Parametric study on the recast layer during EDWC of a Ni-rich NiTi shape memory alloy

Abstract

Shape memory alloys (SMAs) have exceptional properties, namely, shape memory effect, superelasticity and other enriched physical and mechanical properties. The conventional machining of these alloys is associated with several severe difficulties. Electric discharge wire cutting (EDWC), an advanced machining process, is utilized to machine Ni_50.89Ti_49.11 SMA under this investigation. The aim of this investigation was to reveal the effect of EDWC variable parameters such as pulse on time (T_ON), wire feed (WF) rate, spark gap voltage (SV), wire tension (WT) and pulse off time (T_OFF) on recast-layer thickness (RLT) and a foreign element atomic content (FEAC) using the one-factor-at-a-time approach. Scanning electron microscope equipped with energy dispersive X-ray spectroscopy facility was utilized to analyse RLT and FEAC. RLT and FEAC are varied linearly and nonlinearly respectively with T_ON, T_OFF and SV. A thick recast layer with a high percentage of FEAC was formed on the machined surface of Ni_50.89Ti_49.11 SMA at a higher T_ON and a lower T_OFF and SV. However, RLT and FEAC are slightly varied with WF and WT.