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.

Micro-Portion Image Analysis of Light Elements in Fe–Cr Based Alloys by Time-of-Flight Secondary Ion Mass Spectrometry

“…One of the limitations in the study on hydrogen embrittlement is the difficulty of microscopic analysis of hydrogen in steels compared to other light elements, since the solubility of hydrogen in the steels at about room temperature is low. [3][4][5][6][7] Thus, it is necessary to establish analysis methods of the microscopic distribution of hydrogen experimentally, although the mechanism of hydrogen embrittlement has been mainly investigated based on atomistic models [8][9][10][11] and the mechanical properties and the relevant phenomena have been investigated in detail. [12][13][14][15] On the other hand, analytical methods for investigating the distribution of hydrogen in steels are limited, as the use of vacuum is generally required in such analytical apparatuses.…”

“…We conclude that the deuterium diffused out of the sample at room temperature, as the diffusivity of hydrogen is quite high in body-centered-cubic (bcc) Fe-based alloys. [4][5][6][7] However, it is noted that deuterium was detected in the depth profiles of the duplex stainless steel charged with 2 H 2 O, while it was not detected after annealing. This indicates that deuterium diffuses out of the sample during annealing, and the diffusion of deuterium is slow in the duplex stainless steel at room temperature.…”

Fully quantum mechanical calculation of the diffusivity of hydrogen in iron using the tight-binding approximation and path integral theory

“…[3][4][5][6] This high H diffusivity results from the very low activation energies due to the quantum nature of H. 2 The existence of microstructural imperfections (vacancies, solute atoms, dislocations, grain boundaries, etc.) introduces low energy trapping sites within the lattice which retard the overall diffusion rate.…”

Infusion of hydrogen into nanostructured bainitic steel

“…However, it was assumed in the current model that this value is proportional to the volume fraction of bainitic ferrite. The diffusivity of hydrogen in ferrite considered here was D 0 =5.8x10 -8 m 2 s -1 and the activation energy, Q=4.5 kJ/mol [34]. The number of trap sites at α/γ interfaces, Nt 1 , was assumed proportional to the surface area per unit volume and dislocation density [35].…”