Fatigue behavior of thin hard coated specimens made of 7075

7xxx series aluminum alloys are used to manufacture machine components with good strength and low mass. The application of thin surface films can improve the erosion resistance of these alloys and their corrosion resistance, which are scarce. Low temperature PVD (Physical Vapor Deposition) coatings can increase the surface properties of the components without greatly influencing the mechanical properties. The deposition process induces high residual compressive stress on the surface, which favorably modifies the fatigue strength, but also defects, which have the opposite effect. The changes in fatigue behavior of 7075-T6 alloy induced by the deposition of a surface layer of PVD DLC (Diamond-Like Carbon) are described in this paper. The tests performed on some uncoated samples and others with DLC show that the fatigue strength of the uncoated samples is higher within 2ڄ105 - 107 cycles range. The fatigue strength of the two kinds of samples is approximately equal within the range of 2ڄ106 - 107 cycles. The failure mechanism is studied with the help of fracture surface microscopy and finite element analysis. The compressive stress state on the surface of the specimen associated with the surface layer deposition causes fatigue crack initiation under the surface of the specimen, if the sample does not present defects.