Stress corrosion cracking in the context of deep geological nuclear disposal – investigations on P235 and P265 steels

ABSTRACTStress corrosion cracking of P235 and P265 steels is investigated through slow strain rate and constant deformation tests on samples exposed in a cell reproducing the underground conditions of the French deep geological nuclear disposal, at 25 and 90°C. The samples were taken from the base metal, the heat affected zone and the fusion zone of a P265 steel weld joint. Tests were performed at the free corrosion potential and under polarisation in the cathodic or anodic domains. Long-term constant deformation tests were also carried out to evaluate the behaviour of the material under static loading in hydrated clay environment. The results show a significant sensitivity of the tested materials to environmental cracking in the experimental conditions, with an enhancement of the effect of the environment for the weld metal. A mechanism of hydrogen embrittlement is proposed to be responsible for the cracking phenomenon. Susceptibility to environmental assisted cracking observed during these tests indicat...