Materials Sciences and Applications, 2018, 9, 228-245 http://www.scirp.org/journal/msa ISSN Online: 2153-1188 ISSN Print: 2153-117X DOI: 10.4236/msa.2018.92015 Feb. 5, 2018 228 Materials Sciences and Applications Influence of MIG/MAG Welding Process on Mechanical and Pitting Corrosion Behaviors on the Super-Duplex Stainless Steel SAF 2507 Welded Joints Bruno Leonardy S. Lopes 1 , Samuel F. Rodrigues 1 , Eden S. Silva 1,2 , Gedeon S. Reis 1 , Waldemir dos P. Martins 1 , Juvenilson Costa Damascena 1 , Valdemar S. Leal 1 1 Graduate Program in Materials Engineering, Federal Institute of Education, Science and Technology of Maranhão—IFMA, São Luís, MA, Brazil 2 Engineering Coordination, Universidade UNICEUMA, São Luís, MA, Brazil Abstract The main objective of this research is to better understand the correlation between the constituent phases presented in the super-duplex steel SAF 2507 when it is under welding process by arc shielding gas MIG-MAG (Metal Inert Gas-Metal Active Gas). Conventional short circuit transfer and derivative STT (Surface Tension Transfer) using the 2594 welding wire as a filler metal and the effects on welding power in hardness, toughness and pitting corrosion are considered here. The results showed that the welding energy (Ew) changed the α/γ-phase’s balance and occasionally formed σ-phase in ferrite grain boundaries which led to changes in hardness, toughness and pitting corrosion resistance in molten zone (MZ), heat activated zone (HAZ) and metal base regions (MB). Furthermore, the increased amount of γ-phase improved the pitting corrosion resistance index (PRENγ) mainly in the MZ. This is due to decrease of α-phase fraction and formation of coarser grains, for higher weld- ing energy. The toughness in the MZ decreased with less formation of γ-phase, coalescence of ferritic grains and localized formation of σ-phase, raising the hardness in the HAZ when the welding energy was lower. Keywords Super-Duplex Steels, Welding, Toughness, Pitting Corrosion, Microhardness 1. Introduction The development of alloys means major advances in the manufacture of high How to cite this paper: Lopes, B.L.S., Rodrigues, S.F., Silva, E.S., Reis, G.S., Mar- tins, W. dos P., Damascena, J.C. and Leal, V.S. (2018) Influence of MIG/MAG Weld- ing Process on Mechanical and Pitting Corrosion Behaviors on the Super-Duplex Stainless Steel SAF 2507 Welded Joints. Materials Sciences and Applications, 9, 228-245. https://doi.org/10.4236/msa.2018.92015 Received: October 18, 2017 Accepted: February 2, 2018 Published: February 5, 2018 Copyright © 2018 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access