Modeling of microfracture-induced wear and wear transition in sliding of polycrystalline alumina ceramics

Abstract

An equation has been proposed to describe sliding wear caused by microfracture in polycrystalline alumina ceramics. The wear equation has been simplified, and grain size dependence for dry sliding wear data by Wu et al. has been shown to agree with this equation. For lubricated sliding in a ball-on-flat configuration, modification of the equation is necessary. A concept of equivalent “real” contact area for lubricated contacts is introduced to account for the different stresses at the interface as the contact conditions change before and after a wear transition. Microfracture occurs when superimposed stress exceeds a critical threshold. The decrease in surface conformity due to surface roughening and trapping of pulled-out grains can significantly increase the magnitude of the contact stresses, which leads to high wear rates. We incorporate the contact geometry effects into the microfracture wear equation. This new wear equation provides a self-consistent data fitting of load dependent wear transition in lubricated sliding of alumina observed by Cho et al. The implications of this model are discussed.