An In Situ Method for Simultaneous Friction Measurements and Imaging of Interfacial Tribochemical Film Growth in Lubricated Contacts
An In Situ Method for Simultaneous Friction Measurements and Imaging of Interfacial Tribochemical Film Growth in Lubricated Contacts
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DOI：
10.1007/s11249-018-1112-0
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发表时间：
2018-11
影响因子：
3.2
通讯作者：
N. Gosvami;J. Ma;R. Carpick
中科院分区：
文献类型：
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作者：
N. Gosvami;J. Ma;R. Carpick
宏观润滑滑动接触的摩擦学研究对于广泛的工业应用至关重要，包括汽车发动机，齿轮，轴承和任何其他相对运动的接触表面。然而，现有的技术无法访问埋滑动界面的高空间分辨率抑制发展的基本见解的摩擦学过程中发挥作用。在这里，我们展示了一种新的和一般的原位方法，原子力显微镜（AFM）的基础上，微米级的球形探针连接到一个标准的微加工AFM悬臂，然后在基板上滑动，同时沉浸在液体润滑剂。在这种情况下，使用钢胶体探针和钢基底，并且在室温和100 °C下将触点浸入具有二烷基二硫代磷酸锌（ZDDP）添加剂的商业聚α烯烃油中，但是该方法可用于宽范围的材料组合、润滑剂和温度。我们证明，在原位测量的摩擦力和基体上的摩擦化学膜的形态演变可以同时实现与纳米级的空间分辨率。此外，我们表明，滑动区是容易访问的进一步表征与更高的空间分辨率，使用标准的AFM探针与纳米级的尖端半径。非原位表征的微米级探针和样品也是可行的，这是通过获得高分辨率AFM形貌成像的最终状态的探针证明。
Tribological investigations of macroscopic lubricated sliding contacts are critical for a wide range of industrial applications including automotive engines, gears, bearings, and any other contacting surfaces in relative motion. However, the inability of existing techniques to access buried sliding interfaces with high spatial resolution inhibits the development of fundamental insights into the tribological processes at play. Here we demonstrate a novel and general in situ method, based on atomic force microscopy (AFM), in which micrometer-scale spherical probes are attached to a standard microfabricated AFM cantilever which is then slid over a substrate while immersed in a liquid lubricant. In this case, steel colloidal probes and steel substrates were used, and the contact was immersed in a commercial polyalphaolefin oil with zinc dialkyl dithiophosphate (ZDDP) additive at both room temperature and 100 °C, but the method can be used for a broad range of material combinations, lubricants, and temperatures. We demonstrate that the in situ measurements of friction force and the morphological evolution of the tribochemical films on the substrate can be simultaneously achieved with nanometer-level spatial resolution. In addition, we demonstrate that the sliding zone is readily accessible for further characterization with higher spatial resolution using standard AFM probes with nanometer-scale tip radii. Ex situ characterization of the micrometer-scale probe and the sample is also feasible, which is demonstrated by acquiring high-resolution AFM topographic imaging of the final state of the probe.