Application of Finite Element, Phase-field, and CALPHAD-based Methods to Additive Manufacturing of Ni-based Superalloys

摘要

Numerical simulations are used in this work to investigate aspects ofmicrostructure and microsegregation during rapid solidification of a Ni-basedsuperalloy in a laser powder bed fusion additive manufacturing process. Thermalmodeling by finite element analysis simulates the laser melt pool, with surfacetemperatures in agreement with in situ thermographic measurements on Inconel625. Geometric and thermal features of the simulated melt pools are extractedand used in subsequent mesoscale simulations. Solidification in the melt poolis simulated on two length scales. For the multicomponent alloy Inconel 625,microsegregation between dendrite arms is calculated using the Scheil-Gulliversolidification model and DICTRA software. Phase-field simulations, using Ni-Nbas a binary analogue to Inconel 625, produced microstructures with primarycellular/dendritic arm spacings in agreement with measured spacings inexperimentally observed microstructures and a lesser extent of microsegregationthan predicted by DICTRA simulations. The composition profiles are used tocompare thermodynamic driving forces for nucleation against experimentallyobserved precipitates identified by electron and X-ray diffraction analyses.Our analysis lists the precipitates that may form from FCC phase of enrichedinterdendritic compositions and compares these against experimentally observedphases from 1 h heat treatments at two temperatures: stress relief at 1143 K(870{\deg}C) or homogenization at 1423 K (1150{\deg}C).