Relationships between in-flight characteristics and microstructural properties of plasma sprayed yttria stabilised zirconia

摘要

The effects of in-flight particle characteristics on the microstructural properties of air plasma sprayed yttria-stabilised zirconia were studied. In-flight particle data was acquired with respect to coating stand-off distance and contour plots created. Porosity and hardness of the coatings was measured and plotted over the same area. Particle velocity and temperature were strongly affected by particle size distribution. Smaller particles above the torch central axis travelled on average 10 m/s slower than larger particles located in the centre and lower section of the plume. The section of the plasma plume exhibiting the highest temperatures and velocities falls approximately 2 mm over the range of stand-off distances. This section is also seen to generate dense and hard coatings with less than 7% porosity and hardness values in the order of 700 HV. Furthermore, Reynolds numbers were determined from the in-flight particle data. Reynolds numbers exceeding 1000 produced coatings with less than 5% porosity.