A diffusion–precipitation model for gaseous nitriding of Fe-2 wt.% V alloy

A diffusion–precipitation model for gaseous nitriding of a Fe-2 wt.% V binary alloy has been presented. The nitriding treatment is assumed to be completely realized in the ferritic zone. The model takes into account both nitrogen diffusion and vanadium nitride precipitation. The VN precipitation was obtained with the assumption that it exists a local thermodynamic equilibrium between the matrix phase and the precipitate. The thermodynamic equilibrium calculations are based on Gibbs energies minimization, which were performed by the Thermocalc software. The suggested model allowed the prediction of the nitrogen profiles, and also takes into account the nitrogen excess phenomenon. This nitrogen excess has been explained by the presence of iron atoms within the precipitate. The theoretical results of the model have been compared to the experimental data given in the literature. A good agreement was then noticed between the experimental data and the numerical results.

► Simulation of binary Fe–V nitriding was realized on the diffusion zone.
► The model takes into account nitrogen diffusion in ferrite and VN precipitation.
► VN precipitation was considered via thermodynamic equilibrium calculation.
► The model predicts nitrogen profile and highlights nitrogen excess phenomenon.
► The model was validated by using experimental data available on literature.