Effect of Solution Annealing Treatment Parameters on Sensitization Behavior of SS321

Abstract Stabilized SS321 can get sensitized during multi-pass welding, due to dissolution of TiC and subsequent chromium carbide precipitation in the sensitization temperature range. Hence, it is important to understand the TiC dissolution behavior in SS321 and its effect on sensitization. In this work, sensitization behavior of SS321 was studied through a series of solution annealing heat treatments in the range of 1100-1200 °C for durations of 0.25-1 h, followed by heat treatments at 675 °C for durations in the range of 1-50 h, which has not been reported earlier. Characterization using optical microscopy, SEM and 3D optical profilometer was done, and results were correlated with degree of sensitization (DOS). TiC dissolved more at 1200 °C as compared to 1100 °C, resulting in higher DOS after subsequent heat treatment at 675 °C. Increase in holding time at 1200 °C increased the DOS value till 0.5 h followed by no appreciable change till 1 h. This was explained by considering the opposing effects of grain size and TiC dissolution on DOS. The effect of aging for 50 h at 675 °C on DOS value was discussed and correlated with volume of grain boundary attacked region evaluated from 3D optical profilometer.