Oxide Nucleation and Oxide Scale Evolution During Austenitization of 22MnB5 Steel

Oxide-scale evolution during the austenitization process is a critical factor affecting the surface quality and subsequent processing performance of press-hardened steels. However, the dynamic evolution of oxide nucleation and the relationship between substrate characteristics and oxide-scale adhesion remain insufficiently understood. In this study, the oxidation behavior of conventional 22MnB5 steel (Steel 1) and Si/Cr-modified 22MnB5 steel (Steel 2) during austenitization was comparatively investigated. High-temperature confocal laser scanning microscopy (HT-CLSM) was employed for in-situ observation of the early-stage oxidation process, while XRD, SEM/EDS, EBSD, and nano-scratch testing were conducted to characterize the oxide-scale structure, phase constitution, microstructural characteristics, and damage response. The results reveal that the oxide nucleation and growth behavior are strongly influenced by the combined effects of alloy composition and substrate microstructure. Steel 2 exhibits a more uniform oxide-scale morphology and improved damage resistance compared with Steel 1, which is associated with its modified composition and refined substrate microstructure. This work provides insights into the dynamic oxidation behavior and oxide-scale evolution mechanisms of 22MnB5 steel during austenitization and highlights the importance of considering both chemical composition and substrate characteristics in controlling oxide-scale adhesion.