Microstructural observation of the sintering behavior of nanostructured yttria stabilized zirconia

Abstract

Multilayer thermal barrier coatings are being investigated for high temperature applications by employing 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 NiCrAIY coated steel substrates using the Praxair SG-100 plasma torch. The coatings were heat treated and the microstructure evaluated. Heat treating the samples lead 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. Porosity change during the sintering process was measured and the microstructure observed using electron microscopy. The nanostructured coatings were compared to conventional YSZ coatings.