On the Assessment and Rationalization of Heterogeneous Nucleation in Investment Cast Superalloys

Abstract Liquid metal/ceramic reactions are studied using an experimental arrangement reliant on differential scanning calorimetry. The undercooling needed to stimulate solidification is shown to depend strongly not only upon the chemistry of the ceramic but also the oxygen partial pressure. Ceramics based upon Y 2 O 3 and related compounds are emphasized. Characterization using electron microscopy of the interfacial reaction products is used to rationalize the reaction pathways. Our results shed light on the importance of the ceramic mould chemistry in promoting nucleation in these systems. This insight carries significant implications for practical applications, including (i) evaluating zircon sources and impurity effects; (ii) developing new mould formulation less prone to secondary grain nucleation in casting regions isolated from the advancing solidification front; and (iii) identification of grain refiners tailored for equiaxed solidification in superalloy castings.