Surface moisture or humidity impacting the lubrication property is a ubiquitous phenomenon in tribological systems, which is demonstrated by a combination of molecular dynamics (MD) simulation and experiment for the organic friction modifier (OFM)-containing lubricant. The stearic acid and poly-α-olefin 4cSt (PAO4) were chosen as the OFM and base oil molecules, respectively. The physical adsorption indicates that on the moist surface water molecules are preferentially adsorbed on friction surface, and even make OFM adsorption film thoroughly leave surface and mix with base oil. In shear process, the adsorption of water film and desorption OFM film are further enhanced, particularly under higher shear rate. The simulated friction coefficient (that is proportional to shear rate) increases firstly and then decreases with thickening water film, in good agreement with experiments, while the slip length shows a contrary change. The wear increases with humidity due to tribochemistry revealing the continuous formation and removal of Si-O-Si network. The tribological discrepancy of OFM-containing lubricant in dry and humid conditions is attributed to the slip plane’s transformation from the interface between OFM adsorption film and lubricant bulk to the interface between adsorbed water films. This work provides a new thought to understand the boundary lubrication and failure of lubricant in humid environments, likely water is not always harmful in oil lubrication systems.

表面水分或湿度影响润滑性能是摩擦系统中普遍存在的现象，分子动力学（MD）模拟和含有机摩擦改性剂（OFM）润滑剂的实验相结合证明了这一现象。硬脂酸和聚α-烯烃4cSt (PAO4) 分别被选为OFM 和基础油分子。物理吸附表明，在潮湿的表面，水分子优先吸附在摩擦表面，甚至使OFM吸附膜彻底离开表面并与基础油混合。在剪切过程中，水膜的吸附和OFM膜的解吸进一步增强，特别是在较高剪切速率下。模拟的摩擦系数（与剪切速率成正比）随着水膜的增厚先增大后减小，与实验结果吻合较好，而滑移长度则呈现相反的变化。由于摩擦化学，磨损随着湿度的增加而增加，揭示了 Si-O-Si 网络的连续形成和去除。含 OFM 润滑剂在干燥和潮湿条件下的摩擦学差异归因于滑移面从 OFM 吸附膜和润滑剂本体之间的界面转变为吸附水膜之间的界面。这项工作为理解潮湿环境中的边界润滑和润滑剂失效提供了新的思路，可能水在油润滑系统中并不总是有害的。