Structure and tribological performance of modified layer on Ti6Al4V alloy by plasma-based ion implantation with oxygen

Ti6Al4V alloy was implanted with oxygen by using plasma based ion implantation (PBII) at pulsed voltage ranging from −10 to −50 kV. In order to maintain a lower implantation temperature, an oil cooling working table was employed. The thicknesses of modified layer of samples implanted at −30 and −50 kV are about 117 and 182 nm, respectively. There is crystalline rutile phase in the modified layer of sample implanted at high implanted voltage, but this phase has not detected for sample implanted at low voltage. The hardness of the implanted layer increases with implanted voltage, and the increasing factor of peak hardness reaches 1.6-2.6. The hardening effect exists even at depths larger than the maximum reach of implanted oxygen, as seen by XPS data. In the initial stage of friction, implanted samples have a low friction coefficient comparing with untreated. Wear resistance increases with implanted voltage, and maximum increase from sample implanted at −50 kV reaches two times untreated one. The wear mechanism of implanted samples is abrasive-dominated and adhesive, furthermore the level of adhesive decreases with implanted voltage.