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In this study, MeltFlow software was used to simulate the vacuum arc remelting of C700R-1 alloy and examine the effect of cooling rate on ingot properties. In situ observations, optical microscopy, field emission scanning electron microscopy, and electron probe microanalysis were performed to investigate the evolution of the solid–liquid interface, alloy microstructure, segregation characteristics, and back diffusion at various cooling rates from 1 to 20 °C/min. The obtained results revealed that with an increase in the alloy cooling rate, the dendrites were considerably refined, and the size of precipitates decreased. The composition of the μ phase did not change significantly with the cooling rate, whereas the MC carbides composition depended on the solidification temperature. W, Ti, Nb, and Mo elements demonstrated a distinct segregation trend, and their segregation degrees first increased and then decreased with an increase in the cooling rate. In contrast, the segregation degrees of Al, Ni, Cr, and Co elements were very small. Additionally, the effective partition coefficients of Ti, Nb, and Mo first decreased and then increased with increasing cooling rate. The alloy segregation degree reached a maximum value at a cooling rate of 6.8 °C/min. Finally, back diffusion in the solid observed at a very low cooling rate reduced the degree of dendrite segregation and volume of the precipitated phase. The findings of this study can help evaluate the microsegregation behavior of large-sized C700R-1 alloy ingots. [ABSTRACT FROM AUTHOR]