Effect of long-term thermal aging on the fracture toughness of austenitic stainless steel base and weld metals

摘要

Compact tension specimens taken from FFTF primary piping materials (Type 316 stainless steel (SS) and 16-8-2 SS weld metal) and from reactor vessel materials (304 SS and 308 SS weld metal) were heated in laboratory furnaces from 100,000 hours. Fracture toughness testing was performed on these specimens, which are 7.62- and 25.4-mm thick, respectively at the aging temperature (482 and 427 degrees). Results were analyzed with the multiple-specimen method. Thermal aging continues to reduce the fracture toughness of FFTF component materials. Results show that thermal aging has a strong effect on the toughness degradation of weld metals, particularly for 16-8-2 SS weld whose aged/unaged Jc ratio is only 0.31 after 100,000-hour aging. The fracture toughness of the 308 and 16-8-2 SS weld metals fluctuated during 20,000 to 50,000-hour aging but deteriorated as the aging time increased to 100,000 hours; the toughness degradation is significant. Fracture control based on a fracture mechanics approach should be considered