Abstract
The aim of the study presented in this paper was to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. In order to achieve these goals; a number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry including; high purity powders for sintering resistance, Dysprosia stabilised Zirconia powders and powders containing porosity formers. Agglomerated & Sintered (A&S) and Hollow Oven Spherical Powder (HOSP) morphologies were used to attain beneficial microstructures. Finally, dual layer coatings were produced using the different powder morphologies. Evaluation of the thermal conductivity of the coating systems from room temperature to 1200°C was conducted using laser flash technique. Tests were done on as-sprayed samples and samples heat treated for 100 hours at 1150°C in order to evaluate the first stage sintering resistance of the coating systems. Thermal conductivity results were correlated to coating microstructure using image analysis of porosity and crack content. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings.
