Hydrogen trapping models in steel

This article describes the role of hydrogen trapping in steel. Trapping inc reases the solubility of hydrogen and decreases the diffusivity. Traps are characterized by their nature, i:e., reversible or irreversible, saturable or unsaturable. A dislocation core is a saturable, reversible trap, while v oids and crack are unsaturable, reversible traps. A trap model based on sat urable, reversible traps is developed, which is slightly different from the trap model of McNabb and Foster. In equilibrium, the trap model correspond s to Oriani's trap model. Kumnick and Johnson found experimentally that the trap density increases as the plastic strain increases. Using their trap d ata, it is shown that equilibrium between hydrogen in lattice sites and tra p sites can be assumed when strain rates are used as in standard tensile te sts.