Microstructural and mechanical characterization of the porous anodic TiO₂ layer on titanium

Porous TiO₂ layer was fabricated on the titanium surface using an anodic spark oxidation technique for biomedical application. The microstructural and mechanical characterization of TiO₂ layer was performed. Results show that the fabricated TiO₂ layer exhibited a porous surface and poorly-crystallized structure, and an inner layer containing numerous cavities was observed near the oxide-sub-strate interface. The mechanical characteristics of TiO₂ layer were greatly influenced by its microstructural features. The performed shear test showed that the shear fracture of oxide layer took place primarily within the cavity-containing layer. The performed tensile fatigue loading resulted in multiple cracking to occur in the oxide layer with distinctive inclined cracking driven by slip band in the titanium substrate, and localized spallation of oxide layer was also observed. Despite extensive fatigue damage in the oxide layer, the fatigue life of titanium was not significantly influenced by the present anodization treatment.