Laser-assisted Zr/ZrO2 coating on Ti for load-bearing implants

Oxidized Zr alloys have been shown to exhibit lower friction and superior wear properties, suggesting that they could be used in hip and knee implants. However, conventional oxidation of Zr alloys above 500 degrees C, in dry air, for several hours has been shown to have detrimental effects on the substrate's properties. In this work, we deposited pure Zr on Ti, then oxidized the coating using a continuous-wave Nd:YAG laser, which facilitated localized heating to elevated temperatures without affecting the substrate. Laser-assisted oxidation resulted in a 7 mu m thick fully dense ZrO2 layer on Zr in which an increase in oxidation kinetics was evident due to an increase in the laser power and/or the oxygen partial pressure. Due to its high surface energy and wettability, the wear rate of laser-oxidized Zr was two orders of magnitude less compared to that of as-deposited Zr. The oxidized coatings showed comparable in vitro biocompatibility to that of pure Ti and excellent in vitro cell-material interactions. This article reports the processing of Zr/ZrO2 coatings on Ti using lasers, and the influence of laser parameters and oxygen partial pressure on the coating's mechanical, microstructural, wear and in vitro biological properties using human osteoblast cells. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.