The possibility of preparing a carbon-affected surface layer on the VNbTaMoW high entropy alloy (HEA) samples prepared using the SPS method was investigated. Four HEA samples were prepared under sintering temperatures of 1600, 1700, 1800 and 1900°C, along with two samples with 10 and 50 mol.% added carbon at 1900°C. All samples were characterized by scanning electron microscopy and evaluated through HV0.1 Vickers indentation at the surface layer and in its near proximity. A homogeneous carbide layer with thickness of 68 μm for 10 mol.% and 94 μm for 50 mol.% and increased hardness was observed at the surface of the HEA samples with added carbon. The added carbon can dramatically (300°C) change the densification temperature and diffusion, so that a continuous layer of high-entropy carbide was formed.
Ronschak et al. (Fri,) studied this question.