Mechanical properties and deformation mechanisms of (Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C high‐entropy ceramics characterized by nanoindentation and scratch tests

Abstract

High-entropy carbides ceramics (HECCs) have attracted extensive attention for their broad application prospects in harsh environments, due to the excellent properties. In this work, the (Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C HECCs were prepared using spark plasma sintering at 1800 °C. Then, mechanical properties of HECCs were tested by nanoindentation and scratch tests under different loading conditions. Finally, the mechanical properties and deformation mechanisms were discussed in detail. The density of sintered HECCs reached 8.98 g/cm3, with a relative density of 95.63%. The HECCs demonstrated a single-phase with rocksalt microstructures. The elastic modulus of HECCs was almost a constant under different strain rates, while the hardness obviously increased as the indentation strain rate increasing. In addition, a simple fitted formula was developed to establish the function of hardness and strain rate. Under a relative low scratch load, the HECCs exhibited complete elastic–plastic deformation, and the material removal mechanism was plastic deformation. With increasing scratch load, the material removal mechanism of HECCs transformed into the combined action of plastic deformation and brittle fracture. Furthermore, the deformation mechanisms of HECCs were also influenced by the scratch velocity. At a higher scratch velocity, more local fractures at the micro-scale occurred, and the numbers and sizes of chips and debris also increased.