Evaluation of tool wear and surface roughness in high-speed dry turning of Incoloy 800

Machining of Incoloy 800 is challenging, which can be attributed to the low thermal conductivity, hot strength, accord for insert material and propensity to work harder. This study evaluates the influence of carbide tool-insert wear (rake, flank) and surface roughness (R-a) under process variables (cutting speed, feed rate and depth of cut) in high-speed dry turning of Incoloy 800. The essence of chip formation in Incoloy 800 in the context of coolant-less turning operation was also investigated. The turning experiments were performed in relation to Taguchi's experimental design, with three factors with three levels: cutting speed (175, 200 and 225 m/min), feed rate (0.15, 0.2 and 0.25 mm/rev) and depth of cut (0.6, 0.8 and 1 mm). The experimental observations confirm that abrasion, adhesion and diffusion are the prime tool wear mechanisms responsible for tool failure. The formation of built-up edge (BUE) during the turning process was predominant, and excess BUE was observed at higher cutting parameters. The crater formation was found to be more severe at higher cutting conditions. The cutting speed has a firm hold on tool wear and surface roughness. The variation of surface roughness showed almost a cyclic trend and was found to decrease with an increase in the nose radius.