Wire Arc Additive Manufacturing (WAAM), one of oldest Additive Manufacturing (AM) techniques, gained attention in the past decade for its high deposition rate and lower cost compared to powder-based technologies. For maintenance and repair applications, especially in the case of large aircraft engine components, reducing lead times represents a significant improvement in the repair cycles. Cold Metal Transfer (CMT), a modified form of Metal Inert Gas (MIG) welding, is an excellent candidate for Ni-based superalloy parts in the hot section of the engine as it produces low heat input welds with low distortion and relatively small residual stresses.

This study focuses on the microstructure and mechanical properties of a precipitation hardened Ni-based superalloy – Waspaloy – manufactured by CMT. Due to its high content in Al and Ti, this superalloy is generally not considered as readily weldable, and has a high susceptibility to strain age cracking (SAC). Waspaloy filler wire was deposited onto a wrought laminated Waspaloy substrate using a welding robot, in the form of multiple beads vertically stacked, creating a wall. Microstructural analyses (SEM and EBSD) were carried out and revealed columnar grains with a strong <001> texture and oriented dendritic structure within. γ’ particles distribution was characterized in both interdendritic and dendritic regions. EDS analyses confirmed a major chemical segregation, especially in the case of Ti and Al. The presence of common AM defects like cracks and porosity was investigated using tomography. No cracks were highlighted, and a small amount of small spherical pores (< 50µm) was found. Moreover, SEM observations of the samples also did not showcase any liquation or solidification cracking. Finally, tensile and creep tests up to 850 °C were conducted on both vertical and horizontal samples in order to assess anisotropy in the as-deposited material and how it can be modified through heat treatments.