Liquid metal as novel lubricant in a wide temperature range from −10 to 800 °C

Microscopic contacts commonly exist on the surfaces when applying loads between the frictional pairs. Under harsh environments, such as extremely high temperature and load, sliding devices will encounter devastating wear loss, eventually leading to the materials failure. Traditional liquid lubricants could only work in a narrow temperature range due to their poor thermal stabilities. A kind of room temperature liquid metal (LM), Ga68.5In21.5Sn10, could be used in an ultra-wide range of temperatures. In this work, the tribological properties of LM has been investigated for Si3N4/steel contact at three temperatures (−10, 20 and 800 °C), which was the first research in such wide range of temperature for liquid lubricants. Results indicate that LM exhibited excellent tribological performances. Surface analyses suggest that the predominant properties at −10 and 20 °C were ascribed to the tribofilms composed of metal oxides, such as Fe2O3, Ga2O3, In2O3, and SnO2. The main product intermetallic compound FeGa3 contributed to forming the boundary lubrication film at 800 °C.