Considerations for metallographic observation of intergranular attack in Alloy 600 steam generator tubes

This technical note provides some considerations for the metallographic observation of intergranular attack (IGA) in Alloy 600 steam generator tubes. The IGA region was crazed along the grain boundaries through a deformation by an applied stress. The direction and extent of the crazing depended on those of the applied stress. It was found that an IGA defect can be misevaluated as a stress corrosion crack. Therefore, special caution should be taken during the destructive examination of the pulled-out tubes from operating steam generators.