Ductile-brittle transitions and wear maps for the erosion and abrasion of brittle materials

Transitions in wear rate and mechanism are a common feature of the erosive and abrasive wear of ceramics and other brittle materials. In such cases, a relatively small change in applied conditions, such as impact velocity or angle in the case of erosion, or of applied load in abrasion, results in a significant change in the mechanism of wear. Such a transition often represents a change in the extent or nature of fracture, leading to a concomitant change in the rate of material removal. Transitions in wear mechanism can also be associated with a change in the shape, hardness or size of the abrasive particles. In this paper, theoretical models for the onset of fracture and plastic flow in a material being eroded or abraded, and also in the abrasive or erosive particles, are used to define regimes over which a single wear mechanism will be dominant. A method is outlined by which these regimes can be illustrated graphically on plots of particle size against impact velocity or applied load, and it is suggested that in this way `maps' showing wear rates and mechanisms might be developed for the abrasive and erosive wear of brittle materials.