Control of Droplet Size in Suspension Plasma Spray Process

Suspension plasma spray is now one of the promising processes for preparing the ceramic coatings. Many studies had been carried out and found that the coatings via the SPS process had unique microstructure in nano/submicron order. In this study, the suspensions of yttria stabilized zirconia with various solids ratio were sprayed, and the effect on the coating microstructure was evaluated. It was revealed that the size of droplets on the substrate affects significantly on the microstructure, and suspension content and the spraying distance are the most significant aspects to control droplets diameter. Spraying with the proper parameters, it was possible to obtain dense or porous coatings in wider range than conventional plasma spraying process. It can be proposed there are two threshold diameters of droplets from the microstructure point of view. The coating microstructure changes on these thresholds drastically. More detailed discussion on the relationship among spraying parameters, droplets diameter and the microstructure will be referred.