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The Influence of Subcritical Annealing and Cold Working on the Hydrogen Embrittlement Susceptibility of X65 D Pipeline Steel

Abstract:

This study investigated the effect of subcritical heat treatment and cold work on the hydrogen embrittlement (HE) susceptibility of the X65 D pipeline steel, representative of the Dampier-Bunbury Natural Gas Pipeline (DBNGP). Specimens were subjected to sub-critical annealing at 200°C, 400°C, or 600°C for 2 h or cold drawn to 5% reduction in area. Linearly increasing stress tests (LISTs) indicated subcritical annealing reduced strength and increased ductility, while cold working increased strength and decreased ductility. Hydrogen charging reduced the ductility of all specimens. Both subcritical annealing and cold working decreased somewhat the degree of HE. This was attributed to both treatments stabilising the dislocation distribution which possibly reduced the severity of hydrogen-enhanced localised plasticity (HELP). The novelty of this study lies in the evaluation of practical production changes and their influence on the HE of this steel.