Tribological Behavior of Heat Treated Ni-rich NiTi Alloys

Effects of heat treatments and applied loads on the tribological behavior of Ti-56.5 wt. % Ni and Ti-57.5 wt. % Ni alloys were investigated. Wear tests were performed on a pin-on-disk tribometer under normal loads of 20 N and 60 N at a sliding speed of 0.3 m/s. The results indicated that the alloys aged at 700 °C showed lower hardness comparing to the alloys aged at 400 °C. Under an applied load of 20 N, the samples aged at 700 °C showed better wear behavior in comparison with the samples aged at 400 °C with a higher hardness. This could be attributed to higher toughness of the samples aged at 700 °C. The results also showed that the wear of the samples aged at 400 °C decreased with the increase in normal load. However, there was an increase in the wear of the samples aged at 700 °C with the increase of load. Formation and stability of tribological layers on the contacting surfaces could be the main reason for the reduction of the wear of the samples aged at 400 °C with the increase in normal load.