Fracture Resistance of Cast Stainless Steels after Thermal Aging for up to 10000 Hours

This work package, Cast Stainless Steel Aging, aims to achieve a comprehensive scientific understanding on the aging and failure phenomena in cast austenitic stainless steels (CASSs) using holistic experimental and modeling means and to provide a practical and science-based model to predict the degree of thermal degradation of CASS components in extended-term operations. The test materials in the project include four model CASSs (CF3, CF3M, CF8, and CF8M), four EPRI-provided CASSs (CF3, two CF8s, and CF8M), and two reference wrought materials (304L and 316L), which contain a wide variety of d-ferrite contents (2–33%). These materials have been thermally aged at two light water reactor (LWR)-relevant temperatures (290 and 330°C) and at two accelerated-aging temperatures (360 and 400°C) for up to three years. In the fiscal year, the fracture toughness testing and J-R curve calculation were completed for the ten CASS and wrought materials aged up to 10,000 hours. This report is to present the results of the static fracture (J-R) testing for the model and EPRI-provided CASS materials after thermal aging up to 10,000 hours. First, a new aging parameter (A) was defined to present the aging degradation of mechanical properties against the common variable. This definition is used to scale an aging time at a temperature to the effective aging time at a reference temperature based on Arrhenius equation, which is a rate theory equation for thermally activated mechanisms. Second, the fracture test results are presented in the forms of fracture resistance (J-R or J-?a) curves, KJQ versus A curves, and tabulated crack length and fracture toughness data for ~460 fracture tests. Third, the fracture test results indicate that the fracture toughness tends to increase in early aging; after a short time, however, it decreases with aging parameter at a rate depending on the volume fraction of d-ferrite. Overall, the decrease of static fracture toughness due to thermal aging is less sign. Authors: Byun, Thak Sang (ORCID:0000000308604936); Collins, David A.; Barkley, Emily L.; Lach, Timothy G. (ORCID:0000000247454179). DOE Contract: AC05-76RL01830