Oxidation behavior of YGdSi silicide at 1500°C

• The oxidation of YGdSi at 1500°C via rapid heating was conducted, and the oxidation behavior was investigated. • A tri-layer scale formed on the surface of YGdSi, and the formation mechanism was discussed. • The low oxygen partial pressure of reaction interface causes the selective oxidation of Y and Gd. SiC-fiber reinforced SiC ceramic matrix composites require environmental barrier coatings (EBCs) to avoid corrosion from water vapor of the engine environment. However, service temperature of EBCs is limited by the low melting point of Si bond coatings. Rare earth silicides (RESis) are considered candidate coatings for use above 1500°C, but their oxidation mechanism under actual service conditions still needs to be clarified. This study investigated the oxidation behavior of YGdSi at 1500°C in air via rapid heating to simulate the service conditions of space engines. Results indicated that YGdSi exhibited good structural stability after oxidation for 50 h, and a tri-layer scale formed on the surface. The oxidation scale of YGdSi consists of RE 2 SiO 5 and RE 2 O 3 with different ratios of Y and Gd, and Si phase precipitates inwardly. This work provides guidance for the application of RESi as abond coating of EBC.