Effect of substrate concave pattern on splat formation of yttria-stabilized zirconia in atmospheric plasma spraying

Splat morphology of yttria-stabilized zirconia (YSZ) on a microconcave-patterned substrate was investigated by both numerical and experimental approaches under a dc-rf hybrid-plasma spray condition. The spreading behavior of molten droplets on a microdimple pattern was numerically simulated in a three-dimensional form. For comparison, impact of a YSZ droplet onto a microdimple pattern of a quartz glass substrate was studied in situ utilizing thermal emissions from the droplet. Concave aspects of a substrate surface play an important role in fingering/splashing of a spreading droplet as well as convex patterns. The main mechanism that causes splashing is likely due to the slipping of a spreading droplet at the edge of concave patterns. The viscosity decrease of the spreading droplet enhances the droplet splash.