Isothermal and cycling properties of zirconia-based thermal barrier coatings deposited by PECVD

Columnar 100-200-mum-thick Y2O3 partially stabilised ZrO2 thermal barrier coatings have been deposited by PECVD at temperatures between 700 and 900 degreesC on alumina and NiPtAl-coated superalloy substrates, at rates which could exceed 250 mum h(-1). The high temperature behaviour of the coatings has been investigated with respect to isothermal (at 1100-1400 degreesC) and cycling (at 1100 degreesC) ageing. The tetragonal phase t' destabilisation scheme leads to the formation of a low yttria tetragonal phase t and a second high yttria tetragonal phase, labelled t'(l). The good thermal cycling behaviour of coatings deposited at 900 degreesC (> 400 1-h cycles), as well as room and high temperature thermal conductivity measurements, confirm the similarity with EBPVD TBCs. The thermally grown oxide formation, which was not optimised here, limits the lifetime in cyclic conditions. The more porous 700 degreesC coatings, that are less resistant to sintering at high temperatures, also exhibit a good resistance to thermal cycling. These results and the high growth rates position the PECVD technique as a valuable alternative process for TBC manufacturing suitable for industrial requirements. (C) 2001 Elsevier Science B.V. All rights reserved.