Thermal expansion and phase transformations of nitrogen-expanded austenite studied with in situ synchrotron X-ray diffraction

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Abstract

Nitrogen-expanded austenite, _N, with high and low nitrogen contents was produced from AISI 316 grade stainless steel powder by gaseous nitriding in ammonia/hydrogen gas mixtures. In situ synchrotron X-ray diffraction was applied to investigate the thermal expansion and thermal stability of expanded austenite in the temperature range 385–920 K. Evaluation of the diffractograms of the sample with a high nitrogen content, corresponding to an occupancy of the interstitial lattice of 56%, with Rietveld refinement yielded a best convergence after including the stacking fault probability as a fitting parameter. The stacking fault density is constant for temperatures up to 680 K, whereafter it decreases to nil. Surprisingly, a transition phase with composition M4N (M = Fe, Cr, Ni, Mo) appears for temperatures above 770 K. The linear coefficient of thermal expansion depends on the nitrogen content and is lowest for the sample with a high level of nitrogen.
Original languageEnglish
JournalJournal of Applied Crystallography
Volume47
Pages (from-to)819–826
ISSN0021-8898
DOIs
Publication statusPublished - 2014

Cite this

@article{54758ed7f7de4636bee1b6ae1c98d1a5,
title = "Thermal expansion and phase transformations of nitrogen-expanded austenite studied with in situ synchrotron X-ray diffraction",
abstract = "Nitrogen-expanded austenite, _N, with high and low nitrogen contents was produced from AISI 316 grade stainless steel powder by gaseous nitriding in ammonia/hydrogen gas mixtures. In situ synchrotron X-ray diffraction was applied to investigate the thermal expansion and thermal stability of expanded austenite in the temperature range 385–920 K. Evaluation of the diffractograms of the sample with a high nitrogen content, corresponding to an occupancy of the interstitial lattice of 56{\%}, with Rietveld refinement yielded a best convergence after including the stacking fault probability as a fitting parameter. The stacking fault density is constant for temperatures up to 680 K, whereafter it decreases to nil. Surprisingly, a transition phase with composition M4N (M = Fe, Cr, Ni, Mo) appears for temperatures above 770 K. The linear coefficient of thermal expansion depends on the nitrogen content and is lowest for the sample with a high level of nitrogen.",
author = "Bastian Brink and Kenny St{\aa}hl and Christiansen, {Thomas Lundin} and Somers, {Marcel A. J.}",
year = "2014",
doi = "10.1107/S1600576714005214",
language = "English",
volume = "47",
pages = "819–826",
journal = "Journal of Applied Crystallography",
issn = "0021-8898",
publisher = "Wiley-Blackwell",

}

TY - JOUR

T1 - Thermal expansion and phase transformations of nitrogen-expanded austenite studied with in situ synchrotron X-ray diffraction

AU - Brink, Bastian

AU - Ståhl, Kenny

AU - Christiansen, Thomas Lundin

AU - Somers, Marcel A. J.

PY - 2014

Y1 - 2014

N2 - Nitrogen-expanded austenite, _N, with high and low nitrogen contents was produced from AISI 316 grade stainless steel powder by gaseous nitriding in ammonia/hydrogen gas mixtures. In situ synchrotron X-ray diffraction was applied to investigate the thermal expansion and thermal stability of expanded austenite in the temperature range 385–920 K. Evaluation of the diffractograms of the sample with a high nitrogen content, corresponding to an occupancy of the interstitial lattice of 56%, with Rietveld refinement yielded a best convergence after including the stacking fault probability as a fitting parameter. The stacking fault density is constant for temperatures up to 680 K, whereafter it decreases to nil. Surprisingly, a transition phase with composition M4N (M = Fe, Cr, Ni, Mo) appears for temperatures above 770 K. The linear coefficient of thermal expansion depends on the nitrogen content and is lowest for the sample with a high level of nitrogen.

AB - Nitrogen-expanded austenite, _N, with high and low nitrogen contents was produced from AISI 316 grade stainless steel powder by gaseous nitriding in ammonia/hydrogen gas mixtures. In situ synchrotron X-ray diffraction was applied to investigate the thermal expansion and thermal stability of expanded austenite in the temperature range 385–920 K. Evaluation of the diffractograms of the sample with a high nitrogen content, corresponding to an occupancy of the interstitial lattice of 56%, with Rietveld refinement yielded a best convergence after including the stacking fault probability as a fitting parameter. The stacking fault density is constant for temperatures up to 680 K, whereafter it decreases to nil. Surprisingly, a transition phase with composition M4N (M = Fe, Cr, Ni, Mo) appears for temperatures above 770 K. The linear coefficient of thermal expansion depends on the nitrogen content and is lowest for the sample with a high level of nitrogen.

U2 - 10.1107/S1600576714005214

DO - 10.1107/S1600576714005214

M3 - Journal article

VL - 47

SP - 819

EP - 826

JO - Journal of Applied Crystallography

JF - Journal of Applied Crystallography

SN - 0021-8898

ER -