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  • Chevrel phase  (3)
  • corrosion  (3)
  • 1
    Electronic Resource
    Electronic Resource
    High-temperature sulfidation of Fe-30Mo alloys containing ternary additions of Al (1991)
    Springer
    Oxidation of metals 35 (1991), S. 349-373 
    Details
    ISSN: 1573-4889
    Keywords: sulfidation ; Fe-Mo-Al alloys ; Chevrel phase ; Al0.5Mo2S4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fe-30Mo alloys containing up to 9.1 wt% Al were sulfidized at 0.01 atm sulfur vapor over the temperature range of 700–900°C. The sulfidation kinetics followed the parabolic rate law for all alloys at all temperatures. For alloys containing small and intermediate amounts of Al (〈4.8 wt.%), a duplex sulfide scale formed. The outer layers of the scales were found to be relatively compact FeS in all cases; whereas the inner layers were composed of the layered compound MoS 2 (intercalated with iron), the Chevrel compound Fe x Mo 6 S 8,a spinel double sulfide Al x Mo 2 S 4,depending on the Al content of the alloy and the sulfidation temperature. Extremely thin scales were found on the alloys with higher Al contents. Accordingly, extremely slow sulfidation rates were observed—even slower than the sulfidation rate of pure Mo. The transition of the sulfidation kinetics from a high-rate active mode to a low-rate passive mode requires both a critical Al content in the alloy and a critical Mo content. Because of the two-phase nature of the alloys, the latter requirement implies a critical volume fraction of the intermetallic second-phase in the alloy, which has been known as the “multiphase effect.” Interestingly, the “multiphase effect” in these alloys was also a function of the Al content in the alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664708
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  • 2
    Electronic Resource
    Electronic Resource
    The corrosion of Fe-Mo alloys in H2/H2O/H2S atmospheres (1992)
    Springer
    Oxidation of metals 37 (1992), S. 389-411 
    Details
    ISSN: 1573-4889
    Keywords: sulfidation ; Fe-Mo alloys ; bilayered scales ; FeMo2S4 ; Chevrel phase
    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 of Fe-Mo alloys containing up to 40 wt.% Mo was studied over the temperature range 600–980
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00666627
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  • 3
    Electronic Resource
    Electronic Resource
    The corrosion behavior of Fe-Nb-Al alloys in H2/H2O/H2S atmospheres (1993)
    Springer
    Oxidation of metals 39 (1993), S. 317-352 
    Details
    ISSN: 1573-4889
    Keywords: corrosion ; Fe-Nb-Al alloys ; (Fe, Al)xNb2S4 ; Nb3S4 ; Al2O3
    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 eight Fe-Nb-Al ternary alloys was studied over the temperature range 700–980°C in H2/H2O/H2S atmospheres. The corrosion kinetics followed the parabolic rate law for all alloys at all temperatures. The corrosion rates were reduced with increasing Nb content for Fe-x Nb -3Al alloys, the most pronounced reduction occurred as the Nb content increased from 30 to 40 wt.%. The corrosion rate of Fe-30Nb decreased by six orders of magnitude at 700°C and by five orders of magnitude at 800°C or above by the addition of 10 wt.% aluminum. The scales formed on low-Al alloys (≤3 wt.% Al) were duplex, consisting of an outer layer of iron sulfide (with Al dissolved near the outer-/inner-layer interface) and an inner complex layer of FexNb2S4(FeNb2S4 or FeNb3S6), FeS, Nb3S4 (only detected for Nb contents of 30 wt.% or higher) and uncorroded Fe2Nb. No oxides were detected on the low-Al alloys after corrosion at any temperature. Platinum markers were found to be located at the interface between the inner and outer scales for the low-Al alloys, suggesting that the outer scale grew by the outward transport of cations (Fe and Al) and the inner scale grew by the inward transport of sulfur. The scales formed on high-Al alloys (≥5 wt.% Al) were complex, consisting primarily of Nb3S4, Al2O3 and (Fe, Al)xNb2S4, and minor amounts of (Fe, Al)S and uncorroded intermetallics (FeAl and Fe2Nb). The formation of Nb3S4 and Al2O3 blocked the transport of iron through the inner scale, resulting in the significant reduction of the corrosion rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664660
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of Al on the corrosion behavior of Ni-Mo in a H2/H2O/H2S gas mixture (1993)
    Springer
    Oxidation of metals 40 (1993), S. 119-154 
    Details
    ISSN: 1573-4889
    Keywords: mixed gas ; Ni-Mo-Al alloys ; Al2O3 ; MoS2 ; Al0.55Mo2S4 ; Chevrel phase
    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 seven Ni-Mo-Al alloys was investigated over the temperature range of 600–950°C in a mixed-gas atmosphere of H 2/H 2O/H 2 S. The parabolic law was followed at low temperatures, while linear kinetics were generally observed at higher temperatures. At a fixed Mo content, the transition from parabolic to linear kinetics shifted to higher temperature with increasing Al concentration. Double-layered scales generally formed on alloys having a low Al content, consisting of an outer layer of nickel sulfide and a complex inner scale. The thickness of the outer scale and the inner scale decreased as the Al content increased. The outer scale became porous and discontinuous with increasing Al content and temperature. Al 2 O 3 was detected in the scales of all alloys corroded at higher temperatures (≥ 800°C), even though the amount of Al 2 O 3 was very small in some cases. The decrease in corrosion rate with increasing Al content may be attributed to the formation of Al 2 O 3,Al 0.55 Mo 2 S 4,and Al 2 S 3 in the inner scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665262
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Al on high-temperature corrosion of Co-15a/oNb alloys in H2-H2O-H2S environments (1994)
    Springer
    Oxidation of metals 41 (1994), S. 115-138 
    Details
    ISSN: 1573-4889
    Keywords: corrosion ; Al2O3 ; Co−Nb−Al ; Nb3S4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Co−15 at.% Nb alloys containing up to 15 at.% Al were corroded in gaseous H2−H2O−H2S mixtures over the temperature range of 600–900°C. The corrosion kinetics followed the parabolic rate law at all temperatures. Corrosion resistance improved with increasing Al content except at 900°C. Duplex scales formed on alloys consisting of an outer layer of cobalt sulfide and a heterophasic inner layer. A small amount of Al2O3 was found only on Co−15Nb−15Al. Contrary to what formed in Co−Nb binary alloys, neither NbS2 nor NbO2 were found in the inner layer of all alloys, but Nb3S4 did form. The absence of NbS2 and NbO2 is due to the formation of stable Al2O3 and Al2S3 that effectively blocked the inward diffusion of oxygen and sulfur, respectively, and to the reduction of activity of Nb by Al additions in the alloys. Intercalation of ions in the empty hexagonal channels of Nb3S4 is associated with the blockage of the transport of cobalt. An unknown phase (possibly Al0.5NbS2) was detected. Alloys corroded at 900°C were abnormally fast and formed a scale containing CoNb3S6 and Co. Pt markers were found at the interface between the inner and outer layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01196646
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  • 6
    Electronic Resource
    Electronic Resource
    High-temperature corrosion of Co-15Mo alloys containing ternary additions of Al in mixed-gas environments (1993)
    Springer
    Oxidation of metals 40 (1993), S. 155-177 
    Details
    ISSN: 1573-4889
    Keywords: sulfidation ; corrosion ; Al2O3 ; Co-Mo-Al alloys ; 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 The corrosion behavior of Co-15 at.% Mo alloys containing up to 20at.% Al in gaseous H 2 -H 2 O-H 2 S mixtures was studied over the temperature range of 600–900°C. The corrosion kinetics of all alloys followed the parabolic rate law over the temperature range of interest. Corrosion resistance increased with increasing aluminum content. Complex scales formed on the alloys, consisting of an outer layer of cobalt sulfide and a heterophasic inner layer. Al 2 O 3 formed only at high temperatures in alloys having aluminum additions of 15at.% or more. The absence of Al 2 O 3 in some cases is due to the small volume fraction of the intermetallic phase CoAl in the alloys and the nature of the slow growth rate of Al 2 O 3.Improvement in corrosion resistance is attributed to the presence of a ternary sulfide, Al 0.55 Mo 2 S 4,and Al 2 O 3 in the inner layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665263
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