High Entropy Carbide - Ni Based Cermets Prepared By In-Situ Carbothermal Reduction Of Transition Metal Oxides

Abstract

Fully dense high entropy carbide (Nb0.2Ta0.2V0.2Ti0.2W0.2)C - 10.64 wt.% Ni-based cermets were prepared by in-situ carbothermal reduction of mixtures of transition metal oxides from Group IV, V and VIB by a one-step reactive sintering technique. The molar ratio of metal oxides and graphite in the starting powder mixtures was varied and the evolution of the microstructure, grain size and morphology of the HEC phase was studied in detail. The in-situ carbothermal reduction of oxides resulted in a high entropy carbide phase with a homogeneous backscattered electron atomic number contrast with an extremely faint core-rim structure. This study demonstrates a facile and cost-effective alternative synthesis approach to prepare chemically complex high entropy carbide based cermets in a one-step pressureless sintering cycle. The two-phase HEC-Ni cermets exhibits an excellent hardness around 16.5 GPa and an acceptable fracture toughness around 7.5 MPa.m1/2.