Mohammad Ali Mohtadi Bonab

In this study, the hydrogen embrittlement and corrosion behavior of X100 pipeline steel (Ref) was investigated after various heat treatments, including one-step austenitizing at 880 C (HT3), 830 C (HT2), and 780 C (HT1) for 90 min, oil quenching to room temperature, tempering at 600 C for 30 min, and air cooling to room temperature. Potentiodynamic polarisation was performed to assess the electrochemical corrosion behavior, while the Charpy impact test and Vickers microhardness measurement were performed to assess the hydrogen embrittlement susceptibility before and after hydrogen charging. SEM, EBSD, and EDS were used to further characterize the fractured surface and crystallographic texture of specimens, while XRD was used to evaluate the macro-texture and corrosion products. The results of the Charpy impact and hardness tests showed that the high hardness and low impact energy values in the Reference and HT3 specimens were linked to a higher susceptibility to hydrogen embrittlement, indicating that the hardness values and Charpy impact energy, respectively, increased and decreased with a decrease in the hydrogen embrittlement resistance. The micro-texture results from the EBSD analysis showed that the HT3 and Ref. specimens had higher Kernel average misorientation (KAM) values and higher deformed grains fractions than those of the HT2 and HT1 specimens, resulting in lower corrosion resistance. The HT2 specimen had an optimal combination of beneficial ({110}, {111}, {332}) and harmful texture components ({100}), showing that corrosion resistance can be improved.