Hydrogen-induced toughness drop in weld coarse-grained heat-affected zones of linepipe steel

In this study, hydrogen effects on the impact toughness of simulated coarse-grained heat-affected zones (CGHAZs) in a linepipe steel were investigated in search of the possible “local brittle zone phenomenon” in hydrogen pipeline welds. After hydrogen charging, the inter-critically reheated and unaltered CGHAZ exhibited very low impact energies as well as occurrence of splitting. This hydrogen-induced toughness drop is discussed in terms of combined effects of brittle microstructures and hydrogen trapping.