Fluoride-ion enhanced the electrochemical surface texturing of Ti6Al4V alloy via in situ EDM and ECM with patterned tool

This research paper presents an innovative approach to fabricating enhanced-quality hierarchical surface micro-textures on Ti6Al4V alloy by synergistically employing in situ electrical discharge machining (EDM) and electrochemical machining (ECM) processes. The hierarchical structure encompasses three levels: a primary level at a few hundred micrometers, a secondary level at a few tens of micrometers, and a ternary level at sub-micrometer scales. Despite the precision achieved in generating the primary-level texture through EDM using a chemically patterned tool, inherent thermal damages and surface defects, such as micro-craters and irregularities, pose challenges. Unlike usual ex situ chemical or electrochemical post-processing methods, this study introduces in situ ECM post-processing (ECM) with the same patterned tool. This approach enhances the quality of EDMed surfaces without compromising geometrical accuracy, offering anisotropic dissolution along the feature depth. To ensure geometrical accuracy, an experimentally validated finite element method-based transient numerical simulation model is developed. This model accurately predicts the evolution of the feature profile during the ECM operation. Furthermore, ECM with a fluoride ion–containing electrolyte introduces additional secondary and ternary levels of hierarchical textures. Fluoride ions play a pivotal role in augmenting material removal during ECM, particularly in areas around micro-crevices and pores, shaping the secondary-level texture.