Effects of hydrogen on the mechanical properties of oxide dispersion strengthening steels

The effects of hydrogen on the mechanical properties of oxide dispersion strengthened (ODS) steels were investigated by means of tensile tests at room temperature. Cathodic hydrogen charging was carried out before and during deformation in a sulfuric acid solution by imposing a constant current density in the range of 100 to −520 A/m2. With increasing charging current density, the loss of ductility increased accompanied by a change in fracture mode from ductile to intergranular fracture. The critical hydrogen concentration in ODS steels required to transition from ductile to brittle fracture was in the range of 10–12 wppm, which approximately 10 times larger than that of a 9Cr–2W martensitic steel. In addition, the susceptibility to hydrogen embrittlement of ODS steels strongly depended on specimen sampling orientation.