Patent ID: 7192637
Filing Date: 2007-03-20
Classification: C22C,C23C,Y10T

Abstract:
1. A coated cutting tool insert comprising 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, the cemented carbide substrate has a binder phase enriched surface zone with a thickness of >20 μm; and the coating comprises a first bonding layer adjacent the cemented carbide substrate of TiN, a first layer adjacent the first bonding layer of Ti(C,N) having a thickness of from about 3 to 15 μm, a second bonding layer of Ti(C,O,N) followed by an alumina layer having a thickness of from about 3 to 15 μm, said alumina layer being composed of α-Al wherein a total thickness of the coating is less than 40 μm, the thickness of the first Ti(C,N) layer is 1–2 times the thickness of the alumina layer, and the thickness of the outer Ti(C,N) layer is 0.1–1.2 times the thickness of the first Ti(C,N) layer and the alumina layers, wherein the cubic carbide-forming metals comprises one or more of titanium, tantalum and niobium, and the binder phase-enriched surface zone has a thickness of 21–50 μm, and wherein the substrate comprises cubic carbides such that a ratio of tantalum to niobium is 1.0–2.5 and a ratio of titanium to niobium is 0.5–1.5.