Modeling of compound layer growth during nitriding of pure iron

This paper presents a physical model which describes the layer growth kinetics and the nitrogen concentration profiles during gaseous or plasma nitriding of pure iron. The model is related to a one dimensional moving boundary value problem where the initial concentration profiles are assumed to be linear and a new boundary condition at the diffusion zone is proposed. The model is solved by using a classical finite difference scheme (FDM-CS) and the Heat Balance Integral Method (HBIM). Due to the proposed boundary condition at the diffusion zone, the numerical solutions can be validated through a simple physical analysis of mass transport theory in the asymptotic time limit. The results obtained are compared, and observed to be in good agreement with available experimental data and other approximate solutions reported in the literature. Key words: Advanced characterization, coatings, plasma nitriding, finite difference, heat balance.