Analysis of ferrite formed in a 321 grade austenitic stainless steel.pdf (984.92 kB)
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Analysis of ferrite formed in 321 grade austenitic stainless steel

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journal contribution
posted on 30.07.2015 by Graham Green, Rebecca Higginson, Simon Hogg, Sarah Spindler, Christopher Hamm, J. Najorka
A significant fraction of ferrite has been identified in a 321 grade austenitic stainless steel in the solution heat treated condition. The microstructures were analysed using electron backscatter diffraction, energy dispersive X-ray spectroscopy and X-ray diffraction (XRD) and the stability of the ferrite investigated using heat treatments in a tube furnace, dilatometry and high temperature XRD. The ferrite dissolved ,800uC, then formed again on cooling at temperatures under 200uC. Thermodynamic predictions showed a significant ferrite content at room temperature under equilibrium conditions, and the DeLong diagrams predict an austenitezmartensite microstructure in the cast condition. Sensitivity analysis on the DeLong diagram has shown that the nitrogen content had a large effect on the austenite stability. The instability of the austenite and the subsequent transformation to ferrite on cooling can be attributed to low nitrogen content measured in the as received material. It was found that thermal aging of the material caused further transformation of austenite to ferrite as well as the formation of sigma phase that appears higher in nitrogen than the matrix phases. The diffusion of nitrogen into sigma phase may cause instability of the austenite, which could cause further transformation of austenite to ferrite on cooling from the aging temperature. The transformation of austenite to ferrite is known to be accompanied by an increase in volume, which may be of relevance to components made with tight dimensional tolerances.

Funding

The authors would like to thank EDF Energy and Loughborough University for providing the funding and the materials for this project.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Published in

MATERIALS SCIENCE AND TECHNOLOGY

Volume

31

Issue

4

Pages

418 - 425 (8)

Citation

GREEN, G. ... et al, 2015. Analysis of ferrite formed in 321 grade austenitic stainless steel. Materials Science and Technology, 31 (4), pp.418-425.

Publisher

Maney Publishing / © Institute of Materials, Minerals and Mining

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2015

ISSN

0267-0836

Language

en

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