Abstract
1 min readThis report presents results of a two year research program to study damage mechanisms associated with high-temperature, high-pressure, hydrogen service (i.e., coal conversion applications) and affecting metallurgical stability and mechanical properties, in particular, fatigue crack propagation and creep rupture properties, of weld metal and heat affected zone (HAZ) regions in thick section weldments in two Cr-Mo steels, namely 3Cr-1-1/2Mo-1/2Ni steel, hereafter referred to as Berkeley steel, and 3Cr-1Mo-1/4V-Ti-B, referred to as JSW (Japan Steel Works) steel. In addition, suggestions on how microstructures might be modified to avoid such damage are discussed. As base metal tests on specimens from laboratory-sized heats had shown good resistance to environmentally-induced damage, the objective of the work was to discern whether such properties could be maintained in thick-section weldments in materials taken from relatively large (commercial size) heats. Both materials, in the PWHT/undamaged state, exhibited identical fatigue crack growth behavior above approx.10/sup -6/ mm/cycle. At near-threshold levels, the JSW steel displayed marginally lower growth rates and a higher threshold stress intensity, ..delta..K/sub TH/. When PWHT materials were exposed to environmentally-induced damage (i.e., high temperature/high pressure hydrogen), little effect was observed on fatigue propagation behavior at both near-threshold and higher growth rates. 72 refs., 41 figs.,more » 13 tabs.« less
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