Perspective: revisiting surface roughness in electrochemical machining and the paradoxes

Abstract

Electrochemical machining (ECM) represents a prominent electrochemistry-driven technique for surface flattening, post-processing, and (ultra-)precision machining, attracting considerable research interests recently. The method exhibits advantages in the machining of hard-to-machine nickel (Ni) superalloys, particularly those created via additive manufacturing approaches such as laser powder bed fusion (LPBF), in which enhanced microstructural features and mechanical properties are achieved with compromised surface quality. This study explores the intricate relationship between Ni alloy-specific microstructures, such as carbide precipitates, and the principles of electrochemistry integral to ECM. It further emphasizes the emerging requirement to re-examine the surface quality outcomes of ECM. We present a concise overview of the inherent paradoxes in ECM, encompassing the prediction of surface roughness range, the quantification of charge transfer coefficients, the efficiency of material removal, and the temporal dependence of the ECM process. These paradoxes necessitate systematic experimental and theoretical research to advance our understanding, and we wish to welcome, stimulate, and urge more raised awareness and attention to this matter about ECM surface quality control and prediction.