In Situ Analysis of the Effect of Ultrasonic Cavitation on Electrochemical Polishing of Additively Manufactured Metal Surfaces

Abstract

The effects of a hybrid process that combines ultrasonic cavitation and electrochemical polishing on the electrochemical behavior and the resulting surface characteristics of additively manufactured 316-L stainless steel were investigated. In situ potentiodynamic scans and electrochemical impedance spectroscopy (EIS) were conducted to gain a fundamental understanding of the effect of ultrasonic cavitation on the electrochemical processes involved, considering the influence of electrolyte temperature at 60 and 70 °C. The potentiodynamic scans revealed that increasing the ultrasonic excitation amplitude from 20 to 80 µm at 20 µm intervals and temperature from 60 to 70 °C led to reduced polishing resistance, and elevated passivation current density at equivalent applied potentials, thus leading to an increased polishing rate. These findings are attributed to intensified cavitation near the material surface, which promoted anodic dissolution reactions and accelerated the polishing rate. In situ EIS measurements provided valuable information on the charge transfer resistance and double-layer capacitance and their influence on the hybrid process. Specifically, higher ultrasonic amplitudes and elevated temperatures contributed to enhanced electrical double-layer formation and ion adsorption, resulting in a faster rate of polishing, indicating the efficacy of the hybrid process. These findings enhance our understanding of the complex interactions between ultrasonic cavitation and electrochemical dissolution processes that occur during ultrasonic cavitation-assisted electrochemical polishing. The research provides valuable insights for optimizing the process and its potential application in the post-processing of metal additive manufactured parts.