Structure of transient oxides formed on nicrai alloys

Smialek, James L.; Gíbala, R.

doi:10.1007/bf02662381

Cited by 71 publications

(42 citation statements)

References 31 publications

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“…During heating, crystallization of the native oxide must occur, and, according to the AES depth profile seen in Fig. 1 The presence of the rod-shaped bands mixed in an Al 2 O 3 oxide layer has rarely been observed on other alloys, although similar phenomenon was reported in scales formed on NiCrAl [23]. The fact that these bands disappear with oxidation time indicates that they are formed during the initial stage of oxidation.…”

Section: Discussionmentioning

confidence: 77%

Al₂O₃scale development on iron aluminides

2006

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Section: Discussionmentioning

confidence: 77%

Al₂O₃scale development on iron aluminides

2006

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“…cations [3][4][5][6][7] and simultaneous vacancy injection at the metal-scale interface [14] With oxidation time the a-Al 2 O 3 grains first form due to nucleation by phase transformation from h-Al 2 O 3 at the metal-scale interface and provide nucleation sites for new a-alumina that then also grows at the metal-scale interface by oxidation reaction involving inward diffusion of O 2-by grain boundaries and forms distinctive imprints in the substrate. The nucleation site [33]. It is noteworthy that even though the predominant diffusing species during the growth of a-alumina is oxygen, experimental work [10] has proven that Al outward diffusion also takes place to a minor extent.…”

Section: S/tem Analysis Of Cross-sectional Microstructure After 100 Hmentioning

confidence: 99%

Characterization of Alumina Scales Grown on a 2nd Generation Single Crystal Ni Superalloy During Isothermal Oxidation at 1050, 1100 and 1150 °C

Swadźba

Wiedermann

et al. 2014

Oxid Met

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This paper concerns microstructural characterization of alumina scales formed on a 2nd generation single crystal Ni superalloy during isothermal oxidation in dry oxygen at 1050, 1100 and 1150°C for 100 h. Samples for high resolution characterization of Al 2 O 3 scales were prepared using a focused ion beam (FIB) method. High resolution TEM and S/TEM techniques were used for a detailed characterization and a direct comparison of the phase composition and chemistry of the oxide scales formed during high temperature oxidation. The growth of transient h-Al 2 O 3 and its transformation to a-alumina is addressed for each oxidation temperature along with the differences in the diffusion of reactive elements, such as Hf, Zr and Y, through grain boundaries of the a phase. The h to a transformation front was proven to move from the metal-scale to the scale-gas interface. The results presented in this paper indicate that after 100 h of oxidation at 1050 and 1100°C there are still some h-alumina grains remaining and even in the regions where the transformation to a was finished the surface retained the whisker-like morphology.

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“…The grain size of transition alumina that grows initially on alloy surfaces upon oxidation is extremely fine, in the range of a few nanometers 23,26 . The α-Al 2 O 3 grains that first nucleated at the scale/alloy interface are sub-micron in size 68 .…”

Section: Transport Rates Through Alumina Scalesmentioning

confidence: 99%

Impurity Effects on Alumina Scale Growth

Hou¹

2003

Journal of the American Ceramic Society

139

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Most high temperature resistant alloys oxidize to form an external alumina layer, or scale, whose slow growth protects the underlying alloy from continued aggressive oxidation. The growth of the Al 2 O 3 scale is controlled by the transport of oxygen inward and aluminum outward through it, with the rate dominated by the fastest diffusing specie down the fastest path. Components in the alloy can be incorporated into the growing Al 2 O 3 layer, hence affect the transport rates of oxygen and/or aluminum. This paper summarizes existing experimental data to assess the possible effect of these incorporated impurities on the growth rate and transport properties of Al 2 O 3 scales formed on Fe, Ni and Pt based alloys. The amount and distribution of the alloy base metal, sulfur impurity and reactive elements, such as Hf, Y, Zr and Ce, in the alumina scale are evaluated. Their effect on the oxidation and transport rates through the scale are discussed and compared with Al and O diffusion rates deduced from creep studies.

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Structure of transient oxides formed on nicrai alloys

Cited by 71 publications

References 31 publications

Al₂O₃scale development on iron aluminides

Al₂O₃scale development on iron aluminides

Characterization of Alumina Scales Grown on a 2nd Generation Single Crystal Ni Superalloy During Isothermal Oxidation at 1050, 1100 and 1150 °C

Impurity Effects on Alumina Scale Growth

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Structure of transient oxides formed on nicrai alloys

Cited by 71 publications

References 31 publications

Al2O3scale development on iron aluminides

Al2O3scale development on iron aluminides

Characterization of Alumina Scales Grown on a 2nd Generation Single Crystal Ni Superalloy During Isothermal Oxidation at 1050, 1100 and 1150 °C

Impurity Effects on Alumina Scale Growth

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Al₂O₃scale development on iron aluminides

Al₂O₃scale development on iron aluminides