{"title":"Formation of Protective Aluminum-Oxide Layer on the Surface of Fe-Cr-Al Sintered-Metal-Fibers via Multi-Stage Thermal Oxidation","authors":"Loai Ben Naji, Osama M. Ibrahim, Khaled J. Al-Fadhalah","volume":143,"journal":"International Journal of Chemical and Materials Engineering","pagesStart":596,"pagesEnd":600,"ISSN":"1307-6892","URL":"https:\/\/publications.waset.org\/pdf\/10009752","abstract":"
The objective of this paper is to investigate the formation and adhesion of a protective aluminum-oxide (Al2<\/sub>O3<\/sub>, alumina) layer on the surface of Iron-Chromium-Aluminum Alloy (Fe-Cr-Al) sintered-metal-fibers. The oxide-scale layer was developed via multi-stage thermal oxidation at 930 o<\/sup>C for 1 hour, followed by 1 hour at 960 o<\/sup>C, and finally at 990 o<\/sup>C for 2 hours. Scanning Electron Microscope (SEM) images show that the multi-stage thermal oxidation resulted in the formation of predominantly Al2<\/sub>O3<\/sub> platelets-like and whiskers. SEM images also reveal non-uniform oxide-scale growth on the surface of the fibers. Furthermore, peeling\/spalling of the alumina protective layer occurred after minimum handling, which indicates weak adhesion forces between the protective layer and the base metal alloy. Energy Dispersive Spectroscopy (EDS) analysis of the heat-treated Fe-Cr-Al sintered-metal-fibers confirmed the high aluminum content on the surface of the protective layer, and the low aluminum content on the exposed base metal alloy surface. In conclusion, the failure of the oxide-scale protective layer exposes the base metal alloy to further oxidation, and the fragile non-uniform oxide-scale is not suitable as a support for catalysts.<\/p>\r\n","references":"[1]\tD. Whittle, and J. Stringer, \u201cDispersions resistance by additions of reactive elements or oxide improvements in high-temperature oxidation,\u201d Philosophical Transactions of the Royal Society A, 295, 1980, doi: 10.1098\/rsta.1980.0124.\r\n[2]\tR. Prescott, and M. Graham, \u201cThe formation of aluminum oxide scales on high-temperature alloys,\u201d Oxidation of Metals, Vol. 38, Nos. 3\/4, 1992.\r\n[3]\tJ. Herbelin, and M. Mantel, \u201cEffects of Al Addition and Minor Elements on Oxidation Behaviour of FeCr Alloys,\u201d Journal de Physique IV Colloque, 05 (C7), pp.C7-365-C7-374, 1995.\r\n[4]\tA. Strawbridge and P. Hou, \u201cThe role of reactive elements in oxide scale adhesion,\u201d Materials at High Temperatures, 12:2-3, 177-181, 1994, doi: 10.1080\/09603409.1994.11689484.\r\n[5]\tK. Ishii, M. Kohno, S. Ishikawa, and S. Satoh, \u201cEffect of rare-earth elements on high-oxidation resistance of Fe-20Cr-5Al alloy foils,\u201d Materials Transactions, JIM, Vol. 38, No. 9, pp 787-792, 1997.\r\n[6]\tC. Badini, and F. Laurella, \u201cOxidation of FeCrAl alloy: influence of temperature and atmosphere on scale growth rate and mechanism,\u201d Surface and Coatings Technology, 135 291\u2013298, 2001.\r\n[7]\tH. Kadiri, H. Molins, Y. Bienvenu, and M. Horstemeyer, \u201cAbnormal high growth rates of metastable aluminas on FeCrAl alloys, \u201c Oxidation of Metals, 64: 63-97, 2005 doi: 10.1007\/s11085-005-5715-0.\r\n[8]\tJ. Samad, J. Nychka, and N. Semagina, \u201cStructured catalysts via multiple stage thermal oxidation synthesis of FeCrAlly alloy sintered microfibers,\u201d Chemical Engineering Journal, 168 470\u2013476, 2011.\r\n[9]\tR. Zhou, and R. Snyder, \u201cStructures and transformation mechanisms of the Eta. Gamma and Theta transition aluminas,\u201d Acta Crystallographica Section B, 47 617\u2013630, 1991.\r\n[10]\tW. Fei, S. Kuiry, and S. Seal, \u201cInhibition of metastable alumina formation on Fe\u2013Cr\u2013Al\u2013Y alloy fibers at high temperature using titania coating,\u201d Oxidation of Metals, 62 29\u201344, 2004.\r\n[11]\tB. Pint, J. Martin, and L. Hobbs,\u201d The oxidation mechanism of \u03b8-Al2O3 scales,\u201d Solid State Ionics, 78, 99-107, 1995.\r\n[12]\tG. Vaneman, and D. Sigler, \"Accelerated whisker growth on iron\u2013chromium\u2013aluminum alloy foil,\u201d Patent US 4915751, 1990.\r\n[13]\tR. Molins, A. Germidis, and E. Andrieu, in Microscopy of Oxidation 3: Proceedings of the Third International Conference on the Microscopy of Oxidation. S. B. Newcomb and J. A. Little, eds., p. 3, Institute of Materials, London, 1997.\r\n[14]\tC. Badini, and F. Laurella, \u201cOxidation of FeCrAl alloy: influence of temperature and atmosphere on scale growth rate and mechanism,\u201d Surface and Coatings Technology, 135, 291-298, 2001.","publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 143, 2018"}