Hydrogen embrittlement (HE) and hydrogen-induced cracking (HIC) behaviour of a X65 steel pipeline weldment were investigated using slow strain rate tensile (SSRT) testing of specimens that were specifically extracted from different zones of the weldment (i.e., weld metal (WM), heat-affected zone (HAZ), and base metal (BM)). The WM was found to be the most susceptible zone to HE and HIC, while BM the least. Analysis of microstructure, fracture surface, secondary crack formation, and mechanical behaviour revealed that the high HE susceptibility of WM is correlated to microstructural features including Ti-rich inclusions, martensite/austenite (M/A) constituents, and prior austenite grain boundaries (PAGBs).
The resistance to ductile fracture propagation remains a weak point in gas transmission pipelines’ safety since the emerging of this risk more than half a century ago. Full-scale burst tests of pressurized gas pipeline sections are performed to verify the ability of pipeline steel to arrest the crack propagation. However, motivated by the commitment to specific predictive models, the main outcome from full-scale burst tests (FSBT) has been in form of a binary “propagation/arrest” metric corresponding to each pipe in the test section. In the absence of a reliable laboratory-scale test demonstrating correlation with the full-scale resistance to ductile fracture propagation, such approach does not appear reasonable since it leaves line pipe manufacturers with very little clue regarding the preferential metallurgical designs. This work aims to better quantify the crack propagation resistance in FSBT providing metallurgists with a target property and facilitating the development of a