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 α-Al 2 O 3 crystal grains and sulfur, and has a TC(006) of more than 5 in texture coefficient TC(hkl). The sulfur has a concentration distribution in which a concentration of the sulfur decreases in a direction away from a base-material-side surface of the α-Al 2 O 3 layer, in a thickness direction of the α-Al 2 O 3 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 comprising an α-Al 2 O 3 nucleation phase and having a base-material-side surface and an opposite surface opposite to the base-material-side surface,
the α-Al 2 O 3 layer containing a plurality of α-Al 2 O 3 crystal grains and sulfur, and having a TC(006) of more than 5 in texture coefficient TC(hkl), and
the sulfur having a concentration distribution in which a concentration of the sulfur decreases in a direction away from the base-material-side surface of the α-Al 2 O 3 layer, in a thickness direction of the α-Al 2 O 3 layer, wherein
the concentration distribution satisfies a relation: an S content at point X>an S content at point Y, wherein point X is a point directly above and contacting an interface between the α-Al 2 O 3 layer and the base material or is a point directly above and contacting an interface between the α-Al 2 O 3 layer and an adjacent layer, and point Y is a point immediately below the opposite surface of the α-Al 2 O 3 layer,
the S content at point X shows a maximum value in the thickness direction of the α-Al 2 O 3 layer, and
the adjacent layer is a layer adjacent to the α-Al 2 O 3 layer and is located on the same side as the base material, in the thickness direction of the α-Al 2 O 3 layer.
2. The surface-coated cutting tool according to claim 1 , wherein
the α-Al 2 O 3 crystal grains having a grain size of 0.2 to 2 μm occupy 20 to 80% by area of a measurement surface, the measurement surface is in parallel with a surface of the α-Al 2 O 3 layer or parallel with an interface between the α-Al 2 O 3 layer and an adjacent layer, the adjacent layer is adjacent to the α-Al 2 O 3 layer and located on an opposite side to the base material, and the measurement surface is located at a depth of 0.5 μm from the surface of the α-Al 2 O 3 layer or the interface.
3. The surface-coated cutting tool according to claim 1 , wherein
the TC(006) is more than 6.
4. The surface-coated cutting tool according to claim 1 , wherein
the TC(006) is more than 7.
5. The surface-coated cutting tool according to claim 1 , wherein
a maximum concentration Csmax of the sulfur in the concentration distribution appears in a region of 1 μm from an interface between the α-Al 2 O 3 layer and the base material, or from an interface between the α-Al 2 O 3 layer and a layer adjacent to the α-Al 2 O 3 layer and located on the same side as the base material, in the thickness direction of the α-Al 2 O 3 layer, and
a minimum concentration Csmin of the sulfur in the concentration distribution appears in a region of 1 μm from a surface of the α-Al 2 O 3 layer or from an interface between the α-Al 2 O 3 layer and a layer adjacent to the α-Al 2 O 3 layer and located on an opposite side to the base material, in the thickness direction of the α-Al 2 O 3 layer, and
the Csmax is 0.005 to 1 at. %, the Csmin is 0.001 to 0.1 at. %, and the Csmax and the Csmin meet a relation Csmax>Csmin.
6. The surface-coated cutting tool according to claim 1 , wherein
a maximum concentration Csmax of the sulfur in the concentration distribution is 0.005 to 1 at. %.
7. The surface-coated cutting tool according to claim 1 , wherein
the α-Al 2 O 3 layer has an average layer thickness of 1 to 15 μm.
8. The surface-coated cutting tool according to claim 1 , wherein
in a surface of the coating, an outermost surface layer in which any one of Ti carbide, Ti nitride, and Ti boride is a main component is disposed.
9. The surface-coated cutting tool according to claim 1 , wherein
the coating has an intermediate layer between the α-Al 2 O 3 layer and the base material,
the intermediate layer contains acicular TiCNO or acicular TiBN and has an average layer thickness of 0.3 to 1 μm, and
a difference between a maximum thickness and a minimum thickness of the intermediate layer is 0.3 μm or more.
10. The surface-coated cutting tool according to claim 1 , wherein
a content of H2S gas contained in a raw material gas in a nucleation formation of the α-Al 2 O 3 layer is 0.5 to 5 vol. %.
11. A method of manufacturing a surface-coated cutting tool as recited in claim 1 , the method comprising the 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 H2S gas contained in a raw material gas in an initial stage of formation of the α-Al 2 O 3 layer being 0.5 to 5 vol %, and the content of H2S gas being momentarily increased to 0.65 to 7 vol %.