Surface integrity aspects for NiTi shape memory alloys during wire electric discharge machining: A review

NiTi shape memory alloys (SMAs) are extensively used in various significant areas such as aerospace industries, biomedical sector, automobile industries, and robotics field because of their inherent properties, namely, shape memory effect and superelasticity. Nevertheless, the machining of these alloys is a problematic task by conventional machining practices because of various difficulties such as strain hardening, tool failure, high machining time, and poor surface quality. In recent years, researchers have explored various advanced/unconventional machining processes to surmount these challenges and improve the performance characteristics of NiTi SMAs. Wire electrical discharge machining (WEDM) is an effective and reasonable alternative to machine these hard-to-machine alloys among the other available advanced machining processes. A brief overview, characteristics, applications, and conventional machining of NiTi SMAs have been incorporated in this study. This review article provides substantial insight into the various aspects of surface integrity (SI) for NiTi SMAs using WEDM. The current study highlights literature review on the research work accomplished so far in the domain of SI aspects for NiTi-based SMAs, namely, surface characteristics, react layer, phase analysis, elemental composition, micro-hardness, shape recovery ability, and residual stress in WEDM.