Three-body abrasion of a cast zinc–aluminium alloy: influence of Al 2O 3 dispersoid and abrasive medium

Abstract

Three-body abrasive wear characteristics of a cast zinc–aluminium alloy — 10 wt.% alumina particle composite have been analysed in the present investigation. Silicon carbide, sand and zircon particles were used as the abrasive media. In order to see the influence of alumina dispersoid particles on the abrasive wear behaviour, the similarly processed matrix alloy was also tested under identical conditions. The composite exhibited less wear rate than the matrix alloy irrespective of the test conditions. This was attributed to the wear resistance offered by the hard dispersoid phase, thereby protecting the softer matrix. Further, the SiC abrasive caused maximum wear rate while the specimens experienced the minimum when abraded against zircon particles; sand particles led to intermediate wear response. Wear rate of the samples decreased progressively with distance until a steady-state value was attained. Abrasion-induced work hardening was thought to be responsible for the decreasing wear rate with distance. Increased hardness of the (subsurface) regions as compared to that of the bulk also supported the view. Further, the rate of reduction in wear rate with distance was relatively more for the matrix alloy than the composite. This behaviour was more clearly visible and, at the same time, the extent of reduction in the wear rate with distance was maximum in the case of the SiC abrasive. Sand was observed to be more damaging than zircon despite its less hardness (than the latter). This could be owing to the sharp/angular shape of the sand abrasive in comparison to the round shaped zircon particles suggesting the predominant effect of the particle shape over the hardness of the abrasive. More severe loading conditions led to larger wear rates because of the greater depth of cut and more surface/subsurface damage. Observed wear response of the samples has been supplemented with the features of wear surfaces and subsurface regions. The latter also enabled an understanding of the operating wear mechanisms.