A simplified diffusion model designed to predict the thickness, microstructure of nitrided layer on the pure iron, and the nitrogen profile is reported. The error function model based on Fick's laws was used to study the growth kinetics of gamma' phase during the gas nitriding process. The validity of the generated computer program was checked by comparing our simulation results with the experimental data taken from the literature and a fairly good agreement is achieved between calculated and experimentally measured values. (c) 2004 Elsevier B.V. All rights reserved.