Mechanism of electrical discharge and electrochemical hybrid sinking machining using water-in-oil nanoemulsion: processing phenomena and multiphysics simulation

Electrical discharge and electrochemical hybrid sinking machining (EDCSM) using a water-in-oil (W/O) nanoemulsion demonstrates high-quality machined surface and good machining accuracy. However, the specific machining mechanism of this technology remains unclear, lacking direct observational comparisons between machining phenomena and the multiphysics simulation model. To investigate the machining mechanism of EDCSM using a W/O nanoemulsion, this study employs experimental methods, multiphysics simulations, and high-speed imaging techniques to compare machining processes across different media. This study elucidates the advantages of the W/O nanoemulsion as a machining medium in electrical discharge machining and electrochemical machining (ECM) processes compared to kerosene medium and electrolytes, along with the synergistic mechanism of EDCSM. The results demonstrate that the W/O nanoemulsion exhibits significant advantages, revealing its dual characteristics of alternating discharge effects and electrolytic dissolution at the microscopic scale. High-speed imaging data reveal that discharge channels in the W/O nanoemulsion medium exhibit finer structures, shorter durations, and higher electrochemical localization. Microbubbles generated during discharge play a crucial role in regulating energy release within the localized reaction zone and facilitating the removal of molten products. Combined with multiphysics simulation results, this confirms the presence of larger discharge craters, fewer recast layers, and highly localized electrochemical machining phenomena, consistent with experimental observations.