Effect of surface chemical etching on the lubricated reciprocating wear of honed Al-Si alloy

To improve the wear resistance of the honed Al-Si alloy cylinder liner, the chemical etching was applied on the surface of the Al-Si alloy samples. The effect of the etching time on the wear behaviors of the etched surface was investigated using an in-house designed reciprocating wear machine with oil lubrication. Meanwhile, the tribological properties were related to the changes in the surface morphology of the Al-Si alloy samples before and after the wear tests to analyze the associated underlying wear mechanisms. Results show that 5% NaOH solution is an effective chemical agent to etch the surface of Al-Si alloy samples. The 2min etched Al-Si alloy samples exhibits low friction coefficient and small weight loss, indicating a good wear behavior of the properly etched surface. The insufficiently etched surface was found when the etching time was less than 2min. Rare silicon particles are exposed due to the little removal of the aluminum on the surface, such that aluminum will be in direct contact with the piston ring during friction, causing adhesive wear. In contrast, overetching leads to the even more seriously worn out surface as observed in the samples etched for more than 3min. The silicon particles tends to debond from the matrix with the increase of etching depth, then serve as the abrasive grains in the friction, resulting in the considerable increase of the friction coefficient and weight loss.