Fracture and Fatigue Crack Growth Performance of a Vintage X60 Pipeline Material in Gaseous H2 and Comparison With Wet Sour Service Available to Purchase

Fracture toughness and fatigue crack growth testing was performed on the parent and weld microstructures of a vintage offshore API 5L X60 grade pipeline material to assess the impact of various partial pressures of gaseous H₂. Fracture toughness values were found to reduce compared to the in-air values as expected, and fatigue performance was consistent with published literature for ΔK above 5 MPa√m. At ΔK below 5 MPa√m the fatigue crack growth curve is higher than predicted, which is suspected to be driven by time dependent sustained cracking mechanism. This phenomenon appears to be a function of the applied pressure (i.e. the max stress intensity factor) and the microstructure. In comparison to the wet sour service the gaseous hydrogen appears less detrimental to the material performance at low partial pressure H₂ (representative of a 10% blends) and becomes similar to the NACE Region 2/3 with low pH sour performance at higher partial pressures of H₂.