Patent ID: 7431977

Claim:
A cutting tool insert comprising a cemented carbide body and a coating wherein said cemented carbide body comprises WC with an average grain size of from about 1.5 to about 2.5 μm, of from about 7.3 to about 7.9 wt-% Co and from about 1.0 to about 1.8 wt % cubic carbides of metals Ta and Nb and a highly W-alloyed binder phase with a CW-ratio of 0.86-0.94 with less than about 3 vol-% eta-phase and said coating comprising: a first, innermost layer of TiC x N y O z with x+y+z=1, y>x and z less than about 0.2 with equiaxed grains with size less than about 0.5 μm and a total thickness of from about 0.1 to about 1.5 μm, a layer of TiC x N y with x+y=1, x greater than about 0.3 and y greater than about 0.3 with a thickness of from about 4.5 to about 9.5 μm with columnar grains with an average diameter of less than about 5 μm, a layer of a smooth, fine-grained, from about 0.5 to about 2 μm average grain size α-Al 2 O 3 with a thickness of from about 4.5 to about 9.5 μm, wherein said insert has an uncoated cutting edge having a radius of 35-60 μm.