Surface-coated titanium carbonitride-based cermet cutting tool having excellent chipping resistance

Abstract

A surface-coated titanium carbonitride-based cermet cutting tool is a surface-coated TiCN-based cermet cutting tool in which a Ti compound layer that is a hard coating layer is deposited as a first layer on the surface of a TiCN-based cermet body containing W and Mo, and a Mo-enriched layer having an average thickness of 0.5 to 10 nm is formed at an interface between a TiCN phase of the body and the hard coating layer.

Claims

1. A surface-coated TiCN-based cermet cutting tool, comprising: a body made of a TiCN-based cermet containing a TiCN phase as a hard phase component and containing 1 to 10 at % of each of W and Mo; and a hard coating layer which is a first layer deposited on a surface of the body made of the TiCN-based cermet and is formed of any of a Ti carbide, a Ti nitride, a Ti carbonitride, a Ti oxycarbide, and a Ti oxycarbonitride, wherein a Mo-enriched layer having an average thickness of 0.5 to 10 nm is formed at an interface between the TiCN phase of the body and the hard coating layer.

2. The surface-coated TiCN-based cermet cutting tool according to claim 1, wherein, in a case where the interface between the TiCN phase of the body and the hard coating layer is observed in a longitudinal section of the surface-coated TiCN-based cermet cutting tool, the Mo-enriched layer is formed at an interface having a length of 60% or more of that of the interface between the TiCN phase of the body and the hard coating layer.

3. The surface-coated TiCN-based cermet cutting tool according to claim 1, wherein, in addition to the Mo-enriched layer, a W-enriched layer having an average thickness of 0.5 to 10 nm is formed at the interface between the TiCN phase of the body and the hard coating layer.

4. The surface-coated TiCN-based cermet cutting tool according to claim 3, wherein, in a case where the interface between the TiCN phase of the body and the hard coating layer is observed in the longitudinal section of the surface-coated TiCN-based cermet cutting tool, the W-enriched layer is formed at an interface having a length of 60% or more of that of the interface between the TiCN phase of the body and the hard coating layer.

5. The surface-coated TiCN-based cermet cutting tool according to claim 2, wherein, in addition to the Mo-enriched layer, a W-enriched layer having an average thickness of 0.5 to 10 nm is formed at the interface between the TiCN phase of the body and the hard coating layer.

6. The surface-coated TiCN-based cermet cutting tool according to claim 5, wherein, in a case where the interface between the TiCN phase of the body and the hard coating layer is observed in the longitudinal section of the surface-coated TiCN-based cermet cutting tool, the W-enriched layer is formed at an interface having a length of 60% or more of that of the interface between the TiCN phase of the body and the hard coating layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic sectional view illustrating Mo or Mo- and W-enriched layers formed at an interface between a TiCN phase of a body formed of a TiCN-based cermet and a hard coating layer in a surface-coated TiCN-based cermet cutting tool of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(2) Next, an embodiment of a hard coating layer of a surface-coated TiCN-based cermet cutting tool of the present invention will be described in more detail.

(3) The surface-coated TiCN-based cermet cutting tool of this embodiment includes: a body made of a TiCN-based cermet containing a TiCN phase as a hard phase component and containing 1 to 10 at % of each of W and Mo; and a hard coating layer which is a first layer deposited on the surface of the body made of the TiCN-based cermet and is formed of any of a Ti carbide, a Ti nitride, a Ti carbonitride, a Ti oxycarbide, and a Ti oxycarbonitride, in which a Mo-enriched layer having an average thickness of 0.5 to 10 nm is formed at an interface between the TiCN phase of the body and the hard coating layer. Hereinafter, the body made of the TiCN-based cermet is sometimes called a cermet body.

(4) W and Mo:

(5) W and Mo as components contained in the TiCN-based cermet contribute to solid-solution strengthening of a binder phase and an improvement in the strength and hardness of the cermet body through the generation of a hard phase. However, when the amount thereof is less than 1 at %, this effect cannot be expected, and the Mo-enriched layer and a W-enriched layer cannot be formed at predetermined concentrations in predetermined amounts at the interface between the TiCN phase of the body and the hard coating layer.

(6) On the other hand, when the amount of each of W and Mo in the TiCN-based cermet is more than 10 at %, a reduction in the strength of the cermet body is incurred due to precipitation of the carbide, the nitride, and the carbonitride. Therefore, the amount of W and Mo in the TiCN-based cermet is determined to be 1 to 10 at %. The amount of W and Mo in the TiCN-based cermet is preferably 2 at % to 8 at %, and more preferably 2 at % to 5 at %.

(7) The amount of W and Mo in the TiCN-based cermet is determined by a mixing composition of raw materials (metallic powders) when the cermet body is produced.

(8) Mo-Enriched Layer:

(9) In this embodiment, in the cermet body, before the deposition of any of the Ti carbide, the Ti nitride, the Ti carbonitride, the Ti oxycarbide, and the Ti oxycarbonitride as the first layer, Ti etching, which will be described later, is performed on the surface of the cermet body to cause Mo to be unevenly distributed in the TiCN phase of the surface of the cermet body. In addition, by causing Mo to be unevenly distributed in the TiCN phase of the surface of the cermet body and forming the Mo-enriched layer, wettability of the cermet body and the hard coating layer is improved, and chemical bonds between the cermet body and the hard coating layer become strong. Therefore, the adhesive strength between the hard coating layer and the cermet body can be improved.

(10) When the average thickness of the Mo-enriched layer formed at the interface between the TiCN phase of the cermet body and the hard coating layer is smaller than 0.5 nm, the improvement in the adhesion strength cannot be expected. When the average thickness thereof is greater than 10 nm, cracks propagate in the Mo-enriched layer and thus the adhesion strength is reduced. Therefore, the average thickness of the Mo-enriched layer is determined to be 0.5 to 10 nm. The average thickness of the Mo-enriched layer is preferably 2 nm to 8 nm, and more preferably 3 nm to 7 nm.

(11) The Mo-enriched layer unevenly distributed on the TiCN phase of the surface of the cermet body is a region having a Mo content of 5 to 50 at % at the interface between the TiCN phase and the hard coating layer.

(12) When the Mo content of the interface between the TiCN phase and the hard coating layer is less than 5 at %, the Mo-enriched layer slightly contributes to the improvement in the adhesion strength. When the Mo content is more than 50 at %, the interface has metallic properties and the effect of strengthening chemical bonds between the cermet body and the hard coating layer is degraded. Therefore, at the interface between the TiCN phase and the hard coating layer, a region which has a Mo content of 5 to 50 at % and satisfies the average thickness is determined as the Mo-enriched layer.

(13) The Mo-enriched layer can be specified in the following method. Compositional mapping of a longitudinal section of the surface-coated TiCN-based cermet cutting tool is performed in a visual field at 10,000 using a transmission electron microscope (TEM) and an energy-dispersive X-ray analyzer, a TiCN phase in the cermet body is specified, a region including the interface between the TiCN phase and the hard coating layer is observed in a visual field at 500,000, a line is drawn into a length of 50 nm to be perpendicular to the interface between the TiCN phase and the hard coating layer so as to intersect the interface between the TiCN phase and the hard coating layer at the center of the line segment, line analysis including the interface between the TiCN phase and the hard coating layer is performed by performing compositional analysis on the line at intervals of 0.5 nm, and a region having an (average) Mo content of 5 to 50 at % at five measurement points is specified. In addition, in the region having a Mo content of 5 to 50 at %, a portion having a thickness of 0.5 to 10 nm is determined as the Mo-enriched layer. Line analysis is performed on five TiCN phases, and the average value of the thicknesses of the five points is determined as the average thickness.

(14) The TiCN phase in the cermet body is a phase formed of Ti, C, and N and does not contain Mo and W. That is, a TiCNMo composition phase, a TiCNW composition phase, and the like in the cermet body are phases excluded from the TiCN phase.

(15) In addition, in the case where the interface between the TiCN phase of the cermet body and the hard coating layer is observed in the longitudinal section of the surface-coated TiCN-based cermet cutting tool, regarding an interface length ratio at which the Mo-enriched layer is formed, the adhesion strength is further improved in a case where the Mo-enriched layer is formed at an interface having a length of 60% or more of that of the interface between the TiCN phase of the body and the hard coating layer. Therefore, it is preferable that the interface length ratio of the Mo-enriched layer formed at the interface between the TiCN phase of the cermet body and the hard coating layer be 60% or more. The interface length ratio of the Mo-enriched layer is more preferably 80% or more. Although not particularly limited, the upper limit of the interface length ratio of the Mo-enriched layer may be 95%.

(16) W-Enriched Layer:

(17) In this embodiment, in the cermet body, before the deposition of any of the Ti carbide, the Ti nitride, the Ti carbonitride, the Ti oxycarbide, and the Ti oxycarbonitride as the first layer, Ti etching is performed on the surface of the cermet body to cause W as well as Mo to be unevenly distributed in the TiCN phase of the surface of the cermet body. In addition, by causing W as well as Mo to be unevenly distributed in the TiCN phase of the surface of the cermet body and forming the W-enriched layer, wettability of the cermet body and the hard coating layer is improved, and chemical bonds between the cermet body and the hard coating layer become strong. Therefore, the adhesive strength between the hard coating layer and the cermet body can be further improved.

(18) When the average thickness of the W-enriched layer formed at the interface between the TiCN phase of the cermet body and the hard coating layer is smaller than 0.5 nm, the improvement in the adhesion strength cannot be expected. When the average thickness thereof is greater than 10 nm, cracks propagate in the W-enriched layer and thus the adhesion strength is reduced. Therefore, it is preferable that the average thickness of the W-enriched layer be 0.5 to 10 nm. The average thickness of the W-enriched layer is preferably 2 nm to 8 nm, and more preferably 3 nm to 7 nm.

(19) The W-enriched layer unevenly distributed on the TiCN phase of the surface of the cermet body means a region having a W content of 5 to 50 at % at the interface between the TiCN phase and the hard coating layer.

(20) When the W content of the interface between the TiCN phase and the hard coating layer is less than 5 at %, the W-enriched layer slightly contributes to the improvement in the adhesion strength. When the W content is more than 50 at %, the interface has metallic properties and the effect of strengthening chemical bonds between the cermet body and the hard coating layer is degraded. Therefore, it is preferable that at the interface between the TiCN phase and the hard coating layer, a region which has a W content of 5 to 50 at % and satisfies the average thickness be determined as the W-enriched layer.

(21) The W-enriched layer can be specified in the same method as the method to specify the Mo-enriched layer described above. That is, a region having a W content of 5 to 50 at % is specified through line analysis described above. In addition, a portion having a thickness of 0.5 to 10 nm in the region having a W content of 5 to 50 at % may be determined as the W-enriched layer. Line analysis is performed on five TiCN phases, and the average value of the thicknesses of the five points is determined as the average thickness.

(22) In addition, in the case where the interface between the TiCN phase of the cermet body and the hard coating layer is observed in the longitudinal section of the surface-coated TiCN-based cermet cutting tool, regarding an interface length ratio at which the W-enriched layer is formed, the adhesion strength is further improved in a case where the W-enriched layer is formed at an interface having a length of 60% or more of that of the interface between the TiCN phase of the body and the hard coating layer. Therefore, it is preferable that the interface length ratio of the W-enriched layer formed at the interface between the TiCN phase of the cermet body and the hard coating layer be 60% or more. The interface length ratio of the W-enriched layer is more preferably 80% or more. Although not particularly limited, the upper limit of the interface length ratio of the W-enriched layer may be 95%.

(23) Regarding the interface length ratios of the Mo-enriched layer and the W-enriched layer, during measurement using the transmission electron microscope (TEM) and the energy-dispersive X-ray analyzer described above, compositional mapping is performed in a visual field including the interface between the TiCN phase in the cermet body and the hard coating layer at 500,000, the length of the interface between the TiCN phase and the hard coating layer is obtained, a region in which the Mo content or the W content is 5 to 50% is drawn as a curve, and the length thereof is obtained. By dividing the length of the region in which the Mo content or the W content is 5 to 50% by the length of the interface, the interface length ratio of the Mo-enriched layer and the interface length ratio of the W-enriched layer formed at the interface between the TiCN phase and the hard coating layer are obtained.

(24) Formation of Mo-Enriched Layer and W-Enriched Layer:

(25) In this embodiment, before the deposition of any of the Ti carbide, the Ti nitride, the Ti carbonitride, the Ti oxycarbide, and the Ti oxycarbonitride as the first layer on the cermet body, for example, Mo and W can be caused to be unevenly distributed in the TiCN phase of the surface of the body by performing Ti etching on the surface of the cermet body under the following condition of first to fourth stages.

(26) First stage TiCl.sub.4: 3.0% to 5.0%, H.sub.2: remainder, 3 to 7 kPa, 700 C. to 800 C., 5 to 20 minutes

(27) Second stage Ar: 100%, 3 to 7 kPa, 700 C. to 800 C.

(28) Third stage TiCl.sub.4: 1.0% to 3.0%, H.sub.2: remainder, 3 to 7 kPa, 800 C. to 900 C., 5 to 20 minutes

(29) Fourth stage Ar: 100%, 3 to 7 kPa, 800 C. to 900 C.

(30) Through the Ti etching, Mo and W contained in the cermet body can be caused to be unevenly distributed in the TiCN phase of the surface of the body.

(31) Next, an example of the surface-coated TiCN-based cermet cutting tool of the present invention will be described in detail.

(32) As an example of the present invention, an example in which any of the Ti carbide, the Ti nitride, the Ti carbonitride, the Ti oxycarbide, and the Ti oxycarbonitride is deposited as the first layer of the hard coating layer on the surface of the cermet body is described. However, in the present invention, further deposition of a well-known hard coating layer such as an Al.sub.2O.sub.3 layer, a composite nitride layer or a composite oxide layer of Ti and Al, and a composite nitride layer or a composite oxide layer of Cr and Al after forming the first layer, or deposition of a Ti carbide layer, a Ti nitride layer, a Ti carbonitride layer, a Ti oxycarbide layer, and a Ti oxycarbonitride layer as the outermost surface layer of the hard coating layer is not impeded.

EXAMPLES

(33) As raw material powders, a TiCN (TiC/TiN=50/50 in terms of mass ratio) powder, a Mo.sub.2C powder, a ZrC powder, a NbC powder, a TaC powder, a WC powder, a Co powder, and a Ni powder, all of which had an average grain size of 0.5 m to 2 m, were prepared, and the raw material powders were mixed in mixing compositions shown in Table 1, 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 1540 C. for one hour. After the sintering, a cutting edge portion was subjected to honing to have a radius R of 0.07 mm, thereby forming cermet bodies 1 to 10 having insert shapes according to ISO standard CNMG120412.

(34) In Table 1, as the mixing ratios, at % of Mo and W are also shown.

(35) TABLE-US-00001 TABLE 1 Mixing composition (mass %) (at % (at % Type Co Ni Mo.sub.2C of Mo) WC of W) ZrC TaC NbC TiCN Cermet 1 12 6 10 4.2 15 3.3 7 Remainder body 2 7 7 7.5 3.0 15 3.1 5 Remainder 3 8 8 10 3.8 5.5 1.1 4 5 Remainder 4 9 6 6 2.4 13 2.7 6 2 Remainder 5 8 5 10 4.0 10 2.1 1 8 Remainder 6 5 5 23.5 9.8 10 2.2 5 Remainder 7 8 8 2.5 1.0 20 4.3 2 4 3 Remainder 8 7 8 5 1.9 14 2.8 7 Remainder 9 6 7 10 4.0 15 3.2 4 3 Remainder 10 9 6 6 3.0 38 9.9 1 5 Remainder

(36) Subsequently, Ti etching was performed on the cermet body under the conditions of the first to fourth stages shown in Table 2 before the formation of the first layer of the hard coating layer on the surfaces of the tool bodies 1 to 10 using a chemical vapor deposition apparatus.

(37) Each of conditions of Condition A to Condition G shown in Table 2 had a first stage, a second stage, a third stage, and a fourth stage in order from the top.

(38) Thereafter, under the conditions shown in Table 3, a Ti compound layer formed of any of a Ti carbide, a Ti nitride, a Ti carbonitride, a Ti oxycarbide, and a Ti oxycarbonitride shown in Table 4 was deposited on the surface of the cermet body as the first layer.

(39) In addition, the types of the hard coating layer of Table 3 are displayed in Tables 4 and 5 as follows. TiC layer=TiC, TiN layer (first layer)=TiN shown as the first layer of Tables 4 and 5, TiN layer (other layers)=TiN shown as the second to fourth layers in Tables 4 and 5, 1-TiC.sub.0.5N.sub.0.5 layer=1-TiCN, TiCN layer=TiCN, TiCO layer=TiCO, TiCNO layer=TiCNO, and Al.sub.2O.sub.3 layer=Al.sub.2O.sub.3.

(40) Next, by further depositing a Ti compound layer shown in Table 4 (formation of second to fourth layers) under the conditions shown in Table 3, surface-coated TiCN-based cermet cutting tools of the present invention (hereinafter, referred to as the present invention coated tools) 1 to 8 and 14 to 16 shown in Table 4 were produced.

(41) In addition, regarding some of those, by depositing an Al.sub.2O.sub.3 layer (upper layer) shown in Table 4 on the deposited Ti compound layer (lower layer) under the conditions shown in Table 3, the present invention coated tools 9 to 13 shown in Table 4 were produced.

(42) For the purpose of comparison, regarding some of the same tool bodies 1 to 10, Ti etching was performed on the cermet body under the conditions shown in Table 2 before the first layer of the hard coating layer was formed on the surface of the tool body by the chemical vapor deposition apparatus.

(43) Thereafter, on the surface of the cermet body including the tool body which was not subjected to Ti etching, the Ti compound layer formed of any of a Ti carbide, a Ti nitride, a Ti carbonitride, a Ti oxycarbide, and a Ti oxycarbonitride shown in Table 5 was deposited as the first layer under the conditions shown in Table 3.

(44) Next, under the conditions shown in Table 3, the Ti compound layers shown in Table 5 were further deposited (formation of second to fourth layers), thereby producing surface-coated TiCN-based cermet cutting tools of comparative examples (hereinafter, referred to as comparative example coated tools) 1 to 8 shown in Table 5.

(45) In addition, regarding some of those, an Al.sub.2O.sub.3 layer (upper layer) shown in Table 5 was deposited on the deposited Ti compound layer (lower layer) under the conditions shown in Table 3, thereby producing comparative example coated tools 9 to 13 shown in Table 5.

(46) Compositional mapping was performed on the present invention coated tools 1 to 16 and the comparative example coated tools 1 to 13 produced above in a visual field at 10,000 using the transmission electron microscope (TEM) and the energy-dispersive X-ray analyzer, a TiCN phase in the cermet body was specified, a line was drawn into a length of 50 nm to be perpendicular to the interface between the TiCN phase and the hard coating layer in a visual field including the interface between the TiCN phase and the hard coating layer at 500,000 so as to intersect the interface between the TiCN phase and the hard coating layer at the center of the line segment, and line analysis including the interface between the TiCN phase and the hard coating layer was performed by performing compositional analysis on the line.

(47) From the results, a region in which the Mo content or the W content was 5 to 50 at % was specified as an enriched layer, and the thickness of the enriched layer was obtained. Moreover, the line analysis was performed on five TiCN phases, and by obtaining averages, the average thicknesses of the Mo-enriched layer and the W-enriched layer, the Mo content of the Mo-enriched layer, and the W content of the W-enriched layer were obtained.

(48) Tables 4 and 5 show the results.

(49) In addition, regarding the interface length ratios of the Mo-enriched layer and the W-enriched layer, during measurement using the transmission electron microscope (TEM) and the energy-dispersive X-ray analyzer, compositional mapping was performed in a visual field including the interface between the TiCN phase in the cermet body and the hard coating layer at 500,000, the length of the interface between the TiCN phase and the hard coating layer was obtained, a region in which the Mo content or the W content is 5 to 50% was drawn as a curve, and the length thereof was obtained. By dividing the length of the region in which the Mo content or the W content was 5 to 50% by the length of the interface, the interface length ratio of the Mo-enriched layer and the interface length ratio of the W-enriched layer formed at the interface between the TiCN phase and the hard coating layer were obtained.

(50) Tables 4 and 5 show the results.

(51) In addition, the layer thickness of each of the layers constituting the hard coating layers of the present invention coated tools 1 to 16 and the comparative example coated tools 1 to 13 was measured using a scanning electron microscope (the magnification was set to an appropriate value in a range of 5,000 to 200,000), and the layer thicknesses of five points in an observation visual field were measured and averaged to obtain the average layer thickness.

(52) TABLE-US-00002 TABLE 2 Ti etching conditions Condition Reaction gas composition Pressure Temperature Time type (vol %) (kPa) ( C.) (min) Condition TiCl.sub.4: 4.0%, H.sub.2: remainder 5 750 10 A Ar: 100% 5 750 5 TiCl.sub.4: 2.0%, H.sub.2: remainder 5 850 10 Ar: 100% 5 850 5 Condition TiCl.sub.4: 5.0%, H.sub.2: remainder 7 700 5 B Ar: 100% 7 700 5 TiCl.sub.4: 3.0%, H.sub.2: remainder 7 800 5 Ar: 100% 7 800 5 Condition TiCl.sub.4: 3.0%, H.sub.2: remainder 3 800 20 C Ar: 100% 3 800 5 TiCl.sub.4: 1.0%, H.sub.2: remainder 3 900 20 Ar: 100% 3 900 5 Condition TiCl.sub.4: 5.0%, H.sub.2: remainder 7 800 20 D Ar: 100% 7 800 10 TiCl.sub.4: 3.0%, H.sub.2: remainder 7 900 20 Ar: 100% 7 900 10 Condition TiCl.sub.4: 3.0%, H.sub.2: remainder 3 700 5 E Ar: 100% 3 700 3 TiCl.sub.4: 1.0%, H.sub.2: remainder 3 800 5 Ar: 100% 3 800 3 Condition TiCl.sub.4: 2.0%, H.sub.2: remainder 2 650 3 F Ar: 100% 2 650 3 TiCl.sub.4: 0.5%, H.sub.2: remainder 2 750 3 Ar: 100% 2 750 3 Condition TiCl.sub.4: 6.0%, H.sub.2: remainder 8 850 30 G Ar: 100% 8 850 5 TiCl.sub.4: 4.0%, H.sub.2: remainder 8 950 30 Ar: 100% 8 950 5

(53) TABLE-US-00003 TABLE 3 Forming conditions (pressure of reaction atmosphere is Hard coating layer expressed as kPa and temperature is expressed as C.) Composition (numbers Reaction gas composition Reaction atmosphere Type indicate atomic ratios) (vol %) Pressure Temperature TiC layer TiC TiCl.sub.4: 4.2%, CH.sub.4: 8.5%, H.sub.2: remainder 7 1020 TiN layer (first layer) TiN TiCl.sub.4: 4.2%, N.sub.2: 30%, H.sub.2: remainder 30 900 TiN layer (other layers) TiN TiCl.sub.4: 4.2%, N.sub.2: 35%, H.sub.2: remainder 50 1040 1-TiC.sub.0.5N.sub.0.5 layer TiC.sub.0.5N.sub.0.5 TiCl.sub.4: 4.2%, N.sub.2: 20%, CH.sub.3CN: 0.6%, H.sub.2: remainder 7 900 TiCN layer TiC.sub.0.5N.sub.0.5 TiCl.sub.4: 4.2%, N.sub.2: 20%, CH.sub.4: 4%, H.sub.2: remainder 12 1020 TiCO layer TiC.sub.0.5O.sub.0.5 TiCl.sub.4: 4.2%, CO: 4%, H.sub.2: remainder 7 1020 TiCNO layer TiC.sub.0.3N.sub.0.3O.sub.0.4 TiCl.sub.4: 4.2%, CO: 3%, CH.sub.4: 3%, N.sub.2: 20%, H.sub.2: remainder 20 1020 Al.sub.2O.sub.3 layer Al.sub.2O.sub.3 AlCl.sub.3: 3%, CO.sub.2: 6%, HCl: 8%, H.sub.2S: 0.4%, H.sub.2: remainder 7 1000

(54) TABLE-US-00004 TABLE 4 Hard coating layer Enriched layer formed at interface between Lower layer TiCN phase and hard coating layer (Ti compound layer) Ti Mo-enriched layer W-enriched layer First layer etching Interface Interface Average Tool type Mo length W length layer body (see Thickness content ratio Thickness content ratio thickness Type symbol Table 2) (nm) (at %) (%) (nm) (at %) (%) Type (m) Present 1 1 A 3 20 90 3 17 85 TiN 1 invention 2 2 B 1 15 64 1 16 64 TiN 1 coated 3 3 E 5 17 81 0.3 3 52 TiN 1 tool 4 4 A 7 12 88 7 14 85 TiN 1 5 5 B 6 21 95 9 10 93 TiN 1 6 6 D 10 50 93 2 11 65 TiN 0.5 7 7 E 0.5 5 60 0.5 5 60 TiN 0.5 8 8 C 5 9 85 6 14 83 1-TiCN 1 9 9 C 7 19 89 7 18 88 TiN 0.5 10 10 D 9 14 94 14 61 92 TiN 1.5 11 1 D 6 20 85 10 50 83 TiN 1.5 12 2 B 9 16 89 9 15 88 TiN 1.5 13 3 A 4 18 91 3 6 86 1-TiCN 7 14 8 F 1 12 55 2 7 63 TiN 1 15 5 F 4 18 91 0.3 4 63 TiN 0.5 16 6 F 4 18 91 0.6 6 57 TiN 1.5 Hard coating layer Lower layer (Ti compound layer) Second layer Third layer Fourth layer Total Average Average Average average Average layer layer layer layer layer thickness of upper thickness thickness thickness thickness layer (Al.sub.2O.sub.3) Type Type (m) Type (m) Type (m) (m) (m) Present 1 1-TiCN 12 TiN 1 14 invention 2 1-TiCN 7 TiN 1.5 9.5 coated 3 1-TiCN 4 TiC 2 7 tool 4 1-TiCN 9 10 5 1-TiCN 6 TiN 0.5 7.5 6 1-TiCN 2 TiC 0.3 2.8 7 1-TiCN 10 TiC 1.5 12 8 TiCN 15 TiN 0.5 16.5 9 1-TiCN 8 TiCO 0.5 TiCNO 0.5 9.5 7 10 TiC 1 TiCN 8 TiCO 1 11.5 15 11 TiC 1 1-TiCN 6 TiCNO 0.5 9 10 12 1-TiCN 4 TiCNO 1.5 7 12 13 TiCO 1 8 7 14 1-TiCN 5 TiN 1.5 7.5 15 1-TiCN 10 TiN 1 11.5 16 1-TiCN 7 TiN 1 9.5

(55) TABLE-US-00005 TABLE 5 Hard coating layer Enriched layer formed at interface between Lower layer TiCN phase and hard coating layer (Ti compound layer) Ti Mo-enriched layer W-enriched layer First layer etching Interface Interface Average Tool type Mo length W length layer body (see Thickness content ratio Thickness content ratio thickness Type symbol Table 2) (nm) (at %) (%) (nm) (at %) (%) Type (m) Comparative 1 1 TiN 1 example 2 2 TiN 1 coated 3 3 TiN 1 tool 4 4 TiN 1 5 5 TiN 1 6 6 G 15 55 92 10 41 87 TiN 0.5 7 7 F 0.3 3 65 0.5 5 53 TiN 0.5 8 8 1-TiCN 1 9 9 TiN 0.5 10 10 TiN 1.5 11 1 TiN 1.5 12 2 TiN 1.5 13 3 1-TiCN 7 Hard coating layer Lower layer (Ti compound layer) Second layer Third layer Fourth layer Total Average Average Average average Average layer layer layer layer layer thickness of upper thickness thickness thickness thickness layer (Al.sub.2O.sub.3) Type Type (m) Type (m) Type (m) (m) (m) Comparative 1 1-TiCN 12 TiN 1 14 example 2 1-TiCN 7 TiN 1.5 9.5 coated 3 1-TiCN 4 TiC 2 7 tool 4 1-TiCN 9 10 5 1-TiCN 6 TiN 0.5 7.5 6 1-TiCN 2 TiC 0.3 2.8 7 1-TiCN 10 TiC 1.5 12 8 TiCN 15 TiN 0.5 16.5 9 1-TiCN 8 TiCO 0.5 TiCNO 0.5 9.5 7 10 TiC 1 TiCN 8 TiCO 1 11.5 15 11 TiC 1 1-TiCN 6 TiCNO 0.5 9 10 12 1-TiCN 4 TiCNO 1.5 7 12 13 TiCO 1 8 7

(56) 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, regarding the present invention coated tools 1 to 16 and the comparative example coated tools 1 to 13,

(57) a wet high-speed intermittent cutting test for ductile cast iron (a typical cutting speed was 200 m/min) was conducted under conditions (cutting conditions A) including:

(58) Work material: a round bar with four longitudinal grooves formed at equal intervals in the longitudinal direction of JIS-FCD 700-2 (ISO 1083/700-2)

(59) Cutting speed: 350 m/min

(60) Depth of cut: 1.4 mm

(61) Feed rate: 0.3 mm/rev

(62) Cutting oil agent: present

(63) Cutting time: 6 minutes, and

(64) a dry high-speed intermittent cutting test for alloy steel (a typical cutting speed was 300 m/min) was conducted under conditions (cutting conditions B) including:

(65) Work material: a round bar with four longitudinal grooves formed at equal intervals in the longitudinal direction of JIS SCM440

(66) Cutting speed: 410 m/min

(67) Depth of cut: 2.0 mm

(68) Feed rate: 0.3 mm/rev

(69) Cutting time: 6 minutes.

(70) In both the cutting tests, the flank wear width of a cutting edge was measured.

(71) The measurement results are shown in Table 6.

(72) TABLE-US-00006 TABLE 6 Flank wear width Cutting test results (mm) (min) Cutting Cutting Cutting Cutting conditions conditions conditions conditions Type (A) (B) Type (A) (B) Present 1 0.12 0.13 Comparative 1 2.8 2.9 invention 2 0.15 0.14 example 2 2.3 2.5 coated 3 0.27 0.26 coated 3 1.2 1.2 tool 4 0.17 0.17 tool 4 2.5 2.6 5 0.18 0.17 5 1.5 1.4 6 0.24 0.24 6 3.5 3.7 7 0.26 0.25 7 3.3 3.5 8 0.19 0.18 8 2.0 2.1 9 0.17 0.16 9 2.2 2.3 10 0.26 0.26 10 2.1 2.2 11 0.23 0.22 11 2.7 2.8 12 0.18 0.18 12 2.8 3.0 13 0.11 0.11 13 2.6 2.7 14 0.28 0.28 15 0.26 0.26 16 0.26 0.26
(In the table, the cutting test results of the Comparative example coated tools indicate cutting time (min) until the service life was reached due to fine chipping, defects, peeling, or the like generated in the hard coating layer.)

(73) From the results shown in Tables 4 and 6, it is apparent that regarding the present invention coated tools 1 to 16, in the surface-coated TiCN-based cermet cutting tools in which any of the Ti carbide, the Ti nitride, the Ti carbonitride, the Ti oxycarbide, and the Ti oxycarbonitride as the first layer is deposited as the hard coating layer, the Mo-enriched layer and the W-enriched layer having predetermined thicknesses, predetermined amounts, and predetermined interface lengths are formed at the interface between the TiCN phase of the body and the hard coating layer, and accordingly, chemical bonds between the cermet body and the hard coating layer become strong via W and Mo unevenly distributed at the interface. Therefore, the hard coating layer as a coating has excellent adhesive strength to the cermet body, and exhibits excellent chipping resistance and wear resistance during long-term use even in a case of being used for high-speed intermittent cutting work of cast iron, alloy steel, or the like in which a high load is exerted on a cutting edge.

(74) That is, regarding the present invention coated tools 1 to 16, under any of the cutting conditions A and the cutting conditions B, abnormal damage such as chipping, defects, and peeling did not occur in the hard coating layer within a cutting time (6 minutes) and a service life was not reached. Therefore, after the cutting tests, wear, that is, the flank wear width (mm) of the hard coating layer of the coated tool was measured.

(75) In addition, regarding the present invention coated tools 1 to 16, when the present invention coated tool 3 in which the thickness and the interface length ratio of the W-enriched layer did not satisfy the preferable ranges of the present invention and the present invention coated tool 1 in which the thickness and the interface length ratio of the W-enriched layer satisfied the preferable ranges of the present invention were compared to each other, the present invention coated tool 1 had a smaller flank wear width and had a tendency toward a further improvement in adhesion strength.

(76) When the present invention coated tool 14 in which the interface length ratio of the Mo-enriched layer did not satisfy the preferable range of the present invention and the present invention coated tool 8 in which the interface length ratio of the Mo-enriched layer satisfied the preferable range of the present invention were compared to each other, the present invention coated tool 8 had a smaller flank wear width and had a tendency toward a further improvement in adhesion strength.

(77) When the present invention coated tool 15 in which the thickness of the W-enriched layer did not satisfy the preferable range of the present invention and the present invention coated tool 5 in which the thickness of the W-enriched layer satisfied the preferable range of the present invention were compared to each other, the present invention coated tool 5 had a smaller flank wear width and had a tendency toward a further improvement in adhesion strength.

(78) When the present invention coated tool 16 in which the interface length ratio of the W-enriched layer did not satisfy the preferable range of the present invention and the present invention coated tool 6 in which the interface length ratio of the W-enriched layer satisfied the preferable range of the present invention were compared to each other, the present invention coated tool 6 had a smaller flank wear width and had a tendency toward a further improvement in adhesion strength.

(79) Contrary to this, from the results shown in Tables 5 and 6, it is apparent that regarding each of the comparative example coated tools 1 to 13, since the Mo-enriched layer and the W-enriched layer having predetermined thicknesses, predetermined amounts, and predetermined interface lengths were not formed at the interface between the TiCN phase of the body and the hard coating layer, during high-speed intermittent cutting work of cast iron, alloy steel, or the like in which a high load was exerted on a cutting edge, abnormal damage such as chipping, defects, and peeling occurred and a service life was reached within a relatively short period of time.

(80) That is, regarding the comparative example coated tools 1 to 13, under any of the cutting conditions A and the cutting conditions B, abnormal damage such as chipping, defects, and peeling occurred in the hard coating layer within a cutting time (6 minutes) and a service life was reached. Accordingly, the flank wear width (mm) of the cutting edge was not measured. Therefore, the service lives of the comparative example coated tools 1 to 13 are shown as cutting test results (minutes) in Table 6.

(81) For example, even when the Mo-enriched layer and the W-enriched layer were formed, in the comparative example coated tool 6 in which the thickness of the Mo-enriched layer was greater than the range of the present invention, cracks were observed in the Mo-enriched layer, peeling occurred early, and the service life was reached such that the adhesion strength was degraded. In addition, even when the Mo-enriched layer and the W-enriched layer were formed, in the comparative example coated tool 7 in which the thickness of the Mo-enriched layer was smaller than the range of the present invention, similarly, peeling occurred early, and the service life was reached such that the adhesion strength was degraded.

INDUSTRIAL APPLICABILITY

(82) As described above, the coated tool of the present invention exhibits excellent cutting performance in a case where cast iron or the like is provided for high-speed intermittent cutting work in which high-temperature heat is generated, and can be used as coated tools for various work materials. Furthermore, excellent wear resistance is exhibited during long-term use, and thus the coated tool can satisfactorily achieve enhancement in the performance of a cutting apparatus, power saving and energy saving during cutting work, and a further reduction in cost.