Effect of Surface Topography on ZDDP Tribofilm Formation During Running-in Stage Subject to Boundary Lubrication

Experimental investigations have been conducted to study the effects of surface topography on ZDDP (zinc dialkyldithiophosphate) chemical tribofilm formation during running-in stage under boundary lubrication conditions. The scope of presented work has been limited and focused on reciprocating motion under boundary lubrication to simulate the upper and lower dead centre of piston ring movement, which is prone to adhesive wear failure. Several surface topographies were designed and fabricated to measure, compare coefficient of friction and ZDDP critical time of tribofilm formation. Rubbing surfaces and their corresponding tribofilms were characterized by SEM and EDX. Mechanisms of surface topography effects on the critical time of ZDDP tribofilm formation is presented and discussed. Results from this study have demonstrated that the surface topography has a significant influence on the critical time of ZDDP tribofilm formation during running-in process and corresponding wear performance. This research provides an opportunity to augment anti-wear performance under boundary lubrication condition. This can be achieved by optimizing surface morphology design to influence the formation of anti-wear tribofilms during the running-in stage. In turn, this will result in interacting component’s service life enhancement and significant cost savings from mitigated wear.