Abstract
Diffusion processes in Al 2 O 3 scales formed on NiCrAl + Zr alloys were studied by the proton activation technique employing the 18 O isotope as a tracer. The 18 O profiles identified a zone of oxide penetration beneath the external scale. Both this subscale formation and the outer Al 2 O 3 scale thickness were shown by this technique to increase with Zr content in the alloy. Estimated k p 's from scale thicknesses were in agreement with gravimetric measurements for various Zr levels. Alternate exposures in O and 18 O revealed that oxygen inward transport was the primary growth mechanism. A qualitative analysis of these 18 O profiles indicated that the oxygen transport was primarily via short-circuit paths, such as grain boundaries.
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Reddy, K.P.R., Smialek, J.L. & Cooper, A.R. 18O Tracer studies of Al2O3 scale formation on NiCrAl alloys. Oxid Met 17, 429–449 (1982). https://doi.org/10.1007/BF00742122
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DOI: https://doi.org/10.1007/BF00742122