Tribological behavior of NiTi alloy in martensitic and austenitic states

The wear behavior of Ti–50.3 at% Ni alloy in martensitic and austenitic states was studied. The alloy was prepared in a Vacuum Induction Melting furnace, forged at 800 °C, annealed at 1000 °C for 12 h, quenched in water, then aged at 400 °C for 1 h and followed by water quenching. The phase transformation temperatures were measured by differential scanning calorimetry. The shape memory and pseudoelasticity properties of NiTi were obtained by three-point bending test. The highest deflection recovery due to the pseudoelasticity was observed at temperature of 50 °C. The wear tests were conducted using a pin-on-disk tribometer in a water media at temperatures ranging from 0 °C to 50 °C. The results showed that the wear rate of NiTi alloy was decreased as the wear testing temperature increased. This was mainly attributed to the pseudoelasticity effect and higher strength of the alloy in the austenitic state at temperature of 50 °C. The results also showed a lower coefficient of friction in the austenitic state compared to the martensitic state.