INSITU WEAR EXPERIMENTS IN THE SCANNING AUGER SPECTROMETER

Sliding contact experiments have been conducted in the chamber of a high resolution Auger spectrometer. A pin-on-disk wear tester has been used. The Auger surface analysis capability has been used to characterize the disk surface before and after sliding in the chamber. The effect of surface chemistry on metal transfer during sliding contact and on boundary lubrication of zinc dialkyldithiophosphate (ZDDP) has been investigated. Hydrocarbon 'contamination' from fabrication of the steel disk caused an induction period during sliding in which friction was low and no transfer occurred. The contaminant was eventually worn off but transfer did not take place until the native oxide film was substantially removed also. The oxide film on the steel surface plays an essential role in the boundary lubrication process of ZDDP. A resulting iron sulfide film effectively inhibits adhesive wear. This film was found only in the wear tracks, showing that the contact stress conditions trigger the boundary film reactions.