Thermal Aging Degradation Mechanisms
EMSL Project ID
50570
Abstract
The objective of this research is to continue the investigation on the microstructural and chemical evolution of cast stainless steels subjected to accelerated thermal aging conditions relevant to nuclear light water reactor conditions, and to correlate this evolution with changes in mechanical and fracture behavior of the materials. We propose to use the Local Electrode Atom Probe (LEAP) 4000X HR located at EMSL to elucidate the structural and elemental changes at the sub-micron to nano-scale as a result of thermal aging at reactor-relevant temperatures. Successful completion of this research will provide an important component to extend the lifetime of current light water reactors and to provide a basic understanding of the temperature-dependence of thermal aging on microstructural and chemical evolution in these materials. In the upcoming work, we will investigate the austenite-ferrite interface specifically and the role of aging time and temperature on microstructural evolution on the different alloys. We will also characterize, using APT and STEM, the fracture surface and crack tip in thermally-aged steels. This type of systematic study taking into account the effects of composition, aging time, and aging temperature has not been completed before. Also, this thermal aging embrittlement has only been observed in accelerated aging conditions at temperatures of 400 oC or higher, and the cast stainless steel grades used in nuclear plants have performed well without experiencing real embrittlement. It has been speculated that long-term thermal aging for 60 years could lead to further decomposition of designed phases and increase of precipitation of other phases, thus resulting in significantly increased susceptibility to embrittlement or other degradation due to the thermal aging-radiation synergistic effect, irradiation-induced degradation, stress-corrosion cracking, and general corrosion. Hence, in this work, thermal aging mechanisms will be investigated at conditions relevant to LWR power plant conditions.
Project Details
Start Date
2018-10-08
End Date
2019-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members