Hydrogen embrittlement phenomena and mechanisms

Mechanisms of hydrogen embrittlement in steels and other materials are described, and the evidence supporting various hypotheses, such as those based on hydride formation, hydrogen-enhanced decohesion, hydrogen-enhanced localised plasticity, adsorption-induced dislocation emission, and hydrogen-vacancy interactions, are summarised. The relative importance of these mechanisms for different fracture modes and materials are discussed based on detailed fractographic observations and critical experiments.