Wear and abrasiveness of hard carbon-containing coatings under variation of the load

The influence of load on the wear and abrasiveness of hard boron carbide (nominally B4C) thin films is studied. We analyze the wear and abrasiveness data obtained from pin-on-disk tests in which the disks are coated and the counterparts (sliders) are steel balls. It is assumed that the dominant mechanism for slider wear by these nominally smooth coatings is mechanical abrasion of the slider by nano-scale asperities having relatively large attack angles, i.e. by sharp asperities. We propose a model in which we assume that (1) the abrasiveness of a contact is proportional to the number of asperities in the contact; (2) the areal contact density is uniform; and (3) the effect of increasing the load is to enlarge the initial apparent contact region between the ball and the disk. Using this model, the observed dependence of the wear rate on load follows relationships that are similar to Hertzian relationships.