or less, 0.37 or less, 0.35 or less. d may be 0.30 ≤ d ≤ 0.40 or 0.31 ≤ d ≤ 0.37.

[0084] In the third unit layer, the lower limit of e is more than 0, and may be 0.01 or more, 0.02 or more, 0.04 or more, 0.05 or more. The upper limit of e is 0.10 or less, and may be 0.08 or less, 0.07 or less, 0.06 or less. e may be 0.01 ≤ e ≤ 0.08 or 0.02 ≤ e ≤ 0.07.

[0085] In the fourth unit layer, the lower limit of f is 0.35 or more, or may be 0.40 or more, 0.41 or more, 0.42 or more, 0.43 or more, or 0.45 or more. The upper limit of f is less than 0.55 and may be 0.50 or less. f may be 0.40≦f<0.55, or 0.45≦f≦0.50.

[0086] In the fourth unit layer, the lower limit of g is more than 0, and may be 0.01 or more, 0.02 or more, or 0.04 or more. The upper limit of g is 0.10 or less, 0.08 or less, or 0.06 or less. g is 0.01≦ g ≦0.10 is acceptable, and 0.02≦ g It may be ≦0.06.

[0087] In the second layer, the lower limit of fd is 0.05 or more, and may be 0.08 or more, 0.10 or more, or 0.11 or more. The upper limit of fd is 0.20 or less, and may be 0.18 or less. fd may be 0.08≦fd≦0.18, or 0.10≦fd≦0.18.

[0088] Ti of the third unit layer d Al 1-d-e B e d and e in N, Ti in the fourth unit layer f Al 1-f-g B g f and g in N are the Ti of the first unit layer mentioned above. a Al 1-a-b B b Ti in a, b and second unit layers in N c Al 1-c It is measured in the same way as c in N. It has been confirmed that there is no variation in the measurement results even if the measurement points are arbitrarily selected as long as the same cutting tool is used for the measurement.

[0089] <X-ray diffraction analysis of the second layer> In the X-ray diffraction spectrum of the second layer, the ratio I(200) / I(002) of the peak intensity I(200) derived from the (200) plane to the peak intensity I(002) derived from the (002) plane is 2 or more, and the half-width of the peak derived from the (002) plane is 2 degrees or more. This improves the hardness and toughness of the second layer, and excellent wear resistance and chipping resistance can be obtained. The "peak intensity I(002) derived from the (002) plane" means the diffraction intensity (peak height) of the highest peak among the X-ray diffraction peaks derived from the (002) plane of the hexagonal crystal. The "peak intensity I(200) derived from the (200) plane" means the diffraction intensity (peak height) of the highest peak among the X-ray diffraction peaks derived from the (200) plane of the cubic crystal. If a peak derived from the (002) plane of the hexagonal crystal is present in the X-ray diffraction spectrum of the second layer, it is confirmed that the second layer contains a hexagonal crystal structure. If the X-ray diffraction spectrum of the second layer shows a peak due to the (200) plane of the cubic crystal, it is confirmed that the second layer contains a cubic crystal structure. A ratio I(200) / I(002) of 2 or more means that a mixed crystal of cubic and hexagonal crystals is formed in the second layer.

[0090] The conditions of the X-ray diffraction analysis for measuring the peak intensity I(002) and the peak intensity I(200) are as follows. Scan axis: 2θ-θ X-ray source: Cu-Kα ray (1.541862Å) Detector: 0-dimensional detector (scintillation counter) Tube voltage: 45kV Tube current: 40mA Incident optics: Use of mirrors Receiving optical system: Use of analyzer crystal (PW3098 / 27) Step: 0.03° Accumulation time: 2 seconds Scan range (2θ): 20°~80°

[0091] At three arbitrary points in the second layer, X-ray diffraction measurement (XRD measurement) is performed by the θ / 2θ method to obtain the X-ray diffraction intensity of a predetermined crystal plane, and the average value of the obtained X-ray diffraction intensities at the three points is regarded as the X-ray diffraction intensity of the predetermined crystal plane. The X-ray diffraction intensity of the (200) plane corresponds to the X-ray diffraction intensity at about 2θ=43 to 44°, and the X-ray diffraction intensity of the (002) plane corresponds to the X-ray diffraction intensity at about 2θ=30 to 40°. Examples of devices used for X-ray diffraction measurement include "SmartLab" (trade name) manufactured by Rigaku Corporation and "X'pert" (trade name) manufactured by PANalytical Corporation.

[0092] The lower limit of the ratio I(200) / I(002) is 2 or more, and may be 2.0 or more, 2.2 or more, or 2.3 or more. The upper limit of the ratio I(200) / I(002) may be, for example, 10 or less, less than 10, 5 or less, or 3 or less. The ratio I(200) / I(002) may be 2 or more and 10 or less, or 2 or more and 5 or less.

[0093] The half-width of the peak derived from the (002) plane being 2 degrees or more means that hexagonal crystals are finely dispersed in the second layer, improving hardness and toughness. The lower limit of the half-width of the peak derived from the (002) plane is 2 degrees or more, and may be 2.0 degrees or more, or 2.2 degrees or more. The upper limit of the half-width of the peak derived from the (002) plane may be 4 degrees or less, or may be 3 degrees or less. The lower limit of the half-width of the peak derived from the (002) plane may be 2 degrees or more, or 2.2 degrees or more, or 2.4 degrees or more. The half-width of the peak derived from the (002) plane may be 2 degrees or more and 4 degrees or less, or may be 2 degrees or more and 3 degrees or less.

[0094] [Embodiment 2: Manufacturing method of cutting tool] In embodiment 2, a method for manufacturing the cutting tool of embodiment 1 will be described. The manufacturing method of embodiment 2 can include a step of preparing a substrate and a step of forming a coating on the substrate. Each step will be described in detail below.

[0095] <Process of preparing substrate> In the step of preparing a substrate, a substrate 10 is prepared. As the substrate 10, the substrate described in the first embodiment can be used.

[0096] <Step of forming coating> In the step of forming the coating, the coating 20 is formed on the substrate 10. In the second embodiment, the coating 20 can be formed by a physical vapor deposition (PVD) method. Specific examples of the PVD method include an arc ion plating (AIP) method, a balanced magnetron sputtering (BMS) method, and an unbalanced magnetron sputtering (UBMS) method. In the second embodiment, it is preferable to use the arc ion plating.

[0097] In the AIP method, an arc discharge is generated using a target material as a cathode. This causes the target material to evaporate and ionize. The ions are then deposited on the surface of the substrate 10 to which a negative bias voltage is applied. The AIP method is excellent in terms of the ionization rate of the target material.

[0098] A film forming apparatus used in the AIP method will be described with reference to Figures 2 and 3. As shown in Figure 2, the film forming apparatus 200 includes a chamber 201. The chamber 201 is provided with a gas inlet 202 for introducing a source gas into the chamber 201, and a gas exhaust port 203 for discharging the source gas from the chamber 201 to the outside. The gas exhaust port 203 is connected to a vacuum pump (not shown). The pressure in the chamber 201 is adjusted by the amount of gas introduced and discharged.

[0099] A rotary table 204 is disposed within the chamber 201. A substrate holder 205 for holding a substrate 10 is attached to the rotary table 204. The substrate holder 205 is connected to the negative terminal of a bias power supply 206. The positive terminal of the bias power supply 206 is earthed.

[0100] As shown in Fig. 3, a plurality of targets 211, 212, 213, and 214 are attached to the side wall of the chamber 201. As shown in Fig. 2, each of the targets 211 and 212 is connected to the negative pole of a DC power supply 221 and 222, respectively. The DC power supplies 221 and 222 are variable power supplies, and their positive poles are earthed. Although not shown in Fig. 2, the same applies to the targets 213 and 214. A specific operation will be described below.

[0101] The substrate 10 is held by the substrate holder 205. The pressure in the chamber 201 is reduced to 1.0×10 -4 The pressure is adjusted to 500 Pa. While rotating the turntable 204, the temperature of the substrate 10 is adjusted to 500° C. by a heater (not shown) attached to the film forming apparatus 200.

[0102] Ar gas is introduced from the gas inlet 202, and the pressure inside the chamber 201 is adjusted to 3.0 Pa. While maintaining the same pressure, the voltage of the bias power supply 206 is gradually changed and finally adjusted to −1000 V. Then, the surface of the substrate 10 is cleaned by ion bombardment processing using Ar ions.

[0103] Next, in the case where the coating includes an underlayer, the underlayer is formed on the surface of the substrate 10. For example, a TiCN layer, a TiN layer, or a TiCNO layer is formed on the surface of the substrate 10.

[0104] Next, a second layer is formed on the surface of the substrate 10 or the surface of the underlayer. The composition of each target material is selected so as to obtain the composition of the third unit layer and the fourth unit layer. Each target material is set at a predetermined position, nitrogen gas is introduced from the gas inlet 202, and the second layer is formed while rotating the turntable 204. When forming the second layer, the substrate is maintained at a temperature of 400 to 800°C, the reaction gas pressure is maintained at 1 to 10 Pa (nitrogen gas partial pressure is 5 to 10 Pa), and an arc current of 80 to 200 A is alternately supplied to the evaporation source for forming the third unit layer and the evaporation source for forming the fourth unit layer while gradually changing the voltage of the bias power supply within a range of 30 to 200 V (DC power supply). As a result, metal ions are generated from the evaporation source for forming the third unit layer and the evaporation source for forming the fourth unit layer, and when the substrate faces the evaporation source for forming the third unit layer, the third unit layer is formed, and when the substrate faces the evaporation source for forming the fourth unit layer, the fourth unit layer is formed. Moreover, by forming the film while changing the voltage of the bias power supply as described above, it is possible to achieve both high hardness and cutting edge quality of the second layer. The supply of the arc current is stopped when a predetermined time has elapsed. When forming the second layer, the rotation speed of the substrate is adjusted to adjust the thickness of each of the third unit layer and the fourth unit layer. Furthermore, the thickness of the second layer is adjusted to be within a predetermined range by adjusting the film formation time. In addition to the part involved in the cutting process (for example, the rake face near the cutting edge), the second layer may be formed on the surface of the substrate other than the part involved in the cutting process.

[0105] In one aspect of this embodiment, the substrate may be maintained at a temperature of 500 to 600°C, the reactive gas pressure may be maintained at 5 to 10 Pa (nitrogen gas partial pressure is 5 to 8 Pa), and the voltage of the bias power supply may be gradually changed in the range of 30 to 200 V (DC power supply), while an arc current of 80 to 120 A may be alternately supplied to the evaporation source for forming the third unit layer and the evaporation source for forming the fourth unit layer. In this way, it is possible to form a mixed crystal structure of cubic crystals and hexagonal crystals in the second layer. By forming such a mixed crystal structure, the coarsening of the crystal grains of the cubic crystals and the hexagonal crystals is suppressed, and thus the toughness and heat resistance of the second layer are improved.

[0106] Next, the first layer is formed on the second layer. The composition of each target material is selected so as to obtain the composition of the first unit layer and the second unit layer. Each target material is set at a predetermined position, nitrogen gas is introduced from the gas inlet 202, and the first layer is formed while rotating the turntable 204. The formation conditions of the first layer are as follows.

[0107] <Conditions for forming the first layer> Base material temperature: 400~800℃ Bias voltage: -400~-20V Arc current: 80~200A Reactant gas pressure: 2~10Pa

[0108] The substrate temperature, reaction gas pressure, bias voltage and arc current are set to constant values ​​within the above ranges, or are varied continuously within the above ranges.

[0109] The multilayer structure in which the first unit layers and the second unit layers are alternately laminated can be formed by appropriately combining the following methods (A) to (D). (A) In the AIP method, a plurality of target materials (sintered alloys) having different compositions are used. (B) In the AIP method, the bias voltage applied to the substrate 10 during film formation is changed within the bias voltage range described in the above-mentioned conditions for forming the first layer. (C) In the AIP method, the gas flow rate is changed. (D) In ​​the AIP method, the substrate 10 is rotated and the rotation period is controlled.

[0110] Next, when the coating includes a surface layer, for example, the surface layer is formed on the surface of the first layer.

[0111] As a result of the above, a cutting tool 100 including the substrate 10 and the coating 20 provided on the substrate 10 can be manufactured. EXAMPLES

[0112] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0113] [Example 1] <Cutting tool manufacturing> A cutting tool was produced and its tool life was evaluated as follows.

[0114] A cutting tip made of cemented carbide (model number: CNMG120408 (manufactured by Sumitomo Electric Hardmetal Corp.)) was prepared as a substrate. The cemented carbide contained WC particles (90% by mass) and Co (10% by mass). The average particle size of the WC particles was 1 to 2 μm.

[0115] A coating was formed on the substrate using a film-forming apparatus having the configuration shown in Figures 2 and 3. First, the surface of the substrate was cleaned by ion bombardment treatment with Ar ions. The specific conditions of the ion bombardment treatment are as described in the second embodiment.

[0116] Next, the target materials were set at predetermined positions in the film forming apparatus. The composition of each target material was adjusted so as to obtain the compositions of the first and second unit layers shown in Table 1, and the compositions of the third and fourth unit layers shown in Table 2.

[0117] The second layer was formed on the substrate. Specifically, nitrogen gas was introduced from a gas inlet, and the third and fourth unit layers were alternately formed while rotating the turntable, thereby forming the second layer. The substrate was maintained at a temperature of 550°C, the reaction gas pressure was maintained at 8 Pa (nitrogen gas partial pressure: 8 Pa), and an arc current of 90 A was alternately supplied to the evaporation source for forming the third unit layer and the evaporation source for forming the fourth unit layer while gradually changing the voltage of the bias power supply in the range of 35 to 180 V. The thickness and number of layers of the third and fourth unit layers were adjusted by the rotation speed of the substrate.

[0118] Next, the first layer was formed on the second layer. Specifically, the first layer was formed on the second layer by alternately forming the first unit layer and the second unit layer while introducing nitrogen gas from the gas inlet and rotating the rotary table. The conditions for forming the first layer of each sample were a substrate temperature of 400 to 800°C, a bias voltage of -400 to -20V, an arc current of 80 to 200A, and a reaction gas pressure of 2 to 10Pa. The substrate temperature, reaction gas pressure, bias voltage, and arc current were either constant within the above ranges, or were continuously changed within the above ranges. The thickness and number of layers of each of the first unit layer and the second unit layer were adjusted by the rotation speed of the substrate. The above process resulted in a cutting tool of each sample.

[0119] <Evaluation> <Coating composition> For the coating of each sample, the composition, average thickness, number of layers, average thickness of the first layer and the second layer, percentage of the number of titanium atoms to the total number of titanium and aluminum atoms in the first layer (shown as "(T2 / T1) x 100" in Table 1), nanoindentation hardness of the first layer (shown as "hardness" in Table 1), ratio I(200) / I(002) of the second layer, and half width of the peak derived from the (002) plane (shown as "(002) peak half width" in Table 2) were measured. The measurement method for each item is as described in the first embodiment. The results are shown in Tables 1 and 2. In Table 1, the notation "1" for "number of layers" indicates that only one first unit layer or one second unit layer was formed. In Table 1, the notation "-" indicates that the corresponding layer was not formed.

[0120] [Table 1]

[0121] [Table 2]

[0122] <Cutting test> Using the cutting tools of each sample, turning was performed under the following conditions, and the cutting distance was measured until the width of the chipping, measured from the flank, reached 0.5 mm or more. The longer the cutting distance, the better the crater wear resistance and chipping resistance, and the longer the tool life. The results are shown in the "Cutting Distance" column of "Cutting Test" in Table 3.

[0123] (Cutting conditions) Work material: SUS316 round material Cutting speed: 200m / min Feed rate: 0.2mm / rev Depth of cut: 1.5mm Wet method The above cutting conditions apply to turning (high speed cutting) of stainless steel.

[0124] [Table 3]

[0125] <Evaluation> Samples 1 to 15 correspond to Examples. Samples 21 to 28 correspond to Comparative Examples. It was confirmed that Samples 1 to 15 had a longer tool life than Samples 21 to 28.

[0126] Although the embodiments and examples of the present disclosure have been described above, it is intended from the outset that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present disclosure is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0127] 1 first unit layer, 2 second unit layer, 3 third unit layer, 4 fourth unit layer, 10 substrate, 20 coating, 21 first layer, 22 second layer, 24, 24a, 24b, 24c crystal grain, 25 crystal grain boundary, 50 atom, 100 cutting tool, 200 film formation device, 201 chamber, 202 gas inlet, 203 gas exhaust port, 204 rotating table, 205 substrate holder, 206 bias power supply, 211, 212, 213, 214 target material, 221, 222 DC power supply

Claims

1. A cutting tool comprising a substrate and a coating provided on the substrate, the coating comprises a first layer and a second layer; The second layer is provided at a position closer to the substrate than the first layer, The first layer has a multilayer structure in which first unit layers and second unit layers are alternately laminated, the first unit layer has an average thickness of 2 nm or more and 50 nm or less; the second unit layer has an average thickness of 2 nm or more and 50 nm or less; The first unit layer is Ti ａ A １－ａ－ｂ B ｂ It consists of N, Where: 0.30≦a≦0.50, 0<b≦0.10 is satisfied, The second unit layer is Ti ｃ A １－ｃ It consists of N, Where: 0.70≦c≦1.00 is satisfied, in the first layer, a percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number T1 of titanium and aluminum atoms is 60% or more; the second layer has a multilayer structure in which third unit layers and fourth unit layers are alternately laminated; the third unit layer has an average thickness of 2 nm or more and 100 nm or less; the fourth unit layer has an average thickness of 2 nm or more and 100 nm or less; The third unit layer is Ti ｄ A １－ｄ－ｅ B ｅ It consists of N, The fourth unit layer is Ti ｆ A １－ｆ－ｇ B ｇ It consists of N, Where: 0.25≦d<0.45, 0<e≦0.10, 0.35≦f<0.55, 0<g≦0.10, 0.05≦f−d≦0.20 is satisfied, in an X-ray diffraction spectrum of the second layer, a ratio I(200) / I(002) of a peak intensity I(200) originating from a (200) plane to a peak intensity I(002) originating from a (002) plane is 2 or more, and a half-width of the peak originating from the (002) plane is 2 degrees or more.

2. The cutting tool according to claim 1 , wherein the first layer has a nanoindentation hardness of 30 GPa or more at 25° C.

3. The cutting tool according to claim 1 or 2, wherein the first layer has an average thickness of 1.0 μm or more and 20 μm or less.

4. The cutting tool according to claim 1 or 2, wherein the second layer has an average thickness of 0.5 μm or more and 10 μm or less.

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