Mechanisms of graphite lubrication in rolling contacts

在齿轮或滚动轴承等机器元件中，润滑脂和润滑油主要用作润滑剂。然而，简单的油基润滑剂特别是在100°C左右分解，并可能导致系统磨损和故障。添加剂可以抵消分解，但也有其他限制，如降低环境相容性。此外，固体润滑剂（如石墨、MoS2或PTFE）是一种替代品，石墨可能是最古老的固体润滑剂之一，但在技术上仍经常使用。该研究项目的中心目标是设计一种实用的概念，用于高负荷滚动接触的终身润滑。为此，转移层的建立过程进行了研究，通过微观摩擦学和原子模拟。分析了影响润滑油膜结构及其与金属表面附着力的因素。在微观层面上，石墨接触的供应机制正在研究使用的轴向球轴承为例。除其他事项外，表面粗糙度在第一个资助期内对转移层的形成有很大的影响，并将在第二个资助期内进行深入研究。石墨润滑推力球轴承的概念设计正在宏观层面上进行。这里的目的是考虑到原子水平的结果，例如，需要对石墨出口进行密封，以确保轴承中有一定的水含量。例如，通过考虑有利于转移层形成的一定表面粗糙度，实现了在微观水平上的研究的影响。

In machine elements such as gears or rolling bearings, greases and oils are mainly used as lubricants. However, simple oil-based lubricants in particular decompose at around 100°C and can lead to wear and failure of the systems. Additives can counteract decomposition, but have other limitations, such as reduced environmental compatibility. In addition, the group of solid lubricants (e.g. graphite, MoS2 or PTFE) represents an alternative, whereby graphite is probably one of the oldest, but still very frequently used solid lubricants in technology.The central objective of the research project is to design a practical concept for the lifetime lubrication of highly loaded rolling contacts with graphite. For this purpose, the build-up process of the transfer layer is investigated by means of micro-tribometry and atomistic simulation. Influencing variables that determine the lubricant film structure and its adhesion to the metal surface are analyzed. At the micro level, the provision mechanisms of graphite in contact are being investigated using the axial ball bearing as an example. Among other things, the surface roughness has shown a strong influence on the transfer layer formation in the first funding period and will be investigated in depth in the second funding phase. The conceptual design of a graphite-lubricated thrust ball bearing is being carried out at the macro level. The aim here is the production of demonstrators taking into account the results at the atomic level, which, for example, require sealing against the graphite exit to ensure a certain water content in the bearing. The influence of the investigations at the micro level is achieved, for example, by taking into account a certain surface roughness that favors transfer layer formation.