Search

Model alloys 9Cr-25Ni-1.5Mo-5Si and 9Cr-25Ni-1.5Mo-3Si with lower Cr and higher Ni and Si contents than 316L SS were to simulate the grain boundary chemical compositions resulting from irradiation induced segregation in irradiated austenitic stainless steels. The effect of Si-addition in the model alloys on the oxide film formed in alkaline high temperature water at 290 oC was investigated by Raman spectroscopy, scanning electron microscopy and XPS. Compact layer was observed on all the alloys after exposure for 24h or longer. The outer layer oxides on model alloys were larger than that on 316L SS after the same immersion period. The oxide films formed on 316L SS and 9Cr-26Ni-5Si after exposure to the alkaline water at 290 oC for 120 h had a duplex structure. The oxide film formed on 316L SS was thicker than that on 9Cr-25Ni-1.5Mo-5Si alloy. Oxides of silicon was identified in the inner oxide layer 9Cr-25Ni-1.5Mo-5Si alloy but not significant on 316L SS.

The microstructure and the oxide films formed on Ni-base alloy cladding in simulated pressurized water reactor (PWR) primary water environments at 325degC were characterized. There was a steep drop of iron content and increase of Ni and Cr content in the Ni-base alloy cladding near the fusion line, and a relatively mild drop of iron content and the resultant increase of Ni and Cr contents at the location about 3.8 mm away from the fusion line. The surface oxide morphologies were observed by scanning electron microscopy and the cross-section morphologies and chemical composition of the oxide films were measured by transmission electron microscopy (TEM) and energy dispersive spectrometer. After 146 h immersion in PWR primary water, there were more oxide particles on the cladding alloy at the location closer to the cladding fusion line. After 1860 h immersion in PWR primary water, fine oxide particles on the specimen surface were covered with sparsely distributed large oxide particles. The oxide film after 1860h immersion exhibited a duplex structure, which was thicker at the location closer to the fusion zone, according to TEM results. The outer layer was rich in iron and the inner layer was rich in chromium. Both the inner and the outer oxide films were depleted in Ni, despite of the high Ni content in the alloy matrix.

The microstructure and the oxide films formed on Ni-base alloy cladding in simulated pressurized water reactor (PWR) primary water environments at 325°C were characterized. There was a steep drop of iron content and increase of Ni and Cr content in the Ni-base alloy cladding near the fusion line, and a relatively mild drop of iron content and the resultant increase of Ni and Cr contents at the location about 3.8 mm away from the fusion line. The surface oxide morphologies were observed by scanning electron microscopy and the cross-section morphologies and chemical composition of the oxide films were measured by transmission electron microscopy (TEM) and energy dispersive spectrometer. After 146 h immersion in PWR primary water, there were more oxide particles on the cladding alloy at the location closer to the cladding fusion line. After 1860 h immersion in PWR primary water, fine oxide particles on the specimen surface were covered with sparsely distributed large oxide particles. The oxide film after 1860h immersion exhibited a duplex structure, which was thicker at the location closer to the fusion zone, according to TEM results. The outer layer was rich in iron and the inner layer was rich in chromium. Both the inner and the outer oxide films were depleted in Ni, despite of the high Ni content in the alloy matrix.

Model alloys 9Cr-25Ni-1.5Mo-5Si and 9Cr-25Ni-1.5Mo-3Si with lower Cr and higher Ni and Si contents than 316L SS were to simulate the grain boundary chemical compositions resulting from irradiation induced segregation in irradiated austenitic stainless steels. The effect of Si-addition in the model alloys on the oxide film formed in alkaline high temperature water at 290 oC was investigated by Raman spectroscopy, scanning electron microscopy and XPS. Compact layer was observed on all the alloys after exposure for 24h or longer. The outer layer oxides on model alloys were larger than that on 316L SS after the same immersion period. The oxide films formed on 316L SS and 9Cr-26Ni-5Si after exposure to the alkaline water at 290 oC for 120 h had a duplex structure. The oxide film formed on 316L SS was thicker than that on 9Cr-25Ni-1.5Mo-5Si alloy. Oxides of silicon was identified in the inner oxide layer 9Cr-25Ni-1.5Mo-5Si alloy but not significant on 316L SS.