Tribological behavior of aluminum alloys in a vibratory finishing process

Abstract

The contact forces and tribological behavior of aluminum alloys (AA6061-T6 and AA1100-O) in a vibratory finishing process have been investigated. A new surface force sensor was used to measure simultaneously the normal and tangential forces produced by the ceramic media in a tub vibratory finishing machine. These forces were then correlated with the resulting changes in surface roughness, hardness and wear rate of aluminum disks attached to a cylindrical carrier, as well as with the residual curvature of the finished metal sheets. The principal variables were the degree of lubrication, finishing duration, and aluminum alloy. Further observations of media motion obtained using a miniature video camera and SEM micrographs of impact craters helped determine the contact mechanics of the finishing media and the wear mechanisms of AA1100-O and AA6061-T6 alloys. Comparisons are made throughout with similar data obtained previously with a smaller, less energetic bowl finisher. Experimental results revealed that, in the dry finishing condition, media contact tends to the normal direction, with increased media sliding occurring in the water-sprayed condition. Hardness and roughness changes of the workpiece were strongly dependant on the lubrication condition. Furthermore, in the dry condition, mass gain was observed as media debris became embedded in the workpiece surface, while in the water-sprayed condition this effect was prevented by the washing action of the water. The residual curvature of the disks increased with finishing duration until it reached a steady value. Residual curvature was also measured on Almen strips fastened to the ends of a second carrier, and differences between wet and dry finishing are discussed.