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- Title
Precipitation within localised chromium-enriched regions in a Type 316H austenitic stainless steel.
- Authors
Warren, A. D.; Griffiths, I. J.; Flewitt, P. E. J.
- Abstract
A Type 316H austenitic stainless steel component containing Cr and impurity element-rich localised regions arising from component fabrication was aged for a prolonged period during service at a temperature of approximately 550 °C. These regions make up approximately 5% of the total volume of the microstructure. Previous work has shown that these regions contain ferrite and carbide precipitates and a finer austenite grain size than the adjacent matrix. The present study has used high-resolution transmission electron microscopy combined with compositional microanalysis to show that these regions have a highly complex microstructure containing G phase, chi phase and intragranular γ′ precipitates within the austenite grains. There is phosphorus migration to the chi austenite phase boundary, and the basis for this equilibrium impurity segregation is discussed. A Cr-depleted region was observed surrounding the chi phase precipitates, and the impact of this on the other precipitates is considered. The diversity of precipitates in these Cr-rich regions means that they behave significantly differently to the bulk material under long-term creep conditions leading to preferred nucleation and growth of creep cavities and the formation of localised creep cracks during service.
- Subjects
CHROMIUM; PRECIPITATION (Chemistry); AUSTENITIC stainless steel; INDUSTRIAL contamination; FABRICATION (Manufacturing); CREEP (Materials)
- Publication
Journal of Materials Science, 2018, Vol 53, Issue 8, p6183
- ISSN
0022-2461
- Publication type
Article
- DOI
10.1007/s10853-017-1748-4