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

• The FeCrAl alloy has low oxidation rate at 1200 °C, the weight during oxidation increases.
• The composition of oxide layer on alloy surface mainly consists of FeO and Al2O3 at 1000 °C.
• While the product at 1200 °C is only Al2O3.
• The oxidation behavior at 1200 °C refers to the growth of Al2O3 layer.
• Low concentration of Cr and Al still keeps an excellent steam oxidation resistance.

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.