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

Abstract

The use of stainless steel 316L (SS 316L) in industries such as medical, marine, aerospace, bio-medical, and automobile sectors is increasing rapidly. Electrochemical micro-machining (ECMM) is the apt method for machining SS 316L due to its burr-free machining surface, no residual stress, and high precision. However, there are some limitations found in the usage of strong electrolytes such as HCl, H2SO4, KOH, NaNO3, and NaCl, which are reportedly facing difficulties in disposing it to the environment and handling issues. Hence, this paper addresses to overcome the disadvantages faced in ECMM process when using strong electrolytes to machine SS 316L, so therefore different organic electrolytes such as tartaric acid (C4H6O6), citric acid (C6H8O7), and a combination of tartaric and citric acid electrolyte (mixed electrolyte) are considered to select the best electrolyte. Process parameters like machining voltage, duty cycle, and electrolyte concentration are included in determining the performance of machining. The performance of ECMM is evaluated using material removal rate (MRR) and overcut. The overcut of tartaric acid electrolyte is found to be 179% less than mixed electrolyte for the parameter combination of 12 g/l, 11 V, and 85%. 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 realise the effect of electrolyte on the machining surface.