Improved water vapor resistance of environmental barrier coatings densified by aluminum infiltration

A dense environmental barrier coating (EBC) was designed via aluminum infiltration into open pores or cracks to eliminate premature coating failure induced by the rapid permeation of oxidants through these pores. The water vapor corrosion performance of the EBC with and without aluminum infiltration was investigated at 1350 °C for 300 h under flowing 50%H2O–50%O2 gas. The infiltrated coating exhibited decrease silicon loss by more than 80%, almost no phase decomposition, and no continuous thermally grown oxide (TGO), furthermore, TGO thickness at the crack-root decreased by ∼90%. The excellent resistance is primarily attributed to the channel pores being filled with aluminum, which eliminates the rapid permeation of oxidants. In addition, a continuous refractory ytterbium aluminum garnet (YbAG) layer was formed in situ on the EBC surface, this layer exhibited sufficient stability in steam, rendering the EBC less permeable to oxidants.