Patent ID: 7132153

Claim:
A cutting tool insert for turning of cast irons, comprising a cemented carbide body and a coating, said body having a composition of from about 3.0 to about 9.0 wt. % Co, from about 4.0 to about 10.0 wt. % of cubic carbonitride forming elements from groups IVb and Vb of the periodic table, N, C, and WC, and a from about 5 to about 50 μm thick surface zone, which is binder phase enriched and nearly free of cubic carbonitride phase, with a maximum binder phase content in the surface zone of from about 1.2 to about 3 by volume of the bulk binder phase content, said coating comprising: a first, innermost layer of TiC x N y O z with 0.7≦x+y+z≦1 with equiaxed grains and a total thickness <2 μm; a layer of TiC x N y O z with 0.7≦x+y+z ≦1 with a thickness of from about 3 to about 14 μm with columnar grains; and at least one layer of Al 2 O 3 with a thickness of from about 2 to about 14 μm.