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  • Articles  (8)
  • sulfidation  (8)
  • Springer  (8)
  • American Association for the Advancement of Science (AAAS)
  • SciELO Brazil
  • 2005-2009
  • 1985-1989  (8)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (8)
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  • Articles  (8)
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Keywords
Publisher
  • Springer  (8)
  • American Association for the Advancement of Science (AAAS)
  • SciELO Brazil
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Year
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  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (8)
  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    High-temperature sulfidation of Mo-50 Wt.% Re (1989)
    Springer
    Oxidation of metals 31 (1989), S. 453-478 
    Details
    ISSN: 1573-4889
    Keywords: Mo-50Re ; sulfidation ; x-phase ; MoS2 sulfur interstitials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Mo-50Re was sulfidized over the range of 1000–1100°C in sulfur vapor at pressures of 10−4 and 10−2 atm. The reaction kinetics followed the parabolic rate law with an activation energy of 55.4 kcal/mole for $$p_{S_2 } = 10^{ - 4} $$ and 48.2 kcal/mole for $$p_{S_2 } = 10^{ - 2} $$ atm. The pressure dependence varied between +1/4 to +1/6 for the slope of a plot of log Kp vs log $$p_{S_2 } $$ . Analysis of the diffusional processes occurring in both the scale and the alloy substrate gave an expression for the ratio of the thickness of the scale and of the χ-phase as a function of the corresponding rate constants for the growth of each layer. Finally, the conditions required for the formation of the χ-phase layer between the outer scale and the alloy substrate were obtained in terms of the ratio between the diffusion coefficients of the two metals in the intermetallic compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666467
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of 1 wt.% yttrium addition on high-temperature sulfidation behavior of Fe-15Cr-4Al alloy (1987)
    Springer
    Oxidation of metals 28 (1987), S. 127-153 
    Details
    ISSN: 1573-4889
    Keywords: Kinetics ; yttrium addition ; sulfidation ; sulfides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract High-temperature sulfidation studies have been carried out on Fe-15Cr-4Al with and without 1% Y in the temperature range 700–1000°C in an H 2-H2 S environment over the sulfur pressure range of 10 −9−10−3 atm. Two-layered and three-layered sulfide scales were observed in both alloys at low and high sulfur pressures, respectively. The pegging phenomenon, similar to that occurring in high-temperature oxidation, across the innermost layer and substrate was observed in the case of the yttrium-containing alloy. Yttrium was found to be associated with aluminum and chromium sulfides. The role of yttrium was more evident at low than at high sulfur pressures and was found to reduce the parabolic rate constants by a factor of about one-half to one-seventh, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656703
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of preoxidation on the corrosion of some superalloys in coal char (1988)
    Springer
    Oxidation of metals 29 (1988), S. 307-325 
    Details
    ISSN: 1573-4889
    Keywords: Preoxidation ; sulfidation ; coal char ; chromia films ; alumina films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Preoxidation of several chromia-forming and of several alumina-forming alloys at temperatures ranging from 982 to 1260°C in either water-saturated argon or in air was performed prior to corrosion in coal char. Chromia films offered no protection to subsequent sulfidation in char. The chromia films were adherent but permitted rapid inward penetration of sulfur and outward penetration of cations to form extensive sulfides. Alumina films offered protection for much longer times than did chromia films, but localized cracking and/or spalling of the alumina permitted rapid attack at the exposed areas. The addition of yttrium as either a metallic element or as an oxide dispersion improved the mechanical stability of the films and prolonged the period of protectiveness. Alumina films would provide an excellent protective barrier, if thick crack-free films could be grown at reasonable temperatures. The low growth rates at very high temperatures and the susceptibility of alumina films to crack and spall during thermal cycling suggest that preoxidation will not offer adequate corrosion resistance for alloys exposed to char in goal gasifiers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751802
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of preoxidation of some Ni, Fe, and Co-Base alloys on subsequent sulfidation at 982°C in sulfur vapor (1988)
    Springer
    Oxidation of metals 30 (1988), S. 433-463 
    Details
    ISSN: 1573-4889
    Keywords: preoxidation ; sulfidation ; chromia formers ; alumina formers ; spalling ; nickel-base alloys ; iron-base alloys ; cobalt-base 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 effect of preoxidation was studied on the subsequent sulfidation in sulfur vapor at a pressure of 0.1 atm at 982°C on numerous iron, nickel, and cobalt-base alloys which were either chromia or alumina formers. In general, alumina films were much more protective than chromia films, but the efficacy of preoxidation in reducing sulfidation rates depended more upon perfection of the films and whether cracking and/or spatting occurred. Increasing oxidefilm thickness had a beneficial effect until either penetration of the films by sulfur or cracking occurred, after which sulfidation rates were sometimes greater than for nonpreoxidized samples. The enhanced sulfidation rates are attributed to sulfidation of a solute-depleted substrate, the solute having been selectively removed by oxide formation. One alloy, MA 956, containing 0.5 Y2O3 as fine dispersions which normally provide spatting resistance, still exhibited extensive cracking and spalling of the oxide and was not much better than alloys without dispersoids or reactive-metal additions. The use of preoxidation to reduce sulfidation rates is not viable under the extreme conditions used. Preoxidation is conceptually a good method for inhibiting sulfidation at lower temperatures and much lower sulfur pressures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00659010
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  • 8
    Electronic Resource
    Electronic Resource
    High-temperature sulfidation behavior of Ni-Nb alloys (1989)
    Springer
    Oxidation of metals 31 (1989), S. 237-263 
    Details
    ISSN: 1573-4889
    Keywords: sulfidation ; nickel-niobium ; multilayered scale ; NbS2 ; NiNb3S6
    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 properties of Ni-Nb alloys containing additions of niobium up to 40 wt.% have been studied at $$P_{S_2 } = 0.01$$ atm over the temperature range 550-700 °C. The sulfidation reactions followed the parabolic rate law; the sulfidation rates decreased with increasing amounts of niobium. An Arrhenius plot of the rate constants gave activation energies of 25.0+3.5 kcal/ mole. The scales formed on Ni-Nb alloys were multilayered, generally consisting of an outer layer of nickel sulfide ( NiS1+x and Ni3S2) and an inner complex layer of NiNb3S6 plus NbS2. The position of the original metal surface was notedy platinum-wire marker experiments to be the interface between the inner andouter layers. The location of the marker indicates that the outer layer, generally greater in thickness than the inner layer, grew by outward diffusion of the nickel cations, and the inner layer formed probably by the inward diffusion of sulfur. Neither preferential sulfidation nor internal sulfidation was observed. The development of the scale structures from the transient stage to steady state was also studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00846688
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