Role of niobium in the high-temperature oxidation of titanium

We compared the oxidation of Ti and Ti-2 at.% Nb at 800 degrees C in Ar-20% O2 and in sequential 16O2 -18O2 atmo-spheres to clarify the role of niobium in the high-temperature oxidation of titanium. Niobium had no effect on the amount of oxygen dissolved in the metal or on oxygen diffusion in the metal. Instead, niobium enhanced oxidation resistance by segregating to TiO2 grain boundaries, where it likely slowed outward Ti diffusion. These findings spotlight doping of TiO2 grain boundaries as a strategy for improving the oxidation resistance of Ti alloys and, more generally, TiO2-forming alloys.