Investigation of dendrite-boundary microchemistry in alloy 182 using auger electron spectroscopy analysis

Interdendritic stress corrosion cracking (IDSCC) of Alloy 182 weld metal in nickel-based alloy weldments in high-temperature water has been a major concern in the management and prediction of plant life. It is of great importance to understand the mechanism of IDSCC, e.g., the relationship of IDSCC behavior to the microchemistry at the dendrite boundary. In this study, the microchemistry of the dendrite boundary in Alloy 182 weld metal was studied using auger electron spectroscopy (AES) analysis. Interdendritic (ID) facets were obtained by fracturing hydrogen-charged specimens using slow-strain-rate tensile (SSRT) tests that were performed in the high-vacuum chamber of the AES system. The fracture surface was identified by secondary electron imaging and point analyzed by AES. The AES spectra that were obtained from both ID facets and transdendritic (TD) surfaces were qualitatively and quantitatively analyzed. Composition-depth profiles of the ID facet were also obtained. Heterogeneous distribution of chromium and segregation of phosphorous on the ID surfaces were revealed.