Effects of alloyed La, Cu and B on the oxidation of Fe-22Cr ferritic stainless steels under simulated cathode side atmosphere of solid oxide fuel cell interconnects

Discontinuous oxidation of La (0.14-0.52 wt.%), Cu (0.17-1.74 wt.%) and B (48-109 ppm) alloyed Fe‐22Cr ferritic stainless steels, and Crofer 22 APU (0.047 wt.% La), have been studied at 800 °C, in flowing air‐2% H2O atmosphere, for 1300 h. The determined parabolic rate constants (1.65-2.58 × 10‐4 mg2 cm‐4 h‐1) are quite close to each other. Benefits of high La‐alloying are not caused by the reduction in oxidation, but rather by the alteration in scale growth direction. On the other hand, high Cu‐alloying promotes the segregation of Cu at the scale/alloy interface, which suppresses the sub‐surface and/or internal oxidation.