Alloy development for high temperature applications using the high entropy concept

Purpose and goal

- Increasing the configurational entropy of the Ni based high Fe-Cr superalloy into higher levels (1.5R; where R=8.314 J/K.mol), - Alloy production using casting under protective atmosphere, - Comparable mechanical stability at high temperatures (yield strength ~600-700 MPa from room temperature up to 750°C), - 5% improvement in specific strength at up to 750°C, - Preliminary study of the corrosion resistance of the alloy, - Preliminary production cost estimation compared to the reference superalloy.

Expected results and effects

- 13 alloys were cast and heat treated for optimization of the mechanical properties, - The configurational entropy of all modified alloys was higher than the base alloy. At least 5 alloys had configurational entropy of >1.5R (high entropy superalloy), - Obtained well-above 700 MPa Yield strength at room and elevated temperatures (up to 750°C), - Improved specific strength (strength over density) for between 12% to around 25% at room and elevated temperatures (up to 750°C), - Polarization corrosion testing was conducted on selected alloys, - Preliminary cost estimation was conducted.

Planned approach and implementation

The results were very satisfying for the project consortium and thus the idea will be further pursued by applying for continuation of the project for the next 3 years. The set criteria was >5% improvement in specific strength of the reference alloy (Ni-base superalloy) at room and elevated temperature (up to 750°C); for some alloys the specific strength was improved for more than 12% and around 25% at room and elevated temperature (up to 750°C). This was a promising result for a pre-study project, that showed a great potential for development of superalloys using the proposed concept.