Corrosion behavior of Zircaloy-4 sheets produced under various hot-rolling and annealing conditions
- Sumitomo Metal Industries, Ltd., Hyogo (Japan). Advanced Technology Research Laboratories
The uniform corrosion resistance of Zircaloy-4 sheets produced under various hot-rolling and annealing conditions was investigated. The uniform corrosion resistance in static steam at 673 K improved with an increasing cumulative annealing parameter ({Sigma}A). However, to clarify the physical meaning of the annealing parameter and the different combinations of various heating stages, the effects of individual manufacturing conditions that influence the corrosion behavior and ripening behavior of the precipitates were investigated. As a result, the annealing temperature after hot-rolling influenced the uniform corrosion more significantly than the intermediate annealing and the final annealing temperatures. Size distributions of the intermetallic compound precipitates that were observed by means of a scanning electron microscope (SEM) with an image analyzer were examined for a correlation with weight gain. The percentage of small precipitates below 100 nm in size was important in determining corrosion resistance and had a good correlation with the annealing parameter; that is, if the percentage was lower than 30%, the corrosion resistance was satisfactory. Also, the frequency of precipitates under 100 nm in size decreased sharply with increasing annealing temperature after hot-rolling. The intermetallic compounds that were incorporated into the ZrO{sub 2} oxide scale and the scale/metal interface were observed by a transmission electron microscope (TEM). The incorporated intermetallic precipitates were observed to have changed their composition; that is, the iron content decreased and the iron/chromium (Fe/Cr) ratio for the zirconium-chromium-iron intermetallic precipitate was approximately 1 compared to approximately 2 in the Zircaloy matrix. During oxidation, iron from the intermetallic compound precipitates scattered more into the oxide than chromium.
- OSTI ID:
- 55659
- Report Number(s):
- CONF-930611--; ISBN 0-8031-2011-7
- Country of Publication:
- United States
- Language:
- English
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