Minimum Quantity Lubrication Using Nano-Graphite Cutting Fluids for Sustainable Machining of AISI 4140 under Different Cutting Conditions

Traditionally, cutting fluids are applied in large quantities to reduce the cutting forces and temperatures in machining. However, in view of environmental and occupational health concerns with the conventional cutting fluids, industries are moving towards minimum quantity lubrication (MQL). MQL application is environment-friendly, provides good working conditions to employees, and is economical and hence sustainable. The present work studies the effect of MQL that utilizes cutting fluid with nano-graphite particles during the turning of AISI 4140 at varying ranges of cutting velocity, feed, and depth of cut. Taguchi's design of experiments was used to limit the number of experiments. Cutting forces and surface roughness were measured and the performance of the formulated nano-graphite cutting fluid was compared to dry machining, flood lubrication, and MQL application of the conventional cutting fluid (without nanoparticles) at the considered range of cutting parameters. It was noticed that MQL with nanofluids offers a superior machining performance compared to other considered methods of lubrication. The optimum levels of the cutting parameters were determined using Taguchi analysis for all the lubricating conditions. Confirmation tests were carried out at the optimal conditions to establish the dependence of machining performance on lubricating methods.