Feasibility of using electrostatic monitoring for oil lubricated ceramic to steel sliding contacts

Previous work has shown that electrostatic charge signals can be used to detect the onset of wear in lubricated tribocontacts. Preliminary investigations have shown the viability of this system when tested on a laboratory-based pin-on-disc rig, a reciprocating laboratory wear rig [1-3] and in an FZG gear scuffing rig [4,5]. These preliminary experiments have indicated several charging mechanisms could be involved within highly stressed lubricated contacts, namely tribocharging, exo-emissions, surface charge variations and debris generation [6,7]. This paper details further studies looking at the levels of charge generated by lubricated hybrid (silicon nitride sliding on bearing steel) contacts. Correlation between the charge levels generated within hybrid contacts under fully lubricated conditions and the resulting wear rates is investigated. Results from the Pin-on-Disc tests for silicon nitride against various bearing steels contacts, lubricated by Mobil Jet II, are presented and compared to steel on steel contact performance. The materials are ranked based on their performance during the wear tests. The wear mechanisms of hybrid contacts are discussed based on the on-line multi-sensor monitoring results and the post-test wear surface observation by 3-D laser profilometry measurements.