SURFACE MECHANICAL-PROPERTIES OF ALUMINA MATRIX NANOCOMPOSITES

We have examined the surface properties of alumina/silicon carbide nan ocomposites containing 5 vol.% SiC particles of 4 different size distr ibutions with mean particle size from 12 to 115 nm. In all cases the n anocomposites were more resistant to a severe erosive wear environment than monolithic alumina of similar grain size. The resistance to wear increases with decreasing SiC particle size. We have measured the dam age introduced to these ceramics during lapping and polishing by three techniques: counting surface flaws visible to an optical microscope, measuring surface elastic constants using an acoustic microscope, and determining surface crack sizes using a Hertzian indentation technique . Surface observation and Hertzian indentation show the nanocomposites to have both a smaller mean defect size and fewer large defects than similar grain size alumina. This is supported by our acoustic microsco pe results which show a lower lever of surface damage in the nanocompo sites after a given lapping or polishing process. (C) 1997 Acta Metall urgica Inc.