Precipitation of sigma-phase and creep-fatigue behavior of 308L steel weldment

Abstract

The creep-fatigue properties of a 308L steel weldment after different post-weld heat treatments (PWHT) are investigated. The microstructure and phase transformation of the as-welded and PWHT weldments are examined using scanning and transmission electron microscopy. Special attention is paid to the decomposition of delta-ferrite and the precipitation of sigma-phase. Energy dispersive spectroscopy is also used for detecting the elements distribution. The results show that PWHT promotes the creep-fatigue resistance of the weldment. delta-Ferrite mainly transforms into secondary austenite and sigma-phase. The decomposition ratio of delta-ferrite shows a tendency to decrease after high temperature PWHT. This can be attributed to the reduction of silicon segregation near the delta/gamma interface. (C) 2007 Elsevier B.V. All rights reserved.