Coated cutting tool

Abstract

Provided is a coated cutting tool of long tool life and that affords superior machined surface quality. A coated cutting tool includes a substrate, and a coating layer formed on the substrate. The coated cutting tool includes at least one flank face, at least one rake face, and a honing section rounded and connecting the flank face and the rake face. The coating layer includes a lower layer, an intermediate layer and an upper layer, in this order from the side of the substrate. The lower layer is composed of one, or two or more Ti compound layers made up of a Ti compound of Ti and at least one element selected from the group consisting of C, N, O and B. The intermediate layer contains α-type AlO. The upper layer contains a compound represented by following formula (1): Ti(CNO) (1). An average thickness of the coating layer on the flank face side is 5.0 μm more and 30.0 μm or less. A first cross section positioned at a distance of up to 1 μm towards the substrate, from an interface of the intermediate layer and the upper layer side, the cross section being parallel to an interface of the substrate and the lower layer, satisfies the condition represented by following expression (i): RSA≥40 (i). A second cross section, positioned at a distance of up to 1 μm from the interface of the upper layer and the intermediate layer side towards an interface on the opposite side, the cross section being parallel to the interface of the substrate and the lower layer, satisfies the condition represented by following expression (ii): RSB≥40 (ii). The intermediate layer is exposed at least at the honing section.