Coated cutting tool

1. A coated cutting tool comprising a substrate coated with a multi-layered wear resistant coating including a layer of α-Al 2 O 3 and a MTCVD layer of titanium carbonitride Ti x C y N 1-y , with 0.85≤x≤1.3—and 0.4≤y≤0.85, deposited on the α-Al 2 O 3 layer, wherein the MTCVD Ti x C y N 1-y layer exhibits a mean hardness of 25-37 GPa, and wherein the Ti x C y N 1-y exhibits a texture coefficient TC(hkl), as measured by X-ray diffraction using CuKα radiation and θ-2θ scan, the TC(hkl) being defined according to Harris formula:

TC

⁡

(

hkl

)

=

I

⁡

(

hkl

)

I

0

⁡

(

hkl

)

⁡

[

1

n

⁢

∑

n

=

1

n

⁢

I

⁡

(

hkl

)

I

0

⁡

(

hkl

)

]

-

1

,

wherein

I(hkl) is the measured intensity (integrated area) of the (hkl) reflection;

I 0 (hkl) is standard intensity of the standard powder diffraction data according to JCPDS card no. 42-1489;

n is the number of reflections used in the calculation, and where the (hkl) reflections used are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0) and (4 2 2);

TC(1 1 1)≥3; and

wherein the α-Al 2 O 3 layer exhibits a texture coefficient TC(hkl), as measured by X-ray diffraction using CuKα radiation an θ-2θ scan, defined according to Harris formula, wherein I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, I 0 (hkl) is standard intensity of the standard powder diffraction data according to JCPDS card no. 00-010-0173, n is the number of reflections used in the calculation, and where the (hkl) reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0) and (0 0 12) and TC(0 0 12)≥7.

2. The coated cutting tool according to claim 1 , wherein the thickness of the MTCVD Ti x C y N 1-y layer is 1-10 μm.

3. The coated cutting tool according to claim 1 , wherein the thickness of the α-Al 2 O 3 layer is 0.3-7 μm.

4. The coated cutting tool according to claim 1 , wherein the coating includes a further layer of titanium carbonitride Ti u C v N 1-v , with 0.85≤u≤1.3, and 0.4≤v≤0.85, located between the substrate and the α-Al 2 O 3 layer.

5. The coated cutting tool according to of claim 4 , wherein the thickness of the Ti u C v N 1-v layer is 3-20 μm.

6. The coated cutting tool according to claim 4 , wherein the Ti u C v N 1-v layer located between the α-Al 2 O 3 layer and the substrate exhibits a texture coefficient TC(hkl), as measured by X-ray diffraction using CuKα radiation and θ-2θ scan, defined according to Harris formula where I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, I 0 (hkl) is the standard intensity according to JCPDS card No. 42-1489, n is the number of reflections, the reflections used in the calculation are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0) and (4 2 2), and wherein TC(4 2 2)≥3.

7. The coated cutting tool according to claim 4 , wherein the MTCVD Ti x C y N 1-y layer exhibits a higher mean hardness than the Ti u C y N 1-v layer.

8. The coated cutting tool according to claim 1 , wherein the coating has a total thickness of 4-32 μm.

9. The coated cutting tool according to claim 1 , wherein the substrate is selected from cemented carbide, cermet, ceramics, steel or cubic boron nitride.

10. The coated cutting tool of claim 1 , wherein the α-Al 2 O 3 layer and the Ti x C y N 1-y layer are columnar.

11. The coated cutting tool of claim 1 , wherein the α-Al 2 O 3 layer and the Ti x C y N 1-y layer are deposited by chemical vapor deposition (CVD).

12. A method for producing a coated cutting tool having a substrate, the method comprising the steps of

a) depositing a layer of Ti u C v N 1-v by MTCVD at a temperature of 600-900° C. on the substrate;

b) depositing a layer of α-Al 2 O 3 by CVD at a temperature of 800-1200° ° C. on top of the Ti u C v N 1-v layer;

c) depositing a layer of titanium carbonitride Ti x C y N 1-y layer on top of the Al 2 O 3 layer by MTCVD at a temperature of 600-900° C. in an atmosphere comprising TiCl 4 , CH 3 CN, N 2 and H 2 in an amount of 3-13 vol % H 2 and 83-94 vol % N 2 , wherein the MTCVD Ti x C y N 1-y layer exhibits a mean hardness of 25-37 GPa, and wherein the Ti x C y N 1-y exhibits a texture coefficient TC(hkl), as measured by X-ray diffraction using CuKα radiation and θ-2θ scan, the TC(hkl) being defined according to Harris formula:

TC

⁡

(

hkl

)

=

I

⁡

(

hkl

)

I

0

⁡

(

hkl

)

⁡

[

1

n

⁢

∑

n

=

1

n

⁢

I

⁡

(

hkl

)

I

0

⁡

(

hkl

)

]

-

1

,

wherein

I(hkl) is the measured intensity (integrated area) of the (hkl) reflection;

I 0 (hkl) is standard intensity of the standard powder diffraction data according to JCPDS card no. 42-1489;

n is the number of reflections used in the calculation, and where the (hkl) reflections used are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0) and (4 2 2); and

wherein TC(1 1 1)≥3.