Fatigue behaviour of 2011-T6 aluminium alloy coated with PVD WC/C, PA-CVD DLC and PE-CVD SiOx coatings

In this paper, the effect of three different thin hard coatings on the fatigue behaviour of 2011-T6 aluminium alloy was investigated. The coatings were DLC, SiOx and WC/C deposited with CVD and PVD processes. The fatigue limit at 107 load cycles was evaluated for both coated and uncoated specimens in a rotating bending machine (R=?1). The DLC and SiOx films did not significantly enhance the fatigue limit of the studied alloy, whereas a slight beneficial effect was produced by the WC/C film. Subsurface fatigue cracks nucleated in the WC/C-coated samples, as revealed by SEM micrographs of the fracture surfaces. It was therefore argued that the enhancement in the fatigue resistance of the WC/C-coated specimens could be due to residual compressive stress distributions introduced in the surface layers of the base material by the deposition process. The interface delamination was investigated with scratch tests and WC/C showed the best adhesion to the aluminium alloy.