Dépouillements

Internal oxidation of Fe–3%Si alloys annealed under H2O–H2 atmosphere / S. Yamazaki in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 476–480 Titre : Internal oxidation of Fe–3%Si alloys annealed under H2O–H2 atmosphere Type de document : texte imprimé Auteurs : S. Yamazaki, Auteur ; F. Takahashi, Auteur ; T. Kubota, Auteur Année de publication : 2011 Article en page(s) : pp. 476–480 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Internal  oxidation  Oxygen  diffusion  Precipitate  morphology  Silicon  steel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Internal oxidation phenomena during decarburization annealing are very important in the manufacturing process of grain oriented electrical steel. In the present study, the internal oxidation of nearly pure Fe–3%Si alloy was investigated, as a basic study for decarburization annealing. Annealing was performed at various equation image ratios and at 1123 K for 300 s. The transition of external to internal oxidation took place at equation image around 0.01. The morphologies of oxide in the internal oxidation zone (IOZ) were filamentary or needle-like shapes and different from the reported oxide shapes in industrial electrical steel. These peculiar morphologies affected the kinetic aspects such as the depth and the enrichment of oxide in the IOZ. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005862/abstract [article] Internal oxidation of Fe–3%Si alloys annealed under H2O–H2 atmosphere [texte imprimé] / S. Yamazaki, Auteur ; F. Takahashi, Auteur ; T. Kubota, Auteur . - 2011 . - pp. 476–480. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 476–480 Mots-clés : Internal  oxidation  Oxygen  diffusion  Precipitate  morphology  Silicon  steel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Internal oxidation phenomena during decarburization annealing are very important in the manufacturing process of grain oriented electrical steel. In the present study, the internal oxidation of nearly pure Fe–3%Si alloy was investigated, as a basic study for decarburization annealing. Annealing was performed at various equation image ratios and at 1123 K for 300 s. The transition of external to internal oxidation took place at equation image around 0.01. The morphologies of oxide in the internal oxidation zone (IOZ) were filamentary or needle-like shapes and different from the reported oxide shapes in industrial electrical steel. These peculiar morphologies affected the kinetic aspects such as the depth and the enrichment of oxide in the IOZ. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005862/abstract

Influence of minor additions on the emissivity of the oxide scale of FeCrAlY alloys during resistance heating / H. Hattendorf in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 481–489 Titre : Influence of minor additions on the emissivity of the oxide scale of FeCrAlY alloys during resistance heating Type de document : texte imprimé Auteurs : H. Hattendorf, Auteur Année de publication : 2011 Article en page(s) : pp. 481–489 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Alumina  scale  Emissivity  FeCrAlY  alloys  Internal  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Chromium aluminum yttrium (FeCrAlY) alloys owe their low oxidation rate to the formation of a slow growing α-alumina scale. For material used for heating elements not only the life time and the behavior of the resistance during the life time is of relevance, but also the emission coefficient of the oxide scale. The power density JS produced by resistance heating of strip with 50 µm thickness and about 5–6 mm width at 1050 °C is approximately equal to the radiant flux density, which is according to Stefan–Boltzmann's law proportional to the total emission coefficient εg. Resistance heating tests were performed on samples made from FeCrAlY alloys with different zirconium and carbon content. The “high zirconium” containing FeCrAlY alloys (zirconium > about 0.10%) have a higher power density/emissivity than the “low zirconium” alloys. In parallel with this, all samples with higher power density/emissivity have internal oxidation and therefore a “rough” metal–oxide interface. Thus, one cause for the increase of the emissivity of the scale could be this rough metal–oxide interface; other causes could be a higher amount of zirconium incorporated into the scale, more pores and/or different grain structure in the scale. Additionally the carbon content influences the appearance of a higher emissivity and the internal oxidation. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005869/abstract [article] Influence of minor additions on the emissivity of the oxide scale of FeCrAlY alloys during resistance heating [texte imprimé] / H. Hattendorf, Auteur . - 2011 . - pp. 481–489. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 481–489 Mots-clés : Alumina  scale  Emissivity  FeCrAlY  alloys  Internal  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Chromium aluminum yttrium (FeCrAlY) alloys owe their low oxidation rate to the formation of a slow growing α-alumina scale. For material used for heating elements not only the life time and the behavior of the resistance during the life time is of relevance, but also the emission coefficient of the oxide scale. The power density JS produced by resistance heating of strip with 50 µm thickness and about 5–6 mm width at 1050 °C is approximately equal to the radiant flux density, which is according to Stefan–Boltzmann's law proportional to the total emission coefficient εg. Resistance heating tests were performed on samples made from FeCrAlY alloys with different zirconium and carbon content. The “high zirconium” containing FeCrAlY alloys (zirconium > about 0.10%) have a higher power density/emissivity than the “low zirconium” alloys. In parallel with this, all samples with higher power density/emissivity have internal oxidation and therefore a “rough” metal–oxide interface. Thus, one cause for the increase of the emissivity of the scale could be this rough metal–oxide interface; other causes could be a higher amount of zirconium incorporated into the scale, more pores and/or different grain structure in the scale. Additionally the carbon content influences the appearance of a higher emissivity and the internal oxidation. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005869/abstract

Scale growth process at 1473 K on unmodified and yttrium- or chromium-implanted B-NiAl / J. Jedlinski in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 490–495 Titre : Scale growth process at 1473 K on unmodified and yttrium- or chromium-implanted B-NiAl Type de document : texte imprimé Auteurs : J. Jedlinski, Auteur ; J.-L. Grosseau-Poussard, Auteur ; Bonnet, G., Auteur Année de publication : 2011 Article en page(s) : pp. 490–495 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : β-NiAl  Y-  and  Cr-  additions  scale  growth  mechanism Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Early oxidation of unmodified and yttrium-implanted or chromium-implanted β-NiAl intermetallic compound at 1473 K was studied using a combination of two-stage-oxidation exposure with 18O2 as a tracer, SIMS elemental distribution analysis (depth profiling and imaging modes) and photoluminescence spectroscopy analysis of the scale phase composition. It was found that phase transformation of transient aluminium oxides, represented by θ- Al2O3 into stable and protective α-Al2O3 occurs locally and is affected by implanted additions: Yttrium retarded while chromium appeared to accelerate it. Typical patch- and/or web-like scale morphology of the growing scales was observed. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005852/abstract [article] Scale growth process at 1473 K on unmodified and yttrium- or chromium-implanted B-NiAl [texte imprimé] / J. Jedlinski, Auteur ; J.-L. Grosseau-Poussard, Auteur ; Bonnet, G., Auteur . - 2011 . - pp. 490–495. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 490–495 Mots-clés : β-NiAl  Y-  and  Cr-  additions  scale  growth  mechanism Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Early oxidation of unmodified and yttrium-implanted or chromium-implanted β-NiAl intermetallic compound at 1473 K was studied using a combination of two-stage-oxidation exposure with 18O2 as a tracer, SIMS elemental distribution analysis (depth profiling and imaging modes) and photoluminescence spectroscopy analysis of the scale phase composition. It was found that phase transformation of transient aluminium oxides, represented by θ- Al2O3 into stable and protective α-Al2O3 occurs locally and is affected by implanted additions: Yttrium retarded while chromium appeared to accelerate it. Typical patch- and/or web-like scale morphology of the growing scales was observed. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005852/abstract

Effect of water vapour on cyclic oxidation of Fe–Cr alloys / N. K. Othman in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 496–503 Titre : Effect of water vapour on cyclic oxidation of Fe–Cr alloys Type de document : texte imprimé Auteurs : N. K. Othman, Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur Année de publication : 2011 Article en page(s) : pp. 496–503 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Alloy  depletion  Breakaway  Cyclic  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model Fe–Cr alloys containing 9, 17 or 25 wt% Cr were subjected to repeated 1 h cycles of exposure at 700 °C to flowing gas mixtures of Ar-20O2, Ar-20O2-5H2O and Ar-5O2-20H2O (all in volume %) for up to 400 cycles. The kinetics and morphological development of these reactions were compared with those found during isothermal exposure to the same gases. Under isothermal conditions, all alloys developed thin protective chromium-rich scales in dry oxygen. Addition of 5% H2O induced breakaway for Fe-9Cr within 48 h, but had little effect on higher chromium alloys. Isothermal chromia scale growth on Fe-17Cr and Fe-25Cr was accelerated by the addition of 20% H2O, but breakaway did not result. Under cyclic conditions in dry oxygen, Fe-9Cr quickly entered breakaway, oxidising according to fast, linear kinetics, but the higher chromium alloys exhibited protective behaviour. When 5% H2O was added to the oxygen, the 17% Cr alloy also underwent fast breakaway oxidation, but Fe-25Cr continued to be protected by a chromia scale. In the 20% H2O gas, all alloys failed under cyclic conditions, producing thick, iron-rich oxide scales. The synergistic effects of water vapour and temperature cycling are discussed in terms of alloy chromium depletion and the effects of H2O(g) on oxide transport properties. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005866/abstract [article] Effect of water vapour on cyclic oxidation of Fe–Cr alloys [texte imprimé] / N. K. Othman, Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur . - 2011 . - pp. 496–503. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 496–503 Mots-clés : Alloy  depletion  Breakaway  Cyclic  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model Fe–Cr alloys containing 9, 17 or 25 wt% Cr were subjected to repeated 1 h cycles of exposure at 700 °C to flowing gas mixtures of Ar-20O2, Ar-20O2-5H2O and Ar-5O2-20H2O (all in volume %) for up to 400 cycles. The kinetics and morphological development of these reactions were compared with those found during isothermal exposure to the same gases. Under isothermal conditions, all alloys developed thin protective chromium-rich scales in dry oxygen. Addition of 5% H2O induced breakaway for Fe-9Cr within 48 h, but had little effect on higher chromium alloys. Isothermal chromia scale growth on Fe-17Cr and Fe-25Cr was accelerated by the addition of 20% H2O, but breakaway did not result. Under cyclic conditions in dry oxygen, Fe-9Cr quickly entered breakaway, oxidising according to fast, linear kinetics, but the higher chromium alloys exhibited protective behaviour. When 5% H2O was added to the oxygen, the 17% Cr alloy also underwent fast breakaway oxidation, but Fe-25Cr continued to be protected by a chromia scale. In the 20% H2O gas, all alloys failed under cyclic conditions, producing thick, iron-rich oxide scales. The synergistic effects of water vapour and temperature cycling are discussed in terms of alloy chromium depletion and the effects of H2O(g) on oxide transport properties. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005866/abstract

Temperature and gas composition dependence of internal oxidation kinetics of an Fe[BOND]10%Cr alloy in water vapour containing environments / J. Zurek in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 504–513 Titre : Temperature and gas composition dependence of internal oxidation kinetics of an Fe[BOND]10%Cr alloy in water vapour containing environments Type de document : texte imprimé Auteurs : J. Zurek, Auteur ; G. H. Meier, Auteur ; E. Wessel, Auteur Année de publication : 2011 Article en page(s) : pp. 504–513 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Chromia  Internal  oxidation  Model  alloy  Water  vapour Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Recently it was proposed, that the hampered formation of external protective chromia scales on FeCr-alloys in water vapour containing, low-pO2 gases is correlated with enhanced internal oxidation of chromium. In the present study the internal oxidation kinetics of Fe[BOND]10Cr (in mass%) during isothermal oxidation in Ar[BOND]H2[BOND]H2O mixtures at temperatures in the range 800–1050 °C has been investigated. It was found that the tendency for Cr to become internally oxidized decreased with decreasing temperature. At the higher test temperatures the internal oxide precipitates consisted of Fe/Cr-spinel. With decreasing temperature the precipitates near the oxidation front gradually exhibited increasing amounts of chromia. At 900 °C the oxidation morphology in the Ar[BOND]H2 base gas mixture changed from exclusive internal oxidation of Cr at a water vapour content of 2% towards a combined internal Cr oxidation and external Fe-oxide formation at higher water vapour partial pressures. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005865/abstract [article] Temperature and gas composition dependence of internal oxidation kinetics of an Fe[BOND]10%Cr alloy in water vapour containing environments [texte imprimé] / J. Zurek, Auteur ; G. H. Meier, Auteur ; E. Wessel, Auteur . - 2011 . - pp. 504–513. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 504–513 Mots-clés : Chromia  Internal  oxidation  Model  alloy  Water  vapour Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Recently it was proposed, that the hampered formation of external protective chromia scales on FeCr-alloys in water vapour containing, low-pO2 gases is correlated with enhanced internal oxidation of chromium. In the present study the internal oxidation kinetics of Fe[BOND]10Cr (in mass%) during isothermal oxidation in Ar[BOND]H2[BOND]H2O mixtures at temperatures in the range 800–1050 °C has been investigated. It was found that the tendency for Cr to become internally oxidized decreased with decreasing temperature. At the higher test temperatures the internal oxide precipitates consisted of Fe/Cr-spinel. With decreasing temperature the precipitates near the oxidation front gradually exhibited increasing amounts of chromia. At 900 °C the oxidation morphology in the Ar[BOND]H2 base gas mixture changed from exclusive internal oxidation of Cr at a water vapour content of 2% towards a combined internal Cr oxidation and external Fe-oxide formation at higher water vapour partial pressures. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005865/abstract

Oxidation of a novel CeO2-dispersed chromium coating in wet air / X. Peng in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 514–520 Titre : Oxidation of a novel CeO2-dispersed chromium coating in wet air Type de document : texte imprimé Auteurs : X. Peng, Auteur ; J. Yan, Auteur ; L. Zheng, Auteur Année de publication : 2011 Article en page(s) : pp. 514–520 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Chromized  coating  Electrodeposition  Ni–CeO2  composite  film  Pack  cementation  Wet  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An electrodeposited Ni–CeO2 composite was used as a “precursor film” for a novel CeO2-dispersed chromium coating deposited using a traditional pack cementation method. The substrate was a carbon steel. For comparison, chromium coatings were also prepared on the untreated and pure Ni-film-treated carbon steel using the same pack cementation conditions. Oxidation in 5% O2 + 40% H2O + N2 at 900 °C showed that, compared to the CeO2-free coating counterparts, the CeO2-dispersed chromium coating exhibited greatly increased oxidation resistance, owing to the development of a denser and more slowly growing chromia scale. The slow growth of the scale was correlated with the CeO2 dispersion exerting the so-called “reactive elemental effect (REE)” on oxidation. The oxidation mechanisms in wet air of the various types of coatings were compared to those in dry air and are fully discussed in this work. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005868/abstract [article] Oxidation of a novel CeO2-dispersed chromium coating in wet air [texte imprimé] / X. Peng, Auteur ; J. Yan, Auteur ; L. Zheng, Auteur . - 2011 . - pp. 514–520. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 514–520 Mots-clés : Chromized  coating  Electrodeposition  Ni–CeO2  composite  film  Pack  cementation  Wet  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : An electrodeposited Ni–CeO2 composite was used as a “precursor film” for a novel CeO2-dispersed chromium coating deposited using a traditional pack cementation method. The substrate was a carbon steel. For comparison, chromium coatings were also prepared on the untreated and pure Ni-film-treated carbon steel using the same pack cementation conditions. Oxidation in 5% O2 + 40% H2O + N2 at 900 °C showed that, compared to the CeO2-free coating counterparts, the CeO2-dispersed chromium coating exhibited greatly increased oxidation resistance, owing to the development of a denser and more slowly growing chromia scale. The slow growth of the scale was correlated with the CeO2 dispersion exerting the so-called “reactive elemental effect (REE)” on oxidation. The oxidation mechanisms in wet air of the various types of coatings were compared to those in dry air and are fully discussed in this work. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005868/abstract

Metal dusting behaviour of several nickel- and cobalt-base alloys in CO-H2-H2O atmosphere / Wu, Q. in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 521–530 Titre : Metal dusting behaviour of several nickel- and cobalt-base alloys in CO-H2-H2O atmosphere Type de document : texte imprimé Auteurs : Wu, Q., Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur Année de publication : 2011 Article en page(s) : pp. 521–530 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Carburization  Cobalt  Graphite  Iron  Metal  dusting  Nickel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The metal dusting behaviour of total 11 nickel- and cobalt-base alloys at 680 °C in a gas of 68%CO[BOND]31%H2[BOND]1%H2O (aC = 19.0, equation image = 5.4 × 10−25  atm) was investigated. All samples were electropolished and reacted in a thermal cycling apparatus. On the basis of their reaction kinetics, these alloys can be classified into three groups: the first, with rapid carbon uptake and significant metal wastage, consists of alloys of relatively high iron content (AC 66, 800H and NS-163); the second, with intermediate rates, consists of some Co-base alloys (HAYNES 188, HAYNES 25 and ULTIMET) and the third, with very low reaction rates, consists of nickel-base alloys with high chromium levels (601, HAYNES HR 160, 230, G-35 and EN 105). An external chromia scale protected group 3 alloys from carburization and dusting. However, this protective scale was damaged and not rehealed for group 1 and group 2 alloys, allowing carbon attack. In all cases, coke deposited on the surface with two typical morphologies: filaments and graphite particle clusters. Subsurface spinel formation in high iron-content alloys led to rapid dusting due to the significant volume expansion. Alloy carbon permeability was calculated from a simple law of mixtures, and shown to correlate reasonably well with initial dusting rate except for one cobalt-base alloy in which iron spinel formation was significant. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005863/abstract [article] Metal dusting behaviour of several nickel- and cobalt-base alloys in CO-H2-H2O atmosphere [texte imprimé] / Wu, Q., Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur . - 2011 . - pp. 521–530. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 521–530 Mots-clés : Carburization  Cobalt  Graphite  Iron  Metal  dusting  Nickel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The metal dusting behaviour of total 11 nickel- and cobalt-base alloys at 680 °C in a gas of 68%CO[BOND]31%H2[BOND]1%H2O (aC = 19.0, equation image = 5.4 × 10−25  atm) was investigated. All samples were electropolished and reacted in a thermal cycling apparatus. On the basis of their reaction kinetics, these alloys can be classified into three groups: the first, with rapid carbon uptake and significant metal wastage, consists of alloys of relatively high iron content (AC 66, 800H and NS-163); the second, with intermediate rates, consists of some Co-base alloys (HAYNES 188, HAYNES 25 and ULTIMET) and the third, with very low reaction rates, consists of nickel-base alloys with high chromium levels (601, HAYNES HR 160, 230, G-35 and EN 105). An external chromia scale protected group 3 alloys from carburization and dusting. However, this protective scale was damaged and not rehealed for group 1 and group 2 alloys, allowing carbon attack. In all cases, coke deposited on the surface with two typical morphologies: filaments and graphite particle clusters. Subsurface spinel formation in high iron-content alloys led to rapid dusting due to the significant volume expansion. Alloy carbon permeability was calculated from a simple law of mixtures, and shown to correlate reasonably well with initial dusting rate except for one cobalt-base alloy in which iron spinel formation was significant. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005863/abstract

Modelling of the oxide scale formation on Fe-Cr steel during exposure in liquid lead-bismuth eutectic in the 450–600 °C temperature range / L. Martinelli in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 531–542 Titre : Modelling of the oxide scale formation on Fe-Cr steel during exposure in liquid lead-bismuth eutectic in the 450–600 °C temperature range Type de document : texte imprimé Auteurs : L. Martinelli, Auteur ; F. Balbaud-Célérier, Auteur Année de publication : 2011 Article en page(s) : pp. 531–542 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Fe-Cr  Magnetite,  Spinel  Oxidation  mechanism  Pb-Bi Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Previous studies showed that the oxidation of T91 (Fe-9Cr martensitic steel) in liquid Pb-Bi eutectic leads to the formation of a duplex oxide layer containing an inner Fe2.3Cr0.7O4 spinel layer and an upper magnetite layer. The magnetite layer is easily removed by the Pb-Bi flow when the oxygen concentration is low and the flow velocity is high. This phenomenon is not currently understood. The magnetite layer growth rate is limited by the iron diffusion in the oxide layer lattice. The Fe-Cr spinel layer grows in the nanometric cavities formed at the Fe-Cr spinel /T91 interface by the outwards diffusion of iron. Due to this mechanism the growth rate of the Fe-Cr spinel layer is linked to that of magnetite. A modelling of this mechanism is presented. The modelling is in agreement with the experimental data in the case of a high oxygen concentration. However, the calculated oxide scale thicknesses are systematically lower than the experimental values in the case of a low oxygen concentration when the iron diffusion only occurs via interstitials in the oxide scale. Consequently, the estimation of the iron diffusion coefficient, when diffusion occurs via interstitials, is not reliable. To have a better estimation of this iron diffusion coefficient in the Fe-Cr spinel, when diffusion occurs via interstitials, a fit is done using experimental data coming from the European DEMETRA project. Although this evaluation is only based on a fit on the experimental data, it permits to estimate the oxide layer growth kinetics in case of the formation of the described duplex oxide layer, for each oxygen concentration (leading to a vacancy and/or an interstitial diffusion), each temperature between 450 and 620 °C and each hydrodynamic flow. This model shows that the hydrodynamic flow affects the corrosion rate only by the removal of the upper magnetite layer leading to an increase of the oxygen concentration at the spinel/magnetite interface. The oxidation mechanism is thus neither changed by the Pb-Bi flow nor by the oxygen concentration. However, the oxygen concentration modifies the iron diffusion process in the oxide lattice. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005871/abstract [article] Modelling of the oxide scale formation on Fe-Cr steel during exposure in liquid lead-bismuth eutectic in the 450–600 °C temperature range [texte imprimé] / L. Martinelli, Auteur ; F. Balbaud-Célérier, Auteur . - 2011 . - pp. 531–542. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 531–542 Mots-clés : Fe-Cr  Magnetite,  Spinel  Oxidation  mechanism  Pb-Bi Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Previous studies showed that the oxidation of T91 (Fe-9Cr martensitic steel) in liquid Pb-Bi eutectic leads to the formation of a duplex oxide layer containing an inner Fe2.3Cr0.7O4 spinel layer and an upper magnetite layer. The magnetite layer is easily removed by the Pb-Bi flow when the oxygen concentration is low and the flow velocity is high. This phenomenon is not currently understood. The magnetite layer growth rate is limited by the iron diffusion in the oxide layer lattice. The Fe-Cr spinel layer grows in the nanometric cavities formed at the Fe-Cr spinel /T91 interface by the outwards diffusion of iron. Due to this mechanism the growth rate of the Fe-Cr spinel layer is linked to that of magnetite. A modelling of this mechanism is presented. The modelling is in agreement with the experimental data in the case of a high oxygen concentration. However, the calculated oxide scale thicknesses are systematically lower than the experimental values in the case of a low oxygen concentration when the iron diffusion only occurs via interstitials in the oxide scale. Consequently, the estimation of the iron diffusion coefficient, when diffusion occurs via interstitials, is not reliable. To have a better estimation of this iron diffusion coefficient in the Fe-Cr spinel, when diffusion occurs via interstitials, a fit is done using experimental data coming from the European DEMETRA project. Although this evaluation is only based on a fit on the experimental data, it permits to estimate the oxide layer growth kinetics in case of the formation of the described duplex oxide layer, for each oxygen concentration (leading to a vacancy and/or an interstitial diffusion), each temperature between 450 and 620 °C and each hydrodynamic flow. This model shows that the hydrodynamic flow affects the corrosion rate only by the removal of the upper magnetite layer leading to an increase of the oxygen concentration at the spinel/magnetite interface. The oxidation mechanism is thus neither changed by the Pb-Bi flow nor by the oxygen concentration. However, the oxygen concentration modifies the iron diffusion process in the oxide lattice. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005871/abstract

Superheater fireside corrosion mechanisms in MSWI plants: Lab-scale study and on-site results / J. M. Brossard in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 543–548 Titre : Superheater fireside corrosion mechanisms in MSWI plants: Lab-scale study and on-site results Type de document : texte imprimé Auteurs : J. M. Brossard, Auteur ; I. Diop, Auteur ; X. Chaucherie, Auteur Année de publication : 2011 Article en page(s) : pp. 543–548 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Fireside  corrosion  Temperature  gradient  Velocity  of  flue  gas  Waste-to-energy  boiler Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Combustion of municipal waste generates highly corrosive gases (HCl, SO2, NaCl, KCl, and heavy metals chlorides) and ashes containing alkaline chlorides and sulfates. Currently, corrosion phenomena are particularly observed on superheater's tubes. Corrosion rates depend mainly on installation design, operating conditions i.e., gas and steam temperature and velocity of the flue gas containing ashes. This paper presents the results obtained using an innovative laboratory-scale corrosion unit, which simulates MSWI boilers conditions characterized by a temperature gradient at the metal tube in the presence of corrosive gases and ashes. The presented corrosion tests were realized on carbon steel at fixed metal temperature (400 °C). The influence of the flue gas temperature, synthetic ashes composition, and flue gas flow pattern were investigated. After corrosion test, cross sections of tube samples were characterized to evaluate thickness loss and estimate corrosion rate while the elements present in corrosion layers were analyzed. Corrosion tests were carried out twice in order to validate the accuracy and reproducibility of results. First results highlight the key role of molten phase related to the ash composition and flue gas temperature as well as the deposit morphology, related to the flue gas flow pattern, on the mechanisms and corrosion rates. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005849/abstract [article] Superheater fireside corrosion mechanisms in MSWI plants: Lab-scale study and on-site results [texte imprimé] / J. M. Brossard, Auteur ; I. Diop, Auteur ; X. Chaucherie, Auteur . - 2011 . - pp. 543–548. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 543–548 Mots-clés : Fireside  corrosion  Temperature  gradient  Velocity  of  flue  gas  Waste-to-energy  boiler Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Combustion of municipal waste generates highly corrosive gases (HCl, SO2, NaCl, KCl, and heavy metals chlorides) and ashes containing alkaline chlorides and sulfates. Currently, corrosion phenomena are particularly observed on superheater's tubes. Corrosion rates depend mainly on installation design, operating conditions i.e., gas and steam temperature and velocity of the flue gas containing ashes. This paper presents the results obtained using an innovative laboratory-scale corrosion unit, which simulates MSWI boilers conditions characterized by a temperature gradient at the metal tube in the presence of corrosive gases and ashes. The presented corrosion tests were realized on carbon steel at fixed metal temperature (400 °C). The influence of the flue gas temperature, synthetic ashes composition, and flue gas flow pattern were investigated. After corrosion test, cross sections of tube samples were characterized to evaluate thickness loss and estimate corrosion rate while the elements present in corrosion layers were analyzed. Corrosion tests were carried out twice in order to validate the accuracy and reproducibility of results. First results highlight the key role of molten phase related to the ash composition and flue gas temperature as well as the deposit morphology, related to the flue gas flow pattern, on the mechanisms and corrosion rates. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005849/abstract

Performance of Al-rich oxidation resistant coatings for Fe-base alloys / B. A. Pint in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 549–560 Titre : Performance of Al-rich oxidation resistant coatings for Fe-base alloys Type de document : texte imprimé Auteurs : B. A. Pint, Auteur ; Y. Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. 549–560 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Coating  Ferritic  alloys  Austenitic  alloys  H2O  effect  Interdiffusion  Lifetime  model Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The oxidation resistance of Al-rich coatings made by chemical vapor deposition and pack cementation was examined on representative ferritic-martensitic (FM, e.g. Grade 91, Fe-9Cr-1Mo) and austenitic steel substrates at 650°-800 °C. To evaluate the potential benefits and problems with these alumina-forming coatings, oxidation exposures were conducted in a humid air environment where the uncoated substrates experience rapid oxidation, similar to steam. Exposure temperatures were increased to accelerate failure by oxidation and interdiffusion of Al into the substrate. The difference in the coefficient of thermal expansion (CTE) between coating and substrate was found to cause cracking and coating failure during rapid thermal cycling on thicker coatings with Fe-Al intermetallic phases. Therefore, thinner coatings with less Al and a ferritic Fe(Al) structure were evaluated more extensively and tested to failure at 700° and 800 °C on FM steels. The remaining Al content at failure was measured and used to improve a previously developed coating lifetime model. At 700° and 800 °C, thin coated austenitic specimens continue to exhibit protective behavior at more than double the lifetime of a similar coating on FM steel. The longer lifetime was attributed to the ferritic coating-austenitic substrate phase boundary inhibiting Al interdiffusion. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005884/abstract [article] Performance of Al-rich oxidation resistant coatings for Fe-base alloys [texte imprimé] / B. A. Pint, Auteur ; Y. Zhang, Auteur . - 2011 . - pp. 549–560. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 549–560 Mots-clés : Coating  Ferritic  alloys  Austenitic  alloys  H2O  effect  Interdiffusion  Lifetime  model Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The oxidation resistance of Al-rich coatings made by chemical vapor deposition and pack cementation was examined on representative ferritic-martensitic (FM, e.g. Grade 91, Fe-9Cr-1Mo) and austenitic steel substrates at 650°-800 °C. To evaluate the potential benefits and problems with these alumina-forming coatings, oxidation exposures were conducted in a humid air environment where the uncoated substrates experience rapid oxidation, similar to steam. Exposure temperatures were increased to accelerate failure by oxidation and interdiffusion of Al into the substrate. The difference in the coefficient of thermal expansion (CTE) between coating and substrate was found to cause cracking and coating failure during rapid thermal cycling on thicker coatings with Fe-Al intermetallic phases. Therefore, thinner coatings with less Al and a ferritic Fe(Al) structure were evaluated more extensively and tested to failure at 700° and 800 °C on FM steels. The remaining Al content at failure was measured and used to improve a previously developed coating lifetime model. At 700° and 800 °C, thin coated austenitic specimens continue to exhibit protective behavior at more than double the lifetime of a similar coating on FM steel. The longer lifetime was attributed to the ferritic coating-austenitic substrate phase boundary inhibiting Al interdiffusion. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005884/abstract

Comparison between field and laboratory steam oxidation testing on aluminide coatings on P92 / A. Agüero in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 561–568 Titre : Comparison between field and laboratory steam oxidation testing on aluminide coatings on P92 Type de document : texte imprimé Auteurs : A. Agüero, Auteur ; V. Gonzlez, Auteur ; M. Gutierrez, Auteur Année de publication : 2011 Article en page(s) : pp. 561–568 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Aluminide  coatings  Field  testing  Ferritic  steels  Power  plants  Steam  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Steam oxidation has become an important issue for steam power plants as operating temperatures increase from the current 550 to 600–650 °C. For the last 10 years several groups have been carrying out steam oxidation testing of both uncoated substrates and coatings in the laboratory. On the other hand, field testing results are very scarce. In this paper, a comparison of laboratory steam oxidation testing with field test results carried out by Alstom at the Kraftwerk Westfalen power station located in Hamm, Germany will be presented. Both slurry deposited aluminide coatings and uncoated P92 steel have been included in the study. Under steam (atmospheric pressure) and isothermal conditions in the laboratory at 650 °C, spallation of oxides formed on ferritic steels occurs after significantly longer time when compared to exposure to real operating conditions. Oxide spallation results in serious damage in steam power plants by obstructing heat exchanger tubes, erosion of valves and turbine blades, etc. Moreover, the thickness of the oxide scales formed under field testing conditions is significantly higher after similar exposure. On the other hand, aluminide coated P92, which exhibit thickness through cracks, have shown to be stable in the laboratory for up to 60 000 h at 650 °C under steam, without evidence of crack propagation. However, field test results indicate that some degree of crack propagation occurs but without causing substrate attack up to 21 700 h of exposure. Moreover, the aluminium oxide observed in both laboratory and field tested specimens is different. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005874/abstract [article] Comparison between field and laboratory steam oxidation testing on aluminide coatings on P92 [texte imprimé] / A. Agüero, Auteur ; V. Gonzlez, Auteur ; M. Gutierrez, Auteur . - 2011 . - pp. 561–568. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 561–568 Mots-clés : Aluminide  coatings  Field  testing  Ferritic  steels  Power  plants  Steam  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Steam oxidation has become an important issue for steam power plants as operating temperatures increase from the current 550 to 600–650 °C. For the last 10 years several groups have been carrying out steam oxidation testing of both uncoated substrates and coatings in the laboratory. On the other hand, field testing results are very scarce. In this paper, a comparison of laboratory steam oxidation testing with field test results carried out by Alstom at the Kraftwerk Westfalen power station located in Hamm, Germany will be presented. Both slurry deposited aluminide coatings and uncoated P92 steel have been included in the study. Under steam (atmospheric pressure) and isothermal conditions in the laboratory at 650 °C, spallation of oxides formed on ferritic steels occurs after significantly longer time when compared to exposure to real operating conditions. Oxide spallation results in serious damage in steam power plants by obstructing heat exchanger tubes, erosion of valves and turbine blades, etc. Moreover, the thickness of the oxide scales formed under field testing conditions is significantly higher after similar exposure. On the other hand, aluminide coated P92, which exhibit thickness through cracks, have shown to be stable in the laboratory for up to 60 000 h at 650 °C under steam, without evidence of crack propagation. However, field test results indicate that some degree of crack propagation occurs but without causing substrate attack up to 21 700 h of exposure. Moreover, the aluminium oxide observed in both laboratory and field tested specimens is different. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005874/abstract

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