Effects of the Shielding Gas and Substrate Thickness on Dilution and Microstructure of Inconel® 625 MIG/MAG Welded Coatings

Abstract Inconel® 625 alloy is a corrosion-resistant nickel-based superalloy, often deposited onto cheaper substrates due to its high cost. In this research, deposition of Inconel 625 was carried out by MIG/MAG (Metal Inert Gas/Metal Active Gas) welding process due to its ease of operation, automation and productivity. The main purpose of this work is to evaluate the shielding gas and substrate thickness on the cooling rate, dilution and microstructure of Inconel® 625 coatings welded by the MIG/MAG process. The cooling rate during deposition was measured using thermocouples. Dilution was evaluated from macrographs of cross section of the welded coatings using Image J software. The microstructure of the coatings was assessed via SEM/EDS (Scanning Electron Microscope/Energy Dispersive Spectroscopy) and X-ray diffraction (XRD). The results showed that cooling rates were higher for plates welded with Ar + 25% He, leading to lower dilution. In the microstructure, a γ-Ni matrix with precipitated phases of Mo and Nb was identified.