Investigation of Pulse Electrochemical Machining of Zr-Based Bulk Metallic Glasses in NaNO3-Ethylene Glycol Electrolyte

Abstract

Zr-based bulk metallic glasses (BMGs) have unique mechanical and chemical properties, which has attracted much attention from academia and industry. Electrochemical machining (ECM) is a non-contact subtractive method very suitable for these materials without grain boundaries. Nevertheless, past work on ECM of Zr-based BMGs indicated the infeasibility of the traditional non-acid water-based electrolytes. In this research, microsecond pulse ECM of Zr-based BMGs in the NaNO3-ethylene glycol (EG) electrolyte has been explored to overcome the difficulties in conventional salt water-based electrolytes. First, polarization behaviors of four kinds of Zr-based BMGs and related elementals in NaNO3-EG electrolyte were derived to examine the passive and transpassive performance. The dissolution mechanism of Zr-based BMGs according to the dwell time was investigated based on XPS analysis. The effects of the current density and pulse parameters were evaluated according to the surface quality, the groove profile, etc. The results show that pulse parameters have a great influence on stray corrosion, due to the high content of late transition metal components on the surface. Taking micro dimples as an example, the NaNO3-EG electrolyte exhibit ability of reducing the pitting corrosion and offering smooth surfaces with acceptable stray corrosion and high machining localization.