Susceptibility of Dissimilar IN600 Welded Joints to Stress Corrosion Cracking Using Slow Strain Rate Test in Sodium Electrolytes

• Published in: Metals (Basel ) 2022-07, Vol.12 (7), p.1112
• Main Authors: Granados-Becerra, Heriberto, López-Morelos, Víctor H., Contreras, Antonio, Curiel-López, Francisco Fernando, García-Hernández, Rafael, González-Sánchez, Jorge Antonio, Cortés, Eduardo
• Format: Article
• Language: English
• Subjects: Alloys; Corrosion rate; Corrosion resistance; Crack initiation; Crack propagation; Ductility; Electrochemical noise; Electrode polarization; Electrolytes; Gas metal arc welding; Grain boundaries; Inconel 600 (IN600); Laves phase; localization index; Mechanical properties; Metal fatigue; Microcracks; Microscopy; Nickel base alloys; Plastic properties; Plates; polarization test; Shielding; Slow strain rate; slow strain rate test; Sodium hydroxide; Sodium thiosulfate; Solid solutions; Steel; Stress corrosion cracking; Superalloys; Tensile strength; Uniform attack (corrosion); Welded joints
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met12071112

The stress corrosion cracking (SCC) behavior of aged plates of Inconel 600 welded to Inconel 600 plates in the as-received condition was studied using the slow strain rate test (SSRT) in two sodium containing electrolytes at 25 and 80 °C. The aged plate was used to simulate damage by the operation service. Electrochemical noise (EN) was used to monitor the SCC. The plates were gas metal arc welded (GMAW) employing ERNiCrMo-3 and ER310 filler wires along with 95% Ar + 3% N2 + 2% O2 and 97% Ar + 3% N2 as the shielding gas, respectively. The microstructure of the welded joints was characterized using optical and scanning electron microscopy. The results of the SCC revealed that when sodium thiosulfate was used, the loss in plasticity was higher in the NiCrMo-3 joint with around a 20 percent decrease. Conversely, in the 310 welds, the loss in plasticity was higher in the sodium hydroxide, which diminished by 12 percent. A few secondary microcracks were observed in the transversal section in specimens of both welds. The results of the EN showed an increase in the potential and current when the sample reached the tensile strength and then decreased when the neck was formed; these changes indicate that some events occurred during the SSRT. The EN data showed two types of corrosion: general corrosion for NiCrMo-3 and mixed corrosion for the 310 welded joint in both environments. Electrochemical polarization was also employed to understand the mechanism of SCC.