Effect of silicon on oxidation behavior of 9Cr-ODS steel at 650 °C

Abstract

The effect of silicon content on the evolution of oxide layer and oxides in Si-containing 9Cr-ODS steel during 5, 20 and 50 h oxidation was studied. The experiment was carried out at 650 °C in air. XRD was used to analyze oxide phase at different oxidation times. The morphology and elemental composition of the oxides were investigated by SEM/EDS. With the silicon content increasing, the oxidation resistance of ODS steel was improved. The oxide layer of 0.5 wt%Si specimen was mainly composed of Fe2O3, and the Mn-rich and Cr-rich oxides were found at oxidation 50 h. The Si-rich oxide layer was gradually generated in the 4 wt%Si specimen with the increase of the oxidation times. Meanwhile, a discontinuous Mn-rich and Cr-rich oxide layer was found on the surface of 4 wt%Si specimen steel after 50 h of oxidation. The reason is that the diffusion of Fe3+ was prevented by Si-rich oxide layer. Moreover, the diffusion rate of Cr and Mn was increased by a large amount of Si-doped. Consequently, the addition of Si is beneficial to the oxidation resistance of ODS steel.