Coated cutting tool

1. A coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, wherein:

the coating layer comprises at least one α-type aluminum oxide layer, a TiCN layer having an average thickness of from 10 μm or more to 20 μm or less, and an intermediate layer comprised of TiCNO; and

in the α-type aluminum oxide layer, a texture coefficient TC (0,0,12) of a (0,0,12) plane represented by formula (1) below is from 4.0 or more to 8.4 or less, and a texture coefficient TC (0,1,8) of a (0,1,8) plane represented by formula (2) below is from 0.5 or more to 3.0 or less.

TC

⁡

(

0

,

0

,

12

)

=

I

⁡

(

0

,

0

,

12

)

I

0

⁡

(

0

,

0

,

12

)

⁢

{

1

9

⁢

∑

I

⁡

(

h

,

k

,

l

)

I

0

⁡

(

h

,

k

,

l

)

}

-

1

(

1

)

TC

⁡

(

0

,

1

,

8

)

=

I

⁡

(

0

,

1

,

8

)

I

0

⁡

(

0

,

1

,

8

)

⁢

{

1

9

⁢

∑

I

⁡

(

h

,

k

,

l

)

I

0

⁡

(

h

,

k

,

l

)

}

-

1

(

2

)

(In formulae (1) and (2), I (h,k,l) denotes a peak intensity for an (h,k,l) plane in X-ray diffraction of the α-type aluminum oxide layer, I 0 (h,k,l) denotes a standard diffraction intensity for an (h,k,l) plane which is indicated on JCPDS Card No. 10-0173 for α-type aluminum oxide, and (h,k,l) refers to the nine crystal planes of (0,1,2), (1,0,4), (1,1,0), (1,1,3), (1,1,6), (0,1,8), (2,1,4), (3,0,0) and (0,0,12)).

2. The coated cutting tool according to claim 1 , wherein, in the α-type aluminum oxide layer, the texture coefficient TC (0,0,12) is from 5.0 or more to 8.2 or less.

3. The coated cutting tool according to claim 1 , wherein, in the α-type aluminum oxide layer, the texture coefficient TC (0,1,8) is from 1.0 or more to 2.5 or less.

4. The coated cutting tool according to claim 1 , wherein a residual stress value in a (1,1,6) plane of the α-type aluminum oxide layer is, in at least part thereof, from −300 MPa or higher to 300 MPa or lower.

5. The coated cutting tool according to claim 1 , wherein an average thickness of the α-type aluminum oxide layer is from 1.0 μm or more to 15.0 μm or less.

6. The coated cutting tool according to claim 1 , wherein an average thickness of the coating layer is from 3.0 μm or more to 30.0 μm or less.

7. The coated cutting tool according to claim 1 , wherein the substrate is a cermet or a ceramic body.

8. The coated cutting tool according to claim 2 , wherein, in the α-type aluminum oxide layer, the texture coefficient TC (0,1,8) is from 1.0 or more to 2.5 or less.

9. The coated cutting tool according to claim 2 , wherein an average thickness of the α-type aluminum oxide layer is from 1.0 μm or more to 15.0 μm or less.

10. The coated cutting tool according to claim 3 , wherein an average thickness of the α-type aluminum oxide layer is from 1.0 μm or more to 15.0 μm or less.

11. The coated cutting tool according to claim 2 , wherein the coating layer comprises, between the substrate and the α-type aluminum oxide layer, a Ti compound layer containing TiN.

12. The coated cutting tool according to claim 3 , wherein the coating layer comprises, between the substrate and the α-type aluminum oxide layer, a Ti compound layer containing TiN.

13. The coated cutting tool according to claim 5 , wherein the coating layer comprises, between the substrate and the α-type aluminum oxide layer, a Ti compound layer containing TiN.

14. The coated cutting tool according to claim 2 , wherein an average thickness of the coating layer is from 3.0 μm or more to 30.0 μm or less.

15. The coated cutting tool according to claim 3 , wherein an average thickness of the coating layer is from 3.0 μm or more to 30.0 μm or less.

16. The coated cutting tool according to claim 5 , wherein an average thickness of the coating layer is from 3.0 μm or more to 30.0 μm or less.

17. The coated cutting tool according to claim 4 , wherein an average thickness of the coating layer is from 3.0 μm or more to 30.0 μm or less.