Continuous formation and removal mechanism of tribolayer on silicon carbide under water lubricated conditions: A ReaxFF reactive molecular dynamics study

To reveal the mechanism why low friction state of SiC/water system is maintained through the repeated formation and removal processes of tribolayer, we performed molecular dynamics sliding simulations. Our results revealed that tribochemical reactions of amorphous SiC (a-SiC) with water form tribolayer consisting of silica-based layer and carbon layer, and constant supply of silica-based layer by continuous tribochemical reactions is required to maintain hydrodynamic lubrication, whereas the carbon layer prevents adhesion. However, if carbon layer covers the entire interface, it would prevent hydrodynamic lubrication. We proposed here that uneven distribution of chemical bonds in the a-SiC substrate is important for maintaining hydrodynamic lubrication and low friction, because such distribution continuously forms the silica-based layer and carbon layer at the same time.