In-situ synthesis of Ti–Al intermetallic compounds coating on Ti alloy by magnetron sputtering deposition followed by vacuum annealing

Abstract

In this study, a thin Ti–Al intermetallic compounds (IMCs) coating was in-situ synthesized on a titanium alloy substrate through magnetron sputtering of Al followed by vacuum annealing. The microstructure, composition distribution, nanoindentation and microhardness, scratch and wear behavior of the obtained Ti–Al IMCs coating were investigated. It was found that TiAl3 is formed at the surface, and very thin TiAl and Ti3Al layers exist between the TiAl3 layer and the substrate. The microhardness of the TiAl3 (11.17 GPa) is almost twice as that of the substrate (6.03 GPa), and no cracking occurs during the indentation process. Microstructure observation and composition analysis suggest that metallurgical bonding is formed between the Ti–Al IMCs coating and the substrate, leading to a high bonding strength and almost no peeling during the whole scratch test. The tribological test reveals that the Ti–Al IMCs coating exhibits a lower friction coefficient and a much lower wear rate than those of the substrate, and the major wear mechanism of the Ti–Al IMCs coating is abrasive wear. Based on the findings, the in-situ synthesis of Ti–Al IMCs coating via magnetron sputtering followed by vacuum annealing can be considered a promising method to effectively improve the wear resistance of the Ti alloy.