Investigations on WAAM using copper-based alloys for ship propeller manufacturing

Wire Arc Additive Manufacturing (WAAM) offers unprecedented design and engineering advantages in the design of structures. It combines the advantages of conventional additive processes in terms of the ability to manufacture complex internal structures with the relatively high build-up rate (deposition rate) of a metal inert gas-shielded (MIG) welding process with. Within the current research project, the technology is being investigated and further developed with regard to its use for maritime structures. Maritime structures, such as ship propellers, are largely made of copper-based alloys with a good combination of mechanical strength and corrosion resistance. Due to the special application and environmental conditions, high demands are placed on the mechanical-technological properties. Within the framework of thermal joining technology, this project deals with the mechanized welding of multi-material aluminum bronzes for propeller manufacturing applications up to a diameter of 2 m. Here, the propeller is to have a hollow, optimized structure provided with support structures. A special feature of shape welding is the periodically recurring heat input by the welding process. For this reason, the homogeneity of the resulting microstructure and thus the quasi-isotropic mechanical-technological properties are in the center of attention. Within this study, three different welding filler materials, CuAl8Ni2Fe2Mn2, CuAl9Ni5Fe3Mn2 and CuMn13Al8Fe3Ni2 are investigated within a robotic workcell. The Fronius TPS600i welding power source used offers the possibility of using the cold metal transfer (CMT) process in addition to the conventional pulsed arc process, which lowers the heat input by means of an active wire return movement in the short-circuit phase. Results of initial buildup welds in the form of wall-shaped structures are shown. The investigation of misaligned buildup strategies, such as overlap specimens, as well as buildup-welded quasi-solids simulating the propeller root is also part of the process optimization. Mechanicaltechnological analyses in the form of quasi-static tensile tests, fatigue tests, Charpy impact bending tests, fractographic analyses and investigations of the corrosion behavior are presented.