Effect of Minor Cerium Addition on the Oxidation Behavior of Silicon in Ferritic/Martensitic Steel Exposed to Lead-Bismuth Eutectic at 500°C

Si-containing ferritic/martensitic steels with 0 and 0.017 wt.% cerium (Ce) were exposed to lead-bismuth eutectic at 500 degrees C for 1500 h. The addition of Ce led to a transition of the SiO2 layer from continuous to discontinuous and the formation of Si-poor areas in the matrix below the oxide scale. These changes caused an unexpected thickening of the oxide scale on the Ce-doped steel, which differs from findings in other studies. In this study, the Ce mainly located within the grains is preferentially oxidized to form CeO2 during corrosion. CeO2 can act as a nucleation site that promotes the formation, growth and aggregation of SiO2 around it. Consequently, the SiO2 layer becomes less effective at preventing elemental diffusion along grain boundaries.