Synergistic lubrication effect of Al2O3 and MoS2 nanoparticles confined between iron surfaces: a molecular dynamics study

Nonequilibrium molecular dynamics (NEMD) simulations were performed to investigate the tribology behaviors of Al2O3 and MoS2 nanoparticles confined between iron (Fe) slabs. Results indicated that the combined use of these two nanoparticles yielded the lowest and most stable friction force, normal force, interface temperature and wear rate, which exhibited a significant synergistic lubrication effect. A novel parameter the rolling/sliding motion coefficient (Krs) was proposed to evaluate the motion pattern of spherical Al2O3. There were 51% rolling + 49% sliding motion when used alone and 91% rolling + 9% sliding in the existence of MoS2. Similarly, about 72.3% of the friction was shared by interlayer sliding of MoS2 monolayers in the presence of Al2O3, which was higher than used alone (54.8%). Then, the diffusion of atoms at the friction interface was explored to reveal the synergistic lubrication mechanism. The tribofilm formed by the diffusion of Fe and S atoms could protect the metal surfaces from further wear. The adsorption of S atoms to Al2O3 nanoparticle could promote its rolling effect and prevent it from embedding into iron matrix. Besides, Al2O3 could also facilitate the separation of MoS2 monolayers to enhance their interlayer sliding effect.