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Abstract

A cutting insert preferably for milling of extremely highly alloyed grey cast iron, of a substrate and a coating and methods of making and using the insert are disclosed. The cemented carbide substrate includes WC, of from about 3 to about 8 weight-% Co and less than about 0.5 weight-% carbides of metals from groups IVb, Vb or VIb of the periodic table. The coating has a first, innermost layer of TiC.sub.xN.sub.yO.sub.z with x+y+z=1, y>x and z less than about 0.2, preferably y greater than about 0.8, and z=0, with equiaxed grains with size less than about 0.5 .mu.m and a total thickness of from about 0.1 to about 1.5 .mu.m, a layer of TiC.sub.xN.sub.y with x+y=1, x greater than about 0.3 and y greater than about 0.3, preferably x greater than or equal to about 0.5, with a thickness of greater than about 3 to about 5 .mu.m with columnar grains with an average diameter of less than about 5 .mu.m, a layer of a smooth, fine-grained, grain size of from about 0.5 to about 2 .mu.m, .kappa.-Al.sub.2O.sub.3 with a thickness of from about 0.5 to about 3 .mu.m and an outermost layer of TiN with a thickness of less than about 2 .mu.m.

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