Ethanol has emerged as a promising alternative to fossil fuels, but its use can lead to significant dilution in lubricants, particularly during cold start or heavy traffic. This dilution can affect the performance of additives, including friction modifiers like molybdenum dithiocarbamate (MoDTC), which are designed to reduce friction under extreme contact conditions. Prior research suggests that ethanol may impact the performance of MoDTC, prompting this study’s goal to investigate the effects of ethanol on MoDTC tribofilms and their friction response under boundary lubrication conditions. Therefore, reciprocating tribological tests were performed with fully formulated lubricants containing MoDTC with varying ethanol concentrations. The results indicate that a critical ethanol dilution level inhibits friction reduction by MoDTC activation, resulting in friction coefficients (COFs) similar to the base oil. Surfaces tested with simple mixtures of polyalphaolefin (PAO) + MoDTC showed increased COFs with added ethanol. Analysis of tested surfaces using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy near the edge structure (XANES) revealed the presence of sulfates, MoO₃, MoS₂, and MoS_xO_y compounds in the tribofilms formed on the surfaces, with and without ethanol diluted in the lubricant. However, the addition of ethanol increased the sulfates and MoO₃ content of the tribofilms at the expense of friction-reducing compounds such as MoS₂ and MoS_xO_y. These findings suggest that ethanol dilution in lubricants containing MoDTC creates an oxygen-rich interfacial medium that favors the formation of compounds with insufficient friction-reducing capabilities.

乙醇已成为化石燃料的一种有前景的替代品，但其使用可能会导致润滑油显着稀释，特别是在冷启动或交通繁忙时。这种稀释会影响添加剂的性能，包括二硫代氨基甲酸钼 (MoDTC) 等摩擦改性剂，这些添加剂旨在减少极端接触条件下的摩擦。先前的研究表明乙醇可能会影响 MoDTC 的性能，因此本研究的目标是研究乙醇对 MoDTC 摩擦膜的影响及其在边界润滑条件下的摩擦响应。因此，使用含有不同乙醇浓度的 MoDTC 的全配方润滑剂进行了往复摩擦学测试。结果表明，临界乙醇稀释水平会抑制 MoDTC 活化导致的摩擦减少，从而导致摩擦系数 (COF) 与基础油相似。使用聚 α 烯烃 (PAO) + MoDTC 的简单混合物进行的表面测试表明，添加乙醇后 COF 会增加。使用拉曼光谱、X 射线光电子能谱 (XPS) 和边缘结构附近的 X 射线吸收光谱 (XANES) 对测试表面进行分析，结果表明存在硫酸盐、MoO ₃ 、MoS ₂ O _y 化合物在表面上形成的摩擦膜中，无论是否在润滑剂中稀释乙醇。然而，乙醇的添加增加了摩擦膜的硫酸盐和 MoO ₃ 含量，但牺牲了 MoS ₂ 和 MoS _x O 等减摩化合物。 _y 。这些发现表明，用乙醇稀释含有 MoDTC 的润滑剂会产生富氧界面介质，有利于形成减摩能力不足的化合物。