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 cuttin
g speed and feed rate to tool performance to be in excess of 80 per cent, w
ith 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 addition
al failure modes observed when machining with the T2 and T3 tool grades res
pectively. The coarse grain size and high cobalt content contributed to the
very poor performance of the multicoated T2 grade insert, while the improv
ed microhardness of the PVD-TiN coating gave the single layer coated T3 gra
de a comparable performance with the multicoated T1 grade. Attrition wear w
as the principal wear mechanism at lower speed conditions. while dissolutio
n/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 th
e tool composition.