NSUF 16-649: Irradiation Effect in the Heterogeneous Hardening of Cast Austenitic Stainless Steels

The duplex cast austenitic stainless steels (CASS) possess excellent corrosion resistance and mechanical properties, and are used in light water reactor internals. However, CASS experience hardening and embrittlement due to extended exposures to elevated temperatures and/or neutron irradiations. Previously, the microstructure of neutron irradiated CASS had been characterized by using TEM and APT. G-phase precipitates and a-a phase separation were observed in ferrite, while defect clusters were observed in austenite. On the other hand, J-R curve tests showed a further reduce in fracture toughness due to a combination of thermal aging and irradiation. Because of the distinct microstructures observed in ferrite and austenite, the changes in mechanical property in two phases may be significantly different, and should be accessed individually. This work is planned to measure the hardness of the two phases in neutron irradiated CASS at un-aged and aged conditions by using nanoindentation. The output of the proposed study will provide the first knowledge of micro-scale heterogeneity of irradiation hardening in CASS, a crucial knowledge to correlate the obtained microstructures and the macro-scale mechanical test results. This proposed research will provide fundamental understandings for evaluating CASS during the extended reactor life of 60 years and beyond.

Additional Info

Field	Value
Abstract	The duplex cast austenitic stainless steels (CASS) possess excellent corrosion resistance and mechanical properties, and are used in light water reactor internals. However, CASS experience hardening and embrittlement due to extended exposures to elevated temperatures and/or neutron irradiations. Previously, the microstructure of neutron irradiated CASS had been characterized by using TEM and APT. G-phase precipitates and a-a phase separation were observed in ferrite, while defect clusters were observed in austenite. On the other hand, J-R curve tests showed a further reduce in fracture toughness due to a combination of thermal aging and irradiation. Because of the distinct microstructures observed in ferrite and austenite, the changes in mechanical property in two phases may be significantly different, and should be accessed individually. This work is planned to measure the hardness of the two phases in neutron irradiated CASS at un-aged and aged conditions by using nanoindentation. The output of the proposed study will provide the first knowledge of micro-scale heterogeneity of irradiation hardening in CASS, a crucial knowledge to correlate the obtained microstructures and the macro-scale mechanical test results. This proposed research will provide fundamental understandings for evaluating CASS during the extended reactor life of 60 years and beyond.
Award Announced Date	2016-04-11T00:00:00
Awarded Institution	Center for Advanced Energy Studies
Facility	Microscopy and Characterization Suite
Facility Tech Lead	Alina Zackrone, Yaqiao Wu
Irradiation Facility	None
PI	WEIYING CHEN
PI Email	[email protected]
Project Type	RTE
RTE Number	649