Effects of laser remelting on microstructure and shear properties of bonding interface in hybrid metal additive manufacturing process

A hybrid metal additive manufacturing method for complex structures and high-precision parts was investigated to realize both high-efficiency forming with wire arc additive manufacturing (WAAM) and precise forming with laser metal deposition (LMD). In this method, a part is decomposed into sub-volumes. Then, the sub-volumes with relatively simple structural features are formed through WAAM as a substrate, and the other sub-volumes with more complex structures or small-sized features are formed through LMD on this substrate. However, the mechanical properties of the bonding interface could be reduced if the latter sub-volumes were directly deposited by LMD on the rough WAAM substrate surface. In order to avoid unnecessary machining processes between WAAM and LMD for high efficiency and ensure the mechanical properties of the WAAM–LMD bonding interface, a laser remelting method was applied to improve the profile of the WAAM substrate surface. A simulation model of the heat transfer and fluid flow in the laser remelting process was established, and the influences of the laser power and scanning speed on the surface-profile improvement were researched by simulation and verified by experiments, which allowed the remelting process parameters to be optimized. Furthermore, the LMD-formed volumes were deposited directly on the WAAM-formed substrate after surface milling and laser remelting. Then, the microstructures and shear properties of the bonding interfaces formed using the three process methods were compared, and the feasibility of using the laser remelting method to improve the bonding interface performance was verified.