Nanoindentation and tribology of a (Hf-Ta-Zr-Nb-Ti)C high-entropy carbide

• A (Hf-Ta-Zr-Nb-Ti)C high-entropy carbide was produced by Spark Plasma Sintering. • The sample was a single-phase material with a high relative density of 99.4 %. • Mechanical wear with limited grain pull-out was observed during tribological tests. • Nanohardness of grains and grain boundary vicinities were 38.5 ± 0.5 GPa and 35.5 ± 1.0 GPa. • The increasing wear rate was correlated to the decreasing nanohardness of the worn surface. A (Hf-Ta-Zr-Nb-Ti)C high-entropy carbide was prepared by ball milling and a two-step Spark Plasma Sintering process, achieving a single-phase ceramic sample with a high relative density of 99.4 %. The wear resistance of the sample was measured by tribology and micro-scale mechanical behaviour was studied by nanoindentation on both the non-deformed and worn surfaces. Grains and the vicinity of grain boundaries exhibited high hardness values of 38.5 ± 0.5 GPa and 35.5 ± 1.0 GPa with similar Young’s moduli of 562 ± 11 GPa and 547 ± 16 GPa, respectively. The dominant wear mechanism was mechanical wear with limited grain pull-out and fracture, and with a localized and thin tribo-layer formation. The specific wear rate exhibited an increase with the increasing load from 2.53·10 −6 mm 3 /Nm at 5 N to 9.03·10 −6 mm 3 /Nm at 50 N. This was correlated to the decrease of nanohardness of the worn surfaces with increasing wear load, which is attributed to the increased number of microcracks.