A novel alloy design approach in developing CoNi-based high entropy superalloy using high entropy alloys thermodynamic and spark plasma sintering

This study introduces an innovative alloy design strategy by integrating HEAs principles to develop CoNi-based high entropy superalloys (HESAs). The powder of designed HESA produced using gas atomization and consolidated using spark plasma sintering (SPS). The alloy design strategy validated by CALPHAD to mitigate detrimental phase precipitation and segregation during powder production, material consolidation, and post-processing heat treatments. CoNi-HESA powder with a calculated mixing entropy of 1.568R was successfully developed and consolidated using SPS. Optimization of SPS parameters at 1175 °C, 10 min, and 100 °C/min achieved a relative density of 99.9%. Subsequent heat treatments further improved the material's characteristics. Solutionizing at 1190±10 °C for 2 h with water quenching resulted in a fine grain structure of ∼7 μm grain size. Aging at 900 °C for 24 h, followed by water quenching, yielded uniformly distributed fine γ' precipitates comprising approximately 65% of the γ matrix, without unwanted secondary precipitates or TCP phases. This study demonstrates the effectiveness of the novel approach in designing CoNi-based HESAs and optimizing their properties through careful process parameter selection and post-heat treatment cycles. The combination of thermodynamic calculations, HEA principles, and powder metallurgy techniques offers a promising approach for developing advanced high entropy superalloys with tailored microstructures.