Oxidation behavior of ferritic stainless steels in simulated automotive exhaust gas containing 5Â vol.% water vapor

In this study, the effect of alloying elements, cerium (Ce) and tungsten (W), on the oxidation behavior of medium chromium ferritic stainless steel in simulated automotive exhaust gases containing 5 vol.% H2O was studied in the temperature range of 950-1100 °C for 5 h. The oxidation kinetics and oxide film characteristics were analyzed by means of thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM) and elemental probe micro-analyzer (EPMA). The growth rate of oxidation and oxidation mass gain were significantly decreased on the addition of Ce. A dense, uniform, and thin oxide scale formed on Ce-containing steels. The steel containing Ce and ∼0.5 wt% W displayed similar oxidation behavior compared to the steel containing only Ce. A large number of cracks and pores existed in the oxide film and oxide/metal interface leading to the spallation of oxide film, when the addition of W reached ∼1.0 wt%.