In:
Metallurgical and Materials Transactions A, Springer Science and Business Media LLC, Vol. 52, No. 11 ( 2021-11), p. 4957-4973
Abstract:
A Fe–3wt pctSi alloy was gas nitrided to study the effect of Si on the Fe nitride formation. Both ε -Fe 3 N 1+ x and γ ′-Fe 4 N were observed at nitriding conditions only allowing to form single-phase γ ′ layers in pure α -Fe. During short nitriding times, ε and γ ′ simultaneously grow in contact with Si-supersaturated α -Fe(Si). Both nitrides almost invariably exhibit crystallographic orientation relationships with α -Fe, which are indicative of a partially displacive transformation of α -Fe being involved in the initial formation of ε and γ ′. Due to Si constraining the Fe nitride growth, such transformation mechanism becomes highly important to the nitride layer formation, causing α -Fe-grain-dependent variations in the nitride layer morphology and thickness, as well as microstructure refinement within the nitride layer. After prolonged nitriding, α -Fe is depleted in Si due the pronounced precipitation of Si-rich nitride in α -Fe. The growth mode of the compound layer changes, now advancing by conventional planar-type growth. During nitriding times of 1 to 48 hours, ε exists in contact with the NH 3 /H 2 -containing nitriding atmosphere at a nitriding potential of 1 atm −1/2 and 540 °C, only allowing for the formation of γ ′ in pure Fe, indicating that Si affects the thermodynamic stability ranges of ε and γ ′.
Type of Medium:
Online Resource
ISSN:
1073-5623
,
1543-1940
DOI:
10.1007/s11661-021-06441-z
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2021
detail.hit.zdb_id:
1179415-X
detail.hit.zdb_id:
2037517-7
detail.hit.zdb_id:
192156-3
SSG:
19,1
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