INVESTIGATION OF THE Y- AND Hf-DOPED AlCoCrFeNi HIGH ENTROPY ALLOY COATINGS’ STRUCTURE AND PHASE COMPOSITION FORMED BY ELECTRICAL EXPLOSION METHODS

10.25712/ASTU.1811-1416.2026.02.006

Abstract

This paper presents the results of a study of the microstructure and phase composition of Y- and Hf-doped AlCoCrFeNi high-entropy alloy coatings produced by electrical-explosion spraying onto Inconel 718 substrates in four processing modes. Thin plates formed by compacting high-entropy alloy powders prepared via mechanical alloying in a planetary mill were used as electro-explosive conductors. X-ray phase analysis revealed similar phase compositions in all studied specimens. The coatings contain two FCC phases, one BCC phase, and small mass fractions of the AlNi₃ intermetallic phase. The coatings exhibit a similar microstructure regardless of the spraying mode. Increasing the discharge energy during electrical-explosion spraying increases the maximum coating thickness and through-thickness heterogeneity, while the number density of spherical aluminium oxide inclusions decreases. A transition layer was observed at the coating–substrate interface; it consists of thin, horizontally oriented sublayers of the Y- and Hf-doped AlCoCrFeNi high-entropy alloy alternating with Inconel 718. Such periodic structures were detected in all specimens. A thicker transition layer with a larger number of sublayers was observed beneath regions of greater coating thickness. The results confirm the technological applicability of electrical-explosion spraying for producing high-entropy alloy bond coatings for prospective thermal barrier coating systems.