Retention of implanted hydrogen and helium in martensitic stainless steels and their effects on mechanical properties

Martensitic stainless steels are candidate materials for the target structure of the European Spallation Source (ESS). Hydrogen and helium produced by nuclear transmutation in the proton beam and in the energetic neutron field cause changes of material properties in addition to those caused by atomic displacement. The present work presents results of diffusion and retention of hydrogen and helium, derived from permeation and thermal desorption experiments. Furthermore synergy effects are discussed which occur when hydrogen is retained due to the presence of helium. Measurements of the effect of hydrogen and helium on hardness and tensile properties are given and results on fracture, creep rupture and fatigue are reviewed.