In this paper, the efficiency of gas nitriding on pure iron is observed regarding two types of pre-treatments prior to nitriding: chemical reduction by H-2 and nanocrystallization by NanoPeening (R). Thermogravimetric analysis reveals that both pre-treatments result in an increase in the transformation rate of nitrogen during the first 200 min of nitriding. Moreover, glow discharge optical spectrometry reveals that nanocrystallization by NanoPeening (R) leads to a deeper penetration of nitrogen in the material. (C) 2017 Elsevier B.V. All rights reserved.