High-temperature sulphidation behavior of niobium
- Univ. of Northumbria, Newcastle-upon-Tyne (United Kingdom)
The high temperature degradation behavior of niobium has been studied at temperatures of 750, 850 and 950 C in H{sub 2}/H{sub 2}S gas mixtures, such that the partial pressure of sulphur was 10{sup {minus}1} Pa. Periods of exposure varied from 4 hours to 240 hours. For all periods of exposure the reaction product was identified as NbS{sub 2} Parabolic kinetics were exhibited for all conditions of exposure. The parabolic rate constants were determined as 10{sup {minus}13}/10{sup {minus}11} g{sup 2}/cm{sup 4}/sec. Single layer reaction products were identified in most cases. An indication of a sub-scale formation was, however, noted for the longest period of exposure at the higher partial pressure of sulphur. The method of degradation was by outward diffusion of sulphur ions. The activation energy was determined as 154 kJ/mole at the specified partial pressure of sulphur (10{sup {minus}1}Pa). It was already known that niobium was resistant to sulphidizing atmospheres, displaying a low to very low rate of sulphidation. It could be argued, therefore, that the inclusion of niobium into a coating based on a conventional superalloy could result in the formations of a protective niobium sulphide in selective atmospheres.
- OSTI ID:
- 233978
- Report Number(s):
- CONF-950908-; ISBN 0-87170-539-7; TRN: IM9624%%82
- Resource Relation:
- Conference: 2. international conference on heat resistant materials, Gatlinburg, TN (United States), 11-14 Sep 1995; Other Information: PBD: 1995; Related Information: Is Part Of Heat-resistant materials 2. Conference proceedings of the 2. international conference on heat-resistant materials; Natesan, K. [ed.] [Argonne National Lab., IL (United States)]; Ganesan, P. [ed.] [INCO Alloys International, Inc., Huntington, WV (United States)]; Lai, G.Y. [ed.] [Haynes International, Inc., Kokomo, IN (United States)]; PB: 687 p.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
01 COAL, LIGNITE, AND PEAT
NIOBIUM
SULFIDATION
COAL GASIFICATION
MATERIALS
HYDROGEN
HYDROGEN SULFIDES
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
KINETICS
CHEMICAL REACTIONS
ACTIVATION ENERGY
OPTICAL MICROSCOPY
SCANNING ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ELECTRON MICROPROBE ANALYSIS
NIOBIUM SULFIDES
WEIGHT MEASUREMENT
SCALING
EXPERIMENTAL DATA