Hydrogen adsorption in phase and grain boundaries of pearlitic steels and its effects on tensile strength

Molecular dynamic simulations are invoked to study hydrogen (H) adsorption as well as its effects on the strength of pearlitic steels. In particular, the effects of H on the strength of the cementite (Fe₃C)–ferrite interphase and the ferrite–ferrite grain boundaries are investigated. It is observed that the thickness of the cementite phase and the ferrite grain boundary orientation influences H adsorption: the amount of adsorbed H atoms decreases linearly with the thickness of the cementite phase; the Σ3 ferrite grain boundaries with ~ 30° or 75° orientation trap the most H atoms. Upon comparing the tensile strength of atomic structures before and after the H adsorption, it is observed that the strength of the cementite–ferrite interface is increased after H adsorption. H adsorption and H cluster formation at or near the grain boundaries are observed to affect the strength and failure modes of the ferrite–ferrite grain boundaries. Graphical abstract: [Figure not available: see fulltext.]