Addition of Nitrogen and Nickel in the fusion zone of plasma transferred arc weldments in UNS 32760 super duplex stainless steel: Effect on the microstructure and on the pitting corrosion resistance

摘要

Super duplex stainless steels exhibit excellent combination of strength and corrosion resistance, due to their strict composition control and ferrite-austenite phase balance. Nevertheless this balance is in general disturbed in the fusion zone and in the HAZ of weldments due to rapid cooling rates, leading to inferior corrosion and mechanical properties. The scope of the present work is to study the effect a) of addition of nitrogen in the plasma operation gases and b) of higher nickel content in the filler metal, on the microstructure and on pitting corrosion resistance of the fusion zone in super duplex stainless steels welded by the plasma transferred arc technique. It is shown that nitrogen addition in the plasma operation gases and higher nickel content in the filler metal have both a positive effect on the α/γ phase balance and on pitting resistance of the fusion zone of the weldments.