Microstructural and Mechanical Characterization of Eutectic AlCoCrFeNi₂.₁ High-Entropy Alloy Coating Produced by HVOF

Single-phase face-centred cubic (FCC) high-entropy alloys (HEAs) are known for their ductility, while single-phase base-centred cubic (BCC) HEAs exhibit high hardness and strength. However, balancing ductility and strength within single-phase HEAs remains a challenge. Eutectic high-entropy alloys (EHAs), which feature combining both soft and hard phases, are regarded as promising materials with superior mechanical properties compared to single-phase HEAs. In this study, an AlCoCrFeNi_2.1 EHEA coating was produced using high-velocity oxygen fuel (HVOF) spraying technique. The powder and resulting coating were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). Phase prediction was performed using the CALPHAD approach, including both equilibrium and non-equilibrium (Scheil) simulations. A detailed correlation between the microstructure and mechanical properties was established through nanoindentation and microhardness testing. Furthermore, the room temperature sliding wear resistance of the coating was evaluated. This study highlights the potential of AlCoCrFeNi_2.1 EHEA coatings, demonstrating a promising combination of mechanical properties suitable for advanced engineering applications.