Mechanical aspects of the Charpy impact test

The simultaneous action of cathodic hydrogen charging and slow mechanical loading on precracked samples of 316L stainless steel is examined in order to assess the flaw tolerance of this steel, which has been included in the group of possible structural materials for the first wall of the future fusion reactors. The steel is shown to retain a significant part of its flaw tolerance even in the most severe test conditions, but the loading rate is found to change the damage phenomenology of hydrogen from bifurcated crack extension to multi-cracking and enlargement of the blunted crack tip. This change is explained on the basis of a competition mechanism between hydrogen action and mechanical deformation. © 1999 Published by Elsevier Science S.A. All rights reserved.