SEM studies of material damage in alumina ceramics by angular single and multiple particle impacts

Abstract

The mechanisms of erosion in alumina ceramics have been investigated by scanning electron microscopy. The five commercial aluminas tested ranged from pure alumina to those containing different proportions of silicate glassy phase and zirconia. In single particle impact tests, the targets were impacted with 1035 μm angular SiC particles and in multiple particle tests with 151 μm SiC particles. The particles were always impacted under normal impact condition with an impingement velocity of 50 m s −1. It was found that whereas brittle failure was the basic erosion mechanism, the morphological features of eroded surfaces were quite different for different materials and depended upon their compositions. The presence of secondary phases improved the bonding between alumina grains and also increased toughness by absorbing part of the impact energy. Therefore, the erosion resistance was enhanced by the presence of secondary phases in alumina. The erosion rates of these materials are analyzed briefly in terms of the erosion mechanisms. It was found that the classical lateral cracks which are typical of brittle indentation fracture were not present on the eroded surfaces of aluminas.