Zn based hydroxyapatite based coatings deposited on a novel FeMoTaTiZr high entropy alloy used for bone implants

In this paper, a novel biocompatible alloy defined as FeMoTaTiZr was obtained and functionalized by hydroxyapatite-based coatings (HAP) in order to increase their biocompatibility, bioactivity, and resistance to corrosion for to be used as bone implants. To obtain the surface with antibacterial properties, the HAP coatings were doped with small amount of Zn. The alloy was prepared using the VAR (Vacuum Arc Remelting) equipment, while the coatings by RF magnetron sputtering method. The EDS analysis confirmed the presence of Ca and P in the case of all developed coatings, having Ca/P ratio ranged from 1.69 (undoped HAP) to 1.96 (Zn doped HAP). The (Ca+Zn)/P ration was of about 2.15 for the Zn doped HAP coatings. The XRD and ATR-FTIR investigations confirmed the presence of calcium phosphate phases. After coating with HAP, the roughness of uncoated substrates increased with 1.4 times, and it was considerably increased by the Zn addition with 2.4 times. The electrochemical tests showed that the un-doped HAP exhibited good corrosion behavior, while Zn doped HAP coatings have a high dissolution rate in fetal bovine serum, being more proper as a biodegradable material.