Hot corrosion and air oxidation behavior of pulsed current gas tungsten arc welded and CO₂ laser beam welded SMO 254 at 800 °C

Abstract

This research aims to investigate the hot corrosion behaviour of SMO 254 steel samples after PCGTA and CO₂ laser beam welding, as well as air oxidation. A salt mixture simulated the waste incinerator environment involving 40 wt. % Na₂SO₄ + 40 wt. % K₂SO₄ + 10 wt. % NaCl + 10 wt. % KCl are employed. The hot corrosion tests were carried out for 103.33 h at 800 °C, with a thermogravimetric investigation availed to calculate the impact of corrosion. The weight gain rate for PCGTAW molten salt corroded specimens is greater (33.45 mg/cm²) than the weight gain rate for CO₂ Laser molten salt corroded specimens, which is 67.55% higher. The weight of the hot corroded sample rises in the molten salt surroundings due to the creation of compounds including CrS, FeMo₂S₄, Na₂S, Fe₂O₃, K₂S₃, Cl₄CrNa₂. CO₂ LBW air oxidation has the lowest rate of corrosion due to the synthesis of beneficial oxides, such as NiCr₂O₄, NiO, and Cr₂O₃. Optical microscopy and SEM/EDS were employed on both surface and cross-sectional surfaces to get microstructure at the interface of the fusion region, parent metal, and fusion region using point mapping, line mapping, and X-ray mapping techniques. The corrosion products produced during corrosion were studied using XRD.

Keywords:

• PCGTA welding
• CO₂ laser beam welding
• hot corrosion
• thermogravimetric method

Acknowledgements

The researchers are grateful to the Vellore Institute of Technology, Vellore campus, and ARCI, Hyderabad for assisting in the completion of the experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).