Microstructure evolution and elevated temperature wear performance of in-situ laser-synthesized Ti-25Al-17Nb coating on Ti-6Al-4V

A ternary Ti-25Al-17 Nb coating (89.5 vol. % O phase and 4.3 vol. % α2 phase) was fabricated from the pre-alloyed powder by in-situ laser synthesis. The powder was laser scanned to form α2 phase at high temperature and subsequently precipitated primary Ti2AlNb phase (O phase) in an acicular structure; while the secondary fine acicular O phase was squeezed due to the expansion of α2 phase with induced some edge dislocations and mixed dislocations. The dense and hard Al2O3 film gradually replaced the loose and porous TiO2 oxide film as an oxygen diffusion barrier, thereby reducing the possibility of brittle oxide formation and significantly increasing the wear resistance and oxidation resistance, results in an excellent wear resistance at 800 ℃