Superduplex nitrogen alloying
The targeted enrichment of the material with nitrogen to stabilize the austenite phase and significantly increase the pitting resistance equivalent in chloride-containing media.
Superduplex is a highly alloyed steel with plenty of nitrogen in it. This ensures that enough austenite forms during welding and the structure remains stable. If you don't pay attention, the ferrite-to-austenite ratio flips, and the part loses its corrosion protection – especially in chloride-containing environments. When welding, you have to keep an eye on the heat input. Too much heat or slow cooling coarsens the structure and makes the weld brittle. Use a filler metal that matches the base metal and also contains nitrogen, otherwise you won't get a clean weld. It's important not to let the interpass temperature get too high. If you cool the weld too slowly after welding, unwanted phases precipitate. So: work cleanly, don't overheat, and the nitrogen does the rest.