High temperature lubrication and mechanism of sodium carbonate by interface tailoring
© 2020 This paper reports the potential application of sodium carbonate as an environmentally friendly and inexpensive high-temperature lubricant for hot rolling of steel. This process has been simulated by ball-on-disc sliding tests at temperatures of 645 to 920 °C. Compared with unlubricated conditions, reductions in friction and wear of 68% and 98% respectively were achieved during sliding at 730 °C with a contact pressure of 0.84 GPa. The significant improvement of the tribological properties was attributed to the tribo-induced melting of sodium carbonate at the sliding interface, which acted as a liquid lubrication layer and formed a shear-induced nano-gradient tribofilm structure. The sodium carbonate melt was readily sheared and produced low friction and negligible wear. The nano-gradient tribofilm structure which formed under sliding inhibits cracking and spalling, resulted in a low wear due to strain delocalization. These findings highlight the potential application of a low cost, low hazard sodium carbonate as a high temperature lubricant for hot metal forming. It also provides insights into the tribological mechanisms of high temperature lubrication.