Cutting tools

Abstract

A cutting tool according to the present invention includes a base material and a coating disposed on the base material. The coating includes a first layer, and the base material includes a hard phase and a bonded phase. The hard phase is made of tungsten carbide particles and the bonded phase is made of metallic cobalt. The first layer is made of aluminum oxide or titanium aluminum nitride. The base material has a first region. The first region is sandwiched between an interface between the base material and the coating and a virtual plane VS1 that passes through a position 0.5 μm from the interface toward the base material side and is parallel to the interface. The proportion of the total length of line segments located between a straight line, which is included on a virtual plane VS2 located an equal distance from the interface and from the virtual plane VS1, and the bonding phase, with respect to the length of the straight line is 50-90%, and the roughness RzJIS of the surface of the base material in contact with the coating is 1.0 μm or less.

Description

[Technical Field]

[0001] This disclosure relates to cutting tools. [Background technology]

[0002] Conventionally, cutting tools comprising a base material and a coating disposed on the base material have been used for cutting processes (Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 05-237707 [Patent Document 2] Japanese Patent Publication No. 2002-331403 [Patent Document 3] Japanese Patent Publication No. 2013-220521 [Overview of the Initiative]

[0004] The cutting tools disclosed herein are A cutting tool comprising a base material and a coating disposed on the base material, The coating includes a first layer, The substrate consists of a hard phase and a binder phase. The hard phase consists of tungsten carbide particles. The bonding phase consists of metallic cobalt. The first layer is made of aluminum oxide or titanium aluminum nitride. The substrate has a first region, The first region is the region sandwiched between the interface between the substrate and the coating, and a virtual plane VS1 that passes through a position 0.5 μm away from the interface toward the substrate and is parallel to the interface. The ratio of the sum of the lengths of the line segments located in the line and the bonding phase to the length of the line included in the virtual surface VS2, which is equal in distance from the interface and from the virtual surface VS1, is between 50% and 90%. The roughness Rz of the surface of the substrate that is in contact with the coating.JIS It is 1.0 μm or less. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 is a schematic cross-sectional view illustrating one embodiment of the cutting tool of this disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view illustrating another embodiment of the cutting tool of the present disclosure. [Figure 3] Figure 3 is a schematic cross-sectional view illustrating another embodiment of the cutting tool of the present disclosure. [Figure 4] Figure 4 is a schematic cross-sectional view of an example of a CVD (Chemical Vapor Deposition) apparatus used in the manufacture of the cutting tools of this disclosure. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] In recent years, the demand for improved tool life has been increasing, and in particular, further improvements in tool life are required in intermittent turning of cast iron. Two important factors for further improving tool life in intermittent turning of cast iron are "wear resistance" and "fracture resistance." Furthermore, in terms of improving wear resistance, cutting tools have been used in intermittent turning of cast iron that comprise a base material and a coating disposed on the base material, wherein the coating includes a first layer, the base material consists of a hard phase and a binder phase, the hard phase consists of tungsten carbide particles, the binder phase consists of metallic cobalt, and the first layer consists of aluminum oxide or titanium aluminum nitride. However, with such coatings, the coating tends to peel easily, resulting in insufficient "fracture resistance." Also, minute damage resulting from insufficient "fracture resistance" could easily lead to wear (i.e., insufficient "wear resistance"). Therefore, by combining excellent "wear resistance" and excellent "fracture resistance," it is necessary to extend tool life, especially in intermittent turning of cast iron.

[0007] Therefore, an object of the present disclosure is to provide a cutting tool having a long tool life, particularly in interrupted turning of cast iron.

[0008] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cutting tool having a long tool life, particularly in interrupted turning of cast iron.

[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 disposed on the substrate, where the coating includes a first layer, the substrate is composed of a hard phase and a binder phase, the hard phase is composed of tungsten carbide particles, the binder phase is composed of metallic cobalt, the first layer is composed of aluminum oxide or titanium aluminum nitride, the substrate has a first region, the first region is a region sandwiched between an interface between the substrate and the coating and a virtual plane VS1 passing through a position 0.5 μm away from the interface toward the substrate side and parallel to the interface, the ratio of the total length of line segments located on the straight line and the binder phase to the length of a straight line included in a virtual plane VS2 where the distance from the interface and the distance from the virtual plane VS1 are equal is 50% or more and 90% or less, the roughness Rz of the surface of the substrate in contact with the coating JIS is 1.0 μm or less.

[0010] According to the present disclosure, it is possible to provide a cutting tool having a long tool life, particularly in interrupted turning of cast iron.

[0011] (2) In (1) above, the ratio of the sum of the lengths of the line segments located in the line and the bonding phase to the length of the line included in the virtual plane VS2, which is at the same distance from the interface and from the virtual plane VS1, is measured in a cross section along the normal direction of the interface between the substrate and the coating, The roughness Rz of the surface of the substrate in contact with the coating JIS This can be measured in accordance with JIS B0601:2001 in the cross-section along the normal direction of the interface between the substrate and the coating.

[0012] (3) In (1) or (2) above, the substrate has a second region, The second region is a region sandwiched between the interface between the substrate and the coating and a virtual plane VS3 that passes through a position 2.0 μm away from the interface toward the substrate and is parallel to the interface. The proportion of voids in the second region may be between 0% and 1.5% by volume. This makes it possible to provide a cutting tool with a longer tool life, especially in intermittent turning of cast iron.

[0013] (4) In (3) above, the proportion occupied by the void in the second region can be measured in a cross section along the direction normal to the interface between the substrate and the coating.

[0014] (5) In any of (1) to (4) above, the coating further comprises a second layer, The first layer is placed on the second layer, The second layer may be made of titanium carbonitride. This makes it possible to provide a cutting tool with a longer tool life, especially in intermittent turning of cast iron.

[0015] (6) In (5) above, the thickness of the second layer may be greater than 0 μm and less than or equal to 10 μm. This makes it possible to provide a cutting tool with a longer tool life, especially in intermittent turning of cast iron.

[0016] (7) In any of (1) to (6) above, the thickness of the first layer may be 2.0 μm or more and 10 μm or less. This makes it possible to provide a cutting tool with a longer tool life, especially in intermittent turning of cast iron.

[0017] (8) In any of (1) to (7) above, the particle size of the tungsten carbide particles may be 0.3 μm or more and 3.0 μm or less. This makes it possible to provide a cutting tool with a longer tool life, especially in intermittent turning of cast iron.

[0018] (9) In any of (1) to (8) above, the base material may contain 8.0% to 20% by volume of the binding phase. This makes it possible to provide a cutting tool with a longer tool life, especially in intermittent turning of cast iron.

[0019] [Details of the embodiments of this disclosure] A specific example of a cutting tool according to one embodiment of this disclosure (hereinafter also referred to as "this embodiment") will be described below with reference to the drawings. In the drawings of this disclosure, the same reference numerals represent the same part or a corresponding part. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0020] In this disclosure, the notation "A~B" means an upper and lower limit of the range (i.e., A or greater and B or less), and if there is no unit specified for A, but a unit is specified only for B, then the unit for A and the unit for B are the same.

[0021] In this disclosure, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

[0022] [Embodiment 1: Cutting Tool] A cutting tool according to one embodiment of this disclosure will be described with reference to Figures 1 to 3. One embodiment of this disclosure (hereinafter also referred to as "this embodiment") is A cutting tool 10 comprising a base material 1 and a coating 2 disposed on the base material 1, The coating 2 includes the first layer 3, The substrate 1 consists of a hard phase and a binder phase. The hard phase consists of tungsten carbide particles. The bonding phase consists of metallic cobalt. The first layer 3 is made of aluminum oxide or titanium aluminum nitride. The base material 1 has a first region R1, The first region R1 is a region sandwiched between the interface between the substrate 1 and the coating 2, and a virtual plane VS1 that passes through a position 0.5 μm away from the interface toward the substrate 1 and is parallel to the interface. The ratio of the sum of the lengths of the line segments located in the line and the bonding phase (hereinafter also referred to as "L2") to the length of the line included in the virtual surface VS2 that is equal in distance from the interface and from the virtual surface VS1 (hereinafter also referred to as "L1") is between 50% and 90%. The roughness Rz of the surface of the substrate 1 that is in contact with the coating 2 JIS It is 1.0 μm or less.

[0023] According to this disclosure, it is possible to provide cutting tools with long tool life, especially in intermittent turning of cast iron. The reason for this is presumed to be as follows.

[0024] (a) The substrate 1 has a first region R1, which is a region sandwiched between the interface between the substrate 1 and the coating 2 and a virtual plane VS1 that passes through a position 0.5 μm away from the interface toward the substrate 1 and is parallel to the interface, and the ratio of the sum of the lengths of the line segments located in the line and the bonding phase to the length of the line included in the virtual plane VS2, which is equal in distance from the interface and from the virtual plane VS1, is 50% or more and 90% or less. This improves the adhesion between the substrate 1 and the coating 2, thereby improving "wear resistance" and "fracture resistance".

[0025] (b) Roughness Rz of the surface of the substrate 1 in contact with the coating 2 JIS The thickness is 1.0 μm or less. This makes it easier for the coating 2 to form uniformly, which improves the strength of the coating 2, and thus improves both "abrasion resistance" and "fracture resistance".

[0026] In other words, according to this disclosure, the cutting tool 10 can possess both excellent "wear resistance" and excellent "fracture resistance," making it possible to provide a cutting tool with a long tool life, especially in intermittent turning of cast iron.

[0027] ≪Cutting tools≫ As shown in Figures 1 to 3, a cutting tool 10 according to one embodiment of the present disclosure comprises a base material 1 and a coating 2 disposed on the base material 1. The coating 2 may cover the entire surface of the base material 1, but even if a part of the base material 1 is not covered by the coating 2, or if the configuration of the coating 2 is partially different, it does not depart from the scope of this embodiment. If a part of the base material 1 is not covered by the coating 2, the coating 2 may be arranged to cover at least the surface of the portion of the base material 1 that is involved in cutting. In this specification, the portion of the base material 1 that is involved in cutting means the area of ​​the base material 1 enclosed by its cutting edge and a hypothetical plane whose distance from the cutting edge towards the base material 1, along the perpendicular to the tangent to the cutting edge, is, for example, 5 mm, 3 mm, 2 mm, 1 mm, or 0.5 mm, depending on the size and shape of the base material 1.

[0028] The cutting tool 10 of this embodiment can be suitably used as a cutting tool 10 such as a drill, end mill, replaceable cutting tip for drills, replaceable cutting tip for end mills, replaceable cutting tip for milling, replaceable cutting tip for turning, metal saw, gear cutting tool, reamer, tap, etc.

[0029] ≪Base material≫ The substrate 1 consists of a hard phase and a binder phase. Here, "consisting of a hard phase and a binder phase" means that other hard phases (e.g., carbides, nitrides, carbonitrides, and mixtures thereof of Ti, Ta, Nb, etc.) may be included, as long as they do not impair the effects of the present disclosure.

[0030] The base material 1 may contain 80% to 92% by volume of the hard phase. In other words, the hard phase content in the base material 1 may be 80% to 92% by volume. This allows the cutting tool 1 to have a longer tool life, especially in intermittent turning of cast iron. The lower limit of the hard phase content in the base material 1 may be 80% or more by volume, 81% or more by volume, or 82% or more by volume. The upper limit of the hard phase content in the base material 1 may be 92% or less by volume, 91% or less by volume, or 90% or less by volume. The hard phase content in the base material 1 may be 81% to 91% by volume, or 82% to 90% by volume.

[0031] The base material 1 may contain a binder phase of 8.0% to 20% by volume. In other words, the binder phase content in the base material 1 may be 8.0% to 20% by volume. This allows the cutting tool 1 to have a longer tool life, especially in intermittent turning of cast iron. The lower limit of the binder phase content in the base material 1 may be 8.0% or more by volume, 9.0% or more by volume, or 10.0% or more by volume. The upper limit of the binder phase content in the base material 1 may be 20% or less by volume, 19% or less by volume, or 18% or less by volume. The binder phase content in the base material 1 may be 9.0% to 19% by volume, or 10.0% to 18% by volume.

[0032] The "hard phase content in substrate 1" and the "binding phase content in substrate 1" are determined by the following method. First, a 5000x magnification image is obtained from an arbitrary cross-section of substrate 1 using a scanning electron microscope (SEM). An arbitrary "10 μm × 10 μm rectangular field of view" is identified in the image. Next, the area of ​​the hard phase and the area of ​​the binding phase are measured within this rectangular field of view using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ). Then, the "hard phase content in substrate 1" is determined by calculating the ratio of the hard phase area to the area of ​​the rectangular field of view as a percentage. Similarly, the "binding phase content in substrate 1" is determined by calculating the ratio of the binding phase area to the area of ​​the rectangular field of view as a percentage. It has been confirmed that, as long as measurements are taken on the same substrate 1, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0033] <Hard phase> The hard phase consists of tungsten carbide particles. As a result, the base material 1 has an excellent balance of hardness and strength, especially at high temperatures, and when used in a cutting tool 10, it can contribute to extending the lifespan of the cutting tool 10. Here, "consisting of tungsten carbide particles" means that it may contain other metal elements, precipitates, etc., as long as it does not impair the effects of this disclosure. Examples of other metal elements include Ni, Cr, Fe, etc. Examples of precipitates include TiC, TiCN, NbC, etc.

[0034] In the cutting tool 10, the composition of the hard phase can be determined by performing a mapping analysis on a cross-section of any substrate 1 using energy-dispersive X-ray spectroscopy (EDS) attached to a scanning electron microscope (SEM). It has been confirmed that, as long as the measurement is performed on the same substrate 1, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0035] The particle size of the tungsten carbide particles may be between 0.3 μm and 3.0 μm. This makes it easier to achieve a better balance between hardness and toughness, so that cutting tool 1 has a longer tool life, especially in intermittent turning of cast iron. The lower limit of the particle size of the tungsten carbide particles may be 0.3 μm or more, 0.5 μm or more, or 0.7 μm or more. The upper limit of the particle size of the tungsten carbide particles may be 3.0 μm or less, 2.6 μm or less, or 2.5 μm or less. The particle size of the tungsten carbide particles may be between 0.5 μm and 2.6 μm, or between 0.7 μm and 2.5 μm.

[0036] The particle size of tungsten carbide particles can be determined by the following method. First, an arbitrary cross-section of the substrate 1 is obtained, and a processed surface is obtained by performing mirror polishing on the cross-section. Next, an image is obtained by taking a picture of the processed surface at a magnification of 5000x using a scanning electron microscope. Next, the particle size (Heywood diameter: equivalent diameter of an equal-area circle) of 20 WC particles is measured using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ) for any "20 μm × 20 μm rectangular measurement field" in the captured image. Next, the same measurement is performed for each of the other four arbitrary "20 μm × 20 μm rectangular measurement fields" in the captured image. Finally, the "particle size of tungsten carbide particles" is determined by calculating the average value of the particle size (Heywood diameter: equivalent diameter of an equal-area circle) of a total of 100 WC particles.

[0037] <Binded phase> The bonding phase consists of metallic cobalt. Here, "consisting of metallic cobalt" means that it may include other metallic elements, precipitates, etc., as long as it does not impair the effects of this disclosure. Examples of other metallic elements include Ni, Cr, Fe, etc. Examples of precipitates include TiC, TiCN, NbC, etc.

[0038] In the cutting tool 10, the composition of the bonding phase can be specified by performing mapping analysis on an arbitrary cross-section using EDS attached to SEM.

[0039] <Rz of the surface of the substrate in contact with the coating JIS > The roughness Rz of the surface of the substrate 1 in contact with the coating 2 JIS is 1.0 μm or less. Thereby, "wear resistance" and "chipping resistance" can be improved. The roughness Rz of the surface of the substrate 1 in contact with the coating 2 JIS The lower limit may be 0 μm or more, but from the viewpoint of manufacturing, it can be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more. The roughness Rz of the surface of the substrate 1 in contact with the coating 2 JIS The upper limit may be 0.9 μm or less, 0.8 μm or less, 0.7 μm or less. The roughness Rz of the surface of the substrate 1 in contact with the coating 2 JIS may be 0 μm or more and 1.0 μm or less, 0 μm or more and 0.9 μm or less, 0 μm or more and 0.8 μm or less.

[0040] The roughness Rz of the surface of the substrate 1 in contact with the coating 2 JISThis can be measured in accordance with JIS B0601:2001 in a cross-section along the normal direction of the interface between the substrate 1 and the coating 2. More specifically, first, an image is obtained by imaging at 1000x magnification using an SEM in a cross-section along the normal direction of the interface between the substrate 1 and the coating 2. Next, in this image, an arbitrary observation field of view of a 10 μm × 10 μm rectangle containing the interface is identified at 10000x magnification. In this observation field, the interface is assumed to pass through any pair of opposing sides. Next, the "ten-point average roughness of the interface" in this observation field is identified by extracting interface contour information using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ). Next, the "ten-point average roughness of the interface" is identified for four other arbitrary observation fields in the above image. Next, by calculating the average value of the "ten-point average roughness of the interface" in a total of five observation fields, the roughness Rz of the surface of the substrate 1 in contact with the coating 2 is determined. JIS Identify.

[0041] Furthermore, it has been confirmed that, as long as the same cutting tool 10 is used for measurement, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0042] <First area> The substrate 1 has a first region R1. The first region R1 is the region sandwiched between the interface between the substrate 1 and the coating 2, and a virtual plane VS1 that passes through a position 0.5 μm away from the interface toward the substrate 1 and is parallel to the interface.

[0043] The ratio of the sum of the lengths of the line segments located in the bonding phase to the length of the line included in the virtual surface VS2, which is equal in distance from the interface and from the virtual surface VS1 (L1), is 50% or more and 90% or less. This improves the "wear resistance" and "fracture resistance" of the cutting tool 1. The lower limit of this ratio may be 55% or more, 60% or more, or 65% or more. The upper limit of this ratio may be 85% or less, 80% or less, or 75% or less. This ratio may be 55% or more and 85% or less, 60% or more and 80% or less, or 65% or more and 75% or less. In Figure 1, the "distance between the interface of the base material 1 and the coating 2 and the virtual surface VS2" is denoted as D1. Also in Figure 1, the "distance between the virtual surface VS2 and the virtual surface VS1" is denoted as D2. The statement "the distance from the above interface and the distance from the above virtual surface VS1 are equal" can be rephrased as "D1 and D2 are equal."

[0044] The ratio of the sum of the lengths of the line segments located in the bonding phase and the line (L2) to the length of the line (L1) contained in the virtual plane VS2, which is equal in distance from the interface and the virtual plane VS1, can be measured in a cross section along the normal direction of the interface between the substrate 1 and the coating 2. More specifically, first, an observation image is taken of the cross section at 1000x magnification using a scanning electron microscope. Next, an arbitrary "20 μm × 20 μm rectangular field of view" is identified in the observation image. Here, the line is assumed to pass through any pair of opposite sides in the rectangular field of view. Next, L1 and L2 are measured in the line within the rectangular field of view using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ). Next, the ratio of L2 to L1 (L2 / L1) × 100 is calculated.

[0045] Furthermore, it has been confirmed that, as long as the same cutting tool 10 is used for measurement, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0046] <Second area> The base material 1 has a second region R2, which is a region sandwiched between the interface between the base material 1 and the coating 2, and a virtual plane VS3 that passes 2.0 μm away from the interface toward the base material 1 and is parallel to the interface, and the proportion occupied by voids in the second region R2 may be 0 volume% or more and 1.5 volume% or less. This makes it easier to suppress the decrease in strength of the base material 1, so that the cutting tool 1 has a longer tool life, especially in intermittent turning of cast iron. The lower limit of this proportion may be 0 volume% or more, 0.2 volume% or more, or 0.3 volume% or more. The upper limit of this proportion may be 1.5 volume% or less, 1.3 volume% or less, or 1.1 volume% or less. This proportion may be 0.2 volume% or more and 1.3 volume% or less, or 0.3 volume% or more and 1.1 volume% or less.

[0047] The proportion occupied by voids in the second region R2 can be measured in a cross-section along the normal direction of the interface between the substrate 1 and the coating 2. More specifically, first, an image is obtained by imaging at 1000x magnification using an SEM in a cross-section along the normal direction of the interface between the substrate 1 and the coating 2. Next, in this image, an arbitrary observation field of view of a rectangle of 10 μm × 10 μm is identified at 10000x magnification. In this observation field, the interface is assumed to pass through any pair of opposing sides. Next, using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ), the area of ​​the "second region R2" and the area of ​​the "voids in the second region R2" in this observation field are identified. Next, the proportion of the area of ​​the "voids in the second region R2" to the area of ​​the "second region R2" is calculated as a percentage. Next, in the image above, calculate the percentage of the area occupied by "voids in the second region R2" relative to the area of ​​"second region R2" for any four other observation fields. Then, determine the "percentage occupied by voids in the second region R2" by calculating the average of the percentages of the area occupied by "voids in the second region R2" relative to the area of ​​"second region R2" for a total of five observation fields.

[0048] Furthermore, it has been confirmed that, as long as the same cutting tool 10 is used for measurement, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0049] ≪Coating≫ <Shape of the coating> The thickness of coating 2 may be between 2.0 μm and 20 μm. If the lower limit of the thickness of coating 2 is less than 2.0 μm, tool life tends to be insufficient. If the upper limit of the thickness of coating 2 is greater than 20 μm, stress is generated within the coating 2 during cutting, which tends to cause peeling or fracture. The lower limit of the thickness of coating 2 may be 2.0 μm or more, 3.0 μm or more, or 4.0 μm or more. The upper limit of the thickness of coating 2 may be 20 μm or less, 19 μm or less, or 18 μm or less. The thickness of coating 2 may be between 3.0 μm and 19 μm, or between 4.0 μm and 18 μm.

[0050] The thickness of coating 2 can be determined by the following method. It can be measured by observing a cross-section along the normal direction of the interface between substrate 1 and coating 2 using a scanning electron microscope (SEM). Specifically, the observation magnification of the cross-sectional sample is set to 1000x, the observation field is a rectangular field of view of 120 μm × 100 μm, the thickness width is measured at three points in one field of view, and the average value is taken as the "thickness". The same method is used for the thickness of each layer described later, unless otherwise specified.

[0051] As long as the same cutting tool 10 is used for measurement, it has been confirmed that there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0052] ≪First layer≫ <Composition of the first layer> The coating 2 includes a first layer 3. The first layer 3 is made of aluminum oxide or titanium aluminum nitride. This suppresses the reaction between the cutting tool 10 and the workpiece. Here, "made of aluminum oxide or titanium aluminum nitride" means that other components may be included as long as they do not impair the effects of this disclosure. Examples of other components include carbon atoms, chromium atoms, etc.

[0053] The composition of the first layer 3 can be determined by performing point analysis on any cross-section using the EDS attached to the SEM. It has been confirmed that there is no variation in the measurement results even if the measurement location is arbitrarily selected, as long as the same cutting tool 10 is used for measurement.

[0054] <Shape of the first layer> The thickness of the first layer 3 may be between 2.0 μm and 10 μm. This maximizes the effect of coating 2. The lower limit of the thickness of the first layer 3 may be 2.0 μm or more, 3.0 μm or more, or 4.0 μm or more. The upper limit of the thickness of the first layer 3 may be 10 μm or less, 9 μm or less, or 8 μm or less. The thickness of the first layer 3 may be between 3.0 μm and 9 μm, or between 4.0 μm and 8 μm.

[0055] ≪Second layer≫ <Composition of the second layer> The coating 2 further includes a second layer 4, the first layer 3 being placed on the second layer 4, and the second layer 4 may be made of titanium carbonitride. This allows the cutting tool 1 to have a longer tool life, especially in intermittent turning of cast iron. Here, "made of titanium carbonitride" means that it may contain other components as long as it does not impair the effects of this disclosure. Other components include, for example, Si atoms.

[0056] The composition of the second layer 4 can be determined by performing point analysis on any cross-section using the EDS attached to the SEM. It has been confirmed that there is no variation in the measurement results even if the measurement location is arbitrarily selected, as long as the same cutting tool 10 is used for measurement.

[0057] <Shape of the second layer> The thickness of the second layer 4 may be greater than 0 μm and less than or equal to 10 μm. This allows the cutting tool 1 to have a longer tool life, especially in intermittent turning of cast iron. The lower limit of the thickness of the second layer 4 may be greater than 0 μm, 1 μm or more, or 2 μm or more. The upper limit of the thickness of the second layer 4 may be less than or equal to 10 μm, 9 μm or less, or 8 μm or less. The thickness of the second layer 4 may be between 1 μm and 9 μm, or between 2 μm and 8 μm.

[0058] ≪Base layer≫ <Composition of the sublayer> The coating 2 further includes an underlayer 5 in contact with the substrate 1, and the underlayer 5 may be made of titanium nitride. This allows for a longer tool life, especially in intermittent turning of cast iron. When the coating 2 further includes an underlayer 5 in contact with the substrate 1 and the coating 2 further includes a second layer 4, the second layer 4 is placed on the underlayer 5 and the first layer 3 is placed on the second layer 4. When the coating 2 further includes an underlayer 5 in contact with the substrate 1 and the coating 2 does not include the second layer 4, the first layer 3 is placed on the underlayer 5. Furthermore, "made of titanium nitride" here means that it may contain other components as long as it does not impair the effects of this disclosure. Examples of other components include oxygen atoms.

[0059] The composition of the underlying layer 5 can be determined by performing point analysis on any cross-section using the EDS attached to the SEM. It has been confirmed that there is no variation in the measurement results even if the measurement location is arbitrarily selected, as long as the same cutting tool 10 is used for measurement.

[0060] <Shape of the underlying layer> The thickness of the base layer 5 may be between 0.1 μm and 1.0 μm. This allows the cutting tool 1 to have a longer tool life, especially in intermittent turning of cast iron. The lower limit of the thickness of the base layer 5 may be 0.1 μm or more, 0.2 μm or more, or 0.3 μm or more. The upper limit of the thickness of the base layer 5 may be 1.0 μm or less, 0.9 μm or less, or 0.8 μm or less. The thickness of the base layer 5 may be between 0.2 μm and 0.9 μm, or between 0.3 μm and 0.8 μm.

[0061] <<Other layers>> The coating 2 may further include other layers. If the coating 2 includes the second layer 4 and the base layer 5, other layers may include, for example, a "first intermediate layer located between the first layer 3 and the second layer 4" (not shown), a "second intermediate layer located between the second layer 4 and the base layer 5" (not shown), and a "surface layer located on the surface of the coating 2" (not shown). If the coating 2 includes the second layer 4 but does not include the base layer 5, other layers may include, for example, a "first intermediate layer located between the first layer 3 and the second layer 4" (not shown) and a "surface layer located on the surface of the coating 2" (not shown). If the coating 2 includes the base layer 5 but does not include the second layer 4, other layers may include, for example, a "third intermediate layer located between the first layer 3 and the base layer 5" (not shown) and a "surface layer located on the surface of the coating 2" (not shown).

[0062] [Embodiment 2: Method for manufacturing a cutting tool] The method for manufacturing the cutting tool of this embodiment will be explained with reference to Figure 4. Figure 4 is a schematic cross-sectional view of an example of a CVD apparatus used in the manufacture of the cutting tool of this embodiment.

[0063] The method for manufacturing a cutting tool according to this embodiment is the method for manufacturing a cutting tool according to Embodiment 1, and comprises a first step of preparing a base material and a second step of forming a coating on the base material. The first step includes, in this order, a first A step of obtaining a mixed powder by mixing tungsten carbide powder (WC powder) and cobalt powder (Co powder), a first B step of obtaining a molded body by drying the mixed powder and then molding it into a predetermined shape, a first C step of obtaining a base material intermediate by sintering the molded body, and a first D step of obtaining a base material by performing a surface treatment on the base material intermediate. The second step includes a second A step of forming a first layer by CVD. The second step may further include a second B step of forming a second layer by CVD, a second C step of forming a base layer by CVD, or both. If the second step further includes the second B step and does not include the second C step, the second step includes the second B step and the second A step in this order. If the second process further includes process 2C but does not include process 2B, then the second process includes process 2C and process 2A in that order. If the second process further includes process 2B and process 2C, then the second process includes process 2C, process 2B, and process 2A in that order. Details of each process are described below.

[0064] ≪1st process≫ <1A process> In step 1A, a mixed powder is obtained by mixing WC powder and Co powder. For mixing, for example, a ball mill can be used. In step 1A, other materials can be mixed in addition to WC powder and Co powder. Examples of other materials include TiC, TiCN, NbC, etc. The composition of the mixed powder can be, for example, as follows, per 100 parts by mass of the mixed powder. (Composition of mixed powder) WC powder: 88 parts by mass or more and 95 parts by mass or less Co powder: 5 parts by mass or more and 12 parts by mass or less

[0065] <1B process> In step 1B, the mixed powder is dried and then molded into a predetermined shape to obtain a molded body. Examples of such shapes include the shapes of "SEET13T3AGSN-G" and "CNMG120408N-GZ" manufactured by Sumitomo Electric Hardmetal Co., Ltd.

[0066] <1C process> In the first C step, a substrate intermediate is obtained by sintering the above molded body. More specifically, sintering can be carried out under the following conditions. (Conditions for sintering) Sintering temperature: 1300°C to 1500°C Sintering time: 40 minutes to 90 minutes

[0067] <1D process> In the first D step, the substrate is obtained by performing a surface treatment on the substrate intermediate. More specifically, the surface treatment is performed under the following conditions: "the ratio of the total length of the line segments located in the line and the binder phase to the total length of the line included in the virtual surface VS2" and "the roughness Rz of the surface in contact with the coating of the substrate". JIS The range can be set to the desired range. (Surface treatment conditions) Method: Brush polishing Polishing time: 60 seconds or more and 240 seconds or less

[0068] If the second B step described later is not performed, the proportion of voids in the second region can be set to a desired range by using brush polishing as the method for the first D step. On the other hand, if the second B step described later is performed, the proportion of voids in the second region can be set to a desired range by using brush polishing as the method for the first D step and by keeping the temperature inside the reaction vessel 32 in the second B step below 900°C.

[0069] The material of the brush used for brush polishing can be, for example, diamond abrasive grains or ceramic abrasive grains. The abrasive grain size of the diamond abrasive grains and the abrasive grain size of the ceramic abrasive grains can be, for example, 10 μm or more and 100 μm or less.

[0070] ≪Second process≫ In the second step, a coating is formed on the substrate to obtain a cutting tool. The coating is formed using, for example, the CVD apparatus shown in Figure 4. The CVD apparatus 30 comprises a plurality of substrate setting jigs 31 for holding the substrate 1, and a reaction vessel 32 made of heat-resistant alloy steel that covers the substrate setting jigs 31. A temperature control device 33 for controlling the temperature inside the reaction vessel 32 is provided around the reaction vessel 32. The reaction vessel 32 is provided with a gas inlet pipe 35 having a gas inlet port 34. The gas inlet pipe 35 extends vertically in the internal space of the reaction vessel 32 where the substrate setting jigs 31 are placed, and is rotatable about the vertical axis, and is provided with a plurality of ejection holes (through holes 36) for ejecting gas into the reaction vessel 32. Using this CVD apparatus 30, the first layer, second layer, and base layer constituting the coating can be formed as follows.

[0071] If the coating includes the "other layer" described in Embodiment 1, the second step may further include a step of forming the "other layer". The "other layer" can be formed by a conventionally known method.

[0072] <Step 2A: Process for forming the first layer using the CVD method> In step 2A, the first layer is formed by the CVD method. More specifically, in the substrate set jig 31 on which the substrate 10 is placed, the reaction gas for the first layer is introduced into the reaction vessel 32 from the gas introduction pipe 35 while controlling the temperature and pressure inside the reaction vessel 32 within a predetermined range. As a result, the first layer is formed on the substrate 10.

[0073] A mixed gas of AlCl3, TiCl4, CO2, H2S, NH3, HCl, N2, and H2 can be used as the reaction gas for the first layer.

[0074] The AlCl3 content in the mixed gas may be between 0.7% and 2.0% by volume. The TiCl4 content in the mixed gas may be between 0% and 0.2% by volume. The CO2 content in the mixed gas may be between 0% and 4.5% by volume. The H2S content in the mixed gas may be between 0% and 0.2% by volume. The NH3 content in the mixed gas may be between 0% and 2.8% by volume. The HCl content in the mixed gas may be between 0.2% and 3.5% by volume. The N2 content in the mixed gas may be between 0% and 35% by volume. The H2 content in the mixed gas may be between 60% and 95% by volume.

[0075] The flow rate of the reaction gas for the first layer (in other words, the total gas flow rate for the first layer) may be 50 L / min or more and 70 L / min or less.

[0076] The temperature inside the reaction vessel 32 is controlled to be between 850°C and 1000°C. The pressure inside the reaction vessel 32 may be controlled to be between 3.0 kPa and 7.0 kPa. The gas introduction pipe 35 may be rotated when introducing gas.

[0077] Regarding the above manufacturing method, the characteristics of the first layer can be changed by controlling each condition of the CVD method. For example, the thickness of the first layer can be controlled by adjusting the film deposition time.

[0078] <Step 2B: Process to form the second layer using the CVD method> In step 2B, the second layer is formed by the CVD method. More specifically, before step 2A is performed, in the substrate set jig 31 on which the substrate 10 is placed, the reaction gas for the second layer is introduced into the reaction vessel 32 from the gas introduction pipe 35 while controlling the temperature and pressure inside the reaction vessel 32 within a predetermined range. This forms the second layer.

[0079] A mixed gas of TiCl4, CH3CN, and H2 can be used as the reaction gas for the second layer.

[0080] The TiCl4 content in the mixed gas may be between 1.0% by volume and 3.0% by volume. The CH3CN content in the mixed gas may be between 0.5% by volume and 1.0% by volume. The H2 content in the mixed gas may be between 96% by volume and 98.5% by volume.

[0081] The flow rate of the reaction gas for the second layer (in other words, the total gas flow rate for the second layer) may be 50 L / min or more and 60 L / min or less.

[0082] The temperature inside the reaction vessel 32 may be controlled to be between 800°C and 860°C, and the pressure inside the reaction vessel 32 may be controlled to be between 8kPa and 10kPa. Furthermore, the gas introduction pipe 35 may be rotated when introducing the gas.

[0083] Regarding the above manufacturing method, the characteristics of the second layer can be changed by controlling each condition of the CVD method. For example, the thickness of the second layer can be controlled by adjusting the film deposition time.

[0084] <Step 2C: Process of forming the base layer using the CVD method> In step 2C, a base layer is formed by the CVD method. More specifically, if step 2 includes step 2B, before step 2B is performed, the reaction gas for the base layer is introduced into the reaction vessel 32 from the gas introduction pipe 35 while controlling the temperature and pressure inside the reaction vessel 32 within a predetermined range in the base material set jig 31 on which the base material 10 is placed. On the other hand, if step 2 does not include step 2B, before step 2A is performed, the reaction gas for the base layer is introduced into the reaction vessel 32 from the gas introduction pipe 35 while controlling the temperature and pressure inside the reaction vessel 32 within a predetermined range in the base material set jig 31 on which the base material 10 is placed. Through these steps, the base layer is formed.

[0085] A mixed gas of TiCl4, N2, and H2 can be used as the raw material gas for the subsoil.

[0086] The TiCl4 content in the mixed gas may be between 1% and 3% by volume. The N2 content in the mixed gas may be between 38% and 42% by volume. The H2 content in the mixed gas may be between 55% and 61% by volume.

[0087] The flow rate of the reaction gas for the subsoil (in other words, the total gas flow rate for the subsoil) may be 60 L / min or more and 70 L / min or less.

[0088] The temperature inside the reaction vessel 32 may be controlled to be between 800°C and 900°C, and the pressure inside the reaction vessel 32 may be controlled to be between 5kPa and 10kPa. Furthermore, the gas introduction pipe 35 may be rotated when introducing the gas.

[0089] Regarding the above manufacturing method, the characteristics of the substrate layer can be changed by controlling each condition of the CVD method. For example, the thickness of the substrate layer can be controlled by adjusting the film deposition time.

[0090] <Other processes> The second step may include surface treatment steps such as surface grinding and shot blasting, in addition to the steps described above. [Examples]

[0091] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0092] <<Manufacturing of cutting tools>> Cutting tools for samples 1-24 and 101-106 were fabricated as follows.

[0093] <1A process> A mixed powder was obtained by mixing "Uniform Grain Tungsten Carbide Powder" (trademark), a WC powder manufactured by Allied Material Co., Ltd., with Co powder (average particle size: 2.0 μm) using a ball mill. In this process, the WC powder and Co powder were used in the amounts listed in Tables 1 and 2 per 100 parts by mass of the mixed powder.

[0094] <1B process> The above mixed powder was dried at 500°C for 30 minutes, and then molded into the shape of "CNMG120408N-GZ" manufactured by Sumitomo Electric Hardmetal Co., Ltd. to obtain a molded body.

[0095] <1C process> A substrate intermediate was obtained by sintering the above molded body under the conditions described in Tables 1 and 2.

[0096] <1D process> The substrate was obtained by performing surface treatment on the substrate intermediate under the conditions described in Tables 1 and 2. Note that in the "Method" column of Tables 1 and 2, "brush polishing" means that "brush polishing" was performed using "brush wire" (manufactured by Toray Industries, Inc.). Similarly, in the "Method" column of Tables 1 and 2, "blast polishing" means that "blast polishing" was performed using "blast media" (manufactured by Toray Industries, Inc.).

[0097] <2nd C process> For the substrates of samples 1, 1-1, 2-23, and 101-106, a sublayer was formed by CVD under the conditions described in Tables 3 and 4, to the thicknesses described in Tables 11 and 12. Note that if "-" is entered in any of the columns for "Temperature [°C]", "Pressure [kPa]", "Total Gas Flow Rate [L / min]", and "Reaction Gas Composition" in Tables 3 and 4, it means that step 2C was not performed.

[0098] <2B process> For the substrates of samples 1, 1-1, 2, 3, 5-23, and samples 101-103, a second layer was formed by CVD under the conditions described in Tables 5 and 6, to the thicknesses described in Tables 11 and 12. Similarly, for the substrate of sample 24, a second layer was formed by CVD under the conditions described in Table 6, to the thicknesses described in Tables 11 and 12. Note that if "-" is entered in any of the columns for "Temperature [°C]", "Pressure [kPa]", "Total Gas Flow Rate [L / min]", and "Reaction Gas Composition" in Tables 5 and 6, it means that step 2B was not performed.

[0099] <2nd A process> For the second layers of samples 1, 1-1, 2, 3, 5-24, and samples 101-103, a first layer was formed by CVD under the conditions described in Tables 7 and 8, to the thicknesses described in Tables 11 and 12. Similarly, for the substrate of sample 1-2, a first layer was formed by CVD under the conditions described in Table 7, to the thicknesses described in Tables 11 and 12. Furthermore, for the underlayers of samples 4 and 104-106, a first layer was formed by CVD under the conditions described in Tables 7 and 8, to the thicknesses described in Tables 11 and 12.

[0100] Following the above procedure, cutting tools for samples 1-24 and 101-106 were fabricated.

[0101] [Table 1]

[0102] [Table 2]

[0103] [Table 3]

[0104] [Table 4]

[0105] [Table 5]

[0106] [Table 6]

[0107] [Table 7]

[0108] [Table 8]

[0109] [Table 9]

[0110] [Table 10]

[0111] [Table 11]

[0112] [Table 12]

[0113] ≪Evaluation of Substrate Properties≫ <Composition of the hard phase> For each cutting tool used with a sample, the composition of the hard phase was determined using the method described in Embodiment 1. The results obtained are recorded in the "Composition" column of the "Hard Phase" column in Tables 9 and 10. If "WC particles" is written in the "Composition" column of the "Hard Phase" column in Tables 9 and 10, it means that the hard phase consists of tungsten carbide particles.

[0114] <Content ratio of hard phase in base material> For the cutting tools according to each sample, the content ratio of the hard phase in the base material was determined by the method described in Embodiment 1. The obtained results are described in the column of "Content ratio [volume %]" in the column of "Hard phase" in Tables 9 and 10.

[0115] <Particle size of tungsten carbide particles> For the cutting tools according to each sample, the particle size of the tungsten carbide particles was determined by the method described in Embodiment 1. The obtained results are described in the column of "Particle size of WC particles [μm]" in Tables 9 and 10.

[0116] <Composition of bonding phase> For the cutting tools according to each sample, the composition of the bonding phase was determined by the method described in Embodiment 1. The obtained results are described in the column of "Composition" in the column of "Bonding phase" in Tables 9 and 10. When it is described as "metal Co" in the column of "Composition" in the column of "Bonding phase" in Tables 9 and 10, it means that the bonding phase consists of metal cobalt.

[0117] <Content ratio of bonding phase in base material> For the cutting tools according to each sample, the content ratio of the bonding phase in the base material was determined by the method described in Embodiment 1. The obtained results are described in the column of "Content ratio [volume %]" in the column of "Bonding phase" in Tables 9 and 10.

[0118] <Ratio occupied by L2 with respect to L1> For the cutting tools according to each sample, the "ratio occupied by the total length (L2) of the line segments located at the straight line and the bonding phase with respect to the length (L1) of the straight line included in the virtual plane VS2" was determined by the method described in Embodiment 1. The obtained results are described in the column of "(L2 / L1)×100 [%]" in Tables 9 and 10.

[0119] <Ratio occupied by voids in the second region> For each cutting tool used with a sample, the proportion of voids in the second region was determined using the method described in Embodiment 1. The results obtained are shown in the "Proportion of Voids in the Second Region [Volume %]" column of Tables 9 and 10.

[0120] <Roughness of the surface in contact with the substrate coating Rz JIS > For each cutting tool used with a sample, the surface roughness Rz of the surface in contact with the substrate coating. JIS The roughness Rz was determined by the method described in Embodiment 1. The obtained results are shown in Tables 9 and 10. JIS Enter the value in the "[μm]" column.

[0121] ≪Evaluation of coating properties≫ <Composition of the sublayer> For each cutting tool used with a sample, the composition of the underlayer was determined using the method described in Embodiment 1. The results obtained are recorded in the "Composition" column of the "Underlayer" column in Tables 11 and 12. If "TiN" is written in the "Composition" column of the "Underlayer" column in Tables 11 and 12, it means that the underlayer consists of titanium nitride. If "-" is written in the "Composition" column of the "Underlayer" column in Tables 11 and 12, it means that there is no underlayer.

[0122] <Thickness of the base layer> For each cutting tool used with a sample, the thickness of the underlying layer was determined using the method described in Embodiment 1. The results obtained are recorded in the "Thickness [μm]" column of the "Underlying Layer" column in Tables 11 and 12.

[0123] <Composition of the second layer> For each cutting tool used with a sample, the composition of the second layer was determined using the method described in Embodiment 1. The results obtained are recorded in the "Composition" column of the "Second Layer" column in Tables 11 and 12. If "TiCN" is written in the "Composition" column of the "Second Layer" column in Tables 11 and 12, it means that the second layer consists of titanium carbonitride. If "-" is written in the "Composition" column of the "Second Layer" column in Tables 11 and 12, it means that the second layer does not exist.

[0124] <Thickness of the second layer> For each cutting tool used with a sample, the thickness of the second layer was determined using the method described in Embodiment 1. The results obtained are recorded in the "Thickness [μm]" column under the "Second Layer" column in Tables 11 and 12.

[0125] <Composition of the first layer> For each cutting tool related to a sample, the composition of the first layer was determined by the method described in Embodiment 1. The obtained results are recorded in the "Composition" column of the "First Layer" column in Tables 11 and 12. If "Al2O3" is written in the "Composition" column of the "First Layer" column in Tables 11 and 12, it means that the first layer consists of aluminum oxide. If "AlTiN" is written in the "Composition" column of the "First Layer" column in Tables 11 and 12, it means that the first layer consists of titanium aluminum nitride.

[0126] <Thickness of the first layer> For each cutting tool used with a sample, the thickness of the first layer was determined using the method described in Embodiment 1. The results obtained are recorded in the "Thickness [μm]" column under "First Layer" in Tables 11 and 12.

[0127] <Thickness of the coating> For each cutting tool used with a sample, the thickness of the coating was determined using the method described in Embodiment 1. The results obtained are recorded in the "Thickness [μm]" column under the "Overall" column in Tables 11 and 12.

[0128] Cutting Test Cutting tests were performed using the cutting tools for each sample under the following cutting conditions. Tool life was measured as the time during which damage progressed through a combination of wear and chipping, and the maximum flank wear amount Vbmax [mm] of the cutting tool's edge exceeded 0.3 mm. The results obtained are recorded in the "Tool Life [minutes]" column of Tables 11 and 12. (Cutting conditions) Workpiece material: FCD700 (grooved round bar) Machining: Outer diameter turning of grooved round bar Cutting speed: 150m / min Feed rate: 0.2mm / rev Cutting fluid: Water-soluble cutting oil The cutting conditions described above correspond to the cutting conditions for intermittent turning of cast iron.

[0129] The cutting tools for samples 1 to 24 correspond to the examples. The cutting tools for samples 101 to 106 correspond to the comparative examples. From the results in Tables 11 and 12, it was found that the cutting tools for samples 1 to 24 have a longer tool life compared to the cutting tools for samples 101 to 106, even in intermittent turning of cast iron.

[0130] Based on the above, it was found that the cutting tools used in samples 1 to 24 exhibited long tool life even in intermittent turning of cast iron.

[0131] As described above, embodiments and examples of this disclosure have been explained, but it is also intended from the outset that the configurations of each of the above embodiments and examples may be combined as appropriate or modified in various ways.

[0132] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope. [Explanation of Symbols]

[0133] 1 Substrate, 2 Coating, 3 First layer, 4 Second layer, 5 Underlayer, 10 Cutting tool, 30 CVD apparatus, 31 Substrate setting jig, 32 Reaction vessel, 33 Temperature control device, 34 Gas inlet, 35 Gas inlet pipe, 36 Through hole

Claims

1. A cutting tool comprising a base material and a coating disposed on the base material, The coating includes a first layer, The aforementioned substrate consists of a hard phase and a binder phase. The aforementioned hard phase consists of tungsten carbide particles. The aforementioned bonding phase consists of metallic cobalt, The first layer is made of aluminum oxide or titanium aluminum nitride. The substrate has a first region, The first region is the region sandwiched between the interface between the substrate and the coating and a virtual plane VS1 that passes through a position 0.5 μm away from the interface toward the substrate and is parallel to the interface. The ratio of the sum of the lengths of the line segments located in the line and the bonding phase to the length of the line included in the virtual surface VS2, which is at the same distance from the interface and the virtual surface VS1, is 50% or more and 90% or less. The roughness Rz of the surface of the substrate in contact with the coating ＪＩＳ A cutting tool with a diameter of 1.0 μm or less.

2. The ratio of the sum of the lengths of the line segments located in the line and the bonding phase to the length of the line included in the virtual surface VS2, which is equal in distance from the interface and from the virtual surface VS1, is measured in a cross section along the normal direction of the interface between the substrate and the coating. The roughness Rz of the surface of the substrate in contact with the coating ＪＩＳ The cutting tool according to claim 1, wherein the measurement is taken in accordance with JIS B0601:2001 at the cross-section along the normal direction of the interface between the substrate and the coating.

3. The substrate has a second region, The second region is the region sandwiched between the interface between the substrate and the coating and a virtual plane VS3 that passes through a position 2.0 μm away from the interface toward the substrate and is parallel to the interface. The cutting tool according to claim 1 or claim 2, wherein the proportion of voids in the second region is 0 volume% or more and 1.5 volume% or less.

4. The cutting tool according to claim 3, wherein the proportion occupied by the void in the second region is measured in a cross-section along the normal direction of the interface between the substrate and the coating.

5. The coating further comprises a second layer, The first layer is placed on the second layer, The cutting tool according to claim 1 or claim 2, wherein the second layer is made of titanium carbonitride.

6. The cutting tool according to claim 5, wherein the thickness of the second layer is greater than 0 μm and less than or equal to 10 μm.

7. The cutting tool according to claim 1 or claim 2, wherein the thickness of the first layer is 2.0 μm or more and 10 μm or less.

8. The cutting tool according to claim 1 or claim 2, wherein the particle size of the tungsten carbide particles is 0.3 μm or more and 3.0 μm or less.

9. The cutting tool according to claim 1 or claim 2, wherein the substrate contains 8.0% by volume or more and 20% by volume or less of the binding phase.

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