Development and characterization of high entropy superalloy by powder metallurgy

Abstract

Designing the precipitation strengthened alloy for high temperature application using high entropy alloy (HEA) concept led to the development of high entropy superalloys (HESAs) and microstructure similar to Ni based superalloys. The Ni content increased beyond 35 at. % to improve the fraction of ordered γʹ precipitate. Limiting the use of Ni between 40 to 50 at. % and the use of lightweight elements (compared to Ni and other refractory elements) results in cost and density reduction. This approach can present a cost-effective alternative for Ni-based superalloys. The study concentrates on the development of HESAs and investigation of effect of Ni content and process parameters by mechanical alloying (MA) followed by spark plasma sintering (SPS). The entropy effect stabilizes the matrix for further addition of elements. The mechanical alloying of constituent elements Ni, Co, Cr, Fe, Al, and Ti shows the formation of FCC solid solution from XRD patterns. The particle size consists of small fragments and large layered flat particles. The crystallite size and lattice strains are in agreement with the increase in milling time.