Duplex 2205 (UNS S32205) Stainless Steel: High Strength + Chloride SCC Resistance

Duplex 2205 is limited to -46°C (-50°F) minimum (lower than this, ferrite undergoes ductile-to-brittle transition and Charpy values drop precipitously) and +300°C (570°F) maximum. Above 300°C, the ferrite phase decomposes via '475°C embrittlement' — precipitation of alpha-prime Cr-rich phase causing catastrophic loss of toughness within hours at 475°C and months at 300-350°C. This is irreversible. For applications above 300°C, use a super-austenitic (254 SMO, AL-6XN) or nickel alloy (Alloy 625, C-276). For sub-arctic/cryogenic applications below -46°C, use 304L or 9% nickel steel.

Yes — but the dissimilar weld requires careful filler selection. Use ER2209 filler (overalloyed with nickel to promote sufficient austenite formation in the as-deposited weld metal despite the fast cooling rate). Using 316L filler on a 2205-to-316L joint produces an under-alloyed weld with excessive ferrite (poor toughness and corrosion resistance). Using 2209 filler, the weld pool composition will be intermediate between the two base metals and should form an acceptable duplex structure. Post-weld solution annealing is generally not required for thin-section single-pass welds, but multi-pass welds benefit from solution annealing at 1020-1100°C followed by water quench.