Machinability behaviour of Inconel 718 alloy using nano lubrication: Process optimisation and effects of nano-cutting fluid

The machining of nickel-based superalloys presents significant challenges including excessive heat generation, rapid tool degradation, and compromised surface quality, making it one of the most demanding operations in sustainable advanced manufacturing. Conventional mineral based cutting fluids remain widely used to manage heat and tool wear during machining, but their toxicity and poor biodegradability continue to pose environmental and occupational health risks. To address this, the present study formulated a biodegradable nano-cutting fluid using non-edible Croton megalocarpus seed oil as the base, reinforced with 0.5 wt% graphene nanoparticles, and evaluated its performance during the turning of Inconel 718. To examine how cutting speed, feed rate, and depth of cut affect cutting temperature and surface roughness, a Box-Behnken experimental design was employed. The newly formulated nano-cutting fluid was evaluated against Croton megalocarpus base oil as a reference. With the addition of graphene nanoparticles, the cutting fluid achieved up to 23% reduction in cutting temperature and 9.4% improvement in surface roughness. These findings suggest that graphene-reinforced Croton megalocarpus oil offers a viable, environmentally sustainable alternative to conventional mineral-based fluids for machining difficult-to-cut superalloys.