Experimental Researches Of The Grease Durability Via Microscopic Investigation

The working life of a bearing depends on the aging characteristics of the lubricant. Aging produces physical, structural and rheological modifications in the grease that have rarely been studied from an overall stand-point. Also, analysis of used greases can be a valuable source of information on the mechanisms involved when a bearing is lubricated with grease. From this point of view, it is very useful to establish a few criteria for the grease life time, as follows: modification of the physical and chemical properties of the greases, modification of the rheological parameters, modification of the global electrical resistance of the grease film and modification of the microscopically grease structure and apparition of the wear particles. The paper proposes a comparative study of greases in the fresh state and after use in ball bearings, analysing the modification of the rheological and structural properties. The mechanical aging test was carried out on an experimental stand and the grease structure was studied using a scanning electron microscope. The rheological properties were studied on a cone and plate Brookfield viscometer.