Tsai Anna E, Komvopoulos Kyriakos
Department of Mechanical Engineering, University of California, Berkeley, CA 94720, USA.
Materials (Basel). 2024 May 14;17(10):2324. doi: 10.3390/ma17102324.
The antiwear properties of tribofilms formed on steel surfaces lubricated with various multi-component lubricants were investigated at an elevated temperature and under load-speed conditions conducive to sliding in the boundary lubrication regime. The lubricants contained base oil, reduced-level (secondary) zinc dialkyl dithiophosphate (ZDDP), and nitrogenous dispersant. The wear resistance of the tribofilms produced from different oil blends was evaluated in the context of the rate of change in the sliding track volume (wear rate for material loss) and the load-bearing capacity, chemical composition, and thickness of the tribofilms. Surface profilometry and scanning electron microscopy were used to quantify the wear performance and detect the prevailing wear mechanisms, whereas X-ray photoelectron spectroscopy elucidated the chemical composition and thickness of the tribofilms. The oil blends without ZDDP did not produce tribofilms with adequate antiwear properties, whereas the oil blends containing ZDDP and dispersant generated tribofilms with antiwear characteristics comparable to those of tribofilms produced from blends with a higher ZDDP content. Although dispersants can suspend oil contaminants and preserve the cleanness of the sliding surfaces, it was found that they can also reduce the antiwear efficacy of ZDDP. This was attributed to an additive-dispersant antagonistic behavior for surface adsorption sites affecting tribofilm chemistry and mechanical properties. Among the blends containing a mixture of ZDDP and dispersant, the best antiwear properties were demonstrated by the tribofilm produced from the blend consisting of base oil, 0.05 wt% ZDDP, and a bis-succinimide dispersant treated with ethylene carbonate. The findings of this investigation demonstrate the potential of multi-component lubricants with reduced-content ZDDP and nitrogen-based dispersant to form effective antiwear tribofilms.
在高温以及有利于边界润滑状态下滑动的载荷-速度条件下，研究了用各种多组分润滑剂润滑的钢表面上形成的摩擦膜的抗磨性能。这些润滑剂包含基础油、低含量（二级）二烷基二硫代磷酸锌（ZDDP）和含氮分散剂。根据滑动轨迹体积的变化率（材料损失的磨损率）以及摩擦膜的承载能力、化学成分和厚度，评估了由不同油 blend 产生的摩擦膜的耐磨性。使用表面轮廓仪和扫描电子显微镜来量化磨损性能并检测主要的磨损机制，而 X 射线光电子能谱则阐明了摩擦膜的化学成分和厚度。不含 ZDDP 的油 blend 不会产生具有足够抗磨性能的摩擦膜，而含有 ZDDP 和分散剂的油 blend 产生的摩擦膜具有与由较高 ZDDP 含量的 blend 产生的摩擦膜相当的抗磨特性。尽管分散剂可以悬浮油污染物并保持滑动表面的清洁，但发现它们也会降低 ZDDP 的抗磨效果。这归因于添加剂-分散剂对影响摩擦膜化学和机械性能的表面吸附位点的拮抗行为。在含有 ZDDP 和分散剂混合物的 blend 中，由基础油、0.05 wt% ZDDP 和经碳酸亚乙酯处理的双琥珀酰亚胺分散剂组成的 blend 所产生的摩擦膜表现出最佳的抗磨性能。这项研究的结果表明了具有低含量 ZDDP 和氮基分散剂的多组分润滑剂形成有效抗磨摩擦膜的潜力。
