Mechanism of hydrogen embrittlement in iron

Determine the unequivocal mechanism by which hydrogen embrittles iron, including how hydrogen-induced changes in bonding and cohesion produce fracture susceptibility.

Background

The paper investigates hydrogen embrittlement in iron by combining traction–separation calculations with density functional theory and crystal orbital Hamilton population analysis. It focuses on how hydrogen modifies Fe–Fe and Fe–H bonding across an iron fracture plane and argues that electrostatic repulsion between hydrogen-covered fracture surfaces contributes to reduced cohesion.

Despite numerous proposed explanations involving bulk defects, surfaces, grain boundaries, vacancies, and hydrogen-enhanced decohesion, the paper presents the underlying mechanism as unresolved. The stated problem therefore concerns identifying the definitive, comprehensive physical mechanism responsible for hydrogen embrittlement in iron.