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

Martensitic stainless steels are candidate materials for the target structu re of the European Spallation Source (ESS). Hydrogen and helium produced by nuclear transmutation in the proton beam and in the energetic neutron fiel d cause changes of material properties in addition to those caused by atomi c displacement. The present work presents results of diffusion and retentio n of hydrogen and helium, derived from permeation and thermal desorption ex periments. Furthermore synergy effects are discussed which occur when hydro gen is retained due to the presence of helium. Measurements of the effect o f hydrogen and helium on hardness and tensile properties are given and resu lts on fracture, creep rupture and fatigue are reviewed. (C) 2001 Elsevier Science B.V. All rights reserved.