Influence of the annealing treatment on the tribocorrosion properties of Ca and P containing TiO2 produced by plasma electrolytic oxidation

Abstract

Titanium is widely used as implant material; however, regardless of the excellent properties such as low density, corrosion resistance and biocompatibility, it usually presents poor tribological behaviour. The plasma electrolytic oxidation (PEO) technique produces a high hardness ceramic layer on the titanium surface, by the interaction of anodic oxide growth and plasma channel shock caused by the dielectric breakdown at high voltages taking place in an aqueous electrolyte. The characteristics of the oxide layer, such as the roughness, thickness, porosity, crystallinity and chemical composition, can be tailored changing the PEO parameters or by a posterior annealing treatment at temperatures above 400 °C. This work aims to evaluate the influence of the PEO voltage and annealing treatment on the tribocorrosion properties. Cp–titanium were submitted to PEO treatment at 300 and 400 V for 1 min in an electrolyte containing Ca and P. The annealing treatment was carried out at 600 °C for 1 h following slow cooling at furnace. Surface properties were evaluated by X-ray diffraction, scanning electron microscopy (SEM/EDS) and profilometry. Tribocorrosion was evaluated using a linear reciprocating ball on flat tribometer with a three-electrode electrochemical cell coupled to potentiostat/galvanostat in Phosphate Buffered Saline solution. Results show that PEO layer increases the tribocorrosion resistance of bare titanium significantly. The tribocorrosion resistance is also increased by the presence of rutile phase through voltage or posterior heat treatment.