Fatigue behaviour of corrosion resistant surface thin hard coatings

Corrosion resistance of metal components and structures can be improved by using thin hard coatings. Among the coatings recently developed the PVD coatings act as good corrosion barrier and enable to increase the surface hardness and wear resistance of the coated components. Appropriately designed PVD coatings can increase the fatigue resistance of mechanical components too and would enable to enhance the mechanical behaviour in aggressive environments. In this paper the fatigue behaviour of corrosion resistant surface thin hard coatings is studied. A survey of recent fatigue test results on steel and light alloys, on coated and uncoated, smooth and notched specimens, is reported. A numerical procedure to foresee the number of cycle to failure of coated components is described and applied to spur gears.