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

Abstract

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 SiCf/SiC CMCs from water vapor at 1300 °C for over 205 h. Almost all Y2SiO5 transforms into Y4.67(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.