Characterization and process evaluation of Ni–Ti–Fe shape memory alloy macro-spheres directly fabricated via rotating electrode process

Highlights: • Ni–Ti–Fe SMA balls were directly made via REP process with bimodal size distribution. • These microspheres were formed via liquid ligament breaking mechanism. • These macrospheres show chemical homogeneity and uniform mechanical properties. • EBSD results show randomized grain orientation ensuring uniform deformation behaviour. - Abstract: The present work demonstrates the manufacture of spherical millimeter sized macro-spheres of Ni–Ti–Fe shape memory alloy (SMA) for self-seizing bearing application through rotating electrode process (REP) through a set of optimized REP parameters and subsequent characterization. Image analysis has revealed that these macro-spheres follow a bimodal size distribution with larger mass fraction is about 1.5 mm and that of smaller mass fraction has a mean value of 0.4 mm. Differential scanning calorimetry (DSC) and compressive load–deformation behaviour confirm that both chemical and mechanical properties are consistent before and after REP. Microstructural characterization was carried out using high-resolution scanning electron microscope with electron backscattered diffraction (EBSD) technique. Process evaluation shows that there spheres form through the liquid ligament breakdown mechanism