High-temperature oxidation behavior and mechanism of 18Cr–Mo-type ferritic stainless steel containing W and Ce in simulated automotive exhaust gas

The high melting point element W and the rare earth element Ce were added to 18Cr–Mo (444-type) ferritic stainless steel to improve its high-temperature oxidation resistance in exhaust gas. A simulated exhaust gas was filled in the simultaneous thermal analyzer to simulate the service environment, and the oxidation behavior in high-temperature exhaust gas environment of 444-type ferritic stainless steel alloyed with W and Ce was investigated. The oxide structure and composition formed in this process were analyzed and characterized by scanning electron microscopy/energy-dispersive spectroscopy and electron probe analysis, and the mechanism of W and Ce in the oxidation process was revealed. The results show that 18Cr–Mo ferritic stainless steel containing W and Ce has better oxidation resistance in high-temperature exhaust gas. The element W can promote the precipitation of Laves phase at the matrix/interface, inhibit the interface diffusion of oxidizing elements and prevent the inward growth of the oxide film. The element Ce can suppress the volume of SiO₂ at the oxide film/interface, reducing the breakaway oxidation caused by cracking of the oxide film. The CeO₂ provides nucleation sites for oxide particles, promoting the healing of cracks and voids within the oxide film.