Wire Electric Discharge Machining Induced Surface Integrity for Ni 55.95 Ti 44.05 Shape Memory Alloy

The current study unveils the variation of surface integrity aspects (micro-hardness, surface crack density, and surface characteristics) for Ni_55.95Ti_44.05 shape memory alloy (SMA) with wire electric discharge machining (WEDM) process parameters, namely, pulse off time, wire tension, spark gap voltage, wire feed rate and pulse on time. The experimental results reveal that micro-hardness displays direct relationship with spark gap voltage, pulse on time, and pulse off time whereas surface crack density shows direct relationship with pulse on time and inverse trend with spark gap voltage and pulse off time. Wire tension and wire feed rate show trivial effect on both surface crack density and micro-hardness. Machined surface comprises crater, micro-cracks, micro-voids, pockmarks, and lumps of debris while inspecting through a scanning electron microscope (SEM). During energy-dispersive X-ray spectroscopy (EDS) analysis, the foreign elements namely carbon, oxygen, copper and zinc were also detected on the surface. The high energy density at higher pulse on time adversely affects the surface morphology. The formation of large size craters (deep and wide) with more cracks on the machined surface were observed at lower pulse off time as compared to higher pulse off time.