Study on hydrogen embrittlement susceptibility of X80 steel through in-situ gaseous hydrogen permeation and slow strain rate tensile tests

Hydrogen embrittlement is a serious threat to the safety operation for hydrogen blended natural gas pipelines. To determine the critical safety hydrogen blending ratio, in-situ high-pressure gaseous hydrogen permeation tests and slow strain rate tensile tests of X80 pipeline steel were conducted in the simulated hydrogen blended natural gas environments with 0–20 vol% hydrogen. The permeability characteristics, mechanical properties and fracture morphologies were systematically analyzed, and the embrittlement mechanism was discussed. Results show that the subsurface hydrogen concentration, ductility loss and hydrogen embrittlement susceptibility increased significantly as hydrogen blending ratio increased from 10% to 15%. Moreover, a positive correlation between subsurface hydrogen concentration and hydrogen embrittlement index was revealed. Combining the gaseous hydrogen permeation, SSRT results and fracture analysis, the 10% hydrogen blending ratio was determined as the conservative critical value for the safety operation of X80 hydrogen blended natural gas pipelines.