Wire-arc additive manufacturing of nickel aluminum bronze/stainless steel hybrid parts – Interfacial characterization, prospects, and problems

Abstract

Hybrid parts of nickel aluminum bronze (NAB) and 316L stainless steel were fabricated using a commercially available wire-arc additive manufacturing (WAAM) technology to evaluate the feasibility and cracking tendency. Focused Ion beam (FIB) based Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Electron Backscatter Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were used to characterize the built (NAB)-substrate (SS) interfacial characteristics. FIB extracted a selected region of the interface, and the spatial distribution of the interface across several sections was characterized by using the state-of-the-art technique for 3D EBSD mapping. A metallurgically bonded interface without any pores and cracks, with the inter-diffusion region in a thickness of 2 μm, was formed, which was further confirmed by a video with the results of 3D reconstructed EBSD maps. The interface did not exhibit any strong texture orientation owing to the control of the thermal gradient as NAB is more conductive than 316L. EDS elemental mapping confirmed that Fe3Al intermetallic was formed at the NAB/SS bimetallic-joint interface. Occasional liquation cracks on the grain boundaries in the heat-affected zone (HAZ) of 316L substrate were observed. Fe-Al based intermetallic formation, along with the penetration of copper along the HAZ cracks, was noticed. The problems associated were highlighted, and remedial measures were suggested to open up the possibilities of additive manufacturing to fabricate NAB-Stainless steel hybrid parts for industrial repair and maintenance applications.