Relationship between wear rate, surface pullout and microstructure during abrasive wear of alumina and alumina/SiC nanocomposites

Aluminas and alumina/SiC composites with systematic variations in microstructure were subjected to an abrasive wear test. The wear rate, area fraction of pullout by brittle fracture on the worn surfaces and the pullout dimensions were measured. The wear properties were optimised by a high SiC content, intergranular SiC particles and small alumina grain size, but were insensitive to the SiC particle size. The wear rate depended only on the amount of pullout and this was explained in terms of a simple model for mixed plasticity and brittle fracture controlled wear. The primary cause of the property improvements in the nanocomposites was a reduction in size of the individual pullouts owing to the geometrical effect of the change in fracture mode induced by the SiC. A secondary effect with high SiC contents was a reduction in the pullout formation rate, which was explained in terms of the suppression of twinning and dislocation pileups by intragranular SiC particles.