Stability of oxides/environmental barrier coating candidate materials in high-temperature, high-velocity steam

摘要

Stability of oxides/Environmental Barrier Coating (EBC) candidate materials in high-temperature, high-velocity steam has been characterized using a steam-jet furnace modeled after Lucato et al [1]. The objective of this work is to quantify stability of oxides for use as coatings on SiC-based composites in turbine engine environments with the long term goal of developing thermochemical life prediction models for EBCs. SiO_2, TiO_2, Y_2O_3, and rare earth silicates were exposed in one atmosphere steam flowing at approximately 170 m/s at temperatures between 1200 and 1400°C for times up to 375 h. Oxide recession, attributed to formation of volatile metal hydroxides, was measured for SiO_2, TiO_2 and Y_2O_3. The SiO_2 recession rates were consistent with values predicted assuming loss of material was limited by transport of Si(OH)_4(g) through a laminar gas boundary layer. TiO_2 single crystal recession was slightly less than SiO_2 but too rapid for use in a turbine environment. Y_2O_3 recession was not measureable within the sensitivity of techniques used here.