Influence of rotational speed on surface states after stream finishing

The stream finishing process proved to be an efficient production process for mechanical surface modification. In particular the rotational speed of a bowl containing the media represents an effective process variable for increasing relative velocity between workpiece and media. Increased work hardening effects and induced compressive residual stresses in the near surface region are expected. In this work the temporal influence of the rotational speed of the bowl on work hardening, residual stresses and surface topography are investigated on quenched and tempered AISI4140 plane specimen with the aim of determining the optimal processing time for surface modification. Furthermore, it is investigated whether grain refinement occurs during stream finishing. A modified Almen system is used as an efficient method for characterizing changes in residual stresses and surface topography during stream finishing. While depth ranges of residual stresses and work hardening showed to be affected by the rotational speed of the bowl and the processing time during stream finishing, residual stress states at the surface showed to be invariant. Increased process efficiency can be obtained by stream finishing using high rotational speed yielding higher depths of induced compressive residual stresses and work hardening in the near surface region in a shorter processing time. (C) 2018 The Authors. Published by Elsevier Ltd.