ISSN 2594-5327
49º Congresso anual — Vol. 49, Num. 1 (1994)
Título
Autoria
DOI
Downloads
Resumo
The oxidation of two Co-Nb alloys containing 15 and 30 wt.% Nb has been studied at 800°C both in 1 atm of pure O₂ and in H₂–CO₂ mixtures providing an oxygen pressure of 10⁻²⁰ atm, below the dissociation pressure of cobalt oxide. The samples of both alloys corroded at the low oxygen pressure show only an internal oxidation region composed of a mixture of alpha cobalt and niobium oxides (Nb₂O₅ or/and NbO₂), which formed from the Co₃Nb phase. At high oxygen pressures the two alloys formed an outer scale containing an outermost layer of pure CoO followed by an inner layer containing a mixture of a double Co-Nb oxide with CoO. Finally, a region of internal oxidation of Nb developed also within the alloy. No layer of Nb-depleted alloy formed at the interface between the unaffected alloy and the region of internal oxidation at both oxygen pressures. The corrosion mechanism is examined with special reference to the effect of the low solubility of niobium in cobalt and to the relation between the microstructure of the alloys and of the scales.
Palavras-chave
Co-Nb alloys, high temperature, oxidation, corrosion, microstructure
Como citar
Monteiro, M.J.; Rizzo, F.C.; Lopes, M.F. Silva; Niu, Y.; Gesmundo, F..
THE OXIDATION OF TWO Co-Nb ALLOYS AT 800°C UNDER 10⁻²⁰ AND 1 ATM OXYGEN,
p. 5004-5019.
In: 49º Congresso anual,
Rio de Janeiro, Brasil,
1994.
ISSN: 2594-5327, DOI 10.5151/2594-5327-49v11-01-16
