Oxide scales characterization of micro-alloyed steel at high temperature

A micro-alloyed steel was oxidized at different temperature between 900 °C and 1200 °C in 80%N2–15%CO2–5%O2 atmosphere. As compared with the pure iron, an additional layer between the matrix and the oxide scale was detected in the micro-alloyed steel. The micro-alloying elements, mainly Si and Mo, are found accumulated in the subscale in the form of Laves phases. As the Laves phases can impede the diffusion of iron ion and electron across the subscale, the micro-alloyed steel shows a lower oxidation rate than that of pure iron. Moreover, the existence of the subscale results in a different thickness ratio of hematite, magnetite and wustite in the micro-alloyed steel as compared with that in pure iron. It is also found that the surface roughness of oxide scale significantly depends on the content of hematite.