Stump Benjamin C, Zhou Yan, Luo Huimin, Leonard Donovan N, Viola Michael B, Qu Jun
Research & Development Center, General Motors , 30470 Harley Earl Boulevard , Warren , Michigan 48092-2031 , United States.
ACS Appl Mater Interfaces. 2019 Aug 21;11(33):30484-30492. doi: 10.1021/acsami.9b10001. Epub 2019 Aug 12.
Oil-soluble ionic liquids (ILs) have recently been demonstrated as effective lubricant additives of friction reduction and wear protection for sliding contacts. However, their functionality in mitigating rolling contact fatigue (RCF) is little known. Because of the distinct surface damage modes, different types of surface protective additives often are used in lubricants for sliding and rolling contacts. Therefore, the lubricating characteristics and mechanisms of ILs learned in sliding contacts from the earlier work may not be translatable to rolling contacts. This study explores the feasibility of using phosphonium-phosphate, ammonium-phosphate, and phosphonium-carboxylate ILs as candidate additives in rolling-sliding boundary lubrication, and results suggested that an IL could be either beneficial or detrimental on RCF depending on its chemistry. Particularly, the best-performing phosphonium-phosphate IL at 2% addition made a low-viscosity base oil significantly outperform a more viscous commercial gear oil in reducing the RCF surface damage and associated vibration noise. This IL generated a thicker, smoother, and more homogeneous tribofilm compared with commercial additives, which is likely responsible for the superior RCF protection. Results here suggest good potential for using appropriate IL additives to allow the use of low-viscosity gear and axle fluids for improved efficiency and durability.
油溶性离子液体（ILs）最近已被证明是用于滑动接触的有效减摩和抗磨润滑添加剂。然而，它们在减轻滚动接触疲劳（RCF）方面的功能却鲜为人知。由于表面损伤模式不同，滑动和滚动接触的润滑剂中通常使用不同类型的表面保护添加剂。因此，早期工作中在滑动接触中了解到的离子液体的润滑特性和机理可能不适用于滚动接触。本研究探讨了使用鏻 - 磷酸盐、铵 - 磷酸盐和鏻 - 羧酸盐离子液体作为滚动 - 滑动边界润滑候选添加剂的可行性，结果表明，离子液体对滚动接触疲劳可能有益也可能有害，这取决于其化学性质。特别是，添加2%性能最佳的鏻 - 磷酸盐离子液体时，一种低粘度基础油在减少滚动接触疲劳表面损伤和相关振动噪声方面明显优于一种粘度更高的商用齿轮油。与商用添加剂相比，这种离子液体生成了更厚、更光滑且更均匀的摩擦膜，这可能是其卓越的滚动接触疲劳保护性能的原因。这里的结果表明，使用合适的离子液体添加剂具有良好的潜力，能够允许使用低粘度齿轮和轴用流体来提高效率和耐久性。
