Mechanical Behaviour of PVD CrN Coated Steels Evaluated by Means of FEM Modelling

PVD (Physical Vapour Deposition) surface coatings have received increasing interest for tribological applications thanks to the enhancement of surface hardness of treated components. Despite the good wear resistance of such coatings, the fatigue behaviour of the substrate material may be affected by too steep changes in the residual stress field gradient and microhardness inducing coating cracks or detachments from the substrate. In the present paper the residual stress measurements, combined with FEM simulation and microstructural analysis, were used to characterize the fatigue behaviour of thin-coated components and to develop a model for fatigue life prediction. The fatigue behaviour characterization was carried out by means of four-point bending tests, while the microstructure of the substrate and coating materials was evaluated by means of SEM observations, nanoindentation tests and residual stress measurements. Numerical FEM models were developed with the aim of giving the designer a useful predictive tool of the fatigue behaviour of thin-coated components. Experimental tests carried out both on 2205 duplex stainless steel and on AISI H11 tool steel coated with CrN PVD coating (5 ?m thick) enabled validation of the numerical model.