Microstructure of YSZ Coatings Deposited by PS-PVD Using 45 kW Shrouded Plasma Torch

In this study, a conventional 80 kW class plasma spraying system was used to produce yttria-stabilized-zirconia (YSZ) coatings by PS-PVD at a pressure of 100 Pa. A shroud was attached in the front of the plasma nozzle to restrain expansion of plasma jet. The torch was operated at an arc power of 45 kW and YSZ coatings were deposited at a powder feed rate of 0.2 g/min. Optical emission spectroscopy was used to diagnose the particle state in plasma jet. The surface morphology and cross-sectional morphology of coatings was characterized by field emission scanning electron microscope. It is found that the amount of YSZ evaporation is significantly enhanced through using a shroud. The coatings with a hybrid microstructure of splats and nanoclusters were deposited perpendicular to the coatings. The nanostructured clusters deposited out of the vapor are presented at splat interfaces. It is evident that using powders specially designed for PS-PVD and controlling heating of plasma jet to spray particles, PS-PVD deposition for a hybrid microstructure consisting of vapor phase deposit can be realized through conventional plasma spray system. Columnar grain structured YSZ can also be deposited by pure vapor phase at the side surface of the substrate.