Material Response of Environmental Barrier Coated Ceramic Matrix Composites In Combustion Environments

Abstract

To improve combined-cycle efficiency, next generation gas turbines will have higher combustor outlet temperature and less cooling air for hot section components. High-temperature ceramic matrix composites (CMCs), such as those formed with SiC fibers and a SiC matrix, can survive increasingly extreme environments due to their strong mechanical properties at high-temperature conditions. However, due to the recession of SiC in water vapor containing atmospheres, environmental barrier coatings (EBCs) must be applied to protect the CMC substrate. This work uses an emerging method of manufacturing CMCs through a field assisted sintering technology (FAST). The FAST system combines elevated pressure, temperature, and electrical field effects to produce a CMC in rapid time with exceptional characteristics. EBCs are applied to the CMCs through the same FAST process, without the need for a bond coat. The CMCs are tested for 100 hours in a burner rig that provides conditions that mimic the states in gas turbine combustors. A characterization of the environments is provided including the sample surface temperature and the heat flux through the samples. Post-exposure characterization of the CMCs showed that the integrated CMC-EBC possessed robust resistance to direct combustion exposures due to the dense co-sintered EBC and CMC materials, preventing ingress through open channels, and the high adhesion from functionally-graded steps. This work demonstrates the first viable integrated CMC-EBCs for combustion applications via FAST processing and significantly impacts turbine development as a novel, rapid, and effective pathway for scaled developments.