Investigation into surface quality of Inconel 625 processed with micro-electrochemical machining

Abstract

This article aims to investigate the effects of various process parameters, including electrolyte concentration, applied voltage, tool feed rate, and pulse frequency, on the average surface roughness (Ra) and roundness error (RE) during micro-electrochemical drilling of nickel-based superalloy (Inconel 625). The conducted experimentation has been performed on the in-house fabricated micro-electrochemical setup designed for performing various advanced machining operations at a miniature scale. The statistical results confirmed the accuracy and consistency of the developed mathematical models. The Ra and RE both are notably influenced by the considered input parameters, particularly applied potential difference and pulse frequency. The obtained minimum and maximum values of Ra were 0.458 µm and 1.241 µm, respectively, while the minimum and maximum values of RE were 36.484 µm and 102.794 µm, correspondingly. Furthermore, the microstructure of processed work surfaces was examined and evaluated with the field emission scanning electron microscope. The analysis revealed detailed insights into various surface integrity aspects such as the zones of stray current effect, developed micro pits, deposition of metal globules, intergranular attack, and formation of electrolytic products.