Formation and stability of oxide layer in FeCrAl fuel cladding material under high-temperature steam

The high-temperature steam oxidation (HTSO) experiment of FeCrAl alloy was carried out at 1000 °C and 1200 °C by simultaneous thermal analyzer. The oxidation kinetics curves and characteristics of generated oxide layer were analyzed. The results show FeCrAl alloy exhibits remarkable HTSO resistance with an oxidation constant (kp) over three orders of magnitude lower than that of zirconium alloy. By XRD and XPS, the oxide layer consists of FeO and Al2O3 and a little Fe2O3 and Cr2O3 at 1000 °C. When steam oxidized at 1200 °C, there is only Al2O3 on the surface with the volatilization of CrO3. The micromorphology shows the generated oxide layer at 1200 °C is thicker than that at 1000 °C due to the accelerated growth of Al2O3 at high temperature. The oxide layer at 1200 °C presents distinct folds and peeling because of cyclic thermal stress, oxidation of chromium matrix, reduction of oxide adhesion and the gap crack between oxide layers.