Cutting tool

Abstract

This cutting tool comprises a substrate and a coating provided on the substrate. The coating includes an alumina layer provided on the substrate, an intermediate layer provided directly on the alumina layer, and a titanium carbonitride layer provided directly on the intermediate layer. The intermediate layer is made of titanium oxycarbonitride, and the titanium carbonitride layer is made of a compound represented by TixCyN(1-y). At a point A, which is 0.2 μm away from an interface I between the intermediate layer and the titanium carbonitride layer in a thickness direction toward the titanium carbonitride layer, an atomic ratio xA of titanium in the titanium carbonitride layer is 1.3 to 1.6, and an atomic ratio yA of carbon in the titanium carbonitride layer is 0.4 to 0.6. At a point B in the titanium carbonitride layer located on an opposite side of the interface I, which is 1.0 μm away from an interface J in a thickness direction toward the titanium carbonitride layer, an atomic ratio xB of titanium in the titanium carbonitride layer is 0.8 to 1.2, and an atomic ratio yB of carbon in the titanium carbonitride layer is 0.3 to 0.5. At a point C, which is the midpoint between point A and point B, an atomic ratio xC of titanium in the titanium carbonitride layer exceeds the atomic ratio xB and is less than the atomic ratio xA, and an atomic ratio yC of carbon in the titanium carbonitride layer is greater than the atomic ratio yB and less than the atomic ratio yA. The thickness of the intermediate layer is 0.5 μm to 1.5 μm, and the thickness of the titanium carbonitride layer is 1.5 μm to 3.5 μm.

Description

cutting tools

[0001] The present disclosure relates to cutting tools.

[0002] Conventionally, cutting tools having a substrate coated with a coating have been used. For example, Japanese Patent Application Publication No. 2020-516469 (Patent Document 1) discloses a coated cutting tool having a substrate coated with a wear-resistant multilayer coating, in which the wear-resistant multilayer coating is made of α-Al ２ O ３ layer and the α-Al ２ O ３ a titanium carbonitride layer Ti deposited on the layer ｘ C ｙ N １－ｙ (wherein 0.85≦x≦1.3, preferably 1.1≦x≦1.3, 0.4≦y≦0.85), wherein Ti ｘ C ｙ N １－ｙ discloses a coated cutting tool that exhibits a texture coefficient TC(hkl) defined by the Harris equation, as measured by X-ray diffraction using CuKα radiation and a θ-2θ scan, where the (hkl) reflections used are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), and (4 2 2), and where TC(1 1 1)≧3.

[0003] Furthermore, International Publication No. 2021 / 193676 (Patent Document 2) discloses a coated tool having a substrate and a coating layer located on the substrate, the coated tool comprising a first surface, a second surface adjacent to the first surface, and a cutting edge located on at least a part of a ridge line portion between the first surface and the second surface, and the coating layer is made of Al ２ O ３The present invention discloses a coated tool having a first coating layer including a first layer containing particles and a second layer located on the first layer, the second layer having, in order from the substrate side, a first film, a second film in contact with the first film, and a third film in contact with the second film, the first film, the second film, and the third film each containing Ti, and the first film, the second film, and the third film each containing at least one selected from C and N, where the N content contained in the first film is defined as a first N amount, the N content contained in the second film is defined as a second N amount, and the N content contained in the third film is defined as a third N amount, the relationship of first N amount > third N amount > second N amount is satisfied.

[0004] Patent Publication No. 2020-516469 International Publication No. 2021 / 193676

[0005] A cutting tool according to the present disclosure is a cutting tool comprising a substrate and a coating provided on the substrate, wherein the coating includes an alumina layer provided on the substrate, an intermediate layer provided directly on the alumina layer, and a titanium carbonitride layer provided directly on the intermediate layer, the intermediate layer being made of titanium oxycarbonitride, and the titanium carbonitride layer being made of Ti ｘ C ｙ N （１－ｙ） and at a point A 0.2 μm away from an interface I between the intermediate layer and the titanium carbonitride layer toward the titanium carbonitride layer in a thickness direction, the titanium atomic ratio x Ａ is 1.3 or more and 1.6 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ａ is 0.4 or more and 0.6 or less, and at a point B in the titanium carbonitride layer located on the opposite side of the interface I and 1.0 μm away from the interface J in the thickness direction toward the titanium carbonitride layer, the atomic ratio x of titanium in the titanium carbonitride layer is Ｂ is 0.8 or more and 1.2 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ is 0.3 or more and 0.5 or less, and at point C which is the midpoint between point A and point B, the atomic ratio x of titanium in the titanium carbonitride layer is Ｃ is the atomic ratio xＢ exceeding the atomic ratio x Ａ the atomic ratio y of carbon in the titanium carbonitride layer is less than Ｃ is the atomic ratio y Ｂ exceeding the atomic ratio y Ａ the thickness of the intermediate layer is 0.5 μm or more and 1.5 μm or less, and the thickness of the titanium carbonitride layer is 1.5 μm or more and 3.5 μm or less.

[0006] Fig. 1 is a perspective view illustrating one embodiment of a substrate of a cutting tool. Fig. 2 is a schematic cross-sectional view of a cutting tool according to one embodiment of this invention. Fig. 3 is a schematic cross-sectional view of a cutting tool according to another embodiment of this invention. Fig. 4 is a schematic cross-sectional view of a coating layer according to one embodiment of this invention. Fig. 5 is a schematic cross-sectional view of an example of a chemical vapor deposition apparatus used to produce a coating.

[0007] [Problem to be Solved by the Present Disclosure] The cutting tools disclosed in Patent Documents 1 and 2 have coatings with the above-described configurations, which are expected to improve wear resistance and thereby extend the life of the cutting tools. Furthermore, the cutting tool disclosed in Patent Document 2 has improved adhesion resistance as well as wear resistance.

[0008] However, in recent years, cutting processes have become faster and more efficient, which has increased the load on cutting tools and shortened their lifespans, creating a demand for further improvements in the mechanical properties (e.g., wear resistance, peeling resistance, and chipping resistance) of coatings on cutting tools.

[0009] The present disclosure has been made in view of the above circumstances, and has an object to provide a cutting tool that is excellent in wear resistance and peeling resistance.

[0010] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cutting tool that is excellent in wear resistance and peeling resistance.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] [1] A cutting tool according to the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, wherein the coating includes an alumina layer provided on the substrate, an intermediate layer provided directly on the alumina layer, and a titanium carbonitride layer provided directly on the intermediate layer, wherein the intermediate layer is made of titanium oxycarbonitride, and the titanium carbonitride layer is made of Ti ｘ C ｙ N （１－ｙ） and at a point A 0.2 μm away from an interface I between the intermediate layer and the titanium carbonitride layer toward the titanium carbonitride layer in a thickness direction, the titanium atomic ratio x Ａ is 1.3 or more and 1.6 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ａ is 0.4 or more and 0.6 or less, and at a point B in the titanium carbonitride layer located on the opposite side of the interface I and 1.0 μm away from the interface J in the thickness direction toward the titanium carbonitride layer, the atomic ratio x of titanium in the titanium carbonitride layer is Ｂ is 0.8 or more and 1.2 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ is 0.3 or more and 0.5 or less, and at point C which is the midpoint between point A and point B, the atomic ratio x of titanium in the titanium carbonitride layer is Ｃ is the atomic ratio x Ｂ exceeding the atomic ratio x Ａ the atomic ratio y of carbon in the titanium carbonitride layer is less than Ｃ is the atomic ratio y Ｂ exceeding the atomic ratio y Ａ the thickness of the intermediate layer is 0.5 μm or more and 1.5 μm or less, and the thickness of the titanium carbonitride layer is 1.5 μm or more and 3.5 μm or less.

[0013] The cutting tool has the above-described configuration, resulting in excellent wear resistance and peeling resistance. Here, "wear resistance" refers to the resistance of the coating to wear when used in cutting. "Peeling resistance" refers to the resistance of the titanium carbonitride layer to peeling from the intermediate layer when used in cutting. Peeling resistance can also be expressed as "adhesion." Conventionally, a titanium oxycarbonitride layer has been formed on a titanium carbonitride layer. In this case, needle-shaped crystals of titanium oxycarbonitride are formed on the titanium carbonitride layer (columnar crystals). Therefore, the anchoring effect of the needle-shaped crystals improves the peeling resistance of both layers. However, a method of improving the peeling resistance of both layers by reversing the stacking order of the titanium carbonitride layer and the titanium oxycarbonitride layer has not been known until now. As a result of extensive research, the inventors have found for the first time that, when a titanium carbonitride layer is formed on a titanium oxycarbonitride layer (intermediate layer), increasing the atomic ratio of titanium on the intermediate layer side of the titanium carbonitride layer makes it easier for carbon and nitrogen constituting the intermediate layer to diffuse into the titanium carbonitride layer, thereby improving the peeling resistance of both layers while maintaining the wear resistance of the titanium carbonitride layer.

[0014] [2] The thickness of the alumina layer may be 2 μm or more and 20 μm or less. By specifying the thickness in this way, the cutting tool has even better wear resistance.

[0015] [3] At the point A, the atomic ratio x of titanium in the titanium carbonitride layer Ａ is 1.4 or more and 1.5 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ａ may be 0.45 or more and 0.55 or less. By specifying it in this way, the cutting tool has even better peeling resistance.

[0016] [4] At the point B, the atomic ratio x of titanium in the titanium carbonitride layer Ｂ is 0.8 or more and 1.1 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ may be 0.3 or more and 0.45 or less. By specifying it in this way, the cutting tool has even more excellent wear resistance.

[0017] [5] The thickness of the coating may be 6 μm or more and 30 μm or less. By specifying it in this way, the cutting tool has even better wear resistance.

[0018] [6] The coating may further include a base layer provided between the substrate and the alumina layer. By specifying in this way, the cutting tool has even better wear resistance.

[0019] [7] The coating may further include a surface layer provided on the titanium carbonitride layer. By specifying in this way, a cutting tool having excellent visibility of a used cutting edge can be obtained.

[0020] [Details of the embodiment of the present disclosure] Hereinafter, one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described. However, the present embodiment is not limited to this. In this specification, the notation in the form of "X to Z" means the upper and lower limits of a range (i.e., X or more and Z or less), and when no unit is specified for X and only a unit is specified for Z, the unit of X and the unit of Z are the same. Furthermore, in this specification, when a compound is expressed by a chemical formula in which the composition ratio of the constituent elements is not limited, such as "TiC", the chemical formula is considered to include all conventionally known composition ratios (element ratios). In this case, the above chemical formula is considered to include not only stoichiometric compositions but also non-stoichiometric compositions. For example, the chemical formula of "TiC" does not include the stoichiometric composition "Ti １ C １ " as well as, for example, "Ti １ C ０．８ This also applies to the description of compounds other than "TiC."

[0021] <Cutting Tool> A cutting tool according to the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, wherein the coating includes an alumina layer provided on the substrate, an intermediate layer provided directly on the alumina layer, and a titanium carbonitride layer provided directly on the intermediate layer, wherein the intermediate layer is made of titanium oxycarbonitride, and the titanium carbonitride layer is made of Ti ｘ C ｙ N （１－ｙ）and at a point A 0.2 μm away from an interface I between the intermediate layer and the titanium carbonitride layer toward the titanium carbonitride layer in a thickness direction, the titanium atomic ratio x Ａ is 1.3 or more and 1.6 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ａ is 0.4 or more and 0.6 or less, and at a point B in the titanium carbonitride layer located on the opposite side of the interface I and 1.0 μm away from the interface J in the thickness direction toward the titanium carbonitride layer, the atomic ratio x of titanium in the titanium carbonitride layer is Ｂ is 0.8 or more and 1.2 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ is 0.3 or more and 0.5 or less, and at point C which is the midpoint between point A and point B, the atomic ratio x of titanium in the titanium carbonitride layer is Ｃ is the atomic ratio x Ｂ exceeding the atomic ratio x Ａ the atomic ratio y of carbon in the titanium carbonitride layer is less than Ｃ is the atomic ratio y Ｂ exceeding the atomic ratio y Ａ the thickness of the intermediate layer is 0.5 μm or more and 1.5 μm or less, and the thickness of the titanium carbonitride layer is 1.5 μm or more and 3.5 μm or less.

[0022] The cutting tool 50 of this embodiment includes a substrate 10 and a coating 40 provided on the substrate 10 (hereinafter, sometimes simply referred to as the "cutting tool") (FIG. 2). The coating 40 includes an alumina layer 20 provided on the substrate 10, an intermediate layer 21 provided directly on the alumina layer 20, and a titanium carbonitride layer 22 provided directly on the intermediate layer 21. In addition to the layers described above, the cutting tool 50 may further include a base layer 23 provided between the substrate 10 and the alumina layer 20 (FIG. 3). The cutting tool 50 may further include a surface layer 24 provided on the titanium carbonitride layer 22 (FIG. 3). The base layer 23, the surface layer 24, and other layers will be described later.

[0023] In one aspect of this embodiment, the coating may cover the rake face of the substrate, or may cover a portion other than the rake face (for example, a flank.) The cutting tool may be, for example, a drill, an end mill, an indexable cutting tip for a drill, an indexable cutting tip for an end mill, an indexable cutting tip for a milling cutter, an indexable cutting tip for a turning cutter, a metal saw, a gear cutting tool, a reamer, or a tap.

[0024] <Substrate> The substrate of this embodiment can be any substrate as long as it is conventionally known as this kind of substrate.For example, the substrate can comprise at least one selected from the group consisting of cemented carbide (for example, tungsten carbide (WC)-based cemented carbide, cemented carbide that contains Co in addition to WC, cemented carbide that adds carbonitrides such as Cr, Ti, Ta, Nb in addition to WC), cermet (mainly composed of TiC, TiN, TiCN etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide etc.), cubic boron nitride sintered body (cBN sintered body) and diamond sintered body, and can comprise at least one selected from the group consisting of cemented carbide, cermet and cBN sintered body.

[0025] Among these various substrates, WC-based cemented carbide or cBN sintered body may be particularly selected because these substrates have an excellent balance between hardness and strength, particularly at high temperatures, and have excellent properties as substrates for cutting tools for the above-mentioned applications.

[0026] When a cemented carbide is used as the substrate, the effect of this embodiment is exhibited even if the cemented carbide contains free carbon or an abnormal phase called the η phase in its structure. The substrate used in this embodiment may have its surface modified. For example, a β-free layer may be formed on the surface of a cemented carbide, or a surface-hardened layer may be formed on the surface of a cBN sintered compact. The effect of this embodiment is exhibited even if the surface is modified in this way.

[0027] FIG. 1 is a perspective view illustrating one embodiment of a substrate for a cutting tool. A substrate having such a shape is used, for example, as a substrate for an indexable cutting insert for turning. The substrate 10 has a rake face 1, a flank 2, and a cutting edge ridge 3 where the rake face 1 and the flank 2 intersect. In other words, the rake face 1 and the flank 2 are surfaces connected with the cutting edge ridge 3 sandwiched between them. The cutting edge ridge 3 forms the tip of the cutting edge of the substrate 10. The shape of the substrate 10 can also be understood as the shape of the cutting tool.

[0028] When the cutting tool is an indexable cutting insert, the substrate 10 may have a shape with or without a chip breaker. The shape of the cutting edge ridge 3 includes any of a sharp edge (a ridge where the rake face and the flank intersect), a honing (a shape in which a radius is added to the sharp edge), a negative land (a chamfered shape), and a shape that combines a honing and a negative land.

[0029] 1, the shape of the substrate 10 and the names of the various parts thereof will be described with the same terms as above for the shape and names of the various parts of the cutting tool 50 according to this embodiment that correspond to the substrate 10. That is, the cutting tool has a rake face, a flank face, and a cutting edge ridge connecting the rake face and the flank face.

[0030] <Coating> The coating 40 according to this embodiment includes an alumina layer 20 provided on the substrate 10, an intermediate layer 21 provided directly on the alumina layer 20, and a titanium carbonitride layer 22 provided directly on the intermediate layer 21 (see FIG. 2). The "coating" covers at least a portion of the substrate (e.g., the rake face that comes into contact with the workpiece during cutting), thereby improving various properties of the cutting tool, such as chipping resistance, wear resistance, adhesion resistance, and peeling resistance. The coating may cover not only a portion of the substrate, but also the entire substrate. However, even if a portion of the substrate is not coated with the coating or the coating has a partially different configuration, this does not depart from the scope of this embodiment.

[0031] The thickness of the coating may be 6 μm or more and 30 μm or less, or 6 μm or more and 25 μm or less. Here, the thickness of the coating refers to the sum of the thicknesses of the layers constituting the coating. Examples of "layers constituting the coating" include the alumina layer, intermediate layer, titanium carbonitride layer, underlayer, and surface layer described below. The thickness of the coating can be determined, for example, by measuring 10 arbitrary points on a cross-sectional sample parallel to the normal direction of the substrate surface using a field emission scanning electron microscope (SEM) and averaging the thicknesses at the 10 measured points. The measured cross-section of the cross-sectional sample is then polished by ion milling. The same applies to measuring the thickness of the alumina layer, intermediate layer, titanium carbonitride layer, underlayer, and surface layer described below. An example of a field emission scanning electron microscope is the SU3500 (product name) manufactured by Hitachi High-Technologies Corporation. An example of an ion milling device is the IM4000 (product name) manufactured by Hitachi High-Technologies Corporation.

[0032] (Alumina Layer) The alumina layer 20 in this embodiment is provided on the substrate 10. Here, "provided on the substrate" is not limited to a case where the alumina layer is provided directly on the substrate (see FIG. 2), but also includes a case where the alumina layer is provided on the substrate via another layer (see FIG. 3). That is, the alumina layer may be provided directly on the substrate, or may be provided on the substrate via another layer, such as a base layer, as long as the effects of the present disclosure are achieved.

[0033] The alumina layer is made of aluminum oxide (Al ２ O ３ The aluminum oxide may be composed of only α-type aluminum oxide (α-Al), or may be composed of aluminum oxide and inevitable impurities. Examples of the inevitable impurities include chlorine and sulfur. The aluminum oxide may be composed of α-type aluminum oxide (α-Al ２ O ３ ) may also be used.

[0034] The thickness of the alumina layer may be 2 μm or more and 20 μm or less, 3 μm or more and 15 μm or less, or 4 μm or more and 10 μm or less. The thickness of the alumina layer can be confirmed by observing a vertical cross section of the substrate and the coating using an SEM in the same manner as described above.

[0035] (Intermediate Layer) The intermediate layer 21 according to this embodiment is provided directly on the alumina layer 20 (FIG. 2). The intermediate layer is made of titanium oxycarbonitride. In one aspect of this embodiment, the intermediate layer may be made of only titanium oxycarbonitride, or may be made of titanium oxycarbonitride and inevitable impurities. Examples of the inevitable impurities include oxygen and chlorine.

[0036] The thickness of the intermediate layer is 0.5 μm or more and 1.5 μm or less, and may be 0.6 μm or more and 1.4 μm or less, or may be 0.7 μm or more and 1.3 μm or less. The thickness of the intermediate layer can be confirmed by observing a vertical cross section of the substrate and the coating using an SEM in the same manner as described above.

[0037] (Titanium carbonitride layer) In this embodiment, the titanium carbonitride layer 22 is provided directly on the intermediate layer 21. The titanium carbonitride layer is made of Ti ｘ C ｙ N （１－ｙ） The titanium carbonitride layer may have another layer, such as a surface layer, formed thereon. The titanium carbonitride layer may also be the outermost layer of the coating.

[0038] (Atomic Ratio at Each Point of Titanium Carbonitride Layer) In the present embodiment, point A in the titanium carbonitride layer 22 is a point 0.2 μm away from interface I between the intermediate layer 21 and the titanium carbonitride layer 22 toward the titanium carbonitride layer 22 in the thickness direction ( FIG. 4 ). Point B in the titanium carbonitride layer 22 is a point 1.0 μm away from interface J in the titanium carbonitride layer 22 located on the opposite side of interface I toward the titanium carbonitride layer 22 in the thickness direction ( FIG. 4 ). The interface J may be parallel to interface I. In the present embodiment, the term “parallel” is not limited to geometric parallelism, but also encompasses approximate parallelism. When the titanium carbonitride layer 22 is located on the outermost surface of a coating, the interface J can be understood as the surface of the titanium carbonitride layer 22. When another layer (e.g., a surface layer) is provided directly on the titanium carbonitride layer, the interface J can be understood as the interface between the titanium carbonitride layer and the other layer. Point C in the titanium carbonitride layer 22 is the midpoint between point A and point B (FIG. 4). Point C is a point on a line connecting point A and point B, and can also be understood as a point equidistant from point A and point B.

[0039] At the point A, the atomic ratio x of titanium in the titanium carbonitride layer Ａ is 1.3 or more and 1.6 or less, and may be 1.4 or more and 1.5 or less.

[0040] At the point A, the atomic ratio y of carbon in the titanium carbonitride layer Ａ is 0.4 or more and 0.6 or less, and may be 0.45 or more and 0.55 or less.

[0041] In one aspect of this embodiment, at point A, the atomic ratio x of titanium in the titanium carbonitride layer is Ａ is 1.4 or more and 1.5 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ａ may be 0.45 or more and 0.55 or less.

[0042] Here, "atomic ratio x Ａ " and "atomic ratio y Ａ" means "atomic ratio x at point A" and "atomic ratio y at point A", respectively. Ｂ ”, “atomic ratio y Ｂ ”, “atomic ratio x Ｃ " and "atomic ratio y Ｃ The same applies to "." These atomic ratios are based on the sum of the atomic ratio of carbon and the atomic ratio of nitrogen in the titanium carbonitride layer.

[0043] The atomic ratio of each element (e.g., titanium, carbon, nitrogen, oxygen) can be determined by performing line analysis on a cross-sectional sample parallel to the normal direction of the surface of the above-mentioned substrate using an energy dispersive X-ray spectrometer (EDX device) attached to an SEM. Specifically, first, the cut surface of the cross-sectional sample is polished using a cross-section polisher (CP processing) or the like. Linear analysis is performed on the polished cut surface using an EDX device along a direction intersecting the intermediate layer and the titanium carbonitride layer. The above-mentioned "direction intersecting the intermediate layer and the titanium carbonitride layer" may also be a direction perpendicular to interface I. The measurement pitch in this case is 0.1 μm. An example of an EDX measurement device is the JED-2300 (trade name) manufactured by JEOL Ltd.

[0044] Next, based on the results of the linear analysis, a graph is created in which the distance from the measurement start point is plotted on the X axis (horizontal axis) and the atomic percentage (at%) of each element to be measured is plotted on the Y axis (vertical axis). Based on this graph, the point where the atomic percentage of oxygen becomes undetectable (1 at% or less) and is closest to the intermediate layer is designated as "interface I between the intermediate layer and the titanium carbonitride layer" (see FIG. 4). Based on this graph, the point where the atomic percentage of carbon becomes 1 at% and is farthest from the intermediate layer is designated as "interface J." Based on interface I and interface J, points A, B, and C are defined. Then, based on the graph, the atomic ratios of each element at points A, B, and C are calculated.

[0045] The above-mentioned measurement was carried out at least three times, and the average value of the atomic ratio of each element obtained in each measurement was defined as "atomic ratio x Ａ ”, “atomic ratio yＡ ”, “atomic ratio x Ｂ ”, “atomic ratio y Ｂ ”, “atomic ratio x Ｃ " and "atomic ratio y Ｃ "

[0046] At the point B, the atomic ratio x of titanium in the titanium carbonitride layer Ｂ is 0.8 or more and 1.2 or less, and may be 0.8 or more and 1.1 or less, or may be 0.9 or more and 1.1 or less.

[0047] At the point B, the atomic ratio y of carbon in the titanium carbonitride layer Ｂ is 0.3 or more and 0.5 or less, and may be 0.3 or more and 0.45 or less, or may be 0.3 or more and 0.4 or less.

[0048] In one aspect of this embodiment, at point B, the atomic ratio x of titanium in the titanium carbonitride layer is Ｂ is 0.8 or more and 1.1 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ may be 0.3 or more and 0.45 or less, and the atomic ratio x of titanium in the titanium carbonitride layer may be Ｂ is 0.9 or more and 1.1 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ may be 0.3 or more and 0.4 or less.

[0049] At point C, the atomic ratio x of titanium in the titanium carbonitride layer Ｃ is the atomic ratio x Ｂ exceeding the atomic ratio x Ａ is less than.

[0050] At the point C, the atomic ratio y of carbon in the titanium carbonitride layer Ｃ is the atomic ratio y Ｂ exceeding the atomic ratio y Ａ is less than.

[0051] In one aspect of this embodiment, the titanium carbonitride layer may or may not have an interface within the layer. In this case, it goes without saying that an interface existing within the layer cannot be the interface I or the interface J.

[0052] Conventionally, a titanium oxycarbonitride layer has been formed on a titanium carbonitride layer. In this case, needle-shaped crystals of titanium oxycarbonitride are formed on the titanium carbonitride layer (columnar crystals). Therefore, the anchoring effect of the needle-shaped crystals improves the peeling resistance of both layers. However, if the stacking order of the titanium carbonitride layer and the titanium oxycarbonitride layer is reversed, the anchoring effect is not obtained, and there is room for improvement in the peeling resistance of both layers when a titanium carbonitride layer is formed directly on a titanium oxycarbonitride layer. In the titanium carbonitride layer according to the present disclosure, titanium atoms are unevenly distributed on the intermediate layer side of the titanium carbonitride layer. Therefore, carbon and nitrogen constituting the intermediate layer are easily diffused into the titanium carbonitride layer, improving the peeling resistance regardless of the crystalline state of both layers while maintaining the wear resistance of the titanium carbonitride layer.

[0053] The thickness of the titanium carbonitride layer is 1.5 μm or more and 3.5 μm or less, or may be 1.7 μm or more and 3.3 μm or less, or may be 2.0 μm or more and 3.0 μm or less. The thickness of the titanium carbonitride layer can be confirmed by observing vertical cross sections of the substrate and coating using an SEM in the same manner as described above.

[0054] (Underlayer) The coating 40 may further include an underlayer 23 provided between the substrate 10 and the alumina layer 20 (see FIG. 3). The underlayer 23 may include titanium nitride (TiN), titanium carbonitride (TiCN), or titanium oxycarbonitride (TiCNO). Each of TiN, TiCN, and TiCNO may be a cubic crystal.

[0055] The thickness of the underlayer may be 3 μm or more and 20 μm or less, or 5 μm or more and 15 μm or less, and such a thickness can be confirmed by observing a vertical cross section of the substrate and the coating using an SEM in the same manner as described above.

[0056] (Surface Layer) The coating 40 may further include a surface layer 24 provided on the titanium carbonitride layer 22. The surface layer 24 may include a compound consisting of titanium element and at least one element selected from the group consisting of C, N, and B. In one aspect of the present embodiment, the composition of the surface layer may be different from the composition of the titanium carbonitride layer.

[0057] The compounds contained in the surface layer 24 include, for example, TiC, TiN, TiCN, and TiB. ２ etc.

[0058] The thickness of the surface layer may be 0.1 μm or more and 1.5 μm or less, or 0.2 μm or more and 1.0 μm or less. Such a thickness can be confirmed by observing a vertical cross section of the substrate and the coating using an SEM, as described above.

[0059] (Other Layers) The coating may further include other layers as long as the effects of the cutting tool according to this embodiment are not impaired. The other layers may have the same or different compositions as the alumina layer, the intermediate layer, the titanium carbonitride layer, the base layer, or the surface layer. Examples of compounds contained in the other layers include TiN, TiCN, TiBN, and Al. ２ O ３ The order of lamination of the other layers is not particularly limited. The thickness of the other layers is not particularly limited as long as the effects of the present embodiment are not impaired, and examples thereof include 0.1 μm or more and 20 μm or less.

[0060] <<Method of Manufacturing Cutting Tool>> The method of manufacturing a cutting tool according to this embodiment includes: a first step (hereinafter may be simply referred to as the "first step") of preparing the substrate; a second step (hereinafter may be simply referred to as the "second step") of forming the alumina layer on the substrate by chemical vapor deposition; a third step (hereinafter may be simply referred to as the "third step") of forming the intermediate layer directly on the alumina layer by chemical vapor deposition; and a fourth step (hereinafter may be simply referred to as the "fourth step") of forming the titanium carbonitride layer directly on the intermediate layer by chemical vapor deposition, wherein in the fourth step, the titanium carbonitride layer is formed at a temperature of 950°C or higher and 1030°C or lower using source gases including a gas containing titanium as a constituent element, a gas containing nitrogen as a constituent element, and a gas containing carbon as a constituent element, while decreasing the flow rate of the gas containing titanium as a constituent element and increasing the flow rate of the gas containing nitrogen as a constituent element.

[0061] <First Step: Preparing a Substrate> In the first step, a substrate is prepared. For example, a cemented carbide substrate is prepared as the substrate. The cemented carbide substrate may be a commercially available product or may be manufactured by a general powder metallurgy method. When manufactured by a general powder metallurgy method, for example, WC powder and Co powder are mixed using a ball mill or the like to obtain a mixed powder. The mixed powder is dried and then molded into a predetermined shape to obtain a compact. The molded body is then sintered to obtain a WC—Co-based cemented carbide (sintered body). Next, the sintered body is subjected to a predetermined cutting edge processing such as honing, thereby producing a substrate made of a WC—Co-based cemented carbide. In the first step, any substrate other than those described above can be prepared as long as it is a substrate known in the art as this type of substrate.

[0062] <Second step: Step of forming an alumina layer on a substrate> In the second step, an alumina layer is formed on the substrate by chemical vapor deposition (CVD) using a source gas containing a gas containing aluminum as a constituent element and a gas containing oxygen as a constituent element.

[0063] FIG. 5 is a schematic cross-sectional view showing an example of a chemical vapor deposition apparatus (CVD apparatus) used to produce the coating. The second step will be described below with reference to FIG. 5 . The CVD apparatus 30 includes a plurality of substrate setting jigs 31 for holding the substrates 10 and a heat-resistant alloy steel reaction vessel 32 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 introduction pipe 35 having a gas introduction port 34. The gas introduction pipe 35 extends vertically in the internal space of the reaction vessel 32 in which the substrate setting jigs 31 are placed, and is rotatable about the vertical axis. The gas introduction pipe 35 is also provided with a plurality of ejection holes 36 for ejecting gas into the reaction vessel 32. Using this CVD apparatus 30, the alumina layer or the like that constitutes the coating can be formed as follows.

[0064] First, the substrate 10 is placed in the substrate setting jig 31, and a source gas for the alumina layer is introduced into the reaction vessel 32 from the gas inlet pipe 35 while controlling the temperature and pressure within a predetermined range. In this way, the alumina layer 20 is formed on the substrate 10. Here, before forming the alumina layer 20 (i.e., before the second step), a source gas for the underlayer may be introduced into the reaction vessel 32 from the gas inlet pipe 35, thereby forming an underlayer (e.g., a layer containing TiN) on the surface of the substrate 10. Hereinafter, a method for forming the alumina layer 20 after forming an underlayer on the surface of the substrate 10 will be described.

[0065] The source gas for the underlayer is not particularly limited. For example, when forming a TiN layer, TiCl ４ and N ２ When forming a TiCN layer, the source gas may be, for example, a mixed gas of TiCl ４ , N ２ , C.H. ３ C.N., C.H. ４ , and C ２ H ４ When forming a TiCNO layer, the source gas may be, for example, a mixed gas of TiCl ４ , N ２ , CO, and CH４ Examples of the gas mixture include:

[0066] The temperature inside the reaction vessel 32 when the underlayer is formed may be controlled to 1000 to 1100° C. The pressure inside the reaction vessel 32 when the underlayer is formed may be controlled to 0.1 to 1013 hPa. The carrier gas may be H ２ When introducing the gases, the gas introduction pipe 35 may be rotated by a driving unit (not shown). This allows the gases to be uniformly dispersed within the reaction vessel 32.

[0067] Furthermore, the underlayer may be formed by MT (Medium Temperature)-CVD. Unlike CVD (hereinafter also referred to as "HT-CVD"), which is performed at a temperature of 1000 to 1100°C, the MT-CVD method is a method of forming a layer by maintaining the temperature inside the reaction vessel 32 at a relatively low temperature of 850 to 950°C. Since the MT-CVD method is performed at a relatively low temperature compared to the HT-CVD method, damage to the substrate 10 due to heating can be reduced. In particular, when the underlayer is a TiN layer, it may be formed by MT-CVD.

[0068] Next, the alumina layer is formed on the underlayer. ３ , CO, CO ２ , HCl and H ２ A mixed gas containing S may also be used.

[0069] AlCl in the source gas ３ The content ratio of AlCl may be 1 to 5 volume %, 1.5 to 4 volume %, or 2 to 3.5 volume %. ３ The flow rate may be, for example, 0.5 to 3.5 L / min.

[0070] The content of CO in the raw material gas may be 0.5 to 4 vol%, 0.8 to 3.5 vol%, or 1 to 2.5 vol%. The flow rate of CO may be, for example, 0.5 to 2 L / min.

[0071] CO in the raw gas ２The content of CO may be 0.2 to 2.5% by volume, 0.3 to 2% by volume, or 0.5 to 1.5% by volume. ２ The flow rate may be, for example, 0.4 to 1.5 L / min.

[0072] The content of HCl in the source gas may be 1 to 6 vol %, 1.5 to 5.5 vol %, or 2 to 4.5 vol %. The flow rate of HCl may be, for example, 0.5 to 4.5 L / min.

[0073] H in the source gas ２ The content of S may be 0.5 to 3.5% by volume, 1.0 to 3.0% by volume, or 1.5 to 2.5% by volume. ２ The flow rate of S may be, for example, 0.3 to 2.5 L / min.

[0074] The temperature inside the reaction vessel 32 may be controlled to 950 to 1000° C. The pressure inside the reaction vessel 32 may be controlled to 50 to 100 hPa. ２ As described above, the gas introduction pipe 35 may be rotated when introducing the gas.

[0075] In the above manufacturing method, the state of each layer changes by controlling each condition of the CVD method. For example, the composition of each layer is determined by the composition of the source gas introduced into the reaction vessel 32. The thickness of each layer is controlled by the execution time (film formation time).

[0076] <Third Step: Step of Forming Intermediate Layer Directly on Alumina Layer> In the third step, the intermediate layer is formed directly on the alumina layer by chemical vapor deposition. The intermediate layer is made of titanium oxycarbonitride.

[0077] The source gas for the titanium oxycarbonitride layer is, for example, TiCl ４ , C.H. ４ , N ２ A mixed gas of HCl and CO may also be used.

[0078] TiCl in the source gas ４The content ratio of TiCl may be 2 to 7 volume %, 3 to 6 volume %, or 3.5 to 5.5 volume %. ４ The flow rate may be, for example, 1.4 to 4.9 L / min.

[0079] CH in the raw material gas ４ The content ratio of may be 2 to 7 volume %, may be 2.5 to 6.5 volume %, or may be 3 to 6 volume %. ４ The flow rate may be, for example, 1 to 5 L / min.

[0080] N in the raw material gas ２ The content ratio of N may be 5 to 35% by volume, 7.5 to 30% by volume, or 10 to 25% by volume. ２ The flow rate may be, for example, 3.5 to 24.5 L / min.

[0081] The content of CO in the raw material gas may be 1.5 to 4.5 vol%, 2.0 to 4.0 vol%, or 2.5 to 3.5 vol%. The flow rate of CO may be, for example, 0.8 to 2.3 L / min.

[0082] The temperature inside the reaction vessel 32 may be controlled to 950 to 1000° C. The pressure inside the reaction vessel 32 may be controlled to 50 to 200 hPa. ２ As described above, the gas introduction pipe 35 may be rotated when introducing the gas.

[0083] <Fourth Step: Step of Forming a Titanium Carbonitride Layer Directly on the Intermediate Layer> In the fourth step, a titanium carbonitride layer is formed directly on the intermediate layer by chemical vapor deposition. In the fourth step, the titanium carbonitride layer is formed at a temperature of 950°C to 1030°C using a source gas containing a gas containing titanium as a constituent element, a gas containing nitrogen as a constituent element, and a gas containing carbon as a constituent element, while decreasing the flow rate of the gas containing titanium as a constituent element and increasing the flow rate of the gas containing nitrogen as a constituent element. In one aspect of this embodiment, the flow rate of the source gas in the fourth step may be 80 to 120 L / min. The flow rate of the source gas can also be understood as the sum of the flow rates of the respective gases constituting the source gas.

[0084] The source gas is, for example, TiCl ４ (gas containing titanium as a constituent element), CH ４ (gas containing carbon as a constituent element), CH ３ CN and N ２ A mixed gas of nitrogen and argon (gas containing nitrogen as a constituent element) is used.

[0085] TiCl in the source gas ４ The content ratio of TiCl may be 0.5 to 4% by volume, 1.0 to 3.5% by volume, or 1.5 to 3.0% by volume. ４ The flow rate may be, for example, 0.35 to 2.8 L / min.

[0086] CH in the raw material gas ４ The content ratio of may be 2 to 7 volume %, may be 2.5 to 6.5 volume %, or may be 3 to 6 volume %. ４ The flow rate may be, for example, 1 to 5 L / min.

[0087] CH in the raw material gas ３ The CN content may be 0.1 to 0.5% by volume, 0.1 to 0.4% by volume, or 0.1 to 0.3% by volume. ３ The flow rate of CN may be, for example, 0.07 to 0.35 L / min.

[0088] N in the raw material gas ２ The content ratio of N may be 5 to 60% by volume, 7.5 to 55% by volume, or 10 to 50% by volume. ２ The flow rate may be, for example, 3.5 to 42 L / min.

[0089] The temperature inside the reaction vessel 32 may be controlled to 950 to 1000° C. The pressure inside the reaction vessel 32 may be controlled to 50 to 200 hPa. ２ As described above, the gas introduction pipe 35 may be rotated when introducing the gas.

[0090] In one aspect of this embodiment, the temperature at which the fourth step is performed may be 950°C or higher and 1030°C or lower, or 980°C or higher and 1010°C or lower.

[0091] In the fourth step, the rate of decrease in the flow rate of the gas containing titanium as a constituent element is 0.05 L / min. ２ 0.5L / min or more ２ It may be less than 0.05 L / min ２ More than 0.3L / min ２ It may be the following:

[0092] In the fourth step, the flow rate of the gas containing nitrogen as a constituent element is increased at a rate of 0.01 L / min. ２ Over 1.0 L / min ２ It may be less than 0.05 L / min ２ 0.5L / min or more ２ It may be the following:

[0093] <Other Steps> In addition to the steps described above, the manufacturing method according to this embodiment may include additional steps as appropriate, provided that the effects of this embodiment are not impaired. Examples of such additional steps include forming a surface layer on the titanium carbonitride layer and blasting the coating. There are no particular limitations on the method for forming the surface layer, and examples include a method of forming it by a CVD method or the like.

[0094] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0095] <<Preparation of Cutting Tool>> <First Step: Step of Preparing Substrate>> As the substrate, a cemented carbide cutting tip (shape: CNMG120408N-UX, manufactured by Sumitomo Electric Hardmetal Corporation, JIS B4120 (2013)) having a composition consisting of TaC (2.0 mass%), NbC (1.0 mass%), Co (10.0 mass%) and WC (balance) (including unavoidable impurities) was prepared.

[0096] <Step of forming underlayer> For samples 21, 23, and 24, before the second step described below, an underlayer was formed on the prepared substrate using a CVD apparatus with the source gas composition and film formation conditions listed in Table 1. The film formation time was adjusted appropriately to achieve the thickness shown in Table 5-2. The thickness and composition of the underlayer are also shown in Table 5-2. In Table 5-2, the composition of the underlayer is listed along with the thickness. For example, the notation "TiCN (3)" means that a TiCN layer (thickness 3 μm) was formed.

[0097]

[0098] <Second Step: Step of Forming an Alumina Layer on a Substrate> An alumina layer was formed on the prepared substrate or a substrate on which a base layer had been formed using a CVD apparatus, and the process then moved to the third step. The conditions for forming the alumina layer are shown in Table 2. The deposition time was adjusted appropriately to achieve the thicknesses shown in Tables 5-1 and 5-2. The thicknesses of the alumina layers are also shown in Tables 5-1 and 5-2.

[0099]

[0100] <Third Step: Step of Forming an Intermediate Layer Directly on the Alumina Layer> Next, an intermediate layer (a layer made of titanium oxycarbonitride) was formed directly on the alumina layer of the substrate using a CVD apparatus. The conditions for forming the intermediate layer are shown in Table 3. The deposition time was adjusted appropriately to achieve the thicknesses shown in Tables 5-1 and 5-2. The thicknesses of the intermediate layer are also shown in Tables 5-1 and 5-2.

[0101]

[0102] <Fourth Step: Step of Forming a Titanium Carbonitride Layer Directly on the Intermediate Layer> Next, a titanium carbonitride layer was formed directly on the intermediate layer of the substrate on which the intermediate layer had been formed, using a CVD apparatus. The conditions for forming the titanium carbonitride layer are shown in Tables 4-1 to 4-4. For Samples 21 to 24, the same conditions as for Sample 18 were used. In the fourth step, the titanium carbonitride layer was formed by changing the composition of the source gas from the beginning (5 minutes) to the middle (50 minutes) to the end (10 minutes), as shown in Tables 4-1 to 4-4. Specifically, TiCl ４ With decreasing gas and N ２ The film was formed while increasing the gas flow rate. The film formation time was adjusted appropriately to achieve the thicknesses shown in Tables 5-1 and 5-2. The thicknesses of the titanium carbonitride layers are also shown in Tables 5-1 and 5-2.

[0103]

[0104]

[0105]

[0106]

[0107] <Step of forming surface layer> For samples 22 to 24, a surface layer was formed on the substrate on which the titanium carbonitride layer was formed using a CVD apparatus. The conditions for forming the surface layer are shown below. The thickness and composition of the surface layer are shown in Table 5-2. In Tables 5-1 and 5-2, a "-" indicates that the corresponding layer was not formed. (In the case of TiN) Source gas composition: TiCl ４ (8.0vol%), N ２ (35.0vol%), H ２ (Remainder) Total gas flow rate: 60 L / min Pressure: 300 hPa Temperature: 1005°C (in the case of TiC) Raw material gas composition: TiCl ４ (3.5vol%), CH ４ (4.5vol%), H ２ (Remainder) Total gas flow rate: 40 L / min Pressure: 80 hPa Temperature: 1005°C

[0108]

[0109]

[0110] Using the above procedure, cutting tools of Samples 1 to 24 were produced. Here, Samples 2 to 4, Samples 7 to 9, Samples 12 to 14, Samples 17 to 19, and Samples 21 to 24 correspond to Examples, and Samples 1, 5, 6, 10, 11, 15, 16, and 20 correspond to Comparative Examples.

[0111] <Evaluation of Cutting Tool Properties> Using the sample cutting tools prepared as described above, the properties of the cutting tools were evaluated as follows.

[0112] <Measurement of Thickness of Each Layer Constituting the Coating> The thickness of each layer constituting the coating was determined by measuring 10 arbitrary points on a cross-sectional sample parallel to the normal direction of the surface of the substrate using a field emission scanning electron microscope (SEM) (manufactured by Hitachi High-Technologies Corporation, product name: SU3500) and calculating the average value of the thicknesses measured at the 10 points. The cross-section of the cross-sectional sample was then polished by ion milling (manufactured by Hitachi High-Technologies Corporation, product name: IM4000) before the measurement. The results are shown in Tables 5-1 and 5-2.

[0113] <Atomic Ratios at Each Point of the Titanium Carbonitride Layer (EDX Measurement)> The atomic ratios of each element (titanium, carbon, nitrogen, oxygen) at points A, B, and C of the titanium carbonitride layer were determined by performing line analysis on a cross-sectional sample parallel to the normal direction of the surface of the above-mentioned substrate using an energy dispersive X-ray spectrometer (EDX device) attached to an SEM. Specifically, the cut surface of the cross-sectional sample was first polished using a cross-section polisher. Linear analysis was performed on the polished cut surface using the EDX device along a direction intersecting the intermediate layer and the titanium carbonitride layer (a direction perpendicular to interface I described below). The measurement pitch was 0.1 μm. (Conditions for Measurement Using the EDX Device) Measurement device: JEOL Ltd., product name: JED-2300

[0114] Based on the results of the linear analysis, a graph was created in which the distance from the measurement start point was plotted on the X axis (horizontal axis) and the atomic percentage (at%) of each element to be measured was plotted on the Y axis (vertical axis). Based on this graph, the point where the atomic percentage of oxygen was undetectable (1 at% or less) and was closest to the intermediate layer was designated as "interface I between the intermediate layer and the titanium carbonitride layer" (see, for example, Figure 4). Based on this graph, the point where the atomic percentage of carbon was 1 at% and was farthest from the intermediate layer was designated as "interface J" (see, for example, Figure 4). Based on interfaces I and J, points A, B, and C of the titanium carbonitride layer were defined as follows (see, for example, Figure 4). Point A: A point 0.2 μm away from interface I toward the titanium carbonitride layer in the thickness direction. Point B: A point 1.0 μm away from interface J toward the titanium carbonitride layer in the thickness direction. Point C: A point on the line connecting points A and B, equidistant from points A and B.

[0115] Then, based on the graph, the atomic ratio of each element at points A, B, and C of the titanium carbonitride layer was determined. Such measurements were carried out three times, and the average values ​​of the atomic ratios of each element determined in each measurement were designated as "atomic ratio x Ａ ”, “atomic ratio y Ａ ”, “atomic ratio x Ｂ ”, “atomic ratio y Ｂ ”, “atomic ratio x Ｃ " and "atomic ratio y Ｃ The results are shown in Tables 6-1 and 6-2. The atomic ratios in Tables 6-1 and 6-2 are based on the sum of the atomic ratio of carbon and the atomic ratio of nitrogen in the titanium carbonitride layer.

[0116]

[0117]

[0118] <Cutting Test> (Cutting Evaluation: Continuous Processing Test, Evaluation of Wear Resistance and Peel Resistance) Cutting was performed under the following cutting conditions using the cutting tools of the samples (samples 1 to 24) prepared as described above, and the exposed area (mm 2 ) of the base material on the flank face was measured every minute of cutting time. ２) was measured. ２ The time over which this limit was exceeded was recorded as the life of the cutting tool. The results are shown in Tables 6-1 and 6-2. The longer the cutting time, the better the cutting tool can be evaluated as having wear resistance on the flank face. Also, the longer the cutting time, the better the cutting tool can be evaluated as having peeling resistance. This is because high peeling resistance prevents the titanium carbonitride layer from peeling off and suppresses wear on the flank face. Cutting conditions for continuous machining Workpiece: SCM440 (shape: round bar) Cutting speed: 250 m / min Feed rate: 0.2 mm / rev Depth of cut: 2.0 mm Cutting oil: Yes (wet)

[0119] The results in Tables 6-1 and 6-2 show that the cutting tools of Samples 2 to 4, 7 to 9, 12 to 14, 17 to 19, and 21 to 24 (cutting tools of the examples) achieved good results, with cutting times of 12 minutes or more in the cutting evaluation. On the other hand, the cutting tools of Samples 1, 5, 6, 10, 11, 15, 16, and 20 (cutting tools of the comparative examples) achieved cutting times of less than 10 minutes in the cutting evaluation. These results demonstrate that the cutting tools of the examples have superior wear resistance and peeling resistance compared to the cutting tools of the comparative examples.

[0120] From the above results, it was found that the cutting tools of the examples were superior in wear resistance and peeling resistance to the cutting tools of the comparative examples.

[0121] Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined.

[0122] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0123] DESCRIPTION OF SYMBOLS 1 Rake face, 2 Flank face, 3 Cutting edge ridge, 10 Base material, 20 Alumina layer, 21 Intermediate layer, 22 Titanium carbonitride layer, 23 Undercoat layer, 24 Surface layer, 30 CVD apparatus, 31 Base material setting jig, 32 Reaction vessel, 33 Temperature control device, 34 Gas inlet, 35 Gas inlet pipe, 36 Ejection hole, 40 Coating, 50 Cutting tool, A Point A, B Point B, C Point C, I Interface I, J Interface J

Claims

1. A cutting tool comprising a substrate and a coating provided on the substrate, wherein the coating includes an alumina layer provided on the substrate, an intermediate layer provided directly on the alumina layer, and a titanium carbonitride layer provided directly on the intermediate layer, wherein the intermediate layer is made of titanium oxycarbonitride, and the titanium carbonitride layer is made of Ti ｘ C ｙ N （１－ｙ） and at a point A 0.2 μm away from an interface I between the intermediate layer and the titanium carbonitride layer toward the titanium carbonitride layer in a thickness direction, the titanium atomic ratio x Ａ is 1.3 or more and 1.6 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ａ is 0.4 or more and 0.6 or less, and at a point B in the titanium carbonitride layer located on the opposite side of the interface I and 1.0 μm away from the interface J in the thickness direction toward the titanium carbonitride layer, the atomic ratio x of titanium in the titanium carbonitride layer is Ｂ is 0.8 or more and 1.2 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ is 0.3 or more and 0.5 or less, and at point C which is the midpoint between point A and point B, the atomic ratio x of titanium in the titanium carbonitride layer is Ｃ is the atomic ratio x Ｂ exceeding the atomic ratio x Ａ the atomic ratio y of carbon in the titanium carbonitride layer is less than Ｃ is the atomic ratio y Ｂ exceeding the atomic ratio y Ａ a thickness of the intermediate layer is 0.5 μm or more and 1.5 μm or less, and a thickness of the titanium carbonitride layer is 1.5 μm or more and 3.5 μm or less.

2. The cutting tool according to claim 1, wherein the thickness of the alumina layer is 2 μm or more and 20 μm or less.

3. At point A, the atomic ratio x of titanium in the titanium carbonitride layer Ａ is 1.4 or more and 1.5 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ａ The cutting tool according to claim 1 or 2, wherein is equal to or greater than 0.45 and equal to or less than 0.

55.

4. At point B, the atomic ratio x of titanium in the titanium carbonitride layer Ｂ is 0.8 or more and 1.1 or less, and the atomic ratio y of carbon in the titanium carbonitride layer is Ｂ The cutting tool according to claim 1 , wherein is equal to or greater than 0.3 and is equal to or less than 0.

45.

5. A cutting tool according to any one of claims 1 to 4, wherein the coating has a thickness of 6 μm or more and 30 μm or less.

6. A cutting tool according to any one of claims 1 to 5, wherein the coating further includes a primer layer provided between the substrate and the alumina layer.

7. A cutting tool according to any one of claims 1 to 6, wherein the coating further comprises a surface layer disposed on the titanium carbonitride layer.

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