Xu Nan, Wang Chun, Yang Liuquan, Jose Gin, Morina Ardian
Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
ACS Appl Mater Interfaces. 2022 Jan 12;14(1):2071-2081. doi: 10.1021/acsami.1c21824. Epub 2021 Dec 30.
Solid-liquid lubricating systems have received significant attention as a promising way for energy saving and emission control. For deeply understanding their tribological behaviors, it is necessary to study interaction mechanisms between solid and liquid lubricants from the tribochemical viewpoint, as tribofilms formed by tribochemical products on contact surfaces critically affect the whole tribological process. Continually or periodically monitoring tribofilm formation and evolution can contribute significantly to clarifying its dominating role in tribological behavior under boundary lubrication. However, detecting tribofilms in situ remains a big challenge for conventional surface analytical approaches, mainly due to their limitations in accessing tribofilms or low signal intensities of thin tribofilms. In this study, highly sensitive Raman-based profilometry with in situ potential has been developed for detecting molybdenum dialkyldithiocarbamate (MoDTC)-derived tribofilms and exploring their effect on a-C:H wear over time. The optical properties of tribochemical products formed on the coating surface in different wear stages could result in extra attenuation of Raman signal intensities in the form of measurement deviations in wear depth. By monitoring the deviations, key information of tribofilm compositions was obtained and a two-stage wear progression mechanism was proposed for the first time to clarify the detrimental effect of MoDTC-derived tribofilms on a-C:H wear by combining detailed structure and composition analyses.
固液润滑系统作为一种节能和排放控制的有前景的方式受到了广泛关注。为了深入理解其摩擦学行为，有必要从摩擦化学的角度研究固体和液体润滑剂之间的相互作用机制，因为接触表面上摩擦化学反应产物形成的摩擦膜对整个摩擦学过程有至关重要的影响。持续或定期监测摩擦膜的形成和演变对于阐明其在边界润滑下摩擦学行为中的主导作用有显著贡献。然而，对于传统的表面分析方法来说，原位检测摩擦膜仍然是一个巨大的挑战，主要是因为它们在检测摩擦膜方面存在局限性，或者薄摩擦膜的信号强度较低。在本研究中，已经开发了具有原位电位的高灵敏度拉曼轮廓仪，用于检测二烷基二硫代氨基甲酸钼（MoDTC）衍生的摩擦膜，并探索其随时间对非晶碳氢（a-C:H）磨损的影响。在不同磨损阶段涂层表面形成的摩擦化学反应产物的光学性质可能会以磨损深度测量偏差的形式导致拉曼信号强度的额外衰减。通过监测这些偏差，获得了摩擦膜成分的关键信息，并首次提出了两阶段磨损进展机制，通过结合详细的结构和成分分析来阐明MoDTC衍生的摩擦膜对a-C:H磨损的有害影响。
