Prediction of optimized composition for enhanced mechanical and electrochemical response of Zr-C-N-Ag coatings for medical devices

Abstract

The necessity of improving the performance of existing biocompatible materials promotes the investigation of new approaches to solve biocompatibility problems caused by low chemical stability and poor mechanical performance of implanted materials. Envisioning those problems and considering the current reported complications of implanted stainless steel 316L devices, this work aimed to produce new Zr-C-N-Ag coatings and to predict an optimal composition to provide the required electrochemical stability and mechanical performance to the stainless steel 316L. The coatings were deposited by dual unbalance magnetron sputtering and characterized in terms of chemical, structural, mechanical and electrochemical properties to optimize their functional properties by means of a second-order response surface methodology. The optimization process revealed that the best mechanical and electrochemical performance was reached when stoichiometric ZrC0.5N0.5 phase is the main constituent of the materials, with low amounts of silver (<8 at.%) and residual oxygen, mainly explained by the electrochemical stability and mechanical performance of the Zr-C-N solid solution. The current density applied to the silver target was identified as the main parameter affecting the final properties of the films due to its direct relation to the incorporation of metallic silver in the system. However, the reactive gases, as well as the high amount of residual oxygen, were also found to be significant in the process.