Transition of Microscale Tribological Regimes from Severe Plastic Deformation to Lubricant Precipitation with Rising Temperatures.

Although high-temperature (HT) solid-lubricating coatings have been developed to control the friction and wear of tribological interfaces operating under HT conditions, the wear and lubrication mechanisms are not well understood. Here, we proposed silicon-assisted sample heating and platinum deposition colloidal probe reinforcement methods, thereby achieving microscale tribological tests between Ni-based alloy microspheres and HT solid-lubricating coatings up to 710 °C in ultrahigh-vacuum atomic force microscopy. The friction evolutions at 465 and 710 °C were significantly different, attributed to a transition of tribological regimes from wear characterized with oxide film removal and severe plastic deformation to lubrication precipitation and enrichment at the sliding interface. Further, we investigated the conditions of oxide film removal and fluoride precipitation, as well as their effects on friction. The tribological system construction scheme in this work can be utilized to study microscale friction, wear, and lubrication issues between various materials at extreme HT.