Effect of CO₂ partial pressure on SCC behavior of welded X80 pipeline in simulated soil solution

Ming WU,Xu CHEN*,Chuan HE and Jun XIAO College of Petroleum Engineering,Liaoning Shihua University,Fushun 113001,China

摘 要：The stress corrosion cracking (SCC) behavior of welded X80 pipeline steel in simulated Ku’erle soil solution was studied by means of electrochemical impedance spectroscopy (EIS) and slow strain rate tests (SSRT).The microstructure of the welded steel was observed by optical microscopy (OM).It is demonstrated that the microstructure of the weld metal consists of acicular ferrite and grain boundary ferrite,while that of heat affected zone (HAZ) is a mixture of acicular ferrite and bainitic ferrite microconstituents.The microstructure of the base steel is composed of ferrite and pearlite.The anodic dissolution of X80 pipeline steel in simulated Ku erle soil solution could be enhanced and the SCC sensitivity increased with the increase of CO2 partial pressure.The SCC mechanism of X80 pipeline is a mixing mechanism of hydrogen embrittlement combined with anodic dissolution,and the hydrogen embrittlement plays a leading role.The higher SCC sensitivity of the weld metal was attributed to the metallurgical transformation,local hardening and residual stress.

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