J. Phys. IV France 120 (2004) 777-783
DOI: 10.1051/jp4:2004120090

Three-dimensional numerical simulation of the nitriding process

P. Duranton¹, J. Devaux¹, M. Larreur², R. Fortunier³ and J.-M. Bergheau<sup>4

1</sup>  ESI France, 64 Bd. Vivier Merle, 69485 Lyon Cedex 03, France
²  Eurocopter, Aéroport International / Marseille-Provence, 13725 Marignane, France
³  École des Mines, Dépt. MEM, 158 cours Fauriel, 42023 Saint Étienne Cedex 02, France
⁴  LTDS, UMR5513 CNRS/ECL/ENISE, 58 rue Jean Parot, 42023 Saint Étienne Cedex 02, France

Abstract
This paper presents a three-dimensional numerical simulation of a nitriding process applied to an industrial component. The aim of the simulation is to predict the residual stresses and distortions due to volume changes induced by chromium nitride (CrN) and carbides (M₂3C₆ et M₄C₃) formation. The simulation is performed in two steps. The diffusion of nitrogen and the precipitation of chrome nitride and carbides are first simulated. Then stresses and strains are calculated, assuming an elastic behaviour of the component, and using a volume expansion due to the precipitate concentration. The proposed approach is applied on a gear tooth. Small holes and details were neglected. For symmetry reasons, only half a tooth is taken into account. As the main phenomena take place through the first millimetre from the outer surface, a special attention was paid on meshing. The mesh used for the diffusion and precipitation analysis is composed of 1 130 000 nodes and 1 110 000 elements. For the mechanical analysis, a coarser mesh including only 165 000 nodes and 290 000 elements was used.

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