TRIBOLOGICAL BEHAVIOR AND MECHANISM OF MOS₂/DIAMOND-LIKE CARBON MULTILAYER STRUCTURES

The performance of friction materials directly affects the safety and reliability of automotive braking systems. Composites comprising molybdenum disulfide (MoS₂) and diamond-like carbon (DLC) have attracted considerable research interest because they combine excellent self-lubricating properties with high hardness and low friction. In this study, molecular dynamics simulations were performed to systematically investigate the nanoscale frictional behavior and local deformation mechanisms of MoS₂/DLC multilayer composites. To address the stringent requirements for high-temperature stability and wear resistance in automotive brake materials, sliding friction models of MoS₂ films and MoS₂/DLC multilayer composites were constructed. The effects of normal load, sliding velocity, temperature, DLC layer depth, and number of DLC layers on tribological performance were examined. Under the same normal load, the composites exhibited higher friction coefficients but generally fewer atoms removed by wear than the MoS₂ films, indicating that incorporating DLC layers reduced material damage while modifying tangential resistance. Analyses of shear strain and morphology revealed that the DLC layers altered direct contact between the abrasive particle and MoS₂ and accommodated deformation within the contact region through local subsidence and wrinkling. As the sliding velocity increased from 20 to 160 m/s, the friction coefficient of the composite increased from 0.2512 to 0.5484. In contrast, increasing the temperature from 300 to 800 K slightly decreased the friction coefficient from 0.3724 to 0.3590. Varying the DLC layer position changed the material in direct contact with the abrasive particle and the local shear strain distribution, while the friction force exhibited similar evolution trends across structures with different layer positions. At a fixed individual DLC layer thickness, increasing the number of DLC layers from two to five produced an upward trend in the average friction coefficient and altered the spatial distribution of high-shear-strain regions. These changes reflected the combined effects of layer number and total DLC content. These findings demonstrate that the incorporation and spatial arrangement of DLC layers jointly regulate frictional resistance and local deformation, suggesting that optimizing DLC layer depth and number can help balance frictional resistance and damage resistance.