Simultaneous hardening and toughening of a high‐entropy (NbTaZrW)C ceramic carbide using SiC particle

Abstract

AbstractPreviously, we have found that (NbTaZrW)C exhibits a good combination of nanohardness and toughness. In this report, we explore the possibility to further increase the overall properties of this high‐entropy carbide ceramic (HECC) through introducing SiC particle (SiCP). To this end, a series of (NbTaZrW)C–xSiC ceramic composites (x = 0/5/15/30/50 vol.%) were fabricated using spark plasma sintering (SPS), their microstructure and mechanical properties were characterized. Our results reveal a grain refinement effects of SiCP, an agglomeration of SiCP with (1 0 0) plane preferentially perpendicular to the SPS‐pressing direction and the formation of a transition region with various stoichiometric ratio of (NbTaZrW)xC1−x in the (NbTaZrW)C–SiCP vicinity. The elastic modulus, microhardness, and flexural strength of the HECCs show tight positive relations with the SiCP content and the beneficial effect of SiCP to the fracture toughness of (NbTaZrW)C becomes evident once the content of SiCP reaches 30 vol.%. Altogether, (NbTaZrW)C–50%SiC, which has a microhardness of 22 GPa, a flexural strength of 455 MPa, and an indentation fracture toughness of 6.54 MPa m1/2, presents the optimal combination of mechanical properties among the investigated composites. Mechanistically, the strengthening effect of SiCP introduction arises from the intrinsic high hardness of SiCP and the SiCP‐induced grain refinement and the toughening effect is mainly associated with crack bridging mechanism.