High-temperature oxidation behavior of novel martensitic heat-resistant steel exposed to an ambient air atmosphere

Abstract

With the development of ultra-supercritical units toward higher operating temperatures and pressures, fourth-generation heat-resistant steels have become critical materials for enhancing the service life of key pressure-bearing components. This study investigated the high-temperature oxidation behavior of a novel martensitic heat-resistant steel exposed to air at temperatures ranging from 600 °C to 900 °C for 8 h. The oxidation behavior and mechanisms were analyzed through thermodynamic analysis, weight gain assessment, and microstructural characterization. At different temperatures, the oxidation weight gain curves followed linear, parabolic, and logarithmic patterns. With the increase of temperature, the oxide film gradually changes from thin and continuous dense to discontinuous and loose, covering the whole substrate surface. The increase in oxide layer thickness significantly hindered the mutual diffusion of Fe and O. At 900 °C, the porous oxide layer stratified into a Cr- and Fe-rich inner layer and an Fe-rich outer layer. Fe and O were uniformly distributed in the oxidation products, while Cr tended to enrich in the inner oxide layer. The thickening of the oxide layer and its morphological transformation from granular to dense layered significantly enhance the high-temperature oxidation resistance of heat-resistant steels.