Weldability of 6% Superaustenitic Stainless Steel for Seawater Applications

Abstract

Corrosion resistant alloy welds for seawater applications are necessary to be over-alloyed with Cr, Mo and nitrogen to have an increased Pitting Index value. The desired weld chemistry also requires less microsegregation of Cr and Mo and precipitation free microstruciure not only for higher corrosion resistance but also for good mechanical properties and weld hot-cracking resistance. Based on such requisites for the welds, nitrogen-added Ni-based filler metal, 22Cr-60Ni-9Mo-0.1N, was developed for the welding of a 6%Mo superaustenitic stainless steel.The weldment by the newly developed filler metal showed excellent chloride corrosion resistance comparable to the base metal. The weld solidification and microstructure were fully austenitic without any other phases and brittle precipitates in the whole weld. Thereby, the weldment also offered good ductility, toughness and hot-cracking resistance superior to the weldment by the conventional Alloy 625 filler metal.