Sustainable Dry Turning of Inconel 625: Taguchi–GRA With Pareto/Knee Analysis and NSGA II Validation of Energy, Tool Life, Surface Quality, and Productivity Trade Offs

Abstract

Sustainable dry turning necessitates the reduction of energy intensity while maintaining production and quality. This research examines Inconel 625 under dry settings employing a Taguchi L9(3³) design (speed S, feed f, depth d) and a framework that integrates specific energy consumption (SEC) with tool life estimation, surface roughness, and material removal rate (MRR). The cutting power is calculated using the measured main cutting force Fc and kinematics; only Fc was documented, which represents the primary factor in cutting power during turning. Tool wear was quantified for each edge and converted into the expected tool life T_pred at VB* = 221 μm. Grey Relational Analysis (Set A: SEC↓, Ra↓, T_pred↑, MRR↑) yields a scalar ranking, whereas a continuous Pareto frontier in the (MRR, SEC) plane is established by sampling quadratic response surfaces throughout a dense grid and validated by Non-dominated Sorting Genetic Algorithm (NSGA II/ε constraint). The knee point is determined via the Kneedle method, which identifies the maximum distance. Results indicate: (i) feed predominantly influences Ra and tool life stress, whereas depth is the primary factor for MRR and SEC; (ii) the optimal GRA (s=50 m/min, f=0.08 mm/rev, d=1.0 mm) is situated near, yet within, the frontier; (iii) the unconstrained knee at MRR≈4.75 cm³/min and SEC≈0.002613 kWh/cm³ presents a well-balanced compromise. The integrated Taguchi–GRA–Pareto/knee methodology produces practical, energy-conscious parameter configurations for sustainable dry machining of Inconel 625.