Mechanical properties and structure of Ti-6A1-4V alloy implanted with different light ions

The effect of N⁺ and C^- implantation on the properties of Ti-6Al-4V alloy is widely documented. However, some authors claim that other light ions, such as O⁺ or B⁺, also have an effect on this alloy, improving its mechanical properties. In this work, Ti-6Al-4V alloy samples have been implanted with C⁺, N⁺ and O⁺ light ions. Energies from 50 to 180 keV and doses of the order of 10¹⁷ ion cm^-2 have been used, keeping the substrate temperature below 500°C. Mechanical properties such as the hardness or elastic recovery have been evaluated by means of microindentation tests, with a loading-unloading cycle at loads up to 10 mN. An increase in surface hardness of more than 100% has been observed in most of the implanted samples. Pin-on-disc wear tests under lubricated conditions have been performed to evaluate and compare the tribological behaviour of implanted samples against ultrahigh molecular weight polyethylene. A decrease in the friction coefficient from 0.1 to 0.05, resulting from ion implantation, has been observed. Unlubricated wear tests using an alumina ball on a Ti-6Al-4V disc have also been carried out. Wear tracks on the Ti-6Al-4V, evaluated by means of optical profilometry and scanning electron microscopy, have shown that implantation can improve the abrasive wear resistance by two orders of magnitude. X-ray photoelectron spectroscopy analyses also were carried out on selected samples, showing the presence of hard phases, such as oxides or carbides, in the implanted samples.