Patent ID: RE40005

Claim:
A cutting tool insert comprising a coating and a cemented carbide body, said cemented carbide body comprising WC, 5-10 weight % Co and <0.5 weight % cubic carbides of metals from groups IVb, Vb, or VIb of the periodic table with a highly W-alloyed binder phase having a CW-ratio of 0.75-0.93 and a surface composition of the cemented carbide body being well-defined, the amount of Co on the surface being within −4 weight % to +4 weight % of the nominal Co content of the body and said coating comprising: a first, innermost, layer of TiC x N y O z with x+y+z=1 and y>x and z<0.1, with a thickness of 0.1-2 μm, and with equiaxed grains having a size <0.5 μm; a layer of TiC x N y O z where x+y+z=1, and z=0, x>0.3 and y>0.3, with a thickness of 5-10 μm with columnar grains having a diameter of <2 μm; a layer of TiC x N y O z where x+y+z=1, z<0.5 and x>y with a thickness of 0.1-2 μm and with equiaxed or needle-like grains having a size <0.5 μm; a layer of smooth, textured, fine-grained α-Al 2 O 3 having a grain size of 0.5-2 μm with a thickness of 3-6 μm; and an outer layer of TiC x N y O z where x+y+z=1, z<0.05 with a thickness of 0.5-3 μm and a grain size <1 μm, the outer coating layer having been removed in at least the edge line so that the Al 2 O 3 layer is on top along the cutting edge line and the outer layer of TiC x N y O z is the top layer on the clearance side.