Degradation of ferritic stainless steels at 1200 °C in air

Abstract

Three commercial ferritic stainless steels were investigated at 1200°C by a thermogravimetric analyser (TGA) in air. The oxidation kinetics of the ferritic stainless steels differed significantly. The adhesion of the Cr 2 O 3 scale, the morphology of the SiO 2 , with or without (Cr, Mn) 3 O 4 spinel on the top can greatly influence the oxidation and the degradation behaviour of the steels. Although the SUS430 steel had less Cr among the ferritic stainless steels (16.2 wt% Cr), it did not show more degradation behaviour than the B443NT steel (21.0 wt% Cr). The spallation of the protective oxide scale on the B443NT steel was caused by vacancy condensation at the scale/substrate interface where the SiO 2 particles were and the developed compressive stresses within the oxide scale during oxidation. (Cr, Mn) 3 O 4 spinel on the top of the Cr 2 O 3 scale on the B445J1M steel influenced its evaporation rate. The thermodynamic aspect of the chemical composition and oxidation atmosphere of the Fe-Cr-O system was also discussed.

Study on the Effect of Niobium on the High Temperature Oxidation Resistance of Ferritic Stainless Steel

“…The Cr 2 O 3 reaction in the Cr 2 O 3 , Fe 2 O 3 and TiO 2 mixed oxide layer is depleted, resulting in voids like Figure 7c. At this point, the chromium content supplied by the matrix is insufficient, so Cr 2 O 3 cannot be formed again on the matrix without oxide layer protection in the cavity, and the matrix will directly participate in oxidation [19]. Stainless steel can protect the substrate by adhering Cr2O3 on its surface in non-high-temperature working environments.…”

“…The Cr2O3 reaction in the Cr2O3, Fe2O3 and TiO2 mixed oxide layer is depleted, resulting in voids like Figure 7c. At this point, the chromium content supplied by the matrix is insufficient, so Cr2O3 cannot be formed again on the matrix without oxide layer protection in the cavity, and the matrix will directly participate in oxidation [19]. In order to analyze the impact of precipitates on the resistance to high-temperature oxidation performance, typical morphologies of precipitates in two samples, Figures 11 and 12, were observed using TEM.…”