Coated cutting tool for turning of steel

摘要

A cutting tool insert includes a cemented carbide substrate and a coating. The cemented carbide substrate comprises WC, 4-7 wt % cobalt, 6-9 wt % cubic carbide forming metals from the groups IVB and VB, preferably titanium, tantalum and niobium, with a binder phase enriched surface zone with a thickness of >20 mum, preferably between 21 and 50 mum. The coating comprises a first layer adjacent the cemented carbide substrate of Ti(C,N) having a thickness of from about 3 to about 15 mum, an alumina layer adjacent said first layer having a thickness of from about 3 to about 15 mum, said alumina layer being composed of alpha-Al₂O₃, a further layer adjacent the alumina layer of a Ti(C,N) or Ti(C,O,N) having a thickness of from about 1 to 10 mum. The total thickness of the coating being less than 30 mum, preferably less than 20 mum. Inserts according to the invention exhibit favourable wear resistance and edge strength when turning steel.