Wear behavior of (Mo-Nb-Ta-V-W)C high-entropy carbide

Wear characteristics of an (Mo-Nb-Ta-V-W)C high-entropy carbide were investigated using ball-on-flat technique. The experimental material with a high relative density of 99.0%, single phase, average grain diameter of 10.7 mu m, and nanohardness of grains 28.6 GPa was prepared by ball-milling and two-step field-assisted sintering. The tribological test was realized during dry sliding in air with the SiC ball as tribological partner at applied loads 5, 25, and 50 N. The microstructure, deformation, and damage characteristics were studied using scanning electron microscopy and confocal electron microscopy. The friction coefficient values during the test with 5 and 25 N were very similar and stable, with a value of approximately .4, whereas during the test with 50 N, it decreased from the value of .48-.42. The specific wear rate increased with increasing load from 3.71 x 10(-7) mm(3)/N m at 5 N to 2.59 x 10(-6) mm(3)/N m at 50 N. The dominant wear mechanism was mechanical wear with intensive grains pullout, fracture, and powder formation, without visible tribochemical reactions and tribo-layer formation. The wear rate decreased due to the created rolling contacts among the tribopartners thanks to the hard and spherical nanopowders present.