Effectiveness of an externally added solid lubricant on the sliding wear response of a zinc?aluminium alloy, its composite and cast iron

Abstract

The role played by an externally added solid lubricant like graphite towards controlling the sliding wear behaviour of a zinc-based alloy has been examined in this study. The influence of dispersing hard silicon carbide particles in the alloy was also investigated by testing the composite in identical test conditions. The wear performance of the zinc-based alloy and its composite was compared with that of a gray cast iron. Wear tests were performed in oil lubricated environment. Composition of the lubricant was changed by adding various quantities of graphite (particles) to the oil. The study suggests that the wear response (in terms of wear rate, frictional heating and friction coefficient) of the samples improved in the presence of suspended graphite particles in the oil lubricant. However, this improvement was noticed up to a critical content of graphite particles only and the trend reversed at still higher graphite contents. The zinc-based (matrix) alloy revealed highest wear rate. Dispersoid silicon carbide particles showed a significant improvement in the wear performance of the matrix alloy. The cast iron performed in between the matrix alloy and composite. The frictional heating and friction coefficient were the highest for the composite while the cast iron and the matrix alloy showed a mixed response. Examinations of wear surfaces, subsurface regions and debris particles helped to substantiate the observed wear response of the samples.