Influence of carbon-based solid lubricant on fretting wear response for alumina-based ceramics versus cobalt superalloy contact

In aircraft motors, blade-disk contacts are subject to fretting wear that implies surface degradation due to relative small-amplitude oscillatory movements. The present work investigates one selected alumina-based ceramics as a protective coating for the composite subjected to fretting wear against the HS25® disk. This contact is compared to its equivalent with a thin layer of carbon-based solid lubricant applied on the same ceramic coating between 100 and 700 °C. Under unlubricated conditions, wear is abrasive, whereas lubricated interfaces show the formation of 40 μm thick adhesive glaze layer. With this glaze layer, wear volume is reduced by at least a factor of 10 compared to a naked interface. This third body becomes unstable under 500 °C, even if an intermediate tribofilm is created to relatively limit wear. Chemical analyses show that the third body is composed of debris from both counterparts that are probably aggregated together by the lubricant's binding agent. Besides, wear volume is strongly related to a sintering process whose progress depends on the debris' ability to be grinded, mixed together and compacted.