Microstructure and corrosion behavior of welded joint between 2507 super duplex stainless steel and E690 low alloy steel

Microstructure and corrosion behavior of welded joints between super duplex stainless steel 2507 and low alloy steel E690 were characterized herein. The joints are composed of base metal and heat affected zone (HAZ) of the two steels, weld metal, and dilution zone at the interface between weld metal and HAZ of E690 steel. Concentration gradients of Fe, Ni, Cr, and Mo exist between fusion boundary and Type-II boundary, and martensite band with a high hardness is formed. The changes of microstructure, element diffusion in different regions, and local acidification in E690 HAZ lead to heterogeneous corrosion attacks on the welded joints in artificial seawater. After long-term exposure, a corrosion groove is generated at the HAZ of E690 adjacent to the interface, where high stress corrosion cracking vulnerability is expected.