Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior

The relative content of strengthening element tantalum (Ta) and oxidation-resistant element chromium (Cr) is an essential value for superalloys to obtain an excellent combination of oxidation resistance and mechanical properties. In the present paper, the isothermal oxidation behavior of several sin...

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Autores principales:	Jianxiu Chang, Wenhao Feng, Wenwen Zhao, Hongmin Jia, Yanming Liu, Sheji Luo, Dong Wang, Jiasheng Dong
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	superalloy high-temperature oxidation tantalum oxide Crystallography QD901-999
Acceso en línea:	https://doaj.org/article/9de8ee6e4bd447eb9006be35292cd922
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spelling	oai:doaj.org-article:9de8ee6e4bd447eb9006be35292cd9222021-11-25T17:19:38ZInvestigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior10.3390/cryst111114212073-4352https://doaj.org/article/9de8ee6e4bd447eb9006be35292cd9222021-11-01T00:00:00Zhttps://www.mdpi.com/2073-4352/11/11/1421https://doaj.org/toc/2073-4352The relative content of strengthening element tantalum (Ta) and oxidation-resistant element chromium (Cr) is an essential value for superalloys to obtain an excellent combination of oxidation resistance and mechanical properties. In the present paper, the isothermal oxidation behavior of several single crystal Ni-base superalloys with different Ta/Cr (wt. %, similarly hereinafter) ratios at 1000 °C in static air has been systematically investigated to explore the optimal Ta/Cr for excellent oxidation resistance. A detailed microstructure study using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and an electro-probe microanalyzer (EPMA) was performed to reveal the oxidation products and mechanisms. For all alloys, a three-layer structured scale consisting of an outer (Cr, Al, Ti, Ni, Ta)-O layer, an inner Al<sub>2</sub>O<sub>3</sub> layer and an inner nitride layer was formed. As Ta/Cr increased, the amounts of Ta-containing products, cracks, holes and inner nitride increased. Meanwhile, the completeness of the Al<sub>2</sub>O<sub>3</sub> layer got worse. It was shown that if Ta/Cr ≤ 0.5, Ta increased the growth rate of Cr<sub>2</sub>O<sub>3</sub> via the doping effect induced by Ta cations. If Ta/Cr > 0.5, Ta reduced the completeness of Cr<sub>2</sub>O<sub>3</sub> through competitive growth of Ta<sub>2</sub>O<sub>5</sub> and Cr<sub>2</sub>O<sub>3</sub>. A good oxidation performance can be expected with the value Ta/Cr ≤ 0.5.Jianxiu ChangWenhao FengWenwen ZhaoHongmin JiaYanming LiuSheji LuoDong WangJiasheng DongMDPI AGarticlesuperalloyhigh-temperature oxidationtantalum oxideCrystallographyQD901-999ENCrystals, Vol 11, Iss 1421, p 1421 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	superalloy high-temperature oxidation tantalum oxide Crystallography QD901-999
spellingShingle	superalloy high-temperature oxidation tantalum oxide Crystallography QD901-999 Jianxiu Chang Wenhao Feng Wenwen Zhao Hongmin Jia Yanming Liu Sheji Luo Dong Wang Jiasheng Dong Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior
description	The relative content of strengthening element tantalum (Ta) and oxidation-resistant element chromium (Cr) is an essential value for superalloys to obtain an excellent combination of oxidation resistance and mechanical properties. In the present paper, the isothermal oxidation behavior of several single crystal Ni-base superalloys with different Ta/Cr (wt. %, similarly hereinafter) ratios at 1000 °C in static air has been systematically investigated to explore the optimal Ta/Cr for excellent oxidation resistance. A detailed microstructure study using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and an electro-probe microanalyzer (EPMA) was performed to reveal the oxidation products and mechanisms. For all alloys, a three-layer structured scale consisting of an outer (Cr, Al, Ti, Ni, Ta)-O layer, an inner Al<sub>2</sub>O<sub>3</sub> layer and an inner nitride layer was formed. As Ta/Cr increased, the amounts of Ta-containing products, cracks, holes and inner nitride increased. Meanwhile, the completeness of the Al<sub>2</sub>O<sub>3</sub> layer got worse. It was shown that if Ta/Cr ≤ 0.5, Ta increased the growth rate of Cr<sub>2</sub>O<sub>3</sub> via the doping effect induced by Ta cations. If Ta/Cr > 0.5, Ta reduced the completeness of Cr<sub>2</sub>O<sub>3</sub> through competitive growth of Ta<sub>2</sub>O<sub>5</sub> and Cr<sub>2</sub>O<sub>3</sub>. A good oxidation performance can be expected with the value Ta/Cr ≤ 0.5.
format	article
author	Jianxiu Chang Wenhao Feng Wenwen Zhao Hongmin Jia Yanming Liu Sheji Luo Dong Wang Jiasheng Dong
author_facet	Jianxiu Chang Wenhao Feng Wenwen Zhao Hongmin Jia Yanming Liu Sheji Luo Dong Wang Jiasheng Dong
author_sort	Jianxiu Chang
title	Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior
title_short	Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior
title_full	Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior
title_fullStr	Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior
title_full_unstemmed	Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior
title_sort	investigation on optimal ta/cr ratio of a single crystal ni-base superalloy in view of the isothermal oxidation behavior
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/9de8ee6e4bd447eb9006be35292cd922
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Investigation on Optimal Ta/Cr Ratio of a Single Crystal Ni-Base Superalloy in View of the Isothermal Oxidation Behavior

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