Studies on Y₂O₃-dispersed Co_1.7Cr_0.4Ni_2.5Al_2.4Nb_0.23 high entropy alloy coated with HVOF for bond coat application in TBC system

Oxide dispersion in high-entropy alloy (HEA) improves mechanical properties, corrosion resistance, and high-temperature oxidation. Several studies have been reported on oxide-dispersed high-entropy alloys prepared by Spark plasma sintering and hot pressing, but only a few on coating. This study aims to investigate a novel Fe-free Co 1.7 Cr 0.4 Ni 2.5 Al 2.4 Nb 0.23 HEA dispersed with oxide (1 wt % Y 2 O 3 ) for bond coat application in the thermal barrier coatings (TBC) System. The elemental powders in desired stoichiometry along with yttria were milled for 5 h in a planetary ball mill with a ball-to-powder ratio of 10:1 at a speed of 300 rpm followed by heat treatment at 1050 °C for 1 h in argon. ODHEA bond coat and yttria-stabilized zirconia (YSZ) topcoat was coated by high-velocity oxygen fuel (HVOF) and air plasma spray on a nickel superalloy substrate, respectively. The coating shows the formation of FCC, BCC and Laves phase. The hardness and Young’s modulus for the coating were approximately 610 HV and 172 GPa. Good oxidation resistance with an average TGO layer thickness of less than 7 µm was observed after 100 h of isothermal oxidation.