Microstructural Effects on Creep-Fatigue Life of Alloy 709
Cyclic testing has been carried out to characterize the fatigue and creep-fatigue behavior of Alloy 709, an advanced austenitic structural alloy. Specimens were machined from several plates of 709, subjected to different processing conditions and resulting in varying microstructures in the specimens, dependent on both the plate used for the machining and the location the specimen originated from within the plate. The cyclic testing has been conducted primarily at a single fatigue and creep-fatigue condition, which was at 650 °C and 1.0% total strain (+/-0.5% strain). For creep-fatigue, a 30 min. hold time at peak tensile strain was introduced. The combined results of the cyclic testing and post-test metallographic characterization suggest that the investigated microstructures, ultimately controlled by the processing conditions, have limited influence on the Alloy 709 fatigue cycle life. In contrast, some effect on the creep-fatigue cycle life due to the microstructure was observed, specifically that the presence of large grains may negatively impact the creep-fatigue resistance. The number of cycles to failure at the selected creep-fatigue condition varied by up to a factor of 5 for the specimens tested. Specimens with an optimum microstructure, a uniform distribution of grains with diameters less than approximately 200 ?m, resulted in a creep-fatigue resistance similar to that of 316-type stainless steel. The majority of the Alloy 709 cyclic test data has been previously reported in milestone reports - and the microstructural and processing details for the specific heats have been reported by Yamamoto et al. - This summary report includes creep-fatigue test results on three additional heats (011502F, 011502H, and 011539 (note, same plate as ORNL 011593)) for which the processing and microstructural details are available in previous reports.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 1484713
- Report Number(s):
- INL/EXT-17-41079-Rev001
- Country of Publication:
- United States
- Language:
- English
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Microstructural Effects on Creep-Fatigue Life of Alloy 709