Effect of Al on the High‐Temperature Oxidation of Ferritic Stainless Steel in a Synthetic Automotive Exhaust Gas

The influence of Al addition on ferritic stainless steel oxidation resistance has been investigated. Experiments are performed using a synthetic automotive exhaust gas at 950 °C and 1050 °C. In the case of 0Al steel, a double‐layered oxide scale is observed at both temperatures. At 1050 °C, the oxide scale exhibits cracking due to thermal stress. Oxidizing atmosphere penetration results in Si enrichment at the oxide scale/substrate interface. Ultimately, multilayered Si‐rich bands are formed sequentially in the oxide scale. In contrast, 0.7Al steel forms a protective Al 2 O 3 layer at the oxide scale/substrate interface, and needle‐shaped Al 2 O 3 is formed under it due to volume shrinkage. Anion and cation diffusion are inhibited by the upper Al 2 O 3 layer, preventing substrate corrosion. The findings of this work demonstrate a significant enhancement of oxidation resistance due to Al addition.