The effect of large heat input on the microstructure and corrosion behaviour of simulated heat affected zone in 2205 duplex stainless steel

In the simulated heat affected zone of 2205 duplex stainless steels, effects of large welding heat inputs on the microstructure and corrosion behaviour were investigated. Reformed austenite content increased with the coarsening of grain boundary austenite (GBA) and the growth of intragranular austenite (IGA) and Widmanstatten austenite (WA), thus improving the low temperature toughness and affecting corrosion state. Reduction of chromium nitrides contributed to better resistance to pitting corrosion. Moreover, the pitting corrosion and intergranular corrosion were improved resulting from the formation of more GBA and WA. The specimen with a Δt8/5 of 100 s presents better comprehensive performance.

► The GBA formed when Δt8/5 is 20 s and then became coarser with slower cooling time.
► Increasing heat input shifted the pitting potential (Epit) to more noble value.
► Reduction of chromium nitrides contributes to the resistance to pitting corrosion.
► More GBA and WA formation contributes to pitting and intergranular corrosion resistance.
► The resistance to IGC in simulated HAZ of DSSs increased with larger heat input.