Effect of silicon on the oxidation resistance of 9 wt.% Cr heat resistance steels in 550 °C lead-bismuth eutectic

• The oxide film presents a three-layers structure.
• The oxidation is the diffusion controlled process and fits for the parabolic law.
• Si improves the oxidation resistance for 9 wt.% Cr steel in lead-bismuth eutectic.
• The continuous dense Cr2O3 and SiO2 mixture layer improves the oxidation resistance.

The oxidation resistance of 9 wt.% Cr heat resistance steel with silicon content ranging from 0 to 1.36 wt.% in 550 °C lead-bismuth eutectic was investigated. The silicon content had little influence on the macro-structure of the oxide film. The oxide film presented a three-layers structure. The outer layer was PbO·xFe2O3 and Fe3O4 while the inner layer was mainly FeCr2O4. The formation of thin continuous dense Cr2O3 and SiO2 mixture layer impeded the growth of Fe-rich oxide film, which improved the oxidation resistance in high silicon content. A oxidation process model was put forward to well explain this phenomenon.