Coated cutting tool

Abstract

A non-limiting example of the coated cutting tool of the present application has a substrate and a coating layer on the substrate. The coating layer has a first coating layer having a first layer containing Al2O3 particles and a second layer on the first layer. The second layer has, in order from the substrate side, a first film, a second film in contact with the first film, and a third film in contact with the second film. The first film, the second film, and the third film each contain Ti. The first film, the second film, and the third film each contain at least one selected from C and N. When the amount of N contained in the first film is a first N amount, the amount of N contained in the second film is a second N amount, and the amount of N contained in the third film is a third N amount, the following relationship is satisfied: the first N amount > the third N amount > the second N amount.

Description

[0001] Cross-referencing of related applications

[0002] This application claims priority to Japanese Patent Application No. 2020-057684, filed on March 27, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to coated cutting tools. Background Technology

[0004] As a coated cutting tool, for example, the surface-coated cutting tool described in Japanese Patent Application Publication No. 2017-221992 (Patent Document 1) is known. The surface-coated cutting tool described in Patent Document 1 has a coating comprising an inner layer and an outer layer on a substrate. The inner layer, which is in contact with the outer layer, contains an alumina layer. The outer layer comprises a multilayer structure consisting of three or more layers, each layer constituting the multilayer structure containing titanium. Summary of the Invention

[0005] A non-limiting example of the coated cutting tool of the present invention has a substrate and a coating on the substrate. The coated cutting tool includes: a first surface; a second surface adjacent to the first surface; and a cutting edge located on at least a portion of the edge portion of the first surface and the second surface. The coating has a first coating layer containing Al2O3 particles and a second layer above the first layer. The second layer, from the substrate side, sequentially comprises: a first film; a second film in contact with the first film; and a third film in contact with the second film. The first film, the second film, and the third film each contain Ti. The first film, the second film, and the third film each contain at least one selected from C and N. When the N content in the first film is defined as a first N amount, the N content in the second film as a second N amount, and the N content in the third film as a third N amount, the relationship of first N amount > third N amount > second N amount is satisfied. Attached Figure Description

[0006] Figure 1 This is a perspective view of a coated cutting tool representing a non-limiting embodiment of the present invention.

[0007] Figure 2 yes Figure 1 The cross-sectional view of section II-II of the coated cutting tool shown.

[0008] Figure 3 It's enlarged. Figure 2 An enlarged view of region A1 shown.

[0009] Figure 4 It's enlarged. Figure 2 An enlarged view of region A2 shown.

[0010] Figure 5 This is a perspective view of a cutting tool representing a non-limiting embodiment of the present invention. Detailed Implementation

[0011] Coated Cutting Tools

[0012] Hereinafter, a coating tool 1 according to a non-limiting embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, in the figures referred to below, only the main components necessary for illustrating the embodiment are simplified for ease of explanation. Therefore, the coating tool 1 may include any structural components not shown in the figures. In addition, the component dimensions in the figures do not faithfully represent the actual dimensions of the structural components or the dimensional ratios of each component.

[0013] exist Figures 1-4 In this example, as one example of coated cutting tool 1, a cutting insert suitable for use as a cutting tool when machining a workpiece is shown. Besides cutting tools, coated cutting tool 1 can also be applied to, for example, wear-resistant parts such as sliding parts and molds, tools such as digging tools and cutting tools, and impact-resistant parts. Furthermore, the applications of coated cutting tool 1 are not limited to the examples shown.

[0014] The coated cutting tool 1 may have a substrate 2 and a coating 3 located on the substrate 2.

[0015] Examples of materials for the substrate 2 include cemented carbide, ceramics, and metals. Examples of cemented carbides include those composed of a binder phase of ferrous metals such as Co (cobalt) and Ni (nickel), and those composed of WC (tungsten carbide) and at least one selected from the groups of carbides, nitrides, and carbonitrides of metals other than WC from Groups 4, 5, and 6 of the periodic table, as needed. Other examples of cemented carbides include Ti-based cermets. Examples of ceramics include Si3N4 (silicon nitride), Al2O3 (alumina), diamond, and cBN (cubic boron nitride). Examples of metals include carbon steel, high-speed steel, and alloy steel. However, the material of the substrate 2 is not limited to the examples listed.

[0016] The coating 3 may cover the entire surface 4 of the substrate 2, or it may cover only a portion of it. When the coating 3 covers only a portion of the surface 4 of the substrate 2, it may also be referred to as the coating 3 being located on at least a portion of the substrate 2.

[0017] Coating 3 can be formed by chemical vapor deposition (CVD). In other words, coating 3 can be a CVD film.

[0018] The coating 3 is not limited to a specific thickness. For example, the thickness of the coating 3 can be set from 1 to 30 μm. Furthermore, the thickness, structure, and crystal shape constituting the coating 3 can be measured, for example, by cross-sectional observation using an electron microscope. Examples of electron microscopes include, for example, scanning electron microscopes (SEM) and transmission electron microscopes (TEM).

[0019] Coated cutting tool 1, such as Figure 1 and Figure 2 The non-limiting example shown may include: a first surface 5 (upper surface); a second surface 6 (side surface) adjacent to the first surface 5; and a cutting edge 7 located at least a portion of the edge portion of the first surface 5 and the second surface 6.

[0020] The first face 5 can be the rake face. The entire first face 5 can be the rake face, or a portion of it can be the rake face. For example, the area along the cutting edge 7 in the first face 5 can be the rake face.

[0021] The second surface 6 can be the flank face. The entire surface of the second surface 6 can be a flank face, or a portion of it can be a flank face. For example, the area along the cutting edge 7 of the second surface 6 can be a flank face.

[0022] The cutting edge 7 can be located on a portion of the edge, or it can be located on the entire edge. The cutting edge 7 can be used for cutting the workpiece.

[0023] Coated cutting tool 1, such as Figure 1 As shown in the non-limiting example, it can be a quadrilateral plate shape. Furthermore, the shape of the coating tool 1 is not limited to a quadrilateral plate shape. For example, the first surface 5 can also be triangular, pentagonal, hexagonal, or circular. Additionally, the coating tool 1 can also be cylindrical.

[0024] The coating tool 1 is not limited to a specific size. For example, the length of one side of the first surface 5 can be set to about 3 to 20 mm. In addition, the height from the first surface 5 to the surface (lower surface) located on the opposite side of the first surface 5 can be set to about 5 to 20 mm.

[0025] Here, coating 3 is as follows Figure 3 As a non-limiting example, it may have a first coating 8. The first coating 8 may have a first layer 9 and a second layer 10 located on top of the first layer 9.

[0026] The first layer, 9, can contain Al2O3 particles. The first layer, 9, can be an Al2O3 layer. An Al2O3 layer means a layer containing Al2O3 as its main component. A "main component" means the component with the highest mass percentage compared to other components.

[0027] The second layer 10 may, starting from the substrate 2 side, sequentially have a first membrane 11, a second membrane 12 connected to the first membrane 11, and a third membrane 13 connected to the second membrane 12.

[0028] The first membrane 11, the second membrane 12, and the third membrane 13 may each contain Ti (titanium). In addition, the first membrane 11, the second membrane 12, and the third membrane 13 may each contain at least one selected from C (carbon) and N (nitrogen).

[0029] More specifically, the first membrane 11, the second membrane 12, and the third membrane 13 may each contain a titanium compound. The first membrane 11, the second membrane 12, and the third membrane 13 may each contain a titanium compound as a main component. Examples of titanium compounds include, for instance, titanium carbides, nitrides, oxides, carbonitrides, carbon oxides, and carbonitrides.

[0030] Let the N content contained in the first membrane 11 be the first N amount, the N content contained in the second membrane 12 be the second N amount, and the N content contained in the third membrane 13 be the third N amount, then the relationship of first N amount > third N amount > second N amount can be satisfied.

[0031] When the above relationships are satisfied, the first membrane 11 is the easiest to peel off among the first membrane 11, the second membrane 12, and the third membrane 13. In other words, the first membrane 11 has the lowest adhesion among the first membrane 11, the second membrane 12, and the third membrane 13. In addition, the first membrane 11 has the best anti-adhesion properties among the first membrane 11, the second membrane 12, and the third membrane 13.

[0032] When the above relationship is satisfied, the second membrane 12 is the membrane with the highest hardness among the first membrane 11, the second membrane 12 and the third membrane 13. On the other hand, the second membrane 12 has the lowest anti-adhesion among the first membrane 11, the second membrane 12 and the third membrane 13.

[0033] When the above relationship is satisfied, the hardness, peel resistance and anti-adhesion of the third membrane 13 are between those of the first membrane 11 and the second membrane 12.

[0034] The coated cutting tool 1, which has the above-described coating structure and has films with such a configuration, has excellent wear resistance and anti-adhesion properties.

[0035] The first, second, and third N quantities are not limited to specific values. For example, the first N quantity can be set to 45–55 atomic percent. The second N quantity can be set to 0–25 atomic percent. The third N quantity can be set to 25–45 atomic percent. The N content can be, for example, a value measured by energy-dispersive X-ray analysis (EDS).

[0036] The first film 11 may contain Ti(C) x1 N y1 Oz1 Particles with the following structure (0≤x1≤1, 0≤y1≤1, 0≤z1<1, x1+y1+z1=1). The second film 12 may contain Ti(C) particles. x2 N y2 O z2 Particles containing the following parameters: (0≤x²≤1, 0≤y²≤1, 0≤z²<1, x²+y²+z²=1). The third film 13 may contain Ti(C) particles. x3 N y3 O z3 Particles of the following type (0≤x3≤1, 0≤y3≤1, 0≤z3<1, x3+y3+z3=1).

[0037] It can be y1 = 1. That is, the first membrane 11 can contain TiN particles. Furthermore, the first membrane 11 can be a TiN membrane. A TiN membrane means a membrane containing TiN as its main component. This is defined in the same way for other membranes.

[0038] It can be x2 = 1. Alternatively, it can be 0 < x3 < 1, 0 < y3 < 1, z3 = 0. That is, the second film 12 can contain TiC particles, and the third film 13 can contain TiCN particles. The second film 12 can be a TiC film, and the third film 13 can be a TiCN film.

[0039] It can be 0 < x2 < 1, 0 < y2 < 1, z2 = 0. Alternatively, it can be 0 < x3 < 1, 0 < y3 < 1, z3 = 0. That is, the second film 12 and the third film 13 can each contain TiCN particles. The second film 12 and the third film 13 can each be a TiCN film.

[0040] When the second membrane 12 and the third membrane 13 each contain TiCN particles, X2 can be greater than X3. That is, the C content in the second membrane 12 can be greater than the C content in the third membrane 13.

[0041] The third film 13 may contain both carbon (C) and nitrogen (N). The N / (C+N) ratio in the third film 13 may be 0.7 or higher. Alternatively, the N / (C+N) ratio in the third film 13 may be 0.9 or lower. N / (C+N) can be the atomic ratio of N to the sum of C and N. N / (C+N) can be measured, for example, by energy-dispersive X-ray diffraction (EDS) analysis. Furthermore, N / (C+N) represents the atomic ratio.

[0042] The thicknesses of the first membrane 11, the second membrane 12, and the third membrane 13 can be the same, or they can be different. For example, the thickness of the second membrane 12 can be greater than the thickness of the first membrane 11 and the thickness of the third membrane 13. In this case, the wear resistance is high.

[0043] The thicknesses of the first membrane 11, the second membrane 12, and the third membrane 13 are not limited to specific values. For example, the thickness of the first membrane 11 can be set to 0.1–0.5 μm. The thickness of the second membrane 12 can be set to 0.5–1.0 μm. The thickness of the third membrane 13 can be set to 0.3–0.7 μm. The thickness of the second membrane 12 can account for more than 40% of the total thickness of the second layer 10.

[0044] Furthermore, the thickness of the second layer 10 can be the same as the thickness of the first layer 9, or it can be different. For example, the thickness of the second layer 10 can be greater than the thickness of the first layer 9.

[0045] The second layer 10 may be in contact with the first layer 9, or it may not be in contact with the first layer 9. Similarly, the first layer 9 may be in contact with the substrate 2, or it may not be in contact with the substrate 2. For example, the first coating 8 may have other layers located between the first layer 9 and the second layer 10, and it may also have other layers located between the substrate 2 and the first layer 9. The other layers may contain TiN particles, TiC particles, or TiCN particles. The other layers may be TiN films, TiC films, or TiCN films.

[0046] The first coating 8 can be located on the first face 5 (rake face). In this case, the first face 5 has high wear resistance and anti-adhesion properties.

[0047] The first coating 8 can be located on the second surface 6 (the back face). In this case, the second surface 6 has high wear resistance and anti-adhesion properties.

[0048] Coating 3 Figure 4 In one non-limiting example shown, a second coating 14 may be provided. The second coating 14 may have a third layer 15. The third layer 15 may contain Al2O3 particles. The third layer 15 may be an Al2O3 layer. The third layer 15 may be the outermost layer.

[0049] The second coating 14 can be located on the second surface 6 (back face). In this case, the second surface 6 has high anti-adhesion properties.

[0050] The second coating 14 can be located on the first surface 5 (rake face). In this case, the first surface 5 has high anti-adhesion properties.

[0051] The first coating 8 can be located on the first surface 5 (front face), and the second coating 14 can be located on the second surface 6 (back face). In this case, the first surface 5 has high wear resistance and anti-adhesion, while the second surface 6 has high anti-adhesion.

[0052] Alternatively, the first coating 8 can be located on the second surface 6 (flank face), and the second coating 14 can be located on the first surface 5 (front face). In this case, the first surface 5 has high anti-adhesion properties, while the second surface 6 has high wear resistance and anti-adhesion properties.

[0053] <Manufacturing Method of Coated Cutting Tools>

[0054] Next, a method for manufacturing a coated cutting tool according to a non-limiting embodiment of the present invention will be described, exemplified by manufacturing a coated cutting tool 1.

[0055] First, a substrate 2 can be prepared. Taking the preparation of a substrate 2 made of cemented carbide as an example, we will explain how to prepare a substrate 2. First, metal powder, carbon powder, etc., can be appropriately added to inorganic powders such as metal carbides, nitrides, carbonitrides, and oxides that can form the substrate 2 by firing, and mixed to obtain a mixed powder. Second, this mixed powder can be formed into a specified tool shape using known forming methods such as stamping, casting, extrusion, and cold isostatic pressing to obtain a shaped body. Then, the obtained shaped body can be fired in a vacuum or a non-oxidizing atmosphere to obtain the substrate 2. The surface 4 of the substrate 2 can be ground or honed.

[0056] Next, a coating 3 can be formed on the surface 4 of the obtained substrate 2 by CVD to obtain the coated tool 1.

[0057] like Figure 3 In one non-limiting example shown, when the first layer 9 is in contact with the substrate 2, the first layer 9 (Al2O3 layer) can be formed first. First, the reaction gas composition can be adjusted to include: aluminum trichloride (AlCl3) gas at 0.5–5% by volume, hydrogen chloride (HCl) gas at 0.5–3.5% by volume, carbon dioxide (CO2) gas at 0.5–5% by volume, hydrogen sulfide (H2S) gas at less than 0.5% by volume, with the remainder being hydrogen (H2). Then, this mixture can be introduced into a furnace, the temperature set at 930–1010°C, the pressure set at 5–10 kPa, and the time set at 30–300 minutes to form the first layer 9. Furthermore, these film-forming conditions can also be applied to the third layer 15.

[0058] Next, the first membrane 11, the second membrane 12, and the third membrane 13 in the second layer 10 can be formed in sequence.

[0059] As the first film 11, the case of forming a TiN film will be described as an example. First, the composition of the reaction gas can be adjusted to form a mixed gas as follows: titanium tetrachloride (TiCl4) gas is 0.1 to 10% by volume, nitrogen (N2) gas is 10 to 60% by volume, and the remainder is hydrogen (H2) gas. Then, this mixed gas can be introduced into the furnace, the temperature is set at 800 to 1010°C, the pressure is set at 10 to 85 kPa, and the time is set at 10 to 60 minutes to form the first film 11, which is the TiN film.

[0060] Next, as the second membrane 12, the case of forming a TiC membrane will be described. First, the composition of the reaction gas can be adjusted to form a mixed gas as follows: titanium tetrachloride (TiCl4) gas is 0.1 to 30% by volume, methane (CH4) gas is 0.1 to 20% by volume, and the remainder is hydrogen (H2). Then, this mixed gas is introduced into the furnace, the temperature is set at 800 to 1100°C, the pressure is set at 10 to 85 kPa, and the time is set at 10 to 120 minutes to form the second membrane 12 as a TiC membrane.

[0061] Next, the formation of a TiCN film as the third film 13 will be explained as an example. First, the reaction gas composition can be adjusted to include: 0.1–10% by volume titanium tetrachloride (TiCl4), 10–60% by volume nitrogen (N2), 0.1–15% by volume methane (CH4), and the remainder hydrogen (H2). This mixture can then be introduced into a furnace, with the temperature set at 800–1100°C, the pressure at 5–30 kPa, and the time at 20–100 minutes, to form the third film 13, which is a TiCN film. This film formation condition can also be applied when the second film 12 is a TiCN film. Furthermore, for example, in the above reaction gas composition, a higher proportion of N2 results in a larger N / (C+N) ratio. Conversely, a lower proportion of N2 results in a smaller N / (C+N) ratio.

[0062] Here, when forming the first membrane 11, the second membrane 12, and the third membrane 13, by adjusting the composition of the reactant gas, the N content in the first membrane 11, the second membrane 12, and the third membrane 13 can reach the level of first N amount > third N amount > second N amount.

[0063] In the resulting coated cutting tool 1, the area including the cutting edge 7 can be ground. As a result, the area including the cutting edge 7 becomes smooth, which suppresses the adhesion of the material being cut and improves the chipping resistance of the cutting edge 7.

[0064] Furthermore, the above-described manufacturing method is one example of a method for manufacturing the coated cutting tool 1. Therefore, the coated cutting tool 1 is not limited to being manufactured by the above-described manufacturing method.

[0065] <Cutting Tools>

[0066] like Figure 5 As shown in a non-limiting example, the cutting tool 101 of a non-limiting embodiment of the present invention may have: a tool holder 102 having a length from a first end 102a to a second end 102b and having a slot 103 located on the first end 102a side; and a coated tool 1 located in the slot 103. Furthermore, in Figure 5The example shown is a case where the coating tool 1 has a through hole through which the coating tool 1 is fixed to the slot 103 by a screw 104.

[0067] The present invention will now be described in detail with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0068] Example

[0069] [Samples No. 1-8]

[0070] <Making of Coated Knives>

[0071] First, the matrix is ​​prepared. Specifically, WC powder with an average particle size of 1.2 μm is mixed with metallic Co powder (6% by mass), TiC (titanium carbide) powder (2.0% by mass), and Cr3C2 (chromium carbide) powder (0.2% by mass) with an average particle size of 1.5 μm. The mixture is then stamped into a cutting tool shape (CNMG120408) to obtain a shaped body. The obtained shaped body is dewaxed and sintered at 1400°C for 1 hour under a vacuum of 0.5–100 Pa to prepare a matrix made of cemented carbide. The rake face (first face) of the prepared matrix is ​​then honed by brushing.

[0072] Next, a film coating (second layer) is formed on the obtained substrate using CVD under the film formation conditions shown in Table 1, to obtain the coated tool (cutting insert) shown in Table 2.

[0073] Furthermore, the coated tools shown in Table 2 all have an Al2O3 layer (first layer) formed on the substrate. The film formation conditions and thickness of the Al2O3 layer are as follows.

[0074] AlCl3 gas: 4.0 vol%

[0075] HCl gas: 1.0% by volume

[0076] CO2 gas: 4.5% by volume

[0077] H2S gas: 0.3% by volume

[0078] H2 gas: Balance

[0079] Temperature: 1000℃

[0080] Pressure: 10 kPa

[0081] Time: 300 minutes

[0082] Thickness: 5.0μm

[0083] In Tables 1 and 2, each compound is represented by its chemical symbol. The coating thicknesses shown in Table 1, and the thicknesses of the Al2O3 layers mentioned above, are values ​​obtained through cross-sectional observation using SEM. Furthermore, in Table 1, films labeled as TiN substantially do not contain C, and their N / (C+N) ratio is approximately 1; films labeled as TiC substantially do not contain N, and their N / (C+N) ratio is approximately 0. Additionally, in Table 1, the N / (C+N) ratio of the TiCN film in sample No. 1 is 0.8, the N / (C+N) ratio of the TiCN films in samples No. 2–7 is 0.7, and the N / (C+N) ratio of the TiCN film in sample No. 8 is 0.5.

[0084] <Evaluation>

[0085] The appearance color of the coated cutting tools was visually evaluated. The results are shown in Table 1. Additionally, wear resistance and adhesion to the cutting edge were evaluated. The measurement methods are presented below, and the results are shown in Table 2.

[0086] <Cutting Evaluation Conditions>

[0087] Abrasion resistance evaluation

[0088] Machining method: Turning

[0089] Workpiece: SCM435 round bar

[0090] Cutting speed: 300m / min

[0091] Feed: 0.3mm / rev

[0092] Depth of cut: 1.5mm

[0093] Processing status: wet

[0094] Evaluation item: Confirm the wear on the flank face during a cutting time of 20 minutes.

[0095] Anti-adhesion evaluation

[0096] Machining method: Turning

[0097] Workpiece: S45C round bar

[0098] Cutting speed: 100m / min

[0099] Feed: 0.1 mm / rev

[0100] Depth of cut: 1.0mm

[0101] Processing status: wet

[0102] Evaluation item: Confirm the adhesion of the cutting edge during the 5-minute cutting time.

[0103] Table 2 records the back face wear (Vb) at a cutting time of 20 minutes and the edge adhesion status at a cutting time of 5 minutes. The edge adhesion column in Table 2 describes the two parameters of edge adhesion and chipping according to the following criteria: Regarding the edge adhesion status, "◎" indicates no adhesion and no chipping. "〇" indicates no chipping, but a small amount of adhesion can be identified. "△" indicates no chipping, but the amount of adhesion is greater than "〇". "×" indicates adhesion occurred, and chipping occurred due to adhesion.

[0104] Table 1

[0105]

[0106] Table 2

[0107]

[0108] As shown in Table 2, samples No. 3 to 8, which correspond to the examples, all exhibited superior cutting performance compared to samples No. 1 to 2, which correspond to the comparative examples.

[0109] Symbol Explanation

[0110] 1… Coated cutting tools (inserts)

[0111] 2…matrix

[0112] 3…coating

[0113] 4…Surface

[0114] 5…First page

[0115] 6…Second page

[0116] 7…blade

[0117] 8…First Coating

[0118] 9…First Floor

[0119] 10…Second layer

[0120] 11…First Membrane

[0121] 12…Second membrane

[0122] 13…Third Membrane

[0123] 14…Second Coating

[0124] 15…Third floor

[0125] 101…Cutting tools

[0126] 102…handle

[0127] 102a…First end

[0128] 102b…Second end

[0129] 103…card slot

[0130] 104… screws

Claims

1. A coated cutting tool having a substrate and a coating disposed on the substrate, wherein, The coated cutting tool includes: a first surface; a second surface adjacent to the first surface; and a cutting edge located on at least a portion of the edge portion of the first surface and the second surface. The coating has a first coating, the first coating having: The first layer containing Al2O3 particles; The second floor is located above the first floor. The second layer, starting from the substrate side, has the following in sequence: First membrane; The second membrane is in contact with the first membrane; The third membrane is in contact with the second membrane. The first film contains TiN, the second film contains TiC, and the third film contains TiCN. Let the N content contained in the first membrane be the first N amount. The N content contained in the second membrane is the second N amount. When the N content contained in the third membrane is the third N amount, The relationship is satisfied: First N quantity > Third N quantity > Second N quantity. On an atomic ratio basis, the N / (C+N) ratio in the third membrane is 0.7 or higher.

2. A coated cutting tool having a substrate and a coating disposed on the substrate, wherein, The coated cutting tool includes: a first surface; a second surface adjacent to the first surface; and a cutting edge located on at least a portion of the edge portion of the first surface and the second surface. The coating has a first coating, the first coating having: The first layer containing Al2O3 particles; The second floor is located above the first floor. The second layer, starting from the substrate side, has the following in sequence: First membrane; The second membrane is in contact with the first membrane; The third membrane is in contact with the second membrane. The first membrane, the second membrane, and the third membrane each contain Ti. The first membrane and the second membrane each contain at least one selected from C and N, and the third membrane contains C and N. Let the N content contained in the first membrane be the first N amount. The N content contained in the second membrane is the second N amount. When the N content contained in the third membrane is the third N amount, The relationship is satisfied: First N quantity > Third N quantity > Second N quantity. The thickness of the second membrane is greater than the thickness of the first membrane and the thickness of the third membrane. On an atomic ratio basis, the N / (C+N) ratio in the third membrane is 0.7 or higher.

3. The coated cutting tool of claim 1 or 2 wherein, The thickness of the second film is greater than 0.5 μm and less than 1.0 μm.

4. A cutting tool, comprising: A tool holder having a length from a first end to a second end and having a slot located on the side of the first end; The coated cutting tool located in the slot according to any one of claims 1 to 3.

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