Microstructural Analysis and Multiresponse Optimization During ECM of Inconel 825 Using Hybrid Approach

In the current study, electrochemical machining of Inconel 825, a Ni-based super alloy, was carried out using tungsten as a tool electrode material and NaCl as electrolyte. The present investigation attaches particular emphasis on explaining the mechanism of material removal of Ni-based super alloys in the ECM process. The influence of various ECM parameters such as voltage (V), concentration (C), and tool feed (F) has been investigated on the evolution of the surface morphology of Inconel 825 after ECM. Different performance measures in ECM such as material removal rate (MRR), surface roughness (SR), and radial overcut (ROC) have been measured. Grey relational analysis that uses grey relational grade as performance index has been adopted to simultaneously optimize multiple performance characteristics and determine optimal combination of ECM parameters. Moreover, principal component analysis is utilized to determine the weighting values corresponding to various output responses so that their relative importance can be adequately expressed. Optimal condition was found to be V = 16 V, C = 45 g/L, and F = 0.3 mm/min. Confirmation test was further performed to authenticate the approach applied for determining the optimal conditions that resulted in MRR of 20.867 mm³/min, SR of 0.156 µm, and ROC of 0.0697 mm, which were superior to those corresponding to all previous experimental runs.