Effect of Plasma Characteristics on the Composition and Properties of Silicate Environmental Barrier Coatings

SiC based Ceramic Matrix Composites (CMCs) are intended to work as replacements for much denser metallic superalloys nowadays used in in most of the parts subjected to high temperatures in turbines. Environmental Barrier Coatings (EBCs) are the coating systems deposited on those CMCs to prevent the water vapor corrosion promoted by the high temperature combustion environments. Different materials have been tested in the last three decades to converge towards the 2^nd Generation of EBCs that consist in a system where the topcoat facing the combustion atmosphere is a rare-earth (RE) silicate. Among them, Yb₂Si₂O₇ has emerged as the ideal candidate due to its inherent phase stability, moderate recession rate in water vapor atmospheres and a coefficient of thermal expansion that match that of SiC based ceramics. The main characteristics of Re-silicates processed by Air Plasma Spraying are the shift in the original feedstock composition and the development of Yb₂O₃ enriched phases due to the preferential volatilization of SiO₂ and the mainly amorphous character of the as sprayed coatings. In this work are presented the efforts made to understand the APS processing-material interrelations in Yb₂Si₂O₇-based EBCs and how they affect to the coatings properties