The development of fabrication technologies suitable for the production of fine, high-quality metallic powders of conventional and novel alloys is crucial to the development of the powder metallurgy route. The plasma-assisted centrifugal atomization process was developed by Metasphere Technology AB for the production of spherical cast tungsten carbide, and subsequently acquired by Höganäs AB. In the standard implementation of the process, feedstock material in the form of crushed powder is fed into a rotating crucible, melted by a transferred plasma arc, and atomized in the form of fine, spherical droplets. The capability to melt alloys and compounds with melting temperatures above 3,000 ᵒC, combined with the extremely rapid solidification of the ejected droplets, allows for the processing of metastable refractory alloys that cannot be obtained otherwise.

The main objectives of this work were to (1) better understand the role of the centrifugal atomization mechanism on the microstructure and the mechanical properties of the final powders, and (2) explore the capabilities of a pilot-scale plasma-assisted centrifugal atomization unit for the design and development of novel refractory alloys.

The local mechanical characterization of micron-sized powders of hard and brittle compounds is challenging. The use of three-dimensional topography images to measure the residual imprints of microindentation hardness tests has been proposed, ultimately enabling a reliable comparison among CTC powders fabricated by different methods. The microindentation hardness, the micro-pillar compressive strength, and the resistance to cyclic compressive loading of entire particles were extensively investigated in centrifugally-atomized CTC powders subjected to different heat treatments. 

Suitable processing routes for the fabrication of spherical powders of a compositionally complex Ti-V-Zr-Nb-Mo-Hf-Ta-W refractory high-entropy alloy have been developed. The preparation of pre-alloyed feedstock material by partial sintering followed by cryogenic crushing was considered. Subsequently, the simultaneous melting, alloying, and atomization of a blend of elemental powders was envisaged as an alternative to the time-consuming cryogenic crushing. The microstructure, the indentation hardness, the phase stability, the prospects of consolidation into bulk alloys, and the hydrogenation behavior of the alloys thus produced have been extensively investigated.