316系低炭素ステンレス鋼溶接金属の BWR 炉水温度域における熱時効脆化の評価
To evaluate the rate of thermal embrittlement of type 316 low-carbon stainless steel weld metal at BWR operating temperature, aging test at 310°C, 335°C, and 400°C was carried out. Hardness of each ferrite and austenite phase of s pecimens was measured selectively by microhardness tester. Hardness of ferrite was increased apparently with all three aging temperatures, whereas hardness of austenite was not changed. Changes in the microstructure of ferrite ag ed at 310°C for 11,000h and 18,000h were analyzed by TEM. It has been revealed that hardening of ferrite with aging at 310°C was result of spinodal decomposition. Arrhenius plot for hardening rate of ferrite at each three aging te mperature was plotted, and apparent activation energy was estimated. Using the apparent activation energy, hardening rate at 288°C was discussed.