Experimental characterisation of an elastohydrodynamic contact and of a thin hard coating by means of a pin-on-disk tribometer

The present thesis project is the outcome of an extended experimental investigation on tribology within the framework of a joint research project between Politecnico di Torino (IT) and Anton Paar TriTec SA (CH). It deals with the revision of the most commonly used standard for the pin-on-disk tribometers: ASTM G99. The aim is to develop one new procedure for coatings and one reference procedure for the diagnostics on pin-on-disk tribometers. As this paper covers two separate issues within the subject of tribology, it has two distinct sections. In Part I, the experimental results from several tests carried out with a particular elastohydrodynamic lubricated condition free of oil bath are presented and discussed. This kind of contact is successfully exploited to reproduce a repeatable no-wear tribological condition with a very stable friction coefficient. A reference procedure for diagnostics is then formulated. In Part II, the tribological characterization of a commonly used hard coating (a PVD TiN) is presented and results from tests with various configurations, material pairs and parameters are discussed. This proves that it is possible to obtain stable and sufficiently repeatable friction curves through which a characteristic value of the coefficient of friction is extrapolated.