Hydrogen transport and trapping in ODS-EUROFER

The gas evolution permeation technique has been used to investigate the interaction of hydrogen with the oxide dispersion strengthened (ODS) reduced activation ferritic–martensitic (RAFM) steel EUROFER. The measurements were performed over the temperature range of 420–777 K with hydrogen driving pressures ranging from 2.5 × 103 to 1.0 × 105 Pa. The resultant diffusive transport parameters are a permeability of Φ (mol m−1 Pa−1/2 s−1) = 1.22 × 10−8 exp(−34.6 (kJ mol−1)/RT), a diffusivity of D (m2 s−1) = 1.33 × 10−6 exp(−30.4 (kJ mol−1)/RT) and a Sieverts’ constant of Ks (mol m−3 Pa−1/2) = 9.21 × 10−3 exp(−4.2 (kJ mol−1)/RT). The resultant trapping parameters have been a trap density of Nt = 2.0 × 1025 m−3 and trapping energy of Et = 44.9 kJ mol−1. All the hydrogen transport parameters obtained for the ODS-EUROFER are compared to the available data obtained for the base material EUROFER in order to study the influence of the particular micro-structure of ODS in the hydrogen transport. Other RAFM steels of the same kind are included in the comparative analysis. The presence of yttria nanoparticles induces a marked trapping phenomenon and provokes a decrease in the diffusivity and an increase in the solubility of hydrogen in the material at low temperature.