Experimental investigation of surfactant-mixed electrolyte into electrochemical discharge machining (ECDM) process

Abstract

Using electrochemical discharge machining (ECDM), is the most appropriate method to create microchannels on glass pieces by applying chemical and thermal phenomena simultaneously. Several parameters affect the quality of microchannels. Thickness of gas film surrounded the tool-electrode is one of the most effective parameters, which thinner gas film would result in higher machining quality. In this study, according to the theoretical analysis of the single gas bubble formed at the tool electrode surface, it has been found that the wettability of tool electrode and surface tension between the bubble and electrolyte affect the gas film thickness. In the experiments, two most widely used surfactants which are anionic surfactant Sodium dodecyl sulfate (SDS) and cationic surfactant Cetyltrimethylammonium bromide (CTAB) in various concentrations, were dissolved in the 25wt% KOH and NaOH alkaline solutions in order to reduce the gas film thickness by affecting the physicochemical properties of the electrolyte and the wettability of the electrode. The results obtained from the experiments indicated that in the presence of surfactant microchannels with higher material removal rate (MRR), lower overcut and heat affected zone (HAZ) were fabricated. Also, due to decrement of thermal conductivity and increment of viscosity of the electrolyte in the presence of surfactant, the surface quality of microchannels were improved. For example, at a voltage of 35V and presence of 0.036wt% CTAB in KOH, the surface quality improved 73% and the hardness of channel edge enhanced 144%. Increase in hardness of channel edge, indicates that the HAZ is reduced. Among different concentrations of surfactants, the critical micelle concentration (CMC) has the most influence on the machining performance. Since the cationic surfactant CTAB has lower CMC and also enhances the chemical etching by presenting more OH radicals on the glass, it has more influences on the process outputs compared to the anionic surfactant SDS.