Effect of Droplet Characteristics and Substrate Surface Topography on the Final Morphology of Plasma-Sprayed Zirconia Single Splats

Abstract

The morphology of atmospheric plasma-sprayed yttria-stabilized zirconia single splats has been studied. Single splats of plasma-sprayed ZrO2-7%Y2O3 powder have been collected on polished stainless steel substrates kept at three different temperatures (room temperature, 300 °C, and 600 °C). The effect of heating on the substrates’ surface topography was evaluated. The effects of spray process parameters such as substrate temperature, particle temperature, and velocity on the morphology of single splats was studied. Variation of splat shape with location within the footprint of plasma spray was investigated. Pore and microcrack formation, splashing behavior, splat/substrate, and splat/splat interfaces were analyzed. Splat morphology and diameter, satellite particles, and splashing behavior were recorded using both scanning electron microscopy and image analysis. Splat/substrate and splat/splat interfaces were studied from cross sections prepared by focused ion beam milling. Results showed primarily disk-shape morphology and no evidence of delamination along the splat/substrate interface at 600 °C substrate temperature. Overlapped splats showed evidence of melting (microwelding) at splat boundaries. Splat thickness was measured to be less than 1 μm for all spray conditions.