In this study, a novel single face-centered cubic (FCC) phase CoNi-based high entropy superalloy (HESA) was successfully produced using fully prealloyed gas atomized powders and spark plasma sintering (SPS). The alloy design process incorporated high entropy alloy (HEA) principles and thermodynamic calculations (CALPHAD) to predict phase transformations at various production stages, including powder production, SPS processing, and heat treatment of the HESAs. The resulting alloys exhibited a relative density of 99.9%, ultimate tensile strength (UTS) of 800 MPa, and a hardness of approximately 400 HV1. Comprehensive microstructural and fractographic analyses demonstrated the absence of detrimental secondary and/or topologically closed-packed (TCP) phases within the developed alloy. Thermal analysis results revealed that an increase in the entropy of mixing resulted in a correspondingly high volume fraction of the gamma prime (γ') phase (70%) and an elevated solvus temperature of 1165 °C. These findings highlight the significant impact of HEA principles in the design of CoNi-based superalloys, accelerating the development of this alloy family for advanced manufacturing technologies.
