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The authors made a brief review of recent publications by foreign and domestic researchers on the structure, phase composition, and properties of films and coatings of five-component high-entropy alloys (HEA) on various substrates and modification of the HEA surface by various types of processing. The main methods of applying films and coatings are considered: magnetron sputtering, thermal sputtering, laser sputtering, and electrodeposition. Particular attention is paid to the deposition of coatings on stainless steels and titanium alloys. The positive change in the tribological, strength properties, and corrosion resistance of film coatings in a wide temperature range is analyzed and possible causes of the observed effects are discussed. The role of solid solution strengthening, formation of fine-grained structure, and the formation of oxide layers enriched with one of the HEA components were taken into account. The authors identified new methods for applying coatings from HEA and subsequent processing. Using Nb and Ti doping as an example, their role in increasing microhardness, wear resistance, and reducing the friction coefficient in coatings were revealed. Electrolytic polishing, electroerosive machining, mechanical polishing and their combination are considered among the methods of HEA surface treatment. A number of works propose a method of powder borating to increase the surface strength and wear resistance of HEAs. The paper considers analysis of works on electron-beam processing as one of the promising and high efficient methods of HEA surface hardening.

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Используя технологию холодного переноса металла (проволочно-дуговое аддитивное производство (WAAM), совмещенное со сварочной наплавкой (СМТ)) на подложке из сплава 5083 сформировано покрытие высокоэнтропийным сплавом (ВЭС) Al-Fe-Cr-Co-Ni неэквиатомного состава. Методами современного физического материаловедения выполнен анализ структуры, фазового и элементного состава, дефектной субструктуры системы «покрытие-подложка». Показано, что элементный и фазовый состав, дефектная субструктура покрытия зависят от расстояния до зоны контакта покрытия и подложки. В слое толщиной до 200 мкм, примыкающем к зоне контакта, выявлено присутствие включений второй фазы на границах зерен ВЭС, обогащенной атомами хрома и железа. Микродифракционным анализом установлено, что это включения Al8Cr5. В зоне перемешивания покрытия и подложки выявлено формирование нанокристаллической фазы Al2O3 и MgAlO размером 10-20 нм и субзеренной структуры (размер субзерен 140-170 нм. Структура 1-го типа характеризуется неоднородным распределением химических элементов ВЭС, выявлены области пластинчатой формы, обогащенные атомами Cr и сферической формы, обогащенные атомами Ni, Fe, Co. По границам субзерен структуры располагаются наноразмерные частицы (NiCo)3, Al4 и Al13Fe4. Высказано предположение о физических механизмах повышения твердости материала в зоне контакта «покрытие-подложка».

High-entropy alloys (HEAs) are a new class of materials consisting of at least five elements in equiatomic or near-equiatomic ratio. HEAs are subjected to various types of surface treatment to improve their properties. One of the most promising methods of surface hardening is electron beam processing. This study aims to examine the structure, elemental, and phase composition of the AlCrFeCoNi HEA surface layer after the deposition of a (B + Cr) film and irradiation with a pulsed electron beam. HEA samples of non-equiatomic composition (33.4 Al; 8.3 Cr; 17.1 Fe; 5.4 Co; 35.7 Ni, at. %), fabricated by wire-arc additive manufacturing (WAAM), were used as study objects. Modification of the HEA surface layer was carried out by a complex method combining deposition of (B + Cr) film samples on the surface and irradiation with a pulsed electron beam in an argon medium. The mode of modification was identified. It makes it possible to increase microhardness (almost two times) and wear resistance (more than five times), reduce the friction coefficient of the HEA surface layer by 1.3 times due to the decrease in the average grain size, formation of particles of borides and oxyborides of complex elemental composition, the introduction of boron atoms into the crystal lattice of HEA.