Plasma-sprayed YSZ coatings: Microstructural features and resistance to molten metals

Yttria Stabilized Zirconia (YSZ) coatings deposited by plasma spraying are widely used as thermal barriers onto metallic substrates, due to their attractive thermal properties and chemical inertia. In the present study, YSZ coatings were deposited onto steel substrates and their microstructure was investigated with X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The micro- and nano-scopic structural features were correlated to the performance of the coatings against corrosion by molten metals, which could simulate the industrial conditions of numerous applications. More precisely, in-scale porosity of the coatings and crystal parameters modifications were systematically examined and correlated to the corrosion behaviour in molten zinc, tin and aluminium baths for a 6 days testing period. The structural stability of the ceramic coating at high temperature, as well as the reactivity of the molten metal on the ceramic surface were preliminarily evaluated by thermogravimetric analysis and differential scanning calorimetry.