Cyclic deformation behaviour, microstructural evolution and fatigue life of duplex steel AISI 329 LN

• Characterisation of the fatigue behaviour in the HCF and VHCF regime of AISI 329 LN.
• Application of “PHYBALLIT” in the HCF regime for AISI 329 LN.
• Fatigue induced microstructural changes were characterized by TEM investigations.
• TEM micrographs can be used to validate the “PHYBALLIT” calculation.
• The “PHYBALLIT”-curve is in a very good accordance to conventionally determined data.

This paper summarises fatigue results obtained on the duplex steel AISI 329 LN (German designation 1.4462). For the characterisation of the fatigue behaviour, the mechanical stress–strain hysteresis loops, the temperature change and the evolution of the electrical resistance were monitored. Transmission electron microscopy was performed to investigate the microstructural changes caused by the fatigue loading. The data were used to apply the fatigue life calculation method “PHYBALLIT”. This procedure requires only one load increase test and two constant amplitude tests for a timesaving and material-efficient assessment of S–N (Woehler) curves. The method has already been successfully applied to different carbon and austenitic steels as well as lightweight materials. The results show an excellent agreement between the conventionally determined and the calculated fatigue lifetimes. This agreement is rationalized on a microstructural basis.