Cyclic Thermal Oxidation Evaluation to Improve Ti6Al4V Surface in Applications as Biomaterial

Abstract

Thermal oxidation treatments are widely used to modify titanium surfaces. Thermally oxidized titanium alloys are used as biomaterials due to their better surface properties, such as corrosion resistance. However, the use of cyclic thermal treatment for this purpose has not yet been reported. This paper’s objective was to compare roughness, microhardness and corrosion resistance after cyclic and conventional isothermal heat treatments in a Ti6Al4V alloy. The heat treatments were performed over a period of 24 h with a maximum temperature of 650 °C, and cyclic conditions were executed from 200 to 400 °C for 48 cycles, each lasting 0.5 h. After the thermal treatments, roughness was measured through profilometer and atomic force microscopy, Vickers microhardness was evaluated, and polarization corrosion tests were performed in simulated body fluid. All treatments increased surface roughness, microhardness and corrosion resistance at 500 mV above open-circuit potential in polarization tests, compared to the material without oxidation. These results are associated with rutile formation, observed through XRD analysis. Although the isothermal and cyclic treatments presented similar behaviors, the 650-200 °C cyclic heat treatment provided an intermediate roughness and produced a slightly better corrosion resistance, demonstrating that cyclic thermal treatments are a viable alternative for improving titanium alloy surface properties.