Computational Materials Assessment of High-Entropy Alloys and Entropic Stabilization of Nickel Superalloys for Turbine Applications

for industrial gas turbine (IGT) components with its computational alloy design tools and methods. QuesTek is uniquely qualified to find HEAs suitable for turbine components with extensive experience in superalloy design and the rapid development of materials databases. Phase I efforts will focus on finding HEA compositions that exhibit suitable phase equilibria for blade applications (e.g. FCC/L12 two phase equilibria). The search will begin with the construction and validation of a large CALPHAD (CALculation of PHAse Diagrams) thermodynamic database specifically designed for HEA compositions, as current CALPHAD databases are not sufficiently accurate at equiatomic compositions. Such CALPHAD databases are an essential component of any materials design effort and will offer quantitative predictions of phase stability. The HEA database will be based on experimental data as well as exhaustive high-throughput density functional theory (DFT) calculations of the mixing enthalpies for all combinatorially possible FCC, BCC, and L12 ternary solid solutions. DFT calculations will be performed at the University of Illinois at Urbana-Champaign National Center for Supercomputing Applications. Potential IGT HEA compositions will be identified using the HEA CALPHAD database and then experimentally verified by lab-scale alloy synthesis and characterization. Phase II will consist of applying QuesTeks Integrated Computational Materials Engineering (ICME) technologies on promising Phase I HEAs to optimize composition and processing for improved strength and stability. The feasibility and commercialization of HEA turbine blades will be examined on full-scale prototypes, with full heats of the alloys produced by a specialty alloys producer and blade components tested by an IGT OEM. Phase II will also include extension of the HEA CALPHAD database with additional elements and phases from high-throughput DFT calculations. This will enable the prediction of additional HEA compositions and exploration of the effect of minor alloying elements (e.g. C, N, and S) on HEA properties. Keywords: High entropy alloy (HEA), superalloy, turbine, CALPHAD, density functional theory (DFT), high-throughput, thermodynamics, stability, phase equilibria, Integrated Computational Materials Engineering (ICME) Summary for members of Congress: The efficiency of power generation from industrial gas turbines increases with higher combustion temperatures, but the poor high-temperature properties of current materials limits operating temperature and, thus, efficiency. This proposed work will enable the use of a newly discovered class of high-temperature materials, high entropy alloys, to allow for higher operating temperatures, and therefore dramatically improve power generation efficiency.