Surface Preparation of Nickel-Based Superalloy Using Electropolishing

In this study, the surface preparation of a Ni-based superalloy was performed via electropolishing using a mixed H₃PO₄-H₂SO₄ electrolyte. The effects of polishing voltage on the phase structure, surface morphology, elemental composition, and surface roughness were investigated. X-ray diffraction (XRD) analysis showed no formation of new phases and no change in the crystal structure after polishing. EDS analysis of specimen at 10 V showed a relative enrichment of Al, Cr, and Ti at the polished surface. SEM observations showed improved surface uniformity as the voltage increased from 6 V to 10 V, whereas further increasing the voltage to 12 V resulted in surface deterioration. The surface roughness (Ra) decreased from an initial Ra of 2.31 ± 0.08 µm to a minimum of 1.08 ± 0.05 µm at the voltage of 10 V. The numerical simulation results of the maximum polishing depth at different applied voltages provide supporting evidence for the voltage-dependent material-removal behavior and demonstrate the effect of applied voltage on material removal during electropolishing.