Nanocomposites and nanomaterials

Nanostructured high-entropy alloy – alternative binder phase to Co in cemented carbides
Nakonechnyi S.O., Yurkova  A.I., Minitskiy A.V., Loboda P.I. 
High-Temperature Materials and Powder MetallurgyDepartment, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Prospect Peremohy, 37, Kyiv-03056, Ukraine. 
E-mail: sergeynuts@gmail.com 

Co is the most widely used metal binder in cemented carbides due its excellent wetting, adhesion and adequate mechanical properties. However for the developments in the field of hardmetal, finding alternative materials for substituting Co as the binder phase is necessary due to such reasons: the scarcity of Co makes it a high-priced product; the low corrosion and wear resistance of WC/Co cannot meet the increasing demand on performance under severe working conditions; as being classified genotoxic and carcinogenic, Co dust released during production process is largely responsible for occupational diseases of plant maintenance personnel [1]. Recent researches claimed that high-entropy alloys (HEAs) can be a promising binder for WC cermets with enhanced properties due to inhibiting WC coarsening [2,3].
A nanoсrystalline NiFeCrWMo HEA, synthesized by mechanical alloying, was used as the binder phase for substituting Co to fabricate WC–HEA composites by sintering with electron–beam source. The microstructure and mechanical properties of the sintered composites were studied with X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy (EDS) and microindentation technique. Compared with cobalt binder, the nanoсrystalline NiFeCrWMo HEA binder has an advantage on the inhibition of WC grain growth due to the sluggish diffusion effect, and the average WC grain size decreases. It has been shown that nanoсrystalline NiFeCrWMo HEA can be used as a binder for the ultrafine-grained WC-based cemented carbide with high mechanical characteristics. The WC–HEA-cemented carbide has better performances than the traditional WC–Co-cemented carbide.

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