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A series of directional solidification experiments have been conducted to elucidate the formation mechanism of eta and Cr-rich phases in the Ni-base superalloy IN792 + Hf. Both eta and Cr-rich phases were found to be the final solidification products developed from the remaining liquid after c/c¢ eutectic reaction. The (Ti + Ta + Hf)/Al ratio in the residual liquid played a significant role in the nucleation of eta phase. During the solidification of c/c¢ eutectic, the continual increase of (Ti + Ta + Hf)/Al ratio in the residual liquid eventually led to the completion of c/c¢ eutectic reaction and caused the nucleation of eta phase. The results of electron probe microanalysis and transmission electron microscopy revealed that the Cr-rich phase was Cr, Mo, and W containing M 5 B 3 and M 3 B 2 type borides. The formation of these boride phases was found to be strongly influenced by the formation of c/c¢ eutectic. Because of the limited solubility of Cr, Mo, and W in c¢ phase, these elements were enriched in the residual liquid during the solidification of c/c¢ eutectic. In addition, boron would preferentially segregate into liquid due to its very limited solubility in both c and c¢ phases so that the possibility of boride formation in the residual liquid ahead of the c/c¢ eutectic was increased. A modified Scheil model was adopted to explain the influence of solidification rate on the formation of eta phase and borides, and the results were discussed.