Abstract
Environmental barrier coatings (EBCs) are used to mitigate chemical reactions between SiC ceramic matrix composite (CMC) components and the H2O in combustion gas in turbine hot sections. CMCs are currently temperature-limited by the Si-bond coating, which melts at ~ 1414 °C. This work explores EBCs where the bond coating was removed to achieve higher operating temperatures. Various versions of enhanced roughness SiC were utilized to improve EBC adhesion to the substrates prior to 1 h furnace cycle testing in steam at 1250–1425 °C. The enhanced SiC roughness resulted in short coating lifetimes as the roughness was oxidized away with SiO2 formation. Further, isothermal furnace exposures at 1400–1600 °C showed Yb2Si2O7/Yb2SiO5 EBC microstructural changes, resulting in premature debonding from the substrates. This work provides baseline requirements for the development of both next-generation EBCs and bond coating strategies to overcome the current limitation of the Si-bond coating melting temperature.
