PhD opportunities

SUBJECT OF THESIS PROVIDED Modeling the surface state of reactor vessel nozzle for a better prediction of stress corrosion cracking susceptibility

Thesis proposal

Area of expertiseMaterials science and engineering
Doctoral SchoolSMI - Sciences des Mtiers de l'Ingnieur
SupervisorMme Ccilie DUHAMEL
Co-supervisorM. Vincent GUIPONT
Research unitCentre of materials
ContactDUHAMEL Ccilie
http://www.mat.mines-paristech.fr/Accueil/Propositions-de-theses/
KeywordsStress corrosion cracking, surface state, residual stresses
AbstractThe aim of this study is to have a better understanding of the effect of the surface state on the stress corrosion cracking susceptibility of nickel-based alloys used in the nuclear industry.

Stress corrosion cracking is one of the main degradation modes of some nickel-based alloys used in the primary circuit of pressurized water reactors (PWR). This phenomenon leads to the initiation and then the propagation of intergranular cracks under the synergetic effects of a corrosive environment and a tensile stress state. Models are being developed to estimate and predict SCC initiation and propagation of industrial components made of nickel-based alloys such as reactor vessel nozzle. Besides, numerical simulation of SCC is also being developed in order to base the predictions on stress and strain fields as realistic as possible, i.e. taking into account 3D effects (in terms of geometry, materials and loading). To improve the simulations, it becomes now necessary to better take into account representative surface states that affect more specifically the initiation step and the first stages of crack propagation.

The objective of the PhD thesis is to model the surface state of industrial components in terms of microstructure and mechanical state in order to improve the oxidation and initiation models used to predict the first stages of stress corrosion cracking.

As a first step, representative surface states resulting (i) from the key steps of nozzle fabrication and (ii) from surface modification by laser shock peening (used as a mitigation technique during in-service operation) will be produced and characterized (microstructure and residual stresses). Then, the variability of surface parameters will be modeled to be implemented in the nozzle modeling by finite element simulations.

Mechanical and oxidation tests will then be performed on the as-prepared materials in order to improve the existing oxidation and SCC initiation models used to predict the first stages of stress corrosion cracking.

Techniques to be used during the project :
- Metallography, scanning and transmission electron microscopy, microanalysis, EBSD
- X-ray diffraction (residual stress measurements), 3D Profilometry,
- Laser shock peening
- Microhardness, Nanoindentation
- Oxidation and stress corrosion tests
- Finite element simulation
ProfileTypical profile for a thesis at MINES ParisTech: Engineer and / or Master of Science - Good level of general and scientific culture. Good level of knowledge of French (B2 level in french is required) and English. (B2 level in english is required) Good analytical, synthesis, innovation and communication skills. Qualities of adaptability and creativity. Teaching skills. Motivation for research activity. Coherent professional project.

Applicants should supply the following :
a detailed resume
a covering letter explaining the applicants motivation for the position
detailed exam results
two references : the name and contact details of at least two people who could be contacted
to provide an appreciation of the candidate
Your notes of M1, M2
level of English equivalent TOEIC

to be sent to recrutement_these@mat.mines-paristech.fr
FundingConvention CIFRE