A simple diffusion model for the growth kinetics of g 0 iron nitride on the pure iron substrate M. Keddam a, * , M.E. Djeghlal b , L. Barrallier c a De ´partement de S.D.M, Faculte ´ de Ge ´nie Me ´canique et Ge ´nie des Proce ´de ´s, B.P. No. 32, 16111, El-Alia, Bab-Ezzouar, Alger, Algeria b Laboratoire de Ge ´nie et Sciences Des Mate ´riaux, De ´partement de Me ´tallurgie, Ecole Nationale Polytechnique, 10 Avenue Hassen Badi, B.P. No. 182, 16200, El-Harrach, Alger, Algeria c Laboratoire Me ´caSurf, E.N.S.A.M, 2 Cours des Arts et Me ´tiers, 13167 Aix-en-Provence, Cedex 1, France Received 8 July 2004; received in revised form 23 August 2004; accepted 1 September 2004 Available online 18 October 2004 Abstract 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 g 0 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. # 2004 Elsevier B.V. All rights reserved. Keywords: Fe–N binary system; Fick’s laws; Nitrogen diffusion; Growth kinetics; Iron nitride 1. Introduction Gas nitriding is a technologically important surface treatment process which is well known to improve the tribological properties, the fatigue endurance and the corrosion resistance [1]. Depending on the composition of the nitriding atmosphere and the temperature, a compound layer that consists mainly of e-Fe 2–3 N and/or g 0 -Fe 4 N is produced on the surface of the pure iron, and beneath the layer, a diffusion zone where nitrogen is dissolved interstitially in the iron matrix. Understanding of the gas nitriding of pure iron provides an essential, general basis for the subsequent modeling of gas nitriding of Fe–C alloys and alloyed steels. Hence, in order to optimize process control, it is necessary to have a clear understanding of the basic phenomenon which is the nitrogen diffusion. In case of iron gas nitriding, several papers have been published [2–10] on the modeling of the www.elsevier.com/locate/apsusc Applied Surface Science 242 (2005) 369–374 * Corresponding author. Tel.: +213 21 24 79 19; fax: +213 21 24 79 19. E-mail address: keddam@yahoo.fr (M. Keddam). 0169-4332/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2004.09.003