Microstructure and nanomechanical behaviour of wire-arc additive manufactured nickel-based superalloy C276

The Hastelloy C276 superalloy is one of the versatile and promising alloys considered for high-temperature applications. In the present work, the crystallographic properties and nanomechanical behaviour of Hastelloy C276 superalloy manufactured via gas metal arc welding (GMAW) based wire-arc additive manufacturing (WAAM) were evaluated. The WAAM-processed C276 superalloy mainly comprises columnar dendrites with the predominant <100> and <111> textures at the middle region. Also, p phases rich in Mo and W were noticed within the interdendritic regions of the austenitic matrix. Small-scale mechanical testing revealed that the WAAM-processed Hastelloy C276 superalloy exhibited a reduced elastic modulus compared to its wrought counterpart. The average nanohardness (H) and reduced elastic modulus (Er) in the horizontal direction were 5.40 ± 0.51 GPa and 192.42 ± 4.50 GPa, and 4.28 ± 0.14 GPa and 122.26 ± 2.0 GPa in the vertical direction. From the nanoindentation responses, the dendritic cores have a reduced nanohardness than that of the interdendritic regions due to the localized segregation of Mo and W in the interdendritic regions, resulting in solid solution hardening. The H³/Er² ratio revealed the comparable plastic deformation resistance of WAAM-processed Hastelloy C276 in the horizontal and vertical directions at the nanoscale level.