Electric field influence on the formation and evolution of vapor gas envelope in electrolytic plasma polishing

Electrolytic plasma polishing is an advanced technique for refining metal surfaces, particularly with intricate geometries, where the vapor-gas envelope (VGE) plays a crucial role in determining process efficiency and quality. Nonetheless, the nonlinear physics governing VGE dynamics, particularly the interactions between fluid dynamics, electrostrictive effects, and electric fields, remain inadequately explored. This research introduces a new mechanism for VGE evolution based on bubble deformation driven by nonlinear electric field interactions. A mathematical model derived from the Navier–Stokes equation, coupled with electrohydrodynamic forces, was developed to investigate VGE dynamics under varying voltage levels. Numerical simulations of electric field intensity, conductivity distribution, and pressure fields revealed the dominant role of electrostrictive forces in driving nanoscale vapor cavity deformation. The uneven electric forces generate mechanical stress, inducing nonlinear phenomena such as bubble contraction, coalescence, and expansion, further triggering nucleate boiling and film boiling. High-speed imaging of experiments using a linearly increasing voltage pulse validated the numerical results, showing how varying electric field strengths alter VGE formation, conductivity behavior, and temperature changes. At high field intensities (9 × 104 to 14 × 104 V/m), the balance between fluid dynamic pressure and electrostrictive forces stabilizes the VGE, forming negative pressure regions and enhanced bubble coalescence. Finally, the experimentally measured conductivity verifies the accuracy of the fluid model, and an empirical model of heat flow and temperature during the VGE process is established. The findings highlight the significance of electrostrictive forces in shaping VGE behavior and provide theoretical and practical insights for optimizing high-quality polishing processes.