Project Details
Projekt
Wear Protection in Roller Bearings due to Reaction Layer Formation at minimal Additive Concentration and Microtextured Surfaces
Subject Area
Engineering Design, Machine Elements, Product Development
Term
from 2011 to 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 200413972
In tribological systems, additive-containing lubricants are used for wear protection. The additives form reaction layers on the surface of the tribological contact bodies. In the first project period of the priority program, appropriate run-in procedures were established for the formation of desired reaction layers in rolling bearings. Additionally, the potential reduction in additive concentration and the consequent environmental relief from hazardous components was demonstrated. This aspect was investigated under real life conditions with wear-critical roller bearings and the widely used anti-wear additive zinc-dialkyldithiophosphate. During run-in and given the right conditions, reaction layers are formed within few minutes and are sufficiently resistant to avoid wear even under severe mixed lubrication conditions. In addition to the operational parameters and the surface stress, the lubricant quantity in the contact was shown to impact the reaction layer formation. To clarify the governing mechanisms of the reaction layer formation, the first aspect of this research project is the identification of extreme cases of minimal complete layer formation, depending on the operating parameters, and the micro analytical characterisation of the layer structure and composition. Additionally, the impact of the surface texture on the reaction layer formation is to be studied, given that the topography minima can act as micro-reservoirs for the lubricant and that the stress peaks at the roughness spikes enhance the reaction layer formation. Laser interference metallurgy will be employed to this end, to fabricate well-defined periodic surface textures with feature sizes in the micrometer range on the rolling bearing surface. In first experiments on axial cylinder roller bearings the potential for wear reduction of these micro textures was demonstrated. In this research project the mechanisms should be explored through variation of the operation parameters and surface texture. As a second aspect of the research project, the impact of the micro textures on the fatigue life time of rolling bearings is investigated. For this purpose, the influence of the surface texture and the lubricant additivation on the fatigue life time of axial and radial rolling bearings is studied. The local pressure is calculated with the real surface topography of the laser texture in order to quantify its effect. With the help of damage analyses, possible fatigue scenarios are identified in the case of failure.
DFG Programme
Priority Programmes
Subproject of
SPP 1551:
Resource Efficient Constructional Elements
