Under fluid film lubrication, the particulate contaminants in the fluid cause three-body abrasive wear on critical surfaces. The wear not only depends on the hardness of the wearing surface (Hj), but also on the hardnesses of its opposing surface (Hb) and the involved abrasives (Ha). In this paper, the hardness effect, particularly the relationships among these three hardnesses, is studied, by exploring the interdependence between two hardness ratios: the ratio between two rubbing surfaces (Hb/Hj) and the ratio between the surface to be protected (usually the harder surface) and the abrasives (Hj/Ha). Three types of journal-bearing pairs (Hb/Hj = 0.75, 0.6, and 0.3) were tested, subjected to four abrasive particles (Hj/Ha ranges from 0.14 to 2.75). The wear linearly varies with the Hj/Ha value at each metal hardness ratio on log-log diagram. The empirical constants in the wear function are obtained. The critical hardness ratio and the wear coefficient are also analyzed.

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