Stress Corrosion Cracking and Internal Oxidation of Alloy 600 in High Temperature Hydrogenated Steam and Water

摘要: In this study, the possibility of using low pressure hydrogenated steam to simulate primary water reactor conditions is examined. The oxides formed on Alloy 600 (WF675) between 350 Celsius and 500 in (with a ratio oxygen at Ni/NiO system 20) have been characterised analytical electron microscopy (AEM) compared oxide that high autoclave with 30 cc/kg hydrogen.Preferential oxidation grain boundaries bulk internal were observed samples prepared by polishing suspension (OPS). Conversely, mechanically ground grit produced continuous, protective film which suppressed preferential oxidation. surface preparation changed form both tests. rate has determined be K_{oxide} = Aexp{-Q/RT}with A 2.27�10^(?3) m^(2)s^(?1) Q 221 kJ.mol^(?1) (activation energy) for WF675 5.04 � 10^(?7) 171 15% cold worked WF675. These values are consistent activation energy stress corrosion cracking (PWSCC) initiation.Bulk diffusivities calculated from after h exposures. At diffusivity was 1.79�10^(?20) 1.21�10^(?20) WF675, 400 1.49�10^(?22) m^(2)s^(?1).The Cr-depletion associated assessed AEM. asymmetric it could not accounted local variations diffusion rate. Chemically induced boundary migration suggested as possible explanation.Constant load SCC tests conducted shown similar trend classical dependency PWSCC function potential. also two finishes, OPS grit. all tests, significantly more failures initiated surface.