EVALUATION OF CERMET CUTTING TOOLS MATERIALS WHEN MACHINING G-17 CAST-IRON

Two grades of cermet cutting tools have been used for the machining of G-17 cast iron at various cutting conditions. Comparative trials were carried out with coated (TiC + Al2O3) carbide tools at similar cutting conditions. The test results show that the coated carbide inserts generally outperformed the cermet tools under the conditions tested, mainly due to their high strength level and better thermal properties enhanced by the coating materials. Flank wear was the predominant failure mode in all the tools tested. Some of the tools were also rejected due to the generation of poor surface finish on the machined surface, due perhaps to a mechanical type of wear mechanism, i. e., chipping, which usually alters the cutting edge geometry. Analysis of the tools suggests that the attrition wear mechanism is dominant at slower speeds, even when cutting at a high feed rate, while a combination of attrition and thermally-related wear mechanisms, i.e., diffusion and plastic deformation, occurred at high speed conditions