High-Temperature Environmental Barrier Coating for Silicon Carbide Composites

A key limitation in the use of silicon carbide based composites (SiC/SiC) in the next generation turbine engines is their poor oxidation resistance and SiO2 recession at high temperatures particularly in the presence of water vapor.   The primary objective of an environmental barrier coating (EBC) is to provide the necessary protection to SiC/SiC composites from water vapor attack and to reduce the SiO2 recession. Current EBCs are all Silicon based and suffer from surface recession. UES Inc. proposes to study the effectiveness of novel CTE graded rare earth phosphates with various monazite/xenotime compositions devoid of silicon, for environmental protection of SiC-based ceramics in combustion environment above 1500ºC.  Further, UES proposes to use porous YAG as a top coat to enable the EBCs to function as TBCs at 1650ºC. BENEFIT: It is anticipated that under the Phase I program, EBC/TBC that protect Si-based composites from oxidation and SiO2 recession will be developed.  In the phase II program, the coating techniques will be fined tuned and UES will work closely with COI composites to scale up the coating process. At the end of Phase II, we anticipate licensing the EBC/TBC to COI.)