Hydrogen effects on tensile properties of EUROFER 97 and ODS-EUROFER steels

Hydrogen effects on the mechanical tensile properties of the ferrite-martensite EUROFER 97 and ODS-EUROFER steels were studied after electrochemical hydrogen charging at room temperature. Hydrogen was introduced into the steels from 0.1 N NaOH solution under controlled cathodic potential. Hydrogen TDS measurements show that yttria nanoparticles increase considerably the hydrogen uptake in ODS-EUROFER steel in comparison to that in EUROFER 97 steel. Hydrogen has only a minor effect on the yield stress and tensile strength of the studied steels. EUROFER 97 and ODS-EUROFER steels manifest rather different sensitivity to hydrogen embrittlement. It is shown that hydrogen reduces markedly elongation to fracture of ODS-EUROFER steel, if hydrogen concentration exceeds a certain critical value. FEG-SEM fractography observations evidence the intergranular fracture mode of ODS-EUROFER steel. The possible role of yttria nanoparticles in the hydrogen embrittlement mechanism is discussed.