The effect of expanded graphite with sodium metasilicate as lubricant at high temperature

Lubrication is vital in enabling the key machinery contact components to operate durably and reliably at extremely high temperatures for space aviation and metal forming. In this work, the expanded graphite in sodium metasilicate solution as high temperature lubricant was evaluated using a ball-on-disc tribometer. The results suggest that the use of this mixture can remarkably reduce the friction and wear of steel counterparts by up to 85% and 60% at 850 degrees C, respectively, compared with unlubricated condition. These improvements result from the formed tribo-layer containing amorphous carbon and sodium carbonate melt, as well as the two different ordered crystal layers on the rubbing interface induced by high temperature, pressure and shear. The expanded graphite in sodium metasilicate solution studied here for the first time will extend its application for high temperature lubrication due to its excellent performance. (C) 2019 Elsevier Ltd. All rights reserved.