MACHINABILITY INVESTIGATION OF CRYOGENICALLY TREATED HARDENED AISI 4140 ALLOY STEEL USING CBN INSERT UNDER SUSTAINABLE FINISH DRY HARD TURNING

Abstract

Cryogenic treatments have been applied to enhance both wear and abrasion resistance for the cutting inserts. Therefore, many investigations focused on the shallow and deep cryogenic treatments in terms of their performance on the machinability criteria. This paper presents a detailed analysis on machinability investigation of cryogenically treated hardened 4140 steel (55 HRC), and sustainability assessment in hard machining on finishing mode carried out at dry cutting regime. A series of machining trials have been performed under varied cutting conditions (feed, depth of cut and speed) following the L-9 orthogonal array design experimental layout for analysis of various responses along with cost estimation in hard turning. Moreover, the machining parameters are optimized and mathematically formulated for the minimization of various responses using a multiobjective optimization method. Finally, considering the motivational idea of Go green-Think green-Act green, a unique novel approach has been proposed concerning economic evaluation and sustainability assessment in hard turning for safer and cleaner approach of environment friendly manufacturing. According to statistical analysis, feed influenced both surface roughness and cutting force significantly. Because of cryogenic treatment both surface roughness and cutting force diminished. It is noticed that with high speed, low feed, and depth of cut both force and roughness value declined. The tool life of CBN was 44 min and considering the same, Gilbert's machining economic model calculated the overall machining cost per part of square 80.86 in the machining of hardened AISI 4140 steel. The outcomes clearly established that machining under dry conditions provides environment friendliness, technologically viable, and economically feasible to improve sustainability.