Fatigue crack behaviour of composite- and mono-coated marine structural components

In this study, experimental and numerical studies of fatigue crack growth (FCG) mechanisms in coated and uncoated structural components of EN8 steel (EN8) and aluminium alloy 6063 (AA6063) samples were compared. Electroplating (EP) (of nickel (Ni) and chromium (Cr)) and physical vapour deposition technique (PVD) (of aluminium nitride (Al-N) and nanocrystalline layers of titanium aluminium nitride (Ti-Al-N)) methods were used for mono and composite metallic coatings of EN8 and AA6063. The present study focuses on the implications of the coating-substrate interface during FCG initiation and propagation by considering the loading-bearing ability of the coating. Fatigue cracking mechanism depends on coating fracture toughness (FT) at the interface of mono-composite coating and its thickness. In comparison, composite-coated PVD samples proved better than mono-coated electroplated samples due to the delayed plastic deformation process on the surface of the substrate sample.