Review-Electrochemical Discharge Machining: Gas Film Electrochemical Aspects, Stability Parameters, and Research Work

Electrochemical discharge machining (ECDM) utilizes the principle of thermal melting and chemical dissolution for machining "non-conductive" materials like ceramics, glass, silicon wafers. These materials exhibit colossal applications in the fields of MEMS and lab-on-chips. Since its first demonstration, different aspects of the ECDM process have been studied for improving its efficiency. However, only a few numbers of studies were delineated to comprehend the mechanism of gas film and effective parameters for its stability concerning the machining repeatability. This paper comprehensively reviews the gas film mechanism concentrating on bubble formation, bubble adherence, bubble amalgamation, departure and breakdown behavior. The parameters for controlling the gas film stability such as voltage, current, gas film formation time, gas film thickness, surface tension, viscosity, surface topography, magnetic field, tool electrode's motions and material, are also likewise discussed. Moreover, research findings on ECDM performance based on discrete input parameters is also covered and presented. It was concluded that stabilized gas film significantly influences machining efficacy and can be achieved effectively by controlling the electrolyte's electrochemical properties, tool electrode shape and motions. Further, the paper underlines the future possibilities that may have the potential to enhance the ECDM performance.