Study of the effect of the silver content on the structural and mechanical behavior of Ag–ZrCN coatings for orthopedic prostheses

With the increase of elderly population and health problems that are arising nowadays, hip joint prostheses are being widely used. However, it is estimated that 20% of hip replacement surgeries simply fails after few years, mainly due to wear fatigue. Bearing this in mind, this work reports on the development of new coatings that are able to sustain long and innocuous life inside the patient, which will confer to the usual biomaterials improved physical, mechanical and tribological properties. In particular, the development of multifunctional coatings based on Ag-ZrCN, prepared by DC reactive magnetron sputtering using two targets, Zr and a modified Zr target, in an Ar + C2H2 + N2 atmosphere. Silver pellets were placed in the erosion area of the alloyed Zr target in order to obtain a silver content up to 8 at.%. The structural results obtained by x-ray diffraction show that the coatings crystallize in a NaCl crystal structure typical of ZrC1 -xNx. The increase of Ag content promoted the formation of an additional a-CNx amorphous phase, besides a silver crystalline phase. Hardness is decreasing, as increasing silver content. Despite the low thicknesses, adhesion values (LC3) can be considered as good. Dynamic fatigue results suggest that these coatings system can be a real asset in terms of mechanical properties, by improving the performance of usual Stainless Steel 316 L biomaterials.

IF acknowledges the financial support of FCT-Fundacao para a Ciencia e a Tecnologia through grant SFRH/BD/71139/2010. The authors are grateful to Doctor Tomas Polcar, Czech Technical University in Prague, Czech Republic, for her assistance in carrying out the Raman spectroscopic analysis and A.C. Mota for the mechanical assays.This research is partially sponsored by FEDER funds through the program COMPETE- Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the projects ANTIMICROBCOAT - PTDC/CTM/102853/2008 and in the framework of the Strategic Projects PEST-C/FIS/UI607/2011, and PEST-C/EME/U10285/2011.The authors thank the FCT Strategic Project PEST-0E/EQB/LA0023/2013 and the Project "BioHealth - Biotechnology and Bioengineering approaches to improve health quality", Ref. NORTE-07-0124-FEDER000027, co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER. The authors also acknowledge the project "Consolidating Research Expertise and Resources on Cellular and Molecular Biotechnology at CEB/IBB", Ref. ECOMP-01-0124-FEDER027462.