Patent ID: 7655293

Claim:
A CVD coated cutting tool insert of cemented carbide, cermet or ceramics comprising a body of generally polygonal or round shape having at least one rake face and at least one clearance face, said insert being at least partly coated with a from about 2 to about 10 μm thick coating including at least one layer of TiC x N y and an α-Al 2 O 3 -layer being the outer layer at least on the rake face wherein (a) 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 about 1 to about 8 μm where x≧0, y≧0 and x+y=1, and a tensile stress level of from about 10 to about 300 MPa and the α-Al 2 O 3 -layer has a thickness of from about 1 to about 5 μm and is the outermost layer with an XRD-diffraction intensity ratio I(012)/I(024)≧1.5 and with a mean Ra value MRa<0.1 μm as measured on ten randomly selected areas, 10×10 μm 2 , by AFM-technique or (b) on only said at least one rake face the TiC x N y -layer has a thickness of from about 1 to about 8 μm, where x≧0, y≧0 and x+y=1, and a tensile stress level of from about 10 to about 300 MPa and the α-Al 2 O 3 -layer with a thickness of from about 1 to about 5 μm is the outermost layer with an XRD-diffraction intensity ratio I(012)/I(024)≧1.5 and a mean Ra value MRa<0.1 μm as measured on ten randomly selected areas, 10×10 μm 2 , by AFM-technique and (c) on said at least one clearance face the TiC x N y -layer has a tensile stress in the range from about 600 to about 1000 MPa and the α-Al 2 O 3 -layer has an XRD-diffraction intensity ratio I(012)/I(024)<1.5.