SURFACE-COATED CUTTING TOOL

Abstract

A surface-coated cutting tool includes a tool body made of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet and a hard coating layer that includes a lower layer and an upper layer and formed on the tool body. The lower layer is composed of a Ti compound layer including at least a TiCN layer. The upper layer includes an Al.sub.2O.sub.3 layer having an -type crystal structure. In the Al.sub.2O.sub.3 crystal grains of the upper layer, when a coincidence grain boundary distribution graph is measured, sulfur is segregated in a grain boundary of 31 or more and a grain boundary length thereof is 20% to 50% relative to the whole grain boundary length in the constituent atom sharing lattice point form of 3 or more. Absolute values of residual stress of a flank face and a rake face are 100 MPa or less.

Claims

1. A surface-coated cutting tool comprising: a tool body that is made of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet; and a hard coating layer that includes a lower layer and an upper layer and is formed on a surface of the tool body, wherein (a) the lower layer has a total average layer thickness of 3 to 20 m and includes two or more of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer, and at least one of the layers is a Ti compound layer including a TiCN layer, (b) the upper layer has a average layer thickness of 2 to 15 m and includes an Al.sub.2O.sub.3 layer having an -type crystal structure, and (c) regarding Al.sub.2O.sub.3 crystal grains of the upper layer, in a case where a polished cross-section is subjected to observation and elemental analysis using high angle annular dark field scanning transmission electron microscopy and observation using a field-emission-type scanning electron microscope and an electron beam backward scattering diffraction device, angles between each of normal lines of crystal lattice planes formed of corundum hexagonal crystal lattices and a normal line of the polished cross-section are measured, and from results of the measurement, a crystal orientation relationship between the mutually adjacent crystal lattices is calculated and the distribution of lattice points (constituent atom sharing lattice points) where respective constituent atoms constituting a crystal lattice interface share one constituent atom between the crystal lattices is calculated; in a case where a constituent atom sharing lattice point form in which N lattice points that do not share any constituent atoms between the constituent atom sharing lattice points are present is expressed by N+1, distribution ratios of individuals of N+1 are calculated; and in a coincidence grain boundary distribution graph showing ratios of respective coincidence grain boundary lengths formed of the constituent atom sharing lattice points in the whole coincidence grain boundary length, sulfur is segregated in a grain boundary in the constituent atom sharing lattice point form of 31 or more, and a grain boundary length thereof is 20% to 50% relative to the whole grain boundary length in the constituent atom sharing lattice point form of 3 or more.

2. The surface-coated cutting tool according to claim 1, wherein the outermost surface layer of the lower layer (a) includes the TiCN layer having a layer thickness of at least 500 nm or more and contains oxygen only in a depth region with a depth of up to 500 nm from an interface between the TiCN layer and the upper layer, except for oxygen as inevitable impurities, and an average content of the oxygen contained in the depth region is 1 to 3 atom % of a total content of Ti, C, N, and O contained in the depth region.

3. The surface-coated cutting tool according to claim 1, wherein regarding the Al.sub.2O.sub.3 crystal grains of the upper layer, in a case where, using a field-emission-type scanning electron microscope and an electron beam backward scattering diffraction device, crystal grains having a corundum hexagonal crystal lattice that are present within a measurement range of a polished cross-section are individually irradiated with electron beams to measure inclined angles between normal lines of (0001) planes that are crystal planes of the crystal grains and a normal line of the surface of the tool body, and the measured inclined angles of 0 to 45 degrees among the measured inclined angles are divided every pitch of 0.25 degrees and expressed by a inclined angle frequency distribution made by totalizing the frequencies present within the respective divisions, a maximum peak is present in a inclined angle division of 0 to 10 degrees, and a total of frequencies present in the range of 0 to 10 degrees is 50% or greater of the entire frequencies in a inclined angle frequency distribution graph.

4. The surface-coated cutting tool according to claim 1, wherein absolute values of residual stresses of a flank face and a rake face of the surface-coated cutting tool are 100 MPa or less.

5. The surface-coated cutting tool according to claim 2, wherein regarding the Al.sub.2O.sub.3 crystal grains of the upper layer, in a case where, using a field-emission-type scanning electron microscope and an electron beam backward scattering diffraction device, crystal grains having a corundum hexagonal crystal lattice that are present within a measurement range of a polished cross-section are individually irradiated with electron beams to measure inclined angles between normal lines of (0001) planes that are crystal planes of the crystal grains and a normal line of the surface of the tool body, and the measured inclined angles of 0 to 45 degrees among the measured inclined angles are divided every pitch of 0.25 degrees and expressed by a inclined angle frequency distribution made by totalizing the frequencies present within the respective divisions, a maximum peak is present in a inclined angle division of 0 to 10 degrees, and a total of frequencies present in the range of 0 to 10 degrees is 50% or greater of the entire frequencies in a inclined angle frequency distribution graph.

6. The surface-coated cutting tool according to claim 2, wherein absolute values of residual stresses of a flank face and a rake face of the surface-coated cutting tool are 100 MPa or less.

7. The surface-coated cutting tool according to claim 3, wherein absolute values of residual stresses of a flank face and a rake face of the surface-coated cutting tool are 100 MPa or less.

8. The surface-coated cutting tool according to claim 5, wherein absolute values of residual stresses of a flank face and a rake face of the surface-coated cutting tool are 100 MPa or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0074] These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawing(s), wherein like designations denote like elements in the various views, and wherein:

[0075] FIG. 1 is a schematic view of a cross-section in a direction vertical to a surface of a tool body regarding an invention coated tool.

[0076] FIG. 2 shows an example of a coincidence grain boundary distribution graph regarding an invention coated tool.

[0077] FIG. 3 shows an example of a inclined angle frequency distribution graph regarding the invention coated tool.

DETAILED DESCRIPTION OF THE INVENTION

[0078] Embodiments of a coated tool of the invention will be described in detail based on examples.

Examples

[0079] A WC powder, a TiC powder, a ZrC powder, a TaC powder, a NbC powder, a Cr.sub.3C.sub.2 powder, a TiN powder, and a Co powder having an average grain size of 1 to 3 m were prepared as raw material powders, and these raw material powders were blended according to a blending composition shown in Table 1. Wax was further added and mixed therewith using a ball mill for 24 hours in acetone and dried under reduced pressure. Thereafter, the resulting material was press-formed into a green compact having a predetermined shape at a pressure of 98 MPa, and this green compact was vacuum-sintered by being kept at a predetermined temperature of 1370 C. to 1470 C. for 1 hour in a vacuum of 5 Pa. After sintering, tool bodies A to E made of a WC-based cemented carbide and having an insert shape defined in ISO-CNMG120408 were produced.

[0080] A TiCN powder (TiC/TiN=50/50 in terms of mass ratio), a ZrC powder, a TaC powder, a NbC powder, a Mo.sub.2C powder, a WC powder, a Co powder, and a Ni powder having an average grain size of 0.5 to 2 m were prepared as raw material powders. These raw material powders were blended according to a blending composition shown in Table 2, wet-mixed using a ball mill for 24 hours, and dried. Thereafter, the resulting material was press-formed into a green compact at a pressure of 98 MPa, and this green compact was sintered by being kept at a temperature of 1500 C. for 1 hour under a nitrogen atmosphere of 1.3 kPa. After sintering, tool bodies a to e made of a TiCN-based cermet and having an insert shape defined in ISO-CNMG120412 were produced.

[0081] Next, each of the tool bodies A to E and a to e was put into a normal chemical vapor deposition device to produce invention coated tools 1 to 13 according to the following procedures.

[0082] (a) First, under conditions shown in Table 3, a Ti compound layer was deposited as a lower layer having a target layer thickness shown in Table 7.

[0083] (b) Next, under conditions shown in Table 4, an oxygen-containing TiCN layer (that is, 0.5 to 3 atom % (O/(Ti+C+N+O)100) of oxygen was contained only in a depth region with a depth of up to 500 nm from a surface of the layer) was formed as an outermost surface layer of the lower layer so as to have a target layer thickness shown in Table 8. In the oxygen-containing TiCN layer type D of Table 4, a CO gas was not added during 5 to 30 minutes before termination of the vapor deposition time.

[0084] (c) Next, under conditions shown in Table 5, an oxidation treatment (lower layer surface treatment) was performed on the TiCN layer as the outermost surface of the lower layer using a mixture gas of CO and CO.sub.2.

[0085] (d) Next, initial growth of Al.sub.2O.sub.3 was performed under initial growth conditions shown in Table 6, and deposition was performed under upper layer forming conditions shown in Table 6 until a target layer thickness shown in Table 8 was obtained.

[0086] (e) Next, a polishing treatment including a wet blast treatment was performed with 200 meshes of Al.sub.2O.sub.3 grains at a projection pressure of 0.12 MPa to produce the invention coated tools 1 to 13 shown in Table 8.

[0087] For comparison, the steps (b), (c), (d), and (e) were performed under conditions departing from the production conditions of the invention coated tools 1 to 13, and thus comparative coated tools 1 to 13 shown in Table 9 were produced.

[0088] Next, regarding Al.sub.2O.sub.3 of the upper layer of the hard coating layer, angles of normal lines of crystal lattice planes of the Al.sub.2O.sub.3 crystal grains were measured using a field-emission-type scanning electron microscope and an electron beam backward scattering diffraction device, and from the results of the measurement, a crystal orientation relationship between the mutually adjacent crystal lattices was calculated to obtain a coincidence grain boundary distribution graph of Al.sub.2O.sub.3 of the upper layer.

[0089] Specifically, the coincidence grain boundary distribution graph was measured by the following method.

[0090] In a state in which a cross-section of the Al.sub.2O.sub.3 layer as the upper layer of each of the invention coated tools 1 to 13 was treated to be a polished surface, the coated tool was set in a lens tube of a field-emission-type scanning electron microscope, and crystal grains having a corundum hexagonal crystal lattice present within a measurement range of the polished cross-section was individually irradiated with electron beams having an accelerating voltage of 15 kV at an incident angle of 70 degrees with respect to the polished cross-section and an illumination current of 1 nA. More specifically, in a region that was 50 m wide in a direction parallel to the surface of the base body and whose upper limit was a layer thickness of the Al.sub.2O.sub.3 layer in a direction perpendicular to the direction of the surface of the base body, electron beams were irradiated at intervals of 0.1 m/step using an electron beam backward scattering diffraction device, and orientations of normal lines of the planes of the crystal lattices constituting the crystal grains were measured at the respective measurement points irradiated with the electron beams. From results of the measurement, a crystal orientation relationship between the crystal lattices at the adjacent measurement points was calculated. From results of the calculation, among the mutually adjacent measurement points, it was regarded that a crystal grain boundary was present between measurement points between which the crystal orientation angle difference was 5 degrees or greater, a group of the measurement points surrounded by the crystal grain boundary was specified as one crystal grain, and the entire crystal grains were specified. With this, in a case where the crystal orientation relationship between the measurement points constituting a crystal lattice interface was within the range of an error =5 with respect to a value of the angle between the crystal grains constituting the coincidence grain boundary as described in the literatures such as the article of H. Grimmer, etc, it was regarded that a coincidence grain boundary was present between measurement points, and a ratio of N+1 coincidence grain boundary relative to the whole grain boundary length was obtained. The measurement results are shown in Table 8 as a distribution ratio (%) of 3. As a method of calculating the distribution ratio of 31 or more, coincidence grain boundary lengths of 3, 7, 11, 17, 19, 21, 23, and 29 were calculated from the obtained measurement results, and a value obtained by subtracting the sum of the coincidence grain boundary lengths from the whole coincidence grain boundary length was used and obtained as a distribution ratio (%) of 31 or more.

[0091] The measurement results are shown in Table 8.

[0092] Next, regarding the Al.sub.2O.sub.3 layer as the upper layer of the comparative coated tools 1 to 13, a coincidence grain boundary distribution graph was obtained by the same method as in the cases of the invention coated tools 1 to 13.

[0093] The measurement results are shown in Table 9.

[0094] FIG. 2 shows an example of the coincidence grain boundary distribution graph obtained regarding the invention coated tool 1 obtained by the measurement.

[0095] Next, regarding the Al.sub.2O.sub.3 crystal grains constituting the upper layer of the invention coated tools 1 to 13, elemental map analysis was performed by an energy dispersive-type X-ray analysis method using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) in the measurement range of the polished cross-section in which the constituent atom sharing lattice point form had been measured, to perform the measurement regarding the segregation of sulfur in the Al.sub.2O.sub.3 crystal grain boundary. The measured elements were Al, O, Cl, and S.

[0096] The state in which sulfur is segregated in a grain boundary of the Al.sub.2O.sub.3 crystal grains is defined to be that when line analysis is performed on the elemental map data, a value obtained by subtracting the background value at the time of the measurement from the strength by the sulfur atoms on the grain boundary of the Al.sub.2O.sub.3 crystal grains is three or more times the average value of a value obtained by subtracting the background value at the time of the measurement from the strength by the sulfur atoms in the Al.sub.2O.sub.3 crystal grains. Among the grain boundary lengths of the Al.sub.2O.sub.3 crystal grains of the constituent atom sharing lattice point form of 31 or more, the grain boundary length in the constituent atom sharing lattice point form of 31 or more in which sulfur is segregated is calculated using a field-emission-type scanning electron microscope and an electron beam backward scattering diffraction device, and then divided by the whole grain boundary length in the constituent atom sharing lattice point form of 3 or more to obtain a ratio thereof.

[0097] The value thereof is shown in Table 8.

[0098] Next, regarding the Al.sub.2O.sub.3 layer as the upper layer of the comparative coated tools 1 to 13, a ratio of the grain boundary length in the constituent atom sharing lattice point form of 31 or more in which sulfur was segregated among the grain boundary lengths of the Al.sub.2O.sub.3 crystal grains in the constituent atom sharing lattice point form of 31 or more was obtained relative to the whole grain boundary length in the constituent atom sharing lattice point form of 3 or more in the same manner as in the same manner of the invention coated tools 1 to 13.

[0099] The value thereof is shown in Table 9.

[0100] In a case where the segregation of the sulfur in the grain boundary in the constituent atom sharing lattice point form of 31 or more is less than 20%, predetermined cracks are not formed, and thus the peeling resistance effect is reduced. In a case where the segregation of the sulfur is greater than 50%, the upper layer itself embrittles.

[0101] Next, regarding the TiCN layer constituting the outermost surface layer of the lower layer in the invention coated tools 1 to 13 and the comparative coated tools 1 to 13, the average oxygen content (=O/(Ti+C+N+O)100) in a depth region with a depth of up to 500 nm in a layer thickness direction of the TiCN layer was obtained as follows: using an Auger electron spectral analyzer, a polished cross-section of the coated tool was irradiated with electron beams having a diameter of 10 nm in a distance range corresponding to the film thickness of the Ti carbide layer from the outermost surface of the Ti carbonitride layer of the lower layer to measure intensities of Auger peaks of Ti, C, N, and O, and a ratio of the Auger peak intensity of O was calculated from the sum of the peak intensities. With the above-described method, the maximum oxygen content (=O/(Ti+C+N+O)100) in a depth region deeper than 500 nm was obtained to obtain a content of oxygen other than impurities. The maximum oxygen content is the maximum value of the oxygen content in the depth region deeper than 500 nm.

[0102] The values of the average oxygen content in the depth region with a depth of up to 500 nm and the maximum oxygen content in the depth region deeper than 500 nm are shown in Tables 8 and 9.

[0103] In addition, in order to obtain a content of the oxygen inevitably contained in the TiCN layer, chemical vapor deposition was performed under the following conditions on the surface of a tool body separately made of a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet.

[0104] Composition of Reaction Gas (vol %): 2% to 10% of TiCl.sub.4, 0.5% to 1.0% of CH.sub.3CN, 25% to 60% of N.sub.2, H.sub.2 as balance

[0105] Reaction Atmosphere Temperature: 780 C. to 930 C.

[0106] Reaction Atmosphere Pressure: 6 to 10 kPa

[0107] Accordingly, a TiCN (hereinafter, referred to as inevitable oxygen-containing TiCN) layer intentionally containing no oxygen was formed with a layer thickness of 3 m or greater. The content of the oxygen contained inevitably in a region deeper than 100 nm in a layer thickness direction from a surface of the inevitable oxygen-containing TiCN layer was obtained from a ratio of the content of O to a total content of Ti, C, N, and O contained in the depth region using an Auger electron spectral analyzer, and the content of the inevitable oxygen obtained within an accuracy range of the Auger electron spectral analyzer was set to be less than 0.5 atom %.

[0108] In addition, regarding the Al.sub.2O.sub.3 layer as the upper layer of the invention coated tools 1 to 13 and the comparative coated tools 1 to 13, in a state in which the longitudinal section of the upper layer was treated to be a polished surface, the coated tool was set in a lens tube of a field-emission-type scanning electron microscope, and crystal grains having a corundum hexagonal crystal lattice present within a measurement range of the polished cross-section was individually irradiated with electron beams having an accelerating voltage of 15 kV at an incident angle of 70 degrees with respect to the polished cross-section and an illumination current of 1 nA. Within a measurement range having a length of 100 m in a direction horizontal to the surface of the tool body and a distance that was equal to or less than the film thickness along the cross-section in a direction vertical to the surface of the tool body, inclined angles between normal lines of the (0001) planes that were crystal planes of the crystal grains and a normal line of the surface of the base body were measured at intervals of 0.01 m/step using an electron beam backward scattering diffraction device. The measured inclined angles of 0 to 45 degrees among the measured inclined angles were divided every pitch of 0.25 degrees, and a inclined angle frequency distribution graph was made by totalizing the frequencies present within the respective divisions.

[0109] A maximum peak was present in a inclined angle division of 0 to 10 degrees, and a total of the frequencies present in the range of 0 to 10 degrees was obtained as a frequency ratio in the entire frequencies in the inclined angle frequency distribution graph.

[0110] The results thereof are shown in Tables 8 and 9.

[0111] FIG. 3 shows an example of the inclined angle frequency distribution graph obtained regarding the invention coated tool 1 by the measurement.

[0112] Next, residual stresses of a flank face and a rake face including at least a cutting edge ridge line part of the invention coated tools 1 to 13 and the comparative coated tools 1 to 13 were measured through the following method.

[0113] A measurement sample was inserted into an X-ray analyzer and X-rays were made incident on a measurement surface (flank face or rake face) of the tool body using Cu (wavelength: 0.1541 nm) as an X-ray source. A (13-4,10) plane was selected as the crystal plane of Al.sub.2O.sub.3 to be measured and the stress was measured using a sin.sup.2 method.

[0114] Tables 8 and 9 show the absolute values of the measured residual stress values.

[0115] Thicknesses of the constituent layers of the hard coating layer in the invention coated tools 1 to 13 and the comparative coated tools 1 to 13 were measured (longitudinal section measurement) using a scanning electron microscope, and all of the layers had a average layer thickness (a average value obtained through the measurement at 5 points) that was substantially the same as a target layer thickness.

TABLE-US-00001 TABLE 1 Blending Composition (mass %) Type Co TiC ZrC TaC NbC Cr.sub.3C.sub.2 TiN WC Tool A 5.1 0.5 1.5 2.0 Balance body B 5.5 1.5 0.5 1.0 1.0 Balance C 6.8 1.0 0.3 1.5 Balance D 7.8 1.5 1.0 1.0 Balance E 11.1 2.5 1.5 Balance

TABLE-US-00002 TABLE 2 Blending Composition (mass %) Type Co Ni ZrC TaC NbC Mo.sub.2C WC TiCN Tool a 8.5 7.5 0.5 6.5 5.0 13.0 Balance body b 7.0 5.5 0.5 3.0 1.0 8.5 7.0 Balance c 11.0 4.0 6.5 1.0 6.5 10.5 Balance d 11.6 4.5 5.0 0.5 6.5 11.5 Balance e 13.0 3.5 1.5 0.5 9.5 10.0 Balance

TABLE-US-00003 TABLE 3 Lower Layer (Ti compound layer) Target Forming Conditions (The pressure of the reaction Composition atmosphere is represented by KPa, and the (The numerical temperature is represented by C.) values indicate Composition of Reaction Reaction Atmosphere Type atom ratios) Gas (vol %) Pressure Temperature TiC Layer TiC TiCl.sub.4: 4.2%, CH.sub.4: 8.5%, H.sub.2: 7 1020 balance TiN Layer TiN TiCl.sub.4: 4.2%, N.sub.2: 30%, H.sub.2: 30 900 (first layer) balance TiN Layer TiN TiCl.sub.4: 4.2%, N.sub.2: 35%, H.sub.2: 50 1040 (another layer) balance l-TiCN Layer*1 TiC.sub.0.5N.sub.0.5 TiCl.sub.4: 4.2%, N.sub.2: 20%, 7 880 CH.sub.3CN: 0.6%, H.sub.2: balance TiCN Layer TiC.sub.0.5N.sub.0.5 TiCl.sub.4: 4.2%, N.sub.2: 20%, CH.sub.4: 12 1000 4%, H.sub.2: balance TiCO Layer TiC.sub.0.5O.sub.0.5 TiCl.sub.4: 4.2%, CO: 4%, H.sub.2: 7 1020 balance TiCNO Layer TiC.sub.0.2N.sub.0.3O.sub.0.5 TiCl.sub.4: 4.2%, CO: 4%, CH.sub.4: 20 1020 3%, N.sub.2: 20%, H.sub.2: balance *1TiCN layer having a longitudinally grown crystal structure

TABLE-US-00004 TABLE 4 Forming Conditions (The pressure of the CO Gas Added During 5 Type of reaction atmosphere is represented by KPa, and to 30 minutes Before Oxygen- the temperature is represented by C.) Termination of Vapor Containing Composition of Reaction Atmosphere Deposition Time TiCN Layer Reaction Gas (vol %) Pressure Temperature (vol %) A TiCl.sub.4: 4%, CH.sub.3CN: 7 870 3 0.8%, N.sub.2: 40%, H.sub.2: balance B TiCl.sub.4: 2%, CH.sub.3CN: 5 930 1 0.5%, N.sub.2: 25%, H.sub.2: balance C TiCl.sub.4: 10%, CH.sub.3CN: 15 780 5 1%, N.sub.2: 60%, H.sub.2: balance D TiCl.sub.4: 25%, CH.sub.3CN: 10 830 (comparative) 1.5%, N.sub.2: 40%, H.sub.2: balance

TABLE-US-00005 TABLE 5 Treatment Conditions (The pressure of the reaction atmosphere is Type of represented by KPa, and the temperature is represented by C.) Surface Treatment Treatment for Reaction Atmosphere Time Lower Layer Composition of Reaction Gas (vol %) Pressure Temperature (min) A CO: 4%, CO.sub.2: 4%, H.sub.2: balance 10 900 30 B CO: 5%, CO.sub.2: 5%, H.sub.2: balance 15 950 20 C CO: 3%, CO.sub.2: 3%, H.sub.2: balance 5 850 60 D CO: 7%, CO.sub.2: 7%, H.sub.2: balance 7 1000 30 (comparative)

TABLE-US-00006 TABLE 6 Forming Conditions (The pressure of the reaction atmosphere is represented by KPa, and the Formation of Hard Coating Layer temperature is represented by C.) Forming Reaction Atmosphere Treatment Time Step Type Symbol Composition of Reaction Gas (vol %) Pressure Temperature (min) Initial Growth A AlCl.sub.3: 2.0%, CO.sub.2: 1.0%, HCl: 0.7%, H.sub.2: balance 7 900 30 Conditions B AlCl.sub.3: 1.5%, CO.sub.2: 1.5%, HCl: 0.5%, H.sub.2: balance 15 950 20 C AlCl.sub.3: 3.0%, CO.sub.2: 5.0%, HCl: 1.0%, H.sub.2: balance 5 850 90 D AlCl.sub.3: 0.5%, CO.sub.2: 2.0%, HCl: 0.3%, H.sub.2: balance 10 920 60 E AlCl.sub.3: 2.5%, CO.sub.2: 3.0%, HCl: 0.5%, H.sub.2: balance 8 1050 50 (comparative) Upper Layer Forming a AlCl.sub.3: 2.0%, CO.sub.2: 3.0%, HCl: 1.5%, H.sub.2S: 0.8%, 7 900 (until target upper Conditions H.sub.2: balance layer thickness is b AlCl.sub.3: 1.5%, CO.sub.2: 2.0%, HCl: 0.5%, H.sub.2S: 0.5%, 15 950 obtained) H.sub.2: balance c AlCl.sub.3: 3.5%, CO.sub.2: 10.0%, HCl: 2.0%, H.sub.2S: 1.0%, 5 850 H.sub.2: balance d AlCl.sub.3: 5.0%, CO.sub.2: 7.0%, HCl: 1.3%, H.sub.2S: 1.5%, 10 920 H.sub.2: balance e AlCl.sub.3: 2.0%, CO.sub.2: 6.0%, HCl: 1.5%, H.sub.2S: 0.3%, 8 1050 (comparative) H.sub.2: balance

TABLE-US-00007 TABLE 7 Hard Coating Layer Lower Layer (The numerical values of the lower lines represent a Symbol target average layer thickness of (m) of each layer) Tool First Second Third Fourth Type body Layer Layer Layer Layer Invention Coated 1 A TiN l-TiCN Tools/Comparative (0.5) (7) Coated Tools 2 a TiC TiN TiCN l-TiCN (1) (0.5) (3) (5) 3 B TiN l-TiCN TiN (0.2) (13) (0.3) 4 b TiC l-TiCN TiCNO (0.5) (8) (0.5) 5 C TiN TiCN TiN (1) (6) (0.5) 6 c TiN l-TiCN (0.5) (4) 7 d TiN TiCN TiN TiCO (1) (3) (0.3) (0.3) 8 D TiN l-TiCN (0.2) (6) 9 E TiN TiCN (0.5) (2) 10 e TiN l-TiCN (1) (7) 11 A TiC TiN l-TiCN (1) (0.5) (18) 12 D TiN l-TiCN (0.3) (4.5) 13 b TiC TiCN l-TiCN (0.5) (2.5) (12)

TABLE-US-00008 TABLE 8 Hard Coating Layer Outermost Surface Layer of Lower Layer Average Oxygen Maximum Content Oxygen in Depth Content Region in Depth with Region Depth of Deeper Type of up to 500 nm Than 500 nm Type of Surface Oxygen- in in Treatment Containing Layer Layer Target for Lower TiCN Layer Thickness Thickness Layer Layer Symbol (see Table Direction Direction Thickness (see Type of Tool body 4) (atom %) (atom %) (m) Table 5) Invention 1 A A 2.1 0.3 0.6 A coated 2 a B 1.2 0.2 0.5 C Tools 3 B C 2.8 0.3 1.0 B 4 b B 1.5 0.3 0.7 B 5 C C 3.0 0.4 0.8 A 6 c A 1.9 0.3 1.1 C 7 d A 2.2 0.4 0.7 C 8 D D 0.6 0.1 0.8 B 9 E B 1.6 0.2 0.5 A 10 e C 2.6 0.4 0.7 A 11 A C 2.4 0.2 0.5 C 12 D A 2.0 0.3 0.9 B 13 b B 1.0 0.2 1.0 A Hard Coating Layer Upper Layer Ratio of Grain Boundary Ratio of Length of Frequencies 31 in in 0 to 10 Which S is Degrees in Segregated Which Absolute Upper Relative Maximum Value of Absolute Initial Layer to Whole Peak is Residual Value of Growth Forming Target Grain Present in Stress Residual Conditions Conditions Layer Boundary 0 to 10 of Flank Stress of (see Table (see Table Thickness Length Degrees Face Rake Face Type 6) 6) (m) (%) (%) (MPa) (MPa) Invention 1 A a 7.5 35 55 85 95 coated 2 D d 12.0 46 60 130 170 Tools 3 B b 6.0 23 50 72 81 4 D a 15.0 27 62 175 189 5 C c 3.0 39 42 66 73 6 C c 5.0 33 46 80 88 7 B d 3.5 50 53 90 99 8 A d 2.0 42 38 113 120 9 B b 5.5 20 52 77 95 10 D b 4.0 26 55 90 84 11 A b 5.0 31 60 126 142 12 A a 7.0 37 63 140 155 13 A d 9.0 40 68 79 91

TABLE-US-00009 TABLE 9 Hard Coating Layer Outermost Surface Layer of Lower Layer Average Oxygen Maximum Content Oxygen in Depth Content Region in Depth with Region Depth of Deeper Type of up to 500 nm Than 500 nm Type of Surface Oxygen- in in Treatment Containing Layer Layer Target for Lower TiCN Layer Thickness Thickness Layer Layer Symbol (see Table Direction Direction Thickness (see Type of Tool body 4) (atom %) (atom %) (m) Table 5) Comparative 1 A A 2.1 0.3 0.6 D Coated 2 a B 1.2 0.2 0.5 C Tools 3 B C 2.8 0.3 1.0 B 4 b B 1.5 0.3 0.7 D 5 C C 3.0 0.4 0.8 A 6 c A 1.9 0.3 1.1 C 7 d A 2.2 0.4 0.7 D 8 D D 0.6 0.1 0.8 D 9 E B 1.6 0.2 0.5 A 10 e C 2.6 0.4 0.7 A 11 A C 2.4 0.2 0.5 D 12 D A 2.0 0.3 0.9 B 13 b B 1.0 0.2 1.0 C Hard Coating Layer Upper Layer Ratio of Grain Boundary Ratio of Length of Frequencies 31 in in 0 to 10 Which S is Degrees in Segregated Which Absolute Absolute Upper Relative Maximum Value of Value of Initial Layer to Whole Peak is Residual Residual Growth Forming Target Grain Present in Stress Stress Conditions Conditions Layer Boundary 0 to 10 of Flank of Rake (see Table (see Table Thickness Length Degrees Face Face Type 6) 6) (m) (%) (%) (MPa) (MPa) Comparative 1 E e 7.5 5 35 242 261 Coated 2 D e 12.0 8 40 410 388 Tools 3 E d 6.0 60 66 126 150 4 C c 15.0 11 45 322 350 5 E e 3.0 5 25 199 215 6 C e 5.0 9 31 264 255 7 A a 3.5 18 29 148 170 8 D b 2.0 15 22 320 285 9 B e 5.5 3 29 222 256 10 E b 4.0 8 41 189 224 11 B d 5.0 55 59 301 335 12 E e 7.0 11 30 256 284 13 B e 9.0 8 32 278 210

[0116] Next, the various coated tools of the invention coated tools 1 to 13 and the comparative coated tools 1 to 13 were subjected to a dry high-speed intermittent high feed rate cutting test (normal cutting speed, depth of cut, and feed rate: 200 m/min, 1.5 mm, and 0.3 mm/rev) of alloy steel under the following conditions (called cutting conditions A) in a state in which the coated tool was screw-fixed to a tip end portion of a turning tool made of tool steel by a fixing tool.

[0117] Work Material: 4 Longitudinal grooves were formed at regular intervals in a length direction of JIS.SCM440

[0118] Cutting Speed: 350 m/min

[0119] Depth of Cut: 1.5 mm

[0120] Feed Rate: 0.4 mm/rev

[0121] Cutting Time: 5 minutes

[0122] The coated tools were subjected to a dry high feed cutting test (normal cutting speed, depth of cut, and feed rate: 200 m/min, 1.5 mm, and 0.3 mm/rev) of nickel-chromium-molybdenum alloy steel under the following conditions (called cutting conditions B).

[0123] Work Material: Round bar of JIS.SNCM439

[0124] Cutting Speed: 100 m/min

[0125] Depth of Cut: 1.5 mm

[0126] Feed Rate: 1.1 mm/rev

[0127] Cutting Time: 5 minutes

[0128] The coated tools were subjected to a dry high-speed intermittent high feed and large depth of cutting test (normal cutting speed, depth of cut, and feed rate: 250 m/min, 1.5 mm, and 0.3 mm/rev) of cast iron under the following conditions (called cutting conditions C).

[0129] Work Material: Round bar of JIS.FC300 with 4 longitudinal grooves formed at regular intervals in a length direction

[0130] Cutting Speed: 450 m/min

[0131] Depth of Cut: 1.5 mm

[0132] Feed Rate: 0.4 mm/rev

[0133] Cutting Time: 5 minutes

[0134] In any cutting test, a width of wear of the flank face of a cutting edge was measured.

[0135] The results of the measurements are shown in Table 10.

TABLE-US-00010 TABLE 10 Flank Wear Width (mm) Cutting Test Results (min) Cutting Cutting Cutting Cutting Cutting Cutting Conditions Conditions Conditions Conditions Conditions Conditions Type (A) (B) (C) Type (A) (B) (C) Invention 1 0.13 0.14 0.18 Comparative 1 **1.5 *0.7 **1.4 Coated 2 0.17 0.15 0.21 Coated 2 **1.8 *1.0 **1.9 Tools 3 0.24 0.22 0.26 Tools 3 *0.9 *2.5 *1.0 4 0.18 0.15 0.21 4 **1.9 *0.9 **2.0 5 0.25 0.18 0.25 5 *1.2 *0.6 **1.7 6 0.21 0.17 0.28 6 **1.5 *1.1 **1.2 7 0.18 0.20 0.23 7 **1.7 *1.3 **1.8 8 0.28 0.30 0.27 8 **0.6 *0.4 **0.8 9 0.22 0.25 0.29 9 *0.9 *1.4 *1.3 10 0.17 0.18 0.19 10 *1.6 *1.2 **1.1 11 0.15 0.13 0.16 11 *1.1 *2.3 *0.9 12 0.17 0.20 0.23 12 **1.3 *1.7 **1.5 13 0.15 0.16 0.20 13 *1.8 *1.4 **2.0 (In the table, the symbol *represents the occurrence of peeling of the hard coating layer, and the symbol **represents a cutting time until the service life is reached due to the occurrence of chipping of the hard coating layer.)

[0136] From the results shown in Table 10, in the invention coated tools 1 to 13, the upper layer thereof had excellent peeling resistance and chipping resistance, and thus the coated tools exhibited excellent cutting performance over a long period of use.

[0137] On the other hand, in the comparative coated tools 1 to 13, the service life was reached for a relatively short period of time due to the occurrence of peeling and/or chipping of the hard coating layer in high-speed heavy cutting or high-speed intermittent cutting.

INDUSTRIAL APPLICABILITY

[0138] As described above, a coated tool according to the invention exhibits excellent cutting performance over a long period of use with no generation of peeling and/or chipping of a hard coating layer in continuous cutting or intermittent cutting of various steels, cast irons, and the like under normal conditions, and even under severe cutting conditions such as heavy cutting conditions with high-speed, large depth of cut and high feed rate in which a high load is exerted on a cutting edge. Therefore, it is possible for the coated tool according to the invention to sufficiently satisfactorily cope with power saving, energy saving, and cost reduction in cutting in addition to an improvement in performance of the cutting device.