Elastic-Plastic Fracture Toughness Characteristics of Irradiated 316H Stainless Steel

Abstract

In the frame of an irradiation program of American Iron and Steel Institute (AISI) 316H (Unified Numbering System [UNS] S31 400) stainless steel at fast (E > 0.1 MeV) ranging from 0.1 to 2 dpa, the fracture toughness of the steel was measured, using the J parameter, at 0, 0.1, and 0.3 dpa at 350 and 550°C. A dimensional analysis has been used to derive J resistance curves as well as JIc values for the base material and its welds. The specimens used were three-point bend (3PB) specimens, 20 mm high by 15 mm thick by 80 mm effective span. A noteworthy result concerning the base material is the lowering at 550°C and 0.1 dpa of dJ/da by about 50% and of JIc by about 35%. The other dJ/da and JIc values were not significantly altered at 550°C. Apart from this case, generally low degradation of base metal properties is found at both temperatures between the nonirradiated and the irradiated material. The weld material exhibits significantly lower initiation toughness and tearings moduli in the preirradiation and post-irradiation conditions, but these fracture mechanics (FM) characteristics are practically unaltered at both temperatures and at the above mentioned fluence levels. The heat-affected zone (HAZ) material was also studied. It was found that all J-Δa values were bounded on the upper side by the base material at 350°C and on the lower side by the welded material at 550°C for corresponding fluence levels.

Improvement of a model to predict static fracture toughness of austenitic materials under neutron irradiation

“…Recent experimental studies into static fracture toughness of irradiated austenitic materials in Russia and abroad [27][28][29][30], as well as previous results [31][32][33][34][35][36], significantly improved the database which was used for development of the model [2]. Critical review of these experimental data in terms of new information about the influence of neutron irradiation on austenitic materials made it possible to develop the predicting dependence of static fracture toughness of austenitic materials without drawbacks of the previous model.…”