Cutting tool

Abstract

A cutting tool comprises a substrate and a coating disposed on the substrate, wherein the coating comprises a first layer, the first layer comprises a plurality of crystal grains, and the crystal grains are composed of Al x Ti 1‑x C y N 1‑y The invention relates to a method for manufacturing a film of a first embodiment of the present invention, wherein x is greater than 0.65 and less than 0.95, y is greater than 0 and less than 0.1, in a first region formed by a region sandwiched between the surface S1 of the first layer or an interface S2 on the surface side of the first layer and a first imaginary plane VS1, the average aspect ratio of the grains is less than 3.0, in a second region formed by a region sandwiched between the first imaginary plane VS1 and an interface S3 on the substrate side of the first layer, the average aspect ratio of the grains is greater than 3.0 and less than 10.0, the first imaginary plane VS1 passes through a point 1 μm away from the surface S1 or the interface S2 toward the substrate side and is parallel to the surface S1 or the interface S2, the grains include grains having a cubic crystal structure, the area ratio of the grains having a cubic crystal structure in the first layer is greater than 90%, the average aspect ratio and the area ratio are measured on a cross-section along a normal to the interface between the substrate and the coating, and the thickness of the first layer is greater than 2 μm and less than 20 μm.

Description

Technical Field

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

[0002] Conventionally, cutting tools with a coating formed on a substrate have been used for cutting steel, castings, and the like (Japanese Patent Application Publication No. 2016-30319 (Patent Document 1)). Patent Document 1 discloses a cutting tool in which a coating layer having a predetermined thickness includes an AlTiCN layer, and the AlTiCN layer forms a columnar structure in the thickness direction. This structure is expected to improve the wear resistance of the cutting tool.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-30319 Summary of the Invention

[0006] The cutting tool disclosed herein is a cutting tool comprising a substrate and a coating disposed on the substrate.

[0007] The coating comprises a first layer,

[0008] The first layer contains multiple grains.

[0009] The grains are made of Al x Ti 1-x C y N 1-y constitute,

[0010] The x is greater than 0.65 and less than 0.95,

[0011] The y is greater than or equal to 0 and less than 0.1,

[0012] In a first region formed by a region sandwiched between the surface S1 of the first layer or an interface S2 on the surface side of the first layer and the first virtual plane VS1, the average aspect ratio of the crystal grains is 3.0 or less.

[0013] In the second region formed by the region sandwiched between the first virtual plane VS1 and the interface S3 on the substrate side of the first layer, the average aspect ratio of the crystal grains exceeds 3.0 and is 10.0 or less.

[0014] The first virtual plane VS1 passes through a point 1 μm away from the surface S1 or the interface S2 toward the substrate side and is parallel to the surface S1 or the interface S2.

[0015] The crystal grains include crystal grains having a cubic crystal structure,

[0016] In the first layer, the area ratio of crystal grains having a cubic structure is 90% or more.

[0017] The average aspect ratio and the area ratio are measured on a cross section along the normal line of the interface between the substrate and the coating.

[0018] The thickness of the first layer is not less than 2 μm and not more than 20 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [ Figure 1 ] Figure 1 is a perspective view illustrating one embodiment of the cutting tool of the present disclosure.

[0020] [ Figure 2 ] Figure 2 yes Figure 1 Cross-sectional view along line II-II.

[0021] [ Figure 3 ] Figure 3 This is a schematic cross-sectional view illustrating one embodiment of the cutting tool disclosed herein.

[0022] [ Figure 4 ] Figure 4 This is a schematic cross-sectional view illustrating another embodiment of the cutting tool disclosed herein.

[0023] [ Figure 5 ] Figure 5 It is a schematic cross-sectional view further illustrating another embodiment of the cutting tool disclosed herein.

[0024] [ Figure 6 ] Figure 6 This is an example of an IPF map produced in one embodiment of the cutting tool disclosed herein.

[0025] [ Figure 7 ] Figure 7 This is an example of a crystal phase diagram produced in one embodiment of the cutting tool disclosed herein.

[0026] [ Figure 8 ] Figure 8 is an example of a schematic cross-sectional view of the cutting tool disclosed herein.

[0027] [ Figure 9 ] Figure 9 This is a schematic cross-sectional view illustrating one embodiment of the first layer in the cutting tool of the present disclosure.

[0028] [ Figure 10 ] Figure 10 This is a schematic cross-sectional view of a CVD apparatus used in manufacturing the cutting tool of the present disclosure. DETAILED DESCRIPTION

[0029] [Problems to be Solved by the Present Disclosure]

[0030] Conventionally, when machining gray cast iron, as a measure to combat dust from chips discharged during machining, cutting is sometimes performed under wet conditions using cutting oil. While wet machining of gray cast iron using cutting tools with an AlTiCN layer rarely progresses wear on the rake face, thermal cracking and flank wear are more likely to occur, shortening the tool life. Therefore, there is a demand for cutting tools with a long tool life, even in wet machining of gray cast iron.

[0031] [Effects of the Present Disclosure]

[0032] According to the present disclosure, it is possible to provide a cutting tool having a long tool life even in wet machining of gray cast iron in particular.

[0033] [Description of Embodiments of the Present Disclosure]

[0034] First, embodiments of the present disclosure will be listed and described.

[0035] (1) The cutting tool disclosed herein is a cutting tool comprising a substrate and a coating disposed on the substrate.

[0036] The coating comprises a first layer,

[0037] The first layer contains multiple grains.

[0038] The grains are made of Al x Ti 1-x C y N 1-y constitute,

[0039] The x is greater than 0.65 and less than 0.95,

[0040] The y is greater than or equal to 0 and less than 0.1,

[0041] In a first region formed by a region sandwiched between the surface S1 of the first layer or an interface S2 on the surface side of the first layer and the first virtual plane VS1, the average aspect ratio of the crystal grains is 3.0 or less.

[0042] In the second region formed by the region sandwiched between the first virtual plane VS1 and the interface S3 on the substrate side of the first layer, the average aspect ratio of the crystal grains exceeds 3.0 and is 10.0 or less.

[0043] The first imaginary plane VS1 passes through a point 1 μm away from the surface S1 or the interface S2 toward the substrate side and is parallel to the surface S1 or the interface S2.

[0044] The crystal grains include crystal grains having a cubic crystal structure,

[0045] In the first layer, the area ratio of crystal grains having a cubic structure is 90% or more.

[0046] The average aspect ratio and the area ratio are measured on a cross section along the normal line of the interface between the substrate and the coating.

[0047] The thickness of the first layer is not less than 2 μm and not more than 20 μm.

[0048] The cutting tool of the present disclosure can have a long tool life even in wet machining of gray cast iron.

[0049] (2) The compressive residual stress of the first layer is preferably 1.0 GPa or more and less than 4.5 GPa. This further improves the heat crack resistance of the cutting tool.

[0050] (3) The hardness of the first layer is preferably 30 GPa or more and 40 GPa or less. This further improves the wear resistance of the cutting tool.

[0051] [Details of the embodiments of the present disclosure]

[0052] A specific example of a cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is described below with reference to the accompanying drawings. In the drawings of this disclosure, identical reference numerals denote identical or equivalent parts. Furthermore, for clarity and simplicity of the drawings, dimensional relationships such as length, width, thickness, and depth are appropriately altered and do not necessarily represent actual dimensional relationships.

[0053] In this specification, expressions in the form of "A to B" refer to the upper and lower limits of a range (i.e., greater than A and less than B). When no unit is recorded for A and only the unit is recorded for B, the unit of A is the same as the unit of B.

[0054] In this specification, when compounds are represented by chemical formulas, unless the atomic ratio is specifically limited, all conventionally known atomic ratios are included, and the atomic ratios are not limited to those within the stoichiometric range. For example, when "AlTiCN" is described, the ratio of the number of atoms constituting AlTiCN includes all conventionally known atomic ratios.

[0055] In the crystallographic descriptions in this specification, individual planes are indicated by parentheses.

[0056] [Embodiment 1: Cutting Tool]

[0057] like Figure 8 As shown, the cutting tool 1 according to this embodiment is a cutting tool 1 including a base material 10 and a coating 14 disposed on the base material 10.

[0058] The coating 14 includes a first layer 11,

[0059] The first layer 11 includes a plurality of crystal grains.

[0060] The grains are made of Al x Ti 1-x C y N 1-y constitute,

[0061] The x is greater than 0.65 and less than 0.95,

[0062] The y is greater than or equal to 0 and less than 0.1,

[0063] In the first region R1 formed by the surface S1 of the first layer 11 or the region sandwiched between the interface S2 on the surface side of the first layer 11 and the first virtual plane VS1, the average aspect ratio of the crystal grains is 3.0 or less.

[0064] In the second region R2 formed by the region sandwiched between the first virtual plane VS1 and the interface S3 on the substrate side of the first layer 11, the average aspect ratio of the crystal grains exceeds 3.0 and is 10.0 or less.

[0065] The first imaginary plane VS1 passes through a point 1 μm away from the surface S1 or the interface S2 toward the substrate side and is parallel to the surface S1 or the interface S2.

[0066] The crystal grains include crystal grains having a cubic crystal structure,

[0067] In the first layer 11, the area ratio of crystal grains having a cubic structure is 90% or more.

[0068] The average aspect ratio and the area ratio are measured on a cross section along the normal line of the interface between the substrate 10 and the coating 14.

[0069] The thickness of the first layer 11 is not less than 2 μm and not more than 20 μm.

[0070] The cutting tool disclosed herein can have a long tool life even in wet machining of gray cast iron. The reason for this is presumably as follows.

[0071] (a) The crystal grains include crystal grains having a cubic structure. In the first layer, the area ratio of the crystal grains having the cubic structure is 90% or more. Therefore, the first layer has high hardness, and the cutting tool can have excellent wear resistance. It should be noted that "wear resistance" here refers to the resistance of the coating to wear during cutting.

[0072] (b) As described in (a) above, x Ti1-x C y N 1-y Cutting tools with a cubic crystal structure that accounts for 90% or more of their constituent grains exhibit excellent wear resistance. However, such tools often tend to have grains that form a columnar structure in the film thickness direction. Consequently, in such cutting tools, since the grain boundaries extend in the film thickness direction, when used for wet machining of gray cast iron, thermal cracking tends to occur more readily on the rake face than in the film thickness direction.

[0073] However, in the cutting tool of this embodiment, the average aspect ratio of the grains in the first region, defined by the surface S1 of the first layer or the interface S2 on the surface side of the first layer, and the first imaginary plane VS1, is 3.0 or less. This suppresses the extension of the grain boundaries of the grains in the film thickness direction within the first layer. Consequently, linear crack propagation in the film thickness direction within the first layer is suppressed. Consequently, the cutting tool of this embodiment exhibits excellent heat crack resistance on the rake face even when used for wet machining of gray cast iron. It should be noted that "heat crack resistance" herein refers to the resistance to cracking on the cutting edge during cutting operations where the cutting edge reaches high temperatures.

[0074] (c) In the cutting tool of this embodiment, the average aspect ratio of the crystal grains in the second region formed by the region sandwiched between the first imaginary plane VS1 and the interface S3 on the substrate side of the first layer exceeds 3.0 and is not more than 10.0. This facilitates the formation of a columnar structure of the crystal grains in the film thickness direction, and thus the first layer enhances deformation of the cutting tool in the shear direction. Therefore, the cutting tool of this embodiment can exhibit excellent wear resistance not only on the rake face but also on the flank face, even when used for wet machining of gray cast iron.

[0075] That is, the cutting tool according to the present embodiment has excellent wear resistance and excellent heat crack resistance, and thus can have a long tool life.

[0076] The cutting tools involved in this embodiment can be, for example, a drill, an end mill, a cutting blade indexable cutting insert for a drill, a cutting blade indexable cutting insert for an end mill, a cutting blade indexable cutting insert for milling, a cutting blade indexable cutting insert for turning, a metal saw, a gear cutting tool, a reamer, a tap, etc.

[0077] Figure 1 This is a perspective view illustrating one embodiment of the cutting tool 1 of the present disclosure. Figure 2 yes Figure 1A cutting tool 1 of this shape is used as a cutting edge indexable cutting insert such as a cutting edge indexable cutting insert for turning. The cutting tool 1 includes a rake face 1a, a flank face 1b, and a cutting edge portion 1c connecting the rake face 1a and the flank face 1b.

[0078] <Base Material>

[0079] The substrate of the present embodiment can be any substrate as long as it is a conventionally known substrate. For example, the substrate preferably comprises one selected from the group consisting of cemented carbide (e.g., tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide to which carbonitrides such as Cr, Ti, Ta, and Nb are added in addition to WC, etc.), cermet (materials having TiC, TiN, TiCN, etc. as main components), high-speed steel, ceramics (TiC, SiC, SiN, AlN, Al2O3, etc.), cubic boron nitride sintered body (cBN sintered body), and diamond sintered body.

[0080] Among these various substrates, cemented carbide (particularly WC-based cemented carbide) and cermet (particularly TiCN-based cermet) are particularly preferred. This is because these substrates have an excellent balance between hardness and strength, especially at high temperatures, and thus have excellent properties as substrates for cutting tools for the above-mentioned applications.

[0081] When cemented carbide is used as the substrate, the effects of this embodiment can be achieved even if the texture of such cemented carbide contains free carbon or an abnormal phase known as η phase. It should be noted that the surface of the substrate used in this embodiment can also be modified. For example, in the case of cemented carbide, a de-β layer can be formed on the surface; or in the case of a cBN sintered body, a surface hardened layer can be formed. Even with such surface modifications, the effects of this embodiment can be achieved.

[0082] When the cutting tool is an indexable cutting insert (such as an indexable cutting insert for turning or milling), the substrate may or may not have a chip breaker. The shape of the cutting edge portion may include any of the following: a sharp edge (the ridge where the rake face and the flank face intersect), a honed edge (a shape obtained by rounding a sharp edge), a negative land (a chamfered shape), or a combination of a honed edge and a negative land.

[0083] <Lamination>

[0084] Figure 3 This is a schematic cross-sectional view illustrating one embodiment of the cutting tool disclosed herein. Figure 4 This is a schematic cross-sectional view illustrating another embodiment of the cutting tool disclosed herein. Figure 5 1 is a schematic cross-sectional view further illustrating another embodiment of the cutting tool disclosed herein. The coating 14 according to this embodiment includes a first layer 11 ( Figures 3 to 5 ). The "coating" has the effect of improving the various properties of the cutting tool, such as peeling resistance, defect resistance, and wear resistance, by covering at least a portion of the above-mentioned substrate (for example, a portion of the front cutting edge). The above-mentioned coating 14 preferably covers the entire surface of the above-mentioned substrate 10. However, even if a portion of the above-mentioned substrate 10 is not covered by the above-mentioned coating 14, or the composition of the coating 14 is partially different, it does not deviate from the scope of the present embodiment. It should be noted that the "peeling resistance" here refers to the resistance to peeling of the above-mentioned coating 14 from the above-mentioned substrate 10.

[0085] The thickness of the above-mentioned film is preferably not less than 2 μm and not more than 25 μm, more preferably not less than 2 μm and not more than 18 μm, and further preferably not less than 3 μm and not more than 12 μm. Here, the thickness of the film refers to the sum of the thicknesses of the respective layers constituting the film. As the "layers constituting the film", for example, the above-mentioned first layer and other layers described later as layers other than the above-mentioned first layer can be listed. The thickness of the above-mentioned film can be obtained, for example, by measuring any 10 points in a cross-sectional sample parallel to the normal direction of the surface of the substrate using a transmission electron microscope (TEM) and taking the average value of the thickness of the 10 measured points. As the above-mentioned cross-sectional sample, for example, a sample obtained by thinning the cross section of the above-mentioned cutting tool using an ion slicing device can be listed. The same is true for measuring the thickness of the above-mentioned first layer and the above-mentioned other layers. As a transmission electron microscope, for example, JEM-2100F (trade name) manufactured by JEOL Ltd. can be listed.

[0086] The coating includes a first layer. In one aspect of this embodiment, a plurality of first layers may be provided, as long as the effect exerted by the cutting tool is maintained. For example, when the coating includes two first layers, the coating may further include an intermediate layer (another layer) provided between the two first layers.

[0087] (Layer 1)

[0088] The first layer of this embodiment includes a plurality of crystal grains. The first layer may be composed solely of the crystal grains or may include other components. Examples of the other components include TiN, TiC, Al2O3, TiCN, TiCNO, and TiBN.

[0089] (Grain)

[0090] The crystal grains in this embodiment are made of Al x Ti1-x C y N 1-y Here, “the grains are composed of Al x Ti 1-x C y N 1-y "Composition" is not limited to only Al x Ti 1-x C y N 1-y The way of composition also includes the meaning of Al x Ti 1-x C y N 1-y Contains all except Al x Ti 1-x C y N 1-y Any method other than the above-mentioned components may be used as long as the effects of the present disclosure are achieved.

[0091] The above x is greater than 0.65 and less than 0.95. This allows the cutting tool to have excellent heat resistance. In addition, the above x is preferably greater than 0.7 and less than 0.95, more preferably greater than 0.75 and less than 0.95, and even more preferably greater than 0.80 and less than 0.90.

[0092] The above-mentioned y is greater than or equal to 0 and less than 0.1. When the carbon content in the above-mentioned grains is a trace amount within the range of 0≤y<0.1, the wear resistance is improved by improving the lubricity. On the other hand, when y deviates from the above-mentioned range, the defect resistance and crack resistance are reduced, which is not preferred. In addition, the above-mentioned y is preferably greater than or equal to 0 and less than 0.08, more preferably greater than or equal to 0 and less than 0.06, and further preferably greater than or equal to 0 and less than 0.05. In addition, from the perspective of manufacturing, the lower limit of the above-mentioned y can be set to greater than or equal to 0.01 or greater than or equal to 0.02.

[0093] By using an EDX (Energy Dispersive X-ray spectroscopy) device attached to a SEM or TEM, it can be confirmed that the above-mentioned crystal grains are composed of Al x Ti 1-x C y N 1-yThe x mentioned above is greater than 0.65 and less than 0.95, and the y mentioned above is greater than 0 and less than 0.1. Specifically, first, an arbitrary position of the cutting tool is cut along the film thickness direction to prepare a sample containing a cross section of the coating. Then, with respect to the first layer in the coating, 5 rectangular measurement fields of 2 μm×2 μm are arbitrarily selected, and the area is analyzed. Here, the midpoint of the diagonal of the rectangle passes through the midpoint of the thickness direction of the first layer (the midpoint of the thickness direction between S1 described later or S2 described later and S3 described later), and the two sides of the opposite group of the rectangle are parallel to S3 described later. Thus, by determining x and y representing the atomic ratio of each element contained in an arbitrary measurement area, the average values of the x and y are obtained, thereby determining the composition of the above-mentioned grains.

[0094] (Average aspect ratio of crystal grains in the first region)

[0095] In the first region formed by the surface S1 of the first layer or the interface S2 on the surface side of the first layer and the first imaginary plane VS1, the average aspect ratio of the grains is 3.0 or less. The first imaginary plane VS1 passes through a location 1 μm away from the surface S1 or the interface S2 to the substrate side and is parallel to the surface S1 or the interface S2. As a result, in the first layer, the grain boundaries of the grains can be suppressed from extending in the film thickness direction. Therefore, in the first layer, cracks in the film thickness direction can be suppressed from developing linearly. Therefore, the cutting tool of this embodiment can have excellent heat crack resistance on the front cutting edge even when used for wet machining of gray cast iron. The lower limit of the average aspect ratio is preferably 1.0 or more. In addition, from a manufacturing point of view, the lower limit of the average aspect ratio can be set to 1.2 or more, or 1.4 or more. In addition, the upper limit of the average aspect ratio is preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. The average aspect ratio is preferably 1.0 to 3.0, more preferably 1.0 to 2.5, and even more preferably 1.0 to 2.0.

[0096] (Average aspect ratio of crystal grains in the second region)

[0097] In the second region formed by the region clamped by the first imaginary plane VS1 and the interface S3 on the substrate side of the first layer, the average aspect ratio of the grains exceeds 3.0 and is less than 10.0. Thus, since the grains easily form a columnar structure in the film thickness direction, the deformation of the first layer in the shear direction of the cutting tool is enhanced. Therefore, the cutting tool of this embodiment can have excellent wear resistance on the front and rear cutting edges even when used for wet machining of gray cast iron. The lower limit of the above-mentioned average aspect ratio is preferably greater than 4.0, more preferably greater than 5.0, and further preferably greater than 6.0. In addition, the upper limit of the above-mentioned average aspect ratio is preferably less than 9.0, more preferably less than 8.0, and further preferably less than 7.0. In addition, the above-mentioned average aspect ratio is preferably greater than 3.0 and less than 9.0, more preferably greater than 4.0 and less than 9.0, and further preferably greater than 4.0 and less than 8.0.

[0098] <Method for Measuring Average Aspect Ratio of Crystal Grains in Each of the First and Second Regions>

[0099] The average aspect ratio of the crystal grains in the first region and the average aspect ratio of the crystal grains in the second region are measured on a cross section along the normal line of the interface between the substrate and the coating. Specific measurement methods are described in (A1) to (A7) below.

[0100] (A1) The cutting tool sample is embedded in epoxy resin and then ground. Using a cross-section polishing device (manufactured by JEOL), the ground cutting tool is cut under the conditions of 6kV and 6 hours, and then fine-machined under the conditions of 1.5kV and 1 hour. Cutting is performed in the normal direction along the surface of the cutting tool. The normal line of the surface of the cutting tool is roughly parallel to the normal line of the interface between the substrate and the coating. Therefore, by the above-mentioned cutting, a cross-section along the normal line of the interface between the substrate and the coating of the above-mentioned first layer is obtained.

[0101] The above-mentioned cutting can be performed at any position of the cutting tool, regardless of the rake face or the flank face, as long as it is performed at a position at least 0.1 mm away from the cutting edge portion in a direction parallel to the cutting tool surface.

[0102] (A2) The cross section was subjected to EBSD analysis under the following measurement conditions using a field emission scanning electron microscope (FE-SEM) (product name: "SUPRA35VP", manufactured by Carl Zeiss) equipped with an electron beam backscatter diffraction device (EBSD device).

[0103] (Measurement conditions)

[0104] Accelerating voltage: 15 kV

[0105] Current value: 1.8nA

[0106] Irradiation current: 60μm (with HC)

[0107] Exp: Long 0.03s

[0108] Binning: 8×8

[0109] WD: 15mm

[0110] Tilt: 70°

[0111] Step size: 0.02 μm

[0112] BKD: Background Subtraction, Dynamic Background Subtraction, Normalize Intensity Histogram

[0113] Photography magnification: 20,000 times

[0114] Grain boundary definition: above 15°

[0115] In addition, with respect to EBSD analysis, data is collected on a surface area (observation area) on the above-mentioned cross section that includes at least the entire length from the surface S1 of the first layer or the interface S2 on the surface side of the first layer to the interface S3 on the substrate side (including the length of the entire thickness of the first layer) × 10 μm (the length in the direction parallel to the interface S3 on the substrate side of the first layer).

[0116] The data collected by EBSD analysis was cleaned up by using the CI Dilation method (single iteration) and Grain CI Standardization to identify only data with a CI greater than 0.1. The CI value was calculated using the Voting method. Specifically, CI = (V1 - V2) / Videal (V1, 2: first and second solutions, Videal: ideal solution).

[0117] (A3) The EBSD analysis results were analyzed using commercially available software (trade name: "OIM7.1", manufactured by TSL Solutions Co., Ltd.) to create an IPF map (Inverse Pole Figure map). In creating this IPF map, grain boundaries are defined when the orientation angle between adjacent measurement points is 15° or greater. This IPF map shows the shape of each grain and displays the orientation of each grain using color. Figure 6 An example of the above-mentioned IPF diagram produced in the cutting tool of this embodiment is shown. Figure 6 The black area in the figure indicates that the above CI is less than or equal to 0.1. Figure 6 The black area in the figure is the area where the shape of each grain cannot be identified due to the noise reduction process. Figure 6 In the figure, the left side toward the paper is the surface side of the cutting tool, and the right side toward the paper is the base material side of the cutting tool.

[0118] (A4) Figure 8 The schematic cross-sectional view of is a schematic cross-sectional view illustrating one embodiment of the cutting tool disclosed herein. Figure 8 On the above-mentioned IPF diagram, first, the surface S1 of the first layer 11 or the interface S2 on the surface side of the first layer 11 (in Figure 8 In the diagram, since no other layers are formed on the first layer 11, the interface S2 is represented by the symbol (S2) and the first imaginary plane VS1. Next, a measurement region (first region R1) is set, encompassing the entire length from S1 or S2 to VS1 (the length in the thickness direction of the first layer 11) × 10 μm (the length in a direction parallel to the interface S3 on the substrate side of the first layer 11). It should be noted that in the above IPF diagram, the method for setting S1, S2, and VS1 is as follows.

[0119] (How to set S1, S2 and VS1)

[0120] S1: If the surface of the first layer is smooth, the smooth surface is set as S1. Alternatively, if the surface of the first layer has a concavo-convex shape, first, on the IPF diagram, set: an imaginary line VL1 (not shown) that passes through at least one point on the surface of the first layer, is parallel to the interface between the coating and the substrate, and has the longest distance from the interface between the coating and the substrate; and an imaginary line VL2 (not shown) that passes through at least one point on the surface of the first layer, is parallel to the interface between the coating and the substrate, and has the shortest distance from the interface between the coating and the substrate. Next, a straight line that is equal in distance from VL1 and VL2 and is parallel to the interface between the coating and the substrate is set as the position of S1 on the IPF diagram. It should be noted that in the IPF diagram, the smooth surface and the concavo-convex shape can be identified by identifying the smooth surface or the concavo-convex shape on an SEM image having the same field of view as the IPF diagram, and then overlaying the SEM image in which the smooth surface or the concavo-convex shape is identified with the IPF diagram. The above-mentioned SEM images were obtained by using the above-mentioned FE-SEM.

[0121] S2: Line analysis is performed in the thickness direction of the coating with any point on the surface of the coating as the base point. The above-mentioned line analysis is performed by EDX (Energy Dispersive X-ray Spectroscopy) attached to the SEM. In addition, in the above-mentioned line analysis, the beam diameter is set to 0.9 nm, the scanning interval is set to 0.1 μm, and the acceleration voltage is set to 15 kV. Thus, the point representing the maximum value of the atomic number ratio of the metal element unique to the first layer in the first layer (for example, when the upper layer connected to the first layer is Al2O3, it is Ti element) is determined. Then, among the points representing the half value of the maximum value, a point P1 (not shown) is determined, which is located on the surface side and closest to the point representing the maximum value with the point representing the maximum value as the base point. Next, select another arbitrary point on the film surface and, similarly, among the points representing the half-value of the maximum atomic ratio of the first-layer-specific metal element (e.g., Ti when the upper layer adjacent to the first layer is Al2O3), determine a point P2 (not shown) located on the surface side and closest to the point representing the maximum atomic ratio, starting from the point representing the maximum atomic ratio. Next, set the straight line connecting P1 and P2 as position S2 on the aforementioned IPF diagram.

[0122] VS1: A plane passing through a point 1 μm away from S1 or S2 toward the substrate and parallel to S1 or S2 is set as a first virtual plane VS1.

[0123] (A5) Reference Figure 8 On the above-mentioned IPF diagram, the interface S3 on the substrate side of the above-mentioned first layer is set using the setting method described later. Next, an imaginary line L1 is set that passes through a point 0.3 μm away from S3 toward the S1 or S2 side and is parallel to S3. Next, a measurement region (second region R2) is set that includes the entire length from the above-mentioned VS1 to the above-mentioned L1 (the length in the film thickness direction of the first layer 11) × 10 μm (the length in the direction parallel to the interface S3 on the substrate 10 side of the first layer 11). It should be noted that the setting method of S3 in the above-mentioned IPF diagram is as follows.

[0124] (S3 setting method)

[0125] S3: Line analysis is performed in the thickness direction of the coating with any point on the surface of the coating as the base point. The above-mentioned line analysis is performed by EDX (Energy Dispersive X-ray Spectroscopy) attached to the SEM. In addition, in the above-mentioned line analysis, the beam diameter is set to 0.9 nm, the scanning interval is set to 0.1 μm, and the acceleration voltage is set to 15 kV. Thus, the point representing the maximum value of the atomic ratio of the metal element unique to the first layer in the first layer (for example, when the lower layer connected to the first layer is a TiN layer, it is the Al element) is determined. Then, among the points representing the half value of the maximum value, point P3 (not shown) is determined, which is located on the substrate side and closest to the point representing the maximum value with the point representing the maximum value as the base point. Next, select another arbitrary point on the coating surface and, similarly, identify a point P4 (not shown) located on the substrate side and closest to the point showing the maximum value, with the point showing the maximum value as the base point, from among the points representing half the maximum value of the atomic ratio of the metal element unique to the first layer (for example, Al when the lower layer adjacent to the first layer is a TiN layer). Next, set the straight line connecting P3 and P4 as position S3 on the aforementioned IPF diagram.

[0126] (A6) Figure 9 This is a schematic cross-sectional view illustrating one embodiment of the first layer of the cutting tool disclosed herein. Figure 9 The total area of the first region R1 and the area of the grains 20a included in the measurement region (first region R1) are calculated. Next, the total area of the grains 20a included in the measurement region (first region R1) relative to the total area of the first region R1 (including Figure 6 The proportion of the area represented by black in the

[0127] After confirming that the above ratio is 25% or more, proceed to (A7) described below. If the above ratio is less than 25%, Figure 9 As shown, there are many grains 21b that span VS1, that is, the entire first layer forms columnar crystals. Therefore, the grains must form a columnar structure in the entire area of the first layer in the film thickness direction. As a result, in the first region R1, the average aspect ratio of the grains is considered to exceed 3.0.

[0128] Here, the total area of the first region R1 is calculated by including the entire length from S1 or S2 to VS1 (the length in the film thickness direction of the first layer 11) × 10 μm (the length in the direction parallel to the interface S3 on the substrate 10 side of the first layer 11). In addition, here, the total area of the grains 20a contained in the measurement area (first region R1) is calculated by analyzing the grains extracted under the above-mentioned EBSD measurement conditions using commercially available software (trade name: "OIM7.1", manufactured by TSL Solutions Co., Ltd.). In addition, here, the grains 20a contained in the measurement area (first region R1) refer to the grains that exist only in the measurement area (first region R1) as a whole. That is, as Figure 9 As shown, the crystal grains 21 a straddling S1 or S2 and the crystal grains 21 b straddling VS1 are distinguished from the crystal grains 20 a included in the measurement region (first region R1 ).

[0129] (A7) The aspect ratios of all the crystal grains 20a contained in the measurement area (first region R1) are measured respectively, and their average value is calculated. The average value of the aspect ratios is equivalent to the "average aspect ratio of the crystal grains in the first region R1". The aspect ratios of all the crystal grains 20b contained in the measurement area (second region R2) are measured respectively, and their average value is calculated. The average value of the aspect ratios is equivalent to the "average aspect ratio of the crystal grains in the second region R2". In this specification, the aspect ratio is defined as the value obtained by dividing the maximum diameter a of the crystal grain by the short diameter b of the crystal grain. The maximum diameter a of the crystal grain is defined as: when the coordinate position of the pixel at the outermost periphery of the crystal grain is set to (x i ,y i ) and (x j ,y j ) and the calculation formula "d 2 =(x i -x j ) 2 +(y i -y j ) 2 " represents the value of d, through a grain (x i ,y i ) and (x j ,y j The short diameter b of the grain is the value calculated by the formula "b = A (grain area) / πa". Here, Figure 9 As shown in FIG. 1 , the crystal grains 20b included in the measurement region (second region R2) are crystal grains existing only in the measurement region (second region R2). Figure 9 As shown, the crystal grains 21 b extending over VS1 and the crystal grains 21 c extending over L1 are distinguished from the crystal grains 20 b included in the measurement region (second region R2 ).

[0130] It was confirmed that, for the same cutting tool, even if a different measurement range was arbitrarily selected and the above-mentioned measurement was performed within the measurement range, the same result could be obtained.

[0131] (Area ratio of crystal grains with cubic structure)

[0132] The above-mentioned crystal grains include crystal grains having a cubic crystal structure. In addition, in the above-mentioned first layer, the area ratio occupied by the crystal grains having a cubic crystal structure is 90% or more. As a result, the first layer can have high hardness and the cutting tool can have excellent wear resistance. The lower limit of the above-mentioned area ratio is preferably 92% or more, more preferably 95% or more, and further preferably 98% or more. In addition, the upper limit of the above-mentioned area ratio is preferably 100% or less. In addition, from a manufacturing point of view, the upper limit of the above-mentioned area ratio can be set to 99% or less. In addition, the above-mentioned area ratio is preferably 90% or more and 100% or less, more preferably 95% or more and 100% or less, and further preferably 98% or more and 100% or less.

[0133] <Method for measuring the area ratio of crystal grains having a cubic crystal structure>

[0134] In the first layer, the area ratio of crystal grains having a cubic structure is measured on a cross section along the normal line of the interface between the substrate and the coating. Specific measurement methods are described below in (B1) to (B4).

[0135] (B1) EBSD analysis is performed on a cross section of the cutting tool according to the same procedures as (A1) and (A2) described in the above-mentioned "Method for measuring the average aspect ratio of crystal grains in the first region and the second region".

[0136] (B2) The EBSD analysis results were analyzed using commercially available software (trade name: "OIM7.1", manufactured by TSL Solutions Co., Ltd.) to create a phase diagram. Figure 7 As shown, the crystal system of each grain is represented by different colors. In this embodiment, the cubic crystal system and the hexagonal crystal system are mainly shown. It should be noted that Figure 7 The black area in the figure indicates that the above CI is less than or equal to 0.1. Figure 7 The black area in the figure is the area where the crystal system of each grain cannot be identified due to the noise reduction process. Figure 7 In the figure, the left side toward the paper is the surface side of the cutting tool, and the right side toward the paper is the base material side of the cutting tool.

[0137] (B3) Figure 8As shown, on the above-mentioned phase diagram, first, the surface S1 of the first layer 11 or the interface S2 on the surface side of the first layer 11 and the interface S3 on the substrate side of the first layer are set using the same setting method as described above. Next, a first imaginary line L1 is set, passing through a point 0.3 μm away from S3 toward the S1 or S2 side and parallel to S3. Next, a measurement area is set that includes the entire length from S1 or S2 to L1 (the length in the film thickness direction of the first layer 11) × 10 μm (the length in the direction parallel to the interface S3 on the substrate 10 side of the first layer 11).

[0138] (B4) In the measurement region, the percentage of the area of cubic crystal grains relative to the area of the entire region represented by the crystal system is calculated. This percentage corresponds to the "area ratio of crystal grains having a cubic crystal structure in the first layer." Here, "the entire region represented by the crystal system" refers to "the region excluding the region where the crystal system cannot be determined from the measurement region."

[0139] It was confirmed that, for the same cutting tool, even if a different measurement range was arbitrarily selected and the above-mentioned measurement was performed within the measurement range, the same result could be obtained.

[0140] (Compressive residual stress of the first layer)

[0141] The compressive residual stress of the first layer is preferably 1.0 GPa or more and less than 4.5 GPa. This can suppress the development of cracks generated during processing, thereby further improving the heat cracking resistance of the cutting tool. The lower limit of the above-mentioned compressive residual stress is preferably 1.0 GPa or more, more preferably 2.0 GPa or more, and even more preferably 2.5 GPa or more. In addition, the upper limit of the above-mentioned compressive residual stress is preferably less than 4.5 GPa. In addition, from a manufacturing point of view, the upper limit of the above-mentioned compressive residual stress can be less than 4.0 GPa and less than 3.5 GPa. In addition, the above-mentioned compressive residual stress is more preferably 2.0 GPa or more and less than 4.5 GPa, and even more preferably 2.5 GPa or more and less than 4.5 GPa.

[0142] <Method for measuring compressive residual stress of the first layer>

[0143] The compressive residual stress can be determined, for example, by the 2θ-sin2ψ method (tilt method) using X-rays. The measurement conditions are as follows. For example, the average compressive residual stress at any three or more points within 5 mm from the honing position on the rake face of the cutting tool toward the center of the tool is determined.

[0144] (Measurement conditions)

[0145] X-ray output: 8.04keV

[0146] X-ray source: radioactive light

[0147] Measuring surface: (200) surface

[0148] Detector: Flat panel display

[0149] Spot size: 1.5mm×0.5mm

[0150] Scan axis: 2θ / θ

[0151] Scan mode: CONTINUOUS

[0152] (Hardness of the first layer)

[0153] The hardness of the first layer is preferably 30 GPa or more and 40 GPa or less. This further improves the wear resistance of the cutting tool. The lower limit of the hardness is preferably 30 GPa or more, more preferably 31 GPa or more, and even more preferably 32 GPa or more. Furthermore, the upper limit of the hardness is preferably 40 GPa or less, more preferably 39 GPa or less, and even more preferably 38 GPa or less. Furthermore, the hardness is more preferably 31 GPa or more and 40 GPa or less, and even more preferably 32 GPa or more and 39 GPa or less.

[0154] <Method for measuring the hardness of the first layer>

[0155] The hardness was measured by a method based on ISO 14577, and the measurement load was set to 10 mN (1 g).

[0156] (Thickness of the first layer)

[0157] The thickness of the first layer in this embodiment is 2 μm to 20 μm. This improves wear resistance. The lower limit of the thickness of the first layer is preferably 3 μm or more, more preferably 4 μm or more, and even more preferably 5 μm or more. The upper limit of the thickness of the first layer is preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The thickness of the first layer is preferably 2 μm to 12 μm, more preferably 3 μm to 10 μm or less.

[0158] (Other layers)

[0159] As long as the effects of this embodiment are not impaired, the above-mentioned coating may further include the above-mentioned other layers. Figure 4 and Figure 5 As shown, examples of the other layers include a base layer 12 and a surface layer 13 .

[0160] (basal layer)

[0161] The base layer 12 is disposed between the substrate 10 and the first layer 11. Examples of the base layer include a TiN layer. The average thickness of the base layer is preferably 0.1 μm to 20 μm. This allows the coating to exhibit excellent wear resistance and defect resistance. Furthermore, the average thickness of the base layer is more preferably 0.2 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

[0162] (Surface layer)

[0163] The surface layer 13 is preferably composed primarily of, for example, a carbide, nitride, or boride of Ti (titanium). The surface layer 13 is the layer closest to the surface of the coating 14. However, it may not be formed on the cutting edge. For example, the surface layer may be located directly above the first layer.

[0164] "Comprising any one of Ti carbide, nitride, or boride as a main component" means containing 90% by mass or more of any one of Ti carbide, nitride, and boride. Furthermore, this means that, excluding unavoidable impurities, the material is preferably composed of any one of Ti carbide, nitride, and boride.

[0165] Of any of Ti carbides, nitrides, and carbonitrides, a Ti nitride (i.e., a compound represented by TiN) is particularly preferred as the main component of the surface layer. TiN has the clearest color (golden) of these compounds, making it easier to identify the corner of the cutting tip after use (identifying the used area). The surface layer is preferably composed of a TiN layer.

[0166] The average thickness of the surface layer is preferably 0.05 μm to 1 μm. This improves the adhesion between the surface layer and the adjacent layer. The average thickness of the surface layer is more preferably 0.1 μm to 0.8 μm, and even more preferably 0.2 μm to 0.6 μm.

[0167] [Embodiment 2: Method for manufacturing a cutting tool]

[0168] The manufacturing method of the cutting tool according to the present embodiment includes:

[0169] a first step of preparing the substrate (hereinafter sometimes referred to as "the first step"); and

[0170] A second step (hereinafter sometimes simply referred to as "second step") is performed to form the coating on the substrate using a chemical vapor deposition (CVD) method.

[0171] The second step comprises spraying aluminum halide gas, titanium halide gas, ammonia gas, and hydrogen gas onto the substrate in an atmosphere of 650°C to 900°C and 0.1 kPa to 30 kPa. The manufacturing method may further include a third step (hereinafter sometimes referred to as the "third step") of sandblasting the film obtained in the second step.

[0172] <Step 1: Preparing a Base Material>

[0173] In the first step, a substrate is prepared. For example, a cemented carbide substrate is prepared as the substrate. The cemented carbide substrate can be a commercially available product or can be manufactured by a general powder metallurgy method. When manufactured by a general powder metallurgy method, WC powder and Co powder are mixed to obtain a mixed powder, for example, by a ball mill or the like. After the mixed powder is dried, it is formed into a predetermined shape (for example, SEET13T3AGSN-G, etc.) to obtain a formed body. Further, the formed body is sintered to obtain a WC-Co based cemented carbide (sintered body). Then, by subjecting the sintered body to predetermined cutting edge processing such as honing, a substrate composed of a WC-Co based cemented carbide can be manufactured. In the first step, even a substrate other than the above-mentioned substrate can be prepared as long as it is a substrate known in the past.

[0174] <Step 2: Step of Forming a Film on a Substrate>

[0175] In the second step, a coating comprising the first layer is formed on the substrate using a CVD method. Specifically, aluminum halide gas, titanium halide gas, ammonia gas (hereinafter collectively referred to as "raw material gases"), and a carrier gas are sprayed onto the substrate in an atmosphere of 650°C to 900°C and 0.1 kPa to 30 kPa, thereby forming a coating comprising the first layer. This produces the cutting tool of this embodiment. This step can be performed using, for example, the CVD apparatus described below.

[0176] (CVD equipment)

[0177] Figure 10 A schematic cross-sectional view showing an example of a CVD apparatus 50 used in manufacturing a cutting tool according to this embodiment. Figure 10 As shown, the CVD apparatus 50 includes a substrate placement jig 52 for placing the substrate 10, and a reaction vessel 53 made of heat-resistant alloy steel that encloses the substrate placement jig 52. Furthermore, a temperature control device 54 is provided around the reaction vessel 53 to control the temperature within the reaction vessel 53. In this embodiment, the substrate 10 is preferably placed on a protrusion provided on the substrate placement jig 52. This arrangement allows for uniform film formation on the rake face, flank face, and cutting edge.

[0178] In the reaction vessel 53, a gas inlet pipe 55 extends vertically within the interior of the reaction vessel 53 and is rotatably arranged about the vertical axis. The gas inlet pipe 55 is provided with a plurality of through-holes for injecting gas onto the tool substrate. In this embodiment, it is preferable to provide sufficient spacing between the through-holes for injecting gas and the substrate 10. This prevents the generation of turbulent flow.

[0179] Furthermore, the reaction container 53 is provided with a gas exhaust pipe 56 for exhausting the gas inside to the outside. The gas inside the reaction container 53 is exhausted to the outside of the reaction container 53 from a gas exhaust port 57 via the gas exhaust pipe 56 .

[0180] The reaction vessel 53 is maintained at an atmosphere of 650°C to 900°C (preferably 700°C to 770°C) and a pressure of 0.1 kPa to 30 kPa (preferably 0.2 kPa to 5.0 kPa). The gas inlet pipe 55 has multiple through-holes, allowing the introduced gas to be injected into the reaction vessel 53 from different through-holes. As indicated by the rotation arrows in the figure, the gas inlet pipe 55 rotates about the axis at a speed of, for example, 2 rpm to 4 rpm. This allows for uniform injection onto the substrate.

[0181] Examples of aluminum halide gases include aluminum chloride gas (AlCl₃ gas, Al₂Cl₆ gas). AlCl₃ gas is preferably used. The concentration (volume %) of the aluminum halide gas, based on the total volume of all gases introduced into the reaction vessel (hereinafter also referred to as the "total volume of introduced gas"), is preferably 0.1 volume % to 1.0 volume %, and more preferably 0.2 volume % to 0.8 volume %.

[0182] Examples of titanium halide gases include titanium (IV) chloride gas (TiCl4 gas) and titanium (III) chloride gas (TiCl3 gas). Titanium (IV) chloride gas is preferably used. The concentration (volume %) of the titanium halide gas, based on the total volume of the introduced gas, is preferably from 0.05 volume % to 0.3 volume %, and more preferably from 0.1 volume % to 0.2 volume %.

[0183] The concentration (volume %) of the ammonia gas is preferably 0.2% by volume to 3.0% by volume, and more preferably 0.5% by volume to 2.0% by volume, based on the total volume of the introduced gas.

[0184] In addition to the above-mentioned raw material gases, ethylene gas (C2H4) can also be used. The concentration (volume %) of the ethylene gas is preferably not less than 0 volume % and not more than 0.3 volume % based on the total volume of the introduced gas.

[0185] Examples of the carrier gas include argon and hydrogen. Hydrogen is preferably used. The carrier gas concentration (volume %) is preferably 90% to 99% by volume, more preferably 95% to 99% by volume, based on the total volume of the introduced gas.

[0186] In the second step, the second region is first formed while maintaining the total gas flow rate of the introduced gases constant by maintaining the flow rates of the raw material gas and the carrier gas constant (hereinafter referred to as "step 2A"). This allows the average aspect ratio of the grains in the second region to exceed 3.0 and be less than 10.0. The reason for this is presumably as follows.

[0187] When forming an AlTiCN film using CVD, the probability of adsorption on specific crystal planes increases when the gas flow rate is constant, making it easier for the crystal grains to grow in a columnar shape. This is presumably responsible for increasing the aspect ratio of the crystal grains.

[0188] The thickness of the second region is adjusted by the film formation time. The total gas flow rate in the 2A step can be set to a point within the range of 80 L / min to 120 L / min, for example.

[0189] After step 2A, the first region is formed under the conditions described below by varying the total gas flow rate of the introduced gas by varying the flow rate of the carrier gas (hereinafter also referred to as "step 2B"). This allows the average aspect ratio of the grains in the first region to be reduced to 3.0 or less. The reason for this is presumably as follows.

[0190] As mentioned above, when forming AlTiCN films using the CVD method, the probability of adsorption on specific crystal planes increases when the gas flow rate is constant, thus facilitating columnar grain growth. On the other hand, it is speculated that when the overall flow rate of the introduced gas is altered by varying the carrier gas flow rate during film formation, the probability of the raw material gas adsorbing on specific crystal planes decreases, making columnar grain growth more difficult, and thus reducing the grain aspect ratio. The present inventors have newly discovered that by varying the total gas flow rate of the introduced gas, the average aspect ratio of the grains can be reduced to 3.0 or less.

[0191] It should be noted that, in the past, pressure control was difficult because AlTiCN films were formed under high vacuum. Therefore, the gas flow rate was typically kept constant. If the gas flow rate were varied during AlTiCN film formation, and the pressure fluctuated significantly, it would be expected that defects would be easily generated in the AlTiCN film. Therefore, those skilled in the art do not employ the method unique to this embodiment, which varies the gas flow rate during AlTiCN film formation.

[0192] In step 2B, the total gas flow rate introduced into the reaction vessel can be varied under the following conditions, for example. Here, "total gas flow rate" refers to the total volumetric flow rate of gas introduced into the CVD furnace per unit time, assuming that the gas under standard conditions (0°C, 1 atmosphere) is an ideal gas.

[0193] Flow rate (average): 100L / min

[0194] Flow rate (variable range): 80L / min to 120L / min

[0195] Cycle: 5 minutes to 15 minutes (When it exceeds 15 minutes, the aspect ratio in the first area tends to increase)

[0196] When the total gas flow rate is set to the above range, the flow rate of the carrier gas in the introduced gas can be set to, for example, the following.

[0197] Flow rate (average): 98% by volume

[0198] Flow rate (variable range): 97% by volume or more and 99% by volume or less

[0199] Cycle: more than 5 minutes and less than 15 minutes

[0200] In addition to the steps 2A and 2B for forming the first layer, the second step may further include steps for forming other layers such as a base layer and a surface layer. The other layers may be formed by conventional methods.

[0201] <Step 3: Sandblasting>

[0202] In this step, the coating is subjected to sandblasting. The conditions for the sandblasting are as follows: By performing the sandblasting, a desired compressive residual stress can be imparted to the coating.

[0203] (Sandblasting conditions)

[0204] Medium: Alumina particles, 500g

[0205] Projection angle: 45°

[0206] Projection distance: 30mm or more and 100mm or less

[0207] Projection time: more than 2 seconds and less than 8 seconds

[0208] Projection pressure: 0.1MPa or more and 0.3MPa or less

[0209] Speed: 60rpm

[0210] <Other Processes>

[0211] In the production method according to the present embodiment, in addition to the above-mentioned steps, a surface treatment step and the like may be appropriately performed.

[0212] Example

[0213] This embodiment will be described in more detail with reference to examples, but this embodiment is not limited to these examples.

[0214] Manufacturing of Cutting Tools

[0215] In order to produce the cutting tools of samples No. 1 to 20, a cemented carbide cutting insert (manufactured by Sumitomo Electric Hardmetal Co., Ltd.) with a composition consisting of 2.0 wt% TaC, 1.0 wt% NbC, 10.0 wt% Co, and the remainder WC (including inevitable impurities) and in the shape of SEET13T3AGSN-G was prepared as a base material (first step).

[0216] Next, a coating is formed on the surface of the above-mentioned substrate (second process). Specifically, in Samples No. 1 to No. 19, the CVD method is first performed on the entire surface of the substrate according to the formation conditions of the base layer described in Table 1. Next, in Samples No. 1 to No. 19, the CVD method is performed on the entire surface of the above-mentioned base layer according to the formation conditions of the first layer described in Table 2 (2A process), and then the CVD method is performed according to the formation conditions of the first layer described in Table 3 (2B process). In addition, in Sample No. 20, the CVD method is performed on the entire surface of the above-mentioned substrate according to the formation conditions of the first layer described in Table 2 (2A process), and then the CVD method is performed according to the formation conditions of the first layer described in Table 3 (2B process). The film formation time of the 2A process and the 2B process was adjusted so that the thickness of the entire first layer becomes as described in the "Thickness of the first layer (μm)" column of Tables 6 and 7. Next, in Sample No. 19, the CVD method was performed according to the conditions for forming the surface layer described in Table 4. In the above manner, the second step was performed.

[0217] [Table 1]

[0218]

[0219] [Table 2]

[0220]

[0221] [Table 3]

[0222]

[0223] [Table 4]

[0224]

[0225] Further, after forming the coating film as described above, the third process is carried out according to the conditions of the sandblasting treatment described in Table 5.

[0226] [Table 5]

[0227]

[0228] By carrying out the above processes, cutting tools of Specimen Nos. 1 to 20 having the configurations shown in Table 6 and Table 7 were fabricated.

[0229] "Evaluation of Characteristics of Cutting Tools"

[0230] Using the cutting tools of Specimen Nos. 1 to 20 fabricated as described above, each characteristic of the cutting tools was evaluated as follows. It should be noted that the cutting tools of Specimen Nos. 1 to 9 and 17 to 20 correspond to the embodiments, and the cutting tools of Specimen Nos. 10 to 16 correspond to the comparative examples.

[0231] "Measurement of Thickness of Coating Film etc."

[0232] For the cutting tools of Specimen Nos. 1 to Specimen No. 20, the thicknesses of the coating film, the first layer which is the layer constituting the coating film, and the base layer were obtained by the method described in Embodiment 1. The obtained results were respectively recorded in the items of "Thickness of the First Layer (μm)" in Table 6 and Table 7, the item of "Thickness of the Base Layer (μm)" in Table 6, and the item of "Thickness of the Surface Layer (μm)" in Table 6.

[0233] [Table 6]

[0234]

[0235] "Measurement of x (Average Value) and y (Average Value)"

[0236] For the cutting tools of Specimen Nos. 1 to Specimen No. 20, x (average value) and y (average value) were obtained by the method described in Embodiment 1. The obtained results were respectively recorded in the items of "Al" in Table 6 and Table 7 x Ti 1-x C y N1-y ” in the “x(average)” and “y(average)” items.

[0237] <Measurement of Average Aspect Ratio of Crystal Grains in the First and Second Regions>

[0238] For cutting tools of Samples No. 1 to No. 20, the average aspect ratio of the grains in the first region and the average aspect ratio of the grains in the second region were determined using the method described in Embodiment 1. The obtained results are recorded in the "Average aspect ratio of the grains in the first region" and "Average aspect ratio of the grains in the second region" columns of Table 7, respectively.

[0239] [Table 7]

[0240]

[0241] <Measurement of Area Ratio>

[0242] For cutting tools of Samples No. 1 to No. 20, the area ratio of crystal grains having a cubic structure in the first layer was determined by the method described in Embodiment 1. The obtained results are recorded in the "Area ratio (%)" column of Table 7.

[0243] <Measurement of compressive residual stress>

[0244] For the cutting tools of Sample No. 1 to Sample No. 20, the compressive residual stress of the first layer was determined by the method described in Embodiment 1. The obtained results are recorded in the "Compressive Residual Stress (GPa)" column of Table 7.

[0245] <Determination of Hardness>

[0246] For the cutting tools of Sample No. 1 to Sample No. 20, the hardness of the first layer was determined by the method described in Embodiment 1. The obtained results are recorded in the "Hardness (GPa)" column of Table 7.

[0247] Cutting Test

[0248] The obtained cutting tool was used to perform cutting processing under the cutting conditions shown below. A cutting distance of 300 mm was defined as one pass, and damage was confirmed every one pass. The number of passes until the tool was defective due to thermal cracking and flank wear was evaluated. Here, "defective" means that the maximum flank wear exceeded 0.4 mm. The results are recorded in the "Cutting Test (Passes)" item of Table 7. Here, the number of passes until the tool was defective was 25 or more, which means that the heat crack resistance and wear resistance were good. In other words, the number of passes of 25 or more means that the tool has a long life.

[0249] (Cutting conditions)

[0250] Cutting material: FC250 block (100mm×80mm)

[0251] Cutting speed: 250m / min

[0252] Feed rate: 0.2mm / t

[0253] Cutting depth: 2.0mm

[0254] Wet / Dry: Wet

[0255] These cutting conditions are equivalent to wet machining of gray cast iron.

[0256] <Results>

[0257] The results in Table 7 show that the cutting tools of Samples Nos. 1 to 9 and 17 to 20 according to the Examples exhibit superior heat cracking resistance and wear resistance during wet machining of gray cast iron, compared to the cutting tools of Samples Nos. 10 to 16 according to the Comparative Examples. This indicates that the cutting tools of Samples Nos. 1 to 9 and 17 to 20 according to the Examples exhibit long tool life even during wet machining of gray cast iron.

[0258] As described above, the embodiments and examples of the present disclosure have been described. However, it is initially intended that the configurations of the above-described embodiments and examples may be appropriately combined or various modifications may be made.

[0259] The embodiments and examples disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present invention is not indicated by the embodiments and examples described above, but by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0260] Explanation of symbols

[0261] 1 Cutting tool, 1a Rake face, 1b Flank face, 1c Cutting edge portion, 10 Substrate, 11 First layer, 12 Base layer, 13 Surface layer, 14 Coating, 20a Grains included in the first region, 20b Grains included in the second region, 21a Grains spanning S1 or S2, 21b Grains spanning VS1, 21c Grains spanning L1, 50 CVD apparatus, 52 Substrate setting jig, 53 Reaction container, 54 Temperature control device, 55 Gas inlet pipe, 56 Gas exhaust pipe, 57 Gas exhaust port, S1 Surface of the first layer, S2 Interface on the surface side of the first layer, S3 Interface on the substrate side of the first layer, L1 First imaginary line, R1 First region, R2 Second region

Claims

1. A cutting tool comprising a substrate and a coating disposed on the substrate. The coating comprises a first layer, The first layer includes a plurality of grains, The grains are made of Al x Ti 1-x C y N 1-y constitute, The x exceeds 0.65 and is less than 0.95, The y is greater than or equal to 0 and less than 0.1, In a first region formed by a region sandwiched between the surface S1 of the first layer or an interface S2 on the surface side of the first layer and the first virtual plane VS1, the average aspect ratio of the crystal grains is 3.0 or less. In the second region formed by the region sandwiched between the first virtual plane VS1 and the interface S3 on the substrate side of the first layer, the average aspect ratio of the crystal grains exceeds 3.0 and is 10.0 or less. The first virtual plane VS1 passes through a point 1 μm away from the surface S1 or the interface S2 toward the substrate side and is parallel to the surface S1 or the interface S2. The crystal grains include crystal grains having a cubic crystal structure, In the first layer, the area ratio of crystal grains having a cubic crystal structure is 90% or more. The average aspect ratio and the area ratio are measured on a cross section along a normal line of an interface between the substrate and the coating. The thickness of the first layer is not less than 2 μm and not more than 20 μm.

2. The cutting tool according to claim 1, wherein In the first region, the average aspect ratio is 2.5 or less.

3. The cutting tool according to claim 1, wherein In the first region, the average aspect ratio is 2.0 or less.

4. The cutting tool according to claim 1, wherein In the first region, the average aspect ratio is 1.8 or less.

5. The cutting tool according to any one of claims 1 to 4, wherein: In the second region, the average aspect ratio exceeds 3.0 and is 9.0 or less.

6. The cutting tool according to any one of claims 1 to 4, wherein: In the second region, the average aspect ratio is 4.0 to 9.

0.

7. The cutting tool according to any one of claims 1 to 4, wherein: In the second region, the average aspect ratio is 4.0 to 8.

0.

8. The cutting tool according to any one of claims 1 to 4, wherein: The area ratio is 92% or more.

9. The cutting tool according to any one of claims 1 to 4, wherein: The area ratio is 95% or more.

10. The cutting tool according to any one of claims 1 to 4, wherein: The area ratio is 98% or more.

11. The cutting tool according to any one of claims 1 to 4, wherein: The thickness of the first layer is not less than 2 μm and not more than 12 μm.

12. The cutting tool according to any one of claims 1 to 4, wherein: The thickness of the first layer is 3 μm or more and 10 μm or less.

13. The cutting tool according to any one of claims 1 to 4, wherein: The compressive residual stress of the first layer is greater than or equal to 1.0 GPa and less than 4.5 GPa.

14. The cutting tool according to any one of claims 1 to 4, wherein: The hardness of the first layer is 30 GPa or more and 40 GPa or less.

15. The cutting tool according to any one of claims 1 to 4, wherein: The thickness of the coating is not less than 2 μm and not more than 25 μm.

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