Hydrogen Effects on X80 Pipeline Steel Under High-Pressure Natural Gas-Hydrogen Mixtures

Blending hydrogen into the existing natural gas pipeline has been proposed as a means of increasing the output of renewable energy systems such as large wind farms. At present, X80 pipeline steel is commonly used for transporting natural gas. However, the pipeline steel is subjected to concurrent hydrogen invasion with mechanical loading while being exposed to hydrogen containing environments directly, and then hydrogen embrittlement (HE) of metals may occur. In accordance with ASTM standards, the mechanical properties of X80 pipeline steel have been tested in natural gas/hydrogen mixtures with 0, 5.0, 10.0, 20.0 and 50.0vol%2hydrogen at the pressure of 12MPa. The results indicates that X80 pipeline steel is susceptible to hydrogen-induced embrittlement in natural gas/hydrogen mixtures and the HE susceptibility increases with the hydrogen partial pressure. Additionally, the HE susceptibility depends on the textured micostructure caused by hot rolling, especially for the notch specimen. From the designed life calculation by the measured fatigue data, it is found that the designed life of the X80 steel pipeline is degraded by the added hydrogen dramatically.