Initiation of PWSCC of weld alloy 182

International audienceEven if Alloy 182 is usually exhibiting a high susceptibility to cracking in the laboratory, the field experience did not reveal to date a significant susceptibility to primary water stress corrosion cracking (PWSCC) in pressurized water reactors (PWRs), when the welds have been perfectly stress relieved. However, recently, an increasing number of cracks have been reported in the USA, Sweden and Japan on Alloy 182 and a few cases on Alloy 82. This paper addresses the work on initiation of PWSCC engaged at EDF R&D. The main objective is to calibrate an engineering model to predict the time to initiate IGSCC vs. temperature and loading for 182 weld metals having a high susceptibility to PWSCC

Amorçage de la corrosion sous contrainte (CSC) en milieu primiaire des réacteurs à eau sous pression (REP) dans les soudures en alliages base nickel 182

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Grain boundary oxidation of nickel base welds 182/82 in simulated PWR primary water

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Intergranular oxidation of nickel-base alloys : potentialities of focused ion beam tomography

International audienceThe present work focuses on the intergranular oxidation of Alloy 600 and its weld material Alloy 82 after exposure in simulated primary water at 340–360 °C during 1000–1400 h. The effects of intergranular chromium carbides, grain boundary character and pre-straining are studied either on industrial heats or model microstructures. Three-dimensional reconstructions of well-chosen grain boundaries are obtained using focused ion beam tomography in a scanning electron microscope. The 3D characterizations show that (1) twin boundaries are less susceptible to oxidation than high-angle grain boundaries; (2) intergranular chromium carbides delay the intergranular oxidation kinetics; (3) the intergranular oxidation depth is quite homogeneous along a given grain boundary except when strain heterogeneity exists in its vicinity, (4) strain heterogeneity tends to accelerate the intergranular oxidation kinetics; and (5) crack initiation in the oxidized grain boundary occurs at the alloy/oxide interface