Friction measurement on Ni-Hard 4 during high pressure crushing of silica

A novel high pressure shear cell has been used to study friction phenomena between crushed silica and Ni-Hard 4 at surface stresses commonly experienced in ore crushers. Surface normal loads of more than 300 MPa were used, together with tangential loads sufficient to initiate and maintain slip at the crushing surface. Under these load conditions, the friction coefficient increased with sliding distance, rising from an initial value of less than 0.1 and leveling off to a plateau value of about 0.4–0.6 in the first few millimeters of shear displacement. The variation of friction coefficient with shear displacement could be divided into three stages: the first dominated by particle rearrangement in the abrasive bed, a second transition stage where particle rearrangement and particle crushing occurred together, and a third dominated by a slowly evolving layer of fine powder adjacent to the crushing surface. This last stage was characterized by a relatively stable (plateau) value for the friction coefficient. This plateau was a weak function of the normal load.