Effect of cBN content and additives on sliding and surface fatigue wear of spark plasma sintered Al2O3-cBN composites

Cutting tools containing superhard phases enable efficient dry machining resulting in reduced human and environmental risks. In the current work, spark plasma sintered composites containing up to 20 vol% cBN in Al2O3-based matrix with an addition of 15 vol% ZrO2 or 10 vol% TiN have been tested under dry sliding (with multiple restarting to better simulate real working conditions) and surface fatigue (with in-situ monitoring of acceleration indicating evolution of the test area) conditions. Dry sliding was carried under two configurations of "ball above sample" and "ball below sample" to study the effect of wear debris entrapment in a wear scar. The importance of a longer test duration (40 000 s, i.e. more than 10 h) during sliding of extensively polished ceramic materials with "mild" wear regime is emphasized. The reason for long running-in process with characteristic threshold is explained. The worn surfaces were studied using scanning electron microscopy, energy dispersive spectroscopy and 3D profilometry to understand the responsible wear mechanisms. The wear rates are reported in comparison to pure Al2O3 ceramic. The surface fatigue test was able to identify the material (Al2O3-20cBN15ZrO2) that according to previous research by authors exhibits lowest wear in dry cutting conditions.