Corrosion behaviors and mechanisms of ytterbium silicate environmental barrier coatings by molten calcium-magnesium-alumino-silicate melts

[Display omitted] •Phase composition significantly influenced the corrosion behaviors and mechanisms.•The Yb2O3-rich coatings exhibited better corrosion resistance.•The existence of appropriate amount of Yb2O3 can improve the corrosion resistance.•The formation reaction of garnet was beneficial to forming dense apatite layer. The ytterbium silicate coatings with different contents of Yb2O3, Yb2SiO5 and Yb2Si2O7 phases were explored on their corrosion resistance to CMAS melts at 1400 ℃. Results showed that Yb2O3-rich coatings dissolved into CMAS melts and reprecipitated garnet and apatite phases, the reaction of producing garnet was beneficial to the formation of dense apatite layer, which can prevent the molten CMAS from penetrating into the coating. However, no dense apatite layer was observed in the corroded Yb2Si2O7-rich coatings. The accelerated recession in the Yb2Si2O7-rich coatings might be ascribed to the increased fraction of CMAS melts within the reaction layer.