Designing lutetium silicate environmental barrier coatings for silicon nitride and its recession behavior in steam jets

Abstract

To protect silicon nitride ceramics from water vapor corrosion and oxidation, a new multi-layered environmental barrier coating (EBC) system was developed. The EBC system consisted of a highly dense Lu2SiO5/Lu2Si2O7 binary phase layer and slightly porous Lu2SiO5/Lu2Si2O7 layer, which were coated by a sputtering and dipping technique, respectively. A steam jet exposure test was conducted at 1300 oC for 500 hours with 35 m/s water vapor velocity. Each grain of the dip-coated layer was peeled off from the surface during the test. Also, the highly dense sputter coated layer converted into a porous layer after the test.