Development of Cost-Effective Microstructure and Isothermal Oxidation-Resistant Bond Coats on Inconel 718 by Atmospheric Plasma-Sprayed NiCoCrAlFe High-Entropy Alloy

Ni-based superalloy (Inconel 718) has been widely employed in aircraft, gas turbine engines, and turbocharger rotor equipment, due to its high strength and long fatigue life, but inadequate oxidation resistance has restricted high-temperature applications. In the current study, a NiCoCrAlFe high-entropy alloy (HEA) coating was fabricated on Inconel 718 using low energy ball-milled/blended elemental powders thermally sprayed by an atmospheric plasma spraying process. The microstructural and isothermal oxidation behavior of the NiCoCrAlFe HEA bond coats at 1000°C was studied. The result revealed that the microstructure of the HEA coatings consists of dark and light phases in the lamellar structure. The dark phases are relatively hard and are oxides, while the soft phase is the HEA phases spread in the microstructure. The novel NiCoCrAlFe high-entropy bond coat exhibits a considerably low oxidation rate and slow (Al 2 O 3 ) TGO formation on the surface of the bond coats at elevated temperatures and exposure for extended durations. In conclusion, the present study provides a workable approach for enhancing the oxidation resistance of Inconel 718 alloy in high-temperature conditions.