Effect of different electrolytes on electrochemical micro-machining of SS 316L

Abstract

The use of stainless steel 316L (SS 316L) in the medical, marine, aerospace, bio-medical, and automobile sectors increases rapidly. Electrochemical micro-machining (ECMM) is the appropriate method for machining SS 316L due to its burr-free machining surface, no residual stress, and high precision. However, some limitations are found in using strong electrolytes, such as HCl, H2SO4, KOH, NaNO3, and NaCl, which reportedly face difficulties in disposing to the environment and handling issues. Hence, this paper addresses overcoming the disadvantages encountered in the ECMM process when using strong electrolytes to machine SS 316L. Therefore, different organic electrolytes such as tartaric acid (C4H6O6), citric acid (C6H8O7), and a combination of tartaric and citric acid (mixed electrolyte) are considered to select the best electrolyte. Process parameters like machining voltage, duty cycle, and electrolyte concentration are included in determining machining performance. The performance of ECMM is evaluated using material removal rate (MRR) and overcut. The overcut of tartaric acid electrolyte is 179% less than mixed electrolyte for the parameter combination of 12 g/l, 11 V, and 85%. On the other hand, the mixed electrolyte shows 114.2% higher MRR than the tartaric acid electrolyte for the parameter solutions of 25%, 11 V, and 20 g/l. Furthermore, the citric acid electrolyte shows the second-lowest overcut and higher MRR in all aspects of machining performance. Field emission scanning electron microscope (FESEM) studies are carried out to realize the effect of electrolytes on the machining surface.