Patent ID: RE39987

Claim:
A cutting tool insert for turning of steel comprising a cemented carbide body and a coating thereon, the cemented carbide body including WC, 5-11 wt % Co and 2-10 wt % cubic carbides of groups IVb, Vb and/or VIb of the periodic table and a highly W-alloyed binder phase with a CW-ratio of 0.76-0.92, the coating comprising: a first layer of TiC x N y O z having a thickness of 0.1-2 μm and equiaxed grains <0.5 μm in size; a second layer of TiC x N y O z having a thickness of 3-15 μm and columnar grains <5 μm in diameter; and a third layer of a smooth, fine-grained κ-Al 2 O 3 -layer having a thickness of 1-9 μm.