Analysis of potentials to improve the machining of hybrid workpieces

Hybrid workpieces made of different materials are part of current research to investigate new design concepts for high-performance components. Cutting conditions and chip formation mechanisms change during machining based on different material properties and chemical compositions. This leads to different residual stresses in the subsurface, which influence the service life of the component. This paper examines the potential of improving workpiece quality and processing productivity of hybrid workpieces by material-specific machining. Furthermore, residual stress gradients in the transition zone were determined in order to analyze in further investigations its influence on the service behavior. The passive forces have a major influence on the residual stresses. By means of process parameter adaptation, the process forces can thus be specifically influenced and consequently the gradient in the material transition zone can be set therefore in a defined manner. For this purposes, the difference in process force during longitudinal turning of an aluminum–steel compound (EN-AW6082/20MnCr5) and a steel–steel compound (C22.8/41Cr4) was investigated. The resulting geometry errors, profile height deviation and surface roughness variance were measured for a wide parameter range and the residual stresses were compared for both material compounds. The optimization of the machining time through material-specific adaptation of the process parameters was calculated for six workpieces. The study shows the potential to reduce geometry errors and shorten the machining time for hybrid workpieces, if the process parameters are adapted to current machined material.