Biotribological behavior of Ag-ZrCxN1-x coatings against UHMWPE for joint prostheses devices

This study aims to evaluate the structural, mechanical and tribological properties of zirconium carbonitrides (ZrCxN1-x) coatings with embedded silver nanoparticles, produced with the intention of achieving a material with enhanced multi-functional properties, including mechanical strength, corrosion resistance, tribological performance and antibacterial behavior suitable for their use in joint prostheses. The coatings were deposited by direct current (DC) reactive magnetron sputtering onto 316 L stainless steel, changing the silver content from 0 to 20 at% by modifying the current density applied to the targets. Different nitrogen and acetylene gas fluxes were used as reactive gases. The coatings revealed different mixtures of crystalline ZrCxN1-x, silver nanoparticles and amorphous carbon phases. The hardness of the films was found to be mainly controlled by the ratio between the hard (ZrCxN1-x) and soft (Ag and amorphous carbon) phases in the films, fluctuating between 7.4 and 20.4 GPa. The coefficient of friction, measured against ultra-high molecular weight polyethylene (UHMWPE) in Hank's balanced salt solution with 10 gL(-1) albumin, is governed by the surface roughness and hardness. The UHMWPE wear rates were in the same order of magnitude (between 1.4 and 2.0 × 10(-6)mm(3)N(-1)m(-1)), justified by the effect of the protective layer of albumin formed during the tests. The small differences were due to the hydrophobic/hydrophilic character of the surface, as well as to the silver content.This research is partially sponsored by FEDER funds through the program COMPETE- Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundação para a Ciência e a Tecnologia, under the projects ANTIMICROBCOAT—PTDC/CTM/102853/2008 and in the framework of the Strategic Projects PEST-C/FIS/UI607/ 2011”, PEST-C/EME/UI0285/2011 and SFRH/BD/80947/2011. This work has also been supported by the Spanish MEC through the Consolider FUNCOAT (CSD2008-00023) project and Junta de Andalucía (P10-TEP-67182 project).