High-Temperature Steam Oxidation Behavior of Fe22Cr5Al3Mo-xY Alloy Under Simulated LOCA Condition

An increased temperature causes the breakaway oxidation of zirconium alloys and the loss of structural integrity under the loss of coolant accident (LOCA). Thus, to enhance the inherent safety of nuclear reactors, the idea of developing accident-tolerant fuel (ATF) is proposed. One of the promising candidate materials for ATF cladding is FeCrAl alloy. The theoretical basis and guidance for FeCrAl alloy's composition optimization can be obtained by investigating the effects of alloying elements on the oxidation behavior and mechanism. Thus, the effect of Y on the oxidation behavior of Fe22Cr5Al3Mo alloy in 1000 and 1200 degrees C high-temperature steam was investigated in this study. Two types of Fe22Cr5Al3Mo-xY (x = 0, 0.15, mass fraction, %) alloys, denoted as 0Y and 0.15Y, respectively, were fabricated and oxidized in 1000 and 1200 degrees C high-temperature steam for 2 h, employing a simultaneous thermal analyzer. The microstructure, crystal structure, and composition of the samples before and after oxidation were analyzed using XRD, FIB, EDS, and TEM. The findings indicate that adding 0.15%Y increases the weight gain rate of FeCrAl alloy in 1000 degrees C high-temperature steam, but decreases the weight gain rate of FeCrAl alloy in 1200 degrees C high-temperature steam. Furthermore, adding 0.15%Y can inhibite the formation of ridge morphology on the surface of oxide film and improve the thickness uniformity and interface flatness of oxide film. The oxide films formed on the 0Y and 0.15Y alloys are both alpha-Al2O3 under the condition of 1000 and 1200 degrees C high-temperature steam for 2 h. In the Al2O3 oxide film, there is hcp-(Cr, Fe)(2)O-3 paralleled to the oxide/metal (O/M) interface. AlYO3, Y2O3, and Fe(Cr, Al)(2)O-4 are present in the Y-rich oxides growing toward the matrix in 0.15Y alloy oxidized in 1200 degrees C steam. The effect of Y on the oxidation behavior of FeCrAl alloy at various temperatures was discussed from the viewpoint of the influence of Y on the microstructure evolution of oxide film.