Fracture Toughness of X80 Pipeline Steel after Electrochemical Hydrogen Charging in Different States

The fracture toughness of X80 pipeline steel after static electrochemical hydrogen charging and dynamic electrochemical hydrogen charging was investigated by tensile tests and slow strain rate tests(SSRT).The experimental results indicate that under the static hydrogen charging condition,the fracture toughness increased with the increase of current density when current density was lower than 12.5 mA/cm2.Otherwise,the effect of current density on fracture toughness was opposite.Under the SSRT condition,dynamic electrochemical hydrogen charging decreased the fracture toughness of X80 pipeline steel considerably and followed a certain function relationship with the current density of hydrogen charging.The fractograph of the X80 pipeline steel after static hydrogen charging exhibited typical ductile dimple fracture pattern,the size and depth of which was smaller than those without hydrogen charging.The fractograph showed areas of cleavage under SSRT condition with dynamic hydrogen charging.