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

• Published in: Wear 2001-04, Vol.249 (1-2), p.117-126
• Main Authors: YAO, M, PAGE, N. W
• Format: Article
• Language: English
• Subjects: Applied sciences; Contact of materials. Friction. Wear; Exact sciences and technology; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy
• ISSN: 0043-1648; 1873-2577

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 > 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 < 0.1 and leveling off to a plateau value of approx0.4-0.6 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. Analytical and experimental results showed that larger abrasive particles preferentially penetrate the surface and, as a result, cause the most extensive ploughing damage. Thus, if fine particles are concentrated at the crushing surface they can protect that surface from penetration and ploughing by larger particles, a feature also observed experimentally. An energy analysis of the crushing and wear event revealed that interparticle friction and particle fracture occurring within the bed of abrasive material contributes significantly to the energy consumed as a result of shear displacement.