Cutting Tools

Abstract

A cutting tool comprises: a substrate and a coating arranged on the substrate, the coating comprising an α-Al2O3 layer composed of a plurality of α-Al2O3 particles, the average particle size a of the α-Al2O3 particles in a first region of the α-Al2O3 layer is greater than 0.10 μm and less than 0.30 μm, the average particle size b of the α-Al2O3 particles in a second region is greater than 0.30 μm and less than 0.50 μm, the average particle size c of the α-Al2O3 particles in a third region is greater than 0.10 μm and less than 0.30 μm, and b / a is greater than 1.5 and less than 5.0.

Description

Technical Field

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

[0002] Cutting tools having a coating formed on a substrate have long been used. Alumina having an α-type crystal structure (hereinafter also referred to as "α-Al2O3") has excellent mechanical properties and is therefore used as a coating material (Japanese Patent Publication No. 6-316758 (Patent Document 1), Japanese Patent Publication No. 2013-111720 (Patent Document 2)).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 6-316758

[0006] Patent Document 2: Japanese Patent Application Publication No. 2013-111720 Summary of the invention

[0007] The cutting tool disclosed herein has:

[0008] A substrate, and a coating disposed on the substrate,

[0009] The coating comprises an α-Al2O3 layer,

[0010] The α-Al2O3 layer is composed of a plurality of α-Al2O3 particles.

[0011] The α-Al2O3 layer includes a first region, a second region and a third region,

[0012] The first region is a region sandwiched between the interface P1 on the substrate side of the α-Al 2 O 3 layer and a virtual plane S1 at a distance of 0.5 μm from the interface P1 to the surface side of the coating.

[0013] The second region is a region sandwiched between the virtual surface S1 and a virtual surface S2 that is 1.0 μm away from the virtual surface S1 toward the surface side of the coating.

[0014] The third region is a region sandwiched between the surface P2 of the α-Al2O3 layer or the interface P3 on the surface side of the film of the α-Al2O3 layer and a virtual plane S3 at a distance of 1.0 μm from the surface P2 or the interface P3 toward the substrate side.

[0015] The average particle size a of the α-Al2O3 particles in the first region is not less than 0.10 μm and not more than 0.30 μm,

[0016] The average particle size b of the α-Al2O3 particles in the second region is not less than 0.30 μm and not more than 0.50 μm,

[0017] The average particle size c of the α-Al2O3 particles in the third region is not less than 0.10 μm and not more than 0.30 μm,

[0018] The ratio b / a of a to b is 1.5 or more and 5.0 or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [ Figure 1 ] Figure 1 This is a schematic diagram showing an example of a cross section of the cutting tool according to the first embodiment.

[0020] [ Figure 2 ] Figure 2 This is a schematic diagram showing another example of the cross section of the cutting tool according to the first embodiment.

[0021] [ Figure 3 ] Figure 3 This is a schematic diagram showing another example of the cross section of the cutting tool according to the first embodiment.

[0022] [ Figure 4 ] Figure 4 This is a schematic diagram showing another example of the cross section of the cutting tool according to the first embodiment.

[0023] [ Figure 5 ] Figure 5 This is a diagram schematically showing an example of a backscattered electron image of an α-Al 2 O 3 layer.

[0024] [ Figure 6 ] Figure 6 This is a diagram for explaining the method of measuring the average particle size of the α-Al2O3 layer.

[0025] [ Figure 7 ] Figure 7 This is a diagram for explaining the method of measuring the average particle size of the α-Al2O3 layer. DETAILED DESCRIPTION

[0026] [Problems to be Solved by the Present Disclosure]

[0027] The α-Al2O3 layer has excellent mechanical properties, but the adhesion with other layers and the defect resistance need to be further improved. In addition, in high-hardness steel, the wear resistance also needs to be further improved.

[0028] Therefore, an object of the present disclosure is to provide a tool having a long tool life even in efficient machining of high-hardness steel.

[0029] [Effects of the present disclosure]

[0030] The cutting tool of the present disclosure can have a long tool life even in high-efficiency machining of high-hardness steel.

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

[0032] First, embodiments of the present disclosure are listed and described.

[0033] (1) The cutting tool disclosed herein comprises:

[0034] A substrate, and a coating disposed on the substrate,

[0035] The coating comprises an α-Al2O3 layer,

[0036] The α-Al2O3 layer is composed of a plurality of α-Al2O3 particles.

[0037] The α-Al2O3 layer includes a first region, a second region and a third region,

[0038] The first region is a region sandwiched between the interface P1 on the substrate side of the α-Al 2 O 3 layer and a virtual plane S1 at a distance of 0.5 μm from the interface P1 to the surface side of the coating.

[0039] The second region is a region sandwiched between the virtual surface S1 and a virtual surface S2 that is 1.0 μm away from the virtual surface S1 toward the surface side of the coating.

[0040] The third region is a region sandwiched between the surface P2 of the α-Al2O3 layer or the interface P3 on the surface side of the film of the α-Al2O3 layer and a virtual plane S3 at a distance of 1.0 μm from the surface P2 or the interface P3 toward the substrate side.

[0041] The average particle size a of the α-Al2O3 particles in the first region is not less than 0.10 μm and not more than 0.30 μm,

[0042] The average particle size b of the α-Al2O3 particles in the second region is not less than 0.30 μm and not more than 0.50 μm,

[0043] The average particle size c of the α-Al2O3 particles in the third region is not less than 0.10 μm and not more than 0.30 μm,

[0044] The ratio b / a of a to b is 1.5 or more and 5.0 or less.

[0045] The cutting tool of the present disclosure can have a long tool life even in high-efficiency machining of high-hardness steel.

[0046] (2) The average particle size c is preferably 0.16 μm or more and 0.24 μm or less. This improves the wear resistance of the cutting tool.

[0047] (3) The b / a is preferably 1.5 or more and 2.5 or less. This improves the adhesion between the first region and the second region, and improves the defect resistance.

[0048] (4) The average thickness of the α-Al2O3 layer is preferably 3 μm or more and 15 μm or less. This allows for both excellent wear resistance and defect resistance.

[0049] (5) The TC(0 0 12) in the texture coefficient TC(hkl) of the α-Al2O3 layer is preferably greater than or equal to 3. This improves the wear resistance of the cutting tool.

[0050] [Detailed description of embodiments of the present disclosure]

[0051] When developing a tool having a long tool life even in efficient machining of high-hardness steel, the present inventors used conventional cutting tools described in Patent Documents 1 and 2 to perform efficient machining of high-hardness steel and observed the state of the tool after machining.

[0052] The wear loss is large in Patent Document 1. This is presumably because the grain size of the aluminum oxide layer in Patent Document 1 is relatively large, 0.5 μm to 3 μm.

[0053] The tool of Patent Document 2 tends to be easily defective. It is presumed that the reason for this is that, in Patent Document 2, the grain size of the lower side of the aluminum oxide layer is greatly different from the grain size of the surface side, and an interface between crystal grains is generated at the boundary between the lower side and the upper side, and this interface becomes the starting point of crack propagation.

[0054] Based on the above findings, the inventors have conducted in-depth research and have completed the cutting tool disclosed in the present invention, which has excellent wear resistance and defect resistance and has a long tool life. Hereinafter, a specific example of the cutting tool disclosed in the present invention will be described with reference to the accompanying drawings. In the drawings disclosed in the present invention, the same reference symbols represent the same parts or equivalent parts. In addition, in order to make the drawings clear and simple, the dimensional relationships such as length, width, thickness, and depth are appropriately changed, and do not necessarily represent the actual dimensional relationships.

[0055] In this specification, the expression of the form "A to B" refers to the upper and lower limits of a range (i.e., greater than A and less than B). When no unit is recorded for A and only the unit is recorded for B, the unit of A is the same as the unit of B.

[0056] In this specification, when a compound is represented by a chemical formula, when the atomic ratio is not particularly limited, it includes all atomic ratios known in the past, and should not be limited to the atomic ratio within the stoichiometric range. For example, when it is recorded as "TiCN", the ratio of the number of atoms constituting TiCN includes all atomic ratios known in the past.

[0057] [Embodiment 1: Cutting Tool]

[0058] A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as “this embodiment”) includes:

[0059] A substrate, and a coating disposed on the substrate,

[0060] The coating comprises an α-Al2O3 layer,

[0061] The α-Al2O3 layer is composed of a plurality of α-Al2O3 particles.

[0062] The α-Al2O3 layer includes a first region, a second region and a third region,

[0063] The first region is a region sandwiched between the interface P1 on the substrate side of the α-Al 2 O 3 layer and a virtual plane S1 at a distance of 0.5 μm from the interface P1 to the surface side of the coating.

[0064] The second region is a region sandwiched between the virtual surface S1 and a virtual surface S2 that is 1.0 μm away from the virtual surface S1 toward the surface side of the coating.

[0065] The third region is a region sandwiched between the surface P2 of the α-Al2O3 layer or the interface P3 on the surface side of the film of the α-Al2O3 layer and a virtual plane S3 at a distance of 1.0 μm from the surface P2 or the interface P3 toward the substrate side.

[0066] The average particle size a of the α-Al2O3 particles in the first region is not less than 0.10 μm and not more than 0.30 μm,

[0067] The average particle size b of the α-Al2O3 particles in the second region is not less than 0.30 μm and not more than 0.50 μm,

[0068] The average particle size c of the α-Al2O3 particles in the third region is not less than 0.10 μm and not more than 0.30 μm,

[0069] The ratio b / a of a to b is 1.5 or more and 5.0 or less.

[0070] The cutting tool of the present embodiment can have a long tool life even in high-efficiency machining of high-hardness steel. The reason for this is not clear, but it is presumed to be the following (i) to (vi).

[0071] (i) In the cutting tool of the present embodiment, the average particle size a of the α-Al2O3 particles in the first region of the α-Al2O3 layer (hereinafter also referred to as "the average particle size a in the first region") is as small as 0.10 μm or more and 0.30 μm or less. Therefore, the adhesion between the α-Al2O3 layer and the layer on the substrate side in contact with the α-Al2O3 layer (hereinafter also referred to as "base layer"), or the substrate in contact with the α-Al2O3 layer is relatively large. Therefore, during cutting, it is difficult to generate crack propagation starting from the interface between the α-Al2O3 layer and the base layer or the substrate, so that the cutting tool has excellent defect resistance. In addition, when the average particle size a in the first region is within the above range, the resistance to welding and peeling is improved.

[0072] (ii) In the cutting tool of the present embodiment, the difference between the average grain size a of the first region of the α-Al2O3 layer and the average grain size b of the α-Al2O3 particles in the second region (hereinafter also referred to as "the average grain size b of the second region") is small, and the difference between the average grain size b of the second region and the average grain size c of the α-Al2O3 particles in the third region (hereinafter also referred to as "the average grain size c of the third region") is small. Therefore, the interface generated between the first region and the second region and between the second region and the third region due to the difference in grain size is suppressed. In the α-Al2O3 layer, the generation of the interface as the starting point of the crack is suppressed, so the adhesion between the first region, the second region and the third region is increased, so that the cutting tool has excellent defect resistance.

[0073] (iii) In the cutting tool of the present embodiment, in the substrate side region of the α-Al2O3 layer, the particle size of the α-Al2O3 particles gradually increases from the substrate side toward the tool surface side. Therefore, the crack propagation distance from the tool surface becomes longer, thereby suppressing the expansion of the crack on the substrate side of the α-Al2O3 layer. Therefore, the cutting tool has excellent defect resistance.

[0074] (iv) In the cutting tool of this embodiment, the average grain size c of the third region of the α-Al2O3 layer is greater than 0.10 μm, thereby suppressing crack propagation from the tool surface, and thus the cutting tool has excellent defect resistance. Since the average grain size c is less than 0.30 μm, the cutting tool has excellent wear resistance.

[0075] (v) In the cutting tool of the present embodiment, the ratio b / a of the average particle diameter a of the first region of the α-Al2O3 layer to the average particle diameter b of the second region is 1.5 or more, and the average particle diameter b is larger than the average particle diameter a, so that in the first region and the second region, cracks are difficult to propagate in the thickness direction of the coating, so that the cutting tool has excellent defect resistance. In addition, b / a is less than 5, and the difference between the average particle diameter a and the average particle diameter b is small, so the interface generated by the particle diameter difference is suppressed. In the α-Al2O3 layer, the generation of the interface as the starting point of the crack is suppressed, so the adhesion between the first region and the second region is increased, so that the cutting tool has excellent defect resistance.

[0076] (vi) As described in (i) to (v) above, the cutting tool of the present embodiment has excellent chipping resistance and wear resistance, and can have a long tool life even in high-efficiency machining of high-hardness steel.

[0077] <Cutting tool structure>

[0078] like Figure 1 As shown, the cutting tool 1 of the present embodiment comprises a substrate 10 and a coating 15 disposed on the substrate 10, the coating 15 comprising an α-Al2O3 layer 11. The coating 15 preferably covers at least a portion of the cutting portion of the front cutting edge of the substrate, preferably covers at least a portion of the cutting portion of the substrate, and more preferably covers the entire surface of the substrate. The cutting portion of the substrate refers to an area on the substrate surface that is within 1.5 mm from the cutting edge line. Even if a portion of the substrate is not covered by the coating, or the composition of the coating is partially different, it does not deviate from the scope of the present disclosure.

[0079] <Application of cutting tools>

[0080] The cutting tools disclosed herein can be, for example, a drill, an end mill (e.g., a ball end mill), an indexable cutting insert for a drill, an indexable cutting insert for an end mill, an indexable cutting insert for milling, an indexable cutting insert for turning, a metal saw, a gear cutting tool, a reamer, a tap, and the like.

[0081] <Base material>

[0082] The substrate 10 includes a rake face and a flank face, and any substrate can be used as the substrate as long as it is a conventionally known substrate. For example, it is preferably any one of cemented carbide (for example, WC-Co cemented carbide and other WC-based cemented carbide, which may contain carbonitrides of Ti, Ta, Nb, etc.), cermet (materials with TiC, TiN, TiCN, etc. as main components), high-speed steel, ceramic (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body, or diamond sintered body.

[0083] Among these various substrates, cemented carbide (especially WC-based cemented carbide) or cermet (especially TiCN-based cermet) is preferably selected. These substrates have excellent balance between hardness and strength at high temperatures, so that they have excellent properties as the substrate of the cutting tool for the above-mentioned purpose. When using WC-based cemented carbide as the substrate, its texture may contain free carbon and abnormal layers such as η phase or ε phase.

[0084] The surface of the substrate may also be modified. For example, in the case of cemented carbide, a de-β layer may be formed on the surface; or in the case of cermet, a surface hardening layer may be formed. Even if the surface of the substrate is modified, the desired effect can be achieved.

[0085] In the case where the cutting tool is a cutting insert with an indexable cutting edge, the substrate may or may not have a chip breaker. The shape of the cutting edge ridgeline may be any of the following shapes: a sharp edge (a ridge formed by the intersection of the front cutting edge and the back cutting edge), a honed edge (a shape obtained by giving a rounded corner to the sharp edge), a negative land (a chamfered shape), or a shape obtained by combining a honed edge and a negative land.

[0086] <Lamination>

[0087] The coating includes an α-Al 2 O 3 layer. For example, the coating may include one or more α-Al 2 O 3 layers and may further include a plurality of other layers.

[0088] In addition to the α-Al2O3 layer 11, the coating 15 may also include other layers. Figure 2 As shown in the cutting tool 21 , the coating 25 may further include a base layer 12 arranged between the substrate 10 and the α-Al 2 O 3 layer 11 .

[0089] like Figure 3 As shown in the cutting tool 31 , the coating 35 may include a surface layer 13 disposed on the α-Al 2 O 3 layer 11 in addition to the base layer 12 .

[0090] like Figure 4 As shown in the cutting tool 41, in addition to the base layer 12 and the surface layer 13, the coating 45 may further include an intermediate layer 14 disposed between the base layer 12 and the α-Al2O3 layer 11. The base layer, the surface layer, and the intermediate layer will be described in detail later.

[0091] The average thickness of the entire coating disposed on the substrate is preferably 3 μm to 30 μm. This allows the coating to have excellent wear resistance and peeling resistance. The average thickness of the coating is more preferably 5 μm to 25 μm, and even more preferably 8 μm to 20 μm.

[0092] The thickness of the coating is measured, for example, by obtaining a cross-sectional sample parallel to the normal direction of the surface of the substrate and observing the sample using a scanning transmission electron microscope (STEM). Examples of the scanning transmission electron microscope include JEM-2100F (trade name) manufactured by JEOL Ltd.

[0093] When "thickness" is mentioned in this specification, the thickness refers to the average thickness. Specifically, the observation magnification of the cross-section sample is set to 5000 times, and a rectangular measurement field of (30 μm in the direction parallel to the substrate surface) × (the distance including the overall thickness of the coating) is set in the electron microscope image, and the thickness dimensions at 10 locations in the field of view are measured, and the average value is set as "thickness". The thickness and average thickness of the base layer, intermediate layer and surface layer described below are also measured and calculated in the same manner.

[0094] It is to be noted that it has been confirmed that, in the same sample, even if a plurality of measurement fields including the coating on the rake face or the coating on the flank face are arbitrarily selected and the above-mentioned measurement is performed in the measurement fields to calculate the above-mentioned average thickness, the same result can be obtained.

[0095] <α-Al2O3 layer>

[0096] (Composition of α-Al2O3 layer)

[0097] In the present embodiment, the α-Al2O3 layer is composed of a plurality of α-Al2O3 (aluminum oxide having an α-type crystal structure) particles. That is, the α-Al2O3 layer is composed of polycrystalline α-Al2O3. As long as the effect of the present embodiment can be exerted, the α-Al2O3 layer may contain unavoidable impurities, etc. That is, as long as the effect of the present disclosure is not impaired, it is allowed to contain other components in the α-Al2O3 layer.

[0098] In the present embodiment, the α-Al 2 O 3 layer 11 disposed on the rake face of the substrate 10 includes a first region A1, a second region A2, and a third region A3. In the present specification, the first region A1, the second region A2, and the third region A3 are defined as the following regions.

[0099] The first region A1 is a region between the interface P1 of the α-Al2O3 layer 11 on the substrate 10 side and a virtual surface S1 0.5 μm away from the interface P1 to the surface P2 of the coating 15. Here, the interface P1 is included in the first region A1, but the virtual surface S1 is not included in the first region A1.

[0100] The second region A2 is a region sandwiched between the virtual surface S1 and the virtual surface S2 which is 1.0 μm away from the virtual surface S1 toward the surface P2 of the coating 15. Here, the virtual surface S1 and the virtual surface S2 are included in the second region A2.

[0101] When the α-Al2O3 layer 11 is arranged on the outermost surface of the coating (for example, Figure 1 and Figure 2 ), the third region A3 is a region sandwiched between the surface P2 of the α-Al2O3 layer 11 and a virtual surface S3 which is 1.0 μm away from the surface P2 toward the substrate side. Here, the surface P2 and the virtual surface S3 are included in the third region A3.

[0102] When other layers (surface layers) are arranged on the α-Al2O3 layer 11 (for example, Figure 3 and Figure 4 ), the third region A3 is a region sandwiched between the interface P3 on the surface side of the film of the α-Al2O3 layer 11 and a virtual surface S3 at a distance of 1.0 μm from the interface P3 to the substrate 10. Here, the interface P3 and the virtual surface S3 are included in the third region A3.

[0103] The second region and the third region may be in contact with each other. In addition, another region may be arranged between the second region and the third region. In this case, the other region is a region sandwiched between the virtual surface S2 and the virtual surface S3.

[0104] (Average particle size of α-Al2O3 particles)

[0105] In this embodiment, the average particle size a of the α-Al2O3 particles in the first region is greater than 0.10 μm and less than 0.30 μm, the average particle size b of the α-Al2O3 particles in the second region is greater than 0.30 μm and less than 0.50 μm, the average particle size c of the α-Al2O3 particles in the third region is greater than 0.10 μm and less than 0.30 μm, and the ratio of a to b, b / a, is greater than 1.5 and less than 5.0.

[0106] When the average particle size a of the α-Al2O3 particles in the first region is 0.10 μm or more and 0.30 μm or less, the adhesion between the α-Al2O3 layer and the layer on the substrate side in contact with the α-Al2O3 layer or the substrate in contact with the α-Al2O3 layer increases. Therefore, during cutting, it is difficult to generate crack extension starting from the interface between the α-Al2O3 layer and the base layer or the substrate, and the cutting tool has excellent defect resistance. From the viewpoint of improving adhesion and defect resistance, the average particle size a is preferably 0.12 μm or more and 0.28 μm or less, more preferably 0.14 μm or more and 0.26 μm or less, and further preferably 0.16 μm or more and 0.24 μm or less.

[0107] When the average particle size b of the α-Al2O3 particles in the second region is 0.30 μm or more, the crack propagation from the tool surface can be suppressed, thereby improving the defect resistance. On the other hand, when the average particle size b is 0.50 μm or less, since the difference with the average particle size a of the α-Al2O3 particles in the first region is small, the interface generated by the difference in particle size between the first region and the second region is suppressed. As a result, it is difficult to generate crack propagation starting from the interface, and the reduction of the adhesion between the first region and the second region is suppressed, so that the cutting tool can have excellent defect resistance. Furthermore, the difference between the average particle size b of the α-Al2O3 particles in the second region and the average particle size c of the α-Al2O3 particles in the third region is small, so the interface generated by the difference in particle size between the second region and the third region is suppressed. As a result, it is difficult to generate crack propagation starting from the interface, and the reduction of the adhesion between the second region and the third region is suppressed, so that the cutting tool can have excellent defect resistance. From the viewpoint of improving adhesion and defect resistance, the average particle diameter b is preferably 0.32 μm to 0.48 μm, more preferably 0.34 μm to 0.46 μm, and even more preferably 0.36 μm to 0.44 μm.

[0108] Since the average particle size c of the α-Al2O3 particles in the third region is 0.10 μm or more, crack propagation from the tool surface is suppressed, so that the cutting tool can have excellent defect resistance. Since the average particle size c is 0.30 μm or less, the cutting tool can have excellent wear resistance. The average particle size c is preferably 0.12 μm or more and 0.28 μm or less, more preferably 0.14 μm or more and 0.26 μm or less, and further preferably 0.16 μm or more and 0.24 μm or less.

[0109] The ratio b / a of the average particle diameter a to the average particle diameter b is 1.5 or more and 5.0 or less. When the ratio b / a is 1.5 or more, the average particle diameter b is larger than the average particle diameter a, so that cracks are difficult to expand in the thickness direction of the first region and the second region, so that the cutting tool has excellent defect resistance. In addition, when b / a is 5 or less, since the difference between the average particle diameter a and the average particle diameter b is small, the adhesion between the first region and the second region is improved, and the generation of cracks at the first region and the second region is suppressed. Thus, the cutting tool has excellent wear resistance.

[0110] In this specification, the average particle diameter a, the average particle diameter b, and the average particle diameter c are measured by the following procedures (A1) to (A7).

[0111] (A1) A cutting tool is cut along the normal line 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 ion milled using Ar ions to make the cross section mirror-finished. The conditions for the ion milling are as follows.

[0112] Accelerating voltage: 6kV

[0113] Irradiation angle: 0° from the straight line parallel to the thickness direction of the α-Al2O3 layer in the cross section of the α-Al2O3 layer

[0114] Exposure time: 6 hours

[0115] (A2) A cross section of the mirror surface state was observed at 5000 times using a field emission scanning electron microscope (EF-SEM) to obtain a backscattered electron image (EBSD). Figure 5 This is a diagram schematically showing an example of EBSD.

[0116] (A3) In the above EBSD, 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 in the normal direction along the rake face is less than 0.5 μm is determined, and the measurement range is set to include this region. The measurement range is set to a rectangle of (transverse direction (direction parallel to the rake face): 30 μm) × (vertical direction (normal direction of the rake face): length including the entire coating).

[0117] (A4) In the above-mentioned measurement range, a reference line LS1 is set at a midpoint between the valley bottom B1 and the peak top T1 of the interface P1.

[0118] (A5) The lateral particle size of the α-Al2O3 particles is measured on the line L1 which is 0.2 μm away from the reference line LS1 in the surface direction of the cutting tool. The particle sizes of all α-Al2O3 particles in the measurement range are measured, and the average value of these is taken as the average particle size a of the α-Al2O3 particles in the first region.

[0119] (A6) The lateral particle size of the α-Al2O3 particles is measured on the line L2 which is 1.1 μm away from the reference line LS1 in the surface direction of the cutting tool. The particle sizes of all α-Al2O3 particles in the measurement range are measured, and the average value of these is taken as the average particle size b of the α-Al2O3 particles in the second region.

[0120] (A7) In the above measurement range, when the α-Al2O3 layer is arranged on the outermost surface of the coating, the lateral particle size of the α-Al2O3 particles is measured on a line L3 that is 0.6 μm away from the surface P2 of the α-Al2O3 layer in the substrate direction; or when a surface layer is arranged on the α-Al2O3 layer, the lateral particle size of the α-Al2O3 particles is measured on a line L3 that is 0.6 μm away from the interface P3 (the interface between the α-Al2O3 layer and the surface layer) on the surface side of the coating of the α-Al2O3 layer in the substrate direction. The particle sizes of all α-Al2O3 particles in the measurement range are measured, and the average value of these is taken as the average particle size c of the α-Al2O3 particles in the third region. It should be noted that when the surface P2 and the interface P3 have projections and depressions, the above line L3 is set at a position 0.6 μm away from a line in the substrate direction that passes through the valley bottom closest to the substrate side in the measurement range and is parallel to the above reference line LS1.

[0121] In the above (A5), the difference between the bottom of the interface B1 and the top of the interface T1 is large (for example, 0.5 μm). Figure 6 As shown, in the case where the line L1 exists inside the substrate, inside the substrate (for example, by Figure 6 The particle size of the α-Al 2 O 3 particles is not measured on the line L1 (the area indicated by X), but the particle size of the α-Al 2 O 3 particles is measured only in the α-Al 2 O 3 layer, and the average particle size a is calculated.

[0122] When setting the above line L1, if Figure 7As shown, the inventors set lines La1 to Ld1 passing through positions with an interval of 0.1 μm in the range of 0.1 μm or more and less than 0.5 μm from the reference line LS1 in the normal direction along the rake face in the first region, and measured the particle sizes of all α-Al2O3 particles in the measurement range on each line and on the interface S1, and calculated the average value of these. The results confirmed that when the average particle size on the line Lb1 corresponding to the line L1 is 0.10 μm or more and 0.30 μm or less, the average particle size on the lines La1 to Ld1 and the interface S1 is also 0.10 μm or more and 0.30 μm or less. It is speculated that the reason is that in the initial stage of nucleation, the orientation and concavity of the substrate are greatly affected, so the Al2O3 crystals do not grow in a columnar shape (or a state where the cross-sectional particle size increases toward the surface), but in a granular shape (the degree of vertical / parallel to the interface is equal).

[0123] It has been confirmed that even if different measurement ranges are arbitrarily selected in the same cutting tool and the above measurement is performed within the measurement range, the same result can be obtained. It has been further confirmed that even if different measurement ranges are arbitrarily selected in different cutting tools and the above measurement is performed within the measurement range, the same result can be obtained. Therefore, the average particle size on line L1 is 0.10 μm or more and 0.30 μm or less, which means that the average particle size a of the α-Al2O3 particles in the first region is 0.10 μm or more and 0.30 μm or less.

[0124] When setting the above line L2, if Figure 7 As shown, the inventors set lines La2 to Lf2 passing through positions with an interval of 0.2 μm in the range of 0.5 μm to 1.5 μm from the reference line LS1 in the normal direction along the front cutting edge in the second region, and measured the particle sizes of all α-Al2O3 particles in the measurement range on each line, and calculated the average value of these. The results confirmed that when the average particle size on line Ld2 corresponding to line L2 is 0.30 μm to 0.50 μm, the average particle size on lines La2 to Lf2 is also 0.30 μm to 0.50 μm. The reason is speculated as follows. The second region is a transitional region from nucleation to crystal growth. In the first region, in addition to gas conditions, nucleation is also caused by the influence of the orientation, concavity, etc. of the substrate, but in the second region, the influence of gas conditions is dominant, and nuclei (orientation, shape, etc.) different from those in the first region are dominant. It is presumed that the crystals generated by nucleation are eliminated, while stable nuclei are generated under new gas conditions, so the overall number of particles does not change significantly, and the change in particle size is also not significant. In addition, in the present disclosure, by adjusting the gas conditions when the first region and the second region are formed, the elimination of crystals and nucleation are smoothly transitioned, thereby expanding the second region in the thickness direction and maintaining the particle size.

[0125] It has been confirmed that even if different measurement ranges are arbitrarily selected in the same cutting tool and the above measurement is performed within the measurement range, the same result can be obtained. It has been further confirmed that even if different measurement ranges are arbitrarily selected in different cutting tools and the above measurement is performed within the measurement range, the same result can be obtained. Therefore, the average particle size on line L2 is 0.30 μm or more and 0.50 μm or less means that the average particle size b of the α-Al2O3 particles in the second region is 0.30 μm or more and 0.50 μm or less.

[0126] When the above line L3 is set, Figure 7 As shown, the inventors set lines La3 to Lf3 passing through positions with an interval of 0.2 μm in the range of 0 μm to 1.0 μm from the surface P2 of the α-Al2O3 layer or the interface P3 on the surface side of the coating of the α-Al2O3 layer in the normal direction of the rake face in the third region, and measured the particle sizes of all α-Al2O3 particles in the measurement range on each line, and calculated the average value of these. The results confirmed that when the average particle size on the line Ld3 corresponding to the line L3 is 0.10 μm to 0.30 μm, the average particle size on the lines La3 to Lf3 is also 0.10 μm to 0.30 μm. It is speculated that the reason is that the third region is a complete crystal growth region and the number of crystals changes little.

[0127] It has been confirmed that even if different measurement ranges are arbitrarily selected in the same cutting tool and the above measurement is performed within the measurement range, the same result can be obtained. It has been further confirmed that even if different measurement ranges are arbitrarily selected in different cutting tools and the above measurement is performed within the measurement range, the same result can be obtained. Therefore, the average particle size on line L3 is 0.10 μm or more and 0.30 μm or less means that the average particle size c of α-Al2O3 particles in the third region is 0.10 μm or more and 0.30 μm or less.

[0128] It has been confirmed that in the cutting tool, when the average particle size a of the α-Al2O3 particles in the first region is greater than 0.10 μm and less than 0.30 μm, the average particle size b of the α-Al2O3 particles in the second region is greater than 0.30 μm and less than 0.50 μm, the average particle size c of the α-Al2O3 particles in the third region is greater than 0.10 μm and less than 0.30 μm, and the ratio b / a of a to b is greater than 1.5 and less than 5.0, even if the distance between line L2 and line L3 changes, it has no effect on the effect.

[0129] In view of the above, the cutting tool of the present embodiment can also be expressed as follows.

[0130] The cutting tool disclosed herein has:

[0131] A substrate, and a coating disposed on the substrate,

[0132] The coating includes an α-Al2O3 layer.

[0133] The α-Al2O3 layer is composed of a plurality of α-Al2O3 particles.

[0134] In a cross section along the normal line of the surface of the coating,

[0135] The average particle size of the α-Al2O3 particles on a line L1 at a distance of 0.2 μm from a reference line LS1 based on the interface between the substrate and the α-Al2O3 layer to the α-Al2O3 layer side is 0.10 μm or more and 0.30 μm or less.

[0136] The average particle size of the α-Al 2 O 3 particles on the line L2 which is 1.1 μm away from the reference line LS1 toward the α-Al 2 O 3 layer side is 0.30 μm or more and 0.50 μm or less.

[0137] The average particle size of the α-Al2O3 particles on the line L3 at a distance of 0.6 μm from the surface P2 of the α-Al2O3 layer or the interface P3 on the surface side of the film of the α-Al2O3 layer to the α-Al2O3 layer side is 0.10 μm or more and 0.30 μm or less,

[0138] The ratio b / a of a to b is 1.5 or more and 5.0 or less.

[0139] (b / a)

[0140] In the cutting tool of the present embodiment, the ratio b / a of the average particle size a of the first region of the α-Al2O3 layer to the average particle size b of the second region is 1.5 or more and 5.0 or less. When b / a is 1.5 or more, the average particle size b is larger than the average particle size a, so it is difficult for cracks to extend in the thickness direction of the first region and the second region, so that the cutting tool has excellent defect resistance. In addition, when b / a is 5 or less, the difference between the average particle size a and the average particle size b is small, so the adhesion between the first region and the second region is improved, and cracks are suppressed in the first region and the second region. Thus, the cutting tool has excellent wear resistance.

[0141] From the viewpoint of improving the adhesion between the first region and the second region and improving the defect resistance, b / a is preferably 1.5 to 2.5, more preferably 1.7 to 2.3, and even more preferably 1.9 to 2.1.

[0142] (Texture coefficient)

[0143] In the present disclosure, in the texture coefficient TC(hkl) shown in the following formula (1), TC(0 0 12) of the α-Al2O3 layer is preferably 3 or more. Thus, the α-Al2O3 layer can have excellent wear resistance. Therefore, the cutting tool can have a long tool life.

[0144] [Mathematical formula 1]

[0145]

[0146] In formula (1), I(hkl) represents the X-ray diffraction intensity of the (hkl) reflection surface, and I0(hkl) represents the standard intensity of the ICDD PDF card number 00-010-0173. In addition, n in formula (1) represents the number of reflections used in the calculation, which is 8 in this embodiment. The (hkl) surfaces used for reflection are (0 1 2), (1 0 4), (1 1 0), (0 0 12), (1 1 3), (02 4), (1 16), and (3 0 0).

[0147] ICDD (registered trademark) is the abbreviation of International Centre for Diffraction Data, and PDF (registered trademark) is the abbreviation of Powder Diffraction File.

[0148] It should be noted that TC(0 0 12) of the α-Al 2 O 3 layer of this embodiment can be expressed by the following formula (2).

[0149] [Mathematical formula 2]

[0150]

[0151] Therefore, “in the texture coefficient TC(hkl), TC(0 0 12) is 3 or more” means that the value obtained by the above formula (2) obtained by substituting TC(0 0 12) into the above formula (1) is 3 or more.

[0152] The value of TC (0 0 12) is more preferably 4 or more, and further preferably 5 or more. 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 there are 8 reflecting surfaces used in the calculation, it is sufficient to set it to 8 or less. The value of TC (0 0 12) can be set to 3 or more and 8 or less, 4 or more and 8 or 5 or more and 8 or less.

[0153] In the present disclosure, in the texture coefficient TC(hkl) shown in the above formula (1), TC(1 1 0) of the α-Al2O3 layer is preferably greater than 2. Thus, the α-Al2O3 layer can have excellent defect resistance. Therefore, the cutting tool can have a long tool life.

[0154] It should be noted that TC(1 1 0) of the α-Al 2 O 3 layer of this embodiment can be expressed by the following formula (3).

[0155] [Mathematical formula 3]

[0156]

[0157] Therefore, “in the texture coefficient TC(hkl), TC(1 1 0) is 2 or more” means that the value obtained by substituting TC(1 1 0) into the above formula (1) is 2 or more.

[0158] The value of TC (1 1 0) is more preferably 2.5 or more, and further preferably 3 or more. The larger the value of TC (1 1 0), the more effectively the defect resistance can be improved. There is no upper limit to the value of TC (1 1 0), but since there are 8 reflective surfaces used in the calculation, it can be set to 8 or less. The value of TC (1 1 0) can be set to 2 or more and 8 or less, 2.5 or more and 8 or more, or 3 or more and 8 or less.

[0159] The measurement of TC (hkl) as described above can be performed by analysis using an X-ray diffraction device. TC (hkl) can be measured, for example, using SmartLb / a (registered trademark) manufactured by Rigaku Co., Ltd. (scanning speed: 21.7° / min, step length: 0.01°, scanning range: 15 to 140°) under the following conditions. It should be noted that in this embodiment, the result of measuring TC (hkl) using an X-ray diffraction device is referred to as "XRD result".

[0160] Characteristic X-ray: Cu-Kα

[0161] Tube voltage: 45kV

[0162] Tube current: 200mA

[0163] Filter: Multilayer mirror

[0164] Optical system: focusing method

[0165] X-ray diffraction method: θ-2θ method

[0166] When using an X-ray diffraction device, X-rays are irradiated onto the front face of the cutting tool. Usually, bumps and depressions are formed on the front face, while the back face is flat, so in order to eliminate interference factors, it is preferred to irradiate the back face with X-rays. In particular, X-rays are irradiated at a position on the back face within a range of about 2 to 4 mm extending from the cutting edge ridge. As a result, the reproducibility of the results is improved. It should be noted that in the present embodiment, the TC (hkl) value of the α-Al2O3 layer on the back face of the substrate is the same as the TC (hkl) value of the α-Al2O3 layer on the front face of the substrate.

[0167] It is to be noted that it has been confirmed that the same result can be obtained even if a plurality of measurement positions are arbitrarily selected in the same sample and the above-mentioned measurement is performed at each measurement position.

[0168] (thickness)

[0169] The average thickness of the α-Al2O3 layer is preferably 3 μm or more and 15 μm or less. Thus, it can have both excellent wear resistance and defect resistance. From the viewpoint of improving wear resistance, the lower limit of the average thickness of the α-Al2O3 layer is preferably 3 μm or more, more preferably 4 μm or more, and further preferably 5 μm or more. When the average thickness of the α-Al2O3 layer is less than 3 μm, the average particle size a, average particle size b, average particle size c and b / a of the above-mentioned α-Al2O3 cannot be specified due to insufficient thickness. From the viewpoint of improving defect resistance, the upper limit of the average thickness of the α-Al2O3 layer is preferably 15 μm or less, preferably 10 μm or less, more preferably 9 μm or less, and further preferably 8 μm or less. The average thickness of the α-Al2O3 layer is preferably 3 μm or more and 10 μm or less, more preferably 4 μm or more and 9 μm or less, and further preferably 5 μm or more and 8 μm or less.

[0170] As described above, the thickness of the α-Al2O3 layer can be confirmed by observing a cross-section sample of the cutting tool using a scanning transmission electron microscope (STEM), etc. Here, the observation field is the measurement range set when measuring the particle size of the above-mentioned α-Al2O3 particles.

[0171] It is to be noted that it was confirmed that similar results can be obtained even when a plurality of measurement ranges including the coating on the rake face or the coating on the flank face are arbitrarily selected for the same sample and the above-mentioned measurement is performed for each measurement range.

[0172] <Other floors>

[0173] As mentioned above, in addition to the α-Al2O3 layer, the coating may also include other layers. Figure 2 to Figure 4 As shown, as other layers, a base layer 12, a surface layer 13, an intermediate layer 14, etc. can be listed.

[0174] (basal layer)

[0175] The base layer is disposed between the substrate and the α-Al2O3 layer. As the base layer, for example, a TiN layer can be cited. The average thickness of the TiN layer is preferably 0.1 μm or more and 20 μm or less. Thus, the coating can have excellent wear resistance and defect resistance.

[0176] (Surface layer)

[0177] As the surface layer, for example, any one of Ti (titanium) carbide, nitride or boride is preferably used as the main component. The surface layer is a layer arranged on the outermost side of the coating. However, there are also cases where the surface layer is not formed on the cutting edge ridge. For example, the surface layer is arranged directly above the α-Al2O3 layer.

[0178] “Main component: any one of carbides, nitrides, and borides of Ti” means any one of carbides, nitrides, and borides of Ti containing 90% by mass or more. In addition, this means that it is preferably composed of any one of carbides, nitrides, and borides of Ti, excluding unavoidable impurities.

[0179] Among any of Ti carbides, nitrides and carbonitrides, it is particularly preferred that the surface layer be composed mainly of Ti nitrides (i.e., compounds represented by TiN). TiN has the clearest color (golden) among these compounds, and therefore has the advantage of being easy to identify the tip of the cutting blade after cutting (identify the used part). The surface layer is preferably composed of a TiN layer.

[0180] The average thickness of the surface layer is preferably 0.05 μm or more and 1 μm or less. Thus, the adhesion between the surface layer and the adjacent layer is improved. The upper limit of the average thickness of the surface layer can be set to 0.8 μm or less and 0.6 μm or less. The lower limit of the average thickness can be set to 0.1 μm or more and 0.2 μm or more.

[0181] <Middle layer>

[0182] The intermediate layer is arranged between the base layer and the α-Al2O3 layer. As the intermediate layer, for example, a TiCN layer and a TiCNO layer can be cited. Since the TiCN layer and the TiCNO layer have excellent wear resistance, more suitable wear resistance can be imparted by coating. The average thickness of the intermediate layer is preferably 1 μm or more and 20 μm or less. Here, the average thickness of the intermediate layer refers to: when the intermediate layer is formed by two or more layers, the average of the total thickness of the two or more layers.

[0183] [Embodiment 2: Method for manufacturing cutting tool]

[0184] The cutting tool of the first embodiment can be manufactured by forming a coating on a substrate using a chemical vapor deposition (CVD) method. In the case where other layers other than the α-Al2O3 layer are formed in the coating, the other layers can be formed using a chemical vapor deposition device under conventionally known conditions. On the other hand, the α-Al2O3 layer can be formed, for example, by the following method. It should be noted that the cutting tool of the first embodiment is not limited to being manufactured by the following manufacturing method, and can also be manufactured by other manufacturing methods.

[0185] The film forming conditions of the α-Al2O3 layer can be set, for example, to: temperature 950-1050°C, pressure 10-50 hPa, gas flow rate (total gas flow rate) 50-100 L / min. "Total gas flow rate" means: the total volume flow rate introduced into the CVD furnace per unit time when the gas under standard conditions (0°C, 1 atmosphere) is set as an ideal gas.

[0186] AlCl3, HCl, CO2, H2S and H2 were used as raw material gases. The amount of HCl in the raw material gas was changed according to the thickness of the α-Al2O3 layer formed from the beginning of film formation. Specifically, it was as follows.

[0187] From the beginning of film formation until the thickness of the α-Al2O3 layer is less than 0.5 μm, the raw material gas composition is set to: HCl: 7.5 volume % to 9 volume %, AlCl3: 2 volume % to 5 volume %, CO2: 0.1 volume % to 6 volume %, H2S: 0.1 volume % to 1 volume %, and H2: the remaining volume % when the entire raw material gas is set to 100 volume %, thereby forming the first region.

[0188] Next, until the thickness of the α-Al2O3 layer is 0.5 μm or more and 1.5 μm or less, the raw material gas composition is set to: HCl: 6 volume % or more and less than 7.5 volume %, and the amount of H2 in the raw material gas is increased by the amount of HCl reduced compared to when the first region is formed, and the composition of other gases is the same as when the first region is formed. Thus, the second region is formed.

[0189] Next, the same raw material gas as that of the second region is used until the thickness of the α-Al 2 O 3 layer becomes 1.0 μm smaller than the final thickness of the α-Al 2 O 3 layer.

[0190] Next, from a thickness 1.0 μm less than the final thickness of the α-Al2O3 layer to the surface of the α-Al2O3 layer, the raw material gas composition was set to: HCl: 7.5 volume % or more and less than 9.0 volume %, and the amount of H2 decreased by the amount of HCl in the raw material gas compared to the formation of the second region, and the composition of other gases was the same as that of the formation of the second region. Thus, the third region was formed.

[0191] In the past, HCl was used to suppress the excessive generation of α-Al2O3 during film formation and the formation of α-Al2O3 particles in the gas phase. When α-Al2O3 particles are formed in the gas phase, it is difficult to form an α-Al2O3 layer on the substrate. On the other hand, it is believed that when the amount of HCl in the raw gas is large, the film formation rate decreases. Therefore, it is technical common sense to set the amount of HCl in the raw gas to the minimum required limit, and those skilled in the art do not have the technical idea to increase the amount of HCl in the raw gas.

[0192] Compared with the conventional technical common sense, in the present embodiment, as described above, the particle size of the α-Al2O3 particles is controlled by changing the amount of HCl. Furthermore, the amount of HCl in the raw gas used to form the first region, the second region, and the third region is greater than the amount of HCl in the raw gas used to form the α-Al2O3 layer in the past (for example, 2.8% by volume or more and less than 6% by volume). As a result, the average particle size of the α-Al2O3 particles in the first region, the second region, and the third region becomes smaller. This is a new discovery of the inventors. The inventors and others have completed the cutting tool of the present embodiment based on this new discovery.

[0193] [Note 1]

[0194] The cutting tool disclosed herein has:

[0195] A substrate, and a coating disposed on the substrate,

[0196] The coating includes an α-Al2O3 layer.

[0197] The α-Al2O3 layer is composed of a plurality of α-Al2O3 particles.

[0198] In a cross section along the normal line of the surface of the coating,

[0199] The average particle size of the α-Al2O3 particles on a line L1 at a distance of 0.2 μm from a reference line LS1 based on the interface between the substrate and the α-Al2O3 layer to the α-Al2O3 layer side is 0.10 μm or more and 0.30 μm or less.

[0200] The average particle size of the α-Al 2 O 3 particles on the line L2 which is 1.1 μm away from the reference line LS1 toward the α-Al 2 O 3 layer side is 0.30 μm or more and 0.50 μm or less.

[0201] The average particle size of the α-Al2O3 particles on the line L3 at a distance of 0.6 μm from the surface P2 of the α-Al2O3 layer or the interface P3 on the surface side of the film of the α-Al2O3 layer to the α-Al2O3 layer side is 0.10 μm or more and 0.30 μm or less,

[0202] The ratio b / a of a to b is 1.5 or more and 5.0 or less.

[0203] Example

[0204] This embodiment will be described in more detail with reference to examples, but this embodiment is not limited to these examples.

[0205] [Sample 1 to Sample 28, Sample 1-1 to Sample 1-9]

[0206] The raw material powders composed of the blending composition described in Table 1 were uniformly mixed, pressed into a predetermined shape, and then sintered at 1300-1500° C. for 1-2 hours to obtain a substrate made of cemented carbide (shape: model CNMG120408N-UX (made by Sumitomo Electric Hardmetal)). The "remainder" in Table 1 indicates the remainder of WC in the blending composition (mass %).

[0207] [Table 1]

[0208]

[0209] <Film formation>

[0210] A coating is formed on the surface of the substrate obtained above to produce a cutting tool. Specifically, the substrate is placed in a chemical vapor deposition device, and a coating is formed on the substrate using a chemical vapor deposition method. The composition of the coating of each sample is shown in Table 2.

[0211] [Table 2]

[0212]

[0213] A TiN layer (base layer), a TiCN layer (intermediate layer), a TiCNO layer (intermediate layer), an α-Al2O3 layer, and a TiN layer (surface layer) are sequentially formed on the substrate. The thickness of the TiN layer (base layer) is 0.4 μm, the thickness of the TiCN layer (intermediate layer) is 6.5 μm, the thickness of the TiCNO layer (intermediate layer) is 0.7 μm, and the thickness of the TiN (surface layer) is 0.7 μm. "None" in Table 1 means that the layer is not formed in the sample.

[0214] Table 3 shows the film formation conditions of the TiN layer (base layer), the TiCN layer (intermediate layer), the TiCNO layer (intermediate layer), and the TiN layer (surface layer).

[0215] [Table 3]

[0216]

[0217] The film forming conditions, raw material gas composition and average thickness of the α-Al2O3 layer of each sample are shown in Table 4. The "remainder" in Table 4 represents the remainder of the raw material gas composition (volume %) of H2 gas. The formation conditions of the α-Al2O3 layer were set to: temperature 1000°C, pressure 70hPa, raw material gas introduction rate (total gas flow rate) 60L / min, and the gas pipe for spraying the raw material gas was rotated at 2rpm while the substrate was fixed.

[0218] [Table 4]

[0219]

[0220] For example, the film forming conditions of sample 1 are as follows. From the film forming of the α-Al2O3 layer until the thickness of the α-Al2O3 layer reaches 0.5 μm, a raw material gas having the following composition is used: 2.2 volume % AlCl3, 8.3 volume % HCl, 3.0 volume % CO2, 0.6 volume % H2S, and the remainder is composed of H2. Thus, the first region is formed.

[0221] Next, from the time when the thickness of the α-Al2O3 layer exceeded 0.5 μm to the thickness (7 μm) obtained by subtracting 1 μm from the average thickness (8 μm) of the α-Al2O3 layer, the amount of HCl in the raw material gas was set to 6.7 volume %, and the amount of residual H2 was changed accordingly, and the raw material gas with the same formulation as that used in forming the first region was used. Thus, the second region was formed.

[0222] Next, the amount of HCl in the raw material gas was set to 8.3 volume % at 1 μm from the surface of the α-Al2O3 layer, and the amount of residual H2 was changed accordingly, and the raw material gas with the same formulation as that used in the film formation of the second region was used. Thus, the third region was formed.

[0223] <Evaluation of α-Al2O3 layer>

[0224] For the α-Al2O3 layer of each sample, the average particle size a of the first region, the average particle size b of the second region, the average particle size c of the third region, TC (0 0 12) and TC (1 1 0) were measured. The measurement method of these is the same as the method shown in Implementation Example 1, so the description thereof will not be repeated. The results are shown in the columns of "Particle size a", "Particle size b", "Particle size c", "TC (0 0 12)" and "TC (1 10)" in Table 5.

[0225] Furthermore, the value of b / a was calculated based on the average particle diameter a and the average particle diameter b. The results are shown in the "b / a" column of Table 5.

[0226] [Table 5]

[0227]

[0228] <Cutting Evaluation 1>

[0229] Using the cutting tool obtained above, a cutting test was carried out under the following cutting condition 1. Using 20 different cutting edges, each cutting edge was cut for 20 seconds to confirm whether there was any breakage. Here, "breakage" refers to a notch of 500 μm or more. Among the 20 cutting edges, the proportion of the cutting edges that were broken was calculated to obtain the breakage rate (%). That is, breakage rate (%) = (number of broken cutting edges / 20) × 100. When the breakage rate is less than 55%, it is judged that the cutting tool has excellent defect resistance and a long tool life. The results are shown in the "Cutting Evaluation 1 Breakage Rate (%)" column of Table 5.

[0230] (Cutting condition 1)

[0231] Cutting material: SCM440 (round bar with grooves)

[0232] Processing: Intermittent turning of the outer diameter of a round bar with grooves

[0233] Cutting speed: 120m / min

[0234] Feed rate: 0.1mm / revolution

[0235] Cutting amount: 2.0mm

[0236] Cutting fluid: None

[0237] The above cutting conditions correspond to efficient machining of high-hardness steel.

[0238] <Cutting Evaluation 2>

[0239] Using the cutting tool obtained above, a cutting test was carried out under the following cutting condition 2. The average wear amount Vb (mm) of the flank side of the cutting tool after cutting for 15 minutes was measured. Here, "average wear amount" refers to the length obtained by averaging the distance from the ridge to the end of the flank worn. When the average wear amount Vb is 0.21 mm or less, it is judged that the cutting tool has excellent wear resistance and a long tool life. The results are shown in the "Cutting Evaluation 2 Vb (mm)" column of Table 5.

[0240] (Cutting condition 2)

[0241] Cutting material: SUJ2

[0242] Processing: Round bar outer diameter turning

[0243] Cutting speed: 280m / min

[0244] Feed rate: 0.1mm / revolution

[0245] Cutting amount: 2.0mm

[0246] Cutting fluid: water-soluble cutting oil

[0247] The above cutting conditions correspond to efficient machining of high-hardness steel.

[0248] <Investigation>

[0249] The cutting tools of samples 1 to 3, 5, 7, 9, 12, 13, 15, 17, 19 to 28 correspond to the examples. It was confirmed that the samples of these examples have excellent defect resistance and wear resistance and a long tool life. In particular, it was confirmed that the wear resistance improvement effect is very excellent for wear in the form of uniform wear such as flank wear.

[0250] In the sample of the above-mentioned embodiment, in the substrate side region of the α-Al2O3 layer, the particle size of the α-Al2O3 particles gradually increases from the substrate side toward the tool surface side. Therefore, it is presumed that: the particle size of the α-Al2O3 layer near the surface is smaller than before, but the crack propagation distance from the tool surface is long, and the crack propagation in the substrate side region of the α-Al2O3 layer is suppressed, so the defect resistance is good.

[0251] The thickness of the α-Al2O3 layer of Sample 1 and Sample 2 is the same. The average particle size a, average particle size b and average particle size c of Sample 1 are the same as the average particle size a, average particle size b and average particle size c of Sample 2. In Sample 1, TC(0 0 12) is greater than TC(1 10). In Sample 2, TC(1 1 0) is greater than TC(0 0 12). It was confirmed that the wear resistance of Sample 1 is better than that of Sample 2. On the other hand, it was confirmed that the defect resistance of Sample 2 is better than that of Sample 1. From the above, it can be confirmed that when the thickness of the α-Al2O3 layer, the average particle size a of the first region, the average particle size b of the second region and the average particle size c of the third region are the same, the larger the TC(0 0 12), the higher the wear resistance, and the larger the TC(1 1 0), the higher the defect resistance. This tendency can also be confirmed from the comparison between Sample 10 and Sample 11.

[0252] Samples 4, 6, 8, 10, 11, 14, 16, 18, and 1-1 to 1-9 correspond to comparative examples, and these samples have insufficient defect resistance and / or wear resistance, and have short tool life.

[0253] As mentioned above, although the embodiment and the example of the present disclosure have been described, it is initially intended that the configurations of the above-described embodiments and the examples may be appropriately combined or various modifications may be made.

[0254] The embodiments and examples disclosed herein are illustrative in all aspects and are not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0255] Explanation of symbols

[0256] 1, 21, 31, 41 cutting tool, 10 substrate, 11 α-Al2O3 layer, 12 base layer, 13 surface layer, 14 intermediate layer, 15, 25, 35, 45 coating, A1 first region, A2 second region, A3 third region, P1, P3 interface, P2 surface, S1, S2, S3 virtual surface, B1 peak of P1, T1 valley of P1, LS1 baseline, L1, L2 lines.

Claims

1. A cutting tool comprising: A substrate, and a coating disposed on the substrate, The coating comprises an α-Al2O3 layer, The α-Al2O3 layer is composed of a plurality of α-Al2O3 particles. The α-Al2O3 layer includes a first region, a second region and a third region, The first region is a region sandwiched between the interface P1 on the substrate side of the α-Al 2 O 3 layer and a virtual plane S1 at a distance of 0.5 μm from the interface P1 to the surface side of the coating. The second region is a region sandwiched between the virtual surface S1 and a virtual surface S2 that is 1.0 μm away from the virtual surface S1 toward the surface side of the coating. The third region is a region sandwiched between the surface P2 of the α-Al2O3 layer or the interface P3 on the surface side of the film of the α-Al2O3 layer and a virtual plane S3 at a distance of 1.0 μm from the surface P2 or the interface P3 toward the substrate side. The average particle size a of the α-Al2O3 particles in the first region is not less than 0.10 μm and not more than 0.30 μm, The average particle size b of the α-Al2O3 particles in the second region is not less than 0.30 μm and not more than 0.50 μm, The average particle size c of the α-Al2O3 particles in the third region is greater than or equal to 0.10 μm and less than 0.30 μm, The ratio b / a of a to b is 1.5 or more and 5.0 or less.

2. The cutting tool according to claim 1, wherein: The average particle size c is not less than 0.12 μm and not more than 0.28 μm.

3. The cutting tool according to claim 2, wherein: The average particle size c is not less than 0.14 μm and not more than 0.26 μm.

4. The cutting tool according to claim 3, wherein: The average particle size c is not less than 0.16 μm and not more than 0.24 μm.

5. The cutting tool according to any one of claims 1 to 4, wherein: The average particle size a is not less than 0.12 μm and not more than 0.28 μm.

6. The cutting tool according to claim 5, wherein: The average particle size a is not less than 0.14 μm and not more than 0.26 μm.

7. The cutting tool according to claim 6, wherein: The average particle size a is not less than 0.16 μm and not more than 0.24 μm.

8. The cutting tool according to any one of claims 1 to 4, wherein: The average particle size b is not less than 0.32 μm and not more than 0.48 μm.

9. The cutting tool according to claim 8, wherein: The average particle size b is not less than 0.34 μm and not more than 0.46 μm.

10. The cutting tool according to claim 9, wherein: The average particle size b is not less than 0.36 μm and not more than 0.44 μm.

11. The cutting tool according to any one of claims 1 to 4, wherein: The b / a is 1.5 or more and 2.5 or less.

12. The cutting tool according to claim 11, wherein: The b / a is 1.7 or more and 2.3 or less.

13. The cutting tool according to claim 12, wherein: The b / a is 1.9 or more and 2.1 or less.

14. The cutting tool according to any one of claims 1 to 4, wherein: The average thickness of the α-Al 2 O 3 layer is greater than or equal to 3 μm and less than or equal to 15 μm.

15. The cutting tool according to any one of claims 1 to 4, wherein: The α-Al2O3 layer has a texture coefficient TC(h kl) of TC(0 0 12) of 3 or more.

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