Experimental study of the effect of microtexturing on oil lubricated ceramic/steel friction pairs

The objective of the research work was to study the potential of commercial ceramics such as Al2O3, Al2O3–ZrO2 and SiC in pairing with steel 100Cr6 and laser-assisted deterministic microtexturing of the flat functional surfaces as design element for fast running friction systems, such as multiple disc clutches, under unidirectional oil lubricated sliding. A more fundamental part of the study was oriented towards understanding of the effect of microtexturing on mechanisms at mixed or boundary lubrication and development of lubricating oil film in the contact area. Experiments were carried out with pellet/disc geometry at relatively low velocities ≤0.3 m/s and normal loads ≤10 N using a model test with an attached microscope for in situ observation of the contact area. In the second part, friction behaviour of the different ceramic materials with and without microtexturing was characterised using a friction test rig at sliding velocities up to 10 m/s and normal loads ≤60 N under more practical-oriented conditions. Results showed that frictional behaviour was significantly influenced by the ceramic material and features of microtexturing, e.g. dimples, channels, width, depth and area coverage fraction. Improved understanding of operating mechanisms and design rules of microtexturing for controlling friction coefficient at practical sliding systems was obtained from a descriptive model.