Wire arc additive manufacturing of porous metal using welding pore defects

A novel wire arc additive manufacturing process is proposed to produce porous metal (PM). The innovation is to convert harmful welding pore defects into a beneficial structure of PM, and then the PM parts can be additive manufactured layer by layer. Air was transferred to the molten pool as pore promoters to maximize the formation of the welding pore defects. The triple-wire indirect arc process was used for fabricating multi-layer parts to reduce interlayer filling. The primary advantage is that the process can directly produce macro-pore structures rather than depositing pore walls along micro paths in laser additive manufacturing. The uniform diameter of the pore ranges from 500 to 2700 μm, and the typical porosity is 64%, 49%, and 87%. The process could achieve a high deposition rate of 11.5 kg/h. Due to martensite formation, the pore walls can achieve high microhardness of over 200 HV.