Study on Improvement of Surface Roughness and Induced Residual Stress for Additively Manufactured Metal Parts by Abrasive Flow Machining

摘要

Fabrication freedom is provided for production of metal parts with complex geometries that cannot be fabricated by conventional subtractive manufacturing, as rapid advancements in additive manufacturing (AM). However, as the quality of as-built surfaces of AM metal parts is far inferior to service requirements, the drawbacks in fabricating metal parts by AM include the poor as-built surface roughness inherent to balling effect and powder adhesion, the tensile residual stress in surface layer inherent to AM building process. In this paper, the additively manufactured aluminum alloy workpiece is polished by abrasive flow machining (AFM), and the effect of the process parameters of AFM on the workpiece's surface integrity is taken into account, i.e. surface roughness and compressive residual stresses induced. Results of the experiments show that surface roughness is significantly improved after AFM process and surface defects due to powder accumulations is also removed. Furthermore, compressive residual stresses are induced in layer inferior to the machined surface after AFM polishing process. It is proved that AFM offers effective finishing and improvement in surface integrity of AM parts, providing a feasible way to finish AM parts with complex inner surfaces.