Patent ID: 7431542

Claim:
Cutting insert comprising a substrate and a coating wherein said substrate comprises WC with an average grain size of from about 1 to about 2.5 μm, from about 5 to about 8 wt-% Co and 0 wt-% cubic carbides of metals Ta, Ti and or Nb and a highly W-alloyed binder phase with a CW-ratio of 0.75-0.93 with less than about 1 vol-% eta-phase and said coating comprises a first, innermost layer of TiC x N y O z with x+y+z=1, y>x and z less than about 0.2 with equiaxed grains with size less than about 0.5 μm and a total thickness of from about 0.1 to about 1.5 μm, a layer of TiC x N y with x+y=1, x greater than about 0.3 and y greater than about 0.3 with a thickness of greater than about 3 to about 5 μm with columnar grains with an average diameter of less than about 5 μm, a layer of a smooth, fine-grained, grain size of from about 0.5 to about 2 μm, κ-Al 2 O 3 with a thickness of from about 0.5 to about 3 μm, and an outermost layer of TiN with a thickness of less than about 2 μm, wherein the outermost TiN-layer is missing along the cutting edge, and wherein a radius of the uncoated cutting edge is from about 20 to about 50 μm.