Development of air plasma sprayed environmental barrier coatings for Al2O3/Al2O3 ceramic matrix composites

Abstract

Environmental barrier coatings (EBC) are considered to pave the way for the application of ceramic matrix composites (CMC) in turbine engines. Low thermal mismatch, good adherence, microstructural stability and resistance against hot corrosion are key issues. Due to their high chemical stability and low thermal mismatch, YAG and Y2O3 are considered attractive EBC materials for CMC manufactured from Al2O3 fibers and matrices. Laboratory-scale specimen as well as prototypic CMC components were coated with well adherent YAG and Y2O3 coatings by means of air plasma spraying (APS), respectively. Whereas YAG and Al2O3 are inherently compatible, i.e. do not react at high temperatures, Y2O3 and Al2O3 exhibit formation of a thin interdiffusion and reaction zone consisting of a sequence of thermodynamically stable Y-aluminates. APS YAG and Y2O3-coatings exhibit a favorable resistance against hot corrosion by water-vapor or inorganic particles commonly referred to as CMAS corrosion.