Properties of alumina matrix composites reinforced with SiC whisker and carbon nanotubes

The microstructure and mechanical properties of Al2O3 containing 0, 0.1, 0.5 or 1.0 wt% multi-walled carbon nanotubes (MWCNTs) were examined with/without the addition of 25 wt% SiC whisker (SiCw) for cutting tool applications. Eight types of composites with different compositions and a density >99% could be manufactured by optimizing the hot-pressing conditions. The addition of MWCNTs had negligible effects on the mechanical properties of the resulting Al2O3-MWCNTs composites due to agglomeration and the retardation of sintering. On the other hand, the incorporation of SiCw to Al2O3 enhanced the mechanical properties significantly, which enabled the cutting of Inconel 718 super-alloy. Both K1C and the flexural strength of Al2O3-SiCw-MWCNTs were improved by >60% compared to those of the Al2O3-MWCNTs composites. Moreover, it was proposed that the MWCNTs in the Al2O3-SiCw reduced the wear of the cutting tool by lubrication when the high composite density was ensured.