Abstract
The repurposing of existing natural gas pipeline networks for hydrogen transport is a vital component of global decarbonization strategies. However, the structural integrity of these systems is challenged by hydrogen-induced degradation, specifically hydrogen-enhanced fatigue crack growth (HA-FCG). While constant-amplitude loading in hydrogen is well-studied, the impact of overload (OL) cycles, which occur during hydrostatic testing or during operational pressure fluctuations, remains poorly understood in Hydrogen environments, contrary to the well-known effect of overload in air or inert environments. This study addresses the knowledge gap by investigating how a single overload event affects subsequent crack propagation in vintage X65 pipeline steel through fractographic analysis, with a focus on the critical interaction between the overload-induced zone and hydrogen embrittlement.