Microstructural Investigation of BaTiO3 Plasma Sprayed Coating Deposited by Splash and Disk-Like Splats

Abstract

In the thermal spray process, particulate materials can be melted by plasma atmosphere due to its high local temperature from 8700 ^◦C to 15,000 ^◦C. Therefore, the material powders turn into droplets after being melted by injection into the hot flame. Molten droplets are accelerated toward a substrate and form the splats which quickly solidify; finally, the film is formed by pile-up splats. Splat morphology and post treatment can determine the microstructure, mechanical and physical properties of the coating. In this study, BaTiO₃ films were deposited onto a mirror polished stainless steel substrates kept at room temperature and 500 ^◦C. At the elevated temperatures, the desorbtion of adsorbates and condensate at the substrate surface are the most important factor which change the morphology of the splats, from irregular- splash morphology to disk-like shape. Splat morphology can determine sprayed film microstructure and effect on the coating properties. The morphology of individual splats and the post treated films were studied using scanning electron microscopy. Results indicated that the porosity in the film produced at room temperature was higher than that in the film deposited on the heated substrates. Also, results show post heat treatment can improve physical and mechanical properties of the sprayed coating.