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

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.