The influence of particle in-flight properties on the microstructure of coatings deposited by the supersonic atmospheric plasma spraying

In this work, yttria-stabilised zirconia (YSZ) coatings were deposited by a high-efficiency supersonic atmospheric plasma spraying (SAPS) system. During spraying, the in-flight properties (including velocity and surface temperature) of the sprayed particles were diagnosed on-line by a commercially available Spray Watch 2i system positioned normal to the spraying axis. The effect of the in-flight properties of the sprayed particles on the microstructure of the coatings was studied, with the aim of achieving improved knowledge on the accurate control of their coating quality. The VT value, defined as a function of the in-flight velocity of the particles and the surface temperature of the substrate, was observed to be directly proportional to the reciprocal of the porosity and structure uniformity of the coatings, which indicated that the structure of the SAPS-coatings can be tailored by adjusting the VT value of the sprayed particles.