The fracture toughness behaviour of austenitic steels and weld metal including the effects of thermal ageing and irradiation

Abstract

Stainless steel components used in nuclear power plant must be capable of maintaining reasonable mechanical properties after thermal ageing and irradiation damage has accumulated over the lifetime of the system. This study examines the fracture toughness behaviour of wrought and welded Type 316 material in long-term thermally aged and irradiated conditions. The results indicate that whilst some potentially detrimental microstructural changes have occurred during ageing, the degradation in mechanical properties is not large. In wrought material some comparisons are made between the toughness of Type 316 grade and recent results obtained on modified Type 316LN grade materials. The effects of welding processes on oxygen and inclusion content have been quantified in MMA and TIG welds, and the results have been used to explain the higher toughness of TIG-welded material. Comparisons of fracture toughness after irradiation have also been made between arc welds in Type 316 and other grades.