Effect of cold working on the hydrogen trapping phenomena in pure iron

Abstract

Hydrogen trapping in iron with various types and amounts of trapping sites was investigated through permeation experiments. The apparent hydrogen diffusivity decreases as the degree of cold working increases. This decrease is attributed to an increase in dislocation density and microvoid concentration. Analysis of the permeation data suggests that hydrogen binding energies of dislocation and microvoid are 25.6 kJ/mole and 29.1 kJ/mole, respectively. The data further show that the apparent hydrogen diffusivity increases as applied hydrogen pressure increases. Energy level diagrams around various trapping sites are proposed.