High-Entropy Alloy-Based Coatings

The concept high-entropy alloys (HEAs) was based on the idea that high configurational entropy resulted from mixing multiple principal elements that can promote the formation of a stable single-phase solid solution. HEA-based coatings are a new type of coating which have been developed based on the HEA concept. HEA-based coatings are currently of great research interest in materials science due to their compositional freedom and excellent properties, such as superior hardness and toughness, strong resistance to wear, corrosion and oxidation, as well as exceptional thermal stability. This chapter summarizes the state-of-the-art in the emerging field of HEA-based coatings, including high-entropy metallic coatings and high-entropy ceramic coatings, focusing on their preparation technologies, microstructures, and properties. Furthermore, this chapter discusses the mechanisms and design criteria for the formation of specific crystal structures and microstructures, and for achieving desired properties. Finally, it is suggested that a further understanding of nanoscale deformation mechanisms and high-throughput experiments are needed to realize the full potential of HEA-based coatings. In view of their extraordinary properties and richness of compositional design, it is envisaged that HEA-based coatings are highly competitive candidates for protective coatings in a range of applications.