Fe2B layer growth kinetics on ASTM A307 steel evaluated by two diffusion models

In this study, we implemented two simple models to simulate the growth of the Fe2B layer on ASTM A307 steel through boriding. The first model considered steady-state boron diffusion, while the second model incorporated transient regime effects. In the steady-state model, the boron concentration profile within the Fe2B layer exhibited linearity. By correlating the boron chemical potential with the inward mass flux at the (Fe2B/substrate) interface, we confirmed the parabolic nature of layer growth. Both models were employed to determine the boron activation energies, yielding the same value of approximately 164 kJ mol−1. Experimental validation of the two models was conducted under two additional boriding conditions (1323 K for 1.5 and 2 h). Finally, the simulated layer thicknesses matched with the experimental values.