Cutting tool

Abstract

A cutting tool, wherein the cutting tool is provided with a base material and a coating film provided on the base material, the coating film includes a titanium compound layer provided on the base material and an α-Al2O3 layer provided directly above the titanium compound layer, the α-Al2O3 layer is composed of a plurality of α-Al2O3 particles, the α-Al2O3 layer includes a region A1 and a region A2, the region A1 is a region sandwiched between an imaginary surface SA2 and an imaginary surface SA3, the imaginary surface SA2 is an imaginary surface having a distance of 0.5 μm from an interface P1 of the titanium compound layer and the α-Al2O3 layer to a surface side of the coating film, the imaginary surface SA3 is an imaginary surface having a distance of 1.0 μm from the interface P1 to the surface side of the coating film, the region A2 is a region sandwiched between the interface P1 and an imaginary surface SA1, the imaginary surface SA1 is an imaginary surface having a distance of 0.3 μm from the interface P1 to the surface side of the coating film, the titanium compound layer is composed of a plurality of titanium compound particles, the titanium compound particles are one selected from the group consisting of TiCN particles, TiCNO particles, TiAlCN particles, and TiAlCNO particles, the titanium compound layer includes a region B1 and a region B2, the region B1 is a region sandwiched between an imaginary surface SB2 and an imaginary surface SB3, the imaginary surface SB2 is an imaginary surface having a distance of 0.5 μm from the interface P1 to the base material side, the imaginary surface SB3 is an imaginary surface having a distance of 1.0 μm from the interface P1 to the base material side, the region B2 is a region sandwiched between the interface P1 and an imaginary surface SB1, the imaginary surface SB1 is an imaginary surface having a distance of 0.3 μm from the interface P1 to the base material side, the average particle diameter a1 of the α-Al2O3 particles in the region A1, the average particle diameter a2 of the α-Al2O3 particles in the region A2, the average particle diameter b1 of the titanium compound particles in the region B1, and the average particle diameter b2 of the titanium compound particles in the region B2 show the following relationships of Formulas 1 to 3, 0.80 ≤ a2 / b2 ≤ 1.27 Formula 1 1.50 ≤ a1 / a2 ≤ 10 Formula 2 1.45 ≤ b1 / b2 ≤ 5 Formula 3 the average particle diameter b1 is 0.10 μm or more and 0.50 μm or less.

Description

Technical Field

[0001] This disclosure relates to a cutting tool. Background Technology

[0002] Cutting tools with coatings formed on substrates have been used for a long time. Alumina (hereinafter also referred to as "α-Al2O3"), which has an α-type crystal structure, has excellent mechanical properties and has therefore been used as a coating material (Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-96303 Summary of the Invention

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

[0007] The coating comprises a titanium compound layer disposed on the substrate and an α-Al₂O₃ layer disposed directly above the titanium compound layer.

[0008] The α-Al₂O₃ layer is composed of multiple α-Al₂O₃ particles.

[0009] The α-Al2O3 layer includes region A1 and region A2.

[0010] Region A1 is the area sandwiched between imaginary surfaces SA2 and SA3. Imaginary surface SA2 is a 0.5 μm distance from the interface P1 between the titanium compound layer and the α-Al2O3 layer to the surface of the coating. Imaginary surface SA3 is a 1.0 μm distance from the interface P1 to the surface of the coating.

[0011] Region A2 is the area sandwiched between interface P1 and imaginary surface SA1, where imaginary surface SA1 is an imaginary surface 0.3 μm away from interface P1 towards the surface of the coating.

[0012] The titanium compound layer is composed of multiple titanium compound particles.

[0013] The titanium compound particles are selected from the group consisting of TiCN particles, TiCNO particles, TiAlCN particles, and TiAlCNO particles.

[0014] The titanium compound layer includes region B1 and region B2.

[0015] Region B1 is the area sandwiched between imaginary surfaces SB2 and SB3. Imaginary surface SB2 is an imaginary surface extending 0.5 μm from interface P1 towards the substrate side, and imaginary surface SB3 is an imaginary surface extending 1.0 μm from interface P1 towards the substrate side.

[0016] Region B2 is the area sandwiched between interface P1 and imaginary surface SB1, where imaginary surface SB1 is an imaginary surface extending 0.3 μm from interface P1 toward the substrate side.

[0017] The average particle size a1 of the α-Al2O3 particles in region A1, the average particle size a2 of the α-Al2O3 particles in region A2, the average particle size b1 of the titanium compound particles in region B1, and the average particle size b2 of the titanium compound particles in region B2 are shown to be related by the following equations 1 to 3.

[0018] 0.80≤a² / b²≤1.27 (Equation 1)

[0019] 1.50≤a1 / a2≤10 (Equation 2)

[0020] 1.45≤b1 / b2≤5 (Equation 3)

[0021] The average particle size b1 is greater than 0.10 μm and less than 0.50 μm. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing an example of a cross-section of the cutting tool according to Embodiment 1.

[0023] Figure 2 This is a schematic diagram showing another example of a cross-section of the cutting tool involved in Embodiment 1.

[0024] Figure 3 This is a diagram illustrating the methods for determining the particle size of α-Al2O3 particles and titanium compound particles.

[0025] Figure 4 This is a diagram illustrating the methods for determining the particle size of α-Al2O3 particles and titanium compound particles. Detailed Implementation

[0026] [The problem this disclosure aims to solve]

[0027] Although the mechanical properties of the α-Al2O3 layer are excellent, further improvement in the adhesion to other layers and the resistance to defects is required. In Patent Document 1, in order to improve the chipping resistance and peeling resistance of a cutting tool, at the interface between the lower layer (titanium compound layer) and the upper layer (α-Al2O3 layer), the ratio b1 / a1 of the number of grains a1 on the titanium compound layer side to the number of grains b1 on the α-Al2O3 layer side is adjusted to 0.8 < b1 / a1 < 1.2. In Patent Document 1, in order to perform this adjustment, after pretreatment of the titanium compound layer, the α-Al2O3 layer is formed. Therefore, a layer having a composition different from the main part of the titanium compound layer is formed near the above interface of the titanium compound layer. In this layer with a different composition, the adhesion force decreases, peeling is likely to occur, and a sufficient tool life cannot be obtained. Therefore, in a cutting tool having an α-Al2O3 layer as a coating film, further improvement in the tool life is required.

[0028] Therefore, an object of the present disclosure is to provide a cutting tool having an α-Al2O3 layer as a coating film, which has a long tool life.

[0029] [Effects of the Present Disclosure]

[0030] The cutting tool of the present disclosure includes an α-Al2O3 layer as a coating film and can have a long tool life.

[0031] [Description of Embodiments of the Present Disclosure]

[0032] First, embodiments of the present disclosure will be described.

[0033] (1) The cutting tool of the present disclosure includes a substrate and a coating film disposed on the substrate.

[0034] The coating film includes a titanium compound layer disposed on the substrate and an α-Al2O3 layer disposed directly above the titanium compound layer.

[0035] The α-Al2O3 layer is composed of a plurality of α-Al2O3 particles.

[0036] The α-Al2O3 layer includes a region A1 and a region A2.

[0037] The region A1 is a region sandwiched between a virtual plane SA2 and a virtual plane SA3. The virtual plane SA2 is a virtual plane at a distance of 0.5 μm from the interface P1 between the titanium compound layer and the α-Al2O3 layer toward the surface side of the coating film, and the virtual plane SA3 is a virtual plane at a distance of 1.0 μm from the interface P1 toward the surface side of the coating film.

[0038] Region A2 is the area sandwiched between interface P1 and imaginary surface SA1, where imaginary surface SA1 is an imaginary surface 0.3 μm away from interface P1 towards the surface of the coating.

[0039] The titanium compound layer is composed of multiple titanium compound particles.

[0040] The titanium compound particles are selected from the group consisting of TiCN particles, TiCNO particles, TiAlCN particles, and TiAlCNO particles.

[0041] The titanium compound layer includes region B1 and region B2.

[0042] Region B1 is the area sandwiched between imaginary surfaces SB2 and SB3. Imaginary surface SB2 is an imaginary surface extending 0.5 μm from interface P1 towards the substrate side, and imaginary surface SB3 is an imaginary surface extending 1.0 μm from interface P1 towards the substrate side.

[0043] Region B2 is the area sandwiched between interface P1 and imaginary surface SB1, where imaginary surface SB1 is an imaginary surface extending 0.3 μm from interface P1 toward the substrate side.

[0044] The average particle size a1 of the α-Al2O3 particles in region A1, the average particle size a2 of the α-Al2O3 particles in region A2, the average particle size b1 of the titanium compound particles in region B1, and the average particle size b2 of the titanium compound particles in region B2 are shown to be related by the following equations 1 to 3.

[0045] 0.80≤a² / b²≤1.27 (Equation 1)

[0046] 1.50≤a1 / a2≤10 (Equation 2)

[0047] 1.45≤b1 / b2≤5 (Equation 3)

[0048] The average particle size b1 is greater than 0.10 μm and less than 0.50 μm.

[0049] The cutting tool disclosed herein comprises an α-Al2O3 layer as a coating, which enables it to have a longer tool life.

[0050] (2) Preferably, the ratio R1 of the number of carbon atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms, and the ratio R2 of the number of carbon atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms, is R1 / R2, which is 0.9 or more and 1.1 or less.

[0051] The ratio R3 of the total number of carbon and nitrogen atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms is 0.8 or more and 1.0 or less.

[0052] The ratio R4 of the total number of carbon and nitrogen atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms is 0.8 or more and 1.0 or less.

[0053] Therefore, the composition of the titanium compound layer is generally uniform, and the formation of interfaces caused by compositional variations can be suppressed within the titanium compound layer. This suppresses the formation of cracks originating at the interfaces within the coating, thereby improving the peel resistance of the cutting tool.

[0054] (3) Preferably, the ratio of the average particle size a1 to the average particle size b1, a1 / b1, is 1.50 or more and 5 or less.

[0055] The average particle size a1 is greater than 0.40 μm and less than 1.00 μm.

[0056] As a result, the durability of cutting tools is improved.

[0057] (4) Preferably, the average thickness of the titanium compound layer is 1.0 μm or more and 15 μm or less.

[0058] The average thickness of the α-Al2O3 layer is greater than 1.0 μm and less than 15 μm.

[0059] As a result, the wear resistance, chipping resistance, and peeling resistance of cutting tools are improved.

[0060] (5) Preferably, the α-Al2O3 layer has an orientation index TC(hkl) of 3 or more.

[0061] Therefore, the α-Al2O3 layer exhibits excellent wear resistance. Consequently, the cutting tool can have a longer tool life.

[0062] (6) Preferably, the coating comprises a TiN layer disposed between the substrate and the titanium compound layer.

[0063] Therefore, the coating can have excellent wear resistance and damage resistance.

[0064] [Details of the embodiments disclosed herein]

[0065] Hereinafter, specific examples of the cutting tools of this disclosure will be described with reference to the accompanying drawings. In the drawings of this disclosure, the same reference numerals denote the same or equivalent parts. In addition, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for the clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0066] In this specification, expressions such as "A~B" refer to the upper and lower limits of a range (i.e., above A and below B). If no unit is recorded in A but only in B, the unit of A is the same as the unit of B.

[0067] In this specification, when compounds are represented by chemical formulas, all conventionally known atomic ratios are included unless otherwise specified, and are not necessarily limited to atomic ratios within the stoichiometric range. For example, when referred to as "TiCN", the ratio of the number of atoms constituting TiCN includes all conventionally known atomic ratios.

[0068] In this disclosure, when more than one value is recorded as both the lower and upper limits of a numerical range, combinations of any value recorded in the lower limit and any value recorded in the upper limit are also disclosed. For example, when a1 or higher, b1 or higher, and c1 or higher are recorded as the lower limit, and a2 or lower, b2 or lower, and c2 or lower are recorded as the upper limit, the following combinations are disclosed: a1 or higher and a2 or lower, a1 or higher and b2 or lower, a1 or higher and c2 or lower, b1 or higher and a2 or lower, b1 or higher and b2 or lower, b1 or higher and c2 or lower, c1 or higher and a2 or lower, c1 or higher and b2 or lower, and c1 or higher and c2 or lower.

[0069] [Implementation Method 1: Cutting Tool]

[0070] One embodiment of this disclosure (hereinafter also referred to as "this embodiment") is a cutting tool having a substrate and a coating disposed on the substrate.

[0071] The coating comprises a titanium compound layer disposed on the substrate and an α-Al2O3 layer disposed directly above the titanium compound layer.

[0072] The α-Al₂O₃ layer is composed of multiple α-Al₂O₃ particles.

[0073] The α-Al2O3 layer includes region A1 and region A2.

[0074] Region A1 is the area sandwiched between imaginary surfaces SA2 and SA3. The distance from the interface P1 between the titanium compound layer and the α-Al2O3 layer to the surface of the coating is 0.5 μm for imaginary surface SA2, and the distance from the interface P1 to the surface of the coating is 1.0 μm for imaginary surface SA3.

[0075] Region A2 is the area sandwiched between interface P1 and imaginary surface SA1, which is 0.3 μm away from interface P1 towards the surface of the coating.

[0076] The titanium compound layer is composed of multiple titanium compound particles.

[0077] The titanium compound particles are selected from the group consisting of TiCN particles, TiCNO particles, TiAlCN particles, and TiAlCNO particles.

[0078] The titanium compound layer includes region B1 and region B2.

[0079] Region B1 is the area sandwiched between imaginary surfaces SB2 and SB3. The distance from interface P1 to the substrate side of imaginary surface SB2 is 0.5 μm, and the distance from interface P1 to the substrate side of imaginary surface SB3 is 1.0 μm.

[0080] Region B2 is the area sandwiched between interface P1 and imaginary surface SB1, which is 0.3 μm away from interface P1 towards the substrate.

[0081] The average particle size a1 of the α-Al2O3 particles in region A1, the average particle size a2 of the α-Al2O3 particles in region A2, the average particle size b1 of the titanium compound particles in region B1, and the average particle size b2 of the titanium compound particles in region B2 are shown to be related by the following equations 1 to 3.

[0082] 0.80≤a² / b²≤1.27 (Equation 1)

[0083] 1.50≤a1 / a2≤10 (Equation 2)

[0084] 1.45≤b1 / b2≤5 (Equation 3)

[0085] The average particle size b1 is above 0.1 μm and below 0.5 μm.

[0086] The cutting tool of this embodiment is a cutting tool with an α-Al2O3 layer as a coating, which can have a longer tool life. The reason for this is not yet clear, but it is speculated as described in (i) to (iv) below.

[0087] (i) In the cutting tool of this embodiment, the ratio of the average particle size a2 of region A2 of the α-Al2O3 layer to the average particle size b2 of region B2 of the titanium compound layer, a2 / b2, is 0.80 or more and 1.27 or less. That is, the difference between the average particle size a2 and the average particle size b2 is small near the interface between the α-Al2O3 layer and the titanium compound layer. Therefore, the formation of the interface caused by the particle size difference between region A2 and region B2 can be suppressed. In the coating of this cutting tool, the formation of the interface that becomes the starting point of cracking is suppressed, so the adhesion between region A2 and region B2 is large, and the cutting tool has excellent peel resistance and chip resistance.

[0088] (ii) In the cutting tool of this embodiment, since the ratio of the average particle size a1 of region A1 to the average particle size a2 of region A2 of the α-Al2O3 layer is 1.50 or more, the average particle size a1 is larger than the average particle size a2. Therefore, in regions A1 and A2, cracks are less likely to propagate in the thickness direction of the coating, and the cutting tool has excellent resistance to defects.

[0089] (iii) In the cutting tool of this embodiment, the ratio of the average particle size b1 of region B1 to the average particle size b2 of region B2 of the titanium compound layer, b1 / b2, is 1.45 or more. Since the average particle size b1 is larger than the average particle size b2, cracks are less likely to propagate in the thickness direction of the coating in both regions B1 and B2, resulting in excellent chip resistance of the cutting tool. Furthermore, b1 / b2 is less than 5, and the difference between the average particle size b1 and the average particle size b2 is small, thus suppressing the formation of interfaces caused by particle size differences.

[0090] (iv) In the cutting tool of this embodiment, since the average grain size b1 of region B1 of the titanium compound layer is 0.10 μm or more, the propagation of cracks from the tool surface can be suppressed, and the cutting tool has excellent resistance to chipping. Since the average grain size b1 is 0.50 μm or less, the hardness of the titanium compound layer is increased, and the cutting tool has excellent wear resistance.

[0091] <Components of Cutting Tools>

[0092] like Figure 1As shown, the cutting tool 1 of this embodiment includes a substrate 10 and a coating 15 disposed on the substrate 10. The coating 15 includes an α-Al₂O₃ layer 11 and a titanium compound layer 14. Preferably, the coating 15 covers at least a portion of the cutting portion of the rake face of the substrate, more preferably, it covers at least a portion of the cutting portion of the substrate, and even more preferably, it covers the entire surface of the substrate. The cutting portion of the substrate refers to the area on the surface of the substrate within 1.5 mm of the cutting edge. Even if a part of the substrate is not covered by the coating or the composition of the coating is partially different, it does not depart from the scope of this disclosure.

[0093] <Applications of Cutting Tools>

[0094] The cutting tools disclosed herein may be, for example, drill bits, end mills (e.g., ball end mills), indexable cutting inserts for drill bits, indexable cutting inserts for end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metalworking saws, gear cutting tools, reamers, taps, etc.

[0095] <Substrate>

[0096] The substrate 10 includes a rake face and a flank face. Any conventionally known substrate can be used as such a substrate. For example, it is preferably any of the following: cemented carbide (e.g., WC-based cemented carbide such as WC-Co cemented carbide, which may contain carbonitrides such as Ti, Ta, and Nb), cermet (mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, alumina, etc.), cubic boron nitride sintered body, or diamond sintered body.

[0097] Among these various substrates, cemented carbide (especially WC-based cemented carbide) or cermet (especially TiCN-based cermet) are preferred. These substrates exhibit excellent balance between hardness and strength at high temperatures, making them superior substrates for cutting tools used in the aforementioned applications. When using WC-based cemented carbide as the substrate, its microstructure may contain free carbon and anomalous layers known as the η-phase or ε-phase.

[0098] Furthermore, the surface of the substrate can be modified. For example, in the case of cemented carbide, a de-β layer can be formed on its surface, and in the case of cermet, a surface-hardened layer can be formed. The substrate exhibits the desired effect even after its surface has been modified.

[0099] When the cutting tool is an indexable cutting insert, the substrate may or may not have a chip breaker. The shape of the tool tip edge can be any of the following: a sharp edge (the edge where the rake face and flank face intersect), honing (giving the sharp edge a rounded corner), a negative cutting edge (beveling), or a combination of honing and a negative cutting edge.

[0100] <Lamination>

[0101] The Composition of Coating

[0102] like Figure 1 As shown, the coating 15 includes a titanium compound layer 14 and an α-Al₂O₃ layer 11 disposed directly above the titanium compound layer 14. In addition to the α-Al₂O₃ layer and the titanium compound layer, the coating may also include other layers.

[0103] like Figure 2 As shown, the coating 15 of the cutting tool 1 may further include a TiN layer 12 disposed between the substrate 10 and the titanium compound layer 14. Additionally, it may include a surface layer 13 disposed on the α-Al₂O₃ layer 11. Details of the TiN layer and the surface layer will be described later.

[0104] From the viewpoint of improving wear resistance, the lower limit of the average thickness of the overall coating disposed on the substrate is preferably 2 μm or more, 3 μm or more, 5 μm or more, 8 μm or more, 10 μm or more, 11 μm or more, 16 μm or more, 20 μm or more, or 23 μm or more. Particularly preferred are 11 μm or more, 16 μm or more, or 20 μm or more. From the viewpoint of improving peel resistance, the upper limit of the average thickness of the overall coating is preferably 23 μm or less, 20 μm or less, or 16 μm or less. The average thickness of the overall coating is preferably 11 μm or more and 23 μm or less, 16 μm or more and 23 μm or less, or 20 μm or more and 23 μm or less.

[0105] The thickness of the aforementioned coating is determined, for example, by observing a cross-sectional sample parallel to the normal direction of the substrate surface using a scanning transmission electron microscope (STEM). An example of a scanning transmission electron microscope is the JEM-2100F (trade name) manufactured by Nippon Egis Corporation.

[0106] When "thickness" is mentioned in this specification, it refers to the average thickness. Specifically, the magnification of the cross-sectional sample is set to 5000x, and a rectangular measurement field of view (30 μm in the direction parallel to the substrate surface) × (the distance including the entire thickness of the coating) is set in the electron microscope image. The thickness amplitude at ten locations within this field of view is measured, and the average value is taken as the "thickness". The average thickness of the α-Al2O3 layer, titanium compound layer, TiN layer, and surface layer described below is also measured and calculated in the same way.

[0107] Furthermore, it was confirmed that even if multiple measurement fields containing the coating on the rake face or the coating on the flank face are arbitrarily selected in the same sample and the above measurements are performed in these measurement fields, the above average thickness can be calculated, and the same result can be obtained.

[0108] <α-Al2O3 layer>

[0109] Composition of α-Al2O3 layers

[0110] In this embodiment, the α-Al₂O₃ layer is composed of multiple α-Al₂O₃ (alumina with an α-type crystal structure) particles. That is, the α-Al₂O₃ layer is composed of polycrystalline α-Al₂O₃. As long as the effects of this embodiment are achieved, the α-Al₂O₃ layer may contain unavoidable impurities. Chlorine (Cl) is an example of such unavoidable impurities. The content of unavoidable impurities in the α-Al₂O₃ layer is preferably 3% by mass or less. The content of unavoidable impurities in the α-Al₂O₃ layer is determined by secondary ion mass spectrometry (SIMS).

[0111] like Figure 1 As shown, the α-Al₂O₃ layer 11 includes region A1 and region A2. In this specification, region A1 and region A2 are defined as follows.

[0112] Region A1 is the area sandwiched between imaginary surfaces SA2 and SA3. The distance from the interface P1 between the titanium compound layer 14 and the α-Al2O3 layer 11 to the surface P2 side of the coating 15 of imaginary surface SA2 is 0.5 μm, and the distance from the interface P1 to the surface P2 side of the coating 15 of imaginary surface SA3 is 1.0 μm. Imaginary surfaces SA2 and SA3 are contained within region A1.

[0113] Region A2 is the area sandwiched between interface P1 and imaginary surface SA1. The imaginary surface SA1 is 0.3 μm away from interface P1 toward surface P2 of the coating 15. Imaginary surface SA1 is contained within region A2, while interface P1 is not contained within region A2.

[0114] Average particle size of α-Al2O3 particles

[0115] In this embodiment, from the viewpoint of suppressing the progression of cracks from the tool surface and improving damage resistance, the lower limit of the average particle size a1 of the α-Al2O3 particles in region A1 is preferably 0.40 μm or more, 0.42 μm or more, 0.45 μm or more, or 0.50 μm or more. From the viewpoint of suppressing the formation of an interface caused by the particle size difference a2 between the α-Al2O3 particles in region A2 and the α-Al2O3 particles in region A2, suppressing the progression of cracks originating from this interface, and improving damage resistance, the upper limit of the average particle size a1 is preferably 1.00 μm or less, 0.95 μm or less, 0.90 μm or less, 0.85 μm or less, or 0.80 μm or less. The average particle size a1 is preferably 0.40 μm or more and 1.00 μm or less, 0.45 μm or more and 0.90 μm or less, or 0.50 μm or more and 0.80 μm or less.

[0116] In this embodiment, from the viewpoint of improving adhesion to the titanium compound layer, the lower limit of the average particle size a2 of the α-Al2O3 particles in region A2 is preferably 0.05 μm or more, 0.06 μm or more, 0.09 μm or more, 0.10 μm or more, or 0.15 μm or more. From the viewpoint of improving hardness, the upper limit of the average particle size a2 is preferably 0.30 μm or less, 0.28 μm or less, or 0.25 μm or less. The average particle size a2 is preferably 0.05 μm or more and 0.30 μm or less, 0.10 μm or more and 0.28 μm or less, or 0.15 μm or more and 0.25 μm or less.

[0117] In this embodiment, the ratio of average particle size a1 to average particle size a2, a1 / a2, is 1.50 or more and 10 or less. This results in a cutting tool exhibiting excellent resistance to chipping. The lower limit of the ratio a1 / a2 is 1.50 or more, preferably 2.00 or more, 2.50 or more, 2.67 or more, 3.00 or more, 3.33 or more, or 3.50 or more. The upper limit of the ratio a1 / a2 is 10 or less, preferably 9.00 or less, 8.89 or less, 8.00 or less, 7.00 or less, 6.67 or less, or 6.00 or less. The ratio a1 / a2 is preferably 2.00 or more and 10 or less, 2.50 or more and 8.00 or less, or 3.50 or more and 6.00 or less.

[0118] In this specification, the average particle size a1 and the average particle size a2 are measured according to the following steps (A1) to (A6).

[0119] (A1) A cutting tool is used to cut along the normal of the rake face of the substrate using a diamond wire to expose the cross-section of the α-Al2O3 layer. The exposed cross-section is then subjected to Ar ion milling to achieve a mirror finish. The conditions for this ion milling are described below.

[0120] Accelerating voltage: 6kV

[0121] Irradiation angle: 0° from a straight line parallel to the thickness direction of the α-Al2O3 layer in the cross-section.

[0122] Irradiation time: 6 hours

[0123] (A2) The cross-section of the mirror surface was observed at 5000x magnification using a field emission scanning electron microscope (EF-SEM) to obtain backscattered electron images (EBSD). Figure 3 This is a diagram illustrating the method for determining the particle size of α-Al2O3 particles, schematically showing an example of this cross-section.

[0124] (A3) In the above EBSD, the measurement range is defined to include the region where the difference D1 between the valley bottom B1 and the peak T1 of the interface P1 on the substrate side of the α-Al2O3 layer along the normal direction of the rake face is less than 0.5 μm. This measurement range is a rectangle (lateral (direction parallel to the rake face): 30 μm) × (longitudinal (normal direction of the rake face): length including the entire coating).

[0125] (A4) Within the above measurement range, a baseline LS1 is set at the midpoint between the valley bottom B1 and the mountain top T1 of interface P1.

[0126] (A5) The transverse particle size of α-Al2O3 particles is measured on line L1, which is 0.2 μm away from the reference line LS1 in the direction of the cutting tool. The particle size of all α-Al2O3 particles in the measurement range is measured, and their average value is taken as the average particle size a2 of α-Al2O3 particles in region A2.

[0127] (A6) The transverse particle size of α-Al2O3 particles is measured on line L2, which is 0.8 μm away from the reference line LS1 in the direction of the cutting tool. The particle size of all α-Al2O3 particles in the measurement range is measured, and their average value is taken as the average particle size a1 of α-Al2O3 particles in region A1.

[0128] In the above (A5), the difference between the valley bottom B1 and the mountain top T1 of the interface is relatively large (e.g., exceeding 0.5 μm), such as... Figure 4 As shown, line L1 also exists inside the titanium compound layer 14, within the titanium compound layer 14 (e.g. Figure 4 The particle size of α-Al2O3 particles is not measured on line L1 (in the region shown by x), but only within the α-Al2O3 layer. The average particle size a2 is then calculated.

[0129] When setting the aforementioned line L1, the inventors of this invention, in region A2, within a range of 0 μm to 0.3 μm from the reference line LS1 along the normal direction of the rake face, set multiple measurement lines (e.g., a line 0.05 μm from the reference line LS1, a line 0.10 μm from the reference line LS1, and a line 0.15 μm from the reference line LS1) at intervals of 0.05 μm. On each line, the particle size of all α-Al2O3 particles within the measurement range was measured, and their average value was calculated. As a result, it was confirmed that the average particle size of the α-Al2O3 particles on the line corresponding to line L1 at a distance of 0.2 μm from the reference line LS1 was approximately the same as the average particle size of the α-Al2O3 particles on the aforementioned multiple measurement lines. The reason is speculated to be that, in the early stages of nucleation, the orientation and unevenness of the substrate significantly influence the growth of Al2O3 crystals. Therefore, Al2O3 crystals do not grow into columnar shapes (or a state where the cross-sectional grain size increases towards the surface), but rather into granular shapes (perpendicular to the interface and to some extent uniform in parallel). As mentioned above, the average grain size of α-Al2O3 particles on line L1 can be regarded as the average grain size a2 of α-Al2O3 particles in region A2.

[0130] It was confirmed that the same results could be obtained even when arbitrarily selecting different measurement ranges within the same cutting tool and performing the above measurements within those ranges. Furthermore, it was confirmed that the same results could be obtained even when arbitrarily selecting different measurement ranges within different cutting tools and performing the above measurements within those ranges.

[0131] When setting the aforementioned line L2, the inventors of this invention, in region A1, within a range 0.5 μm to 1.0 μm from the reference line LS1 along the normal direction of the rake face, set multiple measurement lines (e.g., a line 0.50 μm from the reference line LS1, a line 0.55 μm from the reference line LS1, and a line 0.60 μm from the reference line LS1) at intervals of 0.05 μm. On each line, the particle size of all α-Al2O3 particles within the measurement range was measured, and their average values ​​were calculated. As a result, it was confirmed that the average particle size of the α-Al2O3 particles on the line corresponding to line L2 at a distance of 0.8 μm from the reference line LS1 was approximately the same as the average particle size of the α-Al2O3 particles on the aforementioned multiple measurement lines. The reason for this is speculated to be as follows.

[0132] Region A1 is a transitional region from nucleation to crystal growth. In region A2, nucleation is influenced by the orientation and unevenness of the substrate in addition to gas conditions. However, in region A1, the influence of gas conditions is dominant, unlike in region A2 where nuclei (orientation, shape, etc.) are dominant. Since the crystals generated during nucleation are eliminated, and stable nuclei are generated under new gas conditions, it is presumed that the overall number of particles will not change significantly, and the particle size will not change much. Furthermore, in this embodiment, by adjusting the gas conditions during the formation of regions A2 and A1, the elimination of crystals and the transition between nucleation are smoothly achieved, thereby allowing region A1 to expand in the thickness direction while maintaining the particle size. Based on the above, the average particle size of the α-Al2O3 particles on line L2 can be considered as the average particle size a1 of the α-Al2O3 particles in region A1.

[0133] It was confirmed that even when arbitrarily selecting different measurement ranges within the same cutting tool and performing the above measurements within those ranges, the same results could be obtained. Furthermore, it was confirmed that even when arbitrarily selecting different measurement ranges within different cutting tools and performing the above measurements within those ranges, the same results could be obtained.

[0134] Average thickness of the α-Al₂O₃ layer

[0135] In this embodiment, the average thickness of the α-Al₂O₃ layer is preferably 1.0 μm or more and 15 μm or less. This allows the cutting tool to achieve both excellent wear resistance and chip resistance. From the viewpoint of improving wear resistance, the lower limit of the average thickness of the α-Al₂O₃ layer is preferably 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, or 5.0 μm or more. From the viewpoint of improving chip resistance, the upper limit of the average thickness of the α-Al₂O₃ layer is preferably 15 μm or less, 10 μm or less, 9 μm or less, or 8 μm or less. The average thickness of the α-Al₂O₃ layer is preferably 1.0 μm or more and 15 μm or less, 2.0 μm or more and 10 μm or less, 3.0 μm or more and 9 μm or less, or 5.0 μm or more and 8 μm or less.

[0136] As described above, the thickness of the α-Al₂O₃ layer can be confirmed by observing a cross-sectional sample of the cutting tool using a scanning transmission electron microscope (STEM). Here, the field of view is the measurement range set when measuring the particle size of the aforementioned α-Al₂O₃ particles.

[0137] Furthermore, it was confirmed that even when multiple measurement ranges containing coatings on the rake face or the flank face are arbitrarily selected in the same sample and the above measurements are performed on each measurement range, the same results can be obtained.

[0138] Orientation Index of α-Al2O3 Particles

[0139] In this embodiment, it is preferable that the orientation index TC(hkl) of the α-Al2O3 layer is 3 or more in the following formula (1). Therefore, the α-Al2O3 layer exhibits excellent wear resistance. Consequently, the cutting tool can have a longer tool life.

[0140] [Number 1]

[0141]

[0142] In equation (1), I(hkl) represents the X-ray diffraction intensity of the (hkl) reflecting surface, and I0(hkl) represents the standard intensity of the ICDD PDF card number 00-010-0173. Additionally, n in equation (1) represents the reflection number used in the calculation, which is 8 in this embodiment. The (hkl) surfaces used in the reflection are (012), (104), (110), (0 0 12), (113), (024), (116), and (300).

[0143] ICDD (registered trademark) is short for International Centre for Diffraction Data. PDF (registered trademark) is short for Powder Diffraction File.

[0144] Furthermore, the TC(0 0 12) of the α-Al2O3 layer in this embodiment can be represented by the following formula (2).

[0145] [Number 2]

[0146]

[0147] Therefore, "TC(0 0 12) is 3 or more in the orientation index TC(hkl)" means that the value obtained by substituting TC(0 0 12) into the above formula (1) is 3 or more.

[0148] The value of TC(0 0 12) is more preferably 4 or higher, and even more preferably 5 or higher. The larger the value of TC(0 0 12), the more effectively the wear resistance can be improved. There is no upper limit to the value of TC(0 0 12), but since 8 reflective surfaces are used in the calculation, it can be set to 8 or lower. The value of TC(0 0 12) can be set to 3 or higher and 8 or lower, 4 or higher and 8 or lower, or 5 or higher and 8 or lower.

[0149] In this disclosure, the α-Al2O3 layer preferably has an orientation index TC(hkl) of 2 or more in the above formula (1). Therefore, the α-Al2O3 layer exhibits excellent resistance to chipping. Consequently, the cutting tool can have a longer tool life.

[0150] Furthermore, the TC(110) of the α-Al2O3 layer in this embodiment can be represented by the following formula (3).

[0151] [Number 3]

[0152]

[0153] Therefore, "TC(110) is 2 or more in the orientation index TC(hkl)" means that the value obtained by substituting TC(110) into the above formula (3) is 2 or more.

[0154] The value of TC(110) is more preferably 2.5 or higher, and even more preferably 3 or higher. The larger the value of TC(110), the more effectively the damage resistance can be improved. There is no upper limit to the value of TC(110), but since 8 reflective surfaces are used in the calculation, it can be set to 8 or lower. The value of TC(110) can be set to 2 or higher and 8 or lower, 2.5 or higher and 8 or lower, or 3 or higher and 8 or lower.

[0155] The TC(hkl) measured as described above can be performed using an X-ray diffraction apparatus. TC(hkl) can be measured, for example, using a SmartLb / a (registered trademark) manufactured by Rigaku Co., Ltd. (scanning speed: 21.7° / min, step size: 0.01°, scan range: 15–140°) under the following conditions. Furthermore, in this embodiment, the measurement result of TC(hkl) using an X-ray diffraction apparatus is referred to as the "XRD result".

[0156] Characteristic X-rays: Cu-Kα

[0157] Tube voltage: 45kV

[0158] Tube current: 200mA

[0159] Filter: Multilayer mirror

[0160] Optical system: lumped method

[0161] X-ray diffraction method: θ-2θ method

[0162] When using an X-ray diffraction apparatus, the flank face of the cutting tool is irradiated with X-rays. Typically, the rake face has an uneven surface, while the flank face is flat. Therefore, to eliminate interference, it is preferable to irradiate the flank face with X-rays. In particular, X-rays are irradiated on a portion of the flank face extending from the tool tip edge to approximately 2-4 mm. This improves the reproducibility of the results. Furthermore, in this embodiment, the TC(hkl) value of the α-Al₂O₃ layer on the flank face of the substrate is the same as the TC(hkl) value of the α-Al₂O₃ layer on the rake face of the substrate.

[0163] Furthermore, it was confirmed that even if multiple measurement sites are arbitrarily selected in the same sample and the above measurements are performed on each measurement site, the same results can be obtained.

[0164] <Titanium compound layer>

[0165] Composition of Titanium Compound Layers

[0166] In this embodiment, the titanium compound layer is composed of multiple titanium compound particles, which are selected from the group consisting of TiCN particles, TiCNO particles, TiAlCN particles, and TiAlCNO particles. That is, the titanium compound layer is composed of polycrystalline titanium compounds. As long as the titanium compound layer achieves the effect of this embodiment, it can contain unavoidable impurities. Chlorine (Cl) is an example of such unavoidable impurities. The content of unavoidable impurities in the titanium compound layer is preferably 3% by mass or less. The content of unavoidable impurities in the titanium compound layer is determined by secondary ion mass spectrometry (SIMS).

[0167] like Figure 1 As shown, the titanium compound layer 14 includes region B1 and region B2. In this specification, region B1 and region B2 are defined as follows.

[0168] Region B1 is the area sandwiched between imaginary surfaces SB2 and SB3. The distance from interface P1 to the substrate 10 of imaginary surface SB2 is 0.5 μm, and the distance from interface P1 to the substrate 10 of imaginary surface SB3 is 1.0 μm. Imaginary surfaces SB2 and SB3 are contained within region B1.

[0169] Region B2 is the area sandwiched between interface P1 and imaginary surface SB1, which is 0.3 μm away from interface P1 toward the substrate 10. Imaginary surface SB1 is contained within region B2, while interface P1 is not contained within region B2.

[0170] Average particle size of titanium compound particles

[0171] In this embodiment, the average particle size b1 of the titanium compound particles in region B1 is 0.10 μm or more and 0.50 μm or less. This results in a cutting tool exhibiting excellent chip resistance and wear resistance. From the viewpoint of improving chip resistance, the lower limit of the average particle size b1 is 0.10 μm or more, preferably 0.15 μm or more, 0.17 μm or more, or 0.20 μm or more. From the viewpoint of improving wear resistance, the upper limit of the average particle size b1 is 0.50 μm or less, preferably 0.45 μm or less, 0.40 μm or less, 0.35 μm or less, or 0.32 μm or less. The average particle size b1 is preferably 0.15 μm or more and 0.50 μm or less, 0.20 μm or more and 0.40 μm or less, or 0.20 μm or more and 0.32 μm or less.

[0172] In this embodiment, from the viewpoint of improving adhesion to the α-Al₂O₃ layer, the lower limit of the average particle size b₂ of the titanium compound particles in region B₂ is preferably 0.05 μm or more, 0.06 μm or more, 0.08 μm or more, or 0.10 μm or more. From the viewpoint of improving hardness, the upper limit of the average particle size b₂ is preferably 0.22 μm or less or 0.20 μm or less. The average particle size b₂ is preferably 0.05 μm or more and 0.22 μm or less, 0.06 μm or more and 0.20 μm or less, or 0.10 μm or more and 0.20 μm or less.

[0173] In this embodiment, the ratio of average particle size b1 to average particle size b2, b1 / b2, is 1.45 or more and 5 or less. This results in a cutting tool exhibiting excellent resistance to chipping. The lower limit of the ratio b1 / b2 is 1.45 or more, preferably 1.50 or more, 1.60 or more, 1.67 or more, 1.70 or more, or 2.00 or more. The upper limit of the ratio b1 / b2 is 5 or less, preferably 4.50 or less, 4.00 or less, 3.50 or less, or 3.33 or less. The ratio b1 / b2 is preferably 1.5 or more and 5 or less, or 2.00 or more and 4.00 or less.

[0174] In this specification, the average particle size b1 and average particle size b2 are measured according to the following steps (B1) to (B3).

[0175] (B1) Perform the same steps (A1) to (A4) as described in the method for measuring average particle size a1 and average particle size a2, and set the baseline LS1 within the measurement range of the EBSD image.

[0176] (B2) The transverse particle size of the titanium compound particles is measured on line L3, which is 0.2 μm away from the aforementioned baseline LS1 in the direction of the cutting tool substrate. The particle size of all titanium compound particles in the measurement range is measured, and their average value is taken as the average particle size b2 of the titanium compound particles in region B2.

[0177] (B3) The transverse particle size of the titanium compound particles is measured on line L4, which is 0.8 μm away from the reference line LS1 in the direction of the cutting tool substrate. The particle size of all titanium compound particles in the measurement range is measured, and their average value is taken as the average particle size b1 of the titanium compound particles in region B1.

[0178] In the above (B3), the difference between the valley bottom B1 and the mountain top T1 at the interface is relatively large (e.g., exceeding 0.5 μm), such as... Figure 4 As shown, line L3 also exists inside the α-Al2O3 layer 11. Inside the α-Al2O3 layer 11 (e.g.) Figure 4 The particle size of titanium compound particles is not measured on line L3 (in the region shown by y), but only within the titanium compound layer. The average particle size b2 is then calculated.

[0179] When setting line L3 as described above, the inventors of this invention, in region B2, within a range of 0 μm to 0.3 μm from the reference line LS1 along the normal direction of the rake face, set multiple measurement lines (e.g., a line 0.05 μm from the reference line LS1, a line 0.10 μm from the reference line LS1, and a line 0.15 μm from the reference line LS1) at intervals of 0.05 μm. On each line, the particle size of all titanium compound particles within the measurement range was measured, and their average value was calculated. As a result, it was confirmed that the average particle size of the titanium compound particles on the line corresponding to line L3 at a distance of 0.2 μm from the reference line LS1 was approximately the same as the average particle size of the titanium compound particles on the aforementioned multiple measurement lines. The reason for this is speculated to be as follows.

[0180] Region B2 is a transitional region from nucleation to crystal growth. In region B1, nucleation is influenced by the orientation and unevenness of the substrate in addition to gas conditions. However, in region B2, the influence of gas conditions is dominant, unlike in region B1 where nuclei (orientation, shape, etc.) are dominant. Since the crystals generated during nucleation are eliminated, and stable nuclei are generated under the new gas conditions, it is presumed that the overall number of particles will not change significantly, and the particle size will not change much. Furthermore, in this embodiment, by adjusting the gas conditions during the formation of regions B1 and B2, the elimination of crystals and nucleation are smoothly transitioned, thereby allowing region B2 to expand in the thickness direction while maintaining the particle size. Based on the above, the average particle size of the titanium compound particles on line L3 can be considered as the average particle size b2 of the titanium compound particles in region B2.

[0181] It was confirmed that even when arbitrarily selecting different measurement ranges within the same cutting tool and performing the above measurements within those ranges, the same results could be obtained. Furthermore, it was confirmed that even when arbitrarily selecting different measurement ranges within different cutting tools and performing the above measurements within those ranges, the same results could be obtained.

[0182] When setting line L4, the inventors of this invention, in region B1, within a range of 0.5 μm to 1.0 μm from the reference line LS1 along the normal direction of the rake face, set multiple measurement lines (e.g., a line 0.50 μm from the reference line LS1, a line 0.55 μm from the reference line LS1, and a line 0.60 μm from the reference line LS1) at intervals of 0.05 μm. On each line, the particle size of all titanium compound particles within the measurement range was measured, and their average value was calculated. As a result, it was confirmed that the average particle size of the titanium compound particles on the line corresponding to line L4 at a distance of 0.8 μm from the reference line LS1 was approximately the same as the average particle size of the titanium compound particles on the aforementioned multiple measurement lines. The reasoning is speculated to be that, in the early stages of nucleation, the orientation and unevenness of the substrate significantly influence the growth of titanium compound crystals. Therefore, the crystals do not grow into columnar shapes (or a state where the cross-sectional grain size increases towards the surface), but rather into granular shapes (perpendicular to the interface, and to some extent uniform in size). Based on the above, the average grain size of the titanium compound particles on line L4 can be considered as the average grain size b1 of the titanium compound particles in region B1.

[0183] It was confirmed that even when arbitrarily selecting different measurement ranges within the same cutting tool and performing the above measurements within those ranges, the same results could be obtained. Furthermore, it was confirmed that even when arbitrarily selecting different measurement ranges within different cutting tools and performing the above measurements within those ranges, the same results could be obtained.

[0184] Composition of Titanium Compound Layers

[0185] In this embodiment, preferably, the ratio R1 / R2 of the ratio of the number of carbon atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms to R2 of the ratio of the number of carbon atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms is 0.9 or more and 1.1 or less; the ratio R3 of the total number of carbon and nitrogen atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms is 0.8 or more and 1.0 or less; and the ratio R4 of the total number of carbon and nitrogen atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms is 0.8 or more and 1.0 or less. Therefore, the composition of the titanium compound layer is substantially uniform throughout, and the formation of interfaces caused by compositional variations can be suppressed within the titanium compound layer. Thus, the formation of cracks originating at interfaces can be suppressed in the coating, thereby improving the chip resistance of the cutting tool.

[0186] The lower limit of R1 is preferably 0.4 or higher, 0.45 or higher, or 0.5 or higher. The upper limit of R1 is preferably 0.7 or lower, 0.65 or lower, or 0.6 or lower. R1 is preferably 0.4 or higher and 0.7 or lower, 0.45 or higher and 0.65 or lower, or 0.5 or higher and 0.6 or lower.

[0187] The lower limit of R2 is preferably 0.3 or higher, 0.35 or higher, or 0.4 or higher. The upper limit of R1 is preferably 0.6 or lower, 0.55 or lower, or 0.5 or lower. R1 is preferably 0.3 or higher and 0.6 or lower, 0.35 or higher and 0.55 or lower, or 0.4 or higher and 0.5 or lower.

[0188] The lower limit of the ratio R1 / R2 is preferably 0.9 or higher and 0.95 or higher. The upper limit of the ratio R1 / R2 is preferably 1.1 or lower and 1.05 or lower. The ratio R1 / R2 is preferably 0.9 or higher and 1.1 or lower, and 0.95 or higher and 1.05 or lower.

[0189] The lower limit of R3 is preferably 0.8 or higher, 0.85 or higher, or 0.87 or higher. The upper limit of R3 is preferably 1.0 or lower, 0.95 or lower, or 0.92 or lower. R3 is preferably 0.8 or higher and 1.0 or lower, 0.85 or higher and 0.95 or lower, or 0.87 or higher and 0.92 or lower.

[0190] The lower limit of R4 is preferably 0.8 or higher, 0.85 or higher, or 0.87 or higher. The upper limit of R4 is preferably 1.0 or lower, 0.95 or lower, or 0.92 or lower. R4 is preferably 0.8 or higher and 1.0 or lower, 0.85 or higher and 0.95 or lower, or 0.87 or higher and 0.92 or lower.

[0191] In this specification, R1, R2, R3, and R4 are measured according to the following steps (C1) to (C4).

[0192] (C1) A diamond wire is used to cut along the normal of the rake face of the substrate to prepare a thin sample (approximately 100 nm thick) with exposed cross-section of the titanium compound layer. The exposed cross-section is then subjected to focused ion beam processing (hereinafter also referred to as "FIB processing") to make the cross-section a mirror finish.

[0193] (C2) The cross-section after FIB processing was observed using scanning transmission electron microscopy (STEM) to determine the titanium compound layer. The magnification was 500,000x. A BF-STEM image of the titanium compound layer was obtained. Regions B1 and B2 were identified in this BF-STEM image. The identification of regions B1 and B2 in this BF-STEM image was performed using grain boundary analysis by EBSD.

[0194] In regions B1 and B2, rectangular measurement areas of 100nm × 100nm were defined respectively. It was confirmed that as long as the measurement area is within the range where the applicant conducted the measurement, and as long as the measurement area is located within region B1 or region B2, there is almost no deviation in the measurement results even if rectangular analysis is performed in different measurement areas. Even if the measurement location is set arbitrarily, the results will not change arbitrarily.

[0195] (C3) For the measurement area described above, the composition was determined by rectangular analysis using EDX attached to the STEM. The beam diameter for rectangular analysis was less than 0.5 nm, and the scanning interval was 0.5 nm.

[0196] Based on the results of the rectangular analysis, the following ratios were calculated: the ratio of the number of carbon atoms in the measurement region set in region B1 to the total number of carbon, nitrogen, and oxygen atoms (hereinafter also referred to as R1'); the ratio of the number of carbon atoms in the measurement region set in region B2 to the total number of carbon, nitrogen, and oxygen atoms (hereinafter also referred to as R2'); the ratio of the total number of carbon and nitrogen atoms in the measurement region set in region B1 to the total number of carbon, nitrogen, and oxygen atoms (hereinafter also referred to as R3'); and the ratio of the total number of carbon and nitrogen atoms in the measurement region set in region B2 to the total number of carbon, nitrogen, and oxygen atoms (hereinafter also referred to as R4').

[0197] (C4) Perform the above measurements of R1', R2', R3', and R4' in five different measurement regions. The average value of R1' from these five measurement regions is set as R1 in region B1. The average value of R2' from these five measurement regions is set as R2 in region B2. The average value of R3' from these five measurement regions is set as R3 in region B1. The average value of R4' from these five measurement regions is set as R4 in region B2.

[0198] It was confirmed that as long as the measurement was conducted within the applicant's designated area, the measurement results would be almost unbiased even if the measurement area was arbitrarily selected, and the results would not change arbitrarily even if the measurement site was arbitrarily set.

[0199] Average thickness of the titanium compound layer

[0200] In this embodiment, the average thickness of the titanium compound layer is preferably 1.0 μm or more and 15 μm or less. This allows the cutting tool to achieve both excellent wear resistance and chipping resistance. From the viewpoint of improving wear resistance, the lower limit of the average thickness of the titanium compound layer is preferably 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, or 5.0 μm or more. From the viewpoint of improving chipping resistance, the upper limit of the average thickness of the titanium compound layer is preferably 15 μm or less, 10 μm or less, 9 μm or less, or 8 μm or less. The average thickness of the titanium compound layer is preferably 1.0 μm or more and 15 μm or less, 2.0 μm or more and 10 μm or less, 3.0 μm or more and 9 μm or less, or 5.0 μm or more and 8 μm or less.

[0201] The thickness of the titanium compound layer can be confirmed by observing a cross-sectional sample of the cutting tool using a scanning transmission electron microscope (STEM) as described above. Here, the field of view is the measurement range set when measuring the particle size of the aforementioned titanium compound particles.

[0202] Furthermore, it was confirmed that even when multiple measurement ranges containing coatings on the rake face or the flank face are arbitrarily selected in the same sample and the above measurements are performed on each measurement range, the same results can be obtained.

[0203] <a2 b2>

[0204] In this embodiment, the ratio of average particle size a2 to average particle size b2, a2 / b2, is 0.80 or more and 1.27 or less. This results in a cutting tool exhibiting excellent resistance to peeling and chipping. The lower limit of the ratio a2 / b2 is 0.80 or more, preferably 0.90 or more or 1.00 or more. The upper limit of the ratio a2 / b2 is 1.27 or less, preferably 1.20 or less, 1.15 or less, 1.13 or less, or 1.10 or less. The ratio a2 / b2 is preferably 0.90 or more and 1.15 or less, or 1.00 or more and 1.10 or less.

[0205] <a1 b1>

[0206] In this embodiment, the ratio of average particle size a1 to average particle size b1, a1 / b1, is preferably 1.5 or more and 5 or less. This improves resistance to defects. The lower limit of the ratio a1 / b1 is 1.50 or more, preferably 2.00 or more, 2.27 or more, 2.33 or more, or 2.50 or more. The upper limit of the ratio a1 / b1 is 5 or less, preferably 4.50 or less, 4.00 or less, 3.50 or less, or 3.00 or less. The ratio a1 / b1 is preferably 2.00 or more and 4.50 or less, or 2.50 or more and 4.00 or less.

[0207] <Other Layers>

[0208] Based on the α-Al₂O₃ layer and the titanium compound layer, the coating can include other layers. For example... Figure 2 As shown, other layers include TiN layer 12, surface layer 13, intermediate layer (not shown), etc.

[0209] TiN Layer

[0210] The TiN layer is disposed between the substrate and the titanium compound layer, acting as a base layer. The average thickness of the TiN layer is preferably 0.1 μm or more and 20 μm or less. This results in a coating with excellent wear resistance and chip resistance. The TiN layer can be disposed directly above the substrate. The TiN layer can be configured to be in contact with the titanium compound layer.

[0211] Surface Layer

[0212] As a surface layer, it is preferably composed primarily of any one of titanium carbides, nitrides, or borides. The surface layer is disposed on the outermost side of the coating. However, there are cases where the surface layer is not formed at the blade edge. For example, the surface layer is disposed directly above the α-Al₂O₃ layer.

[0213] "Main component of any one of Ti carbides, nitrides or borides" means containing 90% by mass or more of any one of Ti carbides, nitrides or borides. Furthermore, it preferably consists of any one of Ti carbides, nitrides or borides, excluding unavoidable impurities.

[0214] Of any of the carbides, nitrides, and carbonitrides of Ti, a surface layer composed primarily of Ti nitrides (i.e., compounds represented by TiN) is particularly preferred. TiN has the clearest color among these compounds (appearing golden), thus offering the advantage of easy corner identification (identification of used areas) of the cutting disc after cutting. The surface layer is preferably composed of a TiN layer.

[0215] The average thickness of the surface layer is preferably 0.05 μm or more and 1 μm or less. This improves the adhesion between the surface layer and adjacent layers. The upper limit of the average thickness of the surface layer can be 0.8 μm or less or 0.6 μm or less. The lower limit of the average thickness can be 0.1 μm or more or 0.2 μm or more.

[0216] The Intermediate Layer

[0217] An intermediate layer is disposed between the TiN layer and the titanium compound layer. Examples of intermediate layers include TiCN and TiCNO layers, which have compositions different from the titanium compound layer. Since TiCN and TiCNO layers exhibit excellent wear resistance, appropriate wear resistance can be imparted through coating. The average thickness of the intermediate layer is preferably 1 μm or more and 20 μm or less. Here, when the intermediate layer is formed of two or more layers, the average thickness of the intermediate layer refers to the average of the combined thicknesses of the two or more layers. The intermediate layer can be configured to be in contact with the TiN layer. The intermediate layer can be configured to be in contact with the titanium compound layer. The intermediate layer can be configured to be in contact with both the TiN layer and the titanium compound layer.

[0218] [Implementation Method 2: Method for Manufacturing a Cutting Tool]

[0219] The cutting tool of this embodiment can be manufactured by forming a coating on a substrate using chemical vapor deposition (CVD). The α-Al₂O₃ layer and the titanium compound layer in the coating can be formed, for example, by the following methods. Furthermore, other layers besides the titanium compound layer and the α-Al₂O₃ layer can be formed under conventionally known conditions.

[0220] <Methods for forming titanium compound layers>

[0221] The film-forming conditions for the titanium compound layer can be set, for example, to a temperature of 950–1050 °C, a pressure of 90–130 hPa, and a gas flow rate (total gas flow rate) of 50–100 L / min. In this specification, "total gas flow rate" refers to the total volumetric flow rate introduced into the CVD furnace per unit time, taking the gas under standard conditions (0 °C, 1 atmosphere) as an ideal gas.

[0222] The feed gases used are CH3CN, CH4, TiCl4, CO, N2, AlCl3, and H2. From the start of film formation, the proportions of CH3CN, CH4, N2, and H2 in the feed gases are varied according to the thickness of the formed titanium compound layer. Specifically, as described below.

[0223] When forming a region (region B1) with a distance of 0.5 μm or more and 1.0 μm or less from the interface P1 between the titanium compound layer and the α-Al2O3 layer formed directly above it, the composition of the raw material gas is set as follows: CH3CN: 0.2 vol% or more and 1.0 vol% or less, CH4: 1.0 vol% or more and 2.5 vol% or less, TiCl4: 8.0 vol% or more and 9.0 vol% or less, CO: 0 vol% or more and 1.5 vol% or less, N2: 10.0 vol% or more and 15 vol% or less, AlCl3: 0 vol% or more and 1.5 vol% or less, and H2: the remaining volume when the total raw material gas is set to 100 vol%.

[0224] Next, when forming a region (the region sandwiched between region B1 and region B2) with a distance greater than 0.3 μm and less than 0.5 μm from interface P1, the proportion of the feed gas is changed from the proportion in region B1 to the proportion in region B2 (described later). At this time, adjustments are made to keep the change in each feed gas per unit time constant.

[0225] Next, when forming a region (region B2) at a distance of 0 μm or more and 0.3 μm or less from interface P1, the composition of the feed gas is set as follows: CH3CN: 0.4 vol% or more and 2.0 vol% or less, CH4: 0.8 vol% or more and 2.02 vol% or less, N2: 8.0 vol% or more and 12.0 vol% or less. Compared with the formation of region B1, H2 is increased or decreased in the same manner as the formation of region B1, based on the increase or decrease of the total content of CH3CN, CH4 and N2 in the feed gas. The composition of other gases is the same as the formation of region B1.

[0226] The amount of CH3CN in the feed gas forming region B2 is greater than that in the feed gas forming region B1. Furthermore, the amount of CH4 in the feed gas forming region B2 is less than that in the feed gas forming region B1. Therefore, the average particle size b2 of the titanium compound particles in region B2 is smaller than the average particle size b1 of the titanium compound particles in region B1.

[0227] Previously, when forming titanium compound layers, a combination of CO and CH4 or CH3CN was used as the feed gas. Since CH4 and CH3CN have different reactivity, they were not used simultaneously in the formation of titanium compound layers in the past.

[0228] Compared to conventional technology, in this embodiment, as described above, by simultaneously using CH4 and CH3CN as raw material gases and varying the proportions of CH4 and CH3CN along with N2, it is possible to adjust the particle size of the titanium compound particles solely in the thickness direction of the titanium compound layer without significant changes in composition. This is a novel insight discovered by the inventors of this invention.

[0229] <Methods for forming α-Al2O3 layers>

[0230] The film-forming conditions for the α-Al2O3 layer can be set, for example, to a temperature of 950–1050 °C, a pressure of 60–90 hPa, and a gas flow rate (total gas flow rate) of 50–100 L / min.

[0231] AlCl3, HCl, CO2, H2S, and H2 are used as feed gases. From the start of film formation, the amounts of HCl and H2 in the feed gases are varied according to the thickness of the formed α-Al2O3 layer. Specifically, as described below.

[0232] In the region from the start of film formation to the formation of an α-Al2O3 layer with a thickness of 0.3 μm (region A2), the composition of the raw material gas is set as follows: HCl: 7.5 vol% or more and 11 vol% or less, AlCl3: 2 vol% or more and 5 vol% or less, CO2: 0.1 vol% or more and 6 vol% or less, H2S: 0.1 vol% or more and 1 vol% or less, and H2: the remaining volume when the total raw material gas is set to 100 vol%.

[0233] Next, in the region where the thickness of the α-Al₂O₃ layer exceeds 0.3 μm but is less than 0.5 μm (the region sandwiched between region A2 and region A1), the proportion of the feed gas is changed from the proportion in region A2 to the proportion in region A1 (described later). At this point, adjustments are made to ensure that the change in the amount of each feed gas per unit time remains constant.

[0234] Next, in the region (region A1) where the thickness of the α-Al2O3 layer is 0.5 μm or more and 1.0 μm or less, the composition of the raw material gas is set to HCl: 3.2 vol% or more and 7.0 vol% or less. Compared with the formation of region A2, the amount of H2 is increased accordingly to reduce the amount of HCl in the raw material gas. The composition of other gases is the same as that of the formation of region A2.

[0235] Previously, HCl was used to suppress the excessive formation of α-Al₂O₃ particles in the gas phase during film formation. If α-Al₂O₃ particles form in the gas phase, it is difficult to form an α-Al₂O₃ layer on the substrate. On the other hand, it is believed that a higher amount of HCl in the feed gas reduces the film formation rate. Therefore, it is common knowledge that the amount of HCl in the feed gas should be at the necessary minimum, and those skilled in the art do not have the technical concept of increasing the amount of HCl in the feed gas.

[0236] Compared to conventional techniques, in this embodiment, as described above, the amount of HCl is varied to control the particle size of the α-Al₂O₃ particles. Furthermore, the amount of HCl in the feed gas used to form region A2 is greater than the amount of HCl in the feed gas used in conventional α-Al₂O₃ layer formation (e.g., 2.8 vol% or more and less than 6 vol%). As a result, the average particle size of the α-Al₂O₃ particles in regions A1 and A2 becomes smaller. This is a novel insight discovered by the inventors of this invention.

[0237] [Postscript 12]

[0238] In the cutting tool disclosed herein, the ratio R3 of the total number of carbon and nitrogen atoms in region B1 to the total number of carbon, nitrogen and oxygen atoms can be set to 0.9 or more and 1.0 or less.

[0239] Example

[0240] The embodiments are described in more detail below. However, the embodiments are not limited to these embodiments.

[0241] [Sample 1 to Sample 51, Sample 1-1 to Sample 1-10]

[0242] The raw material powders, consisting of the composition listed in Table 1, are uniformly mixed, pressed into a predetermined shape, and sintered at 1300–1500°C for 1–2 hours to obtain a cemented carbide substrate (shape: model CNMG 120408N-UX (manufactured by Sumitomo Electric Industries, Ltd.)). The "Balance" in Table 1 indicates the remaining portion of WC in the composition (mass %).

[0243] Table 1

[0244]

[0245] <Formation of the coating>

[0246] A cutting tool is manufactured by forming a coating on the surface of the substrate obtained above. Specifically, the substrate is placed in a CVD apparatus, and a coating is formed on the substrate by CVD. The composition of the coating for each sample is shown in Tables 2 and 3. In Tables 2 and 3, "none" indicates that the layer was not formed in the sample.

[0247] Table 2

[0248]

[0249] Table 3

[0250]

[0251] A TiN layer (base layer), a titanium compound layer, an α-Al₂O₃ layer, and a TiN layer (surface layer) are sequentially formed on a substrate. The thickness of the TiN layer (base layer) is 0.4 μm, and the thickness of the TiN layer (surface layer) is 0.7 μm.

[0252] The film formation conditions for the TiN layer (substrate layer) and the TiN layer (surface layer) are shown in Table 4.

[0253] Table 4

[0254]

[0255] The film formation conditions and raw material gas composition of the titanium compound layer for each sample are shown in Tables 5 to 8. In Tables 5 to 8, the "Balance" column for "H2" indicates the remaining portion of the raw material gas composition (volume %) containing H2 gas. During film formation, the gas tube used to eject the raw material gas while fixing the substrate rotated at 2 rpm. The overall thickness of the titanium compound layer is shown in the "Thickness" column of Tables 5 to 8.

[0256]

[0257]

[0258]

[0259]

[0260] For example, the composition of the raw material gas when forming the titanium compound layer of sample 1 is as follows. When forming a region (region B1) at a distance of 0.5 μm or more and 1.0 μm or less from the interface P1 between the titanium compound layer and the α-Al2O3 layer formed directly above it, the raw material gas composition is set as follows: CH3CN: 0.50 vol%, CH4: 2.00 vol%, TiCl4: 8.5 vol%, CO: 1.4 vol%, N2: 12.0 vol%, AlCl3: 0 vol%, and H2: the remaining volume percentage when the total raw material gas is set to 100 vol%. Region B1 is thus formed.

[0261] Next, when forming a region (the region sandwiched between region B1 and region B2) with a distance greater than 0.3 μm and less than 0.5 μm from interface P1, the proportion of the feed gas is changed from the proportion in region B1 to the proportion in region B2 (described later). At this time, adjustments are made to ensure that the change in each feed gas per unit time remains constant.

[0262] Next, when forming the region (region B2) at a distance of 0 μm to 0.3 μm from interface P1, the feed gas composition was set as follows: CH3CN: 1.00 vol%, CH4: 1.50 vol%, TiCl4: 8.5 vol%, CO: 1.4 vol%, N2: 10.0 vol%. Compared to the formation of region B1, H2 was increased to maintain a constant total gas flow rate due to the decrease in the combined content of CH3CN, CH4, and N2 in the feed gas. The overall thickness of the formed titanium compound layer was 8 μm.

[0263] In samples 1-10, the composition of the feed gas used to form the titanium compound layer is as follows. When forming region B1, the feed gas composition was set as follows: CH3CN: 0.60 vol%, TiCl4: 8.0 vol%, CO: 2.0 vol%, N2: 20.0 vol%, and H2: the remaining volume percentage when the total feed gas composition was 100 vol%. The pressure during region B1 formation was 70 hPa. Region B1 was thus formed. When forming region B2, the feed gas composition was set as follows: CH4: 4.00 vol%, TiCl4: 8.0 vol%, CO: 2.0 vol%, N2: 10.0 vol%, and H2: the remaining volume percentage when the total feed gas composition was 100 vol%. The pressure during region B2 formation was 200 hPa. Region B2 was thus formed. In samples 1-10, CH3CN and CH4 were not used simultaneously.

[0264] The raw material gas composition and film formation conditions of the α-Al₂O₃ layer for each sample are shown in Tables 9 and 10. In Tables 9 and 10, the "Balance" in the "H₂" column indicates the remaining portion (volume %) of H₂ gas in the raw material gas composition. During film formation, the gas tube used to eject the raw material gas while fixing the substrate rotated at 2 rpm. The overall thickness of the α-Al₂O₃ layer is shown in the "Thickness" column of Tables 9 and 10.

[0265] Table 9

[0266]

[0267] Table 10

[0268]

[0269] For example, the film formation conditions for the α-Al₂O₃ layer of sample 1 are as follows. When forming the region (region A2) with a thickness of 0.3 μm of α-Al₂O₃ layer, the feed gas composition is set as follows: AlCl₃: 2.2 vol%, HCl: 9.0 vol%, CO₂: 3.0 vol%, H₂S: 0.6 vol%, and H₂: the remaining volume percentage when the total feed gas is set to 100 vol%.

[0270] Next, in the region where the thickness of the α-Al₂O₃ layer exceeds 0.3 μm but is less than 0.5 μm (the region sandwiched between region A2 and region A1), the proportion of the feed gas is changed from the proportion in region A2 to the proportion in region A1 (described later). At this point, adjustments are made to ensure that the change in the amount of each feed gas per unit time remains constant.

[0271] Next, in the region (region A1) where the thickness of the α-Al₂O₃ layer is 0.5 μm or more and 1.0 μm or less, the feed gas composition is set to HCl: 5.5% by volume. Compared to the formation of region A2, H₂ is increased to maintain a constant total gas flow rate due to the decrease in the HCl content in the feed gas. The composition of other gases is the same as that in the formation of region A2. The overall thickness of the formed α-Al₂O₃ layer is 8 μm.

[0272] <Evaluation of Titanium Compound Layers>

[0273] For the titanium compound layer of each sample, the following measurements were taken: average particle size b1 of region B1, average particle size b2 of region B2, ratio R1 of the number of carbon atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms, ratio R2 of the number of carbon atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms, ratio R1 / R2, ratio R3 of the total number of carbon and nitrogen atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms, ratio R4 of the total number of carbon and nitrogen atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms, and the composition of the titanium compound particles. The methods for these measurements are as described in Embodiment 1, and therefore will not be repeated. The results are shown in the columns "Particle Size b1", "Particle Size b2", "R1", "R2", "R1 / R2", "R3", "R4", and "Titanium Compound Particle Composition" in Tables 11 to 14.

[0274] <Evaluation of the α-Al2O3 layer>

[0275] For the α-Al2O3 layer of each sample, the average particle size a1 of region A1, the average particle size a2 of region A2, and the orientation index TC (0 0 12) were measured. The measurement method is as described in Embodiment 1, so its description will not be repeated. The results are shown in the "particle size a1", "particle size a2", and "TC (0 0 12)" columns of Tables 11 to 14.

[0276] <a2 / b2、a1 / a2、b1 / b2>

[0277] Based on the measured average particle sizes a1, a2, b1, and b2, the values ​​of a2 / b2, a1 / a2, and b1 / b2 are calculated.

[0278] The results are shown in the "a2 / b2", "a1 / a2", and "b1 / b2" columns of Tables 11 to 14.

[0279]

[0280]

[0281]

[0282]

[0283] <Tool Life Evaluation>

[0284] Cutting tests were conducted using the cutting tools obtained above to evaluate their resistance to chipping, peeling, and wear. Specifically, the evaluations described in Cutting Evaluation 1 to Cutting Evaluation 3 below were performed. In this specification, if all evaluations of resistance to chipping, peeling, and wear are satisfactory according to the criteria described in Cutting Evaluation 1 to Cutting Evaluation 3 below, the tool life is judged to be long.

[0285] <Cutting Evaluation 1>

[0286] Using the cutting tool obtained above, a cutting test was conducted under cutting condition 1 below to evaluate its resistance to chipping. Using 20 different cutting edges, each cutting was performed for 20 seconds to check for breakage. Here, "breakage" refers to a notch of 500 μm or larger. The proportion of cutting edges that broke out among the 20 cutting edges was calculated to obtain the breakage rate (%). That is, breakage rate (%) = (number of broken cutting edges / 20) × 100. In this embodiment, the cutting tool exhibits good resistance to chipping when the breakage rate is less than 65%. The results are shown in the "Cut Evaluation 1 Breakage Rate (%)" column of Tables 11 to 14.

[0287] Cutting Condition 1

[0288] Workpiece to be machined: SCM440 (grooved round bar)

[0289] Machining: Intermittent turning of the outer diameter of a grooved round bar

[0290] Cutting speed: 120m / min

[0291] Feed rate: 0.15 mm / rev

[0292] Cut depth: 2.0mm

[0293] Cutting fluid: None

[0294] The above cutting conditions are equivalent to an experiment simulating interrupted turning of chromium-molybdenum steel.

[0295] <Cutting Evaluation 2>

[0296] Using the cutting tool obtained above, a cutting test was conducted under cutting condition 2 described below to evaluate the corrosion resistance. The maximum wear amount Vbmax (mm) on the flank face of the cutting tool was measured after 15 minutes of cutting. "Maximum wear amount" refers to the maximum value of the distance from the edge to the end of the flank face where wear occurs. The smaller the maximum wear amount, the better the peel resistance. In this embodiment, the peel resistance of the cutting tool is good when the maximum wear amount is less than 0.50 mm. The results are shown in the "Vbmax (mm)" column of "Cutting Evaluation 2" in Tables 11 to 14.

[0297] Cutting Condition 2

[0298] Workpiece to be machined: SCM 415

[0299] Machining: Turning the outer diameter of the round bar

[0300] Cutting speed: 180m / min

[0301] Feed rate: 0.15 mm / rev

[0302] Cut depth: 2.0mm

[0303] Cutting fluid: water-soluble cutting oil

[0304] The above cutting conditions are equivalent to a test simulating a process where weld spalling is likely to occur.

[0305] <Cutting Evaluation 3>

[0306] Using the cutting tool obtained above, a cutting test was conducted under cutting condition 3 described below. The average wear amount Vb (mm) on the flank face of the cutting tool was measured after 15 minutes of cutting. "Average wear amount" refers to the average length of the distance from the edge to the end of the flank face where wear occurs. In this embodiment, the cutting tool exhibits good wear resistance when the average wear amount is less than 0.40 mm. The results are shown in the "Vb (mm)" column of "Cutting Evaluation 3" in Tables 11 to 14.

[0307] Cutting Condition 3

[0308] Workpiece to be cut: S45C

[0309] Machining: Turning the outer diameter of the round bar

[0310] Cutting speed: 250 m / min

[0311] Feed rate: 0.25 mm / rev

[0312] Cut depth: 2.0mm

[0313] Cutting fluid: water-soluble cutting oil

[0314] The cutting conditions described above are equivalent to a test simulating continuous machining.

[0315] <Inspection>

[0316] The cutting tools of specimens 1 to 49 are equivalent to the examples. These specimens were confirmed to have excellent resistance to chipping, excellent resistance to peeling, and excellent resistance to wear, with a long tool life.

[0317] The cutting tools of specimens 1-1 to 1-10 are equivalent to comparative examples. Specimens 1-4 and 1-9 exhibit insufficient resistance to chipping. Specimens 1-1 to 1-3, 1-5, 1-6, and 1-8 to 1-10 exhibit insufficient resistance to peeling. Specimens 1-7 exhibits insufficient resistance to wear.

[0318] The embodiments and examples of this disclosure have been described above, but it is also intended from the outset that the above-described embodiments and examples may be appropriately combined or modified.

[0319] The embodiments and examples disclosed herein should be considered exemplary in all respects, and not restrictive. The scope of the invention is defined not by the foregoing embodiments and examples, but by the claims, and is intended to include all modifications equivalent to and within the scope of the claims.

[0320] Explanation of reference numerals in the attached figures

[0321] 1: Cutting tool; 10: Substrate; 11: α-Al2O3 layer; 12: TiN layer; 13: Surface layer; 14: Titanium compound layer; 15: Coating; A1: Region A1; A2: Region A2; B1: Region B1; B2: Region B2; P1: Interface; P2: Surface; SA1, SA2, SA3, SB1, SB2, SB3: Imaginary surfaces; LS1: Baseline; L1, L2, L3, L4: Lines.

Claims

1. A cutting tool, wherein, The cutting tool has a substrate and a coating disposed on the substrate. The coating comprises a titanium compound layer disposed on the substrate and an α-Al₂O₃ layer disposed directly above the titanium compound layer. The α-Al₂O₃ layer is composed of multiple α-Al₂O₃ particles. The α-Al2O3 layer includes region A1 and region A2. Region A1 is the area sandwiched between imaginary surfaces SA2 and SA3. Imaginary surface SA2 is a 0.5 μm distance from the interface P1 between the titanium compound layer and the α-Al2O3 layer to the surface of the coating. Imaginary surface SA3 is a 1.0 μm distance from the interface P1 to the surface of the coating. Region A2 is the area sandwiched between interface P1 and imaginary surface SA1, where imaginary surface SA1 is an imaginary surface 0.3 μm away from interface P1 towards the surface of the coating. The titanium compound layer is composed of multiple titanium compound particles. The titanium compound particles are selected from the group consisting of TiCN particles, TiCNO particles, TiAlCN particles, and TiAlCNO particles. The titanium compound layer includes region B1 and region B2. Region B1 is the area sandwiched between imaginary surfaces SB2 and SB3. Imaginary surface SB2 is an imaginary surface extending 0.5 μm from interface P1 towards the substrate side, and imaginary surface SB3 is an imaginary surface extending 1.0 μm from interface P1 towards the substrate side. Region B2 is the area sandwiched between interface P1 and imaginary surface SB1, where imaginary surface SB1 is an imaginary surface extending 0.3 μm from interface P1 toward the substrate side. The average particle size a1 of the α-Al2O3 particles in region A1, the average particle size a2 of the α-Al2O3 particles in region A2, the average particle size b1 of the titanium compound particles in region B1, and the average particle size b2 of the titanium compound particles in region B2 are shown to be related by the following equations 1 to 3. 0.80≤a² / b²≤1.27 (Equation 1) 1.50≤a1 / a2≤10 (Equation 2) 1.45≤b1 / b2≤5 (Equation 3) The average particle size b1 is greater than 0.10 μm and less than 0.50 μm.

2. The cutting tool according to claim 1, wherein, The ratio R1 of the number of carbon atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms, and the ratio R2 of the number of carbon atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms, are both greater than 0.9 and less than 1.

1. The ratio R3 of the total number of carbon and nitrogen atoms in region B1 to the total number of carbon, nitrogen, and oxygen atoms is 0.8 or more and 1.0 or less. The ratio R4 of the total number of carbon and nitrogen atoms in region B2 to the total number of carbon, nitrogen, and oxygen atoms is 0.8 or more and 1.0 or less.

3. The cutting tool according to claim 1 or 2, wherein, The ratio of the average particle size a1 to the average particle size b1, a1 / b1, is greater than 1.50 and less than 5. The average particle size a1 is greater than 0.40 μm and less than 1.00 μm.

4. The cutting tool according to claim 1 or 2, wherein, The average thickness of the titanium compound layer is greater than 1.0 μm and less than 15 μm. The average thickness of the α-Al2O3 layer is greater than 1.0 μm and less than 15 μm.

5. The cutting tool according to claim 1 or 2, wherein, The α-Al2O3 layer has an orientation index TC(hkl) of 3 or higher.

6. The cutting tool according to claim 1 or 2, wherein, The coating comprises a TiN layer disposed between the substrate and the titanium compound layer.

7. The cutting tool according to claim 1 or 2, wherein, The ratio of the average particle size a2 to the average particle size b2, a2 / b2, is greater than 1.00 and less than 1.

10.

8. The cutting tool according to claim 1 or 2, wherein, The ratio of the average particle size a1 to the average particle size a2, a1 / a2, is greater than 2.00 and less than 10.

9. The cutting tool according to claim 1 or 2, wherein, The ratio of the average particle size b1 to the average particle size b2, b1 / b2, is greater than 1.50 and less than 5.

10. The cutting tool according to claim 1 or 2, wherein, The ratio of the average particle size a1 to the average particle size b1, a1 / b1, is greater than 2.00 and less than 4.

50.

11. The cutting tool according to claim 1 or 2, wherein, The average particle size b1 is greater than 0.15 μm and less than 0.50 μm.

12. The cutting tool according to claim 5, wherein, The TC(0012) is 4 or higher.

13. The cutting tool according to claim 1 or 2, wherein, The average particle size a1 is greater than 0.30 μm and less than 1.20 μm.

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