Diffusion mechanisms of carbon and nitrogen during bainite transformation: a simulation-based study

• Nitrogen redistributes faster than carbon during bainite formation in Fe-based alloys. • Enhanced N diffusion significantly impacts bainitic transformation kinetics. • Results align with experimental data, highlighting N’s role in bainite formation. Despite extensive research, the bainitic transformation in steels remains a subject of considerable debate, particularly regarding its underlying mechanisms. While the majority of research has focused on carbon (C)-alloyed steels, the role of nitrogen (N) in bainite formation remains less understood due to the limited solubility of N in steel. This study aims to elucidate the diffusion behavior of C and N within the iron lattices, with the objective of understanding their impact on the bainitic transformation. Diffusion simulations were conducted in the context of bainite formation in Fe-C and Fe-N systems. These simulations demonstrated a substantially faster redistribution of N in comparison to C from the bainitic ferrite to the surrounding austenite. This finding indicates a substantial influence on the kinetics of bainite formation, a conclusion that is consistent with observations in experimentally determined literature data.