Influence of the Gas Protection Composition on Dilution of 4130 80K Material Overlaid with 625 Alloy by Hot Twin Wire GTAW Process

Inconel 625 is a nickel-based alloy used in oil and gas equipment due to its outstanding corrosion resistance in seawater, chloride-containing environments, and mainly due to corrosion resistance against the production fluid coming from the reservoirs. However, since Inconel 625 is a high-alloyed material, quite more expensive than low-alloy steels used on most parts of christmas trees and other subsea equipment, their use is desired to be optimized as much as possible. One technique largely employed in the oil and gas industry is the cladding of less noble materials with alloy 625 by Gas tungsten arc welding (GTAW) process. The optimization of the weld dilution of overlays together to the quantity of deposited filler metal is a subjected under study for several researchers around the world, however, not much literature is found about this type of study for Inconel 625 by GTAW hot wire method. This work aims to help academic and oil and gas business community providing information related to alloy 625 overlay welding. Weld beads of Inconel 625 (ERNiCrMo-3) were deposited on AISI 4130 80k by GTAW twin hot wire process, with three shielding gas compositions. The usage of helium on gas mixtures utilized on this work showed two antagonistic behaviors regarding the improvement of the quantity of filler metal used and the weld dilution. The smallest reinforcement was obtained with the highest quantity of helium on shielding gas mixture, while highest amount of helium caused an increase in the weld penetration, and thus in the dilution. Pure argon showed the best dilution results, but bigger reinforcement than helium high amounted shielding gas mixture.