Hydrogen embrittlement poses significant challenges for integrating hydrogen into existing natural gas pipelines. This phenomenon, where metals become brittle and fracture due to the penetration of hydrogen, can compromise the integrity of steel pipelines.
Research led by L.M. Santana and colleagues, published on October 28, 2024, in the International Journal of Hydrogen Energy, investigates this issue using innovative approaches.
Traditional Disk Pressure Tests (DPT), which pressurize clamped disks until they fail, often result in fractures at the clamping zones, complicating failure analysis. To address this, researchers redesigned the disk geometries. By modifying these geometries, they controlled the failure locations, ensuring the fractures occurred away from the clamping zones. This modification preserves the inherent setup while enhancing test reliability.
The study rigorously tested two steel grades, vintage X52 pipeline steel and modern E355 modified steel, under varied pressure rise rates using both helium and hydrogen. The results were telling. The failure pressures under hydrogen exposure illustrated significant hydrogen embrittlement compared to helium. This marked difference underscored hydrogen’s detrimental impact on steel integrity.
Beyond physical tests, the team employed simulations linking hydrogen trap density to plastic strain. These models successfully matched the experimental data, illustrating how hydrogen atoms diffuse and get trapped within the steel’s microstructure. They also explored how trap binding energy and trap density evolve, correlating closely with the embrittlement depth observed experimentally.
The outcomes of this research hold substantial implications for pipeline safety. The new geometries and comprehensive testing apparatus provide a clearer understanding of how hydrogen embrittlement occurs and evolves. Such insights are crucial for developing more resistant materials and ensuring the safe integration of hydrogen into pipeline systems.
