Authors: ChangJiu Li Jiao Zou HuiBin Huo JianTao Yao GuanJun Yang
Publish Date: 2015/09/03
Volume: 25, Issue: 1-2, Pages: 264-272
Abstract
Highefficiency gas turbines require hightemperature sealing by use of abradable porous ceramic coatings to increase engine efficiency In this study porous Al2O3 coatings were deposited by flame spraying the coatings were applied in a semimolten state by controlled melting of the sprayed powder particles The effects of the degree of melting of the sprayed particles which depends on spraying conditions on coating microstructure and porosity were investigated The degree of melting of the sprayed particles was characterized by use of 3D confocal laser microscopy The porosity of the coating was estimated by image analysis The results showed that the degree of melting of alumina particles can be changed from 70 to 30 and thus coating porosity can be increased from 30 up to over 70 The standard hardness test yielded no useful data for porous coatings deposited by use of sprayed particles with a degree of melting 60 and a hardness of 32–75 HR15Y for Al2O3 coatings deposited by use of sprayed particles with a degree of melting 60 Pinondisk abrasion tests performed at room temperature by use of an Inconel 738 IN738 nickelbased superalloy pin with a spherical tip 5 mm in diameter were conducted on the porous alumina coating to evaluate its abrasion behavior It was found that for coatings of hardness 32 HR15Y and porosity 40 the wear weight loss of the IN738 pin was negligible despite the high rate of wear of the coating It is evident that flamesprayed porous alumina coatings of high porosity prepared by this approach have potential for use as abradable coatings for gas turbines operating at high temperaturesThis project was financially supported by the Fund for the Doctoral Program of Higher Education of China grant no 20120201130002 and the National Basic Research Program of China 2012CB625100 The authors are grateful for the support from the European Program Marie Curie IPACTS no 268696
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