Type 316 CFM centrifugally cast stainless steel pipe is used for coolant piping, involving service at 288 deg C to 316 deg C. The possibility material property degradation due to thermal aging occurring on the long service life of this piping was investigated in an experimental program. Test sections were aged at 427 deg C for periods of 100-3000 h to study the effects of aging. Tests conducted on the aged material included tensile, Charpy, J-integral toughness and fatigue crack growth in both air and the pressurized water reactor environment.
Ferrite levels of the steel were also determined and the test specimens were selectively examined metallographically, supplemented by fractography and X-ray diffraction. Changes in the fracture toughness properties were observed, as evidenced by a reduction of the Charpy and JIc properties, but the fatigue crack growth properties were essentially unaffected. Mechanisms are suggested for the observed changes in properties. Fracture toughness and fatigue characteristics of centrifugally cast type stainless steel pipe after simulated thermal service conditions.