Effect of hydrogen on the fracture toughness of X65 high-frequency welded pipeline

The effect of hydrogen on the fracture toughness of X65 high-frequency welded (HFW) pipelines was investigated both in a hydrogen environment and in air. The hydrogen environment was created by in situ hydrogen charging, using a simulated soil solution as the electrolyte. Four current densities were used, namely 1, 2, 4, and 8 mA/cm2. The fracture toughness was characterized by the crack tip opening displacement (CTOD). The CTOD values of the base metal and weld metal decreased with increasing hydrogen charging current density, and a higher reduction was seen in the weld metal. In addition, the hydrogen permeation and electron backscattered diffraction (EBSD) measurements were also applied to the base metal and weld metal to evaluate the hydrogen-induced cracking (HIC) susceptibility. The results showed that the weld metal had a higher HIC susceptibility than that of the base metal.