Direct observation of hydrogen trapped by NbC in steel using small-angle neutron scattering

Small-angle neutron scattering has been measured for 97.62Fe–0.23C–0.25Nb–1.90Ni (at.%) steel with and without hydrogen charging. The intensity of the scattering from nanosized NbC is higher for samples with hydrogen than for those without hydrogen. The enhanced scattering intensity for samples with hydrogen disappears after hydrogen desorption heat treatment. This result provides direct structural evidence for the trapping of hydrogen by NbC.