Structure and tribological performance by nitrogen and oxygen plasma based ion implantation on Ti6Al4V alloy

Ti6Al4V alloy was implanted with nitrogen-oxygen mixture by using plasma based ion implantation (PBII) at pulsed voltage −10, −30 and −50 kV. The implantation was up to 6 × 10¹⁷ ions/cm² fluence. The changes in chemical composition, structure and hardness of the modified surfaces were studied by XPS and nanoindentation measurements. According to XPS, it was found that the modified layer was predominantly TiO₂, but contained small amounts of TiO, Ti₂O₃, TiN and Al₂O₃ between the outmost layer and metallic substrate. Surface hardness and wear resistance of the samples increased significantly after PBII treatment, the wear rate of the sample implanted N₂-O₂ mixture at −50 kV decreased eight times than the untreated one. The sample implanted N₂-O₂ mixture showed better wear resistance than that of the sample only implanted oxygen at − 50 kV. The wear mechanism of untreated sample was abrasive-dominated and adhesive, and the wear scar of the sample implanted at −50 kV was characterized by abrasive wear-type ploughing.