Reaction between environmental barrier coatings material Er2Si2O7 and a calcia-magnesia-alumina-silica melt

The suitability of sintered erbium disilicate (Er2Si2O7) as an environmental barrier coatings (EBCs) for gas turbine applications was assessed by characterizing its high-temperature corrosion behavior in contact with a synthetic calcia-magnesia-alumina-silica (CMAS) melt. Er2Si2O7 was fabricated using spark plasma sintering at 1400 °C for 20 min. Corrosion tests were performed by coating sintered Er2Si2O7 pellets with CMAS and heating them to 1400 °C for 2, 12, and 48 h. High-temperature X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis were used to identify and analyze the reaction products. The two materials were found to react chemically to form an apatite phase, Ca2Er8(SiO4)6O2, at their interface. The Ca2Er8(SiO4)6O2 grains were observed to have shard-like morphologies oriented perpendicular to the Er2Si2O7 surface; the reaction layer thickened with increasing heat-treatment time, with the thickness after exposure for 48 h approximately three times the thickness after 2 h.