The tribological behaviors of various metallic cations in tapping of a titanium alloy

In this paper, various metallic cations, including Na+, K+, Ca2+ and Ba2+, were introduced into water-based lubricating additives. Their tribological behaviors were investigated by the tapping test of a Ti-6Al-4V alloy. Among them, Ba-containing compound showed the best lubricating performance. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the surface morphology and chemical states of elements, respectively. It was found that the worn surface consisted of multiple oxides, which implies that tribooxidation predominated during the frictional process under aqueous lubrication. Furthermore, barium titanate (BaTiO3) could be detected on the tapped surface, the existence of which was proposed to be responsible for its corresponding performance.