Effect of nitrogen which is one of the most important elements in duplex stainless steels was investigated on resistances to pitting corrosion and stress corrosion cracking (SCC) in various environments. The increase in nitrogen content increases these resistances in the base metal, which is due to the improvement in the resistance of γ-phase which has lower chromium and molybdenum contents compared to α-phase. Nitrogen is an essential element to sustain the corrosion resistance of the heat affected zone (HAZ) which is heated up to 1350°C or higher, because nitrogen accelerates the formation of γ-phase during the cooling process after welding and avoids the precipitation of chromium carbides or nitrides at grain boundaries. When the nitrogen content is less than 0.08% in 22%Cr, 5.5%Ni and 3%Mo base composition the HAZ has little γ-phase to lead to the high susceptibility to inter- granular corrosion and IGSCC occurs even in pure CO2-Cl− environment containing no H2S. Nitrogen has little effect on the precipitation behavior of the base metal by aging heat treatment around 700°C.

Subject
Materials, Intergranular stress corrosion cracking, Stainless alloys, Base metals, Sodium chloride solution, Nitrogen content, Nitrogen, Pitting, Corrosion resistance, Duplex stainless steel, Intergranular corrosion, Stress corrosion cracking, Austenite
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1986
Association for Materials Protection and Performance (AMPP)
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