Residual stress state behaviour under fatigue loading in duplex stainless steel

Abstract

The lifetime of duplex stainless steel parts experiencing cyclic fatigue is directly influenced by the residual stress levels present in the ferrite and austenite phases. This paper analyses the behaviour of the residual stress fields in both phases introduced by a shot peen-ing treatment. The X-ray diffraction technique is used to investigate the stress levels both on the sample surface and in subsurface layers, after low fatigue cycles. The results show that the compressive residual stress levels introduced by the shot peening treatment in both phases improves the fatigue life of the material. However, the cyclical loads produce partial or total relief in these residual stresses fields. A scanning electron microscopy study of the samples shows that the shot peening process induces the formation of micro cracks only in the ferrite phase. The largest variations in the total compressive residual stress level also occur in this phase.