Effects of different microstructural parameters on the corrosion and cracking resistance of pipeline steels: A review

Several environmental challenges such as corrosion, low temperature, hydrogen-induced cracking (HIC), stress corrosion cracking (SCC), sulfide stress corrosion cracking (SSCC), and various other failure mechanisms contribute to the deterioration of the mechanical properties of pipeline steels, ultimately resulting in failure. In this review, diverse hydrogen attack sources, their possible failure mechanisms, and various strategies for their mitigation in different environments are explored. Optimizing the microstructure of pipeline steels can greatly improve their resistance to corrosion and cracking. This involves tailoring several microstructural parameters like the phase composition, dislocation density, crystallographic texture, grain size, grain boundary, and inclusions/precipitates, amongst others to the needs of the steel's service environment. The evolving research landscape concerning the role of these microstructural parameters in corrosion, HIC, SCC, and other failure mechanisms was discussed in this study. It was established that crystallographic texture and grain boundary characteristics have roles to play in improving the SCC resistance of pipeline steels. However, the degree to which crystallographic texture, amidst other microstructural parameters, affects cracking is not yet established. For instance, the direct influence of crystallographic texture in the arrest of propagating cracks is still unclear and debated, while low-angle grain boundaries and CSL boundaries have been seen to arrest cracks in steels. It was also established that dislocation density, amongst other microstructural parameters, has a more profound effect on the HIC resistance of pipeline steels. Furthermore, this review examines the effect of hydrogen in pipeline welds. It investigates strategies to adapt existing pipelines' microstructure to meet the demands of operations in arctic environments. It was established that grain size, amongst other microstructural parameters, has a more profound effect on the mechanical properties of pipelines designated for cold applications. Finally, this review explores recent advancements in the transportation of gaseous hydrogen using existing pipeline steels (natural gas infrastructure). Ultimately, this study reinforces the importance of microstructure optimization in pipelines designated for different service environments, detailing the contribution of individual microstructural parameters to their overall performance and failure susceptibility in these environments.