Effect of Solution Treatment on Microstructure and Corrosion Resistance Performance of HIPed Net-Shaped Duplex Stainless Steel SAF2507

This study systematically investigates the effect of solution treatment on the microstructure and corrosion resistance of duplex stainless steel SAF2507 fabricated by direct hot isostatic pressing (HIP). The HIP specimens were solution treated at 1080 °C for 1 h, followed by comprehensive characterization using SEM, EDS, EBSD, XRD, XPS, and electrochemical testing in 3.5 wt% NaCl solution. Results indicate that solution treatment effectively dissolved intermetallic precipitates, promoted a more uniform distribution of ferrite and austenite phases, and reduced microstructural heterogeneity. Electrochemical impedance spectroscopy and potentiodynamic polarization tests showed that the treated samples exhibited a wider passive region and higher charge transfer resistance, indicating enhanced passivation behavior. XPS analysis further revealed an increased proportion of Cr2O3 and O2− and decreased Fehy3+ and H2O content in the passive film, suggesting improved compactness and chemical stability. Surface morphology analysis confirmed a significant reduction in pitting corrosion after treatment. These findings demonstrate that solution treatment is an effective post-processing method to enhance the corrosion resistance of HIP-fabricated SAF2507 duplex stainless steel.