Corrosion studies and thermogravimetric analysis performed on activated tungsten inert gas and hot wire tungsten inert gas welded super austenitic stainless steel AISI 904L

Abstract

Attributed to the remarkable resistance offered against various types of corrosion, AISI 904L is used for a wide range of challenging applications. In this context, this research aims to conduct an in-depth corrosion study about the base material and weldments of 10 mm thick AISI 904L plates fabricated by autogenous activated tungsten inert gas (ATIG) welding and hot wire tungsten inert gas (HWTIG) welding techniques. The pitting resistance effective number (PREN) is analyzed to evaluate pitting corrosion resistance. The Tafel plot is drawn and evaluated for the electrochemical corrosion of base metal and weldments in a 3.5% NaCl solution, while the specimens immersed in 3.5% NaCl solution at 650^oC for 24 hours are evaluated for hot corrosion behavior. Thermogravimetric analysis (TGA) is performed at 30⁰C–900⁰C to study material behavior at elevated temperatures. Results indicate that the base metal, ATIG weldment, and HWTIG weldment have a PREN of 34. During Tafel plot analysis, the ATIG weldment displayed a corrosion rate of 0.02792 mm/year while the HWTIG weldment recorded 0.02091 mm/year. Corrosion rates of ATIG and HWTIG weldments during hot corrosion studies are 14.93 mm/year and 12.69 mm/year, respectively. During TGA analysis, the ATIG weldment suffered a weight loss of 12.42% while the HWTIG weldment lost only 9.68% of its weight during the process. FESEM + EDS analysis confirmed the presence of unmixed flux particles in the ATIG weldment, which could be attributed to the weldment’s poor performance. In general, this research cemented the supremacy of the HWTIG weldment over the ATIG weldment with improved corrosion resistance and thermal stability. This study also contributed to a better understanding of the corrosion behavior of AISI 904L weldments under different environments that this superior grade of stainless steel alloy may encounter during its real-life applications.