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  • 1
    Electronic Resource
    Electronic Resource
    Low-temperature oxidation of Fe-24 wt.%Cr (1979)
    Springer
    Oxidation of metals 13 (1979), S. 437-456 
    Details
    ISSN: 1573-4889
    Keywords: Fe-Cr ; oxidation ; kinetics ; oxide morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ferritic polycrystalline Fe-24 wt.% Cr was oxidized in pure oxygen at 190 ≤ T≤490° C and pressures in the range 5.3×10−2–13.3 Pa for periods of up to 5 hr. The reaction proceeded in three stages. An initial period of accelerating rate was accompanied by oxide island nucleation and growth. Following island coalescence the rate was approximately logarithmic at low temperatures and somewhat slower than parabolic at high temperatures. Rate control during this period was thought to be due to mass transport through the oxide grain boundaries left by the island impingement process. During these first two stages the oxide formed was γ-M2O3 with possibly some spinel. The final stage of reaction involved the appearance of α-M2O3 on the outer oxide surface and a substantial slowing of the oxidation rate due to the low diffusivity in this phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00605109
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  • 2
    Electronic Resource
    Electronic Resource
    Sulfidation behavior of austeno-ferritic steels (1984)
    Springer
    Oxidation of metals 21 (1984), S. 103-118 
    Details
    ISSN: 1573-4889
    Keywords: duplex steels ; sulfidation ; kinetics ; transport processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Two austeno-ferritic stainless steels were sulfidized at temperatures of 783, 873, and 963 K under sulfur pressures in the range 4×10−12 to 3×10−5 atm. In all cases a triplex scale developed, consisting of an outermost layer of (Fe, Cr)1−xS, an intermediate layer of FeCr2S4, and an innermost layer of porous (Cr, Fe)1−xS containing particles of Mo2S3. Parabolic kinetics were observed except at the lowest temperature where one of the steels reacted according to irregular kinetics. The Mo2S3 particles in the innermost layer acted as inert markers, imaging the former positions of the steels' ferrite phase in which Mo is enriched. The lamellar microstructure of the steel was thus reproduced in the innermost sulfide layer. The positions of the Mo2S3 particles together with the porosity of the inner layer are taken to imply inward sulfur transport through this layer and outward metal transport through all three layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00741466
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of internal nitridation reactions in ammonia and in nitrogen (1995)
    Springer
    Oxidation of metals 44 (1995), S. 453-474 
    Details
    ISSN: 1573-4889
    Keywords: stainless steel ; nickel alloys ; chromium nitride ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Nine commercial high-temperature alloys were reacted with NH3 and with N2-5%H2 at temperatures of 1000–1200°C. In all cases extensive internal nitridation developed according to parabolic kinetics. Reaction with N2 produced precipitates of Cr2N plus, at 1000°C, some external CrN, in accordance with thermodynamic prediction. However NH3 produced an external scale of CrN and a near-surface zone of internal CrN as well as a deeper zone of Cr2N at 1100 and 1200°C. The CrN phase is metastable, and results from catalytic dissociation of NH3, which produces a high effective nitrogen activity. This high activity also leads to faster internal-precipitation reactions, whereas reaction rates in nitrogen are in reasonable agreement with Wagner's model of rate control by inwardly diffusing nitrogen at its equilibrium solubility. Precipitate morphologies are complex, reflecting the importance of the energy barrier to homogeneous nucleation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01058247
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of scale constitution on the carburization of heat resistant steels (1986)
    Springer
    Oxidation of metals 26 (1986), S. 417-430 
    Details
    ISSN: 1573-4889
    Keywords: cyclic carburization-oxidation ; carbides ; austenite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several austenitic heat-resistant steels were exposed to alternating periods of carburization at 1273 K [a c= 1,po2〈10−28 atm] and oxidation at 973°K [a c≈ O,po2 = 0.2 atm]. In all cases the depth of internal carbide precipitation increased with cumulative carburization time. It was found that the carburization rates of high nickel content alloys were unaffected by intermittent oxidation cycles, whereas the low nickel, high iron content alloys experienced a reduction in carburization rate subsequent to oxidation treatment. The latter group of alloys formed external scales of chromium-rich M7C3 which were shown by sulfur tracing experiments to be gas permeable. It was concluded, therefore, that oxidation of these materials led to blockage of cracks and holes in the scales, thereby decreasing the surface carbon activity and hence the carburization rate. High nickel, low iron alloys formed external scales of chromium-rich M7C3 covered by Cr3C2. These scales were shown to have very low gas permeabilities. It was concluded that the carbon activity at the surface of these alloys was controlled by scale-alloy equilibration, and was therefore not affected by brief periods of oxidation. The pattern of carbide scale formation is qualitatively consistent with the thermodynamics of the Fe-Cr-C system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00659345
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  • 5
    Electronic Resource
    Electronic Resource
    Hydrogen doping effects in the sulfidation of molybdenum (1991)
    Springer
    Oxidation of metals 36 (1991), S. 15-25 
    Details
    ISSN: 1573-4889
    Keywords: anions ; diffusion ; intercalation ; point defects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The kinetics of molybdenum sulfidation have been studied in H2S/H2 gas mixtures at 1173 K. Sulphur partial pressures were controlled by the equilibrium reaction between H2S, H2, and S2. Pure molybdenum metal was sulfidized at a fixed $$p{_S} _{_2 } $$ value of 133 Pa with varying H2S and H2 partial pressures, and at fixed H2S partial pressures of 5.06×10 pa4 and 5.06×103 Pa with varying hydrogen and sulfur partial pressures. The gravimetric sulfidation kinetics were parabolic under all conditions. X-ray diffraction analysis of the reaction product scale revealed the presence of MoS2 only. The sulfide scales were of uniform thickness, had a compact morphology, and were tightly adherent to the metal. The sulfidation rates at a fixed sulfur partial pressure increased with increasing hydrogen partial pressure. At fixed $$p{_H} _{_2} {_S} $$ values, the rate was almost constant at high $$p{_H} _{_2 } $$ values, but increased substantially as $$p{_H} _{_2 } $$ was decreased. Defect models for hydrogen dissolution in MoS2 are developed and compared with the experimental results. It is concluded that the sulfidation rate effects are due to hydride anion occupation of interlayer sites in MoS2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938454
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  • 6
    Electronic Resource
    Electronic Resource
    High-temperature corrosion in mixed gas environments (1995)
    Springer
    Oxidation of metals 44 (1995), S. 239-264 
    Details
    ISSN: 1573-4889
    Keywords: oxidation ; carburization ; sulfidation ; scaling ; internal precipitation ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Scaling reactions between pure metals and multiple oxidant gases are reviewed briefly. It is recognized that elemental oxidant activities are usually so low that the actual reactant species are heteronuclear molecules such as SO2, CO2, etc. The formation of duplex, sulfide-oxide scales on iron and manganese, even when sulfide is unstable with respect to oxide, is attributed to direct reaction with SO2. The persistence of the metastable sulfide is due to its preservation by the rapidly growing scale. The reaction of pure chromium with a number of mixed gases is also discussed. The continued formation of carbides and nitrides beneath an external Cr2O3 scale layer indicates that the latter material is permeable to gas species. Interaction among different gas species is observed, and is attributed to selective adsorption on internal surfaces within the chromium oxide. New work on the reaction of alloys with mixed gases is reported. Several austenitic heat-resistant alloys were exposed at 1000°C to gases containing one, two or all of the oxidants carbon, sulfur and oxygen. Gases containing two or more oxidants produced multiple zones of internal precipitation. The precipitates were chromium-rich oxides, sulfides and carbides arranged in order of thermodynamic stability: oxides beneath the external scale, carbides deepest within the alloys and sulfides in an intermediate zone overlapping the oxide zone. Each precipitate zone widened according to parabolic kinetics. This finding confirms the as yet untested prediction made by J. L. Meijering in 1971. However, the rate at which a particular zone grows changes according to presence of other oxidants. Interactions between the oxidants can be large and reaction rates are currently not predictable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046729
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