Multi criteria decision making based optimization for sustainable machining in alloy 2091

This work aims to evaluate the impact of liquid nitrogen (LN₂) aided cryogenic machining on alloy 2091's surface integrity (SI) characteristics. LN₂ aided conditions are used for face milling with CVD inserts, and the results are compared with traditional (dry) milling. The majority of the SI's key characteristics, including roughness, microhardness, microstructure, residual stresses, and corrosion resistance, have been researched. ANOVA and signal to noise ratio plots are two statistical methods that have been used to determine how SI characteristics behave in relation to milling parameters. Furthermore, MCDM techniques like COPRAS and TOPSIS were used to establish the ideal milling settings. The machining temperature was lowered by up to 30% when LN₂ was used. The outcomes demonstrated the benefits of cryogenic milling for a notable rise in the SI. Cryogenic machining increased microhardness by up to 14% and decreased roughness by up to 29% when compared to dry machining. Because of the decreased machining temperature, the cryogenic state resulted in compressive residual stress on the alloy's surface. The findings demonstrate that under all circumstances, neither the integrity of the grain nor the alloy microstructure are harmed. Both setups using MCDM approaches yielded the same outcome in identifying the optimal condition.