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  • 1
    Electronic Resource
    Electronic Resource
    Morphological development of oxide-sulfide scales on iron and iron-manganese alloys (1987)
    Springer
    Oxidation of metals 28 (1987), S. 165-181 
    Details
    ISSN: 1573-4889
    Keywords: Iron ; iron-manganese alloys ; oxidation-sulfidation ; scale morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Pure iron and alloys containing 2, 15, 25, and 50 wt. % manganese have been reacted at 1073 K in controlled gas atmospheres of SO 2-CO 2-CO-N 2.Equilibrium gas compositions were such that (1) FeS was stable but not FeO, or (2) both FeS and FeO were stable, or (3) FeO was stable but not FeS; in all cases, both MnS and MnO were stable. Under all reaction conditions, pure iron corroded to produce both sulfide and oxide. The resultant scale morphologies were consistent with local solid-gas equilibrium for the case in which both oxide and sulfide were stable but in the other cases indicated that equilibrium was not achieved and that direct reaction with SO 2 (g) was responsible for corrosion. Additions of manganese did not greatly alter the scale morphologies. Under reaction conditions that were oxidizing and sulfidizing, very high levels of manganese were required to reduce the corrosion rate. On the other hand, relatively low levels had a beneficial effect both when FeO but not FeS was thermodynamically stable and similarly when FeS but not FeO was stable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656705
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  • 2
    Electronic Resource
    Electronic Resource
    Carburization kinetics of heat-resistant steels (1982)
    Springer
    Oxidation of metals 18 (1982), S. 229-243 
    Details
    ISSN: 1573-4889
    Keywords: Austenitic steels ; carburization ; carbon diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A series of 21 commercial austenitic heat-resistant alloys was carburized in H2-C3H6 atmospheres which were reducing to Cr2O3 and SiO2 and which provided a carbon activity of one. Reactions were carried out at 900⩽T⩽1100°C and the resulting depth of carburization was measured metallographically. All alloys showed parabolic carburization kinetics after an initial brief period, at low temperatures, of more rapid reaction. The apparent activation energies for carburization are discussed in terms of carbon solubilities and diffusion coefficients. It is concluded that Wagner's theory of internal oxidation is quantitatively applicable to simple alloys but not to alloys which contain additions of reactive elements. The effectiveness of additions of niobium, aluminum, titanium, and silicon is demonstrated and is discussed in the context of Wagner's theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656570
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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Sulfidation behavior of an aluminum-manganese steel (1986)
    Springer
    Oxidation of metals 25 (1986), S. 107-119 
    Details
    ISSN: 1573-4889
    Keywords: manganese sulfide ; scaling kinetics ; nodules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An alloy steel containing 4.5 weight percent (w/o) manganese, 8.8 w/o aluminum, and 0.36 w/o carbon was sulfidized at temperatures of 973, 1073, and 1173 K in flowing H2/H2S gas mixtures corresponding to sulfur partial pressures in the range 10−8-10−4 atm. Slow parabolic weight uptake kinetics were observed at T=973 K whenP s 2≤10-7 atm and at T =1073 K when PS 2=10-7 atm. Under these conditions, a thin external scale rich in α-MnS was formed. At higher values of PS 2 at these temperatures, and at all values of PS 2 [(Fe, Mn)S plus (Fe, Mn)Al2S4] porous layer, which grew by inward sulfur transport, and an outer region of FeS, which grew by outward diffusion of iron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807999
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  • 6
    Electronic Resource
    Electronic Resource
    Thermodynamics of ionic diffusion and oxidation rate equations (1988)
    Springer
    Oxidation of metals 29 (1988), S. 169-185 
    Details
    ISSN: 1573-4889
    Keywords: Ionic diflusion ; oxidation rate ; point defects ; relative building units
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Diffusional flux equations for individual lattice species and defects are related to phenomenological mass-transport equations using the concept of relative building units. These units conserve sites and charge but represent local constitutional change within a crystal resulting either from equilibration with another phase or from diffusion within the crystal. Using the example of a metal deficit, solid solution oxide (A1ξ Bξ)1−δ0, a simple thermodynamic method is arrived at for producing an exhaustive listing of units capable of participating in diffusion during an oxidation reaction. A combination of the flux contributions due to these different units then permits a calculation of the phenomenological transport coefficients in terms of microscopic kinetic and concentration variables. This description, together with a precise statement of the Gibbs-Duhem equation, permits an examination of the usual approximations in oxidation rate equations: the neglect of diffusional interactions and of nonstoichiometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656355
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  • 7
    Electronic Resource
    Electronic Resource
    Parabolic growth of solid-solution scales: Effect of deviations from stoichiometry (1988)
    Springer
    Oxidation of metals 30 (1988), S. 391-403 
    Details
    ISSN: 1573-4889
    Keywords: alloy oxidation ; solid-solution scales ; nonstoichiometry
    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 deviations from the stoichiometric composition of solid-solution oxides formed during the oxidation of a binary alloy is considered by taking into account its influence on the activities of the oxide components using an approximate expression. Calculations carried out for two systems, the Co-Ni and Co-Fe alloys, forming CoO-NiO and CoO-FeO solid-solution scales, show that the effect of this factor on the form of the calculated profile of oxide composition through the scale is negligible in the former case but significant in the latter. Inclusion of this effect in the theoretical treatment for the Co-Fe system yields results that are in better agreement with the experimental data than are those calculated by means of the classic treatment, which neglects this aspect. This finding results from the larger magnitude of the deviation from Stoichiometry in the CoO-FeO system as compared with the CoO-NiO system. In neither case does the nonstoichiometry affect significantly the magnitude of the calculated rate constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00659007
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of aluminum on the oxidation of 25Cr-35Ni cast steels (1984)
    Springer
    Oxidation of metals 22 (1984), S. 227-245 
    Details
    ISSN: 1573-4889
    Keywords: internal oxidation ; carbide 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 kinetics and morphological development during reaction of two cast austenitic steels at 1000°C in pure dry oxygen at 20 kPa are reported. Both steels contained approximately 25 wt.% Cr and 35 wt.% Ni and, in addition, one steel contained 3.3 wt. %. Both steels oxidized to form external scales consisting mainly of Cr2O3 with a thin outer layer of manganese rich spinel. Scale growth kinetics were parabolic, and somewhat faster rates were observed for the aluminum bearing steel. In both steels, deep internal oxidation occurred at the site of primary (interdendritic) carbides. The kinetics of this process were parabolic, and rate control was attributed to oxygen diffusion along the interface between internal oxide and matrix metal. In the aluminum-free steel, interdendritic carbides were converted to chromium rich oxide, but when aluminum was present, a sheath of aluminum rich oxide formed around the carbides. In this latter case, the rate of interdendritic penetration was somewhat slower. The aluminum bearing steel also formed large numbers of rod-shaped Al2O3 precipitates within the austenitic dendrites. Deepening of the Al2O3 precipitate zone also proceeded according to parabolic kinetics at a rate consistent with rate control by diffusion of oxygen along the oxide-alloy interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656577
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  • 9
    Electronic Resource
    Electronic Resource
    Morphological evolution during sulfidation of an iron-nickel alloy (1989)
    Springer
    Oxidation of metals 31 (1989), S. 105-121 
    Details
    ISSN: 1573-4889
    Keywords: surface reactions ; whiskers ; catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An Fe-41 wt.% Ni alloy was reacted at 793, 888, and 938K with H2-H2S-N2 mixtures corresponding to equilibrium $$p_{S_2 } $$ levels of 3×10−4−0.65Pa and varying degrees of nitrogen dilution. At 793 K and low values of $$p_{H_2 S} $$ and $$p_{S_2 } $$ , a compact layer of almost pure Fe1−δS was the only product. At $$p_{H_2 S} $$ values of 5×103−1×104 Pa, large growths of nickel-rich sulfide whiskers formed on top of the compact layer. At $$p_{H_2 S} $$ =2.2×104 and $$p_{S_2 } $$ = 1.8×10−3 Pa, the whiskers were replaced by a compact layer of (Ni, Fe)1−δS. Kinetics were irregular at 793 K, but at the higher temperatures parabolic kinetics were observed after an initial period of slow reaction, during which a compact layer of Fe1−δS was the only product. The onset of parabolic kinetics corresponded to the appearance of an additional zone of nickel-rich sulfide. This zone was made up of whiskers, except at high $$p_{H_2 S} $$ .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665489
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  • 10
    Electronic Resource
    Electronic Resource
    Morphological studies of coking on heat-resistant alloys (1985)
    Springer
    Journal of materials science 20 (1985), S. 4035-4044 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The deposition of coke from a propylene-hydrogen mixture on to a range of austenitic Fe-Cr-Ni base alloys has been studied. Morphological investigations reveal the formation of a chromium-rich carbide layer on the surface of the alloys. This layer is initially protective, but eventually develops defects from which coke filaments grow. The formation of these filaments is catalysed by the chromium-depleted metal which becomes accessible to the gas following failure of the carbide layer. Once catalytic coke formation commences, it is maintained by the presence within the coke of small metal particles rich in iron and nickel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552396
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