EFFECT OF NITROGEN ON CORROSION OF DUPLEX STAINLESS-STEEL WELD METAL

A type 329J1 duplex stainless steel was gas tungsten are welded withou t filler material in an Ar-N-2 gas mixture atmosphere with the aim of changing only the nitrogen content in the weld metal. The effect of ni trogen on the microstructure and corrosion properties of the weld meta l was examined. An increase in nitrogen partial pressure increased the nitrogen content of the weld metal and brought reductions in the ferr ite content and the quantity of Cr2N nitride precipitates. Three corro sion parameters, namely, critical pitting temperature (CPT), pitting p otential, and corrosion rate, were measured for weld metals having dif ferent nitrogen contents. The CPT and pitting potential increased and corrosion rate decreased with increasing nitrogen content of the weld metal. The corrosion behaviour was explained in tel ms of changes in m icrostructure and pitting index depending on the nitrogen content of t he weld metal.