This bulletin presents an interpretative review of the literature and an analysis of the available data relating to the effect of long-term (nominal 10,000 hours or greater), elevated temperature exposure on the notched impact properties and the fracture toughness of austenitic steels and high nickel alloys. The chief emphasis is on the alloys, grades, and product forms of those materials accepted for use in ASME Boiler and Pressure Vessel Code construction. Specifically, these materials include the 200, the 300, and the XM series wrought austenitic steels, the CF series austenitic steel castings, weld filler alloys used in welding austenitic steels, and the wrought grades of high nickel alloys. The effects of the changes in notch impact values and fracture toughness as a result of the exposure are analyzed and evaluated in relation to the ASME Code design loadings and stresses for these materials.

Publication of this report - WRC Bulletin No. 378 was sponsored by the Materials and Fabrication Division of the Pressure Vessel Research Council.