Erosion of atmospheric plasma sprayed rare earth oxide coatings under air suspended corundum particles

Purpose This study systematically investigated the effect of the binary rare earth oxide of La2O3 and Sm2O3 on the properties of the Al2O3/TiO2 (AT) coating, including phase transform, wear behavior, etc. Design/methodology/approach AT coatings mixed with different components of binary rare earth oxides of La2O3 and Sm2O3 are prepared by atmospheric plasma spraying. The adhesion strength, micro-hardness, phase transition and tribological behavior of coatings are systematically investigated. Findings The X-ray diffraction (XRD) analysis shows that phase transformation is obvious after spraying, and a-Al2O3 is almost translated into γ-Al2O3 when La2O3 and Sm2O3 are doped together. Meanwhile, solid solution generated between rare earth oxide and Al2O3/TiO2 coatings results in disappearance of TiO2 and rare earth oxide phase. The photos under the scanning electron microscope (SEM) indicate that binary rare earth oxide could increase the melting degree of powder and decrease porosity of coatings.The increasing of Sm2O3 rarely affect micro-hardness and adhesion strength, and the coating with 4 per cent Sm2O3 and 1 per cent La2O3 exhibits the best wear resistance and lowest friction coefficient among all the samples. Originality/value AT coatings mixed with different components of binary rare earth oxide of La2O3 and Sm2O3 are prepared by atmospheric plasma spraying. Binary rare earth oxide could increase the melting degree of powder and decrease porosity of AT coatings.

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Rare Earth Oxide Coatings for Life Extension of Chromia Forming Alloys

Elevated Temperature Coatings ◽

10.1002/9781118787694.ch15 ◽

2013 ◽

pp. 197-207

Author(s):

Stela M.C. Fernandes ◽

Lalgudi V. Ramanathan

Keyword(s):

Rare Earth ◽

Rare Earth Oxide ◽

Life Extension ◽

Oxide Coatings

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From lotus effect to petal effect: Tuning the water adhesion of non-wetting rare earth oxide coatings

Journal of the European Ceramic Society ◽

10.1016/j.jeurceramsoc.2019.12.003 ◽

2020 ◽

Vol 40 (4) ◽

pp. 1692-1702 ◽

Cited By ~ 2

Author(s):

Pengyun Xu ◽

Thomas W. Coyle ◽

Larry Pershin ◽

Javad Mostaghimi

Keyword(s):

Rare Earth ◽

Rare Earth Oxide ◽

Oxide Coatings ◽

Lotus Effect ◽

Water Adhesion

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Porosity and Its Significance in Plasma-Sprayed Coatings

Coatings ◽

10.3390/coatings9070460 ◽

2019 ◽

Vol 9 (7) ◽

pp. 460 ◽

Cited By ~ 16

Author(s):

John Gerald Odhiambo ◽

WenGe Li ◽

YuanTao Zhao ◽

ChengLong Li

Keyword(s):

Working Environment ◽

Atmospheric Plasma ◽

Formation Mechanisms ◽

Multilayer Coatings ◽

Oxide Coatings ◽

Spraying Parameters ◽

Plasma Sprayed Coatings ◽

Sprayed Coating ◽

Plasma Sprayed ◽

Sprayed Coatings

Porosity in plasma-sprayed coatings is vital for most engineering applications. Porosity has its merits and demerits depending on the functionality of the coating and the immediate working environment. Consequently, the formation mechanisms and development of porosity have been extensively explored to find out modes of controlling porosity in plasma-sprayed coatings. In this work, a comprehensive review of porosity on plasma-sprayed coatings is established. The formation and development of porosity on plasma-sprayed coatings are governed by set spraying parameters. Optimized set spraying parameters have been used to achieve the most favorable coatings with minimum defects. Even with the optimized set spraying parameters, defects like porosity still occur. Here, we discuss other ways that can be used to control porosity in plasma-sprayed coating with emphasis to atmospheric plasma-sprayed chromium oxide coatings. Techniques like multilayer coatings, nanostructured coatings, doping with rare earth elements, laser surface re-melting and a combination of the above methods have been suggested in adjusting porosity. The influences of porosity on microstructure, properties of plasma-sprayed coatings and the measurement methods of porosity have also been reviewed.

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Electrosynthesis of Rare Earth Oxide Coatings for High Temperature Applications

Materials Science Forum ◽

10.4028/www.scientific.net/msf.696.336 ◽

2011 ◽

Vol 696 ◽

pp. 336-341 ◽

Cited By ~ 12

Author(s):

F. Pedraza ◽

Baptiste Bouchaud ◽

J. Balmain ◽

G. Bonnet ◽

Justine Menuey

Keyword(s):

Rare Earth ◽

Rare Earth Oxide ◽

Shear Stresses ◽

X Ray Diffraction ◽

Oxide Coatings ◽

Cathodic Electrodeposition ◽

Practical Applications ◽

Xrd Patterns ◽

Base Superalloy

Rare earth oxides are commonly employed as dopants or coatings to improve the development and adherence of alumina scales. However, for practical applications, doping is difficult to control and the use of coatings is preferred. Nevertheless the thickness of such coatings is relatively limited for long term exposures at high temperatures and thicker coatings are hence required. With this in mind, the cathodic electrodeposition technique has been investigated in this work. The results show that deposits of about 20 µm RExOOHycoatings can be obtained on a Ni superalloy in 20 min. The applied current density and time significantly influence the microstructure, thickness, crystallite size and number of oxygen vacancies of the coatings. Their needle-like microstructure is indicative of non negligible amounts of rare earth hydroxides. However, the hydroxide peaks overlap with the oxide peaks in the X-ray diffraction (XRD) patterns. XRD also suggests that the coatings are either amorphous or of nanocrystalline nature, as supported by Raman spectroscopy. Their multicracked morphology is related to the shear stresses between the coating and the substrate, hydrogen bubbling and mostly by drying of the coatings in air. The number of cracks is increased after a heat treatment which also allows full crystallization of the RExOycoating and pre-oxidation (α-Al2O3) of the superalloy. The combined effect of both oxides results in an improved oxidation resistance of the Ni-base superalloy at 1100°C in air.

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