Pitting evolution of hyper duplex stainless steel 2707 at nose temperature by electrochemical tests and developed mixed potential model

Abstract

Effect of aging at 900 ℃ on the microstructure and pitting of HDSS 2707 was examined. The pitting resistance of HDSS 2707 decreases over the first 10 h because of the presence of the secondary precipitates, and then increases due to Cr/Mo back diffusion from the matrix into the Cr/Mo-depleted regions. Pitting nucleates around the sigma phase, and propagates within the ferrite, but is blocked by austenite. The developed Mixed Potential Model (MPM) was used to analyze the character of the barrier layer, which is in accordance with the potentiodynamic polarization experiments and morphological observation of pitting.