Process research of the powder bed-based 5-axis additive/subtractive hybrid manufacturing for internal features

Additive/subtractive hybrid manufacturing (ASHM) has emerged as a promising solution to overcome the surface roughness and dimensional accuracy issues commonly encountered in the traditional additive manufacturing (AM) process. Particularly, when processing complex internal features using laser powder bed fusion (L-PBF), there are limitations in the existing powder bed-based (PB-based) ASHM processes. Therefore, this study developed a novel PB-based 5-axis ASHM system to address the challenges. The PB-based 5-axis ASHM process was proposed and validated through in situ manufacturing of internal cavity and internal channel features by using Inconel 718. The results demonstrated significant improvements in surface quality, with a reduction in surface roughness to below Ra 0.8 μm, a 77.5 % increase in dimensional accuracy, and closure of surface pore defects. The study further explored the comprehensive effects of the PB-based ASHM process on microstructure and mechanical performance, revealing the formation of low-angle grain boundaries (LAGBs) caused by side milling process and lack-of-fusion (LOF) defects resulting from interval AM process. The results showed that the hybrid process enhanced strength and surface hardness but significantly reduced elongation of the material, with optimal performance observed in specimens determined by AM matrix and process alternation frequency at small-cutting-volume conditions. Additionally, the impacts of milling chips on the PB-based ASHM process for parts with minimal cross-sectional variation were demonstrated to be controllable in this study. Overall, the PB-based 5-axis ASHM system development and process research offer a promising approach to manufacturing more kinds of complex internal features, contributing to the wider application in the future.