Ecological, economical and technological perspectives based sustainability assessment in hybrid-cooling assisted machining of Ti-6Al-4 V alloy

Abstract

Ti-6Al-4 V alloy is a well-acknowledged standard material for the application of modern aerospace, surgical equipment, and prosthetic body parts owing to its stable thermo-physical properties at elevated temperature. However, this structure stability imparts its low thermal conductivity that leads to buildup of heat at tool-workpiece interface during machining which subsequently has a damaging effect on the tool cutting edge. Several biodegradable cutting fluids have already been attempted controlling the heat generation, environmental footprints to improve the overall machinability. In this endeavor, the effectiveness of dry, liquid nitrogen (LN2) and hybrid cryogenic and minimum quantity lubrication (LN2 + MQL) conditions was evaluated in terms of important machinability indicators for instance surface roughness, cutting forces and temperature. The environmental parameters such as total cycle time, productivity, economic analysis, energy consumption and carbon emissions were also analyzed under these cooling conditions. Lastly, the sustainability assessment of process parameters was calculated with the help of the Analytic Hierarchy Process (AHP) coupled with the Technique for Order Preference Based on Similarity to Ideal Solution (TOPSIS) techniques. Findings have exhibited superior cooling/lubrication effect under LN2 + MQL conditions lowering the machining as well as environmental indices. The improvement in cycle time and productivity of LN2 and LN2 + MQL was appeared to be 29.01% and 34.21% as compared with dry turning. The sustainability assessment results also revealed that the lower cutting parameters under LN2 + MQL produced best results to achieve the overall sustainability index.