Hydrogen-affected fatigue crack propagation at various loading frequencies and gaseous hydrogen pressures in commercially pure iron

Hydrogen-Affected Fatigue Crack Growth (HAFCG) in commercially pure iron has been characterized in terms of hydrogen gas pressure, loading frequency and stress intensity factor range Delta K. A higher hydrogen gas pressure decreases the critical value of Delta K triggering the HAFCG enhancement, and a lower loading frequency increases the HAFCG enhancement. Intergranular FCG in the non-accelerated regime is likely caused by the hydrogen-induced microvoid coalescence along the grain boundary, while a brittle cyclic cleavage fracture in the accelerated regime can be explained in terms of crack tip sharpening and hydrogen-enhanced decohesion process.