Achieving high tribological and corrosion performances via a new approach: Al₂O₃/CrN duplex coatings

Owing to growth defects, the CrN coating–substrate system may suffer from severe corrosion and wear attack in a marine environment, which limits the coating protection against the 316L substrate. To improve the efficiency, a new approach of fabricating Al₂O₃/CrN duplex coatings to achieve excellent corrosion and wear performances was provided by sealing the growth defects and extending the deposition time of the CrN layer. The Al₂O₃/CrN duplex coatings were obtained by multi-arc ion plating system sputter CrN layers combined with sequential atomic layer deposition Al₂O₃ layers. The morphology and structure of the as-deposited coating were investigated by scanning electron microscopy and x-ray photoelectron spectroscopy. The corrosion performances and tribological properties of the Al₂O₃/CrN duplex coatings in a seawater environment were investigated. The results showed that the density of the duplex coating decreases as the CrN layer thickness increases. The Al₂O₃/CrN duplex coatings with a suitable CrN layer thickness exhibited superior corrosion resistance in a seawater environment, which may be ascribed to the Al₂O₃ layer filling or sealing the partial growth defects of the CrN layer and playing a good barrier role to prevent the infiltration and penetration of corrosive media. Furthermore, the wear rate of the Al₂O₃/CrN duplex coating was reduced more than 30% compared to the single CrN coating of the same thickness. The good wear resistance of Al₂O₃/CrN duplex coatings was attributed to the synergistic effect of the dense structure, high wear resistance of the Al₂O₃ layer, and the supporting effect of the CrN layer as well as the formation of the lubricating component of CaCO₃ and Mg(OH)₂ during wear progress.