Clustering and ordering of nitrogen in nuclear grade 316LN austenitic stainless steel

The high misfit strains associated with nitrogen addition and the high chemical affinity with chromium result in a significant driving force for the formation of Cr-N clusters in austenitic steels. The microstructural signatures of cluster formation in nuclear grade 316LN austenitic stainless steel during the early stages of aging at 1123 K are discussed. Aging beyond 25 h results in transformation of fcc clusters to hexagonal Cr2N precipitates. Strain induced ordering of nitrogen in Cr2N precipitates due to continued ageing is also highlighted