A highly dense Lu-Si-O EBC (environmental barrier coating) layer was successfully coated on silicon nitride ceramics by a sputtering method. A Lu2Si2O7/Lu2SiO5 complex composition layer was obtained by heat treatment at 1450°C in air. Hydro corrosion tests were performed at 1300°C for 100 hours in a 30 wt% water vapor environment. The highly dense Lu2Si2O7/ Lu2SiO5 EBC layer protected the silicon nitride from corrosion by water vapor attack. The weight loss of this sample at 1.1 × 10−6 g/cm2·h, was similar to that of a hot pressed Lu2Si2O7 which showed a weight loss of 1.4 × 10−6 g/cm2·h. On the other hand, the weight of a silicon nitride ceramic with no EBC layer increased by 1.2 × 10−4 g/cm2·h.

Keywords: EBC, Lu2Si2O7, water vapor corrosion