Wear studies on Al-Si automotive alloy under dry, fresh and used engine oil sliding environments

A comparative study has been made on the wear behavior of eutectic Al-Si automotive alloy under a dry, fresh and used engine oil sliding environment. The wear tests have been conducted using a standard pin-on-disc apparatus. The results show that with silicon content, the wear loss decreases up to the eutectic composition, mainly for an increase in strength through Si-rich intermetallics. Therefore the lower wear rate along with the coefficient of friction is observed under dry sliding environment. Under the engine oil environment, the lubricating film controls the wear, so the results are the lowest wear rate and coefficient of friction. Used oil shows both wear rate and friction coefficient to some extent higher due to the presence of heavy and harmful chemical compounds. Wear test surfaces are examined by optical and SEM analysis and found that higher abrasive wear and plastic deformation on the worn surfaces are created in dry sliding condition as well as lower Si added alloy. On the worn surface under engine oil lubricating condition, smooth surface morphology is observed as form a lubrication film and thumbs down any direct contact on the moveable surfaces. Higher Si-added alloys contain superior fine intermetallics due to ageing, which is responsible for such smooth worn surfaces.