Microstructure and mechanical properties of ultra-hard spherical refractory high-entropy alloy powders fabricated by plasma spheroidization.

Spherical NbMoTaW high entropy alloy (HEA) powders with a uniform particle size distribution (d 50 = 35.0 μm) were successfully prepared by using a novel industrial method combining spray drying and plasma spheroidization. The HEA powder presents an overall single body-centered-cubic structure, yet with cellular elemental segregation mainly involving Nb and W at the nanometer-scale. The microhardness of the HEA powder is 10.09 GPa, about 50% higher than that of the HEA with the same composition in bulk state. This ultra-high microhardness endows the HEA powder with potential for application as superhard materials. In addition, the new preparation method of spherical refractory HEAs powder also would be of great significance for the future development of refractory HEAs (or complex refractory alloys) towards industrial applications, especially those based on 3D printing and thermal coatings. Image 1 • Pherical NbMoTaW high entropy alloy powders can be prepared by combining spray drying and plasma spheroidization. • The HEA prealloyed powders have smooth surface, dense interior and uniform chemical composition. • The microhardness of the HEA powder is 10.09 GPa, about 50% higher than that of the NbMoTaW HEA in bulk state. [ABSTRACT FROM AUTHOR]