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The aim of this study is to present the fretting tribological behaviour of stainless steel/graphite and stainless steel/carbon impregnated with silver couples in a dry shaft/bearing contact with thrust. Two contact geometries are investigated: cylinder-in-cylinder and plan/plan. Both of them are subjected to low-amplitude (20 to 250 μm) oscillatory movements, with temperature reaching 270 °C. The morphological and profile analyses performed on rubbing surfaces showed various aspects of wear: prints, craters, scratches and transfer. This permits each degradation to be linked its location, development and origin. In the carbon impregnated with silver bearing, we have observed the migration of the metal from the bulk of material to the contact area leading to the silver/silver contact with a high friction coefficient. This migration observed at the contact temperature around 270 °C which is lower than the silver melting temperature is apparently due to various mechanical aspects like the periodic loading. Finally, we present the experimental results of the tribological behaviour and we discuss the physical phenomena which induce a loss of tribological performance of these contacts. |
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