In this research, three types of super austenitic stainless steel (SASS) with nitrogen levels of 0.2, 0.28, and 0.38 wt.% were developed. By maintaining a relatively high manganese content of approximately 1.5 wt.% and nickel content of around 18 wt.%, nitrogen was fully incorporated into the austenite, resulting in alloy samples designated as 0.2N, 0.3N and 0.4N. The hot-rolled plates of these alloys underwent a solution treatment at 1180°C for 30 min, followed by aging at 950°C for durations of 30 min, 2 h and 6 h, respectively. The influence of nitrogen content on phase precipitation behaviour was examined through various micro-structure characterisation techniques. The corrosion resistance of the samples was further evaluated using potentiodynamic polarisation experiments, Electrochemical impedance spectroscopy (EIS) and double loop-electrochemical potentiokinetic reactivation (DL-EPR) method. The results indicated that with an increase in nitrogen (N) addition, the quantity of σ phases decreased while and the formation of Cr₂N phases increased during the same aging period. Furthermore, at the same aging duration, the 0.3N SASS exhibited the highest pitting resistance and the lowest degree of sensitization (DOS) value compared to all other steels, attributed to the minimal precipitates present along the grain boundaries.

The inhibition of Mo segregation and phase precipitation is vital for improving the hot workability and corrosion resistance of superaustentic stainless steels (SASS). The boron non-equilibrium segregation of S31254 SASS was implemented through solid solution, air cooling, and diffusion at low-temperature treatment (SADT). The precipitation process and intergranular corrosion (IGC) of S31254 SASS with various boron distributions were researched at a sensitive temperature. The second phases were observed and identified by SEM and TEM. IGC susceptibility was evaluated by double-loop potentiodynamic reactivation (DL-EPR) measurements. The SADT treatment promoted more segregation of B at the grain boundary, leading to lower amounts of grain boundary precipitation before aging for 6 h. The decrease of σ phases in B-regulated samples enhances the IGC resistance, compared with the samples without B addition specimens.