The aim of this work is to propose a model to explain the microscopic mechanism of Stress Corrosion Cracking (SCC) in PWR water of stainless steels or nickel base alloys. Molecular Dynamics (DM) simulations on bicrystal or Ni have been carried out with hydrogen at the grain boundary (GB) (Eta 5). Two temperatures have been tested : IK and 562K. Literature reports that Transmission Electronic Microscopy analysis at the crack tip (CT) reveals the presence of an oxide. As this oxide bas a 15% lattice parameter higher than the alloy, it induces a pressure on the crack lips (CL). The role of this pressure and hydrogen will be particularly addressed. Simulations without hydrogen nor pressure on the CL shows ductile fracture with blunting of the CT. On the contrary, when a compressive strength is applied on the CL and hydrogen is present at the GB, the rupture is brittle with a GB cleavage. A SCC model bas been inferred from these results.
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