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Thermal shock characteristics of plasma sprayed mullite coatings

Ramaswamy, P and Seetharamu, S and Rao, KJ and Varma, KBR (1998) Thermal shock characteristics of plasma sprayed mullite coatings. In: Journal of Thermal Spray Technology, 07 (04). pp. 497-504.

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Abstract

Commercially available mullite (3Al(2)O(3). 2SiO(2)) powders containing oxides of calcium and iron as impurities, have been made suitable for plasma spraying by using an organic binder. Stainless steel substrates covered with Ni-22Cr-10Al-1.0Y bond coat were spray coated with mullite, The 425 mu m thick coatings were subjected to thermal shock cycling under burner rig conditions between 1000 and 1200 degrees C and less than 200 degrees C with holding times of 1, 5, and 30 min. While the coatings withstood as high as 1000 shock cycles without failure between 1000 and 200 degrees C, spallation occurred early at 120 cycles when shocked from 1200 degrees C, The coatings appeared to go through a process of self erosion at high temperatures resulting in loss of material. Also observed were changes attributable to melting of the silicate grains, which smooth down the surface. Oxidation of the bond coat did not appear to influence the failure, These observations were supported by detailed scanning electron microscopy and quantitative chemical composition analysis, differential thermal analysis, and surface roughness measurements.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to ASM International.
Keywords: mullite;oxidation resistant;plasma spray;thermal barrier coating;thermal shock resistance;zirconia.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 31 Dec 2009 06:39
Last Modified: 19 Sep 2010 05:28
URI: http://eprints.iisc.ernet.in/id/eprint/19416

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