ISSN 2594-5327
49º Congresso anual — Vol. 49, Num. 1 (1994)
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The oxidation of two Ni-Nb alloys containing 15 and 30 wt.% Nb has been studied at 800°C both in 1 atm of pure O₂ and in an H₂–CO₂ mixture providing an oxygen pressure of 10⁻²⁰ atm, below the dissociation pressure of nickel oxide. The scales formed on both alloys at 10⁻²⁰ atm O₂ show only an internal oxidation region composed of a mixture of alpha nickel and niobium oxides (Nb₂O₅ or/and NbO₂), which formed from both Ni₃Nb and Ni₆Nb. At high oxygen pressures the two alloys formed an outer scale containing an outermost layer of pure NiO followed by an inner layer containing mainly a double Ni-Nb oxide mixed with NiO. Finally, a region of internal oxidation of Nb also developed within the alloy. A thin layer of Nb-depleted alloy phase 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 nickel.
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Ni-Nb alloys, high temperature, oxidation, oxygen pressure, internal oxidation
Como citar
Oliveira, J.F.; Rizzo, F.C.; Lopes, M.F. Silva; Niu, Y.; Gesmundo, F..
The Oxidation of Two Ni-Nb Alloys at 800°C under 10⁻²⁰ and 1 atm Oxygen,
p. 5264-5277.
In: 49º Congresso anual,
Rio de Janeiro, Brasil,
1994.
ISSN: 2594-5327, DOI 10.5151/2594-5327-49v11-261-274
