Surface coated cutting tool

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 (Ti1-xAlx)(CyN1-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.