Water vapor and CMAS corrosion tests of Y₂SiO₅/Si thermal and environmental barrier coating

Thermal and environmental barrier coatings (TEBCs), an up-to-date concept, are introduced to protect silicon-based ceramic matrix composites (CMCs) from not only high-temperature water vapor but also alkali salts from volcanic ash and dust suspended in the atmosphere. Both high-temperature steam and CMAS will cause Si-based CMCs to deteriorate rapidly. By executing the corrosion test against high-temperature water vapor, we find that the Y₂SiO₅/Si double-layer TEBC can effectively protect SiC_f/SiC CMCs from water vapor at 1300 °C for over 205 h. Almost all Y₂SiO₅ transforms into Y_4.67(SiO₄)₃O after the corrosion test. It is also found that in the CMAS corrosion test, the reaction zone formed between the CMAS and Y₂SiO₅ layers prevents the mutual diffusion of elements in the CMAS and Y₂SiO₅ layers. The apparent activation energy of the reaction between CMAS and Y₂SiO₅ in the 1200–1300 °C temperature range is calculated to be 713.749 kJ/mol. These findings provide a reference for selecting appropriate materials for TEBCs.