Metallographic preparation and degradation of the τ-phase (FeAl 2S 4) formed after high-temperature oxidation–sulfidation of Fe–Al alloys
The stability of corrosion products formed after high-temperature exposure of an Fe–5 wt.% Al alloy in an oxidizing–sulfidizing environment was investigated both during metallographic preparation and subsequent exposure to the ambient environment. The primary phases formed were an outer layer of iro...
Gespeichert in:
Veröffentlicht in: | Materials characterization 2000-09, Vol.45 (3), p.241-249 |
---|---|
Hauptverfasser: | , , |
Format: | Artikel |
Sprache: | eng |
Schlagworte: | |
Online-Zugang: | Volltext |
Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
Zusammenfassung: | The stability of corrosion products formed after high-temperature exposure of an Fe–5 wt.% Al alloy in an oxidizing–sulfidizing environment was investigated both during metallographic preparation and subsequent exposure to the ambient environment. The primary phases formed were an outer layer of iron sulfide (Fe
1−
x
S) and an inner layer composed of τ-plates (FeAl
2S
4) and iron sulfide particles. No difficulties were found concerning the stability of the iron sulfide phases, but it is known that the τ-phase is easily hydrolyzed by water. Therefore, standard metallographic procedures where water is used as a lubricant and/or cleansing solution during preparation could not be exercised. Using scanning electron microscopy, energy dispersive spectroscopy, and electron probe microanalysis, the effect of the use of various lubricants and/or cleansing solutions was examined in order to produce good quality, polished cross-sections of the corrosion scales. The best results were obtained using 200-proof dehydrated ethyl alcohol as the lubricant and cleansing solution. It was also observed that post-exposure of polished samples to the ambient environment degraded the microstructure with time. It is believed that moisture from the air reacted with the τ-phase, resulting in the evolution of hydrogen sulfide gas. |
---|---|
ISSN: | 1044-5803 1873-4189 |
DOI: | 10.1016/S1044-5803(00)00082-6 |