MRi is teaming with Ohio Aerospace Institute and Exotherm Corporation to conduct innovative processing developments to improve the erosion and impact performance of environmental barrier coatings for SiC/SiC high temperature composites. The effort will be to both improve the bond coat layer and to improve the structure of Mullite +BSAS inner layer and the top layers using SHS prepared powders of ( HfO2+ ScO3) in combination with plasma spraying. CMCs such as SiC/SiC are porous so infiltration can lead to degradation of EBCs associated with oxidation of the interface coating, as opposed to the moisture induced matrix erosion which is the primary problem in the higher temperature applications referenced above. The core of our proposed effort will aim to improve bond coats with dual layer bond layers that bond better to the SiC/SiC and prevent low temperature glasses forming at the mullite interface. The effort will also investigate the improvement of the structure of Mullite +BSAS and the top layers of (HfO2+ ScO3) using reaction synthesis (SHS) prepared powders of in combination with plasma spraying. After developing new composition and structure of bond coat and the top coat, SiC/SiC coupons will be coated and tested including mechanical property measurements after 100 hours of exposure to intermediate temperature and after cyclic humidity and high temperature exposures. Investigator between Phase I and I Option will also evaluate erosion and impact resistance of the more promising EBC compositions.
Benefit: Improved EBCs for SiC/SiC is an important enabling technology for high temperature ceramic matrix composites (CMCs) such as SiC/SiC, since currently their use in more severe environments is limited by their oxidation and corrosion. Higher operating temperatures for jet engines used to power most military aircraft and rotorcraft are increasingly being demanded. These higher temperatures cannot be met by metals therefore CMCs have to be integrated into the most critical sections of the jet engines, including hot section combustors, stators and rotors. EBCs that survive and protect CMCs in the increasingly severe engine environments are essential to higher lift, lighter weight engines in all DoD and eventually in commercial aircraft. Immediately the improved EBCs will find application in Navy and Army rotorcraft as heavy lift requirements are demanding CMCs be integrated into their engines. The Air Force and Marines also have similar requirements on the Joint Strike Fighter to get more fuel efficiency and to extend their mission. EBCs for CMCs therefore are a critical path technology for all future DoD jet engines. As such, there will be a very high demand for the materials and processes that go into these improved EBCs.
Keywords: nanophases, nanophases, bond coats, impact resitance, top coats, Reaction synthesis, Environmental Barrier Coatings, erosion resitant, plasma spray coating, ebc
