Mechanical and wear properties of CoNiAlSiSb and CoNiAlSiIn ferromagnetic shape memory alloys: an experimental assessment

Abstract

CoNiAl based ferromagnetic shape memory alloys (FSMAs) are used in various engineering fields, but still need to be improved for tribological applications. In the present study, dry sliding wear behavior of CoNiAlSiSb and CoNiAlSiIn FSMAs was investigated as they were articulated against an alumina abrasive ball using a ball-on-disk tribometer. The experiments were carried out at a load of 20 N, a sliding velocity of 20 mm/s and a sliding distance of 250 m. The worn surfaces were assessed using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The mechanical properties of the CoNiAl based FSMAs were investigated using the nanoindentation technique. The results showed that as compared to CoNiAlSiSb, CoNiAlSiIn FSMA showed a 42% increase in the Young’s modulus and a 10% increase in the microhardness. The mean coefficient of friction (COF) of CoNiAlSiIn (0.56) was observed to be slightly lower than that of CoNiAlSiSb (0.58). The higher hardness and elastic modulus of CoNiAlSiIn than CoNiAlSiIn caused only a 7% increase in the wear resistance. The operative wear mechanisms were abrasion, adhesion and plastic deformation. In conclusion, even though the difference in the tribological performance of the two FSMA surfaces was fairly small, CoNiAlSiIn exhibited better results and thereby would be more preferable.