Enhanced wear resistance of NiTi alloy by surface modification with Nb ion implantation

Niobium ion implantation is found to significantly decrease the friction coefficient and improve wear resistance of NiTi shape memory alloy. Scanning electron microscope (SEM) observations indicate that surface grooves formed on NiTi during the mechanical polishing are removed after Nb ion implantation. Dry friction tests show that Nb implanted NiTi samples exhibit a lower friction coefficient, narrower wear tracks, fewer wear debris generated, 46 %–62 % reduction in wear width, and 29 %–49 % reduction in wear depth compared with the untreated NiTi. Wear resistance is related to the incident parameters, and the Nb implanted NiTi with the incident dose of 2.5 × 10¹⁷ ions·cm⁻², and incident current of 2 mA behaves the best wear performance. The lubricating of Nb₂O₅, good oxidation resistance of Nb in NiTi, and increased micro-hardness of NiTi are responsible for the enhanced wear resistance.