Effects of ‘impact’ and abrasive particle size on the performance of white cast irons relative to low-alloy steels in laboratory ball mills

Abstract

In mineral grinding mills, media and liners are consumed by abrasion, corrosion, and fracture-related damage mechanisms. White cast irons (carbide-reinforced composites) can provide substantially greater wear life than martensitic steels of comparable bulk hardness, but the magnitude of benefit depends on abrasive mineral characteristics. Their performance might also be influenced by mill operating parameters. Since increasing mill rotation speed increases the proportion of high-angle impingement compared to sliding, and since ‘impact’ is commonly expected to promote fracture-related damage mechanisms in brittle materials, it might be assumed that increasing speed will degrade white cast iron performance. However, such assumptions require scrutiny. Using the laboratory ball mill abrasion test (BMAT), the effects of impact severity on relative performance of white cast irons were quantified. Contrary to intuitive expectations, increasing impact severity appeared to improve white iron relative performance. Micro-fracture is known to be influenced by the abrasive's mineral constitution; but the results demonstrate an influence from abrasive particle size — fine particles being less capable of damaging the eutectic carbide network. The observed effects of mill operating parameters were all explicable in terms of their effect on particle size; hence were manifestations of simple abrasive wear processes, not impact-related damage mechanisms.