Microstructures of ZrO2-8wt.%Y2O3 coatings prepared by a plasma laser hybrid spraying technique

Thermal barrier coatings (TBCs) consisting of a yttria partially stabilized zirconia layer and MCrAIY bond coatings have been widely used to improve the performance of hot-section components used in gas turbines. To improve the lifetime of TBC coatings, post-treatments of sprayed coatings and simultaneous spraying processes by a plasma laser hybrid technique have been tried. An analytic technique using a low-viscosity resin with a fluorescent dye under a high vacuum has been investigated for the accurate observation of the microstructure of TBCs prepared by post laser treatment and a laser hybrid spraying process. As a result of water quenching tests, coatings prepared by post laser treatments and laser hybrid spraying processes showed significantly improved thermal shock resistance compared to as-sprayed coatings. The relationship of the microstructure of TBCs, which was modified by laser treatment, and thermal shock resistance has been evaluated by the careful observation of samples and optimum process conditions are suggested for improving the thermal shock resistance of TBCs. (C) 2002 Elsevier Science B.V. All rights reserved.