The effect of the embrittlement on the fatigue limit and crack propagation in a duplex stainless steel during high cycle fatigue

In order to evaluate the effects that the “475° embrittlement” produces on the fatigue life during high-cycle fatigue, stress-controlled cyclic loading tests were conducted on a standard duplex stainless steel in two different heat treatment conditions (homogenized and embrittled). Transmission (TEM) and scanning electron microscopy (SEM) in combination with automated electron back-scattered diffraction (EBSD) techniques were carried out to analyze the surface damage as well as the initiation and propagation of fatigue cracks. These studies have revealed that the fatigue limit of the embrittled samples is substantially larger than that of the conventional samples at 107 cycles in the homogenized condition. Finally, an existing numerical short-crack propagation model was adapted using the stereological values obtained by EBSD to reproduce the propagation of microstructural fatigue cracks in the homogenized and embrittled conditions.