Failure analysis of a functionally graded multilayer coated stainless steel pipe for hydrogen storage

In this study, a plane strain finite element analysis (FEA) was employed to investigate failure mechanisms of a hydrogen storage pipe system made of 316L stainless steel pipe coated with pure and functionally graded (FG) ceramic layers composed of Al2O3 and SiC. The system was studied for different common failure mechanisms, i.e., delamination, surface cracking and buckling delamination, upon cooling from an elevated stress-free temperature. Finally, the composition and thickness of the coating layers were considered as the main controlling factors and investigated for their influence on the studied failure mechanisms. It was observed that the most energetically favourable cracking mechanism for this type of system was surface cracking with the propagation of these cracks eventually leading to different failure paths. Buckling was found to be as less energetically favourable compared to surface cracking with the buckling resistance being enhanced by changing the coating thickness and composition factor.