Microstructure and high-temperature oxidation resistance of Ti-Al-Nb coatings on a Ti-6Al-4V alloy fabricated by laser surface alloying

In this study, Ti-Al-xNb coatings were deposited on a Ti-6Al-4V alloy by laser surface alloying in order to investigate their oxidation resistance. A Ti-Al coating was fabricated for comparison. It was found that the Ti-Al and Ti-Al-xNb coatings were composed of TiAl and Ti3Al phases. Nb addition reduced the cracking tendency of the Ti-Al-xNb coatings. The Ti-Al and Ti-Al-xNb coatings exhibited good high-temperature oxidation resistance at 800 °C. In comparison, Ti-Al-xNb (x = 10, 20, 30 and 40) coatings had better high-temperature oxidation resistance and Ti-Al-40Nb coating had the best high-temperature oxidation resistance. The mechanism of Nb that improves the high-temperature oxidation resistance of Ti-Al-xNb coatings includes preventing the internal diffusion of oxygen, inhibiting the formation of TiO2, promoting the formation of Al2O3 and increasing the adhesion of the oxide scales.