Abstract: A surface-coated cutting tool comprises a tool substrate comprising a cBN sinter and a hard coating layer including a lower sublayer ? and an upper sublayer ? on the surface of the cutting edge; wherein ? satisfies (Al1-xTix)N (0.40?x?0.60); ? satisfies (Al1-y-zTiyBz)N (0.40?y?0.60 and 0.01?z?0.10); in the sublayer ?, the variation in the concentration of the B component is repeated; the average Bmaxav of the maxima in the concentration of the B component satisfies z<Bmaxav?2.0×z, and the average Bminav of the minima in the concentration of the B component satisfies 0?Bminav<z; and the average thickness t? of ? and the average thickness t? of ? satisfy expression: 2.0?<t?/t??6.0; and the residual stress ? of the overall hard coating layer satisfies ?2.0 GPa????0.5 GPa.

Abstract: A surface-coated cutting tool has excellent welding resistance and fracturing resistance and comprises a hard coating layer, including at least a lower layer and an upper layer, formed on a surface of a cutting tool body. The lower layer is formed of one layer or two or more layers of a TiC layer, a TiN layer, a TiCN layer, a TiCO layer, and a TiCNO layer. The upper layer is found as an Al2O3 layer on a surface of the lower layer. On at least an outermost surface of the upper layer of a rake face, a zirconium oxide layer is formed in an area ratio of 30% to 70%. The Al2O3 layer on the rake face has a tensile residual stress of 10 to 200 MPa and a surface roughness Ra is 0.25 ?m or less.