Hydrogen analysis ahead of the fatigue crack tip in the high strength steel

The secondary ion mass spectrometry method has been employed to analyse the distribution of hydrogen concentration in the zone of the fatigue crack tip and at its edges in the martensitic high strength steel. Changes in hydrogen concentration were observed in the vicinity of the propagating crack tip and at a remote site. The hydrogen peak is reduced and moves away from the fatigue crack tip with the increase of the maximum stress intensity factor. The physical failure criterion based on the hydrogen peak in the vicinity of the fatigue crack tip and the maximum stress intensity factor has been proposed. The criterion reflects changes in the hydrogen peak which resulted from the hydrogen redistribution due to the increase of the maximum stress intensity factor as the crack length increases under fatigue loading.