The Effect of Substrate Properties on Plasma Spraying of Submicron Ceramic Suspensions Using a Continuous Ink Jet Printer

摘要

The effect of the substrate properties, namely temperature and position, on the deposits formed by the new process of plasma spraying of submicron ceramic suspensions using a continuous ink jet printer was investigated. The substrate temperature was shown to have a considerable effect on the structure of deposits formed. At low substrate temperatures the splats produced were irregular and poorly shaped. Preheating the substrate to a temperature above 400 deg C produced circular splats. Such dependence of splat morphology on the substrate temperature was compared with that observed for conventional plasma spraying. Splats formed by the new method were an order of magnitude smaller than conventionally sprayed splats and spats smaller than several microns were found to be free from microcracking. Overspraying to form coatings showed that when the substrate was far form the plasma (low substrate temperature) a poorly densified coating was produced. Placing the substrate closer to the plasma (hotter substrate) resulted in a more coherent and denser coating being produced. These effects were explained in terms of the spreading and cooling rate experienced by the molten drops as they impinge on the substrate.