Substrate temperature dependence of splat morphology for plasma-sprayed cast iron on aluminum surface

In the plasma-sprayed coatings, the morphology of the splats plays an important role in optimizing the microstructure and performance of the coating. Especially, the splashing of impinging droplets during deposition weakens the splat-substrate/intersplat bonding and increases the porosity of the coating. Consequently, the integration of the coating is deteriorated. In the present study, cast iron particles were plasma-sprayed on the surface of polished aluminum substrate to form a single splat. During spraying, the surface of aluminum substrate was preheated in a temperature range from 25 °C to 320 °C. The impact of the substrate preheating temperature on the morphology of the splats was studied using a field emission scanning electron microscope. Results showed that the substrate temperature had significant effects on the morphology of splats. At room temperature, the splats mainly exhibited a splash type with network or radial lines on the splat periphery. While, the splashed splats deposited onto a high temperature substrate showed a star shape on the splat periphery. When the substrate was preheated to 130 °C, the mean percentage of the splashed splats decreased to a minimum value of 18.4% and the disk-like splats prevailed. With the increase of the substrate temperature from 130 °C to 290 °C, the mean percentage of the splashed splats increased monotonically to 78.3%. When the substrate temperature reached to 320 °C, the mean percentage of the splashed splats slightly reduced to 76.6%.