Wear protection in rolling bearings by preconditioning of the workpiece surfaces in manufacturing

滚动轴承是机器的中心元件，用于传递机器部件之间同时相对运动的力。润滑油中使用极压（EP）和抗磨（AW）添加剂等，保证了使用寿命和减少意外停机。添加剂通过在表面形成添加剂诱导的反应层来保护滚动轴承表面免受磨损。这些层防止直接接触的金属表面在混合摩擦的制度，从而确保磨损保护。目前使用的添加剂，如二烷基二硫代磷酸锌（ZDDP），在生态毒理学上存在问题，而且由于其硫和磷含量，会对组件的使用寿命产生负面影响。此外，还发现了ZDDP对损伤现象（白蚀裂纹和微点蚀）的促进作用。因此，其目的是降低润滑油中的添加剂浓度或避免使用有害添加剂。初步研究表明，如果在磨合过程中形成反应层，即使在润滑剂中不添加添加剂，也能保证滚动轴承的磨损保护。添加剂会形成一个初始的防磨损反应层，在反应层形成后，只需重新生成反应层。通过适当的表面调理，进一步开发降低添加剂浓度的潜力是本项目的目标，以便在生产过程中已经产生初始反应层。滚动轴承主要由100Cr6钢制造，并通过磨削加工。磨削过程中的热-机械-化学载荷会影响工件的内边界层。此外，高温会与周围介质，特别是冷却润滑剂发生化学反应，形成反应层，即外边界层。在磨削过程中边界层的形成是否对滚动轴承的后期运行具有减少磨损的作用还不充分清楚。通过了解磨削过程中工艺输入变量与边界层形成之间的因果关系，可以通过磨削对初始边界层特性进行特定调整，减少或替代高负荷滚动轴承磨合阶段，并将轴承后期运行中的润滑剂添加剂降至最低。因此，该合作项目的目标是解释初始边界层形成作为磨削过程中过程输入变量的函数，以及它们在不同添加剂浓度下对层形成的影响，以及对滚动轴承磨损行为的影响。

Rolling bearings are a central machine element for the transmission of forces with simultaneous relative movement between machine components. The service life and the reduction of unplanned shutdowns is guaranteed by the use of Extreme Pressure (EP) and Anti Wear (AW) additives in the lubricant, among other things. The additives protect the rolling bearings’ surfaces against wear by forming additive-induced reaction layers on the surface. These layers prevent direct contact of the metallic surfaces in the regime of mixed friction and thus ensure wear protection. Currently used additives, e.g. zinc dialkyldithiophosphate (ZDDP), are ecotoxicologically questionable and furthermore, can negatively influence the service life of components due to their sulphur and phosphorus content. In addition, a damage-promoting effect of ZDDP on the damage phenomena white etching cracks (WEC) and micro pitting is known. Therefore, the aim is to reduce the additive concentration in the lubricant or to avoid the use of harmful additives.Preliminary work shows that the wear protection in the rolling bearing is guaranteed even without additives in the lubricant, if the formation of the reaction layer took place in a run-in process. The additives lead to an initial wear-protecting reaction layer and only have to regenerate the layer after its formation. The further development of this potential for reducing the additive concentration is the objective in this project by means of a suitable surface conditioning, so that the initial reaction layer is already produced during production process.Rolling bearings are mainly manufactured from 100Cr6 steel and are finished by grinding. The thermo-mechanical-chemical loads during grinding influence the inner boundary layer of the workpiece. In addition, high temperatures can cause chemical reactions with the surrounding media, especially the cooling lubricant, and reaction layers, i.e. an outer boundary layer, can be formed. If a boundary layer’s formation during grinding has a wear-reducing effect in the later operation of the rolling bearing is not sufficiently known. By knowing the cause-effect relationships between the process input variables during grinding and the formation of the boundary layer, the run-in phases of highly loaded rolling bearings could be reduced or substituted and lubricant additives in the later operation of the bearing could be minimized by a specific adjustment of the initial boundary layer properties by means of grinding. The goal of this cooperation project is therefore to explain the initial boundary layer formation as a function of the process input variables during grinding and their effect on the layer formation at different additive concentrations as well as on the wear behaviour of rolling bearings.