ISSN 2594-5327
48º Congresso anual — Vol. 48, Num. 1 (1993)
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The corrosion of alloys based on Fe, Co, and Ni and containing 15 and 30 wt.% Nb has been studied at 800 °C in H₂-H₂S mixtures providing 10⁻⁶ atm S₂, and also 10⁻⁴ atm S₂ for the Co-Nb alloys. The scales formed on the Fe-Nb and Co-Nb alloys under 10⁻⁶ atm S₂ were duplex and presented an outer layer of single-phase base-metal sulfide and an inner complex layer containing both Nb and the base metal. The Co-Nb alloys corroded under 10⁻⁶ atm S₂ formed only the double sulfide mixed with particles of a Co-rich metallic phase. Finally, the Ni-Nb alloys formed only one complex layer containing a mixture of Ni sulfide, double sulfide, and particles of metallic nickel. The addition of Nb to iron and cobalt significantly reduced their corrosion rates. The effect was maximum for the Co-Nb alloys under 10⁻⁶ atm S₂, when pure Co was not attacked. However, under all conditions, the Fe-Nb and Co-Nb alloys corroded more rapidly than pure niobium. The fast corrosion of the two Ni-Nb alloys is mainly a result of the formation of a liquid Ni-S solution, which allows rapid transport of metals outward and possibly also of sulfur inward, eliminating solid-state diffusion as a rate-controlling step of the reaction.
Palavras-chave
Binary alloys, Niobium effect, Sulfidation, High temperatures, H₂-H₂S atmosphere
Como citar
Niu, Y.; Gesmundo, F.; Viani, F.; Pizzo, P..
The Sulfidation Behavior of Fe-Nb, Co-Nb and Ni-Nb Alloys in H₂-H₂S Mixtures at 800°C,
p. 215-244.
In: 48º Congresso anual,
Rio de Janeiro, Brasil,
1993.
ISSN: 2594-5327, DOI 10.5151/2594-5327-48v1-215-244
