Investigation into WECM of nitinol SMA using ozonated NaNO 3 electrolyte

Abstract

Wire electrochemical machining (WECM) was developed to address micromachining issues as a result of technological improvement. Ozone (O₃) is enhanced to increase its oxidizing capability, corrosive behavior, and overall machining performance in basic aqueous neutral electrolytes. In order to improve machining performance, this article elaborates on the effect of ozonated aqueous solution of NaNO₃ in the WECM for nitinol shape memory alloy (SMA). The superiority of machined microgrooves is tested for surface topography, dimensional accuracy, and homogeneity. The experiments were conducted using a 1 mm thick nitinol specimen and 50 µm smooth cylindrical tungsten wire as an electrode. Output responses were measured, and fabricated microgroove parameters were cautiously examined under an optical microscope and coherent correlation interferometer (CCI) profilometer for their dimensions, that is average width mean depth and surface roughness (Ra), and graphs were plotted to understand the effect of ozonated NaNO₃ electrolyte with different electrolyte concentration and pulse voltages in comparison to non-ozonated NaNO₃ electrolyte. The minimum average Ra of 0.1542 µm has been obtained using 0.2 M NaNO₃ ozonated electrolyte at 5V pulse voltage compared to Ra of 0.3857 µm using non-ozonated electrolyte. It shows more than 60% improvement in the surface quality of nitinol using 0.2 M NaNO₃ ozonated electrolyte. Further, the width overcut has been reduced to a great extent with an improvement of groove depth by more than 50% using ozonated electrolytes compared to non-ozonated NaNO₃ electrolytes showing expeditiously removal of sludge and dissolved products and increased efficacy of dissolution than non-ozonated electrolytes. Also, the homogeneous microslit of 124 µm average slit width has been successfully fabricated using the ozonated electrolyte.