Cementite Residual Stress Analysis in Gas-nitrided Low Alloy Steels
TypeArticles dans des revues avec comité de lecture
This paper deals with the measurement of residual stresses in cementite after gas-nitriding of a 33CrMoV12-9 steel. During nitriding, precipitation of nanometric alloying elements nitrides and cementite at grain boundaries occurs leading to an increase of superficial hardness and providing compressive residual stresses in the surface layer. The stress state in the ferritic matrix has generally been measured to characterize the mechanical behaviour of the nitrided case while the other phases are not taken into account. In order to better understand the mechanical behaviour (e.g. fatigue life and localization of cracks initiation) of heterogeneous material such as in case of nitrided surfaces, the nature (sign, level) of residual stresses (or pseudo-macro-stresses) of the present phases can be calculated from measurements using X-ray diffraction to select the considered phase. Due to a low volume fraction of cementite through a nitrided case, an approach based on X-ray and electron backscattered diffractions (XRD and EBSD respectively) is proposed to perform stress measurements in cementite. An optimization of the surface preparation (by mechanical and/or chemical polishing techniques) prior to EBSD analysis was performed in order to minimize deformation induced by surface preparation. Pseudo-macro-stresses were calculated in tempered martensite and cementite. Results are compared to local residual stress measurements carried out by a cross-correlation method using EBSD patterns.
Files in this item
Showing items related by title, author, creator and subject.
WEIL, Hadrien; JEGOU, Sébastien; BARRALLIER, Laurent; COURLEUX, Alice; BECK, G. (2016)The present study aims to develop an algorithm able to predict the fatigue lifetime of nitrided steels. Linear multi-axial fatigue criteria are used to take into account the gradients of mechanical properties provided by ...
GUILLOT, Benjamin; JEGOU, Sébastien; BARRALLIER, Laurent (ASM International, 2016)Machining is known to introduce plastic straining and residual stress gradients in surface of mechanical parts. If not controlled, the mechanical state of a surface can influence adsorption and diffusion of atoms during ...
BARRALLIER, Laurent; JEGOU, Sébastien (2015)Le traitement thermochimique de nitruration est un traitement de surface permettant d'améliorer la durée de vie en fatigue des pièces traitées. Les dernières avancées dans ce domaine permettent de définir les paramètres ...
Evolution des contraintes résiduelles dans la couche de diffusion d’un acier modèle Fe-Cr-C nitruré JEGOU, Sébastien; BARRALLIER, Laurent; KUBLER, Régis; SOMERS, Marcel (2011)Limiter la fatigue et la corrosion des pièces est possible grâce à une nitruration. Des contraintes résiduelles en découlent. Le rôle de la diffusion du carbone sur le développement de ces contraintes a été étudié sur un ...
Effect of stress on passivation kinetics and passivation modelling of 304L stainless steel in acidic medium MUBARAK, Hazem; BARRALLIER, Laurent; JEGOU, Sébastien; VOLOVITCH, Polina; OGLE, Kévin (2015)Stress Corrosion Cracking (SCC) is a typical failure of engineering materials applied in corrosive environments. In light water reactors for example, this results in loss of electrical capacity and related costs of repair ...