Abstract
Abstract
Tool life and wear models were fitted for machining a martensitic stainless steel (JETHETE) with three ceramic-coated carbides [CVD-Ti(C,N)/Al2O3 (T1), CVD-Ti(C,N)/TiC/Al2O3 (T2) and PVD-TiN (T3)] using statistical regression analysis. The statistical analysis revealed the contribution of the cutting speed and feed rate to tool performance to be in excess of 80 per cent, with the cutting speed showing the greater degree of influence. Significant nose wear was the common failure mode observed at higher speed conditions. Plastic deformation and chipping/fracture at the cutting edge were additional failure modes observed when machining with the T2 and T3 tool grades respectively. The coarse grain size and high cobalt content contributed to the very poor performance of the multicoated T2 grade insert, while the improved microhardness of the PVD-TiN coating gave the single layer coated T3 grade a comparable performance with the multicoated T1 grade. Attrition wear was the principal wear mechanism at lower speed conditions, while dissolution/diffusion and abrasion were additional wear mechanisms when machining at higher speed conditions. A higher degree of diffusion wear occurred on the T3 grade insert owing to the relatively lower level of cubic carbides in the tool composition.