The role of prow-deposits in the wear of abrasive grits by superficial fracture

Abstract

Prevailing concepts of wear of abrasive grits assume a mechanism of slow attritious wear land formation or one of cutting edge destruction by chipping. A second attritious wear mechanism is reported, involving rapid land wear by superficial fracture. Transfer of prow-deposits from the workpiece to wear lands accompanies rapid land wear by fracture. Crack nucleation, in the region of tensile stress generated at asperity junctions, leads to crater generation. Fragment production yields larger individual wear particles than competing attrition processes. The resulting wear rate of an abrasive is 10 to 50 times larger than attrition wear rates generating polished surfaces. Differences in fracture wear rate, among the abrasives studied, result from the varied character of microstructural flaws in the grits. The spacing, size and shape of these flaws affect the fragment size and fracture frequency. Adherent prow-deposits of various sizes form on abrasive grits contacting metal workpieces during sliding, micromilling and grinding. Deposition on the wear lands depends on workpiece properties and environmental conditions. Strong adhesion and ductility of the workpiece favor formation of prow-deposits on grit asperities.