Evaporation enhancement of YSZ spray particles for PS-PVD by modifying the nozzle in conventional 80 kW plasma spray system

摘要

In this paper, a modified nozzle with a large orifice was used to reduce the velocity of plasma jet in order to prolong the dwelling time of spray particle in plasma jet. Optical emission spectrometer (OES) was employed to characterize the temperature, electron number density, also the quantity of Zr atoms and Zr~(1+) ions in plasma jet. The deposition characteristics of YSZ coatings by PS-PVD using 80 kW plasma spray system in vacuum at the condition of droplet filtering were examined. Field emission-scanning electron microscope (FE-SEM) was used to characterize the microstructure of the YSZ coatings. The results show that the temperature and electron number density of plasma jet with the modified nozzle of large orifice are larger than that with the normal nozzle. The cross sectional morphology of the fracture coating deposited through droplet filtering reveals a columnar-structure. The surface morphology of coating exhibits a typical island-structure which is composed of nano-particles. Through droplet filtering, the thickness of columnar-structured coating deposited with modified nozzle is much larger than that with the normal nozzle. The higher temperature and electron number density enhance the intensity of YSZ particle evaporation, resulting in a higher deposition rate with modified nozzle than that with normal nozzle.