In-Situ Functionally Graded Oxide Matrix Composite for Gas Turbine Applications

Current ceramic matrix composites (CMCs), being evaluated for use in gas turbine engines, require a coating ¿ either an environmental barrier (EBC) or a thermal protection layer (TPS) ¿ to reach the required operating temperatures. Because these coatings are subject to degradation, eliminating the need for them would lead to improved reliability and decreased costs. This project will develop an in situ, functionally-graded oxide-matrix-composite design. In order to minimize thermal stresses, the design includes resistance to thermal and environmental attack on the hot side (a porous YAG-rich layer with low fiber volume fraction), and supports a low thermal gradient on the cold side (a denser, more alumina-rich layer with a high fiber volume fraction). Phase I will focus on concept validation through mechanical testing and exposure of test specimens. Flat panels of the in situ, functionally-graded oxide matrix composite (FGCMC) will be fabricated and subjected to mechanical testing after exposure to a thermal gradient. Portions of the panels will be evaluated after exposure in a simulated gas turbine environment and compared with data for current state-of-the-art materials. Finite element modeling of FGCMC components also will be performed. Phase II will focus on producing a component for evaluation in service. Commercial Applications and other Benefits as described by the awardee: An alternative material for use in gas turbine applications should have significant economic and environmental effects. A material that allows for higher operating temperatures would allow more efficient fuel burning and, thereby, lead to reduced fuel consumption and lower NOx emissions. The advantages afforded by these materials would benefit users of gas turbine engines (both industry and consumer) in the form of lower costs and a cleaner environment.