Research on the effect of hydrogen on the low-cycle fatigue property of the heat-affected zone of the X80 welded pipe

Purpose This research aims to investigate the fatigue fracture mechanism of the heat-affected zone (HAZ) of the X80 welded pipes after being affected by hydrogen, thereby enhancing the safety of hydrogen transportation pipelines. Design/methodology/approach This study used thermal simulation, electrochemical hydrogen charging and low-cycle fatigue testing, combined with microstructural analysis, to systematically investigate the low-cycle fatigue behavior of various subzones in the HAZ of X80 welded pipe. Findings The results show that hydrogen significantly reduces the fatigue life of the HAZ. The coarse-grain HAZ suffers the most severe damage, with the average fatigue life decreasing by 78%, while the fine-grain HAZ has the strongest resistance to hydrogen damage, with the average fatigue life decreasing by 43%. Originality/value In this work, the microscopic mechanisms of hydrogen-induced fatigue damage were elucidated from perspectives including microstructural evolution, grain boundary characteristic changes and dislocation behavior. The research results will provide theoretical guidance for the design of hydrogen resistance in the HAZ of welded pipelines for hydrogen transport.