Info On Nb Nitride formation with ERNiCrMo-3 & Duplex SS

I don't know of any specific web articles on this, but it does make sense. In micro and low alloy steels, Nb is considered a nitride former. Nitrogen is also an inerstitial element, so has a high diffusivity, so it would be able to travel at the higher temperatures.

We've commonly welded duplex to carbon steel and duplex to Alloy 625 with ERNiCrMo-3 and have not had any reported cracking incidents. It is known that creep ductility is adversely affected when in high temperature service due to presence of Niobium carbo-nitrides.

There is no question that nobium forms carbides and nitrides. The amount of nitrogen, carbon and niobium present will determine what forms ( NbC or NbN ) and at what temperature. The loss of nitrogen in solution will definitly alter mechanical and corrosion properties. Whether they have contributed to a weld failure is something you haven't provided enough facts on for conjecture.