Abstract
In this study, AlCoCrFeMnNiTi based refractory-free high entropy superalloys (HESA) were prepared by powder injection moulding (PIM) for aviation applications. Aging was done in order to enhance mechanical properties. Ni-based superalloys are expensive and heavy due to expensive alloying elements with high density. Strength, oxidation and creep resistance of the high entropy alloys are low for engine applications. HESA would be cheaper and lighter than superalloys and would have higher strength, creep resistance and oxidation resistance than high entropy alloys. In order to obtain solid solution, mixing entropy and mixing enthalpy values were adjusted. Valance electron concentrations was adjusted in order to obtain face centered cubic structure. There is grain-coarseing and segregation in HESA produced by vacuum arc melting. HESA with finer grain sizes and low segregation could be produced by using mechanical alloying (MA)-PIM. Alloy powders were prepared by MA. Alloys with high solid solubility, complex shaped, fine grained superalloy specimens were produced by MA-PIM. Polymer binder consisted polyethylene, paraffin, and stearic acid. Feedstock consisted of 45% of binder and 55% of alloy powder. PIM was carried out at 185°C. After the PIM, binder was removed by chemical debinding and thermal debinding. Sintering was carried out at 1,250°C. Elevated temperature properties of the HESA was enhanced by intermetallic precipitates which were obtained by alloying and heat treatments. Corrosion properties, high temperature oxidation properties, thermal properties, mechanical properties were determined.