Hybrid- and ceramic rolling bearings with modified surface and low friction rolling contact

Conventional steel bearings often fail under extreme strains. All ceramic bearings and bearings with ceramic rolling bodies, the so called hybrid ceramic bearings, provide a good alternative for such applications. However, important fields of application of the hybrid- and all ceramic bearings can be accessed only, if long lasting load capacity and easy motion of dry running bearings can be ensured even under increased loads. A main objective is to reduce friction within the rolling contact and to significantly enhance the rolling strength particularly in unlubricated contact through modification of the working surfaces of the bearing rings and roll bodies. The approaches are: optimised DLC coatings on steel for hybrid bearings and the incorporating of friction minimising additions of BN and TiN into the Silicon Nitride bulk material for hybrid and ceramic bearings. Coatings yielded good results in lab scale while the friction reducing Si3N4-composites already showed their potential to significantly reduce the rolling friction in underlubricated bearings. A new method of surface treatment of Si3N4 was developed based on a shot peening process. Under optimized conditions load capacity of a ball on plate contact can be increased remarkable. Additionally, in an innovative approach the project focuses on intelligent adaptation of the rolling contact macrogeometry of ball bearings. This development, intended to allow a load related control of the bearing characteristics, now is in the status of numeric and practical evaluation. The work described is funded by BMBF within the MaTech programme (Projects 03N2002 and 03N2018).