Optimizing mechanical properties and Ag ion release rate of silver coatings deposited on Ti-based high entropy alloys

Abstract

This paper details the characterization of microstructure, texture, mechanical properties, and ion release behavior of antibacterial Ag thin films sputtered on two novel biomedical high entropy alloys (HEAs), namely the Ti23Ta10Hf27Nb12Zr28 (HEA-Ti23) and Ti28Ta10Hf30Nb14Zr18 (HEA-Ti28) alloys. Specifically, the influences of varying deposition time and Ar flow rate were investigated to reveal the mechanisms dictating the microstructure, texture, and mechanical properties of the coatings. In addition, static immersion experiments were carried out in simulated body fluid (SBF) for 28 days to establish the relationship between ion release from the coatings and the deposition parameters, microstructure, and surface texture. It was shown that texture evolution in Ag thin films depends on both film thickness and Ar flow rate, such that there exists a critical thickness at which the energy minimization mechanism is altered. A very good correlation was also observed between an increase in (111) peak intensity and a decrease in released Ag ion fraction. Overall, the findings of the work presented herein suggest that the alterations in Ag deposition parameters could be optimized to obtain the desired mechanical properties while enhancing the biocompatibility of the HEA substrates by coating them with antibacterial Ag films.