1989 Volume 7 Issue 1 Pages 94-100
22% Cr-3% Mo duplex stainless steels in which Ni and N contents were varied independently were prepared and base metal and TIG weld metal were subjected to pitting corrosion tests in 6% FeCl3. The critical pitting temperature at which pitting corrosion occurred was evaluated and the pitting site was observed. The pitting test results were examined metallurgically from the viewpoint of the precipitation of Cr carbide and nitride and the distribution of elements between ferrite phase and austenite phase.
Since the pitting corrosion resistance of austenite phase is mainly dominant in base metal, the decrease of Ni and the increase of N cause the increase of N in austenite phase and improve the total corrosion resistance. As the decrease of Ni and N reduces the generation of austenite phase and results in the precipitation of Cr carbide and nitride in weld metal, the decrease of Ni and N deteriorates the pitting corrosion resistance of weld metal.
