Bio-corrosion, mechanical and microstructural properties of TiTaMoVZr high-entropy alloy film on Ti-6Al-4V substrate

Abstract

In recent years, high entropy alloys (HEA) have gained much attention due to their high corrosion resistance and mechanical properties. As a target, a high entropy TiTaMoVZr alloy with a atomic ratio of 20% was cast. Following that, the Ti-6Al-4V substrate was coated using the radio frequency magnetron sputtering technique. This process took place at a temperature of 400 degrees C under two different atmospheres of argon and air. HEA thin films' mechanical, biological, and corrosion properties were investigated. The biocompatibility of these films was evaluated by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. Based on the results, these films formed an amorphous phase with a higher hardness than the substrate. Also, the wettability and roughness of the surface of the films were higher compared to the substrate, which improved cell viability and their adhesion to the films surface. Because of their chemical compositions and unique structures, the films were more corrosion resistant than Ti6Al4V substrates were obtained. SEM investigation showed that there were more cracks on the surface of non-oxide high entropy films compared to the high entropy oxide deposit. The oxide film had no visible cracks, and also the thickness of the oxide high entropy film was more significant than the non-oxide film, which resulted in improved corrosion properties. Also, the Polarization resistance of the non-oxide (176 x 10(4) Omega.cm(2)) and oxide (218 x 10(4) Omega.cm(2)) films increased compared to the substrate (324 x 10(3) Omega.cm(2)). Furthermore, the coated samples had higher Young's modulus and nanohardness than Ti6Al4V samples. This was attributed to the amorphous structure and the absence of defects such as dislocations and slip planes in the coating. Cell viability was improved for coated samples, however, atmospheric change in coating conditions did not significantly affect this cell viability.