GRAIN-SIZE DEPENDENCE OF THE WEAR OF ALUMINA

A simple model is presented which, although empirical in nature, is consistent with experimental observations on the wear and abrasion rates of high purity alumina of tailored grain size. It is postulated that the critical wear process, reduced to its simplest terms, involves the nucleation and propagation of grain boundary microcracks. A microcrack is nucleated and travels at a characteristic velocity along a low energy grain face until a multi-boundary junction is encountered, when development of the crack is temporarily inhibited. The crack thus progresses with alternating periods of steady growth and delay, and ultimately causes the local loss of material through grain detachment. It is shown that this model leads to a wear rate grain-size dependence of the form seen for a variety of conditions such as erosion, sawing, grinding and sliding.