Study on the Sliding Tribological Behavior of Oleic Acid-Modified MoS₂ under Boundary Lubrication

The effects of MoS₂ and MoS₂ modified by adding oleic acid (OA) on the friction properties of lithium-based grease under boundary lubrication conditions are studied by molecular dynamics (MD) simulation and experiment. A rough wall boundary lubrication MD model with peaks and grooves is established to simulate the mechanical properties and lubrication effects of three lubrication systems on rough walls for the relative shear velocity between the two solid walls of 5 m/s at 500 MPa. The stress, wear amount, friction force, normal pressure, and friction heat of the friction surface are quantitively calculated. Simultaneously, a Retc friction and wear testing machine is used to measure the friction coefficient under different concentrations of additives and different pressures. The results show that the grease added with MoS₂ can reduce friction, wear, and the temperature between friction pairs. However, under high pressure and shear, MoS₂ can easily agglomerate and accumulate in the pits, reducing the lubricating effect. At the same time, since OA-modified MoS₂ can reduce agglomeration, the modified MoS₂ is adsorbed on the metal wall surface, forming a stable lubricant film. The main contributions of this article can be found in combining MD simulation and experimentation, establishing the connection between micronano structures and macroscopic properties, exploring the mechanism of the influence of wall roughness and particle size on the friction performance of lubricating oil, and providing a theory for predicting and developing high-performance new lubricating grease.