Hydrogen embrittlement of the Ni-base Alloy 600 correlated with hydrogen transport by dislocations

Hydrogen transport by dislocations is one of the mechanisms reported in the literature to be responsible for the hydrogen embrittlement (H.E.) of some metals even if it needs to be associated with one or several cracking mechanisms. This study brings new evidence of dislocation sweeping of hydrogen and some arguments in favor of its contribution to the H.E. mechanism of Alloy 600 (Ni-Cr-Fe). A study of tritium desorption assisted by the plastic deformation has been conducted by coupling a beta counting technique and a tensile test. The experimental results obtained with Alloy 600 strongly support the mechanism of hydrogen transport by dislocations. The H.E. characteristics of Alloy 600 have been measured on smooth tensile specimens in relationship with the microstructure and the testing conditions. The influence of different parameters including the prestrain level, the strain rate and the temperature supports the role of hydrogen transport in the embrittlement process and the existence of local hydrogen enrichment associated with dislocations pile-ups. (C) 1999 Elsevier Science S.A. All rights reserved.