Revealing Corrosion Mechanism of Si-doping 9wt.% Cr F/M Steels in Oxygen-Saturated Static and Flowing LBE at 550°C

9 wt. % Cr F/M steels with Si content of 0 wt. %, 0.4 wt. %, 0.7 wt. % and 1.0 wt. % were prepared and tested in oxygen-saturated static and flowing LBE at 550 degrees C for 2000 h. Results show that Si doping facilitated the formation of the early-stage oxide film, extended the incubation period for accelerated oxidation (up to 1500 h similar to 2000 h for 1.0 wt. % specimen in static LBE) and reduced the growth rate of oxide films. Si is found distributed in the form of a nano-scale Si-enriched oxide layer at the oxide film/substrate interface and martensite lath interfaces, acting as a reticular diffusion barrier, mitigating the oxide film growth rate. Although flowing LBE (1.85 m/s) significantly weakens these effects, but overall, Si-containing F/M steels exhibit enhanced oxidation resistance compared to Si-free counterparts.