November 05, 2021
(10:30 am - noon)
Weldments are metallurgically distinct from the surrounding base metal (BM). The presence of tensile residual stresses makes the weldments susceptible to premature failures well in advance of the BM, especially when they are exposed to severe service environment. Two types of service-related failures will be discussed in this presentation, including chloride-induced stress corrosion cracking (CISCC) in the austenitic stainless steel weldments of spent fuel canisters, and stress relaxation cracking (SRC) in thick stainless steel weldments for high temperature applications. CISCC is one of the primary safety concerns during the dry storage of used nuclear fuel at independent spent fuel storage installations in coastal areas. In terms of reheat cracking, over 50 issues have been reported for austenitic steels in multiple countries in heat-affected zone (HAZ) and weld metal, particularly in HAZ without post weld heat treatment (PWHT). A fundamental understanding of the failure conditions can be achieved by combining finite element modeling, thermodynamic calculations, thermomechanical experiments, and metallurgical characterizations.
Zhenzhen Yu is an associate professor in the department of Metallurgical and Materials Engineering (MME) at Colorado School of Mines, and the Director of the Center for Joining, Welding and Coatings Research (CWJCR). She received MS and PhD degrees from the Department of Materials Science and Engineering at the University of Tennessee, Knoxville and B.S. degree from Mechanical Engineering at East China University of Science and Technology. Before joining CSM, she worked as a postdoctoral research associate at Oak Ridge National Laboratory. Her research interests include weld metallurgy, development of similar/dissimilar joining technologies, weld consumables design, and simulation and characterization of transient material states. She received the National Science Foundation Faculty Early Career Development CAREER Award, McKay-Helm Award, Prof. Koichi Masubuchi Award, and the A.F. Davis Silver Medal Award.