The exceptional oxidation of Ti6Al4V alloy with a pre-deposited silver layer

Abstract

For the first time, we discovered the exceptional oxidation phenomenon on Ti6Al4V alloy. A thin layer of silver was pre-deposited via PVD on a Ti6Al4V alloy surface before ceramic conversion treatment (CCT) based on thermal oxidation in air at 620 °C. The pre-deposited silver particles accelerated the oxidation of the Ti6Al4V alloy by up to 50 times, and also helped to produce a thick compact surface oxide layer with a larger surface area compared to a non-silver pre-treated surface. However, silver had a less profound effect on the oxidation of other titanium alloys that didn’t contain vanadium, additionally the silver particles tended to agglomerate on their surfaces, particularly for commercially pure titanium (CPTi). Systematic work examining the impact of vanadium found that vanadium together with silver played a critical role in activating oxygen and promoting its diffusion in the oxide layer, thus dramatically accelerating the oxidation of the vanadium-containing titanium alloys with a pre-deposited Ag layer in CCT. SEM/EDX, TEM, XRD and XPS analyses on the surface phase constituents and microstructure helped to explicate the rapid oxidation mechanism of pre-deposited silver on Ti6Al4V surfaces, and thus provide a new insight into modifying the titanium alloys surface efficiently.