Research of estimation method of thermal aging embrittlement on cast austenitic stainless steel

Thermal embrittlement of cast austenitic stainless steel components from the decommissioned advanced thermal prototype reactor Fugen has been characterized. Cast stainless steel materials were obtained from recirculation pump casing. The actual time at temperature for the materials was 138,000 h at 275degC. The 'Fugen' material show modest decrease in Charpy-impact properties and a small increase in micro-Vickers hardness in ferrite phase because of thermal aging at relatively low service temperatures. The fracture toughness prediction method (H3T model) predicts slightly lower values for Charpy-impact energy obtained from the Fugen material. The results from microstructural analysis suggest that the prediction method have the potential to provide higher accuracy by considerations of the activation energy for embrittlement at low service temperatures. (author)