ISSN:
1573-4889
Keywords:
nickel alloys
;
cobalt alloys
;
oxidation rate
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Oxidation of nickel- and cobalt-base alloys, containing small additions of a higher valent second metal, in oxygen or air at high temperatures results in the formation of relatively complicated scale morphologies which change subtly with increasing additions of the second element and its characteristics. The various factors that can influence the oxidation behavior of such alloys are assessed and correlated with the oxidation kinetics and scale morphology types. For very dilute alloys the increase in oxidation rate compared with that of the corresponding pure metal (nickel or cobalt) is largely due to doping of the external oxides. However, once the solubility limit of the second metal in this oxide is exceeded, additional increases in second metal content of the alloy can either increase further or decrease the oxidation rate. The exact behavior depends on the relative interplay of factors such as internal oxide formation and coalescence, blocking effects of incorporated internal oxide or pores in the scale, short-circuit paths through the scale, doping, and the relative diffusion rates of the two metals in the scale. Probable rate-determining steps for oxidation of different alloy composition ranges are proposed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00606401
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