Microstructure characteristics of wire arc additive manufactured Ni-Al intermetallic compounds

An initial attempt had been made to fabricate Ni-Al intermetallic compounds (IMCs) by wire arc additive manufacturing (WAAM) in order to overcome the disadvantages of traditional casting-melting method such as complex process and long production cycle. The effects of wire Ni content on the microstructure and mechanical properties of the deposited thin-wall samples were studied. It was found that the deposited microstructure varied from M-NiAl/Ni3Al to bulk-like Ni3Al + gamma-Ni/gamma'-Ni3Al by increasing the Ni content. The average microhardness of the deposition firstly decreased from 437.6 HV0.3 to the minimum of 255.4 HV0.3 with the increase of the Ni content because of the decrease of the M-NiAl with high hardness. It then increased to 302.1 HV0.3 owing to the increase of the strengthened phase of gamma'. The thermodynamic behavior in Ni-Al system was calculated to discuss the transformation mechanism of the WAAMed Ni-Al IMCs.