Journal ArticleDOI
The high-temperature oxidation of nickel-20 wt. % chromium alloys containing dispersed oxide phases
TLDR
In this paper, it was shown that the scale-forming reaction of Ni-20 wt. % Cr2O3 scales on dispersion-free systems must involve shortcircuit diffusion of chromium through the scale, and that it seems probable that an effect of the dispersion must be to retard or eliminate this short-circuit process.Abstract:
Alloys of Ni-20 wt. % Cr containing 3 vol. % of a dispersed oxide phase have been prepared by a mechanical alloying method and oxidized in oxygen at 100 Torr in the temperature range of 900 to 1200°C. It appears that the dispersed oxide has four distinct effects on the oxidation: (1) the selective oxidation of chromium to form a continuous protective Cr2O3scale is promoted; (2) the rate of growth of Cr2O3is reduced compared with particle-free alloys; (3) the adhesion of the Cr2O3is greatly improved; and (4)the scale-forming reaction appears to be at the scale-metal interface in alloys containing a dispersion, but at the scale-oxygen interface in alloys without a dispersion. It appears that the nature of the dispersed oxide is not important, since very similar effects can be obtained with ThO2,Y2O3,and CeO2dispersions. It is demonstrated that a logical deduction from this evidence is that the growth of Cr2O3scales on dispersion-free systems must involve short-circuit diffusion of chromium through the scale, and that it seems probable that an effect of the dispersion must be to retard or eliminate this short-circuit process. It is suggested that the oxide particles act as nucleation centers for the oxide, thus reducing the oxide grain size; and it is shown that this simple hypothesis is sufficient to explain a number of the experimental observations.read more
Citations
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Experimental observations in support of the dynamic-segregation theory to explain the reactive-element effect
TL;DR: In this article, a model was developed to explain the effects associated with the addition of reactive elements that is based on the segregation of reactive-element ions to scale grain boundaries and the metal-oxide interface.
Journal ArticleDOI
The influence of alloying elements on the development and maintenance of protective scales
TL;DR: In this article, the important principles that determine the establishment, growth and long-term maintenance of protective Cr2O3, Al 2O3 and SiO2 scales on hightemperature iron-, nickel-and cobalt-base alloys are reviewed and discussed.
Journal ArticleDOI
Microstructure, adhesion and growth kinetics of protective scales on metals and alloys
H. Hindam,D. P. Whittle +1 more
TL;DR: In this article, the complex interrelationships among growth kinetics, microstructure, and adhesion of protective Cr2O3 and Al 2O3 scales is critically reviewed.
Journal ArticleDOI
The influence of yttrium additions on the oxide-scale adhesion to an iron-chromium-aluminum alloy
TL;DR: In this paper, the authors examined the oxidation behavior of an Fe-27%Cr-4%Al alloy and similar alloys containing 0.023% and 0.82% Y in 1 atm oxygen at 1200°C and found that the oxide formed on the yttrium-free alloy develops a highly convoluted configuration, resulting from lateral growth of the oxide.
Journal ArticleDOI
The formation of aluminum oxide scales on high-temperature alloys
R. Prescott,M. J. Graham +1 more
TL;DR: A review of the extensive literature relating to the formation of protective α-Al2O3 scales on alloys at high temperature is given in this paper, where the authors focus on the proposed mechanisms of scale growth based on observations of scale morphologies and microstructures, inert-marker experiments and the distribution of oxygen isotope tracers within thermally grown oxides.
References
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Journal ArticleDOI
Self-diffusion of oxygen in single crystal and polycrystalline aluminum oxide
Y. Oishi,W. D. Kingery +1 more
TL;DR: The self-diffusion coefficient of oxygen has been determined as a function of temperature in single crystal and polycrystalline aluminum oxide at temperatures up to 1780°C as mentioned in this paper.
Journal ArticleDOI
The Effect of Oxide Volatilization on the Oxidation Kinetics of Cr and Fe‐Cr Alloys
TL;DR: In this paper, the authors derived equations which describe the oxidation behavior of a system in which both diffusive and gas/oxide interface processes occur simultaneously, and applied these equations to the oxidation of Cr and Fe-Cr alloys.
Journal ArticleDOI
Oxidation/Vaporization Kinetics of Cr2O3
H. C. Graham,H. H. Davis +1 more
TL;DR: In this article, both hot-pressed and sintered Cr2O3 pellets were investigated in O2/Ar gas mixtures and the dependence of the weight loss on the O2 partial pressure, the gas flow rate, and the total pressure was determined independently.
Journal ArticleDOI
The oxidation of TD NiC (Ni-20Cr-2 vol pct ThO2) between 900° and 1200°C
C. S. Giggins,F. S. Pettit +1 more
TL;DR: In this paper, the authors studied the performance of TD NiC at temperatures between 900° and 1200°C and showed that the ThO2 dispersion in this alloy improves the oxidation properties of this alloy by promoting the selective oxidation of chromium and decreasing the growth rate of the Cr2O3 scale.
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