Cutting tools

Abstract

Provided is a cutting tool comprising a substrate and a coating disposed on the substrate. The coating contains a first layer. The first layer has a multilayer structure in which a first unit layer and a second unit layer are alternately laminated. The average thickness of the first unit layer is 2-50 nm, the average thickness of the second unit layer is 2-50 nm, and the average thickness of the first layer is 1.0-20 μm. The first unit layer is made of TiaAl1-a-bBbN, where 0.30≤a≤0.50 and 0<b≤0.10. The second unit layer is made of TicAl1-cN, where 0.70≤c≤1.00. In the first layer, the percentage of the number of titanium atoms T2 with respect to the total number of titanium and aluminum atoms T1, (T2 / T1)×100, is at least 60%.

Description

Technical Field

[0001] The present disclosure relates to a cutting tool.

Background Art

[0002] Conventionally, for improving the performance of cutting tools, the development of coatings for coating the surfaces of base materials made of cemented carbide, cubic boron nitride sintered bodies, etc. has been advanced (for example, Patent Document 1, Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] The cutting tool of the present disclosure is a cutting tool including a base material and a coating provided on the base material, the coating includes a first layer, the first layer has a multilayer structure in which first unit layers and second unit layers are alternately laminated, the average thickness of the first unit layer is 2 nm or more and 50 nm or less, the average thickness of the second unit layer is 2 nm or more and 50 nm or less, the average thickness of the first layer is 1.0 μm or more and 20 μm or less, the first unit layer is composed of Ti b Al 1-a-b B b N, where 0.30 ≦ a ≦ 0.50, 0 < b ≦ 0.10 is satisfied, the second unit layer is composed of Ti c Al 1-c N, where 0.70 ≦ c ≦ 1.00 is satisfied, In the first layer, the percentage of the number of titanium atoms T2 relative to the total number of titanium and aluminum atoms T1 (T2 / T1) × 100 is 60% or more, which is the cutting tool. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the configuration of a cutting tool according to Embodiment 1. [Figure 1A] Figure 1A is a schematic cross-sectional view showing an example of the configuration of a cutting tool according to Embodiment 2. [Figure 2] Figure 2 is a diagram illustrating the measurement area when measuring the diameter of the largest inscribed circle of the crystal grains in the first layer. [Figure 3] Figure 3 is a diagram illustrating the method for measuring the diameter of the largest inscribed circle of the crystal grains in the first layer, and schematically shows a bright-field image of the measurement field. [Figure 3A] Figure 3A is a diagram illustrating the positional relationship between the crystal grains and the first and second unit layers. [Figure 4] Figure 4 is a schematic cross-sectional view showing an example of the configuration of a film deposition apparatus. [Figure 5] Figure 5 is a schematic cross-sectional view showing an example of the configuration of a film deposition apparatus. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] In recent years, the demand for cost reduction has been increasing, and there is a growing need for longer tool life. For example, in both high-speed, low-feed machining and low-speed, high-feed machining, there is a demand for cutting tools with long tool life.

[0007] Therefore, the purpose of this disclosure is to provide a cutting tool with a long tool life.

[0008] [Effects of this disclosure] The cutting tools of this disclosure can have a long tool life.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) The cutting tool of the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, where the coating includes a first layer, the first layer has a multilayer structure in which a first unit layer and a second unit layer are alternately laminated, the average thickness of the first unit layer is 2 nm or more and 50 nm or less, the average thickness of the second unit layer is 2 nm or more and 50 nm or less, the average thickness of the first layer is 1.0 μm or more and 20 μm or less, the first unit layer is composed of Ti a Al 1-a-b B b N, here, 0.30 ≦ a ≦ 0.50, 0 < b ≦ 0.10, is satisfied, the second unit layer is composed of Ti c Al 1-c N, here, 0.70 ≦ c ≦ 1.00, is satisfied, in the first layer, the percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number of titanium and aluminum atoms T1 is 60% or more. The cutting tool is as described above.

[0010] The cutting tool of the present disclosure can have a long tool life.

[0011] (2) In the above (1), the nanoindentation hardness of the first layer at 25 °C may be 30 GPa or more. According to this, the wear resistance of the cutting tool is improved.

[0012] (3) The cutting tool of the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, where the coating includes a first A layer, The first A layer has a multilayer structure in which the first unit layer and the third unit layer are alternately laminated, The average thickness of the first unit layer is 2 nm or more and 50 nm or less, The average thickness of the third unit layer is 2 nm or more and 50 nm or less, The average thickness of the first A layer is 1.0 μm or more and 20 μm or less, The first unit layer is Ti a Al 1-a-b B b and consists of N, Here, 0.30 ≦ a ≦ 0.50, 0 < b ≦ 0.10, which is satisfied, The third unit layer is Ti d Al 1-d-e B e and consists of N, Here, 0.70 ≦ d < 1.00, 0 < e ≦ 0.10, which is satisfied, In the first A layer, the percentage (T4 / T3)×100 of the number of titanium atoms T4 to the total number of titanium and aluminum atoms T3 is 60% or more, and it is a cutting tool.

[0013] The cutting tool of the present disclosure can have a long tool life.

[0014] (4) In the above (3), the nanoindentation hardness of the first A layer at 25°C may be 30 GPa or more. According to this, the wear resistance of the cutting tool is improved.

[0015] [Details of Embodiments of the Present Disclosure] Specific examples of the cutting tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same parts or corresponding parts. Also, dimensional relationships such as length, width, thickness, depth, etc. are appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0016] In this disclosure, the notation "A~B" means an upper and lower limit of the range (i.e., A or greater and B or less), and if there is no unit specified for A, but a unit is specified only for B, then the unit for A and the unit for B are the same.

[0017] In this disclosure, when compounds and other elements are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range. For example, when "TiN" is written, the ratio of the number of atoms constituting TiN includes all conventionally known atomic ratios.

[0018] In this disclosure, if one or more numerical values ​​are listed as the lower limit and upper limit of a numerical range, any combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit shall also be disclosed. For example, if the lower limit is listed as a1 or greater, b1 or greater, c1 or greater, and the upper limit is listed as a2 or less, b2 or less, c2 or less, then the following shall be disclosed: a1 or greater and a2 or less, a1 or greater and b2 or less, a1 or greater and c2 or less, b1 or greater and a2 or less, b1 or greater and b2 or less, b1 or greater and c2 or less, c1 or greater and a2 or less, c1 or greater and b2 or less, c1 or greater and c2 or less.

[0019] [Embodiment 1: Cutting Tool] The cutting tool in one embodiment of this disclosure (hereinafter also referred to as "Embodiment 1") is A cutting tool comprising a base material and a coating provided on the base material, The coating includes a first layer, The first layer consists of a multilayer structure in which a first unit layer and a second unit layer are stacked alternately. The average thickness of the first unit layer is 2 nm or more and 50 nm or less. The average thickness of the second unit layer is 2 nm or more and 50 nm or less. The average thickness of the first layer is 1.0 μm or more and 20 μm or less. The first unit layer is Ti a Al 1-a-b B b It consists of N, Here, 0.30 ≤ a ≤ 0.50, 0 < b ≤ 0.10, and satisfies The second unit layer is Ti c Al 1-c N and consists of Here, 0.70 ≤ c ≤ 1.00, and satisfies In the first layer, the percentage (T2 / T1)×100 of the number of titanium atoms T2 to the total number of titanium and aluminum atoms T1 is 60% or more, and it is a cutting tool.

[0020] The cutting tool of the present disclosure can have a long tool life. The reason is speculated as follows.

[0021] (i) The coating of the cutting tool of the present disclosure includes a first layer having a multilayer structure in which the first unit layer and the second unit layer are alternately laminated. The first unit layer and the second unit layer have different compositions from each other. Therefore, near the interface between the first unit layer and the second unit layer, the progress of cracks from the surface of the coating generated during the use of the cutting tool can be suppressed. In addition, since the average thickness of each of the first unit layer and the second unit layer is 2 nm or more and 50 nm or less, and the average thickness of the first layer is 1.0 μm or more and 20 μm or less, the number of laminations of the first unit layer and the second unit layer in the first layer is large, and the effect of suppressing the progress of cracks is further improved. Therefore, large-scale damage to the coating can be suppressed, and the tool life of the cutting tool is prolonged.

[0022] (ii) The first unit layer is Ti a Al 1-a-b B b N (where 0.30 ≤ a ≤ 0.50 and 0 < b ≤ 0.10 are satisfied). The first unit layer has improved hardness due to the addition of a small amount of boron (B) to TiAlN. The second unit layer is Ti c Al 1-cThe first layer consists of N (where 0.70 ≤ c ≤ 1.00). The second unit layer has a high titanium (Ti) content and excellent high-temperature stability. In this disclosure, the first layer has a multilayer structure in which a first unit layer with high hardness and a second unit layer with excellent high-temperature stability are alternately stacked, so that stable hardness is obtained even at high temperatures and crater wear resistance is improved. Crater wear is wear that occurs mainly on the rake face of the cutting tool, caused by frictional heat between the cutting tool and the chip. Furthermore, since the first layer has a multilayer structure in which a first unit layer with high hardness and a second unit layer with lower hardness than the first unit layer are alternately stacked, fracture resistance is also improved. Therefore, the crater wear resistance and fracture resistance of the coating are improved in a balanced manner, and the tool life of the cutting tool is extended.

[0023] (iii) The first unit layer and the second unit layer have different Ti and Al content. As a result, the first unit layer and the second unit layer have different crystal lattices, causing crystal lattice distortion in the first layer, which allows the first layer to have high hardness.

[0024] (iv) In the first layer, the percentage of the number of titanium atoms T2 relative to the total number of titanium and aluminum atoms T1 (T2 / T1) × 100 is 60% or more. According to this, the first layer can have excellent crater wear resistance, and the tool life of the cutting tool will be extended.

[0025] <Cutting tools> The cutting tool of Embodiment 1 is not particularly limited in shape, application, etc., as long as it is a cutting tool. The cutting tool of Embodiment 1 may be, for example, a drill, an end mill, an replaceable tip for milling, an replaceable tip for turning, a metal saw, a gear cutting tool, a reamer, a tap, or an insert for pin milling of a crankshaft.

[0026] Figure 1 is a schematic partial cross-sectional view showing an example of the configuration of a cutting tool according to Embodiment 1. The cutting tool 100 comprises a base material 10 and a coating 20 provided on the base material 10. The coating 20 includes a first layer 21, and the first layer 21 has a multilayer structure in which a first unit layer 1 and a second unit layer 2 are alternately stacked.

[0027] ≪Base material≫ The base material 10 is not particularly limited. The base material 10 may be made of, for example, cemented carbide, cermet, high-speed steel, ceramics, cubic boron nitride sintered body, and diamond sintered body. The base material 10 is preferably made of cemented carbide because cemented carbide has excellent wear resistance.

[0028] A cemented carbide is a sintered body primarily composed of WC (tungsten carbide) particles. A cemented carbide contains a hard phase and a binder phase. The hard phase contains WC particles. The binder phase binds the WC particles together. The binder phase contains, for example, Co (cobalt). The binder phase may further contain, for example, TiC (titanium carbide), TaC (tantalum carbide), NbC (niobium carbide), etc.

[0029] Carbide alloys may contain impurities that are inevitably introduced during their manufacturing process. Carbide alloys may also contain free carbon or abnormal layers referred to as "η layers" in their structure. Furthermore, carbide alloys may be surface-modified. For example, carbide alloys may contain de-β layers on their surface.

[0030] The cemented carbide may contain 85% to 98% by mass of WC particles and 2% to 15% by mass of Co. The average particle size of the WC particles may be 0.2 μm to 4 μm.

[0031] Co is softer than WC particles. As described later, the soft Co can be removed by applying ion bombardment treatment to the surface of the substrate 10. Since the cemented carbide has the above composition and the WC particles have the above average particle size, a moderate level of unevenness is formed on the surface after the Co is removed. By forming a coating 20 on such a surface, an anchoring effect is exhibited, and it is believed that the adhesion between the coating 20 and the substrate 10 is improved.

[0032] Here, the particle size of the WC particles is defined as the diameter of the circle circumscribing the two-dimensional projection image of the WC particles. The particle size is measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). That is, the cemented carbide is cut, and the cut surface is observed with an SEM or TEM. In the observed image, the diameter of the circle circumscribing the WC particles is considered to be the particle size of the WC particles. In the observed image, the particle sizes of 10 or more (preferably 50 or more, more preferably 100 or more) randomly selected WC particles are measured, and the arithmetic mean is taken as the average particle size of the WC particles. For observation, it is desirable to prepare the cut surface by cross-section polishing using a cross-section polisher (CP) or a focused ion beam (FIB), etc.

[0033] ≪Coating≫ The coating 20 is provided on the substrate 10. The coating 20 may be provided on a part of the surface of the substrate 10 or on the entire surface. However, the coating 20 is provided on at least the portion of the surface of the substrate 10 corresponding to the cutting edge. In this disclosure, the portion of the surface of the substrate 10 corresponding to the cutting edge means an area on the surface of the substrate 10 within a distance of at least 500 μm or 2 mm from the cutting edge. As long as the effects of this disclosure are not impaired, the absence of a coating on at least a portion of the portion corresponding to the cutting edge does not constitute a departure from the scope of this disclosure.

[0034] The coating 20 includes a first layer 21. The coating 20 may include other layers together with the first layer 21, as long as they do not impair the effects of the present disclosure. For example, the coating 20 may include one or both of a second layer 22 provided between the substrate 10 and the first layer 21 and a third layer 23 provided on the outermost surface of the coating 20. A known underlayer may be applied to the second layer. Examples of such underlayers include a TiCN layer, a TiN layer, or a TiCNO layer. A known surface layer may be applied to the third layer. Examples of such surface layers include a TiC layer, a TiN layer, or a TiCN layer.

[0035] The lamination structure of the coating 20 does not need to be uniform throughout the entire coating 20; the lamination structure may differ in parts.

[0036] The thickness of the coating 20 may be between 1.0 μm and 25 μm. A thickness of 1.0 μm or more improves abrasion resistance. A thickness of 25 μm or less improves chipping resistance. The thickness of the coating 20 may also be between 2.0 μm and 16 μm, or between 3.0 μm and 12 μm. Here, the thickness of the coating refers to the sum of the thicknesses of each layer constituting the coating. Examples of "layers constituting the coating" include the first layer, the second layer, the third layer, etc.

[0037] The thickness of each layer constituting the coating is measured by obtaining a thin section sample (hereinafter also referred to as "cross-sectional sample") with a cross-section parallel to the normal direction of the surface of the cutting tool, and observing the cross-sectional sample with a scanning transmission electron microscope (STEM). An example of a scanning transmission electron microscope is the JEM-2100F (product name) manufactured by JEOL Ltd. The observation magnification of the cross-sectional sample is set to 5000 to 10000 times, and the thickness of each layer is measured at five points, and the arithmetic mean of these measurements is defined as the "thickness of each layer."

[0038] As long as the same cutting tool is used for measurement, it has been confirmed that there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0039] ≪First layer≫ The first layer 21 consists of a multilayer structure in which first unit layers 1 and second unit layers 2 are alternately stacked. The number of layers is not particularly limited, as long as the average thickness of each of the first unit layers 1 and second unit layers 2 is 2 nm or more and 50 nm or less, and the average thickness of the first layer is 1.0 μm or more and 20 μm or less. The number of layers refers to the number of first unit layers 1 and second unit layers 2 each contained in the first layer 21. The number of layers may be 10 or more and 5000 or less, 200 or more and 500 or more and 500 or more and 1000 or less. In the first layer 21, the layer closest to the substrate 10 may be either the first unit layer 1 or the second unit layer 2. Also, in the first layer 21, the layer furthest from the substrate 10 may be either the first unit layer 1 or the second unit layer 2.

[0040] The average thickness of the first layer is 1.0 μm or more and 20 μm or less. An average thickness of 1.0 μm or more for the first layer improves wear resistance. An average thickness of 20 μm or less for the first layer improves chipping resistance. The lower limit of the average thickness of the first layer is 1.0 μm or more, and may be 2.0 μm or more, or 3.0 μm or more. The upper limit of the average thickness of the first layer is 20 μm or less, and may be 18 μm or less, 16 μm or less, or 12 μm or less. The average thickness of the first layer is 1.0 μm or more and 20 μm or less, and may be 2.0 μm or more and 16 μm or less, or 3.0 μm or more and 12 μm or less.

[0041] ≪Average thickness of the first and second unit layers≫ The average thickness of the first unit layer 1 is between 2 nm and 50 nm, and the average thickness of the second unit layer 2 is between 2 nm and 50 nm. In the first layer, the alternating stacking of such thin layers can suppress crack propagation. If the average thickness of one or both of the first unit layer 1 and the second unit layer 2 is less than 2 nm, the compositions of the first unit layer 1 and the second unit layer 2 may mix, potentially reducing the crack propagation suppression effect. If the average thickness of one or both of the first unit layer 1 and the second unit layer 2 is greater than 50 nm, potentially reducing the delamination suppression effect. The average thickness of the first unit layer and the average thickness of the second unit layer may be the same or different.

[0042] The lower limit of the average thickness of the first unit layer is 2 nm or more, but may also be 4 nm or more, 6 nm or more, or 8 nm or more. The upper limit of the average thickness of the first unit layer is 50 nm or less, but may also be 46 nm or less, 40 nm or less, or 30 nm or less. The average thickness of the first unit layer is 2 nm or more and 50 nm or less, but may also be 4 nm or more and 40 nm or less, or 6 nm or more and 30 nm or less.

[0043] The lower limit of the average thickness of the second unit layer is 2 nm or more, but may also be 4 nm or more, 6 nm or more, or 8 nm or more. The upper limit of the average thickness of the second unit layer is 50 nm or less, but may also be 46 nm or less, 40 nm or less, or 30 nm or less. The average thickness of the second unit layer is 2 nm or more and 50 nm or less, but may also be 4 nm or more and 40 nm or less, or 6 nm or more and 30 nm or less.

[0044] The method for measuring the average thickness of each of the first unit layer and the second unit layer is as follows. A thin sample of the cross-section of the cutting tool parallel to the normal direction of the surface of the cutting tool (hereinafter, also referred to as "cross-section sample") is obtained. The cross-section sample is observed with a scanning transmission electron microscope (STEM). Examples of the scanning transmission electron microscope include JEM-2100F (trade name) manufactured by JEOL Ltd. The observation magnification of the cross-section sample shall be appropriately adjusted according to the thicknesses of the first unit layer 1 and the second unit layer 2. For example, the observation magnification can be about 1 million times. In one first unit layer, the thicknesses at 5 locations are measured. The arithmetic mean value of the thicknesses at the 5 locations of the first unit layer is calculated, and this arithmetic mean value is taken as the average thickness of the first unit layer. In one second unit layer, the thicknesses at 5 locations are measured.

[0045] For each of the five different first unit layers, the average thickness of the first unit layer is measured by the above procedure. The arithmetic mean value of the average thicknesses of the five first unit layers is obtained. In the present disclosure, this arithmetic mean value is taken as the average thickness of the first unit layer. For each of the five different second unit layers, the average thickness of the second unit layer is measured by the above procedure. The arithmetic mean value of the average thicknesses of the five second unit layers is obtained. In the present disclosure, this arithmetic mean value is taken as the average thickness of the second unit layer.

[0046] As long as the measurement is performed with the same cutting tool, it has been confirmed that there is no variation in the measurement results even if the measurement locations are arbitrarily selected.

[0047] ≪Composition of the first unit layer and the second unit layer≫ In the cutting tool of the present disclosure, the first unit layer is composed of Ti a Al 1-a-b B b N, where 0.30 ≤ a ≤ 0.50, 0 < b ≤ 0.10 are satisfied, and the second unit layer is composed of Ti c Al 1-c N, where 0.70 ≤ c ≤ 1.00 is satisfied. As long as the effects of the present disclosure are not impaired, the first unit layer can contain impurities together with Ti a Al 1-a-b B b N. The first unit layer is Ti a Al1-a-b B b It can consist of N and impurities. The second unit layer may be Ti, as long as it does not impair the effects of the present disclosure. c Al 1-c It can contain impurities along with N. The second unit layer is Ti c Al 1-c It can consist of N and impurities. Examples of impurities include carbon (C) and oxygen (O).

[0048] In the first unit layer, the lower limit of a is 0.30 or greater, but may also be 0.35 or greater, or 0.37 or greater. The upper limit of a is 0.50 or less, but may also be 0.45 or less, or 0.40 or less. a may also be 0.35 ≤ a ≤ 0.45, or 0.37 ≤ a ≤ 0.40.

[0049] In the first unit layer, the lower limit of b is greater than 0, and may be greater than or equal to 0.01, 0.02, or 0.04. The upper limit of b is less than or equal to 0.10, and may be less than or equal to 0.08 or 0.07. b may also be 0.01 ≤ b ≤ 0.08 or 0.02 ≤ b ≤ 0.07.

[0050] In the second unit layer, the lower limit of c is 0.70 or greater, but may also be 0.75 or greater, or 0.80 or greater. The upper limit of c is 1.00 or less, but may also be 0.95 or less, or 0.90 or less. c may also be 0.75 ≤ d ≤ 0.95, or 0.80 ≤ d ≤ 0.90.

[0051] Ti in the first unit layer a Al 1-a-b B b a, b and Ti in the second unit layer in N c Al 1-cc in N is determined by measuring the composition of each layer using energy dispersive X-ray spectrometry (EDX). For compositional analysis, an EDX unit attached to a transmission electron microscope (TEM-EDX) is used. An example of an EDX unit is the JED-2300™ manufactured by JEOL Ltd.

[0052] The above compositional analysis is performed using the following procedure: A thin section sample (hereinafter also referred to as "cross-sectional sample") is obtained, with a cross-section parallel to the normal direction of the surface of the cutting tool. While observing the cross-sectional sample with a TEM, EDX analysis is performed at five arbitrarily selected points within one first unit layer 1 or one second unit layer 2. The first and second unit layers can be distinguished by the difference in contrast. Here, the "five arbitrarily selected points" shall be selected from different crystal grains. The composition of the first and second unit layers is determined by taking the arithmetic mean of the composition ratios of each element obtained from the five measurements.

[0053] For each of the five different first unit layers, the composition of the first unit layer is determined using the procedure described above. In this disclosure, the average of the compositions of the five first unit layers is defined as the composition of the first unit layer, and based on this, a and b are identified. For each of the five different second unit layers, the composition of the second unit layer is determined using the procedure described above. In this disclosure, the average of the compositions of the five second unit layers is defined as the composition of the second unit layer, and based on this, c is identified.

[0054] As long as the same cutting tool is used for measurement, it has been confirmed that there is no variation in the measurement results even if the measurement point is arbitrarily selected.

[0055] ≪Composition of the first layer≫ In the first layer, the percentage of the number of titanium atoms T2 relative to the total number of titanium and aluminum atoms T1 (T2 / T1) × 100 (hereinafter also referred to as "percentage (T2 / T1) × 100") is 60% or more. According to this, the first layer can have excellent crater wear resistance. The lower limit of percentage (T2 / T1) × 100 is 60% or more from the viewpoint of improving crater wear resistance, but may also be 63% or more, or 66% or more. The upper limit of percentage (T2 / T1) × 100 is 80% or less, may also be 77% or less, or may also be 75% or less from the viewpoint of improving oxidation resistance. Percentage (T2 / T1) × 100 may be 60% or more and 80% or less, may also be 63% or more and 77% or less, or may also be 66% or more and 75% or less.

[0056] The percentage (T2 / T1) × 100 in the first layer is measured using TEM-EDX. An example of an EDX instrument is the JED-2300 (product name) manufactured by JEOL Ltd. The percentage (T2 / T1) × 100 is measured using the following procedure.

[0057] A thin section sample (hereinafter also referred to as "cross-sectional sample") is obtained, with the cross-section parallel to the normal direction of the surface of the cutting tool. While observing the cross-sectional sample with a TEM, EDX analysis is performed in five arbitrarily selected fields of view within the first layer to measure the percentage of the number of titanium atoms T2 relative to the total number of titanium and aluminum atoms T1 (T2 / T1) × 100. Here, the "five arbitrarily selected fields of view" are set so as not to overlap with each other. The range of one field of view is 200 × 200 nm. In this disclosure, the arithmetic mean of the percentages (T2 / T1) × 100 obtained from the measurements of the five fields of view is defined as the percentage (T2 / T1) × 100 in the first layer.

[0058] As long as the same cutting tool is used for measurement, it has been confirmed that there is no variation in the measurement results even if the measurement point is arbitrarily selected.

[0059] ≪Nanoindentation hardness of the first layer≫ The nanoindentation hardness of the first layer at 25°C may be 30 GPa or higher. This improves the wear resistance of the cutting tool. The lower limit of the nanoindentation hardness may be 32 GPa or higher, or 34 GPa or higher. The upper limit of the nanoindentation hardness is not particularly limited, but from a manufacturing standpoint, it may be 60 GPa or lower, 40 GPa or lower, or 36 GPa or lower. The nanoindentation hardness may be 30 GPa or higher and 60 GPa or lower, 32 GPa or higher and 60 GPa or lower, or 34 GPa or higher and 60 GPa or lower.

[0060] The nanoindentation hardness of the first layer at 25°C is measured by nanoindentation according to the standard procedure specified in "ISO 14577-1: 2015 Metallic materials - Instrumented indentation test for hardness and materials parameters -". The measuring instrument used is the "ENT-1100a" manufactured by Elionix. The indentation load of the indenter is set to 1g. The indenter is pressed into the first layer in a direction perpendicular to the cross-section (i.e., parallel to the surface of the cutting tool) in a cross-section parallel to the normal direction of the surface of the cutting tool.

[0061] The above measurements are performed at five locations on a single sample. The average of the nanoindentation hardness values ​​from these five locations is taken as the nanoindentation hardness of the first layer. Any data that appears to be an anomaly will be excluded.

[0062] As long as the same cutting tool is used for measurement, it has been confirmed that there is no variation in the measurement results even if the measurement point is arbitrarily selected.

[0063] ≪Diameter of the largest inscribed circle of the crystal grains in the first layer≫ The first layer consists of multiple crystal grains, and the diameter of the largest inscribed circle of the crystal grains may be between 5 nm and 500 nm. This improves the crater wear resistance of the cutting tool. The first layer of this disclosure may include, to the extent that it does not impair the effects of this disclosure, regions that do not constitute crystal grains (regions with random atomic arrangement) along with the multiple crystal grains.

[0064] The upper limit of the diameter of the maximum inscribed circle of the above crystal grain may be 500 nm or less, 450 nm or less, or 400 nm or less, from the viewpoint of improving wear resistance and fracture resistance. The lower limit of the diameter of the maximum inscribed circle of the crystal grain may be 5 nm or more, 7 nm or more, or 10 nm or more, from the viewpoint of suppressing a decrease in film hardness due to excessive grain refinement. The diameter of the maximum inscribed circle of the crystal grain may be 5 nm or more and 500 nm or less, 7 nm or more and 450 nm or less, or 10 nm or more and 400 nm or less.

[0065] The method for measuring the diameter of the largest inscribed circle of the above crystal grain is as follows: Obtain a thin section sample (thickness: approximately 10-100 nm, hereinafter also referred to as "section sample") of the cross-section of the cutting tool parallel to the normal direction of the cutting tool's surface. Observe the section sample with a transmission electron microscope (TEM) and obtain a bright-field image. The observation magnification should be 1 million to 5 million times. The bright-field image should be obtained so as shown in Figure 2, including a region A sandwiched between line L2, which is 0.2 μm from line L1 indicating the center of the average thickness direction of the first layer to the substrate side, and line L3, which is 0.2 μm from line L1 to the surface side of the coating. Within region A, arbitrarily set a rectangular measurement field of view of 150 nm × 150 nm.

[0066] Within the measurement field described above, regions with an atomic arrangement of ±0.5° or less are identified and defined as crystal grains. The method for identifying regions with an atomic arrangement of ±0.5° or less and crystal grains will be explained using Figure 3.

[0067] Figure 3 is a schematic diagram showing an example of a bright-field image of the measurement field described above. In Figure 3, atoms are indicated by black dots labeled with symbol 50. Note that only a portion of the atoms are shown in Figure 3. In the bright-field image, the regularly arranged atoms 50 are connected by line segments that result in the closest interatomic distance. In Figure 3, these line segments are indicated by L10-L14, L20-L22, and L30-L34. The region where the angle between the line segments is ±0.5° or less (i.e., between -0.5° and 0.5°) is defined as a crystal grain.

[0068] In Figure 3, the angle between line segments L10 to L14 is ±0.5° or less, and the region containing these line segments corresponds to crystal grain 24a. The angle between line segments L20 to L22 is ±0.5° or less, and the region containing these line segments corresponds to crystal grain 24b. The angle between line segments L30 to L34 is ±0.5° or less, and the region containing these line segments corresponds to crystal grain 24c.

[0069] Determine the diameter of the largest inscribed circle for each crystal grain within the measurement field described above. The diameter of the largest inscribed circle refers to the diameter of the largest inscribed circle that can be drawn inside the crystal grain and that contacts at least a portion of the outer edge of the crystal grain.

[0070] In Figure 3, the diameter of the largest inscribed circle 25a of crystal grain 24a is D1. The diameter of the largest inscribed circle 25b of crystal grain 24b is D2. The diameter of the largest inscribed circle 25c of crystal grain 24c is D3. When D1, D2, and D3 are all 50 nm or less, it is confirmed that the first layer shown in Figure 3 consists of multiple crystal grains, and the diameter of the largest inscribed circle of each crystal grain is 50 nm or less.

[0071] As long as the same cutting tool is used for measurement, it has been confirmed that there is no variation in the measurement results of the diameter of the largest inscribed circle of the crystal grain, even when the above measurement field of view is arbitrarily set.

[0072] In Figure 3, spaces exist between crystal grains 24a, 24b, and 24c, but in reality, crystal grains exist within these spaces. Since the thickness of the cross-sectional sample for TEM is approximately 10-100 nm, the bright-field image also reflects information in the depth direction. In regions where multiple crystal grains overlap in the thickness direction of the sample, a regular atomic arrangement cannot be observed in the bright-field image. Therefore, these overlapping regions are not identified as crystal grains using the above identification method.

[0073] ≪Positional relationship between crystal grains and the first and second unit layers≫ The positional relationship between the crystal grains and the first and second unit layers will be explained using Figure 3A. Figure 3A is a schematic diagram showing a cross-section along the film thickness direction of the first layer of Embodiment 1. As shown in Figure 3A, the first layer 21 consists of a multilayer structure in which the first unit layer 1 and the second unit layer 2 are alternately stacked. Figure 3A shows a plurality of crystal grains 24, and the boundaries between the crystal grains 24 are shown as crystal grain boundaries 25. Each crystal grain 24 can consist only of the first unit layer or the second unit layer. Furthermore, each crystal grain 24 can exist across one or more first unit layers and one or more second unit layers. That is, each crystal grain 24 can have a lamellar structure in which the first unit layer and the second unit layer are alternately stacked.

[0074] [Embodiment 2: Cutting Tools] The cutting tool in one embodiment of this disclosure (hereinafter also referred to as "Embodiment 2") is A cutting tool comprising a base material and a coating provided on the base material, The coating includes a first A layer, The aforementioned 1A layer consists of a multilayer structure in which a first unit layer and a third unit layer are alternately stacked. The average thickness of the first unit layer is 2 nm or more and 50 nm or less. The average thickness of the third unit layer is between 2 nm and 50 nm. The average thickness of the 1A layer is 1.0 μm or more and 20 μm or less. The first unit layer is Ti a Al 1-a-b B bconsisting of N, Here, 0.30 ≤ a ≤ 0.50, 0 < b ≤ 0.10, and satisfies the third unit layer is Ti d Al 1-d-e B e consisting of N, Here, 0.70 ≤ d < 1.00, 0 < e ≤ 0.10, and satisfies In the first A layer, the percentage (T4 / T3)×100 of the number of titanium atoms T4 to the total number of titanium and aluminum atoms T3 is 60% or more, and it is a cutting tool.

[0075] The cutting tool of the present disclosure can have a long tool life. The reason is presumed as follows.

[0076] (i) The coating of the cutting tool of the present disclosure includes a first A layer having a multilayer structure in which the first unit layer and the third unit layer are alternately laminated. The first unit layer and the third unit layer have different compositions from each other. Therefore, near the interface between the first unit layer and the third unit layer, the progress of cracks from the surface of the coating generated during the use of the cutting tool can be suppressed. Further, since the average thickness of each of the first unit layer and the third unit layer is 2 nm or more and 50 nm or less, and the average thickness of the first A layer is 1.0 μm or more and 20 μm or less, the number of laminations of the first unit layer and the third unit layer in the first A layer is large, and the effect of suppressing the progress of cracks is further improved. Thus, large-scale damage to the coating can be suppressed, and the tool life of the cutting tool is prolonged.

[0077] (ii) The first unit layer is Ti a Al 1-a-b B b N (where 0.30 ≤ a ≤ 0.50, 0 < b ≤ 0.10 is satisfied). The first unit layer has improved hardness due to the addition of a small amount of boron (B) to TiAlN. The third unit layer is Ti d Al 1-d-e B eIt consists of N (where 0.70 ≤ d < 1.00 and 0 < e ≤ 0.10). In the third unit layer, a small amount of boron (B) is added to TiAlN, improving the hardness. The third unit layer has a high Ti content and excellent high-temperature stability. In the present disclosure, since the first A layer has a multilayer structure in which the high-hardness first unit layer and the third unit layer with excellent high-temperature stability are alternately laminated, stable hardness can be obtained even at high temperatures, and crater wear resistance is improved. Further, since the first A layer has a multilayer structure in which the high-hardness first unit layer and the third unit layer with a lower hardness than the first unit layer are alternately laminated, chipping resistance is also improved. Therefore, the crater wear resistance and chipping resistance of the coating are improved in a balanced manner, and the tool life of the cutting tool is prolonged.

[0078] (iii) The first unit layer and the third unit layer have different Ti contents and Al contents. Therefore, the crystal lattices of the first unit layer and the third unit layer are different, lattice strain occurs in the first A layer, and the first A layer can have high hardness.

[0079] (iv) In the first A layer, the percentage (T4 / T3)×100 of the number of Ti atoms T4 to the total number of Ti and Al atoms T3 is 60% or more. According to this, the first A layer can have excellent crater wear resistance and chipping resistance, and the tool life of the cutting tool is prolonged.

[0080] <Cutting tool> The cutting tool of Embodiment 2 can have basically the same configuration as the cutting tool of Embodiment 1 except for the configuration of the first A layer. FIG. 1A is a schematic partial cross-sectional view showing an example of the configuration of the cutting tool of Embodiment 2. The cutting tool 100 includes a substrate 10 and a coating 20 provided on the substrate 10. The coating 20 includes a first A layer 21A, and the first A layer 21A has a multilayer structure in which the first unit layer 1 and the third unit layer 3 are alternately laminated.

[0081] In Embodiment 2, the cutting tool and substrate can have the same configuration as in Embodiment 1. In Embodiment 2, the coating can have the same configuration as in Embodiment 1, except for the configuration of the first A layer. The "first A layer" will be described below.

[0082] ≪Layer 1A≫ The first A layer 21A consists of a multilayer structure in which first unit layers 1 and third unit layers 3 are alternately stacked. The number of layers is not particularly limited, as long as the average thickness of each of the first unit layers 1 and third unit layers 3 is 2 nm or more and 50 nm or less, and the average thickness of the first A layer is 1.0 μm or more and 20 μm or less. The number of layers refers to the number of first unit layers 1 and third unit layers 3 each included in the first A layer 21A. The number of layers may be 10 or more and 5000 or less, 200 or more and 500 or more and 500 or more and 1000 or less. In the first A layer, the layer closest to the substrate 10 may be either the first unit layer 1 or the third unit layer 3. Also, in the first A layer, the layer furthest from the substrate 10 may be either the first unit layer 1 or the third unit layer 3.

[0083] The average thickness of the 1A layer is 1.0 μm or more and 20 μm or less. An average thickness of 1.0 μm or more improves wear resistance. An average thickness of 20 μm or less improves chipping resistance. The lower limit of the average thickness of the 1A layer is 1.0 μm or more, and may be 2.0 μm or more, or 3.0 μm or more. The upper limit of the average thickness of the 1A layer is 20 μm or less, and may be 18 μm or less, 16 μm or less, or 12 μm or less. The average thickness of the 1A layer is 1.0 μm or more and 20 μm or less, and may be 2.0 μm or more and 16 μm or less, or 3.0 μm or more and 12 μm or less.

[0084] ≪Average thickness of the first and third unit layers≫ The average thickness of the first unit layer can be as described in Embodiment 1.

[0085] The lower limit of the average thickness of the third unit layer is 2 nm or more, and may be 4 nm or more, 6 nm or more, or 8 nm or more. The upper limit of the average thickness of the third unit layer is 50 nm or less, and may be 46 nm or less, 40 nm or less, or 30 nm or less. The average thickness of the third unit layer is 2 nm or more and 50 nm or less, and may be 4 nm or more and 40 nm or less, or 6 nm or more and 30 nm or less.

[0086] The average thickness of the first unit layer and the average thickness of the third unit layer may be the same or different. The average thickness of each of the first unit layer and the third unit layer is measured by reading the second unit layer as the third unit layer in the measurement method of the average thickness of each of the first unit layer and the second unit layer described in Embodiment 1.

[0087] ≪Composition of the first unit layer and the third unit layer≫ In the cutting tool of the present disclosure, the first unit layer is Ti a Al 1-a-b B b N, where 0.30 ≤ a ≤ 0.50, 0 < b ≤ 0.10 are satisfied, and the third unit layer is Ti d Al 1-d-e B e N, where 0.70 ≤ d < 1.00, 0 < e ≤ 0.10 are satisfied. As long as the effects of the present disclosure are not impaired, the first unit layer can contain impurities together with Ti a Al 1-a-b B b N. The first unit layer can consist of Ti a Al 1-a-b B b N and impurities. As long as the effects of the present disclosure are not impaired, the third unit layer can contain impurities together with Ti d Al 1-d-e B e N. The third unit layer can consist of Ti d Al 1-d-e B e N and impurities. Examples of the impurities include carbon (C) and oxygen (O).

[0088] The composition of the first unit layer can be as described in Embodiment 1.

[0089] In the third unit layer, the lower limit of d is 0.70 or greater, but may also be 0.75 or greater, or 0.80 or greater. The upper limit of d is less than 1.00, but may also be 0.99 or less, or 0.95 or less, or 0.90 or less. d may also be 0.70 ≤ d ≤ 0.99, 0.75 ≤ d ≤ 0.99, or 0.80 ≤ d ≤ 0.95.

[0090] In the third unit layer, the lower limit of e is greater than 0, and may be greater than or equal to 0.01, 0.02, or 0.04. The upper limit of b is less than or equal to 0.10, and may be less than or equal to 0.08 or 0.06. b may also be 0.01 ≤ b ≤ 0.08 or 0.02 ≤ b ≤ 0.06.

[0091] Ti in the first unit layer a Al 1-a-b B b a, b and Ti in the third unit layer in N d Al 1-d-e B e In N, d and e are determined by measuring the composition of each layer using energy dispersive X-ray spectrometry (EDX). Specifically, in the method for measuring the composition of the first and second unit layers described in Embodiment 1, the second unit layer is replaced with the third unit layer for measurement.

[0092] ≪Composition of Layer 1A≫ In the 1A layer, the percentage of the number of titanium atoms T4 relative to the total number of titanium and aluminum atoms T3 (T4 / T3) × 100 (hereinafter also referred to as "percentage (T4 / T3) × 100") is 60% or more. According to this, the 1A layer can have excellent crater wear resistance. The lower limit of percentage (T4 / T3) × 100 is 60% or more from the viewpoint of improving crater wear resistance, but may also be 63% or more, or 66% or more. The upper limit of percentage (T4 / T3) × 100 is 80% or less, may also be 77% or less, or may also be 75% or less from the viewpoint of improving oxidation resistance. Percentage (T4 / T3) × 100 may be 60% or more and 80% or less, may also be 63% or more and 77% or less, or may also be 66% or more and 75% or less.

[0093] The percentage (T4 / T3) × 100 in layer 1A is measured using TEM-EDX. Specifically, in the method for measuring the percentage (T2 / T1) × 100 in the first layer described in Embodiment 1, the measurement is performed by substituting "first layer" with "layer 1A".

[0094] ≪Nanoindentation hardness of the 1A layer≫ The nanoindentation hardness of the 1A layer at 25°C may be 30 GPa or higher. This improves the wear resistance of the cutting tool. The lower limit of the nanoindentation hardness may be 32 GPa or higher, or 34 GPa or higher. The upper limit of the nanoindentation hardness is not particularly limited, but from a manufacturing standpoint, it may be 60 GPa or lower, 40 GPa or lower, or 36 GPa or lower. The nanoindentation hardness may be 30 GPa or higher and 60 GPa or lower, 32 GPa or higher and 60 GPa or lower, or 34 GPa or higher and 60 GPa or lower.

[0095] The nanoindentation hardness of the 1A layer at 25°C is measured in the method for measuring the nanoindentation hardness of the 1 layer at 25°C described in Embodiment 1, by substituting "1 layer" for "1A layer".

[0096] <<Diameter of the largest inscribed circle of the crystal grain in layer 1A>> The first A layer consists of multiple crystal grains, and the diameter of the largest inscribed circle of the crystal grains may be between 5 nm and 500 nm. This improves the crater wear resistance of the cutting tool. The first A layer of this disclosure may include, to the extent that it does not impair the effects of this disclosure, regions that do not constitute crystal grains (regions with random atomic arrangement) along with the multiple crystal grains.

[0097] The upper limit of the diameter of the maximum inscribed circle of the above crystal grain may be 500 nm or less, 450 nm or less, or 400 nm or less, from the viewpoint of improving wear resistance and fracture resistance. The lower limit of the diameter of the maximum inscribed circle of the crystal grain may be 5 nm or more, 7 nm or more, or 10 nm or more, from the viewpoint of suppressing a decrease in film hardness due to excessive grain refinement. The diameter of the maximum inscribed circle of the crystal grain may be 5 nm or more and 500 nm or less, 7 nm or more and 450 nm or less, or 10 nm or more and 400 nm or less.

[0098] In Embodiment 2, the diameter of the largest inscribed circle of a crystal grain is measured by replacing the first layer with the first A layer in the method for measuring the diameter of the largest inscribed circle of a crystal grain described in Embodiment 1.

[0099] In Embodiment 2, the positional relationship between the crystal grains and the first and third unit layers is described by substituting the second unit layer with the third unit layer in the positional relationship between the crystal grains and the first and second unit layers described in Embodiment 1.

[0100] [Embodiment 3: Method for manufacturing a cutting tool] Embodiment 3 describes the manufacturing methods for cutting tools according to Embodiments 1 and 2. The manufacturing method of Embodiment 3 may include the steps of preparing a substrate and forming a coating on the substrate. Details of each step are described below.

[0101] <<Process for preparing the base material>> In the process of preparing the base material, the base material 10 is prepared. The base material 10 can be the base material described in Embodiment 1 and Embodiment 2.

[0102] ≪Process for forming a coating≫ In the process of forming the coating, a coating 20 is formed on the substrate 10. In Embodiment 3, the coating 20 can be formed by the Physical Vapor Deposition (PVD) method. Specific examples of PVD methods include Arc Ion Plating (AIP), Balanced Magnetron Sputtering (BMS), and Unbalanced Magnetron Sputtering (UBMS). In Embodiment 3, it is preferable to use Arc Ion Plating.

[0103] In the AIP method, an arc discharge is generated using the target material as the cathode. This causes the target material to evaporate and ionize. The ions are then deposited on the surface of the substrate 10 to which a negative bias voltage is applied. The AIP method is superior in terms of the ionization rate of the target material.

[0104] The film deposition apparatus used in the AIP method will be explained with reference to Figures 4 and 5. As shown in Figure 4, the film deposition apparatus 200 includes a chamber 201. The chamber 201 is provided with a gas inlet 202 for introducing the raw material gas into the chamber 201, and a gas exhaust port 203 for discharging the raw material gas from the chamber 201 to the outside. The gas exhaust port 203 is connected to a vacuum pump (not shown). The pressure inside the chamber 201 is adjusted by the amount of gas introduced and discharged.

[0105] A rotary table 204 is located inside the chamber 201. A substrate holder 205 for holding the substrate 10 is attached to the rotary table 204. The substrate holder 205 is connected to the negative terminal of the bias power supply 206. The positive terminal of the bias power supply 206 is grounded.

[0106] As shown in Figure 5, multiple target materials 211, 212, 213, and 214 are attached to the side wall of the chamber 201. As shown in Figure 4, each target material 211 and 212 is connected to the negative terminal of the DC power supply 221 and 222, respectively. The DC power supplies 221 and 222 are variable power supplies, and their positive terminals are grounded. Although not shown in Figure 4, the same applies to target materials 213 and 214. The specific operation will be described below.

[0107] The substrate 10 is held in the substrate holder 205. Using a vacuum pump, the pressure inside the chamber 201 is set to 1.0 × 10⁻⁶. -4 Adjust to Pa. While rotating the rotary table 204, the temperature of the substrate 10 is adjusted to 500°C using a heater (not shown) attached to the film deposition apparatus 200.

[0108] Ar gas is introduced through the gas inlet 202 to adjust the pressure inside the chamber 201 to 3.0 Pa. While maintaining this pressure, the voltage of the bias power supply 206 is gradually changed until it is finally adjusted to -1000 V. Then, the surface of the substrate 10 is cleaned by ion bombardment treatment with Ar ions.

[0109] Next, if the coating includes a second layer 22, the second layer 22 is formed on the surface of the substrate 10. For example, a TiCN layer, a TiN layer, or a TiCNO layer is formed on the surface of the substrate 10.

[0110] Next, the first layer or the first A layer is formed on the surface of the substrate 10 or the surface of the second layer 22. The composition of each target material is selected so as to obtain the compositions of the first unit layer 1, the second unit layer 2, and the third unit layer 3. Each target material is set in a predetermined position, nitrogen gas is introduced from the gas inlet 202, and the first layer 21 or the first A layer 21A is formed while rotating the rotary table 204. The formation conditions for the first layer 21 and the first A layer are as follows.

[0111] <Formation conditions for the first layer and the first A layer> Base material temperature: 400~800℃ Bias voltage: -400 to -20V Arc current: 80~200A Reaction gas pressure: 2-10 Pa

[0112] The substrate temperature, reaction gas pressure, bias voltage, and arc current are either kept constant within the above range, or continuously varied within the above range.

[0113] A multilayer structure in which a first unit layer and a second unit layer are stacked alternately, or a multilayer structure in which a first unit layer and a third unit layer are stacked alternately, can be formed by appropriately combining the following methods (A) to (D). (A) In the AIP method, multiple target materials (sintered alloys) with different compositions are used. (B) In the AIP method, during film formation, the bias voltage applied to the substrate 10 is varied within the bias voltage range described above for the formation conditions of the first layer and the first A layer. (C) In the AIP method, the gas flow rate is changed. (D) In ​​the AIP method, the substrate 10 is rotated and its rotation period is controlled.

[0114] Next, if the coating includes a third layer 23, for example, the third layer 23 is formed on the surface of the first layer 21 or the first A layer 21A.

[0115] Based on the above, a cutting tool 100 comprising a base material 10 and a coating 20 provided on the base material 10 can be manufactured. [Examples]

[0116] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0117] [Example 1] <Manufacturing of cutting tools> Cutting tools were fabricated and their tool life evaluated as follows.

[0118] A cutting tip made of cemented carbide (model number: CNMG120408 (manufactured by Sumitomo Electric Hardmetal Co., Ltd.)) was prepared as the base material. This cemented carbide contains WC particles (90% by mass) and Co (10% by mass). The average particle size of the WC particles is 1 to 2 μm.

[0119] A film was formed on the above substrate using a film deposition apparatus having the configuration shown in Figures 4 and 5. First, the surface of the substrate was cleaned by ion bombardment treatment with Ar ions. The specific conditions for the ion bombardment treatment are as described in Embodiment 3.

[0120] Next, the target material was set in the designated position in the film deposition apparatus. The composition of each target material was adjusted to obtain the compositions of the first and second unit layers described in Tables 1 and 2.

[0121] Nitrogen gas was introduced through a gas inlet, and the first layer was formed by alternately creating the first and second unit layers while rotating the rotary table. The conditions for forming the first layer of each sample were: substrate temperature 400-800°C, bias voltage -400--20V, arc current 80-200A, and reaction gas pressure 2-10Pa. The substrate temperature, reaction gas pressure, bias voltage, and arc current were kept constant within the above ranges, or continuously varied within the above ranges. The thickness and number of layers of the first and second unit layers were adjusted by the rotation speed of the substrate.

[0122] [Table 1]

[0123] [Table 2]

[0124] <Rating> ≪Composition of the coating≫ For each sample's coating, the composition of the first and second unit layers, the average thickness of the first unit layer, the average thickness of the second unit layer, the average thickness of the first layer, the number of layers of each of the first and second unit layers, the percentage of titanium atoms relative to the total number of titanium and aluminum atoms in the first layer (indicated as "(T2 / T1)×100" in Tables 1 and 2), and the nanoindentation hardness of the first layer (indicated as "hardness" in Tables 1 and 2) were measured. The measurement method for each item is as described in Embodiment 1. The results are shown in Tables 1 and 2. In Table 2, "1" for "Number of Layers" indicates that only one layer of either the first or second unit layer was formed.

[0125] ≪Cutting Test 1≫ Turning was performed using the cutting tool for each sample under the following conditions, and the cutting distance until the crater wear width reached 0.3 mm was measured. A longer cutting distance indicates better crater wear resistance and longer tool life. The results are shown in the "Cutting Test 1" column of Tables 1 and 2.

[0126] (Cutting conditions) Work material: SUS316 Cutting speed: 120m / min Feed rate: 0.3mm / rev Cutting depth: 2.0 mm Wet method The above cutting conditions apply to turning (low-speed, high-feed machining) of stainless steel.

[0127] <Rating> Samples 1 to 15 are examples. Samples 101 to 117 are comparative examples. It was confirmed that samples 1 to 15 had a longer tool life than samples 101 to 117.

[0128] [Example 2] <Manufacturing of cutting tools> Cutting tools were fabricated and their tool life evaluated as follows.

[0129] As the substrate, the same substrate as in Example 1 was prepared. A film was formed on the substrate using a film deposition apparatus having the configuration shown in Figures 4 and 5. First, the surface of the substrate was cleaned by ion bombardment treatment with Ar ions. The specific conditions for the ion bombardment treatment are as described in Embodiment 3.

[0130] Next, the target material was set in the designated position in the film deposition apparatus. The composition of each target material was adjusted to obtain the compositions of the first and third unit layers described in Tables 3 and 4.

[0131] Nitrogen gas was introduced through a gas inlet, and the first and third unit layers were formed alternately while the rotary table rotated, thereby creating the first A layer. The formation conditions for the first A layer of each sample were: substrate temperature 400-800°C, bias voltage -400--20V, arc current 80-200A, and reaction gas pressure 2-10Pa. The substrate temperature, reaction gas pressure, bias voltage, and arc current were kept constant within the above ranges, or continuously varied within the above ranges. The thickness and number of layers of the first and third unit layers were adjusted by the rotation speed of the substrate.

[0132] [Table 3]

[0133] [Table 4]

[0134] <Rating> ≪Composition of the coating≫ For each sample's coating, the composition of the first and third unit layers, the average thickness of the first unit layer, the average thickness of the third unit layer, the average thickness of the 1A layer, the number of layers of the first and third unit layers respectively, the percentage of titanium atoms relative to the total number of titanium and aluminum atoms in the 1A layer (indicated as "(T4 / T3)×100" in Tables 3 and 4), and the nanoindentation hardness of the 1A layer (indicated as "hardness" in Tables 3 and 4) were measured. The measurement method for each item is as described in Embodiment 1. The results are shown in Tables 3 and 4. In Table 4, "1" for "Number of Layers" indicates that only one layer of the first or third unit layer was formed.

[0135] ≪Cutting Test 2≫ Turning was performed using the cutting tool for each sample under the following conditions, and the cutting distance until the crater wear width reached 0.3 mm was measured. A longer cutting distance indicates better crater wear resistance and longer tool life. The results are shown in the "Cutting Test 2" column of Table 2.

[0136] (Cutting conditions) Work material: SCM435 Cutting speed: 300m / min Feed rate: 0.15mm / rev Cutting depth: 1.0 mm Wet method The above cutting conditions apply to turning (high-speed, low-feed machining) of chromium-molybdenum steel.

[0137] <Rating> Samples 21 to 40 are examples. Samples 120 to 137 are comparative examples. It was confirmed that samples 11 to 40 had a longer tool life than samples 120 to 137.

[0138] As described above, the embodiments and examples of this disclosure have been explained, but it is also intended from the outset that the configurations of each of the embodiments and examples described above may be combined or modified in various ways as appropriate. The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents. [Explanation of symbols]

[0139] 1 First unit layer, 2 Second unit layer, 3 Third unit layer, 10 Substrate, 20 Coating, 21 First layer, 21A FirstA layer, 22 Second layer, 23 Third layer, 24, 24a, 24b, 24c Crystal grains, 25 Crystal grain boundaries, 50 Atoms, 100 Cutting tool, 200 Film deposition apparatus, 201 Chamber, 202 Gas inlet, 203 Gas exhaust, 204 Rotary table, 205 Substrate holder, 206 Bias power supply, 211, 212, 213, 214 Target material, 221, 222 DC power supply

Claims

1. A cutting tool comprising a base material and a coating provided on the base material, The coating includes a first layer, The first layer consists of a multilayer structure in which a first unit layer and a second unit layer are stacked alternately. The average thickness of the first unit layer is 2 nm or more and 50 nm or less. The average thickness of the second unit layer is 2 nm or more and 50 nm or less. The average thickness of the first layer is 1.0 μm or more and 20 μm or less. The first unit layer is Ti ａ Al １－ａ－ｂ B ｂ Consists of N, Here, 0.30 ≤ a ≤ 0.50, Satisfying 0 < b ≤ 0.10, The second unit layer is Ti ｃ Al １－ｃ Consists of N, Here, Satisfying 0.70 ≤ c ≤ 1.00, A cutting tool in which, in the first layer, the percentage of the number of titanium atoms T2 relative to the total number of titanium and aluminum atoms T1 (T2 / T1) × 100 is 60% or more.

2. The cutting tool according to claim 1, wherein the nanoindentation hardness of the first layer at 25°C is 30 GPa or more.

3. A cutting tool comprising a base material and a coating provided on the base material, The coating includes a first A layer, The aforementioned first A layer has a multilayer structure in which a first unit layer and a third unit layer are stacked alternately. The average thickness of the first unit layer is 2 nm or more and 50 nm or less. The average thickness of the third unit layer is 2 nm or more and 50 nm or less. The average thickness of the first A layer is 1.0 μm or more and 20 μm or less. The first unit layer is Ti ａ Al １－ａ－ｂ B ｂ Consists of N, Here, 0.30 ≤ a ≤ 0.50, Satisfying 0 < b ≤ 0.10, The third unit layer is Ti ｄ Al １－ｄ－ｅ B ｅ and consists of N Here, 0.70 ≤ d < 1.00, Satisfying 0 < e ≤ 0.10, A cutting tool in which, in the first A layer, the percentage of the number of titanium atoms T4 relative to the total number of titanium and aluminum atoms T3 (T4 / T3) × 100 is 60% or more.

4. The cutting tool according to claim 3, wherein the nanoindentation hardness of the first A layer at 25°C is 30 GPa or more.

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