Effect of Solution Treatment Temperature on Microstructure, Mechanical Properties and Corrosion Resistance of Ultra-High Nitrogen Stainless Steel

Ultra-high nitrogen (N > 3 wt pct) austenitic stainless steel has been prepared by powder metallurgy. However, a large amount of nitride (CrN) precipitation leads to a decrease in corrosion resistance. In order to further improve the comprehensive performance of ultra-high nitrogen austenitic stainless steel, high temperature solution treatment has been carried out in this work. The microstructure, mechanical properties, and corrosion resistance of samples treated by different solution temperatures were investigated through various characterization and testing methods. The results indicate that high temperature solution treatment can promote the decomposition and spheroidization of nitrides, improve the microstructural morphology and distribution uniformity, and significantly enhance corrosion resistance. Especially the solution treatment at 1200 °C achieved the optimal combination of mechanical properties and corrosion resistance. Based on the analysis of TEM and EBSD, this enhancement is attributed to the reduction in both the quantity and size of CrN precipitates following the solution treatment. Additionally, the interface between CrN and austenite becomes less distinct, accompanied by a more ordered atomic arrangement. And, an increase in the density of austenite dislocations and the proportion of small-angle grain boundaries is observed.