WEB Thermodynamic assessment and modelling of interactions in liquid Ni alloys/oxide systemsThursday (28.05.2020) 13:15 - 13:15 Poster Room Part of:
Information about the high temperature interactions between liquid alloys and refractory oxide materials is of practical importance in view of the investment casting processes of Ni based superalloys where the contact between molten alloys and the ceramic materials used as cores or shells occurs. Such information may be obtained experimentally from specific wetting tests followed by microstructural and microchemical characterization. At the same time, the thermodynamic modeling by CALPHAD of the reactivity in alloys-oxides systems allows to interpret the experimental findings, to foresee the interfacial reactivity and to perform extrapolations toward non-studied domains of temperature or composition.
These are the topics of the project INSURFCAST (INnovative SURFaces for superalloys CASTing processes).
In this work, a thermodynamic database has been developed and calculations have been done successfully in order to improve our understanding of the interactions in liquid Ni alloys/oxide systems. The phase diagrams obtained by CALPHAD were used to interpret the microstructures of metal/ceramic samples that were characterized after sessile-drop wetting tests of liquid NiHf and NiCrHf alloys in contact to Al2O3 at 1500 °C. Hf present in Ni-based liquid alloys strongly reacted with sapphire forming HfO2 layers and inclusions; on the other hand, Cr decreased the contact angles of Ni melts without forming interfacial layers during liquid/solid contact.
These results can have an importance that goes beyond the casting industry, as they can be helpful in the design of advanced metal-ceramic brazing processes, production of Metal Matrix-Composites as well as of coatings for high temperature applications.
This work is part of the Project INSURFCAST financed within the ERA-LEARN 2020 support action funded by EU-H2020, M-ERA.NET Joint Call 2016, Project 4164.