Uncovering the hardening mechanism of multi-component carbide ceramics based on the coupling effect of covalent bond enhancement and lattice distortion

The hardening mechanism of multi-component carbide ceramic has been investigated in detail through a combination of experiments, first-principles calculations, and ab initio molecular dynamics (AIMD). Eight dense carbide ceramics were prepared by spark plasma sintering. Compulsorily, all the multi-component carbide samples have similar carbon content, grain size, and uniform compositional distribution by optimizing the sintering process and adjusting the initial raw materials. Hence the interference of other factors on the hardness of multi-component carbide ceramics is minimized. The effects of changes in the elemental species on the lattice distortion, bond strength, bonding properties, and electronic structure of multi-component carbide ceramics were thoroughly analyzed. These results show that the hardening of multi-component carbide ceramic can be attributed to the coupling of solid solution strengthening caused by lattice distortion and covalent bond strengthening. Besides, the “host lattice” of multi-component carbide ceramics is defined based on the concept of supporting lattice. The present work is of great significance for a deeper understanding of the hardening mechanism of multi-component carbide ceramics and the design of superhard multi-component carbides.