475oC Embrittlement and Room Temperature Fatigue of Duplex Stainless Steel

Abstract

Duplex stainless steels (DSSs) are two-phase materials consisting of both the ferritic and the austenitic phase. The alloys are prone to embrittlement particularly in the temperature range between 280°C and 512°C. This so-called 475°C embrittlement is caused by a decomposition of the ferritic phase into a chromium-rich α' and an iron-rich α phase. The objective of this study is to develop a better understanding of the embrittling process of DSS of type SAF 2205. Embrittled and non-embrittled DSS was fatigue tested in stress-controlled tests at 475°C and in strain-controlled tests at room temperature. The high temperature fatigue tests were stopped at different cycle numbers in order to characterize the changing material conditions by means of room-temperature tensile tests and scanning electron microscopy pictures of the fracture surfaces.