Failure of thin film lubrication — A detailed study of the lubricant film breakdown mechanism

The mechanism of breakdown of the lubricant film in a concentrated steel contact has been studied by examining friction-time diagrams as functions of sliding speed (ranging from 0.0007 to 0.7 m s^?1) and normal force on the contact. It was found that, even at the lower speed of 0.0007 m s^?1, the load-carrying capacity of the contact still depends strongly on lubricant viscosity. Over the whole range of speeds, lubricant film breakdown can be explained in terms of a major disturbance in the steady state condition, which is characteristic of (partial) elastohydrodynamic lubrication. In that condition, oxidation of microasperities which enter the surface zone keeps abreast of metal-to-metal junction formation.