SURFACE-COATED CUTTING TOOL HAVING EXCELLENT CHIP RESISTANCE

Abstract

A surface-coated cutting tool has a hard coating layer and a tool body, which is coated with a lower layer including a TiCN layer having at least an NaCl type face-centered cubic crystal structure and an upper layer formed of a TiAlCN layer having a single phase crystal structure of NaCl type face-centered cubic crystals or a mixed phase crystal structure of NaCl type face-centered cubic crystals and hexagonal crystals. The tool body is further coated with an outermost surface layer including an Al.sub.2O.sub.3 layer, when the layer of a complex nitride or complex carbonitride of Ti and Al is expressed by the composition formula: (Ti.sub.1-xAl.sub.x)(C.sub.yN.sub.1-y), the average amount Xave of Al in Ti and Al and the average amount Yave of C in C and N (both Xave and Yave are atomic ratios) respectively satisfy 0.60≦Xave≦0.95 and 0≦Yave≦0.005.

Claims

1. A surface-coated cutting tool comprising: a hard coating layer constituted by a lower layer and an upper layer; and a tool body on a surface of which the hard coating layer is formed, said tool body being made of any of tungsten carbide-based cemented carbide, titanium carbonitride-based cermet, and a cubic boron nitride-based ultrahigh-pressure sintered body, wherein (a) the lower layer is a Ti compound layer that is formed of one layer or two or more layers of a Ti carbide layer, a Ti nitride layer, a Ti carbonitride layer, a Ti oxycarbide layer, and a Ti oxycarbonitride layer and has a total average layer thickness of 1 μm to 20 μm, and includes a Ti carbonitride layer having at least an NaCl type face-centered cubic crystal structure, (b) the upper layer is a layer of a complex nitride or complex carbonitride of Ti and Al having a single phase crystal structure of NaCl type face-centered cubic crystals or a mixed phase crystal structure of NaCl type face-centered cubic crystals and hexagonal crystals with an average layer thickness of 1 μm to 20 μm, (c) in a case where the layer of a complex nitride or complex carbonitride of Ti and Al is expressed by the composition formula: (Ti.sub.1-xAl.sub.x)(C.sub.yN.sub.1-y), an average amount Xave of Al in a total amount of Ti and Al and an average amount Yave of C in a total amount of C and N (both Xave and Yave are atomic ratios) respectively satisfy 0.60≦Xave≦0.95 and 0≦Yave≦0.005, and (d) regarding the Ti carbonitride layer having an NaCl type face-centered cubic crystal structure in the lower layer and the layer of a complex nitride or complex carbonitride of Ti and Al having an NaCl type face-centered cubic crystal structure in the upper layer, in a case where crystal orientations of individual crystal grains are analyzed in a longitudinal sectional direction perpendicular to the tool body using an electron backscatter diffraction apparatus and inclined angles of normal lines of crystal planes of the individual crystal grains with respect to a normal line of the surface of the body are measured, crystal grains, which are crystal grains adjacent to each other via an interface between the upper layer and lower layer and have a difference in orientation between a normal direction of an (hkl) plane of the crystal grains having an NaCl type face-centered cubic crystal structure in the lower layer and a normal direction of an (hkl) plane of the crystal grains having an NaCl type face-centered cubic crystal structure in the upper layer of 5 degrees or lower, are present at the interface between the upper layer and the lower layer, and a linear density of the crystal grains is 2 crystal grains/10 μm or more.

2. The surface-coated cutting tool according to claim 1, wherein regarding the Ti carbonitride layer having an NaCl type face-centered cubic crystal structure in the lower layer and the layer of a complex nitride or complex carbonitride of Ti and Al having an NaCl type face-centered cubic crystal structure in the upper layer, in a case where the crystal orientations of the individual crystal grains are analyzed in the longitudinal sectional direction perpendicular to the tool body using the electron backscatter diffraction apparatus and the inclined angles of the normal lines of the crystal planes of the individual crystal grains with respect to the normal line of the surface of the body are measured, an area ratio of the crystal grains, which are the crystal grains adjacent to each other via the interface between the upper layer and lower layer and have a difference in orientation between the normal direction of the (hkl) plane of the crystal grains having an NaCl type face-centered cubic crystal structure in the lower layer and the normal direction of the (hkl) plane of the crystal grains having an NaCl type face-centered cubic crystal structure in the upper layer of 5 degrees or lower, to a total area of the crystal grains adjacent to each other via the interface between the upper layer and the lower layer is 30% by area or more.

3. The surface-coated cutting tool according to claim 1, wherein, regarding the layer of a complex nitride or complex carbonitride of Ti and Al, in a case where the layer is observed in the longitudinal sectional direction, a columnar structure in which the crystal grains of the complex nitride or complex carbonitride of Ti and Al having an NaCl type face-centered cubic structure in the layer have an average grain width W of 0.1 μm to 2.0 μm and an average aspect ratio A of 2 to 10 is included.

4. The surface-coated cutting tool according to claim 1, wherein a surface of the upper layer formed of the layer of a complex nitride or complex carbonitride of Ti and Al having a single phase crystal structure of NaCl type face-centered cubic crystals or a mixed phase crystal structure of NaCl type face-centered cubic crystals and hexagonal crystals with an average layer thickness of 1 μm to 20 μm is further coated with an outermost surface layer which has an average layer thickness of 1 μm to 25 μm and includes at least an Al.sub.2O.sub.3 layer.

5. The surface-coated cutting tool according to claim 2, wherein, regarding the layer of a complex nitride or complex carbonitride of Ti and Al, in a case where the layer is observed in the longitudinal sectional direction, a columnar structure in which the crystal grains of the complex nitride or complex carbonitride of Ti and Me having an NaCl type face-centered cubic structure in the layer have an average grain width W of 0.1 μm to 2.0 μm and an average aspect ratio A of 2 to 10 is included.

6. The surface-coated cutting tool according to claim 2, wherein a surface of the upper layer formed of the layer of a complex nitride or complex carbonitride of Ti and Al having a single phase crystal structure of NaCl type face-centered cubic crystals or a mixed phase crystal structure of NaCl type face-centered cubic crystals and hexagonal crystals with an average layer thickness of 1 μm to 20 μm is further coated with an outermost surface layer which has an average layer thickness of 1 μm to 25 μm and includes at least an Al.sub.2O.sub.3 layer.

7. The surface-coated cutting tool according to claim 3, wherein a surface of the upper layer formed of the layer of a complex nitride or complex carbonitride of Ti and Al having a single phase crystal structure of NaCl type face-centered cubic crystals or a mixed phase crystal structure of NaCl type face-centered cubic crystals and hexagonal crystals with an average layer thickness of 1 μm to 20 μm is further coated with an outermost surface layer which has an average layer thickness of 1 μm to 25 μm and includes at least an Al.sub.2O.sub.3 layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] 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:

[0063] FIG. 1 is a schematic view of the layer structure of a hard coating layer of the present invention including a TiCN layer (lower layer) having an NaCl type face-centered cubic crystal structure and a TiAlCN layer (upper layer) having an NaCl type face-centered cubic crystal structure.

DETAILED DESCRIPTION OF THE INVENTION

[0064] Next, a coated tool of the present invention will be described in detail using examples.

Example 1

[0065] As raw material powders, a WC powder, a TiC powder, a TaC powder, an NbC powder, a Cr.sub.3C.sub.2 powder, and a Co powder, all of which had an average grain size of 1 μm to 3 μm, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 1. Wax was further added thereto, and the mixture was blended in acetone by a ball mill for 24 hours and was decompressed and dried. Thereafter, the resultant was press-formed into compacts having predetermined shapes at a pressure of 98 MPa, and the compacts were sintered in a vacuum at 5 Pa under the condition that the compacts were held at a predetermined temperature in a range of 1370° C. to 1470° C. for one hour. After the sintering, tool bodies A to C made of WC-based cemented carbide with insert shapes according to ISO standard SEEN1203AFSN were produced.

[0066] In addition, as raw material powders, a TiCN (TiC/TiN=50/50 in terms of mass ratio) powder, an Mo.sub.2C powder, a ZrC powder, an NbC powder, a WC powder, a Co powder, and an Ni powder, all of which had an average grain size of 0.5 μm to 2 μm, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 2, were subjected to wet mixing by a ball mill for 24 hours, and were dried. Thereafter, the resultant was press-formed into compacts at a pressure of 98 MPa, and the compacts were sintered in a nitrogen atmosphere at 1.3 kPa under the condition that the compacts were held at a temperature of 1500° C. for one hour. After the sintering, a tool body D made of TiCN-based cermet with insert shapes according to ISO standard SEEN1203AFSN was produced.

[0067] Next, using a chemical vapor deposition apparatus, present invention coated tools 1 to 13 were produced by forming, on the surfaces of the tool bodies A to D,

[0068] first, lower layers shown in Table 6 under forming conditions shown in Table 3, and

[0069] subsequently, forming upper layers under forming conditions A to J shown in Tables 4 and 5 in which a gas group A of NH.sub.3 and H.sub.2 and a gas group B of TiCl.sub.4, AlCl.sub.3, NH.sub.3, N.sub.2, C.sub.2H.sub.4, and H.sub.2 were used and in each gas supply method, a reaction gas composition (% by volume with respect to the total amount of the gas group A and the gas group B) included a gas group A of NH.sub.3: 1.5% to 3.0% and H.sub.2: 50% to 75% and a gas group B of TiCl.sub.4: 0.1% to 0.15%, AlCl.sub.3: 0.3% to 0.5%, N.sub.2: 0% to 2%, C.sub.2H.sub.4: 0% to 0.05%, and H.sub.2: the remainder, a reaction atmosphere pressure was 2 kPa to 5 kPa, a reaction atmosphere temperature was 700° C. to 900° C., a supply period was 1 second to 5 seconds, a gas supply time per one period was 0.15 seconds to 0.25 seconds, and a phase difference in supply between gas group A and gas group B was 0.10 seconds to 0.20 seconds, through a thermal CVD method for a predetermined time.

[0070] In addition, regarding the present invention coated tools 11 to 13, upper layers shown in Table 6 were formed under the forming conditions shown in Table 3.

[0071] In addition, for the purpose of comparison, lower layers shown in Table 6 were formed on the surfaces of the tool bodies A to D under the forming conditions shown in Table 3, and like the present invention coated tools 1 to 13, hard coating layers including at least a layer of a complex nitride or complex carbonitride of Ti and Al were deposited thereon to have target layer thicknesses (μm) shown in FIG. 7 under the conditions shown in Tables 3, 4, and 5.

[0072] In addition, like the present invention coated tools 11 to 13, upper layers shown in Table 6 were formed in the comparative coated tools 11 to 13 under the forming conditions shown in Table 3.

[0073] The section of each of constituent layers of the present invention coated tools 1 to 13 and the comparative coated tools 1 to 13 in the direction perpendicular to the tool body was measured using a scanning electron microscope (at a magnification of 5,000×). An average layer thickness was obtained by measuring and averaging the layer thicknesses of five points in an observation visual field. All of the results showed substantially the same average layer thicknesses as the target layer thicknesses shown in Tables 6 and 7.

[0074] In addition, regarding the average amount Xave of Al of the TiAlCN layer of the upper layer, a sample, of which the surface was polished, was irradiated with electron beams from the sample surface side, and the average amount Xave of Al was obtained by averaging 10 points of the analytic result of obtained characteristic X-rays, using an electron probe micro-analyzer (EPMA).

[0075] In addition, the average amount Yave of C was obtained by secondary ion mass spectrometry (SIMS). Ion beams were emitted toward a range of 70 μm×70 μm from the sample surface side, and the concentration of components emitted by a sputtering action was measured in a depth direction. The average amount Yave of C represents the average value of the TiAlCN layer in the depth direction. However, the amount of C excludes an unavoidable amount of C, which was included even though gas containing C was not intentionally used as a gas raw material. Specifically, the amount (atomic ratio) of the component C contained in the TiAlCN layer in a case where the amount of supplied C.sub.2H.sub.4 was set to 0 was obtained as the unavoidable amount of C, and a value obtained by subtracting the unavoidable amount of C from the amount (atomic ratio) of the component C contained in the TiAlCN layer obtained in a case where C.sub.2H.sub.4 was intentionally supplied was obtained as Yave.

[0076] Regarding the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer in the hard coating layer, the crystal orientations of individual crystal grains were analyzed using a field emission scanning electron microscope, the inclined angles of the normal lines of the crystal planes of the individual crystal grains with respect to the normal line of the surface of the tool body were measured, and the difference between the inclined angles of the normal lines of the crystal planes (for example, (hkl) planes) of the individual crystal grains measured for the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer, which were adjacent to each other via the interface, with respect to the normal line of the surface of the tool body were obtained. Depending on whether or not the difference was 5 degrees or lower, it is determined whether or not the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer, which were adjacent to each other via the interface and measured as described above, correspond to the crystal grains specified in the present invention.

[0077] That is, regarding the present invention coated tools 1 to 13 and the comparative coated tools 1 to 13, a measurement range (2.0 μm×50 μm) of a polished section of 1.0 μm in the thickness direction of the lower layer from the interface between the upper layer and the lower layer, 1.0 μm in the thickness direction of the upper layer, and 50 μm in the direction parallel to the surface of the tool body was set in the body tube of a field emission scanning electron microscope, an electron beam was emitted toward each of the crystal grains having a cubic crystal lattice, which were present in the measurement range of the polished surface at an incident angle of 70 degrees with respect to the polished surface at an acceleration voltage of 15 kV and an emission current of 1 nA. The inclined angles of the normal lines of the (hkl) planes which were crystal planes of the crystal grains with respect to the normal line of the surface of the tool body were measured for the measurement area of 2.0×50 μm using an electron backscatter diffraction imaging device at an interval of 0.1 μm/step. For example, in a case where the inclined angle of the normal line of the (hkl) plane of the TiCN crystal grains of the lower layer with respect to the normal line of the surface of the tool body was referred to as α (degrees) and the inclined angle of the normal line of the (hkl) plane of the TiAlCN crystal grains of the upper layer with respect to the normal line of the surface of the tool body was referred to as β (degrees), whether or not the absolute value (=|α (degrees)−β (degrees)|) of the difference between the inclined angles was 5 degrees or lower was obtained. In a case where the difference between the inclined angles was 5 degrees or lower, the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer, which were adjacent to each other via the interface and measured as described above, were determined as epitaxially grown crystal grains.

[0078] In addition, the number of crystal grains determined as the epitaxially grown crystal grains was obtained as the number per unit length of the interface between the upper layer and the lower layer.

[0079] In addition, in the present invention, when the number of crystal grains determined as the epitaxially grown crystal grains is counted, the number of TiCN crystal grains adjacent via the interface is counted as 1, and the number of TiAlCN crystal grains adjacent via the interface is counted as 1.

[0080] Furthermore, the area ratio (% by area) of the crystal grains determined as the epitaxially grown crystal grains to the total area of the crystal grains adjacent to each other at the interface between the upper layer and the lower layer was measured.

[0081] The obtained values are shown in Tables 6 and 7.

[0082] In addition, regarding the present invention coated tools 1 to 13 and the comparative coated tools 1 to 13, the individual crystal grains in the (Ti.sub.1-xAl.sub.x)(C.sub.yN.sub.1-y) layer included in the layer of a complex nitride or complex carbonitride, which were present in a range of a length of 10 μm in the direction parallel to the surface of the tool body were observed from the film section side perpendicular to the surface of the tool body using a scanning electron microscope (at a magnification of 5,000× and 20,000×) in the sectional direction as the direction perpendicular to the tool body, the maximum grain widths w in the direction parallel to the surface of the body and the maximum grain lengths 1 in the direction perpendicular to the surface of the body were measured to calculate the aspect ratio a(=l/w) of each of the crystal grains. The average value of the aspect ratios a obtained for the individual crystal grains was calculated as an average aspect ratio A. In addition, the average value of the grain widths w obtained for the individual crystal grains was calculated as an average grain width W. The obtained values are shown in Tables 6 and 7.

TABLE-US-00001 TABLE 1 Mixing composition (mass %) Type Co TiC TaC NbC Cr.sub.3C.sub.2 WC Tool body A 8.0 1.5 — 3.0 0.4 Remainder B 8.5 — 1.8 0.2 — Remainder C 7.0 — — — — Remainder

TABLE-US-00002 TABLE 2 Mixing composition (mass %) Type Co Ni ZrC NbC Mo.sub.2C WC TiCN Tool body D 8 5 1 6 6 10 Remainder

TABLE-US-00003 TABLE 3 Forming conditions (pressure of reaction atmosphere is expressed as kPa and temperature is expressed as ° C.) Constituent layers of hard coating layer Reaction gas composition Reaction atmosphere Type Formation symbol (% by volume) Pressure Temperature (Ti.sub.1−xAl.sub.x)(C.sub.yNi.sub.1−y) TiAlCN TiAlCN See Table 4 See Table 5 See Table 5 layer Ti compound TiC TiC TiCl.sub.4: 4.2%, CH.sub.4: 8.5%, 7 900 layer H.sub.2: remainder TiN TiN-(1) TiCl.sub.4: 4.2%, N.sub.2: 30%, H.sub.2: 20 900 remainder TiN-(2) TiCl.sub.4: 4.2%, N.sub.2: 35%, H.sub.2: 7 780 remainder l-TiCN I-TiCN TiCl.sub.4: 2%, CH.sub.3CN: 0.7%, 7 780 N.sub.2: 10%, H.sub.2: remainder TiCNO TiCNO TiCl.sub.4: 2%, CH.sub.3CN: 0.7%, 7 780 CO.sub.2: 1%, N.sub.2: 10%, H.sub.2: remainder Al.sub.2O.sub.3 layer Al.sub.2O.sub.3 Al.sub.2O.sub.3 AlCl.sub.3: 2.2%, CO.sub.2: 5.5%, 7 800 HCl: 2.2%, H.sub.2S: 0.2%, H.sub.2: remainder

TABLE-US-00004 TABLE 4 Forming conditions (reaction gas composition indicates proportion in total Formation of hard amount of gas group A and gas group B) coating layer Reaction gas group A Process type Formation symbol composition (% by volume) Reaction gas group B composition (% by volume) Present A NH.sub.3: 2.5%, H.sub.2: 68%, TiCl.sub.4: 0.10%, AlCl.sub.3: 0.30%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder invention B NH.sub.3: 3.0%, H.sub.2: 56%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.35%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder film forming C NH.sub.3: 2.2%, H.sub.2: 71%, TiCl.sub.4: 0.14%, AlCl.sub.3: 0.35%, N.sub.2: 2%, C.sub.2H.sub.4: 0.05%, H.sub.2 as remainder process D NH.sub.3: 1.5%, H.sub.2: 62%, TiCl.sub.4: 0.11%, AlCl.sub.3: 0.33%, N.sub.2: 1%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder E NH.sub.3: 2.8%, H.sub.2: 65%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.45%, N.sub.2: 0%, C.sub.2H.sub.4: 0.05%, H.sub.2 as remainder F NH.sub.3: 2.0%, H.sub.2: 50%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.30%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder G NH.sub.3: 1.8%, H.sub.2: 59%, TiCl.sub.4: 0.14%, AlCl.sub.3: 0.42%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder H NH.sub.3: 2.7%, H.sub.2: 64%, TiCl.sub.4: 0.14%, AlCl.sub.3: 0.38%, N.sub.2: 2%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder I NH.sub.3: 1.9%, H.sub.2: 75%, TiCl.sub.4: 0.13%, AlCl.sub.3: 0.33%, N.sub.2: 1%, C.sub.2H.sub.4: 0.05%, H.sub.2 as remainder J NH.sub.3: 2.5%, H.sub.2: 60%, TiCl.sub.4: 0.11%, AlCl.sub.3: 0.50%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder Comparative  A′ NH.sub.3: 2.0%, H.sub.2: 57%, TiCl.sub.4: 0.14%, AlCl.sub.3: 0.33%, N.sub.2: 5%, C.sub.2H.sub.4: 0.1%, H.sub.2 as remainder film forming  B′ NH.sub.3: 4.0%, H.sub.2: 70%, TiCl.sub.4: 0.10%, AlCl.sub.3: 0.40%, N.sub.2: 2%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder process  C′ NH.sub.3: 1.5%, H.sub.2: 78%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.38%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder  D′ NH.sub.3: 2.1%, H.sub.2: 66%, TiCl.sub.4: 0.08%, AlCl.sub.3: 0.48%, N.sub.2: 1%, C.sub.2H.sub.4: 0.05%, H.sub.2 as remainder  E′ NH.sub.3: 1.8%, H.sub.2: 54%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.20%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder  F′ NH.sub.3: 3.0%, H.sub.2: 61%, TiCl.sub.4: 0.20%, AlCl.sub.3: 0.29%, N.sub.2: 0%, C.sub.2H.sub.4: 0.15%, H.sub.2 as remainder  G′ NH.sub.3: 2.7%, H.sub.2: 45%, TiCl.sub.4: 0.07%, AlCl.sub.3: 0.56%, N.sub.2: 2%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder  H′ NH.sub.3: 2.6%, H.sub.2: 59%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.23%, N.sub.2: 0%, C.sub.2H.sub.4: 0.05%, H.sub.2 as remainder  I′ NH.sub.3: 3.5%, H.sub.2: 42%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.30%, N.sub.2: 1%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder  J′ NH.sub.3: 2.3%, H.sub.2: 64%, TiCl.sub.4: 0.15%, AlCl.sub.3: 0.64%, N.sub.2: 0%, C.sub.2H.sub.4: 0%, H.sub.2 as remainder

TABLE-US-00005 TABLE 5 Forming conditions (pressure of reaction atmosphere is expressed as kPa and temperature is expressed as ° C.) Phase Gas group A Gas group B difference Supply Supply in supply Formation of hard time time between gas coating layer Supply per one Supply per one group A and Process Formation period period period period gas group B Reaction atmosphere type symbol (sec) (sec) (sec) (sec) (sec) Pressure Temperature Present A 4 0.20 4 0.20 0.10 5.0 750 invention B 2 0.15 2 0.15 0.15 3.5 800 film C 3 0.20 3 0.20 0.10 4.5 800 forming D 4 0.20 4 0.20 0.20 2.0 900 process E 1 0.25 1 0.25 0.10 3.0 750 F 4 0.20 4 0.20 0.15 4.5 700 G 5 0.15 5 0.15 0.15 5.0 800 H 3 0.25 3 0.25 0.20 4.0 850 I 2 0.20 2 0.20 0.10 2.5 800 J 4 0.20 4 0.20 0.20 4.0 750 Comparative  A′ — — — — — 3.5 850 film  B′ — — — — — 5.0 800 forming  C′ — — — — — 6.0 950 process  D′ — — — — — 2.5 750  E′ — — — — — 4.0 650  F′ — — — — — 4.5 800  G′ — — — — — 1.5 700  H′ — — — — — 3.0 750  I′ — — — — — 5.0 900  J′ — — — — — 4.5 800

TABLE-US-00006 TABLE 6 Hard coating layer Lower layer (numerical value Upper layer at the bottom indicates the Upper layer average target layer thickness (TiAlCN layer) of the layer (μm)) forming process Amount Amount Tool body First Second Third formation symbol of Al of C Type symbol layer layer layer (see Tables 4 and 5) Xave Yave Present 1 A TiN-(1) I-TiCN — D 0.80 0.0001 invention (0.3) (2) or less coated 2 B TiC I-TiCN-(1) TiCNO A 0.83 0.0001 tool (0.5) (1) (0.3) or less 3 C TiN-(2) I-TiCN — B 0.71 0.0001 (0.5) (1) or less 4 D TiN-(2) I-TiCN — C 0.82 0.0032 (0.3) (2) 5 A TiN-(1) I-TiCN — E 0.78 0.0024 (0.3) (1) 6 B TiN-(1) TiN-(2) I-TiCN F 0.62 0.0001 (0.3) (0.3) (2) or less 7 D TiN-(2) I-TiCN — G 0.86 0.0001 (0.5) (1) or less 8 C TiC TiN-(2) I-TiCN H 0.75 0.0001 (1) (0.5) (1) or less 9 A TiC I-TiCN TiCNO I 0.70 0.0046 (0.5) (1) (0.5) 10 B TiN-(2) I-TiCN TiCNO J 0.93 0.0001 (0.5) (1) (0.5) or less 11 C TiN-(1) I-TiCN — A 0.81 0.0001 (0.5) (1) or less 12 D TiN-(2) I-TiCN — C 0.73 0.0036 (0.5) (0.5) 13 A TiN-(1) I-TiCN — G 0.87 0.0001 (0.3) (1) or less Hard coating layer Upper layer Crystal grains having difference Outermost surface layer in orientation of (numerical value at the 5 degrees or lower bottom indicates the Number per Area Average Target average target layer 10 μm ratio grain Average layer thickness of the layer (μm)) (grains/ (% by width aspect thickness First Second Type 10 μm) area) W (μm) ratio A (μm) layer layer Present 1 6.2 41 0.7 4.1 3 — — invention 2 2.8 28 1.6 2.5 4 — — coated 3 10.4 53 0.4 6.8 3 — — tool 4 5.3 57 1.4 2.0 3 — — 5 7.4 62 1.3 3.7 5 — — 6 8.5 71 0.8 4.6 4 — — 7 3.3 36 1.1 3.8 5 — — 8 27.2 59 0.2 9.8 2 — — 9 4.5 68 1.5 1.9 3 — — 10 2.2 24 2.2 1.5 4 — — 11 2.5 26 1.7 1.7 3 I-TiCN Al.sub.2O.sub.3 (0.5) (1) 12 5.7 55 1.3 1.4 2 TiCNO Al.sub.2O.sub.3 (0.5) (2) 13 3.6 38 1.0 4.0 4 TiCNO Al.sub.2O.sub.3 (0.3) (1) (Note) “Crystal grains having difference in orientation of 5 degrees or lower” means crystal grains in which the difference in orientation between normal directions of crystal planes of TiCN crystal grains of the lower layer and TiAlCN crystal grains of the upper layer, which are adjacent to each other via the interface between the upper layer and the lower layer is 5 degrees or lower.

TABLE-US-00007 TABLE 7 Hard coating layer Lower layer (numerical value Upper layer at the bottom indicates the Upper layer average target layer thickness (TiAlCN layer) of the layer (μm)) forming process Amount Amount Tool body First Second Third formation symbol of Al of C Type symbol layer layer layer (see Tables 4 and 5) Xave Yave Comparative 1 A TiN-(1) I-TiCN — A′ 0.69.sup.  0.0085 * coated tool (0.3) (1) 2 B TiC I-TiCN-(1) — B′ 0.94.sup.  0.0001 (0.5) (2) or less 3 C TiN-(2) I-TiCN — C′ 0.73.sup.  0.0001 (0.5) (1) or less 4 D TiN-(2) I-TiCN — D′ 0.98 * 0.0026   (0.3) (2) 5 A TiN-(1) I-TiCN — E′ 0.48 * 0.0001 (0.3) (1) or less 6 B TiN-(1) TiN-(2) I-TiCN F′ 0.51 * 0.0075 * (0.3) (0.3) (2) 7 D TiN-(2) I-TiCN — G′ 0.99 * 0.0001 (0.5) (2) or less 8 C TiC TiN-(2) I-TiCN H′ 0.53 * 0.0039   (1) (0.5) (1) 9 A TiC I-TiCN — I′ 0.62.sup.  0.0001 (0.5) (2) or less 10 B TiN-(2) I-TiCN — J′ 0.96 * 0.0001 (0.5) (1) or less 11 C TiN-(1) I-TiCN — A′ 0.70.sup.  0.0092 * (0.5) (1) 12 D TiN-(2) I-TiCN — B′ 0.93.sup.  0.0001 (0.5) (1) or less 13 A TiN-(1) I-TiCN — E′ 0.46 * 0.0001 (0.3) (1) or less Hard coating layer Upper layer Crystal grains having difference Outermost surface layer in orientation of (numerical value at the 5 degrees or lower bottom indicates the Number per Area Average Target average target layer 10 μm ratio grain Average layer thickness of the layer (μm)) (grains/ (% by width aspect thickness First Second Type 10 μm) area) W (μm) ratio A (μm) layer layer Comparative 1 0.6 * 4 2.6 1.4 4 — — coated tool 2 0.0 * 0 — — 3 — — 3 0.3 * 2 1.3 2.2 3 — — 4 0.0 * 0 — — 4 — — 5 0.5 * 3 0.7 5.1 5 — — 6 0.0 * 0 2.1 1.4 3 — — 7 0.0 * 0 — — 2 — — 8 0.0 * 0 1.7 1.3 4 — — 9 0.0 * 0  0.07 15.4  3 — — 10 0.0 * 0 — — 4 — — 11 0.3 * 2 2.4 1.2 3 I-TiCN Al.sub.2O.sub.3 (0.5) (1) 12 0.0 * 0 — — 3 TiCNO Al.sub.2O.sub.3 (0.5) (1) 13 0.1 * 1 0.6 2.5 2 I-TiCN Al.sub.2O.sub.3 (0.3) (1) (Note 1) “Crystal grains having difference in orientation of 5 degrees or lower” means crystal grains in which the difference in orientation between normal directions of crystal planes of TiCN crystal grains of the lower layer and TiAlCN crystal grains of the upper layer, which are adjacent to each other via the interface between the upper layer and the lower layer is 5 degrees or lower. (Note 2) Mark * in boxes indicates outside of the range of the present invention. (Note 3) Comparative example tools 2, 4, 7, 10, and 12 are fine grains crystals, and columnar crystals are not observed.

[0083] Next, in a state in which each of the various coated tools was clamped to a cutter tip end portion made of tool steel with a cutter diameter of 125 mm by a fixing tool, the present invention coated tools 1 to 13 and the comparative coated tools 1 to 13 were subjected to dry high-speed face milling, which is a type of high-speed intermittent cutting of carbon steel, and a center-cut cutting test, and the flank wear width of a cutting edge was measured. The results are shown in Table 8.

[0084] Tool body: tungsten carbide-based cemented carbide, titanium carbonitride-based cermet

[0085] Cutting test: dry high-speed face milling, center-cut cutting

[0086] Work material: a block material with a width of 100 mm and a length of 400 mm of JIS SCM440

[0087] Rotational speed: 968 min.sup.−1

[0088] Cutting speed: 380 m/min

[0089] Depth of cut: 1.5 mm

[0090] Feed per edge: 0.1 mm/edge

[0091] Cutting time: 8 minutes.

TABLE-US-00008 TABLE 8 Flank Cutting wear width test results Type (mm) Type (min) Present invention 1 0.16 Comparative 1 5.7 * coated tool 2 0.19 coated tool 2 6.4 * 3 0.14 3 6.7 * 4 0.13 4 4.3 * 5 0.11 5 5.3 * 6 0.18 6 5.2 * 7 0.15 7 4.1 * 8 0.14 8 5.5 * 9 0.16 9 6.0 * 10 0.18 10 4.6 * 11 0.13 11 7.3 * 12 0.12 12 7.1 * 13 0.14 13 5.8 * Mark * in boxes of comparative coated tools indicates a cutting time (min) until the end of a service life caused by the occurrence of chipping.

Example 2

[0092] As raw material powders, a WC powder, a TiC powder, a ZrC powder, a TaC powder, an NbC powder, a Cr.sub.3C.sub.2 powder, a TiN powder, and a Co powder, all of which had an average grain size of 1 μm to 3 μm, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 9. Wax was further added thereto, and the mixture was blended in acetone by a ball mill for 24 hours and was decompressed and dried. Thereafter, the resultant was press-formed into compacts having predetermined shapes at a pressure of 98 MPa, and the compacts were sintered in a vacuum at 5 Pa under the condition that the compacts were held at a predetermined temperature in a range of 1370° C. to 1470° C. for one hour. After the sintering, each of tool bodies E to G made of WC-based cemented carbide with insert shapes according to ISO standard CNMG120412 was produced by performing honing with R: 0.07 mm on a cutting edge portion.

[0093] In addition, as raw material powders, a TiCN (TiC/TiN=50/50 in terms of mass ratio) powder, an NbC powder, a WC powder, a Co powder, and an Ni powder, all of which had an average grain size of 0.5 μm to 2 μm, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 10, were subjected to wet mixing by a ball mill for 24 hours, and were dried. Thereafter, the resultant was press-formed into a compact at a pressure of 98 MPa, and the compact was sintered in a nitrogen atmosphere at 1.3 kPa under the condition that the compact was held at a temperature of 1500° C. for one hour. After the sintering, a tool body H made of TiCN-based cermet with an insert shape according to ISO standard CNMG120412 was produced by performing honing with R: 0.09 mm on a cutting edge portion.

[0094] Next, present invention coated tools 14 to 26 shown in Table 11 were produced by first forming lower layers shown in Table 11 on the surfaces of the tool bodies E to G and the tool body H using a chemical vapor deposition apparatus under the conditions shown in Tables 3, 4, and 5 in the same method as that in Example 1, and subsequently depositing (Ti.sub.1-xAl.sub.x)(C.sub.yN.sub.1-y) layers thereon.

[0095] In addition, an upper layer shown in Table 11 was formed in the present invention coated tools 20 to 26 under the forming conditions shown in Table 3.

[0096] In addition, for the purpose of comparison, comparative coated tools 14 to 26 shown in Table 12 were produced by depositing hard coating layers on the surfaces of the same cutting tool bodies E to G and the tool body H to have target layer thicknesses shown in Table 12 under the conditions shown in Tables 3, 4, and 5 using a typical chemical vapor deposition apparatus, like the present invention coated tools.

[0097] In addition, like the present invention coated tools 20 to 26, an upper layer shown in Table 12 was formed in the comparative coated tools 20 to 26 under the forming conditions shown in Table 3.

[0098] The section of each of constituent layers of the present invention coated tools 14 to 26 and the comparative coated tools 14 to 26 was measured using a scanning electron microscope (at a magnification of 5,000×). An average layer thickness was obtained by measuring and averaging the layer thicknesses of five points in an observation visual field. All of the results showed substantially the same average layer thicknesses as the target layer thicknesses shown in Tables 11 and 12.

[0099] The average amount Xave of Al and the average amount Yave of C of the TiAlCN layer of the upper layer were obtained using an electron probe micro-analyzer (EPMA) as in Example 1.

[0100] In addition, regarding the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer, which were adjacent to each other via the interface, using a field emission scanning electron microscope, the inclined angle α (degrees) of the normal line of the (hkl) plane of the TiCN crystal grains of the lower layer with respect to the normal line of the surface of the tool body, the inclined angle β (degrees) of the normal line of the (hkl) plane of the TiAlCN crystal grains of the upper layer with respect to the normal line of the surface of the tool body, and the absolute value (=|α (degrees)−β (degrees)|) of the difference between the inclined angles were obtained. The number of TiCN crystal grains of the lower layer and the number of TiAlCN crystal grains of the upper layer, in which the value was 5 degrees or lower, were counted, and the number per unit length of the interface between the upper layer and the lower layer was obtained.

[0101] Furthermore, the area ratio (% by area) of the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer which satisfy |α (degrees)−β (degrees)|≦5 (degrees) to the total area of the crystal grains adjacent to each other at the interface between the upper layer and the lower layer was obtained.

[0102] In addition, the average grain width W and the average aspect ratio A of the crystal grains were obtained as in Example 1.

[0103] The obtained values are shown in Tables 11 and 12.

TABLE-US-00009 TABLE 9 Mixing composition (mass %) Type Co TiC ZrC TaC NbC Cr.sub.3C.sub.2 TiN WC Tool E 6.5 — 1.5 — 2.9 0.1 1.5 Remainder body F 7.6 2.6 — 4.0 0.5 — 1.1 Remainder G 6.0 — — — — — — Remainder

TABLE-US-00010 TABLE 10 Mixing composition (mass %) Type Co Ni NbC WC TiCN Tool body H 11 4 6 15 Remainder

TABLE-US-00011 TABLE 11 Hard coating layer Lower layer (numerical value Upper layer at the bottom indicates the Upper layer average target layer thickness (TiAlCN layer) of the layer (μm)) forming process Amount Amount Tool body First Second Third formation symbol of Al of C Type symbol layer layer layer (see Tables 4 and 5) Xave Yave Present 14 E TiN-(1) I-TiCN — D 0.79 0.0001 invention (0.3) (6) or less coated 15 F TiC TiN-(1) I-TiCN A 0.85 0.0001 tool (2) (1) (15) or less 16 G TiN-(2) I-TiCN — B 0.73 0.0001 (0.5) (5) or less 17 H TiN-(2) I-TiCN — C 0.83 0.0028 (0.3) (5) 18 E TiN-(1) I-TiCN — E 0.77 0.0016 (0.3) (7) 19 F TiN-(1) TiN-(2) I-TiCN F 0.60 0.0001 (0.3) (0.3) (6) or less 20 G TiN-(2) I-TiCN — G 0.84 0.0001 (1) (12) or less 21 H TiC TiN-(2) I-TiCN I 0.71 0.0049 (2.5) (0.5) (14) 22 E TiC I-TiCN — H 0.74 0.0001 (0.5) (8) or less 23 F TiN-(2) I-TiCN — J 0.94 0.0001 (0.5) (5) or less 24 G TiN-(1) I-TiCN — B 0.73 0.0001 (0.5) (9) or less 25 H TiN-(2) I-TiCN — F 0.64 0.0001 (0.5) (6) or less 26 E TiN-(1) I-TiCN — I 0.69 0.0042 (0.3) (5) Hard coating layer Upper layer Crystal grains having difference in Outermost surface layer orientation of 5 (numerical value at the degrees or lower bottom indicates the Number per Area Average Target average target layer 10 μm ratio grain Average layer thickness of the layer (μm)) (grains/ (% by width aspect thickness First Second Third Fourth Type 10 μm) area) W (μm) ratio A (μm) layer layer layer layer Present 14 6.5 44 0.8 7.4 10 — — — — invention 15 3.0 31 1.4 5.1 8 — — — — coated 16 11.2 59 0.3 7.2 17 — — — — tool 17 5.0 51 1.6 4.2 18 — — — — 18 7.1 58 1.6 7.8 14 — — — — 19 8.8 72 0.7 6.3 12 — — — — 20 3.9 40 1.0 4.4 9 — — — — 21 4.8 66 1.3 3.4 10 TiN-(2) — — — (1) 22 25.4 52 0.1 13.4 9 I-TiCN TiN-(2) — — (3) (1) 23 2.0 22 1.9 1.8 8 I-TiCN Al.sub.2O.sub.3 — — (2) (5) 24 10.6 57 0.6 5.6 10 TiCNO Al.sub.2O.sub.3 — — (1) (4) 25 8.4 68 0.9 5.7 7 TiCNO Al.sub.2O.sub.3 — — (0.3) (6) 26 4.5 62 1.7 2.1 10 TiN-(2) I-TiCN TiCNO Al.sub.2O.sub.3 (0.3) (0.5) (1) (5) (Note) “Crystal grains having difference in orientation of 5 degrees or lower” means crystal grains in which the difference in orientation between normal directions of crystal planes of TiCN crystal grains of the lower layer and TiAlCN crystal grains of the upper layer, which are adjacent to each other via the interface between the upper layer and the lower layer is 5 degrees or lower.

TABLE-US-00012 TABLE 12 Hard coating layer Upper layer Crystal grains having difference Lower layer (numerical value Upper layer in orientation of at the bottom indicates the (TiAlCN layer) 5 degrees or lower average target layer forming process Number per Area Tool thickness of the layer (μm)) formation symbol Amount Amount 10 μm ratio body First Second Third (see Tables of Al of C (grains/ (% by Type symbol layer layer layer 4 and 5) Xave Yave 10 μm) area) Comparative 14 E TiN-(1) I-TiCN — A′ 0.67.sup.  0.0085 * 0.2 * 1 coated tool (0.3) (2) 15 F TiC TiN-(1) I-TiCN B′ 0.93.sup.  0.0001 0.0 * 0 (2) (1) (15) or less 16 G TiN-(2) I-TiCN — C′ 0.71.sup.  0.0001 0.1 * 1 (0.5) (5) or less 17 H TiN-(2) I-TiCN — D′ 0.99 * 0.0026   0.0 * 0 (0.3) (5) 18 E TiN-(1) I-TiCN — E′ 0.46 * 0.0001 0.4 * 2 (0.3) (4) or less 19 F TiN-(1) TiN-(2) I-TiCN F′ 0.53 * 0.0075 * 0.0 * 0 (0.3) (0.3) (6) 20 G TiN-(2) I-TiCN — G′ 0.99 * 0.0001 0.0 * 0 (1) (12) or less 21 H TiC TiN-(2) I-TiCN H′ 0.54 * 0.0039   0.0 * 0 (2.5) (0.5) (14) 22 E TiC I-TiCN — I′ 0.64.sup.  0.0001 0.0 * 0 (0.5) (2) or less 23 F TiN-(2) I-TiCN — J′ 0.97 * 0.0001 0.0 * 0 (0.5) (5) or less 24 G TiN-(1) I-TiCN — C′ 0.70.sup.  0.0001 0.0 * 0 (0.5) (4) or less 25 H TiN-(2) I-TiCN — H′ 0.52 * 0.0033   0.0 * 0 (0.5) (6) 26 E TiN-(1) I-TiCN — J′ 0.97 * 0.0001 0.3 * 2 (0.3) (5) or less Outermost surface layer (numerical value at the Hard coating layer bottom indicates the Upper layer average target layer Average Average Target layer thickness of the layer (μm)) grain width aspect thickness First Second Third Fourth Type W (μm) ratio A (μm) layer layer layer layer Comparative 14 2.3 1.6 10 — — — — coated tool 15 — — 8 — — — — 16 1.5 2.4 17 — — — — 17 — — 18 — — — — 18 0.4 6.0 14 — — — — 19 1.9 1.7 12 — — — — 20 — — 9 — — — — 21 2.1 1.1 10 TiN-(2) — — — (1) 22  0.06 17.8  9 I-TiCN TiN-(2) — — (3) (1) 23 — — 8 I-TiCN Al.sub.2O.sub.3 — — (2) (5) 24 1.2 2.8 10 TiCNO Al.sub.2O.sub.3 — — (1) (4) 25 1.9 1.4 7 TiCNO Al.sub.2O.sub.3 — — (0.3) (6) 26 — — 10 TiN-(2) I-TiCN TiCNO Al.sub.2O.sub.3 (0.3) (0.5) (1) (5) (Note 1) “Crystal grains having difference in orientation of 5 degrees or lower” means crystal grains in which the difference in orientation between normal directions of crystal planes of TiCN crystal grains of the lower layer and TiAlCN crystal grains of the upper layer, which are adjacent to each other via the interface between the upper layer and the lower layer is 5 degrees or lower. (Note 2) Mark * in boxes indicates outside of the range of the present invention. (Note 3) Comparative example tools 15, 17, 20, 23, and 26 are fine grains crystals, and columnar crystals are not observed.

[0104] Next, in a state in which each of the various coated tools was screwed to a tip end portion of an insert holder made of tool steel by a fixing tool, the present invention coated tools 14 to 26 and the comparative coated tools 14 to 26 were subjected to a dry high-speed intermittent cutting test for carbon steel, and a wet high-speed intermittent cutting test for cast iron, which will be described below, and the flank wear width of a cutting edge was measured in either case.

[0105] Cutting conditions 1:

[0106] Work material: a round bar with four longitudinal grooves formed at equal intervals in the longitudinal direction of JIS S45C

[0107] Cutting speed: 380 m/min

[0108] Depth of cut: 1.5 mm

[0109] Feed: 0.25 mm/rev

[0110] Cutting time: 5 minutes,

[0111] (a typical cutting speed is 220 m/min)

[0112] Cutting conditions 2:

[0113] Work material: a round bar with four longitudinal grooves formed at equal intervals in the longitudinal direction of JIS FCD700

[0114] Cutting speed: 320 m/min

[0115] Depth of cut: 1.5 mm

[0116] Feed: 0.1 mm/rev

[0117] Cutting time: 5 minutes,

[0118] (a typical cutting speed is 200 m/min)

[0119] The results of the cutting test are shown in Table 13.

TABLE-US-00013 TABLE 13 Flank wear Cutting test width (mm) results (min) Cutting Cutting Cutting Cutting condi- condi- condi- condi- Type tions 1 tions 2 Type tions 1 tions 2 Present 14 0.13 0.15 Comparative 14 3.5 * 3.1 * invention 15 0.15 0.17 coated tool 15 4.0 * 3.5 * coated 16 0.14 0.15 16 4.2 * 3.7 * tool 17 0.13 0.14 17 2.5 * 1.9 * 18 0.10 0.11 18 3.1 * 2.6 * 19 0.19 0.18 19 3.0 * 2.4 * 20 0.15 0.14 20 2.3 * 1.8 * 21 0.18 0.19 21 3.3 * 2.8 * 22 0.11 0.12 22 3.8 * 3.4 * 23 0.16 0.14 23 2.7 * 2.1 * 24 0.14 0.13 24 4.7 * 4.2 * 25 0.15 0.13 25 4.5 * 3.9 * 26 0.13 0.11 26 3.8 * 3.3 * Mark * in boxes of comparative coated tools indicates a cutting time (min) until the end of a service life caused by the occurrence of chipping.

Example 3

[0120] As raw material powders, a cBN powder, a TiN powder, a TiCN powder, a TiC powder, an Al powder, and an Al.sub.2O.sub.3 powder, all of which had an average grain size of 0.5 μm to 4 μm, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 14. The mixture was subjected to wet mixing by a ball mill for 80 hours and was dried. Thereafter, the resultant was press-formed into compacts having dimensions with a diameter of 50 mm and a thickness of 1.5 mm at a pressure of 120 MPa, and the compacts were then sintered in a vacuum at a pressure of 1 Pa under the condition that the compacts were held at a predetermined temperature in a range of 900° C. to 1300° C. for 60 minutes, thereby producing cutting edge preliminary sintered bodies. In a state in which the preliminary sintered body was superimposed on a support piece made of WC-based cemented carbide, which was additionally prepared to contain Co: 8 mass % and WC: the remainder and have dimensions with a diameter of 50 mm and a thickness of 2 mm, the resultant was loaded in a typical ultrahigh-pressure sintering apparatus, and was subjected to ultrahigh-pressure sintering under typical conditions including a pressure of 4 GPa and a holding time of 0.8 hours at a predetermined temperature in a range of 1200° C. to 1400° C. After the sintering, upper and lower surfaces were polished using a diamond grinding wheel, and were split into predetermined dimensions by a wire electric discharge machining apparatus. Furthermore, the resultant was brazed to a brazing portion (corner portion) of an insert body made of WC-based cemented carbide having a composition including Co: 5 mass %, TaC: 5 mass %, and WC: the remainder and a shape (a 80° rhombic shape with a thickness of 4.76 mm and an inscribed circle diameter of 12.7 mm) according to JIS standard CNGA120412 using a brazing filler metal made of a Ti—Zr—Cu alloy having a composition including Zr: 37.5%, Cu: 25%, and Ti: the remainder in terms of mass %, and the outer circumference thereof was machined into predetermined dimensions. Thereafter, each of tool bodies a and b with an insert shape according to ISO standard CNGA120412 was produced by performing honing with a width of 0.13 mm and an angle of 25° on a cutting edge portion and performing finish polishing on the resultant.

TABLE-US-00014 TABLE 14 Mixing composition (mass %) Type TiN TiC Al Al.sub.2O.sub.3 cBN Tool body a 50 — 5 3 Remainder b — 50 4 3 Remainder

[0121] Next, present invention coated tools 27 to 32 shown in Table 15 were produced by first forming lower layers shown in Table 15 on the surfaces of the tool bodies a and b using a typical chemical vapor deposition apparatus under the conditions shown in Tables 3, 4, and 5 in the same methods as those in Examples 1 and 2, and subsequently depositing hard coating layers including (Ti.sub.1-xAl.sub.x)(C.sub.yN.sub.1-y) layers thereon to have target layer thicknesses.

[0122] In addition, a lower layer and an upper layer shown in Table 15 were formed in the present invention coated tools 30 to 32 under the forming conditions shown in Table 3.

[0123] In addition, for the purpose of comparison, exemplary coated tools 27 to 32 shown in Table 16 were produced by depositing hard coating layers on the surfaces of the same cutting tool bodies a and b to have target layer thicknesses shown in Table 16 under the conditions shown in Tables 3, 4, and 5 using a typical chemical vapor deposition apparatus, like the present invention coated tools.

[0124] The sections of the present invention coated tools 27 to 32 and the exemplary coated tools 27 to 32 were measured using a scanning electron microscope, and an average layer thickness was obtained by measuring and averaging the layer thicknesses of five points in an observation visual field.

[0125] The average amount Xave of Al and the average amount Yave of C of the TiAlCN layer of the upper layer were obtained using an electron probe micro-analyzer (EPMA) as in Example 1.

[0126] In addition, regarding the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer, which were adjacent to each other via the interface, using a field emission scanning electron microscope, the inclined angle α (degrees) of the normal line of the (hkl) plane of the TiCN crystal grains of the lower layer with respect to the normal line of the surface of the tool body, the inclined angle β (degrees) of the normal line of the (hkl) plane of the TiAlCN crystal grains of the upper layer with respect to the normal line of the surface of the tool body, and the absolute value (=|α (degrees)−β (degrees)|) of the difference between the inclined angles were obtained. The number of TiCN crystal grains of the lower layer and the number of TiAlCN crystal grains of the upper layer, in which the value was 5 degrees or lower, were counted, and the number per unit length of the interface between the upper layer and the lower layer was obtained.

[0127] Furthermore, the area ratio (% by area) of the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer which satisfy |α (degrees)−β (degrees)|≦5 (degrees) to the total area of the crystal grains adjacent to each other at the interface between the upper layer and the lower layer was obtained.

[0128] In addition, the average grain width W and the average aspect ratio A of the crystal grains were obtained as in Example 1.

[0129] The obtained values are shown in Tables 15 and 16.

TABLE-US-00015 TABLE 15 Hard coating layer Upper layer Crystal grains having difference in Lower layer (numerical value Upper layer orientation of 5 at the bottom indicates the (TiAlCN layer) degrees or lower average target layer forming process Number per Area Tool thickness of the layer (μm)) formation symbol Amount Amount 10 μm ratio body First Second (see Tables of Al of C (grains/ (% by Type symbol layer layer 4 and 5) Xave Yave 10 μm) area) Present 27 a TiN-(2) I-TiCN A 0.82 0.0001 2.5 27 invention (0.3) (1) or less coated 28 b TiN-(2) I-TiCN B 0.70 0.0001 9.7 50 tool (0.5) (1) or less 29 a TiN-(2) I-TiCN E 0.79 0.0016 7.6 63 (0.3) (2) 30 b TiN-(2) I-TiCN G 0.89 0.0001 3.1 35 (0.3) (1) or less 31 a TiN-(2) I-TiCN I 0.72 0.0044 4.9 63 (0.3) (1) 32 b TiN-(2) I-TiCN J 0.92 0.0001 2.1 20 (0.5) (2) or less Outermost surface layer (numerical value at the Hard coating layer bottom indicates the Upper layer average target layer Average Target layer thickness of the layer (μm)) grain width Average aspect thickness First Second Type W (μm) ratio A (μm) layer layer Present 27 1.5 1.9 3 — — invention 28 0.3 6.5 2 — — coated 29 1.1 1.7 2 — — tool 30 0.8 3.7 3 — — 31 1.8 1.1 2 TiN-(2) — (0.3) 32 2.0 0.5 1 TiN-(2) — (0.5) (Note) “Crystal grains having difference in orientation of 5 degrees or lower” means crystal grains in which the difference of orientation between normal directions of crystal planes of TiCN crystal grains of the lower layer and TiAlCN crystal grains of the upper layer, which are adjacent to each other via the interface between the upper layer and the lower layer is 5 degrees or lower.

TABLE-US-00016 TABLE 16 Hard coating layer Upper layer Crystal grains having difference in Lower layer (numerical value Upper layer orientation of 5 at the bottom indicates the (TiAlCN layer) degrees or lower average target layer forming process Number per Area Tool thicknessof the layer (μm)) formation symbol Amount Amount 10 μm ratio body First Second (see Tables of Al of C (grains/ (% by Type symbol layer layer 4 and 5) Xave Yave 10 μm) area) Comparative 27 a TiN-(2) I-TiCN B′ 0.91.sup.  0.0001 0.0 * 0 coated tool (0.3) (1) or less 28 b TiN-(2) I-TiCN D′ 0.99 * 0.0023 0.0 * 0 (0.5) (1) 29 a TiN-(2) I-TiCN F′ 0.52 * .sup. 0.0069 * 0.0 * 0 (0.3) (1) 30 b TiN-(2) I-TiCN G′ 0.99 * 0.0001 0.0 * 0 (0.3) (1) or less 31 a TiN-(2) I-TiCN H′ 0.56 * 0.0044 0.1 * 1 (0.3) (1) 32 b TiN-(2) I-TiCN J′ 0.97 * 0.0001 0.0 * 0 (0.5) (1) or less Outermost surface layer (numerical value at the Hard coating layer bottom indicates the Upper layer average target layer Average Target layer thickness of the layer (μm)) grain width Average aspect thickness First Second Type W (μm) ratio A (μm) layer layer Comparative 27 — — 3 — — coated tool 28 — — 2 — — 29 2.2 0.8 2 — — 30 — — 3 — — 31 1.8 1.4 3 TiN-(2) — (0.3) 32 — — 2 TiN-(2) — (0.5) (Note 1) “Crystal grains having difference in orientation of 5 degrees or lower” means crystal grains in which the difference in orientation between normal directions of crystal planes of TiCN crystal grains of the lower layer and TiAlCN crystal grains of the upper layer, which are adjacent to each other via the interface between the upper layer and the lower layer is 5 degrees or lower. (Note 2) Mark * in boxes indicates outside of the range of the present invention. (Note 3) Comparative example tools 27, 28, 30, and 32 are fine grains crystals, and columnar crystals are not observed.

[0130] Next, in a state in which each of the various coated tools was screwed to a tip end portion of an insert holder made of tool steel by a fixing tool, the present invention coated tools 27 to 32 and the comparative coated tools 27 to 32 were subjected to a dry high-speed intermittent cutting work test for carburized alloy steel, which will be described below, and the flank wear width of a cutting edge was measured.

[0131] Work material: a round bar with four longitudinal grooves formed at equal intervals in the longitudinal direction of JIS SCr420 (hardness: HRC62)

[0132] Cutting speed: 255 m/min

[0133] Depth of cut: 0.12 mm

[0134] Feed: 0.1 mm/rev

[0135] Cutting time: 4 minutes

[0136] The results of the cutting test are shown in Table 17.

TABLE-US-00017 TABLE 17 Flank Cutting wear width test results Type (mm) Type (min) Present invention 27 0.12 Comparative 27 3.2 * coated tool 28 0.11 coated tool 28 2.0 * 29 0.08 29 2.7 * 30 0.10 30 2.1 * 31 0.07 31 2.9 * 32 0.10 32 2.3 * Mark * in boxes of comparative coated tools indicates a cutting time (min) until the end of a service life caused by the occurrence of chipping.

[0137] From the results shown in Tables 6 to 8, 11 to 13, and 15 to 17, regarding the present invention coated tools 1 to 32, the TiCN crystal grains of the lower layer and the TiAlCN crystal grains of the upper layer, which are adjacent to each other via the interface, are epitaxially grown, and thus the adhesion density at the interface is improved. Accordingly, even in a case of being used for high-speed intermittent heavy cutting conditions in which high-temperature heat is generated and high intermittent and impact loads are exerted on a cutting edge, the hard coating layer achieves excellent chipping resistance and peeling resistance, and thus exhibits excellent cutting performance during long-term use.

[0138] Contrary to this, it is apparent that regarding the comparative coated tools 1 to 32, chipping and peeling had occurred in the hard coating layer during high-speed intermittent heavy cutting, and thus the end of the service life thereof is reached within a short time.

INDUSTRIAL APPLICABILITY

[0139] In the coated tools of the present invention, the occurrence of chipping and peeling in the hard coating layer is suppressed during continuous cutting or intermittent cutting of various steels, cast iron, and the like under typical conditions, and even under severe cutting conditions such as high-speed intermittent heavy cutting in which high intermittent and impact loads are exerted on a cutting edge, and thus excellent cutting performance is exhibited during long-term use, thereby sufficiently satisfying an improvement in performance of a cutting device, power saving and energy saving during cutting, and a further reduction in costs.