Fundamental multiscale investigations for improved service life calculation of solid lubricated rolling bearings in vacuum

提高真空中固体润滑滚动轴承使用寿命计算的基础多尺度研究

• 批准号: 508541414
• 负责人: Professor Dr.-Ing. Benoit Merle
• 金额: --
• 依托单位: Computer-Chemie-Centrum (CCC)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/508541414?language=en
• 关键词: Fundamental; multiscale; investigations; improved; service

The project aims at developing a mechanistic, microstructure based model for calculating the service life of MoS2 solid lubricated rolling bearings, with emphasis on radial bearings. These bearings are typically used in severe environments, such as vacuum, e.g. in vehicles used for extraterrestrial planetary exploration. The only service life calculation model available in the literature relies on an empirical approach, which does not take into account the microstructure of the films. Our findings from the first funding period evidence that coating geometrically complex surfaces by PVD invariably results in dendritic-lamellar MoS2 growth. Upon tribological loading, this initially nanoporous coating is turned into a compact film exhibiting a basal texture, which corresponds to the most desirable condition for tribological purposes. This transformation largely governs the subsequent tribological behavior of the film, including the processes of removal and transport of MoS2 solid lubricant. It is therefore paramount to fully apprehend this transition step and integrate it into the model. Failure to do so would cause large errors inservice life prediction. The strong interplays between deformation mechanisms, microstructure and tribological loading call for a scale bridging approach, stretching from atomistic simulations of fundamental processes, to microscale characterization of material transformations and macroscale tribological tests on model components. The atomistic structure of the films will be resolved by HRTEM following FIB lift-out and will be subsequently modelled by DFT and semi-empirical potentials. Furthermore, nanoindentation and nanowear experiments will be performed in situ in the SEM, whilemacroscale tribological tests will take place in vacuum on twin-discs and ball bearings. This arsenal of techniques will allow us to gain a fundamental understanding of (a) the textural reorientation and the microstructural changes taking place during the transition step; (b) the removal and transport of MoS2, the formation of a tribofilm, its adhesion and the resulting volume of effectively available solid lubricant, as a function of intrinsic (microstructure, texture, porosity) and extrinsic (contact loading, substrate roughness) factors. This will allow us to extend the service life calculation model from Birkhofer. These enhancements will be validated by test bench experiments. The new knowledge will serve as a basis for optimizing the transition behavior so as to extend the service lifetime of the bearings, e.g. through post-deposition treatments or controlled running-in. The planned investigations will contribute to improving our general understanding of the relationship between tribologically induced microstructural changes and the wear behavior of solid lubricants.

该项目旨在开发一种机械的、基于微观结构的模型，用于计算MoS2固体润滑滚动轴承的使用寿命，重点是径向轴承。这些轴承通常用于恶劣的环境，如真空，例如用于地外行星探测的车辆。文献中唯一可用的使用寿命计算模型依赖于经验方法，该方法没有考虑薄膜的微观结构。我们在第一个资助期的发现证明，PVD涂层几何复杂的表面总是导致枝状片层MoS2生长。在摩擦学加载后，这种最初的纳米多孔涂层转变为具有基本纹理的致密膜，这符合摩擦学目的的最理想条件。这种转变在很大程度上控制了薄膜的后续摩擦学行为，包括MoS2固体润滑剂的去除和传输过程。因此，充分理解这个过渡步骤并将其集成到模型中是至关重要的。如果不这样做，将导致使用寿命预测出现较大误差。变形机制、微观结构和摩擦学载荷之间的强烈相互作用要求采用尺度桥接方法，从基本过程的原子模拟延伸到材料转化的微观表征和模型部件的宏观摩擦学测试。薄膜的原子结构将在FIB提升后通过HRTEM进行解析，随后将通过DFT和半经验势进行建模。此外，纳米压痕和纳米磨损实验将在扫描电镜中原位进行，而宏观尺度的摩擦学测试将在真空中对双盘和滚珠轴承进行。这些技术将使我们能够获得以下方面的基本理解：(a)在过渡步骤中发生的纹理重新定向和微观结构变化；(b) MoS2的去除和传输，摩擦膜的形成，其附着力以及由此产生的有效可用固体润滑剂的体积，作为内在（微观结构，质地，孔隙率）和外在（接触载荷，衬底粗糙度）因素的函数。这将使我们能够扩展Birkhofer的使用寿命计算模型。这些增强将通过试验台实验进行验证。新知识将作为优化过渡行为的基础，从而延长轴承的使用寿命，例如通过沉积后处理或控制磨合。计划中的研究将有助于提高我们对摩擦学诱导的微观结构变化与固体润滑剂磨损行为之间关系的总体理解。