Aging precipitation behaviors of Nb-contained 316LN SS

Precipitation behaviors of Nb-contained 316LN austenitic stainless steels during isothermally aging at 650, 750 and 800 °C up to 1000 h have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrolytic extraction experiment. The experimental results show that, long-term thermal aging process introduced signification amount of precipitates both at grain boundaries and on dislocations inside austenitic matrix to Nb-contained 316LN SS. The quantitative calculation of precipitates volume fraction confirmed the sensitive aging temperature was approximate 750 °C. The precipitation behavior of minor phases during Nb-contained 316LN SS different aging treatment was summarized. In Nb-contained 316LN SS aging process, Z-CrNbN phase was the first and predominant nitride phase. Nb element addition into 316LN SS, promoted the formation of σ-FeCrMo and η-Fe2Mo phase, restrained the formation of carbide Cr23C6. •Precipitation behaviors of Nb-contained 316LN SS during thermal aging was investigated.•Precipitation reactions, phase perferred nucleation site and sensitive temperature were summarized.•Effect of Nb element addition on precipitation behaviors in 316LN SS thermal aging process.