Surface-coated cutting tool with excellent adhesion-induced chipping resistance and peel resistance

Abstract

In the surface-coated cutting tool, a Ti compound layer containing at least nitrogen and carbon is formed on a surface of cutting tool substrate, a nitrogen concentration in the Ti compound layer, in a case of being measured in a direction perpendicular to the surface of the cutting tool substrate in a vicinity of a cutting edge, gradually increases as a distance from cutting tool substrate increases within a range of 0.20 μm from the surface of the cutting tool substrate toward the Ti compound layer, an average concentration gradient of the nitrogen concentration is 20 at %/μm or more and 300 at %/μm or less, and an average nitrogen concentration in the Ti compound layer in the vicinity of the cutting edge is lower than an average nitrogen concentration in the Ti compound layer at a position of a flank face away from the cutting edge by 3 at % or more.

Claims

1. A surface-coated cutting tool comprising a hard coating layer on a surface of a cutting tool substrate made of WC-based cemented carbide or TiCN-based cermet, the hard coating layer comprises: (a) a Ti compound layer containing at least nitrogen and carbon is formed on the surface of the cutting tool substrate, (b) in a vicinity of a cutting edge of the cutting tool substrate, in a case where a nitrogen concentration in the Ti compound layer is measured in a direction perpendicular to the surface of the cutting tool substrate, within a range of 0.20 μm from the surface of the cutting tool substrate toward the Ti compound layer, the nitrogen concentration in the Ti compound layer gradually increases as a distance from the cutting tool substrate increases, and an average concentration gradient of the nitrogen concentration is 20 at %/μm or more and 300 at %/μm or less, and (c) an average nitrogen concentration in the Ti compound layer formed on a top of the surface of the cutting tool substrate in the vicinity of the cutting edge is lower than an average nitrogen concentration in the Ti compound layer formed on the top of the surface of the cutting tool substrate at a position of a flank face away from the cutting edge by 3 at % or more.

2. The surface-coated cutting tool according to claim 1, wherein, in the Ti compound layer formed on the top of the surface of the cutting tool substrate at the position of the flank face away from the cutting edge, in a case where a nitrogen concentration and a carbon concentration are measured along a direction parallel to the surface of the cutting tool substrate, a low nitrogen region having a high carbon concentration and a low nitrogen concentration (including zero nitrogen concentration) and a high nitrogen region having a high nitrogen concentration and a low carbon concentration (including zero carbon concentration) are present.

3. The surface-coated cutting tool according to claim 1, further comprising one or more Ti compound layers formed on the surface of the Ti compound layer containing at least nitrogen and carbon and formed on the top of the surface of the cutting tool substrate.

4. The surface-coated cutting tool according to claim 3, further comprising an Al.sub.2O.sub.3 layer having an α-form or κ-form crystal structure formed on a surface of the one or more Ti compound layers.

5. The surface-coated cutting tool according to claim 2, further comprising one or more Ti compound layers formed on the surface of the Ti compound layer containing at least nitrogen and carbon and formed on the top of the surface of the cutting tool substrate.

6. The surface-coated cutting tool according to claim 5, further comprising an Al.sub.2O.sub.3 layer having an α-form or κ-form crystal structure formed on a surface of the one or more Ti compound layers.

7. The surface-coated cutting tool according to claim 1, wherein the position of the flank face away from the cutting edge is a position 0.4 mm to 0.6 mm away from a honing portion toward the flank face side.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates an example of a schematic longitudinal sectional view of a hard coating layer formed on the surface of a cutting tool substrate 1 in the vicinity of a cutting edge of a coated tool of the present invention.

(2) FIG. 2 is an example of a schematic longitudinal sectional view of the hard coating layer formed on the surface of the cutting tool substrate 1 at a position of a flank face of the coated tool of the present invention away from the cutting edge, where (a) illustrates an aspect, and (b) illustrates another aspect.

DESCRIPTION OF EMBODIMENTS

(3) Next, the coated tool of the present invention will be described in detail with reference to examples.

Example 1

(4) As raw material powders, 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, all of which had an average particle size of 1 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, cutting tool bodies A and B made of WC-based cemented carbide with insert shapes specified in ISO CNMG120408 were produced by performing honing with R: 0.04 mm on the cutting edge portion.

(5) In addition, as raw material powders, a TiCN (TiC/TiN=50/50 in terms of mass ratio) powder, a NbC powder, a TaC powder, a WC powder, a ZrC powder, a Mo.sub.2C powder, a Co powder, and a Ni powder, all of which had an average particle size of 0.5 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 a compact at a pressure of 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 1540° C. for one hour. After the sintering, a cutting tool substrate C made of TiCN-based cermet with an insert shape according to ISO standard CNMG120408 was produced by performing honing with R: 0.04 mm on the cutting edge portion.

(6) Next, using a typical chemical vapor deposition apparatus, the first Ti compound layer 2 illustrated in FIG. 1 and the first Ti compound layer 2′ illustrated in FIG. 2(a) were deposited on the surfaces of the cutting tool bodies A to C under the conditions indicated as forming symbols A to D in Table 3.

(7) For example, forming conditions by forming symbol A are more specifically described as follows. (a) First, a TiN layer was deposited on the surface of the cutting tool substrate 1 including the vicinity of the cutting edge and the position of the flank face away from the cutting edge under conditions A shown in Table 3.

(8) (b) Next, only the TiN layer formed to cover the vicinity of the cutting edge of the cutting tool substrate 1 was removed with a brush.

(9) (c) Next, on the surface of the cutting tool substrate 1 including the vicinity of the cutting edge, from which the TiN layer was removed with the brush, and the position of the flank face away from the cutting edge, a TiCN layer having a low nitrogen concentration was deposited under conditions A shown in Table 3, and deposition was continued under the same conditions A shown in Table 3 while gradually changing gas conditions and the pressure of the reaction atmosphere to forming conditions of TiCN having a high nitrogen concentration, whereby the first Ti compound layer 2 shown in Table 6 was formed in the vicinity of the cutting edge, and similarly, the first Ti compound layer 2′ shown in Table 6 was formed at the position of the flank face away from the cutting edge.

(10) (d) Next, for some of the cutting tool bodies, on the surfaces of the first Ti compound layer 2 and the first Ti compound layer 2′, the second Ti compound layer 3, and the Al.sub.2O.sub.3 layer 4 or a TiN layer as the outermost layer for cutting edge identification, shown in Table 5 were deposited under the conditions shown in Table 4.

(11) By the film formation described above, present invention coated tools 1 to 14, in which the first Ti compound layer 2 shown in Table 6 was formed on the top of the surface of the cutting tool substrate 1 in the vicinity of the cutting edge and the first Ti compound layer 2′ shown in Table 6 was formed on the top of the surface of the cutting tool substrate 1 at the position of the flank face away from the cutting edge, were produced.

(12) In addition, by the film formation described above, as shown in Table 6, the first Ti compound layer 2 in which the nitrogen concentration was gradually increased over a range of 0.2 μm from the surface of the cutting tool substrate 1 in the vicinity of the cutting edge in a direction perpendicular thereto toward the inside of the first Ti compound layer 2 and the average concentration gradient of the nitrogen concentration was 20 at %/μm or more and 300 at %/μm or less was formed, and furthermore, the first Ti compound layer 2 in which the average nitrogen concentration in the first Ti compound layer 2 was lower than the average nitrogen concentration of the first Ti compound layer 2′ by 3 at % or more was formed.

(13) In addition, for the purpose of comparison, under the conditions indicated as forming symbols G and H in Table 3, the first Ti compound layer 2 and the first Ti compound layer 2′ were deposited on the surfaces of the cutting tool bodies A to C, and furthermore, similarly, under the conditions shown in Table 4, the second Ti compound layer 3, and the Al.sub.2O.sub.3 layer 4 having an α-form or κ-form crystal structure shown in Table 5, and furthermore, for some of the cutting tool bodies, the TiN layer as the outermost layer for cutting edge identification, were formed, whereby comparative example coated tools 1 to 14 shown in Table 7 were produced.

(14) In the vicinity of the interface between the surfaces of the cutting tool bodies 1 of the present invention coated tool 1 to 14 and the comparative example coated tool 1 to 14, the first Ti compound layer 2, and the first Ti compound layer 2′, the nitrogen concentration (at %) at various positions in the first Ti compound layer 2 in the vicinity of the cutting edge and in the first Ti compound layer 2′ at the position of the flank face away from the cutting edge were measured by Auger electron spectroscopy.

(15) More specifically, first, in the vicinity of the cutting edge, angular lapping was performed on a surface inclined by 15° with respect to the thickness direction, and CP polishing was performed.

(16) Next, line analysis was performed in a region in the vicinity of the interface sandwiching the interface between the surface of the cutting tool substrate 1 and the first Ti compound layer 2, and each of the nitrogen concentration at a position corresponding to 0.04 μm toward the inside of the first Ti compound layer 2 from the interface between the surface of the cutting tool substrate 1 and the first Ti compound layer 2 (This position is referred to as “position A”. The position A is a “position of 0.04 μm from the interface between the surface of the cutting tool substrate 1 and the first Ti compound layer 2 toward the inside of the first Ti compound layer 2 in a case where polishing was performed on a surface parallel to the thickness direction”. Therefore, in a case of analysis by lapping of the surface inclined by 15° with respect to the thickness direction, owing to 0.04/sin(15°)=0.15, a position of 0.15 μm from the interface between the surface of the cutting tool substrate 1 and the first Ti compound layer 2 toward the inside of the first Ti compound layer 2 is the position A.), the nitrogen concentration at a position corresponding to 0.12 μm from the interface toward the inside of the first Ti compound layer 2 (referred to as “position B”), and the nitrogen concentration at a position corresponding to 0.20 μm from the interface toward the inside of the first Ti compound layer 2 (referred to as “position C”) was measured.

(17) In addition, the line analysis described above was performed on five different regions in the vicinity of the interface, the nitrogen concentrations measured at each position were averaged, and this value was obtained as the “nitrogen concentration (at %)” at each position of the first Ti compound layer 2.

(18) The nitrogen concentrations (at %) at various positions in the first Ti compound layer 2′ at the position of the flank face away from the cutting edge were measured in the same method as described above, the nitrogen concentrations measured at each position of the flank face away from the cutting edge were averaged, and this value was obtained as the “nitrogen concentration (at %)” at each position of the first Ti compound layer 2′.

(19) It is presumed that there may be a case where the amount of nitrogen at the position A is not 50 at % as in “the position of the flank face away from the cutting edge” of the present invention example coated tool 1 although TiN is formed because carbon was slightly diffused from the tool substrate.

(20) Furthermore, from the “nitrogen concentrations (at %)” of the first Ti compound layer 2 and the first Ti compound layer 2′ obtained as described above, the average concentration gradient of the nitrogen concentration between the position A and the position B of the first Ti compound layer 2 and the first Ti compound layer 2′ was calculated as average concentration gradient BA (at %/μm)=(nitrogen concentration at position B−nitrogen concentration at position A)/(0.12−0.04), and the average concentration gradient of the nitrogen concentration between the position B and the position C was calculated as average concentration gradient CB (at %/μm)=(nitrogen concentration at position C−nitrogen concentration at position B)/(0.20−0.12).

(21) Table 6 shows the “nitrogen concentration (at %)”, the average concentration gradient BA (at %/μm), and the average concentration gradient CB (at %/μm) obtained as above.

(22) Here, “both the average concentration gradient BA (at %/μm) and the average concentration gradient CB (at %/μm) are 20 at %/μm or more and 300 at %/μm or less” means that “in a case where the nitrogen concentration from the surface of the cutting tool substrate 1 in the direction perpendicular thereto in the vicinity of the cutting edge is measured, within a range of 0.20 μm from the surface of the cutting tool substrate 1 toward the first Ti compound layer 2 side, the nitrogen concentration in the first Ti compound layer 2 gradually increases as the distance from the cutting tool substrate 1 increases, and the average concentration gradient of the nitrogen concentration is 20 at %/μm or more and 300 at %/μm or less”.

(23) As for a method of forming the first Ti compound layer 2 and the first Ti compound layer 2′, in addition to a method of gradually changing the gas concentration and the film forming atmosphere pressure, gas conditions may be changed in stages.

(24) Even in this case, when the condition that “both the average concentration gradient BA (at %/μm) and the average concentration gradient CB (at %/μm) are 20 at %/μm or more and 300 at %/μm or less” is satisfied, the first Ti compound layer 2 and the first Ti compound layer 2′ excellent in adhesion and peeling resistance can be obtained.

(25) In addition, in the first Ti compound layer 2 in the vicinity of the cutting edge and the first Ti compound layer 2′ at the position of the flank face away from the cutting edge, the average nitrogen concentration of the entire layer was obtained by the following method, and the difference between the average nitrogen concentration of the first Ti compound layer 2 and the average nitrogen concentration of the first Ti compound layer 2′ at the position of the flank face away from the cutting edge was calculated.

(26) That is, the measurement method and definition of the average nitrogen concentration of the layer mentioned in the present invention are as follows.

(27) Through a line scan of Auger electron spectroscopy, by performing a line scan vertically on the cutting tool substrate and TiCN interface with a line width of 10 μm, each of the nitrogen concentration (Ca) at a position (position A) corresponding to 0.04 μm from the interface between the surface of the cutting tool substrate 1 and the first Ti compound layer 2 toward the inside of the first Ti compound layer 2, the nitrogen concentration (Cb) at a position (referred to as “position B”) corresponding to 0.12 μm toward the inside of the first Ti compound layer 2, and the nitrogen concentration (Cc) at a position (referred to as “position C”) corresponding to 0.20 μm from the interface toward the inside of the first Ti compound layer 2 is measured, and the average value (Ca+Cb+Cc)/3 of the nitrogen concentrations at the three positions A, B, and C is obtained.

(28) This line scan is performed on five different cutting tool bodies and TiCN interfaces, and the average value of (Ca+Cb+Cc)/3 of the five interfaces is defined as the “average nitrogen concentration of the layer”.

(29) Table 6 and Table 7 show these values.

(30) The layer thickness of each constituent layer of the present invention coated tools 1 to 14 and the comparative example coated tools 1 to 14 produced as described above was measured using a scanning electron microscope, and the average layer thickness thereof was obtained.

(31) Table 5 to Table 7 show these values.

(32) TABLE-US-00001 TABLE 1 Mixing composition (mass %) Kind Co TiC ZrC TaC NbC Cr.sub.3C.sub.2 TiN WC Cutting tool 8 0.5 — — — 0.5 0.5 Re- substrate A mainder Cutting tool 10 — 0.5 0.5 0.5 — 0.5 Re- substrate B mainder

(33) TABLE-US-00002 TABLE 2 Mixing composition (mass %) Kind NbC TaC WC ZrC Mo.sub.2C Co Ni TiCN Cutting tool 0.5 0.5 10 0.5 2 12 3 Remainder substrate C

(34) TABLE-US-00003 TABLE 3 First Ti compound layer Forming conditions (pressure of reaction atmosphere cs expressed as kPa and temperature is expressed as ° C.) Forming Reaction atmosphere symbol Forming method Reaction gas composition (vol %) Pressure Temperature A After forming TiN, remove only TiN in the vicinity TiN TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 of a cutting edge with a brush, form low-nitrogen Low-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 20%, 6 900 TiCN, and subsequently perform film formation by TiCN H.sub.2: remainder gradually changing gas conditions and the pressure of a reaction atmosphere to high-nitrogen TiCN High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.1%, N.sub.2: 20%, 9 900 forming conditions, thereby forming a first Ti TiCN H.sub.2: remainder compound layer 2 and a first Ti compound layer 2′. High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.1%, N.sub.2: 20%, 6 900 B After forming high-nitrogen TiCN, remove only the TiCN H.sub.2: remainder high-nitrogen TiCN in vicinity of a cutting edge with Low-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, CH.sub.4: 1.0%, 6 900 a brush, form low-nitrogen TiCN, and subsequently TiCN (first H.sub.2: remainder perform film formation by changing gas conditions stage) and the pressure of a reaction atmosphere to TiN TiCN (second TiCl.sub.4: 4.2%, CH.sub.3CN: 0.6%, N.sub.2: 20%, 8 900 forming conditions in three stages, thereby forming a stage) H.sub.2: remainder first Ti compound layer 2 and a first Ti compound TiN (third TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 layer 2′. stage) C Form TiCN, and subsequently perform film TiCN TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 20%, 6 900 formation by gradually changing gas conditions and H.sub.2: remainder the pressure of a reaction atmosphere to TiN forming TiN TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 conditions. Next, after removing, with a brush, TiCN in which the N concentration in a flank face excluding the vicinity of a cutting edge was gradually changed, form TiN, thereby forming a first Ti compound layer. D Form TiN, remove only TiN in the vicinity of a TiN TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 cutting edge with a brush, form TiC, and TiC (first TiCl.sub.4: 4.2%, CH.sub.4: 8.5%, H.sub.2: remainder 7 1000 subsequently perform film formation by changing stage) gas conditions and the pressure of a reaction TiCN (second TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 20%, 6 900 atmosphere to TiN forming conditions in three stage) H.sub.2: remainder stages, thereby forming a first Ti compound layer. TiN (third TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 stage) E Form only TiN as a first Ti compound layer. TiN TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 F Form only TiC as a first Ti compound layer. TiC TiCl.sub.4: 4.2%, CH.sub.4: 8.5%, H.sub.2: remainder 7 1000 G Form low-nitrogen TiCN, and subsequently perform Low-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 20%, film formation by gradually changing gas conditions TiCN H.sub.2: remainder 6 900 and the pressure of a reaction atmosphere to high- High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.1%, N.sub.2: 20%, 9 900 nitrogen TiCN forming conditions, thereby forming TiCN H.sub.2: remainder a first Ti compound layer. H Form TiN, remove only TiN in the vicinity of a TiN TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 cutting edge with a brush, form low-nitrogen TiCN, Low-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 20%, 6 900 and subsequently perform film formation by TiCN H.sub.2: remainder gradually changing gas conditions and the pressure High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.9%, N.sub.2: 20%, 7 900 of a reaction atmosphere to high-nitrogen TiCN TiCN H.sub.2: remainder forming conditions, thereby forming a first Ti compound layer.

(35) TABLE-US-00004 TABLE 4 Forming conditions (pressure of reaction atmosphere is expressed as kPa and temperature is expressed as ° C.) Reaction atmosphere Kind Reaction gas composition (vol %) Pressure Temperature Second Ti TiC TiCl.sub.4: 4.2%, CH.sub.4: 8.5%, H.sub.2: remainder 7 1000 compound l-TiCN TiCl.sub.4: 2%, CH.sub.3CN: 0.7%, N.sub.2: 10%, H.sub.2: 7 900 layer remainder TiCN TiCl.sub.4: 2%, CH.sub.4: 1%, N.sub.2: 15%, H.sub.2: remainder 13 1000 TiN TiCl.sub.4: 4.2%, N.sub.2: 35%, H.sub.2: remainder 50 1040 TiCNO TiCl.sub.4: 2%, CO: 1%, CH.sub.4: 1%, N.sub.2: 5%, 13 1000 H.sub.2: remainder Al.sub.2O.sub.3 α-Al.sub.2O.sub.3 AlCl.sub.3: 2.2%, CO.sub.2: 6.5%, HCl: 2.2%, H.sub.2S: 7 1000 layer 0.2%, H.sub.2: remainder κ-Al.sub.2O.sub.3 AlCl.sub.3: 3.0%, CO.sub.2: 5.0%, H.sub.2S: 0.3%, 7 970 H.sub.2: remainder Outermost TiN TiCl.sub.4: 4.2%, N.sub.2: 35%, H.sub.2: remainder 50 1040 layer

(36) TABLE-US-00005 TABLE 5 Outermost Second Ti compound layer 3 Al.sub.2O.sub.3 layer 4 layer Cutting Average Average Average Average tool layer layer layer layer substrate thickness thickness thickness thickness Kind symbol Kind (μm) Kind (μm) Kind (μm) (μm) Present 1 15 A l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — invention 2 16 A l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — coated tool and 3 17 A l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — comparative 4 18 A l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — example 5 19 A l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — coated tool 6 20 A TiCN 8 — — α-Al.sub.2O.sub.3 3 0.5 7 21 A l-TiCN 8 TiCNO 1 κ-Al.sub.2O.sub.3 1 0.5 8 22 A l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — 9 23 B l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — 10 24 B TiCN 8 — — α-Al.sub.2O.sub.3 3 0.5 11 25 C l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — 12 26 C l-TiCN 4 TiCNO 1 α-Al.sub.2O.sub.3 3 — 13 27 A l-TiCN 6 TiC 1 — — — 14 28 A TiC 4 TiN 1 — — —

(37) TABLE-US-00006 TABLE 6 First Ti compound layer 2, first Ti compound layer 2′ First Ti compound layer 2 in vicinity of cutting edge Component concentration in direction perpendicular to surface of cutting tool substrate Cutting Nitrogen Average Average Average tool concentration (at %) concentration concentration nitrogen substrate Forming Position Position Position gradient BA gradient CB concentration Kind symbol symbol A B C (at %/μm) (at %/μm) (at %) Present 1 A A 28 34 39 75 63 34 invention 2 A B 21 32 43 138 138 32 coated 3 A C 26 34 42 100 100 34 tool 4 A C 26 29 31 38 25 29 5 A C 24 36 48 150 150 36 6 A C 26 34 42 100 100 34 7 A C 26 34 42 100 100 34 8 A D 1 22 44 263 275 22 9 B A 27 34 39 88 63 33 10 B C 25 33 42 100 113 33 11 C A 28 34 39 75 63 34 12 C C 26 34 42 100 100 34 13 A C 26 34 42 100 100 34 14 A C 26 34 42 100 100 34 First Ti compound layer 2, first Ti compound layer 2′ First Ti Difference in compound First Ti compound layer 2′ at position of average nitrogen layer 2 in flank face away from cutting edge concentration vicinity of Direction perpendicular to surface between first cutting edge of cutting tool substrate Ti compound Cutting Average Nitrogen Average Average layer 2 and tool layer concentration (at %) nitrogen layer first Ti substrate thickness Position Position Position concentration thickness compound layer Kind symbol (μm) A B C (at %) (μm) 2′ (at %) Present 1 A 0.3 49 50 28 42 0.45 8 invention 2 A 0.3 38 38 37 38 0.5 6 coated 3 A 0.6 49 50 50 50 0.3 16 tool 4 A 1.3 49 50 50 50 0.3 21 5 A 0.48 49 50 50 50 0.25 14 6 A 0.6 49 50 50 50 0.3 16 7 A 0.6 49 50 50 50 0.3 16 8 A 0.3 49 50 5 35 0.45 13 9 B 0.3 47 49 27 41 0.45 8 10 B 0.6 48 49 50 49 0.3 16 11 C 0.3 50 50 28 43 0.45 9 12 C 0.6 50 50 50 50 0.3 16 13 A 0.6 50 50 50 50 0.3 16 14 A 0.6 50 50 50 50 0.3 16

(38) TABLE-US-00007 TABLE 7 First Ti compound layer 2 Direction perpendicular to surface of cutting tool substrate in vicinity of cutting edge Cutting Nitrogen Average Average Average tool concentration (at %) concentration concentration nitrogen substrate Forming Position Position Position gradient BA gradient CB concentration Kind symbol symbol A B C (at %/μm) (at %/μm) (at %) Comparative 1 A D 0 24 49 300 313 24 example 2 A E 49 50 50 13 0 50 coated tool 3 A F 0 0 0 0 0 0 4 A G 28 34 39 75 63 34 5 A H 25 26 27 13 13 26 6 A G 28 34 39 75 63 34 7 A G 28 34 39 75 63 34 8 A B 21 32 43 150 138 32 9 B D 0 24 49 300 313 24 10 B G 28 34 39 75 63 34 11 C D 0 24 49 300 313 24 12 C G 28 34 39 75 63 34 13 A G 28 34 39 75 63 34 14 A G 28 34 39 75 63 34 Difference in First Ti compound layer 2′ average nitrogen First Ti Direction perpendicular to surface of cutting concentration compound tool substrate at position of flank face away between first layer 2 from cutting edge Ti compound Average Nitrogen Average Average layer 2 and layer concentration (at %) nitrogen layer first Ti thickness Position Position Position concentration thickness compound layer Kind (μm) A B C (at %) (μm) 2′ (at %) Comparative 1 0.23 49 50 3 34 0.37 10 example 2 0.3 49 50 50 50 0.45 0 coated tool 3 0.3 0 0 0 0 0.45 0 4 0.3 29 34 39 34 0.3 0 5 0.5 49 50 25 41 0.65 15 6 0.3 29 34 39 34 0.3 0 7 0.3 29 34 39 34 0.3 0 8 0.3 38 38 26 34 0.4 2 9 0.23 49 50 3 34 0.37 10 10 0.29 29 34 39 34 0.29 0 11 0.23 49 50 3 34 0.37 10 12 0.29 30 34 39 34 0.29 0 13 0.3 29 34 39 34 0.3 0 14 0.3 29 34 39 34 0.3 0

(39) Next, in a state in which each of the present invention coated tools 1 to 14 and the comparative example coated tools 1 to 14 was screwed to a tip end portion of an insert holder made of tool steel by a fixing tool, under conditions including

(40) Work material: a round bar with one longitudinal groove formed in the longitudinal direction of JIS SUS329,

(41) Cutting speed: 130 m/min,

(42) Depth of cut: 2.0 mm,

(43) Feed: 0.40 mm/rev,

(44) Cutting time: 1.0 minute, and

(45) Cutting oil: water-soluble coolant,

(46) a wet intermittent cutting work test of duplex stainless steel was conducted, and

(47) the flank face wear width (mm) was measured and visually observed to check the damage state in the vicinity of the cutting edge and the damage state at the position of the flank face away from the cutting edge.

(48) Table 8 shows the results.

(49) TABLE-US-00008 TABLE 8 Flank Flank face wear Visual face wear Visual width observation width observation Kind (mm) results Kind (mm) results Present 1 0.14 Peeling and Comparative 1 0.55 Adhesion- invention adhesion- example induced coated induced coated tool chipping tool chipping absent present 2 0.16 Peeling and 2 0.39 Peeling present adhesion- induced chipping absent 3 0.13 Peeling and 3 0.42 Small peeling adhesion- present induced chipping absent 4 0.13 Peeling and 4 0.35 Peeling present adhesion- induced chipping absent 5 0.15 Peeling and 5 0.41 Peeling and adhesion- adhesion- induced induced chipping absent chipping absent 6 0.17 Peeling and 6 0.43 Peeling present adhesion- induced chipping absent 7 0.14 Peeling and 7 — Fractured after adhesion- processing for induced 50 seconds chipping absent 8 0.16 Peeling and 8 — Fractured after adhesion- processing for induced 55 seconds chipping absent 9 0.13 Peeling and 9 0.46 Adhesion- adhesion- induced induced chipping chipping absent present 10 0.13 Peeling and 10 0.5  Peeling present adhesion- induced chipping absent 11 0.15 Peeling and 11 0.42 Small peeling adhesion- present induced chipping absent 12 0.14 Peeling and 12 — Fractured after adhesion- processing for induced 40 seconds chipping absent 13 0.28 Peeling and 13 — Fractured after adhesion- processing for induced 55 seconds chipping absent 14 0.27 Peeling and 14 — Fractured after adhesion- processing for induced 40 seconds chipping absent

(50) From the results shown in Table 8, in the present invention coated tools 1 to 14, the first Ti compound layer 2 containing at least nitrogen and carbon is formed to cover the vicinity of the cutting edge on the top of the surface of the cutting tool substrate, a nitrogen concentration distribution in which the nitrogen concentration gradually increases over a range of 0.2 μm from the surface of the cutting tool substrate in a direction perpendicular thereto toward the inside of the layer is formed, and the average nitrogen concentration in the first Ti compound layer 2 formed on the top of the surface of the cutting tool substrate in the vicinity of the cutting edge is lower than the average nitrogen concentration of the first Ti compound layer 2′ formed on the top of the surface of the cutting tool substrate at the position of the flank face away from the cutting edge by 3 at % or more, whereby the occurrence of peeling due to thermal stress in the vicinity of the cutting edge and the occurrence of peeling caused by the deformation of the cutting tool substrate can be suppressed, and furthermore, the occurrence of peeling caused by the deformation of the cutting tool substrate at the position of the flank face away from the cutting edge can be suppressed.

(51) Contrary to this, in the comparative example coated tools, it is obvious that since the first Ti compound layer 2 and the first Ti compound layer 2′ having the layer structure specified in the present invention are not formed, the tool life is short due to the occurrence of peeling caused by thermal stress or deformation of the cutting tool substrate and the cutting performance is inferior to that of the present invention coated tools.

Example 2

(52) Next, the first Ti compound layer 2 illustrated in FIG. 1 and the first Ti compound layer 2″ illustrated in FIG. 2(b) were deposited on the surfaces of the cutting tool bodies A to C using a typical chemical vapor deposition apparatus under the conditions indicated as forming symbols J to M in Table 9.

(53) For example, forming conditions by forming symbol J are as follows.

(54) (a) First, a small amount of TiCN having a high nitrogen concentration was deposited on the surface of the cutting tool substrate 1 including the vicinity of the cutting edge and the position of the flank face away from the cutting edge under conditions J shown in Table 9.

(55) (b) Next, only the small amount of TiCN having a high nitrogen concentration, which was deposited in the vicinity of the cutting edge of the cutting tool substrate 1 was removed with a brush.

(56) (c) Next, a TiCN layer having a low nitrogen concentration was deposited under conditions J shown in Table 9 on the surface of the cutting tool substrate 1 including the vicinity of the cutting edge, from which the TiCN having a high nitrogen concentration was removed with a brush, and the position of the flank face away from the cutting edge, and deposition was continued while adjusting gas conditions and the pressure of the reaction atmosphere to gradually increase the N concentration such that the TiCN layer (or TiN layer) having a high nitrogen concentration is finally deposited,

(57) the first Ti compound layer 2 shown in Table 10 was formed in the vicinity of the cutting edge, and the first Ti compound layer 2″ shown in Table 10 was formed at the position of the flank face away from the cutting edge.

(58) (d) Next, for some of the cutting tool bodies, on the surfaces of the first Ti compound layer 2 and the first Ti compound layer 2″, the second Ti compound layer 3, and the Al.sub.2O.sub.3 layer 4 or a TiN layer as the outermost layer for cutting edge identification, shown in Table 5 were formed under the conditions shown in Table 4.

(59) By the film formation described above, present invention coated tools 15 to 28 in which the first Ti compound layer 2 shown in Table 10 was formed on the top of the surface of the cutting tool substrate 1 in the vicinity of the cutting edge and the first Ti compound layer 2″ shown in Table 10 was formed on the top of the surface of the cutting tool substrate 1 at the position of the flank face away from the cutting edge were produced.

(60) In addition, by the film formation described above, as shown in Table 10, the first Ti compound layer 2 in which the nitrogen concentration was gradually increased over a range of 0.2 μm from the surface of the cutting tool substrate 1 in the vicinity of the cutting edge in a direction perpendicular thereto toward the inside of the first Ti compound layer 2 and the average concentration gradient of the nitrogen concentration was 20 at %/μm or more and 300 at %/μm or less was formed, and furthermore, the first Ti compound layer 2 in which the average nitrogen concentration in the first Ti compound layer 2 was lower than the average nitrogen concentration of the first Ti compound layer 2″ by 3 at % or more was formed.

(61) Furthermore, by the film formation described above, in the first Ti compound layer 2″ formed on the top of the surface of the cutting tool substrate 1 at the position of the flank face away from the cutting edge, as shown in Table 10, a low nitrogen region and a high nitrogen region were formed in a direction parallel to the surface of the cutting tool substrate 1.

(62) In the first Ti compound layer 2 formed on the top of the surface of the cutting tool substrate 1 in the vicinity of the cutting edge and the first Ti compound layer 2″ formed on the top of the surface of the cutting tool substrate 1 at the position away from the cutting edge in the present invention coated tools 15 to 28, in the same manner as in Example 1, the nitrogen concentration (at %) from the surface of the cutting tool substrate 1 in the direction perpendicular thereto was measured by Auger electron spectroscopy, and was obtained as the “nitrogen concentration (at %)” at each position of the first Ti compound layer 2 or the first Ti compound layer 2″.

(63) In addition, in the first Ti compound layer 2, the average concentration gradient BA (at %/μm) and the average concentration gradient CB (at %/μm) were calculated.

(64) Furthermore, in the first Ti compound layer 2 in the vicinity of the cutting edge and the first Ti compound layer 2″ at the position of the flank face away from the cutting edge, the average nitrogen concentration of the entire layer was obtained, and the difference between the average nitrogen concentration of the first Ti compound layer 2 and the average nitrogen concentration of the first Ti compound layer 2″ at the position of the flank face away from the cutting edge was calculated.

(65) Table 10 shows the results.

(66) By performing a line analysis on the first Ti compound layer 2″ formed on the top of the surface of the cutting tool substrate 1 at the position away from the cutting edge in the present invention coated tools 15 to 28, at a distance of 0.04 μm from the surface of the cutting tool substrate 1 along the direction parallel to the surface of the cutting tool substrate 1, by Auger electron spectroscopy, the nitrogen concentration (at %) and the carbon concentration (at %) were measured.

(67) Next, five low nitrogen regions were specified from the local minimum of the measured nitrogen concentration and the local maximum of the carbon concentration, and five high nitrogen regions were specified from the local maximum of the nitrogen concentration and the local minimum of the carbon concentration.

(68) Next, the values measured in the low nitrogen region and the high nitrogen region were averaged, and these values were obtained as the nitrogen concentration (at %) and the carbon concentration (at %) in each region of the low nitrogen region and the high nitrogen region.

(69) Table 10 shows the results.

(70) The layer thickness of each constituent layer of the present invention coated tools 15 to 28 was measured using the scanning electron microscope, and the average layer thickness thereof was obtained.

(71) Table 5 and Table 10 show these values.

(72) TABLE-US-00009 TABLE 9 First Ti compound layer Forming conditions (pressure of reaction atmosphere is expressed as kPa and temperature is expressed as ° C.) Forming Reaction atmosphere symbol Forming method Reaction gas composition (vol %) Pressure Temperature J After depositing a small amount of high-nitrogen TiCN, High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.1%, N.sub.2: 20%, 9 900 remove only the high-nitrogen TiCN in the vicinity of a TiCN H.sub.2: remainder cutting edge with a brush, form a low-nitrogen TiCN Low-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 10%, 6 900 layer, and subsequently form a first Ti compound layer 2 TiCN H.sub.2: remainder and a first Ti compound layer 2″ by gradually changing High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.1%, N.sub.2: 20%, 9 900 gas conditions and the pressure of a reaction atmosphere TiCN H.sub.2: remainder to high-nitrogen TiCN layer forming conditions. K After depositing a small amount of TiN, remove only the TiN (small TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 TiN in the vicinity of a cutting edge with a brush, form amount) low-nitrogen TiCN, and subsequently form a Low-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 20%, 6 900 first Ti compound layer 2 and a first Ti compound layer TiCN H.sub.2: remainder 2′ by gradually changing gas conditions and the pressure High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.1%, N.sub.2: 20%, 9 900 of a reaction atmosphere to high-nitrogen TiCN forming TiCN H.sub.2: remainder conditions. L After depositing a small amount of high-nitrogen TiCN, High-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 0.1%, N.sub.2: 20%, 6 900 remove only the high-nitrogen TiCN in the vicinity of a TiCN (small H.sub.2: remainder cutting edge with a brush, form low-nitrogen TiCN, and amount) subsequently form a first Ti compound layer 2 and a first Low-nitrogen TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, CH.sub.4: 6 900 Ti compound layer 2′ by changing gas conditions and the TiCN (first 1.0%, H.sub.2: remainder pressure of a reaction atmosphere to TiN layer forming stage) conditions in three stages. TiCN (second TiCl.sub.4: 4.2%, CH.sub.3CN: 0.6%, N.sub.2: 20%, 8 900 stage) H.sub.2: remainder TiN (third TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 stage) M After depositing a small amount of TiN, remove only the TiN (small TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 TiN in the vicinity of a cutting edge with a brush, form amount) TiC, and subsequently form a first Ti compound layer' by TiC (first TiCl.sub.4: 4.2%, CH.sub.4: 8.5%, H.sub.2: 7 1000 changing gas conditions and the pressure of a reaction stage) remainder atmosphere to TiN forming conditions in three stages. TiCN (second TiCl.sub.4: 4.2%, CH.sub.3CN: 1.0%, N.sub.2: 20%, 6 900 stage) H.sub.2: remainder TiN (third TiCl.sub.4: 4.2%, N.sub.2: 20%, H.sub.2: remainder 10 900 stage)

(73) TABLE-US-00010 TABLE 10 First Ti compound layer 2, first Ti compound layer 2′ First Ti compound layer 2″ at First Ti compound layer 2 in vicinity of cutting edge position of flank face away Component concentration in direction from cutting edge perpendicular to surface of cutting Component concentration tool substrate in direction perpendicular Average Average to surface of cutting concen- concen- tool substrate Nitrogen tration tration Average Average Nitrogen Cutting concentration (at %) gradient gradient nitrogen layer concentration (at %) tool sub- Posi- Posi- Posi- BA CB concen- thick- Posi- Posi- Posi- strate Forming tion tion tion (at %/ (at %/ tration ness tion tion tion Kind symbol symbol A B C μm) μm) (at %) (mm) A B C Present 15 A J 28 34 39 75 63 34 0.3 29 34 39 invention 16 A K 28 34 39 75 63 34 0.3 28 34 39 coated 17 A L 20 32 43 150 138 32 0.3 20 32 43 tool 18 A L 20 32 43 150 138 32 1 21 32 43 19 A L 20 32 43 150 138 32 0.23 20 32 43 20 A L 20 32 43 150 138 32 0.3 21 32 43 21 A L 20 32 43 150 138 32 0.3 20 32 43 22 A M 1 22 44 263 275 22 0.3 1 22 44 23 B J 27 34 39 88 63 33 0.3 27 34 39 24 B L 25 33 42 100 113 33 0.3 25 33 42 25 C J 26 34 39 100 63 33 0.3 28 34 39 26 C L 26 34 42 100 100 34 0.3 26 34 42 27 A L 26 34 42 100 100 34 0.3 27 34 42 28 A L 26 34 42 100 100 34 0.3 26 34 42 First Ti compound layer 2, first Ti compound layer 2′ First Ti compound layer 2″ at position of flank face away from cutting edge Component concentration in direction Difference in perpendicular to surface of cutting average nitrogen tool substrate concentration High nitrogen Low nitrogen between first region region Average Average Ti compound Nitrogen Nitrogen Nitrogen Nitrogen nitrogen layer layer 2 and concen- concen- concen- concen- concen- thick- first Ti tration tration tration tration tration ness compound layer Kind (at %) (at %) (at %) (at %) (at %) (μm) 2″ (at %) Present 15 39 12 29 21 38 0.35 4 invention 16 50 0 28 22 40 0.35 6 coated 17 38 12 20 30 36 0.35 4 tool 18 37 13 21 29 36 1.05 4 19 38 12 20 30 36 0.28 4 20 39 11 21 29 37 0.35 5 21 38 12 20 30 36 0.35 4 22 50 0 1 49 35 0.35 13 23 36 14 27 23 37 0.35 4 24 37 13 25 25 37 0.35 4 25 38 12 28 22 37 0.35 4 26 38 12 26 24 38 0.35 4 27 38 12 27 23 38 0.35 4 28 38 12 26 24 38 0.35 4

(74) Next, in a state in which each of the present invention coated tools 15 to 28 was screwed to a tip end portion of an insert holder made of tool steel by a fixing tool, under the same cutting conditions as those of Example 1, a wet intermittent cutting work test of duplex stainless steel was conducted, and the flank face wear width (mm) was measured and visually observed to check the damage state in the vicinity of the cutting edge and the damage state at the position of the flank face away from the cutting edge.

(75) Table 11 shows the results.

(76) TABLE-US-00011 TABLE 11 Flank face wear Kind width (mm) Visual observation results Present 15 0.08 Peeling and adhesion-induced invention chipping absent coated tool 16 0.07 Peeling and adhesion-induced chipping absent 17 0.08 Peeling and adhesion-induced chipping absent 18 0.08 Peeling and adhesion-induced chipping absent 19 0.09 Peeling and adhesion-induced chipping absent 20 0.1 Peeling and adhesion-induced chipping absent 21 0.08 Peeling and adhesion-induced chipping absent 22 0.07 Peeling and adhesion-induced chipping absent 23 0.1 Peeling and adhesion-induced chipping absent 24 0.08 Peeling and adhesion-induced chipping absent 25 0.09 Peeling and adhesion-induced chipping absent 26 0.1 Peeling and adhesion-induced chipping absent 27 0.18 Peeling and adhesion-induced chipping absent 28 0.17 Peeling and adhesion-induced chipping absent

(77) From the results shown in Table 11, in the present invention coated tools 15 to 28, in addition to the effects by the first Ti compound layer 2, since the first Ti compound layer 2″ is formed at the position of the flank face away from the cutting edge, the occurrence of adhesion-induced chipping and peeling is further prevented.

(78) As is apparent from the cutting test results shown in Table 8 and Table 11, the present invention coated tools 1 to 14 and 15 to 28 do not cause the occurrence of adhesion-induced chipping and peeling during intermittent cutting work on a difficult-to-cut material such as duplex stainless steel and exhibit excellent wear resistance for a long-term usage, thereby achieving an increase in the service life of the coated tool.

INDUSTRIAL APPLICABILITY

(79) As described above, the coated tool of the present invention exhibits not only excellent cutting performance during intermittent cutting work on duplex stainless steel but also excellent cutting performance for a long-term usage without causing the occurrence of adhesion-induced chipping, peeling, and the like during intermittent cutting work during which a high load is exerted on the edge tip of various difficult-to-cut materials, thereby achieving an increase in the service life.

REFERENCE SIGNS LIST

(80) 1: cutting tool substrate 2: first Ti compound layer (first layer) 2′: first Ti compound layer (first layer) 2″: first Ti compound layer (first layer) 3: second Ti compound layer (second layer) 4: Al.sub.2O.sub.3 layer 5: TiC region or TiCN region having low nitrogen concentration 6: TiN region or TiCN region having high nitrogen concentration 7: low nitrogen region (TiC or TiCN region having low nitrogen concentration formed in direction parallel to surface of cutting tool substrate) 8: high nitrogen region (TiN or TiCN region having high nitrogen concentration formed in direction parallel to surface of cutting tool substrate) L: direction parallel to surface of cutting tool substrate for measuring high nitrogen region and low nitrogen region