Apport de la diffraction des rayons X à l’étude d’un acier faiblement allié nitruré ioniquement par plasma

Contribution of X-ray diffraction to the study of a plasma ion nitrited low alloyed steel

¹ Laboratoire de Mécanique de Lille, URA CNRS 1441, U. S. T. Lille. IUT A GMP, Villeneuve d’Ascq, France
² Laboratoire Hydrogenio PROPMEC COPPE UFRJ, Université Fédérale de Rio de Janeiro, Brésil

Abstract

The present work deals with the use of X-ray diffraction to complete the metallographic study of a plasma ion nitrited low alloyed steel. This method allows to determine and quantify the nature and repartition of constituants present after three times of treatment (1/2 h, 16 h, 28 h). Microdeformations as well as coherent domain sizes linked to dislocation network are also determined using this method. We show that the formation of the combination layer delays the nitriding process playing the role of a diffusion barrier between the bulk material and the nitriding medium. For the larger nitriding time, the combination layer, at first only constituted of γ’ nitride, is transformed partly in ε nitride. This transformation is accompagned simultaneously by the formation of pores into the combination layer. The microhardness profile of the diffusion layer do not follow the nitride content profile, then the hardness increase has to be linked to the dislocation density and arrangement.