Experimental investigation into machinability of hardened AISI D6 steel using newly developed AlTiSiN coated carbide tools under sustainable finish dry hard turning

Abstract

In the present study, a newly developed AlTiSiN coating material deposited on carbide insert by scalable pulsed power plasma (SPPP) technique is used for machinability investigation of hardened AISI D6 die steel (65HRC) in finish dry turning. Also, the cutting tool is characterized by various diagnostic tests to evaluate the effectiveness of nanocomposite AlTISiN coating material and its cutting performance. A series of machining trials have been performed under varied cutting conditions (feed, depth of cut, speed) to investigate the machinability concerning surface roughness, flank wear, and chip morphology. Further, an approach towards multi-response optimization and predictive modelling for minimization of flank wear and surface roughness have been performed using response surface methodology. Finally, a unique approach has been proposed for economic analysis and sustainability assessment in hard turning. Result shows that the nanostructured AlTiSiN coating developed lower range of tool wear (VB = 0.044–0.076 mm), produced surface finish (Ra) within 0.322–0.905 µm which is approaching the surface quality to that of cylindrical grinding because of minimum friction coefficient, good bonding capability and enhancement in hardness as well as wear resistance of coating material. Statistical analysis reveals that Ra and VB are influenced principally by feed (84.14%) and cutting speed (53.43%), respectively. With the tool life of 34 min, Gilbert's machining economic model calculated the overall machining cost per part of Rs.61.04 in hard turning using coated carbide insert. Chip morphology confirmed the formation of serrated type saw tooth chips. It is established that machining under dry condition provides environment friendliness, techno-economically feasible to improve sustainability.