On the influence of manufacturing practices on the SCC behavior of Alloy 690 steam generator tubing
- Babcock and Wilcox International Div., Cambridge, Ontario (Canada)
- Babcock and Wilcox Research Div., Alliance, OH (United States)
Thermally treated (TT) Alloy 690 is the tubing materials of choice for replacement steam generators (RSGs) throughout the world. It is manufactured using a variety of processing methods with regards to melt practice and thermomechanical forming. Studies assessing the IGSCC resistance of Alloy 690 TT SG tubing have identified a variability in the corrosion performance of nominally identical alloys. While tubing of comparable bulk chemistry may exhibit variations in microchemistry as a result of different melt practice, the correlation between melt practice and SCC resistance is difficult to assess due to other contributing factors. The other contributing factors are identified in this investigation as microstructural features whose generation is dependent on features of particular strain-anneal forming methods by which SG tubes are fabricated. In this study the microstructural characteristics which appear to affect inservice corrosion performance of Alloy 690 TT SG tubes were evaluated. The studies included extensive microstructural examinations in addition to CERT tests performed on actual Alloy 690 TT nuclear SG tubing. The CERT test results indicate that Alloy 690 TT tubing processed at higher mill anneal temperatures display the highest degree of stress corrosion cracking (SCC) resistance. This observation is discussed with reference to carbide distributions, textural aspects and grain boundary orientation character.
- OSTI ID:
- 409743
- Report Number(s):
- CONF-9510292--; ISBN 1-57570-008-4
- Country of Publication:
- United States
- Language:
- English
Similar Records
Role of microstructure in caustic stress corrosion cracking of Alloy 690
Study of IGA/SCC behavior of alloy 600 and 690 SG tubing materials in high temperature solutions