Preparation and molten salt corrosion research of composite environmental barrier coatings of Lu2Si2O7 and Lu2SiO5

Rare earth silicates have been investigated to evaluate their potential as an advanced environmental barrier coating (EBC) that has a higher temperature capability than current EBCs. In order to avoid Lu2Si2O7 surface toughness reduction as well as the appearance of cracks under the extreme working environment conditions of the SiC ceramic EBC exposed to a high temperature combustion atmosphere, we combined Lu2Si2O7 and Lu2SiO5 to change the characteristics in the working temperature range. In this paper, we developed a method for improving the coating toughening mechanism by adjusting the ratio of Lu2Si2O7 and Lu2SiO5. By measuring the thermal expansion coefficient of samples, observing the sample corrosion behaviour with molten salt at 950 degrees C, analysing the phase evolution and surface morphology changes of the samples at different corrosion stages, we found that the composite coating had superior chemical compatibility compared to a single component coating, low volatility and excellent corrosion resistance in molten salt.