Empirical and computational based phase predictions of as-cast and thermal spray high entropy alloys

High entropy alloy (HEA) studies rely on the concept that a high configurational entropy may favour a single-phase solid solution (SSS) over intermetallic phases. However, a random selection of elements rarely leads to SSS HEAs. Several authors have implemented strategies such as empirical models and the CALPHAD method to efficiently design HEAs. Most implemented strategies have been tested mainly on as-cast alloys, but their performance in thermal spray HEA coatings is still lacking. In this work, empirical models, and the CALPHAD method, in equilibrium and non-equilibrium, are assessed for phase prediction in HEAs in the as-cast condition and thermal spray coatings. Even though the cooling rates for each processing route deeply vary, the processes show similar phase formation as indicated by a literature review. The CALPHAD equilibrium calculation successfully predicted all the phases in the alloys at specified temperatures. Furthermore, the CALPHAD-based non-equilibrium simulations correctly predict the major phase for thermal spray HEAs. The empirical models also show good prediction capability, but the sigma phase is problematic for the parameter-based models. Therefore, the CALPHAD can be used to efficiently design and develop single-phase HEAs in a higher cooling rate setting, such as thermal spray.