Study on Hydrogen Embrittlement Behavior in Heat-Affected Zone of X80 Welded Pipe

Hydrogen, as a clean energy source, has gradually become an important choice for the energy transformation in the world. Utilizing existing natural gas pipelines for hydrogen-blended transportation is one of the most economical and effective ways to achieve large-scale hydrogen transportation. However, hydrogen can easily penetrate into the pipe material during the hydrogen-blended transportation process, causing damage to the properties of the pipe. The heat-affected zone (HAZ) of the weld, being the weakest part of the pipeline, is highly sensitive to hydrogen embrittlement. The microstructure and properties of the grains in the heat-affected zone undergoes changes during the welding process. Therefore, this paper divides the HAZ of X80 welded pipes into three sub-HAZ, namely the coarse-grained HAZ, fine-grained HAZ, and intercritical HAZ, to study the hydrogen behavior. The results show that the degree of hydrogen damage in each sub-HAZ varies significantly at different strain rates. The coarse-grained HAZ has the highest hydrogen embrittlement sensitivity at low strain rates, while the intercritical HAZ experiences the greatest hydrogen damage at high strain rates. By combining the microstructural differences within each sub-HAZ, the plastic damage mechanism of hydrogen in each sub-HAZ is analyzed, with the aim of providing a scientific basis for the feasibility of using X80 welded pipes in hydrogen-blended transportation.