Coated cutting tool

1. A coated cutting tool comprising:

a substrate; and

a coating, wherein the coating has an inner layer of 4-14 μm thick Ti 1-x Al x N, an intermediate layer of 0.05-1 μm TiCN and at least one outer layer of 1-9 μm α-Al 2 O 3 , wherein the TiCN layer is in epitaxial relation to the Ti 1-x Al x N layer, and wherein said α-Al 2 O 3 layer exhibits an X-ray diffraction pattern, as measured using CuKα radiation and theta-2theta scan, and a texture coefficient TC(hkl) being defined according to Harris formula

TC

⁢

⁢

(

hkl

)

=

I

⁢

⁢

(

hkl

)

I

⁢

⁢

0

⁢

⁢

(

hkl

)

⁡

[

1

n

⁢

∑

i

=

0

n

⁢

I

⁢

⁢

(

hkl

)

I

⁢

⁢

0

⁢

⁢

(

hkl

)

]

-

1

wherein the (hkl) reflections used are (0 2 4), (1 1 6), (3 0 0) and (0 0 12),

I(hkl)=measured intensity (peak intensity) of the (hkl) reflection,

10(hkl)=standard intensity according to ICDD's PDF-card No. 00-042-1468,

n=number of reflections used in the calculation,

wherein 3<TC(0 0 12)<4.

2. The tool according to claim 1 , wherein the thickness of the intermediate layer of TiCN is 0.05-0.3 μm.

3. The tool according to claim 1 , wherein the TC( 111 ) of the intermediate layer of TiCN is >3, and wherein the texture coefficient TC ( 111 ) is defined as:

TC

⁢

⁢

(

111

)

=

I

⁡

(

111

)

I

0

⁡

(

111

)

⁡

[

1

n

⁢

∑

n

=

1

n

⁢

I

⁢

⁢

(

hkl

)

I

0

⁢

⁢

(

hkl

)

]

-

1

wherein

I(hkl) are the intensities of the diffraction reflections measured by X-ray diffraction,

I 0 (hkl) are the standard intensities of the diffraction reflections according to the pdf card 00-042-1489

n is the number of reflections used in the calculation, and

for the calculation of TC( 111 ) the reflections ( 111 ), ( 200 ), ( 220 ) and ( 311 ) are used.

4. The tool according to claim 1 , wherein the Σ3 grain boundary length to the total grain boundary length in the α-Al 2 O 3 layer is >30%.

5. The tool according to claim 1 , wherein the Ti 1-x Al x N layer has at least 90 vol-% face-centered cubic (fcc) crystal structure.

6. The tool according to claim 1 , wherein the Ti 1-x Al x N layer has a columnar microstructure.

7. The tool according to claim 1 , wherein precipitations of Ti 1-y Al y N are present at grain boundaries of the Ti 1-x Al x N crystallites, said precipitations having a higher Al content than inside crystallites and comprise AN with hexagonal crystal structure (hcp) wherein y>x.

8. The tool according to claim 1 , wherein the Ti 1-x Al x N layer has stoichiometric coefficients of 0.60≤x≤0.90.

9. The tool according to claim 1 , wherein the Ti 1-x Al x N layer has a orientation of the crystal growth with respect to a crystallographic { 111 } plane, characterized by a texture coefficient TC ( 111 ) >3, wherein the texture coefficient TC ( 111 ) is defined as follows:

TC

⁢

⁢

(

111

)

=

I

⁡

(

111

)

I

0

⁡

(

111

)

⁡

[

1

n

⁢

∑

n

=

1

n

⁢

I

⁢

⁢

(

hkl

)

I

0

⁢

⁢

(

hkl

)

]

-

1

wherein

I(hkl) are the intensities of the diffraction reflections measured by X-ray diffraction,

I 0 (hkl) are the standard intensities of the diffraction reflections according to the pdf card 00-046-1200,

n is the number of reflections used in the calculation, and

for the calculation of TC( 111 ) the reflections ( 111 ), ( 200 ), ( 220 ) and ( 311 ) are used.

10. The tool according to claim 1 , wherein the thickness of the TiCN layer is 0.1-0.3 μm.

11. The tool according to claim 1 , wherein an average aspect ratio of the TiCN grains of the TiCN layer is ≤1.

12. The tool according to claim 1 , wherein a coating thickness relation of the Ti 1-x Al x N layer, t(Ti 1-x Al x N), in relation to the thickness of the α-Al 2 O 3 layer, t(α), is t(Ti 1-x Al x N):t(α) from 2:1 to 3:1.

13. The tool according to claim 1 , wherein the coating includes an innermost layer of TiN, a thickness of the innermost layer of TiN being 0.1-2 μm.

14. The tool according to claim 1 , wherein the substrate is cemented carbide.