Turning of high entropy alloy into high entropy carbides by modifying carbon content during reactive sintering

Abstract

High entropy alloys containing equimolar multi-element composition enhance physical properties over traditional alloys. The concept was applied also for high entropy ceramics, but the solid-state reaction is necessary. In this work, high entropy alloy VNbMoTaW reacted with carbon to form high entropy carbide. Direct reaction in Spark Plasma Sintering (SPS) conditions leads to high entropy or entropy aided carbides depending on the amount of present carbon. The entropy aided carbide formed at low carbon concentrations below 0.8 of equimolar content contained all metallic elements, but two separated phases were identified: Nb, Ta or W, Mo rich. The microstructure of the entropy aided carbides is lamellar and refined compared to high entropy carbide (V0.2Nb0.2Mo0.2Ta0.2W0.2)C0.8. The presence of entropy aided carbide decreased the Vickers hardness from 23 GPa to 19 GPa, however, the unique microstructure might enhance other physical properties.