Stress Corrosion Cracking (SCC) consists of two stages, an incubation stage followed by a crack propagation stage. The crack propagation stage can be tracked fairly accurately by using Arrhenius energy values. However, the incubation stage can take a long time (20 years is not uncommon), and is far less predictable with no indication of its development. SCC is also localized making it difficult to detect, and is often only found when cracking has gone through-wall and produced a leak. Welds are known to be areas where SCC originates. Any manufacturing repairs to weld locations produce augmented levels of residual stress in the weld area and increase the probability of SCC.

Manufacturing effects also alter the electro-magnetic property of a material, and by monitoring the changes in electro-magnetic property it is possible to characterize material conditions that contribute to the SCC process. Evaluation of these manufacturing effects on several Reactor Vessel nozzles with Dissimilar Metal Butt Welds (DMBWs) has found electro-magnetic property changes, which can characterize, define and produce images of localized repairs, and also show where lack of adequate stress relieving heat treatments exists.

This electro-magnetic property methodology can predict the development of SCC in the incubation process, and can directly confirm where any initial fabrication repairs were performed, or when lack of proper stress relieving exists. A full material characterization history enabling prediction of the future susceptibility to SCC has been achieved. This complete, material characterization history of Alloy 600 components and stainless steel components was the goal of this research. Eddy Current Testing (ECT) was chosen as the NDE technique of choice, because it is sensitive to surface changes and can detect electro-magnetic property changes. Using an imaging process, which detects electro-magnetic property changes, has successfully characterized the complete history of the investigated materials.

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