Heat-Affected Zone Characterization of X2CrNiN22-2 Lean Duplex Stainless Steel by Metallographic and Electrochemical Techniques

This research aimed to investigate the heat-affected zone of lean duplex stainless steel grade X2CrNiN22-2. Different heat-affected zone microstructures and grain morphologies were developed by Gleeble simulations. The governing microstructures were evaluated by metallographic techniques and electrochemical corrosion measurements. It was found that the 1200-800 C-degrees cooling time significantly affects the microstructure, austenite content, and corrosion properties. The average austenite content in the case of 1 s cooling time is 30.7 +/- 1%, which increased with the longer cooling times up to 38.6 +/- 0.9%. The rapid cooling times resulted in a more ferritic microstructure, which promoted nitride precipitation in the ferrite grains. The nitride precipitations acted as nucleation sites for pitting initiation in 3.5 wt.% NaCl solution. The lowest pitting potential was measured in the case of the most rapidly cooled sample: 573 +/- 31 mV, while the balanced, annealed microstructure had much better pitting corrosion resistance, showing a pitting potential of 1308 +/- 62 mV vs. the Ag/AgCl (KCl sat.) reference electrode. The results of this research can be used in designing welding parameters for the welding of the X2CrNiN22-2 lean duplex stainless steel.