Fracture toughness, fatigue crack propagation and creep rupture behaviour in thick section weldments of 3Cr-Mo pressure-vessel steels developed for high-temperature/high-pressure hydrogen service

Both plane-strain fracture toughness and creep rupture lives were found to be relatively unchanged in the weldment microstructures compared with parent plate, and they were affected little by environmental damage (hydrogen attack) induced by the prior hydrogen exposure. Creep properties, however, were found to be sensitive to post-weld heat treatment. Similarly, fatigue crack growth properties were only marginally affected by prior hydrogen-attack damage, except for tests on weld metal where, compared to the undamaged microstructures, growth rates below approximately 10^-6 m cycle^-1 were accelerated by up to an order of magnitude and fatigue thresholds decreased by around 25%.