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  • 1
    Electronic Resource
    Electronic Resource
    The transition from internal oxidation to continuous-film formation during oxidation of dilute Ni-Si alloys (1987)
    Springer
    Oxidation of metals 28 (1987), S. 309-328 
    Details
    ISSN: 1573-4889
    Keywords: Ni-Si alloys ; internal oxidation ; silica ; transition
    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 of Ni-2.05Si and Ni-4.45Si was studied in oxygen over the range of 600°–1000°C for 18 hr. The oxidation kinetics did not follow a parabolic rate law, bur rather a power law of the form (Δw)n=kt was followed. The value of n ranged from 2.7 to 4.9 for Ni-2.05Si and from 3.0 to 6.4 for Ni-4.45Si. The low-silicon alloy exhibited extensive internal oxidation, whereas the higher-silicon alloy did not internally oxidize. In general, NiO containing little or no silicon formed as an exterior layer on both alloys. The internal oxidation zone in Ni-2.05Si was highly irregular in thickness, and in some areas there was no internal oxidation. The higher-silicon alloy formed a continuous layer of a silicon-rich oxide. X-ray diffraction did not detect silica (amorphous), and no evidence of Ni2SiO4 was observed, although EDAX analysis suggests that small amounts of the silicate might have formed. Theaverage thickness of the internal oxidation zone was found to agree well with calculated values based on oxygen solubility and diffusivity data. No enrichment of silicon occurred in the internal oxidation zone. Calculated values, 0.033 and 0.038 (depending on the model used), of the mole fraction of silicon required for the transition from internal oxidation to continuous silica film formation agreed well with experimental data obtained in both this study and with others reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666725
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  • 2
    Electronic Resource
    Electronic Resource
    Modification of the oxidation behavior of high-purity austenitic Fe-14Cr-14Ni by the addition of silicon (1976)
    Springer
    Oxidation of metals 10 (1976), S. 1-22 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; film spalling ; fayalite ; internal 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 oxidation behavior of Fe-14Cr-14Ni (wt.%) and of the same alloy with additions of 1 and 4% silicon was studied in air over the range of 900-1100° C. The presence of silicon completely changed the nature of the oxide scale formed during oxidation. The base alloy (no silicon) formed a thick outer scale of all three iron oxides and an internally oxidized zone of (Fe,Cr,Ni) spinels. The alloy containing 4% silicon formed an outer layer of Cr2O3 and an inner layer of either (or possibly both) SiO2 and Fe2SiO4. The formation of the iron oxides was completely suppressed. The oxidation rate of the 4% silicon alloy was about 200 times less than that of the base alloy, whereas the 1% silicon alloy exhibited a rate intermediate to the other two alloys. The actual ratio of the oxidation rates may be less than 200 due to possible weight losses by the oxidation of Cr2O3 to the gaseous phase CrO3. The lower oxidation rate of the 4% silicon alloy was attributed to the suppression of iron-oxide formation and the presence of Cr2O3, which is a much more protective scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611695
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  • 3
    Electronic Resource
    Electronic Resource
    Oxide removal and desorption of oxygen from partly oxidized thin films of copper at low pressures (1976)
    Springer
    Oxidation of metals 10 (1976), S. 227-238 
    Details
    ISSN: 1573-4889
    Keywords: desorption of oxygen ; transmission electron microscopy ; in situ oxidation studies ; oxidation of thin films ; nucleation of oxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Partly oxidized copper films were annealed in a controlled vacuum of 10−7 Pa at a temperature of 450° C. The changes discussed below were observed in situ with a specially designed high-resolution transmission electron microscope. The thin, (100)-oriented, single-crystal films of copper had been oxidized immediately prior to the annealing studies at the same temperature and at an oxygen partial pressure of 7×10 −1 Pa, until the desired fraction of the copper film was converted to oxide. It was observed that the oxide disappeared during annealing as long as some copper was left unoxidized. The disappearance of the oxide is explained as being due to dissociation of the oxide at the oxide-metal interface followed by diffusion of oxygen into the metal and desorption of oxygen from the surface of the unoxidized copper. The rate of disappearance of the oxide was found to be proportional to the surface area of unoxidized copper, i.e., the desorption was found to be the rate — limiting step. In the case of heavily oxidized films (〉50%), holes were observed to develop in the oxide near the oxide-metal interface after an annealing period of 2–3 hr. Upon resumption of the oxidation, these holes first disappeared, and the normal oxidation behavior was then resumed. The formation of holes may be explained by vacancy clustering. When completely oxidized films were annealed, recrystallization of the oxide was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618245
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  • 4
    Electronic Resource
    Electronic Resource
    In situ oxidation studies on (001) copper-nickel alloy thin films (1977)
    Springer
    Oxidation of metals 11 (1977), S. 321-334 
    Details
    ISSN: 1573-4889
    Keywords: oxidation of thin films ; initial oxidation of Cu-Ni alloys ; nucleation of oxides ; in situ oxidation ; transmission electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The (001)-oriented, single crystalline thin films of Cu-3% Ni, Cu-4.6% Ni, and Cu-50% Ni alloy were prepared by vapor deposition onto (001) NaCl substrates. The films were subsequently annealed at around 1100°K and oxidized at 725°K at an oxygen partial pressure of 5×10−1 N · m−2 (5× 10−6 atm). High-resolution transmission electron microscopy was employed to observe the changes in situ. For all the alloy concentrations Cu2O and NiO were observed to nucleate and grow independently; no mixed oxides were noted. The shape and growth rates of Cu2O nuclei were similar to those found in previous work on pure copper films. For low-nickel alloy concentrations the NiO nuclei were larger and the number density of NiO was less when compared to the oxidation of pure nickel films. For the Cu-50% Ni films the shape and growth rates of NiO were identical to those for the oxidation of pure nickel films. Low nickel concentrations exhibited a reduced induction period for Cu2O when compared to pure copper films. Cu-50%Ni films showed surface precipitation and growth of NiO first, followed by Cu2O in a typical through -thickness growth after a prolonged induction period. The results are consistent with the previously established oxidation mechanisms of pure copper and pure nickel films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00608015
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  • 5
    Electronic Resource
    Electronic Resource
    International Workshop on “Critical Issues Concerning the Mechanisms of High-Temperature Corrosion” (1985)
    Springer
    Oxidation of metals 23 (1985), S. 253-337 
    Details
    ISSN: 1573-4889
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Conclusions This discussion has highlighted the need for further detailed experimentation, using the array of modern equipment plus the development of new techniques in order to establish the data base for the necessary quantitative models. The most important aspect is to understand the break-down process and to learn how to delay or prevent it. To do this, it is necessary to understand fully the growth mechanism of the protective oxide itself and what determines its “quality.” Specific topics for future work include: a. Porosity measurements in growing scales; b. Diffusion measurements in growing scales; c. Measurement of scale ad(co)hesion; d. How to measure the “quality” of oxide, particularly after pretreatment; e. How to achieve all the above nondestructively; f. Establish experimentally the effects of heat flux; g. Developquantitative models for the time to breakdown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01271116
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of yttrium on the sulfidation behavior of Ni-Cr-Al alloys at 700°C (1986)
    Springer
    Oxidation of metals 25 (1986), S. 1-28 
    Details
    ISSN: 1573-4889
    Keywords: sulfidation ; yttrium ; duplex-sulfide scales ; lamellar sulfides ; 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 sulfidation of Ni-10Cr-5Al, Ni-20Cr-5Al, and Ni-50Cr-5Al, and of the same alloys containing 1% Y, was studied in 0.1 atm sulfur vapor at 700°C. The sulfidation process followed linear kinetics for all the alloys except Ni-50Cr-5Al-1Y, and possibly Ni-50Cr-5Al, which followed the parabolic law. The reaction rates decreased with increasing chromium content in alloys without yttrium, and the addition of yttrium reduced the rates by at least a factor of two for the alloys containing 10 and 20% Cr and by an order of magnitude for Ni-50Cr-5Al. Alloys containing 10 and 20% Cr (with and without yttrium) formed duplex scales consisting of an outer layer of NiS1.03 and an inner lamellar layer of a very fine mixture of Cr2S3 and A12O3 in a matrix of NiS1.03. The two alloys containing 50% Cr formed only a compact layer of Cr2S3, which was brittle and spalled during cooling. The lamellae in the duplex scales were parallel to the specimen surface and bent around corners. The lamellae were thicker than those on Ni-Al binary alloys. The lamellae were also thicker in scales on the 20% Cr alloy than on the 10% Cr alloy. The presence of yttrium refined the lamellae and increased the lamellae density near the scale/metal interface in the 10% alloy, but in the 20% Cr alloy the lammellae were thicker and more closely spaced. Platinum markers were found in the inner portion of the exterior NiS1.03 layer close to the lamellar zone. A counter-current diffusion mechanism is proposed involving outward cation diffusion and inward sulfur diffusion, although diffusion was not rate controlling for alloys containing 10 and 20% Cr. Auger analysis of scales formed on Ni-50Cr-1Y showed an even distribution of yttrium throughout the layer of Cr2S3, suggesting that some yttrium dissolved in the sulfide. The reduced sulfidation rate of samples containing yttrium is explained by the possible dissolution of yttrium as a donor. The presence of Y4+ would then decrease the concentration of interstitial chromium ions in the N-type layer of Cr2S3, which would decrease the reaction rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807994
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics and mechanism of the sulfidation of Fe-Mo alloys (1989)
    Springer
    Oxidation of metals 31 (1989), S. 341-367 
    Details
    ISSN: 1573-4889
    Keywords: Fe-Mo alloys ; sulfidation ; two-phase alloys ; duplex scales ; MoS2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Iron-molybdenum alloys containing up to 40 wt.% molybdenum were exposed to sulfur vapor at a partial pressure of 0.01 atm at temperatures of 600–900°C. Sulfidation kinetics were measured over periods of up to 8 hr using a quartz-spring thermogravimetric method. The sulfidation kinetics of all alloys studied obeyed the parabolic rate law. The sulfidation rate of iron was found to be reduced by factors of 60 at 900°C and 120 at 600°C by the addition of 40 wt.% molybdenum. Duplex sulfide scales formed on all alloys at all temperatures, the scales consisting of an inner layer of mostly MoS2 and an outer layer of FeS. Platinum markers were located at the interface between the outer and inner scales, showing that outward iron diffusion and inward sulfur diffusion through the inner layer occurred. The improved sulfidation resistance was attributed to the formation of the MoS2, which acted as a partially protective barrier to the diffusion of the reacting species. Sulfidation activation energies were found to range from 24.3 to 28.5 kcal mole for the alloys compared to 20.6 kcal/mole, for pure iron. The rate-controlling step was outward iron diffusion through the outer iron sulfide layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666462
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Nb on the high-temperature sulfidation behavior of cobalt (1989)
    Springer
    Oxidation of metals 31 (1989), S. 209-236 
    Details
    ISSN: 1573-4889
    Keywords: sulfidation ; duplex scale ; heterophasic inner layer ; NbS2 ; CoNb2S4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The sulfidation behavior of Co-Nb alloys containing up to 30wt.% Nb was studied in sulfur vapor at a pressure of 0.01 atm in the temperature range of 600–700°C. Increasing niobium content decreased the sulfidation rate, following the parabolic rate law. An activation energy of 25.6 kcal/mole was obtained for Co-10Nb, Co-20Nb, and Co-25Nb, while a value of 20.5 kcal/mole was found for Co-30Nb. All were two-phase alloys, consisting of solid solution α-Co and the intermetallic compound, NbCo3. The two-phase alloys formed a rather thick outer layer of cobalt sulfides and a heterophasic inner layer that was complex. The inner layer always contained the mixed sulfide CoNb2S4 which, depending on the alloy composition, coexisted with cobalt sulfide, NbS2, and / or NbCo3 particles. Short-time sulfidations showed that the solid solution initially sulfidized rapidly to form nodules of cobalt sulfide, whereas the NbCo3 phase formed a thin protective layer of NbS2. The nodules grew laterally until they coalesced into the continuous, outer thick layer, while the NbS2 completely or partially reacted with the cobalt sulfide to form CoNb2S4. Platinum markers were always found at the interface between the inner and outer scales, the location of the original metal surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00846687
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  • 9
    Electronic Resource
    Electronic Resource
    High-temperature sulfidation of Fe-Nb alloys (1989)
    Springer
    Oxidation of metals 32 (1989), S. 273-294 
    Details
    ISSN: 1573-4889
    Keywords: Two-phase alloy sulfidation ; iron-niobium ; FexNbS2 ; blocking effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The sulfidation behavior of Fe-Nb alloys containing up to 30 w/o Nb was studied over the range of 600–900°C in 0.01 aim. S2 vapor. All alloys were two-phase, consisting of an Fe-rich solid solution and Fe2Nb, and followed the parabolic rate law at all temperatures. Scales consisted of two layers-an outer layer of FeS and an inner, complex layer which contained some FeS, FeNb2S4 (possibly some FeNb3S6), NbS2, and intermetallic particles which were either completely or only partially sulfidized. Platinum markers were located always at the interface between the two layers, which corresponded to the original metal surface. Activation energies were 18±3 kcal/mol in close agreement with the 19.8 reported for pure iron. The sulfidation rate decreased markedly with increasing Nb content of the alloys. The decrease is attributed to increasing amounts of Fe2Nb with increasing Nb, the net effect being that the diffusion path for outward iron diffusion through the inner layer is reduced as the Nb content increases. An analysis of the structure of NbS2 reveals that it is easily intercalated with Fe between loosely bonded layers of S-Nb-S. The S-Nb-S layers are covalently bonded which results in very low diffusivities of either S or Nb in pure NbS2. Although intercalated Fe tends to change the Van der Waal's type bonding between layers to more ionic or covalent, Fe diffuses readily between the layers in NbS2. Intercalation of Fe also increases the concentration of sulfur defects in NbS2, which in turn increases the diffusivity of sulfur. Nb was observed to be immobile. Thus, it is thought that either outward iron diffusion or inward sulfur diffusion in the inner layer is the rate-controlling step, in spite of the close agreement of activation energies with that of the sulfidation of pure iron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664802
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of some ternary additions on the sulfidation of Ni-Mo alloys (1990)
    Springer
    Oxidation of metals 33 (1990), S. 103-133 
    Details
    ISSN: 1573-4889
    Keywords: Ni-Mo alloys ; ternary additions ; sulfidation ; MoS2, intercalation ; Al0.55Mo2S4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Five ternary additions, Cr, Ti, Mn, V, and Al were studied at equi-atomicpercent levels (17 a/o) for their effect on the sulfidation behavior of Ni-19a/o Mo (28–30 w/o) over the range of 600–800°C in 0.01 atm S2. Al was by far the most effective addition. A linear decrease in log kp vs. Al content was observed up to 7.5w/o Al, beyond which no further change was observed. All alloys followed the parabolic rate law. Arrhenius plots gave activation energies of 36.9–41.2 Kcal/mol for alloys containing Ti, Cr, Mn, and V, whereas the activation energies for Al-containing alloys were 47.2 Kcal/mol, indicating that a different diffusion process was involved. Complex scales were formed on all alloys, consisting of an outer layer of Nis1+x and complex inner layers which depended upon alloy composition. Two alloys, those with Cr and Mn, formed intermediate layers of Cr2S3 and MnS, respectively, but these layers had little effect on the kinetics. MoS2 was a constituent of the inner scales except for the alloys with Al. A ternary sulfide, Al0.55Mo2S4 and Al2S3 were observed. The presence of the mixed sulfide was always associated with the low sulfidation rates. The formation of MoS2 on alloys results in a different, less-protective behavior than for MoS2 formed on pure Mo. This effect is due to the intercalation of Ni into MoS2 in octahedral positions between the weakly bonded layers of covalently bonded sheets of trigonal prisms. The size of Al+3 is too small to be intercalated, and thus MoS2 is destabilized by Al.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665672
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