Cyclic deformation and fatigue behaviour of ion-nitrided steel

Abstract

The effect of the ion-nitriding process on the axial fatigue and deformation behaviour of SAE 1045 steel was investigated using smooth specimens at room temperature. Both monotonic and cyclic deformation responses of the ion-nitrided specimens are evaluated and compared with those of the core and case materials. A composite model is used to predict the stable cyclic response of the ion-nitrided specimen under constant-amplitude strain cycling. The fatigue tests were strain-controlled and consisted of both constant-amplitude and overstrain tests. Ion nitriding is found to have a significant influence on fatigue life in both the low-cycle and the high-cycle regions. Factors contributing to this influence, which include subsurface nucleation, multiaxial stress state and residual stresses, are discussed. Several cumulative fatigue damage models are used to predict the fatigue life in overstrain tests. Life predictions based on these models are then compared with the experimental data. © 1995.

Publication Title

International Journal of Fatigue

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