Design, production and characterization of novel high entropy superalloys for aviation applications

High Entropy Alloys (HEA) are obtained by mixing at least five elements with equimolar ratio unlike conventional alloys and they are multi component alloy systems exhibiting potential benefical properties for engineering designs. Refractory HEAs (RHEA) become prominent among high temperature materials for production of low emission and efficient aero engines and their components as an alternative to superalloys. In this study, literature survey were firstly carried out and production parameters, mechanical and metallurgical evaluation results of the RHEAs were gathered in database. After database analysis, Mo, Nb, Ti, W, V, and Zr elements were choosen for alloy design activities. After thermodynamic and empirical calculations two RHEAs namely NbTiWVZr and MoNbTiWV, and a complex concentrated alloy (CCA) Nb22,5Ti22,5W10V22,5Zr22,5 were determined to be manufactured in experiments and the effect of different heat treatments on the alloy properties were also investigated. Body centered cubic microstructure were detected in as-cast samples, but after heat treatment process some complex compounds were found in heat treated samples by XRD analysis. Typical dentritic microstructure was seen in all alloys and Zr segregation was identified in heat treated samples. It was observed that the NbTiWVZr ve Nb22,5Ti22,5W10V22,5Zr22,5 alloys exhibited better yield strenght (1000-1100 MPa) up to 600°C compared to superalloys. Moreover the strenght of the alloys were much lower than CM247LC and CMSX-4 nickel based superalloys at 800°C, and oxidation rate was too high at this temperature.