Effect of an iron-enriched aluminium surface fabricated via fine particle peening on tribological behaviour under oil lubrication

Commercial lubricants usually contain various additives that maintain the performance of the oils under multiple situations. Zinc dialkyldithiophosphate, commonly referred to as ZnDTP, is a widely applied antiwear additive that suppresses wear under severe lubricant conditions. Improved wear resistance derived from ZnDTP results from the phosphate-based tribofilm formed due to tribochemical reaction between ZnDTP and the material subjected to the wear. Although this phenomenon has been reported on steel surfaces, the effectiveness of ZnDTP on the aluminum surfaces was considered to be insufficient. In this study, the authors attempted to enhance the antiwear performance of ZnDTP on Al sliding components by modifying the Al surface with fine particle peening (FPP) in advance. By conducting FPP using steel particles, iron elements that were to react with ZnDTP were transferred and then enriched the Al surface. Results of tribological tests demonstrated that Fe elements introduced through FPP likely act as an adsorption site of ZnDTP and contribute to iron phosphate formation. The modified surface enriched with Fe transfer showed reduced wear compared to the unpeened surface when the ZnDTP-derived tribofilm successfully functioned.