Numerical simulation of nitrided layer growth and nitrogen distribution in ε-Fe_2-3N, γ'-Fe₄N and α-Fe during pulse plasma nitriding of pure iron

The surface phase constitution and the kinetics of layer growth in pure iron pulse plasma nitrided at 520 °C for different times were systematically studied, and the relative expressions of the nitrogen concentration profiles in nitrided layers have been deduced. The results show that the nitrided layer consists of ε-Fe_2-3N (ε), γ'-Fe₄N (γ') and α-Fe (α) phases, and its growth in thickness follows a parabolic law. In addition, the growth of a compound layer and diffusion layer and the nitrogen concentration distribution in the nitrided layers can be precisely predicted by employing the mathematical models obtained.