Study of MIG/MAG welding procedures for application of coatings of Inconel 625 nickel alloy on ASTM A387 Gr.11 structural steel

This work aims to study welding techniques applied to repair of components made of ASTM A387 Gr.11 steel, widely used in the oil and gas industry. Due to the working conditions, it is necessary to use materials having good strength and corrosion resistance. UNS N06625 Ni-based alloy (Inconel 625) was used as the filler metal. The MIG/MAG welding process was used to apply the temper bead welding technique with two layers. The methodology of this study was divided in stages, in the first one, exploratory trials were carried out to define the relevance of the studied control factors. In the second step, hardness and microstructure criteria were applied for defining the best heat input relations for the application of the double-layer technique. The double-layer technique was effective in improving the properties of the microstructure in heat-affected zone coatings, intense grain refinement was found. There was also a reduction in microhardness and hardness measurements. Both used shielding gases (Ar + 25% He and Ar + 4% CO2) have achieved heat input relations with positive deviations. In all these relations the heat input of the second layer is greater than the heat input of the first layer. © 2017 Informa UK Limited, trading as Taylor & Francis Group.