Effect of Dislocation Trapping on Hydrogen and Deuterium Diffusion in Iron

Abstract

The diffusion coefficients of hydrogen and deuterium in commercially pure iron deformed and annealed under various conditions have been measured at temperatures between 283 and 318 K by an electrochemical permeation method. The temperature dependence of the diffusion coefficients of hydrogen (DH) and deuterium (DD) is discussed on the basis of the trapping theory by Oriani. Two trapping parameters, the binding energy of hydrogen or deuterium with trapping sites and the trap site density are determined by fitting the diffusion coefficient calculated from the trapping theory to the experimental results. The ratio of the diffusion coefficient of hydrogen to that of deuterium, DH⁄DD, has been found to be dependent on temperature, but not on the trap site density. This indicates that the trap site density and the binding energy are, within an experimental error, the same for hydrogen and deuterium, although the activation energy of diffusion in a normal lattice is found to be mass dependent. The binding energies with trapping sites (dislocations) for both hydrogen and deuterium are determined as about 27 kJ/mol, which shows a good agreement with those reported by Gibala, Oriani and others.