Effect of applied potential on stress corrosion cracking (SCC) behavior of 508III-52M-690 dissi-milar weld joint of safe-end was researched with slow strain rate tensile (SSRT) tests and high temperature electrochemistry tests in high temperature (300℃) water containing 50mg/kg chloride. The results revealed that the SCC susceptibility increases dramatically with the applied potential, then the potential above a critical value exists between －500 and －400mV (versus standard hydrogen electrode). The SCC susceptibility is low and no obvious intergranular or transgranular stress corrosion cracks can be found when the applied potential below the critical value which corresponds to deoxygenated water chemistry. It means the fracture is dominated by mechanical properties and closely relates to the hardness distribution of welded joint. The lower the hardness is, the more easily fractures occur. Therefore, all ductile fractures are located at 52Mb (butt welded) with the lowest hardness. While, when electrode potential is higher than the critical potential, all brittle fractures are located at 508III heat affected zone (508III HAZ) with the lowest corrosion resistance, where exhibits significant SCC behavior with large area intergranular and transgranular stress corrosion cracks. Hence, the dissolved oxygen concentration need be controlled strictly to make sure the corrosion potential is below the critical potential. Besides, the 52Mb and 508III HAZ of this dissimilar weld joint are the most venerable sites to crack which need to be paid high attention to during the operation.
WANG Jiamei1，SU Haozhan1,HE Kun2，ZHANG Lefu1
. Effects of Potential on 508III-52M-690 Dissimilar Weld Joint[J]. Journal of Shanghai Jiaotong University, 2018
, 52(4)
: 447
-454
.
DOI: 10.16183/j.cnki.jsjtu.2018.04.009
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