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A scanning electron microscopic study to observe the changes in the growth morphology of the alpha phased Alumina-13 wt.% titania coatings during plasma spraying

DSpace at IIT Bombay

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Title A scanning electron microscopic study to observe the changes in the growth morphology of the alpha phased Alumina-13 wt.% titania coatings during plasma spraying
 
Creator VENKATARAMAN, R
SINGH, SP
VENKATARAMAN, B
DAS, DK
PATHAK, LC
CHOWDHURY, SG
GHOSH, RN
RAVICHANDRA, D
RAO, GVN
NAIR, K
KATHIRKAR, R
 
Subject stability
alloy
microstructure
solidification
diffraction
texture
powders
phase transitions
scanning electron microscopy
x-ray diffraction
plasma spraying
aluminum oxide
electron back scattered diffraction
 
Description Plasma spraying of Alumina-13 wt.% titania coatings shows preferential stability of a phase, in the as sprayed conditions, to an extent of 15-40%. As reported in the literature, the quantity of this alpha phase can be considered to be closely related to the processing parameters of the air plasma spray process, such as arc current, plasma gas flow rate etc. Normally, a lower value of arc current, results in larger quantity of preferentially stabilized a phase. In this paper, we have attempted to measure the orientation image mapping (OIM) of these alpha phased Alumina-13 wt.% titania coatings with Electron Back Scattered Diffraction. From the OIM, the pole figures for the a phase were established and from appropriate pole figures, such as (0001), (0006), (01T1) and (1011) the growth morphology of the alpha phase could be determined. For larger values of arc current, at which the growth rate is faster and due to the imposed rapid solidification conditions, the hexagonal basal plane of (0001)-H type of the alpha phase tends to align with the (001) type FCC faces of the metastable gamma phase. This alignment can be considered to be similar to a directionally solidified chill cast texture. On the other hand, at slower growth rate and at lower arc current value not only a larger quantity of alpha phase forms, but for accommodation of these larger number of a grains in the thinner section of splats there appears to be a need for a change in the growth morphology. (100)-R type rhombohedral faces, with shorter axial dimensions were found to align in preference to the directional solidified (0001)-H type basal planar arrangement. This type of change in growth morphology can possibly accommodate more a grains for the same thickness of the splat as compared to a basal plane (0001)-H type arrangement. (C) 2008
 
Publisher ELSEVIER SCIENCE SA
 
Date 2011-11-07T16:11:33Z
2011-12-26T13:01:21Z
2011-12-27T05:44:42Z
2011-11-07T16:11:33Z
2011-12-26T13:01:21Z
2011-12-27T05:44:42Z
2008
 
Type Article
 
Identifier SURFACE & COATINGS TECHNOLOGY, 202(21), 5074-5083
0257-8972
http://dx.doi.org/10.1016/j.surfcoat.2008.03.039
http://dspace.library.iitb.ac.in/xmlui/handle/10054/16583
http://hdl.handle.net/10054/16583
 
Language en