Microstructural evolution in two variants of NF709 at 1023 and 1073 K

T. Sourmail and H. K. D. H. Bhadeshia

Abstract

The microstructural state of two grades of the creep-resistant austenitic stainless steels NF709, a Fe-20Cr-25Ni (wt%) based steel, has been studied, in the as-received state, after an additional solution-treatment and after static ageing at 1023 and 1073 K. Although the two variants are chemically similar, they exhibit different microstructures following identical heat-treatment. In particular, Z-phase and σ are found in largely different quantities. The study suggests that a seldom observed variant of the η structure, Cr₃Ni₂SiX, is stabilised by nitrogen. Both steels exhibit a yet undocumented precipitation sequence when compared to more conventional austenitic steels (for which the precipitation sequences have been reviewed).

Metallurgical and Materials Transactions A Vol. 36A, 2005, pp. 23-34.

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Download High-Resolution Figures

NF709_1	NF709_10a	NF709_10b
NF709_11	NF709_12a	NF709_12b
NF709_13	NF709_14a	NF709_14b
NF709_14c	NF709_15	NF709_16a
NF709_16b	NF709_16c	NF709_17a
NF709_17b	NF709_2a	NF709_2b
NF709_2c	NF709_3a	NF709_3b
NF709_4a	NF709_4b	NF709_5a
NF709_5b	NF709_5c	NF709_5d
NF709_5e	NF709_5f	NF709_5g
NF709_6a	NF709_6b	NF709_7a
NF709_7b	NF709_8a	NF709_8b
NF709_8c	NF709_8d	NF709_9a
NF709_9b	Zipped file of postscript format figures.

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