Co-existence of γ'N phase and γN phase on nitrided austenitic Fe–Cr–Ni alloys- I. experiment

H. L. Che, S. Tong, K. S. Wang, M. K. Lei*, Marcel A. J. Somers

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The formation of a metastable and nitrogen-supersaturated f.c.c. interstitial solid solution layer on Fe–Cr–Ni austenitic stainless steel at a moderate temperature around 650–720 K is not entirely understood. In the present work, three groups of austenitic Fe–Cr–Ni alloys, containing systematic variations of chromium, nickel and iron contents were nitrided by plasma-based low-energy ion implantation at 653 K for 4 h and investigated with light-optical microscopy (LOM), electron probe microanalysis (EPMA), (grazing incidence) X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial AISI 304L was included for comparison. For the austenitic alloys with a Cr content below 12 wt.%, a duplex layer is observed in the nitrided case where the interface between the top layer, consisting of γ'-Fe4N like ordered γ'N, and the disordered γN (nitrogen enriched austenite) zone underneath is associated with a decrease in N content. For the alloys with a Cr-content over 12 wt.%, a featureless continuous zone is observed with LOM and a gradual decrease in nitrogen content is measured with EPMA. Nevertheless, a similar duplex structure of outer γ'-Fe4N like ordered γ'N and inner γN is confirmed by XRD and TEM for all nitrided alloys, irrespective of the Cr content. The results are discussed in terms of the short-range order (SRO) promoted by the Cr–N interaction and long-range order (LRO) caused by the Fe–N interaction.
Original languageEnglish
JournalActa Materialia
Volume177
Pages (from-to)35-45
ISSN1359-6454
DOIs
Publication statusPublished - 2019

Keywords

  • Austenitic stainless steels
  • Isostructurality
  • Nitriding
  • Order–disorder phenomena
  • Phase coexistence

Cite this

@article{bc013eb7eec049dbac542d7679a47d65,
title = "Co-existence of γ'N phase and γN phase on nitrided austenitic Fe–Cr–Ni alloys- I. experiment",
abstract = "The formation of a metastable and nitrogen-supersaturated f.c.c. interstitial solid solution layer on Fe–Cr–Ni austenitic stainless steel at a moderate temperature around 650–720 K is not entirely understood. In the present work, three groups of austenitic Fe–Cr–Ni alloys, containing systematic variations of chromium, nickel and iron contents were nitrided by plasma-based low-energy ion implantation at 653 K for 4 h and investigated with light-optical microscopy (LOM), electron probe microanalysis (EPMA), (grazing incidence) X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial AISI 304L was included for comparison. For the austenitic alloys with a Cr content below 12 wt.{\%}, a duplex layer is observed in the nitrided case where the interface between the top layer, consisting of γ'-Fe4N like ordered γ'N, and the disordered γN (nitrogen enriched austenite) zone underneath is associated with a decrease in N content. For the alloys with a Cr-content over 12 wt.{\%}, a featureless continuous zone is observed with LOM and a gradual decrease in nitrogen content is measured with EPMA. Nevertheless, a similar duplex structure of outer γ'-Fe4N like ordered γ'N and inner γN is confirmed by XRD and TEM for all nitrided alloys, irrespective of the Cr content. The results are discussed in terms of the short-range order (SRO) promoted by the Cr–N interaction and long-range order (LRO) caused by the Fe–N interaction.",
keywords = "Austenitic stainless steels, Isostructurality, Nitriding, Order–disorder phenomena, Phase coexistence",
author = "Che, {H. L.} and S. Tong and Wang, {K. S.} and Lei, {M. K.} and Somers, {Marcel A. J.}",
year = "2019",
doi = "10.1016/j.actamat.2019.07.019",
language = "English",
volume = "177",
pages = "35--45",
journal = "Acta Materialia",
issn = "1359-6454",
publisher = "Pergamon Press",

}

Co-existence of γ'N phase and γN phase on nitrided austenitic Fe–Cr–Ni alloys- I. experiment. / Che, H. L.; Tong, S.; Wang, K. S.; Lei, M. K.; Somers, Marcel A. J.

In: Acta Materialia, Vol. 177, 2019, p. 35-45.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Co-existence of γ'N phase and γN phase on nitrided austenitic Fe–Cr–Ni alloys- I. experiment

AU - Che, H. L.

AU - Tong, S.

AU - Wang, K. S.

AU - Lei, M. K.

AU - Somers, Marcel A. J.

PY - 2019

Y1 - 2019

N2 - The formation of a metastable and nitrogen-supersaturated f.c.c. interstitial solid solution layer on Fe–Cr–Ni austenitic stainless steel at a moderate temperature around 650–720 K is not entirely understood. In the present work, three groups of austenitic Fe–Cr–Ni alloys, containing systematic variations of chromium, nickel and iron contents were nitrided by plasma-based low-energy ion implantation at 653 K for 4 h and investigated with light-optical microscopy (LOM), electron probe microanalysis (EPMA), (grazing incidence) X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial AISI 304L was included for comparison. For the austenitic alloys with a Cr content below 12 wt.%, a duplex layer is observed in the nitrided case where the interface between the top layer, consisting of γ'-Fe4N like ordered γ'N, and the disordered γN (nitrogen enriched austenite) zone underneath is associated with a decrease in N content. For the alloys with a Cr-content over 12 wt.%, a featureless continuous zone is observed with LOM and a gradual decrease in nitrogen content is measured with EPMA. Nevertheless, a similar duplex structure of outer γ'-Fe4N like ordered γ'N and inner γN is confirmed by XRD and TEM for all nitrided alloys, irrespective of the Cr content. The results are discussed in terms of the short-range order (SRO) promoted by the Cr–N interaction and long-range order (LRO) caused by the Fe–N interaction.

AB - The formation of a metastable and nitrogen-supersaturated f.c.c. interstitial solid solution layer on Fe–Cr–Ni austenitic stainless steel at a moderate temperature around 650–720 K is not entirely understood. In the present work, three groups of austenitic Fe–Cr–Ni alloys, containing systematic variations of chromium, nickel and iron contents were nitrided by plasma-based low-energy ion implantation at 653 K for 4 h and investigated with light-optical microscopy (LOM), electron probe microanalysis (EPMA), (grazing incidence) X-ray diffraction (XRD) and transmission electron microscopy (TEM). Commercial AISI 304L was included for comparison. For the austenitic alloys with a Cr content below 12 wt.%, a duplex layer is observed in the nitrided case where the interface between the top layer, consisting of γ'-Fe4N like ordered γ'N, and the disordered γN (nitrogen enriched austenite) zone underneath is associated with a decrease in N content. For the alloys with a Cr-content over 12 wt.%, a featureless continuous zone is observed with LOM and a gradual decrease in nitrogen content is measured with EPMA. Nevertheless, a similar duplex structure of outer γ'-Fe4N like ordered γ'N and inner γN is confirmed by XRD and TEM for all nitrided alloys, irrespective of the Cr content. The results are discussed in terms of the short-range order (SRO) promoted by the Cr–N interaction and long-range order (LRO) caused by the Fe–N interaction.

KW - Austenitic stainless steels

KW - Isostructurality

KW - Nitriding

KW - Order–disorder phenomena

KW - Phase coexistence

U2 - 10.1016/j.actamat.2019.07.019

DO - 10.1016/j.actamat.2019.07.019

M3 - Journal article

VL - 177

SP - 35

EP - 45

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

ER -