The relationship of tangential stress to wear particle formation mechanisms

Abstract

Experimental results and observations by scanning electron microscopy have demonstrated that the process of wear particle formation under lubricated sliding conditions is greatly affected by the tangential stress. In these experiments, the normal load was kept constant and the tangential stress was varied by changing the friction coefficient using different friction-reducing additives in the base oil. The predominant wear mechanism is related to the magnitude of friction coefficient attained by the friction modifier. The wear rate and the level of surface damage are greatly reduced if the friction coefficient is lower than a specific threshold value. Under these conditions wear particles are formed from deformation of surface asperities. At higher friction coefficients more wear was observed to occur by the process of plowing and delamination ( i.e. subsurface microvoid and crack formation). Under severe wear conditions and lubrication failure, extremely large amounts of wear and severe surface damage result from the adhesive wear mechanism ( i.e. material transfer across the contact surface).