Microstructure and tribological properties of Si-Y/Al two-step deposition coating prepared on Ti2AlNb based alloy by halide activated pack cementation technique

To enhance the tribological properties of the Ti2AlNb based alloy, a Si-Y/Al coating was prepared by a two-step halide activated pack cementation process including Si-Y co-deposition first and then aluminization. The Si-Y coating and the Si-Y/Al coating both had multilayer structures. After the aluminization, the microhardness of the Si-Y/Al coating decreased a little, but was still much higher than that of the substrate. Its toughness was obviously improved. The tribological properties of the bare alloy, the Si-Y coating and the Si-Y/Al coating were comparatively studied at room temperature and 873 K using SiC balls as the counterparts. The results showed that the Si-Y/Al coating could provide better protection for the Ti2AlNb based alloy than the Si-Y coating. [Display omitted] •A Si-Y/Al coating was formed on a Ti2AlNb based alloy by a two-step HAPC process.•The Si-Y/Al coating possessed much higher microhardness than the substrate.•The toughness of the Si-Y/Al coating was improved after the aluminization.•Al2O3 in the film reduced the CTE mismatch between the film and the Si-Y/Al coating.•The Si-Y/Al coating possessed better tribological properties than the Si-Y coating.