Microstructure and corrosion resistance of Ni-Cu alloy fabricated through wire arc additive manufacturing

Abstract Wire arc additive manufacturing (WAAM) technology is a promising low-cost process for fabricating or restoring marine structures with Ni-Cu alloy. In this work, single pass multi-layer wall of Monel FM60 was deposited with WAAM process. The micrographs revealed the presence of equiaxed and elongated columnar dendrites with minor amount of Cu segregation in Ni-Cu matrix. Due to the complex cyclic thermal history, the microstructure varied along the building direction (BD) and the secondary dendrite army spacing (SDAS) ranged between 5-15 µm. Energy Dispersive X-Ray Analysis (EDS) results confirmed the existence of tiny Ti-rich particles within the Ni-Cu matrix. The WAAM processed Monel FM60 specimens (0.40-0.62 mpy) exhibited better corrosion resistance compared to traditional Monel 400 alloy (0.57-0.67 mpy) in 3.5% NaCl solution. The enhanced corrosion resistance is corroborated to lower depletion of strengthening elements and the pit size ranged between 40-80 µm.