Electrochemical Characterization and Micromachining of Nitinol SMA by WECM Using Citric Acid Mixed H2SO4 Electrolyte

Abstract

Nitinol shape memory alloy (SMA) is a tough material to machine because it is difficult to cut. The results of the current research work demonstrate how two different electrolytes affect the electrochemical behavior in relation to electrochemical machining performance of nitinol. Potentiodynamic polarisation (PDP) and electrochemical impedance spectroscopy (EIS) tests have been conducted using 0.1 M H2SO4 and mixed 0.1 M H2SO4 + 0.1 M citric acid electrolyte. Further, the experimental investigation on the machining characteristics of nitinol during wire electrochemical machining (WECM) has been conducted. It is revealed that the grooves width and depth increase with increase in applied pulse voltage and surface roughness increase with increase in groove depth. The minimum width overcut of machined groove was 18.10 μm in 0.1 M H2SO4 + 0.1 M citric acid at 5 V pulse voltage which is less compared to width overcut of 24.85 μm produced in 0.1 M H2SO4 electrolyte for same parametric machining condition. This specific mixed electrolyte produced average surface roughness (Ra) of 0.0631 μm at 5 V which is lower compared to 0.09055 μm produced using 0.1 M H2SO4 electrolyte. The fabrication of homogeneous average slit width of 92.234 μm using citric acid mixed H2SO4 electrolyte with minimum average surface roughness (Ra) of 0.0691 μm shows the capability of WECM.