Role of Particle Injection Characteristics on Coating Microstructure of Plasma Sprayed Zirconia

Abstract

Yttria-stabilized zirconia (YSZ) powders (50 – 100 μm in diameter) have been used to prepare plasma-sprayed thin ceramic films on the stainless steel and nickel sheets employing non-equilibrium plasma spray technology at atmospheric pressure. The dependency of microstructure of coatings on initial powder characteristics was investigated. Furthermore, effects of various plasma spray conditions on microstructure, crystallite size, phase content of the coatings have been evaluated. Plasma spray zirconium oxide coatings deposited onto different substrates have been characterized using optical microscope, scanning electron microscope (SEM) and X-ray diffractometer (XRD) for study of micro-structure and phase analysis as a part of a process optimisation study. The deposits characteristics were compared with the processing parameters and revealed that the deposit characteristics strongly depended on the in-flight particle parameters. The coating sprayed using finer powder displays better structural characteristics than the counterpart sprayed using coarse-grained powder feed. The density of the film increases with the spray temperature. The crystallite size of the film also exhibits a strong dependency on the spray conditions. It was demonstrated how the spray regime affects the thickness, density and porosity of the obtained films.