Investigation of Molten Salts as Advanced Electrolytes for Use in Electrochemical Machining

This Phase I project proposes an investigation involving molten salt systems as novel electrolytes for use in electrochemical machining (ECM). As the air-breathing propulsion materials (such as titanium and nickel aluminides) used in Navy aircraft jet engines are becoming harder and more brittle, they are more difficult to machine using conventional methods. ECM is believed to be a feasible method to solve these problems since it is a relatively nontraditional fabrication technique based on controlled removal of material by electrochemical dissolution of the work piece. In ECM, the metal removal rate is independent of the relative hardness of the part of the tool. Electrolytes currently in use include aqueous solutions of salts or strong alkali hydroxides which have a number of disadvantages, such as, low conductivities, corrosion, gassing, and bubbling problems. In this work, it is proposed to apply molten salts, e.g., mixed alkali hydroxide melts, as advanced electrolytes for ECM systems so as to improve their functionalities in coping with the ever-increasing use of new super alloys. Feasible molten salt systems and their physical and electrochemical properties will be identified and compared. The novel ECM technique will be demonstrated using selected electrolytes on a specified aircraft gas turbine material.