Microstructural Characterization and Tribological Properties of Atmospheric Plasma Sprayed High Entropy Alloy Coatings

Two different types of high entropy alloy thick coatings (HEAs), namely, AlCrCoFeNiTi and FeCrCoNiW0.3+ 5 at.% C were fabricated using atmospheric plasma spray (APS) on stellite substrate and compared for their various properties. Fine spherical powder particles used for fabrication resulted in homogeneous and surface defect-free (like cracks or voids) coatings with a negligible amount of porosity. The surface roughness and dilution level of both the coatings were found to be 8.56 µm, 7.23 µm, and 3.71%, 3.55% for AlCrCoFeNiTi and FeCrCoNiW0.3+ 5 at.% C alloy, respectively, demonstrating a strong metallurgical bonding between the coatings and substrate. A lamellar microstructure along with precipitates was observed from the microstructural investigation of both coatings. The AlCrCoFeNiTi coating comprised of two BCC phases (A2 and B2) and FeCrCoNiW0.3+ 5 at.% coating consisted of FCC phase with Cr and W rich carbides. The microhardness of AlCrCoFeNiTi alloy coating exhibited 2.16 times higher hardness (761 ± 14 HV0.2) and 4.28 times lower wear rate (2.8 × 10−7 mm3/ Nm) than the substrate. BCC phases, good metallurgical bonding between the matrix and substrate, and defect-free microstructure attributed to the improved wear performance of the aforementioned alloy coating.