Abstract: 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 ?m, preferably between 21 and 50 ?m. 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 ?m, an alumina layer adjacent said first layer having a thickness of from about 3 to about 15 ?m, said alumina layer being composed of ?-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 ?m. The total thickness of the coating being less than 30 ?m, preferably less than 20 ?m. Inserts according to the invention exhibit favourable wear resistance and edge strength when turning steel.

Abstract: 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 ?m, preferably between 21 and 50 ?m. 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 ?m, an alumina layer adjacent said first layer having a thickness of from about 3 to about 15 ?m, said alumina layer being composed of ?-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 ?m. The total thickness of the coating being less than 30 ?m, preferably less than 20 ?m. Inserts according to the invention exhibit favourable wear resistance and edge strength when turning steel.