Fundamental analysis of the transfer lubrication in dry lubricated rolling bearings

固体润滑滚动轴承在许多技术系统中使用，在这些系统中，由于关键环境，如真空或高温，无法使用常规润滑。二硫化钨(WS2)和二硫化钼(MoS2)具有优异的摩擦学性能，是一种干式润滑剂。WS2和MoS2已成功地用作真空和高温条件下金属和陶瓷表面润滑剂的表面涂层和添加剂。最新研究表明，WS2和MoS2具有非凡的潜力，特别是在滚动轴承中，可以提高其寿命，这些固体润滑剂可以加入到聚合物滚动轴承保持架材料中，提供内在的润滑效果。因此，利用固体润滑剂微粒，实现了润滑剂从保持架到滚道的转移，这保持了摩擦膜，这基本上影响了系统的寿命。前人的工作主要集中在滚道的涂层和保持架几何形状的优化上。然后重点研究了基于高性能聚合物和润滑剂颗粒的保持架材料配方。研究还发现，保持架复合材料对轴承寿命也有很大影响。申请者的公司勘探工作随后调查了摩擦系统的每个接触伙伴，以便对润滑剂的运输行为有更基本的了解。对回旋区不同区域的摩擦膜形成进行了初步研究。本项目旨在从根本上了解和解释滚动轴承内的润滑剂输送机制。润滑剂的运输主要从保持架中的油库向滚动件和滚道之间的接触区域进行。为此，申请人系统地挤出含有不同尺寸和浓度的润滑剂颗粒(MoS2、WS2)的聚酰胺(PAI)基质化合物。将生产机械和摩擦学表征的测试样品，以及滚动轴承保持架。在不同加载条件下的摩擦系数和比磨损率将由仪表化的环块模型试验台进行彻底的表征。进一步的信息，特别是球与保持架之间的动态接触，将通过仿真获得。然后将通过表面分析方法对单个滚动轴承部件进行研究。这些将提供有关保持架材料对滚动轴承功能的影响的基本信息。特别是通过对保持架、滚动体和滚道等摩擦学功能表面的化学成分的详细表征，旨在更好地了解摩擦膜的组装和降解过程，并描述固体润滑滚动轴承中转移润滑的作用。

Solid lubricated rolling bearings are used in many technical systems in which conventional lubrications cannot be used due to the critical environment, e.g. vacuum or high temperature. Due to their excellent tribological characteristics, Tungsten disulfide (WS2) and Molybdenum disulfide (MoS2) have proven themselves as dry lubricants. WS2 and MoS2 are already successfully applied as surface coatings and as additives in lubricants for metal and ceramic surfaces under vacuum and high temperature conditions. Newest research indicates that WS2 and MoS2 offer extraordinary potential especially in case of rolling bearings to improve their lifetime, and these solid lubricants can be incorporated into the polymeric rolling bearing cage material and provide an intrinsic lubrication effect. Accordingly, with solid lubricant microparticles a lubricant transfer from the cage to the raceway is achieved, which maintains a tribofilm, that is essentially influencing the lifetime of the system. Previous works have concentrated on the coating of the raceway and the optimization of cage geometry. Then the cage material formulation was focused, which is based on a high performance polymer and lubricant particles. It was found that also the cage composite material exerts strong influence on the bearings' lifetime. Corporate exploratory works of the applicants then investigated each contact partner of the tribosystem in order to gain a more fundamental insight into the transport behavior of lubricants. Initial findings on the tribofilm formation in different zones at the raceway were obtained. This project aims to fundamentally understand and explain the lubricant transport mechanisms within the rolling bearing. Transport of lubricant occurs primarily from its depot in the cage towards the contact area between rolling element and raceway. For this purpose, the applicants systematically extrude compounds with polyamidimide (PAI) matrix that contain various sizes and concentrations of lubricant particles (MoS2, WS2). Test samples for mechanical and tribological characterization, as well as rolling bearing cages will be produced. A thorough characterization of friction coefficient and specific wear rate at varying loading conditions will be performed by instrumented block-on-ring model test rigs. Further information especially for the dynamic contact between ball and cage will be gained by simulation. Individual rolling bearing components will then be investigated by surface analytical methods. These will provide fundamental information on the influence of the cage material to the functionality of the rolling bearing. Especially by the detailed characterization of the chemical composition of the tribologically functional surfaces of cage, rolling element, and raceway it is aimed to better understand the assembly and degradation processes of tribofilms, and to describe the effect of transfer lubrication in solid lubricated rolling bearings.