The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys

Bibliographic Details
Main Author:	Gao, Hang
Language:	English
Published:	Case Western Reserve University School of Graduate Studies / OhioLINK 2012
Subjects:	Materials Science
Online Access:	http://rave.ohiolink.edu/etdc/view?acc_num=case1322551816

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spelling	ndltd-OhioLink-oai-etd.ohiolink.edu-case13225518162021-08-03T05:34:10Z The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys Gao, Hang Materials Science <p>Research has been conducted on the dual phase γ/γ’-NiAlCrHfY(Si) bond coat alloys to determine the effect of 1 at.% of silicon on the evolution of the oxide scale at an early stage of oxidation. The microstructures of oxide scales formed on selected grains of NiAlCrHfY(Si) alloys are compared in this work. Instead of forming an exclusively α-Al<sub>2</sub>O<sub>3</sub> scale, NiAlCrHfY alloys form NiO/spinel as the top layer of the scale and Al<sub>2</sub>O<sub>3</sub> as the bottom layer of the scale, with some voids within the oxide scale and at the Al<sub>2</sub>O<sub>3</sub>/alloy interface. NiAlCrHfYSi alloys form a mostly Al<sub>2</sub>O<sub>3</sub> scale with a small amount of Ni content in the outer part and Ni-rich particles at the inner part. The addition of silicon promotes formation of a scale with less included NiO/spinel and fewer voids; this beneficial effect arises from decreasing the outward diffusion of Ni from the alloy. However, the addition of Si does not prevent void formation at the Al<sub>2</sub>O<sub>3</sub>/alloy interface.</p><p>Some other factors such as grain orientation of the alloy could also influence the formation of the oxide scale. In order to exclude the grain orientation effect, the grain orientation has been determined on the NiAlCrHfY(Si) alloys by EBSD before oxidation. The grains of NiAlCrHfY(Si) with an orientation close to <001> were chosen to be studied in this work. Then NiAlCrHfY(Si) alloys were oxidized under a series of oxidation conditions: 950°C with a hold time of 1 minute; 1150°C with a hold time of 1 minute; 1150°C with a hold time of 30 minutes. STEM-EDS mapping and quantitative analysis were used to study the microstructural evolution and elemental composition of the scales on the NiAlCrHfY(Si) alloys.</p> 2012-01-30 English text Case Western Reserve University School of Graduate Studies / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=case1322551816 http://rave.ohiolink.edu/etdc/view?acc_num=case1322551816 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection	NDLTD
language	English
sources	NDLTD
topic	Materials Science
spellingShingle	Materials Science Gao, Hang The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys
author	Gao, Hang
author_facet	Gao, Hang
author_sort	Gao, Hang
title	The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys
title_short	The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys
title_full	The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys
title_fullStr	The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys
title_full_unstemmed	The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys
title_sort	effect of silicon on the oxidation of dual phase nialcrhfy(si) bond coat alloys
publisher	Case Western Reserve University School of Graduate Studies / OhioLINK
publishDate	2012
url	http://rave.ohiolink.edu/etdc/view?acc_num=case1322551816
work_keys_str_mv	AT gaohang theeffectofsiliconontheoxidationofdualphasenialcrhfysibondcoatalloys AT gaohang effectofsiliconontheoxidationofdualphasenialcrhfysibondcoatalloys
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The Effect of Silicon on the Oxidation of Dual Phase NiAlCrHfY(Si) Bond Coat Alloys

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