Surface layer microhardness and roughness after applying a vibroburnishing process

Abstract

The ball vibroburnishing process of external cylindrical surfaces involves workpiece rotation, while a ball is being pressed and forced to roll on the cylindrical surface, simultaneously, achieving an axial vibration. Experimental research was designed in accordance with the principles of a full factorial experiment with six independent variables at two levels on the test pieces made of two distinct steels, the medium-carbon steel 1C45 and the low-carbon alloy steel 18CrMn4-4. The frequency and amplitude of the vibration motion, ball diameter, radial rolling force, workpiece peripheral speed, and feed rate were considered as process input factors. The process output parameters were the surface roughness parameter Ra, Vickers microhardness of the surface layer measured at a certain distance from the hardened surface, and the hardened layer thickness. Through mathematical processing of the experimental results, power type functions were determined as empirical models. Worth mentioning is the fact that significant influence is exerted by the vibration amplitude on the size of the surface roughness parameter Ra, as well as the vibration motion frequency on the surface layer Vickers microhardness. Keywords: Ball vibroburnishing, Asperity generation, Process input factors, Surface roughness, Surface layer Vickers microhardness, Hardened layer thickness