Synergistic effect of fatigue and hydrogen-induced damage under asymmetric loading of TRIP steel

Abstract

This study investigates the synergistic assessment of cyclic plasticity damage and hydrogen-induced cracking of transformation-induced plasticity (TRIP) steel subjected to asymmetric strain-controlled fatigue loading. The presence of hydrogen in TRIP steel results in cyclic softening throughout its life, suppressing the hardening behavior induced by martensitic transformation. The mild hardening observed in hydrogen-free specimens is attributed to the predominance of hardening induced by martensitic transformation over cyclic softening. The increase in mean strain leads to higher mean stress relaxation, suppressing the compressive stress developed during the deformation-induced martensitic transformation phenomenon. Geometrically necessary dislocation (GND) density map and fractographic images substantiate the hydrogen-enhanced decohesion failure mechanism, decreasing fatigue resistance for hydrogen-induced TRIP steel. The failure mechanisms of the fatigue damage due to the ingress of hydrogen atoms in the material are proposed for further insights.