Hydrogen-assisted fatigue crack growth in ferritic steels – a fractographic study

Abstract

Abstract. Fatigue crack growth (FCG) behavior of a Fe-3wt.%Si ferritic alloy under different environmental conditions using in-situ electrochemical (cathodic) hydrogen (H) charging has been investigated. Three frequencies have been applied. Results clearly show that the FCG rate increased by a factor spanning from 20 to 1000 times, depending on the loading frequencies, when compared to the reference test in air. Lower frequency leads to higher FCG rate. A comprehensive fractographic analysis was carried out: the area fraction of different fracture surface features was measured and taken into statistical analysis. Based on these investigations, the possible mechanisms of H-enhanced FCG are discussed. Similar tests in high-pressure H gas from other studies were also compared and discussed. These results give a preliminary understanding of H effect in fatigue crack propagation procedure in ferritic alloys.

Hydrogen-enhanced fatigue crack growth in a single-edge notched tensile specimen under in-situ hydrogen charging inside an environmental scanning electron microscope

“…9. Previous literature showed similar H-induced "quasi-cleavage" features in various Fe-based BCC alloys under different H-rich environments [24,[39][40][41][42][43][44][45][46]. It is thus considered that one characteristics by H-charging in fractography is the "quasi-cleavage" fracture features.…”