Coated cutting tool
A coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, the coated cutting tool having a rake surface and a flank, in which the coating layer includes an α-type aluminum oxide layer, wherein: the α-type aluminum oxide layer has, on an opposite side to the substrate, a first interface, being the rake surface or a surface substantially parallel to the rake surface, a second interface, being the flank or a surface substantially parallel to the flank, and an intersecting edge between the first interface and the second interface; and the α-type aluminum oxide layer satisfies −600≤σ11≤300, −900≤σ22≤250 and σ11>σ22. (In the above formulae, σ11 denotes a residual stress value (MPa) in a direction parallel to the intersecting edge, σ22 denotes a residual stress value (MPa) in a direction orthogonal to the intersecting edge, and each of the residual stress values is a value measured by a 2D method).
1. A coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, the coated cutting tool having a rake surface and a flank, in which the coating layer includes an α-type aluminum oxide layer, wherein:
the α-type aluminum oxide layer has, on an opposite side to the substrate, a first interface, being the rake surface or a surface substantially parallel to the rake surface, a second interface, being the flank or a surface substantially parallel to the flank, and an intersecting edge between the first interface and the second interface;
the α-type aluminum oxide layer satisfies conditions represented by formulae (A), (B) and (C)
−600≤σ11≤300 (A)
−900≤σ22≤250 (B)
σ11>σ22 (C)
(In the above formulae, σ11 denotes a residual stress value (unit: MPa) in a direction parallel to the intersecting edge, σ22 denotes a residual stress value (unit: MPa) in a direction orthogonal to the intersecting edge, and each of the residual stress values is a value measured by a multi-axial stress measurement method or a full Debye ring fitting method); and
each of the residual stress values is a value measured, in the α-type aluminum oxide layer, at a position 50 μm from the intersecting edge along the first surface.
2. The coated cutting tool according to claim 1 , wherein σ11 is from −600 MPa or higher to 0 MPa or lower and σ22 is from −900 MPa or higher to −100 MPa or lower.
3. The coated cutting tool according to claim 1 , wherein, 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
T
C
(
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
)
(In formula (1), 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 a JCPDS Card No. 10-0173 for α-type aluminum oxide, and (h,k,l) refers to 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)).
4. The coated cutting tool according to claim 1 , wherein the α-type aluminum oxide layer satisfies a condition represented by formula (D) below
σ11−σ22>100 (D).
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:
the coating layer comprises a titanium carbonitride layer, being comprised of titanium carbonitride, between the substrate and the α-type aluminum oxide layer; and
an average thickness of the titanium carbonitride layer is from 1.0 μm or more to 20.0 μm or less.
7. The coated cutting tool according to claim 6 , wherein the coating layer comprises, between the titanium carbonitride layer and the α-type aluminum oxide layer, an intermediate layer comprising a compound of at least one kind selected from the group consisting of a Ti carboxide, a Ti oxynitride and a Ti carboxynitride.
8. The coated cutting tool according to claim 7 , wherein an average thickness of the intermediate layer is from 0.1 μm or more to 1.5 μm or less.
9. 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.
10. The coated cutting tool according to claim 1 , wherein the coating layer comprises a titanium nitride layer, being comprised of titanium nitride, as an outermost layer on a surface of the α-type aluminum oxide layer.
11. The coated cutting tool according to claim 1 , wherein the substrate is any of a cemented carbide, cermet, ceramics and a sintered body containing cubic boron nitride.
12. The coated cutting tool according to any claim 2 , wherein, 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
T
C
(
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
)
(In formula (1), 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 a JCPDS Card No. 10-0173 for α-type aluminum oxide, and (h,k,l) refers to 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)).
13. The coated cutting tool according to claim 2 , wherein the α-type aluminum oxide layer satisfies a condition represented by formula (D) below
σ11−σ22>100 (D).
14. The coated cutting tool according to claim 3 , wherein the α-type aluminum oxide layer satisfies a condition represented by formula (D) below
σ11−σ22>100 (D).
15. 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.