Wear resistance of ZrB2 based ceramic composites

The wear resistance and tribological characteristics of spark plasma sintered ZrB2 + B4C, ZrB2 + SiC and ZrB2 + ZrC composites were investigated under dry sliding conditions at applied loads of 5 N and 50 N in air. The microstructure, deformation and damage characteristics were studied using scanning electron microscopy, confocal electron microscopy, a focused ion beam and atomic force microscopy. The friction coefficient values were very similar for all composites with values ranging from 0.63 to 0.72 and with the lowest value recorded for the ZrB2 + SiC composite at a 5 N applied load. The ZrB2 + ZrC composite was the most wear resistant, with wear rates at a 5 N load of 6.15 × 10−6 mm3/(N·m) and at a 50 N of 7.3 × 10−6 mm3/(N·m). None, or a very limited number of grain pull-outs and/or lateral fractures of grains were found during the wear tests. At the 5 N load, abrasive grooves connected with deformations and Hertzian crack formations were the main wear mechanisms in all systems, with limited crack formations in the ZrB2 + ZrC composite. Tribofilm formations connected with debris origin, oxidation and tribochemical reactions were dominant in all composites, with similar chemical compositions but different sizes and thicknesses at the 50 N load.