Patent ID: RE39894

Claim:
A cutting tool insert for machining steel, comprising a cemented carbide body and a coating, wherein: the cemented carbide body comprises WC, 2-10 wt. % Co, 4-12 wt. % of cubic carbides of metals from groups 4, 5 or 6 of the periodic table, and N in an amount of between 0.9 and 1.7% of the weight of the elements from groups 4 and 5; the cemented carbide body comprises a Co-binder phase which is highly alloyed with W, and has a CW-ratio of 0.75-0.90; the cemented carbide body has a surface zone with a thickness of <20 μm, which is binder phase enriched and essentially cubic carbide free; the cemented carbide body has a cutting edge which has a binder phase content of 0.65-0.75 by volume of the bulk binder phase content, and the binder phase content increases at a constant rate along a line which bisects said cutting edge until it reaches the bulk binder phase content at a distance between 100 and 300 μm from the cutting edge; and the coating comprises a 3-12 μm columnar TiCN layer followed by a 2-12 μm Al 2 O 3 layer.