Patent ID: 7232603

Claim:
A cutting tool insert comprising a cemented carbide body and a coating said cemented carbide body comprising WC, from about 7.3 to about 7.9 wt-% Co and from about 1.0 to about 1.8 wt-% cubic carbides of Ta and Nb, a highly W-alloyed binder phase with a CW-ratio of from about 0.86 to about 0.94, and an edge radius of from about 20 to about 45 μm, said coating comprising a first (innermost) layer of TiC x N y O z with a thickness of from about 0.1 to about 2 μm, and with equiaxed grains with size less than about 0.5 μm, a layer of TiC x N y O z with a thickness of from about 2 to about 10 μm with columnar grains with a diameter of less than about 5 μm, a layer of TiC x N y O z with a thickness of from about 0.1 to about 2 μm and with equiaxed or needlelike grains with size less than about 0.5 μm, and an outer layer of a smooth, textured, finegrained α-Al 2 O 3 layer with a thickness of from about 2 to about 10 μm.