Investigation of Step Annealing Heat Treatment on the Pitting Corrosion Resistance of Super Duplex Stainless Steel Welded Pipes

In this study، the effects of heat treatment on the microstructure and pitting corrosion resistance of super duplex stainless steel welds have been investigated. The results showed that step annealing treatments in the temperature range of 550–1000 °C resulted in a precipitation of sigma phase and Cr2N along the ferrite/austenite and ferrite/ferrite boundaries. At this temperature range، the metastable pits mainly nucleated around the precipitates formed in the grain boundary and ferrite phase. Above 1050 °C، the microstructure contains only austenite and ferrite phases. At this condition، the critical pitting temperature of samples successively arrived to the highest value obtained in this study.