Patent ID: 7087295

Claim:
A coated cutting tool comprising a substrate and a coating on the substrate, the coating comprising an inner layer, an intermediate layer, and an outer layer, each comprising at least one layer; the inner layer: (a) being composed of at least one material selected from the group consisting of the carbide, nitride, carbonitride, boride, boronitride, borocarbonitride, oxide, oxycarbide, oxynitride, and oxycarbonitride of the elements belonging to the IVa, Va, and VIa groups in the periodic table; and (b) including at least one layer having a columnar-crystal structure; the outer layer being composed of at least one oxide selected from the group consisting of aluminum oxide, zirconium oxide, hafnium oxide, and their solid solutions; the intermediate layer: (c) being composed of titanium boronitride, TiB x N y (x, y: atomic %), that satisfies 0.001 <x /( x+y )<0.04 formula 1; (d) having an average thickness of 0.1 to 1 μm; and (e) having a surface roughness of 50 to 500 nm expressed by the vertical distance between the peak line and the valley line within a reference length of 1 μm.