Effect of Heat Energy Input on Electrochemical Properties of Solution-Annealed Super-Duplex Stainless Steel UNS S 32750 Laser Welding
Chang-Won Sung, Byung-Hyun Shin, Wonsub Chung
Abstract
Super duplex stainless steel (SDSS) exhibits a high corrosion resistance in seawater because of the combination of austenite and ferrite present. Laser welding breaks the balance between austenite and ferrite owing to changes in the microstructure during the ferritization. Therefore, the corrosion resistance of the weld zone on SDSS depends on the heat energy input. In this study, we examined the electrochemical behavior of SDSS after laser welding at different heat energy inputs. It was observed that laser welding reduced the corrosion resistance of SDSS, which depended on the heat energy input. The corrosion resistance of the surface of welded SDSS was determined by analyzing the open circuit potential, potentiodynamic polarization tests, critical pitting temperature (CPT), and electrochemical impedance spectroscopy. An increase in the heat energy input decreased the corrosion resistance and the thickness of SDSS and the passivation layer, respectively. However, after full penetration, the CPT of SDSS increased from 48 to 61 °C. The electrochemical properties of SDSS was affected by the surface reactivity and shape of the bead.