Dorgham A, Neville A, Ignatyev K, Mosselmans F, Morina A
Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom.
Rev Sci Instrum. 2017 Jan;88(1):015101. doi: 10.1063/1.4973354.
The complex tribochemical nature of lubricated tribological contacts is inaccessible in real time without altering their initial state. To overcome this issue, a new design of a pin-on-disc tribological apparatus was developed and combined with synchrotron X-ray absorption spectroscopy (XAS). Using the designed apparatus, it is possible to study in situ the transient decomposition reactions of various oil additives on different surfaces under a wide range of realistic operating conditions of contact pressure (1.0-3.0 GPa), temperature (25-120 °C), and sliding speed (30-3000 rpm or 0.15-15 m/s). To test the apparatus, several tribological tests were performed at different shearing times ranging from 2.5 to 60 min. These tests were carried out under helium atmosphere at a temperature of 80 °C, contact pressure of 2.2 GPa, and sliding speed of 50 rpm. The XAS experiments indicate that the zinc dialkyldithiophosphate antiwear additive decomposes in the oil to form a tribofilm on the iron surface at different reaction kinetics from the ones of the thermal film. The tribofilm composition evolves much faster than the one of the thermal film, which confirms that the formation of the tribofilm is a thermally activated process similar to the one of the thermal film but accelerated by shear. Furthermore, the results indicate that the sulfur of the formed film, whether a tribofilm or a thermal film, appears initially in the form of sulfate, with some sulfide, which under heat or shear is reduced into mainly sulfide.
在不改变润滑摩擦接触的初始状态的情况下，无法实时了解其复杂的摩擦化学性质。为克服这一问题，开发了一种新型销盘式摩擦学装置，并将其与同步加速器X射线吸收光谱（XAS）相结合。使用该设计装置，可以在接触压力（1.0 - 3.0 GPa）、温度（25 - 120°C）和滑动速度（30 - 3000 rpm或0.15 - 15 m/s）等各种实际运行条件下，原位研究不同表面上各种油添加剂的瞬态分解反应。为测试该装置，在2.5至60分钟的不同剪切时间下进行了几次摩擦学测试。这些测试在氦气气氛中，温度为80°C、接触压力为2.2 GPa、滑动速度为50 rpm的条件下进行。XAS实验表明，二烷基二硫代磷酸锌抗磨添加剂在油中分解，在铁表面形成摩擦膜，其反应动力学与热膜不同。摩擦膜成分的演变比热膜快得多，这证实了摩擦膜的形成是一个热激活过程，类似于热膜，但受剪切作用加速。此外，结果表明，无论是摩擦膜还是热膜，所形成膜中的硫最初以硫酸盐形式出现，伴有一些硫化物，在加热或剪切作用下主要还原为硫化物。
