Wear Behavior of Grinding Wheels With Superficial Cooling Channels

Abstract

Grinding wheels are used in manufacturing industry to shape and finish different types of materials. To achieve this purpose, the wear resistance of grinding materials and the capacity to promote wear on the opposing surface determine the performance of the grinding part. During the grinding operations high temperatures are developed in the wheel/piece contact which can cause several problems like working material microstructural changes, internal defects (fissures...). In the last years, superficial structured wheels have been developed in order to reduce contact temperature and improve the grinding efficiency and the quality of the produced surface. In this work, two types of channels structures were produced on the surface of a vitrified alumina abrasive composite with: hexagonal and spiral geometries (active area of 95.3 and 91.6%, respectively). The obtained composites produced were characterized in terms of physical properties (density and porosity) and geometric channel features. In order to evaluate the changes on the wear rate and surface morphology pin-on-disc wear tests were performed under lubricated conditions at constant load (20 N) and sliding speed (0.5 m.s−1), at room temperature. An alumina rod (∅5 mm) was used as counterface material creating particularly hard contact conditions. The wear rate of both mating surfaces was measured by gravimetric method. The worn surfaces were characterized by SEM analysis and the tribological results were correlated with the physical properties of the composites and the introduced cooling channels. The dominant wear mechanisms, as identified by SEM analysis, were fine scale abrasive wear of the protruding load carrying particles, which is featured by the formation of wear flats, together with debonding of ceramic particles from the composite contact surface. Comparing with traditional wheels (without cooling channels), a decrease of the wear rate on disc side of 35 and 42% was obtained for, respectively, spiral and hexagonal channel geometries. On the alumina opposite counterface, the wear rate increases 10 and 47% for, respectively, hexagonal and spiral geometries. A significant improvement on the abrasive performance (a wear rate decreases on the abrasive wheel and an increase on the counterface) was achieved with the addition of the two types of channel geometries. The best combination of results (composite and counterface) was obtained for the spiral configuration of the cooling channels (grinding ratio of 0.86).