Patent ID: 8318293

Claim:
A coated cutting tool insert of cemented carbide comprising a body having at least one rake face and at least one clearance face, said insert having a composition of from about 6.4 to about 8.6 wt-% Co, from about 4 to about 8.5 wt-% cubic carbides, balance WC, a CW-ratio in the range from about 0.78 to about 0.92 and having a surface zone of a thickness of from about 10 to about 35 μm, depleted of the cubic carbides TiC, TaC and/or NbC, said insert being at least partly coated with a from about 10 to about 25 μm thick coating including at least one layer of TiC x N y , wherein x≧0, y≧0, and x+y=1, and an α-Al 2 O 3 -layer, wherein the coating on said at least one rake face includes: the TiC x N y -layer having a thickness of from about 5 to about 15 μm, and a tensile stress level of from about 50 to about 390 MPa; and the α-Al 2 O 3 -layer having a thickness of from about 3 to about 12 μm and forming the outermost layer of the coating with an XRD-diffraction intensity ratio I(012)/I(024)≧1.3 and with a mean Ra value MRa<0.12 μm, at least in the chip contact zone on the rake face, as measured on ten randomly selected areas 10×10 μm 2 by AFM-technique, and wherein the coating on said at least one clearance face includes either: the TiC x N y -layer having a tensile stress in the range from about 500 to about 700 MPa; and the α-Al 2 O 3 -layer having an XRD-diffraction intensity ratio I(012)/I(024)<1.5 or the TiC x N y -layer having a thickness of from about 5 to about 15 μm, and a tensile stress level of from about 50 to about 390 MPa; the α-Al 2 O 3 -layer with a thickness of from about 3 to about 12 μm, has an XRD-diffraction intensity ratio I(012)/I(024)≧1.3; and an outermost layer comprising a colored heat resistant paint or a colored PVD-layer.