Stability of the nitrogen S-phase in austenitic stainless steel

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  • School of Metallurgy and Materials


The stability of nitrogen 'S-phase' has been investigated by means of isothermal annealing and TEM in-situ heating observations. The results show that S-phase is a metastable phase. When thermally annealed at certain temperatures for a long enough time, the nitrogen S-phase decomposes into chromium nitrides enveloped by chromium depleted austenite (γN). The incubation time is found to be temperature dependent, ranging from several minutes at 600°C or over to a couple of years at 300°C or below. The decomposition of the S-phase is typical of that for a diffusion limited or thermally activated transformation. A preliminary isothermal transformation (IT) diagram has been constructed, which provides a basic guideline for the application of low temperature plasma nitrided 316 austenitic stainless steel.


Original languageEnglish
Pages (from-to)901-907
Number of pages7
JournalZeitschrift fuer Metallkunde
Issue number11
Publication statusPublished - 1 Nov 1999