Internal oxidation of Ni-Cr-Al alloys under various oxygen partial pressures at 1273 K
Alloys for high temperature application always rely on their ability to form protective, dense Cr2O3 and Al2O3 scales. In case of Ni-Cr binary alloy, a minimum composition of Cr is required for the formation of continuous protective scale. However, addition of small amount of third element such a...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English English |
| Published: |
Trans Tech Publications, Switzerland
2012
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/27472/ http://irep.iium.edu.my/27472/ http://irep.iium.edu.my/27472/ http://irep.iium.edu.my/27472/1/internal_oxidation_of_ni-cr-al_alloys_under_various_oxygen_partial_pressures_at_1273k.pdf http://irep.iium.edu.my/27472/4/27472_Internal%20Oxidation%20of%20Ni-Cr-Al%20Alloys%20under%20_SCOPUS.pdf |
| Summary: | Alloys for high temperature application always rely on their ability to form protective,
dense Cr2O3 and Al2O3 scales. In case of Ni-Cr binary alloy, a minimum composition of Cr is
required for the formation of continuous protective scale. However, addition of small amount of
third element such as Al may results in decrease of required Cr composition to form protective
scale. This study aims to clarify the effect of ternary element on the formation of protective scale
quantitatively. Ni-Cr alloys composed with 2 mass% and 4 mass% of Al were exposed in oxidizing
environment under Cr/Cr2O3, Fe/FeO and Ni/NiO oxygen partial pressure. The oxidation of all
samples is following parabolic rate’s law. XRD and SEM results show that Al2O3 and Cr2O3 are
formed internally. Parabolic rate’s constant of samples oxidized in Ni/NiO oxygen partial pressure
is higher by few magnitude orders. Higher Al concentration decreases the parabolic rate’s constant.
It is concluded that the formation of protective scale is enhanced by the addition of Al as ternary
element in Ni-Cr alloys. |
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