Role of contact frequency on the wear rate of steel in discontinuous sliding contact conditions

This work presents a novel approach of sliding ball-on-disk wear tests where the disc material is investigated. Each part of the wear track on the disc is in discontinuous contact with the counterbody. The contact frequency at each part of the wear track on the disc with the counterbody is defined by the rotation frequency of the disc. The sliding speed is however a function of both the rotation frequency and wear track diameter. In this work, the effect of the contact frequency on friction and wear was investigated on carbon steel in discontinuous sliding contact with corundum balls. Various sliding speeds were used while maintaining the contact frequency at a fixed value, and various contact frequencies were applied at constant sliding speeds.The wear rate of the disk material is shown to depend not only on the usual wear test parameters, namely sliding speed and contact load, but also on contact frequency. Moreover, contact frequency is shown to be a key factor determining the wear mode even at constant sliding speed and load. At contact frequencies above 9 Hz, the dominant wear mechanism is oxidational wear, while at frequencies below 4 Hz the dominant wear mechanism is adhesive wear. This transition from adhesive to oxidational wear takes place together with a change in the type of debris generated and in the value of the coefficient of friction.The validity of the Garcia-Ramil-Celis model proposed earlier for discontinous sliding contact conditions, is demonstrated for the case of carbon steel disks sliding against a chemically inert counterbody.