The interfacial reaction process and phase formation mechanism between the nickel-based superalloy and the SiO2 crucible during vacuum induction melting

Abstract

This work investigated the interfacial reactions between Ni-based superalloys and SiO₂ crucibles during vacuum induction melting. Through thermodynamic and kinetic analyses of the interfacial reactions, the underlying mechanisms of the interactions at the superalloy/SiO₂ interface are elucidated. The interfacial reactions are facilitated by elemental diffusion at the interface. The Al atoms in the alloy preferentially diffuse to the interface, where they react with O atoms diffusing from the crucible to form Al₂O₃. The initially formed Al₂O₃ serves as heterogeneous nucleation sites for TiC. Consequently, a continuous and uniform Al₂O₃ layer, along with a discontinuous TiC layer, formed at the superalloy/SiO₂ interface. Transmission electron microscopy (TEM) analysis confirmed the orientation relationship between the TiC and the superalloy matrix as ${\left[0\bar{1}1\right]}_{\text{TiC}}//{\left[\bar{1}12\right]}_{\gamma }$, indicating that the TiC precipitates from the alloy matrix. A simplified two-factor analysis of variance (ANOVA) of the interfacial reaction layer thickness data reveals that within the temperature range slightly above the melting point of the superalloy, the melting time is the primary factor that significantly affects the thickness of the interfacial reaction layer.