PhD opportunities

PROVIDED - Stress Corrosion Cracking of cold-worked austenitic stainless steels in primary water reactors: influence of dissolved oxygen

Thesis proposal

Area of expertiseMaterials science and engineering
Doctoral SchoolSystems Engineering, Materials, Mechanics, Energy
SupervisorM. Jerme CREPIN
Co-supervisorMme Ccilie DUHAMEL
Research unitCentre of materials
ContactDUHAMEL Ccilie
Starting dateOctober 1st 2019
Keywordsoxidation, stress corrosion cracking, stainless steel
AbstractThe aim of this study is to have a better understanding of the effect of the water chemistry on the stress corrosion cracking susceptibility of cold-worked austenitic stainless steels used in the nuclear industry.

Context and challenges:
Stress corrosion cracking is a degradation mode that leads to the initiation and then the propagation of cracks under the synergetic effects of a corrosive environment and a tensile stress state. It may affect cold-worked austenitic stainless steel components used in the primary circuit of pressurized water reactors. In the primary circuit, that sees the fission reaction, high temperature and high pressure deaerated and hydrogenated water flows. In this environment, oxidation and SCC susceptibility of stainless steels can be influenced by many material, environment and mechanics-related parameters. In particular, the presence of dissolved oxygen can change the SCC cracks morphology (from transgranular to intergranular), and the surface oxidation film features. Oxygenated transients, i.e. reactor operating steps with oxygen injections in nominal primary water, may be an additional detrimental factor.

Scientific objectives:
The aim of this work is to study the influence of dissolved oxygen on the SCC susceptibility in PWR primary water of a cold-worked 316L stainless steel. A special attention is paid to the eventual coupling between strain localization, oxidation, and SCC cracking. For this purpose, SCC tests will be performed in three different environments: PWR primary water with nominal chemistry (reference chemistry) as well as in fully-aerated (high concentration of dissolved oxygen), and oxygenated transients (nominal and aerated conditions are alternately applied) compositions. The resulting cracking networks will be correlated to the microstructural and local strain fields obtained by electron backscatter diffraction (EBSD) and digital image correlation (DIC), respectively.
Besides, the effect of oxygen on the oxidation kinetics and oxide structure and composition was studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations performed on samples exposed to the three environments previously described. Additional XPS (X-ray photoelectron spectrometry) analyses may also be carried out.

Expected results:
Better understanding of the effect of the water chemistry on the SCC mechanisms of austenitic stainless steels in primary water
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.

Prerequisite (specific skills for this thesis):
Strong background in material science
Taste for experimental work
Notions in mechanics are welcome

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
Available transcripts of the semesters of a masters degree
level of English equivalent TOEIC
to be sent to recrutement_these@mat.mines-paristech.fr
FundingContrat de recherche