Development of Fe-Co-Cr-Mn-Ni-C high entropy cast iron (HE cast iron) available for casting in air atmosphere

In this paper, we discuss the development of Fe-Co-Cr-Mn-Ni-C high-entropy alloys (HEAs), which can be cast in air atmosphere (hereafter called HE cast iron alloys). FexCoCrMnNiCy HE cast iron alloys were designed by the addition of carbon to realize the reduction atomosphere during melting and casting, with subsequent thermodynamic calculations for the decrease in the liquidus temperature focusing on the liquidus of carbides and the face-centered cubic (FCC) phase. The ingots were cast with conventional high-frequency melting methods in silica-based crucibles under Ar flow and air atmosphere, respectively. The formation of the FCC phase was observed in the ingots of FexCoCrMnNi (x = 1, 2, and 3) HEAs. Composites of the FCC phase and Cr-rich carbides were obtained in the ingots of FexCoCrMnNiCy HE cast iron alloys with compositions of FeCoCrMnNiC0.2, Fe2CoCrMnNiC0.4, and Fe3CoCrMnNiC0.8. The constituent phases and solidification microstructures of the FexCoCrMnNiCy HE cast iron alloy ingots were not dependent on the processing atmosphere (Ar flow versus air atmosphere).