Role of Si in optimizing the oxidation behavior of Cr-Si alloyed press-hardened steels during hot stamping

Cr-Si alloyed press-hardened steels (PHSs) have garnered considerable attention due to their outstanding resistance to high-temperature oxidation. To elucidate the pivotal role of Si in enhancing the oxidation resistance of these steels, we have systematically developed Cr-Si alloyed PHSs with three distinct Si concentrations (0, 0.72, and 1.48 wt%) and evaluated their oxidation behaviors during hot stamping. It is demonstrated that the incorporation of 1.48 wt% Si into the Cr-Si alloyed PHS exhibits a dual beneficial effect. Specifically, it facilitates the formation of a continuous Cr₂O₃ layer while simultaneously forming a continuous amorphous SiO₂ film. This structure efficiently impedes the outward diffusion of iron ions, thereby conferring exceptional oxidation resistance during hot stamping. Furthermore, the presence of amorphous SiO₂ at the oxide layer/matrix interface has been observed to enhance the adhesion of the oxide layer to the matrix, thereby mitigating the risk of the oxide scale spalling during the stamping phase. This study not only underscores the important role of Si in optimizing the oxidation resistance of Cr-Si alloyed PHS, but also provides valuable guidance for selecting the optimum Si content in such alloys.