Nanostructured and conventional YSZ coatings deposited using APS and TTPR techniques

Multilayer thermal barrier coatings are candidate materials for high temperature applications that are novel because they employ a strain accommodating interlayer. Plasma sprayed coatings of nanostructured feedstock have shown promise in this direction. Layers of nanostructured yttria stabilized zirconia (nano-YSZ) and conventional YSZ were deposited on mullite substrates using the triple torch plasma reactor (TTPR), and on NiCrAlY coated steel substrates using the Praxair SG-100 plasma torch. It has been observed that a wide range of microstructures and porosities can be produced by combining these deposition techniques and varying the feedstock materials. This control over the microstructure enables the achievement of coating properties that can be tailored according to the application and environment. Heat treatment of the microstructure leads to the formation of larger pores with a significant proportion of partially molten particles. The porosity evolved from the partial sintering of the nano-agglomerates. The microstructure was evaluated using electron microscopy. The nanostructured coatings were compared to conventional YSZ coatings in terms of their microstructural development.