DEAERATOR FEEDWATER STORAGE VESSEL WELDMENT CRACKING - SOME FRACTOGRAPHIC AND CRACK EXTENSION DETAILS

The present paper describes the results of a large field surveillance study aimed at understanding and mitigating crack growth in deaerator feedwater storage vessel weldments. It has been demonstrated that this particular type of cracking was widespread in nature, was primarily i nitiated at the bottom of significant surface corrosion pits and that subsequent subcritical crack growth was the result of a fatigue fractu re process. The fatigue crack growth was made up of two different comp onents, viz. an environmental assisted crack. EAC, portion and a pure mechanical portion. Detailed quantitative fractography established tha t the fatigue fracture surfaces contained a mixture of fan-shaped, cle avage-like facets and rough ductile striated regions and that the prop ortions of these failure modes dictated the rate of fatigue crack exte nsion. Finally the finding that fatigue was the primary crack extensio n process in deaerator weldments was further strengthened through a co mparison of quantitative fractrography and crack geometry evolution wi th reported data from the literature. Copyright (C) 1996 Elsevier Scie nce Ltd.