Investigation of Soot Contaminated Lubricant Wear Mechanisms

A detailed investigation has been carried out to understand the effect that soot has on the properties of automotive lubricants. The paper builds on previous work, through testing of different lubricants and increased levels of soot contamination. The objective of the work was to increase the understanding of the wear mechanisms that occur within the contaminated contact zone, to help in future development of a predictive wear model to assist in the valve-train design process. Testing has been carried out using specimens operating under realistic engine conditions, using a reciprocating test-rig specifically designed for this application, where a steel disc is held in a heated bath of oil and a steel ball (replicating a valve train contact) is attached to a reciprocating arm. Detailed analysis of the test specimens has been carried out using scanning electron microscopy (SEM) to identify wear features relating to the proposed wear mechanisms.

The results have revealed how varying lubrication conditions changes the wear rate of engine components and determines the wear mechanism that dominates for specific situations. Testing has also shown the positive effects of advanced engine lubricants to reduce the amount of wear produced.