Abstract

In recent years, with the constant maturity of metal 3D printing technology, the additive manufacturing of IN718, nickel-base superalloy, has attracted very strong attention in the aerospace field. Additive manufacturing, especially the laser powder bed fusion (LPBF) of IN718, has several advantages over the conventionally manufactured IN718 (cast and wrought) because additive manufacturing is more time-saving with lower cost and a lower buy-to-fly ratio. However, 3D printed IN718 components still exhibit defects due to thermal gradient during printing. This thermal gradient affects the mechanical properties of printed parts to a large extent. Performing some special post-processing heat treatment could minimize this problem. However, only heat treatments designed for conventionally manufactured IN718 are currently applied to the printed material. Therefore, establishing and optimizing a thermodynamic database representing the 3D printed IN718 alloy is essential to effectively guide the heat treatment and obtain information on phase formation and transformation.
In this work, firstly, a customized database was constructed by optimizing the phases presented in IN718, starting with the lower-order binary systems, followed by extrapolation to higher-order systems. The customized database is used to calculate the thermodynamic properties and predict phase formation in the IN718 alloy. Furthermore, to validate this database, experimental investigations, including differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), are done to determine the temperature of different phase transitions and the microstructure of the printed IN718 alloy. The modelling results obtained in the current work are more consistent with the current experimental results and the experimental results from the literature than the results obtained using two commercial databases.