Abstract
Recently, the materials research community has seen a great increase in the development of multicomponent alloys, known as high entropy alloys (HEAs) with extraordinary properties and applications. In surface protection and engineering, diverse applications of HEAs are also being counted to benefit from their attractive performances in various environments. Thermally sprayed HEA coatings have outperformed conventional coating materials and have accelerated further advancement in this field. Therefore, this review article overviews the initial developments and outcomes in the field of HEA coatings. The authors have also categorized these HEA coatings in metallic, ceramic, and composite HEA coatings and discussed various developments in each of the categories in detail. Various fabrication strategies, properties, and important applications of these HEAs are highlighted. Further, various issues and future possibilities in this area for coatings development are recommended.
Highlights
Laser-based methods are the most popular and attractive for high entropy alloys (HEAs) coatings due to their attractive features, such as high heat input, rapid process, less material wastage, and eco-friendly process [46,47,48]. This process contributes to a strong coating substrate bonding, uniform microstructure, formation, but there is smaller thermal damage caused due to rapid heating and cooling rates involved in the process
Various microstructural features of the HEA coatings are reported, including equiaxed, columnar grains, dendritic and lamellar structures depending upon the thermal history, such as in laser cladding, laser surface alloying, and plasma spray methods
The fabrication of HEAs coatings involves various non-equilibrium processes owing to severe deformation of the matrix, rapid cooling, chemical and solid-liquid phase changes which degrade the adhesion led to premature failure of the substrate [102,103]
Summary
The various factors affecting the durability and performance of coatings include the composition and type of substrate, residual stresses, adhesion, toughness, service temperature, humidity, and wear [6] In this regard, the coating industry has been continuously evolving in technology throughout the last few decades. For wear-resistant application, the prime goal is to control the surface topography of the base alloy or modifying its mechanical properties to withstand higher weight in dynamic loading applications. This is established by a variety of coating techniques, surface modification, thin film deposition, texturing of deposits, altering the metallurgical bonding, e.g., by micro- or nanojoining of the surface.
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