Quantitative Prediction of Voids Formation in a Growing Nickel Oxide Scale at 1373 K

Akiba, Kojiro; Ueda, Mitsutoshi; Kawamura, Kazutaka; Maruyama, Toru

doi:10.2320/matertrans.mer2007122

Cited by 15 publications

(15 citation statements)

References 17 publications

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“…Grids of uniformed size were traced on each images and area fraction of voids in the scale was measured. It was ass to the cross-sectional area fraction of voids in the scale applied by Akiba et al [11] substrate at 1373 K. Figure 2 shows an example of an area of a sample's 4 spots being analyzed to determine the main SEM micrograph shows the spots for EDX analysis.…”

Section: Fig 3: Schematics Of Samples After Being Crossmentioning

confidence: 99%

Observation On Void Formed In Oxide Scale Of Fe-Cr-Ni Alloy At 1073k In Dry And Humid Environments

Kaderi¹,

Zainal

Ani³

et al. 2012

IIUMEJ

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Void formation in oxide scale during high temperature oxidation is a common phenomenon. Over a long period of time voids will affect the mechanical property of scales by influencing the cracking and spalling. Voids formed in dry environment are different than that of formed in humid environment. With the presence of water vapor in humid environment the formation of void will increase, thus greater number of void compared to that in dry environment. Fe-Cr-Ni alloy samples were exposed isothermally at 1073 K in air (P_(O_2 )= 0.21atm = 2.1×?10?^(5 )Pa) and humid (air + steam) environments. XRD analysis done to all samples confirms that Fe2O3, Fe3O4, NiCr2O4, FeCr2O4, Cr2O3 and NiO phases exist in the scale. EDX analysis done shows varying compositions of Fe,Cr,Ni and O in outer and inner oxide scale, oxide scale/metal interface and metal. Field emission scanning electron microscope (FE-SEM) was used to investigate voids formed in the cross sections of the oxidized samples. Volume fraction of voids in the oxide scale was calculated in accordance to the cross sectional area fraction of voids in the scale. It shows that Fe-Cr-Ni alloy samples exposed in humid environment has as high as 71% more voids than that exposed in dry environment. It is concluded that the humid environment increased the number of void formed in the oxide scale, thus facilitates the exfoliation of protective scale during the high temperature oxidation. ABSTRAK: Pembentukan gelembung udara di dalam lapisan oksida ketika proses pengoksidaan di suhu tinggi merupakan satu fenomena biasa. Pada satu jangka masa yang panjang gelembung-gelembung ini akan memberi kesan kepada sifat mekanikal oksida dengan mempengaruhi pembentukan keretakan dan pengelupasan oksida. Gelembung udara yang terbentuk di dalam persekitaran kering berbeza daripada yang terbentuk di dalam persekitaran lembap. Dengan adanya wap air, pembentukan gelembung akan bertambah berbanding yang terbentuk di dalam persekitaran kering. Sampel aloi Fe-Cr-Ni telah dioksidakan secara isoterma pada suhu 1073 K di dalam udara (P_(O_2 )= 0.21atm = 2.1×?10?^(5 )Pa) dan lembap (udara + wap air). Analisis Pembelauan Sinar – X (XRD) kepada semua sampel menunjukkan oksida yang terbentuk ialah Fe2O3, Fe3O4, NiCr2O4, FeCr2O4, Cr2O3 dan NiO. Analisis Penyebaran Tenaga Sinar – X (EDX) menunjukkan komposisi Fe, Cr, Ni dan O yang berubah - ubah di lapisan oksida luar dan dalam, oksida/ antara muka logam dan logam. Mikroskop Imbasan Elektron-Pancaran Medan (FE-SEM) digunakan untuk meneliti gelembung di dalam oksida pada keratan rentas sampel. Pecahan isi padu gelembung yang terbentuk pada oksida dikira dengan merujuk kepada pecahan luas keratan rentas pada oksida tersebut. Sampel aloi Fe-Cr-Ni yang dioksidakan di dalam persekitaran lembap mempunyai kandungan gelembung udara 71% lebih banyak berbanding dengan yang dioksidakan di dalam persekitaran kering. Kesimpulannya persekitaran lembap meningkatkan bilangan gelembung yang terbentuk di dalam lapisan oksida, sekaligus memudahkan pengelupasan oksida semasa pengoksidaan suhu tinggi.KEYWORDS: high temperature oxidatio;, Fe-Cr-Ni alloy; void formation; quantitative analysis of voi;, dry environment; humid environment

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Section: Fig 3: Schematics Of Samples After Being Crossmentioning

confidence: 99%

Observation On Void Formed In Oxide Scale Of Fe-Cr-Ni Alloy At 1073k In Dry And Humid Environments

Kaderi¹,

Zainal

Ani³

et al. 2012

IIUMEJ

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“…Figure 13 shows the parabolic plots of the scale thickness of both NiO scale and CoO scale formed on nickel and cobalt in Ar-21 %O 2 at 1373 K, which was reported by the present authors. 3,4) The growth rate of CoO scale on cobalt is larger than that of NiO scale on nickel. It indicates that the oxygen consumption rate for the oxidation of cobalt is larger than that of nickel.…”

Section: Measurement Of Thickness Of Gas Boundary Layermentioning

confidence: 99%

“…Present authors 3,4) have demonstrated the prediction of the voids formation in the scales of NiO and CoO formed in high temperature oxidation of nickel and cobalt at 1373 K, and have predicted that the voids in the oxide scale form mainly in the vicinity of the metal/oxide interface in a quantitative manner. These predictions are in good agreement with the morphology that is experimentally observed.…”

Section: Introductionmentioning

confidence: 99%

“…The growth of Fe 3 O 4 , NiO and CoO scales is categorized in this regime. [1][2][3][4] On the other hand, when the scale growth is mainly controlled by mass transport from gas phase to the scale surface ( Fig. 1(b)), the boundary layer is developed and the oxygen chemical potential is much lower than that in the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4] Therefore, oxygen chemical potential at the surface of oxide scale is one of the essential parameters for quantitative analyses of the morphological change in the oxide scale.…”

Section: Introductionmentioning

confidence: 99%

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Continuous Monitoring of Oxygen Chemical Potential at the Surface of Growing Oxide Scales during High Temperature Oxidation of Metals

et al. 2008

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The continuous monitoring of the oxygen chemical potential at a surface of a growing oxide surface formed in high temperature oxidation of a metal was developed. During the oxidation of nickel and cobalt at 1373 K in Ar-21%O 2 gas, the oxygen chemical potentials at the surface of formed NiO scale and CoO scale were slightly smaller than that in the atmosphere, because the growths of these oxide scales were mainly ratelimited by the diffusion of the constituent ions in the scales. The difference of the oxygen chemical potential between at the surface of CoO scale and in the atmosphere was larger than that between at the surface of NiO scale and in the atmosphere under the same oxidation condition, since the oxygen consumption rate for the oxidation of cobalt was larger than that of nickel. In the case of the oxidation of iron at 1373 K in Ar-CO-CO 2 gas mixture, the oxygen chemical potential at the surface of formed FeO scale decreased largely from that in the atmosphere, since the growth of FeO scale was very fast and mainly rate-limited by the mass transport from gas phase to the scale surface. The oxygen chemical potential at the surface of FeO scale increased with increment of CO 2 concentration in the atmosphere.

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Effect of Water Vapor on the High-Temperature Oxidation of Pure Ni

Auchi¹,

Hayashi²,

Toyota³

et al. 2012

Oxid Met

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Quantitative Prediction of Voids Formation in a Growing Nickel Oxide Scale at 1373 K

Cited by 15 publications

References 17 publications

Observation On Void Formed In Oxide Scale Of Fe-Cr-Ni Alloy At 1073k In Dry And Humid Environments

Observation On Void Formed In Oxide Scale Of Fe-Cr-Ni Alloy At 1073k In Dry And Humid Environments

Continuous Monitoring of Oxygen Chemical Potential at the Surface of Growing Oxide Scales during High Temperature Oxidation of Metals

Effect of Water Vapor on the High-Temperature Oxidation of Pure Ni

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