Effect of Post-Weld Heat Treatment on Hardness and Corrosion Resistance of Dissimilar Electron Beam Welded Joints of Inconel 713LC and AISI 4140 Steel

Dissimilar welding of Inconel 713LC superalloy and high strength AISI 4140 steel was conducted using Electron Beam (EB) welding process. The present research study focuses on the effect of post-weld heat treatment (PWHT) on the produced dissimilar joints’ microstructure, mechanical properties and corrosion behavior assessment. PWHT was accomplished at 650°C for 2, 4 and 6 h, following air cooling. The microstructure study was carried out by light optical (LOM) and scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy (EDS) analysis. The mechanical behavior of the EB joints was investigated via Vickers hardness testing. For the assessment of the EB joints’ corrosion resistance, potentiodynamic polarization tests were performed in 3.5 wt.% NaCl solution, at various temperatures. The corrosion products evaluation was carried out by both x-ray Diffraction (XRD) and scanning electron microscopy (SEM). PWHT leds to the microstructure modification of both Inconel 713LC and AISI 4140 in the dissimilar welding zones. The heat treatment holding time increment resulted in the development of more uniform mechanical response among base metals and fusion/heat affected zones, whereas corrosion resistance became progressively weaker.