Surface-coated cutting tool

Abstract

To provide a surface-coated cutting tool having a coated layer that is improved in durability.SOLUTION: In a surface-coated cutting tool, an upper layer includes an α type Al2O3 layer having an average thickness of 1.0-20.0 μm, whereas a lower layer includes a composite nitride layer of Al and Ti that has an average thickness of 1.0-20.0 and that is represented by the formula (AlXTi1-X)N (Xavg being an average value of X is 0.40≤Xavg<0.60). In the α type Al2O3 crystal grains constituting the upper layer, an area ratio of crystal grains for which an angle formed by a normal direction of a substrate surface and a normal line of a {001} plane being a crystal surface of the crystal grains falls within the range of 0-10 degrees, is 30% or more. The composite nitride crystal grains constituting the lower layer have a NaCl type face-centered cubic structure, and an area ratio of crystal grains for which an angle formed by a normal direction of a substrate surface and a normal line of a {111} plane being a crystal surface of the crystal grains falls within the range of 0-10 degrees, is 30% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).

Background Art

[0002] Coated tools in which a coating layer is formed on the surface of a substrate such as tungsten carbide (hereinafter referred to as WC) - based cemented carbide are known and exhibit excellent wear resistance. And various proposals have been made regarding the improvement of the coating layer in order to improve the durability of the coated tool.

[0003] For example, Patent Document 1 describes a coated tool having a coating layer of titanium aluminum nitride, wherein the coating layer of titanium aluminum nitride has a cubic crystal structure, an aluminum content of 0.3 to 60.0% by mass, and a chlorine content of 0.01 to 2% by mass, and the coated tool is said to have high adhesion of the coating layer.

[0004] x Al 1-x N and Ti y Al 1-y Also, for example, Patent Document 2 describes a coated tool in which two types of compounds of N (0 ≦ x < 0.5, 0.5 < y ≦ 1) are alternately laminated repeatedly so that the overall composition of the laminate becomes stoichiometrically aluminum-rich as the coating layer, and the coated tool is said to be excellent in wear resistance and have durability in high-speed cutting and cutting of high-hardness materials.

[0005] Furthermore, for example, Patent Document 3 describes a coated tool having a hard coating made of a metal nitride formed on the surface of a base material by a vapor phase synthesis method having a lattice constant 0.997 to 1.005 times that described in JCPDS and a thickness of 0.01 to 50 μm, and the coated tool is said to be excellent in wear resistance.

Prior Art Documents

Patent Documents

[0006] ​ [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-341008 [Patent Document 2] Japanese Patent Application Publication No. 7-97679 [Patent Document 3] Japanese Patent Application Publication No. 11-335813 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above circumstances and proposals, and has an object to provide a coated tool having a coating layer with improved durability in cutting processing. [Means for solving the problem]

[0008] The surface-coated cutting tool according to an embodiment of the present invention comprises: A substrate and a coating layer on the surface of the substrate are included. The coating layer includes an upper layer and a lower layer, the upper layer has an α-type Al2O3 layer with an average thickness of 1.0 μm or more and 20.0 μm or less, The lower layer has an average thickness of 1.0 μm or more and 20.0 μm or less, and is made of a material having the formula: (Al X Ti 1-X )N(X, the average of X avg , 0.40≦X avg <0.60), In the crystal orientation of the α-type Al2O3 crystal grains constituting the upper layer measured by electron backscatter diffraction on a longitudinal section of the coating layer, the area ratio of crystal grains existing in a range of 0 to 10 degrees between the normal direction to the substrate surface and the normal line to the {001} plane, which is the crystal face of the crystal grain, is 30% or more; the composite nitride crystal grains constituting the lower layer have an NaCl-type face-centered cubic structure, In the crystal orientation of the composite nitride crystal grains constituting the lower layer measured on the longitudinal section by electron backscatter diffraction, the area ratio of crystal grains existing such that the angle between the normal direction to the substrate surface and the normal to the {111} plane, which is the crystal face of the crystal grain, is within a range of 0 to 10 degrees is 30% or more.

[0009] Furthermore, the surface-coated cutting tool according to the above embodiment may satisfy the following items (1) or (1) and (2).

[0010] (1) An intermediate layer is provided between the upper layer and the lower layer, the intermediate layer being composed of one or more Ti compound layers selected from the group consisting of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride-oxycarbonate layer, and having a total average thickness of 0.1 to 5.0 μm.

[0011] (2) Among the layers in the Ti compound layer, the layer in contact with the upper layer is an oxycarbonitride layer. [Effects of the Invention]

[0012] The surface-coated cutting tool has a coating layer that is durable in cutting processing. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic view showing an example of a vertical cross section of a surface-coated cutting tool according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective schematic view of an example of a gas supply pipe in an example of an apparatus for manufacturing the surface-coated cutting tool according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the gas supply pipe of FIG. 2. [Figure 4] 3 is a cross-sectional view showing a gas nozzle of the gas supply pipe of FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Al-Ti composite nitride layers have excellent fracture resistance due to their high hardness, and are widely used as coating layers for surface-coated cutting tools used in interrupted cutting processes. However, as the Al content increases, thermal stability decreases, and hexagonal crystals precipitate during cutting processes where the cutting edge becomes hot, resulting in reduced wear resistance. The inventors have conducted research to prevent this deterioration in wear resistance, and as a result have found that an Al-Ti composite nitride layer with a low Al content has both superior fracture resistance and wear resistance due to its high hardness compared to known TiCN coating layers, even during cutting processes where the cutting edge becomes hot.

[0015] The present inventors have also found that in the lower Al-Ti composite nitride layer, when the crystal grains constituting the composite nitride layer are oriented in the {111} plane, i.e., when the normal to the {111} plane is parallel to the normal direction of the substrate, deformation of the crystal grains due to grain boundary sliding is suppressed, thereby improving toughness and fracture resistance of the coating layer.

[0016] Furthermore, the inventors have found that the provision of an α-type Al2O3 layer as the upper layer improves wear resistance, and that in particular, in cutting processes in which the cutting edge is exposed to high temperatures, chemical wear can be significantly suppressed by providing chemically stable α-type Al2O3, and that in addition, the wear resistance is further improved when the {001} orientation, i.e., the normal to the {001} plane is parallel to the normal direction of the substrate, By forming a Ti compound layer as an intermediate layer between the lower layer and the upper layer, the adhesion between the lower layer and the upper layer is improved, and further, by providing a Ti oxycarbonitride layer directly below the upper layer, the intermediate layer can further stabilize the above-mentioned {001} orientation. I also found out.

[0017] The present invention is based on these findings, and a surface-coated cutting tool according to an embodiment of the present invention will be described below. In this specification and claims, unless otherwise specified, the coating layer refers only to a film formed by chemical vapor deposition (CVD), and when a numerical range is expressed as "L to M" (L and M are both numerical values), this is synonymous with "not less than L and not more than M," and the range includes an upper limit (M) and a lower limit (L), and the upper limit (M) and the lower limit (L) have the same units. Furthermore, unless otherwise specified, the average value is an arithmetic average value.

[0018] 1.Coating layer FIG. 1 shows a schematic diagram of an example of a longitudinal section of a coating layer according to an embodiment of the present invention (a section perpendicular to the surface of the substrate, assuming that there are no minute irregularities on the surface of the substrate). As shown in Figure 1, a coating layer (2) is provided on a substrate (1). The coating layer (2) has an underlayer (5) provided on the substrate (1), a lower layer (3) of a composite nitride layer of Al and Ti provided on the underlayer (5), an upper layer (4) of an α-type Al2O3 layer provided on the lower layer (3), and a surface layer (6) provided on the upper layer. Here, the undercoat layer (5) and the surface layer (6) are provided selectively and are not essential. The following description will focus on the lower layer and upper layer that constitute the coating layer according to this embodiment.

[0019] 1-1. Lower layer The lower layer comprises a composite nitride layer of Al and Ti (hereinafter, sometimes referred to as an (AlTi)N layer).

[0020] (1) Average thickness The average thickness of the lower layer is preferably 1.0 μm or more and 20.0 μm or less. This is because if the average thickness is less than 1.0 μm, the lower layer is too thin to ensure sufficient durability, while if the average thickness exceeds 20.0 μm, the crystal grains in the lower layer tend to become coarse, making chipping more likely to occur. The average thickness of the lower layer is more preferably 3.0 μm or more and 16.0 μm or less.

[0021] (2) Composition The (AlTi)N layer has a composition of the formula: (Al X Ti 1-X)N, the average value of X is X avg , 0.40≦X avg Preferably, X is less than 0.60. avg If the ratio is less than 0.40, the oxidation resistance of the (AlTi)N layer decreases, whereas if the ratio is 0.60 or more, the thermal stability decreases, hexagonal crystals precipitate, and the wear resistance decreases. X avg A more preferable value is 0.45 or more and 0.55 or less.

[0022] (3) Atomic ratio of (AlTi) to N In the lower (AlTi)N layer, the atomic ratio of the metal element (AlTi) to N (nitrogen) is formed to be (AlTi):N=0.8 to 1.2:1, but this range may be exceeded due to unintended disturbances in the film formation conditions described below.

[0023] (5) Crystal structure The (AlTi)N layer has (AlTi)N crystal grains with a NaCl-type face-centered cubic structure. While the presence of (AlTi)N crystal grains with a NaCl-type face-centered cubic structure does not mean that crystal grains other than those with a NaCl-type face-centered cubic structure are included, the presence of crystal grains other than those with a NaCl-type face-centered cubic structure is unintended. The presence of (AlTi)N crystal grains with a NaCl-type face-centered cubic structure is confirmed when measuring the area ratio of crystal grains oriented in a specific crystal plane using electron backscatter diffraction (EBSD), which will be described later.

[0024] (5) {111} plane orientation When the normal to the {111} plane of the crystal grains constituting the lower layer is parallel to the normal direction of the substrate, deformation due to grain boundary sliding of the crystal grains is suppressed, improving toughness and chipping resistance of the coating layer. It is preferable that the area ratio of the crystal grains in the composite nitride crystal grains constituting the lower layer, measured by EBSD on a longitudinal section of the coating layer, in which the angle between the normal to the substrate surface and the normal to the {111} plane, which is the crystal plane of the crystal grain, is within a range of 0 to 10 degrees, is 30% or more.

[0025] If this area ratio is 30% or more, deformation due to grain boundary sliding of crystal grains is suppressed, improving toughness and chipping resistance of the coating layer. The upper limit of this area ratio may be 100%. However, in an example of the manufacturing method described below, the upper limit is about 72%.

[0026] 1-2. Upper layer The upper layer has an α-type Al2O3 layer.

[0027] (1) Average thickness The average thickness of the upper layer is preferably 1.0 μm or more and 20.0 μm or less. The reason is that if the average thickness is less than 1.0 μm, the upper layer is too thin to ensure sufficient durability, while if the average thickness is more than 20.0 μm, the crystal grains in the upper layer tend to become coarse, making chipping more likely to occur. The average thickness of the upper layer is more preferably 3.0 μm or more and 16.0 μm or less.

[0028] (2) Composition The composition of the α-type Al2O3 layer included in the upper layer is not limited to the stoichiometric composition.

[0029] (3) {001} orientation When the normal to the {001} plane of the crystal grains constituting the upper layer is parallel to the normal direction of the substrate, the wear resistance is further improved. The {001} plane orientation is preferably such that, in the crystal orientation of the α-type Al2O3 grains constituting the upper layer measured by electron backscatter diffraction (EBSD) on a longitudinal section of the coating layer, the area ratio of crystal grains existing in a range of 0 to 10 degrees between the normal direction to the substrate surface and the normal line to the {001} plane, which is the crystal plane of the crystal grain, is 30% or more.

[0030] If this area ratio is 30% or more, the abrasion resistance of the coating layer is improved. The upper limit of this area ratio may be 100%. However, in an example of the manufacturing method described below, the upper limit is about 62%.

[0031] 1-3. Middle class It is preferable to provide an intermediate layer between the upper layer and the lower layer, which is a Ti compound layer consisting of one or more Ti compound layers selected from a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer, and a carbonitride oxide layer, and has a total average thickness of 0.1 to 5.0 μm. The intermediate layer having this average thickness improves the adhesion between the lower and upper layers and improves the durability of the coating layer. Furthermore, if the intermediate layer has a Ti oxycarbonitride layer directly below the upper layer, the {001} orientation can be further stabilized.

[0032] 1-4.Other layers (1) Base layer A lower layer having one or more Ti compound layers (not limited to stoichiometric compositions) selected from Ti nitride layers, carbide layers, and carbonitride layers, and having a total average thickness of 0.1 to 20.0 μm may be provided. Providing the lower layer between the substrate and the (AlTi)N layer improves adhesion between the substrate and the (AlTi)N layer. If the total average thickness of the lower layer is less than 0.1 μm, the improvement in adhesion by the lower layer is insufficient. On the other hand, if the total average thickness of the lower layer is greater than 20.0 μm, the crystal grains in the lower layer tend to become coarse, making chipping more likely to occur.

[0033] (2) Surface layer Furthermore, TiN (not limited to stoichiometric composition) may be provided as a surface layer on the surface of the upper layer because TiN has a golden color tone and can be used as an identification layer to distinguish, for example, whether the coated cutting tool is unused or used based on the change in the color tone of the surface of the coated cutting tool. The average thickness of this TiN layer as an identification layer may be 0.1 to 1.0 μm.

[0034] (4) Unintentional Layers When the gas pressure or temperature inside a CVD reactor becomes unstable due to an unpredictable (unintended) cause, a very small amount of a layer different from the base layer, lower layer, middle layer, upper layer, and surface layer may be unintentionally deposited.

[0035] 1-5.Inevitable impurities The lower layer, upper layer, intermediate layer, underlayer, and surface layer may contain trace amounts of Cl as an inevitable impurity. Cl is inevitably present in trace amounts when films are formed by CVD using chloride as a raw material gas. If the Cl content is 0.10 atomic % or less of the total atoms, the Cl provides the (AlTi)N layer with lubricity. In addition to the aforementioned Cl, unavoidable impurities may include unintended impurities (oxygen, carbon) that occur during the manufacturing process.

[0036] 2.Base (1)Material Any known substrate material can be used as long as it does not impede the achievement of the object of the present invention. Examples include WC-based cemented carbide (containing Co in addition to WC, and also containing carbides or nitrides of Ti, Zr, Ta, Nb, Cr, etc.), cermet (containing TiC, TiN, TiCN, etc. as its main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide), and cBN sintered body.

[0037] (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 shape of an insert and the shape of a solid tool.

[0038] 3.Measurement method The average thickness of the lower layer and upper layer, the composition of the lower layer, and the plane orientation (area ratio of crystal grains in which the angle between the substrate normal and a specific plane is within a predetermined range) of this embodiment are determined as follows.

[0039] (1) Average thickness Here, the average thickness of the (AlTi)N layer or the like can be determined as follows: The vertical cross section of the coating layer is polished using an ion milling device or the like. Each layer constituting the coating layer is observed using a scanning electron microscope (SEM), and the boundaries of each layer are defined based on the difference in shading. The thickness of each layer is then measured at multiple locations (e.g., five locations), and the average of these measurements is used to determine the average thickness of each layer. The definition of the surface of the substrate is given below.

[0040] The surface of the substrate is defined as the average line (straight line) of the interface roughness between the substrate and the coating layer in an observed image of the longitudinal section. That is, the interface between the coating layer (if a base layer exists, use the base layer instead of the (AlTi)N layer) and the substrate is determined from the observed image of the longitudinal section, and an average line (straight line) is drawn on the roughness curve of the interface between the coating layer and the substrate, which is defined as the surface of the substrate. The direction perpendicular to this average line is defined as the direction perpendicular to the substrate (normal direction, thickness direction of the coating layer).

[0041] Furthermore, even if the substrate has a curved surface, if the radius of curvature of the curved surface is sufficiently large compared to the thickness of the coating layer, the interface between the coating layer and the substrate in the measurement area will be approximately flat, and the surface of the substrate can be determined using a similar method.

[0042] (2) Atomic ratio of Al to Ti in the (AlTi)N layer The atomic ratio of the components constituting the (AlTi)N layer is determined as follows. The atomic ratio X of Al is measured using an electron probe microanalyzer (EPMA). The surface of the coating layer is polished to expose the (AlTi)N layer. An electron beam is irradiated onto the (AlTi)N layer from the surface side of the sample, and the average value of 10 characteristic X-ray analysis results is used.

[0043] (4) Planar orientation The {111} plane orientation of the lower layer and the {001} plane orientation of the upper layer are measured as follows. The sample with the vertical cross section of the coating layer as the polished surface is set in the lens barrel of a field emission-scanning electron microscope (FE-SEM).

[0044] Using a backscatter diffraction image device (Electron Backscatter Diffraction: EBSD, for example, OIM Data Collection manufactured by EDAX / TSL) attached to the FE-SEM, for example, An electron beam with an accelerating voltage of 15 kV and an irradiation current of 1 nA is applied to the polished surface at an incident angle of 70 degrees, and the EBSD pattern is measured for the coating layer within a measurement range of 50 μm in length horizontally to the substrate surface and the film thickness in a direction perpendicular to the substrate surface at intervals of 0.01 μm / step.

[0045] The data obtained with the EBSD measurement device is processed using analysis software (for example, OIM Data Analysis ver. 7.3 manufactured by EDAX / TSL) to determine the area percentage of crystal grains in the lower layer where the angle between the normal to the substrate surface and the normal to the {111} plane of the (AlTi)N composite nitride crystal grains is in the range of 0 to 10 degrees.Furthermore, the area percentage of crystal grains in the upper layer where the inclination angle between the normal to the substrate surface and the normal to the {001} plane, which is the crystal plane of the α-type Al2O3 crystal grains, is in the range of 0 to 10 degrees is determined.

[0046] The calculation involves analyzing the crystal orientation, determining the pixels measured for the lower layer where the angle between the normal to the substrate surface and the normal to the {111} plane of the (AlTi)N composite nitride crystal grains is within a range of 0 to 10 degrees, and calculating the percentage as the area percentage of the {111} plane oriented crystal grains in the lower layer.Furthermore, determining the pixels measured for the upper layer where the angle between the normal to the substrate surface and the normal to the {001} plane, which is the crystal plane of the α-type Al2O3 crystal grains, is within a range of 0 to 10 degrees, and calculating the percentage as the area percentage of the {001} plane oriented crystal grains in the upper layer.

[0047] 4. Manufacturing method 1) The lower layer, (AlTi)N The method for manufacturing the (AlTi)N layer of this embodiment includes, for example, Gas group A consisting of H2, N2, and NH3; Gas group B consisting of AlCl3, TiCl4, H2, and Ar; This can be carried out by the CVD method using

[0048] Here, gas groups A and B are supplied separately within the reaction chamber of the thermal CVD apparatus up to just before the object to be deposited, where they are mixed and reacted. This is effective for uniformly supplying gas species with high reactivity to each other across the deposition region, thereby forming a uniform coating. The detailed technical content is described, for example, in Japanese Patent Publication No. 6511798.

[0049] 2) The upper layer is the α-type Al2O3 layer For example, it is produced by carrying out chemical vapor deposition in two stages: an initial nucleation stage of α-type Al2O3 and a growth stage of α-type Al2O3.

[0050] <α-Al2O3 initial nucleation conditions> AlCl3, CO2, HCl, and the balance H2 are used as reaction gases. <α-Al2O3 growth conditions> AlCl3, CO2, HCl, H2S, and the balance H2 are used as reaction gases.

[0051] 3) Base layer, intermediate layer and surface layer There are no restrictions on the CVD manufacturing method and manufacturing equipment for the underlayer, intermediate layer, and surface layer, and known methods, equipment, and manufacturing conditions may be appropriately adopted. [Example]

[0052] The present invention will be described below with reference to examples, but is not limited to these examples. That is, an insert cutting tool using a WC-based cemented carbide as the substrate will be described, but the substrate may be made of any material as described above, and may have the shape of a solid tool, as described above.

[0053] 1. Manufacturing the substrate The raw material powders prepared were WC powder, TiC powder, ZrC powder, TaC powder, NbC powder, Cr3C2 powder, TiN powder, and Co powder. These raw material powders were blended according to the composition shown in Table 1, and wax was added. The mixture was ball milled in acetone for 24 hours, dried under reduced pressure, and then pressed into a green compact of the desired shape at a pressure of 98 MPa.

[0054] This green compact was then vacuum sintered, and after sintering, the cutting edge was honed to R: 0.05 mm to produce substrates A to C made of WC-based cemented carbide with the insert shape of CNMG120408-MA manufactured by Mitsubishi Materials Corporation.

[0055] 2. Film formation An (AlTi)N layer was formed on the surface of each of the substrates A to C using the CVD apparatus (see FIGS. 2 to 4) described in Japanese Patent No. 6511798, to obtain Examples 1 to 10 shown in Table 5. The film formation conditions were as shown in Table 2, and were roughly as follows:

[0056] 1) Lower layer Reaction gas composition (content of gas components is in volume %): Gas group A H2: 30.0-50.0%, N2: 1.0-2.0%, NH3: 0.5-1.5% Gas group B AlCl3: 0.10-0.30%, TiCl4: 0.10-0.30%, Ar: 0.1~0.5%, H2: remainder Reaction atmosphere pressure: 4.5 to 5.0 kPa Reaction atmosphere temperature: 750-900℃

[0057] In the CVD apparatus shown in Figs. Gas supply pipe rotation speed: 2~5 rpm Gas supply pipe nozzle angle α:180° β1 and β2: 155° γ1 and γ2: 55°

[0058] 2) Upper layer <α-Al2O3 initial nucleation conditions> Reaction gas composition (volume %): AlCl3: 1.8%, CO2: 3.0%, HCl: 1.5%, balance H2 Reaction atmosphere pressure 7.0~9.0kPa Reaction atmosphere temperature 900~1000℃

[0059] <α-Al2O3 growth conditions> Reaction gas composition (volume %): AlCl3: 1.8%, CO2: 3.0%, HCl: 1.5%, H2S: 0.3~0.5%, balance H2 Reaction atmosphere pressure 7.0~9.0kPa Reaction atmosphere temperature 900~1000℃

[0060] The underlayers and / or surface layers of Examples 3 to 10 were formed using a CVD apparatus normally used for forming coating layers on coated tools under the conditions shown in Table 4, and the underlayers and / or surface layers shown in Table 5 were formed.

[0061] For comparison, (AlTi)N layers were formed on the surfaces of substrates A to C under the film formation conditions shown in Table 2, and Comparative Examples 1 to 10 shown in Table 6 were obtained. In the manufacturing process of the comparative example, the composition of the raw material gas was changed from that of the example. The underlayers and / or surface layers of Comparative Examples 3 to 10 were formed using a CVD apparatus normally used for forming coating layers on coated tools, under the conditions shown in Table 4, to form the underlayers and / or surface layers shown in Table 5.

[0062] Furthermore, for comparison with conventional technology, a TiCN layer and the underlayer, underlayer and surface layer shown in Table 5 were formed on the surfaces of substrates A and C under the conditions shown in Table 4, and Conventional Examples 1 and 2 shown in Table 6 were produced.

[0063] For Examples 1 to 10 and Comparative Examples 1 to 10, the average thickness of each layer, the content of each element, the area ratio of crystal grains in which the angle between the substrate normal and the normal to the {111} plane of the lower layer is 0 to 10°, and the area ratio of crystal grains in which the angle between the substrate normal and the normal to the {001} plane of the upper layer is 0 to 10° were measured using the methods described above. These results are summarized in Table 6.

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] [Table 4]

[0068] [Table 5]

[0069] In Table 5, "-" indicates that no test was performed.

[0070] [Table 6]

[0071] In Table 6, " / " and "-" indicate that there is no applicable item. It was also confirmed that the composite nitride crystals constituting the composite nitride layer in all Examples and Comparative Examples had an NaCl-type face-centered cubic structure.

[0072] Cutting test: Wet end face machining Work material: JIS SCM440 Hollow round bar (outer diameter Φ180, inner diameter Φ50) with four equally spaced grooves (width 20 mm) Cutting speed: 300m / min. Cut: 1.5mm Feed rate: 0.3mm / rev. Number of cuts: 15 passes

[0073] The results of the cutting tests are shown in Table 7. Note that for Comparative Examples 1 to 10 and Conventional Examples 1 and 2, the number of cutting passes until the end of life was caused by chipping or flank wear (life judgment criterion: flank wear width 0.4 mm).

[0074] [Table 7]

[0075] As is clear from the results shown in Table 6, all of Examples 1 to 10 had little wear, no chipping, and improved hardness and toughness, and exhibited excellent cutting performance over a long period of time. In contrast, Comparative Examples 1 to 10 and Conventional Examples 1 and 2 all had a large amount of wear or chipping occurred, and the number of cutting passes imposed in the cutting test was not met, reaching the end of their service life in a short period of time. [Explanation of symbols]

[0076] 1 Base 2 Covering layer 3 Lower layer 4 Upper layer 5 Base layer 6 Surface layer 11 Gas supply pipe 12 Partition member 13 Center of gas supply pipe 14 Gas Group A Distribution Section 15 Gas Group B Distribution Section 16 Gas group A nozzle 17 Gas group B nozzle 18 Center of the outer peripheral opening end of the gas group A nozzle 19 Center of the outer peripheral opening end of the gas group B nozzle 20 squirting mouth α angle β1 angle β2 angle γ1 angle γ2 angle

Claims

1. A surface-coated cutting tool having a substrate and a coating layer on a surface of the substrate, The coating layer includes an upper layer and a lower layer, The upper layer has an average thickness of 1.0 μm or more and 20.0 μm or less. ２ O ３ a layer; The lower layer has an average thickness of 1.0 μm or more and 20.0 μm or less, and is a compound of the formula: (Al Ｘ Ti １－Ｘ ) N(X, the average value of X ａｖｇ is 0.40≦X ａｖｇ <0.60), The α-type Al constituting the upper layer was measured by electron backscatter diffraction on a longitudinal section of the coating layer. ２ O ３ In the crystal orientation of the crystal grains, the area ratio of the crystal grains existing in a range of 0 to 10 degrees between the normal direction of the base surface and the normal line of the {001} crystal plane of the crystal grains is 30% or more; the composite nitride crystal grains constituting the lower layer have an NaCl-type face-centered cubic structure, In the crystal orientation of the composite nitride crystal grains constituting the lower layer measured on the longitudinal section by electron backscatter diffraction, the area ratio of crystal grains existing within an angle between the normal direction to the substrate surface and the normal to the {111} plane, which is the crystal plane of the crystal grain, is within a range of 0 to 10 degrees is 30% or more. A surface-coated cutting tool characterized by:

2. 2. The surface-coated cutting tool according to claim 1, further comprising an intermediate layer between the upper layer and the lower layer, the intermediate layer being made of one or more Ti compound layers selected from the group consisting of a Ti carbide layer, a nitride layer, a carbonitride layer, a carbonate layer and a carbonitride oxide layer, and having a total average thickness of 0.1 to 5.0 μm.

3. 3. The surface-coated cutting tool according to claim 2, wherein the layer in the Ti compound layer that is in contact with the upper layer is an oxycarbonitride layer.

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