Surface-coated cutting tool

Abstract

A surface-coated cutting tool according to the present invention includes a laminated structure layer in which a coating layer has a series of three-part layers. Each three-part layer includes an α layer, a β layer, and a γ layer in a prescribed order. The α layer has an average thickness of αt, the β layer has an average thickness of βt, and the γ layer has an average thickness of γt. The average thickness At of the laminated structure layer is 0.3-6.0 μm. All of αt, βt, and γt are within the range of 1.0-6.0 nm. The α layer contains a first compound having a composition represented by AlxTi1−xN (where, on average, 0.35 ≤ x ≤ 0.55). The β layer contains a second compound having a composition represented by AlyTi1−yN (where, on average, 0.60 ≤ y ≤ 0.80). The γ layer contains a third compound having a composition represented by AlzTi1−z−mMmN (where: M is at least one selected from the group consisting of Cr, Mo, Ta, B, Si, W, and lanthanoids; on average, 0.45 ≤ z ≤ 0.65; on average, 0.01 ≤ m ≤ 0.20; and x < z < y).

Description

surface coated cutting tools

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool). This application claims priority to Japanese Patent Application No. 2024-15539, filed on February 5, 2024. The entire contents of said Japanese patent application are incorporated herein by reference.

[0002] Conventionally, coated tools have been known in which a coating layer is formed on a substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide. There have been proposals to obtain coated tools with improved cutting performance by adjusting the composition and layer structure of the coating layer.

[0003] For example, Patent Document 1 discloses Ti ｘ Al １－ｘ N and Ti ｙ Al １－ｙ The document describes a coated tool having a coating layer in which two types of compounds, N (0≦x<0.5, 0.5<y≦1), are alternately laminated, and the overall composition of the laminate is stoichiometrically aluminum-rich, and the coated tool is said to have excellent wear resistance and chipping resistance.

[0004] Furthermore, for example, Patent Document 2 describes a coated tool having a composite nitride layer of Al and Ti, which has a lower layer and an upper layer, and the lower layer has a crystal grain size 1.25 times or more larger than that of the upper layer, a high elastic modulus, and a low Al content.

[0005] Furthermore, for example, Patent Document 3 discloses a coating layer made of Al １－ｘ１ Ti ｘ１ a plurality of first AlTi layers having a composition of Al １－ｘ２ Ti ｘ２and a plurality of second AlTi layers having a composition of the formula (I), wherein the first AlTi layers and the second AlTi layers are alternately stacked on the substrate, wherein x1 is greater than x2, and the plurality of first AlTi layers have a first region in which, of two adjacent first AlTi layers, the one located farther from the substrate has a thinner thickness than the one located closer to the substrate, and the coated tool is said to have good wear resistance and adhesion of the coating layer.

[0006] Japanese Patent Publication No. 7-97679 Japanese Patent No. 6236606 International Publication No. 2018 / 235747

[0007] The present invention has been made in consideration of the above circumstances and proposals, and an object of the present invention is to provide a cutting tool that exhibits excellent wear resistance when cutting stainless steel and Ni-based heat-resistant alloys in addition to steel and cast iron.

[0008] A surface-coated cutting tool according to an embodiment of the present invention has a substrate and a coating layer, the coating layer including a laminated structure layer having a series of triple layers, each triple layer including, in a predetermined order, an α layer, a β layer, and a γ layer, the α layer having an average thickness αt, the β layer having an average thickness βt, and the γ layer having an average thickness γt, the average thickness At of the entire laminated structure layer being 0.3 μm or more and 6.0 μm or less, the αt, the βt, and the γt all being 1.0 nm or more and 6.0 nm or less, the α layer being Al ｘ Ti １－ｘ N (0.35≦x≦0.55 on average), and the β layer contains Al ｙ Ti １－ｙ N (0.60≦y≦0.80 on average), and the γ layer contains Al ｚ Ti １－ｚ―ｍ M ｍ and a third compound having a composition represented by the formula: N (M is at least one selected from the group consisting of Cr, Mo, Ta, B, Si, W, and lanthanoids, and 0.45≦z≦0.65 on average, 0.01≦m≦0.20 on average, x<z<y).

[0009] The surface-coated cutting tool exhibits excellent wear resistance when used to cut not only steel and cast iron but also stainless steel and Ni-based heat-resistant alloys.

[0010] 1 is a schematic diagram of a longitudinal section of a coating layer in a surface-coated cutting tool according to one embodiment of the present invention; 2 is an example of a graph in which the vertical axis represents the Al atomic concentration and the M atomic concentration, and the horizontal axis represents the distance from the line analysis start point, for a coating layer in a surface-coated cutting tool according to one embodiment of the present invention; 3 is another example of a graph in which the vertical axis represents the Al atomic concentration and the M atomic concentration, and the horizontal axis represents the distance from the line analysis start point, for another coating layer in a surface-coated cutting tool according to one embodiment of the present invention.

[0011] The present inventors have conducted extensive research into coating layers in order to obtain a coated tool that has excellent wear resistance not only when used to cut steel or cast iron, but also when used to cut stainless steel and Ni-based heat-resistant alloys, and as a result have made the following discoveries (1) and (2).

[0012] (1) When a coated tool having a coating layer consisting of two types of AlTiN layers alternately stacked on top of each other, with an average thickness on the order of nanometers and differing only in Al content, decomposition of the AlTiN during cutting (AlTiN decomposes into TiN and AlN) increases the hardness of the coating layer, resulting in a coated tool with excellent wear resistance for cutting steel or cast iron. However, this coating layer may not be able to fully demonstrate its performance in cutting processes that involve oxidative wear. In other words, if the coating layer is composed solely of alternating layers of AlTiN layers with different Al contents, wear resistance during cutting may be reduced.

[0013] (2) Therefore, the present inventors conducted further studies and found that by adding an AlTiMN layer (where M is one or more of Cr, Mo, Ta, B, Si, W, and lanthanoids) in which the difference in the crystal lattice constants of the crystals constituting the AlTiN layers is small and the average thickness is on the order of nanometers to the coating layer formed by alternately laminating the two types of AlTiN layers, the decrease in the wear resistance of the coating layer is minimized, and the oxidation resistance is further improved, so that the coating layer exhibits excellent wear resistance even in cutting environments where oxidation wear occurs, such as when cutting stainless steel or Ni-based heat-resistant alloys.

[0014] That is, each of the elements listed as M has an atomic radius different from that of Al and Ti constituting the AlTiN layer, and therefore functions to introduce a moderate lattice distortion into the TiAlN lattice, increase the hardness of the coating layer, and further improve the oxidation resistance. This function remains the same whether each of the elements listed as M is used alone or in combination. The reason for this is that quantitative studies of these elements have been supported by both thermodynamic calculations and experimental facts.

[0015] The present invention is based on these findings. Below, the coated tool according to an embodiment of the present invention will be described in detail, and the present invention will be explained. In this specification and claims, when a numerical range is expressed using "L to M," this is synonymous with "at least L and at most M," and the range includes the numerical values ​​of the upper limit (M) and the lower limit (L). Furthermore, when a unit is specified only for the upper limit (M), the upper limit (M) and the lower limit (L) have the same unit.

[0016] Hereinafter, a coated tool according to an embodiment will be described.

[0017] 1. Coating Layer The layer structure of the coating layer of a coated tool according to an embodiment of the present invention is as shown schematically in FIG. 1. That is, the coating layer (2) comprises a base layer (3) on a substrate (1), a laminated structure layer (4) on the base layer (3), and a surface layer (5) on the laminated structure layer (4). The laminated structure layer (4) is a stack of thin layers having an average thickness on the order of nanometers, i.e., an α layer (6), a β layer (7), and a γ layer (8) stacked in that order. In FIG. 1, the α layer (6), the β layer (7), and the γ layer (8) are also stacked in that order in the white portion of the laminated structure layer (4). The base layer (3) and the surface layer (5) are provided as needed.

[0018] (1) Average Thickness of the Laminated Structure Layer The average thickness At of the laminated structure layer is preferably 0.3 μm or more and 6.0 μm or less. This is because an average thickness in this range makes it possible to achieve both excellent wear resistance and chipping resistance of the coating layer. The average thickness At of the laminated structure layer is more preferably 0.6 μm or more and 4.0 μm or less.

[0019] (2) Configuration of the laminated structure layer The laminated structure layer is formed by sequentially stacking α layers, β layers, and γ layers on the order of nanometers. The average thicknesses of the α layers, β layers, and γ layers, αt, βt, and γt, respectively, are all 1.0 nm or more and 6.0 nm or less, and it is preferable that 0.7≦βt / αt≦6.0 and 1.0≦γt / βt≦1.3 are satisfied. The reason for this is that satisfying these average thickness relationships enables the coating layer to achieve both excellent wear resistance and fracture resistance.

[0020] Here, a "laminate structure layer having a series of triple layers" refers to a lamination arrangement in which all three types of layers, α, β, and γ, are selected and arranged in order, and there are 3! = 6 different types of lamination units in this sequential lamination. That is, the sequential lamination units (lamination units) are: 1) α layer, β layer, γ layer 2) α layer, γ layer, β layer 3) β layer, γ layer, α layer 4) β layer, α layer, γ layer 5) γ layer, α layer, β layer 6) γ layer, β layer, α layer. From the substrate surface to the tool surface (coating layer surface), this lamination unit repeats without changing the order of the α layer, β layer, and γ layer within the lamination unit, but only the lamination unit closest to the tool surface does not have to be a complete lamination unit. That is, for example, when the lamination unit is configured in the order of α layer, β layer, and γ layer, the lamination unit closest to the tool surface may be a complete lamination unit of α layer, β layer, and γ layer, or α layer, β layer, or just α layer.

[0021] (3) Number of α Layers, β Layers, and γ Layers There are no particular restrictions on the number of α layers, β layers, and γ layers (total number of α layers, β layers, and γ layers), but it is preferably 150 to 6,000, and more preferably 300 to 3,000. The reason for this is as follows: If it is less than 150, the progression of cracks that occur during cutting cannot be sufficiently prevented, which may reduce chipping resistance; on the other hand, if it exceeds 6,000, the number of repetitions increases, which reduces the crystallinity of the laminated structure layer, which reduces hardness and therefore reduces wear resistance.

[0022] (4) Composition of α layer, β layer and γ layer The composition of the compounds constituting the α layer, β layer and γ layer constituting the laminated structure layer is as follows: ｘ Ti １－ｘ N (where x is 0.35≦x≦0.55 on average), and the second compound constituting the β layer is Al ｙ Ti １－ｙ N (where y is 0.60≦y≦0.80 on average), and the third compound constituting the γ layer is Al ｚ Ti １－ｚ―ｍ M ｍ N (M is one or more of Cr, Mo, Ta, B, Si, W and lanthanides, z is 0.45≦z≦0.65 on average, m is 0.01≦m≦0.20 on average, x<z ｇ < ｇ-)

[0023] If the composition of either of the first and second compounds constituting the α and β layers is outside the above range, the hardness may decrease, resulting in a decrease in wear resistance. On the other hand, if the composition of the third compound constituting the γ layer is within the above range, oxidation resistance can be improved without decreasing wear resistance during cutting, and boundary damage that occurs during cutting of stainless steel and Ni-based heat-resistant alloys can be delayed.

[0024] According to an example of the manufacturing method described below, the ratio of (AlTi) to N and the ratio of (AlTiM) to N, i.e., the ratio of the metal element group to nitrogen, are manufactured to be 1:1, but inevitably (unintentionally) there may be some nitrides that are not 1:1. This also applies to other nitrides described below.

[0025] (5) Other Layers Either or both of the surface layer and the underlayer described below may be intentionally included. In addition, unavoidable (unintentional) layers may also be included.

[0026] (5-1) Surface Layer While the laminated structure layer alone can sufficiently achieve the above-mentioned objectives, the coating layer may have a surface layer on the laminated structure layer. The surface layer may be, for example, a layer composed of TiN (the atomic ratio of Ti to N in this TiN is not limited to a stoichiometric ratio). When this surface layer composed of TiN is provided, the layer composed of TiN itself has a golden color tone, and therefore, it can be used as an identification layer to determine the usage state of the coated tool by color tone change. The average thickness of this surface layer functioning as an identification layer may be 0.1 to 1.0 μm.

[0027] (5-2) Underlayer Although the laminated structure layer alone can sufficiently achieve the above-mentioned object, the coating layer may have an underlayer between the laminated structure layer and the substrate. Examples of the underlayer include at least one of a layer made of TiC, a layer made of TiN, a layer made of TiCN, a layer made of a Ti compound, and a layer made of AlTiN, and the average thickness thereof is 0.1 to 1.0 μm. When the average thickness is within this range, the adhesion between the laminated structure layer and the substrate is further improved.

[0028] (5-3) Layers that may be unavoidably formed In this embodiment, the film is formed so that no layers other than the base layer, the laminated structure layer, and the surface layer are present. However, when changing the layer to be formed, an unintended change in pressure or temperature within the film forming apparatus may occur, and a layer containing an unintended compound different from these layers may be formed.

[0029] 3. Substrate (1) Material The substrate used in this embodiment may be any known substrate material as long as it achieves the above-described objective. Examples include cemented carbide (including WC-based cemented carbide, including those containing carbonitrides of Ti, Ta, Nb, etc. in addition to WC and Co), cermet (containing TiC, TiN, TiCN, etc. as its main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), and cBN sintered body.

[0030] (2) Shape The shape of the substrate is not particularly limited as long as it is a shape that can be used as a cutting tool, and examples thereof include the shapes of an insert, a drill, and an end mill.

[0031] 4. Measurement Method 1. Average Thickness of Laminated Structure Layer and Other Layers The overall average thickness of the laminated structure layer constituting the coating layer and the average thickness of the other layers can be determined by observing a longitudinal section (a cross section perpendicular to the surface of the substrate when the surface is treated as a flat surface, ignoring minute irregularities on the surface of the substrate, in the case of an insert; a cross section perpendicular to the axis in the case of an axial tool such as a drill) using an energy dispersive X-ray spectrometer (EDS) attached to a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0032] Here, the surface of the substrate is determined by observing the longitudinal cross section, determining the interface between the substrate and the coating layer by elemental mapping, and arithmetically determining the average straight line of the roughness curve of the interface thus obtained. This is defined as the surface of the substrate, and the direction perpendicular to this surface is defined as the thickness direction of the coating layer.

[0033] 2. Average Thickness At of the Laminated Structure Layer The average thickness At of the laminated structure layer can be determined using EDS attached to an SEM. The vertical direction (thickness direction) is the length including the entire coating layer, and the horizontal direction (direction parallel to the substrate surface) is a 5 μm square, and five or more of these are set (it is desirable that the sides of each observation area are separated by 20 μm or more). Linear analysis is performed to determine the thickness of each layer, and the average is used to determine the average thickness At of the laminated structure layer.

[0034] 3. Average thickness of the α layer, β layer, and γ layer (αt, βt, γt) Because these layers have average thicknesses on the order of nanometers, the average thickness and average composition are measured by line analysis using an EDS attached to a TEM.

[0035] At least four line analyses are carried out in the thickness direction of the coating layer, with a length including at least 10 layers and an interval of 5 μm, using an EDS attached to a TEM (the beam diameter of the line analysis is 0.5 nm, and the interval between observation points can be, for example, 0.5 nm). Ａｌ The percentage (%) of [A Ａｌ / (A Ａｌ +AＴｉ +A Ｍ ) × 100, A Ｍ The percentage (%) of [A Ｍ / (A Ａｌ +A Ｔｉ +A Ｍ ) × 100, where A Ａｌ is the number of aluminum atoms, A Ｔｉ is the number of titanium atoms, A Ｍ is the total number of atoms in M. In Figs. 2 and 3, the vertical axis is A Ａｌ Percentage (%) of and A Ｍ 1 is a graph in which the percentage (%) of the line analysis result is plotted on the horizontal axis, and the distance (D (nm)) from the start point of the line analysis is plotted on the horizontal axis.

[0036] In these graphs, A Ａｌ The positions of the maximum points on the graph on which the line analysis of percentage (%) of A is performed are P1, P2, P3, ... and the positions of the minimum points are Q1, Q2, Q3, ..., Ｍ The positions of the maximum points on the graph where a line analysis of percentage (%) of is performed are designated as points M1, M2, M3, etc. However, points Q and M that exist between the start point of the line analysis and point P1 are excluded.

[0037] 1) When M1 is to the right of Q1, i.e., Q1 is close to point P1 (Figure 2), the intermediate value between Pi and Qi is defined as PQi on the horizontal axis, the intermediate value between Qi and Mi as QMi, and the intermediate value between Mi and Pi+1 as MPi (i = 1 to m: m is the number of maximum and minimum values ​​in the line analysis range). Then, the distance between PQi and QMi is considered to be the thickness of the α layer αti, the distance between QMi and MPi is considered to be the thickness of the γ layer γti, and the distance between MPi and PQi+1 is considered to be the thickness of the β layer βti. The thicknesses of each layer obtained are averaged to obtain the average thickness of each layer per line analysis (αt, βt, γt).

[0038] 2) When M1 is to the left of Q1, i.e., when M1 is close to point P1 (Figure 3), the intermediate value between Pj and Mj is defined as PMj, the intermediate value between Mj and Qj as MQj, and the intermediate value between Qj and Pj+1 as QPj (j = 1 to n, where n is the number of maximum and minimum values ​​in the line analysis range). The distance between PMj and MQj is considered the thickness of the γ layer (γtj), the distance between MQj and QPj as the thickness of the α layer (αtj), and the distance between QPj and PMj+1 as the thickness of the β layer (βtj). The average thicknesses of each layer (αt, βt, γt) per line analysis are then averaged. The chemical compositions at the maximum and minimum points Pi, Qi, and Mi obtained in this way for at least 10 layers are measured and averaged to determine the average composition of each layer.

[0039] Then, an arithmetic average is calculated based on the average thickness of each layer per line analysis, and this is defined as the average thickness (αt, βt, γt) of each layer for all the analysis lines where measurements were performed. In addition, for all the analysis lines, the chemical compositions at the maximum and minimum points Pi, Qi, and Mi of each layer per line analysis are measured for at least 10 layers, and the average composition of each layer can be determined by calculating the arithmetic average.

[0040] 3. Manufacturing Method The coating layer of the coated tool of this embodiment can be manufactured using, for example, an arc ion plating apparatus, and can be formed by using, as the target, an AlTi target and an AlTiM target having compositions corresponding to the compositions of the α layer, β layer, and γ layer, respectively, for forming the laminated structure layer.

[0041] The above description includes the following additional features: (Additional Note 1) A surface-coated cutting tool having a substrate and a coating layer, wherein the coating layer includes a laminated structure layer having a series of triple layers, each triple layer including, in a predetermined order, an α layer, a β layer, and a γ layer, the α layer having an average thickness αt, the β layer having an average thickness βt, and the γ layer having an average thickness γt, the average thickness At of the entire laminated structure layer being 0.3 μm or more and 6.0 μm or less, the αt, the βt, and the γt all being 1.0 nm or more and 6.0 nm or less, the α layer being Al ｘ Ti １－ｘN (0.35≦x≦0.55 on average), and the β layer contains Al ｙ Ti １－ｙ N (0.60≦y≦0.80 on average), and the γ layer contains Al ｚ Ti １－ｚ―ｍ M ｍ and a third compound having a composition expressed by the formula: N (M is at least one selected from the group consisting of Cr, Mo, Ta, B, Si, W and lanthanoids, and an average of 0.45≦z≦0.65, an average of 0.01≦m≦0.20, x<z<y). (Appendix 2) The surface-coated cutting tool according to Appendix 1, which has a surface layer on the laminated structure layer. (Appendix 3) The surface-coated cutting tool according to Appendix 1 or Appendix 2, which has a base layer between the base and the laminated structure layer.

[0042] Next, an example will be described. Here, as an example of the coated tool of the present invention, an insert-shaped coated tool using a WC-based cemented carbide as a substrate will be described, but the substrate can be made of the above-mentioned materials, and the shape can be applied to drills, end mills, etc. as described above.

[0043] First, as raw material powders, Co powder, TiC powder, VC powder, TaC powder, NbC powder, Cr ３ C ２ These raw material powders were blended to the composition shown in Table 1, and wax was added to the mixture, which was then wet mixed in a ball mill for 72 hours, dried under reduced pressure, and then press-molded at a pressure of 100 MPa. These powder compacts were sintered at 1400°C for 1 hour in a vacuum atmosphere of 6 Pa, and processed to the specified dimensions to produce WC-based cemented carbide substrates 1 to 3 having the insert shape of ANSI standard SEEN42AFTN1.

[0044] Next, after ultrasonically cleaning and drying the substrates 1 to 3 in acetone, they were mounted along the outer periphery at a predetermined distance in the radial direction from the central axis on a rotary table in an arc ion plating apparatus to form a coating layer using the apparatus. A target of a predetermined composition was also placed as a cathode (evaporation source).

[0045] Next, the inside of the arc ion plating apparatus was evacuated and maintained at a vacuum of 0.1 Pa or less, and the inside of the apparatus was heated to 600°C with a heater. After that, a DC bias voltage of -1000 V was applied to the substrate rotating on the rotating table, and a current of 100 A was passed between the cathode and anode to bombard the surface of the substrate.

[0046] A nitrogen atmosphere of 2.7 to 7.5 Pa was used as the reactive gas in the arc ion plating apparatus, and the furnace temperature was maintained at the same temperature as shown in Table 2. A DC voltage of −40 to −125 V, as shown in Table 2, was applied to the substrate rotating on the rotating table, and a current of 125 to 210 A was passed between each of the three target electrodes and the anode for forming the laminated structure layer, generating an arc discharge to form an α layer, β layer, and γ layer of a predetermined thickness.

[0047] Then, the deposition of the α layer, β layer, and γ layer was repeated a predetermined number of times to form a laminated structure layer having a desired number of layers.

[0048] Furthermore, in some examples, a nitrogen atmosphere of 0.5 to 7.0 Pa was used as the reactive gas in the arc ion plating apparatus, and the temperature inside the furnace was maintained at 300 to 600°C. A DC voltage of -20 to -500 V was applied to the substrate rotating on the rotating table, and a current of 50 to 250 A was passed between the Ti electrode for forming the surface layer and / or underlayer and the anode to generate an arc discharge, thereby depositing a TiN surface layer and / or TiN underlayer of a predetermined thickness. The results are shown in Table 4.

[0049] For comparison, coating layers were vapor-deposited on the substrates 1 to 3 using the same deposition apparatus as above under the conditions shown in Table 3 to produce coated tools 1 to 9 of the comparative examples (hereinafter referred to as "comparative examples") shown in Table 4. In some comparative examples, a TiN surface layer and / or a TiN underlayer was deposited in the same manner as in the examples.

[0050] The average thickness of the laminated structure layer, and the average thickness and average composition of each layer constituting the laminated structure were determined according to the above-mentioned measurement methods.

[0051]

[0052]

[0053]

[0054] In Table 3, "-" indicates that there is no applicable item.

[0055]

[0056] In Table 4, "number of layers" refers to "the total number of α layers, β layers, and γ layers," and "-" indicates that there is no applicable item.

[0057] Next, cutting tests were carried out for Examples 1 to 9 and Comparative Examples 1 to 9 under the following cutting conditions: One coated tool having an insert shape conforming to the ANSI standard SEEN42AFTN1 was attached to a Mitsubishi Materials SE445R0506E cutter, and cutting tests 1 and 2 were carried out.

[0058] Cutting Test 1 Workpiece: 110 mm wide x 250 mm long block material (made of SCM440) Cutting speed: 180 m / min. Depth of cut: 1.8 mm Feed: 0.14 mm / tooth. Cutting was performed up to a cutting length of 2.5 m, the flank wear width was measured, and the state of wear on the cutting edge was observed.

[0059] Cutting test 2 Workpiece: 60 mm wide x 200 mm long block material (made of Ni-19Cr-19Fe-3Mo-0.9Ti-0.5Al-5.1(Nb+Ta)) Cutting speed: 90 m / min. Depth of cut: 1.8 mm Feed: 0.07 mm / tooth. Cutting was performed up to a cutting length of 2.5 m, the flank wear width was measured, and the state of wear on the cutting edge was observed.

[0060] Cutting Test 3 Workpiece: 60 mm wide x 100 mm long block material (SUS304) Cutting speed: 140 m / min. Depth of cut: 1.8 mm Feed: 0.3 mm / tooth. Cutting was performed up to a cutting length of 2.5 m, the flank wear width was measured, and the state of wear on the cutting edge was observed. The results of the cutting test are shown in Tables 5, 6, and 7.

[0061] In Tables 5, 6, and 7, "*" indicates the cutting length (m) at which the tool reached the end of its service life before reaching the maximum cutting length (2.5 m), and is the cutting length at which an abnormality in the cutting sound occurred.

[0062]

[0063]

[0064]

[0065] The results in Tables 5, 6, and 7 show that Examples 1 to 9 exhibited excellent wear resistance and chipping resistance without any abnormal damage such as chipping or peeling. In contrast, Comparative Examples 1 to 9 showed chipping or progressed flank wear, which clearly led to the end of their life in a short period of time.

[0066] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0067] 1 Base 2 Covering layer 3 Base layer 4 Laminated structure layer 5 Surface layer 6 α layer 7 β layer 8 γ layer

Claims

1. A surface-coated cutting tool having a substrate and a coating layer, wherein the coating layer includes a laminated structure layer having a series of triple layers, each triple layer including, in a predetermined order, an α layer, a β layer, and a γ layer, the α layer having an average thickness αt, the β layer having an average thickness βt, and the γ layer having an average thickness γt, the average thickness At of the entire laminated structure layer being 0.3 μm or more and 6.0 μm or less, the αt, the βt, and the γt all being 1.0 nm or more and 6.0 nm or less, and the α layer being Al ｘ Ti １－ｘ N (0.35≦x≦0.55 on average), and the β layer contains Al ｙ Ti １－ｙ N (0.60≦y≦0.80 on average), and the γ layer contains Al ｚ Ti １－ｚ―ｍ M ｍ a third compound having a composition expressed by the formula: N (M is at least one element selected from the group consisting of Cr, Mo, Ta, B, Si, W, and lanthanoids, and 0.45≦z≦0.65 on average, 0.01≦m≦0.20 on average, and x<z<y).

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