A review on microstructures and mechanical properties of protective nano-multilayered films or coatings

Nano-multilayered films offer a multilayer structure arrangement at several to tens of nanometers. They have hardness, high-temperature oxidation resistance, and low wear rates, making them popular in surface protection fields, such as engineering machinery, cutting tools and molds, and electronic instruments. This paper reviews recent research progress on nano-multilayered films, including their general types, preparation methods, microstructures, mechanical properties, and corrosion resistance. Furthermore, the mechanisms of the high hardness and toughness in nano-multilayered films are analyzed in detail. The future research directions for designing nano-multilayered films with improved strengthening and toughening properties are discussed.