Crack Initiation Behavior of Cold-Worked Alloy 690 in Simulated PWR Primary Water - Role of Starting Microstructure, Applied Stress and Cold Work on Precursor Damage Evolution
Long-term stress corrosion crack (SCC) initiation behavior in Alloy 690 is being evaluated by constant load tensile testing in simulated pressurized water reactor primary water. Seven commercial Alloy 690 heats with different starting microstructures and cold-work levels are being tested at either 90% or 100% of the material yield stress. Previous studies have revealed grain boundary (GB) cavity formation after 7,110 to 9,220 hours of exposure in certain thermally treated (TT) Alloy 690 heats in highly cold-worked (CW) conditions, serving as precursors to intergranular cracks. This paper summarizes the new characterization results for the evolution of GB cavities in four Alloy 690TT heats in 21% and 31%CW conditions loaded at yield stress after 18,400 hours of exposure. Link-up of GB cavities has led to formation of long internal creep cracks, resulting in crack initiation detected by direct current potential drop in a highly CW Alloy 690TT heat with uniform, semi-continuous distribution of small GB carbides. In comparison, highly CW materials featuring larger and more widely spaced GB carbides did not show a significant increase in GB cavity density or size. Quantitative assessments were performed on GB cavity evolution in highly CW specimens for two Alloy 690TT heats demonstrating the strong dependence of GB cavity evolution on applied stress and starting GB microstructure.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1605409
- Report Number(s):
- PNNL-SA-145209
- Resource Relation:
- Conference: 19th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, (EnvDeg 2019), August 18-22, 2019, Boston, MA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Precursor Evolution and Stress Corrosion Cracking Initiation of Cold-Worked Alloy 690 in Simulated Pressurized Water Reactor Primary Water
Precursor evolution and SCC initiation of cold-worked alloy 690 in simulated PWR primary water