Patent ID: 7150772

Claim:
A cutting tool insert comprising a cemented carbide body and a coating, said body having a composition of from about 11.3 to about 12.7 wt% Co, from about 0.5 to about 2.5 wt% total amount of cubic carbides of the metals Ti, Nb and Ta and balance WC, the WC grains having a mean intercept length in the range from about 0.3 to about 0.8 μm, the Co being alloyed with W corresponding to an S-value within the range from about 0.81 to about 0.95, said coating comprising: a first (innermost) layer of TiC x N y O z with 0.7≦x+y+z≦1, 0<z<0.5, and 0<x<y, with equiaxed grains and a total thickness <0.1 and <1 μm; a layer of TiC x N y O z with 0.7≦x+y+z≦1 with a thickness of from about 0.5 to about 5 μm with columnar grains; and a layer of Al 2 O 3 comprising the α-phase with a thickness of from about 0.2 to about 5 μm.