Surface coated cutting tool

1. A surface coated cutting tool comprising:

a cutting tool body made of any one of cemented carbide including tungsten carbide, cermet including titanium carbonitride, and ultra-high pressure sintered material including cubic boron nitride; and

a hard coating layer provided on a surface of the cutting tool body, wherein

the hard coating layer comprises at least a Ti and Al complex carbonitride layer formed by a chemical vapor deposition method,

the complex carbonitride layer includes an alternate laminated structure made of a region A layer and a region B layer, each of which is represented by a composition formula (Ti 1-x Al x )(C y N 1-y ), the alternate laminated structure having an average total layer thickness of 1-10 μm,

in the region A layer, a content ratio x, which is an Al content relative to a total content amount of Ti and Al, satisfies 0.70≦x≦0.80; a content ratio y, which is a C content relative to a total content amount of C and N, satisfies 0.0005≦y≦0.005, each of x and y being atomic ratio; an average grain width W, which is an average value of grain width in a plane parallel to the surface of the cutting tool body, is 0.1 μm or less; and an average grain length L, which is an average value of grain length in a direction perpendicular to the surface of the cutting tool body, is 0.1 μm or less,

in the region B layer, a content ratio x, which is an Al content relative to a total content amount of Ti and Al, satisfies 0.85≦x≦0.95; a content ratio y, which is a C content relative to a total content amount of C and N, satisfies 0.0005≦y≦0.005, each of x and y being atomic ratio; an average grain width W, which is an average value of grain width in a plane parallel to the surface of the cutting tool body, is 0.1 μm to 2.0 μm; and an average grain length L, which is an average value of grain length in a direction perpendicular to the surface of the cutting tool body, is 0.5 μm to 5.0 μm,

the alternate laminated structure includes at least a pair of the region A layer and the region B layer which are alternately arranged, and

a top layer of the alternate laminated structure is the region A layer.

2. The surface coated cutting tool according to claim 1 , wherein

in regard to the region A layer, in a case where a crystal orientation of each of crystal grains is analyzed in a vertical section direction of the Ti and Al complex carbonitride layer using an electron backscatter diffraction apparatus:

both of: a cubic crystal phase, in which an electron backscatter diffraction pattern of a cubic crystal lattice is observed; and a hexagonal crystal phase, in which an electron backscatter diffraction pattern of a hexagonal crystal lattice is observed, are detected; and

an area ratio of the cubic crystal phase relative to a total area of the cubic crystal phase and the hexagonal crystal phase is 50% or more, and

in regard to the region B layer, an area ratio of the hexagonal crystal phase relative to a total area of the cubic crystal phase and the hexagonal crystal phase is 50% or more.

3. The surface coated cutting tool according to claim 2 , wherein

in a case where a lattice constant, a, of the cubic crystal grain is obtained in the complex carbonitride layer from X-ray diffraction, the lattice constant a of the cubic crystal grain satisfies a relationship, 0.05a TiN +0.95a AlN ≦a≦0.4a TiN +0.6a AlN , relative to a lattice constant a TiN , which is a lattice constant of a cubic TiN, and a lattice constant a AlN , which is a lattice constant of a cubic AlN.

4. The surface coated cutting tool according to claim 1 ,

wherein the hard coating layer is formed by a chemical vapor deposition method, a reaction gas component of which includes at least trimethyl aluminum.

5. The surface coated cutting tool according to claim 1 ,

wherein an outermost layer, which is made of at least one layer selected from a group consisting of: Al 2 O 3 layer; TiN layer; TiCN layer; and TiCNO layer, is formed on the Ti and Al complex carbonitride layer as a layer in an outermost part of the surface coated cutting tool.

6. The surface coated cutting tool according to claim 1 ,

wherein an intermediate layer, which is made of TiN layer or TiCN layer, is formed between the surface of the cutting tool body and one of the region B layer closest to the cutting tool body.

7. The surface coated cutting tool according to claim 5 ,

wherein an intermediate layer, which is made of TiN layer or TiCN layer, is formed between the surface of the cutting tool body and one of the region B layer closest to the cutting tool body.

8. The surface coated cutting tool according to claim 1 ,

wherein an average total layer thickness of the complex carbonitride layer relative to an average layer thickness of the hard coating layer is 60% or more and 100% or less.

9. The surface coated cutting tool according to claim 1 ,

wherein one of the region A layer farthest from the cutting tool body is the outermost layer of the surface coated cutting tool, and the one of the region B layer closest to the cutting tool body contacts the surface of the cutting tool body directly.

10. The surface cutting tool body according to claim 1 ,

wherein a ratio between an average total layer thickness of the region A layer and an average total layer thickness of the region B layer is in a range between 1:9 to 9:1.