Multi-objective parametric optimization of electrochemical machining of Inconel-625 superalloy

The high hardness value of Inconel-625 super alloy makes it difficult to machine with traditional machining methods. In this study, the machining of Inconel-625 has been attempted with electrochemical machining. The influence of input process parameters—voltage, feed rate, and flow rate of electrolyte has been studied on the output responses—material removal rate (MRR) and average surface roughness (SR). The experiments were performed following the central composite rotatable design of the response surface methodology. Analysis of variance has been used to test the significance of the process parameters and the model. A comprehensive empirical model representing the relationship between the process parameters and the response parameters has been developed. Further, the desirability function approach was used to acquire the optimal set of parameters. The optimal values of MRR and SR obtained in the study are 0.192837 gm./min and 0.99 μm, respectively, corresponding to the optimum settings of voltage, feed rate of the tool, and flow rate of electrolyte at 13.7 V, 0.20 mm/min, and 2.8 lit/min, respectively. The optimum settings so attained have been substantiated using confirmation experiments. The Confirmation tests show that the error between predicted and experimental values of MRR and SR was 2.02% and 4.8%, respectively, which fall in the acceptable range. Moreover, the surface characteristics of the machined area have been investigated using field emission scanning electron microscopy and 3D optical profilometer to analyze the machined surface's microstructure and 3D surface characteristics.