Investigation of dendrite-boundary microchemistry in alloy 182 using auger electron spectroscopy analysis
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8/8/04
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Investigation of Dendrite-Boundary Microchemistry in Alloy 182 using Auger Electron Spectroscopy Analysis Q.J. PENG, H. YAMAUCHI, and T. SHOJI 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.
I. INTRODUCTION
ALLOY 182 has been widely used as weld metal in light-water-reactor structural components. The interdendritic stress-corrosion cracking (IDSCC) of Alloy 182 weld metal in nickel-based alloy weldments has been a major concern in the management and prediction of plant life. Many investigations have reported that Alloy 182 is susceptible to IDSCC in high-temperature water.[1–4] Therefore, it is of great importance to understand the IDSCC mechanism of the alloy in order to assess the inspection interval and remaining life of components. Of all the mechanisms associated with SCC, the slipdissolution/oxidation model has been accepted by many researchers as a reasonable description of SCC in hightemperature water.[5,6] According to this model, the localmaterial characters (composition, microstructure, etc.) at the crack tip play a significant role in SCC. In the case of Alloy 182, the IDSCC behavior is affected by the microchemistry of the dendrite boundary. To date, few studies have focused on analysis of the microchemistry of the dendrite boundary in Alloy 182. Efforts, therefore, to clarify the microchemistry are needed to better understand IDSCC of Alloy 182. In this study, the auger electron spectroscopy (AES) spectra that were obtained from both interdendritic facets and transdendritic surfaces in Alloy 182 were qualitatively and quantitatively analyzed to characterize the microchemistry of the dendrite boundaries. The most commonly used techniques to characterize the grain-boundary microchemistry are AES and energy-dispersive X-ray analysis in transmission electron microscopy (TEM-EDS). The AES technique is a convenient way to obtain the profile of the microchemistry Q.J. PENG, Postdoctoral Fellow, Japan Society for the Promotion of Science, H. YAMAUCHI, Gradua
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