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Application of computational thermodynamics to the design of a Co-Ni-based ?’-strengthened superalloy

Published

Author(s)

Eric Lass

Abstract

A currently available commercial Calphad thermodynamic database was utilized to investigate its applicability to alloy design in the new class of Co-Ni-based ’-strengthened high temperature alloys. A simple primary design criterion was chosen: maximize the ’ solvus temperature in the six-component Co-Ni-Al-Ti-W-Ta system while ensuring no formation of secondary, potentially deleterious phases. Secondary design considerations included the effects of alloying elements on equilibrium ’ volume fraction and on solidus and liquidus temperatures. The identified composition, Co-30Ni-9Al-3Ti-7W-2Ta, representing a conservative estimate of the maximum allowable concentrations of alloying additions Al, Ti, W, and Ta, was subsequently produced and characterized. The experimentally measured g’ solvus temperature of the new alloy was 1218±3 °C, nearly 90 °C above any previously reported two-phase g-g’ Co-(Ni)-based alloy. No secondary phases were observed in the alloy after annealing at temperatures between 900 °C and 1200 °C. Additional alloy compositions with experimentally measured g’ solvus temperatures in excess of 1260 °C were also identified employing the same basic approach. The efficacy of currently available thermodynamic databases in their application to Co-based g’-strengthened superalloy development is discussed, including expanding design efforts to include additional alloying elements, as well as specific areas for improvement of future databases.
Citation
Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science
Volume
48A
Issue
5

Keywords

Co-based superalloy, Calphad thermodynamics, ICME, computational materials design

Citation

Lass, E. (2017), Application of computational thermodynamics to the design of a Co-Ni-based ?’-strengthened superalloy, Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, [online], https://doi.org/10.1007/s11661-017-4040-y (Accessed April 24, 2024)
Created March 13, 2017, Updated November 10, 2018