Comportement des aciers bainitiques a différentes températures : étude de la cémentite aux grands instruments

Abstract : The multiscale experimental characterization of bainitic steels has been the subject of this research. Two two-phase steels ferrite-cementite were chosen: a 16MND5 steel used to design RPW reactors (Reactor Pressurized Water) and a 2C40 steel. In order to study the mechanical behavior of each phase individually, different thermomechanical characterization tools have been considered. The originality of this work comes from the use of two techniques: in situ tensile tests combined to synchrotron radiation and nanoindentation. A major interest is given to the behavior of cementite. The stresses reached in this phase were determined by two methods. First, analyzes have been performed in ferritic phase by XRD and a mixture law has been used to estimate the stress values in cementite. Then, analyzes have been carried out directly in each phase using synchrotron radiation. The results show that the mixture law is a good tool to describe the stress distribution in each phase of the studied steels. However, it may be not enough because it doesn’t take into account the morphology of the carbide and highly depends on the volume fraction of the cementite: an uncertainty of ± 0.2 % can lead to stress variation of ± 1000 MPa. The local properties of cementite were also analyzed by nanoindentation. The primary results have confirmed that the carbide hardness is 2-3 times greater than the hardness of the matrix.
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  • HAL Id : tel-01513053, version 1

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Razane Ouahab. Comportement des aciers bainitiques a différentes températures : étude de la cémentite aux grands instruments. Mathématiques [math]. Arts et Métiers Paristech, Paris, 2012. Français. ⟨NNT : 2012ENAM0018⟩. ⟨tel-01513053⟩

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