The pitting corrosion mechanism in additively manufactured Ni over-alloyed 22Cr duplex stainless steel at different temperatures

Laser powder bed fusion (LPBF) produced type 2205 duplex stainless steel (DSS) exhibited a nearly fully ferritic microstructure due to rapid solidification. In this study, nickel alloy and DSS 2205 powder were blended as raw materials to fabricate LPBF 22Cr DSS with an austenite content exceeding 20 %. However, variations in microstructure along different build directions resulted in disparities in pitting corrosion resistance. In 0.6 M NaCl solution, the critical pitting potentials (E_pit) of the XOZ and YOZ planes were 190 mV and 77 mV higher, respectively, than that of the XOY plane at 60 °C and 70 °C. Conversely, when the electrolyte temperature increased to 80 °C, the XOY plane displayed a 150 mV higher E_pit compared to the XOZ and YOZ planes. Potentio-static pulse testing (PPT) revealed two distinct pitting nucleation sites on the XOY plane, with three preferred nucleation sites were observed on the YOZ and XOZ planes across the temperature range of 60–80 °C. The driving force for pit nucleation was influenced by electrolyte temperature, leading to a shift in E_pit values: the XOY plane exhibited the lowest E_pit at 60 °C and 70 °C, then became the highest at 80 °C.