Multi-objective optimization and life cycle assessment of eco-friendly cryogenic N2 assisted turning of Ti-6Al-4V

Modern manufacturing industries thrive for energy efficient, clean and sustainable machining processes. However, achieving these objectives becomes difficult especially in machining Ti-6Al-4V as it retains its properties at high temperature. Cryogenic liquid nitrogen (LN2) is a clean machining environment that has potential to improve the machinability performance for Ti-6Al-4V. LN2 promotes sustainability and facilitates low carbon emission. Orientation and number of employed LN2 jets influence the cutting energy, quality and productivity. Moreover, a balance between energy consumption and quality productivity is required for sustainable production. In this respect, this research work studies the cutting force, specific energy, temperature, surface quality (i.e. surface roughness), and material removal rate under the impingement of LN2 as mono-jet and dual-jets. This study has three parts: evaluation of the role of factors on the output parameters, optimization of parameters, and lastly the life cycle assessment (LCA) of cryogenic LN2 assisted machining. Owing to irreconcilable nature of single-objective optimization, multi-response optimization was conducted using Grey-Taguchi integrated approach. It was found that LN2 dual jets were most effective in reducing the specific energy consumption and temperature, and improving surface quality. This can be attributed to the faster and effective heat removal by LN2 from the critical interfaces. Other optimum parameters were cutting speed of 140 m/min and feed rate of 0.16 mm/rev. It was found that LCA showed that there is a clear relation between cooling strategy and environmental aspects such as resources, energy, human health, and biodiversity, etc. that directly affects the machining performance of Ti-6Al-4V alloy. (C) 2018 Elsevier Ltd. All rights reserved.