Effects of Y2O3 on the microstructures and wear resistance of Si–Al–Y co-deposition coatings prepared on Ti–Al alloy by pack cementation technique

Abstract Si–Al–Y co-deposition coatings were prepared on a Ti–Al alloy by pack cementation process at 1050 for 4 h. The effects of pack Y 2 O 3 content (from 0 to 5 wt%) on the microstructure and constituent phases of the co-deposition coatings were studied, the wear resistance of the substrate and the coated specimens were also compared at 600 °C in air. The results showed that the pack Y 2 O 3 content imposed strong influences on both coating structures and phase constituents. The coatings prepared with the pack mixtures containing 1 and 2 wt% Y 2 O 3 were composed of an TiSi 2 out layer, an (Ti, X ) 5 Si 4 and (Ti, X ) 5 Si 3 ( X represents Nb and Cr)middle layer, an TiAl 2 inner layer and an Al-rich interdiffusion zone. However, the constituent phases changed into TiSi 2 ,(Ti, X ) 5 Si 4 and (Ti, X ) 5 Si 3 in the out layer of the coating prepared with the pack mixture containing 3 wt% Y 2 O 3 . Moreover, (Ti, X ) 5 Si 4 and (Ti, X ) 5 Si 3 phases were observed in the outer layers of the coatings prepared with the pack mixtures containing 0 and 5 wt% Y 2 O 3 . The coating growth could be catalyzed obviously when the content of Y 2 O 3 in the pack mixtures increased from 1 to 2 wt%, but this phenomenon was not observed when further increased the pack Y 2 O 3 content to 3 or 5 wt%. Si–Al–Y co-deposition treatment improved the surface hardness and wears resistance of the Ti–Al alloy significantly. The wear resistance of the tested samples could be sorted in the following sequence: 1% Y 2 O 3 -coating > no RE-coating > bare Ti–Al alloy.