Standing contact fatigue behavior of nitrided AISI 316L steels

In this work, an experimental-numerical evaluation of the standing contact fatigue testing of a nitrided AISI 316L steel was developed. The nitride layers were formed at the surface of an AISI 316L steel by a salt bath nitriding process at a temperature of 580 °C for 1, 3 and 5 h of exposure time, obtaining three different layer thicknesses. In order to know the mechanical response and the different mechanisms of damage associated with the standing contact fatigue test, Hertzian tests were performed on a MTS machine by cyclic loading of a sphere on a flat surface formed by the layer/substrate system. The standing contact fatigue test was developed through two main stages. First, the critical loads for each treatment condition were determined by monotonic tests, where the appearance of circular cracks was considered as the failure criterion. Subsequently, cyclic subcritical loads were applied at a frequency of 5 Hz. A numerical model based on the finite element method was developed to evaluate the stress field generated in the system by cyclic contact loads. The results indicate that the thinnest thickness of nitride layer exhibits better resistance to standing contact fatigue. •Nitride layers were evaluated through standing contact fatigue.•The stress field associated with contact damage modes in the nitride layers was obtained by the finite element method.•Cohesive damage was a function of both the range of the maximum principal stress and the amplitude of the radial distance.