Exploring the Impact of Configurational Entropy on the Design and Development of CoNi-Based Superalloys for Sustainable Applications

TL;DR

This study investigates how configurational entropy influences the microstructure and high-temperature performance of CoNi-based superalloys, aiming to guide sustainable alloy design for advanced manufacturing.

Contribution

It demonstrates that increasing configurational entropy through alloying enhances the { extgamma}' solvus temperature and mechanical properties of CoNi-based superalloys.

Findings

Higher configurational entropy raises the { extgamma}' solvus temperature.

Alloying elements significantly affect microstructure and mechanical strength.

Designed alloys show potential for sustainable high-temperature applications.

Abstract

A comprehensive literature review on recently rediscovered Co- and/or CoNi-based superalloys, strengthened by the {\gamma}' phase, revealed a relationship between the configurational entropy of the system and the {\gamma}' solvus temperature. This study was conducted on a high Cr CoNi-based superalloy system with high configurational entropy to test our hypothesis based on the sustainable metallurgy framework. Thermodynamic calculations were performed to design the chemical compositions, followed by vacuum casting and heat treatments to produce the desired alloys. The microstructures were characterized using a scanning electron microscope, electron backscattered diffraction, transmission electron microscope, and differential thermal analysis. Microhardness and nanoindentation tests were employed to measure the mechanical properties. The results showed that both the configurational entropy and the type of alloying elements determine the final high-temperature performance of the alloys. We found that to enhance the higher {\gamma}' solvus temperature, the configurational entropy should be increased by adding {\gamma}' stabilizing elements. The microstructural and mechanical characteristics of the designed alloys before and after heat treatments are discussed in detail. The outcome of this study is beneficial for developing cobalt-based high-entropy superalloys with appropriate processing windows and freezing ranges for advanced sustainable manufacturing purposes, such as using powder bed fusion technologies.