The fatigue crack growth behavior of hydrogenated 9Cr‐1Mo steel: An experimental and numerical study

This research investigates the fatigue crack evolution in P91 steel through experiments and extended finite element method (XFEM) simulation for as‐received and hydrogenated conditions. Hydrogen pre‐charging is performed using a constant current electrochemical method in 1 M sulfuric acid solution. The study compares the experimental fatigue crack growth rate (FCGR) of hydrogenated and as‐received conditions and employs an XFEM simulation to replicate FCGR. The results of the experiments reveal an increased FCGR in hydrogenated specimens. Fracture surface analysis confirms the co‐occurrence of the “hydrogen‐enhanced localized plasticity” (HELP) and “hydrogen‐enhanced decohesion” (HEDE) mechanism (HELP+HEDE, HEDE>HELP). The simulation results closely align with the experimental findings, validating the model's accuracy. Consequently, these findings are the basis for proposing a damage tolerance approach‐based numerical algorithm. This algorithm allows the prediction of component integrity by considering a known crack length. Furthermore, fracture toughness (KIQ) was experimentally evaluated to enhance the understanding of the material's mechanical properties. Highlights The fatigue crack growth rate (FCGR) increases in the presence of hydrogen. The acceleration factor graph shows that FCGR increases with load ratio. The extended finite element method simulation results match the experimental result. SEM images show the occurrence of the HELP+HEDE (HEDE>HELP) mechanism.