Comparative Study of Microstructural Evolution and Mechanical Properties of Inconel^® 718 and Waspaloy^® Welds

Lab. of Physical Metallurgy and Center for Electron Microscopy, School of Mining and Metallurgical Engineering, National Technical University of Athens, Heroon Polytechniou 9, 15780 Athens, Greece,

^* Corresponding author: aggkald@gmail.com

Abstract

This research work focuses on the mechanical behaviour comparative assessment in conjunction with microstructural evolution characterization of Waspaloy^® and Inconel^® 718, following TIG and EB welding. Both of the forth-mentioned alloys are precipitation strengthened Ni-based superalloys, widely used in chemical, petrochemical and aerospace industries. More specifically, Waspaloy^® is strengthened by the precipitation of the ordered fcc gamma prime intermetallic phase, γ΄ - Ni₃(Al,Ti), while Inconel^® 718 is mainly hardened by the ordered bct gamma double prime phase, γ΄΄ - Ni₃Nb, in addition to γ΄. After both welding processes, samples of the above superalloys were subjected to appropriate post-weld heat treatment, according to SAE Aerospace Material Specifications. The mechanical response of the tested specimens is assessed via uniaxial tensile tests, combined with fractography. Furthermore, the microstructural characterization of TIG and EB welds is conducted by Scanning Electron Microscopy (SEM), coupled with Energy Dispersive Spectroscopy (EDS), while phase identification was performed through X-Ray Diffraction (XRD). The main objective of the present research work is to examine the influence of post-weld heat treatment on the Waspaloy^® and Inconel^® EBW and TIG welds microstructural evolution features, correlating them with their corresponding mechanical behaviour.