Influence of intermetallic precipitation on metallurgical, mechanical and pitting behavior of AISI 2205 duplex stainless steel welded joints

Post weld thermal aging of DSS (duplex stainless steel) welds resulted into complex precipitation that comprised of intermetallic carbides, oxides and sigma-phase in different zones of the welds. Maximum ferrite dissolution was observed in the weld metal followed by the HAZ (heat affected zone) and the base metal. Sigma phase precipitated preferentially along γ/δ (austenite/ferrite) interfaces besides the formation of secondary austenite (γ₂). Precipitated joints showed an increase in microhardness and yield strength, whereas their UTS (ultimate tensile strength) did not alter much. Aging resulted into a significant loss of tensile ductility (percentage elongation) which showed a degradation of 15.27% and 62.46% for the base metal and the weld metal respectively. The base metal's impact toughness did not show any appreciable loss, but a severe degradation of around 96% occurred in the impact toughness of the aged weld metal. Fatigue crack growth behavior showed that weld metal possessed superior fatigue strength than the base metal, which upon aging reduced drastically to 48.24 % and 28.44 % respectively. Pitting corrosion studies showed that weld metal exhibited superior pitting resistance than the base metal, and both of them suffered a loss of pitting resistance due to precipitation. (paper)