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 degrees C for 20 min. Corrosion tests were performed by coating sintered Er2Si2O7 pellets with CMAS and heating them to 1400 degrees 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)(6)O-2, at their interface. The Ca2Er8(SiO4)(6)O-2 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.