Very high cycle fatigue of austenitc stainless steels and their welds for reactor internals at ambient trmperature and 300 °C

Abstract

The fatigue assessment of safety relevant components is of importance for ageing management with regard to safety and reliability of nuclear power plants. Austenitic stainless steels are often used for reactor internals due to their excellent mechanical and technological properties as well as their corrosion resistance. During operation reactor internals are subject to mechanical and thermo-mechanical loading which induce low cycle (LCF), high cycle (HCF) and even very high cycle (VHCF) fatigue. While the LCF behavior of austenitic steels is already well investigated the fatigue behavior in the VHCF regime has not been characterized in detail so far. Accordingly, the fatigue curves in the applicable international design codes have been extended from originally 10⁶ to the range of highest load cycles up to 10¹¹ load cycles by extrapolation. Nevertheless, the existing data base for load cycles above 10⁷ is still highly insufficient. The aim of the cooperative project of the Institute of Materials Science and Engineering (WKK) at RPTU Kaiserslautern-Landau, Materials Testing Institute (MPA) Stuttgart and Framatome GmbH, Germany is to create a comprehensive database up to the highest load cycles N = 2·10⁹ for austenitic stainless steels and their welds at ambient and elevated temperature.