Patent ID: 7799413

Claim:
A coated cutting tool insert of cemented carbide comprising: a body of generally polygonal or round shape having at least one rake face and at least one clearance face; and a coating on the body, wherein said insert is at least partly coated with the coating, wherein said body has a composition including 4.4-6.6 wt-% Co, 4-8.5 wt-% cubic carbides, balance WC, a CW-ratio in the range 0.78-0.92 and has a surface zone of a thickness of 10 to 40 μm, depleted from the cubic carbides TiC, TaC and/or NbC, wherein said coating is 10-25 μm thick and includes at least one layer of TiC x N y , where x≧0, y≧0 and x+y=1 and an α-Al 2 O 3 -layer, the α-Al 2 O 3 -layer being the outer layer at least on the rake face, and wherein: (i) on said at least one rake face: the TiC x N y -layer has a thickness of from 3 μm to 15 μm and a tensile stress level of 50-500 MPa, and the α-Al 2 O 3 -layer has a thickness of from 3 μm to 12 μm, is the outermost layer with an XRD-diffraction intensity ratio I(012)/I(024)≧1.3, and has a mean Ra value MRa<0.12 μm at least in the chip contact zone on the rake face, and on said at least one clearance face: the TiC x N y -layer has a tensile stress in the range 500-700 MPa, and the α-Al 2 O 3 -layer has an XRD-diffraction intensity ratio I(012)/I(024)<1.5, or (ii) on said at least one rake face and said at least one clearance face: the TiC x N y -layer has a thickness of from 3 μm to 15 μm and a tensile stress level of 50-500 MPa, the α-Al 2 O 3 -layer has a thickness of from 3 μm to 12 μm, has an XRD-diffraction intensity ratio I(012)/I(024)≧1.3, and is the outermost layer on the rake face with a mean Ra value MRa<0.12 μm at least in the chip contact zone on the rake face, and the outermost layer on said clearance face consists of a colored heat resistant paint or a colored PVD-layer.