OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 4 2024 HEA-based coatings are currently of great interest in materials science due to its compositional freedom and excellent properties, such as excellent hardness and impact toughness, high wear resistance, corrosion and oxidation resistance, and exceptional thermal stability [28]. The methods of applying HEA coatings play a key role in determining its fi nal properties and areas of application. The choice of coating technology directly infl uences the microstructure, phase composition, adhesion to the substrate, as well as the mechanical and functional characteristics of the coating. In recent years, there has been signifi cant interest in the development and improvement of various methods for applying HEA coatings, driven by its unique properties, such as high hardness, wear and corrosion resistance, thermal stability, and mechanical strength. The main methods for applying HEA coatings include laser surfacing, magnetron sputtering, as well as nitriding and oxidation of substrates. Each of these methods has its own advantages and features that make it suitable for diff erent applications and operating conditions. Coatings of high-entropy FeNiCoAlCu alloy obtained by laser surfacing demonstrate high wear resistance. The results of the studies showed that such coatings have good thermal stability at temperatures below 780 °C. It is also noted that it demonstrates good wear characteristics at high temperatures, mainly due to the formation of oxide fi lms on the surface of the coating. The wear mechanisms are predominantly abrasive and oxidative [29]. High-entropy ceramic fi lms obtained by nitriding or oxidizing HEAs substrates exhibit good anti-wear, anti-radiation, anti-corrosion, and anti-oxidation properties. These properties make it attractive for use in extreme conditions, such as high temperature, high strength, and intense radiation [30]. Magnetron sputtering allows the production of HEA fi lms with improved properties. For example, FeCoNiCuAl fi lm obtained by magnetron sputtering exhibits enhanced corrosion and magnetic properties compared to the bulk alloy of similar composition. Studies show that such fi lms have better corrosion resistance than its bulk counterparts [31]. Properties of HEA Coatings The corrosion resistance, magnetic properties, and microstructure of the surfaced and annealed fi lms were investigated. Results show that the surfaced HEA has better corrosion resistance than the bulk HEA of the same composition. The most relevant and notable developments in the fi eld of anti-corrosion properties of coatings are reviewed by international experts in work [32]. In a study conducted by the authors [33], HEA coatings based on FeCoCrNiMoTiW composition, produced by mechanical alloying, were studied. The results showed that the hardness of these coatings exceeds the hardness of most stainless steels by 1.5–2 times, and the dry friction coeffi cients are in the range of 0.08–0.16. This signifi cant diff erence in friction coeffi cients of HEA coatings is due to its nanostructural features and the manifestation of the size dependence of its properties. Thus, the study demonstrated the potential of these coatings in terms of mechanical properties. In the study [34], a comparison was made between HEA coating and steel specimens. Researchers noted that the nanostructured FeCrNiTiZrAl coating has signifi cantly greater hardness and wear resistance compared to stainless steels. Moreover, the friction coeffi cient of the FeCrNiTiZrAl coating is signifi cantly lower than that of other materials, which contributes to an increased service life of products with such coatings. Study [35] showed that the HEA Al0.6CoCrFeNiTi is a promising material for metal thermal insulation coatings due to its combination of low thermal conductivity and high thermal stability. Overall, studies on the properties of HEA coatings have demonstrated its unique properties and potential applications. The results of the studies confi rm the potential of HEAs in the fi eld of mechanical properties, anti-corrosion properties and thermal insulation properties. Thus, HEA coatings may become promising materials for various industries, including aviation, automotive manufacturing, and biomedical industry. Corrosion Resistance of High-Entropy Alloys Corrosion is one of themain causes of material failure in various industries, such as energy, petrochemical, and marine engineering. Therefore, studying the corrosion resistance of HEAs is critical for its use in
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