Abstract
Several kinds of cermaic particles were plasma sprayed and collected on the metallic flat substrate surface held at various temperatures. Effects of both solidification and wetting at particle/substrate interface on the flattening behavior of the particles were investigated.
The linear relation between transition temperature and thermal conductivity of the particle was clearly observed, and the worse the wettability at particle/substrate interface was, the steeper the gradient of the line was. This result indicates that even in the ceramic particles, the rapid solidification at the bottom part of the splat occurs when a temperature of the substrate is close to the transition temperature. The central disk part in the splash splat diminished gradually with decreasing the substrate temperature. Wholly scattered splat could be often observed when the wetting of the particle to the substrate was bad, like in the case of alumina splat on the gold coated metal substrate. Therefore, the occurrence of the splash splat does not always need the rapid initial solidification at collision of the particle to the substrate.
Consequently, the wetting seems to be the most dominating factor in the flattening of the thermal sprayed ceramic particle on the substrate. The rapid solidification is thought to affect on the flattening of the particle when the wetting reaches to some moderate condition.
