Effect of heat treatment on low conductive thermal barrier coatings

Paper in proceeding, 2009

Development of Thermal Barrier Coating (TBC) systems will allow higher combustion temperature which is of interest for all manufactures since it results in higher fuel efficiency and environmentally cleaner emissions. Low thermal conductivity and long service life are the most important properties of these coatings. The objective of the work presented in this paper was to study the influence of a long-term heat treatment (i.e. 1200°C/2000h) on different characteristics of atmospheric plasma sprayed TBCs. Two zirconia feedstock materials were evaluated, namely yttria partially stabilised zirconia and dysprosia partially stabilised zirconia. Several spray conditions were designed and employed in order to achieve different coating morphologies. Microstructure analyses revealed that the coating microstructure was significantly dependent on both operating conditions and heat treatment conditions. Significant changes in coatings porosity occurred during heat treatment. The lowest thermal conductivity was reached with the dysprosia partially stabilised zirconia material. All TBC systems experienced decomposition of the metastable t´ phase during long heat treatment at 1200°C.