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

Abstract

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 10 17 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.