Effect of Solution Annealing on Austenite Morphology and Pitting Corrosion of Super Duplex Stainless Steel UNS S 32750

摘要

The pitting corrosion resistance of super duplex stainless steel (SDSS) varies depending on heattreatment conditions. Therefore, in this study, the volume fraction and morphology of austenite on SDSS were controlled in 6 samples, and the effect on the pitting corrosion after solution annealing was analyzed to of the critical pitting temperature (CPT). The pitting-resistance equivalent (PRE = wt % Cr + 3.3 wt % Mo + 16 wt % N) was became equal by solution annealing, but the CPT exhibited varying values. Despite heat treatment of the solution annealing, the CPT increased by 15.9 °C from 67.5 °C to 83.4 °C. The solution annealing removed the segregation of the chemical composition and assisted in improving the PRE; however, it not removed in a non-uniform morphology of austenite. Therefore, the corrosion resistance of SDSS can be optimized by appropriately controlling the morphology of austenite during the manufacturing process.