Nanostructured oxide composites in PEO coating of β Ti alloys with low elastic modulus for biomedical applications

Abstract

In this work, tribocorrosion of Ti-15Nb, Ti-40Nb, and Ti-33Nb-33Zr biomedical alloys in artificially simulated body fluid is studied by a tribocorrosion technique that allows measuring resistance to corrosion and wear at the same time for alloys coated by PEO technique using a bioactive solution for incorporation calcium, phosphorus, and magnesium that promote the formation of a passive ceramic layer with porosity made by TiO_2. The kinetics parameters were calculated by the taffel curves extrapolation, the coefficient of friction during the process and the morphology and type of wear before, and after PEO coating on the alloys. XRD, SEM, and TEM evaluated a previous structural and microstructural study of the ceramic layer. Tribocorrosion tests were performed using a reciprocating pin-on-disk tribometer under constant load, and a counterpart, Al₂O₃, were used against the alloys in contact pressure on the tribocorrosion mechanisms. Among the β Ti-Nb-(Zr) alloys, an improved wear and corrosion resistance with lower damage was remarked for TN15, TN40, and TNZ33 alloys, with better results for TN40 (r_p=9.8 µm/year), followed by TN15(r_p=15.1 µm/year) and TNZ33(r_p=15.5 µm/year) PEO coated samples. The improvement of tribocorrosion resistance can be attributed to the presence of zirconium oxide (ZrO₂) and rutile (TiO₂), the thickness (TN40: 1.3 µm; TNZ33:5.2 µm; TN15: 6.7 µm) and pore size (TN40: 2.64 µm; TNZ33: 3.68 µm; TN15: 3.09 µm) of the PEO ceramic layer.