Surface modification to mitigate gaseous hydrogen effects in a 1800 MPa martensitic steel

A 0.8 % carbon steel was heat treated in air, resulting in an ultimate tensile strength of 1800 Mpa and a highly ductile, dense and adhering decarburized ferritic layer, approximately 50 μm thick. The chemical composition and mechanical properties of this ferritic layer were thoroughly examined. Tensile testing and fractography revealed that the decarburized ferritic layer serves as a barrier, protecting the ultra-high strength martensitic steel from gaseous hydrogen-assisted fracture. This outcome implies that, in terms of preventing hydrogen-assisted fractures, the low hydrogen permeability of a protective surface layer is less critical compared to adjusted mechanical properties of the bulk material and surface layer.