Slow-Growing Titanium Dioxide on Ti-48Al Porous Alloy Mediated by Nb and Cr Addition: Perspective via Local Metal–Oxygen Bonding Strength

Abstract

TiAl porous alloys exhibit potential for application in high-temperature flue gas filtration, because of their satisfactory mechanical properties and excellent high-temperature creep resistance. However, poor oxidation resistance and corrosion resistance at temperatures exceeding 800 °C considerably limit the practical applications of TiAl porous alloys. The disadvantages of TiAl alloys can be mitigated by adding a specific amount of alloying elements to delay oxygen diffusion. In this study, two kinds of porous alloys, Ti-48Al and Ti-48Al-2Nb-2Cr, are used to evaluate the high-temperature oxidation resistance and sulfidation resistance of TiAl-based porous alloys. With the addition of alloying elements Nb and Cr, the high-temperature oxidation resistance and sulfidation resistance of the TiAl alloys have greatly improved. The mechanisms underlying phase transformation are also explained using the first-principles theory. The excellent antioxidation and anti-sulfidation properties of the Ti-48Al-2Nb-2Cr porous alloy are mainly attributed to the markedly reduced free energy of Al2O3 formation and suppress the presence of TiO2 at elevated temperatures, as explained by first-principles calculations. The Ti-48Al-2Nb-2Cr porous alloy has advanced the application of multiple alloying in high-temperature flue gas filtration.