Investigation on hydrogen-induced damage mechanism and sealing performance of 80S steel premium connections in hydrogen storage conditions

To address the challenges of mechanical degradation and sealing failure in Underground Hydrogen Storage (UHS) tubing strings exposed to hydrogen environments, this study employs a combined methodology of molecular dynamics (MD) simulations, experimental testing, and finite element (FE) analysis to investigate the hydrogen adsorption mechanism of 80S steel and its impact on the sealing performance of premium connections. The results indicate that high-pressure environments significantly lower the energy barrier for hydrogen atoms diffusing into the lattice. Furthermore, experiments confirm the high susceptibility of 80S steel to hydrogen embrittlement (HE); after hydrogen charging, its ultimate tensile strength (UTS) and elongation decreased by 12.33% and 33.9%, respectively. Conversely, a copper coating can effectively inhibit hydrogen permeation. Based on the material degradation data, an FE model of the premium connection coupling hydrogen-induced damage and alternating loads was established. The analysis reveals that the synergistic effect of hydrogen-induced softening and alternating loads triggers premature plastic yielding at the sealing surface. This not only causes a relaxation of the peak contact pressure by approximately 9.6% but also shrinks the enclosed area of the hysteresis loop representing energy dissipation, thereby accelerating sealing failure. Ultimately, this study elucidates the hydrogen-induced damage mechanisms from a multi-scale perspective, providing critical support for the sealing design and safety assessment of 80S steel premium connections under hydrogen service conditions.