Effect of Cr on the high-temperature corrosion of dissimilar AISI 904L and Inconel 625 joints employed in the coal-fired thermal power plant tubes

ABSTRACT

The hot corrosion behaviours of 5-mm-thick plates of dissimilar AISI 904L and Inconel 625 weldments produced by continuous current gas tungsten arc welding process using Ni-Cr-Mo-enriched filler wires (ERNiCrMo-4 and ERNiCrCoMo-1) were investigated. Optical microscopy was used to examine the microstructure of these weldments. The corrosion performance of the weldments and base metals was determined in the mixture of K₂SO₄ + 60% NaCl molten salt (MS) and air oxidation conditions at 700°C for 50 cycles. The thermogravimetric plots derived the corrosion kinetics of the weldments. The microstructure and the elemental analysis of the scales formed on the corroded samples were evaluated by scanning electron microscopy and energy-dispersive spectroscopy. The phases developed on the oxide layers during the corrosion were analysed using X-ray diffraction. The fusion zones of ERNiCrCoMo-1 weldment and AISI 904L base metal were vulnerable to degradation in the MS environment, causing severe cracks and spallation compared to ERNiCrCoMo-1 weldment.

KEYWORDS:

• Inconel 625
• AISI 904L
• CCGTAW
• hot corrosion
• oxidation
• K₂SO₄-NaCl

Acknowledgments

The authors express their sincere gratitude and acknowledge VIT (Deemed-to-be University), Vellore, for granting permission to execute this research work by providing all the required facilities. The authors greatly acknowledge the timely help provided by Mr. Periyasamy, technical assistant, at Bannari Amman Institute of Technology, for carrying out the FESEM analysis. The authors also wish to thank FET-Jain (Deemed-to-be University), Bangalore.

Disclosure statement

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

Additional information

Funding

This research received no external funding.