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  • 1
    Electronic Resource
    Electronic Resource
    The effect of supersaturation on the parabolic rate constant for internal oxidation with production of a pure oxide: An approximate analytical treatment (1982)
    Springer
    Oxidation of metals 17 (1982), S. 99-125 
    Details
    ISSN: 1573-4889
    Keywords: internal oxidation ; binary alloys ; supersaturation ; ternary interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Internal oxidation in binary alloys leading to the precipitation of a pure oxide is examined, taking into account the finite value of the solubility product of the oxide in the base metal, and approximate analytical expressions for the profiles of the concentrations of oxygen and the less noble component are derived. In contradiction with the original analysis by Wagner, it is found that the knowledge of fundamental parameters like the solubility of oxygen and the diffusivity of oxygen and the oxidized metal in the alloy are not sufficient to calculate the parabolic rate constant for internal oxidation. This in fact depends also on the extent of supersaturation required to nucleate new oxide particles in front of the internally oxidized region. In absence of this information only an upper limiting value for the rate constant may be obtained, corresponding to zero supersaturation, while use of the experimental value of the rate constant enables the critical value of the supersaturation for the system examined to be calculated. In addition, the effect of ternary interactions on the oxygen diffusion in the alloy is examined and it is shown how the apparent product of the solubility and diffusivity of oxygen in the base metal as measured from internal oxidation experiments according to Wagner's formulas may be a function of the alloy composition, a fact which is not predicted by simpler treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00606195
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  • 2
    Electronic Resource
    Electronic Resource
    The transition from the formation of mixed scales to the selective oxidation of the most-reactive component in the corrosion of single and two-phase binary alloys (1993)
    Springer
    Oxidation of metals 40 (1993), S. 373-393 
    Details
    ISSN: 1573-4889
    Keywords: selective oxidation ; binary alloys ; two-phase alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The conditions for the transition from the formation of mixed scales to the exclusive oxidation of the component B, forming the most stable oxide, are examined for both single-phase and two-phase binary A-B alloys by taking into account the displacement of the alloy-scale interface due to the growth of the protective oxide. This procedure eliminates the inconsistencies arising from Wagner's classical treatment for single-phase alloys when the interdiffusion coefficient in the alloy is small with respect to the parabolic rate constant for outer-scale growth; but the same procedure leads to a significantly-improved treatment also for two-phase alloys. For the latter systems, the transition is shown to depend also on the solubility of B in the A-rich phase.Moreover, the exclusive growth of the most-stable oxide is more difficult than for single-phase alloys because it requires higher average concentrations of B in the alloy and may even become impossible if the parabolic rate constant of oxidation is large with respect to the interdiffusion coefficient in the alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664498
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  • 3
    Electronic Resource
    Electronic Resource
    Further aspects of the oxidation of binary two-phase alloys (1993)
    Springer
    Oxidation of metals 39 (1993), S. 197-209 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; binary alloys ; two-phase alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The corrosion behavior of binary, two-phase alloys is considered in which the matrix contains mostly the less-noble metal that forms a fast-growing oxide, while the second phase is rich in a component that forms a more stable but slowly-growing oxide. It is assumed that the second phase exists as a dispersion of isolated, rod-like particles. It is further assumed that both phases form external films with no internal oxidation. It is shown that the oxidation behavior of this type of alloy depends on both the oxidation time and the size of the second-phase particles. In particular, for short oxidation times and large second-phase particles the matrix will oxidize faster than the dispersed phase, so that the dispersed particles will be only partly corroded or even incorporated into the matrix-oxide scale as unoxidized islands, forming an irregular alloy-scale interface. On the contrary, for long times and small particle sizes the two phases will tend to oxidize at approximately the same rate, leading to the formation of regular alloy-scale interfaces. The time for the transition between the two corrosion regimes depends not only on the ratio between the rate constants for the growth of the two oxides but also on the size of the dispersed-phase particles, smaller sizes producing shorter transition times. Eventually, under favorable conditions the formation of the fast-growing oxide may even stop, leading to the formation of a protective layer of the most-stable oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665611
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  • 4
    Electronic Resource
    Electronic Resource
    The kinetics of growth and the critical conditions for the formation of the most-stable oxide in the oxidation of binary alloys (1994)
    Springer
    Oxidation of metals 42 (1994), S. 285-301 
    Details
    ISSN: 1573-4889
    Keywords: oxidation kinetics ; protective scales ; binary alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract During the growth of the most-stable oxide BO v in the oxidation of binary alloys containing nonnoble components A and B, the oxygen pressure prevailing at the alloy-scale interface is higher than the corresponding value for equilibrium between BO v and pure B. The effects of this change on the rate constant for the growth of BO v and on the critical concentration of B in the bulk alloy required for the stability of BO v on its surface are examined and discussed. The general treatment is then applied to the growth of NiO on Cu−Ni alloys and of Cr2O3 on Fe−Cr, Co−Cr, and Ni−Cr alloys by using appropriate defect models for these oxides, considering also the possibility of oxide doping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01052028
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  • 5
    Electronic Resource
    Electronic Resource
    The air oxidation of two-phase Cu-Cr alloys at 700–900°C (1997)
    Springer
    Oxidation of metals 48 (1997), S. 357-380 
    Details
    ISSN: 1573-4889
    Keywords: chromium ; copper ; binary alloys ; two-phase alloys ; oxidation ; high temperatures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation in air of three two phase Cu-Cr alloys with nominal Cr contents of 25, 50, and 75 wt. % was studied at 700–900°C. The alloys corroded nearly parabolically, except at 900°C, when the corrosion rates decreased with time more rapidly than predicted by the parabolic rate law. The corrosion rate decreased for higher Cr contents in the alloy under constant temperature and generally increased with temperature for the same alloy composition. The scales were complex and consisted in most cases of an outermost copper oxide layer free from chromium and an inner layer composed of a matrix of copper oxide or of the double oxide Cu2Cr2O4, often containing particles of chromium metal surrounded by chromia and then by the double oxide. Metallic copper was also frequently mixed with chromia. Cr-rich regions tended to form continuous chromia layers at the base of the scale, especially at the highest temperature. No chromium depletion was observed in the alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02153456
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  • 6
    Electronic Resource
    Electronic Resource
    Transition from internal to external oxidation for binary alloys in the presence of an outer scale (1986)
    Springer
    Oxidation of metals 25 (1986), S. 269-282 
    Details
    ISSN: 1573-4889
    Keywords: internal oxidation ; binary alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The critical concentration required for the transition from internal to external oxidation of the most reactive component B of a binary A-B alloy for the case of simultaneous formation of an outer AO scale is calculated by extending Wagner's original analysis, which excluded the presence of an AO oxide. It is shown that the formation of an outer AO scale tends to produce an increase in the critical concentration of B, essentially as a result of a decrease of the enrichment of B in the internal oxidized region. Examples of the calculation of some parameters are presented to examine the effect of the different factors on the properties of internal oxidation and on its transition to the formation of an external scale of the oxide of the less noble component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01072908
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  • 7
    Electronic Resource
    Electronic Resource
    An improved treatment of the conditions for the exclusive oxidation of the most-reactive component in the corrosion of two-phase alloys (1994)
    Springer
    Oxidation of metals 42 (1994), S. 465-483 
    Details
    ISSN: 1573-4889
    Keywords: binary alloys ; two-phase alloys ; oxidation ; high temperatures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The conditions for the exclusive oxidation of the most-reactive component during the corrosion of binary, two-phase alloys by a single oxidant are reexamined by using a more correct form of the mass balance for this component. Moreover, the previous treatment is extended to include the case in which the transition falls in the range of alloy compositions corresponding to the stability of the single phase rich in the most-reactive component. The limiting conditions for the transition in the single and two-phase fields are examined and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046761
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  • 8
    Electronic Resource
    Electronic Resource
    The steady-State corrosion kinetics of two-phase binary alloys forming the most-stable oxide (1996)
    Springer
    Oxidation of metals 46 (1996), S. 383-398 
    Details
    ISSN: 1573-4889
    Keywords: high temperatures ; binary alloys ; two-phase alloys ; oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The steady-state kinetics in the high-temperature oxidation of binary A-B alloys containing a mixture of the conjugated solid solutions of B in A (alpha phase) and A in B (beta phase) with exclusive formation of the most-stable oxide BOv have been examined, assuming that the external scale grows on top of a subsurface layer of alpha phase. The results obtained are compared with the corresponding behavior of alloys which are single phase in the whole range of composition. Under identical values of all the parameters involved the concentration of B at the alloy-scale interface is smaller for two-phase than for single-phase alloys under the same concentration of B in the alloy as a result of the restricted flux of B through the alpha-phase layer. As a consequence of this, the two-phase alloys corrode more slowly than single-phase alloys and this difference increases as the solubility of B in the alpha phase decreases. Finally, the simultaneous formation of BOv both externally and as internal oxide is more likely for two-phase than for single-phase materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048637
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  • 9
    Electronic Resource
    Electronic Resource
    An approximate treatment of the transient state in the corrosion of binary alloys forming the most-stable oxide. Part I: Solid-solution alloys (1997)
    Springer
    Oxidation of metals 47 (1997), S. 91-115 
    Details
    ISSN: 1573-4889
    Keywords: binary alloys ; oxidation ; transient state ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The initial transient stage in the oxidation of binary alloys forming scales exclusively composed of the most stable oxide is examined by means of a simplified approach which avoids the numerical integration of the diffusion equation for the transport of the metal components in the alloy. At variance with previous solutions to this problem obtained by means of numerical methods, this treatment takes into account also the effect of the gas-scale reaction at the outer surface of the oxide. The concentration of the most-reactive component at the alloy surface changes gradually with time from the initial bulk value towards the corresponding steady-state value without involving any minimum, while the overall rate of the reaction presents a gradual transition from an initial nearly linear towards final parabolic behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01682373
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  • 10
    Electronic Resource
    Electronic Resource
    The steady-state corrosion kinetics of single-phase binary alloys with a solubility gap forming the most-stable oxide (1997)
    Springer
    Oxidation of metals 47 (1997), S. 215-235 
    Details
    ISSN: 1573-4889
    Keywords: high temperature ; oxidation ; binary alloys ; steady-state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The steady-state, high-temperature oxidation kinetics of single phase alloys rich in a most-reactive componentB in binaryA-B systems presenting a limited solubility of the two components (beta phase alloys) have been examined assuming the exclusive formation of the most-stable oxideBO v. Alloys sufficiently rich inB can form externalBO v scales directly in contact with the beta phase, while below a criticalB content the growth ofBO v involves also the appearance of an intermediate layer ofB-depleted solid solution ofB inA (alpha phase). The parabolic rate constants for the oxidation of single-phase beta alloys are lower than those of alloys of identicalB content which are single-phase over the whole range of composition (solid-solution alloys) but higher than for two-phase alpha + beta alloys under the same values of all the relevant parameters. Moreover, the tendency of single-phase beta alloys to form the most-stable oxide simultaneously as an external scale and internally to the alloy is greater than for solid-solution alloys but smaller than for two-phase alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01668511
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