Patent ID: 8192793

Claim:
A method of making a cutting tool insert comprising a cemented carbide body and a coating, comprising: preparing by powder metallurgical technique, a cemented carbide body having a composition comprising: about 9.3-10.9 wt % Co; about 0.5-2.5 wt % of metals selected from the group consisting of Group IVb metal, Group Vb metal, Group VIb metal, and combinations thereof; and balance WC; wherein said body has a coercivity of about 10-15 kA/m, and an S-value of about 0.81-0.95; and coating the cemented carbide body with a first (innermost) layer of TiC x N y O z , wherein with 0.7≦x+y+z≦about 1, with equiaxed grains and a total thickness<about 1 μm using known CVD-technique; a second layer of TiC x N y O z with 0.7≦x+y+z≦about 1, with a thickness of about 1-5 μm with columnar grains using medium temperature chemical vapour deposition (MTCVD)-technique with acetonitrile as the carbon and nitrogen source for forming the layer in the temperature range of 700-950° C.; and a layer of textured Al 2 O 3 having an α-phase with a thickness of about 1-5 μm using known CVD-technique; and optionally, depositing a thin TiN top layer on the α-Al 2 O 3 layer.