Abstract
The present failure analysis investigates the failure of copper connectors and bus-bar windings of a 250 MW generator unit, of a steam powered turbine, which failed during service. An exhaustive microstructural and nanomechanical characterization was conducted in-order to determine the failure of copper bus-bar. Microstructure analysis revealed porosities in the brazed region with formation of numerous microconstituent phases. Furthermore, microstructure analysis revealed a network of numerous intergranular porosities on the failed copper side. SEM-EDS analysis of different microconstituents revealed a presence of Ag-rich dendritic phase, Cu-rich phase and lamellar eutectic microconstituents, highlighting a diverse microstructure. Nanoindentation measurements of different microconstituents and phases revealed a stark difference in the indentation hardness, thereby highlighting a strong mismatch between the observed microconstituents and phases.
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