The abrasive wear of steel during rolling-sliding contact with rock counterfaces

Abstract

In many mining operations ( e.g. excavation, drilling, tunnelling, rock crushing), metallic components are forced against abrasive rocks in a complex motion. This study examines the relative importance of combined rolling and sliding motion in the two-body abrasive wear of a low carbon tempered martensitic steel against rock counterfaces. A novel wear test rig has been used to vary the amount of rolling and sliding motion between a rotating steel cylinder and a counter-rotating sandstone (highly abrasive) or limestone (much less abrasive) disc. Weight loss measurements reveal that the wear rate of the steel increases as the amount of motion against the rock counterface is reduced from pure sliding to about 50% sliding (and about 50% rolling). With further reductions in the amount of sliding motion, the wear rate of the steel is reduced because of the formation of corrugations on the sandstone and limestone rock surfaces. Scanning electron microscopy shows that when the amount of motion is reduced from pure sliding to about 50% sliding, the topographical and subsurface physical properties of the worn steel and rock surfaces are modified. Following large amounts of sliding motion (70–80% sliding), the worn steel surface is heavily deformed by shearing in the sliding direction and many of the minerals in the worn rock counterface are crushed and compacted. Reducing the motion to 50% sliding leads to a reduction in the depth of the plastically sheared layer in the worn steel, and the rock surface shows a considerable reduction in the amount of mineral crushing and compaction, with many of the abrasive grains maintaining some angularity. It is concluded, therefore, that the increasing wear rate of the steel with the amount of rolling motion, until the onset of rock surface corrugations, probably results from the rock counterface retaining a higher proportion of angular abrasive minerals.