Surface-coated cutting tool and method of manufacturing the same
A surface-coated cutting tool includes a base material and a coating formed on the base material. The coating includes an α-Al 2 O 3 layer. The α-Al 2 O 3 layer contains a plurality of α-Al 2 O 3 crystal grains and chlorine, and has a TC(006) of more than 5 in texture coefficient TC(hkl). The α-Al 2 O 3 layer includes lower and upper layers, the lower layer is located closer to the base material than the upper layer is, and the upper layer is located opposite to the base material across the lower layer, in a thickness direction of the α-Al 2 O 3 layer. The lower layer has a thickness of 1.0 μm. The upper layer has a thickness of 0.5 μm or more. The chlorine in the lower layer has a concentration distribution in which an atomic concentration C Cl of the chlorine decreases in a direction away from the base material, in a thickness direction of the lower layer.
1. A surface-coated cutting tool comprising a base material and a coating formed on the base material,
the coating including an α-Al 2 O 3 layer,
the α-Al 2 O 3 layer containing a plurality of α-Al 2 O 3 crystal grains and chlorine, and having a TC(006) of more than 5 in texture coefficient TC(hkl),
the α-Al 2 O 3 layer including a lower layer and an upper layer, the lower layer being located closer to the base material than the upper layer is, and the upper layer being located opposite to the base material across the lower layer, in a thickness direction of the α-Al 2 O 3 layer,
the lower layer having a thickness of 1.0 μm,
the upper layer having a thickness of 0.5 μm or more,
the chlorine in the lower layer having a concentration distribution in which an atomic concentration of the chlorine decreases in a direction away from the base material, in a thickness direction of the lower layer.
2. The surface-coated cutting tool according to claim 1 , wherein the chlorine in the lower layer has a maximum atomic concentration of less than 0.3 at. %.
3. The surface-coated cutting tool according to claim 1 , wherein the chlorine in the upper layer has a maximum atomic concentration of less than 0.05 at. %.
4. The surface-coated cutting tool according to claim 1 , wherein
the surface-coated cutting tool satisfies a relation: C ClMAX-1 ≥2C ClMAX-2 ,where C ClMAX-1 represents a maximum atomic concentration of the chlorine in the lower layer and C ClMAX-2 represents a maximum atomic concentration of the chlorine in the upper layer.
5. The surface-coated cutting tool according to claim 1 , wherein
the TC(006) is more than 6.
6. The surface-coated cutting tool according to claim 1 , wherein
the lower layer contains sulfur, and
the lower layer has a C cls distribution in which C cls decreases in the direction away from the base material, in the thickness direction of the lower layer, where C cls represents a numerical value determined by adding together an atomic concentration of the chlorine at a predetermined measurement point in the lower layer and an atomic concentration of the sulfur at the predetermined measurement point.
7. The surface-coated cutting tool according to claim 1 , wherein
the lower layer contains sulfur, and
the lower layer has a C cl/s distribution in which C cl/s decreases in the direction away from the base material, in the thickness direction of the lower layer, where C cl/s represents a numerical value determined by dividing an atomic concentration of the chlorine at a predetermined measurement point in the lower layer by an atomic concentration of the sulfur at the predetermined measurement point.
8. A method of manufacturing a surface-coated cutting tool as recited in claim 1 , the method comprising a step of forming, on the base material by a CVD method, the coating including the α-Al 2 O 3 layer,
in the step, a content of HCl gas contained in a raw material gas being 6 to 10 vol % at a start of formation of the α-Al 2 O 3 layer, and the content of HCl gas being decreased to 0.5 to 6 vol % after the start of formation.