Patent ID: 8142848

Claim:
A method of making a cutting tool insert, comprising: preparing by a powder metallurgical technique a cemented carbide body comprising: about 7.5-8.6 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; balance WC; wherein said body has a coercivity of about 12.0-15.5 kA/m and an S-value of about 0.81-0.95; and coating said cemented carbide body with: a first (innermost) layer of TiC x N y O z with about 0.7≦x+y+z≦about 1 with equiaxed grains and a total thickness<about 1 μm using a chemical vapor deposition (CVD)-technique; a second layer of TiC x N y O z with 0.7 about≦x+y+z≦about 1 and a thickness of about 1-5 μm with columnar grains using a medium temperature chemical vapor deposition (MTCVD)-technique with acetonitrile as the carbon and nitrogen source for forming said second layer of TiC x N y O z in a temperature range of about 700-950° C.; an α-Al 2 O 3 layer having a thickness of about 1-5 μm using a chemical vapor deposition (CVD)-technique; and optionally, depositing a TiN top layer having a thickness less than about 1 μm on said α-Al 2 O 3 layer.