Mechanism of impurities reduction and evaporation of alloying elements for a multi-elements Ni-based superalloy during electron beam remelting

Abstract

The regularity of alloying element evaporation is still one of the most important issues of refining superalloy. The reduction of volatile impurities still has some unclear problems. In our work, electron beam remelting (EBR) has been used to remelt a multi-elements Ni-based superalloy. Chemical compositions under different electron beam parameters are investigated and the weighted average mixing heat is used to describe activity coefficient. EBR can significantly reduce impurities Si, S, N, and O. The reduction of S and O as well as boiling of the melt dams the flow of the Marangoni effect. The temperatures of the area which is bombarded by electron beam remelt by 9 kW, 12 kW, and 15 kW are about 1730 K, 1771 K and 1805 K. The weighted average mixing heat can describe activity coefficient well and shows its significance in theoretical guidance for the preparation of nickel based superalloys.